Two-dimensional van der Waals heterostructures (vdWHs) with band alignment transformation in multi-functional devices.

Two-dimensional van der Waals heterostructures (vdWHs) with tunable band alignment have the potential to be benignant in the development of minimal multi-functional and controllable electronics, but they have received little attention thus far. It is crucial to characterize and control the band alignment in semiconducting vdWHs, which determines the electronic and optoelectronic properties. The future success of optoelectronic devices will require improved electronic property control techniques, such as using an external electric field or strain engineering, to change the electronic structures directly. Herein, we review heterostructures fabricated as transition metal dichalcogenides (TMDCs) as one of their constituent monolayers with other notable 2D materials that can transfer from type-II to type-III (type-III > type-II) band alignment when a biaxial strain or electric field is applied.

Correction: Saeed, S., et al. Enhancement of Photorefraction in Vanadium-Doped Lithium Niobate through Iron and Zirconium Co-Doping. Materials 2019, Vol. 12, 3143.

The authors wish to make the following corrections to this paper [...].

Linear Tuning of Phase-Matching Temperature in LiNbO3:Zr Crystals by MgO Co-Doping.

We grew a series of co-doped LiNbO3 crystals with fixed 1.5 mol % ZrO2 and various MgO concentrations (1.0, 3.0, 4.0, 6.0 mol %), and investigated their optical properties and defect structures. By 3.0 mol % MgO co-doping, the optical damage resistance at 532 nm reached 6.5 × 106 W/cm2, while the phase-matching temperature for doubling 1064 nm was only 29.3 °C-close to room temperature-which was conducive to realizing the 90° phase matching at room temperature by slightly modulating the incident angle of the fundamental beam. Notably, we found that the phase-matching temperature increased linearly with the increase of MgO doping, and this linear dependence helped us to grow the high-quality crystal for room temperature 90° phase matching. Moreover, the defect analysis indicated that the linear tuning of phase-matching temperature might be attributed to Mg Li + + Zr Nb - neutral pairs in crystals.

Enhancement of Photorefraction in Vanadium-Doped Lithium Niobate through Iron and Zirconium Co-Doping.

A series of mono-, double-, and tri-doped LiNbO3 crystals with vanadium were grown by Czochralski method, and their photorefractive properties were investigated. The response time for 0.1 mol% vanadium, 4.0 mol% zirconium, and 0.03 wt.% iron co-doped lithium niobate crystal at 488 nm was shortened to 0.53 s, which is three orders of magnitude shorter than the mono-iron-doped lithium niobate, with a maintained high diffraction efficiency of 57% and an excellent sensitivity of 9.2 cm/J. The Ultraviolet-visible (UV-Vis) and OH- absorption spectra were studied for all crystals tested. The defect structure is discussed, and a defect energy level diagram is proposed. The results show that vanadium, zirconium, and iron co-doped lithium niobate crystals with fast response and a moderately large diffraction efficiency can become another good candidate material for 3D-holographic storage and dynamic holography applications.

P-Type Lithium Niobate Thin Films Fabricated by Nitrogen-Doping.

Nitrogen-doped lithium niobate (LiNbO3:N) thin films were successfully fabricated on a Si-substrate using a nitrogen plasma beam supplied through a radio-frequency plasma apparatus as a dopant source via a pulsed laser deposition (PLD). The films were then characterized using X-Ray Diffraction (XRD) as polycrystalline with the predominant orientations of (012) and (104). The perfect surface appearance of the film was investigated by atomic force microscopy and Hall-effect measurements revealed a rare p-type conductivity in the LiNbO3:N thin film. The hole concentration was 7.31 × 1015 cm-3 with a field-effect mobility of 266 cm²V-1s-1. X-ray Photoelectron Spectroscopy (XPS) indicated that the atom content of nitrogen was 0.87%; N atoms were probably substituted for O sites, which contributed to the p-type conductivity. The realization of p-type LiNbO3:N thin films grown on the Si substrate lead to improvements in the manufacturing of novel optoelectronic devices.

Effect of Defects on Spontaneous Polarization in Pure and Doped LiNbO3: First-Principles Calculations.

Numerous studies have indicated that intrinsic defects in lithium niobate (LN) dominate its physical properties. In an Nb-rich environment, the structure that consists of a niobium anti-site with four lithium vacancies is considered the most stable structure. Based on the density functional theory (DFT), the specific configuration of the four lithium vacancies of LN were explored. The results indicated the most stable structure consisted of two lithium vacancies as the first neighbors and the other two as the second nearest neighbors of Nb anti-site in pure LN, and a similar stable structure was found in the doped LN. We found that the defects dipole moment has no direct contribution to the crystal polarization. Spontaneous polarization is more likely due to the lattice distortion of the crystal. This was verified in the defects structure of Mg2+, Sc3+, and Zr4+ doped LN. The conclusion provides a new understanding about the relationship between defect clusters and crystal polarization.

Comparison of real time polymerase chain reaction with microscopy and antigen detection assay for the diagnosis of malaria.

OBJECTIVE: To determine the sensitivity of a real time polymerase chain reaction (PCR) for malaria diagnosis and to compare its accuracy with microscopy and an antigen based rapid diagnostic test (OptiMal). STUDY DESIGN: Cross-sectional analytical study. PLACE AND DURATION OF STUDY: Military Hospital, Armed Forces Institute of Transfusion and Armed Forces Institute of Pathology, Rawalpindi, from July to December 2011. METHODOLOGY: Venous blood samples of 300 clinically suspected patients of malaria were tested for malaria parasite by microscopy and OptiMal; and malaria parasite index was calculated for the positive samples. Plasmodium genus specific real time PCR was performed on all specimens, targeting small subunit rRNA gene. Diagnostic accuracy of three tests was compared and cost analysis was done. RESULTS: Out of 300 patients, malaria parasite was detected in 110, 106 and 123 patients by microscopy, OptiMAL and PCR respectively. Real time PCR was 100% sensitive while microscopy and OptiMal had sensitivity of 89.4% and 86.2% respectively. All methods were 100% specific. The cost per test was calculated to be 0.2, 2.75 and 3.30 US$ by microscopy, OptiMal and PCR respectively, excluding the once capital cost on PCR equipment. CONCLUSION: Genus specific real time PCR for the diagnosis of malaria was successfully established as a highly sensitive and affordable technology that should be incorporated in the diagnostic algorithm in this country.

Comparison of fine needle aspiration cytology and thyroid scan in solitary thyroid nodule.

Objective. This was a comparative study between FNAC and thyroid scan used to diagnose the solitary thyroid nodule and histopathology was used as gold standard to compare the results of both modalities. We hypothesized that Fine needle aspiration cytology and thyroid scan diagnose solitary thyroid nodule (STN) as accurately as histopathology. Materials and Methods. This study comprised of 50 patients with solitary thyroid nodules (STN) presented to OPD. After clinical examination these patients were referred to Centre for Nuclear Medicine, Mayo Hospital Lahore for thyroid function tests and thyroid scan (TS). These patients underwent FNAC in the department of Pathology and surgery in Mayo Hospital. The cases were operated and evaluated for histopathological changes. Results. On thyroid scan, 40 patients (80%) having cold nodule were labeled as suspicious 10 patients (20%) had hot nodule. On FNAC 23 patients (46%) had benign lesion, 22 patients (44%) had indeterminate lesion and 5 patients (10%) had malignant lesions. On histopathology, 45 patients (90%) were confirmed to have benign lesions and 5 patients (10%), malignant lesions. After comparison of results of thyroid scan and FNAC with histopathology, the sensitivity, specificity, positive predictive value, negative predictive value and diagnostic accuracy of thyroid scan were 80%, 20%, 10%, 90% and 26%, respectively whereas those of FNAC were 80%, 97.7%, 80%, 97.7% and 96%, respectively. Conclusion. Fine needle aspiration was a significantly better predictor of malignancy than thyroid scan and resulted in a smaller proportion of excisions for benign nodules.

Early versus late arterio-venous fistulae: impact on failure rate.

BACKGROUND: Haemodialysis is the primary mode of renal replacement therapy for patients of end stage renal disease. The most important determinant for effective haemodialysis is a reliable vascular access. Arterio-venous (AV) fistula is the closest to be an ideal long-term haemodialysis vascular access. The creation of fistulas or grafts is recommended before starting haemodialysis, this study was undertaken to determine the impact of timing of AV fistula creation on its failure rate. METHODS: It is a descriptive study. All patients with chronic kidney disease (CKD) reporting to Armed Forces Institute of Urology (AFIU) and Military Hospital (MH) Rawalpindi from January 2008 to October 2009 in whom vascular access was created were included. The patients were followed prospectively and a complete data about their haemodialysis and vascular access was maintained. RESULTS: A total of 168 permanent accesses were created in 112 patients in this study. The mean duration of follow-up was 14.05 +/- 4.45 months. Early access creation group included 23 patients and late access creation group included 89 patients. Out of 168 fistulas that were created, 54 fistulas failed with 45 (83.3%) of these from patients of late access creation group. Age, gender and diabetes mellitus (DM) had no significant affect on failure rate of fistulas. CONCLUSION: Timely referral to nephrologists and early creation of permanent vascular access by dedicated team work can improve the success rate of AV fistulae so enhancing quality of life of patients of end stage renal disease.

Acute hepatitis a virus infection presenting with multiorgan dysfunction: a case report.

INTRODUCTION: Acute hepatitis due to hepatitis a virus is usually a benign self-limiting disease conferring lifelong immunity. However, few cases have been reported in literature with fulminant hepatitis. We report this extremely rare case with multiorgan dysfunction including liver failure, hepatic encephalopathy, renal failure, pleural effusion, pericardial effusion and hematologic dysfunction as a sequale of this infection in an otherwise healthy male at the age of 18. CASE PRESENTATION: An 18 years old Pakistani male presented with two days history of fever, cough, headache and vomiting. His condition gradually deteriorated and on day 7 developed multiorgan dysfunction. Initially Immunoglobulin M anti hepatitis a virus was borderline 1.40 but repeated titers one week later confirmed the diagnosis of acute hepatitis a virus infection. CONCLUSION: This original case report highlights the importance of focusing first uncommon manifestations of common illnesses while diagnosing difficult cases. Moreover this case also adds knowledge to the limited available data regarding complications and predictors of prognosis.

Clinical and laboratory findings in acute malaria caused by various plasmodium species.

OBJECTIVE: To find out clinical and laboratory findings in acute malaria caused by various plasmodium species. METHODS: This study was conducted in Department of Medicine and Pathology, Combined Military Hospital, Quetta, Balochistan, from August 2006 to December 2006. Five hundred and two subjects with positive malarial parasite slide were included in the study. Frequencies of alterations in clinical and laboratory parameters were determined in various plasmodium species and reported in percentage. RESULTS: Of 502 patients, 311 were Plasmodium (P.) falciparum, 100 were P. vivax and 91 were mixed infection. Triad of fever, chills and sweating was present in 91% of subjects with all three varieties of P. infection. Splenomegaly was detected in 59-73% individuals with malaria. Thrombocytopenia was the leading haematological alteration associated with various P. species, seen in almost 80% of infected patients. Anaemia and Jaundice were more common in P. falciparum and mixed infection as compared to P. vivax. Serum urea, creatinine and plasma glucose were within normal limits in all the patients with malaria. CONCLUSION: Malaria must be considered as a leading differential diagnosis in an acutely febrile patient with one or more of abnormalities like splenomegaly, fall in blood counts or rise in bilirubin and serum alanine aminotransferase levels.