[Relationship between EGG and the dynamic process of motion sickness induced by optokinetic vection]

OBJECTIVE

To investigate the correlation between Electrogastrography (EGG) and the occurrence of nausea or/and vomit as well as the development of motion sickness (MS) induced by optokinetic stimulation (OPS) and to provide a clue and method for prediction and prevention of MS.

METHOD

Twenty male subjects, aged from 18 to 25 years, performed the test only once with the optokinetic drum rotated around a vertical axis at the speed of 60 degrees/s for 15 min. Nausea and EGG signals were observed and recorded.

RESULT

(1)Both the increment of tachygastric percentage and the decrement of primary wave percentage of EGG in eleven subjects with nausea were significantly larger than those in nine subjects with no nausea (both P < 0.001). (2)The circular vection preceded the changes of EGG in eleven subjects with nausea while the MS scores in eleven subjects with nausea were higher than those in nine subjects with no nausea (P < 0.001). (3)During the rotation of drum, the decrement of primary wave percentage or the increment of tachygastria percentage also preceded the occurrence of nausea in eleven subjects with nausea (both P < 0.01).

CONCLUSION

(l)The changes of EGG in subjects with nausea were significantly greater than those of EGG in subjects with no nausea. (2)There was a close relationship between circular vection or illusory self-rotation and EGG changes as well as the occurring of nausea induced by OPS. (3)Changes of EGG preceded the nausea of MS induced by OPS.

Food stamps are associated with food security and dietary intake of inner-city preschoolers from Hartford, Connecticut

The goal of the present study was to examine the association of the Food Stamp Program with the food security and dietary intake of low-income children from Hartford, CT, who were enrolled in the Supplemental Food Program for Women, Infants, and Children (WIC). We compared the food and nutrition situation of low-income preschoolers who received food stamps (FS, n = 59) with that of those who did not receive food stamps (NFS, n = 40). Children were an average age of 2.7 +/- 0.6 y, and 95% were receiving WIC benefits at the time of the study. Groups were comparable in demographic characteristics, but the socioeconomic status of the FS group was lower than that of the NFS group (P < 0.05). Food security was assessed with the Radimer/Cornell hunger scale, and dietary intake was assessed with a single 24-h recall and a 14-item food frequency questionnaire. Multivariate analyses within the FS group indicated that a monthly duration of food stamps of <4 wk was a predictor of household food security (odds ratio 0.10, 95% confidence interval 0.02-0.56). Food stamp use was associated with above-median energy-adjusted intakes of vitamin B-6 (3.13, 1.16-8.45), folate (2.92, 1.09-7.81) and iron (3.72, 1.31-10.54). The NFS children were more likely to consume <8 mg iron/d (3.73, 1.09-12.80). These results suggest that the Food Stamp Program is associated with food security and preschoolers' micronutrient intake.

[Human physiological regulation in the closed suit with no ventilation]

Objective. To study the effects of the Experimental Closed Suit (ECS) with no active ventilation on human physiological functions and its anti-asphyxic role. Method. Five young healthy male subjects, aged 18-21 years, were tested in the ECS with no active ventilation and no oxygen supply (NAVANOS) when the gas regulatory valve switch was placed on A or B position respectively. Result. (1) Under 1 atm air pressure, each subject could endure at least 15 min while they were aware and resting in the ECS with NAVANOS; (2) There was a balancing period or plateau of the oxygen and the carbon dioxide pressure in the vicinity of the mouth in 5 to 7 min after the sealed helmet was closed, and this period lasted to the end of each test; (3) During the 8-10 min balancing period, the oxygen partial pressure in the vicinity of the mouth ranged from 15.0 to 16.4 kpa, which was slightly hypoxic, and the range of the carbon dioxide partial pressure was 5.21 to 6.49 kPa, which was within the CO2 concentration-time curve of human physiological endurance; (4) No significant difference in human physiological parameters was found when the regulatory valve was placed on A or B position. Conclusion. The anti-asphyxic time of ECS with NAVANOS could at least last 15 min under 1 atm air pressure while the subjects were aware and resting.

[Study on testing method of susceptibility to decompression sickness in aerospace]

Objective. To provide related parameters for astronauts. Method. A study of susceptibility to decompression sickness was carried out in 43 subjects in a hypobaric chamber. Result. Incidence of altitude decompression sickness under rest condition was closely related to age, time of oxygen prebreathing, gas bubble formation rates in the venous blood flow returned to heart and some other physiological indexes. Incidence of decompression sickness was significantly higher in subjects aged 30-36 years than in those aged 19-20 years under the same experimental conditions. In the older subjects body-fat, blood cholesterole and noradrenaline in urine during experiment were significantly higher than those in the younger subjects. It also showed that among persons of the same ages, when prebreathing time was longer, the incidence of decompression sickness was significantly lower under the same experimental conditions. Conclusion. It is desirable that the susceptibility to decompression in astronaut be tested with 1 h oxygen prebreathing before exposure to the altitude of 10000 m for 30 min.

Maternal nutritional status is inversely associated with lactational amenorrhea in Sub-Saharan Africa: results from demographic and health surveys II and III

Breast-feeding is positively associated with the duration of postpartum amenorrhea; thus it is a major determinant of fertility in countries where effective contraceptive methods are not widely available. The objective of these analyses was to examine the association between maternal nutritional status and lactational amenorrhea (LA) among breast-feeding women. Women who were not pregnant, who were breast-feeding, who were not using hormonal contraceptives and who had a child </=2 y old at the time of survey were included in the analyses. Multivariate logistic regression was used to examine this association with the use of Demographic and Health Surveys data collected in seven Sub-Saharan African countries between 1990 and 1994. Analyses were adjusted for nine confounders, including breast-feeding behavior, child nutritional status and child age. Within-country analyses consistently showed the trend of low maternal body mass index (BMI) associated with a higher likelihood of being amenorrheic. Pooled analyses (n = 9839) were performed using two child age groups (<9 mo and 9-24 mo). The <9 mo pooled analysis showed that women with BMI < 18.5 kg/m2 (odds ratio; 95% confidence interval: 1.6; 1.2-2.3) were more likely to remain amenorrheic at the time of the survey than their "better-nourished" counterparts. The 9-24 mo pooled analysis showed that the differential probability of being amenorrheic between undernourished and "better-nourished" women increased with time postpartum, where the adjusted difference in the median duration of amenorrhea associated with maternal nutritional status among breast-feeding women was 1.4 mo. These results suggest that maternal nutritional status plays an independent role in the return of ovulation after delivery.

[Effects of L-arginine on pulmonary circulation and cerebral blood flow in acute and chronic hypoxic rats]

The effects of L-arginine (L-Arg) on pulmonary circulation and cerebral blood flow in acute and chronic hypoxic rats and their mechanism were studied. The results showed that bolus injection of L-Arg 400mg.kg-1 did not inhibit acute hypoxic pulmonary vasoconstriction (HPV), while 800mg.kg-1 could inhibit HPV. Neither of these two doses of L-Arg was found to have any influence on the change in cerebral blood flow during acute hypoxia. Long-term administration of L-Arg (300mg.kg-1/d) could attenuate chronic hypoxic pulmonary hypertension, the increase in pulmonary vascular resistance and right ventricular hypertrophy, and the HPV as well. It did not influence the cerebral blood flow. Since the inhibitor of NO synthetase, NG-nitro-L-arginine methyl ester, could antagonize the effect of L-Arg, it is suggested that an increase in the synthesis of NO might contribute to the effect of L-Arg.

Optical properties of Zircaloy and Zircaloy oxide by ellipsometry

The optical constants of Zircaloy 2 and 4, which are alloys of zirconium and their thermal oxides, are determined by ellipsometry over a 0.3131-3.39-microm wavelength range. Both the refractive index and extinction coefficient of both types of Zircaloy are similar to those of zirconium. Both components of the complex index increase with wavelength from nominal values of 1.135-il.523 at 0.3131 microm to 4.846-i7.345 at 3.39 microm. The refractive indices of the oxide of Zircaloy 2 and 4 heated in air are similar to that of zirconium oxide and decrease in value as a function of wavelength from ~2.3 at 0.3131 microm to ~2.0 at 3.39 microm. The extinction coefficient is both thickness and temperature dependent and varies between ~0.1 and 0.3.

The adsorption, desorption, and exchange reactions of oxygen, hydrogen, and water on platinum surfaces. III. Water adsorption and exchange with oxygen and hydrogen

Ultra-high vacuum thermal desorption experiments have been carried out on the adsorption of water, and the D2O/H and D216O/18O exchange reactions on platinum previously characterized by oxygen and hydrogen adsorption studies. Water is weakly adsorbed and only at T < 150 K, an observation confirmed by using H2 adsorption as a chemical probe for the presence of adsorbed water. The thickness of the adsorbed D2O layers was determined by a novel method involving monitoring the power output of the temperature programmer. Exchange occurs between adsorbed H and a D2O overlayer and the extent of exchange increases with the thickness of the overlayer. Isotope distribution studies show that the surface is heterogeneous and the exchange reaction does not occur at uniform rate. Exchange occurs between adsorbed 18O and a D216O overlayer. The extent of exchange is constant up to T ∼ 300 K showing that D2O is more strongly bound on O-covered Pt presumably as a result of H bonding. Heterogeneity also is apparent in the O-exchange reaction. The apparent activation energies for exchange are 1.8 and 2.9 kcal mol−1 for the half- and fully-covered surfaces, respectively.

The Adsorption, Desorption, and Exchange Reactions of Oxygen, Hydrogen, and Water on Platinum Surfaces. II. Hydrogen Adsorption, Exchange, and Equilibration

The adsorption, desorption, exchange, and equilibration reactions of hydrogen and deuterium on a platinum filament have been investigated by thermal desorption mass spectrometry. A surface saturated with hydrogen at 120 °K has a coverage 4.2 × 1014 molecules cm−2 and gives desorption spectra with four distinct peaks: β1,(165 °K), β2(220 °K), β3(280 °K), and β4(350 °K). Apparent activation energies and pre-exponential factors were determined for the β2-, β3-, and β4-peaks. For both co-adsorption and sequential adsorption of H2 and D2 the mass 2, 3, and 4 desorption spectra have identical shapes and the gas desorbs at equilibrium throughout. It is concluded that hydrogen adsorbs dissociatively. Exchange and equilibration were studied at 120, 210, and 285 °K by determining the surface composition and isotope distribution after varying fractions of preadsorbed H had been replaced. Following exchange at 120 °K the desorption spectra show a higher D content and a lack of equilibrium in the desorbing gas at low temperature. In most other experiments the mass 2,3, and 4 desorption spectra had identical shapes and the gas desorbed at equilibrium. The results are interpreted by a model which requires that the polycrystalline platinum surface is intrinsically heterogeneous. It appears that different mechanisms are unnecessary to interpret the differences in kinetics observed for exchange and equilibration at low temperatures.

The Adsorption, Desorption, and Exchange Reactions of Oxygen, Hydrogen, and Water on Platinum Surfaces. I. Oxygen Interaction

The kinetics of adsorption and desorption of oxygen on a platinum filament have been studied by temperature-programmed desorption mass spectrometry. Oxygen adsorption becomes significant only after any carbon contamination is removed from the surface. At 300 °K oxygen adsorbs dissociatively into an atomic β-state which contains four overlapping sub-states. The initial sticking probability is 0.16 but this falls off rapidly with increasing coverage. A kinetic analysis for desorption from the β2- and β4-states gave Edes≠(β2) = 39 kcal mol−1 and Edes≠(β4) = 54 kcal mol−1 The desorption was first order suggesting a lack of mobility of the adatoms at the desorption temperature (∼700°K). No oxygen atom desorption could be detected in a line-of-sight experiment. Adsorption of a mixture of 32O2 and 36O2 resulted in complete isotopic mixing on desorption. At 115 °K, the β-state still populates first with the same initial sticking probability indicating adsorption is nonactivated. Moreover, the sticking probability remains at its high initial value for a much more extensive coverage range, suggesting a precursor state to adsorption. After the β3- and β4-states are fully occupied, further adsorption into the β-state is competitive with occupation of an α-state which desorbs at low temperatures (∼150°K) with first order kinetics and Edes≠(α) ∼6 kcal mol−1 No isotope mixing occurred in the α-state which is undoubtedly molecular. Prior population of the β1- and β2-states at 300 °K reduced the α-state adsorption at 115 °K suggesting that α and β occupy the same sites. Each site can adsorb either an atom or molecule since each molecule added to the β-state excludes two molecules from the α-state.

The State of Hydrogen Desorbing from Intermediates Formed by Ammonia Interaction with Tungsten Surfaces

Ammonia interaction with a tungsten surface can generate dense adlayers containing nitrogen and hydrogen, i.e. an η-species of surface stoichiometry Ws2N3H. In thermal desorption mass spectrometry experiments, hydrogen desorbing from the η-species interacts with the glass wall in a manner similar to that previously observed for atomic hydrogen. This paper describes two mass spectrometric techniques designed to confirm this conclusion directly. The first method uses a line-of-sight geometry between the tungsten filament and the ionization source of the mass spectrometer and the results indicate that, at least, part of the hydrogen desorbing from the η-species does so atomically. In the second method a multiple wall collision geometry is used but prior saturation of the wall with D atoms will result in an HD+ ion current for desorbing H atoms. The results suggest that 26% of the hydrogen desorbs atomically. Hydrogen atom desorption from the η-species occurs at tungsten filament temperatures below those required for hydrogen atom evaporation from a pure hydrogen adlayer. It is proposed that a reduced binding energy for adsorbed hydrogen atoms and a reduced mobility of these adatoms arises from the presence of a large surface concentration of nitrogen. This will result in the rates of atomic hydrogen desorption and bimolecular recombination becoming comparable at temperatures lower than is the case for pure hydrogen interaction with tungsten. The implications of these results for the ammonia synthesis reaction are discussed.