997 resultados para OMEGA-TERM


Relevância:

60.00% 60.00%

Publicador:

Resumo:

Antikaon condensation and deconfinement phase transition in neutron stars are investigated in a chiral hadronic model (also referred as to the FST model) for the hadronic phase and in the MIT bag model for the deconfined quark matter phase. It is shown that the existence of quark matter phase makes antikaon condensation impossible in neutron stars. The properties of neutron stars are sensitive to the bag constant. For the small values of the bag constant, the pure quark matter core appears and hyperons are strongly suppressed in neutron stars, whereas for the large bag constant, the hadron-quark mixed phase exists in the center of neutron stars. The maximum masses of neutron stars with the quark matter phase are lower than those without the quark matter phase; meanwhile, the maximum masses of neutron stars with the quark matter phase increase with the bag constant.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Anticorrosion performances of polyaniline emeraldine base/epoxy resin (EB/ER) coating on mild steel in 3.5% NaCl solutions of various pH values were investigated by electrochemical impedance spectroscopy (EIS) for 150 days. In neutral solution (pH 6.1), EB/ER coating offered very efficient corrosion protection with respect to pure ER coating, especially when EB content was 5-10%. The impedance at 0.1 Hz of the coating increased in the first 1-40 immersion days and then remained constant above 10(9) Omega cm(2) until 150 days, which in combination with the observation of a Fe2O3/Fe3O4 passive film formed on steel confirmed that the protection of EB was mainly anodic. In acidic or basic solution (pH 1 or 13), EB/ER coating also performed much better than pure ER coating. However, these media weakened the corrosion resistance due to breakdown of the passive film or deterioration of the ER binder.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

AIM: To examine the concentrations of zinc and omega-6 polyunsaturated fatty acids (omega-6 PUFAs) in breast milk, the impact of zinc on omega-6 PUFA metabolism, and the growth rate of infants. METHODS: Forty-one mother-term infant pairs from a rural area of northern Beijing, China, who were 1 month (n = 18, group I) and 3 months (n = 23, group II) old and exclusively breastfed, were studied. The dietary records and the concentrations of zinc and omega-6 PUFAs in the milk of lactating women and the increase in weight and length of their infants during 1 and 3 postnatal months were analysed. RESULTS: The dietary intakes of mothers in the two groups were the same, i.e. high in carbohydrate and low in fat, protein and energy. The maternal zinc intake was 7.5mg/d and thus reached only 34.6% of the current Recommended Nutrient Intake (RNI). The levels of zinc and arachidonic acid (AA, C20:4 omega-6) in the milk of group I were significantly higher than those in group II. Furthermore, significant positive correlations were found between the concentrations of zinc and AA in the breast milk and between the level of milk AA and weight gain. CONCLUSION: Zinc may be a co-factor and essential for essential fatty acids (EFA) metabolism. Thus suboptimal zinc intake may cause EFA imbalance. Further studies of Chinese rural mother-infant pairs are necessary to determine whether zinc supplementation should be recommended when lactation exceeds 3 months.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

omega Ori (HD37490, HR1934) is a Be star known to have presented variations. In order to investigate the nature and origin of its short-term and mid-term variability, a study is performed of several spectral lines (Halpha, Hdelta, HeI 4471, 4713, 4921, 5876, 6678, CII 4267, 6578, 6583, Mg II 4481, Si III 4553 and Si II 6347), based on 249 high signal-to-noise high-resolution spectra taken with 8 telescopes over 22 consecutive nights during the MuSiCoS (Multi SIte COntinuous Spectroscopy) campaign in November-December 1998. The stellar parameters are revisited and the projected rotational velocity (v sin i = 179 km s(-1)) is redetermined using several methods. With the MuSiCoS 98 dataset, a time series analysis of line-profile variations (LPVs) is performed using the Restricted Local Cleanest (RLC) algorithm and a least squares method. The behaviour of the velocity of the centroid of the lines, the equivalent widths and the apparent vsini for several lines, as well as Violet and Red components of photospheric lines affected by emission (red He i lines, Si II 6347, CII 6578, 6583) are analyzed. The non-radial pulsation (NRP) model is examined using phase diagrams and the Fourier-Doppler Imaging (FDI) method. The LPVs are consistent with a NRP mode with l = 2 or 3, \m\ = 2 with frequency 1.03 cd(-1). It is shown that an emission line outburst occurred in the middle of the campaign. Two scenarios are proposed to explain the behaviour of a dense cloud, temporarily orbiting around the star with a frequency 0.46 c d(-1), in relation to the outburst.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

OBJECTIVE: The adjusted effect of long-chain polyunsaturated fatty acid (LCPUFA) intake during pregnancy on adiposity at birth of healthy full-term appropriate-for-gestational age neonates was evaluated. STUDY DESIGN: In a cross-sectional convenience sample of 100 mother and infant dyads, LCPUFA intake during pregnancy was assessed by food frequency questionnaire with nutrient intake calculated using Food Processor Plus. Linear regression models for neonatal body composition measurements, assessed by air displacement plethysmography and anthropometry, were adjusted for maternal LCPUFA intakes, energy and macronutrient intakes, prepregnancy body mass index and gestational weight gain. RESULT: Positive associations between maternal docosahexaenoic acid intake and ponderal index in male offspring (β=0.165; 95% confidence interval (CI): 0.031-0.299; P=0.017), and between n-6:n-3 LCPUFA ratio intake and fat mass (β=0.021; 95% CI: 0.002-0.041; P=0.034) and percentage of fat mass (β=0.636; 95% CI: 0.125-1.147; P=0.016) in female offspring were found. CONCLUSION: Using a reliable validated method to assess body composition, adjusted positive associations between maternal docosahexaenoic acid intake and birth size in male offspring and between n-6:n-3 LCPUFA ratio intake and adiposity in female offspring were found, suggesting that maternal LCPUFA intake strongly influences fetal body composition.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

OBJECTIVES To test the hypothesis that glyco protein 91phox (gp91(phox)) subunit of nicotinamide adenine dinucleotide phosphate [NAD(P) H] oxidase is a fundamental target for physical activity to ameliorate erectile dysfunction (ED). Vascular risk factors are reported to contribute to ED. Regular physical exercise prevents cardiovascular diseases by increasing nitric oxide (NO) production and/or decreasing NO inactivation. METHODS Male Wistar rats received the NO synthesis inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME) for 4 weeks, after which animals were submitted to a run training program for another 4 weeks. Erectile functions were evaluated by in vitro cavernosal relaxations and intracavernous pressure measurements. Expressions of gp91(phox) subunit and neuronal nitric oxidase synthase in erectile tissue, as well as superoxide dismutase activity and nitrite/nitrate (NO(x)) levels were determined. RESULTS The in vitro acetylcholine-and electrical field stimulation-induced cavernosal relaxations, as well as the increases in intracavernous pressure were markedly reduced in sedentary rats treated with L-NAME. Run training significantly restored the impaired cavernosal relaxations. No alterations in the neuronal nitric oxidase synthase protein expression (and its variant penile neuronal nitric oxidase synthase) were detected. A reduction of NO(x) levels and superoxide dismutase activity was observed in L-NAME-treated animals, which was significantly reversed by physical training. Gene expression of subunit gp91(phox) was enhanced by approximately 2-fold in erectile tissue of L-NAME-treated rats, and that was restored to basal levels by run training. CONCLUSIONS Our study shows that ED seen after long-term L-NAME treatment is associated with gp91(phox) subunit upregulation and decreased NO bioavailability. Exercise training reverses the increased oxidative stress in NO-deficient rats, ameliorating the ED. UROLOGY 75: 961-967, 2010. (C) 2009 Elsevier Inc.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Nitric oxide synthase (NOS) inhibitors are largely used to evaluate the NO contribution to pulmonary allergy, but contrasting data have been reported. In this study, pharmacological, biochemical and pharmacokinetic assays were performed to compare the effects of acute and long-term treatment of BALB/C mice with the non-selective NOS inhibitor L-NAME in ovalbumin (OVA)-challenged mice. Acute L-NAME treatment (50 mg/kg, gavage) significantly reduced the eosinophil number in bronchoalveolar lavage fluid (BALF). The inducible NOS (iNOS) inhibitor aminoguanidine (20 mg/kg/day in the drinking water) also significantly reduced the eosinophil number in BALF In contrast, 3-week L-NAME treatment (50 and 150 mg/kg/day in the drinking water) significantly increased the pulmonary eosinophil influx. The constitutive NOS (cNOS) activity in brain and lungs was reduced by both acute and 3-week L-NAME treatments. The pulmonary iNOS activity was reduced by acute L-NAME (or aminoguanidine), but unaffected by 3-week L-NAME treatment. Acute L-NAME (or aminoguanidine) treatment was more efficient to reduce the NO(x) levels compared with 3-week L-NAME treatment. The pharmacokinetic study revealed that L-NAME is not bioavailable when given orally. After acute L-NAME intake, serum concentrations of the metabolite N(omega)-nitro-L-arginine decreased from 30 min to 24 h. In the 3-week L-NAME treatment, the N(omega)-nitro-L-arginine concentration was close to the detection limit. In conclusion, 3-week treatment with L-NAME yields low serum N(omega)-nitro-L-arginine concentrations, causing preferential inhibition of cNOS activity. Therefore, eosinophil influx potentiation by 3-week L-NAME treatment may reflect removal of protective cNOS-derived NO, with no interference on the ongoing inflammation due to iNOS-derived NO. (c) 2008 Elsevier Ltd. All rights reserved.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Long-term propranolol treatment reduces arterial blood pressure in hypertensive individuals mainly by reducing peripheral vascular resistance, but mechanisms underlying their vasodilatory effect remain poorly investigated. This study aimed to investigate whether long-term propranolol administration ameliorates the impairment of relaxing responses of aorta and mesenteric artery from rats made hypertensive by chronic nitric oxide (NO) deficiency, and underlying mechanisms mediating this phenomenon. Male Wistar rats were treated with N-omega-Nitro-L-arginine methyl ester (L-NAME; 20 mg/rat/day) for four weeks. DL-Propranolol (30 mg/rat/day) was given concomitantly to L-NAME in the drinking water. Treatment with L-NAME markedly increased blood pressure, an effect largely attenuated by DL-propranolol. In phenylephrine-precontracted aortic rings, the reduction of relaxing responses for acetylcholine (0.001-10 mu M) in L-NAME group was not modified by DL-propranolol, whereas in mesenteric rings the impairment of acetylcholine-induced relaxation by L-NAME was significantly attenuated by DL-propranolol. In mesenteric rings precontracted with KCl (80 MM), DL-propranolol failed to attenuate the impairment of acetylcholine-induced relaxation by L-NAME. The contractile responses to extracellular CaCl2 (1-10 mM) were increased in L-NAME group, and co-treatment with DL-propranolol reduced this response in both preparations in most Ca2+ concentrations used. The NO2/NO3 plasma levels and superoxide dismutase (SOD) activity were reduced in L-NAME-treated rats, both of which were significantly prevented by DL-propranolol. In conclusion, propranolol-induced amplification of the relaxation to acetylcholine in mesenteric arteries from L-NAME-treated rats is sensitive to depolarization. Additional mechanisms involving blockade of Ca2+ entry in the vascular smooth muscle and increase in NO bioavailability contributes to beneficial effects of long-term propranolol treatment. (C) 2007 Elsevier B.V. All rights reserved.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

OBJECTIVES To test the hypothesis that glyco protein 91phox (gp91(phox)) subunit of nicotinamide adenine dinucleotide phosphate [NAD(P) H] oxidase is a fundamental target for physical activity to ameliorate erectile dysfunction (ED). Vascular risk factors are reported to contribute to ED. Regular physical exercise prevents cardiovascular diseases by increasing nitric oxide (NO) production and/or decreasing NO inactivation.METHODS Male Wistar rats received the NO synthesis inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME) for 4 weeks, after which animals were submitted to a run training program for another 4 weeks. Erectile functions were evaluated by in vitro cavernosal relaxations and intracavernous pressure measurements. Expressions of gp91(phox) subunit and neuronal nitric oxidase synthase in erectile tissue, as well as superoxide dismutase activity and nitrite/nitrate (NO(x)) levels were determined.RESULTS The in vitro acetylcholine-and electrical field stimulation-induced cavernosal relaxations, as well as the increases in intracavernous pressure were markedly reduced in sedentary rats treated with L-NAME. Run training significantly restored the impaired cavernosal relaxations. No alterations in the neuronal nitric oxidase synthase protein expression (and its variant penile neuronal nitric oxidase synthase) were detected. A reduction of NO(x) levels and superoxide dismutase activity was observed in L-NAME-treated animals, which was significantly reversed by physical training. Gene expression of subunit gp91(phox) was enhanced by approximately 2-fold in erectile tissue of L-NAME-treated rats, and that was restored to basal levels by run training.CONCLUSIONS Our study shows that ED seen after long-term L-NAME treatment is associated with gp91(phox) subunit upregulation and decreased NO bioavailability. Exercise training reverses the increased oxidative stress in NO-deficient rats, ameliorating the ED. UROLOGY 75: 961-967, 2010. (C) 2009 Elsevier B.V.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

We numerically investigate the long-term dynamics of the Saturn's small satellites Methone (S/2004 S1), Anthe (S/2007 S4) and Pallene (S/2004 S2). In our numerical integrations, these satellites are disturbed by non-spherical shape of Saturn and the six nearest regular satellites. The stability of the small bodies is studied here by analyzing long-term evolution of their orbital elements.We show that long-term evolution of Pallene is dictated by a quasi secular resonance involving the ascending nodes (12) and longitudes of pericentric distances (pi) of Mimas (subscript 1) and Pallene (subscript 2), which critical argument is pi(2) - pi(1) - Omega(1) + Omega(2) Long-term orbital evolution of Methone and Anthe are probably chaotic since: i) their orbits randomly cross the orbit of Mimas in time scales of thousands years); ii) long-term numerical simulations involving both small satellites are strongly affected by small changes in the initial conditions.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Peanut samples were irradiated (0.0, 5.2, 7.2 or 10.0 kGy), stored for a year (room temperature) and examined every three months. Mycotoxic fungi (MF) were detected in non-irradiated blanched peanuts. A dose of 5.2 kGy was found suitable to prevent MF growth in blanched samples. No MF was detected in in-shell peanuts, with or without irradiation. The colors of the control in-shell and blanched samples were, respectively, 44.72 and 60.21 (L *); 25.20 and 20.38 (Chroma); 53.05 and 86.46 (degrees Hue). The water activities (Aw) were 0.673 and 0.425. The corresponding fatty acids were 13.33% and 12.14% (C16:0), 44.94% and 44.92% (C18:1,omega 9) and 37.10% and 37.63% (C18: 2,omega 6). The total phenolics (TP) were 4.62 and 2.52 mg GAE/g, with antioxidant activities (AA) of 16.97 and 10.36 mu mol TEAC/g. Storage time negatively correlated with Aw (in-shell peanuts) or L *, linoleic acid, TP and AA (in-shell and blanched peanuts) but positively correlated with Aw (blanched peanuts), and with oleic acid (in-shell and blanched peanuts). Irradiation positively correlated with antioxidant activity (blanched peanuts). No correlation was found between irradiation and AA (in-shell samples) or fatty acids and TP (in-shell and blanched peanuts). Irradiation protected against MF and retained both the polyunsaturated fatty acids and polyphenols in the samples.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

A new cold-inducible genetic construct was cloned using a chloroplast-specific omega-3-fatty acid desaturase gene (FAD7) under the control of a cold-inducible promoter (cor15a) from Arabidopsis thaliana. RT-PCR confirmed a marked increase in FAD7 expression, in young Nicotiana tabacum (cv. Havana) plants harboring cor15a-FAD7, after a short-term exposure to cold. When young, cold-induced tobacco seedlings were exposed to low-temperature (0.5, 2 or 3.5 degrees C) for up to 44 days, survival within independent cor15a-FAD7 transgenic lines (40.2-96%) was far superior to the wild type (6.7-10.2%). In addition, the major trienoic fatty acid species remained stable in cold-induced cor15a-FAD7 N. tabacum plants under prolonged cold storage while the levels of hexadecatrienoic acid (16:3) and octadecatrienoic acid (18:3) declined in wild type plants under the same conditions (79 and 20.7% respectively). Electron microscopy showed that chloroplast membrane ultrastructure in cor15a-FAD7 transgenic plants was unaffected by prolonged exposure to cold temperatures. In contrast, wild type plants experienced a loss of granal stacking and disorganization of the thylakoid membrane under the same conditions. Changes in membrane integrity coincided with a precipitous decline in leaf chlorophyll concentration and low survival rates in wild type plants. Cold-induced double transgenic N. alata (cv. Domino Mix) plants, harboring both the cor15a-FAD7 cold-tolerance gene and a cor15a-IPT dark-tolerance gene, exhibited dramatically higher survival rates (89-90%) than wild type plants (2%) under prolonged cold storage under dark conditions (2 degrees C for 50 days).

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Calcifying foraminifera are expected to be endangered by ocean acidification; however, the response of a complete community kept in natural sediment and over multiple generations under controlled laboratory conditions has not been constrained to date. During 6 months of incubation, foraminiferal assemblages were kept and treated in natural sediment with pCO2-enriched seawater of 430, 907, 1865 and 3247 µatm pCO2. The fauna was dominated by Ammonia aomoriensis and Elphidium species, whereas agglutinated species were rare. After 6 months of incubation, pore water alkalinity was much higher in comparison to the overlying seawater. Consequently, the saturation state of Omega calc was much higher in the sediment than in the water column in nearly all pCO2 treatments and remained close to saturation. As a result, the life cycle (population density, growth and reproduction) of living assemblages varied markedly during the experimental period, but was largely unaffected by the pCO2 treatments applied. According to the size-frequency distribution, we conclude that foraminifera start reproduction at a diameter of 250 µm. Mortality of living Ammonia aomoriensis was unaffected, whereas size of large and dead tests decreased with elevated pCO2 from 285 µm (pCO2 from 430 to 1865 µatm) to 258 µm (pCO2 3247 µatm). The total organic content of living Ammonia aomoriensis has been determined to be 4.3% of CaCO3 weight. Living individuals had a calcium carbonate production rate of 0.47 g/m**2/a, whereas dead empty tests accumulated a rate of 0.27 g /m**2/a. Although Omega calc was close to 1, approximately 30% of the empty tests of Ammonia aomoriensis showed dissolution features at high pCO2 of 3247 µatm during the last 2 months of incubation. In contrast, tests of the subdominant species, Elphidium incertum, stayed intact. Our results emphasize that the sensitivity to ocean acidification of the endobenthic foraminifera Ammonia aomoriensis in their natural sediment habitat is much lower compared to the experimental response of specimens isolated from the sediment.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Recent evolution experiments have revealed that marine phytoplankton may adapt to global change, for example to ocean warming or acidification. Long-term adaptation to novel environments is a dynamic process and phenotypic change can take place thousands of generations after exposure to novel conditions. Using the longest evolution experiment performed in any marine species to date (4 yrs, = 2100 generations), we show that in the coccolithophore Emiliania huxleyi, long-term adaptation to ocean acidification is complex and initial phenotypic responses may revert for important traits. While fitness increased continuously, calcification was restored within the first 500 generations but later reduced in response to selection, enhancing physiological declines of calcification in response to ocean acidification. Interestingly, calcification was not constitutively reduced but revealed rates similar to control treatments when transferred back to present-day CO2 conditions. Growth rate increased with time in controls and adaptation treatments, although the effect size of adaptation assessed through reciprocal assay experiments varied. Several trait changes were associated with selection for higher cell division rates under laboratory conditions, such as reduced cell size and lower particulate organic carbon content per cell. Our results show that phytoplankton may evolve phenotypic plasticity that can affect biogeochemically important traits, such as calcification, in an unforeseen way under future ocean conditions.

Relevância:

20.00% 20.00%

Publicador: