Methanol Synthesis Using CO2 and H2 on Nano Silver-Ceria Zirconia Catalysts: Influence of Preparation Method.

Silver catalysts supported on ceria-zirconia (CZ) mechanically mixed oxide were synthesized by wet impregnation and chelating methods. Nominal loadings of 5 wt.% of Ag was deposited on the CZ support. These catalysts were tested for the CO2 hydrogenation reaction to methanol with feed gas composition of CO2-H2 = 3:1 at 250 °C, 20 bar total pressure and GHSV of 1800 h-1. The calcined and reduced catalysts were characterized using XRD, BET, TPR, SEM-EDS, XPS and FTIR-DRIFTs techniques. Finely deposited silver crystallites sized in the range of 20-50 nm were observed through SEM and HR-TEM analysis. TPR and XRD studies demonstrated the presence of Ag2O and metallic silver (Ag0) on CZ support. About 10% of CO formation was observed on chelating catalyst (5Ag/CZ CHE). However, only, 5% CO was observed on impregnated (5Ag/CZ IMP) catalyst. The greater CO formation was associated with ease reduction of Ag2O to metallic silver in 5Ag/CZ CHE catalyst. Further, 70% of methanol selectivity was observed on 5Ag/CZ IMP due to the presence of Ag2O on CZ. FTIR-DRIFTs results revealed the methanol formation via formate intermediates and CO formation via RWGS reaction on the studied catalysts.

Pore-Scale Study of Flow Rate on Colloid Attachment and Remobilization in a Saturated Micromodel.

Colloid attachment is an important retention mechanism. It is influenced by colloid size, pore size, and flow rate, among other factors. In this work, we studied colloid attachment experimentally under various flow rates, as well as colloid release in response to a rapid change of flow rate. Colloid transport experiments under saturated conditions and with different flow rates were conducted in a physical micromodel. The micromodel was made of polydimethylsiloxane (PDMS), which is a hydrophobic polymer. Colloids were hydrophilic fluorescent carboxylate-modified polystyrene latex microspheres with a mean diameter of 300 nm. We could directly observe the movement of colloids within the pores using a confocal microscope. We also obtained concentration breakthrough curves by measuring the fluorescence intensity at the outlet of the micromodel. In addition, our experiments were simulated using a pore-network modeling, PoreFlow, based on the pore structure of the micromodel. Local colloid concentrations were calculated by solving local mass balance equations for all network elements and then averaging resulting concentrations over the whole micromodel. The measured breakthrough curves were successfully simulated using PoreFlow. Observed and calculated breakthrough curves showed that colloid attachment rate was smaller for larger flow rate. Temporally enhance colloid release (remobilization of attached colloids) was observed when the flow rate was increased by a factor of 10. But no colloid remobilization was observed when the flow rate decreased by a factor of 10.

Tobacco carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone initiates and enhances pancreatitis responses.

Clinical studies indicate that cigarette smoking increases the risk for developing acute pancreatitis. The nicotine metabolite 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is a major cigarette smoke toxin. We hypothesized that NNK could sensitize to pancreatitis and examined its effects in isolated rat pancreatic acini and in vivo. In acini, 100 nM NNK caused three- and fivefold activation of trypsinogen and chymotrypsinogen, respectively, above control. Furthermore, NNK pretreatment in acini enhanced zymogen activation in a cerulein pancreatitis model. The long-term effects of NNK were examined in vivo after intraperitoneal injection of NNK (100 mg/kg body wt) three times weekly for 2 wk. NNK alone caused zymogen activation (6-fold for trypsinogen and 2-fold for chymotrypsinogen vs. control), vacuolization, pyknotic nuclei, and edema. This NNK pretreatment followed by treatment with cerulein (40 µg/kg) for 1 h to induce early pancreatitis responses enhanced trypsinogen and chymotrypsinogen activation, as well as other parameters of pancreatitis, compared with cerulein alone. Potential targets of NNK include nicotinic acetylcholine receptors and ß-adrenergic receptors; mRNA for both receptor types was detected in acinar cell preparations. Studies with pharmacological inhibitors of these receptors indicate that NNK can mediate acinar cell responses through an nonneuronal α(7)-nicotinic acetylcholine receptor (α(7)-nAChR). These studies suggest that prolonged exposure to this tobacco toxin can cause pancreatitis and sensitize to disease. Therapies targeting NNK-mediated pathways may prove useful in treatment of smoking-related pancreatitis.

Droplet Imbibition into Paper Coating Layer: Pore-Network Modeling Simulation.

Liquid penetration into thin porous media such as paper is often simulated using continuum-scale single-phase Darcy's law. The underlying assumption was that a sharp invasion front percolates through the layer. To explore this ambiguous assumption and to understand the controlling pore-scale mechanisms, we have developed a dynamic pore-network model to simulate imbibition of a wetting phase from a droplet into a paper coating layer. The realistic pore structures are obtained using the FIB-SEM imaging of the coating material with a minimum resolution of 3.5 nm. Pore network was extracted from FIB-SEM images using Avizo software. Data of extracted pore network are used for statistically generating pore network. Droplet sizes are chosen in the range of those applicable in inkjet printing. Our simulations show no sharp invasion front exists and there is the presence of residual non-wetting phase. In addition, penetration of different sizes of droplets of different material properties into the pore network with different pore body and pore throat sizes are performed. We have found an approximately linear decrease in droplet volume with time. This contradicts the expected t -behavior in vertical imbibition that is obtained using macroscopic single-phase Darcy's law. With increase in flow rate, transition of imbibition invasion front from percolation-like pattern to a more sharper one with less trapping of non-wetting phase is also reported. Our simulations suggest that the single-phase Darcy's law does not adequately describe liquid penetration into materials such as paper coating layer. Instead Richards equation would be a better choice.

Partial reduction of annulated heterocycles as a general route to medium rings containing oxygen and nitrogen.

The preparation of annulated furans and pyrroles is described as part of a general strategy for the synthesis of medium ring heterocycles. After Birch reduction, the corresponding dihydro compounds were oxidatively cleaved to produce medium ring ethers and amines in an efficient manner. This methodology was successfully applied to the formation of eight- and nine-membered cyclic ethers and nine-membered cyclic amines. Attaching a chiral auxiliary (bismethoxymethylpyrrolidine) to the furan allowed the formation of nine-membered ethers in 95% ee.

Interviews with children who experienced major life stress: family and child attributes that predict resilient outcomes.

Demographically comparable groups of children exposed to major life-stress, with stress resilient (SR) and stress affected (SA) outcomes at ages 10 to 12, were interviewed to assess perceptions of their caregiving environments, peer relationships, and themselves. SR children compared with SA children reported more: (1) positive relationships with primary caregivers, (2) stable family environments, (3) inductive and consistent family discipline practices, and (4) positive expectations for their futures. SR girls viewed their mothers as more nurturing than did SA girls. Perceptions of fathers, quality of peer relationships, and global self-concept did not differentiate the groups. A discriminant function analysis identified four variables that correctly classified 74% of the subjects as SR or SA. Findings support the view that caregiver-child relationships play a key role in moderating children's developmental outcomes under conditions of high stress.

Modifying the release of leuprolide from spray dried OED microparticles.

A range of oligosaccharide ester derivatives (OEDs) have been designed as drug delivery matrices for controlled release. The synthetic hormone analogue, leuprolide, was encapsulated within these matrices using hydrophobic ion pairing and solvent spray drying. The particles produced modified the release of leuprolide in vitro (dissolution in phosphate buffered saline) and in vivo (subcutaneous and pulmonary delivery in the rat). Release rate was dependent on drug loading and could be manipulated by choice of OED and by combining different OEDs in different ratios. Leuprolide encapsulated in the OEDs retained biological activity as evidenced by elevation in plasma luteinising hormone levels following subcutaneous injection of leuprolide recovered from OED particles in vitro prior to in vivo administration.

A NMR investigation of adsorption/desorption hysteresis in porous silica gels.

The purpose of this study is to investigate possible differences in geometry and connectivity of the liquid phase in a partially water-satured porous medium between the adsorption and the desorption branches, using a series of silica gels. This was done by comparing the T1 and T2 relaxation times (in 1H and 2H nuclear magnetic resonance (NMR) relaxation) as well as the water self-diffusion coefficient D (in 1H) along the two branches of the adsorption/desorption isotherms. The results show that the two relaxation times and the diffusion coefficient are strongly dependent on the water content (saturation level). When plotted in normalized coordinates, the T1 and T2 vs. P/Po curves fit closely the adsorption/desorption isotherms, which validates the two-population, fast-exchange model. Furthermore, because at equivalent saturation levels, there is no difference between the relaxation times and diffusion coefficients obtained along the adsorption branch and those obtained along the desorption branch, one is led to the conclusion that despite different equilibrium conditions, the geometry and connectivity of the liquid phase are statistically the same along the two branches.

Continuing medical education in primary health care in Saudi Arabia: an epidemiologic study of physicians' needs in the Asir region.

A cross sectional survey was carried out among doctors working in all the 238 Primary Health Care Centers in the Asir Region, Southwestern Saudi Arabia using self administered questionnaire. The response rate was 90.1%. The highly needed aspects of clinical practice include emergency skills (82.3%), diagnostic skills (74.4%) and management of common diseases (65.2%). Aspects that rated low include physical examination techniques, prescription skills, history taking and referral. Areas in medicine that rated high on the doctors' list of needs include critical care (60.7%), obstetrics and gynecology (52.7%) and family and community medicine (52.8%). The most highly preferred means of fulfilling these needs include clinical rounds (73.2%), consultation with specialists (69.8%) and regular lectures (62.5%). The objective of establishing baseline data which are essential for future continuing medical education (CME) planning in the Asir region was achieved in this study. Based on the doctors needs, it was recommended that regional CME units be established and related organizations and institutions that will jointly plan a program of CME be identified.

Reactive dispersive contaminant transport in coastal aquifers: numerical simulation of a reactive Henry problem.

The reactive mixing between seawater and terrestrial water in coastal aquifers influences the water quality of submarine groundwater discharge. While these waters come into contact at the seawater groundwater interface by density driven flow, their chemical components dilute and react through dispersion. A larger interface and wider mixing zone may provide favorable conditions for the natural attenuation of contaminant plumes. It has been claimed that the extent of this mixing is controlled by both, porous media properties and flow conditions. In this study, the interplay between dispersion and reactive processes in coastal aquifers is investigated by means of numerical experiments. Particularly, the impact of dispersion coefficients, the velocity field induced by density driven flow and chemical component reactivities on reactive transport in such aquifers is studied. To do this, a hybrid finite-element finite-volume method and a reactive simulator are coupled, and model accuracy and applicability are assessed. A simple redox reaction is considered to describe the degradation of a contaminant which requires mixing of the contaminated groundwater and the seawater containing the terminal electron acceptor. The resulting degradation is observed for different scenarios considering different magnitudes of dispersion and chemical reactivity. Three reactive transport regimes are found: reaction controlled, reaction-dispersion controlled and dispersion controlled. Computational results suggest that the chemical components' reactivity as well as dispersion coefficients play a significant role on controlling reactive mixing zones and extent of contaminant removal in coastal aquifers. Further, our results confirm that the dilution index is a better alternative to the second central spatial moment of a plume to describe the mixing of reactive solutes in coastal aquifers.

Onchocerca fasciata: histochemical demonstration of succinate and NADH dehydrogenase.

The activities of selected enzymes of the respiratory chain system in Onchocerca fasciata (Filarioidea: Onchocercidae) have been investigated histochemically. Thus, the localization and distributions of NADH dehydrogenase (EC 1.6.99.3), succinate dehydrogenase (SDH) (EC 1.3.99.1) and cytochrome oxidase (EC 1.9.3.1) were investigated in various tissues of the adult female worm by employing MTT, Nitro BT (dehydrogenases) and DAB (cytochrome oxidase). Different tissues varied considerably in their enzymatic activities. The hypodermis and reproductive tissues showed strong and identical localization of NADH and SDH dehydrogenase activities reflecting high metabolic rates. Little or no dehydrogenase activities were observed in the intestine and cuticle. In contrast to the two dehyrogenases, no activity was observed for cytochrome oxidase in any of the tissues in adult or embryonic stages of the worm. The significance of these results with respect to the energy metabolism of the worm is discussed. It is suggested that O. fasciata lacks a classical, mammalian-type respiratory pathway and that oxidative phosphorylation is of no importance as an energy generating pathway in this essentially anaerobic parasite.

Histochemical distribution of hydrolytic enzymes in adult Onchocerca fasciata (Filarioidea: Onchocercidae).

Histochemical techniques were employed to study the tissue distribution of hydrolytic enzymes in adult female Onchocerca fasciata (Filarioidea: Onchocercidae). Different tissues differed considerably in the localization and distribution of the six enzymes studied. Acid phosphatase (AcPase) activity was detected in the cuticle, hypodermis and reproductive organs. Alkaline phosphatase (AlkPase) activity was largely absent. Adenosine triphosphatase (ATPase) was found in the somatic musculature and muscles of the uterine ducts, whereas 5'-nucleotidase (5'-Nu) was restricted to young oocytes and dividing embryos in the female worm. Strong glucose-6-phosphatase (G-6-Pase) activity was demonstrated in the uterine epithelial cells and microfilariae, as was weak activity in the hypodermis. Naphthylamidase (NAM) activity was detected in the hypodermis, with lower activity occurring in the somatic musculature. The possible functions of these enzymes are discussed with respect to their location. The hydrolytic enzymes AcPase and NAM in the body wall are probably involved in absorptive-digestive functions, NAM in the somatic musculature may be concerned with tissue protein turnover, and ATPase, 5'-Nu and G-6-Pase may have a role in active transport and energy metabolism.

Histochemical localization of key glycolytic and related enzymes in adult Onchocerca fasciata.

The activities of some key enzymes of the glycolytic and pentose phosphate pathways were investigated histochemically in adult female Onchocerca fasciata (Nematoda: Filarioidea). The distribution patterns of phosphofructokinase (PFK), aldolase (ALD), glyceraldehyde 3-phosphate dehydrogenase (G3PDH) and glucose 6-phosphate dehydrogenase (G6PDH) in different tissues of the worm were determined by employing NitroBlue Tetrazolium (NBT). The glycolytic enzymes PFK, ALD, and G3PDH were distributed throughout the hypodermal tissue, somatic muscles and reproductive organs. These enzyme activities were predominantly expressed in the hypodermal and reproductive tissues, both of which appeared to be metabolically more active than adjacent tissues. The high activities of the enzymes studied in the hypodermal tissue when compared with the minimal or low activity in the intestinal epithelium support the assumption that the worm's intestine, in contrast to the body wall, plays no significant role in the nutrient acquisition process. The results emphasize that both the glycolytic and hexose monophosphate pathways of carbohydrate metabolism are active components in energy production and biosynthetic processes in the various tissues of the worm. The functional significance of these glucose-metabolizing enzymes has been discussed with regard to their location in the tissues concerned.

Attitude of medical students towards psychiatry.

Findings are presented from a survey of all medical students at the College of Medicine, Abha, Saudi Arabia dealing with students' attitudes towards specialization in psychiatry. The health region of Asir in south-west rural Saudi Arabia, of about one million inhabitants, needs Saudi Nationals to specialize in psychiatry to provide planned future delivery of services. Medical students all over Saudi Arabia, however, have not been choosing psychiatry for their specialization after graduation. The Scientific Committee for Mental Health, convened at the Ministry of Health in Riyadh in February 1986, invited representatives of psychiatry from medical schools in the nation to discuss this priority topic. A year later, a new course called 'Introduction to Psychosomatic Medicine' was introduced as an elective for medical students with its practice at the general hospital. It tries to introduce students to 'voluntary and active as against passive learning ... and problem-solving rather than imposed memorizing' of medicalized forms of psychiatry, an innovation compared with the previous conventional method. A significant difference in attitude was demonstrated between students who had their exposure to psychiatry from this course and those who followed only the conventional methods of learning.

In vivo assessment of intestinal, hepatic, and pulmonary first pass metabolism of propofol in the rat.

PURPOSE: The relative contribution of the intestinal mucosa, liver and lung to the in vivo disposition of propofol in the rat was investigated. METHODS: Propofol (4.9-5.1 mg.kg-1) was administered to groups of rats (n = 4) via the intra-arterial, intravenous, hepatic portal venous and oral routes. The AUC's of propofol were estimated and the fractions of the administered dose escaping first pass metabolism by the gut wall (fG), liver (fH) and lung (fL) were calculated. In addition, transport experiments were carried out using Caco-2 cell monolayers to rule out the possibility that intestinal permeability is limiting the oral absorption of propofol. RESULTS: Values for fG, fH and fL were the following: 0.21 +/- 0.07, 0.61 +/- 0.13, and 0.82 +/- 0.09, respectively. The apparent permeability coefficient of propofol across Caco-2 cell monolayers was 24.2 +/- 0.3 x 10(-6) cm.sec-1, which is similar to the apparent permeability coefficient obtained for propranolol (30.7 +/- 1.7 x 10(-6) cm.sec-1), a compound known to easily cross the intestinal epithelial membranes. The formation of propofol glucuronide, a major metabolite of propofol, could not be demonstrated during the flux experiments across the Caco-2 cell monolayers. CONCLUSIONS: The intestinal mucosa is the main site of first pass metabolism following oral administration of propofol in the rat. Intestinal metabolism could therefore also contribute to the systemic clearance of propofol.

Onchocerca fasciata: enzyme histochemistry and tissue distribution of various dehydrogenases in the adult female worm.

Histochemistry studies of key dehydrogenases in the glycolytic pathway and related enzymes and the tricarboxylic acid (TCA)-cycle enzymes were carried out on adult female Onchocerca fasciata. The distribution pattern and enzymatic activities of 6-phosphogluconate dehydrogenase (6-GPDH), lactate dehydrogenase (LDH), mitochondrial glycerol-3-phosphate dehydrogenase (GPDH), nicotinamide adenine dinucleotide (phosphate) [NAD+(P)]-linked isocitrate dehydrogenase (ICDH), and NAD+(P)-linked malate dehydrogenase (MDH) in various tissues of the worm were determined. Moderate to intense enzyme activities were localized in three main areas, namely, the hypodermis, body-wall muscle, and reproductive tissues. Activity of the formazan reaction product was very low, if at all present, in the intestinal epithelium and was completely absent in the cuticle. On the basis of the present results and earlier observations, it is suggested that glycolysis leading to the end product lactate is the main energy-generating pathway in O. fasciata. The presence of significant activity of 6-GPDH indicates that the pentose-phosphate pathway might be operative in O. fasciata. In light of the activity of some of the TCA-cycle enzymes, ICDH and MDH, demonstrable in O. fasciata, it is possible that an additional pathway (pyruvate-succinate) of glucose metabolism via a reverse sequence of the TCA cycle may also be operative in the worm. The possible functional significance of the enzymes detected is discussed with respect to their location.

Propofol pharmacokinetics in children with biliary atresia.

We studied the pharmacokinetics of an i.v. bolus dose of propofol 2.5-3.0 mg kg-1 in eight children (age 4-24 months) with biliary atresia and in six control (ASA I) children (age 11-43 months). Blood samples were obtained for 4 h after administration of propofol. Blood concentrations of propofol were measured by high pressure liquid chromatography. Systemic clearance of propofol (CI) and volume of distribution at steady state (Vss) showed a highly significant correlation with body weight. Propofol CI and Vss, normalized for body weight, were similar in children with biliary atresia (mean 37.5 (SD 8.3) ml min-1 kg-1 and 3.5 (1.6) litre kg-1, respectively) compared with control children (38.7 (6.8) ml min-1 kg-1 and 2.4 (0.8) litre-1 kg-1, respectively). We conclude that in children with biliary atresia the pharmacokinetics of propofol are similar to those of healthy children.

Glucuronidation of diflunisal, (-)-morphine, 4-nitrophenol, and propofol in liver microsomes of two patients with Crigler-Najjar syndrome type I.

In vitro glucuronidation was studied in liver microsomes from two patients with Crigler-Najjar type I (CN-I) disease and compared with the activity measured in microsomes prepared from six control human livers. The UDP-glucuronosyltransferase (UGT) activity was determined toward the following substrates: 4-nitrophenol, propofol, (-)-morphine (formation of the 3-glucuronide), and diflunisal (formation of the phenolic and acyl glucuronides). Glucuronidation of 4-nitrophenol was reduced in one of the CN-I livers (CN-I No. 1) (0.9 nmol min(-1)mg(-1)) and normal in the other CN-I liver (CN-I No. 2) (3.5 nmol min(-1) mg(-l)) compared to the control livers (5.6 +/- 29 nmol min(-1) mg(-1)), mean +/- S.D.). Propofol glucuronidation was not detectable (i.e. less than 0.100 nmol min(-l) mg(-1) in the CN-I No. 1 liver and normal in the CN-I No. 2 liver (1.78 nmol min(-1) mg(-1) against 1.52 +/ 0.72 nmol min(-l) mg(-) in the control livers). The glucuronidation of (-)-morphine to the 3-glucuronide and the formation of the phenolic and acyl glucuronides of diflunisal were normal in both CN-I livers compared to the control livers. Our results show that CN-I patients are heterogeneous regarding UGT activity toward the phenolic substances 4-nitrophenol and propofol.