Design and Characterization of p-i-n Devices for Betavoltaic Microbatteries on Gallium Nitride

Betavoltaic microbatteries convert nuclear energy released as beta particles directly into electrical energy. These batteries are well suited for electrical applications such as micro-electro-mechanical systems (MEMS), implantable medical devices and sensors. Such devices are often located in hard to access places where long life, micro-size and lightweight are required. The working principle of a betavoltaic device is similar to a photovoltaic device; they differ only in that the electron hole pairs (EHPs) are generated in the device by electrons instead of photons. In this study, the performance of a betavoltaic device fabricated from gallium nitride (GaN) is investigated for beta particle energies equivalent to Tritium (3H) and Nickel-63 (N63) beta sources. GaN is an attractive choice for fabricating betavoltaic devices due to its wide band gap and radiation resistance. Another advantage GaN has is that it can be alloyed with aluminum (Al) to further increase the bandgap, resulting in a higher output power and increased efficiency. Betavoltaic devices were fabricated on p-i-n GaN structures grown by metalorganic chemical vapor deposition (MOCVD). The devices were characterized using current - voltage (IV) measurements without illumination (light or beta), using a laser driven light source, and under an electron beam. Dark IV measurements showed a turn on-voltage of ~ 3.4 V, specific-on-resistance of 15.1 m Ω-cm2, and a leakage current of 0.5 mA at – 10 V. A clear photo-response was observed when IV curves were measured for these devices under a light source at a wavelength of 310 nm (4.0 eV). These devices were tested under an electron beam in order to evaluate their behavior as betavoltaic microbatteries without using radioactive materials. Output power of 70 nW and 640 nW with overall efficiencies of 1.2% and 4.0% were determined at the average energy emission of 3H (5.6 keV) and 63N (17 keV) respectively

Mining Consumer Knowledge from Shopping Experience: A case study on Indian E_Commerce Industry

E_Commerce becomes far much popular in recent years. E Commerce nowadays is almost everywhere. People go through online ; meanwhile, they are more and more accustomed to buy goods via E_Commerce channel. - The E-Commerce web sites are facing lots of problems today. Customers prefer traditional way to purchase the products and not from E-Commerce web sites. If we see the history of E-Commerce, then we get that E-Commerce is the purpose of Internet and the web to conduct business Even in recession, it is thriving and has become one of the most important consumption modes. This study uses cluster analysis to identify the profiles of E_Commerce consumers. The rules between E_Commerce spokespersons and commodities from consumers are recognized by using association analysis. Depicting the marketing knowledge map of spokespersons, the best endorsement portfolio is found out to make recommendations. By the analysis of spokespersons, period, customer profiles and products, four business modes of E_Commerce are proposed for consumers: new product, knowledge, low price and luxury product; the related recommendations are also provided for the industry reference

Female genital schistosomiasis as an evidence of a neglected cause for reproductive ill-health: a retrospective histopathological study from Tanzania

BACKGROUND: Schistosomiasis affects the reproductive health of women. Described sequelae are ectopic pregnancy, infertility, abortion, and cervical lesions and symptoms mimicking cervical cancer and STIs. There are indications that cervical schistosomiasis lesions could become co-factors for viral infection such as HIV and HPV. METHODS: In a retrospective descriptive histopathological study clinical specimens sent between 1999 and 2005 to the pathology department of a consultant hospital in Tanzania were reviewed to analyse the occurrence and features of schistosomiasis in female genital organs. RESULTS: During the study period, schistosomiasis was histopathologically diagnosed in 423 specimens from different organs (0.7% of all specimens examined in the study period), out of those 40% were specimens from female and male organs. The specimens were sent from 24 hospitals in 13 regions of mainland Tanzania. Female genital schistosomiasis was diagnosed in 125 specimens from 111 patients. The main symptoms reported were bleeding disorders (48%), ulcer (17%), tumor (20%), lower abdominal pain (11%) and infertility (7%). The majority of cases with genital schistosomiasis were diagnosed in cervical tissue (71 cases). The confirmation of cervical cancer was specifically requested for 53 women, but the diagnosis could only be verified for 13 patients (25%), in 40 cases only severe cervical schistosomiasis was diagnosed. Vulval/labial schistosomiasis was seen in specimens from young women. Infertility was reported in four patients with schistosomiasis of the Fallopian tubes. CONCLUSION: Genital schistosomiasis adds to the disease burden of women in all age groups. Pathological consequences due to the involvement of different genital organs can be damaging for the affected women. Clinical unawareness of genital schistosomiasis can lead to misdiagnosis and therefore false and ineffective therapy. In endemic areas cervical schistosomiasis should be considered as differential diagnosis of cancer

Cyanobacterial lipopolysaccharides and human health – a review

Cyanobacterial lipopolysaccharide/s (LPS) are frequently cited in the cyanobacteria literature as toxins responsible for a variety of heath effects in humans, from skin rashes to gastrointestinal, respiratory and allergic reactions. The attribution of toxic properties to cyanobacterial LPS dates from the 1970s, when it was thought that lipid A, the toxic moiety of LPS, was structurally and functionally conserved across all Gram-negative bacteria. However, more recent research has shown that this is not the case, and lipid A structures are now known to be very different, expressing properties ranging from LPS agonists, through weak endotoxicity to LPS antagonists. Although cyanobacterial LPS is widely cited as a putative toxin, most of the small number of formal research reports describe cyanobacterial LPS as weakly toxic compared to LPS from the Enterobacteriaceae. We systematically reviewed the literature on cyanobacterial LPS, and also examined the much lager body of literature relating to heterotrophic bacterial LPS and the atypical lipid A structures of some photosynthetic bacteria. While the literature on the biological activity of heterotrophic bacterial LPS is overwhelmingly large and therefore difficult to review for the purposes of exclusion, we were unable to find a convincing body of evidence to suggest that heterotrophic bacterial LPS, in the absence of other virulence factors, is responsible for acute gastrointestinal, dermatological or allergic reactions via natural exposure routes in humans. There is a danger that initial speculation about cyanobacterial LPS may evolve into orthodoxy without basis in research findings. No cyanobacterial lipid A structures have been described and published to date, so a recommendation is made that cyanobacteriologists should not continue to attribute such a diverse range of clinical symptoms to cyanobacterial LPS without research confirmation

DEVELOPMENT OF GALLIUM NITRIDE AND INDIUM GALLIUM PHOSPHIDE BETAVOLTAIC AND ALPHAVOLTAIC DEVICES FOR CONTINUOUS POWER GENERATION

Betavoltaic devices are p-n/p-i-n junction diodes that use the kinetic energy of beta (electron) particles emitted by beta isotopes to create electron-hole pairs and generate electrical power in a similar way as photovoltaic devices use photons energy to generate electrical power. Unlike photovoltaic devices (solar cells), betavoltaic devices can generate electrical power day and night continuously for decades (12 years with 3H (tritium) and 100 years with Ni63 (nickel-63)), enabling new capabilities that are not possible with photovoltaic devices or current state of the art chemical batteries. New capabilities include decade-long continuous power for unattended sensor, tagging/tracking devices, and other electronics placed in remote areas (underwater, polar region, space, etc) where change/charge of batteries is highly inconvenient or impossible. It is expected that wide band gap semiconductors like GaN with an energy gap of 3.4 eV may provide a better performance in terms of output power and stability under beta radiations. However, GaN semiconductor technology is still maturing in terms of growth and fabrication techniques. InGaP has a moderately wide bandgap of 1.86 eV, but it is well advanced in terms of crystal growth and fabrication techniques. Therefore, our study and research focused on the development (design, fabrication, evaluation) and comparison of a wide band gap (GaN) and a moderately high band gap InGaP, that are considered very promising in betavoltaic applications. Betavoltaic devices were fabricated on three GaN p-i-n structures with different i-layer thicknesses (600 nm, 700 nm and 1 µm). Two GaN p-i-n structures were grown on top of a sapphire substrate and the third GaN structure was grown on top of a bulk GaN substrate. InGaP devices were fabricated on an InGaP n-i-p structure grown on top of a gallium arsenide (GaAs) substrate. Devices were characterized using current - voltage (IV) measurements in the dark, using a UV light source, and under an electron beam stimulus to mimic their performance under real beta isotopes. Dark IV measurements confirmed good quality diodes with low leakage currents, and IV curves under the UV light (365nm, 3.40 eV) source showed a clear photo-response. IV curves under the electron beam irradiation at 16 KeV (average energy emission of Ni63 beta source at 250 mCi/cm2) resulted in the output powers of 3.01 µW/cm2 with an efficiency of 12.63 % for the InGaP device, and 3.32 µW/cm2 with an efficiency of 13.2% for the GaN device. InGaP and GaN devices were also exposed under a 4.5 MeV alpha beam to determine their suitability for an alphavoltaic power source (Direct energy conversion). Both InGaP and GaN devices showed degradation in their MPPs under the direct alpha beam exposure. We also investigated an indirect alpha-photovoltaic (APV) power source by employing ZnS phosphor as an intermediate layer to limit this degradation. This ZnS layer absorbs all the alpha energy and converts it into photons to create EHPs in the semiconductor device to generate electrical output power via indirect energy conversion. We determined that even though APV approach prevented radiation damage in the semiconductor device but the degradation rate of ZnS phosphor is faster compared to the degradation rate of GaN and InGaP devices under direct alpha beam exposure