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We study the effect of proton irradiation on Ba(Fe$_{0.96}$Co$_{0.04}$)$_2$As$_2$ superconducting single crystals from combined magnetisation and magnetoresistivity measurements. The study allows the extraction of the values of the apparent pinning energy $U_0$ of the samples prior to and after irradiation, as well as comparison of the values of $U_0$ obtained from the flux-flow reversible region with those from the flux-creep irreversible region. Irradiation reduces $T_c$ modestly, but significantly reduces $U_0$ in both regimes: the critical current density $J_c$ is modified, most strikingly by the disappearance of the second magnetisation peak after irradiation. Analysis of the functional form of the pinning force and of the temperature dependence of $J_c$ for zero field, indicates that proton irradiation in this case has not changed the pinning regime, but has introduced a high density of shallow point-like defects. By consideration of a model that takes into account the effect of disorder on the irreversibility line, the data suggests that irradiation produced a considerable reduction in the average effective disorder overall, consistent with the changes observed in $U_0$ and $J_c$., 5 pages 7 figures

Graphene-based electronics show much promise due to the potential high charge-carrier mobility of the material as well as its flexibility in preparation on different substrates. Recently there has been much evidence suggesting that the wrinkle structures found in pristine graphene inhibit electron transport, reducing device performance. In this study the inhibiting role of standing wrinkles within chemically derived graphene are studied quantitatively using Kelvin force microscopy. Samples were evaluated before and after annealing at 250 C to observe changes in the channel's surface potential dependence on the state of reduction. Annealed samples were found to have inter-flake and intra-flake contribution to the potential drop and that for the latter a correlation between the potential drop magnitude and wrinkle density is found, although there is no correlation with wrinkle height. Statistical averaging across many images demonstrated that the average lower limit of wrinkle resistance in these devices is approximately 4.5 kΩ. Such high resistance demonstrate definitively that elimination of wrinkles within graphene oxide based devices is essential in order to obtain optimum performance. © 2013 Elsevier Ltd. All rights reserved.

Rhenium-188 is a radionuclide with favorable physical characteristics suitable for radiotherapeutic purposes (T1/2 16.9 h, Eβmax 2.12 MeV; Eγ 155 keV (15%)) for radiotherapeutic purposes and can be continually obtained from 188W/188Re generator systems. The preparation conditions of an alumina based 188W/188Re generator are reported. Initially, the W and Re sorption behavior on alumina in NaCl and HCl medium was performed evaluating the following parameters: medium pH, alumina size particle, sorption capacity, and kinetic. Re-188 is not adsorbed in HCl and NaCl medium whereas W-188 is strongly adsorbed in both media at pH

A wet chemical surface treatment for InAs epilayers is investigated to remove the native semiconductor oxide prior to growth of a MgO tunnel barrier and Co ferromagnetic electrode by dc magnetron sputtering. Use of a HCl etch followed by (NH4)2S as the pre-growth surface treatment resulted in pinhole-like features in the tunnel barrier, as observed by conducting atomic force microscopy, but this detrimental effect is avoided if the etch procedure is repeated twice. High resolution transmission electron microscopy revealed that the etched samples had uniform tunnel barriers and reducing the growth temperature of the barrier from 200 to 100 °C significantly improved the abruptness of the semiconductor/barrier interface. Electrical characterization of barrier properties illustrated that all the etched samples showed parabolic differential conductance curves indicative of tunnelling behaviour at 300 K.

Photocatalytic oxidation (PCO) of volatile organic compounds (VOC) over TiO2, exploiting visible light of common fluorescent lamps represents an attractive means of indoor air purification. This work compares activity and its variation with calcination of two commercial TiO2, Hombicat UV100 and Degussa P25, in a complete PCO of n-butanol serving as a convenient representative VOC. The PCO of n-butanol was carried out in a flow through reactor under a relatively long residence time using mostly fluorescent visible (white) light (FWL)-lamp for illumination. Fluorescent black light (UV) (FBL)-lamp was used only for comparison. Under FBL-lamp, 580 ppm n-butanol is completely mineralized over both catalysts. Under FWL-lamp the reaction is considerably slower and Degussa P25 appears more active than Hombicat UV100. For 580 ppm, steady state conversions of less than 95% are attained, but at 145 ppm, a complete mineralization is achieved even over Hombicat UV100. Butanal, propanal and ethanal were identified as the main gaseous intermediate products. In addition, a parallel formation of crotonaldehyde, product of aldolization, was detected. The appearance and concentration of crotonaldehyde depended on PCO conditions, particularly on the characteristics of TiO2. Thermal treatment of TiO2 at ≥623 K has a negative effect on the activity in PCO of both catalysts. Apparently, the calcination causes modification of the surface available active sites that is in part reflected by diminution of specific surface area. The effect of reactor residence time, of inlet concentration and of the relative light intensity on the efficiency of the process was also evaluated.

Microstructural and magnetic characterization were undertaken on high-rate, high-temperature grown YBa2Cu3O7–δ (YBCO) films. The films were of approximately 1 μm thickness and were grown by pulsed laser deposition on (100) SrTiO3 using a high-power industrial laser at growth temperatures between 750 °C and 870 °C and at growth rates of up to 4 μm/min. Two YBCO layers with different c-lattice parameters were observed in the films, the higher c value occurring near the substrate interface and arising from cation disorder and oxygen nonstoichiometry, and the lower one near the film surface arising from cation disorder alone. BaCuO2 precipitates were present near the surface of the films, indicative of partial melting during growth. The amount of BaCuO2 increased with growth temperature. Epitaxial Y2O3 also formed in increasing amounts suggestive of a different partial melting reaction in the films compared to bulk YBCO, where Y2BaCuO5 coexists with liquid. Around 1 MA/cm2 values of high critical current density (Jc) were observed in the films, and the in-field Jc improved with growth temperature despite the fact that the superconducting transition width increased significantly.

A kinetic study of the crystallization of poly(ethylene oxide) (PEO) and of a blend of PEO+poly(bisphenol A-co-epichlorohydrin) (PBE) was performed by using DSC in a non-isothermal program at constant cooling rates. The curves obtained were analyzed by the Kissinger, Ozawa and Friedman methods, with determination of the kinetic parameters in each case. As a consequence of the presence of PBE, the kinetic parameters were altered, leading to the conclusion that PBE has some influence on the crystallization of PEO, modifying its mechanism.

A c -axis oriented YBa 2 Cu 3 O 7-δ (YBCO) film, ∼ 190 nm thick, deposited onto 〈100〉 LaAlO 3 by DC sputtering was irradiated at room temperature with 50-keV 2 H + to a dose of 1 × 10 16 ions cm −2 . The as-implanted sample was divided into several pieces and annealed in a flowing oxygen ambient using rapid thermal annealing (RTA), at various temperatures between 450 and 900°C. RTA at 450°C for 20 s results in the fast diffusion of 2 H out of the film (i.e. the apparent diffusion coefficient is estimated to be larger than 2 × 10 −11 cm 2 /s) but no obvious change is seen in the distribution of 2 H in the substrate. All of the trapped 2 H in the substrate is found to migrate out the sample after RTA at 900°C for 2 min. After 20 s isochronal RTA at temperatures between 450 and 900°C, the relative release fraction of 2 H from the substrate increases near-linearly with increasing anneal temperature. The activation energy (temperature) for 2 H release from the weaker traps in the irradiated substrate is estimated to be ∼1.6 eV (500°C). There are stronger traps in the irradiated substrate, with the activation energy (temperature) for 2 H release from them being estimated to be larger than 2.3 eV (800°C). The behaviour of implanted 2 H during RTA can be explained by the mechanism of 2 H detrapping and re-trapping.

A method is devised to find a lower bound on the loss function of graphite in the oxygen high energy range where that function is expected to assume constant value. It requires obtaining a small ensemble of classical trajectories of oxygen on graphite and making static measurements of an oxygen on ethylene potential energy surface. An oxygen atom is assumed to be bonded to the graphite surface by diabatic curve crossing from its initial repulsive potential. Subsequently, it is assumed to be ejected as part of a carbon monoxide molecule due to surface impact of another incident oxygen atom. A dynamical calculation is suggested to improve on the approximate method of this work. Once an excited state cross channel coupling constant is known, the ratio of the loss function of that excited state to the loss function of the ground state may be estimated at asymptotic oxygen energies.

A Vibrating Sample Magnetometer (VSM) was used to study the magnetic properties of YBa2Cu3O7−x (YBCO) thin films sputtered onto LaAlO3, SrTiO3 and MgO substrates, before and after ion implantation with deuterium and 16O+. By applying the Bean model, the irreversible magnetisation M, was converted into a critical current density Jc, using a length scale Λ determined from a non-destructive technique, at each temperature. The implantation led to significant changes in the superconducting properties of the films. Most notably, for the deuterium implantation in lower Tc films (84K typically), Tc was enhanced by several degrees and M/Λ was enhanced by 1.1 – 1.25 times. In higher Tc films (92K), Tc and Jc were unaltered at the present fluencies used. A similar observation was made for films with a range of Tc values implanted with 16O+; when the Tc was unaltered after implantation, M/Λ was also unchanged, but where Tc was depressed M/Λ was enhanced by a factor of 2.3. Possible mechanisms are discussed.

Thin films of YBa 2 Cu 3 O 7−δ (YBCO) deposited by sputtering on LaAlO 3 and SrTiO 3 substrates have been implanted with 50 keV 2 H + (deuterium) ions at doses of 1 × 10 12 cm −2 and 1 × 10 16 cm −2 . Depth profiles of the high dose implants obtained by secondary ion mass spectrometry (SIMS) were compared with Monte Carlo simulations (TRIM90) and showed evidence of channelling in the substrates. The superconducting transition temperature, T c , measured by a.c. susceptibility (ACS) disappeared for the high dose implanted samples and X-ray diffractometry (XRD) showed that the YBCO c-axis length had increased, indicating a loss in oxygen content. After annealing the implanted samples with a rapid thermal annealer in O 2 and N 2 atmospheres, SIMS profiles indicated the fast diffusion of deuterium out of the films.

A facility has been constructed for studying supersonic flows of hot gases. The facility used an inductively coupled RF plasma torch to increase the stagnation temperature of nitrogen to approximately 4700 K. The gas then flowed through a converging nozzle (4.9 mm diameter throat) and exhausted into a water-cooled test section as an under-expanded, supersonic jet. The high stagnation temperature resulted in the excitation of electronic states and the formation of PPM levels of ions (in particular, N2+) in the jet flow. Emission from the (0,0) bandhead of the N2+ first negative system (B2 Sigma u+-X2 Sigma g+) at 3914.4 AA was used to locate the boundaries of the jet. The rotationally resolved spectra of the (0,0) band were examined using both radiative emission and laser-induced fluorescence in order to measure rotational temperatures in the flow. A comparison was made between the measured flow field properties and those predicted by a method of characteristics (MOC) solution.

Drug concentrations in cerebrospinal fluid have been assumed to be a natural surrogate for total drug exposures in the central nervous system. The present communication reports a data set from a study of 30 compounds in mice. An attempt was made to correlate cerebrospinal fluid and unbound plasma drug concentrations via incorporation of in vitro P-glycoprotein (Pgp)-mediated transport data. 2. Pgp-deficient (Pgp -/-) and wild-type mice were dosed with compounds of interest by oral gavage (orally) at 5 mg kg −1 . Plasma and cerebrospinal fluid samples were collected at 1 h post-dosing, and analysed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) for drug concentrations. Mouse and human Pgp-mediated transport were evaluated in vitro by a bi-directional (B to A and A to B) transport assay using LLC-PK1 cells expressing mouse (mdr1a) and human (MDR1) forms of Pgp, respectively. 3. Compounds with B to A/A to B transport ratios < 2 were defined as non-substrates of Pgp, whereas those exhibiting B to A/A to B transport ratios ≥2 were considered Pgp substrates. Plasma protein bind- ing was also determined in vitro via equilibrium dialysis. Of the 30 compounds, 13 were identified to be mouse Pgp substrates, all of which were also human Pgp substrates, demonstrating a good agreement between mouse and human data. 4. In Pgp wild-type mice, the unbound plasma and cerebrospinal fluid concentrations of the non-Pgp sub - strates correlated well, with a regression slope of approximately 1.0. A similar relationship existed for Pgp substrates in Pgp -/- mice. On the other hand, an improved correlation of cerebrospinal fluid and systemic exposures of the Pgp substrates in Pgp wild-type mice was observed when the unbound plasma concentrations were normalized to the corresponding B to A/A to B transport ratios. 5. These results reinforce the premise that a combined use of unbound plasma drug concentrations and in vitro Pgp transport data may be of value for the estimation of central nervous system exposures.

An efficient procedure for the generation of sequence-specific alterations of the vaccinia virus genome was demonstrated. Homologous DNA recombination within cells infected with vaccinia virus was used for the deletion or replacement of promoter sequences of the viral growth factor gene by a procedure comparable to transplacement in Saccharomyces cerevisiae. This DNA replacement procedure can potentially be used to generate any sequence alteration within the vaccinia virus genome. Deletion of growth factor promoter sequences resulted in a dramatic reduction in growth factor gene transcription and protein synthesis. Replacement of growth factor promoter sequences with promoter sequences of the strong constitutive 40-kDa gene resulted in an increase in gene transcription and protein synthesis and an altered temporal pattern of expression. Virus containing mutations in the growth factor gene demonstrated different plaque morphologies on cell culture monolayers.

Bulk samples of TbFeAsO$_{0.9}$F$_{0.1}$ (T$_{c}$(on) = 50K) were measured by point contact Andreev reflection spectroscopy. The spectra show unambiguous evidence for multiple gap-like features plus the presence of high bias shoulders. By measuring the spectra as a function of temperature with both gold and superconducting niobium tips, we establish that the gap-like features are associated with superconducting order parameter in this material. We discuss whether the well defined zero bias conductance peak that we observe infrequently is associated with a nodal superconducting order parameter., 11 pages, 5 figures, published version

Highly spin polarized Heusler alloys, NiMnSb and Co2MnSi, attract a great deal of interest as potential spin injectors for spintronic applications. Spintronic devices require control of interfacial properties at the ferromagnet:semiconductor contact. To address this issue we report a systematic study of the ordinary and anomalous Hall effect, in Ni1.15Mn0.85Sb films on silicon, as a function of film thickness. In contrast to the bulk stoichiometric material, the Hall carriers in these films become increasingly electron-like as the film thickness decreases, and as the temperature increases from 50 K toward room temperature. High field Hall measurements confirm that this is representative of the majority transport carriers. This suggests that current injected from a NiMnSb:semiconductor interface may not necessarily carry the bulk spin polarization. The films also show a low temperature upturn in the resistivity, which is linked to a discontinuity in the anomalous Hall coefficient. Overall these trends indicate that the application of Heusler alloys as spin injectors will require strictly controlled interfacial engineering, which is likely to be demanding in these ternary alloys.

BACKGROUND Epidemiologic and animal model studies suggest that consumption of soy isoflavones may be associated with reduced risk of prostate cancer (PC). In addition, animal model studies suggest that conjugated linoleic acid (CLA), a natural positional isomer of linoleic acid, inhibits tumor growth in various models, including models of PC. METHODS Based on the above-mentioned data, the objective of the present study was to test the hypothesis that supplementation of the diet with combinations of isoflavone-rich soy protein isolate and CLA would act to inhibit the growth of androgen-independent R-3327-AT-1 rat prostate tumor cells inoculated ectopically into male Copenhagen rats. RESULTS The results of this study indicate that neither an isoflavone-rich soy protein isolate (SPI), nor CLA inhibit the in vivo growth and development of prostate tumor cells when administered in the diet either singly or in combination. Moreover, at the highest concentrations SPI and CLA (i.e., 20% SPI, 1% CLA), there was a statistically significant increase in tumors volume over controls. Administration of SPI at 10% in the diet also enhanced tumor growth, whereas at 5%, SPI exerted no measurable effect. CLA administration alone had no observable effects on AT-1 tumor growth. CONCLUSION These results, in an established rat model, suggest caution in using isoflavone-rich SPI in human studies involving advanced hormone-refractory prostate cancer until further investigation of these effects are completed. Prostate 54: 169–180, 2003. © 2002 Wiley-Liss, Inc.

We have studied the structure of the superconducting gap in MgB2 thin films by means of point-contact spectroscopy using a gold tip. The films were produced by depositing pure boron on a sapphire substrate, using e-beam evaporation, followed by reaction with magnesium vapour. The films have a Tc of 38.6 +- 0.3 K and resistivity of about 20 microOhm cm at 40 K. The point-contact spectra prove directly the existence of a multi-valued order parameter in MgB2, with two distinct values of the gap, DELTA1=2.3+-0.3 meV and DELTA2=6.2+-0.7 meV at 4.2 K. Analysis of the spectra in terms of the Blonder-Tinkham-Klapwijk model reveals that both gaps close simultaneously at the Tc of the film. Possible mechanisms that can explain the intrinsic co-existence of two values of the gap are discussed., 9 pages, 9 figures

A relatively high critical temperature, Tc, approaching 40 K, places the recently-discovered superconductor magnesium diboride (MgB2) intermediate between the families of low- and copper-oxide-based high-temperature superconductors (HTS). Supercurrent flow in MgB2 is unhindered by grain boundaries, unlike the HTS materials. Thus, long polycrystalline MgB2 conductors may be easier to fabricate, and so could fill a potentially important niche of applications in the 20 to 30 K temperature range. However, one disadvantage of MgB2 is that in bulk material the critical current density, Jc, appears to drop more rapidly with increasing magnetic field than it does in the HTS phases. The magnitude and field dependence of Jc are related to the presence of structural defects that can "pin" the quantised magnetic vortices that permeate the material, and prevent them from moving under the action of the Lorentz force. Vortex studies suggest that it is the paucity of suitable defects in MgB2 that causes the rapid decay of Jc with field. Here we show that modest levels of atomic disorder, induced by proton irradiation, enhance the pinning, and so increase Jc significantly at high fields. We anticipate that chemical doping or mechanical processing should be capable of generating similar levels of disorder, and so achieve technologically-attractive performance in MgB2 by economically-viable routes., 5 pages, 4 figures, to be published in Nature (in press)

Epidemiological and experimental studies suggest that consumption of garlic may protect against several types of cancer. Moreover, a plausible hypothesis has been proposed that the biological effects of garlic can be attributed to the enhancing action of a variety of organosulfur compounds, present in garlic, on hepatic phase II carcinogen detoxification enzymes. We have used the N-methylnitrosourea (NMU)-induced rat mammary tumor model to test the chemopreventive effects of a water-soluble organosulfur constituent derived from aged garlic, S-allylcysteine (SAC). Rats were fed diets supplemented with 666 and 2,000 ppm SAC beginning seven days before initiation with NMU (55 days of age) to termination (18 wk post-NMU), at which time mammary tumors were enumerated. At neither dose did SAC exert an inhibitory effect on any index of tumor development, including incidence, latency, multiplicity, or volume, compared with untreated controls. Weight gains in all groups were similar. Assay of serum SAC levels in supplemented groups indicated that SAC concentrations were beneath the limits of detection of the high-performance liquid chromatography system used. These results contradict previous animal model studies indicating that SAC acts as an inhibitory agent in experimental mammary tumorigenesis; reasons for this discrepancy include the possibility that SAC may exhibit nonlinear dose effects.

The influence of the Y doping on the magnetic properties of La0.7.xYxCa0.3MnO3 compounds (x = 0 ; 0.07 ; 0.1 ; 0.15) and on the low field and high field magnetoresistance responses is first investigated by means of transport, susceptibility and magnetisation measurements. It is shown that at low field the variations at 50K of the resistivity with the magnetisation are not dependent of the Y content, and that for x = 0.15 the disappearance of low field magnetoresistance is thus due to antiferromagnetic couplings leading to a low bulk magnetisation value. It is also evidenced that the high field magnetoresistance cannot be an intrinsic effect, but is related to the existence at the surface of the grain of a spin disordered layer that becomes magnetically softer with increasing yttrium content.

In previous studies, we have demonstrated that, while dietary fats were not found to affect the frequency of ras mutation in rat mammary tumors induced by N-nitrosomethylurea (NMU), they did affect final incidence of tumors, supporting the idea that the diet mediates promotion-related changes. As altered p53 expression has been described in 45–55% of human breast cancers, we have used a rat mammary tumor cell line, NMU (ATCC CRL 1743) as a model to determine whether specific fatty acids might affect expression and, in turn, activity of the p53 tumor suppressor gene. Under standard growth conditions (10% FBS), NMU cells over-express p53. Metabolic pulse-chase labeling revealed p53 protein with a prolonged half-life of about 2 hours. To study the effects of specific fatty acids on p53 protein expression, NMU cells were exposed to medium containing high serum (10% FBS), low serum (1% FBS), or low serum plus 1 μg/ml linoleic acid (LA), oleic acid (OA), or docosahexaenoic acid (DHA)). Growth rates for NMU cells were reduced by 30% to 60% in 1% FBS compared with 10% FBS, while addition of LA resulted in an intermediate growth rate and no changes were observed after treatment with OA or DHA. After 3 days in the experimental medium, p53 expression was found to be higher in NMU cells maintained in low serum medium than in those grown in high serum. In the presence of low serum, LA was found to decrease p53 levels, an effect which was not seen with either OA or DHA. Increased p53 expression in cells grown in low serum correlated with their slower growth rate and, similarly, LA was able to decrease p53 expression as well as increasing the growth rate.

Hepatic lipid and apolipoprotein synthesis is increased in the nephrotic syndrome. Catabolism of triglyceride-rich lipoproteins is impaired in nephrotic syndrome but not in rats with hereditary analbuminemia (NA), suggesting that lipid synthesis should be increased by analbuminemia in the absence of proteinuria. In this study the rate of cholesterol and fatty acid synthesis in liver and extrahepatic tissue was measured in female NA and control Sprague-Dawley (SD) rats to determine whether lipid synthesis was indeed increased in isolated analbuminemia and to identify the site(s) of increased lipogenesis. We also measured the concentrations of apolipoproteins (apo) AI, B, and E in plasma, as well as the levels of the respective mRNAs in liver. Plasma cholesterol, triglycerides, and apo AI, B, and E were all increased severalfold in the NA rat (P < 0.001). Although liver apolipoprotein mRNA content was significantly increased (P < 0.001) for apo AI (643%), B (273%), and E (299%), 3-hydroxy-3-methylglutaryl-coenzyme A reductase activity in liver microsomes and hepatic cholesterol synthesis were not significantly increased in the NA rats. Hepatic fatty acid synthesis and intestinal cholesterol synthesis were not increased in the NA rats. Surprisingly, intestinal fatty acid synthesis was elevated by 60% (P < 0.01). The NA rats demonstrated approximately fourfold increases in the incorporation of 3H2O into circulating cholesterol and fatty acids (P < 0.001). A 56% increase in the synthesis of total nonsaponifiable lipid was found in the extravisceral carcass (P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

We present spatially localized magnetic relaxation measurements of the first-order magnetostructural transition in Gd 5 Ge 4 using a scanning Hall probe imaging technique. Relaxation measurements were performed at 6, 10 and 35 K to probe the field-increasing antiferromagnetic (AFM) to ferromagnetic (FM) transition and, when it can occur, the field-decreasing FM to AFM transition. We demonstrate that localized regions relax with time towards the ground state for a given field and temperature and observe different magnetic behaviours at the three measurement temperatures. In particular, the observed magnetic relaxation at 6 K is consistent with the idea of an arrested state at this temperature. Our scanning Hall probe imaging data give an insight into the phase nucleation and growth process of the martensitic-like magnetostructural first-order transition in Gd 5 Ge 4 .

Using a combination of local and global magnetometry, dimensional analysis and numerical simulations we investigate the dynamics of magnetic phase cluster formation across the first-order magnetic-field-driven magnetostructural transition in Gd5Ge4 at 6 K, where the transformation is completely irreversible, and at 35 K, where the reversibility is restored due to rising thermal fluctuations. We have previously shown, using scanning Hall probe images, that the transition involves phase separated clusters. Here we discuss these images in the context of a random nucleation and growth model, focusing on the relation between microscopic and macroscopic behaviours. The purpose of the work is to set up a framework for the analysis of these materials and it has implications for future discoveries of related functional magnetic materials where first-order, disorder-broadened transitions dominate key physical properties.

The characterization of the three major membrane polypeptides indicated to be subunits of the light-harvesting bacteriochlorophyll-protein complexes of Rhodopseudomonas sphaeroides is described. Molecular weight determinations of the three polypeptides have been performed by sedimentation analysis and electrophoretic mobility and the values obtained were in agreement with each other as well as with those derived from compositional studies. NH2- and COOH-terminal amino acid determinations were performed for each of the species; two of the polypeptides produces no reaction with dansyl chloride and were concluded to have blocked amino termini. In each instance, the data were consistent with each of the polypeptides being a single, pure species. Further characterization of the proteins was accomplished by amino acid compositional analysis and peptide mapping of tryptic and chymotryptic digestions of the polypeptides. The number of peptides obtained from the digestions was in agreement with the amino acid compositional data. Two of the polypeptides, 15B and 15C, which possess very similar molecular weights, identical carboxyl termini and apparently blocked amino termini were shown by amino acid analysis and peptide mapping to be structurally discrete species, although related. The relationship between these purified proteins and the known activities and characteristics of the light-harvesting bacteriochlorophyll-protein complexes of R. sphaeroides is discussed.

A type II restriction endonuclease, RshI, has been partially purified from photoheterotrophically grown Rhodopseudomonas sphaeroides strain 2.4.1. The enzyme preparation, after a single DE-52 column fractionation, is free of 5' exonuclease and phosphatase activities but contains a trace of 3' exonuclease activity. Based upon deoxyribonucleic acid (DNA) sequencing data in the vicinity of the enzyme-promoted cleavage of pBR322 DNA, we have concluded that RshI probably recognizes the palinodromic hexanucleotide sequence 5'-CGATCG-3' and cleaves between the T and C. lambda cI857 DNA contains three RshI sites, two of which lie in the replaceable region. The plasmid pBR322, which carries resistances to ampicillin and tetracycline, contains a single RshI site in the ampicillin resistance determinant. Insertion of DNA into the RshI site of pBR322 results in loss of ampicillin resistance but retention of tetracycline resistance, thereby providing a convenient screening procedure for recombinant plasmids.

Aerodynamic Stokes' size distributions and standard sieve size distributions for pulverized coal samples were determined and found to be different in general. Since combustion models of pulverized coal require size distribution data to predict the burning coal particle trajectories, the proper choice of size distribution is critical. This work indicates the Stokes' size distribution must be considered for modeling purposes.

Gas-phase dissociation of fluorine (1Ʃ+g) molecules in an agron bath at 3000 K was studied by using the 3D Monte Carlo classical trajectory (3DMCCT) method. To assess the importance of the potential energy surface (PES) in such calculations, three surfaces, with a fixed, experimentally determined F2dissociation energy, were constructed. These surfaces span the existing experimental uncertainties in the shape of the F2potential. The first potential was the widest and softest; in the second potential the anharmonicity was minimized. The intermediate potential was constructed to ‘localize’ anharmonicity in the energy range in which the collisions are most reactive. The remaining parameters for each PES were estimated from the best available data on interatomic potentials. By using the single uniform ensemble (SUE) method (Kutz, H. D. & Burns, G. J.chem. Phys. 72, 3652-3657 (1980)), large ensembles of trajectories (LET) were generated for the PES. Two such ensembles consisted of 30000 trajectories each and the third of 26200. It was found that the computed one-way-flux equilibrium rate coefficients (Widom, B.Science148, 1555-1560 (1965)) depend in a systematic way upon the anharmonicity of the potential, with the most anharmonic potential yielding the largest rate coefficient. Steady-state reaction-rate constants, which correspond to experimentally observable rate constants, were calculated by the SUE method. It was determined that this method yields (for a given trajectory ensemble, PES and translational temperature) a unique steady-state rate constant, independent of the initial, arbitrarily chosen, state (Tolman, R. C.The principles of statistical mechanics, p. 17. Oxford University Press (1938)) of the LET, and consequently independent of the corresponding initial value of the reaction rate coefficient. For each initial state of the LET, the development of the steady-state rate constant from the equilibrium rate coefficient was smooth, monotonic, and consistent with the detailed properties of the PES. It was found that, although the increased anharmonicity of the F2potential enhanced the equilibrium rate coefficients, it also enhanced the non-equilibrium effects. As a result, the steady-state rate constants were found to be insensitive to the variation of the PES. Thus, the differences among the steady-state rate constants for the three potentials were of the order of their standard errors, which was about 15% or less. On the other hand, the calculated rate constants exceeded the experimental rate constant by a factor of five to six. Because within the limitations of classical mechanics the calculations wereab initio, it was tentatively concluded that the discrepancy of five to six is due to the use of classical mechanics rather than details of the PES structure.

A nonspecific solubilization of the intracytoplasmic membrane proteins from Rhodopseudomonas sphaeroides has been achieved in the absence of detergents. Following removal of the photopigments and phospholipids by acetone/methanol extractions, the protein is quantitatively solubilized in 6 M guanidine thiocyanate which is subsequently exchanged by dialysis for 7 M urea. A urea-soluble protein fraction is obtained which represents 80% of the initial protein and qualitatively contains all the polypeptides of the membrane resolved by sodium dodecyl sulfate-polyacrylamide gel electrophoresis with the exception of the reaction center polypeptides M and L, and the 35.2-kilodalton species. Fractionation of the urea-soluble polypeptides on a Sepharose CL-6B column resolves into separate fractions the two major low molecular weight polypeptides identified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Further examination of these fractions by isoelectric focusing and electrophoresis at pH 4.5 in the presence of 8 M urea reveals the presence of three major species each of which has been purified to homogeneity by a combination of ion exchange chromatography and preparative electrophoretic techniques. It is believed that these three major polypeptides are components of the light-harvesting pigment-protein complexes.

Dynorphin, an opioid peptide, is thought to play an important role in the modulation of nociceptive neural circuits at the level of the spinal cord. In a model of peripheral inflammation and hyperalgesia, an oligodeoxyribonucleotide probe complementary to a portion of preprodynorphin mRNA and antisera to dynorphin A-(1-8) were used to localize changes in dynorphin mRNA and peptide to individual spinal cord neurons. Intraplantar injection in rats of complete Freund's adjuvant resulted in edema and hyperalgesia to radiant heat stimulation of the injected hind paw that reached a peak at 4 days. At the same time, in situ hybridization histochemistry and immunocytochemistry identified an increase in transcription of preprodynorphin mRNA that was paralleled by an increase in dynorphin peptide. These changes were seen in spinal neurons in the medial two-thirds of laminae I and II and in laminae V and VI of lumbar segments receiving innervation from the inflamed paw. Since neurons demonstrating the increase in dynorphin biosynthesis are located in both the superficial and deep dorsal horn laminae, our data provide evidence for opioid modulation of nociceptive neural circuits in these two distinct spinal locations.

The transfer of phospholipids between two membrane substrates catalyzed by a soluble protein fraction from Rhodopseudomonas sphaeroides has been demonstrated. The assay employs purified intracytoplasmic membrane (ICM) vesicles derived from cells of R. sphaeroides grown on [3H]acetate as the phospholipid donor substrate and phosphatidylcholine (70%)/phosphatidylethanolamine (30%) unilamellar liposomes containing [14C]triolein, a nontransferable marker, as the acceptor substrate for transferred phospholipids. Incubation of these two membrane substrates with a 40 to 80% (NH4)2SO4 protein fraction from R. sphaeroides results in the transfer of tritium-labeled ICM phospholipids to the acceptor membrane substrate. Upon completion of the incubation period, the donor ICM vesicles are quantitatively separated from the acceptor liposomes by precipitation with antibody prepared against whole, purified ICM vesicles. Phospholipid transfer is linear with respect to time and protein concentration, is inhibited by trypsin and heat, and shows an absolute dependence upon the presence of acceptor liposomes and the 40 to 80% (NH4)2SO4 protein fraction. Control experiments indicate that no fusion of the donor and acceptor membrane occurs during the incubation period and that, following prolonged incubation there is no detectable degradation of the labeled lipid components. Preliminary data on the phospholipid specificity of the transfer reaction is also presented.

It is shown that there will be strong orienting effects in the collision of two radicals which will invalidate attempts to calculate disproportionation–recombination ratios by simple geometric arguments.

A new type II sequence-specific endonuclease, RsaI, has been identified from Rhodopseudomonas sphaeroides strain 28/5. An RsaI purification scheme that yields enzyme which is free of contaminating exonuclease and phosphatase activities after a single column fractionation has been developed. The enzyme recognized the tetranucleotide sequence 5'-GTAC-3' and cleaved between the T and A, thereby generating flush ends. RsaI should be extremely useful in deoxyribonucleic acid sequencing experiments.

The relative nonequilibrium energy distribution function, in the steady state for the irreversibly reacting Br2 in an argon system at 3500 K, is calculated. It is based upon 44 400 classical 3D trajectories, and uses the single uniform ensemble method [H. D. Kutz and G. Burns, J. Chem. Phys. 72, 3562 (1980)]. Although the raw data display a considerable scatter, they clearly indicate a depletion from the equilibrium distribution function over a wide energy range. A careful statistical study of the data is performed. It is found that their histograms can be described over the entire possible energy range by a simple analytical function with only one adjustable parameter. The best fitting procedure yields a surprisingly narrow goodness of fit. However, an apparent deviation of the fit from the data is observed in the energy region where the reaction channel opens. To that extent, this work sheds a new light on the nature of the steady state in an irreversible reaction.

Incubating Hep G2 cells for 18 h with triparanol, buthiobate and low concentrations (less than 0.5 microM) of U18666A, inhibitors of desmosterol delta 24-reductase, of lanosterol 14 alpha-demethylase and of squalene-2,3-epoxide cyclase (EC 5.4.99.7) respectively, resulted in a decrease of the HMG-CoA (3-hydroxy-3-methylglutaryl-coenzyme A) reductase activity. However, U18666A at concentrations higher than 3 microM increased the HMG-CoA reductase activity in a concentration-dependent manner. None of these inhibitors influenced directly the reductase activity in Hep G2 cell homogenates. Analysis by t.l.c. of 14C-labelled non-saponifiable lipids formed from either [14C]acetate or [14C]mevalonate during the cell incubations confirmed the sites of action of the drugs used. Beside the 14C-labelled substrates of the blocked enzymes and 14C-labelled cholesterol, another non-saponifiable lipid fraction was observed, which behaves as polar sterols on t.l.c. This was the case with triparanol and at those concentrations of U18666A that decreased the reductase activity, suggesting that polar sterols may play a role in suppressing the reductase activity. In the presence of 30 microM-U18666A (sterol formation blocked) the increase produced by simultaneously added compactin could be prevented by addition of mevalonate. This indicates the existence of a non-sterol mevalonate-derived effector in addition to a sterol-dependent regulation. LDL (low-density lipoprotein), which was shown to be able to decrease the compactin-induced increase in reductase activity, could not prevent the U18666A-induced increase. On the contrary, LDL enhanced the U18666A effect, showing that the LDL regulation is not merely the result of introducing cholesterol to the cells.

Differential thermal analysis to 2 kbar of zone-refined p-azoxyanisole in hydrostatic apparatus has corroborated the results of Hulett and of Robbcrecht at lower pressures—initial slopes ≲ 48 deg k...

Canonical Monte Carlo results are reported for the 2:2 aqueous electrolyte in the primitive model. The various theories of dilute coulombic systems are compared with canonical and grand canonical Monte Carlo data on the thermodynamics and structure of this system: HNC, BGY, MPB, and ORPA+B2 are comparably successful, most other theories less so. The MC results show that there are many triple ions or larger clusters even at low concentrations. The problem of extrapolating experimental thermodynamic data for 2:2 electrolytes is discussed.

Five patients with primary biliary cirrhosis and prolonged cholestasis underwent intensive plasmapheresis. The indications for plasmapheresis included intractable pruritus or hypercholesterolemia and xanthomatous neuropathy. Patients noted a rapid improvement of pruritus and fatigue which was sustained as long as plasmapheresis was continued. Cholesterol levels were lowered an average of 10.3 mmol/l and xanthomata were reduced in three of four patients. Two patients with painful neuropathy caused by xanthomata experienced relief of this symptom. The liver and spleen size were not affected by plasmapheresis, and activities of aminotransferases, alkaline phosphatase and titres of mitochondrial antibody remained unchanged. We conclude that plasmapheresis has a role in the therapeutic management of patients with advanced primary biliary cirrhosis who are disabled by the complications of pruritus, xanthomatous neuropathy, or hypercholesterolemia with xanthoma formation.

The kinetics of inactivation of adenylosuccinate lyase by the alkylating agents N-ethyl maleimide and iodoacetamide and by photooxidation have been investigated. The inactivation by the alkylating agents indicates that there are several groups on the enzyme whose reaction affects activity. The presence of AMP, a product of the enzymic reaction, decreases the rate of inactivation by both N-ethyl maleimide and iodoacetamide, while the other product, fumarate, has no effect on the rate. In the case of photoinactivation, the rate is accelerated by the presence of AMP. Fumarate, which again has no effect by itself, causes an overall protection of the enzyme from photoinactivation when added in the presence of AMP. The results, suggesting that fumarate is unable to combine with the free enzyme but does combine with the enzyme–AMP complex, are consistent with the strongly preferred sequence of product release determined by a previous initial-rate kinetic study. Both the kinetics of inactivation and the initial-rate kinetics may be interpreted in terms of a mechanism involving the operation of an enzymic conformational change which is allowed only when either AMP or adenylosuccinate is bound to the enzyme.

In two recent communications we described the results of investigations into the influence of varying initial pressure up to 15 atmospheres on the spontaneous ignition of butane- and pentane-air mixtures, showing that in each case the ignition were located in two distinct and widely separated temperature ranges, location in the higher range occurring at low pressures and in the lower range at high pressures. Transference of an ignition point from the higher to the lower range occurred sharply, at a critical pressure, which depended upon the hydrocarbon concerned and the composition of its mixture with air. The bearing of these observations upon the problem of knock was also discussed. A wide range of explosive media, comprising mainly the higher hydrocarbons contained in liquid fuels, is now being systematically studied, and the present paper summarizes the results obtained for hexane- and isobutane-air mixtures. So far, our results support the view (also recently endorsed by Neumann and Estrovitch) that the lower group of ignition points is the outcome of the survival and further rapid oxidation of certain intermediate bodies, a process favoured by high pressure. whereas the higher group results from ignitions mainly of the products of their thermal decompositions which are favoured by low pressure.

The paper reports on the measurements of maximum exothermic power pulses attainable from a given chemical system. Experimental tests involved the use of a shock tube technique whereby the exothermic process of combustion was controlled by reflected shock, so that it occurred under virtually inviscid flow conditions, while the measurements were performed at a resolution commensurate with the actual rate of chemical reaction. Experimental observations were made by means of a novel method of laser shear interferometry—a cross-breed between holography and the conventional means for measuring refractive index fields, in that, on one hand, it was based on the exploitation of the phase coherence of the laser light beam, recording first a diffraction image of the wave fronts which, for the desired final result, had to be optically reconstructed, and, on the other, it yielded eventually either two-dimensional interferograms or schlieren photographs of the observed phenomena. Chemical systems treated in th...

Hourly average radon-gas concentrations have been measured at elevations of 6.1, 61, 174, and 271 meters on a continuous basis for over 1 year. A search through 5 months of data revealed 383 hours of data that satisfy a steady-state criteria. The steady-state radon profiles correlate with atmospheric stability through a stability ratio and are naturally divided into four categories. The turbulent transfer is parameterized in terms of a radon diffusivity K that is related to general meteorological conditions. An independent specification of K is made based on dimensional reasoning and empirical turbulence statistics in an extension of work by Hanna (1968). A two-layer domain for diffusivity is used in a computational model in which the upper-layer K is independent of height but varies with meteorological conditions; and in the surface layer below 100 meters K is given as K(Z) = K(Z0) (Z/Z0)α.

Differential thermal analysis (DTA) has proven to be among the more reliable and convenient of the several methods devised for the determination of phase boundaries at high pressures and temperatures. This paper discusses in detail the techniques, with the problems of material, design, and operation set forth and an assessment made of the quality of data obtainable by DTA using piston-cylinder apparatus.