Probing microelectromechanical systems in an environmentally controlled chamber using long working distance interferometry.

It is well known that the environment in which micromechanical systems operate significantly affects their performance. It is, therefore, important to characterize micromachine behavior in environments where the humidity, pressure, and chemical composition of the ambient can be precisely controlled. Achieving such a level of environmental control presents significant challenges in view of the required instrumentation. To that end, a custom micromachine characterization system is built that allows for full environmental control (pressure, humidity, and gas composition) while retaining full micromachine characterization techniques (long working distance interferometry, electrical probe connectivity, actuation scripting capability). The system also includes an effective in situ surface cleaning mechanism. As an example of the system's utility, a microcantilever crack healing experiment is conducted and surface adhesion energy measurements are tracked over time after a step change in humidity is applied.

Thermal motion and energetics of self-assembled domain structures: Pb on Cu(111).

Low energy electron microscope measurements of the thermal motion of 50-200 nm diameter Pb islands on Cu(111) are used to establish the nature and determine the strength of interactions that give rise to self-assembly in this two-dimensional, two-phase system. The results show that self-assembled patterns arise from a temperature-independent surface stress difference of approximately 1.2 N/m between the two phases. With increasing Pb coverage, the domain patterns evolve in a manner consistent with models based on dipolar repulsions caused by elastic interactions due to a surface stress difference.

Nanostructures. Self-assembled domain patterns.

The ordered domain patterns that form spontaneously in a wide variety of chemical and physical systems as a result of competing interatomic interactions can be used as templates for fabricating nanostructures. Here we describe a new self-assembling domain pattern on a solid surface that involves two surface structures of lead on copper. The evolution of the system agrees with theoretical predictions, enabling us to probe the interatomic force parameters that are crucial to the process.

High and low luminance letters, acuity reserve, and font effects on reading speed.

We compared reading speed with two fonts, Dutch (serif) and Swiss (sans serif). Text was displayed on a computer monitor, white letters on black, with the RSVP method. Luminance of the letters was either 146.0 or 0.146 cd m-2. Lower-case x-height of the fonts was approximately 5.5 times as large as letter acuity. At the high luminance, there was no difference between reading rates. There was a significant advantage for the Swiss font at the low luminance. The acuity reserve for Swiss was higher than for Dutch at the low luminance, which may account for the difference in reading speeds.

Effects of glucosinolate breakdown products on the hepatic biotransformation system in male rats.

The effects of 5-vinyloxazolidine-2-thione (VOT), 1-cyano-3-butene (CYB) and various isothiocyanates on parameters of hepatic phase I and phase II biotransformation were investigated in male rats after oral treatment for 3 consecutive days. The compounds with the exception of CYB caused increases in liver weight and glutathione S-transferase activity. Cytochrome P-450 level and monooxygenase activities were decreased by the isothiocyanates and CYB. Administration of VOT resulted in contrasting response of monooxygenases: reduced aminopyrine N-demethylation and enhanced aniline hydroxylation. Possible mechanisms were discussed.

Toxicological evaluation of rapeseed products in a subacute feeding study in rats.

Groups of 15 male rats were fed ad libitum for 4 weeks standard diet containing 0, 2.5, 5 or 10% rapeseed protein isolate (RPI), 2.5, 5 or 10% rapeseed extraction residue (RER) or 10% casein. Body weight gain and food intake were recorded weekly. Clinical chemistry analyses, haematology, urinalysis, organ weights and histology were performed terminally. Serum alanine aminotransferase was decreased by RPI, RER and casein, while serum albumin only increased in rats fed RER. Microscopic examinations revealed abnormalities in liver and kidneys of animals at the 10% RPI, RER and casein levels. The absolute liver weights showed increases in the 5 and 10% RER groups and in the 10% RPI group. The relative kidney weights were reduced at all RER levels and in the 2.5% RPI group. Antithyroid activity of the rapeseed products were not noted.

Subacute oral toxicity study of benzyl isothiocyanate in rats.

The subacute toxicity of benzyl isothiocyanate (BITC) was investigated in male rats given oral doses of 0, 50, 100 and 200 mg/kg body weight/day for 4 weeks. Body weight gain and food consumption were decreased with increasing doses of BITC. Haematological changes of toxicological relevance were observed in the highest dose group. BITC administration resulted in increased serum cholesterol level in all treatment groups and decreased serum triglycerides level at 200 mg/kg. Renal dysfunction was indicated by reduced urine volume, proteinuria and enhanced urinary lactate dehydrogenase activity. BITC exposure also affected the weights of various organs and caused histological changes in the ductus choledochus, liver, ileum and mesenteric lymph nodes.

Evidence for multiple terminal oxidases, including cytochrome d, in facultatively alkaliphilic Bacillus firmus OF4.

The terminal oxidase content of Bacillus firmus OF4, a facultative alkaliphile that grows well over the pH range of 7.5 to 10.5, was studied by difference spectroscopy. Evidence was found for three terminal oxidases under different growth conditions. The growth pH and the stage of growth profoundly affected the expression of one of the oxidases, cytochrome d. The other two oxidases, cytochrome caa3 and cytochrome o, were expressed under all growth conditions tested, although the levels of both, especially cytochrome caa3, were higher at more alkaline pH (P.G. Quirk, A.A. Guffanti, R.J. Plass, S. Clejan, and T.A. Krulwich, Biochim. Biophys. Acta, in press). These latter oxidases were identified in everted membrane vesicles by reduced-versus-oxidized difference spectra (absorption maximum at 600 nm for cytochrome caa3) and CO-reduced-versus-reduced difference spectra (absorption maxima at 574 and 414 nm for cytochrome o). All three terminal oxidases were solubilized from everted membranes and partially purified. The difference spectra of the solubilized, partially purified cytochrome caa3 and cytochrome o complexes were consistent with these assignments. Cytochrome d, which has not been identified in a Bacillus species before, was tentatively assigned on the basis of its absorption maxima at 622 and 630 nm in reduced-versus-oxidized and CO-reduced-versus-reduced difference spectra, respectively, resembling the maxima exhibited by the complex found in Escherichia coli. The B. firmus OF4 cytochrome d was reducible by NADH but not by ascorbate-N,N,N',N'-tetramethyl-p-phenylenediamine in everted membrane vesicles. Cytochrome d was expressed under two conditions: in cells growing exponentially at pH 7.5 (but not at pH 10.5) and in cells stationary phase at either pH 7.5 or 10.5. Protein immunoblots with antibodies against subunit I of the E. coli cytochrome d complex reacted only with membrane vesicles that contained spectrally identifiable cytochrome d. Additional evidence that this B. firmus OF4 cytochrome is related to the E. coli complex was obtained with a solubilized, partially purified fraction of cytochrome d that also reacted with antibodies against the subunits of the E. coli cytochrome d.

Protonophore-resistance and cytochrome expression in mutant strains of the facultative alkaliphile Bacillus firmus OF4.

Two protonophore-resistant mutants, designated strains CC1 and CC2, of the facultative alkaliphile Bacillus firmus OF4 811M were isolated. The ability of carbonyl cyanide m-chlorophenylhydrazone (CCCP) to collapse the protonmotive force (delta mu H+) was unimpaired in both mutants. Both resistant strains possessed elevated respiratory rates when grown at pH 7.5, in either the presence or absence of CCCP. Membrane cytochromes were also elevated: cytochrome o in particular in strain CC1, and cytochromes aa3, b, c and o in strain CC2. Strain CC2 also maintained a higher delta mu H+ than the others when grown in the absence of CCCP. When grown in the presence of low concentrations of CCCP, strains CC1 and CC2 both maintained higher values of delta mu H+ than the wild-type parent and correspondingly higher capacities for ATP synthesis. In large-scale batch culture at pH 10.5, both mutant strains grew more slowly than the parent and contained significantly reduced levels of cytochrome o. Cells of stran CC1 also displayed a markedly altered membrane lipid composition when grown at pH 10.5. Unlike previously characterized protonophore-resistant strains of B. subtilis and B. megaterium, neither B. firmus mutant possessed any ability above that of the parent strain to synthesize ATP at given suboptimal values of delta mu H+. Instead, both resistant alkaliphile strains maintained a higher delta mu H+ and a correspondingly higher delta Gp than the parent strain when growing in sublethal concentrations of CCCP, apparently as a result of mutational changes affecting respiratory chain composition. Also of note in both the mutant and the wild-type strains was a marked elevation in the level of one of the multiple terminal oxidases, an aa3-type cytochrome, during growth at pH 7.5 in the presence of CCCP or during growth at pH 10.5, i.e. two conditions that reduce the bulk delta mu H+.

[Toxicological effect of a fatty acid mixture in rats]. / Toxikologische Wirkungen eines Fettsäuregemisches bei Ratten.

The effects of a fatty acids mixture containing nearly 50% odd numbered fatty acids (PC-Säure) were studied in a subchronic toxicity test in male and female rats. The animals received PC-Säure in their diet at levels of 0, 1.25, 2.5 and 5% for 13 weeks. Food intake was increased at 5% PC-Säure level in males. Food efficiency was initially decreased in males and females of this group. Ingestion of PC-Säure resulted in increases of the urine volume and the urinary lactate dehydrogenase activity in both sexes. Male and female rats fed PC-Säure showed elevated serum activities of alkaline phosphatase and leucine aminopeptidase and decreases in serum cholesterol and triglycerides. Dietary PC-Säure elevated the serum creatinine content in males at the two highest levels. A transitory increase in the activity of the serum alanine aminotransferase was observed in females fed 5% PC-Säure. Increased liver and kidney weights were found in both sexes.

[Toxicological evaluation of saccharose carbonic acid esters in basic subchronic feeding trials with rats. 1. Effect of saccharose fatty acid polyester]. / Toxikologische Beurteilung von Saccharosecarbonsäureestern auf der Grundlage subchronischer Fütterungsversuche mit Ratten. 1. Mitt. Wirkung von Saccharosefettsäurepolyester.

Groups of male and female rats received a sucrose fatty acid polyesters containing product (SPE) in their diet for 13 weeks at levels of 0, 5, 10 or 15%. Additional groups were pair-fed to the high-dose SPE-group (standard diet, 92.5%) or given food containing 7.5% hydrogenated lard (HF) or 4.5% fatty acid ethyl ester (FEE). Compared to the controls, there were increases in the food intake in males and females of the SPE-groups, HF- group and FEE-group. Male rats fed SPE showed increases in serum urea nitrogen at all levels, in serum alkaline phosphatase activity and urinary glucose excretion at 10 and 15%, in serum leucine amino-peptidase at 15%. In females dietary SPE increased the blood glucose content and serum alkaline phosphatase activity at 15% and the serum leucine aminopeptidase activity at 10 and 15%.

[Toxicologic evaluation of sucrose carbonic acid esters in basic subchronic feeding studies in rats. 2. Effect of sucroacetoglycerides]. / Toxikologische Beurteilung von Saccharosecarbonsäureestern auf der Grundlage subchronischer Fütterungsversche mit Ratten. 2. Mitt. Wirkung von Sucroacetoglyceriden.

Groups of male and female rats received a sucroacetoglycerides containing product (SAG) for 3 months at dietary levels of 0, 2.5, 5 and 10%. Food consumption was initially increased in females at all SAG-levels. After two weeks significant increases in food intake were observed in males and females fed 10% SAG throughout the feeding period. The serum analysis revealed significantly elevated activity in serum alkaline phosphatase at the highest SAG-level in males and females after 6 weeks and in females after 13 weeks. Histological changes related to the SAG-feeding were noted in the intestinal lymph nodes of male and female animals fed 10% SAG. The no-adverse effect level established in this subchronic feeding study was 5% SAG in the diet of rats, equivalent to a daily intake of 3.6 g/kg body weight in males and 4.0 g/kg in females.

[The subacute toxicity of glucosylthiazolidine-4-carbonic acid in rats]. / Untersuchung der subakuten Toxizität von Glucosylthiazolidin-4-carbonsäure an Ratten.

Glucosylthiazolidine-4-carbonic acid, an intermediate of the Maillard reaction between D-glucose and L-cysteine, was given in doses of 0, 25, 50 or 100 mg/kg b.w. by oral intubation to male and female rats for 21 days. General appearance, growth, food consumption, haematology, urine analysis and serum chemistry including determinations of enzyme activities, organ weights and macroscopic and microscopic pathology were used as criteria for adverse effects. Effects on the kidneys were indicated by oliguria and decreased specific gravity of the urine in males and histopathological changes of the proximal tubules in females. The no-effect dose established from this study is 25 mg/kg b.w.