962 resultados para Repeated Bout Effect
Resumo:
Under the conditions of the rotating wave approximation (RWA), a transition strongly driven by a resonant oscillating field displays the well known symmetric Autler-Townes doublet. However, if the counter-rotating component, neglected in the RWA, is taken into account, the Bloch-Siegert shift gives rise to an Autler-Townes doublet of unequal intensity even in the case of a resonant driving field. This effect is investigated theoretically in a V-shaped three-level double-resonance configuration and the results are presented in this paper. An interesting observation is that the level of asymmetry not only depends on the driving-field intensity but also on the characteristics of the driven system including relaxation rates and equilibrium population distributions.
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Fifty-four Large White gilts were used to determine the effect of body composition at selection (145 d of age) on the onset of puberty and subsequent reproductive development until 202 d of age. Gilts were assigned to one of three groups based on their backfat depth at selection: 10 to 12 mm (L), 13 to 15 mm (M), and 16 to 18 mm (F). All of the F gilts, 92% of the M gilts, and 67% of the L gilts reached puberty by slaughter at 202 d of age. Data from a subgroup (first 67% to reach puberty in each group; L = Lp, M = Mp, and F = Fp) was also used. The M (Mp) and F (Fp) gilts reached puberty at 172 d (166 d) and 170 d (166 d) of age, respectively, but the L (Lp) gilts at 184.5 d were 12 d (18 d) older than M(P < .05), Mp(P < .001), and F(P < .01), Fp (P < .001) gilts. The Lp (97.68 kg) and Mp (98.33 kg) gilts were lighter (P < .01) than Fp (108.72 kg) gilts at puberty. There were no differences (P < .05) among the L, M, and F gilts in terms of backfat depth or weight at puberty. The L (Lp) gilts had a mean of 1.16 (1.75) estrous cycles, which was lower (P < .01) than for M (Mp) and (P < .01) F (Fp) gilts, with 1.96 (2.29) and 2.25 (2.33) cycles, respectively. L (Lp) gilts had fewer (P < .05) follicles, 13.14 (12.63), than either M (Mp), 19.08 (18.71), or F (Fp), 18.25 (17.42) gilts. The number of corpora lutea was not influenced (P > .05) by grouping at selection, but Fp gilts had fewer (P < .05) corpora lutea than Mp or Fp gilts. Live weight at slaughter was not influenced (P > .10) by grouping at selection or subgrouping at puberty. The L gilts with a mean of 18.05 mm of backfat at slaughter were leaner (P < .05) than the F (21.66 mm) but not (P > .10) the M gilts (19.41 mm). Subgrouping had no effect. Fat deposition and protein deposition were higher (P < .05) in those animals that attained puberty. We conclude that the rate of fat and protein deposition seems to be one of the determinants of puberty attainment.
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The synthesis of chromium carbides, Cr7C3 and Cr3C2, by mechanically allowing chromium and carbon powders has been investigated. Milling conditions were found to have a strong influence on the evolution of microstructure, with high collision energies being required to form carbide phases. Milling at intermediate energy levels resulted in the formation of an amorphous phase, and with low energy conditions only grain size refinement of Cr occurred with no evidence of any reaction between Cr and C. The amorphous phase was found to be the precursor to carbide formation. (C) 1997 Elsevier Science S.A.
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The aged garlic extract 'Kyolic' lowers serum cholesterol levels in humans and experimental animals and thus is presumed to have a protective effect against atherosclerosis. However, to date no studies have examined the effect of this substance on the actual development of the disease. In the present study, the right carotid artery of 24 rabbits was de-endothelialized by balloon catheterisation in order to produce a myointimal thickening. After 2 weeks the rabbits were randomly assigned to four groups: Group I received a standard diet; Group II received the standard diet supplemented with 800 mu 1/kg body weight/day 'Kyolic'; Group III received a 1% cholesterol supplemented standard diet; and Group IV received a 1% cholesterol supplemented standard diet plus 'Kyolic'. After 6 weeks, the cholesterol diet caused a 6-fold increase in serum cholesterol level (Group III; 6.4 +/- 0.6 mmol/1) compared to normal diet (Group I; 1.2 +/- 0.4 mmol/1) (P < 0.05) with only a minor, non-significant reduction seen by the addition of 'Kyolic' (Group IV; 6.2 +/- 0.7 mmol/l). Group III rabbits developed fatty streak lesions covering approximately 70 +/- 8% of the surface area of the thoracic aorta, which was significantly reduced to 25 +/- 3% in the 'Kyolic'-treated Group IV. No lesions were present in Groups I and II. The hypercholesterolaemic diet caused an increase in aortic arch cholesterol (2.1 +/- 0.1 mg cholesterol/g tissue) which was significantly reduced by 'Kyolic' supplementation (1.7 +/- 0.2 mg cholesterol/g tissue) (P < 0.05). 'Kyolic' significantly inhibited the development of thickened, lipid-filled lesions in the pre-formed neointimas produced by balloon-catheter injury of the right carotid artery in cholesterol-fed rabbits (intima as percent of artery wall, Group III 42.6 +/- 6.5% versus Group IV 23.8 +/- 2.3%, P < 0.01), but had little effect in rabbits on a standard diet (Group II 18.4 +/- 5.0% versus Group I 16.7 +/- 2.0%). In vitro studies showed that 'Kyolic' has a direct effect on inhibition of smooth muscle proliferation. In conclusion,'Kyolic' treatment reduces fatty streak development, vessel wall cholesterol accumulation and the development of fibro fatty plaques in neointimas of cholesterol-fed rabbits, thus providing protection against the onset of atherosclerosis. (C) 1997 Elsevier Science Ireland Ltd.
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Radiation dose calculations in nuclear medicine depend on quantification of activity via planar and/or tomographic imaging methods. However, both methods have inherent limitations, and the accuracy of activity estimates varies with object size, background levels, and other variables. The goal of this study was to evaluate the limitations of quantitative imaging with planar and single photon emission computed tomography (SPECT) approaches, with a focus on activity quantification for use in calculating absorbed dose estimates for normal organs and tumors. To do this we studied a series of phantoms of varying complexity of geometry, with three radionuclides whose decay schemes varied from simple to complex. Four aqueous concentrations of (99m)Tc, (131)I, and (111)In (74, 185, 370, and 740 kBq mL(-1)) were placed in spheres of four different sizes in a water-filled phantom, with three different levels of activity in the surrounding water. Planar and SPECT images of the phantoms were obtained on a modern SPECT/computed tomography (CT) system. These radionuclides and concentration/background studies were repeated using a cardiac phantom and a modified torso phantom with liver and ""tumor"" regions containing the radionuclide concentrations and with the same varying background levels. Planar quantification was performed using the geometric mean approach, with attenuation correction (AC), and with and without scatter corrections (SC and NSC). SPECT images were reconstructed using attenuation maps (AM) for AC; scatter windows were used to perform SC during image reconstruction. For spherical sources with corrected data, good accuracy was observed (generally within +/- 10% of known values) for the largest sphere (11.5 mL) and for both planar and SPECT methods with (99m)Tc and (131)I, but were poorest and deviated from known values for smaller objects, most notably for (111)In. SPECT quantification was affected by the partial volume effect in smaller objects and generally showed larger errors than the planar results in these cases for all radionuclides. For the cardiac phantom, results were the most accurate of all of the experiments for all radionuclides. Background subtraction was an important factor influencing these results. The contribution of scattered photons was important in quantification with (131)I; if scatter was not accounted for, activity tended to be overestimated using planar quantification methods. For the torso phantom experiments, results show a clear underestimation of activity when compared to previous experiment with spherical sources for all radionuclides. Despite some variations that were observed as the level of background increased, the SPECT results were more consistent across different activity concentrations. Planar or SPECT quantification on state-of-the-art gamma cameras with appropriate quantitative processing can provide accuracies of better than 10% for large objects and modest target-to-background concentrations; however when smaller objects are used, in the presence of higher background, and for nuclides with more complex decay schemes, SPECT quantification methods generally produce better results. Health Phys. 99(5):688-701; 2010
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Attentional accounts of blink facilitation during Pavlovian conditioning predict enhanced reflexes if reflex and unconditional stimuli (US) are from the same modality. Emotional accounts emphasize the importance of US intensity. In Experiment 1, we crossed US modality (tone vs, shock) and intensity in a 2 X 2 between-subjects design. US intensity but not US modality affected blink facilitation. Tn Experiment 2, we demonstrated that the results from Experiment 1 were not due to the motor task requirements employed. In Experiment 3, we used a within-subjects design to investigate the effects of US modality and intensity. Contrary to predictions derived from an attentional account, blink facilitation was larger during conditional stimuli that preceded shock than during those that preceded tones. The present results are not consistent with an attentional account of blink facilitation during Pavlovian conditioning in humans.
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Specific leaf nitrogen (SLN, g/m(2)) is known to affect radiation use efficiency (RUE, g/MJ) in different crops, However, this association and importance have not been well established over a range of different nitrogen regimes for held-grown sunflower (Helianthus annuus L.). An experiment was conducted to investigate different combinations and rates of applied nitrogen on SLN, RUE, and growth of sunflower, A fully irrigated crop was sown on an alluvial-prairie soil (Fluventic Haplustoll) and treated with five combinations of applied nitrogen, Greater nitrogen increased biomass, grain number, and yield, but did not affect harvest index energy-corrected for oil (0.4) or canopy extinction coefficient (0.88), Decreases in biomass accumulation under low nitrogen treatments were associated,vith reductions in leaf area index (LAI) and light interception, When SLN and RUE were examined together, both were less in the anthesis to physiological maturity period, but relatively stable between bud visible and anthesis, However, the effects of canopy SLN on RUE were confounded by high SLN in the top of the canopy and the crop maintaining SLN by reducing LAI, Measurements of leaf CO2 assimilation and theoretical analyses of RUE supported that RUE was related to SLN, The major effect of nitrogen on early growth of sunflower was mediated by leaf area and the distribution of SLN in the canopy rather than direct effects of canopy SLN on RUE alone. Greater responses of RUE to SLN are more evident later in growth, and may be related to the demand of nitrogen by the grain.
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The level of incident radiation and the proportion of radiation that is diffuse affects radiation use efficiency (RUE) in crops, However, the degree of this effect, and its importance to growth and yield of sunflower (Helianthus annuus L.) have not been established. A field experiment was conducted to investigate the effects of radiation environment on RUE, growth, and yield of sunflower. A fully irrigated crop was sown on an alluvial-prairie soil (Fluventic Haplustoll) and was exposed to three distinct radiation environments. In two treatments, the level of incident radiation was reduced by 14 and 20% by suspending tao different types of polyethylene plastic films well above the crop. In addition to the reductions in incident radiation, the proportion of radiation that was diffuse was increased by about 14% in these treatments. Lower incident radiation and increased proportion of diffuse radiation had no effect on total biomass, phenology, leaf area, and the canopy light extinction coefficient (k = 0.89). However, yield was reduced in shaded treatments due to smaller grain size and lower harvest index. Although crop RUE measured over the entire crop cycle (1.25 g/MJ) did not differ significantly among treatments, there was a trend where RUE compensated for less intercepted incident radiation. Theoretical derivations of the response of RUE to different levels of incident radiation supported this finding. Shaded sunflower crops have the ability to produce biomass similar to unshaded crops by increasing RUE, but have lower harvest indices.
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Objectives: To determine the effect of maternal smoking during pregnancy on transient evoked otoacoustic emissions levels in neonates. Methods: This was a cross-sectional study investigating neonates in the maternity ward of a university hospital in the city of Sao Paulo, Brazil. A total of 418 term neonates without prenatal or perinatal complications were evaluated. The neonates were divided into two groups: a study group, which comprised 98 neonates born to mothers who had smoked during pregnancy; and a control group, which comprised 320 neonates born to mothers who had not. In order to compare the two ears and the two groups in terms of the mean overall response and the mean transient evoked otoacoustic emissions in response to acoustic stimuli delivered at different frequencies, we used analysis of variance with repeated measures. Results: The mean overall response and the mean frequency-specific response levels were lower in the neonates in the study group (p < 0.001). The mean difference between the groups was 2.47 dB sound pressure level (95% confidence interval: 1.47-3.48). Conclusions: Maternal smoking during pregnancy had a negative effect on cochlear function, as determined by otoacoustic emissions testing. Therefore, pregnant women should be warned of this additional hazard of smoking. It is important that smoking control be viewed as a public health priority and that strategies for treating tobacco dependence be devised. (C) 2011 Elsevier Ireland Ltd. All rights reserved.
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Background. We aimed at investigating the influence of diabetic neuropathy and previous history of plantar ulcers on electromyography (EMG) of the thigh and calf and on vertical ground reaction forces during gait. Methods. This study involved 45 adults divided into three groups: a control group (n = 16), diabetic neuropathic group (n = 19) and diabetic neuropathic group with previous history of plantar ulceration (it = 10). EMG of the right vastus lateralis, lateral gastrocnemius and tibialis anterior were studied during the stance phase. The peaks and time of peak occurrence were determined and a co-activation index between tibialis anterior and lateral gastrocnemius. In order to represent the effect of the changes in EMG, the first and second peaks and the minimum value of the vertical ground reaction force were also determined. Inter-group comparisons of the electromyographical and ground reaction forces variables were made using three MANCOVA (peaks and times of EMG and peaks of force) and one ANCOVA (co-activation index). Findings. The ulcerated group presented a delayed in the time of the lateral gastrocnemius and vastus lateralis peak occurrence in comparison to control`s. The lateral gastrocnemius delay may be related to the lower second vertical peak in diabetic subjects. However, the delay of the vastus lateralis did not cause any significant change on the first vertical peak. Interpretations. The vastus lateralis and lateral gastrocnemius delay demonstrate that ulcerated diabetic neuropathic patients have a motor deficit that could compromise their ability to walk, which was partially confirmed by changes on ground reaction forces during the push-off phase. (c) 2007 Elsevier Ltd. All rights reserved.
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Objective: This study assessed the effects of an aquatic respiratory exercise-based program in patients with fibromyalgia (FMS). Methods: Forty women, aged between 20 and 60 years, were randomly assigned into two groups of 20 patients: the aquatic respiratory exercise-based program (ARG) and the control group (CTL). The ARG group performed the exercise program for 1 h, four times a week, for 4 weeks which included: (i) warming-Lip; (ii) respiratory exercises, consisting of five different breathing patterns, along With upper, lower limbs and trunk movements (45 min); and (iii) relaxation exercises. Both groups were included in supervised recreational activities of 1 h, once a week, for 4 weeks. Questionnaires were applied before and after intervention to assess quality of life and functional capacity (SF-36, Fibromyalgia Impact Questionnaire [FIQ]), anxiety (Hamilton Anxiety Scale [HAS]), and quality of sleep (Pittsburg Sleep Quality Index [PSQI]). Number of tender points and pain (Visual Analogue Scale [VAS]) were also evaluated. Results: At baseline there was no difference between the two groups, including number of tender points and questionnaire responses. After intervention, the ARG group, compared with the CTL group, showed improvement in SF-36 scores (physical functioning P = 0.001, bodily pain 1) = 0.001, vitality P = 0.009, social functioning P = 0.001, emotional role P = 0.001), in FIQ (total score P = 0.049, work missed P = 0.036, fatigue P = 0.013, morning tiredness P = 0.007) plus in VAS-pain (P = 0.029), VAS-dyspnea (P = 0.04), anxiety (HAS P = 0.005) and quality of sleep (PSQI P = 0.004). Conclusions: The short-term aquatic respiratory exercise-based program improved pain, quality of life, functional capacity, anxiety and quality of sleep in patients with FMS and may be a relevant addition to the treatment of these patients.
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Oligocene resin from New Zealand's Rotowaro coalfield displays DTA and DTG traces similar to those of other fossil resins. It modifies the thermal behaviour of low rank coal in raising the peak combustion temperature and lowering its rate of combustion, a behaviour that may be common among liptinite macerals. The effect is not additive and unlike other coal constituents the resinite component does not deteriorate with time. (C) 1997 Elsevier Science B.V.
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Severe obesity has been associated with adverse effects on physical capacity. In a prospective study, the aerobic capacity of severely obese patients was measured in order to observe the physiological response to weight loss from bariatric surgery. Sixty-five consecutive patients (40.4 +/- 8.4 years old; 93.8% female; body mass index = 49.4 +/- 5.4 kg/m(2)) were evaluated before bariatric surgery and then 6 and 12 months after surgery. Aerobic capacity was assessed with a scientific treadmill to measure maximal oxygen consumption (VO(2max)), heart rate, blood pressure, time on the treadmill, and distance walked (modified Bruce test). For the three observational periods, VO(2max) was 25.4 +/- 9.3, 29.8 +/- 8.1, and 36.7 +/- 8.3 ml/kg/min; time on the treadmill was 5.4 +/- 1.4, 6.4 +/- 1.6, and 8.8 +/- 1.0 min; and distance walked was 401.8 +/- 139.1, 513.4 +/- 159.9, and 690.5 +/- 76.2 m. For these variables, significant results (p = 0.0000) were observed for the two postoperative periods in relation to the preoperative period. Severely obese individuals increased their aerobic capacity after successful bariatric surgery. The data also suggests that a positive and progressive relationship between weight loss and improvement in fitness as a moderate loss of weight 6 months after surgery already showed some benefit and an additional reduction in weight was associated with a better performance in the aerobic capacity tests at the 12-month follow-up.
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1. Mechanically skinned fibres from skeletal muscles of the rat, toad and yabby were used to investigate the effect of saponin treatment on sarcoplasmic reticulum (SR) Ca2+ loading properties. The SR was loaded submaximally under control conditions before and after treatment with saponin and SR Ca2+ was released with caffeine. 2. Treatment with 10 mu g ml(-1) saponin greatly reduced the SR Ca2+ loading ability of skinned fibres from the extensor digitorum longus muscle of the rat with a rate constant of 0.24 min(-1). Saponin concentrations up to 150 mu g ml(-1) and increased exposure time up to 30 min did not further reduce the SR Ca2+ loading ability of the SR, which indicates that the inhibitory action of 10-150 mu g ml(-1) saponin is not dose dependent. The effect of saponin was also not dependent on the state of polarization of the transverse-tubular system. 3. Treatment with saponin at concentrations up to 100 mu g ml(-1) for 30 min did not affect the Ca2+ loading ability of SR in skinned skeletal muscle fibres from the twitch portion of the toad iliofibularis muscle but SR Ca2+ loading ability decreased markedly with a time constant of 0.22 min(-1) in the presence of 150 mu g ml(-1) saponin. 4. The saponin dependent increase in permeability could be reversed in both rat and toad fibres by short treatment with 6 mu M Ruthenium Red, a potent SR Ca2+ channel blocker, suggesting that saponin does affect the SR Ca2+ channel properties in mammalian and anuran skeletal muscle. 5. Treatment of skinned fibres of long sarcomere length (> 6 mu m) from the claw muscle of the yabby (a freshwater decapod crustacean) with 10 mu g ml(-1) saponin for 30 min abolished the ability of the SR to load Ca2+, indicating that saponin affects differently the SR from skeletal muscles of mammals, anurans and crustaceans. 6. is concluded that at relatively low concentrations, saponin causes inhibition of the skeletal SR Ca2+ loading ability in a species dependent manner, probably by increasing the Ca2+ loss through SR Ca2+ release channels.