This is a retrospective single-center study of 417 consecutive patients with coronavirus disease 2019 (COVID-19) admitted to Jaber Al-Ahmad Hospital in Kuwait between February 24, 2020 and May 24, ...2020. In total, 39.3% of patients were asymptomatic, 41% were symptomatic with mild/moderate symptoms, 19.7% were admitted to the intensive care unit (ICU). Most common symptoms in cohort patients were fever (34.3%) and dry cough (32.6%) while shortness in breath was reported in (75.6%) of ICU admissions. Reported complications requiring ICU admission included Sepsis (68.3%), acute respiratory distress syndrome (95.1%) and heart failure (63.4%). ICU patients were more likely to have comorbidities, in comparison to non-ICU patients, including diabetes (35.4% vs 20.3%) and hypertension (40.2% vs 26.9%). Mortality rate of cohort was 14.4% and mean age of death was 54.20 years (± 11.09) and 90% of death cases were males. Chest high-resolution computed tomography for ICU cases reveled multifocal large patchy areas of ground glass opacification mixed with dense consolidation. Cases admitted to ICU showed abnormal levels of markers associated with infection, inflammation, abnormal blood clotting, heart problems and kidney problems. Mean hospital stay for asymptomatic cases was 20.69 days ±8.57 and for mild/moderate cases was 21.4 days ±8.28. Mean stay in ICU to outcome for survivors was 11.95 days ±8.96 and for death cases 13.15 days ±10.02. In this single-center case series of 417 hospitalized COVID-19 patients in Kuwait 39.3% were asymptomatic cases, 41% showed mild/moderate symptoms and 18.7% were admitted to ICU with a mortality rate of 14.4%.
Hydroxyapatite (HAP) powder precursors have been used as starting material for biomedical applications, such as synthetic bone graft materials and scaffold for hard tissue engineering. Considering ...the numerous applications of hydroxyapatite, three different routes for HAP powders preparations was investigated. Two powders were prepared by chemical precipitation reactions at 100
°C and one by mechanochemical reaction. The powders were characterized using chemical analysis, surface area measurements, laser diffraction, X-ray diffraction (XRD) and SEM. The Ca/P ratios were varied from 1.67 to 1.58. The chemical composition, the crystallinity and the agglomeration characters depend on the preparation route. The effect of powder characteristics on the sinterability was investigated. Although, the thermal stability and hence the start of sintering dependents on the Ca/P ratio, the final sintering density and hence the mechanical properties depends on the agglomeration characteristics and the particle size distribution. Hydroxyapatite powder prepared by mechanochemical route have nano-sized crystallites with a uniform smaller agglomerated particle size distribution and have a butter sinterability.
Nano Cd
1−
x
Y
x
S and Cd
1−
x
V
x
S (0 ≤
x
≤ 0.2) systems were synthesized by a thermolysis method. X-ray phase analysis indicated the presence of two phases, cubic and hexagonal structures, for ...some samples. The effect of doping on the cell parameters, Cd-tetrahedron dimension, crystallite size and the mixed phases’ percentages in the sample were examined applying X-ray Rietveld method. The energy gap of Y- or V-doped CdS was determined by ultraviolet spectroscopy technique. It is found out that the energy gap of V-doped CdS is less than the corresponding Y-doped CdS samples. Density function calculation (DFT) was used to confirm the decreasing in energy gap upon doping, and also to study the changes in absorption and dielectric properties of doped and undoped CdS samples in both cubic and hexagonal phases. The photoluminescence measurements revealed the presence of extra sub emissions spectra (yellow and green) upon doping CdS with Y or V compared with undoped CdS sample.
In this work, the effect of carbon quantum dots (CQDs) on the optical and electrical properties of polyvinylidene fluoride (PVDF) has been investigated. Different weight percent (0, 1, 3, 5 and 10 ...wt%) ratios of CQDs/PVDF nanocomposite films were prepared using solution casting technique. The morphological properties of CQDs were examined using a transmission electron microscope (TEM). The optical properties of the prepared plain PVDF and CQDs/PVDF nanocomposite films were measured using UV–Visible spectrophotometer in the wavelength range 190–1200 nm. The direct energy band gap (
E
g dir.
) of the prepared films decreases from 5.28 to 2.96 eV as the wt% ratio of CQDs/PVDF increases from 0 to 10.0%. The DC electrical conductivity (
σ
DC
) of the prepared nanocomposite films are measured in the temperature range from 298 to 398 K. The electrical conductivity of the nanocomposite films has been enhanced six times in magnitude as compared with that of the plain PVDF film, as the wt% ratio of CQDs/PVDF increases up to 10 wt%. The enhancement in the optical and electrical properties of PVDF makes it as a novel candidate in various optoelectronic applications.
We report here a facile, template-free and one-step solvothermal approach for the synthesis of high-temperature stable gold/titania nanocomposite (NCs), providing a new, simple, quick and inexpensive ...wet-chemical route. Our approach is based on the assembly of gold salt and titanium butoxide in dimethyl sulfoxide (DMSO). Also, we present here, for the first time, a cathodically activated Au/TiO2 catalyst with Pt/C activity for the hydrogen evolution reaction (HER) in 0.5 M H2SO4 in the dark. The as-prepared (unactivated) Au/TiO2 NCs exhibits considerable electrocatalytic activity for H2 generation in the dark, with a low onset potential (EHER) of −64 mV vs. RHE, a Tafel slope (-bc) of 60 mV dec−1 and an exchange current density (jo) of 0.12 mA cm−2. Long-term stability and durability tests in 0.5 M H2SO4, employing cyclic voltammetry technique (10,000 of repetitive cycling) and 72 h of chronoamperometry measurements at a high cathodic potential (cathodic activation), reveal that the electrocatalyst activates during such aging processes yielding an activated Au/TiO2 catalyst with Pt/C-like activity for H2 generation (EHER -3 mV, -bc: 35 mV dec−1, and jo: 0.95 mA cm−2). The outstanding HER activity of the activated catalyst is discussed.
Silica-rich dealuminated kaolin (SRDK), produced as a by-product in alum industry, is still considered as waste materials in Egypt. Expansion of aquaculture along the banks of Nile River and its ...canals negatively affects water quality due to formation of ammonia. The current investigation aims to eradicate ammonia from aquaculture systems via an integrated approach of converting SRDK to pure zeolite Y in two-step process. The main constituent of SRDK is amorphous silica with a small amount of unreacted metakaolin and crystalline silica. XRD and FTIR proved that zeolitization started by mechanochemical activation at room temperature. However, hydrothermal treatment at 105 °C and 125 °C produces zeolite Y with different Si/Al ratios and microcrystalline quartz is completely reacted at 125 °C. The adsorption isotherm data of ammonia was best fitted by Freundlich model. Zeolite Y produced from 80% SRDK and 20% metakaolin at 125 °C has a high efficiency to remove ammonia from aquaculture.
Graphical Abstract
Highlights
Silica-rich dealuminated kaolin (SRDK) was converted to pure zeolite Y in two-step process.
Zeolite formation stated by Mechanochemical activation at room temperature.
Hydrothermal treatment at 105 °C and 125 °C produces zeolite Y with different Si/Al ratios.
The ammonia adsorption isotherm was best fitted by Freundlich model.
Zeolite Y produced from SRDK and 20% metakaolin has a high efficiency to remove ammonia from aquaculture.
Thin films of In2O3 and In2O3 doped with Ag+ or Cu2+ were assembled by spray pyrolysis from aqueous solution at 450 °C. The microstructure analysis and optical properties were investigated using XRD, ...SEM, EDX and UV–Vis. spectrophotometer. XRD analysis proved that Ag-doping greatly reduces the crystallites sizes of In2O3 from 96 nm to 59 nm. However, Cu-doping has less pronounced effect on the crystallite sizes than that of Ag doping. The band gap energy of In2O3 decreases with both Cu2+ and Ag+ doping. The change in lattice parameter of cubic In2O3 with Cu and Ag substitutions is compatible with the ionic radius of the substituted ions, i.e. Ag-substitution increases the lattice parameter and Cu-substitution decreases the lattice parameter. The calculated direct band gap of bare In2O3 film is 3.59 eV. Doping In2O3 with Cu2+ and Ag+ decreases the band gap to 3.36 eV and 3.27 eV, respectively. Ag+ substitution in place of In3+ ion in In2O3 cubic lattice causes negative strain value due to the shrinkage of the interplaner spacing of the unit cell. In contrary, replacing In3+ cation with Cu2+ cation expands interplaner distances of the crystallographic planes of In2O3 lattice and causes positive strain value. The present work demonstrates the capability to assemble high quality doped – In2O3 thin films by simple solution based spray pyrolysis.
In ferromagnetic semiconductors, the coupling of magnetic ordering with semiconductor character accelerates the quantum computing. The structural stability, Curie temperature (Tc), spin polarization, ...half magnetic ferromagnetism and transport properties of ZnX2Se4 (X = Ti, V, Cr) chalcogenides for spintronic and thermoelectric applications are studied here by density functional theory (DFT). The highest value of Tc is perceived for ZnCr2Se4. The band structures in both spin channels confirmed half metallic ferromagnetic behavior, which is approved by integer magnetic moments (2, 3, 4) μB of Ti, V and Cr based spinels. The HM behavior is further measured by computing crystal field energy ΔEcrystal, exchange energies Δx(d), Δx (pd) and exchange constants (Noα and Noβ). The thermoelectric properties are addressed in terms of electrical conductivity, thermal conductivity, Seebeck coefficient and power factor in within a temperature range 0–400 K. The positive Seebeck coefficient shows p-type character and the PF is highest for ZnTi2Se4 (1.2 × 1011 W/mK2) among studied compounds.
In this work, the optical and mechanical properties of Fe
2
O
3
nanoparticles (NPs)/chitosan nanocomposite films have been investigated. Nanocomposite films of different weight ratios of Fe
2
O
3
...NPs/chitosan (0, 1, 5, 10, 20 and 30 wt%) were fabricated using casting technique. The optical properties of colloidal Fe
2
O
3
NPs and Fe
2
O
3
NPs/chitosan nanocomposite films were recorded using UV–visible spectrophotometer. As the ratio of Fe
2
O
3
NPs to chitosan increases from 0 to 30%, the energy band gap of Fe
2
O
3
NPs/chitosan films decreases from 3.16 to 2.11 eV. This decrease is due to quantum confinement effect. The mechanical properties of the nanocomposite films as a function of sweeping temperature were measured using a dynamic mechanical analyzer. An enhancement in storage modulus, stiffness and glass transition temperature (T
g
) has been observed as the ratio of Fe
2
O
3
NPs/chitosan increases. T
g
of Fe
2
O
3
NPs/chitosan nanocomposite film shifts towards higher temperature side with respect to pure chitosan film from 152.1 to 166.3 °C as the ratio of Fe
2
O
3
NPs/chitosan increases from 0 to 30 wt%. The increase in T
g
is mainly attributed to the decrease in free volumes and vacancies in the nanocomposite films as the weight ratio of Fe
2
O
3
NPs/chitosan increases.
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