@inproceedings{mitra2020vivo,

title = {In Vivo Flow-Regulated Endothelial Glycocalyx Integrity Leveraged for Targeted Intravenous Nanoparticle Delivery},

author = {Ronodeep Mitra and Ming Cheng and Gerard O'Neil and Praveen Kulkarni and Rajiv Kumar and Srinivas Sridhar and Craig Ferris and James Hamilton and Hanjoong Jo and Eno E Ebong},

year  = {2020},

date = {2020-01-01},

booktitle = {2020 Virtual AIChE Annual Meeting},

organization = {AIChE},

keywords = {},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{bal2019vivo,

title = {In Vivo Endothelial Uptake of Nanoparticles: Impact of Disturbed Flow and Degraded Glycocalyx},

author = {Nandita Bal and Ming Cheng and Rajiv Kumar and Srinivas Sridhar and Eno E Ebong},

year  = {2019},

date = {2019-01-01},

booktitle = {2019 AIChE Annual Meeting},

organization = {AIChE},

abstract = {Statement of Purpose: New and more effective therapies for atherosclerosis-based cardiovascular disease should target early stages of the diseases and specific vascular sites where disease occurs.1 The initiation and localization of atherosclerotic plaques has been linked to the dysfunction of the endothelial glycocalyx (GCX). The GCX breaks down, resulting in compromised endothelial barrier function and an increase in vascular permeability.2 This allows lipids and inflammatory cells to penetrate vessel walls, and at the same time can be leveraged for targeted therapeutic delivery. In previous cell culture studies, enzyme-induced GCX degradation resulted in significantly increased endothelial cell uptake of nanoparticle vehicles that are designed for drug delivery, compared to the effects of intact GCX.3,4 The study presented in this abstract was designed to assess if the cell culture findings translate to selective nanoparticle uptake in animals. Specifically, it was determined if increased nanoparticle uptake occurs in animal endothelial cells that have degraded GCX. The first objective of this animal study was to identify vessel regions with intact versus degraded GCX, and confirm that circulating nanoparticles localize selectively at regions of GCX dysfunction. The second objective was to promote endothelial cell surface-specific localization of these nanoparticles by targeting the intracellular adhesion molecule (ICAM) which is upregulated in pre-atherosclerotic disturbed flow conditions.5

Methods: Mouse models of endothelial dysfunction apply partial ligation of the left carotid artery (LCA) to model acute disturbed flow in the mice, which has been reported to induce endothelial dysfunction.6,7 Seven C57BL/6 mice at 4 weeks of age underwent this partial LCA ligation surgery. Polymer- and biotin-coated 10 nm gold nanospheres (GNS) were administered to the mice at day 26 after LCA ligation. In the case of targeted delivery to the endothelial cell surface, an anti-ICAM peptide was conjugated to the GNS surface before it was administered to the mice. The animals were euthanized 2 days after receiving the GNS without or conjugated with anti-ICAM. The LCA and right carotid artery (RCA) were separately cryopreserved and sectioned onto slides. GCX was imaged after incubating LCA and RCA sections with antibody to block GNS, followed by biotinylated wheat germ agglutinin and horseradish peroxidase conjugated to streptavidin. GNS were imaged after incubation with horseradish peroxidase conjugated to streptavidin. We then applied a fluorescent reagent that reacts with horseradish peroxidase. The blood vessels were imaged by fluorescence microscopy and analyzed using ImageJ for GCX coverage and GNS uptake.



Results: The partial LCA ligation model achieved the goal of creating a vessel with disturbed flow. The model also provided a convenient comparison with a healthy RCA experiencing streamlined flow. The vessel walls of the LCA exhibited a more discontinuous GCX layer on the intima as compared to the RCA, decreasing from 76.3 ± 10.2 % in the RCA to 21.2 ± 5.9 % in the LCA. This observable dysfunction correlated to increased nanoparticle uptake, as the LCA took in approximately 2.5-fold more GNS than the RCA did, based on the fluorescence signal detected in the histology images. The studies to improve endothelial cell surface-specific localization of these nanoparticles by targeting ICAM are still ongoing.



Conclusions: A partial LCA ligation was performed to acutely disturb blood flow in a mouse vessel and observe resultant endothelial GCX dysfunction as well as passive targeting of GNS to affected areas. The affected LCA exhibited lack of continuous GCX layer, as well as increased localization of plolymer-coated GNS that are designed to deliver drug therapies. These results indicate that vessel and GCX dysfunction, both precursors of atherosclerosis and cardiovascular disease, can be induced in a mouse model to study targeted drug delivery. Passive nanoparticle uptake differences between the healthy RCA and disturbed LCA indicate a role of GCX infiltration of nanoparticles to the endothelial cells. The ongoing investigation will determine the effectiveness of active targeting with ICAM to localize these nanoparticles to the endothelial cell surface. This strategy of targeting dysfunctional vessels based on the GCX offers a new approach in cardiovascular disease therapy and prevention.



Acknowledgements: We appreciate funding from National Institutes of Health (K01 HL125499) and the Northeastern University Provost’s Tier 1 Grant.



References:



Weinbaum, S.; et. al, Annu Rev Biomed Eng 2007, 9,121-167.

Becker, B. et. al, Br J Clin Pharmacol 2015, 80, 389-402.

Cheng, et. al, Int. J. Nanomed 2016, 21, 3305-3315.

Cheng, et. al, Int. J. Nanomed 2019, 14, 319-333.

Nakashima et. al, Arteriosclerosis, Thrombosis, and Vascular Biology 1998, 18, 842-851.

Kumar, S.; et. al, J. Lab. Invest. 2017, 97, 935-945

Mitra, et. al, Trans. Med. Comm. 2018, 3-10.},

keywords = {},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{baldwin2019nanoformulationc,

title = {NANOFORMULATION OF TALAZOPARIB SUPPRESSES TUMOR GROWTH AND ASCITES IN A DISSEMINATED CANCER MODEL},

author = {Paige Baldwin and Anders Ohman and Jamie Medina and Daniela Dinulescu and Srinivas Sridhar},

year  = {2019},

date = {2019-01-01},

booktitle = {CLINICAL CANCER RESEARCH},

volume = {25},

number = {22},

pages = {198--198},

organization = {AMER ASSOC CANCER RESEARCH 615 CHESTNUT ST, 17TH FLOOR, PHILADELPHIA, PA~…},

abstract = {Talazoparib, a potent PARP inhibitor (PARPi), induces synthetic lethality in BRCA-deficient cancers making it an attractive candidate for ovarian cancer treatment. However, its potency lends itself to side effects associated more closely with traditional chemotherapeutics than other clinically approved PARPi's. We sought to formulate Talazoparib in a nanoparticle delivery system such that the drug could be administered intraperitoneally, localizing the entire dose at the disease site, to increase therapeutic efficacy and minimize toxicity. NanoTalazoparib was formulated and characterized and found to have a mean diameter of 70 nm and a neutral surface charge. Talazoparib and NanoTalazoparib were tested on a panel of murine tubal and human HGSOC cell lines and dose response compared to the first clinically approved PARPi, Olaparib. Dose response data indicated all cell lines were more sensitive to Talazoparib and NanoTalazoparib than Olaparib and all lines showed the same sensitivity to nanoformulations as free drugs. The human cell lines had various BRCA mutations and deletions, as well as a homologous recombination proficient (HRP) line, however, the HRP line was more sensitive to treatment than some HRD lines. Therapeutic efficacy was tested in vivo in a murine cancer model that mimics disseminated peritoneal disease. NanoTalazoparib 3X weekly for 8 weeks did not shrink tumors but resulted in tumor growth inhibition of 64% while an equivalent dose of oral Talazoparib only resulted in 34% growth inhibition. NanoTalazoparib suppressed the average volume of ascites at the study endpoint by 3.45 times more than oral Talazoparib. H&E staining of the tissues indicated no significant toxicity to the organs of the mononuclear phagocyte system. These results indicate that NanoTalazoparib can be used to localize PARPi therapy to the peritoneal cavity for disseminated late stage ovarian cancer treatment. Our data suggests that NanoTalazoparib could be utilized to delay the formation of tumor ascites for women with HR-deficient disease. While NanoTalazoparib did not effectively treat the disseminated disease at this dose, it may have clinical utility, either in combination with other therapies or as a maintenance therapy. Preclinical data indicates PARP inhibitors potentiate damage when combined with other cytotoxic treatments, however, in the clinic this has resulted in enhanced toxicity, forcing dose reduction and delay. The IP administration of NanoTalazoparib may provide a route to bypass some of the toxicities that have plagued combination treatments.



Supported in part by Rivkin Foundation and CDMRP Ovarian Cancer Research Program



Citation Format: Paige Baldwin, Anders Ohman, Jamie Medina, Daniela Dinulescu, Srinivas Sridhar. NANOFORMULATION OF TALAZOPARIB SUPPRESSES TUMOR GROWTH AND ASCITES IN A DISSEMINATED CANCER MODEL [abstract]. In: Proceedings of the 12th Biennial Ovarian Cancer Research Symposium; Sep 13-15, 2018; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2019;25(22 Suppl):Abstract nr NT-087.



©2019 American Association for Cancer Research.},

keywords = {},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{kunjachan2018best,

title = {BEST IN PHYSICS (THERAPY): Enhanced Drug Delivery by Nanoparticle and Radiation-Mediated Tumor Vascular Modulation},

author = {S Kunjachan and S Kotb and R Kumar and R Pola and M Pechar and F Gremse and R Taleei and F Trichard and V Motto-Ros and L Sancey and others},

year  = {2018},

date = {2018-01-01},

booktitle = {MEDICAL PHYSICS},

volume = {45},

number = {6},

pages = {E535--E535},

organization = {WILEY 111 RIVER ST, HOBOKEN 07030-5774, NJ USA},

keywords = {},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{belz2017sustainedb,

title = {Sustained release of PARP inhibitor Talazoparib and chemotherapeutic Docetaxel from modified brachytherapy spacers for treatment of breast and prostate cancer},

author = {Jodi Belz and Noelle Castilla Ojo and Paige Baldwin and Rajiv Kumar and Anne van de Ven and Karen Liby and Robert Cormack and Mike Makrigiorgos and Srinivas Sridhar},

year  = {2017},

date = {2017-01-01},

booktitle = {CANCER RESEARCH},

volume = {77},

organization = {AMER ASSOC CANCER RESEARCH 615 CHESTNUT ST, 17TH FLOOR, PHILADELPHIA, PA~…},

abstract = {Sustained localized delivery of cancer therapeutics is a safe and effective unique option for local control of tumors. Here we report a novel biodegradable implant with the capability to encapsulate different therapeutics, molecular agents, or nanoparticles for local intratumoral delivery. We have successfully demonstrated in vivo the delivery of PARP inhibitor Talazoparib to treat Brca1-mutated cancers and Docetaxel to treat localized or recurring prostate cancers. This one-time intratumoral injection provides a safe vehicle for the sustained release of PARP inhibitor Talazoparib and chemotherapeutic Docetaxel in contrast to low bioavailability and toxicity associated with oral or systemic delivery.



Methods: Biodegradable implants of 1-2mm length and 0.8mm diameter were loaded with ~50μg Talazoparib for BRCA1-mutated breast cancer studies and ~500μg Docetaxel (DTX) for prostate cancer studies. The implants were characterized in vitro using SEM and HPLC, and the release kinetic studies were carried out in PBS buffer (pH 6.0) at 37°C. The IC50's were determined using an MTS assay in breast cancer cell lines derived from Brca1 Co/Co; MMTV-Cre; p53+/−mice, W0069 and W780, and human-derived prostate cancer, PC3. In vivo studies were carried out in Brca1 Co/Co; MMTV-Cre; p53+/− spontaneous tumored mice for breast cancer studies. Subcutaneous PC3 tumors were xenografted in nude mice. Prostate cancer studies were done with and without radiation. Drug-loaded implants were injected once intratumorally using an 18G brachytherapy needle.



Results: The release profile of the drug from the implant in buffer showed a highly sustained release for multiple weeks at therapeutically relevant doses for both docetaxel and Talazoparib loading implants. Breast cancer cell lines W0069 and W780 were highly sensitive to Talazoparib, most likely due to Brca1 mutation. Following a one-time intratumoral implantation of Talazoparib, tumors reduced in size by an average of 50%, while untreated tumors increased ~5X in size. Talazoparib dosing appeared to be well tolerated by the mice. Docetaxel implants proved to be an effective method for prostate cancer in vivo with no significant weight loss observed. The local docetaxel spacer group showed sustained tumor inhibition compared to empty implants and an equivalent DTX dose given systemically. At 40 days 89% survival was observed for mice treated with localized DTX implants compared with 0% in all other treatment groups. Histology samples were taken from sacrificed mice and immunohistochemistry are currently underway.



Conclusions: Sustained local release of therapeutically relevant doses of Talazoparib and Docetaxel were observed in vitro and in vivo. Therapeutics-loaded implants represent a novel delivery route that are well-tolerated. Sustained release of Talazoparib appears to amplify the therapeutic efficacy of PARP inhibition in BRCA1 mutated breast cancers and sustained release of Docetaxel is an effective chemotherapy option alone or in combination with radiation therapy. These results laid a strong foundation for the use of localized biodegradable implants for the treatment of breast and prostate cancer.



This work was supported by the Army- W81XWH-14-1-0092, Breast Cancer Research Foundation and Northeastern University–Dana Farber Cancer Institute collaborative grant.



Citation Format: Jodi Belz, Noelle Castilla Ojo, Paige Baldwin, Rajiv Kumar, Anne van de Ven, Karen Liby, Robert Cormack, Mike Makrigiorgos, Srinivas Sridhar4. Sustained release of PARP inhibitor Talazoparib and chemotherapeutic Docetaxel from modified brachytherapy spacers for treatment of breast and prostate cancer. [abstract]. In: Proceedings of the AACR Special Conference on Engineering and Physical Sciences in Oncology; 2016 Jun 25-28; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2017;77(2 Suppl):Abstract nr B30.},

keywords = {},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{adedoyin2015injectable,

title = {Injectable bionanocomposite hybrid scaffolds with responsive control for enhanced osteochondral tissue regeneration},

author = {AA Adedoyin and R Kumar and S Sridhar and AK Ekenseair},

year  = {2015},

date = {2015-01-01},

booktitle = {2015 41st Annual Northeast Biomedical Engineering Conference (NEBEC)},

pages = {1--2},

organization = {IEEE},

abstract = {Restoration of articular hyaline cartilage within osteochondral tissue defects has been a principal target in the field of tissue engineering due to poor functional regeneration of this avascular and heterogeneous tissue following current treatment options. The major focus thus far has been in constructing implantable scaffolds, which can be readily designed to offer appropriate mechanical properties. However, the use of implantable scaffolds requires open surgery and often cannot be readily applied to defects of irregular shape. Thus, it has become of high interest to develop minimally invasive and degradable hydrogel-based materials capable of delivering and maintaining encapsulated cells in a non-toxic manner and encouraging functional tissue regeneration. This paper reports on the synthesis and characterization of a novel class of injectable, thermally and chemically dual-gelling bionanocomposite hydrogels from thermogelling macromers (TGMs) based on poly(N-isopropylacrylamide) (pNiPAAm), degradable polyamidoamine (PAMAMs) crosslinking macromers, and functional hybrid inorganic iron oxide (Fe 3 O 4 ) nanoparticles capable of responding to an external magnetic field to stimulate cell activity and control the regenerative process in situ in a spatiotemporal manner.},

keywords = {},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{adedoyin2015synthesis,

title = {Synthesis and Characterization of Injectable Bionanocomposite Hybrid Scaffolds with Responsive Control for Osteochondral Tissue Regeneration},

author = {AA Adedoyin and R Kumar and S Sridhar and AK Ekenseair},

year  = {2015},

date = {2015-01-01},

booktitle = {TISSUE ENGINEERING PART A},

volume = {21},

pages = {S307--S307},

organization = {MARY ANN LIEBERT, INC 140 HUGUENOT STREET, 3RD FL, NEW ROCHELLE, NY 10801 USA},

keywords = {},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{cheng2015glycocalyx,

title = {Glycocalyx Integrity Influences Nanoparticle Uptake by Endothelial Cells},

author = {MJ Cheng and R Kumar and S Sridhar and TJ Webster and EE Ebong},

year  = {2015},

date = {2015-01-01},

booktitle = {TISSUE ENGINEERING PART A},

volume = {21},

pages = {S401--S401},

organization = {MARY ANN LIEBERT, INC 140 HUGUENOT STREET, 3RD FL, NEW ROCHELLE, NY 10801 USA},

keywords = {},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{teh2015targeting,

title = {Targeting integrin alpha v beta 3 receptors with multivalent RGD peptidomimetics},

author = {James Teh and Robert Hanson and Srinivas Sridhar},

year  = {2015},

date = {2015-01-01},

booktitle = {ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY},

volume = {249},

organization = {AMER CHEMICAL SOC 1155 16TH ST, NW, WASHINGTON, DC 20036 USA},

keywords = {},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{belz2014localized,

title = {Localized tumor delivery of radiosensitizers and chemotherapeutics using ‘INCeRT’implants},

author = {Jodi Belz and Rajiv Kumar and Stacey Markovic and Mark Niedre and Srinivas Sridhar and Paul Nguyen and Anthony Damico and Mike Makrigiorgos and Robert Cormack},

year  = {2014},

date = {2014-01-01},

booktitle = {2014 40th Annual Northeast Bioengineering Conference (NEBEC)},

pages = {1--2},

organization = {IEEE},

abstract = {Systemic chemotherapy is often used with radiation therapy in the management of prostate cancer, but leads to severe systemic toxicities. We have introduced a new modality of loco-regional chemoradiation therapy termed in-situ image guided radiation therapy (BIS-IGRT) that offers the potential to deliver planned, localized and sustained delivery of chemotherapy agent, without systemic toxicities, as part of routine minimally invasive image guided radiation therapy procedures. Such image guided chemoradiation therapy replaces inert spacers with no therapeutic impact currently used in brachytherapy, with drug eluting spacers that provide the same spatial benefit with the added localized chemotherapeutic. This new therapeutic modality requires characterization of the drug distribution produced by implantable drug eluters. This work presents imaging based means to measure and compare temporal and spatial properties of diffusion distributions around spacers loaded with multi-sized dye-doped nanoparticles or with free dye. The spacer with optimal diffusive properties was then loaded with chemotherapeutics and inserted intratumorally for efficacy of the local chemotherapy versus the standard systemic dosing.},

keywords = {},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{gharagouzloo2014ute,

title = {UTE angiography with ferumoxytol},

author = {Codi Gharagouzloo and Patrick N McMahon and Srinivas Sridhar},

year  = {2014},

date = {2014-01-01},

booktitle = {2014 40th Annual Northeast Bioengineering Conference (NEBEC)},

pages = {1--2},

organization = {IEEE},

abstract = {Magnetic Resonance Imaging (MRI) is arguably the most clinically pertinent, non-destructive imaging modality for probing deep tissue in the human body. Clinical contrast-enhanced MRI with superparamagnetic iron oxide nanoparticles (SPIONs) is typically performed with T2-weighted imaging. Here we show that ultra-short TE (UTE) imaging with SPIONs produces unambiguous, positive-contrast signals in vivo in mice. Experiments were performed using a SPION containing pharmaceutical, ferumoxytol, in phantoms and in systemic circulation of mice at 7T. 3D UTE angiography was not hampered by susceptibility artifacts or influenced by flow. By negating these effects we were able to produce high SNR and CNR images of the entire vascular system, including the lungs and the heart.},

keywords = {},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{khabiry2014automated,

title = {Automated cell counting method for microgroove based microfluidic device},

author = {Masoud Khabiry and Nader Jalili and Srinivas Sridhar},

year  = {2014},

date = {2014-01-01},

booktitle = {2014 40th Annual Northeast Bioengineering Conference (NEBEC)},

pages = {1--2},

organization = {IEEE},

abstract = {Microfluidic grooves and channels enable the control of cell positioning and capturing of cells in cell-based biosensor applications. Microfluidic devices also provide a platform for cell-based biological assays. Microfluidic channels have been used to capture cells for various cell-based diagnostics and screening applications. The number of cells and cell locations are important factors which will affect the flow pattern in the microfluidic device and consequently induced shear stresses. Moreover, manual cell counting and cell information extraction is a time consuming and tedious task. Automated techniques reduce human errors and expedite the process. Furthermore, it facilitates extraction of information from obtained images for further fluidic analysis.},

keywords = {},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{van2014polymersomes,

title = {Polymersomes for image-guided therapy},

author = {Anne L van de Ven and Benjamin Geilich and Codi Gharagouzloo and Jacob Barlow and Thomas Webster and Srinivas Sridhar},

year  = {2014},

date = {2014-01-01},

booktitle = {2014 40th Annual Northeast Bioengineering Conference (NEBEC)},

pages = {1--2},

organization = {IEEE},

abstract = {Polymersomes are a promising avenue for image-guided therapy of cancer, since they can stably encapsulate a broad range of therapeutic molecules and offer both targeting capacity and stimuli responsiveness. We have formulated highly stable, magnetically activatable polymersomes capable of continuous and pulsed small molecule release. In the proof-of-concept provided here, we demonstrate that these particles are responsive to both external and heat and magnetic fields. At physiologic temperatures, these particles display a sustained release profile that can be reversibly triggered for transient increases in release. The incorporation of fluorescent and iron oxide contrast sources make these particles amenable for quantitative imaging techniques including intravital microscopy (IVM) and ultra-short time-to-echo (UTE) magnetic resonance imaging (MRI). Thus we believe this formulation is uniquely suited for the in vivo study and optimization of externally triggered tumor growth inhibition.},

keywords = {},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{gharagouzloo2013ultrashort,

title = {Ultrashort TE imaging with SPIONs: bright prospects for in vivo applications},

author = {CA Gharagouzloo and S Madi and RT Seethamraju and M Harisinghani and S Sridhar},

year  = {2013},

date = {2013-01-01},

booktitle = {JOURNAL OF NUCLEAR MEDICINE},

volume = {54},

pages = {9--9},

organization = {SOC NUCLEAR MEDICINE INC 1850 SAMUEL MORSE DR, RESTON, VA 20190-5316 USA},

keywords = {},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{teh2013synthesis,

title = {Synthesis and characterization of Arg-Gly-Asp (RGD) peptidomimetics functionalized onto gold nanoparticles},

author = {James L Teh and Robert N Hanson and Srinivas Sridhar},

year  = {2013},

date = {2013-01-01},

booktitle = {ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY},

volume = {245},

organization = {AMER CHEMICAL SOC 1155 16TH ST, NW, WASHINGTON, DC 20036 USA},

keywords = {},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{lu2011slow,

title = {Slow light using negative metamaterials},

author = {WT Lu and YJ Huang and S Sridhar},

year  = {2011},

date = {2011-01-01},

booktitle = {Active Photonic Materials IV},

volume = {8095},

pages = {80951D},

organization = {International Society for Optics and Photonics},

abstract = {A general overview of slow light waveguide structures made of negative metamaterials is presented. We discuss the conditions and the parameter space to achieve zero total energy flow and zero group velocity due to the degeneracy of forward and backward waves in waveguides cladded with single negative metamaterials. Absorptive loss plays a severely limiting role and can prevent achieving the zero group velocity condition. Gain can be introduced either in dielectric or negative metamaterials to restore the zero group velocity condition. This type of slow light waveguide has a large delay bandwidth product and is suitable for use in integrated optoelectronic circuits.

© (2011) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.},

keywords = {},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{alvarado2011effects,

title = {Effects of fibronectin and vitronectin on human fetal osteoblast cell attachment and proliferation on nanostructured titania surfaces},

author = {Melissa Alvarado-Velez and Delva M Rivera-Chacon and Claudia Y Acevedo-Morantes and Latika Menon and Dattatri Nagesha and Evin Gultepe and Srinivas Sridhar and Jaime E Ramirez-Vick and Surinder P Singh},

year  = {2011},

date = {2011-01-01},

booktitle = {ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY},

volume = {241},

organization = {AMER CHEMICAL SOC 1155 16TH ST, NW, WASHINGTON, DC 20036 USA},

keywords = {},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{casse2010beating,

title = {Beating the diffraction limit using a 3D nanowires metamaterials nanolens},

author = {BDF Casse and WT Lu and YJ Huang and E Gultepe and L Menon and S Sridhar},

year  = {2010},

date = {2010-01-01},

booktitle = {Frontiers in Optics},

pages = {FWO3},

organization = {Optical Society of America},

abstract = {Super-resolution imaging using a three-dimensional metamaterials nanolens has been recently reported [B. D. F. Casse et al. Appl. Phys. Lett. 96, 023114 (2010)]. Here, we present validation of the superresolution imaging by the nanolens through extensive control experiments.},

keywords = {},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{didier2010superresolution,

title = {Superresolution Imaging Using a 3D Nanolens Made Up of Bulk Nanowires Metamaterials},

author = {Bernard Didier Frederic Casse and Wentao Lu and Yongjian Huang and Evin Gultepe and Latika Menon and Srinivas Sridhar},

year  = {2010},

date = {2010-01-01},

booktitle = {APS Meeting Abstracts},

abstract = {We report superresolution imaging of large objects, having sub-λ features, over significant distances (>>λ, wavelength) with a resolution well below the diffraction limit in optics, using a metallic nanolens. The metallic nanolens is composed of high aspect ratio gold nanowires embedded in disordered porous alumina template matrix. This composite medium possesses strongly anisotropic optical properties with negative permittivity in the nanowire axis direction, which enables negative refraction, and transports both far-field and near-field components with minimal distortions and with very lowattenuations. The long-distance image transport mechanism is not based on resonances of materials parameters and thus the subwavelength imaging occurs with low loss (Figure-of-merit (FOM) =Re(n)/Im(n)̃12 (much higher than existing metamaterials)) and in a broad spectral range. This nanolens not only exhibits superior optical properties over existing metamaterials-based lenses, but can also be manufactured in large scale (mm size), thereby offering significant potential for applications in optical storage devices, nanolithography and biomedical imaging.},

keywords = {},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{casse2009metallic,

title = {Metallic Nanolens and III-V Nano-Optical Metamaterials Lenses for Subwavelength Imaging and Optoelectronics Applications},

author = {Bernard Didier Casse and Wentao T Lu and Yongjian Huang and Srinivas Sridhar},

year  = {2009},

date = {2009-01-01},

booktitle = {Optics and Photonics for Advanced Energy Technology},

pages = {ThC4},

organization = {Optical Society of America},

abstract = {We report the experimental realization of a metallic nanolens for far-field subwavelength imaging and 3 innovative III-V nano-optical lenses based on negative-index phenomena for optoelectronics applications. This work was supported by AFRL and NSF.},

keywords = {},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{patel2009metallic,

title = {Metallic nanoparticles for biomedical imaging},

author = {Yogesh Patel and Sucharita Saha and Charles DiMarzio and D O'Malley and Dattatri Nagesha and Srinivas Sridhar},

year  = {2009},

date = {2009-01-01},

booktitle = {2009 IEEE International Symposium on Biomedical Imaging: From Nano to Macro},

pages = {759--762},

organization = {IEEE},

abstract = {The plasmon resonance conditions in nano-sized materials leads to local field enhancement resulting in amplified response of various linear and nonlinear optical processes at the nano-scale. In this paper, metallic nanoparticles are imaged using several modalities – brightfield, confocal reflectance, two-photon, and second harmonic generation. Two examples are discussed . Au nanoparticles in the zebrafish spinal column, and Ag nanoparticles in fresh skin excisions. We show that the optical properties of noble-metal nanoparticles offer an attractive alternative to the fluorophore-based staining and labeling of biological samples, and have potential use in a wide range of biological and physical applications.



},

keywords = {},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{banyal2008experimental,

title = {Experimental realization of a generalized superlens using negative refraction at infrared wavelengths},

author = {Ravinder Banyal and BDF Casse and WT Lu and YJ Huang and S Selvarasah and M Dokmeci and CH Perry and S Sridhar},

year  = {2008},

date = {2008-01-01},

booktitle = {APS Meeting Abstracts},

abstract = {We demonstrate experimentally using a near-field scanning optical microscope the imaging of a point source by a generalized superlens fabricated in InGaAsP/InP heterostructure at wavelengths around lambda= 1.5 mum. The theory of superlens imaging with lens equation u+ v= sigmad gives excellent explanation of wave refraction and imaging formation of our superlens with an effective lens property ε eff= 0.43. This can be used as the basis for design optical elements made of photonic crystals.},

keywords = {},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{lu2008effective,

title = {Effective medium theory of photonic crystals},

author = {WT Lu and S Zhang and YJ Huang and S Sridhar},

year  = {2008},

date = {2008-01-01},

booktitle = {APS Meeting Abstracts},

abstract = {We develop an effective medium theory for photonic crystals including negative index metamaterials. This theory is based on field summation within the unit cell. The unit cell is determined by the surface termination. The orientation of the surface breaks the field summation symmetry. This theory is self-consistent. The effective permittivity and permeability tensors will give the exact dispersion relation obtained from the band structure calculation. For waves incident into multilayered structures, our theory gives exact transmittance and reflectance for any wavelengths. For interface with periodic surface structures, our theory gives very accurate results for wavelength down to being comparable with the lattice spacing. By properly taking into account the multiple Bloch modes inside the photonic crystal, our theory can be made to give exact Bragg coefficients.},

keywords = {},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{menon2008negativeb,

title = {Negative Index Metamaterials for Superlenses Based on Metal-Dielectric Nanocomposites},

author = {Latika Menon and Wentao Lu and Adam Friedman and Steven Bennett and Donald Heiman and Srinivas Sridhar},

year  = {2008},

date = {2008-01-01},

booktitle = {APS Meeting Abstracts},

abstract = {Negative index metamaterials are demonstrated based on metal-dielectric nanocomposites. The nanocomposites are prepared using a versatile bottom-up nanofabrication approach involving the incorporation of vertically aligned metal nanowires such as Au and Ag inside dielectric aluminum oxide nanotemplates. Aluminum oxide nanotemplates with specific pore dimensions are fabricated by means of electrochemical anodization. Following this, Au/Ag nanowires with specific wire dimensions are electrodeposited inside the pores. Optical absorbance measurements show resonance peaks corresponding to transverse and longitudinal surface plasmon modes. Peak position and intensity are found to be strongly dependent on nanocomposite dimensions, filling factor (ratio of the volume of metal versus the volume of dielectric) and angle of incidence with respect to the wire axis. A quantitative model based on effective medium theory is in excellent agreement with experimental data, and points to specific composite configurations and wavelength regimes where such structures can have applications as negative refraction media for superlens imaging.},

keywords = {},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{lu2008anisotropic,

title = {Anisotropic nanostructured metamaterials for broadband all-angle negative refractionand flat lens imaging},

author = {Wentao Lu and Srinivas Sridhar},

year  = {2008},

date = {2008-01-01},

booktitle = {APS Meeting Abstracts},

abstract = {We show that a metamaterial consisting of aligned metallic nanowires in a dielectric matrix has strongly anisotropic optical properties. For filling ratio f< 1/2, the composite medium shows two surface plasmon resonances (SPRs): the transverse and longitudinal SPR with wavelengths lambda t< lambda l. For lambda t> lambda l, the longitudinal SPR, the material exhibits Re ε//< 0, Re ε> 0, relative to the nanowires axis, enabling the achievement of broadband all-angle negative refraction and flat lens (superlens) imaging systems. High performance systems made with Au, Ag or Al nanowires in nanoporous templates are designed and predicted to work from the infrared up to ultraviolet frequencies.},

keywords = {},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{gultepe2008nano,

title = {Nano-assembly and Controlled Release Kinetics of Nanoelements from Nanoporous Templates},

author = {E Gultepe and D Nagesha and J McNulty and S Sridhar},

year  = {2008},

date = {2008-01-01},

booktitle = {APS Meeting Abstracts},

abstract = {Nanotemplates and nanoparticles have potential for use in the area of nanomanufacturing and biomedical applications. We are using highly ordered nanoporous alumina as a template for drug delivery and to assemble nanoelements such as latex beads and single wall carbon nanotubes (SWNT) by the means of electrophoresis and/or dielectrophoresis. The results of 100% assembly of latex beads and controlled elution of drugs from nanoporous templates will be discussed. Vertically assembled SWNT and with the IV characteristic as 3D interconnects, will also be presented. We have developed a variety of platforms incorporating superparamagnetic iron oxide nanoparticles for targeted delivery, magnetic hyperthermia and as a contrast agent for magnetic resonance imaging. The results of cell studies on these platforms will be discussed.},

keywords = {},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{selvarasah2007high,

title = {A high aspect ratio, flexible, transparent and low-cost parylene-C shadow mask technology for micropatterning applications},

author = {S Selvarasah and SH Chao and C-L Chen and D Mao and J Hopwood and S Ryley and S Sridhar and A Khademhosseini and A Busnaina and MR Dokmeci},

year  = {2007},

date = {2007-01-01},

booktitle = {TRANSDUCERS 2007-2007 International Solid-State Sensors, Actuators and Microsystems Conference},

pages = {533--536},

organization = {IEEE},

abstract = {In this paper, we present a flexible parylene-C shadow mask technology for creating microscale patterns on flat and curved surfaces. The smallest feature size of 4 μm is demonstrated and the technology is scalable up to full wafer size. With the addition of SU-8 pillars, we also demonstrate multi mask processing with an alignment accuracy of about 5-6 μm. To achieve the smallest features, a low temperature and high aspect ratio (>8:1) parylene etch process is also developed. Utilizing this shadow mask, we successfully patterned proteins and cells on various surfaces (glass, PDMS, methacrylate) up to 9 times. This technology has potential applications for patterning proteins, cells and organic transistors on conventional and/or unconventional substrates.},

keywords = {},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{selvarasah2007three,

title = {A three dimensional multi-walled carbon nanotube based thermal sensor on a flexible parylene substrate},

author = {Selvapraba Selvarasah and Prashanth Makaram and Chia-Ling Chen and Xugang Xiong and Shih-Hsien Chao and Ahmed Busnaina and Srinivas Sridhar and Mehmet R Dokmeci},

year  = {2007},

date = {2007-01-01},

booktitle = {2007 7th IEEE Conference on Nanotechnology (IEEE NANO)},

pages = {1062--1066},

organization = {IEEE},

abstract = {In this paper, we present a flexible parylene-C shadow mask technology for creating microscale patterns on flat and curved surfaces. The smallest feature size of 4 μm is demonstrated and the technology is scalable up to full wafer size. With the addition of SU-8 pillars, we also demonstrate multi mask processing with an alignment accuracy of about 5-6 μm. To achieve the smallest features, a low temperature and high aspect ratio (>8:1) parylene etch process is also developed. Utilizing this shadow mask, we successfully patterned proteins and cells on various surfaces (glass, PDMS, methacrylate) up to 9 times. This technology has potential applications for patterning proteins, cells and organic transistors on conventional and/or unconventional substrates.},

keywords = {},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{lu2006determination,

title = {Determination of Refractive Indices of Photonic Crystals: Theory and Experiments},

author = {Wentao Lu and Srinivas Sridhar},

year  = {2006},

date = {2006-01-01},

booktitle = {APS Meeting Abstracts},

abstract = {We develop a method to calculate the refractive indices of photonic crystal based on plane wave expansion. The appearance of surface waves and subwavelength imaging is explained within this frame. Numerical simulations of 1D and 2D crystals are performed to support our theory. Comparisons are presented with experimental results on microwave photonic crystals.},

keywords = {},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{nagesha2006surface,

title = {Surface-Engineered Nanomaterials for Nanomedicine},

author = {Dattatri Nagesha and Mansoor M Amiji and Srinivas Sridhar},

year  = {2006},

date = {2006-01-01},

booktitle = {ASME 2006 International Manufacturing Science and Engineering Conference},

pages = {363--372},

organization = {American Society of Mechanical Engineers Digital Collection},

abstract = {An important feature of nanoparticles is the increased ratio of surface area to volume resulting in large percentage of the atoms on the surface, making them very reactive and offers opportunities to manipulate the properties through these surface atoms. For the most efficient use of nanoparticles in various applications, including biology and medicine, it is important to be able to manipulate the surface chemistry. This paper describes the synthesis and characterization of nanoparticles and the various surface engineering techniques that are utilized for optimizing their applications in nanomedicine.},

keywords = {},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{vodo2006negativeb,

title = {Negative Refraction in One-Dimensional Photonic Crystal},

author = {Plarenta Vodo and Wentao Lu and Patanjali Parimi and Srinivas Sridhar},

year  = {2006},

date = {2006-01-01},

booktitle = {APS Meeting Abstracts},

abstract = {We demonstrate experimentally negative refraction of plane waves by a one-dimensional Photonic crystal (PhC) prism at microwave frequencies. The prism was fabricated from a microwave alumina PhC acting as a left-handed metamaterial. Focusing of plane waves from a one-dimensional PhC plano-concave lens is predicted theoretically and realized experimentally. The focal point is observed to move with the radius of curvature of the lens. The measured values of refractive index are in complete agreement with those determined from band structure calculations.},

keywords = {},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{wu2006nanofabrication,

title = {Nanofabrication Based on Nanoporous Membranes},

author = {Zhen Wu and L Tian and C Richter and D Nagesha and S Sridhar and L Menon},

year  = {2006},

date = {2006-01-01},

booktitle = {APS Meeting Abstracts},

abstract = {We describe nanofabrication methods to produce nanopore array templates in aluminum oxide and titanium dixode films. The method is based on anodization of thin films of aluminum and titanium under dc conditions in an acid. We also describe non-lithographic means of transferring the pore pattern from such nanoporous membranes onto a generic substrate. This is based on reactive ion etching through the nanoporous template grown directly on the substrate. In our demonstration, a thin alumina template consisting of a hexagonal array of pores ̃50nm in diameter is first deposited on the substrate. The pores reach within 10-20 nm of aluminum, which is protected by an alumina barrier layer. By controlling reactive ion etching conditions, we demonstrate highly anisotropic etching through the aluminum layer, barrier alumina layer and into the substrate. The 50nm pore layer is thus directly transferred to create nanoporous and nanopillar arrays of a variety of materials such as Al, Si, GaN, GaAs, etc. Such nanoporous, nanopillar arrays will be useful in a variety of applications involving biosensors, optoelectronic and spintronic devices.},

keywords = {},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{fu2005hetero,

title = {Hetero-bifunctional poly (ethylene glycol) modified gold nanoparticles as an intracellular tracking and delivery agent},

author = {W Fu and D Shenoy and J Li and C Crasto and G Jones and C Dimarzio and S Sridhar and M Amiji},

year  = {2005},

date = {2005-01-01},

booktitle = {NSTI Nanotech},

volume = {1},

pages = {324--327},

abstract = {To increase the flexibility of surface-attached bio-relevant ligands on gold nanoparticle (NP), hetero-bifunctional poly (ethylene glycol)(PEG), was synthesized having two different functional groups on both the terminals. Coumarin was conjugated to the gold NP through the PEG spacer. The results of cellular cytotoxicity and fluorescence microscopy showed that these NPs were non-toxic and could be internalized in the cells within one hour of incubation.},

keywords = {},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{saini2005superparamagnetic,

title = {Superparamagnetic iron oxide-gold core-shell nanoparticles for biomedical applications},

author = {G Saini and D Shenoy and DK Nagesha and R Kautz and S Sridhar and M Amiji},

year  = {2005},

date = {2005-01-01},

booktitle = {2005 NSTI Nanotechnology Conference and Trade Show-NSTI Nanotech},

pages = {328--331},

abstract = {Iron oxide nanoparticles are used for contrast enhancement in magnetic resonance imaging (MRI). We have prepared gold-coated iron oxide nanoparticles that show no change in their superparamagnetic behavior as a consequence of coating. Their potential use as MRI contrast agents was investigated by monitoring their T2 relaxation time with concentration. Cytotoxicity of these nanoparticles was also studied. The results of these studies are presented.},

keywords = {},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{sridhar2005imaging,

title = {Imaging and negative refraction in left-handed metamaterials},

author = {S Sridhar and PV Parimi and WT Lu and P Vodo and John S Derov},

year  = {2005},

date = {2005-01-01},

booktitle = {Metamaterials},

volume = {5955},

pages = {595505},

organization = {International Society for Optics and Photonics},

abstract = {Negative refraction and left-handed electromagnetism in a photonic crystal are demonstrated in waveguide and free space experiments at microwave frequencies. Precision control to achieve tailor-made refractive indices has been achieved. The negative refraction in these photonic crystals is shown to lead to imaging by a flat lens. We have also developed a generalized theory of flat lens imaging. These results promise potential applications in a variety of optical and microwave systems for communications and imaging.},

keywords = {},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{parimi2004image,

title = {Image formation by and wave propagation in a photonic crystal},

author = {Patanjali Parimi and Plarenta Vodo and Lu Wentao and Emiliano di Gennaro and Srinivas Sridhar},

year  = {2004},

date = {2004-01-01},

booktitle = {APS Meeting Abstracts},

abstract = {Negative refraction and imaging by a flat slab of a material are two of the important consequences of lefthanded electromagnetism. In our recent work we have demonstrated negative refraction and imaging by photonic crystals in the microwave frequency range [1]. The details of image formation are intriguing and urge its investigation. We have carried out microwave measurements in a parallel plate waveguide made of a pair of metallic plates. The Photonic crystal is made of alumina rods arranged on a square lattice such that the electric field is parallel to the axis of the rods. The detector is a dipole antenna which is inserted into the waveguide from outside. HP 8510C network analyzer is used to measure the complex transmission coefficient. The intensity maps of vs. probe position are obtained by scanning the probe using an xy robot, both inside and outside the crystal. The results suggest Bloch wave propagation …},

keywords = {},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{di2004microwave,

title = {Microwave pulse propagation measurements in left-handed materials},

author = {Emiliano Di Gennaro and Patanjali V Parimi and Plarenta Vodo and Wentao Lu and Srinivas Sridhar},

year  = {2004},

date = {2004-01-01},

booktitle = {APS Meeting Abstracts},

abstract = {Left handed electromagnetism is well established in media with negative permeability and permittivity and in photonic crystals [1]. In such media the negative refractive index is accompanied by large dispersion dn/dω, and consequently a very low group velocity is predicted for left-handed metamaterial (LHM). It is well known that an artificial material consisting of interleaved arrays of wires and split ring resonators in a certain microwave frequency range shows left handed behavior. We have carried out pulse measurements on LHM using a transition analyzer in order to measure the group velocity. Time delay measurements are performed in an X-band and parallel plate waveguide. Sending a 100ns width pulse with a carrier frequency ranging between 9 and 11 GHz, we analyze the signal delay due to the sample. The results suggest that the group velocity in the LHM is very low. Pulse delay measurements in photonic crystals are also discussed. Work supported by NSF & AFRL [1]. P. V. Parimi et al., submitted (2003).},

keywords = {},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{sridhar2004imaging,

title = {Imaging by Flat Lens Using Negative Refraction in Microwave Photonic Crystals},

author = {Srinivas Sridhar},

year  = {2004},

date = {2004-01-01},

booktitle = {APS March Meeting Abstracts},

abstract = {Metamaterials with negative indices of refraction exhibit novel aspects of electromagnetic wave propagation. Here we report the observation of negative refraction (NR) at microwave frequencies in metallic and dielectric photonic crystal (PC) prisms. The NR observed in the PC corresponds to left-handed electromagnetism and arises due to the dispersion characteristics of waves in a periodic medium. This mechanism for NR is different from that in metamaterials where locally both the dielectric permittivity and magnetic permeability are negative. The PC prism exhibits both positive and negative refraction in different spectral windows, and experimental results are in complete agreement with band-structure calculations and numerical simulations. A remarkable consequence of NR noted by Veselago is that of focusing by a flat lens. We have demonstrated imaging of a microwave point source by a flat lens fabricated from a PC. We also demonstrate a unique feature of a flat lens, the absence of an optical axis, by moving the object and showing that the image displaces correspondingly. The PC flat lens has some interesting similarities and differences compared with the Veselago lens. Potential applications of negative refraction and flat lens imaging at microwave and optical frequencies, including sub-wavelength image resolution suggested by Pendry, will be described. Collaborators: P.Parimi, W.T.Lu, P.Vodo, J.S.Derov. Supported by National Science Foundation and the Air Force Research Laboratories, Hanscom. 1. "Imaging by flat lens using negative refraction", P.Parimi, W.T.Lu, P.Vodo and S.Sridhar, Nature, v.426, 404 (2003). 2. "Negative refraction and left-handed electromagnetism in metallic microwave photonic crystals", P. Parimi, W.T. Lu, P. Vodo, J. Sokoloff, J.S.Derov and S. Sridhar, cond-mat/0306109.},

keywords = {},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{pradhan2003statistics,

title = {Statistics of the Eigenfunctions of Chaotic and Disordered Quantum Systems: A Disordered Tight Binding Model Calculation},

author = {Prabhakar Pradhan and Wentao T Lu and S Sridhar},

year  = {2003},

date = {2003-01-01},

booktitle = {APS Meeting Abstracts},

abstract = {We analyze the statistical properties of the eigenfunctions of the Anderson disordered tight binding Hamiltonian, for an electron in closed 2-D, chaotic and disordered systems. For chaotic systems, the inverse participation ratio (IPR) that measures the amount of localization of an eigenstate, has a narrow and symmetric distribution peaked around IPR = 3, as predicted by random matrix theory. For disordered systems, the distribution is asymmetric and peaks at IPR > 3. As a function of energy, the IPR distribution decays as a power law with exponent 1/2 at low energies (i.e. more localized state), and saturates at IPR =3 (delocalized state) for larger energies. The spatial intensity auto-correlations of the eigenfunctions are strong for a more localized state at short distances, and they decay via a Friedel oscillation, as predicted by nonlinear sigma models, with a decay length scale corresponding to the localization length. For weak to moderate disorder in 2D, our numerical calculations are consistent with the random matrix theory, non-linear sigma models, and also with our previous experimental results for 2D quantum chaotic and disordered systems.},

keywords = {},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{lu2003perfect,

author = {WT Lu and JB Sokoloff and S Sridhar},

year  = {2003},

date = {2003-01-01},

booktitle = {APS Meeting Abstracts},

abstract = {We study analytically and numerically imaging by Â" perfect lensÂ" made of negative index medium (NIM)(or left-handed meta-material (LHM)). For far field, the perfect lens is only perfect for n=-1. Away from this value, aberration and caustics will be present. For near field imaging with Re ε=-1, the consequences of departure from dielectric matching and losses are discussed. Work supported by NSF-0098801 and AFRL, Hanscom.},

keywords = {},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{sato2003spectral,

title = {Spectral statistics of microwave disordered billiards},

author = {Daisuke Sato and Wentao Lu and Prabhakar Pradhan and Srinivas Sridhar},

year  = {2003},

date = {2003-01-01},

booktitle = {APS Meeting Abstracts},

abstract = {Using a new algorithm to analyze experimental microwave spectra, we are able to accurately obtain nearly 1000 eigenvalues for microwave disordered billiards with no missing energy level. The cumulative level density N (E) of all billiards is in good agreement with the Weyl formula. We also determine statistical measures such as P (s), Delta_3, R_2, Y_2, Sigma_2, and study their dependence on the mean free path and localization length. The experimental results are compared with the supersymmetry sigma model and tight binding calculations. Work supported by NSF-0098801.},

keywords = {},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{hakim2003microwave,

title = {Microwave and Radio Frequency Response of MgB_2.},

author = {Nazih Hakim and Christian Kusko and Srinivas Sridhar},

year  = {2003},

date = {2003-01-01},

booktitle = {APS Meeting Abstracts},

abstract = {Microwave (GHz) and radio frequency (MHz) measurements have been performed on polycrystalline palette, wire, thin film and single crystal samples of MgB_2. The surface impedance, Rs (T)+ iDelta Xs (T), is analyzed for these various samples. The microwave results thus far are consistent with that of a two-gap superconductor. In thin films, the microwave measured gap value of Delta (0)= 1.9 mev is in agreement with the smallest of the two gaps reported in literature for this diboride compound. The relationship of experimental data and current theories of superconductivity in terms of the gap parameter, penetration depth and vortex dynamics in this material will be discussed and presented. Work supported by the Office of Naval Research.},

keywords = {},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{sokoloff2003refraction,

title = {Refraction of Electromagnetic Energy for Wave Packets Incident on a Negative Index Medium: Always Negative},

author = {JB Sokoloff and WT Lu and S Sridhar},

year  = {2003},

date = {2003-01-01},

booktitle = {APS Meeting Abstracts},

abstract = {Since all physical radiation sources admit their radiation in the form of wave packets, we analyze refraction of electromagnetic wave packets on passing from an isotropic positive (PIM) to an isotropic negative index medium (NIM). We definitively show that in all cases the energy is always refracted negatively. For localized waves, the group refraction is always negative. We accomplish this by treating comprehensively group refraction at a PIM-NIM interface by analytical and numerical treatment of several exhaustive examples: localized wave packets, beams, and also a finite number of plane waves. We focus on physically important quantities such as the energy flow and momentum. In all of the cases we show that the energy and momentum refract negatively. We show that in all cases where the wave group does not extend to infinity in the perpendicular direction of the wave vector, the interference pattern also refracts negatively. Work supported by NSF-0098801 and AFRL, Hanscom.



},

keywords = {},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{parimi2003microwave,

title = {Microwave Propagation in Negative Index and Artificial Dielectric Media},

author = {Patanjali Parimi and Plarenta Vodo and Wentao Lu and Srinivas Sridhar},

year  = {2003},

date = {2003-01-01},

booktitle = {APS Meeting Abstracts},

abstract = {Negative index media (NIM) are fabricated by interleaving arrays of split ring resonators and wire strips. Microwave (X-band) waveguide measurements on the NIM yield quantitative information on the material parameters, % tilden(ω)=n^' +in^' ', tildevarepsilon% (ω )=varepsilon ^' +ivarepsilon ^' ' and tilde% μ(ω )=μ ^' +iμ ^' ' . Typical NIM features such as passband in the NIM region expected from the theoretical analysis are observed in the measured data. The n^'(ω) determined from the waveguide transmission parameters (tildeS_11,tildeS_21) is found to vary from -4.8 to-0.3 in the passband region 9.6-10.5GHz. The results show that transmission is optimized for n^' (ω ) -1 and low n^' ' . A detailed investigation of several NIM materials suggests that the characteristic properties of the NIM are dependent on the length of the material, choice of the substrate material, and continuity in the wire strips. Artificial dielectric media fabricated with arrays of wire strips exhibit a characteristic microwave plasmon mode in the X-band region, below which varepsilon ^' (ω )<0. Work supported by the National Science Foundation and the Air Force Research Labs, Hanscom.},

keywords = {},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{hakim2002microwave,

title = {Microwave and Radio Frequency, RF, Measurements on Superconducting MgB_2.},

author = {Nazih Hakim and Patanjali Parimi and Christian Kusko and Srinivas Sridhar},

year  = {2002},

date = {2002-01-01},

booktitle = {APS Meeting Abstracts},

abstract = {< p type=" texpara" tag=" Body Text"> Measurements of the 10GHz surface resistance, Rs, of dense wires, polycrystalline samples, and thin films of MgB 2 are presented. The microwave absorption results are discussed with measurements on low Tc (Nb) and high Tc (YBa_2Cu_3O_6. 95) superconductors. Measurements of the radio frequency penetation depth lambda (T, H) have yielded vortex dynamics parameters such as pinning force constants kappa _p, vortex viscosity eta, critical fields Hc1 and Hc2, and have led to the observation of a vortex mobility transition. The entire field-dependent behavior of the penetration depth lambda (T, H) is well described by a quantitative model of dynamic response of vortex diffusion. The results are analysed in the context of the nature of the superconducting state.< p type=" texpara" tag=" Body Text"> Work supported by the Office off Naval Research.},

keywords = {},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{kaso2002microwave,

title = {Microwave Transmission in Left-Handed Metamaterials},

author = {A Kaso and PV Parimi and S Sridhar and JS Derov},

year  = {2002},

date = {2002-01-01},

booktitle = {APS Meeting Abstracts},

abstract = {As has been already shown, a material with both ε and mu negative can sustain propagation waves. The permittivity ε and permeability mu should necessarily be frequency dependent for the causality principle to hold. We consider the dispersive expressions obtained by theoretical considerations from JB Pendry. We try to obtain some useful insight for pulse propagation, like group velocity v_g, the spreading of the wave packet in time in the disperssive medium. Transmission and reflectivity are computed for a normal incidence of the pulse on the slab. All the above situations can prove useful in the applications of this new metamaterial, such as in the delay lines where high values of the index of refraction are needed. particular attention is given to the frequency range where the material displays n=-1. Experiments are underway exploring the properties of LHM and the results will be discussed.},

keywords = {},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{sridhar2002microwave,

title = {Microwave Properties of Superconducting MgB_2},

author = {S Sridhar},

year  = {2002},

date = {2002-01-01},

booktitle = {APS Meeting Abstracts},

keywords = {},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{bishop2002intrinsic,

title = {Intrinsic Multiscale Structure and Dynamics in Complex Electronic Oxides},

author = {AR Bishop and SR Shenoy and S Sridhar},

year  = {2002},

date = {2002-01-01},

organization = {World Scientific Singapore Proceedings of the Workshop ICTP, Trieste, Italy},

abstract = {High resolution microscopies on many classes of complex systems such as superconducting cuprates, CMR manganites and ferroelectric titanates, have revealed an unsuspected nanoworld of'intrinsically inhomogeneous' states, with stripe-or island-like patterning of charge, spin and structure, over tens or hundreds of lattice spacings. This spontaneous spatial variation or'texturing'shows up in low-frequency or diffusive x-ray and neutron spectra, ultrasonic/electromagnetic/dielectric response, and real-space STM imaging. A physical understanding of such texturing and its relation to properties like superconductivity or CMR behaviour could emerge from ideas such as the competition between long-and short-range interactions; the coupling of spin and charge to lattice strains; and from correlated tilts and distortions of the complex atomic bases of these oxide materials.},

keywords = {},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{lu2002spectra,

title = {Spectra and wave functions of open chaotic billiards},

author = {WT Lu and S Sridhar and others},

year  = {2002},

date = {2002-01-01},

booktitle = {APS Division of Atomic, Molecular and Optical Physics Meeting Abstracts},

abstract = {The quantum spectra and wave functions of the n-disk open chaotic system are studied. The spectra consist of quantum resonances which are calculated in period orbit theory and measured in microwave experiments. The correlation of quantum resonances leads to the classical Ruelle-Pollicott resonances. The scattering wave functions are studied numerically and experimentally. Scars are observed and wave function statistics are analyzed. Spectra and wave functions of divided phase space billiard are also studied. Work supported by NSF-PHY-0098801},

keywords = {},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{sridhar2002quantum,

title = {Quantum Chaos in Microwave Billiards},

author = {Srinivas Sridhar},

year  = {2002},

date = {2002-01-01},

booktitle = {APS Division of Atomic, Molecular and Optical Physics Meeting Abstracts},

abstract = {I discuss some recent themes from microwave experiments designed to explore issues in Quantum Chaos. The experiments measure spectra and eigenfunctions of model geometries in the form of closed and open billiards. The microwave billiards provide a nearly ideal laboratory realization of a particle in hard-wall 2-D potentials, suitable for exploring the quantum-classical correspondence in chaotic systems, and capture the essential features of diverse situations in atomic and optical physics. The experiments reveal universal features of spectral and eigenfunction statistics that are well described by random matrix theory. Non-universal features are also observed, particularly periodic orbit contributions such as scars in eigenfunctions. A systematic trend from chaos to disorder is studied in disordered billiards, where quantum diffusion and interference lead to localization and non-universal behavior of density …

},

keywords = {},

pubstate = {published},

tppubtype = {inproceedings}

}