Grazing-Incidence La/B-Based Multilayer Mirrors for 6.x nm Wavelength.

We studied a possibility of fabricating LaN/B grazing incidence multilayer mirrors for 6.x nm radiation at a relatively large angle of incidence (AOI = 77° off-normal). LaN/B multilayers with a periodicity of 15 nm were successfully fabricated. But when stored in air for one week they showed strong deterioration of the surface due to oxidation of the topmost LaN layers, even though the multilayer was capped with a thin B film. In a series of experiments with variable LaN thickness it was found that the B protective properties depend on the thickness of the underlying LaN layer. Based on these experiments a 15 nm LaN/La/B multilayer with a passivation layer of only 0.4 nm of LaN was fabricated, which did not show any deterioration of the surface within a testing period of half a year. An initial reflectivity of 74.5% at ≈6.66 nm, AOI = 77° off-normal was achieved, which was reduced by 0.5% absolute in half a year, due to contamination of the top B layer.

Characterization of Self-Assembled Monolayers on a Ruthenium Surface.

We have modified and stabilized the ruthenium surface by depositing a self-assembled monolayer (SAM) of 1-hexadecanethiol on a polycrystalline ruthenium thin film. The growth mechanism, dynamics, and stability of these monolayers were studied. SAMs, deposited under ambient conditions, on piranha-cleaned and piranha + H2SO4 cleaned substrates were compared to monolayers formed on H-radical-cleaned Ru surfaces. We found that alkanethiols on H-radical-cleaned Ru formed densely packed monolayers that remained stable when kept in a nitrogen atmosphere. X-ray photoelectron spectroscopy (XPS) shows a distinct sulfur peak (BE = 162.3 eV), corresponding to metal-sulfur bonding. When exposed to ambient conditions, the SAM decayed over a period of hours.

Adsorption and Dissociation of CO2 on Ru(0001).

The adsorption and dissociation of carbon dioxide on a Ru(0001) single crystal surface was investigated by reflection-absorption infrared spectroscopy (RAIRS) and temperature-programmed desorption (TPD) spectroscopy for CO2 adsorbed at 85 K. RAIRS spectroscopy shows that the adsorption of CO2 on a Ru(0001) single crystal is partially dissociative, resulting in CO2 and CO. The CO vibrational mode was also observed to split into two distinct modes, indicating two general populations of CO present at the surface. Furthermore, a time-dependent blue-shift is observed, which is characteristic of increasing CO surface coverage. TPD showed that coverages of up to 0.3 ML were obtained, and no evidence for chemisorption of oxygen on ruthenium was found.

Coexistence of ice clusters and liquid-like water clusters on the Ru(0001) surface.

The RAIRS spectra of water adsorbed on Ru(0001) at 85 K are recorded from 600 cm-1 to 4000 cm-1. Measured at water coverages from 0.13 ML to 2.0 ML, the RAIRS spectra suggest that chemisorption of water on Ru(0001) depends on coverage. Water adsorbs on a clean Ru surface as chemisorbed ice-like clusters (likely through an O-Ru bond) up to 0.33 ML. Above this coverage, the chemisorbed layer saturates. Upon more exposure, water adsorbs as a liquid-like H-bonded layer without bonding to the Ru substrate. The chemisorbed water absorbs 7 times less IR per molecule than the liquid-like structure, which indicates that the orientation of the chemisorbed water is more parallel to the surface. Additionally, the influence of water-Ru bonding on H-bonding is reflected in the OH symmetric stretching mode. Under perturbation from water-Ru bonding, a large red shift (40 cm-1) in the free OH stretching frequency is observed in the chemisorbed clusters. By deconvoluting the main H-bonded OH stretching peak into five Gaussian sub-bands at 2945 ± 5 cm-1, 3210 ± 5 cm-1, 3300 ± 15 cm-1, 3430 ± 5 cm-1 and 3570 ± 10 cm-1, changes in the H-bonding network are rationalized in terms of H-bonding motifs. The donor-acceptor-acceptor motif is significant only in the chemisorbed clusters. On the other hand, the donor-acceptor motif dominates in the liquid-like structure, which increases the disorder present in the adlayer. Although chemisorption is suppressed above 0.33 ML, no structural changes in the ice-like clusters are observed up to multilayer coverage. Therefore, ice-like and liquid-like water coexist in a meta-stable state at 85 K.

Highly efficient blazed grating with multilayer coating for tender X-ray energies.

For photon energies of 1 - 5 keV, blazed gratings with multilayer coating are ideally suited for the suppression of stray and higher orders light in grating monochromators. We developed and characterized a blazed 2000 lines/mm grating coated with a 20 period Cr/C- multilayer. The multilayer d-spacing of 7.3 nm has been adapted to the line distance of 500 nm and the blaze angle of 0.84° in order to provide highest efficiency in the photon energy range between 1.5 keV and 3 keV. Efficiency of the multilayer grating as well as the reflectance of a witness multilayer which were coated simultaneously have been measured. An efficiency of 35% was measured at 2 keV while a maximum efficiency of 55% was achieved at 4 keV. In addition, a strong suppression of higher orders was observed which makes blazed multilayer gratings a favorable dispersing element also for the low X-ray energy range.

High-reflectance La/B-based multilayer mirror for 6.x nm wavelength.

We report a hybrid thin-film deposition procedure to significantly enhance the reflectivity of La/B-based multilayer structures. This is of relevance for applications of multilayer optics at 6.7-nm wavelength and beyond. Such multilayers showed a reflectance of 64.1% at 6.65 nm measured at 1.5-degrees off-normal incidence at PTB (BESSY-II). This was achieved by a special scheme of La passivation. The La layer was nitridated to avoid formation of the optically unfavorable LaBx compound at the B-on-La interface. To avoid the also undesired BN formation at the La-on-B interface, a time-dosed nitridation at the initial stage was applied. This research revealed a good potential for further increase in the reflectivity of multilayer structures at 6.7 nm.

Partial oxidation of methanol on well-ordered V(2)O(5)(001)/Au(111) thin films.

The partial oxidation of methanol to formaldehyde on well-ordered thin V(2)O(5)(001) films supported on Au(111) was studied. Temperature-programmed desorption shows that bulk-terminated surfaces are not reactive, whereas reduced surfaces produce formaldehyde. Formaldehyde desorption occurs between 400 K and 550 K, without evidence for reaction products other than formaldehyde and water. Scanning tunnelling microscopy shows that methanol forms methoxy groups on vanadyl oxygen vacancies. If methanol is adsorbed at low temperature, the available adsorption sites are only partly covered with methoxy groups after warming up to room temperature, whereas prolonged methanol dosing at room temperature leads to full coverage. In order to explain these findings we present a model that essentially comprises recombination of methoxy and hydrogen to methanol in competition with the reaction of two surface hydroxyl groups to form water.

Effect of chronic renal failure with metabolic acidosis on alanine metabolism in isolated liver cells.

BACKGROUND & AIMS: Decreased ureagenesis and gluconeogenesis from alanine have been reported during chronic renal failure in rat. This study addressed the respective roles of plasma-membrane transport and intracellular metabolism in these abnormalities of alanine pathways. METHODS: In hepatocytes isolated from uremic and control rats, we investigated: (1) the influence of uremia on gluconeogenesis and ureagenesis during incubations with alanine; (2) the kinetics of alanine plasma-membrane transport; (3) the relationships between intracellular alanine concentrations and its metabolism. Plasma-membrane alanine transport was assessed after addition of alanine (2 mM) by measuring its intracellular accumulation from 0 to 10 min, in the presence of a transaminase inhibitor. Alanine metabolism was studied in perifused hepatocytes by measuring intracellular alanine concentration together with urea, glucose and lactate production in the presence of increasing concentrations of alanine (0-8 mM). RESULTS: Uremic rats showed decreased plasma bicarbonate. Uremia induced (P<0.05) a decrease in both gluconeogenesis (36%) and ureagenesis (22%). Alanine plasma-membrane transport decreased by 20% during uremia. During perifusions, uremia induced a 30-40% decrease in urea, glucose, and lactate production without modifying intracellular alanine concentration. CONCLUSIONS: In uremic rats with acidosis, hepatocyte alanine utilization was impaired at both plasma-membrane transport and intracellular transamination steps.

[Liver transplantation with a graft taken from a heart transplant patient who was brain-dead]. / Transplantation hépatique avec un greffon prélevé chez un greffé cardiaque en état de mort cérébrale.

The shortage of organ donors has led to progressive softening of selection criteria for organ donation. We report on hepatic transplantation in a 55-year-old woman with primary biliary cirrhosis, whose donor was a 50-year-old heart transplant recipient who became brain stem dead, due to cerebral bleeding 8 months after transplantation. An orthotopic liver transplantation was performed. The postoperative course was uneventful and the recipient was alive and had normal liver function after a 42-month follow-up. Analysis of the literature included ethical consideration, potential hepatotoxic effects of immunosuppressive drugs and modification of the graft immunogenicity. It confirms that transplanted patients should not be a priori excluded from organ donation.

[Dialysis in octagenarians: search for mortality risk factors. Consecutive series of 30 patients]. / La dialyse des octogénaires: recherche de facteurs de risque de mortalité. Série consécutive de 30 patients.

OBJECTIVE: To assess renal replacement therapy in elderly subjects aged 80 years or more in order to depict factors predicting mortality. PATIENTS AND METHODS: We retrospectively studied 30 consecutive patients at the time of starting dialysis from January 1995 to August 1995 and followed this population though March 1996. RESULTS: Only past ischemic heart disease and emergency situations were emphasized as predictor factors of mortality risk. No difference according to mortality between hemodialysis and peritoneal dialysis subgroups was found. CONCLUSION: Excepting usual contraindications for uremic populations, no objective medical criteria are at present time sufficient for excluding chronic renal replacement therapy in very old patients. However, its effect on quality of life must be estimated in order to determine the cost/benefit ratio.

[Anaphrodisia in gilts and sows(author's transl)]. / Anaphrodisie bij gelten en zeugen

The economy of pig breeding and rearing farms is determined mainly by the fertility of the animals. Anaphrodisia causes a considerable disturbance of the fertility. This has a direct effect on the number of litters born per sow per year and thus on the economic results. On the basis of several years of experience at the research station and the production unit of Varkensonderzoekcentrum Nieuw-Dalland the clinical symptoms in gilts and sows are described. Gilts should normally have come into oestrus at the age of about 8 months, and on a well-managed farm about 80% of the sows should come into oestrus within 10 days of weaning, provided that weaning takes place at 5 to 6 weeks. Different forms of anaphrodisia are described, based on the findings of post mortem examinations. These show that in 65-75% of the anaphrodisiac animals the ovaries were insufficiently active. In 20% of the animals that had not shown signs of oestrus, ovulation had in fact taken place. The causes of anaphrodisia must be sought in a disturbance of the hypothalamo-hypophysial ovarian system, in which genetic and health factors play an important role, besides housing and management (insluding feeding). A good keeping of records of sows is indispensable in the solving of the anaphrodisia problem on farms, and this hinges also on an analysis of the farm management and on the power of observation of the farmer. Finally, hormonal therapy is discussed, a distinction being made between breeding and rearing farms.