Synthesis, characterisation and gas permeation studies on microporous silica and alumina-silica membranes for separation of propane and propylene

Microporous silica membranes are known to exhibit molecular sieving effects. However, separation of nearly equal sized molecules is difficult to carry out by size exclusion. Introducing sorption selectivity and keeping the kinetics favourable to facilitate a good contribution of permeation from sorption is a possible solution to enhance selectivity of adsorbing molecules. Results are presented in this paper on the synthesis of a microporous silica membrane with commendable permselectivity between helium and propylene. Modifications are performed on the membrane to improve its almost non-selective nature to propylene/propane mixtures to give practical separation values. Gas separation results on the modified membranes are presented. Surface selectivity on the newly added alumina surface layer is identified as the helping mechanism in realising this separation

Covalent binding studies on the 14C-labeled antitumour compound 2,5-bis(1-aziridinyl)-1,4-benzoquinone. Involvement of semiquinone radical in binding to DNA, and binding to proteins and bacterial macromolecules in situ

2,5-Bis(1-aziridinyl)-1,4-benzoquinone (BABQ) is a compound from which several antitumour drugs are derived, such as Trenimone, Carboquone and Diaziquone (AZQ). The mechanism of DNA binding of BABQ was studied using 14C-labeled BABQ and is in agreement with reduction of the quinone moiety and protonation of the aziridine ring, followed by ring opening and alkylation. The one-electron reduced (semiquinone) form of BABQ alkylates DNA more efficiently than two-electron reduced or non reduced BABQ. Covalent binding to polynucleotides did not unambiguously reveal preference for binding to specific DNA bases. Attempts to elucidate further the molecular structure of DNA adducts by isolation of modified nucleosides from enzymatic digests of reacted DNA failed because of instability of the DNA adducts. The mechanism of covalent binding to protein (bovine serum albumin, BSA) appeared to be completely different from that of covalent binding to DNA. Binding of BABQ to BSA was not enhanced by reduction of the compound and was pH dependent in a way that is opposite to that of DNA alkylation. Glutathione inhibits binding of BABQ to BSA and forms adducts with BABQ in a similar pH dependence as the protein binding. The aziridine group therefore does not seem to be involved in the alkylation of BSA. Incubation of intact E. coli cells, which endogenously reduce BABQ, resulted in binding to both DNA and RNA, but also appreciable protein binding was observed

Workplace Justice in the United States: An Introduction

Wheeler, Klaas, and Mahony provide a thorough analysis of organizational justice systems by exploring nonunion systems of workplace justice and comparing them with the union system, American courts, and systems in 11 other countries.https://research.upjohn.org/up_press/1045/thumbnail.jp

Workplace Justice Without Unions

Wheeler, Klaas, and Mahony provide a thorough analysis of organizational justice systems by exploring nonunion systems of workplace justice and comparing them with the union system, American courts, and systems in 11 other countries.https://research.upjohn.org/up_press/1045/thumbnail.jp

New concepts in echocardiography

If short pulses of high frequency sound are transmitted through the heart, discontinuities in the tissues will produce reflected sound waves or "echoes". There wil! be a delay between a pulse transmission and the arrival of a correspond·mg echo. Together with knowledge of sound velocity this wi!l enable determination of the distance between the transmitterfreceiver and the reflecting interface, thus providing information about cardiac dimensions. Similarly the Doppler effect can be used to provide further diagnostic information. These applications of ultrasound (echocardiography) for the detection of cardiac (mal)function have recently gained acceptance even though interpretation of the information obtained can be difficult. Major reasons for this acceptance are probably that, while

Evolution of pore structure in microporous silica membranes:sol-gel procedures and strategies

Silica membranes exhibiting excellent molecular sieving capability, which would find applications in fuel‐cell electric vehicles with on‐board hydrogen generation, for example, are the aim of the sol‐gel strategies outlined here. It is shown that optimization of the sol‐gel synthesis parameters is important in order to achieve membranes with minimum defects and hence high selectivity. The preparation of the supported membranes is described and the gas permeation behavior of membranes made from different sol compositions reported

3C 48: Stellar Populations and the Kinematics of Stars and Gas in the Host Galaxy

We present deep Keck LRIS spectroscopy of the host galaxy of 3C 48. Our observations at various slit positions sample the different luminous components near the quasar, including the apparent tidal tail to the NW and several strong emission line regions. By fitting Bruzual & Charlot (1996) population synthesis models to our spectra, we obtain ages for the most recent major episodes of star formation in various parts of the host galaxy covered by our slits. There is vigorous current star formation in regions just NE and SE of the quasar and post-starburst regions with ages up to ~10^8 years in other parts of the host galaxy, but most of the NW tidal tail shows no sign of significant recent star formation. We use these model fits, together with the kinematics of the stars and gas, to outline a plausible evolutionary history for the host galaxy, its recent starburst activity, the triggering of the quasar, and the interaction of the radio jet with the ambient gas. There is strong evidence that the 3C 48 host is an ongoing merger, and that it is probably near the peak of its starburst activity. Nevertheless, the quasar itself seems to suffer little extinction, perhaps because we are viewing it along a particularly favorable line-of-sight.Comment: 27 pages plus 11 figures (7 postscript, 4 gif). Postscript version including figures (1840 kb) available at http://www.ifa.hawaii.edu/~canaguby/preprints.html . Accepted for publication in Ap

Sol-gel synthesis of molecular sieving silica membranes

Polymeric silica sol was synthesized by the acid catalyzed hydrolysis and condensation of tetra-ethyl-ortho-silicate. Calcined unsupported membranes made from this sol showed microporous nature. Supported membranes on alumina were prepared by dipping and calcining. Helium showed activated diffusion with an apparent activation energy of 17 kJ mol−1. H2 permeation was comparable to that of helium under identical conditions. N2, Ar, O2, C3H6, C3H8, n-C4H10 and i-C4H10 permeation values were extremely small and therefore difficult to fit appropriate diffusion models. At 303 K hydrocarbon permeation was about 2 times higher than that of N2, Ar or O2. permselectivity around 1000 and helium permeation in the order of 10−7–10−8 mol m−2 s−1 Pa−1 were measured in the temperature range of 303–460 K. Comparison of Eact, selectivity and He and N2 permeation of different samples evidenced the dependence of nitrogen flux on processing defects. Obviously permeation rate of nitrogen molecule was insignificant through majority pores of the membrane

Substrate utilization and metabolic profile in response to overfeeding with a high-fat diet in South Asian and white men:a sedentary lifestyle study

Background For the same BMI, South Asians have a higher body fat percentage, a higher liver fat content and a more adverse metabolic profile than whites. South Asians may have a lower fat oxidation than whites, which could result in an unfavorable metabolic profile when exposed to increased high-fat foods consumption and decreased physical activity as in current modern lifestyle. Objective To determine substrate partitioning, liver fat accumulation and metabolic profile in South Asian and white men in response to overfeeding with high-fat diet under sedentary conditions in a respiration chamber. Design Ten South Asian men (BMI, 18-29 kg/m(2)) and 10 white men (BMI, 22-33 kg/m(2)), matched for body fat percentage, aged 20-40 year were included. A weight maintenance diet (30% fat, 55% carbohydrate, and 15% protein) was given for 3 days. Thereafter, a baseline measurement of liver fat content (1H-MRS) and blood parameters was performed. Subsequently, subjects were overfed (150% energy requirement) with a high-fat diet (60% fat, 25% carbohydrate, and 15% protein) over 3 consecutive days while staying in a respiration chamber mimicking a sedentary lifestyle. Energy expenditure and substrate use were measured for 3 x 24-h. Liver fat and blood parameters were measured again after the subjects left the chamber. Results The 24-h fat oxidation as a percentage of total energy expenditure did not differ between ethnicities (P = 0.30). Overfeeding increased liver fat content (P = 0.02), but the increase did not differ between ethnicities (P = 0.64). In South Asians, overfeeding tended to increase LDL-cholesterol (P = 0.08), tended to decrease glucose clearance (P = 0.06) and tended to elevate insulin response (P = 0.07) slightly more than whites. Conclusions Despite a similar substrate partitioning and similar accretion of liver fat, overfeeding with high-fat under sedentary conditions tended to have more adverse effects on the lipid profile and insulin sensitivity in South Asians.</p

Shocked Molecular Hydrogen in the 3C 326 Radio Galaxy System

The Spitzer spectrum of the giant FR II radio galaxy 3C 326 is dominated by very strong molecular hydrogen emission lines on a faint IR continuum. The H2 emission originates in the northern component of a double-galaxy system associated with 3C 326. The integrated luminosity in H2 pure-rotational lines is 8.0E41 erg/s, which corresponds to 17% of the 8-70 micron luminosity of the galaxy. A wide range of temperatures (125-1000 K) is measured from the H2 0-0 S(0)-S(7) transitions, leading to a warm H2 mass of 1.1E9 Msun. Low-excitation ionic forbidden emission lines are consistent with an optical LINER classification for the active nucleus, which is not luminous enough to power the observed H2 emission. The H2 could be shock-heated by the radio jets, but there is no direct indication of this. More likely, the H2 is shock-heated in a tidal accretion flow induced by interaction with the southern companion galaxy. The latter scenario is supported by an irregular morphology, tidal bridge, and possible tidal tail imaged with IRAC at 3-9 micron. Unlike ULIRGs, which in some cases exhibit H2 line luminosities of comparable strength, 3C 326 shows little star-formation activity (~0.1 Msun/yr). This may represent an important stage in galaxy evolution. Starburst activity and efficient accretion onto the central supermassive black hole may be delayed until the shock-heated H2 can kinematically settle and coolComment: 27 pages, 7 figures, accepted for publication in the Astrophysical Journa