916 resultados para Plasma edge of tokamaks


Relevância:

100.00% 100.00%

Publicador:

Resumo:

The rodent malaria parasite Plasmodium berghei develops in hepatocytes within 48-52h from a single sporozoite into up to 20,000 daughter parasites, so-called merozoites. The cellular and molecular details of this extensive proliferation are still largely unknown. Here we have used a transgenic, RFP-expressing P. berghei parasite line and molecular imaging techniques including intravital microscopy to decipher various aspects of parasite development within the hepatocyte. In late schizont stages, MSP1 is expressed and incorporated into the parasite plasma membrane that finally forms the membrane of developing merozoites by continuous invagination steps. We provide first evidence for activation of a verapamil-sensitive Ca(2+) channel in the plasma membrane of liver stage parasites before invagination occurs. During merozoite formation, the permeability of the parasitophorous vacuole membrane changes considerably before it finally becomes completely disrupted, releasing merozoites into the host cell cytoplasm.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

This study examined the osmoregulatory status of the euryhaline elasmobranch Carcharhinus leucas acclimated to freshwater (FW) and seawater ( SW). Juvenile C. leucas captured in FW ( 3 mOsm l(-1) kg(-1)) were acclimated to SW ( 980 - 1,000 mOsm l(-1) kg(-1)) over 16 days. A FW group was maintained in captivity over a similar time period. In FW, bull sharks were hyper-osmotic regulators, having a plasma osmolarity of 595 mOsm l(-1) kg(-1). In SW, bull sharks had significantly higher plasma osmolarities ( 940 mOsm l(-1) kg(-1)) than FW-acclimated animals and were slightly hypoosmotic to the environment. Plasma Na+, Cl-, K+, Mg2+, Ca2+, urea and trimethylamine oxide (TMAO) concentrations were all significantly higher in bull sharks acclimated to SW, with urea and TMAO showing the greatest increase. Gill, rectal gland, kidney and intestinal tissue were taken from animals acclimated to FW and SW and analysed for maximal Na+/ K+-ATPase activity. Na+/ K+-ATPase activity in the gills and intestine was less than 1 mmol Pi mg(-1) protein h(-1) and there was no difference in activity between FW- and SW-acclimated animals. In contrast Na+/ K+-ATPase activity in the rectal gland and kidney were significantly higher than gill and intestine and showed significant differences between the FW- and SW-acclimated groups. In FW and SW, rectal gland Na+/ K+-ATPase activity was 5.6 +/- 0.8 and 9.2 +/- 0.6 mmol Pi mg(-1) protein h(-1), respectively. Na+/ K+-ATPase activity in the kidney of FW and SW acclimated animals was 8.4 +/- 1.1 and 3.3 +/- 1.1 Pi mg(-1) protein h(-1), respectively. Thus juvenile bull sharks have the osmoregulatory plasticity to acclimate to SW; their preference for the upper reaches of rivers where salinity is low is therefore likely to be for predator avoidance and/or increased food abundance rather than because of a physiological constraint.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

We observed unexpected high plasma concentrations of tobrarriycin (48.5 and 28.1 mg/L) in fingerprick blood samples after the nebulization of tobramycin solution for inhalation (tobramycin 300 mg/5 mL, TOBI(R)) by 2 young children aged 3 years. To investigate whether dermal contamination could be the source of error, 3 adult volunteers were present during another nebulization by a third child (age 2 years). The volunteers had exposure to tobramycin by handling the nebulizer or the nebule and also by inhalation from holding the child and being in close proximity while TOBI(R) was being administered. Five blood samples by fingerprick and 2 by venipuncture were collected and assayed for tobramycin concentration. On each occasion the site was swabbed with alcohol wipes to mimic standard patient sampling methods. One site was resampled after cleaning of hands with 2% chlorhexidine gluconate and water. Tobramycin concentrations from venipuncture 1-2 hours after nebulization were all < 0.2 mg/L except for 1 result of 1.2 mg/L. The tobramycin concentrations from fingerpricks before hand washing varied between 6.8 and 172 mg/L, and after hand washing between 0.3 and 17.6 mg/L. Contamination of fingers with tobramycin is likely to have caused the error in the 2 initial cases and did cause misleadingly elevated levels in the adult volunteers. We caution that therapeutic drug monitoring of nebulized tobramycin should not be done by fingerprick sampling, and care should be taken to avoid contamination of the venipuncture site.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

Cholesterol is a major component of atherosclerotic plaques. Cholesterol accumulation within the arterial intima and atherosclerotic plaques is determined by the difference of cellular cholesterol synthesis and/or influx from apo B-containing lipoproteins and cholesterol efflux. In humans, apo A-I Milano infusion has led to rapid regression of atherosclerosis in coronary arteries. We hypothesised that a multifunctional plasma delipidation process (PDP) would lead to rapid regression of experimental atherosclerosis and probably impact on adipose tissue lipids. In hyperlipidemic animals, the plasma concentrations of cholesterol, triglyceride and phospholipid were, respectively, 6-, 157-, and 18-fold higher than control animals, which consequently resulted in atherosclerosis. PDP consisted of delipidation of plasma with a mixture of butanol-diisopropyl ether (DIPE). PDP removed considerably more lipid from the hyperlipidemic animals than in normolipidemic animals. PDP treatment of hyperlipidemic animals markedly reduced intensity of lipid staining materials in the arterial wall and led to dramatic reduction of lipid in the adipose tissue. Five PDP treatments increased apolipoprotein A1 concentrations in all animals. Biochemical and hematological parameters were unaffected during PDP treatment. These results show that five PDP treatments led to marked reduction in avian atherosclerosis and removal of lipid from adipose tissue. PDP is a highly effective method for rapid regression of atherosclerosis.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

Vascular monocyte retention in the subintima is pivotal to the development of cardiovascular disease and is facilitated by up-regulation of adhesion molecules on monocytes/endothelial cells during oxidative stress. Epidemiological studies have shown that cardiovascular disease risk is inversely proportional to plasma levels of the dietary micronutrients, vitamin C and vitamin E (α-tocopherol). We have tested the hypothesis that α-tocopherol supplementation may alter endothelial/monocyte function and interaction in subjects with normal ascorbate levels (> 50 μM), as ascorbate has been shown to regenerate tocopherol from its oxidised tocopheroxyl radical form in vitro. Healthy male subjects received α-tocopherol supplements (400 IU RRR-α-tocopherol /day for 6 weeks) in a placebo-controlled, double-blind intervention study. There were no significant differences in monocyte CD11b expression, monocyte adhesion to endothelial cells, plasma C-reactive protein or sICAM- 1 concentrations post-supplementation. There was no evidence for nuclear translocation of NF-κB in isolated resting monocytes, nor any effect of α-tocopherol supplementation. However, post-supplementation, sVCAM-1 levels were decreased in all subjects and sE-selectin levels were increased in the vitamin C-replete group only; a weak positive correlation was observed between sE-selectin and α-tocopherol concentration. In conclusion, α-tocopherol supplementation had little effect on cardiovascular disease risk factors in healthy subjects and the effects of tocopherol were not consistently affected by plasma vitamin C concentration. © W. S. Maney & Son Ltd.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

Previous studies indicate that regular consumption of a diet rich in fruits and vegetables is associated with a lower risk for age-related diseases. The aim of the present study was to evaluate whether the often-reported age-related decrease of plasma antioxidants in man depends on differences in dietary intake or on other age- and gender-related factors. In this observational case-control study, thirty-nine community-dwelling healthy subjects aged 65 years and older consuming high intakes of fruits and vegetables daily (HI) and forty-eight healthy subjects aged 65 and older consuming low intakes of fruit and vegetables daily (LI) were enrolled. Plasma levels of retinol, tocopherols, carotenoids and malondialdehyde (MDA) as well as content of protein carbonyls in Ig G were measured. Plasma levels of retinol, tocopherols and carotenoids were significantly higher in group HI than in group LI subjects independent of age and gender. MDA levels were inversely correlated with vitamin A and α-carotene. Protein carbonyls were inversely correlated with γ-tocopherol. In the elderly, a higher daily intake of fruits and vegetables is associated with an improved antioxidant status in comparison to subjects consuming diets poor in fruits and vegetables. Modification of nutritional habits among other lifestyle changes should be encouraged to lower prevalence of disease risk factors in later life. © The Authors 2005.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

Proteome analysis by conventional approaches is biased against hydrophobic membrane proteins, many of which are also of low abundance. We have isolated plasma membrane sheets from bloodstream forms of Trypanosoma brucei by subcellular fractionation, and then applied a battery of complementary protein separation and identification techniques to identify a large number of proteins in this fraction. The results of these analyses have been combined to generate a subproteome for the pellicular plasma membrane of bloodstream forms of T. brucei as well as a separate subproteome for the pellicular cytoskeleton. In parallel, we have used in silico approaches to predict the relative abundance of proteins potentially expressed by bloodstream form trypanosomes, and to identify likely polytopic membrane proteins, providing quality control for the experimentally defined plasma membrane subproteome. We show that the application of multiple high-resolution proteomic techniques to an enriched organelle fraction is a valuable approach for the characterisation of relatively intractable membrane proteomes. We present here the most complete analysis of a protozoan plasma membrane proteome to date and show the presence of a large number of integral membrane proteins, including 11 nucleoside/nucleobase transporters, 15 ion pumps and channels and a large number of adenylate cyclases hitherto listed as putative proteins.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

Plasma or "dry" etching is an essential process for the production of modern microelectronic circuits. However, despite intensive research, many aspects of the etch process are not fully understood. The results of studies of the plasma etching of Si and Si02 in fluorine-containing discharges, and the complementary technique of plasma polymerisation are presented in this thesis. Optical emission spectroscopy with argon actinometry was used as the principle plasma diagnostic. Statistical experimental design was used to model and compare Si and Si02 etch rates in CF4 and SF6 discharges as a function of flow, pressure and power. Etch mechanisms m both systems, including the potential reduction of Si etch rates in CF4 due to fluorocarbon polymer formation, are discussed. Si etch rates in CF4 /SF6 mixtures were successfully accounted for by the models produced. Si etch rates in CF4/C2F6 and CHF3 as a function of the addition of oxygen-containing additives (02, N20 and CO2) are shown to be consistent with a simple competition between F, 0 and CFx species for Si surface sites. For the range of conditions studied, Si02 etch rates were not dependent on F-atom concentration, but the presence of fluorine was essential in order to achieve significant etch rates. The influence of a wide range of electrode materials on the etch rate of Si and Si02 in CF4 and CF4 /02 plasmas was studied. It was found that the Si etch rate in a CF4 plasma was considerably enhanced, relative to an anodised aluminium electrode, in the presence of soda glass or sodium or potassium "doped" quartz. The effect was even more pronounced in a CF4 /02 discharge. In the latter system lead and copper electrodes also enhanced the Si etch rate. These results could not be accounted for by a corresponding rise in atomic fluorine concentration. Three possible etch enhancement mechanisms are discussed. Fluorocarbon polymer deposition was studied, both because of its relevance to etch mechanisms and its intrinsic interest, as a function of fluorocarbon source gas (CF4, C2F6, C3F8 and CHF3), process time, RF power and percentage hydrogen addition. Gas phase concentrations of F, H and CF2 were measured by optical emission spectroscopy, and the resultant polymer structure determined by X-ray photoelectron spectroscopy and infrared spectroscopy. Thermal and electrical properties were measured also. Hydrogen additions are shown to have a dominant role in determining deposition rate and polymer composition. A qualitative description of the polymer growth mechanism is presented which accounts for both changes in growth rate and structure, and leads to an empirical deposition rate model.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

OBJECTIVES: To study possible oxidation of proteins and lipids in plasma and sarcoplasmic reticulum (SR) from skeletal muscles and to assess the effects of pyridoindole antioxidants in rats with adjuvant arthritis (AA) and to analyze modulation of Ca-ATPase activity from SR (SERCA). METHODS: SR was isolated by ultracentrifugation, protein carbonyls in plasma and SR were determined by ELISA. Lipid peroxidation was analyzed by TBARS determination and by mass spectrometry. ATPase activity of SERCA was measured by NADH-coupled enzyme assay. Tryptophan fluorescence was used to analyze conformational alterations. RESULTS: Increase of protein carbonyls and lipid peroxidation was observed in plasma of rats with adjuvant arthritis. Pyridoindole antioxidant stobadine and its methylated derivative SMe1 decreased protein carbonyl formation in plasma, effect of stobadine was significant. Lipid peroxidation of plasma was without any effect of pyridoindole derivatives. Neither protein oxidation nor lipid peroxidation was identified in SR from AA rats. SERCA activity from AA rats increased significantly, stobadine and SMe1 diminished enzyme activity. Ratio of tryptophan fluorescence intensity in SR of AA rats increased and was not influenced by antioxidants. CONCLUSION: Plasma proteins and lipids were oxidatively injured in rats with AA; antioxidants exerted protection only with respect to proteins. In SR, SERCA activity was altered, apparently induced by its conformational changes, as supported by study of tryptophan fluorescence. Stobadine and SMe1 induced a decrease of SERCA activity, elevated in AA rats, but they did not affect conformational changes associated with tryptophan fluorescence.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

Purpose. To evaluate the influence of soft contact lens midperipheral shape profile and edge design on the apparent epithelial thickness and indentation of the ocular surface with lens movement. Methods. Four soft contact lens designs comprising of two different plano midperipheral shape profiles and two edge designs (chiseled and knife edge) of silicone-hydrogel material were examined in 26 subjects aged 24.7 ± 4.6 years, each worn bilaterally in randomized order. Lens movement was imaged enface on insertion, at 2 and 4 hours with a high-speed, high-resolution camera simultaneous to the cross-section of the edge of the contact lens interaction with the ocular surface captured using optical coherence tomography (OCT) nasally, temporally, and inferiorly. Optical imaging distortions were individually corrected for by imaging the apparent distortion of a glass slide surface by the removed lens. Results. Apparent epithelial thickness varied with edge position (P < 0.001). When distortion was corrected for, epithelial indentation decreased with time after insertion (P = 0.010), changed after a blink (P < 0.001), and varied with position on the lens edge (P < 0.001), with the latter being affected by midperipheral lens shape profile and edge design. Horizontal and vertical lens movement did not change with time postinsertion. Vertical motion was affected by midperipheral lens shape profile (P < 0.001) and edge design (P < 0.001). Lens movement was associated with physiologic epithelium thickness for lens midperipheral shape profile and edge designs. Conclusions. Dynamic OCT coupled with high-resolution video demonstrated that soft contact lens movement and image-corrected ocular surface indentation were influenced by both lens edge design and midperipheral lens shape profiles. © 2013 The Association for Research in Vision and Ophthalmology, Inc.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

Background: Proliferative diabetic retinopathy (PDR) may be a response to abnormal angiogenic growth factors such as vascular endothelial growth factor (VEGF), angiopoietin-2 (Ang-2), and the soluble angiopoietin receptor tie-2. The authors hypothesised the following: (a) there are differences in plasma levels of these growth factors in different grades of diabetic retinopathy; and (b) that the effects of intervention with panretinal laser photocoagulation (PRP) for PDR, and angiotensin receptor blockade (using eprosartan) for patients with other grades of diabetic retinopathy will be to reduce levels of the growth factors. Methods: Cross sectional and interventional study (using PRP and eprosartan) in diabetic patients. VEGF, Ang-2, and tie-2 were measured by ELISA. Results: VEGF (p<0.001) and Ang-2 levels (p<0.001) were significantly higher in 93 diabetic patients compared to 20 healthy controls, with the highest levels in grade 2 and grade 3 diabetic retinopathy (p<0.05). Tie-2 was lower in diabetics compared to controls (p = 0.008), with no significant differences between the diabetic subgroups. Overall, VEGF significantly correlated with Ang-2 (p<0.001) and tie-2 (p = 0.004) but the correlation between Ang-2 and tie-2 levels was not significant (p = 0.065). Among diabetic patients only, VEGF levels were significantly correlated with Ang-2 (p<0.001) and tie-2 (p<0.001); the correlation between Ang-2 and tie-2 levels was also significant (p<0.001). There were no statistically significant effects of laser photocoagulation on plasma VEGF, Ang-2, and tie-2 in the 19 patients with PDR, or any effects of eprosartan in the 28 patients with non-proliferative diabetic retinopathy. Conclusion: Increased plasma levels of VEGF and Ang-2, as well as lower soluble tie-2, were found in diabetic patients. The highest VEGF and Ang-2 levels were seen among patients with pre-proliferative and proliferative retinopathy, but there was no relation of tie-2 to the severity of retinopathy. As the majority of previous research into Ang-2 and tie-2 has been in relation to angiogenesis and malignancy, the present study would suggest that Ang-2 and tie-2 may be used as potential indices of angiogenesis in diabetes mellitus (in addition to VEGF) and may help elucidate the role of the angiopoietin/tie-2 system in this condition.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

The growth of highly functionalised poly allyl alcohol films by pulsed plasma polymerisation of CH2 double bond; length as m-dashCHCH2OH on biomedical grade polyurethane has been followed by X-ray photoelectron spectroscopy (XPS) and contact angle measurements. Film thickness is observed to increase approximately linearly with plasma modification time, suggesting a layer-by-layer growth mode of poly allyl alcohol. Water contact angle measurements reveal the change in the surface free energy of wetting decreases linearly with plasma modification up to the monolayer point after which a constant limiting value of −24 mJ m−2 was attained. Films prepared at 20 W plasma power with a duty cycle of 10 μs:500 μs exhibit a high degree of hydroxyl (single bondOH) retention with minimal fragmentation of the monomer observed. Increasing the plasma power up to 125 W is found to improve single bondOH retention at the expense of ether formation generating films close to the monomer stoichiometry. Duty cycle plays an important role in controlling both film composition and thickness, with longer off times increasing single bondOH retention, while longer on times enhance allyl alcohol film growth.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

In this work, we study for the first time the influence of microwave power higher than 2.0 kW on bonded hydrogen impurity incorporation (form and content) in nanocrystalline diamond (NCD) films grown in a 5 kW MPCVD reactor. The NCD samples of different thickness ranging from 25 to 205 μm were obtained through a small amount of simultaneous nitrogen and oxygen addition into conventional about 4% methane in hydrogen reactants by keeping the other operating parameters in the same range as that typically used for the growth of large-grained polycrystalline diamond films. Specific hydrogen point defect in the NCD films is analyzed by using Fourier-transform infrared (FTIR) spectroscopy. When the other operating parameters are kept constant (mainly the input gases), with increasing of microwave power from 2.0 to 3.2 kW (the pressure was increased slightly in order to stabilize the plasma ball of the same size), which simultaneously resulting in the rise of substrate temperature more than 100 °C, the growth rate of the NCD films increases one order of magnitude from 0.3 to 3.0 μm/h, while the content of hydrogen impurity trapped in the NCD films during the growth process decreases with power. It has also been found that a new H related infrared absorption peak appears at 2834 cm-1 in the NCD films grown with a small amount of nitrogen and oxygen addition at power higher than 2.0 kW and increases with power higher than 3.0 kW. According to these new experimental results, the role of high microwave power on diamond growth and hydrogen impurity incorporation is discussed based on the standard growth mechanism of CVD diamonds using CH4/H2 gas mixtures. Our current experimental findings shed light into the incorporation mechanism of hydrogen impurity in NCD films grown with a small amount of nitrogen and oxygen addition into methane/hydrogen plasma.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

Aluminum oxide (Al2O3, or alumina) is a conventional ceramic known for applications such as wear resistant coatings, thermal liners, heaters, crucibles, dielectric systems, etc. However applications of Al 2O3 are limited owing to its inherent brittleness. Due to its excellent mechanical properties and bending strength, carbon nanotubes (CNT) is an ideal reinforcement for Al2O3 matrix to improve its fracture toughness. The role of CNT dispersion in the fracture toughening of the plasma sprayed Al2O3-CNT nanocomposite coating is discussed in the current work. Pretreatment of powder feedstock is required for dispersing CNTs in the matrix. Four coatings namely spray dried Al2O 3 (A-SD), Al2O3 blended with 4wt.% CNT (A4C-B), composite spray dried Al2O3-4wt.% CNT (A4C-SD) and composite spray dried A1203-8wt.% CNT (A8C-SD), are synthesized by plasma spraying. Owing to extreme temperatures and velocities involved in the plasma spraying of ceramics, retention of CNTs in the resulting coatings necessitates optimizing plasma processing parameters using an inflight particle diagnostic sensor. A bimodal microstructure was obtained in the matrix that consists of fully melted and resolidified structure and solid state sintered structure. CNTs are retained both in the fully melted region and solid-state sintered regions of processed coatings. Fracture toughness of A-SD, A4C-B, A4C-SD and A8C-SD coatings was 3.22, 3.86, 4.60 and 5.04 MPa m1/2 respectively. This affirms the improvement of fracture toughness from 20% (in A4C-B coating) to 43% (in A4C-SD coating) when compared to the A-SD coating because of the CNT dispersion. Fracture toughness improvement from 43% (in A4C-SD) to 57% (in A8C-SD) coating is evinced because of the CNT content. Reinforcement by CNTs is described by its bridging, anchoring, hook formation, impact alignment, fusion with splat, and mesh formation. The Al2O3/CNT interface is critical in assisting the stress transfer and utilizing excellent mechanical properties of CNTs. Mathematical and computational modeling using ab-initio principle is applied to understand the wetting behavior at the Al2O 3/CNT interface. Contrasting storage modulus was obtained by nanoindentation (∼210, 250, 250-350 and 325-420 GPa in A-SD, A4C-B, A4C-SD, and A8C-SD coatings respectively) depicting the toughening associated with CNT content and dispersion.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

Aluminum oxide (A1203, or alumina) is a conventional ceramic known for applications such as wear resistant coatings, thermal liners, heaters, crucibles, dielectric systems, etc. However applications of A1203 are limited owing to its inherent brittleness. Due to its excellent mechanical properties and bending strength, carbon nanotubes (CNT) is an ideal reinforcement for A1203 matrix to improve its fracture toughness. The role of CNT dispersion in the fracture toughening of the plasma sprayed A1203-CNT nanocomposite coating is discussed in the current work. Pretreatment of powder feedstock is required for dispersing CNTs in the matrix. Four coatings namely spray dried A1203 (A-SD), A1203 blended with 4wt.% CNT (A4C-B), composite spray dried A1203-4wt.% CNT (A4C-SD) and composite spray dried A1203-8wt.% CNT (A8CSD), are synthesized by plasma spraying. Owing to extreme temperatures and velocities involved in the plasma spraying of ceramics, retention of CNTs in the resulting coatings necessitates optimizing plasma processing parameters using an inflight particle diagnostic sensor. A bimodal microstructure was obtained in the matrix that consists of fully melted and resolidified structure and solid state sintered structure. CNTs are retained both in the fully melted region and solid-state sintered regions of processed coatings. Fracture toughness of A-SD, A4C-B, A4C-SD and A8C-SD coatings was 3.22, 3.86, 4.60 and 5.04 MPa m1/2 respectively. This affirms the improvement of fracture toughness from 20 % (in A4C-B coating) to 43% (in A4C-SD coating) when compared to the A-SD coating because of the CNT dispersion. Fracture toughness improvement from 43 % (in A4C-SD) to 57% (in A8C-SD) coating is evinced because of the CNT content. Reinforcement by CNTs is described by its bridging, anchoring, hook formation, impact alignment, fusion with splat, and mesh formation. The A1203/CNT interface is critical in assisting the stress transfer and utilizing excellent mechanical properties of CNTs. Mathematical and computational modeling using ab-initio principle is applied to understand the wetting behavior at the A1203/CNTinterface. Contrasting storage modulus was obtained by nanoindentation (~ 210, 250, 250-350 and 325-420 GPa in A-SD, A4C-B, A4C-SD, and A8C-SD coatings respectively) depicting the toughening associated with CNT content and dispersion.