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本文介绍了采用复合吸收剂净化天然气的试验结果,在现有三甘醇等脱水剂中添加单乙醇胺,在脱水的同时脱除H_2S,在保证净化气露点低于-21℃的条件下,使净化气中H_2S含量亦低于5mg/m～3。     

A controlled evaluation of an elementary school primary prevention program for eating problems

Researchers have recently called for the development of primary prevention of eating disorders programs aimed at elementary school students. The present study reports on the development of a curriculum for fifth graders designed to encourage healthy eating, exercise, and body image while discouraging calorie-restrictive dieting, exercising for weight loss, and the development of body dissatisfaction. The program consisted of ten lessons taught by the classroom teachers. The influence of the curriculum on (1) knowledge about nutrition, body fat, and dieting; (2) attitudes about fat people and own body (body esteem); and (3) behaviors, including attempts at weight reduction, consumption of fruits and vegetables, and exercising, were evaluated in a pre-post controlled experimental design. There were 222 white public school children who participated in both the pre- and posttesting, 167 of whom were in the classrooms receiving the curriculum. Results indicated that knowledge was broadly improved by the curriculum. There were information improvements in terms of nutrition, effects of dieting, and causes of body fat. Attitudinal changes were less pronounced, although the curriculum did positively affect attitudes about fat people. Behavior, including eating patterns, exercise patterns, weight reduction attempts, and teasing of fat children, was not changed by participation in the curriculum.     

Heterochromatin effects on the frequency and duration of LCR-mediated gene transcription

Organ transplantation is associated with an early bone loss that subsequently increases the risk of osteopenia and bone fractures. It is not known whether bone loss continues in long-term survivors, but persistent bone demineralization could further jeopardize an already diminished bone mass. To better define long-term bone status of kidney transplant recipients (KTR), we conducted cross-sectional and longitudinal evaluations of bone mineral density (BMD) in 70 KTR with a mean posttransplantation time of 8.1 years. BMD was determined by dual-energy X-ray absorptiometry and was repeated in 55 of the patients after a mean follow-up period of 22 +/- 5 months. Lumbar and femoral osteopenia, defined as a BMD lower than 2 standard deviations from mean value of sex- and age-matched controls, was present in 28.6% and 10.5% of patients, respectively. There was a significant negative correlation between cumulative prednisone dose and adjusted lumbar as well as femoral BMD (R = 0.45, P < 0.001 and R = 0.29, P < 0.05, respectively). Five patients had a vertebral BMD below a fracture threshold of 0.777 g/cm2. Vertebral fractures (VF) were found in four men and were associated with higher prednisone dosage (P < 0.05), larger cumulative prednisone dose (P < 0.05), and significantly lower BMD values. According to World Health Organization recent criteria for women, prevalences of lumbar and femoral osteopenia and lumbar and femoral osteoporosis in female patients reach 75%, 65%, 33%, and 10%, respectively. The longitudinal part of the study showed a persistent pathological lumbar demineralization process. Over the study period, BMD, expressed as a percentage of that of controls, decreased from 89 +/- 14% to 86 +/- 14% (P < 0.001). Annual change of bone mass was -1.7 +/- 2.8% per year. Accelerated vertebral bone loss (defined as a decrease of BMD, expressed as a percentage of that of controls, of more than 1% per year) was present in 56% of patients and was associated with higher prednisone dosage (P < 0.01). In conclusion, although VF are relatively infrequent in long-term survivors of renal transplantation, osteopenia is a frequent finding, and a substantial proportion of women present lumbar osteoporosis. An ongoing demineralization process of the spine is also demonstrated and probably contributes to long-term spinal osteoporosis incidence. Prednisone dosage remains the most constantly isolated risk factor.     

Model of a miniature pig catheterized for pharmacokinetic and pharmacodynamic studies of anti-infective agents

The purpose of this study was to examine the role of sleep problems in the etiology of nursing caries. Two-hundred mothers of children (104 with nursing caries and 96 caries free) from ages 2 to 4.5 years were surveyed to determine whether difficulty with child sleep and ensuing sleep-associated feeding might be related to the presence of nursing caries. Differences were noted between these two groups regarding: average number of nights the child slept through the night (P < 0.001); total hours of sleep per night (P < 0.05); frequency of night waking episodes (P < 0.01); feeding on demand upon waking (P < 0.01); using a bottle to assist with falling asleep at night (P < 0.001); and feeding in association with nap time (P < 0.001). Differences also were noted in regard to average age of weaning (P < 0.001). Our findings suggest that sleep problems among young children are a behavioral risk factor for night-time bottle use and early childhood caries.     

Diffraction of millimeter waves by projecting a shadow pattern onto a semiconductor

The transmission of millimeter waves through a semiconductor changes according to the amount of light falling on it. In the experiments reported here, a pattern of light and shadow is projected onto a sheet of semiconductor and the regions of greater and lesser transmission serve as a diffracting object for a millimeter-wave beam. The light source is a quartz tungsten halogen lamp. A lock-in amplifier is employed to overcome difficulties due to the differences in transmitted power being small.     

A study of reinforced refractory concretes

Results of a laboratory study of the properties of corundum concrete with metallic fibers of five compositions are presented. It is shown that some of the fibers affect favorably the strength and heat resistance of the concrete. Industrial tests of parts made of the suggested reinforced concrete have proved these conclusions.Translated from Ogneupory i Tekhnicheskaya Keramika, No. 11, pp. 22–24, November, 1996.     

Pi-coefficient analysis of update algorithms for adaptive systems

This paper finds the appropriate pi-coefficients for a parameter estimation adaptive system and uses them to analyze the stability of two estimation algorithms. The estimation error dynamics of the system are modeled by a linear time-invariant subsystem and a nonlinear time-varying update law in a feedback loop. Then the so-called max-p problems are formulated and solved to obtain the pi-coefficients for the linear subsystem and nonlinear update low. For the investigated system, the quantitative results show that the least-squares update algorithm has larger stability range than that of the gradient algorithm, and the σ-modification scheme gives larger stability ranges for both algorithms.     

Growth and characterization of hot-wall epitaxial CdTe on (111) HgCdTe and CdZnTe substrates

Thin CdTe films were deposited by hot-wall epitaxy (HWE) on (111) HgCdTe and CdZnTe substrates at temperatures from about 140 to 335°C. X-ray rocking curves were used to show that crystal quality of the CdTe (111)B films improved as substrate temperature increased from 140 to about 250°C. Rocking curve values for full width at half maximum (FWHM) decreased from 2–4 degrees at 140–150°C to less than 100 arc-s at 250°C, and a FWHM of 59 arc-s was the lowest value observed near 250°C. The FWHM of the HWE CdTe was found to be insensitive to growth rate below about 400Å/min, but increased to four degrees at 1250Å/min. X-ray diffraction confirmed that films grown on the B-face at higher temperatures were epitaxial, but contained a significant volume fraction, 35% to 50%, of rotational in-plane twins. Electron microscopy confirmed a coarse twin density, and photoluminescence spectra showed an absence of excitonic emission in the HWE films. Simultaneous growth on two (111) HgCdTe substrates with different surface polarities between 230°C and 335°C showed that deposition rate on the A-face decreased relative to that on the B-face as temperature increased. Films grown on the B-face exhibited better surface morphologies than those grown on the A-face.     

Formation Mechanism of MoO3-Doped YSr2Cu3Oy Using the Citrate Process

The formation mechanism of the synthesis of MoO₃-doped YSr₂Cu₃O _y powders using the citrate process was investigated. It was shown that the precursor phase (Sr_{1- x} Y _x )₁₄Cu₂₄O₄₁ played a crucial role in forming the superconducting phase. It was found that the precursor phase (Sr_{1- x} Y _x )₁₄Cu₂₄O₄₁ interacted with water and decomposed when it was heavily milled and heated.