van der Waals heterostructures based on MSSe (M = Mo, W) and graphene-like GaN: enhanced optoelectronic and photocatalytic properties for water splitting.

The geometric structure, electronic, optical and photocatalytic properties of MSSe-g-GaN (M = Mo, W) van der Waals (vdW) heterostructures are investigated by performing first-principles calculations. We find that the MoSSe-g-GaN heterostructure exhibits type-II band alignment for all stacking patterns. While the WSSe-g-GaN heterostructure forms the type-II or type-I band alignment for the stacking model-I or model II, respectively. The average electrostatic potential shows that the potential of g-GaN is deeper than the MSSe monolayer, leading to the formation of an electrostatic field across the interface, causing the transfer of photogenerated electrons and holes. Efficient interfacial formation of interface and charge transfer reduce the work function of MSSe-g-GaN vdW heterostructures as compared to the constituent monolayer. The difference in the carrier mobility for electrons and holes suggests that these heterostructures could be utilized for hole/electron separation. Absorption spectra demonstrate that strong absorption from infrared to visible light in these vdW heterostructures can be achieved. Appropriate valence and conduction band edge positions with standard redox potentials provide enough force to drive the photogenerated electrons and holes to dissociate water into H+/H2 and O2/H2O at pH = 0.

Electronic properties and enhanced photocatalytic performance of van der Waals heterostructures of ZnO and Janus transition metal dichalcogenides.

Vertical stacking of two-dimensional materials into layered van der Waals heterostructures has recently been considered as a promising candidate for photocatalytic and optoelectronic devices because it can combine the advantages of the individual 2D materials. Janus transition metal dichalcogenides (JTMDCs) have emerged as an appealing photocatalytic material due to the desirable electronic properties. Hence, in this work, we systematically investigate the geometric features, electronic properties, charge density difference, work function, band alignment and photocatalytic properties of ZnO-JTMDC heterostructures using first-principles calculations. Due to the different kinds of chalcogen atoms on both sides of JTMDC monolayers, two different possible stacking patterns of ZnO-JTMDC heterostructures have been constructed and considered. We find that all these stacking patterns of ZnO-JTMDC heterostructures are dynamically and energetically feasible. Moreover, both ZnO-MoSSe and ZnO-WSSe heterostructures are indirect band gap semiconductors and present type-I and type-II band alignments for model-I and model-II, respectively. The Rashba spin polarization of the ZnO-WSSe heterostructure for model-I is greater than that in the others. Furthermore, valence (conduction) band edge potentials are calculated to understand the photocatalytic behavior of these systems. Energetically favorable band edge positions in ZnO-Janus heterostructures make them suitable for water splitting at zero pH. We found that the ZnO-Janus heterostructures are promising candidates for water splitting with conduction and valence band edges positioned just outside of the redox interval.

Tailoring the structural and electronic properties of an SnSe2/MoS2 van der Waals heterostructure with an electric field and the insertion of a graphene sheet.

van der Waals heterostructures (vdWHs), obtained by vertically stacking different two-dimensional (2D) layered materials are being considered intensively as potential materials for nanoelectronic and optoelectronic devices because they can show the most potential advantages of individual 2D materials. Here, we construct the SnSe2/MoS2 vdWH and investigate its electronic and optical properties using first-principles calculations. We find that the band structures of both MoS2 and SnSe2 monolayers are well kept in the SnSe2/MoS2 vdWH because of their weakly interacting features via vdW interaction. The SnSe2/MoS2 vdWH forms a type-I band alignment and exhibits an indirect semiconductor band gap of 0.45 eV. The type-I band alignment makes the SnSe2/MoS2 vdWH a promising material for optoelectronic nanodevices, such as light emitting diodes because of ultra-fast recombination of electrons and holes. Moreover, the band gap and band alignment of the SnSe2/MoS2 vdWH can be tailored by the electric field and the insertion of a graphene sheet. After applying an electric field, type-I to type-II and semiconductor to metal transitions can be achieved in the SnSe2/MoS2 vdWH. Besides, when a graphene sheet is inserted into the SnSe2/MoS2 vdWH to form three stacking types of G/SnSe2/MoS2, SnSe2/G/MoS2 and SnSe2/MoS2/G, the p-type semiconductor of the SnSe2/MoS2 vdWH is converted to an n-type Ohmic contact. These findings provide theoretical guidance for designing future nanoelectronic and optoelectronic devices based on the SnSe2/MoS2 vdWH.

Measles susceptibility and immunization: experiences in a forensic psychiatric hospital.

BACKGROUND: In response to a measles outbreak in the community, a measles immunization program was developed at our hospital for forensic psychiatric patients. METHODS: Measles antibody screening of all employees and patients by means of an enzyme-linked immunosorbent assay was followed by vaccination of susceptible persons. RESULTS: Serum samples from 813 employees and 868 patients during a 6-month period were analyzed. The susceptibility rate was 16.15% for employees and 13.60% for patients born in or after 1957. It was 4.67% for employees and 5.40% for patients born before 1957. The overall rate was 7.38% for employees and 8.53% for patients. A rate of 5% is known to be sufficient for transmission in institutions. Vaccine was given to 84.51% of susceptible patients. Vaccine failure occurred in 8.33%. Residual susceptibility rate was 1.84%. CONCLUSIONS: Cost analysis showed that screening of all individuals and immunization of susceptible persons was the most cost-effective method for measles control in our institutional setting.

Surgical and nonsurgical treatment of penetrating injuries to the cervical esophagus.

We presented two patients with gunshot wounds and one patient with a stab wound of the cervical esophagus, managed conservatively, which resulted in no deaths. Results of eight studies of cervical esophageal injuries are reviewed and presented in Table I. One must consider both the surgical and conservative methods of management in planning treatment for the given patient.

Does gastrostomy and fundoplication prevent aspiration pneumonia in mentally retarded persons?

To determine whether gastrostomy and fundoplication prevent aspiration pneumonia in mentally retarded individuals, 105 cases of feeding gastrostomy were examined; 21 subjects had preoperatively diagnosed gastroesophageal reflux. Thirty-nine patients had gastrostomy and fundoplication, 66 patients had gastrostomy alone, and 60 subjects had had aspiration pneumonia before surgery. Recurrent aspiration pneumonia was least in those without preoperative gastroesophageal reflux and who had gastrostomy and fundoplication. Feeding gastrostomy does not prevent aspiration pneumonia. Gastrostomy with fundoplication reduces the likelihood of aspiration pneumonia but still allows a significant number to develop it.

Acute pancreatitis: a complication of Foley catheter gastrostomy.

Acute pancreatitis can be caused by inadvertent migration into the duodenum of the inflated balloon of a Foley gastrostomy catheter. The clinical picture is that of an acute abdomen. The diagnosis is made with a high index of suspicion and confirmed by marked elevation of serum and urine amylase levels. The treatment consists of repositioning of the gastrostomy tube and supportive therapy. Careful external fixation of the tube to the abdominal wall can prevent this complication.

Canine bladder epithelial cells in culture: susceptibility to canine distemper and measles viruses.

A canine bladder epithelial cell strain was established in culture for the study of canine distemper virus. Epithelial cells were scraped off the bladder with a scalpel and were cultured in enriched Eagle's medium. Cells were enzymatically dispersed and passed over 46 population doublings which covered a period of more than 3 years. The cells were heteroploid when karyotyped at passage level 5 and 42. This cell strain permitted direct isolation of canine distemper virus and also showed susceptibility to laboratory strains of measles virus. Seemingly, establishment of cell strains from canine bladder epithelium can be accomplished without difficulty.

Diffuse hepatic fibrosis in congenital cytomegalovirus infection.

Liver dysfunction in congenital cytomegalovirus (CMV) infection is common but usually self-limited. We describe a patient with congenital CMV infection that resulted in diffuse (noncirrhotic) hepatic fibrosis and liver failure. Morphologic patterns of liver disease in congenital CMV are briefly discussed.

A new complication of percutaneous endoscopic gastrostomy.

Two cases of complications of percutaneous endoscopic gastrostomy are described that have not been reported previously. Each had misplacement of a gastrostomy tube in the intestine, one in the transverse colon resulting in profuse diarrhea and metabolic acidosis, and the other in the jejunum causing adhesions with subsequent small bowel obstruction. An explanation of these complications and suggestions for prevention are presented.