Investigation of doped cuprous halides for photovoltaic and display applications

The thesis mainly focuses on the growth and optoelectronic characterisation of the doped cuprous halides (CuX) with high UV/blue emission properties and the light harvesting in the CuBr/Si based heterojunction photovoltaic (PV) cells. Since cuprous halides are short wavelength emitters with high excitonic binding energies, growth of lower resistivity, highly luminescent p and n-type films are essential for the development of the future excitonic based light emitting devices with these materials. We describe the deposition and characterisation of the Zn doped n-type CuCl and oxygen doped p-type CuBr with higher carrier concentration using pulsed dc magnetron sputtering and thermal evaporation followed by oxygen plasma exposure, respectively. The structural and morphological properties of the n-type Zn doped CuCl films are investigated using XRD, SEM and AFM measurements. Our findings show that, the crystallinity of CuCl increases with doping of Zn and the maximum is obtained for the 3 % doped film, beyond which crystallinity decreases. The Zn doping has no deleterious impact on the structural and luminescent properties of CuCl up to a doping percentage of 5. An order of magnitude reduction in the resistivity of the CuCl films is obtained as a result of Zn doping. The resistivity, n-type carrier concentration and carrier mobility corresponding to the 3 % Zn doped films were, respectively 6 Ωcm, ~ 9.8×1018 cm-3 and 0.1 cm2V-1s-1. The influence of Zn doping on the electronic structure of CuCl is investigated using photoemission spectroscopic studies. Our studies on the Cu and Cl core level spectra show the presence of trace amounts of Cu2+ species in the undoped CuCl sample along with the major Cu+ species. This is verified by the observation of the satellite and shoulder peaks in the Cu 2p core level and a higher binding energy tail in the Cl 2p core level spectra. The disappearance of the cupric species with doping of Zn (3 %) is also observed. Furthermore, the shifting of the valence band towards the higher binding energy confirms the filling of the conduction band owing to the Zn doping, which explains the improvement of the conductivity of the doped films. vii We have successfully deposited p-type CuBr films by doping of oxygen. Our findings show that, there is no significant influence on the structural properties of the CuBr up to an oxygen plasma exposure time of 5 min. The investigation of the optical properties confirms good luminescence of the CuBr films up to a plasma exposure time of 3 min. The electrical characterisations of the oxygen plasma exposed films reveal that, oxygen act as a good acceptor for CuBr. The resistivity of the 3 min oxygen plasma exposed samples reduces to the order of ~ 1 Ωcm. SIMS analysis shows that, the diffusion of oxygen is quite good in the CuBr films. The realization of the heterojunction PV cell based on p-CuBr/n-Si is investigated. The I-V characteristics confirm the rectification behaviour of the p-n diode with a turn on voltage of ~ 1 V. The photoresponse properties of the heterojunction are studied by measuring the I-V characteristics under illumination. The photogenerated carrier formation is confirmed by the increased reverse current under illumination of the heterojunction. The wavelength dependence of the photo current was also studied using LED illumination. Development of ultrathin transparent Cr contacts, useful for the electroluminescent device fabrication was also discussed. This can be used as an alternative to well-known Indium Tin Oxide films for the future fabrication of the CuX-based display devices

Arachidonic Acid as a Possible Negative Feedback Inhibitor of Nicotinic Acetylcholine Receptors on Neurons

Neuronal acetylcholine receptors, being highly permeable to calcium, are likely to regulate calcium-dependent events in neurons. Arachidonic acid is a membrane-permeant second messenger that can be released from membrane phospholipids by phospholipases in a calcium-dependent manner. We show here that activation of neuronal acetylcholine receptors triggers release of 3H-arachidonic acid in a calcium-dependent manner from neurons preloaded with the fatty acid. Moreover, low concentrations of arachidonic acid reversibly inhibit the receptors and act most efficiently on receptors likely to have the highest permeability to calcium, namely receptors containing α7 subunits. Low concentrations of arachidonic acid also reversibly inhibit α7- containing receptors expressed in Xenopus oocytes following injection of α7 cRNA. The oocyte results indicate following injection of α7 cRNA. The oocyte results indicate that the inhibition is a feature of the receptors rather than a consequence of neuron-specific machinery. The inhibition is not mediated by specific metabolites of arachidonic acid because the effects can be mimicked by other fatty acids; their effectiveness correlates with their content of double bonds. In contrast to arachidonic effects on calcium currents, inhibition of neuronal nicotinic receptors by the fatty acid cannot be prevented by blocking production of free radicals or by inhibiting protein kinase C. An alternative mechanism is that arachidonic acid binds directly to the receptors or perturbs the local environment in such a manner as to constrain receptor function

Application of Factor Analysis to Identify Dietary Patterns and Use of Factor Scores to Study Their Relationship with Nutritional Status of Adult Rural Populations

The prevalence of chronic energy deficiency (CED) among one-third of the Indian population is attributed to inadequacy of consumption of nutrients. However, considering the complexity of diets among Indians, the relationship between a particular dietary pattern and the nutritional status of the population has not been established so far. A community-based cross-sectional study was undertaken to assess estimates, at district level, of diet and nutritional status in Orissa State, India. Factor analysis was used for exploring the existence of consumption pattern of food and nutrients and their relationship with the nutritional status of rural adult population. Data on 2,864 adult men and 3,525 adult women in Orissa state revealed that there exists six patterns among food-groups explaining 59% of the total variation and three patterns among nutrients that explain 73% of the total variation among both adult men and women. The discriminant function analysis revealed that, overall, 53% of the men were correctly classified as either with chronic energy deficiency (CED) or without CED. Similarly, overall, 54% of the women were correctly classified as either with CED or without CED. The sensitivity of the model was 65% for both men and women, and the specificity was 46% and 41% respectively for men and women. In the case of classification of overweight/obesity, the prediction of the model was about 75% among both men and women, along with high sensitivity. Using factor analysis, the dietary patterns were identified from the food and nutrient intake data. There exists a strong relationship between the dietary patterns and the nutritional status of rural adults. These results will help identify the community people with CED and help planners formulate nutritional interventions accordingly

Treatment for Sulphur Mustard Poisoning -A Review

Sulphur mustard (SM) is a chemical warfare agent of historical and current interest It is a wellknown blistering agent or vesicant SM was extensively used in world war I as a chemical weaponand has been stockpiled by several counbies since that time. SM serves as an ideal war gas and is favoured militarily for its ability to incapacitate rather than to kill. Its use resulted in large numbers ofcasualties requiring prolonged and intensive medical care. Despite Geneva Protocol of 1925, which categorically bnned the production, stockpiling and use of chemical weapons in wars, SM has beenused in several wars, including the Iran-Irnq war during the 1980s, which renewed interest in it.Though, the chemical we'dpons convention was signed by more than 160 counbies in 1993 and wassubsequently ratified by several counbies, the threat from this agent persists due to its clandestineusage during war and also by teITOrist groups. There is no effective and specific antidote for local andsystemic toxicity of SM despite scientific research for more than 75 years. Many compounds weretested as antidotes for SM, but very few of them have been shown to provide some protection. The present review is aimed at evaluating the treatment regime and other clinical measures used to treat  SM victims and the various drugs and chemicals screened as antidotes for SM poisoning in experimental animals

Učinak piridostigmina i fizostigmina na akutnu toksičnost diizopropil fluorofosfata u štakora

Diisopropyl fluorophosphate (DFP) given to rats in lethal concentration (100 mg/m3, by inhalation for 40 min) significantly inhibited acetylcholinesterase activity in the blood, lung, liver and brain, and induced hyperglycaemia and glycogen mobilization in the liver, diaphragm and brain. Pretreatment (maximum sign-free dose) with carbamates, pyridostigmine (0.075 mg/kg, i.m.) or physostigmine (0.1 mg/kg, i.m.) 15 min before exposure to DFP, modified the inhibited acetylcholinesterase activity only in peripheral tissues. However, the hyperglycaemia and glycogen depletion induced by DFP inhalation were not modified by carbamate pretreatment. The time of survival of DFP exposed animals increased after pretreatment with carbamates, more after physostigmine (81 min) than after pyridostigmine (59 min). The animals exposed to DFP exhibited severe tremors and convulsions as compared to the animals pretreated with carbamates.Diizopropil fluorofosfat (DFP), koji su štakori primili u letalnoj koncentraciji (100 mg/m3) inhalacijom tijekom 40 minuta, značajno je inhibirao aktivnost acetilkolinesteraze u krvi, plućima, jetri i mozgu te izazvao hiperglikemiju i doveo do mobilizacije glikogena u jetri, dijafragmi i mozgu. Prethodno intramuskularno tretiranje životinja maksimalnom dozom karbarnata koja još ne izaziva znakove trovanja, i to piridostigminom (0,07.5 mg/kg) ili fizostigminom (0,1 mg/kg) petnaest minuta prije ekspozicije DFP-u dovelo je do promjene u inhibiciji aktivnosti acetilkolinesteraze samo u perifernim tkivima. Međutim, na hiperglikemiju i nedostatnost glikogena koji su bili izazvani inhaliranjem DFP-a prethodno tretiranje karbamatima nije utjecalo. Vrijeme preživljenja životinja koje su bile izložene DFP-u bilo je duže nakon što su životinje primile karbamate. U tom pogledu fizostigmin (81 min) je bio djelotvorniji od piridostigmina (59 minuta). U životinja koje su bile izložene DFP-u primijećeni su jači tremor i konvulzije nego u životinja koje su ranije bile tretirane karbarnatima

Preliminary studies on nannoplankton productivity

The contribution of the nannoplankton to the total productivity was studied for nine months in coastal waters of Cochin. On an average, - nannoplankton accounted for 66.40% of the observed productivity. The mean assimiIation ratios between the total algal and nannoplankton fraction were very low (1.29 and 0.94 respectively)

Therapeutic Efficacy of Saline and Glucose Saline against Dermally applied Sulphur Mustard Intoxication in Mice

A single dose of saline or glucose-saline (5 mg glucose/kg) offered similar protection to mice against sulphur mustard intoxication, the extent of survival being 83 per cent as against 33 per cent without treatment. All the animals were protected when the treatment was extended by another two consecutive days in the glucose-saline treated group. Both saline and glucose-saline treatments could ameliorate the haemoconcentration as well as normalise pO/sub 2/ and % oxygen saturation. The protection conferred is attributed to the probable replenishment of fluid loss

An Efficient Approach for Finding Near Duplicate Web pages using Minimum Weight Overlapping Method

The existence of billions of web data has severely affected the performance and reliability of web search. The presence of near duplicate web pages plays an important role in this performance degradation while integrating data from heterogeneous sources. Web mining faces huge problems due to the existence of such documents. These pages increase the index storage space and thereby increase the serving cost. By introducing efficient methods to detect and remove such documents from the Web not only decreases the computation time but also increases the relevancy of search results. We aim a novel idea for finding near duplicate web pages which can be incorporated in the field of plagiarism detection, spam detection and focused web crawling scenarios. Here we propose an efficient method for finding near duplicates of an input web page, from a huge repository. A TDW matrix based algorithm is proposed with three phases, rendering, filtering and verification, which receives an input web page and a threshold in its first phase, prefix filtering and positional filtering to reduce the size of record set in the second phase and returns an optimal set of near duplicate web pages in the verification phase by using Minimum Weight Overlapping (MWO) method. The experimental results show that our algorithm outperforms in terms of two benchmark measures, precision and recall, and a reduction in the size of competing record set.DOI:http://dx.doi.org/10.11591/ijece.v1i2.7

Integrated case scripts to enhance diagnostic competency

Background: The overwhelmingly high burden of disease and disorder especially in developing countries requires oral physicians to provide optimal dental treatment without complicating individuals’ general health. The opportunity for learners to extract the multiple aspects of a systemic condition and to relate them with the presenting complaint in order to devise an appropriate dental treatment plan is limited by time in chair- side teaching. To overcome the necessity of exposing students to real patients with varying degrees of underlying disease, those in medical and nursing education unanimously employ imaginary scenarios similar to real cases. However, such clinical scripts are seldom practiced in dental education, and the prospect of structured integration is almost never addressed. Objectives: To evaluate the effectiveness of applying systematic and integrated case-based discussion in dental education in terms of enhancing five essential skills to novice Indian dental students. Methods: A mixed- methods study was carried out with thirty graduating third-year students in 5focus groups. The integrated case-based focused group training occurred in 6 weeks and lasted approximately 90 minutes per discussion. Ten case scripts of hypothetical situations were discussed and five integrated modules were organized as a part of this program. Revised Bloom’s taxonomy was adopted to achieve the expected level of competency. Results: Students performance following integrated case-based discussions was improved and their acceptance to this practice is positive. Conclusions: The present study supports the need for course specific, basic science integrated seminars with concurrent case scripts discussion to enhance students’ competencies

Prophylactic Efficacy of Amifostine, DRDE-07, and their Analogues against Percutaneously Administered Nitrogen Mustards and Sulphur Mustard

Nitrogen mustards (HN-1, HN-2 and HN-3) and sulphur mustard are alkylating and blister-inducing chemical warfare agents. This study was aimed at investigating the prophylactic efficacy of amifostine, DRDE-07, and their analogues and some recommended antidotes against dermally-applied nitrogen mustards and sulphur mustard in preventing their systemic toxicity in mice. The antidotes were administered as single oral dose, 30 min prior to the mustard agent application. For DRDE-07, 0.2 LD50 (249 mg/kg) was used and for other analogues, equimolar dose of DRDE-07 was used. For amifostine, N-acetyl cysteine, melatonin and sodium thiosulphate, oral dose was 185 mg/kg, 250 mg/kg, 250 mg/kg, and 1000 mg/kg respectively. The animals were observed for mortality for 14 days. The protection index (PI) was calculated as a ratio of LD50 with treatment to LD50 without treatment. The protection of the antidotes was also determined by intraperitoneal route and half of the oral dose of the antidotes was given. The estimated percutaneous LD50 of HN-1, HN-2, HN-3 and sulphur mustard was 11.9 mg/kg, 20.0 mg/kg, 7.1 mg/kg and 7.1 mg/kg, respectively. Compounds that showed marginal protection against HN-1 were DRDE-10 and melatonin with a PI of 1.4. Compounds that showed marginal protection against HN-2 were amifostine, DRDE-07, DRDE-09, DRDE-30, DRDE-35 and melatonin with a PI of 1.4. Compounds that showed marginal protection against HN-3 were amifostine, DRDE-30, DRDE-35, sodium thiosulphate and melatonin with a PI of 1.7. In the case of sulphur mustard, DRDE-07, DRDE-10, DRDE-21, DRDE-30, and DRDE-35 gave a good protection with a PI of more than 5.0. Amifostine and sodium thiosulphate gave a PI of 4.5 and 4.0, respectively, while DRDE-09, N-acetyl cysteine and melatonin gave less protection against sulphur mustard. Intraperitoneally administered amifostine, DRDE-30, sodium thiosulphate and melatonin gave marginal protection against HN-2 with a PI of 1.2, while intraperitoneally administered amifostine, DRDE-07, DRDE-09, DRDE-10, DRDE-30, DRDE-35 and melatonin gave excellent protection against percutaneously administered sulphur mustard with a PI of more than 5.0. The present study shows, that oral and intraperitoneal administration of amifostine, DRDE-07 and their analogues are effective as prophylactic agents for sulphur mustard systemic toxicity, but not against nitrogen mustards.Defence Science Journal, 2009, 59(5), pp.512-516, DOI:http://dx.doi.org/10.14429/dsj.59.155