Simulations of X-ray absorption spectroscopy and energetic conformation of N-heterocyclic carbenes on Au(111).

It has recently been demonstrated that N-heterocyclic carbenes (NHCs) form self-assembled monolayers (SAMs) on metal surfaces. Consequently, it is important to both characterize and understand their binding modes to fully exploit NHCs in functional surface systems. To assist with this effort, we have performed first-principles total energy calculations for NHCs on Au(111) and simulations of X-ray absorption near edge structure (XANES). The NHCs we have considered are N,N-dimethyl-, N,N-diethyl-, N,N-diisopropylbenzimidazolylidene (BNHCX, with X = Me, Et, and iPr, respectively) and the bis-BNHCX-Au complexes derived from these molecules. We present a comprehensive analysis of the energetic stability of both the BNHCX and the complexes on Au(111) and, for the former, examine the role of the wing group in determining the attachment geometry. Further structural characterization is performed by calculating the nitrogen K-edge X-ray absorption spectra. Our simulated XANES results give insight into (i) the relationship between the BNHCX/Au geometry and the N(1s) → π*/σ*, pre-edge/near-edge, absorption intensities, and (ii) the contributions of the molecular deformation and molecule-surface electronic interaction to the XANES spectrum. These simulated spectra work not only as a map to the BNHCX conformation, but also, combined with electronic structure calculations, provide a clear understanding of recent experimental XANES findings on BNHCX/Au.

Surface and near surface defects in δ-doped Si(1 1 1).

The B/Si(1 1 1)- (√3 x √3)R30° surface reconstruction has recently been used as a platform for supramolecular assembly. However, our understanding of the native defects in this delta-doped system and their corresponding scanning tunnelling microscopy (STM) signatures is incomplete. So we have studied this system using ab initio total energy calculations and scanning tunneling microscopy. We find that although perturbations to the equilibrium geometry of the surface are in general weak, the perturbations to the electronic structure can be quite strong due to the presence of dangling bonds composed of Si-3p(z) orbitals. Additionally, we propose a possible structure for a previously unidentified defect that appears in positive bias constant-current STM images as an equilateral triangular arrangement of Si adatoms with attenuated intensity.

Reply to Comment on 'Bi nanolines on Si(001): registry with the substrate'.

The registry of bismuth dimers, integral components of the bismuth nanoline on Si(001), is examined. In contrast to the currently accepted view, the bismuth dimers are found to be in registry with the two-dimensional lattice created by the silicon dimers. The consequences of this finding are briefly explored.

The equilibrium geometry and electronic structure of Bi nanolines on clean and hydrogenated Si(001) surfaces.

The equilibrium geometry, electronic structure and energetic stability of Bi nanolines on clean and hydrogenated Si(001) surfaces have been examined by means of ab initio total energy calculations and scanning tunnelling microscopy. For the Bi nanolines on a clean Si surface the two most plausible structural models, the Miki or M model (Miki et al 1999 Phys. Rev. B 59 14868) and the Haiku or H model (Owen et al 2002 Phys. Rev. Lett. 88 226104), have been examined in detail. The results of the total energy calculations support the stability of the H model over the M model, in agreement with previous theoretical results. For Bi nanolines on the hydrogenated Si(001) surface, we find that an atomic configuration derived from the H model is also more stable than an atomic configuration derived from the M model. However, the energetically less stable (M) model exhibits better agreement with experimental measurements for equilibrium geometry. The electronic structures of the H and M models are very similar. Both models exhibit a semiconducting character, with the highest occupied Bi-derived bands lying at approximately 0.5 eV below the valence band maximum. Simulated and experimental STM images confirm that at a low negative bias the Bi lines exhibit an 'antiwire' property for both structural models.

Ethanol elimination by rats as a function of reproductive state, gender and nutritional status.

Alcohol elimination was studied in rats of different ages, reproductive states and nutritional deprivation, with the following results: 1) blood levels of ethanol 180 min after a single dose of 1.5 g/kg, ip were significantly higher in adult male (74 days old, N = 5) than in young male rats (34 days old, N = 5): 92.4 +/- 8.4 vs 6.8 +/- 3.4 mg/100 ml, means +/- SD, respectively; 2) when male rats were given a low protein diet for 48 h, blood ethanol levels after a single dose were significantly increased in young males (38.6 +/- 14.6 mg/100 ml) but no effect after a single dose was found in the same animals at an older age (93.2 +/- 5.0 mg/100 ml); 3) blood levels in female rats were higher than in young males both in the virgin and pregnant states, but during lactation a significant drop in blood levels of ethanol was observed. Blood levels of ethanol (mg/100 ml) 180 min after a single dose of 1.5 g/kg, ip, in females, were: virgin (N = 6): 44.9 +/- 16.1, pregnant (N = 5): 40.0 +/- 10.4, lactant (N = 5) 8.8 +/- 5.8. This difference between virgin and pregnant and lactant rats was not related to changes in ADH activity which did not differ between groups. The present study indicates that in male rats the effect of a short-term protein deprivation on ethanol elimination is dependent on the age of the animal. In females, reproductive state is an important factor in determining ethanol elimination.

Ethanol elimination by rats as a function of reproductive state, gender and nutritional status

Alcohol elimination was studied in rats of different ages, reproductive states and nutritional deprivation, with the following results: 1) blood levels of ethanol 180 min after a single dose of 1.5 g/kg, ip were significantly higher in adult male (74 days old, N=5) than in young male rats (34 days old, N = 5): 92.4 ñ 8.4 vs 6.8 + 3.4 mg/lOO ml, means ñ SD, respectively; 2) when male rats were given a low protein diet for 48 h, blood ethanol levels after a single dose were significantly increased in young males (38.6 ñ 14.6 mg/l00 ml) but no effect after a single dose was found in the same animals at an older age (93.2 ñ 5.0 mg/l00 ml); 3) blood levels in female rats were higher than in young males both in the virgin and pregnant states, but during lactation a significant drop in blood levels of ethanol was observed. Blood levels of ethanol (mg/l00 ml) 180 min after a single dose of 1.5 g/kg, ip, in females, were: virgin (N=6): 44.9 ñ 16. 1, pregnant (N = 5): 40.0 ñ 10.4, lactant (N = 5): 8.8 5.8. This difference between virgin and pregnant and lactant rats was not related to changes in ADH activity which did not differ between groups. The present study indicates that in male rats the effect of a short-term protein deprivation on ethanol elimination is dependent on the age of the animal. In females, reproductive state is an important factor in determining ethanol elimination.

Ethanol pharmacokinetics in lactating women.

Experimental studies in rats have demonstrated that lactating females have blood ethanol levels five times lower than those observed in non-lactating rats. The purpose of the present study was to verify if this phenomenon also occurs in human beings. Five lactating (L) and five control (C) women received, after formal agreement to the experimental procedure, 0.4 g/kg of ethanol as vodka (Stolichnaya, USSR), between 9:00 and 10:15 a.m. Blood and milk samples were collected 10, 20, 40, 60, 90, 150 and 180 min after ethanol ingestion. Ethanol levels in blood and milk were measured by gas chromatography using the head space technique. Results indicated that: time to reach maximal blood levels was significantly longer in the L group (L: 48.0 +/- 10.9, C: 31.2 +/- 16.4 min, means +/- SD), area under the curve was smaller when group L was compared to group C (L: 3821.5 +/- 1240.5, C: 5154.8 +/- 1313.7 mg% x min, means +/- SD), ethanol blood levels (mg/dl) at 150 and 180 min were significantly lower in the L group (150: L, 10.5 +/- 5.6; C, 18.7 +/- 6.8; 180: L, 3.9 +/- 2.8; C, 13.2 +/- 6.4, means +/- SD). Concentration of ethanol in milk was similar to concentration in blood. These results indicate the importance of lactation for ethanol pharmacokinetics and raise questions about the pharmacokinetics of other drugs ingested by lactating women.

Ethanol pharmacokinetics in lactating women

Experimental studies in rats have demonstrated that lactating females have blood ethanol levels five times lower than those observed in non-lactating rats. The purpose of the present study was to verify if this phenomenon also occurs in human beings. Five lactating (L) and five control (C) women received, after formal agreement to the experimental procedure, 0.4 g/kg of ethanol as vodka (Stolichnaya, USSR), between 9:00 and 10:15 a.m. Blood and milk samples were collected 10, 20, 40, 60, 90, 150 and 180 min after ethanol ingestion. Ethanol levels in blood and milk were measured by gas chromatography using the head space technique. Results indicated that: time to reach maximal blood levels was significantly longer in the L group (L: 48.0 +/- 10.9, C: 31.2 +/- 16.4 min, means +/- SD), area under the curve was smaller when group L was compared to group C (L: 3821.5 +/- 1240.5, C: 5154.8 +/- 1313.7 mg per cent x min, means +/- SD), ethanol blood levels (mg/dl) at 150 and 180 min were significantly lower in the L group (150: L, 10.5 +/- 5.6; C, 18.7 +/- 6.8; 180: L, 3.9 +/- 2.8; C, 13.2 +/- 6.4, means +/- SD). Concentration of ethanol in milk was similar to concentration in blood. These results indicate the importance of lactation for ethanol pharmacokinetics and raise questions about the pharmacokinetics of other drugs ingested by lactating women

Urogastrone-epidermal growth factor and aspects of sexual maturation in female rats as a function of age at treatment.

The effect of epidermal growth factor (EGF) on sexual maturation of female rats was studied. A within-litter experimental design was employed, so that in each litter each female received four daily injections of EGF (E, 500 ng/g body weight s.c.) or vehicle (V), at one of three ages: days 0-3 (E1, V1), days 8-11 (E2, V2), days 16-19 (E3, V3). Body weight, pinna detachment, incisor eruption, eye opening, auditory startle, visual placing, vaginal opening and first cytological oestrus were assessed. Neonatal treatment with EGF (E1) delayed pinna detachment and the appearance of the auditory startle, but accelerated eye opening. Also, E1, but not E2 and E3, resulted in lower body weight at weaning. Treatment E3 advanced sexual maturation, as indicated by vaginal opening and first cytological oestrus, by 5-6 days. E1 and E2 had no such effect. Hence the sensitive period for the effect of EGF on female rat sexual maturation is later than that for effects on other developmental characteristics and body weight. In a second experiment, ovary and uterus weights were found not to differ between E3 and V3 females killed on the day of vaginal opening of the E3 rats, suggesting that the effect of EGF may be specifically on the perineal epithelium and not on sexual maturation generally.

Seroepidemiologic investigations of human hepatitis caused by A, B, and a possible third virus.

Seroepidemiologic studies were made of normal subjects in populations in the United States and Costa Rica and in family outbreaks of hepatitis in Costa Rica. Hepatitis A affected a majority of children of very young age in Costa Rica, while such experience in persons of high socioeconomic status in the United States did not occur before middle life. Persons of low socioeconomic status (paid plasma donors) and residents and attendants of institutions for the mentally retarded showed a far greater incidence of hepatitis A antibody than did their counterparts in the open community. Hepatitis A and B epidemics occurred in families in Costa Rica with rapid spread to other susceptible members of the group. The disease was clinically apparent in roughly half the cases, whether the responsible agent be hepatitis A or B. Five cases of nonhepatitis A or B (hypothetical hepatitis C) were found and all but one of them were subclinical.

Enzyme activity in the liver and serum of malnourished children in Jamaica

(1) Activities of glutamic pyruvic transaminase, isocitric dehydrogenase and malic dehydrogenase were measured in the liver and serum of children suffering from malnutrition. (2) Death was closely associated with raised serum enzyme activity and bilirubin levels, and low enzyme activity in the liver. (3) The return of liver enzyme activity to normal in the course of recovery was followed. (4) The effect on liver enzymes of a reduced protein intake was observed. A marked fall in liver glutamic pyruvic transaminase activity without any alteration in isocitric dehydrogenase was found. (AU)

A biochemical lesion in fatty liver

Enzymes leak from damaged liver tissue into the blood. An attempt has been made to measure this leakage in needle biopsy pieces of liver. However the results of such procedures are very difficult to interpret because of the absence of 'normal' values and because the biopsy needle probably inflicts differing amounts of trauma each time it is used (AU)

Serum-enzymes during recovery from malnutrition

Serum glutamic-pyruvic-transaminase (G.P.T.) and isocitric-dehydrogenase (I.C.D.) activities have been measured in a number of children recovering from severe malnutrition. Greatly increased serum glutamic-pyruvic-transaminase and isocitric-dehydrogenase levels are found in children recovering from severe malnutrition. These are thought to be part of a physiological response to a good diet, and not an indication of cell injury. Serum-bilirubin is not increased in these children. It is suggested that increased serum-enzyme levels are produced when enzyme synthesis proceeds more rapidly than synthesis of structural components of cells (SUMMARY)

Hepatic failure in malnutrition

Serum glutamic-pyruvic-transaminase, isocitric-dehydrogenase, and bilrubin were measured in malnourished children. Greatly increased levels were found in chlidren who died later. Clinical observations suggest that with modern treatment childern with severe malnutrition survive unless they have hepatic failure. There was no difference in enzyme distribution between the groups of children with marasmus and those with kwashiorkor. It is suggested that leakage of enzymes from liver cells may lead to failure of liver function. Measurements of the enzyme content of some liver-biopsy specimens support this argument (AU)

Transaminase levels in infant malnutrition

Estimation of glutamic pyruvic transaminase, isocitric dehydrogenase and bilirubin were measured in malnourished children. All children that died showed elevation of all three parameters on admission. The 80 percent of the series that showed no such elevated values all survived (AU)