Probing energy barriers and quantum confined states of buried semiconductor heterostructures with ballistic carrier injection: An experimental study

A three-terminal spectroscopy that probes both subsurface energy barriers and interband optical transitions in a semiconductor heterostructure is demonstrated. A metal-base transistor with a unipolar p-type semiconductor collector embedding InAs/GaAs quantum dots (QDs) is studied. Using minority/majority carrier injection, ballistic electron emission spectroscopy and its related hot-carrier scattering spectroscopy measures barrier heights of a buried AlxGa1-xAs layer in conduction band and valence band respectively, the band gap of Al0.4Ga0.6As is therefore determined as 2.037 +/- 0.009 eV at 9 K. Under forward collector bias, interband electroluminescence is induced by the injection of minority carriers with sub-bandgap kinetic energies. Three emission peaks from InAs QDs, InAs wetting layer, and GaAs are observed in concert with minority carrier injection.Comment: 11 pages, 4 figures, submitted to Physical Review

Atomic Bloch-Zener oscillations for sensitive force measurements in a cavity

Cold atoms in an optical lattice execute Bloch-Zener oscillations when they are accelerated. We have performed a theoretical investigation into the case when the optical lattice is the intra-cavity field of a driven Fabry-Perot resonator. When the atoms oscillate inside the resonator, we find that their back-action modulates the phase and intensity of the light transmitted through the cavity. We solve the coupled atom-light equations self-consistently and show that, remarkably, the Bloch period is unaffected by this back-action. The transmitted light provides a way to observe the oscillation continuously, allowing high precision measurements to be made with a small cloud of atoms.Comment: 5 pages, 2 figures. Updated version including cavity heating effect

An economic analysis of groundwater markets and water use efficiency in hard rock area of Hosur union Krishnagiri district of Tamil Nadu

Groundwater selling is a guarantee against deficiency rains in areas where farmers do not have access to surface water irrigation. Therefore, examination of groundwater market development and the efficiency of groundwater use under different water regimes needs to be studied. The objective of the study was (a) to analyse the structure and contact of groundwater markets and (b) to estimate the cost of ground water extraction and selling price in Hosur and Kaveripatinam taluks of Krishnagiri district, Tamil Nadu. Based on the Primary survey, water structures were analysed using simple statistics and measured efficiency by Data Envelopment Analysis. The groundwater market structure demonstrated that the number of irrigation water buyers grows as the size of the farm decreases, while the number of irrigation water sellers grows as the size of the farm increases. The efficiency of groundwater use is estimated by data envelop analysis. According to the data, in a sample of groundwater markets, the seller-buyer concentration ratio was 1:1.13. The cropping intensity and irrigation intensity were highest (89.13 and 93.19 %, respectively) for the self-user+seller category. The selling price of groundwater (Rs. 50 per tank) was marginally higher than the total cost of water extraction (Rs. 28.27 per tank), thereby implying the exploitative nature of groundwater markets. According to findings on input consumption and landholdings, water buyers are resource-strapped farmers who are unlikely to be able to afford the large investments required to install a well

A QKD Protocol Extendable to Support Entanglement and Reduce Unauthorized Information Gain by Randomizing the Bases Lists with Key Values and Invalidate Explicit Privacy Amplification

This paper suggests an improvement to the BB84 scheme in Quantum key distribution. The original scheme has its weakness in letting quantifiably more information gain to an eavesdropper during public announcement of unencrypted bases lists. The security of the secret key comes at the expense of the final key length. We aim at exploiting the randomness of preparation (measurement) basis and the bit values encoded (observed), so as to randomize the bases lists before they are communicated over the public channel. A proof of security is given for our scheme and proven that our protocol results in lesser information gain by Eve in comparison with BB84 and its other extensions. Moreover, an analysis is made on the feasibility of our proposal as such and to support entanglement based QKD. The performance of our protocol is compared in terms of the upper and lower bounds on the tolerable bit error rate. We also quantify the information gain (by Eve) mathematically using the familiar approach of the concept of Shannon entropy. The paper models the attack by Eve in terms of interference in a multi-access quantum channel. Besides, this paper also hints at the invalidation of a separate privacy amplification step in the "prepare-and-measure" protocols in general.Comment: 13 pages, 1 figure, submitted for review to the USENIX 200

Small-worlds: How and why

We investigate small-world networks from the point of view of their origin. While the characteristics of small-world networks are now fairly well understood, there is as yet no work on what drives the emergence of such a network architecture. In situations such as neural or transportation networks, where a physical distance between the nodes of the network exists, we study whether the small-world topology arises as a consequence of a tradeoff between maximal connectivity and minimal wiring. Using simulated annealing, we study the properties of a randomly rewired network as the relative tradeoff between wiring and connectivity is varied. When the network seeks to minimize wiring, a regular graph results. At the other extreme, when connectivity is maximized, a near random network is obtained. In the intermediate regime, a small-world network is formed. However, unlike the model of Watts and Strogatz (Nature {\bf 393}, 440 (1998)), we find an alternate route to small-world behaviour through the formation of hubs, small clusters where one vertex is connected to a large number of neighbours.Comment: 20 pages, latex, 9 figure

A study on drug therapy issues in the department of medicine of a tertiary care teaching hospital-prospective observational study

Background: A drug therapy problem (DTP) is any undesirable event experienced by a patient that involves or is suspected to involve, drug therapy, and that interferes with achieving the desired goals of therapy. The improper use of drugs can lead to patient morbidity and even mortality. DTP s are the clinical territory of the pharmaceutical care practitioner and the resolution of identifying the DTPs help patients to achieve their goals of therapy. Identifying DTPs enables risk quantification and determination of the potential impact of prevention strategies.  DTPs are associated with prolonged length of stay and increased economic burden and results in increased risk of death.Methods: A hospital based, prospective observational study was conducted at department of medicine in Rajah Muthiah medical college and hospital, 80 patients were enrolled in this study based on the inclusion-exclusion criteria. The DTPs were identified using the Cipolle’s method of classification of DTP.Results: The study has shown that 80 of the patients involved in the study had a total of 136 DTPs. An average of 1.7 DTPs were recorded per patient during the study. The most common DTP identified was unnecessary drug therapy accounting to 47%. The absence of valid medical indication was (30%) and (16%) were due to the duplication of therapy. The second most common DTP was unsafe drug for patients, accounting to 45% were due to patient non-compliance and drug interaction which was minor. Need for additional drug therapy was the third most identified accounting 13% were due to medical indication indicate the need of drug therapy.Conclusions: The foremost commonly observed DTP is unnecessary therapy and patient non-compliance to the drugs. The study suggests that DTPs are significantly occurring in hospital can cause the patient for comorbidity, prolonged hospitalization. The study suggests that clinical pharmacist and general practitioners can work together to spot and resolve the DTPs

Biodegradation and antimicrobial properties of zinc oxide–polymer composite materials for urinary stent applications

Research advancements in the field of urinary stents have mainly been in the selection of materials and coatings to address commonly faced problems of encrustation and bacterial adhesion. In this study, polylactic acid (PLA) and polypropylene (PP) were evaluated with zinc oxide (ZnO) coating to assess its ability to reduce or eliminate the problems of encrustation and bacteria adhesion. PLA and PP films were prepared via twin screw extrusion. ZnO microparticles were prepared using sol-gel hydrothermal synthesis. The as-prepared ZnO microparticles were combined in the form of a functional coating and deposited on both polymer substrates using a doctor blade technique. The ZnO-coated PP and PLA samples as well as their uncoated counterparts were characterized from the physicochemical standpoints, antibacterial and biodegradation properties. The results demonstrated that both the polymers preserved their mechanical and thermal properties after coating with ZnO, which showed a better adhesion on PLA than on PP. Moreover, the ZnO coating successfully enhanced the antibacterial properties with respect to bare PP/PLA substrates. All the samples were investigated after immersion in simulated body fluid and artificial urine. The ZnO layer was completely degraded following 21 days immersion in artificial urine irrespective of the substrate, with encrustations more evident in PP and ZnO-coated PP films than PLA and ZnO-coated PLA films. Overall, the addition of ZnO coating on PLA displayed better adhesion, antibacterial activity and delayed the deposition of encrustations in comparison to PP substrates

A six-year study of leiomyomata with emphasis on lipoleiomyoma

Background: Leiomyoma is the most common benign neoplasm of the uterus. Lipoleiomyoma is a rare variant usually affecting women in the postmenopausal age group. Incidence of lipoleiomyoma varies from 0.59% - 2.1%. This study was undertaken to analyse the different variants, degenerative changes and to determine the incidence, clinical and morphological features of lipoleiomyoma amongst all the leiomyomas studied.Methods: This study was done in the Department of Pathology over a period of 6 years. Authors studied 575 patients with leiomyoma constituting a total of 1122 leiomyomata as some patients presented with multiple leiomyomata. Further clinicopathological correlation was done.Results: In the present study 98.03% of leiomyomata were uterine in location, 1.06% were cervical, 0.62% were in broad ligament and 0.26 % were in ovary. Among the 1122 leiomyomata studied, degenerative changes were noted in 19.6% of which hyaline degeneration was the most common. Leiomyoma variants constituted 5.27% of all leiomyomata. The incidence of lipoleiomyoma was 0.71% with size ranging from 3-10cm.Conclusions: Leiomyoma is a common tumor of the uterus and lipoleiomyoma variant is very uncommon with unknown etiology. They occur in postmenopausal as well as reproductive age group. The site of lipoleiomyoma can be uterine or extrauterine location such as broad ligament. Coexistance of metabolic derangement is an observation that may have a role in development of lipoleiomyoma