SIMS depth profiling of multilayer metal-oxide thin films — improved accuracy using a xenon primary ion

Multilayer thin films containing silver and copper, sandwiched in a metal oxide, have been depth profiled by secondary ion mass spectrometry (SIMS) using primary ions of differing mass, energy and chemical reactivity. These results were compared for accuracy with those obtained by Rutherford backscattering spectrometry (RBS). The use of O₂⁺ or O^? as primary ions resulted in severe distortion of the silver ion intensity distribution in the SIMS profile of a ZnO/Ag/ZnO thin film on glass; O₂⁺ bombardment at energies from 3–10 keV resulted in the detection of silver at the glass interface, while the use of O^? caused the silver to be detected closer to the outer surface than expected from RBS results. Primary beams of Ar⁺ and Xe⁺ gave progressively more accurate results for the Zn/Ag/Zn distribution; Xe⁺ at 5.0 keV energy produced profiles that agreed within 10% of RBS-derived values. The same beam conditions, used to profile a double silver layer in ZnO, resulted in some discrepancy in the position of the inner layer, compared to RBS results, and this was attributed to an enhanced sputter rate in the oxide under the outside metal film. Depth profiling of TiO₂/Cu/TiO₂ films with oxygen also resulted in significant distortion of the perceived position of the metal layer, and this was again significantly improved using Xe⁺ primary ions of 6–9 keV energy. The distorting effects of oxygen bombardment can be understood in terms of a migration of metal ions in an electrostatic field created by a charged surface. Ionization of the metallic layer is enhanced by the use of oxygen. By contrast, the use of rare gases reduces the production of ions from the metallic layer which can migrate prior to the onset of sputtering.     

Pricing Risky Debts Under a Markov-modudated Merton Model with Completely Random Measures

We consider the pricing of both fixed rate and floating rate risky debts when the value of a firm is governed by a Markov-modulated generalized jump-diffusion model with the jump component described by a completely random measure process with a Markov-switching compensator; that is, the compensator switches over time according to the states of an economy modelled by a continuous-time Markov chain. We shall employ the well-known tool in actuarial science, namely, the Esscher transform, to determine the price of the risky debts. We shall investigate consequences for the prices of the risky debts of various parametric specifications of the jump component. Sensitivity analysis for the prices of the risky debts with respect to various model parameters will be conducted. We also compare the pricing results obtained from our model with those from the celebrated Merton jump-diffusion model to illustrate the effect of correlated jump times and sizes on the prices of the debts.     

Synthesis and characterization of doped nano-sized ceria–zirconia solid solutions

Two compositions Ce_0.50Zr_0.39La_0.04Y_0.07O_2−δ and Ce_0.25Zr_0.65La_0.04Y_0.06O_2−δ based on ceria-zirconia solid solutions were prepared as nanopowders using a continuous hydrothermal flow synthesis reactor, followed by either freeze-drying or hotplate-drying of the slurry. Each dried nanopowder was then subjected to 10 h heat-treatment at 1000 °C, 1100 °C or 1200 °C in air (to simulate accelerated ageing). The reducibility and hydrogen consumption of the oxidised samples were measured using temperature programmed reduction (TPR) up to 1000 °C. The effects of composition, drying method and heat-treatment temperature were evaluated on the TPR profiles of the materials. The powders were further investigated using a range of analytical methods including UV/Vis spectroscopy (which yielded colour data), Raman spectroscopy, powder X-ray diffraction, BET surface area measurements and X-ray photoelectron spectroscopy (XPS). Chemometric methods were used to investigate relationships between the spectroscopic and total oxygen storage capacity (OSC) data. Principal component analysis (PCA) was used to provide a simple interpretation of the effects of various synthesis and treatment parameters on Raman spectra. Principal component regression (PCR) was used to build regression models relating the Raman spectra and the temperature of hydrogen consumption peak at several set temperatures in the TPR. The total hydrogen consumption of the materials was generally high, while the drying and heat-treatment conditions appeared to have a significant effect on the final properties of the resulting powders, such as the surface area and total oxygen storage capacity.     

DUAL SOURCING COST-OPTIMIZATION WITH UNRESTRICTED LEAD-TIME DISTRIBUTIONS AND ORDER-SPLIT PROPORTIONS

Among recent studies considering the splitting of an order among several suppliers (i.e., in “multiple sourcing”), one group considered only the favorable effect of multiple suppliers on the effective lead time demand and required safety stock, but its effects on the annual order and holding cost components have been ignored. Another group that considers the effect of using two suppliers on all relevant cost components imposes severe restrictions on the suppliers' lead-time distributions as well as the proportion of order-split between the suppliers. Our primary purpose is to present easily-solvable decision models for minimizing the sum of annual holding and ordering costs with two suppliers, subject to a maximum allowable stockout risk; restrictions on lead-time distributions and order-split proportion are completely eliminated. Solving these models gives the optimal total order quantity, reorder point and proportion of split between the two suppliers. Numerical results from our models reveal some unexpected observations; e.g.: (i) In using two suppliers, die reduction of inventory carrying cost (a hitherto unrecognized component) is at least as important, and often considerably more important than the effect of safety-stock-cost reduction, (ii) Although intuitively one might use suppliers with the shortest (mean) lead times, it is actually better to have two suppliers such mat the second supplier's mean lead time is “suitably” larger man the first's; this could mean excluding the one with lowest mean lead times among the candidates for the second supplier, (iii) The optimal proportion of split varies with, among other factors, the difference in the suppliers' mean lead times.     

Step-tunable all-optical wavelength conversion usingcavity-enhanced four-wave mixing

Step tuning of a wavelength converter using cavity-enhanced four-wave mixing in a multimode semiconductor laser is experimentally and theoretically demonstrated. The converter is modulation-format transparent and is shown experimentally to have a high conversion efficiency (>-10 dB) and to be step-tunable over a large conversion range (>2.5 THz). A mathematical model of the wavelength converter is derived and is used to simulate step tuning of this device and to examine the relationship between conversion efficiency and information bandwidth of the converter     

Quinine for nocturnal leg cramps: a meta-analysis including unpublished data

OBJECTIVE: With respect to the use of quinine for the treatment of nocturnal leg cramps, to determine whether the findings of a previously performed meta-analysis of published data are altered with the addition of unpublished data, and whether publication bias is present in this area. DESIGN: A meta-analysis of eight (four published and four unpublished) randomized, double-blind, placebo-controlled trials, seven of which had a crossover design. SETTING: Randomized trials that were available as of July 1997. SUBJECTS: Ambulatory patients (659) who suffered from regular nocturnal leg cramps. MAIN RESULTS: When individual patient data from all crossover studies were pooled, persons had 3.60 (95% confidence interval [CI] 2.15, 5.05) fewer cramps in a 4-week period when taking quinine compared with placebo. This compared with an estimate of 8.83 fewer cramps (95% CI 4.16, 13.49) from pooling published studies alone. The corresponding relative risk reductions were 21% (95% CI 12%, 30%) and 43% (95% CI 21%, 65%), respectively. Compared with placebo, the use of quinine was associated with an increased incidence of side effects, particularly tinnitus. Publication bias is present in the reporting of the efficacy of quinine for this indication, as almost all published studies reported larger estimates of its efficacy than did unpublished studies. CONCLUSIONS: This study confirms that quinine is efficacious in the prevention of nocturnal leg cramps. However, its benefit may not be as large as reported from the pooling of published studies alone. Given the side effect profile of quinine, nonpharmacologic therapy (e.g., regular passive stretching of the affected muscle) is the best first-line treatment. For persons who find this ineffective and whose quality of life is significantly affected, a trial of quinine is warranted. Prescribing physicians must closely monitor the risks and benefits in individual patients. Publication bias is present in this area even though there is controversy about the role of quinine in the treatment of leg cramps. To minimize the possibility of this bias, persons performing medication-related meta-analyses should seek high-quality unpublished data from drug regulatory agencies and pharmaceutical companies.     

Gamma-interferon activates a nuclear protein that binds to the gamma-interferon activation site of the thyroglobulin gene

In 1989, a population-based cohort of persons aged > or = 50 years was established in an urban area of Guinea-Bissau, West Africa. Overall, 346 persons were interviewed in detail about risk behaviors and had capillary blood drawn. Among women, 12.4% were HTLV-1 seropositive, compared with 4.6% in men. No HTLV-2 was found. Seropositivity varied considerably according to place of birth and ethnic group. In women, but not in men, HTLV-1 seropositivity was strongly associated with early sexual debut (10-14 yrs, 33.3%; 15-17 yrs, 26.0%; 18-20 yrs, 6.5%; 21+ yrs, 0%; ptrend = 0.001), lifetime number of male partners (ptrend = 0.006), and the male partner's number of co-wives (ptrend = 0.006). There was also a 3.1-fold increased risk of being HTLV-1 seropositive if the woman was also HIV-2 seropositive. In a multivariate-risk-factor analysis, the strongest association with HTLV-1 was a history of having been bitten by a monkey (n = 11; combined OR adjusted = 10.1; 95% CI 2.3-44.4). Ornamental scarification was associated with a 3.3-fold increased risk. Ethnic affiliation also significantly influenced the risk of being HTLV-1 seropositive. Follow-up performed in January 1996 revealed no difference in survival between HTLV-1-seropositive and -seronegative individuals over 6 years (rate ratio = 1.4, 95% CI 0.7-2.8). In conclusion, this population, which has very high HIV-2 seroprevalence, is also highly endemic for HTLV-1. Whereas sexual behaviors are clearly important for HTLV-1 spread in women, non-sexual risk factors were the only ones of potential importance in men. HTLV-1 had no impact on survival in this older population.     

Age differences in hostility among middle-aged and older adults.

Multiple measures of hostility were administered to middle-aged and older volunteers. There was a positive association between age and self-report measures reflecting hostile beliefs about others, including cynicism and suspiciousness. There was a weak inverse relationship between age and self-report measures of the overt expression of anger and aggression, but no association between age and measures of covert hostility was found. There was a positive relationship between age and an assessment of hostile behavior that was based on the respondent's interaction style during an interview. The magnitude of these age trends did not differ between men (n?=?50) and women (n?=?75). Findings illustrate the multidimensional nature of hostility. They also have practical implications for older people because hostility is associated with psychological well-being and has been shown to have consequences for health and longevity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Evaluation of a selective transport medium for gastric biopsy specimens to be cultured for Helicobacter pylori

Since the means of culturing Helicobacter pylori may not be available in some laboratories, prolonging the survival of this organism during transportation is a major concern in terms of improving detection rates. A selective transport medium was evaluated for the preservation of H. pylori from 254 gastric biopsy specimens collected from a rural area in China where culturing is not feasible. Gastric biopsy specimens were inoculated in sterile broth consisting of brain heart infusion (BHI) broth, horse serum, and yeast extract supplemented with vancomycin, amphotericin B, and nalidixic acid (VAN). Of the 254 biopsy specimens, 238 were identified by histology to have H. pylori infection. Total rates of recovery of H. pylori from the H. pylori-positive gastric biopsy specimens stored in the BHI-VAN broth ranged from 76 to 46% after storage of specimens for 5 to 9 days. In conclusion, the selective medium is useful for prolonging the survival of H. pylori in gastric biopsy specimens for which immediate culture is not feasible.