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We assessed serum homocysteine (tHcy) and folate concentrations among US adolescents before and after fortification of cereal-grain products with folic acid, and associations with demographic, behavioural and physiological factors.
Observational study conducted among participants of a randomized trial.
The Child and Adolescent Trial for Cardiovascular Health (CATCH) study.
Adolescents (n 2445) in grades 8 (pre-fortification, mean age 14 years) and 12 (post-fortification, mean age 18 years).
Average serum concentrations of tHcy, folate and vitamin B6 increased by 17 %, 16 % and 14 %, respectively, while serum concentrations of vitamin B12 decreased by 11 % post-fortification. Folic acid fortification provided, on average, an additional intake of 118 μg folate/d. Male sex (P < 0·0001) and white race (P = 0·0008) were associated with significantly greater increases in tHcy concentration, while increases in BMI (P = 0·006) and serum folate concentration (P < 0·0001) were associated with significant decreases in tHcy concentration. Female sex (P < 0·0001), non-smoking (P < 0·0001), use of multivitamins (P < 0·0001) and higher dietary intake of folate (P = 0·001) were associated with significantly greater increases in serum folate concentrations. From grade 8 to grade 12, the upward age trend in serum tHcy concentration was uninterrupted in its course (P > 0·50); whereas serum folic acid concentration showed a downward trend that incurred a discrete jump upward (17 % higher; P < 0·0001) with fortification. These trends differed significantly for males v. females (P < 0·001 for interaction).
Fortification had a significant impact on improving folate status but not serum tHcy concentrations among US adolescents.
A FIMAG Working Party was set up in 1989 to consider the stochastic investment model proposed by A. D. Wilkie, which had been used by a number of actuaries for various purposes, but had not itself been discussed at the Institute. This is the Report of that Working Party. First, the Wilkie model is described. Then the model is reviewed, and alternative types of model are discussed. Possible applications of the model are considered, and the important question of ‘actuarial judgement’ is introduced. Finally the Report looks at possible future developments. In appendices, Clarkson describes a specific alternative model for inflation, and Wilkie describes some experiments with ARCH models. In further appendices possible applications of stochastic investment models to pension funds, to life assurance and to investment management are discussed.
This paper describes the development of a nitrogen-based passivation technique for interface states near the conduction band edge [Dit(Ec)] in 4H-SiC/SiO2. These states have been observed and characterized in several laboratories for n- and p-SiC since their existence was first proposed by Schorner, et al. . The origin of these states remains a point of discussion, but there is now general agreement that these states are largely responsible for the lower channel mobilities that are reported for n-channel, inversion mode 4H-SiC MOSFETs. Over the past year, much attention has been focused on finding methods by which these states can be passivated. The nitrogen passivation process that is described herein is based on post-oxidation, high temperature anneals in nitric oxide. An NO anneal at atmospheric pressure, 1175°C and 200–400sccm for 2hr reduces the interface state density at Ec-E ≅0.1eV in n-4H-SiC by more than one order of magnitude - from > 3×1013 to approximately 2×1012cm−2eV−1. Measurements for passivated MOSFETs yield effective channel mobilities of approximately 30–35cm2/V-s and low field mobilities of around 100cm2/V-s. These mobilities are the highest yet reported for MOSFETs fabricated with thermal oxides on standard 4H-SiC and represent a significant improvement compared to the single digit mobilities commonly reported for 4H inversion mode devices. The reduction in the interface state density is associated with the passivation of carbon cluster states that have energies near the conduction band edge. However, attempts to optimize the the passivation process for both dry and wet thermal oxides do not appear to reduce Dit(Ec) below about 2×1012cm−2eV−1 (compared to approximately 1010cm−2eV−1 for passivated Si/SiO2). This may be an indication that two types of interface states exist in the upper half of the SiC band gap – one type that is amenable to passivation by nitrogen and one that is not. Following NO passivation, the average breakdown field for dry oxides on p-4H-SiC is higher than the average field for wet oxides (7.6MV/cm compared to 7.1MV/cm at room temperature). However, both breakdown fields are lower than the average value of 8.2MV/cm measured for wet oxide layers that were not passivated. The lower breakdown fields can be attributed to donor-like states that appear near the valence band edge during passivation.
This paper presents a review of new results obtained by a combination of first-principles theory, Z-contrast imaging, and electron-energy-loss spectroscopy in the context of a broader experimental/theoretical program to understand and control the atomic-scale structure of SiCSiO2 interfaces. The ultimate purpose is to achieve low interface trap densities for device applications. Results are given for global bonding arrangements in comparison with those of the Si-SiO2 interface, the mechanism of the oxidation process, the nature of possible interface defects and their passivation by N and H, and the formation and dissolution of C clusters in SiO2 during oxidation and reoxidation.
We report the fabrication of modulation doped Si/Gex Si1−x heterostructures by molecular beam epitaxy. The samples are characterized by Rutherford backscattering spectrometry, cross-sectional transmission electron microscopy, electron beam induced current, Hall measurement, and the magnetoresistance (Shubnikov-de Haas) measurements. Threading dislocation densities of = 106cm−2 are observed for relaxed Ge0.3Si0.7 films on Si (100). The modulation doped structures fabricated on these Ge0.3 Si0.7 films contain two-dimensional electron gases with mobilities ranging from 60,000 to 96,000 cm2/V - s at 4.2 K.
We have grown linearly compositionally graded GexSi1−x structures at high temperatures (700–900°C) on Si substrates to form a surface which resembles a GexSi1−x substrate. We have obtained completely relaxed structures with x≤0.50 and threading dislocation densities in the 105cm−2 - 106cm−2 range. Because of the very low threading dislocation densities, the structures appear dislocation free in conventional transmission electron microscopy (TEM) cross-section and plan view. Employing the electron beam induced current technique (EBIC), we were able to consistently measure these low threading dislocation densities. A direct comparison of two x=0.35 films, one graded in Ge content and one uniform in Ge content, shows that compositional grading decreases the dislocation density by a factor of 100–1000. These. higher quality graded buffers have been used as templates for the subsequent growth of InGaP light emitting diodes (LED) and GexSi1−x/Si two-dimensional electron gas (2DEG) structures. Room temperature operation of orange-red LEDs were obtained at current densities of =600A/cm, and mobilities as high as 96,000 cm2/V-s were achieved at 4.2K in the 2DEG structures.
In this paper we discuss results for the clustering of Ga on GaAs(001). The dominant dynamic process which drives this system toward this three dimensional equilibrium changes from Ostwald ripening at low deposition rates to coalescence at higher deposition rates. The experimental data allow us to test several theoretical predictions for cluster size distributions based on a detailed study of the microscopic processes. These include, at higher deposition rates, the observation of local ripening effects and diffusion limited growth.
To develop and characterise an experimental model of recurrent laryngeal nerve injury for the study of viral gene therapy.
Twenty rats underwent unilateral recurrent laryngeal nerve injury. After vocal fold mobility was observed, larynges were serially sectioned, and immunohistochemical techniques were employed to stain for neurofilament and motor endplates in order for a blinded investigator to determine the percentage of nerve–endplate contact, as a histological indicator of an intact neuromuscular connection.
All animal procedures resulted in complete, ipsilateral vocal fold paralysis that recovered by three weeks. The mean nerve–endplate contact percentage was 11.6 per cent at one week, 53.9 per cent at two weeks, 88.6 per cent at three weeks, 81.7 per cent at four weeks and 86.6 per cent at five weeks. The differences between results at week one and week three were statistically significant (p < 0.01). The mean nerve–endplate contact percentage on the control side was 86.8 per cent.
There was a dramatic, measurable decrease in nerve–endplate contact percentage following crush injury to the recurrent laryngeal nerve. Spontaneous recovery was observed by three weeks post-injury. This model will be used to investigate the potential therapeutic role of viral gene therapy for the treatment of recurrent laryngeal nerve injury.
In August 2003, an outbreak of scombroid fish poisoning occurred at a retreat centre in California, USA. In a retrospective cohort study, 42 (75%) of the 56 dinner attendees who ate escolar fish (Lepidocybium flavobrunneum) met the case definition. Individuals who ate at least 2 oz of fish were 1·5 times more likely to develop symptoms than those who ate less (relative risk 1·5, 95% confidence interval 0·9–2·6), and to develop more symptoms (median 7 vs. 3 symptoms, P=0·03). Patients who took medicine had a longer duration of symptoms than those who did not (median 4 vs. 1·5 h, P=0·05), and experienced a greater number of symptoms (median 8 vs. 3 symptoms, P=0·0002). Samples of fish contained markedly elevated histamine levels (from 2000 to 3800 ppm). This is one of the largest reported outbreaks of scombroid fish poisoning in the United States and was associated with a rare vehicle for scombroid fish poisoning, escolar.
Few controlled studies have examined the use of atypical antipsychotic drugs for prevention of relapse in patients with bipolar I disorder.
To evaluate whether olanzapine plus either lithium or valproate reduces the rate of relapse, compared with lithium or valproate alone.
Patients achieving syndromic remission after 6 weeks'treatment with olanzapine plus either lithium (0.6–1.2 mmol/l) or valproate (50–125 μg/ml) received lithium or valproate plus either olanzapine 5–20 mg/day (combination therapy) or placebo (monotherapy), and were followed in a double-masked trial for 18 months.
The treatment difference in time to relapse into either mania or depression was not significant for syndromic relapse (median time to relapse: combination therapy 94 days, monotherapy40.5 days; P=0.742), but was significant for symptomatic relapse (combination therapy 163 days, monotherapy42 days; P=0.023).
Patients taking olanzapine added to lithium or valproate experienced sustained symptomatic remission, but not syndromic remission, for longer than those receiving lithium or valproate monotherapy.
A general relation between the rate of onset and rate of recovery from non-depolarizing blockade has been demonstrated, with recovery consistently about ten times slower than onset. This observation has led to the suggestion that non-depolarizing agents share a common mechanism of action. Rocuronium, a recently introduced steroidal non-depolarizing agent, is claimed to have a very rapid onset but an intermediate duration and appears to test this hypothesis. To investigate this paradox we have calculated the rates of onset and recovery of rocuronium using the isolated human forearm and compared them with those of pipecuronium. The mean ratio of recovery time/onset time for rocuronium was 31.3, which is significantly greater than that for pipecuronium, 11.6 (P < 0.01). Whilst pipecuronium conforms to the same general relation between onset and offset described previously for other non-depolarizing agents, rocuronium appears to have a disproportionately rapid rate of onset for its rate of recovery. This suggests that onset, recovery, or both onset and recovery, from rocuronium blockade occur in a different manner to that of other non-depolarizing agents.
1.1. In this note it is argued that models of the gilt-edged market which are based on yield curves are unnecessarily restrictive and should not be expected to give a satisfactory statistical ‘fit’ in current conditions. The new model which is formulated relates market prices directly to the life and coupon without diverting into the computation of redemption yields. Indeed, it is suggested that the yield calculation destroys the inherent simplicity of the underlying equations—which follow from a simple assumption concerning the return from different portfolios. The method avoids the inconsistency inherent in the conventional analysis of discounting future investment proceeds at a uniform rate of interest when the yield curve itself implies that interest rates will vary in the future.
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