Transport Properties of a Two-Dimensional PbSe Square Superstructure in an Electrolyte-Gated Transistor.

Self-assembled nanocrystal solids show promise as a versatile platform for novel optoelectronic materials. Superlattices composed of a single layer of lead-chalcogenide and cadmium-chalcogenide nanocrystals with epitaxial connections between the nanocrystals, present outstanding questions to the community regarding their predicted band structure and electronic transport properties. However, the as-prepared materials are intrinsic semiconductors; to occupy the bands in a controlled way, chemical doping or external gating is required. Here, we show that square superlattices of PbSe nanocrystals can be incorporated as a nanocrystal monolayer in a transistor setup with an electrolyte gate. The electron (and hole) density can be controlled by the gate potential, up to 8 electrons per nanocrystal site. The electron mobility at room temperature is 18 cm2/(V s). Our work forms a first step in the investigation of the band structure and electronic transport properties of two-dimensional nanocrystal superlattices with controlled geometry, chemical composition, and carrier density.

Continuous versus batch production of lipids in the microalgae Acutodesmus obliquus.

This work provides a novel quantitative comparison of batch versus continuous microalgal lipid production in the wild type and starchless mutant strain of Acutodesmus obliquus. Both strains showed higher TAG yields on light under batch operation compared to continuous nitrogen limitation. The starchless mutant showed 0.20gTAGmolph-1 for batch and 0.12gTAGmolph-1 for continuous operation, while the wildtype only showed 0.16gTAGmolph-1 for batch and 0.08gTAGmolph-1 for continuous operation. Also, higher TAG contents were found under batch starvation (26% of dry weight for the wildtype and 43% of dry weight for starchless mutant) compared to continuous cultivations (16% of dry weight for the wildtype and 33% of dry weight for starchless mutant). Starch acts as the favoured storage metabolite during nitrogen limitation in A. obliquus, whereas TAG is only accumulated after starch reaches a cellular maximum of 40% of dry weight.

Long-range orientation and atomic attachment of nanocrystals in 2D honeycomb superlattices.

Oriented attachment of synthetic semiconductor nanocrystals is emerging as a route for obtaining new semiconductors that can have Dirac-type electronic bands such as graphene, but also strong spin-orbit coupling. The two-dimensional (2D) assembly geometry will require both atomic coherence and long-range periodicity of the superlattices. We show how the interfacial self-assembly and oriented attachment of nanocrystals results in 2D metal chalcogenide semiconductors with a honeycomb superlattice. We present an extensive atomic and nanoscale characterization of these systems using direct imaging and wave scattering methods. The honeycomb superlattices are atomically coherent and have an octahedral symmetry that is buckled; the nanocrystals occupy two parallel planes. Considerable necking and large-scale atomic motion occurred during the attachment process.

Growth of oil accumulating microalga Neochloris oleoabundans under alkaline-saline conditions.

The effect of elevated pH and salt concentration on the growth of the freshwater microalga Neochloris oleoabundans was investigated. A study was conducted in 24-well plates on the design of a growth medium and subsequently applied in a photobioreactor. An artificial seawater medium with reduced Ca(2+) and PO(4)(3-) could prevent mineral precipitation at high pH levels. Growth was characterized in this new medium at pH 8.1 and at pH 10.0, with 420 mM of total salts. Specific growth rates of 0.08 h(-1) at pH 8.1 and 0.04 h(-1) at pH 10.0 were obtained under controlled turbidostat cultivation. The effect of nitrogen starvation on lipid accumulation was also investigated. Fatty acids content increased not only with nitrogen limitation but also with a pH increase (up to 35% in the dry biomass). Fluorescence microscopy gave visual proof that N. oleoabundans accumulates oil bodies when growing in saline conditions at high pH.

Effects of aggressive behavior and perceived self-efficacy on burnout among staff of homes for the elderly.

This study elicits effects of experienced aggressive behavior and perceived self-efficacy in coping with aggressive behavior on the dimensions of burnout of staff caring for the elderly (N = 551). From the results of the hierarchical regression analysis it appears that physical and psychological aggression and the number of weekly working hours has an effect on emotional exhaustion of staff. Psychological aggression is found to have an effect on depersonalization. The number of weekly working hours and the perceived self-efficacy in turn appear to have an effect on personal accomplishment. Neither sex nor age has an effect on the burnout dimensions. Implications for research and suggestions for work and training of staff caring for the elderly are discussed.

Computer-based simulations enhance clinical experience of dietetics interns.

OBJECTIVE: To determine the impact of computer-based simulations on the performance of dietetics interns in initial clinical rotations. DESIGN: Interns used either a simulation program (Care Planning Simulation System CPSS[) or a computer-based tutorial (Nutrition Care Planning Tutorial NCPT[) during their orientation. Performance of these interns on nutrition care skills was evaluated during their initial clinical rotations. SUBJECTS/SETTING: Participants were 108 dietetics interns from 8 different programs. Each internship had at least 8 interns, and none of the internships awarded a graduate degree. INTERVENTION: Subjects in the experimental group completed nutrition assessment and care planning activities for 3 simulated patients. Subjects in the control group completed a tutorial on assessment and care planning. MAIN OUTCOME MEASURES: Likert scale ratings of 31 behaviors were recorded by clinical preceptors. Behavior statements were grouped into 8 categories and average ratings for each category were determined. STATISTICAL ANALYSIS: Repeated-measures analysis of variance and linear regression were used to compare performance ratings between groups. RESULTS: There were no differences in overall evaluations of the simulation and tutorial groups for the 8-week period. Interns who started clinical rotations immediately after orientation (CPSS-I and NCPT-I groups) were rated lower in all categories than those who began their clinical rotations later (CPSS-D and NCPT-D groups). Maturation and acquisition of general skills likely influenced ratings of interns with delayed clinical rotations. For most categories of behavior the rate of improvement in rating scores was greatest for interns who used CPSS. APPLICATIONS: Computer-based simulations are a promising supplement to current techniques in didactic instruction and may be useful in both didactic and practice settings. Computer-based simulations can provide more varied practice experiences to didactic students and interns in preparation for more skilled entry-level positions in dietetics.

Computer-assisted instruction improves clinical reasoning skills of dietetics students.

OBJECTIVE: The effects of a computer-assisted instruction (CAI) tutorial program on learning clinical reasoning skills were compared in undergraduate dietetics students. DESIGN: A drill-and-practice program to control for time on task, and tutorial program, and a simulation program, as the test vehicle, were developed. The tutorial and simulation programs presented data on a patient with cardiovascular disease. SETTING: Subjects were tested in 30 undergraduate dietetics programs. SUBJECTS: Participants were 413 undergraduate diet therapy students enrolled in a coordinated program in dietetics (CPD) or a didactic program in dietetics (DPD). INTERVENTION: After completion of lectures on cardiovascular disease, subjects were given the drill-and-practice program plus a simulation test (group 1), the tutorial plus a simulation test (group 2), or the simulation test only (group 3). MAIN OUTCOME MEASURES: Scores on the simulation test were compared. Variables included type of CAI, dietetics program, year in school, computer experience, and experience using a medical chart. Mastery of objectives related to lower- and higher-level clinical reasoning skills introduced in the tutorial program was computed. STATISTICAL ANALYSIS: One-way analysis of variance and Student-Newman Keuls tests were conducted to determine any differences among the three groups. Reliability was determined using the Kuder-Richardson Formula 20. RESULTS: The reliability coefficient of the stimulation test was 0.93. Group 2 higher on the simulation test than group 1 or group 3. As a group, the CPD students scored higher than the DPD students. When CPD and DPD students were divided into the three experimental groups, there was no significant difference between the CPD and DPD student simulation scores. Group 2 mastered all objectives for lower-level reasoning skills and the higher-level decision-making objective better than groups 1 and 3. APPLICATIONS/CONCLUSIONS: A computer tutorial program enhanced clinical reasoning skills in undergraduate dietetics students. This type of program could be used to supplement many topics taught in diet therapy and provide DPD students with experimental learning before their clinical intern practicums.

Potassium substitution via the oral route: does its efficacy depend on the anion of the potassium salt?

In an open, randomized study, we investigated the effect of oral potassium chloride (KCl) and of potassium citrate/bicarbonate (K-cit/bic) in 42 patients with hypokalemia (less than or equal to 3.5 mmol/l). In both groups 80 mmol K+ were administered daily. The parameters examined were serum potassium concentration, acid-base status, and urinary electrolyte excretion. Parameters were evaluated on days 0, 2, 4, and 6. With KCl, [K+] increased from 3.2 +/- 0.2 (mean +/- SD) on day 0 to 3.8 +/- 0.4 mmol/l on day 2 (p less than 0.005) and 4.0 +/- 0.5 mmol/l on day 4 (p less than 0.005). On day 6 [K+] was also 4.0 +/- 0.4 mmol/l (p less than 0.005 vs day 0). With K-cit/bic, [K+] increased from 3.2 +/- 0.2 to 3.7 +/- 0.4 on day 2, 3.9 +/- 0.5 on day 4, and 4.1 +/- 0.6 mmol/l on day 6 (all p less than 0.005 vs day 0). The increase of [K+] was not different between the two groups. Blood pH on day 0 was in the normal range in both groups and did not change significantly during the study. There was a decrease of carbon dioxide partial pressure (pCO2) with KCl from 38.7 +/- 4.9 on day 0 to 36.4 +/- 3.6 on day 2 (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Pulmonary sequestration with congenital broncho-oesophageal fistula.

Complaints of older patients due to a congenital broncho-pulmonary foregut malformation are rare. A 53 yr old woman presented with this condition. The diagnosis was made by means of oesophagography, which showed a broncho-oesophageal fistula. Using the supplying vessel, identified by angiography, as a guideline, an operation was carried out to correct the anomaly.

[Caries incidence and oral hygiene level in young school children in Gottingen]. / Kariesbefall und Sanierungsgrad bei Grundschülern in Göttingen.

669 school beginners and 739 fourth-year pupils in Göttingen were examined for caries prevalence and dental hygienic measures. 28% of first-year pupils examined had naturally healthy primary teeth; the average DFS was 6.8. Only 12% of the carious primary tooth surfaces had intact fillings. Carious defects in permanent teeth were restricted to sixth-year molars. Among the fourth-year pupils 26.8% had no caries on their permanent teeth; the average DMFS was 3.9. In this age group 60% of the carious tooth surfaces had been treated and the M components observed were minimal. A total of only 16 sixth-year molars were missing because of caries in all the children examined. A comparison of prevalence rates among different schools revealed considerable differences: Average DMFS values at the various schools ranged from 2.0 to 5.5.

[A selective, need-oriented prevention program for primary schoolchildren - results after two years]. / Ein bedarfsorientiertes Prophylaxeprogramm für Grundschüler.

427 first grade pupils from primary schools in Göttingen participated in a selective, need-oriented preventive program. Following a clinical examination and an additional saliva test the children were assigned to three risk groups, according to the severity of the initial findings. Each group received preventive care of varying intensity. Two years later the children of risk group 1 ("minor caries risk") showed a mean 0.5 and those of risk group 2 ("medium caries risk") a mean 1.0 new DF surfaces. In the children of the high caries risk group the average caries increment was 1.8 DF surfaces. The degree of sanation of the deciduous teeth could be improved from 10% to 47% within the two years' test period. The saliva tests revealed that the number of cariogenic organisms was markedly reduced in the course of the preventive program.

Studies on a new formulation of ceftazidime--ceftazidime arginine--in patients with recurrent chest infections.

One hundred hospital patients with respiratory infections were treated with 1 or 2 g intramuscular injections of ceftazidime sodium or of a new formulation of ceftazidime with arginine three times daily. Clinical and microbiological assessments showed no significant differences in efficacy between the two preparations. Local pain necessitating lignocaine was noted in five of 49 evaluable patients given ceftazidime sodium (10.2%) but in none of the 50 receiving ceftazidime arginine. No other unwanted effects were recorded. The pharmacokinetic results after the 1 g injections showed slightly higher Cmax values with ceftazidime arginine with correspondingly greater 0-7 h AUC values. The mean AUCs were almost identical after the 2 g injections.

Effect of nicotinamide on drug metabolizing enzymes in the neonatal rat.

Sprague-Dawley rats were raised by dams (mother reared, MR) or artificially reared from day 4 to day 11, using chronic intragastric cannulas, and infused with one of four diets: control (AR); or supplemented with nicotinamide-low (LN, 300 mg/l), medium (MN, 750 mg/l), or high (HN, 1500 mg/l). Liver to body weight ratios were higher in all artificially reared groups (AR, LN, MN, HN) compared to MR pups. The amount of recovered hepatic microsomal protein was lower in all artificially reared groups when compared with MR pups. Uridine diphosphoglucuronyl transferase activity with para-nitrophenol as the substrate (UDPGT-PNP) was greater in all of the artificially reared groups compared to the MR group. UDPGT-PNP activity in the HN group was greater than in the AR, LN, or MN groups. Cytochrome P-450 concentration was highest in the MR group, whereas there were no differences among the artificially reared groups. It was concluded that the artificial rearing process stimulated hepatic UDPGT-PNP activity and depressed cytochrome P-450 concentrations, whereas dietary supplementation with nicotinamide during the preweanling period resulted in a further increase in UDPGT-PNP activity.

Paraquat concentration and renal function in mice fed purified and cereal-based diets.

Paraquat, a broad spectrum herbicide, has differential effects in mice depending upon whether a purified or a cereal-based diet is fed. Male ICR mice were fed either a cereal-based closed-formula diet or a purified diet for 7-14 days. After intraperitoneal injection, radiolabeled paraquat was measured in blood, lung, kidney, liver, heart, and urine over a 48-hr period. Accumulation of organic ions was measured in renal tissue slices at 3 hrs after injection of paraquat. Hematocrit, plasma urea nitrogen, and urine volume were measured from 8 to 72 hr after administration of paraquat. From 3 to 12 hr after injection, concentrations of paraquat in plasma, kidney, and liver were greater in mice fed a purified diet than in mice fed a closed-formula diet. Concentration of paraquat in the lung and urine did not differ between dietary groups over a 48-hr period. Three hours after paraquat intake renal tissue organic ion accumulation was higher in mice fed a purified diet. Within 72 hr after paraquat administration plasma urea nitrogen concentration and hematocrit were greater in mice fed a purified diet. Higher tissue concentrations of paraquat in mice fed a purified diet could explain dietary differences previously observed for LD50 and survival time after paraquat injection. While changes in plasma urea and paraquat concentration in the kidney were observed, the effect of a diet-paraquat interaction on renal function was not conclusive, since there was no difference in excretion of paraquat between the dietary groups.

Lack of effect of a purified diet on carbon tetrachloride or oxygen toxicity.

The study was designed to examine the effect of feeding a purified versus a cereal-based closed formula (control) diet on toxicity to carbon tetrachloride or oxygen. Twenty-eight-day-old male ICR mie were fed a purified or cereal-based closed formula diet for 14 or 84 days. After treatment with carbon tetrachloride or exposure to a 100% oxygen atmosphere, survival time and percentage survival were the same for mice fed either diet. In both dietary groups, carbon tetrachloride injection caused a similar decrease in hepatic nonprotein sulfhydryl compounds and glucose-6-phosphatase activity. It was concluded that, unlike previous findings with the herbicide paraquat, toxicity to carbon tetrachloride or oxygen is not increased by feeding a purified diet compared to a closed formula diet. The results provided further evidence to suggest that a free radical-lipid peroxidation process may not be the primary mechanism of the toxic effects of paraquat.

Alteration of toxicity to paraquat in mice fed a purified or cereal-based diet.

Toxicity to several compounds is affected by dietary changes that by themselves do not result in nutrient deficiency or toxicity. The herbicide paraquat was tested to determine whether feeding a cereal-based closed formula diet or a purified diet would affect the sensitivity of mice to paraquat. After an intraperitoneal injection of paraquat, 28-day-old male ICR mice, which had been fed a purified diet for periods of 3 to 84 days, had shorter survival times and lower 7-day percent survivals than mice fed a cereal-base closed formula diet. The median lethal dose of paraquat was significantly lower in mice fed the purified diet rather than the closed formula diet. Median effective time to death was also significantly shorter for male ICR mice fed the purified diet rather than the closed formula diet. Female ICR mice and male B6C3F1 mice fed the purified diet for 7 days were more susceptible to paraquat toxicity than similar mice fed the closed formula diet. Male C57BL/6J mice were more sensitive to the effects of paraquat regardless of the type of diet. Modifying the content of lipid, vitamin E, or selenium, or adding butylated hydroxytoluene to the purified diet did not prevent a decrease in 7-day percent survival and survival time compared to male ICR mice fed a closed formula diet. Male ICR mice fed the purified diet with egg-white protein had significantly longer survival times compared to mice fed the purified diet with casein. It is concluded that strictly defined diets must be used in the study of paraquat toxicity to control for any paraquat-diet interactions.