Characterization of the PEG layer of sterically stabilized liposomes: a SAXS study.

Synchrotron small-angle X-ray scattering analysis of the bilayer structure of a pharmacologically relevant sterically stabilized liposome system is presented. Describing the electron density profile of the bilayer with the superposition of Gaussian functions, the contribution of the poly(ethylene glycol) (PEG) layers to the total electron density was identified. The changes in the thickness of the PEG layer as well as the distribution of the PEG chains among the outer and inner leaflets of the bilayers were followed by changing the molar ratio of the PEG-lipid and the molar weight of the PEG molecule.

Atomic structure and structural stability of Sc75Fe25 nanoglasses.

Nanoglasses are solids consisting of nanometer-sized glassy regions connected by interfaces having a reduced density. We studied the structure of Sc(75)Fe(25) nanoglasses by electron microscopy, positron annihilation spectroscopy, and small-/wide-angle X-ray scattering. The positron annihilation spectroscopy measurements showed that the as-prepared nanoglasses consisted of 65 vol% glassy and 35 vol% interfacial regions. By applying temperature annealing to the nanoglasses and measuring in situ small-angle X-ray scattering, we observed that the width of the interfacial regions increased exponentially as a function of the annealing temperature. A quantitative fit to the small-angle X-ray scattering data using a Debye-Bueche random phase model gave a correlation length that is related to the sizes of the interfacial regions in the nanoglass. The correlation length was found to increase exponentially from 1.3 to 1.7 nm when the sample temperature was increased from 25 to 230 °C. Using simple approximations, we correlate this to an increase in the width of interfacial regions from 0.8 to 1.2 nm, while the volume fraction of interfacial regions increased from 31 to 44%. Using micro-compression measurements, we investigated the deformation behavior of ribbon glass and the corresponding nanoglass. While the nanoglass exhibited a remarkable plasticity even in the annealed state owing to the glass-glass interfaces, the corresponding ribbon glass was brittle. As this difference seems not limited to Sc(75)Fe(25) glasses, the reported result suggest that nanoglasses open the way to glasses with high ductility resulting from the nanometer sized microstructure.

Network structure of polyfluorene sheets as a function of alkyl side chain length.

The formation of self-organized structures in poly(9,9-di-n-alkylfluorene)s ∼1 vol % methylcyclohexane (MCH) and deuterated MCH (MCH-d(14)) solutions was studied at room temperature using neutron and x-ray scattering (with the overall q range of 0.00058-4.29 Å(-1)) and optical spectroscopy. The number of side chain carbons (N) ranged from 6 to 10. The phase behavior was rationalized in terms of polymer overlap, cross-link density, and blending rules. For N=6-9, the system contains isotropic areas and lyotropic areas where sheetlike assemblies (lateral size of >400 Å) and free polymer chains form ribbonlike agglomerates (characteristic dimension of >1500 Å) leading to a gel-like appearance of the solutions. The ribbons are largely packed together with surface fractal characteristics for N=6-7 but become open networklike structures with mass fractal characteristics for N=8-9, until the system goes through a transition to an isotropic phase of overlapping rodlike polymers for N=10. The polymer order within sheets varies allowing classification for loose membranes and ordered sheets, including the so-called ß phase. The polymers within the ordered sheets have restricted motion for N=6-7 but more freedom to vibrate for N=8-9. The nodes in the ribbon network are suggested to contain ordered sheets cross-linking the ribbons together, while the nodes in the isotropic phase appear as weak density fluctuations cross-linking individual chains together. The tendencies for macrophase separation and the formation of non beta sheets decrease while the proportion of free chains increases with increasing N. The fraction of ß phase varies nonlinearly, reaching its maximum at N = 8.

Heterogeneities in CuZr-based bulk metallic glasses studied by x-ray scattering.

Inhomogeneities in two CuZr-based bulk metallic glasses (BMGs) were studied by using synchrotron radiation x-ray scattering techniques. (Cu(4.5/5.5)Ag(1/5.5))(46)Zr(46)Al(8) BMG was found to be more inhomogeneous than Cu(46)Zr(46)Al(8) BMG on the small length scale, where Cu and Ag atoms form enriched zones. Such heterogeneities are locally favorable for forming close-packed icosahedron-like clusters in three-dimensional space, greatly promoting the glass forming ability of this alloy. Upon annealing near the T(g) temperature, the heterogeneities were reduced initially at low temperature and short time annealing, then regenerated again for temperature increase and time extension. The average environment around Zr atoms almost does not change. However, the heterogeneity increases for Cu, Zr and Ag atoms once nanocrystallization happens.

On the chemical state and distribution of Zr- and V-based additives in reactive hydride composites.

Reactive hydride composites (RHCs) are very promising hydrogen storage materials for future applications due to their reduced reaction enthalpies and high gravimetric capacities. At present, the materials' functionality is limited by the reaction kinetics. A significant positive influence can be observed with addition of transition-metal-based additives. To understand the effect of these additives, the chemical state and changes during the reaction as well as the microstructural distribution were investigated using x-ray absorption near-edge structure (XANES) spectroscopy and anomalous small-angle x-ray scattering (ASAXS). In this work, zirconium- and vanadium-based additives were added to 2LiBH4-MgH2 composites and 2LiH-MgB2 composites and measured in the vicinity of the corresponding absorption edge. The measurements reveal the formation of finely distributed zirconium diboride and vanadium-based nanoparticles. The potential mechanisms for the observed influence on the reaction kinetics are discussed.

Association of alcohol consumption and Helicobacter pylori infection in young adulthood and early middle age among patients with gastric complaints. A case-control study on Finnish conscripts, officers and other military personnel.

There is growing evidence that Helicobacter pylori is responsible for a variety of gastric and duodenal changes which can eventually lead to stomach cancer. Little is known about risk factors for H. pylori infection. We re-analyzed the association of alcohol with H. pylori positivity in 451 conscripts, officers and other military personnel endoscoped due to gastric complaints in the Central Military Hospital of Finland in 1987 and 1988. Serology and culture were done in all patients. Alcohol consumption histories were obtained by use of a self-administered questionnaire. We observed a high odds ratio (OR) of H. pylori infection among young adults who were heavy alcohol consumers compared to non-drinkers (OR 5.32, 95% confidence interval: 1.09-25.95). There was evidence of a dose response when heavy and moderate drinkers were compared to non-drinkers (Mantel-Haenszel chi 2 for trend, p = 0.02) in young adulthood. A subgroup of young respondents who reported drinking all classes of alcohol (including hard liquor) showed an even stronger association and more significant dose-response. Multivariate techniques revealed a qualitative interaction of alcohol with H. pylori positivity in different age groups and among old people an inverse association of H. pylori and alcohol consumption was observed. These findings, if confirmed independently, might have implications for preventing a variety of gastric and duodenal lesions, since they allow identification of high risk groups.

Role of metronidazole resistance in therapy of Helicobacter pylori infections.

Susceptibility to metronidazole was determined by disk diffusion tests for 559 strains of Helicobacter pylori isolated from patients. The overall metronidazole resistance was 26%. In males metronidazole-resistant strains made 18% of all H. pylori strains, and in females the corresponding figure was 40% (P less than 0.001). MICs of metronidazole were determined for H. pylori strains from 86 patients undertaking triple therapy, i.e., treatment with colloidal bismuth subcitrate, amoxicillin, and metronidazole. Of the nonresponders who remained culture positive despite the therapy, 69% had strains with metronidazole MICs of greater than or equal to 32 micrograms/ml before the therapy, and all nonresponders had metronidazole-resistant strains after the therapy. Metronidazole resistance was, however, also found in 27% of responders before therapy. To find whether the MICs of metronidazole for H. pylori strains remained constant for longer periods, consecutive isolates sampled several years apart from the same patients were tested in parallel and no changes in the MICs were found. H. pylori was successfully eradicated by the triple therapy from 91% of patients with metronidazole-susceptible pretreatment strains and from 63% of patients with metronidazole-resistant strains before the therapy (P less than 0.01). Although resistance to metronidazole has a significant role in treatment failures in H. pylori infections, high eradication rates can be achieved with the use of the present triple therapy even in populations with a high overall metronidazole resistance rate.

Arthroplasty of the knee joint. With special reference to complications.

Ninety-one arthroplasties of the knee joint--all performed by the same orthopaedic surgeon, were followed for from 6 months to 6 years (mean 3.5 years). At the time of the primary operation the mean age of the patients, most of whom had rheumatoid arthritis, was 60 years. The prostheses most often used were the Geomedic, the modular and the polycentric. The most consistently good results were achieved with the Geomedic prosthesis. The primary arthroplasty failed in 16 knees (17.6%); deep infections developed in four knees (4.4%). In three knees the prosthesis fractured and in two knees the supporting bone fractured. All these fractures occurred in the medial compartment of the knee joint. Loosening of the prosthesis--with or without concomitant infection or fracture of the prosthesis--was the most common local complication (nine knees). Reoperations were performed, during the follow-up period reported on here, on all knees in which complications developed, except one. Eight knees, about 9%, required arthrodesis. In six knees the prosthesis was replaced, and one knee was treated by arthrotomy and closed irrigation. The four deep infections resolved during the follow-up period--one after arthrodesis of the joint and one after arthrotomy and closed irrigation. In the other two knees with deep infection the prosthesis was replaced.

Treatment of acute gouty arthritis with proquazone and indomethacin. A comparative, double-blind trial.

Eighteen patients (11 men and 7 women) suffering from primary or secondary gout, were treated with either proquazone or indomethacin for acute attacks in a double-blind study. There were 9 patients in each treatment group. A marked improvement of clinical symptoms appeared in 2-3 days. In the proquazone group, complete remission was achieved in 6 patients, a good result in one, and a slight improvement in one patient, whereas one patient did not respond to treatment. The corresponding figures for the indomethacin group were 4 cases with complete remission, 4 with a good result, and one not responding to treatment. A significant decrease in s-uric acid values was noted in the proquazone group. In this group too, mild gastrointestinal symptoms appeared in 2 patients.