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Wyniki wyszukiwania dla: stress measurement
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On the use of uniaxial one-parameter damage laws for estimating fatigue life under multiaxial loading
PublikacjaThe goal of this paper is to evaluate the capabilities of different one-parameter fatigue laws to estimate crack initiation in notched components under multiaxial loading. Fatigue damage is accounted for through stress-based, strain-based, and energy-based approaches while the cyclic plasticity at the notch-controlled process zone is estimated using linear-elastic simulations. The results show that energy-based formulations established...
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Assessment of Thermal Stresses in Asphalt Mixtures at Low Temperatures Using the Tensile Creep Test and the Bending Beam Creep Test
PublikacjaThermal stresses are leading factors that influence low-temperature cracking behavior of asphalt pavements. During winter, when the temperature drops to significantly low values, tensile thermal stresses develop as a result of pavement contraction. Creep test methods can be suitable for the assessment of low-temperature properties of asphalt mixtures. To evaluate the influence of creep test methods on the obtained low-temperature...
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Differential expression profile between amygdala and blood during chronic lithium treatment in a rat model of depression – a pilot study
PublikacjaLithium is a mood stabilizer widely used in the pharmacotherapy of bipolar disorder and treatment‑resistant depression. Taking into account dysregulated inflammatory activity in depression and the immunomodulatory role of lithium, we hypothesized that genes associated with inflammatory responses may be potential biomarkers of lithium action. We aimed to compare gene expression changes between the brain and the periphery after...
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Effect of wet Hydrogen Sulfide on Carbon Steels Degradation in Refinery Based on Case Study
PublikacjaMaterial degradation caused by wet hydrogen sulfide (Wet H2S) is one of the major issues in refineries. Carbon steel is the main construction material used in refineries and is subjected not only to thickness loss but the hydrogen is the major concern. H2S leads to high atomic hydrogen penetration in steel which causes degradation in the form of blistering and/or cracking (HIC/SOHIC) and stress cracking in the area of welds and...
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Non-Destructive Assessment of Masonry Pillars using Ultrasonic Tomography
PublikacjaIn this paper, a condition assessment of masonry pillars is presented. Non-destructive tests were performed on an intact pillar as well as three pillars with internal inclusions in the form of a hole, a steel bar grouted by gypsum mortar, and a steel bar grouted by cement mortar. The inspection utilized ultrasonic stress waves and the reconstruction of the velocity distribution was performed by means of computed tomography. The...
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Green and equitable analytical chemistry
PublikacjaGreen analytical chemistry introduces the ideas of reduction ofanalytical activities impact on the environment. However, to bemore sustainable, analytical chemistry should include socialaspects in greater manner. In this light‘equitable’analyticalprocedures, which are easily available in terms of price andapplicability by everyday user, are developed. These positivetrends are observed as many procedures, based on commonlyused for...
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Regulation of Cellular Redox Homeostasis by (–)-Epicatechin and Cocoa Extracts—A Pilot Study
PublikacjaCocoa polyphenols play an important role in protection against diseases in which oxidative stress is implicated as a causal or contributing factor. The main aim of this study was to elucidate the influence of different cocoa extracts and main cocoa bioactive compound (–)-epicatechin on cell growth and support of antioxidant cellular barrier in colon adenocarcinoma cell line model (HT29). Results show that the tested cocoa bioactivity...
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REGULATION OF CELLULAR REDOX HOMEOSTASIS BY (-)-EPICATECHIN AND COCOA EXTRACTS – PILOT STUDY
PublikacjaCocoa polyphenols play an important role in protection against diseases in which oxidative stress is implicated as a causal or contributing factor. The main aim of this study was to elucidate the influence of different cocoa extracts and main cocoa bioactive compound (–)-epicatechin on cell growth and support of antioxidant cellular barrier in colon adenocarcinoma cell line model (HT29). Results show that the tested cocoa bioactivity...
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Investigation of RTS Noise in Reverse Polarized Silicon Carbide Schottky Diodes
PublikacjaOne of the method of electronic device quality and reliability evaluation is observation of its inherent noise. The RTS phenomena usually indicates the presence of large defects in the structure of the material of the device, therefore it can be treated as an indicator of technology quality. In the paper authors present results of RTS investigations in reverse polarized Silicon Carbide Schottky diodes. Devices being studied are...
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Evaluation of thermal cracking probability for asphalt concretes with high percentage of RAP
PublikacjaThe paper presents determination of the probability of thermal cracking of asphalt mixtures with different reclaimed asphalt pavement (RAP) content on the basis of laboratory tests and analytical evaluation using thermal stress development method. Probability was evaluated taking into consideration: the type and gradation of the mixture and the quality and content of RAP. Thermal stresses were determined using two models: elastic and...
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Rheology of liquid crystalline polymers
PublikacjaLiquid crystallinity was invented in the 19th century. It was sometimes called the fourth state of matter because of the ability of macromolecules to generate liquid crystal phases. The main classification divided liquid crystalline polymers (LCPs) into lyotropic and thermotropic types. Interpretation of the rheological behavior of LCP is more complicated than for other polymers. Ordinary polymers are characterized by a normal...
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Analysis of Ceramic Elements with Ring-Crack Defects in Lubricated Rolling Contact
PublikacjaThe properties of ceramics, specifically low density, high hardness, high temperature capability and low coefficient of thermal expansion are of most interest to rolling element manufacturers. Surface ring cracks on lubricating rolling contact fatigue failure has been studied using numerical fracture analysis. Such cracks are very often found on ceramic bearing balls and decrease fatigue life rapidly. The numerical calculations...
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The influence of stainless steels microstructure evolution on the mechanical properties of pressure installation elements
PublikacjaIn this paper results of FEM analysis performed for pipe and 90o elbow, made of super duplex stainless steel, after precipitation of sigma phase (s), were presented. Heat treatment conditions simulate accidental overheating that can occur in nuclear installations after cooling circulation fails. For initial and modified microstructure tensile test was performed and numerical description of work hardening curves was done. Verification...
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Forecasted climate changes and their influence on cities and regions in 2050 in terms of extreme hydrological events
PublikacjaGlobal climate change is a problem which arises numerous theories and uncertainties, especially in terms of speculated human impact. Independent from the fact, what is the main driver for the changes, some of the climate shifts are visible already nowadays. Both contemporary and future cities will have to face such problems. Although climate change may cause numerous effects on different fields, a special stress in this article...
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DNA Methylation Changes Induced by Redox-Active Compounds—Choosing the Right PCR-Based Method
PublikacjaThe impact of catechins on the expression profile of redox-related genes in HT29 cell line has been studied recently by our group using Oxidative Stress RT2 Profiler PCR Array. Within the examined panel of 84 genes, the down-regulation of SRXN1 gene was unique among other up-regulated genes. We hypothesized that the observed down-regulation resulted from DNA methylation and have exploited this observation to choose the proper strategy...
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Antioxidants: a premature scientific hypothesis that reshuffled the traditional food pyramid
PublikacjaAntioxidants present in substantial amounts in foods, plant-based products in particular, have been suggested as chemopreventive agents that can curb the development of undesirable health effects caused by oxidative stress simply by enriching diet in such compounds. This idea has been enthusiastically accepted by consumers, as well as food and pharmaceutical industry, and created great demand for products containing antioxidant...
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New approaches to cutting resistance estimation of wood cutting process with circular-saw blades
PublikacjaTheoretical and experimental determination of values of cutting resistance belongs to the basic and simultaneously the most developed field of mechanics of this process. Energetic effects of wood sawing process are mainly calculated on the basis of the specific cutting resistance which, in wood cutting, is a function on a lot of factors. In this paper new method for calculation of cutting resistance is described. The latter method...
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Ultrasonic diagnostics of concrete T-beams used in bridge structures
PublikacjaThis paper describes a method of ultrasonic diagnostics used for prefabricated concrete elements. The studies are focused on the applicability of nondestructive techniques based on impulse and wave packet induced elastic waves for the condition assessment of T-shaped bridge beams. Experimental tests were performed for the prestressed beam used for the superstructure of the viaduct on A1 highway near Toruń. In addition numerical...
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The influence of stainless steels microstructure evolution on the mechanical properties of pressure installation elements
PublikacjaIn this paper results of FEM analysis performed for pipe and 90o elbow, made of super duplex stainless steel, after precipitation of sigma phase (),were presented. Heat treatment conditions simulate accidental overheating that can occur in nuclear installations after cooling circulation fails. For initial and modified microstructure tensile test was performed and numerical description of work hardening curves was done. Verification...
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Mechanical characterization of a gravel column in a calibration chamber operating as a triaxial cell
PublikacjaA series of tests considering the behavior of gravel columns was performed. A segment of column with a height of 1 m and a diameter of 0.53 m was modelled in a calibration chamber used as a triaxial cell at three different lateral stress applied. The vertical load transferred on the column head was simulated with steady increase of water pressures in the upper and lower membranes. During the loading the volumetric changes in the...
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Failure of cold-formed beam: How does residual stress affect stability?
PublikacjaIn machine industry, stresses are often calculated using simple linear FEM analysis. Occasional failures of elements designed in such a way require recomputation by means of more sophisticated methods, eg. including plasticity and non-linear effects. It usually leads to investigation of failure causes and improvement of an element in order to prevent its unwanted behavior in the future. The study presents the case where both linear...
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Normal stress distribution in built‑up cold‑formed column in relation to interconnecting bolt spacing
PublikacjaIn order to increase a stiffness of cold-formed steel (CFS) elements it is practised to built-up the cross-section. In the analysed case, a main element is strengthened by adding extra chord in contact partially along the column. This additional chord acts as a longitudinal stiffener connected with the main section by series of bolts. Authors check whether rules applied over the years, for hot-rolled elements, can be indiscriminately...
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PSYCHOLOGICAL CAPITAL AND CHALLENGE APPRAISAL FOSTER THRIVING IN THE GLOBALIZED MULTICULTURAL WORKPLACE
PublikacjaThe purpose of the study was to examine the psychological resources which foster thriving in multicultural work settings of multinational corporations (MNCs) - the companies that are evident manifestation of globalization. Although globalized multicultural workplace creates specific job demands that pose unique occupational stress to individuals, some personal resources enable them to deal with these demands and to thrive. Thriving...
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Temperature influences on shear stability of a nanosize plate with piezoelectricity effect
PublikacjaPurpose The purpose of this paper is to predict the mechanical behavior of a piezoelectric nanoplate under shear stability by taking electric voltage into account in thermal environment. Design/methodology/approach Simplified first-order shear deformation theory has been used as a displacement field. Modified couple stress theory has been applied for considering small-size effects. An analytical solution has been taken into account...
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How can the work environment be redesigned to enhance the well-being of individuals with autism?
PublikacjaPurpose – This article examines the opportunities to create optimal conditions for individuals with autism, to work successfully within the contemporary workplace and improve their well-being. These opportunities arise from digital technology (DT) development, enabling the work environment to be remodeled by providing new possibilities and ways of working. The author discusses both technology-based as well as non-technological accommodations...
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Association of Genes Related to Oxidative Stress with the Extent of Coronary Atherosclerosis
PublikacjaOxidative stress is believed to play a critical role in atherosclerosis initiation and progression. In line with this, in a group of 1099 subjects, we determined eight single nucleotide polymorphisms (SNPs) related to oxidative stress (PON1 c.575A>G, MPO c.463G>A, SOD2 c.47T>C, GCLM c.590C>T, NOS3 c.894G>T, NOS3 c.786T>C, CYBA c.214C>T, and CYBA c.932A>G) and assessed the extent of atherosclerosis in coronary arteries based on...
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Experimental study on ultrasonic monitoring of splitting failure in reinforced concrete
PublikacjaThis paper investigates inspection of reinforced concrete elements sensitive to the splitting failure. The behaviour of a reinforced concrete specimen subjected to a tensile stress is considered. The damage detection procedure is based on the ultrasonic wave propagation technique. The piezoelectric transducers are located on both ends of the specimen and the measurements are taken periodically during the incrementally increased...
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GENERALISED HERSCHEL MODEL APPLIED TO BLOOD FLOW MODELLING
PublikacjaThis paper introduces a new rheological model of blood as a certain generalisation of the standard Herschel-Bulkley model. This model is a rheological constitutive equation and belongs to the group of the so-called generalised Newtonian fluids. Experimental data is compared with results, obtained from the new model, to demonstrate that it allows for the best agreement together with Luo-Kuang model. The new model may be easily implemented...
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Resonant DC link inverters for AC motor drive systems – critical evaluation
PublikacjaIn this survey paper, resonant and quasiresonant DC link inverters are reexamined for AC motor drive applications. Critical evaluation of representative topologies is based on simulation and waveform analysis to characterize current/voltage stress of components, control timing constraints and feasibility. A special concern over inverter common-mode voltage and voltage gradient du/dt limitation capacity is discussed for motor bearing...
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Numerical analysis of crack propagation in silicone nitride
PublikacjaThe properties of ceramics, specifically low density, high hardness, high temperature capability and low coefficient of thermal expansion are of most interest to rolling element manufacturers. The influence of ring crack size on rolling contact fatigue failure has been studied using numerical fracture analysis. Such cracks are very often found on ceramic bearing balls and decrease fatigue life rapidly. The numerical calculation...
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Geometrically nonlinear FEM analysis of FGM shells based on neutral physical surface approach in 6-parameter shell theory
PublikacjaThe paper presents the formulation of the elastic constitutive law for functionally graded materials (FGM) on the grounds of nonlinear 6-parameter shell theory with the 6th parameter being the drilling degree of freedom. The material law is derived by through-the-thickness integration of the Cosserat plane stress equations. The constitutive equations are formulated with respect to the neutral physical surface. The influence of...
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Periodic Properties of 1D FE Discrete Models in High Frequency Dynamics
PublikacjaFinite element discrete models of various engineering 1D structures may be considered as structures of certain periodic characteristics. The source of this periodicity comes from the discontinuity of stress/strain field between the elements. This behaviour remains unnoticeable, when low frequency dynamics of these structures is investigated. At high frequency regimes, however, its influence may be strong enough to dominate calculated...
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The Effect of Protrusions on the Initiation of Partial Discharges in XLPE High Voltage Cables
PublikacjaThis paper is focusing on 3D Finite Elements Analysis (FEA) based modelling of protrusions as defects or imperfections in the XLPE high voltage cable. This study is aiming to examine the impact protrusions have on the initiation of partial discharges. Spherical and ellipsoidal protrusions with different sizes at the conductor screen of the high voltage cable is an essential content of this paper. In addition, a spherical gas-filled...
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Surface finite viscoelasticity and surface anti-plane waves
PublikacjaWe introduce the surface viscoelasticity under finite deformations. The theory is straightforward generalization of the Gurtin–Murdoch model to materials with fading memory. Surface viscoelasticity may reflect some surface related creep/stress relaxation phenomena observed at small scales. Discussed model could also describe thin inelastic coatings or thin interfacial layers. The constitutive equations for surface stresses are...
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Enhanced energy conversion as a result of fluid-solid interaction in micro- and nanoscale
PublikacjaIt is known that nano- and micromechanics require new approaches to right describing of surface-like phenomena which lead to an enhanced energy conversion. In this work, a general form of surface forces that consist of a contribution from both the friction and mobility components has been extended to collect the effects of bulk and surface motion of a fluid. Quite similar impact can be observed for a solid-fluid mixture, where...
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Distortional buckling of composite thin-walled columns of a box-type cross section with diaphragms
PublikacjaDistortional buckling of axially compressed columns of box-like composite cross sections with andwithout internal diaphragms is investigated in the framework of one-dimensional theory. The channel membersare composed of unidirectional fibre-reinforced laminate. Two approaches to the member orthotropic materialare applied: homogenization based on the theory of mixture and periodicity cells, and homogenization basedon the Voigt–Reuss...
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Elastoplastic law of Cosserat type in shell theory with drilling rotation
PublikacjaWithin the framework of six-parameter non-linear shell theory, with strain measures of the Cosserat type, we develop small-strain J2-type elastoplastic constitutive relations. The relations are obtained from the Cosserat plane stress relations assumed in each shell layer, by through-the-thickness integration employing the first-order shear theory. The formulation allows for unlimited translations and rotations. The constitutive...
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The influence of high temperature wood drying conditions using air-steam mixture on its properties
PublikacjaThe results of properties change of beech wood after drying process are presented. The wood taken to experiments was from northern part of Pomeranian region in Poland. Before the main high temperature drying process using air-steam mixture, wood was initially dried in an open air conditions. The high temperature drying process was conducted at temperature 120oC, humidity 48%, flow rate of drying medium 2.5m/s and atmospheric pressure....
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Efficiency of acoustic heating in the Maxwell fluid
PublikacjaThe nonlinear effects of sound in a fluid describing by the Maxwell model of the viscous stress tensor is the subject of investigation. Among other, viscoelastic biological media belong to this non-newtonian type of fluids. Generation of heating of the medium caused by nonlinear transfer of acoustic energy, is discussed in details. The governing equation of acoustic heating is derived by means of the special linear combination...
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Process zone in the Single Cantilever Beam under transverse loading. - Part I: Theoretical analysis
PublikacjaSingle Cantilever Beam (SCB) specimen loaded with a transverse force parallel to the crack front is proposed for the analysis of crack propagation phenomena under mixed mode conditions. The stress redistribution in the adhesive layer in the vicinity of the crack front so as the beam deformation are estimated using a Timoshenko beam on elastic foundation model. This model emphasizes the Mode II contribution due to flexural beam...
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Efficiency of acoustic heating in the Maxwell fluid
PublikacjaThe nonlinear effects of sound in a fluid describing by the Maxwell model of the viscous stress tensor is the subject of investigation. Among other, viscoelastic biological media belong to this non-newtonian type of fluids. Generation of heating of the medium caused by nonlinear transfer of acoustic energy, is discussed in details. The governing equation of acoustic heating is derived by means of the special linear combination...
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The selected effects of high temperature air-steam mixture wood drying
PublikacjaThe results of properties change of beech wood after drying process are presented. The wood taken to experiments was from northern part of Pomeranian region in Poland. Before the main high temperature drying process using air-steam mixture, wood was initially dried in an open air conditions. The high temperature drying process was conducted at temperature 120oC, humidity 48%, flow rate of drying medium 2.5m/s and atmospheric pressure....
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Free Vibration of Flexomagnetic Nanostructured Tubes Based on Stress-driven Nonlocal Elasticity
PublikacjaA framework for the flexomagneticity influence is here considered extending the studies about this aspect on the small scale actuators. The developed model accommodates and composes linear Lagrangian strains, Euler-Bernoulli beam approach as well as an extended case of Hamilton’s principle. The nanostructured tube should subsume and incorporate size effect; however, for the sake of avoiding the staggering costs of experiments,...
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M-integral for finite anti-plane shear of a nonlinear elastic matrix with rigid inclusions
PublikacjaThe path-independent M-integral plays an important role in analysis of solids with inhomogeneities. However, the available applications are almost limited to linear-elastic or physically non-linear power law type materials under the assumption of infinitesimal strains. In this paper we formulate the M-integral for a class of hyperelastic solids undergoing finite anti-plane shear deformation. As an application we consider the problem...
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A new finite element with variable Young's modulus
PublikacjaThe Finite Element Method (FEM) is a numerical technique that is well-established in the field of engineering. However, in biological sciences, it is justtaking its first steps. Bone tissue is an example of biological material which isexposed to high loads in its natural environment. Practically every movementof the body results in changing stress levels in the bone. Nature copes with thisvery well but when human intervention is...
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Corrosion degradation impact on mechanical properties of structural steel
PublikacjaRecently, extensive research was conducted regarding the impact of corrosion degradation on the mechanical properties of structural steel. Studies show that at the material level, the microstructure is somewhat unchanged due to corrosion degradation. However, the corrosion causes pits and structural surface irregularities that consequently impact the mean stress-strain response of typical coupon specimens subjected to tensile loading....
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Design of Jack-up Platform for 6 MW Wind Turbine: Parametric Analysis Based Dimensioning of Platform Legs
PublikacjaThe article presents the results of the research conducted within the framework of the project entitled WIND-TU-PLA (ERA-NET, MARTEC II), the general aim of which was to design and analyse supporting structures for wind turbines intended for operation on the South Baltic area. The research part described in the article aimed at developing a preliminary design for a jack-up platform which can operate on water areas with depth of...
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Assembly of Lipopolysaccharide in Escherichia coli Requires the Essential LapB Heat Shock Protein
PublikacjaHere, we describe two new heat shock proteins involved in the assembly of LPS in Escherichia coli, LapA and LapB (lipopolysaccharide assembly protein A and B). lapB mutants were identified based on an increased envelope stress response. Envelope stress responsive pathways control key steps in LPS biogenesis and respond to defects in the LPS assembly. Accordingly, the LPS content in ΔlapB or Δ(lapA lapB) mutants was elevated, with...
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HYGRO-MAGNETIC VIBRATION OF THE SINGLE-WALLED CARBON NANOTUBE WITH NONLINEAR TEMPERATURE DISTRIBUTION BASED ON A MODIFIED BEAM THEORY AND NONLOCAL STRAIN GRADIENT MODEL
PublikacjaIn this study, vibration analysis of single-walled carbon nanotube (SWCNT) has been carried out by using a refined beam theory, namely one variable shear deformation beam theory. This approach has one variable lesser than a contractual shear deformation theory such as first-order shear deformation theory (FSDT) and acts like classical beam approach but with considering shear deformations. The SWCNT has been placed in an axial or...
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No Evidence for Sex-specificity in Vitamin C, E and Fatty Acid Content of Human Milk from Healthy Polish Mothers
PublikacjaHuman milk (HM) is a complex fluid that meets the nutritional needs of infants. Its composition idrfs associated with environmental, maternal, and foetal variables. It provides nutrients and bioactive substances, including cytokines, immunoglobulins, and constituents with antioxidative properties. Boys are reportedly more susceptible to oxidative stress. This study aimed to determine the relationship between infant sex and the...