Effects Of Various Environments Research Articles

Effects of various environments on epigenetic settings and chromosomal damage

Air pollution is a dominant environmental exposure factor with significant health consequences. Unexpectedly, research in a heavily polluted region of the Czech Republic, with traditional heavy industry, revealed repeatedly the lowest frequency of micronuclei in the season with the highest concentrations of air pollutants including carcinogenic benzo[a]pyrene (B[a]P). Molecular findings have been collected for more than 10 years from various locations of the Czech Republic, with differing quality of ambient air. Preliminary conclusions have suggested adaptation of the population from the polluted locality (Ostrava, Moravian-Silesian Region (MSR)) to chronic air pollution exposure. In this study we utilize the previous findings and, for the first time, investigate micronuclei (MN) frequency by type: (i) centromere positive (CEN+) MN, representing chromosomal losses, and (ii) centromere negative (CEN-) MN representing chromosomal breaks. As previous results indicated differences between populations in the expression of XRCC5, a gene involved in the non-homologous end-joining (NHEJ) repair pathway, possible variations in epigenetic settings in this gene were also investigated. This new research was conducted in two seasons in the groups from two localities with different air quality levels (Ostrava (OS) and Prague (PG)). The obtained new results show significantly lower frequencies of chromosomal breaks in the OS subjects, related to the highest air pollution levels (p < 0.001). In contrast, chromosomal losses were comparable between both groups. In addition, significantly lower DNA methylation was found in 14.3% of the analyzed CpG loci of XRCC5 in the population from OS. In conclusion, the epigenetic adaptation (hypomethylation) in XRCC5 involved in the NHEJ repair pathway in the population from the polluted region, was suggested as a reason for the reduced level of chromosomal breaks. Further research is needed to explore the additional mechanisms, including genetic adaptation.

Küresel, Yerel, Mikrosistem ve Bireysel Faktörlerin Türkiye’deki Mülteci Çocukların Eğitim Süreçlerine Etkileri

In this study, a theoretical model framing the education processes of refugee children in Turkey is proposed. This model includes needs, risks, and opportunities, as well as the effects of various environments and actors in which refugee children are involved, on their educational experience. This model, which also focuses on the effects of global dynamics and local policies, has an integrative and developmental structure that allows new dimensions to be added. The method used in the study is secondary literature evaluation. Based on this method, this study synthesizes publications focusing on the various needs (psychological, cultural, and educational) of refugee children whose schooling rates are increasing day by day in Turkey, and on issues such as peer bullying, xenophobia, and trauma that these children face. Thus, the conditions of refugee children in their new environment and the cultural approach necessary for their successful adaptation to Turkey are described. The original model designed by the researcher has the claim to provide a framework for future research and practices in educational services to be provided to refugee children.

Dynamic Cell Imaging: application to the diatom Phaeodactylum tricornutum under environmental stresses

ABSTRACT The dynamic movement of cell organelles is an important and poorly understood component of cellular organization and metabolism. In this work we present a non-invasive non-destructive method (Dynamic Cell Imaging, DCI) based on light scattering and interferometry to monitor dynamic events within photosynthetic cells using the diatom Phaeodactylum tricornutum as a model system. For this monitoring we acquire for a few seconds movies of the signals that are related to the motion of dynamic structures within the cell (denoted scatterers), followed by a statistical analysis of each pixel time series. Illuminating P. tricornutum with LEDs of different wavelengths associated with short pulsed or continuous-wave modes of illumination revealed that dynamic movements depend on chloroplast activity, in agreement with the reduction in the number of pixels with dynamic behaviour after addition of photosystem II inhibitors. We studied P. tricornutum under two environmentally relevant stresses, iron and phosphate deficiency. The major dynamic sites were located within lipid droplets and chloroplast envelope membranes. By comparing standard deviation and cumulative sum analyses of the time series, we showed that within the droplets two types of scatterer movement could be observed: random motion (Brownian type) but also anomalous movements corresponding to a drift which may relate to molecular fluxes within a cell. The method appears to be valuable for studying the effects of various environments on microalgae in the laboratory as well as in natural aquatic environments. HIGHLIGHTS Light scattering is an alternative to fluorescence to rapidly evidence dynamic processes. Lipid droplets are the major metabolic active sites under stress. A non-destructive visualization method suitable for laboratory microalgae and aquatic samples.

Cramér-Rao Lower Bound Analysis for Many-to-One UAV Tracking Using FDOA Measurements

This paper considers the application for tracking of one mobile emitter using a sequence of frequency difference of arrival (FDOA) measurements obtained by single pair of receivers at a time. We suppose there is only one unmanned aerial vehicle (UAV) as emitter without data link relation problems, such as disconnection of data link or false measurements. Each FDOA measurement defines a region of possible emitter locations around a unique hyperbola. These analysis leads to the Cramer-Rao lower bound (CRLB) for estimation of movements. Through the analysis we propose the manner for tracking through the error-ellipsoids acquired from each CRLB. Since the performance measure is the length of error ellipsoid axes, we compare the effects of various environments.

Experimental Study on Fatigue Crack Growth and Residual Strength of Steel 30CrMnSiNi2A under Mixed Corrosive Environments

The effects of five single and three mixed corrosive environments on the fatigue crack growth and residual strength of steel 30CrMnSiNi2A were experimentally studied. The crack growth rates in corrosive environments, obtained by using Paris equation, were compared with crack growth rate in lab air. The results showed that the interactions of aggressive environments with fatigue loads caused the accelerations of fatigue crack growth rates in steel 30CrMnSiNi2A. But the effects of various environments on the fatigue crack growth rate are different. Among the environments the most detrimental one was oil-box zone, followed by cookroom&amp;washroom, tank seeper, 3.5%NaCl, moist air, high altitude and dried air. Also, the test data showed the less effect of various corrosive environments on critical crack length, that is, no direct infection of corrosive environments on residual strength capability dominated by fracture toughness.

Effects of various environments on fatigue crack growth in Laser formed and IM Ti–6Al–4V alloys

The fatigue crack growth behaviors of Laser formed and ingot metallurgy (IM) Ti–6Al–4V alloys were studied in three environments: vacuum, air and 3.5% NaCl solution. Taking the Unified Fatigue Damage Approach, the fatigue crack growth data were analyzed with two intrinsic parameters, stress intensity amplitude Δ K and maximum stress intensity K max, and their limiting values Δ K * and K max * . Fatigue crack growth rates d a/d N were found increase with stress ratio R, highest in 3.5% NaCl solution, somewhat less in air and lowest in vacuum, and higher in IM alloy than in Laser formed one. In 3.5% NaCl solution, stress corrosion cracking (SCC) was superimposed on fatigue at R=0.9 for where K max> K ISCC, the threshold stress intensity for SCC. This and environment-assisted fatigue crack growth were evidenced by the deviation in fatigue crack growth trajectory (Δ K * vs. K max * curve) from the pure fatigue line where Δ K * = K max * . Furthermore, the fractographic features, identified along the trajectory path, reflected the fatigue crack growth behaviors of both alloys in a given environment.

Perceived Risk and Fear of Crime: Gender Differences in Contextual Sensitivity

Studies have been directed at explaining the ‘gender gap’ in the fear of crime: why do women have higher fear levels than men? Previous studies lead to the tentative conclusion that women are more fearful due to their greater vulnerability in risky environments. Yet, the differential effects of various environments on fear levels of men and women is not well understood. In this paper, theories of gender differences in fear of crime are reviewed, along with various potential fear-invoking contexts. One reason so little is known about context is that statistical software designed to better assess contextual effects — hierarchical linear modeling (HLM) — has only recently become widely available. HLM (Bryk and Raudenbush, 1992; Bryk et al., 1996) is used here to model perceived risk and fear of assault among a sample of Stockholm residents. Results show that at the contextual level, women are more influenced by aspects of the environment than are men. We are led to the conclusion that women are especially ecologically vulnerable (Sparks, 1982) whereas men personalize vulnerability.

Vaporization properties of SrUO 3 and BaUO 3 in atmospheres simulating accident conditions

Effects of various environments on vaporization characteristics of BaUO 3 and SrUO 3 have been studied by means of the Knudsen effusion mass spectrometry. Three kinds of Knudsen cells were employed for simulating different accident atmospheres over temperature ranges from 1470 to 1920 K. The vapor pressures obtained in a platinum Knudsen cell were used as the standard values, with which those obtained in other conditions were compared. A graphite Knudsen cell was utilized to simulate the graphite environment of high temperature gas-cooled reactors (HTGR). On the other hand, a specially designed Knudsen cell with a gas inlet system attached to its bottom was employed in order to introduce reactive gases such as D 2(g) or D 2O(g) from the outside of the mass spectrometer into the cell. In this way, the effects of hydrogen or water vapor on the vaporization of fission products barium and strontium were examined.

Rapid calculation of distant shipping noise in an underwater environment

Various methods were explored and developed to simulate distant shipping ambient noise without executing very time-consuming sound propagation models for each surface ship contributing to the overall noise levels. The methods were developed with certain things in mind: the effects of various environments between source and receiver, the proximity of the surface ships to the receiver, horizontal directionality, source levels, vertical arrival structure, overall precision and accuracy, and substantial reductions in time for most runs. There was, of course, a direct trade-off between run times and the precision and accuracy of the answer, but because of the inherent randomness of ambient noise, in many cases the control case (i.e., a noise model with propagation model runs for each ship) differed only slightly from the much speedier alternatives developed here. Run times and results for the two methods were compared and analyzed. [Work supported by ONR, NRL, and the Univ. of New Orleans.]

Effect of solid‐state curing on the viscoelastic properties of poly(phenylene sulfide)

AbstractPPS is a thermosetting/thermoplastic resin. The resin, upon exiting the polymerization process, is generally a low viscosity, low molecular weight material. The thermosetting character is therefore exploited in a solid state cure process in the presence of air at elevated temperatures. This produces a resin with a more desirable property profile. Melt state dynamic mechanical measurements have been made on a series of cured PPS resins to elucidate structural changes that occur on the molecular level during the cure process. Increases in viscosity, non‐Newtonian behavior, and relative elastic response were observed with increasing cure time and have been attributed to an increasing molecular weight and broadening molecular weight distribution achieved through branching/crosslinking. The effects of various environments on curing have also been investigated. © 1993 John Wiley &amp; Sons, Inc.

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An e.s.r. investigation of environmental effects on polymeric materials: 1. Nylon

Mechanical degradation on nylon with time resulting from the effects of various environments combined with strain on nylon are reported. The environments studied were air, O 3, SO 2, NO x , automotive exhaust gas and ultraviolet light. Stress and these oxidizing agents were found to act in a synergistic way to decrease the strength of oriented nylon. Residual strength and number of free radicals formed during final fracture are given as a function of environment, magnitude of the applied strain, and time. While they had much less influence on strength in spherulitic nylon, exposure to sustained strains in these environments resulted in a significant decrease in toughness. The differences in response to the stimuli suggest different mechanisms are responsible for load carrying capability for oriented and spherulitic nylon, and as a consequence, the failure mechanisms differ in the two classes of nylon. It is suggested that in oriented systems tensile strength is due, at least in part, to tie chains that can break under the combined influences of stress, chemical attach and thermal activation. Slip and/or other failure mechanisms active in nonoriented nylon proved to be not as environmentally sensitive.

Inhibition of Corrosion Fatigue in High Strength Aluminum Alloys

Abstract The effects of environment upon the crack growth rate of several high strength aluminum alloys such as 7075-T6, 7075-T73, and 2024-T3 have been investigated. The environments studied were distilled water, tap water, aqueous sodium chloride, aqueous inhibitors with and without sodium chloride, and ambient air. Low cycle corrosion fatigue studies were conducted at 0.1 Hz and R=0.1 on compact-tension specimens. The highest crack growth rates were observed in salt solution and the lowest in ambient air and inhibited solutions. The borax-nitrite base inhibitor virtually eliminates accelerated crack growth by reducing the crack growth rates (in salt solutions by nearly an order of magnitude) to the ambient air value. The apparent threshold for corrosion fatigue, KICF, was not affected by the inorganic inhibitors. However, the results from tests conducted with an organic inhibitor, piperazine, showed nearly 60% increase in KICF. The effects of various environments are shown through microstructural obser...

Surface effects of various environments and of thermosetting resins on the strength of glass

AbstractGlass rods were etched to reduce their surface flaws and hence to increase their flexural strength. They were then subjected to various environments to see how these would affect their strength and hence their surface. It appeared that no liquid environments affected their strength. This included boiling water. The effect of curing resin against the surface was also shown as was subsequent boiling: Shell Epon 828 appeared to increase the strength of the rods, but only when there was a surface treatment of Union Carbide A‐1100 or Owens‐Corning 801.

The rebinder effect and the adsorption-locking of dislocations in lithium fluoride

Abstract Aqueous solutions of long-chain fatty acids can serve as etchants for lithium fluoride. Using such etchants it has been possible to study the effects of various environments on the cross-gliding of screw dislocations at the surface of a crystal. The observations suggest that chemisorbed polar molecules restrict the motion of screw dislocations via ‘adsorption-locking’. An estimate of the possible strength of such locking is made and its existence confirmed by studies on the yielding behaviour of lithium fluoride crystals. In contrast to Rebinder's observations with metal crystals, adsorbed polar molecules cause an increase in yield and critical resolved shear stresses before inducing the lower rate of work-hardening commonly known as the Rebinder effect.

Status report on the environmentalization of traveling-wave tubes

This paper describes the effects of various environments on the performance of periodic-permanent-magnet focused traveling-wave tubes, the design considerations required to enable the tubes to operate under changing environments, and the means of determining satisfactory compliance with environmental specifications. Design considerations discussed include the ruggedization of various component structures, temperature compensation of periodic-permanent-magnet stacks, and the reduction of the effects of high altitude and humidity on tube operation. Equipment and test methods used to evaluate tube performance under simulated environmental conditions are described and both present and anticipated environmental capabilities of several traveling-wave tube designs are discussed.

Measurement of rates of excretion of sweat solutes under physiological conditions.

An apparatus is described which permits the study of rates of excretion of sweat solutes under physiological conditions from an arm, and which permits regulation of skin temperature of the arm independent of ambient conditions. The apparatus permits the collection from the arm of all sweat solutes separately from the associated water. This is accomplished by isolating an arm in a thermoregulated copper cylinder. Air is circulated through the cylinder and the sweat water is collected in a trap system; the solutes are subsequently washed from the arm and the washings are analyzed. It was shown that the rates of excretion of sodium, potassium, chloride, ‘apparent’ creatinine and urea were the same from an arm enclosed in the apparatus as from the unenclosed arm. Thus, the apparatus can be valid44ly used in studying the effects of various environments on sweat gland activity for the five substances measured. Submitted on July 31, 1958