Fundamentals of Large Sensor Networks: Connectivity, Capacity, Clocks and Computation

Sensor networks potentially feature large numbers of nodes that can sense their environment over time, communicate with each other over a wireless network, and process information. They differ from data networks in that the network as a whole may be designed for a specific application. We study the theoretical foundations of such large scale sensor networks, addressing four fundamental issues- connectivity, capacity, clocks and function computation. To begin with, a sensor network must be connected so that information can indeed be exchanged between nodes. The connectivity graph of an ad-hoc network is modeled as a random graph and the critical range for asymptotic connectivity is determined, as well as the critical number of neighbors that a node needs to connect to. Next, given connectivity, we address the issue of how much data can be transported over the sensor network. We present fundamental bounds on capacity under several models, as well as architectural implications for how wireless communication should be organized. Temporal information is important both for the applications of sensor networks as well as their operation.We present fundamental bounds on the synchronizability of clocks in networks, and also present and analyze algorithms for clock synchronization. Finally we turn to the issue of gathering relevant information, that sensor networks are designed to do. One needs to study optimal strategies for in-network aggregation of data, in order to reliably compute a composite function of sensor measurements, as well as the complexity of doing so. We address the issue of how such computation can be performed efficiently in a sensor network and the algorithms for doing so, for some classes of functions.Comment: 10 pages, 3 figures, Submitted to the Proceedings of the IEE

The Link Overlap and Finite Size Effects for the 3D Ising Spin Glass

We study the link overlap between two replicas of an Ising spin glass in three dimensions using the Migdal-Kadanoff approximation and scaling arguments based on the droplet picture. For moderate system sizes, the distribution of the link overlap shows the asymmetric shape and large sample-to-sample variations found in Monte Carlo simulations and usually attributed to replica symmetry breaking. However, the scaling of the width of the distribution, and the link overlap in the presence of a weak coupling between the two replicas are in agreement with the droplet picture. We also discuss why it is impossible to see the asymptotic droplet-like behaviour for moderate system sizes and temperatures not too far below the critical temperature.Comment: 7 pages, 10 figure

Block Copolymer Based Magnetic Nanoclusters for Cancer-Theranostics: Synthesis, Characterization and In Vitro Evaluation

“There is plenty of room at the bottom”. In this visionary lecture in 1959 Prof. Richard Feynman spoke of the interesting ramifications of working with matter at the atomic scale. Since then, scientists have worked relentlessly towards realizing his vision. The influence of nanobiotechnology on material science and polymer chemistry has given rise to a new field called ‘theranostics’, combining drug delivery and diagnostics within the same nanostructures, thereby enabling simultaneous diagnosis, targeted drug delivery and continued therapy monitoring. Iron oxide nanoparticles (MNPs) are one such class of MRI contrast agents that can be converted into theranostic nanomedicines for cancer therapy. However, development of a stable theranostic contrast system comprising of MNPs is complex and requires a careful balance between the therapeutic diagnostic components. We explored the potential of biodegradable hydrophilic block ionomers such as anionic poly (glutamic acid-b-ethylene glycol) and cationic poly (l-lysine-b-ethylene glycol) in formulating stable magnetic nanoclusters (MNCs). These MNCs were extensively characterized for their composition, colloidal stability and factors influencing their MRI capability. Extensive in vitro studies revealed that the anionic cisplatin-loaded MNCs showed minimal non-specific uptake, a highly preferred feature for targeted cancer therapy. Luteinizing hormone releasing hormone receptor (LHRHr) targeting significantly enhanced the uptake of these formulations in LHRHr-positive ovarian cancer cells. LHRHr targeting also helped improve the theranostic efficacy in cisplatin resistant ovarian cancer cells. One the other hand, cationic MNCs were used to demonstrate the potential of MNCs to function as stimuli-responsive theranostic systems capable of releasing the payload in the acidic milieu breast and ovarian cancer cells. These cationic MNCs also exhibited significantly enhanced T2-weighted MRI contrasts at much lower concentrations than the anionic counterparts. Finally, we successfully evaluated the feasibility of kinetically controlled flash nanoprecipitation technique using multi-inlet vortex mixer (MIVM) to formulate well-defined MNCs from non-ionic amphiphilic Pluronic tri-block copolymers. In comparison to self-assembly techniques, flash nanoprecipitation resulted in significant reduction in polydispersity. It was observed that the hydrophobic block-length of the copolymer dictates the extent of encapsulation hydrophobic therapeutic agents along with the MNPs. exhibited the potential to function as both T1 and T2 contrast agents. In summary, looking at the bigger picture, the work presented here emphasizes on the importance of product development in establishing a critical balance between the therapeutic and imaging functionalities when designing an efficient targeted theranostic nanosystems

Managing Equipment for Emergency Obstetric Care in Rural Hospitals

In resource poor countries substantial sums of money, from governments and international donors, are used to purchase equipment for health facilities. WHO estimates that 50-80% of such equipment remains non-functional. This article is based on the experiences from various projects in developing countries in Asia and Africa. The key issues in the purchase, distribution, installation, management and maintenance of equipment for emergency obstetric care (EmOC) services are identified and discussed. Some positive examples are described to show how common equipment management problems are solved.

Exciton generation and dissociation mechanisms in organic bulk heterojunction solar cell materials.

Characterization of the optical and electrical properties of organic solar cell materials is of prime importance to organic solar cell design. This thesis describes the use of capacitive photocurrent measurements to study the exciton generation and dissociation mechanisms of organic solar cell materials. The emphasis is on the study of the methanofullerene derivatives (e.g., PCBM) which act as the electron acceptor material. This is because much work has already been done studying electron donating polymers used in organic solar cells (in an effort to enhance their absorbance coefficient), but less information is available on the acceptor material. In the blend films of MDMO-PPV: PCBM, the charge generation rate in PCBM was discovered to be much higher than would be expected from the absorbance cross-section. This observation led to design of a photovoltage bleaching experiment to examine the charge generation mechanism. Here the effect of illumination by a tunable light source on the open circuit photovoltage of a MDMO-PPV: PCBM bulk heterojunction solar cell was measured. Illumination of light at the PCBM ground state singlet exciton causes a sharp decrease in the photovoltage, while illumination at the ground state MDMO-PPV exciton shows no change. A direct pathway of recombination of above gap generated charge carriers was identified. Photovoltage bleaching results suggests that excitation at the PCBM ground singlet state exciton increases the recombination rate of higher energy excitations, either by acting as a recombination center or by forcing higher energy carriers into short lived states that recombine before reaching the contacts. The fact that the photovoltage bleaching correlates with the ground state PCBM singlet exciton suggests that charge dissociation from PCBM preferentially generates long-lived localized states. Capacitive photocurrent measurements were then performed on isolated methanofullerene derivatives, with the polymer donor material absent. Several low energy transitions were resolved in the optical spectroscopy of methanofullerene derivatives. These low energy states lay below the optical energy band-gap of these materials, so that their presence was unexpected. It was determined that the low energy states overlapped with the plasmon state of the highly conducting substrates (Indium Tin Oxide) which were in close proximity with the PCBM. Plasmon states in ITO have been observed previously, but the results presented in this thesis are unique in that this is the first evidence of charge transfer from the plasmon state of ITO to a high electron affinity fullerene derivative. The results show the evidence of charge transfer from PCBM to ITO over a broad wavelength range of 400 - 2400 nm (3 eV - 0.5 eV). Few materials have been observed to have absorbance and charge transfer over such a large range of energies in the infra-red regime. These results open a new direction for development of organic solar cell design with higher power conversion efficiencies

Dispersion of narrow diameter carbon nanotubes for optical characterization.

Optical properties of carbon nanotubes have recently attracted considerable amount of attention. Due to there direct band gap material characteristic these and dimension of the order of nano meters they find potential applications in the field of nano photonics. Thus the optical study of carbon nanotubes is important for both fundamental research and for the next generation technical applications. In this thesis single walled carbon nanotubes were dispersed in various encapsulates such as surfactants, polymers, proteins etc to separate them individually and study there optical properties. The individually dispersed single walled carbon nanotubes displayed unique absorbance spectra. The optical absorption spectrum of a particular tube is expected to be dominated by a series of relatively sharp inter-band transitions, at energies associated with the van Hove singularities, the absorbance spectrum obtained on our samples were consistent with this expectation. Our samples also showed sharp photoluminescence peaks mostly from the semiconducting single walled carbon nanotubes. The detailed overlap of the absorbance spectra and photoluminescence spectra lead us to believe that our samples contain mainly individual tubes encapsulated in one of the surfactants or polymers. Thin film transistors (TFT) were made with a mesh of single walled carbon nanotubes as the active channel on top of a silicon/silicon oxide substrate, with silicon acting as a back gate and titanium/gold electrodes were evaporated on top of the nanotube film. Photocurrent properties of these thin films were investigated and they showed a huge change in the photocurrent in the presence and absence of the laser light. Thin films of carbon nanotubes were also deposited on rectangular silicon substrates and the influence of applied strain in the presence of laser light was investigated. These films showed a huge change in resistance on application of mechanical strain. Raman measurements were also performed on these thin films and the obtained radial breathing mode (RBM) data helped resolve the diameter of many single walled carbon nanotubes

Comment on "General Method to Determine Replica Symmetry Breaking Transitions"

In a recent letter Marinari et al [Phys. Rev. Lett. 81, 1698 (1998)] introduced a new method to study spin glass transitions and argued that by probing replica symmetry (RS) as opposed to time reversal symmetry (TRS), their method unambiguously shows that replica symmetry breaking (RSB) occurs in short-range spin glasses. In this comment we show that while the new method is indeed useful for studying transitions in systems where TRS is absent (such as the p-spin model studied by them), the conclusion that it shows the existence of RSB in short-range spin glasses is wrong.Comment: 1 page, RevTe

Automated detection of naming conflicts in schema integration: Experiments with quiddities*

This paper discusses experiments involving a method for the automatic detection, prior to the integration of data base schemas, of conflicts in the naming of data elements within these schemas. The method relies on the representation of semantic information (called quiddity) about the data elements present in the various schemas. We develop several inference procedures which, utilizing this information, determine whether to distinctly named elements in fact represent the same object, or if elements with the same name actually represent different objects. The experiments are concerned with (a) examining the accuracy and consistency with which quiddities of data elements might be declared by different database designers, and (b) evaluating the accuracy and errors of these automated procedures. Our results indicate that the method has promise for use in detection of naming conflicts, and that certain inference procedures are superior to others in terms of their accuracy and error ratesNaval Postgraduate School, Monterey, CAhttp://archive.org/details/automateddetecti00bharO&MN Direct FundingNAApproved for public release; distribution is unlimited

A case study to evaluate the effect of Dashamoola Basti in Asthila w.s.r. to Benign Prostate Hyperplasia

BPH (Benign Prostate Hyperplasia) is a histological diagnosis that states the proliferation of smooth muscle and epithelial cells within the transient zone of prostate gland. The incidence and severity of lower urinary tract symptoms (LUTS) are increasing day by day and more likely to occur in old ages. Due to the resemblance of clinical feature, it is correlated to Asthila which is one of the types of Mutraghata according to all the Acharyas. In this case study a male patient came to OPD of SKAMCH&RC and was diagnosed for Asthila w.s.r. to BPH. He was given management like Sarvanga Abhyanga, Sarvanga Bashpa Swedana and Dashamoola Niruha Basti adopted in Kala Basti Pattern followed by oral medication in follow-up period. The patient showed marked improvement in the symptomatology. It was conclusive study to show the effect of Dashamoola Basti in the management of Asthila w.s.r. to benign prostate hyperplasia (BPH

RP-HPLC METHOD DEVELOPMENT AND VALIDATION FOR SIMULTANEOUS ESTIMATION OF PHENYLEPHRINE HYDROCHLORIDE AND EBASTINE IN TABLET DOSAGE FORM

Objective: A new simple, accurate, precise, robust, reproducible and economic RP-HPLC method was developed for Phenylephrine Hydrochloride and Ebastine in marketed tablet dosage form. Methods: The Chromatographic separation was achieved on Thermo BDS Hypersil C18 column (250 mm × 4.6 mm, 5 µm) at ambient temperature. Mobile phase consist of Methanol: Phosphate buffer (30:70v/v), pH 4.0±0.05 was pumped at a flow rate was 1.0 ml/ min and Quantification was achieved with photodiode array (PDA) detection at 215 nm. Results: The method was linear over the concentration range of 5-15 µg/mL (r2 = 0.9994) for Phenylephrine Hydrochloride (PHE) and 5-15 µg/mL (r2 = 0.9947) for Ebastine (EBS). The percentage content for PHE and EBS was found to be 101.08±0.74% and 99.11±0.52%, respectively in the marketed formulation. The LOD and LOQ values for PHE were 0.46 and 1.12 mg/ml, respectively and these values for EBS were 1.41 and 3.41 mg/ml, respectively. These values indicate the sensitivity of method. Percent recovery was 99.69% for PHE and 96.60% for EBS reflects the good accuracy of the method. The developed method was validated for linearity, precision, accuracy, and robustness as per ICH guideline. Conclusion: A simple, precise, accurate, linear and rapid RP-HPLC method was developed and validated as per ICH guidelines. The results suggest that the developed can be applicable in routine analysis for tablets in the pharmaceutical industry