Mathematics, Statistics & Physics: Recent submissions
Now showing items 121-140 of 810
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Instability of Langmuir-beam waves: Kappa-distributed electrons
( American Institute of Physics Inc. , 2023 , Article)In space plasmas, electron populations exhibit non-equilibrium velocity distributions with high-energy tails that are reproduced by the Kappa power-laws and contrast with the Maxwellian distributions often used in theoretical ... -
Kappa-Distributed Electrons in Solar Outflows: Beam-Plasma Instabilities and Radio Emissions
( Springer Science and Business Media B.V. , 2023 , Article)Electrostatic (ES) wave instabilities are assumed to be at the origin of radio emissions from interplanetary shocks, and solar coronal sources are most likely induced by electron beams, more energetic but less dense than ... -
An exploratory study on medications in Qatar homes
( Dove Medical Press Ltd , 2011 , Article)Background: Drug therapy is the most often used intervention for treatment and prevention of disease. However, if used inappropriately, drugs can cause more harm than good. Improper drug storage and disposal can have a ... -
Mechanical and thermal properties of gamma-ray irradiated polyethylene blends
( Elsevier , 2003 , Conference)In this work, the results obtained by gamma-ray irradiation of polyethylene (PE) blends are presented. The blends were produced by injection molding at 220°C with different compositional ratios, i.e. 100/0, 15/85, 25/75, ... -
Compositional transformations in ion implanted polymers
( Elsevier , 2005 , Conference)Changes of surface layer composition produced by ion bombardment of polyethylene and polypropylene samples were studied. These materials are under consideration for load bearing surfaces in biological and technical ... -
Ion beam modification of surface properties of polyethylene
( Elsevier , 2003 , Conference)Improvement of polymer tribological properties is an essential issue for their application when used as parts of machines or artificial human joints. Ion implantation is a very promising technique in this respect. This ... -
Surface layer modification of ion bombarded HDPE
( Elsevier , 2004 , Article)Press-moulded, high density polyethylene (HDPE) samples were subjected to ion bombardment and effects of the modification studied. He+ ions of energy 100 keV or Ar+ ions of energy 130 keV were applied in the range of dose ... -
The effects of ion bombardment of ultra-high molecular weight polyethylene
( Elsevier , 2006 , Article)Ion bombardment is a suitable tool to improve tribological properties of polymers. In this study UHMWPE samples were bombarded with 130keV He ions to the fluences ranging from 1×1014 to 2×1016cm−2. RBS and NRA techniques ... -
Temperature and electric field effects on the dielectric dispersion of modified polyvinyl chloride
( Elsevier , 2003 , Article)The effect of electric field on the dielectric dispersion of modified polyvinyl chloride (PVC) has been investigated. The applied direct current (DC) field strength was ranging from 0 to 104 V cm−1. The complex permitivity ... -
Study on ferroelastic characteristics of gamma irradiated lithium potassium sulfate crystal
( Elsevier , 1999 , Article)A detailed study of the optical absorption vs. γ-irradiation dose for lithium potassium sulfate crystal, LiKSO4 cut out perpendicular to x, y and z directions is presented. The optical density was measured within the ... -
Effectiveness of two and three doses of COVID-19 mRNA vaccines against infection, symptoms, and severity in the pre-omicron era: A time-dependent gradient
( Elsevier , 2024 , Article)BackgroundVaccines were developed and deployed to combat severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. This study aimed to characterize patterns in the protection provided by the BNT162b2 and ... -
Addressing bias in the definition of SARS-CoV-2 reinfection: implications for underestimation
( Frontiers Media , 2024 , Article)Introduction: Reinfections are increasingly becoming a feature in the epidemiology of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. However, accurately defining reinfection poses methodological ... -
Prevalence of hepatitis B and C viruses among migrant workers in Qatar.
( Springer Nature , 2024 , Article)Limited data exist on viral hepatitis among migrant populations. This study investigated the prevalence of current hepatitis B virus (HBV) infection and lifetime hepatitis C virus (HCV) infection among Qatar's migrant craft ... -
The effect of graphene on the activation energy of grain growth for the nanocrystalline thermoelectric n-type Bi2Te2.7Se0.3
( Springer Nature , 2022 , Article)Even though bismuth telluride is frequently produced by mechanical alloying for thermoelectric materials, no data has been published addressing the thermal behavior and activation energy of the milled n-type Bi2Te2.7Se0.3 ... -
Proposing a Nondestructive and Intelligent System for Simultaneous Determining Flow Regime and Void Fraction Percentage of Gas-Liquid Two Phase Flows Using Polychromatic X-Ray Transmission Spectra
( Springer , 2021 , Article)Two phase flows are of particular importance in various research fields. In the current article, a novel system consists of an X-ray tube and one sodium iodide crystal detector with ability of determining type of flow ... -
Synchronization and chimeras in a network of photosensitive FitzHugh-Nagumo neurons
( Springer Science and Business Media B.V. , 2021 , Article)Recently, a photosensitive model has been proposed that takes into account nonlinear encoding and responses of photosensitive neurons that are subject to optical signals. In the model, a photocell term has been added to ... -
Co-doped zigzag graphene nanoribbon based gas sensor for sensitive detection of H2S: DFT study
( Academic Press , 2021 , Article)In this work, we present a highly sensitive gas sensor for the detection of poisonous hydrogen sulfide gas (H2S) based on copper and zinc co-doped zigzag graphene nanoribbon (Cu/Zn-ZGNR). The electronic properties as well ... -
Computational study of metal doped graphene nanoribbon as a potential platform for detection of H2S
( Elsevier Ltd , 2021 , Article)Theoretical investigation for detection of hydrogen sulfide (H2S) gas using hydrogen/nitrogen-terminated armchair graphene nanoribbon (HAGNR and NAGNR) doped with Pt is presented in this study. The investigation was ... -
First principle study of transition metals codoped MoS2 as a gas sensor for the detection of NO and NO2 gases
( Elsevier B.V. , 2021 , Article)Exposure to nitrogen oxides (NOx) has been reported to seriously affect the respiratory systems. More precisely, breathing NOx may lead to the appearance of asthma symptoms, and may also result in the infection with asthma ... -
Sensitive SO2 gas sensor utilizing Pt-doped graphene nanoribbon: First principles investigation
( Elsevier Ltd , 2021 , Article)The objective of this work is to seek a highly sensitive gas sensor for the detection of sulfur dioxide (SO2) by investigating the impacts of passivation as well as metal doping of armchair-edge graphene nanoribbon (AGNR) ...
