First-principles investigation of nonmetal doped single-layer BiOBr as a potential photocatalyst with a low recombination rate.

Nonmetal doping is an effective approach to modify the electronic band structure and enhance the photocatalytic performance of bismuth oxyhalides. Using density functional theory, we systematically examine the fundamental properties of single-layer BiOBr doped with boron (B) and phosphorus (P) atoms. The stability of the doped models is investigated based on the formation energies, where the substitutional doping is found to be energetically more stable under O-rich conditions than under Bi-rich ones. The results showed that substitutional doping of P atoms reduced the bandgap of pristine BiOBr to a greater extent than that of boron substitution. The calculation of the effective masses reveals that B doping can render the electrons and holes of pristine BiOBr lighter and heavier, respectively, resulting in a slower recombination rate of photoexcited electron-hole pairs. Based on the results of HOMO-LUMO calculations, the introduction of B atoms tends to increase the number of photocatalytically active sites. The top of the valence band and the conduction band bottom of the B doped BiOBr monolayer match well with the water redox potentials in an acidic environment. The absorption spectra propose that B(P) doping causes a red-shift. Overall, the results predict that nonmetal-doped BiOBr monolayers have a reduced bandgap, a slow recombination rate, more catalytically active sites, enhanced optical absorption edges, and reduced work functions, which will contribute to superior photocatalytic performance.

Optoelectronic and solar cell applications of Janus monolayers and their van der Waals heterostructures.

Janus monolayers and their van der Waals heterostuctures are investigated by hybrid density functional theory calculations. MoSSe, WSSe, MoSeTe and WSeTe are found to be direct band gap semiconductors. External electric fields are used to transform indirect MoSTe and WSTe to direct band gap semiconductors. MoSSe-WSSe, MoSeTe-WSeTe and MoSTe-WSTe vdW heterostructures are also indirect band gap semiconductors with type-II band alignment. Similar to the corresponding monolayers, in some of the above mentioned vdW heterostructures an external electric field and tensile strain can transform indirect to direct band gaps, while sustaining type-II band alignment. Janus monolayers have lower values of the work function (φ) than their vdW heterostructure counterparts. Furthermore, absorption spectra, absorption efficiency, and valence(conduction) band edge potentials are calculated to understand the optical and photocatalytic behavior of these systems. Red and blue shifts are observed in the position of excitonic peaks due to the induced strain in Janus monolayers. Strong device absorption efficiencies (80-90%) are observed for the WSeTe, MoSTe and WSTe monolayers in the visible, infra-red and ultraviolet regions. Energetically favourable band edge positions in Janus monolayers make them suitable for water splitting at zero pH. We find that the MoSSe-WSSe heterostructure and the MoSTe monolayer are promising candidates for water splitting with conduction and valence band edges positioned just outside of the redox interval.

A spatial and temporal analysis of paediatric central nervous system infections from 2005 to 2015 in Ho Chi Minh City, Vietnam.

Central nervous system infections (CNSI) are a leading cause of death and long-term disability in children. Using ICD-10 data from 2005 to 2015 from three central hospitals in Ho Chi Minh City (HCMC), Vietnam, we exploited generalized additive mixed models (GAMM) to examine the spatial-temporal distribution and spatial and climatic risk factors of paediatric CNSI, excluding tuberculous meningitis, in this setting. From 2005 to 2015, there were 9469 cases of paediatric CNSI; 33% were ⩽1 year old at admission and were mainly diagnosed with presumed bacterial CNSI (BI) (79%), the remainder were >1 year old and mainly diagnosed with presumed non-bacterial CNSI (non-BI) (59%). The urban districts of HCMC in proximity to the hospitals as well as some outer districts had the highest incidences of BI and non-BI; BI incidence was higher in the dry season. Monthly BI incidence exhibited a significant decreasing trend over the study. Both BI and non-BI were significantly associated with lags in monthly average temperature, rainfall, and river water level. Our findings add new insights into this important group of infections in Vietnam, and highlight where resources for the prevention and control of paediatric CNSI should be allocated.

Peeling force spectroscopy: exposing the adhesive nanomechanics of one-dimensional nanostructures.

The physics of adhesion and stiction of one-dimensional nanostructures such as nanotubes, nanowires, and biopolymers on different material substrates is of great interest for the study of biological adhesion and the development of nanoelectronics and nanocomposites. Here, we combine theoretical models and a new mode in the atomic force microscope to investigate quantitatively the physics of nanomechanical peeling of carbon nanotubes and nanocoils on different substrates. We demonstrate that when an initially straight nanotube is peeled from a surface, small perturbations can trigger sudden transitions between different geometric configurations of the nanotube with vastly different interfacial energies. This opens up the possibility of quantitative comparison and control of adhesion between nanotubes or nanowires on different substrates.

Complex dynamics of carbon nanotube probe tips.

Carbon nanotube (CNT) tips in tapping mode atomic force microscopy (AFM) enable very high-resolution imaging, measurements, and manipulation at the nanoscale. We present recent results based on experimental analysis that yield new insights into the dynamics of CNT probe tips in tapping mode AFM. Experimental measurements are presented of the frequency response and dynamic amplitude-distance data of a high-aspect-ratio multi-walled (MW) CNT tip. Higher harmonics of the microcantilever are measured in frequency ranges corresponding to attractive regime and the repulsive regime where the CNT buckles dynamically. Surface scanning is performed using a MWCNT tip on a SiO(2) grating to verify the imaging instabilities associated with MWCNT buckling when used with normal control schemes in the tapping mode. Lastly, the choice of optimal setpoints for tapping mode control using CNT tip are discussed using the experimental results.

A history of low back injury is a risk factor for recurrent back injuries in varsity athletes.

In this prospective study, we investigated whether a history of previous low back injury and dissatisfaction with a coach and teammates could predict future low back injury in varsity athletes during a 1-year follow-up period. Of 679 Yale varsity athletes surveyed in 1999, 18.3% (124) reported that they had sustained a low back injury within the past 5 years, and 6.8% (46) sustained a low back injury in the follow-up season. There were no differences in incidence rates between men and women or between athletes involved in contact or noncontact sports. A history of low back injury was the significant predictor for sustaining low back injury in the following year, and athletes who reported previous low back injury were at three times greater risk. Athletes who still had pain at the time of the survey were six times more likely to sustain a low back injury than were athletes without a history of low back injury. These results suggest that some risk factors associated with a history of low back injury predispose athletes to sustain recurrent injury. They may be congenital or a result of insufficient recovery time after the first low back injury episode.

Immunogenicity and safety of low-dose intradermal rabies vaccination given during an Expanded Programme on immunization session in Viet Nam: results of a comparative randomized trial.

The World Health Organization recently recommended a rabies vaccine pre-exposure schedule using 3 intradermal (i.d.) injections of one-fifth the standard intramuscular (i.m.) dose of current cell culture vaccines as a cost-reducing alternative for developing countries. As a strategy to improve further the acceptability of childhood rabies immunization, we assessed, in a controlled, randomized trial performed in 240 Vietnamese infants, the possibility of associating i.d. administration of a one-fifth dose of purified Vero-cell rabies vaccine (PVRV) with routine Expanded Programme on Immunization vaccines given at 2, 3 and 4 months of age (diphtheria, tetanus, whole-cell pertussis and inactivated poliomyelitis combined vaccine, DTP-IPV). Safety and immunogenicity results were compared with a group of infants given 2 i.m. doses of PVRV (2, 4 months) in association with DTP-IPV (2, 3, 4 months). After i.d. injection, more infants experienced local reactions, particularly redness, but these reactions were generally mild and transient. The rate of systemic reactions was the same in both groups. Although the rabies antibody titres (rapid fluorescent focus inhibition test) were higher 1 month after the third vaccine dose in the i.m. group (30.6 IU/mL vs 12.0 IU/mL in the i.d. group), all infants in both groups had achieved WHO-acceptable protective antibody titres (> or = 0.5 IU/mL) at this time. There was no evidence for any interference between DTP-IPV and rabies vaccine, supporting the interest of a low-dose i.d. PVRV pre-exposure regimen in infants living in rabies-endemic developing countries.

Randomised feasibility trial of pre-exposure rabies vaccination with DTP-IPV in infants.

BACKGROUND: Pre-exposure vaccination against rabies generally simplifies treatment and could be especially beneficial to children in countries where the disease is enzootic. We studied the feasibility of administering to infants pre-exposure rabies vaccination with combined diphtheria, tetanus, whole-cell pertussis, and inactivated poliomyelitis vaccine (DTP-IPV). METHODS: 84 Vietnamese infants were randomly assigned to groups that received three doses of DTP-IPV vaccine at 2, 3, and 4 months of age alone (n = 43) or with two doses of purified Vero cell rabies vaccine (PVRV) at 2 and 4 months (n = 41). The safety and immunogenicity data of the groups were compared. FINDINGS: All infants in both groups developed protective antibody concentrations against diphtheria, tetanus, pertussis, and polio. All infants who received the PVRV vaccine developed protective antibody concentrations against rabies. No serious adverse effects were reported, nor did systemic reactions differ between groups. INTERPRETATION: Administration of PVRV with DTP-IPV proved safe, and elicited what are presumed to be protective antibody concentrations to all antigens in all 41 infants. Confirmation of these results could lead to integration of pre-exposure rabies vaccination into Expanded Programme on Immunisation (EPI) sessions in selected countries where rabies is enzootic.

Deletion mapping on the distal third region of chromosome 1p in multiple endocrine neoplasia type IIA.

Multiple endocrine neoplasia type IIA (MEN IIA) syndrome is an autosomal-dominant endocrine disorder that consists of medullary thyroid carcinoma (MTC), pheochromocytoma, and parathyroid hyperplasia. The susceptibility gene to this disorder has been mapped to chromosome 10. However, molecular studies of tumor cells from patients with familial and sporadic MTC and/or pheochromocytoma have shown a high frequency (50%) of abnormalities on chromosome 1p. In the present study, we examined MTC or pheochromocytoma tumor specimens from eight patients (familial and nonfamilial cases) to investigate gene losses on chromosomes 1 and 10 as potential mechanisms for the tumors' development. The patients studies had homozygous genotypes in their leukocyte DNAs for the chromosome 10 marker used in this study, and the patients were, therefore, uninformative. However, the patients were informative for the chromosome 1 markers and five of the patients' tumor-cell DNAs (63%) had allelic deletions at one or multiple loci on chromosome 1p, and one tumor DNA had evidence of possible gene rearrangement; in all six cases, the abnormalities involved the distal third of chromosome 1p. Furthermore, we determined that the common break point for the 1p deletions was at 1p32. These results suggest that a tumor suppressor gene in this defined region is involved in the development/progression of MTC and pheochromocytoma by being either lost or inactivated.

C-myc, N-myc, N-ras, and c-erb-B: lack of amplification or rearrangement in human medullary thyroid carcinoma and a derivative cell line.

We investigated the copy number and possible rearrangement of the four protooncogenes, c-myc, N-myc, N-ras, and c-erb-B, in DNA from seven untreated primary cancers or metastases of medullary thyroid carcinoma and an established human medullary thyroid carcinoma cell line, TT, using the Southern blotting technique. The purpose of this study was two-fold: 1) to examine whether protooncogene perturbations in medullary thyroid carcinoma could be considered as a prognostic marker; and 2) to determine whether the protooncogenes could have a possible role in medullary thyroid tumorigenesis. Neither amplification nor rearrangement of the protooncogenes was detectable in the DNA from any tumor samples or in the cell line. Our results suggest that DNA-evident amplification and rearrangement of the c-myc, N-myc, N-ras, and c-erb-B oncogenes may not be mechanisms through which these oncogenes become activated in this malignancy.