Does open-beach ship-breaking affect the mineralogical composition of soil more adversely than typical industrial activities?

In Bangladesh, India, and Pakistan the ship breaking (SB) sector dismantles end-of-life ships on open beaches, exposing the environment to the resulting pollution, especially the soil and water. Because SB occurs in the vicinity of other poorly-regulated activities in industrial zones (IZ) in these countries, there is some ambiguity concerning the relative roles played by SB and IZ in the accumulation of hazardous materials in the soil. In the absence of comparative studies, this study investigated the relative levels of soil contamination due to SB or IZ in the same geographic region by taking soil samples from SB and unrelated IZs in Chittagong, Bangladesh. The technogenic input of sixty-four chemical elements into the soil at the SB or IZ were compared with off-site reference values or the natural content of these elements in the Earth's crust and surface. The magnitude of soil contamination by ecotoxic elements, the corresponding bioavailability, and the ecological risks were assessed based on the regulatory reference values (RRVs) and with other approaches using data aggregation. Among the different potentially toxic elements, Cr, Cu, Ni, Pb, and Zn were found to be above the maximum allowable concentration (p < 0.05) in both SB and IZ. Moderate-to-high soil contamination from SB and moderate-to-considerable soil contamination in the IZ were observed. However, the element-bioavailability as ascertained via solid-phase speciation or weak-acid induced leaching, and the evaluation of associated ecological risk both indicated a low hazard quotient for soils from both SB and IZ. The outcome of the current research marked both SB and IZ soils as contaminated but not polluted, yet remediation is suggested. The level of contamination in SB soils was relatively higher than that of IZ. The comparative results presented in this study for the first time will hopefully be useful as a reference for future ecological and geochemical studies concerning the environmental contamination associated with both ship recycling on open beaches and other typical industrial activities.

A Metal-Nitride Nanowire Dual-Photoelectrode Device for Unassisted Solar-to-Hydrogen Conversion under Parallel Illumination.

A dual-photoelectrode device, consisting of a photoanode and photocathode with complementary energy bandgaps, has long been perceived as an ideal scheme for achieving high efficiency, unassisted solar-driven water splitting. Previously reported 2-photon tandem devices, however, generally exhibit an extremely low efficiency (<0.1%), which has been largely limited by the incompatibility between the two photoelectrode materials. Here we show that the use of metal-nitride nanowire photoelectrodes, together with the scheme of parallel illumination by splitting the solar spectrum spatially and spectrally, can break the efficiency bottleneck of conventional 2-photon tandem devices. We have first investigated a dual-photoelectrode device consisting of a GaN nanowire photoanode and an InGaN nanowire photocathode, which exhibited an open circuit potential of 1.3 V and nearly 20-fold enhancement in the power conversion efficiency under visible light illumination (400-600 nm), compared to the individual photoelectrodes in 1 mol/L HBr. We have further demonstrated a dual-photoelectrode device consisting of parallel-connected metal-nitride nanowire photoanodes and a Si/InGaN nanowire photocathode, which can perform unassisted, direct solar-to-hydrogen conversion. A power conversion efficiency of 2% was measured under AM1.5G 1 sun illumination.

Dye-sensitized InGaN nanowire arrays for efficient hydrogen production under visible light irradiation.

Solar water splitting is a key sustainable energy technology for clean, storable and renewable source of energy in the future. Here we report that Merocyanine-540 dye-sensitized and Rh nanoparticle-decorated molecular beam epitaxially grown In0.25Ga0.75N nanowire arrays have produced hydrogen from ethylenediaminetetraacetic acid (EDTA) and acetonitrile mixture solution under green, yellow and orange solar spectra (up to 610 nm) for the first time. An apparent quantum efficiency of 0.3% is demonstrated for wavelengths 525-600 nm, providing a viable approach to harness deep-visible and near-infrared solar energy for efficient and stable water splitting.

Highly stable photoelectrochemical water splitting and hydrogen generation using a double-band InGaN/GaN core/shell nanowire photoanode.

We report on the first demonstration of stable photoelectrochemical water splitting and hydrogen generation on a double-band photoanode in acidic solution (hydrogen bromide), which is achieved by InGaN/GaN core/shell nanowire arrays grown on Si substrate using catalyst-free molecular beam epitaxy. The nanowires are doped n-type using Si to reduce the surface depletion region and increase current conduction. Relatively high incident-photon-to-current-conversion efficiency (up to ~27%) is measured under ultraviolet and visible light irradiation. Under simulated sunlight illumination, steady evolution of molecular hydrogen is further demonstrated.

p-Type InN nanowires.

In this Letter, we demonstrate that with the merit of nanowire structure and a self-catalytic growth process p-type InN can be realized for the first time by "direct" magnesium (Mg) doping. The presence of Mg acceptor energy levels in InN is confirmed by photoluminescence experiments, and a direct evidence of p-type conduction is demonstrated unambiguously by studying the transfer characteristics of InN nanowire field effect transistors. Moreover, the near-surface Fermi-level of InN can be tuned from nearly intrinsic to p-type degenerate by controlling Mg dopant incorporation, which is in contrast to the commonly observed electron accumulation on the grown surfaces of Mg-doped InN films. First-principle calculation using the VASP electronic package further shows that the p-type surface formed on Mg-doped InN nanowires is highly stable energetically.

Frequency of Post Endoscopic Retrograde Cholangiopancreatography Acute Pancreatitis in an Academic Hospital of Bangladesh.

Post-ERCP acute pancreatitis (PEP) is a common and serious complication with high morbidity and mortality rates. There is a paucity of data on the frequency of PEP in a resource constraint setting like Bangladesh. Hence we have conducted a prospective study to determine the frequency of PEP and the factors associated with its occurrence. This prospective, observational study was carried out in Gastroenterology Department of Dhaka Medical College & Hospital, Dhaka, Bangladesh from April 2018 to December 2018 on the consecutive patients who underwent ERCP. PEP and its severity were diagnosed according to consensus definition. Serum lipase was done in all patients before procedure and 24 hours after procedure or if patient develops abdominal pain after the procedure which became earlier. Total 168 patients were included (mean age 46.97±14.35 years; male 72(43.0%). The most common indication of ERCP was choledocholithiasis 97(58.0%) followed by malignant biliary obstruction 45(27.0%), recurrent pyogenic cholangitis 8(5.0%), chronic pancreatitis 4(2.3%), biliary ascariasis 4(2.3%) and others 10(6.0%). Overall post ERCP complication rate was 46(27.3%) including cholangitis 29(17.3%), pancreatitis 16(9.5%), bleeding 12(7.1%), aspiration pneumonia 4(2.4%) and death 3(1.8%). Regarding the severity of PEP, 50.0%, 43.7% and 6.3% patients developed mild, moderate and severe pancreatitis respectively. Number of cannulation attempts >5 times [22(48%) vs. 17(14%); p=0.001], cannulation attempts duration more than 10 minutes [25(55%) vs. 27(22%); p=0.001], unintentional passage of guide wire into the pancreatic duct [8(17%) vs. 18(15%); p=0.001], pancreatic duct contrast injection [12(26%) vs. 2(1.6%); p=0.001] and pre-cut sphincterotomy [16(35%) vs. 6(4.9%); p=0.001] were significantly different between the patients who developed PEP compared to those who did not. In multiple logistic regressions analysis, pancreatic duct contrast injection was significantly associated with PEP [OR 25.523 with 95% CI (4.049- 100.0%)]. Around ten percent patients had developed PEP. Regarding the severity half of them were mild, 44.0% patients had moderate and 6.0% patient had severe type of pancreatitis. Difficult cannulation, unintentional passage of guide wire into the pancreas, pancreatic duct contrast injection and pre-cut sphincterotomy were associated with PEP. Among them pancreatic duct contrast injection had independent significance in the causation of PEP.

High efficiency photoelectrochemical water splitting and hydrogen generation using GaN nanowire photoelectrode.

We have studied the photoelectrochemical properties of both undoped and Si-doped GaN nanowire arrays in 1 mol l(-1) solutions of hydrogen bromide and potassium bromide, which were used separately as electrolytes. It is observed that variations of the photocurrent with bias voltage depend strongly on the n-type doping in GaN nanowires in both electrolytes, which are analyzed in the context of GaN surface band bending and its variation with the incorporation of Si-doping. Maximum incident-photon-to-current-conversion efficiencies of ~15% and 18% are measured for undoped and Si-doped GaN nanowires under ~350 nm light illumination, respectively. Stable hydrogen generation is also observed at a zero bias potential versus the counter-electrode.

Highly efficient, spectrally pure 340 nm ultraviolet emission from AlxGa1-xN nanowire based light emitting diodes.

High crystal quality, vertically aligned AlxGa1-xN nanowire based double heterojunction light emitting diodes (LEDs) are grown on Si substrate by molecular beam epitaxy. Such AlxGa1-xN nanowires exhibit unique core-shell structures, which can significantly suppress surface nonradiative recombination. We successfully demonstrate highly efficient AlxGa1-xN nanowire array based LEDs operating at ∼340 nm. Such nanowire devices exhibit superior electrical and optical performance, including an internal quantum efficiency of ∼59% at room temperature, a relatively small series resistance, highly stable emission characteristics, and the absence of efficiency droop under pulsed biasing conditions.

Tuning the surface charge properties of epitaxial InN nanowires.

We have investigated the correlated surface electronic and optical properties of [0001]-oriented epitaxial InN nanowires grown directly on silicon. By dramatically improving the epitaxial growth process, we have achieved, for the first time, intrinsic InN both within the bulk and at nonpolar InN surfaces. The near-surface Fermi-level was measured to be ∼0.55 eV above the valence band maximum for undoped InN nanowires, suggesting the absence of surface electron accumulation and Fermi-level pinning. This result is in direct contrast to the problematic degenerate two-dimensional electron gas universally observed on grown surfaces of n-type degenerate InN. We have further demonstrated that the surface charge properties of InN nanowires, including the formation of two-dimensional electron gas and the optical emission characteristics can be precisely tuned through controlled n-type doping. At relatively high doping levels in this study, the near-surface Fermi-level was found to be pinned at ∼0.95-1.3 eV above the valence band maximum. Through these trends, well captured by the effective mass and ab initio materials modeling, we have unambiguously identified the definitive role of surface doping in tuning the surface charge properties of InN.

Evaluation of transurethral ethanol ablation of prostate for symptomatic benign prostatic hyperplasia.

Evaluating short-term (03 months) efficacy and safety of transurethral intraprostatic injection of absolute ethanol to treat benign prostatic hyperplasia (BPH). This intervention study was conducted to evaluate 30 patients with benign prostatic hyperplasia treated by transurethral injection of dehydrated ethanol. Mean age was 69.96 years. Endoscopic injection of 6-13.5 ml ethanol was carried out at 4-8 sites in the prostate. International Prostate Symptom Score (IPSS), maximum flow rate, prostate volume, postvoid residual and side effects or complications were measured postoperatively. Mean IPSS (SD) improved significantly from 18.43 ± 2.38 preoperatively to 6.80 ± 1.34 at 03 months of follow-up, mean peak urinary flow rate increased from 7.33 ± 1.19 ml/s to 16.31 ± 1.69 ml/s after 3 months, mean residual urine volume had decreased from 54.16 ± 30.93 ml to 17.01 ± 9.59 ml after 3 months (p<0.05). The prostate volume decreased from 44.66 ± 9.52 gm preoperatively to 32.46 ± 7.78 gm after 3 months (statistically significant at 5% level). There were no intra-operative complications but post-operative haematuria occurred in two patients, urinary retention occurred in two patients after removal of the catheter. Urinary tract infection developed in one patient. Transurethral ethanol ablation of prostate appears to be safe and cost effective. No occurrence of retrograde ejaculation was detected. The short-term effects of ethanol injection at prostate were satisfactory and acceptable as a minimally invasive therapeutic modality in selected patients.

Frequency of Eosinophilic Esophagitis among Patients with Gastroesophageal Reflux Symptoms in an Academic Hospital of Bangladesh: A Cross Sectional Study.

Eosinophilic esophagitis (EoE) is a disease of modern era. It was first described 40 years back. Since then it has drawn an immense interest among the clinicians. It is diagnosed by the presence of eosinophils count ≥15/HPF on esophageal biopsied mucosa in patients with symptoms of esopohageal dysfunction. It is more prevalent among patients with gastroesophageal reflux disease. As its symptoms overlap with that of gastroesophageal reflux disease (GERD), it is frequently overlooked & misdiagnosed which increases patients' sufferings. No data is available in Bangladesh. The objective of the study was to find out the frequency of eosinophilic esophagitis among patients with gastroesophageal reflux symptoms. The study was conducted at the Outpatient department of the department of Gastroenterology of Dhaka Medical College Hospital, Dhaka, Bangladesh from September 2018 to April 2019. One hundred and thirty three (133) consecutive patients with symptoms suggestive of gastroesophageal reflux disease based on validated questionnaire underwent upper GI endoscopy. Biopsies were taken from proximal and distal esophagus as well as any other endoscopically abnormal esophageal mucosal lesion. Among 133 patients with gastroesophageal reflux symptoms, 7 patients (5.3%) were found to be positive for eosinophilic esophagitis. Mean age at diagnosis was 37.28±13.38 years. It was more common in younger age group. Female patients (56%) were more than male patients (44%). Heart burn was the major symptom followed by acid regurgitation. Nocturnal cough showed statistically significant relationship with eosinophilic esophagitis. Although the frequency is low, it may be considered as a differential diagnosis among patients with GERD.

The Role of National Specialist Societies in Influencing Transformational Change in Low-Middle Income Countries - Reflections on the Model of Implementation for a National Endoscopy Training Programme in Bangladesh.

The British Society of Gastroenterology (BSG) and the Bangladesh Gastroenterology Society (BGS) have collaborated on an endoscopy training programme, which has grown up over the past decade from a small scheme borne out of the ideas of consultant gastroenterologists in Swansea, South Wales (United Kingdom) to improve gastroenterology services in Bangladesh to become a formalised training programme with broad reach. In this article, we document the socioeconomic and historical problems that beset Bangladesh, the current training needs of doctors and how the BSG-BGS collaboration has made inroads into changing outcomes both for gastroenterologists in Bangladesh, but also for the populations they serve.

Comprehensive investigation of sequential plasma activated Si/Si bonded interfaces for nano-integration on the wafer scale.

The sequentially plasma activated bonding of silicon wafers has been investigated to facilitate the development of chemical free, room temperature and spontaneous bonding required for nanostructure integration on the wafer scale. The contact angle of the surface and the electrical and nanostructural behavior of the interface have been studied. The contact angle measurements show that the sequentially plasma (reactive ion etching plasma followed by microwave radicals) treated surfaces offer highly reactive and hydrophilic surfaces. These highly reactive surfaces allow spontaneous integration at the nanometer scale without any chemicals, external pressure or heating. Electrical characteristics show that the current transportation across the nanobonded interface is dependent on the plasma parameters. High resolution transmission electron microscopy results confirm nanometer scale bonding which is needed for the integration of nanostructures. The findings can be applied in spontaneous integration of nanostructures such as nanowires/nanotubes/quantum dots on the wafer scale.

Comparative study of endoscopic band ligation and sclerotherapy for treatment of oesophageal varices in cirrhotic patients.

A prospective randomized study was done comparing endoscopic band ligation and sclerotherapy for the treatment of oesophageal varices. Hundred fifty cirrhotic patients with history of bleeding from varices were included in the study. Seventy-five patients got sclerotherapy and 75 got band ligation of varices. Both sclerotherapy and band ligation were continued till obliteration of varices. Clinical as well as the biochemical parameters of the two groups of patients and the severity of the liver diseases were similar in both groups. The mean period of follow up was 337 days for sclerotherapy group and 376 days for band ligation group. The mean time to eradicate the varices was significantly shorter with banding (35+/-4.1 vs 75+/-6.5, p<0.001). The mean number of treatment sessions was significantly less with banding (2.3+/-3.1 vs 5.2+/-2.1, p<.001). Rebleeding was significantly more with sclerotherapy (20 vs. 8 with p<0.01). The variables significantly associated with rebleeding were hypoalbuminaemia (p<.01), and active bleeding at index endoscopy (p<0.001). Different complications like oesophageal ulcer, bleeding from ulcer and the symptoms of oesophageal stricture were more in the sclerotherapy group. There was no significant difference in survival between the two groups. Number of blood transfusions and duration of hospitalization were less in band ligation group. There was no difference in terms of recurrence between the two groups. From the study we suggest that band ligation has less local complications and causes earlier eradication of varices than sclerotherapy. Therefore, band ligation may be the first choice of therapy for oesophageal varices.

Ultrafast Exciton Dynamics in InGaN/GaN and Rh/Cr2O3 Nanoparticle-Decorated InGaN/GaN Nanowires.

Ultrafast exciton and charge-carrier dynamics in InGaN/GaN nanowires (NWs) with and without Rh/Cr2O3 nanoparticle (NP) decoration have been investigated using femtosecond transient absorption (TA) techniques with excitation at 415 nm and white-light probe (450-700 nm). By comparing the TA profiles between InGaN/GaN and InGaN/GaN-Rh/Cr2O3 NWs, an additional decay component on the medium time scale (∼50 ps) was identified with Rh/Cr2O3 decoration, which is attributed to interfacial charge transfer from InGaN/GaN NWs to Rh/Cr2O3 NPs, desired for light energy conversion applications. This is consistent with reduced photoluminescence (PL) of the NWs by the Rh/Cr2O3 NPs. A kinetic model was developed to explain the TA results and gain further insight into the exciton and charge-carrier dynamics.

Visible light-driven efficient overall water splitting using p-type metal-nitride nanowire arrays.

Solar water splitting for hydrogen generation can be a potential source of renewable energy for the future. Here we show that efficient and stable stoichiometric dissociation of water into hydrogen and oxygen can be achieved under visible light by eradicating the potential barrier on nonpolar surfaces of indium gallium nitride nanowires through controlled p-type dopant incorporation. An apparent quantum efficiency of ∼12.3% is achieved for overall neutral (pH∼7.0) water splitting under visible light illumination (400-475 nm). Moreover, using a double-band p-type gallium nitride/indium gallium nitride nanowire heterostructure, we show a solar-to-hydrogen conversion efficiency of ∼1.8% under concentrated sunlight. The dominant effect of near-surface band structure in transforming the photocatalytic performance is elucidated. The stability and efficiency of this recyclable, wafer-level nanoscale metal-nitride photocatalyst in neutral water demonstrates their potential use for large-scale solar-fuel conversion.

Tuning the surface Fermi level on p-type gallium nitride nanowires for efficient overall water splitting.

Solar water splitting is one of the key steps in artificial photosynthesis for future carbon-neutral, storable and sustainable source of energy. Here we show that one of the major obstacles for achieving efficient and stable overall water splitting over the emerging nanostructured photocatalyst is directly related to the uncontrolled surface charge properties. By tuning the Fermi level on the nonpolar surfaces of gallium nitride nanowire arrays, we demonstrate that the quantum efficiency can be enhanced by more than two orders of magnitude. The internal quantum efficiency and activity on p-type gallium nitride nanowires can reach ~51% and ~4.0 mol hydrogen h(-1) g(-1), respectively. The nanowires remain virtually unchanged after over 50,000 µmol gas (hydrogen and oxygen) is produced, which is more than 10,000 times the amount of photocatalyst itself (~4.6 µmol). The essential role of Fermi-level tuning in balancing redox reactions and in enhancing the efficiency and stability is also elucidated.

p-Type dopant incorporation and surface charge properties of catalyst-free GaN nanowires revealed by micro-Raman scattering and X-ray photoelectron spectroscopy.

Micro-Raman scattering and X-ray photoelectron spectroscopy were employed to investigate Mg-doped GaN nanowires. With the increase of Mg doping level, pronounced Mg-induced local vibrational modes were observed. The evolution of longitudinal optical phonon-plasmon coupled mode, together with detailed X-ray photoelectron spectroscopy studies, show that the near-surface region of nanowires can be transformed from weakly n-type to p-type with the increase of Mg doping.

Elevated arsenic and manganese in groundwaters of Murshidabad, West Bengal, India.

High levels of geogenic arsenic (As) and manganese (Mn) in drinking water has led to widespread health problems for the population of West Bengal, India. Here we delineate the extent of occurrences of As and Mn in Murshidabad, where the contaminated aquifers occur at shallow depths between 35 and 40 m and where access to safe drinking water is a critical issue for the local population. A total of 78 well-water samples were taken in 4 blocks on either side of the river Bhagirathi: Nabagram and Kandi (west, Pleistocene sediments), Hariharpara and Beldanga (east, Holocene sediments). High As, total iron (FeT) and low Mn concentrations were found in waters from the Holocene gray sediment aquifers east of the river Bhagirathi, while the opposite was found in the Pleistocene reddish-brown aquifer west of the river Bhagirathi in Murshidabad. Speciation of As in water samples from Holocene sediments revealed the dominant species to be As(III), with ratios of As(III):AsT ranging from 0.55 to 0.98 (average 0.74). There were indications from saturation index estimations that Mn solubility is limited by the precipitation of MnCO3. Tubewells from high As areas in proximity to anthropogenic waste influx sources showing high molar Cl/Br ratios, low SO4(2-) and low NO3(-) demonstrate relatively lower As concentrations, thereby reducing As pollution in those wells. Analyses of core samples (2 in each of the blocks) drilled to a depth of 45 m indicate that there is no significant variation in bulk As (5-20mg/kg) between the Holocene and Pleistocene sediments, indicating that favorable subsurface redox conditions conducive to mobilization are responsible for the release of As. The same applies to Mn, but concentrations vary more widely (20-2000 mg/kg). Sequential extraction of Holocene sediments showed As to be associated with 'specifically sorbed-phosphate-extractable' phases (10-15%) and with 'amorphous and well crystalline Fe-oxyhydroxide' phases (around 37%) at As-contaminated well depths, suggesting that the main As release mechanisms could be either competitive ion exchange with PO4(3-), or the dissolution of Fe oxyhydroxides. In the Pleistocene sediments Mn is predominantly found in the easily exchangeable fraction.

Growth of large-scale vertically aligned GaN nanowires and their heterostructures with high uniformity on SiO(x) by catalyst-free molecular beam epitaxy.

The catalyst-free molecular beam epitaxial growth of GaN nanowires and their heterostructures on a SiOx template is studied in detail. It was found that by optimizing the growth temperature, highly uniform and vertically aligned GaN nanowires and InGaN/GaN heterostructures with excellent optical properties can be obtained on a SiOx template in a large-scale. This work provides an entirely new avenue for GaN nanowire based optoelectronic devices.