Silicon doping by nuclear transmutation

This paper describes, from the view of nuclear physics and radiochemistry, the mode of operation in doping semiconductor silicon with phosphorus by neutron irradiation. In addition to precise control of the irradiation fluence, this includes control of neutron-flux distribution, self-shielding and radioactive products from the silicon matrix and the surface impurities. The accuracy of the resistivity values achieved by this method is better than ± 5% at the predicated value. The good homogeneity of the dopant distribution is shown by the results of location-resolving resistivity measurements as well as by the breakdown radiation emitted by diodes. Neutron-bombarded homogeneously doped silicon (NBH-silicon) is used for routine manufacture of multi-diode vidicons and power devices.     

Neural networks provide superior description of Giardia lamblia inactivation by free chlorine

Use of conventional models to describe data on microbial inactivation during disinfection suffers from limitations with respect to flexibility and direct quantitative incorporation of water quality variables. This paper develops an approach to analysis of such data using neural networks (NNs). Using the data on free chlorine inactivation of Giardia lamblia previously reported, it was found that the use of an NN with a single hidden layer and four hidden neurons provided a superior (better) fit to the data with a reduced number of model parameters when compared to the fitting of this data using a conventional approach. Therefore, the use of NN models should be considered in the future assessment of microbial inactivation during disinfection. Incorporation of additional facets of the disinfection process, such a disinfectant decay, needs to be considered in subsequent development of this approach.     

Bupropion in breast milk: an exposure assessment for potential treatment to prevent post-partum tobacco use

Objectives: To assess potential infant exposure to bupropion and its active metabolites in breast milk such as would occur during treatment to prevent post-partum relapse to tobacco use, and to compare the concentrations of bupropion in urine and saliva with plasma and breast milk.

Design and setting: Cohort study, outpatient clinical research centre.

Subjects: Ten healthy post-partum volunteers who agreed to take bupropion for seven days, pump and discard their breast milk, and have samples of breast milk, plasma, saliva, and urine analysed.

Intervention: Bupropion 150 mg a day for three days and then 300 mg a day for four days.

Main outcome measures: Concentrations of bupropion and its active metabolites (hydroxybupropion, erythrohydrobupropion, threohydrobupropion) in breast milk, plasma, saliva, and urine. Determination of average infant exposure.

Results: The calculated average dosage of bupropion in breast milk was 6.75 µg/kg/day. Therefore, the average infant exposure is 0.14 % of the standard adult dose of bupropion, corrected for the difference in body weight. Considering the sum of bupropion and its active metabolites, the average infant exposure is expected to be 2% of the standard maternal dose on a molar basis. The concentration of bupropion and its active metabolites in breast milk was not associated with age, body mass index, use of oral contraceptive pills, age of infant, or the frequency of breast feeding at the time the study was initiated. The coefficient of determination (r²) between the concentration of bupropion in breast milk and in urine was 0.77 (p < 0.01).

Conclusions: Bupropion and its active metabolites are present in the breast milk of lactating women. The concentrations of bupropion in breast milk and urine were highly correlated. These results indicate that the daily dose of bupropion and metabolites that would be delivered to an infant of a woman taking a therapeutic dose of bupropion is small. These results suggest that the effectiveness of bupropion to prevent post-partum relapse to tobacco use should be evaluated without excluding women who plan to breast feed.

     

A new removable resist for high aspect ratio applications

A variety of different photo resists are used for fabrication of MEMS. Presently good results were reported for SU-8, a chemically amplified negative tone photoresist. But SU-8 has a disadvantage for some applications in LIGA technique, especially in the X-ray mask fabrication. After processing the finished resist pattern are hardly soluble from the substrate. This paper will briefly describe the current status of the development of the new negative tone photoresist CAR 44 whose big advantage is the easy removableness of the cross linked pattern. This work widely uses the contents of the presentation “A New Removable Resist for High Aspect Ratio Applications” to the High Aspect Ratio Micro Structure Technology workshop HARMST 2005 held in Gyeongyu (Republic of Korea), June 10–13, 2005.     

Teachers' stereotypes of Asian, Black, and White students.

This research uses two different measurement operations to examine contemporary stereotypes of Asians, Blacks, and Whites held by an ethnically diverse sample of teachers. Data were drawn from a sample of 188 teachers representing over 160 schools in Southern California. Consistent with previous research, participants endorsed a "model minority" stereotype of Asians with regard to intelligence, academic striving, introversion, and rule compliance. Contrary to expectation, there was substantial congruence in the degree of uniformity and favorableness of the stereotypic traits associated with Blacks and Whites, with participants' revealing both strong positive and negative trait associations. The use of both open-ended and fixed-format measurement strategies revealed some method variation in the assessment of participants racial beliefs, with the open-ended format suggesting more complex and heterogeneous racial representations. Results are discussed in terms of methodological issues in stereotype assessment and implications for reducing the impact of racial biases in psychoeducational evaluations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Excessive cross-linking of caseins by microbial transglutaminase and its impact on physical properties of acidified milk gels

By varying cross-linking intensity, the effect of microbial transglutaminase on acid gels made from casein solution and raw milk was studied. To avoid any impact of heating, N-ethylmaleimide was used for enzyme inactivation after appropriately checking its efficiency. Up to a specific degree of oligomerisation gel stiffness and firmness increased and tan δ, time at gelation onset and syneresis decreased. Above approximately 70% and 25% of cross-linked protein in casein solution and raw milk, respectively, these parameters showed an opposite behaviour, and weak gels with high syneresis were obtained. Substrate differences, such as preferred cross-linking of adjoining κ-caseins on the surface of the micelle enhanced the effect of steric hindrance in raw milk and impaired proper rearrangements upon acidification at a much lower level of oligomerised protein. It is mainly dimeric and trimeric casein that successfully contributed to the enhanced properties of milk protein gels.     

Fullerene-functionalized carbon nanotubes as improved optical limiting devices

We report the synthesis, characterization and optical limiting behavior of a nanohybrid built by grafting C₆₀-fullerenes on carbon nanotubes (CNTs). The nonlinear optical limiting properties of the CNT-C₆₀ complex were investigated at wavelengths where C₆₀ does not absorb. We found that the nanohybrid had superior performances to those of CNTs and fullerenes, either taken individually or as a mixture. This enhanced optical limitation of the nanohybrid suggests not only cooperative but also synergistic effects between the two carbon forms. A mechanism involving higher excitonic states of the CNTs formed by Auger recombination of low energy excitons is proposed.     

The stability of preferences for life-sustaining care among persons with AIDS in the Boston Health Study

In 1982, the World Health Organization (WHO) identified inadequate relief from cancer pain as an international health problem. WHO recommended that governments develop and implement national policies and programs for cancer pain relief. This report evaluates national health policy and the systems of health care delivery in relation to cancer pain management in the new South Africa. This field study included multiple methods of data collection: analysis of documents, field trips with participant observation in sites of care delivery, focused interviews, and in-depth interviews of key informants. The purposive sample of key informants (n = 33) represented multiple stakeholders in a variety of settings. Strengths of the developing health policy include specific recommendations related to palliative care; the shift to universal primary care; policies to support drug availability; the inclusion of morphine and codeine as essential drug at the primary health care level; and the development of a national standard related to cancer pain management. Health services are characterized by two parallel systems of care (private and public) with numerous vestiges of the inequities of apartheid. The management of pain varies by provider and setting; major problems with access exist in the rural areas. Health services in South Africa have been plagued by inequity and inadequate resources. New health policies have set a path to ensure universal access to health care including palliative care for cancer. Their successful implementation is the next necessary step toward improving health services and alleviating the suffering of increasing numbers of individuals with cancer.     

Development of a 100 W rechargeable bipolar zinc/oxygen battery

A bipolar filter press-type electrically rechargeable Zn/O2 battery has been developed. Reticulated copper foam served as substrate for the zinc deposit on the anodic side, and La0.6Ca0.4CoO3-catalysed bifunctional oxygen electrodes were used on the cathodic side of the cells. The 100cm2 unit cell had an open circuit voltage of 1.4V (O2) in moderately alkaline electrolyte. The open circuit voltage and the peak power measured for a stack containing seven cells were sim 10V and sim 90W, respectively. The current-potential behaviour was determined as a function of the number of bipolar cells, and the maximum discharge capacity was determined at different discharge rates.