Insights into the Growth of Ternary WSSe Nanotubes in an Atmospheric CVD Reactor.

The synthesis of complex new nanostructures is challenging but also bears the potential for observing new physiochemical properties and offers unique applications in the long run. High-temperature synthesis of ternary WSe2xS2(1-x) (denoted as WSSe) nanotubes in a pure phase and in substantial quantities is particularly challenging, requiring a unique reactor design and control over several parameters, simultaneously. Here, the growth of WSSe nanotubes with the composition 0 ≤ x < 1 from W18O49 nanowhiskers in an atmospheric chemical vapor deposition (CVD) flow reactor is investigated. The oxide precursor powder is found to be heavily agglomerated, with long nanowhiskers decorating the outer surface of the agglomerates and their core being enriched with oxide microcrystallites. The reaction kinetics with respect to the chalcogen vapors varies substantially between the two kinds of oxide morphologies. Insights into the chemical reactivity and diffusion kinetics of S and Se within W18O49 nanowhishkers and the micro-oxide crystallites were gained through detailed microscopic, spectroscopic analysis of the reaction products and also through density functional theory (DFT) calculations. For safety reasons, the reaction duration was limited to half an hour each. Under these circumstances, the reaction was completed for some 50% of the nanotubes and the other half remained with thick oxide core producing new WOx@WSSe core-shell nanotubes. Furthermore, the selenium reacted rather slowly with the WOx nanowhiskers, whereas the more ionic and smaller sulfur atoms were shown to diffuse and react faster. The yield of the combined hollow and core-shell nanotubes on the periphery of the agglomerated oxide was very high, approaching 100% in parts of the reactor boat. The nanotubes were found to be very thin (∼80% with a diameter <40 nm). The optical properties of the nanotubes were studied, and almost linear bandgap modulation was observed with respect to the selenium content in the nanotubes. This investigation paves the way for further scaling up the synthesis and for a detailed study of the different properties of WSSe nanotubes.

The role of decay accelerating factor in the immunopathogenesis of cytomegalovirus infection.

A wide variety of the host immune elements play an influential role in the defence against cytomegalovirus (CMV) infection. However, the role of complement in the clearance of CMV infection is less well studied. Decay accelerating factor (DAF/CD55) is a membrane-bound complement regulatory protein that inhibits the formation and accelerates the decay of C3-convertase. Here we hypothesize that murine CMV (MCMV) utilizes DAF as an immunoevasive strategy through down-regulation of host adaptive responses against the virus. To test our hypothesis, DAF knock-out (DAF KO) C57BL/6 mice and wild-type (WT) littermates were infected with a sublethal dose of MCMV, and their immune responses were compared. WT mice lost 7·8% of their initial weight within the first 4 days after infection and quickly began to recover. This is in contrast to the DAF KO mice, that lost a total of 19·4% of their initial weight and did not start recovery until 6 days post-infection. Flow cytometric analysis of lung digests revealed that infected DAF KO mice had a significantly increased infiltration of inflammatory cells, the majority being CD8(+) T lymphocytes. Serum levels of tumour necrosis factor (TNF)-α and interferon (IFN)-γ were also increased markedly in the DAF KO mice compared to the infected WT mice. More interestingly, increased viral genome copies (DNA) in the splenocytes of DAF KO mice was accompanied with mRNA transcripts in the DAF KO mice, an indication of active viral replication. These data suggest an intriguing effect of reduced DAF expression on host responses following in vivo MCMV infection.

Increased morbidity and mortality in murine cytomegalovirus-infected mice following allogeneic bone marrow transplant is associated with reduced surface decay accelerating factor expression.

Infection with cytomegalovirus (CMV) remains a significant cause of morbidity and mortality following allogeneic bone marrow transplantation (allo-BMT). The manifestations of CMV infection can range from neurological and haematological abnormalities to diminished graft survival and, in extreme cases, death. Many clinical studies have shown a direct correlation between cytomegalovirus infection and increased morbidity and mortality post allo-BMT, yet the exact mechanism is not well understood. Although driven primarily by T cell responses, the role of complement activation in acute and chronic graft-versus-host disease (GVHD) has also become more evident in recent years. The present studies were performed to examine the effects of murine cytomegalovirus (MCMV) infection on decay accelerating factor (DAF) and MCMVs role in exacerbating morbidity and mortality post-allo-BMT. Mice infected previously with a sublethal dose of MCMV (1 × 105 plaque-forming units) have reduced expression of DAF on lung tissues and lymphocytes following allo-BMT. More importantly, mortality rates post-allo-BMT in recipient DAF knock-out mice receiving wild-type bone marrow are increased, similar to wild-type MCMV-infected recipient mice. Similarly, DAF knock-out mice showed greater intracellular interferon (IFN)-γ production by lung CD8 T cells, and infection with MCMV further exacerbated both intracellular IFN-γ production by CD8 T cells and mortality rates post-allo-BMT. Together, these data support the hypothesis that MCMV infection augments morbidity and mortality post-allo-BMT by reducing surface DAF expression.

High-Rate, Gas-Phase Growth of MoS2 Nested Inorganic Fullerenes and Nanotubes.

The gas-phase reaction between MoO3-x and H(2)S in a reducing atmosphere at elevated temperatures (800 degrees to 950 degrees C) has been used to synthesize large quantities of an almost pure nested inorganic fullerene (IF) phase of MoS(2). A uniform IF phase with a relatively narrow size distribution was obtained. The synthesis of IFs appears to require, in addition to careful control over the growth conditions, a specific turbulent flow regime. The x-ray spectra of the different samples show that, as the average size of the IF decreases, the van der Waals gap along the c axis increases, largely because of the strain involved in folding of the lamella. Large quantities of quite uniform nanotubes were obtained under modified preparation conditions.

Improved orthodontic stainless steel wires coated with inorganic fullerene-like nanoparticles of WS(2) impregnated in electroless nickel-phosphorous film.

OBJECTIVE: To reduce friction between orthodontic stainless wires and bracket by coating the wire with nickel-phosphorous electroless film impregnated with inorganic fullerene-like nanoparticles of tungsten disulfide (IF-WS(2)) which are potent dry lubricants. METHODS: Coating was preformed by inserting stainless steel (SS) wires into electroless solutions of nickel-phosphorus (Ni-P) and IF-WS(2). The coated wires were analyzed by SEM (scanning electron microscope) and EDS (energy-dispersive X-ray spectrometer) as well as by tribological tests using a ball-on-flat device. Friction tests simulating archwire functioning of the coated and uncoated wires were carried out by an Instron machine. The adhesion properties of the coated wires after friction were analyzed by a Raman microscope. RESULTS: SEM/EDS analysis of the coated wires showed clear impregnation of the IF-WS(2) nanoparticles in the Ni-P matrix. The friction coefficient measured by the ball-on-flat tribometer was significantly reduced (from 0.25 to 0.08). The friction forces as measured with the Instron on the coated wire were reduced by up to 54% (4.00 N+/-0.19 uncoated vs. 1.85 N+/-0.21 coated). Raman spectra showed that even after extensive friction tests the Ni-P with the IF-WS(2) nanoparticles is attached to the underlying stainless steel wire. CONCLUSIONS: It is proposed that the wires coated with these nanoparticles might offer a novel opportunity to substantially reduce friction during tooth movement. A few tests undertaken to evaluate the toxicity of the fullerene-like nanoparticles have provided indications that they might be biocompatible.

Time domain dielectric spectroscopy study of human cells. II. Normal and malignant white blood cells.

The dielectric properties of human lymphocyte suspensions were studied by time domain dielectric spectroscopy (TDDS). Nine populations of malignant and normal lymphocytes were investigated. Analysis of the dielectric parameters of cell structural parts were performed in the framework of Maxwell-Wagner mixture formula and the double-shell model of cell. The specific capacitance of the cell membranes was estimated by the Hanai-Asami-Koisumi formula. It was shown that the dielectric permittivity, capacitance and conductivity values of cell membranes are higher for normal lymphocytes than for the malignant ones. The difference of the same parameters for normal B- and T-cells is also discussed.

Dielectric relaxation measurements of 12 kbp plasmid DNA.

The dielectric properties of 12 kbp plasmid DNA have been measured as a function of temperature in the range 5 degrees C to 40 degrees C. Time domain reflectometry was used to obtain dielectric data over the frequency range from 200 kHz to 3 GHz. Values of the frequency dependent polarisability per DNA macromolecule have been determined from the measurements. Possible mechanisms that could account for the dielectric dispersion are also discussed, in particular the counterion fluctuation model of Manning-Mandel-Oosawa.

Time domain dielectric spectroscopy study of human cells. I. Erythrocytes and ghosts.

A method, allowing correction of electrode polarization effect in case of cell suspensions of small volume fraction is proposed. The dielectric behavior of human erythrocytes and erythrocyte ghosts suspensions was studied by time domain dielectric spectroscopy (TDDS) and the estimation of the dielectric constants of cell's structural parts (membrane, cytoplasm) on the basis of suitable models are presented. It was shown that in the case of small volume fraction of cells in suspension, the electrode polarization effect can be taken into account by the additional measurement of the corresponding supernatant. The optimal volume fraction of cells in suspensions in the TDDS measurements was found to be 3%-10%. The erythrocyte and erythrocyte ghost suspensions were found to demonstrate a single dispersion which can be described by the Debye equation. The membrane dielectric constant of different erythrocytes and ghosts was distributed near 5.

Antecedent use of fluoroquinolones is associated with resistance to moxifloxacin in Clostridium difficile.

OBJECTIVE: Moxifloxacin is characterized by high activity against Gram-positive cocci and some Gram-positive and -negative anaerobes, including Clostridium difficile. This study investigates the role of prior quinolone use in relation to patterns of susceptibility of C. difficile to moxifloxacin. METHODS: Sixty-three clinical isolates of C. difficile were investigated for toxigenicity, susceptibility to moxifloxacin, and mutations in the DNA gyrase gene. The medical histories for 50 of these patients were available and used to identify previous fluoroquinolone use. RESULTS: Thirty-three (52.4%) strains showed resistance to moxifloxacin (MICs > or = 16 mg/L). All moxifloxacin-resistant strains harbored a mutation at amino acid codon Ser-83 of gyrA. Forty-five isolates (71.4%) were toxigenic; all moxifloxacin-resistant strains were in this group. Resistance to moxifloxacin was associated with prior use of fluoroquinolones (P-value 0.009, chi-square). CONCLUSIONS: Although the use of moxifloxacin to treat C. difficile-associated diarrhea is not likely to be common, these data show a relationship between antecedent fluoroquinolone use and resistance to moxifloxacin in C. difficile isolates, and raise questions regarding selection pressure for resistance placed on colonizing bacteria exposed to fluoroquinolones. Mutations in gyrA are involved in moxifloxacin resistance.

Fullerene-like WS(2) nanoparticles and nanotubes by the vapor-phase synthesis of WCl(n) and H(2)S.

Inorganic fullerene-like (IF) nanoparticles and nanotubes of WS(2) were synthesized by a gas phase reaction starting from WCl(n) (n = 4, 5, 6) and H(2)S. The effect of the various metal chloride precursors on the formation of the products was investigated during the course of the study. Various parameters have been studied to understand the growth and formation of the IF-WS(2) nanoparticles and nanotubes. The parameters that have been studied include flow rates of the various carrier gases, heating of the precursor metal chlorides and the temperature at which the reactions were carried out. The best set of conditions wherein maximum yields of the high quality pure-phase IF-WS(2) nanoparticles and nanotubes are obtained have been identified. A detailed growth mechanism has been outlined to understand the course of formation of the various products of WS(2).

Dielectric properties of glycerol/water mixtures at temperatures between 10 and 50 degrees C.

At six temperatures T between 10 and 50 degrees C and at mole fractions x(g) of glycerol (0

On the origin of the lattice constant anomaly in nanocrystalline ceria.

The lattice parameter of nanocrystalline ceria films prepared by sputtering was monitored as a function of annealing temperature. Within the temperature range of 150-420 degrees C, an equilibrium with atmospheric oxygen is established within a few hours, whereas grain growth does not occur. On the basis of the experimental results and analysis of literature data, we present a model that posits the formation of a non-uniform grain structure with stoichiometric interiors and oxygen deficient boundaries. This model, based on defect thermodynamics, correctly describes the dependence of the lattice parameter of nanocrystalline ceria on annealing temperature and grain size and can be extended to other materials as well.

Characterization of the Bacteroides fragilis pathogenicity island in human blood culture isolates.

Bacteroides fragilis is an important anaerobic pathogen accounting for up to 10% of bacteremias in adult patients. Enterotoxin producing B. fragilis (ETBF) strains have been identified as enteric pathogens of children and adults. In order to further characterize the B. fragilis pathogenicity island (BfPAI) and using PCR assays for bft- and mpII-metalloprotease genes, we determined the frequency of B. fragilis strains with pattern I (containing the BfPAI and its flanking region), pattern II (lacking both the BfPAI and the flanking region), and pattern III (lacking the BfPAI but containing the flanking region) in 63 blood culture isolates. The results were compared to 197 B. fragilis isolates from different clinical sources. We found 19% of blood culture isolates were pattern I (ETBF), 43% were pattern II (NTBF) and 38% were pattern III (NTBF). Comparatively, B. fragilis isolates from other clinical sources were 10% pattern I, 47% pattern II and 43% pattern III. This suggests that the pathogenicity island and the flanking elements may be general virulence factors of B. fragilis.

Analysis of dielectric spectra of eukaryotic cells by computer modeling.

An analysis of dielectric spectra, obtained by computer modeling, of spherical eukaryotic cells (lymphocytes in particular) is presented. The number of fitting parameters required to describe these spectra is determined. The influence of parameter variation on the spectral shape is illustrated.

Perception of teratogenic risk by pregnant women exposed to drugs and chemicals during the first trimester.

We assessed the perception of teratogenic risk by 80 women attending an antenatal consultation service for drug, chemical, and radiation exposure. Women exposed to agents not known to be teratogenic assigned themselves a risk of 24% +/- 2.8% for major malformation before the relevant medical literature was delivered to them and 14.5% +/- 3% thereafter. These women accurately estimated the risk for major malformation in the general population (5.6% +/- 1.3%). The tendency to terminate pregnancy when exposed to a nonteratogen significantly decreased after the consultation. Eleven patients exposed to drugs known to be teratogenic assigned a risk of 36.2% +/- 11.7% before the interview and did not change their perception thereafter (36.7% +/- 15.8%). Similarly, their tendency to continue or terminate pregnancy did not change; three of them eventually chose to terminate the pregnancy. Advising women about their teratogenic risk early in pregnancy may prevent unjustified termination of many pregnancies and may help to inform women exposed to proven teratogens about the known risk.

Evaluation of an occupational health education program among 11th grade students.

BACKGROUND: There is a paucity of publications on occupational health as part of the educational curricula in high schools. We investigated the extent to which a new occupational health education program for 11th graders succeeded in achieving changes in their knowledge and attitudes. METHODS: Six classrooms were randomly assigned to either 96 participating students or to a control group (n = 100) that did not participate. Data on knowledge, attitudes, and beliefs were collected before and 4 months after completion of the course by means of an anonymous self-reported questionnaire. One point was assigned to each answer that was either correct or in the desired direction. Scoring was measured by adding up the points and then converting the total into a scale of 100. RESULTS: The experimental group had a statistically higher mean score (from 24.56 to 80.74) after completing the course. The control group had low scores at both time 1 (20.15) and time 2 (17.00). At least 50% more students of the experimental group gave correct answers after the course, while there was no such change in the control group. CONCLUSIONS: Our findings indicate that occupational health learning can occur in the secondary school setting and confirm the program's effectiveness in achieving desired changes in the immediate outcome of knowledge, attitudes, and beliefs in different areas of occupational health. The subject of occupational health is a topic with relevance to larger educational objectives and policies. In many countries all over the world as well as in Israel, this curriculum can potentially be integrated into the body of the current instruction of "Life Abilities," which are courses that cover topics that prepare the youngsters for adult lifestyles.

Determinants of recall and recall bias in studying drug and chemical exposure in pregnancy.

Case-control studies on effects of drugs in pregnancy rely heavily on maternal recall. At the Motherisk Program in Toronto we counsel women during early pregnancy on the risk of drug and chemical exposure; subsequently, we follow up the outcome of pregnancy after birth. This cohort has given us an opportunity to assess the magnitude of recall of early pregnancy exposure and determinants likely to affect it in 145 consecutive cases. The mean recall of exposure identity was 62%, while accurate recall of timing of exposure was 37% and of dosage 24%. Exposures that prompted the clinic visit, chronic therapeutic exposures, environmental agents, and known teratogens were recalled significantly better than were other exposures. Accurate report of smoking was significantly higher than of alcohol use (79.4% vs. 59%, respectively, P = .0002). The number of agents consumed by the pregnant woman negatively correlated with her recall; mean recall of 1 agent was 85% vs. only 40% recall of 4 agents. Women greater than or equal to 30 years of age recalled significantly worse (mean +/- SEM, 52 +/- 4%) than women younger than 30 (70 +/- 4%), P = .002) despite a similar mean number of exposures. No difference in mean recall was found between women having normal (n = 112) or adverse pregnancy outcome (n = 33). There was a recall bias in reporting alcohol consumption; postnatally, women with adverse outcome tended to report significantly less than the amount initially reported by them.

Uterine artery embolization for management of interstitial twin ectopic pregnancy: case report.

Interstitial pregnancy is rare and dangerous variation of ectopic pregnancy. We describe a case of unilateral interstitial viable twin pregnancy treated by selective uterine artery embolization. A 23-year-old women with clinical and ultrasonic diagnosis of viable twin interstitial pregnancy was treated by selective uterine artery embolization after failure of systemic methotrexate treatment. Her serum beta-HCG was undetectable 2 months after the procedure and the ultrasound scan 70 days after embolization showed only multiple echogenic spots in the right uterine cornua. This therapeutic modality seems to be effective for conservative management of interstitial ectopic pregnancy, and as a prophylactic measure before surgical intervention to prevent major bleeding.

One-step cloning and expression of Clostridium difficile toxin B gene (tcdB).

The toxin genes of Clostridium difficile have been previously cloned by reconstructing the entire gene in a series of steps in sequence using several cloned fragments. Amplification of a 7.9 kb fragment corresponding to the toxin B gene (tcdB) was obtained with EXPAND Long Template PCR system. The amplified fragment was inserted into the E. coli expression vector pBAD and cloned into competent E. coli TOP 10 cells. tcdB gene sequences representing the complete toxin gene were detected in 3/120 (2.5%) clones analyzed. Culture filtrates of 2/3 clones were found to have cytotoxic activity in human lung fibroblasts. The recombinant protein expressed in E. coli was identified as toxin B by Western immunoblot analysis using C. sordellii antitoxin. This rapid cloning method may be useful in determining the role that individual genes in the pathogenicity locus (PaLoc) play in the virulence of C. difficile. Our results also suggest that the activity of toxin B is independent of other genes in the PaLoc.

Cloning and expression of Clostridium difficile toxin A gene (tcdA) by PCR amplification and use of an expression vector.

Toxigenic Clostridium difficile isolates harbor a 19 kb pathogenicity locus that encodes the genes for toxins A and B. Toxins A and B are among the largest known bacterial toxins expressing potent cytotoxicity and enterotoxicity, and thus the major virulence factors in C. difficile associated diarrhea. Cloning and sequencing of toxin genes is of interest for studies of molecular pathogenesis. We report the amplification and cloning of the complete toxin A gene into an Escherichia coli expression vector. Ten clones analyzed contained the complete toxin A gene. Four of these clones showed cytotoxic activity in cell culture, and were positive for toxin A as determined by ELISA. Toxin A expression was confirmed by Western immunoblot analysis. The presence of cytotoxic activity in cell culture suggests that toxin A activity is independent of other genes in the pathogenicity locus.