Dynamical behaviour of intrinsic Josephson junctions

Intrinsic Josephson Junctions (IJJs) are the subject of much of research due to their potential applications as high frequency oscillators and detectors in the THz range. A number of previous studies use a single junction model to explain their observations, as no fully agreed model for coupled IJJs exists. The influence of one or more IJJs in the voltage state on other junctions in the IJJ array is not yet fully understood. I have studied the dynamical behaviour of Tl_2Ba_2CaCu_2O_8 thin film IJJ arrays, focussing on how one junction in the voltage state influences the other junctions. This I have done by measuring (a) the switching current distributions, and (b) the influence of r.f. irradiation on the DC current-voltage characteristics. I have compared the switching current distributions when switching from the supercurrent branch with those when switching from the first quasiparticle branch. The supercurrent branch was found to be overdamped at the escape frequency whereas the first quasiparticle branch is underdamped, resulting in a larger switching current for the former than the latter. RF irradiation suppresses the mean switching current on the supercurrent branch accompanied by the appearance of a low-voltage flux flow branch. There is however no effect on the switching current of the quasiparticle branches. I explain these results in terms of the dissipative environment in which the junctions are embedded, and, furthermore, that switching of a single IJJ into the voltage state significantly changes the dissipation. IJJs were sub sequently isolated from their environment by FIB-deposited tungsten resistors of resistance between 100 and 500 Ω. The complete resistor-junction-resistor (RJR) structure is multibranched and shows a change in the DC current-voltage characteristics below and above the T^c of the tungsten. However, the presence of high resistance in the RJR structure at 4.2 K needs further investigation

Qualitative Assessment Of Bottled Water In The Middle East

Many brands of bottled water are being produced in the Middle East including the Gulf Cooperation Council (GCC) countries. Over fourteen brands of bottled water could be found in the market of Doha. Use of bottled water has kept on increasing in this region. Reasons for the increase in use of bottled water for drinking have been discussed. The raw water source for the bottled water is groundwater. Most of the manufacturers of the bottled water claim bottled water as "Natural Mineral Water" which is contrary to the definition suggested by the International Bottled Water Association of Washington D.C. In fact there is no such thing as "mineral water" and the term is a misnomer. Samples of various brands of bottled water available in Doha and municipal water were collected during 1993 and 1994 for physical, chemical, and bacteriological analysis. All the samples were found potable and safe for drinking and conform to various drinking water standards. The physical and chemical composition of bottled water varies with time but the concentration of constituents printed on the labels of bottles is always the same. It may be preferable to print the range of concentration on the labels rather than a single value. Moreover the analysis should be monitored and certified by a competent authority, and should be displayed on the label

Effects of Trade Openness on Economic Growth: The Case of African Countries

The relationship between trade and productivity has not been established theoretically. Some researchers have indeed found some, if not complete, support for the view that increasing openness has a positive impact on productivity. This study used a Cobb-Douglas production function as in Miller and Upadhyay (2000) to estimate the impact of FDI, exchange rate, capital-labor ratio and trade openness on GDP for 38 African countries from 1980 to 2008. Data were transformed to natural logs and estimated using alternative panel models; which included one- or-two-way fixed or random effects models. The results found trade openness having a positive relationship with GDP; which is comparable to findings of Ahmed et al.; (2008).Trade Openness, Productivity, Africa, Cobb Douglas Production Function., International Development, International Relations/Trade, Productivity Analysis,

Induced abortions in low socio-economic settlements of Karachi, Pakistan: rates and women\u27s perspectives

Objective: The aim of the study was to determine rates on induced abortions and to identify the perceived and actual reasons for terminating an unplanned pregnancy, health care providers sought, methods used and post-abortion complications.SETTING: Three squatter settlements of Karachi, Pakistan.SUBJECTS: Interviews were conducted on 1,214 ever-married women in the reproductive age group (15-49) with a reproductive history of at least one pregnancy, irrespective of outcome.Methods: A cross-sectional survey from June-August 1997 was conducted in three selected squatter settlements of Karachi.Results: The abortion rate for the past year was 25.5 per 1,000 women of reproductive age group. The post-abortion complication rate reported was 68.5% (61/89), of which fever and heavy vaginal bleeding was the most commonly reported complication (54.1%).CONCLUSION: The results indicate that women are aware of the high mortality and morbidity risk resulting from seeking an unsafe abortion but nevertheless opt for this approach to attain their goal of small family size rather than for a modern method of contraception. Furthermore, healthcare providers, irrespective of legality issues, provide such services due to demand. We suggest that family physicians and other relevant health care providers be trained for post-abortion care including post-abortion family planning counseling with an emphasis on emergency contraceptives

Facilitating inter-spousal communication for birth spacing--a feasibility study of Pakistani couples for policy implications

Objective: To test three practices introduced to couples for adaptation of a non-permanent modern method of family planning and the role that each partner played during the process.SETTING: Urban and sub-urban areas of Karachi, Lahore, and Quetta.Methods: \u27Behavioral trials\u27 was conducted which is a formative research method in which researcher and participants negotiate behavior(s) that the participant agrees to try for a specific amount of time. Interviews were conducted on 72 married couples (144 men and women) living in urban and sub-urban areas of Karachi, Lahore and Quetta. Study participants were either non-users of modern methods of family panning, or using traditional methods. The three behaviors negotiated were: a) Discuss benefits of birth spacing with spouse; b) discuss specific methods of family planning and decide on the most appropriate one and c) initiate use of a modern temporary method of family planning.Results: After the introduction of first practice, of 72 couples 38 reported failure to initiate the discussion with their spouse. Where women initiated the discussion the response from spouse was not as favorable as where men initiated the discussion. After introduction of second practice 28 couples were successful in discussing about selection of a family planning method. Twenty-four couples finally selected and used a method. Traditional users were more likely to adopt a modern method than non-users, especially those with 3-5 children.CONCLUSION: Strategies to cultivate a culture of inter-spousal communication on use of family planning methods should be developed as a component of family planning programs