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1.
Alejandro Hernndez-Belmonte Alejandro Martínez-Cava Ricardo Morn-Navarro Javier Courel-Ibez Jesús G. Pallars 《Biology of sport / Institute of Sport》2021,38(2):235
The purpose of this study was threefold: i) to analyse the load-velocity relationship of the shoulder press (SP) exercise, ii) to investigate the stability (intra-individual variability) of this load-velocity relationship for athletes with different relative strength levels, and after a 10-week velocity-based resistance training (VBT), and iii) to describe the velocity-time pattern of the SP: first peak velocity [Vmax1], minimum velocity [Vmin], and second peak velocity [Vmax2]. This study involves a cross-sectional (T1, n = 48 subjects with low, medium and high strength levels) and longitudinal (T2, n = 24 subjects randomly selected from T1 sample) design. In T1, subjects completed a progressive loading test up to the 1RM in the SP exercise. The barbell mean, peak and mean propulsive velocities (MV, PV and MPV) were monitored. In T2, subjects repeated the loading test after 10 weeks of VBT. There were very close relationships between the %1RM and velocity attained in the three velocity outcomes (T1, R2: MV = 0.970; MPV = 0.969; PV = 0.954), being even stronger at the individual level (T1, R2 = 0.973–0.997). The MPV attained at the 1RM (~0.19 m·s-1) was consistent among different strength levels. Despite the fact that 1RM increased ~17.5% after the VBT programme, average MPV along the load-velocity relationship remained unaltered between T1 and T2 (0.69 ± 0.06 vs. 0.70 ± 0.06 m·s-1). Lastly, the three key parameters of the velocity-time curve were detected from loads > 74.9% 1RM at 14.3% (Vmax1), 46.1% (Vmin), and 88.7% (Vmax2) of the concentric phase. These results may serve as a practical guideline to effectively implement the velocity-based method in the SP exercise. 相似文献
2.
《Journal of electromyography and kinesiology》2014,24(1):120-125
Repetitive exposures to altered gait and movement following lower-limb amputation (LLA) have been suggested to contribute to observed alterations in passive tissue properties and neuromuscular control in/surrounding the lumbar spine. These alterations, in turn, may affect the synergy between passive and active tissues during trunk movements. Eight males with unilateral LLA and eight non-amputation controls completed quasi-static trunk flexion–extension movements in seven distinct conditions of rotation in the transverse plane: 0° (sagittally-symmetric), ±15°, ±30°, and ±45° (sagittally-asymmetric). Electromyographic (EMG) activity of the bilateral lumbar erector spinae and lumbar kinematics were simultaneously recorded. Peak lumbar flexion and EMG-off angles were determined, along with the difference (“DIFF”) between these two angles and the magnitude of peak normalized EMG activities. Persons with unilateral LLA exhibited altered and asymmetric synergies between active and passive trunk tissues during both sagittally-symmetric and -asymmetric trunk flexion movements. Specifically, decreased and asymmetric passive contributions to trunk movements were compensated with increases in the magnitude and duration of active trunk muscle responses. Such alterations in trunk passive and active neuromuscular responses may result from repetitive exposures to abnormal gait and movement subsequent to LLA, and may increase the risk for LBP in this population. 相似文献
3.
XINYOU YIN PAUL C. STRUIK PASCUAL ROMERO JEREMY HARBINSON JOCHEM B. EVERS PETER E. L. VAN DER PUTTEN & JAN VOS 《Plant, cell & environment》2009,32(5):448-464
We appraised the literature and described an approach to estimate the parameters of the Farquhar, von Caemmerer and Berry model using measured CO2 assimilation rate (A) and photosystem II (PSII) electron transport efficiency (Φ2). The approach uses curve fitting to data of A and Φ2 at various levels of incident irradiance (Iinc), intercellular CO2 (Ci) and O2. Estimated parameters include day respiration (Rd), conversion efficiency of Iinc into linear electron transport of PSII under limiting light [κ2(LL)], electron transport capacity (Jmax), curvature factor (θ) for the non‐rectangular hyperbolic response of electron flux to Iinc, ribulose 1·5‐bisphosphate carboxylase/oxygenase (Rubisco) CO2/O2 specificity (Sc/o), Rubisco carboxylation capacity (Vcmax), rate of triose phosphate utilization (Tp) and mesophyll conductance (gm). The method is used to analyse combined gas exchange and chlorophyll fluorescence measurements on leaves of various ages and positions in wheat plants grown at two nitrogen levels. Estimated Sc/o (25 °C) was 3.13 mbar µbar?1; Rd was lower than respiration in the dark; Jmax was lower and θ was higher at 2% than at 21% O2; κ2(LL), Vcmax, Jmax and Tp correlated to leaf nitrogen content; and gm decreased with increasing Ci and with decreasing Iinc. Based on the parameter estimates, we surmised that there was some alternative electron transport. 相似文献
4.
van der Burg JC Casius LJ Kingma I van Dieën JH van Soest AJ 《Biological cybernetics》2005,93(1):54-62
In the first part of lifting movements, the trunk movement is surprisingly resistant to perturbations. This study examined which factors contribute to this perturbation resistance of the trunk during lifting. Three possible mechanisms were studied: force-length-velocity characteristics of muscles, the momentum of the trunk as well as the effect of passive extending of the elbows. A forward dynamics modelling and simulation approach was adopted with two different input signals: (1) stimulation of Hill-type muscles versus (2) net joint moments. Experimental data collected during an unperturbed lifting movement were used as a reference, which a simulated lifting movement had to resemble. Subsequently, the simulated lifting movement was perturbed by applying 10 kg extra mass at the wrist (both before and after lift-off and with/without a fixed elbow), without modifying the input signals. The momentum of the trunk appeared to be insufficient to explain the perturbation resistance of trunk movements as found experimentally. In addition to the momentum of the trunk, the force-length-velocity characteristics of the muscles are necessary to account for the observed perturbation resistance. Initial extension of the elbow due to the mass perturbation delayed the propagation of the load to the shoulder. However, this delay is reduced due to the impedance at the elbow provided by the characteristics of muscles spanning the elbow. So, the force-length-velocity characteristics of the muscles spanning the elbow joint increase the perturbation at the trunk. 相似文献
5.
The effects of chronic exposure of the freshwater rotifer Brachionus calyciflorus to the toxicants lindane and 3,4-dichloroaniline (DCA), were evaluated. The parameters used to determine the toxicity on these compounds were the age-specific and fertility, and the demographic parameters: intrinsic rate of natural increase (r), generation time (T), net reproductive rate (R
o), reproductive value (V
x) and life expectancy (e
o). All the demographic parameters studied decreased with increasing toxicant concentrations. The use of life tables techniques with B. calyciflorus as a test method for the determination of chronic toxicity of xenobiotics is discussed. 相似文献
6.
Oxidative respiration is strongly temperature driven. However, in woody stems, efflux of CO2 to the atmosphere (E
A), commonly used to estimate the rate of respiration (R
S), and stem temperature (T
st) have often been poorly correlated, which we hypothesized was due to transport of respired CO2 in xylem sap, especially under high rates of sap flow (f
s). To test this, we measured E
A, T
st, f
s and xylem sap CO2 concentrations ([CO2*]) in 3-year-old Populus deltoides trees under different weather conditions (sunny and rainy days) in autumn. We also calculated R
S by mass balance as the sum of both outward and internal CO2 fluxes and hypothesized that R
S would correlate better with T
st than E
A. We found that E
A sometimes correlated well with T
st, but not on sunny mornings and afternoons or on rainy days. When the temperature effect on E
A was accounted for, a clear positive relationship between E
A and xylem [CO2*] was found. [CO2*] varied diurnally and increased substantially at night and during periods of rain. Changes in [CO2*] were related to changes in f
s but not T
st. We conclude that changes in both respiration and internal CO2 transport altered E
A. The dominant component flux of R
S was E
A. However, on a 24-h basis, the internal transport flux represented 9–18% and 3–7% of R
S on sunny and rainy days, respectively, indicating that the contribution of stem respiration to forest C balance may be larger
than previously estimated based on E
A measurements. Unexpectedly, the relationship between R
S and T
st was sometimes weak in two of the three trees. We conclude that in addition to temperature, other factors such as water deficits
or substrate availability exert control on the rate of stem respiration so that simple temperature functions are not sufficient
to predict stem respiration. 相似文献
7.
José Enrique Fernández Félix MorenoMaría José Martín-Palomo María Victoria CuevasJosé Manuel Torres-Ruiz Alfonso Moriana 《Environmental and Experimental Botany》2011,72(2):330-338
Sap flux (Q) and trunk diameter variation (TDV) are among the most useful plant-based measurements to detect water stress and to evaluate plant water consumption. The usefulness of both methods decreases, however, when applied to species that, like olive, have an outstanding tolerance to drought and a remarkable capacity to take up water from drying soils. Evidence shows that this problem is greater in old, big trees with heavy fruit load. Our hypothesis is that the analysis of simultaneous measurements of Q and TDV made in the same trees is more useful for assessing irrigation needs in old olive orchards than the use of any of these two methods alone. To test our hypothesis, we analysed relations between Q, TDV, midday stem water potential (Ψstem), relative extractable water and atmospheric demand in an olive orchard of 38-year-old ‘Manzanilla’ trees with heavy fruit load. Measurements were made during one irrigation season (May-October), in fully irrigated trees (FI, 107% of the crop evapotranspiration, ETc, supplied by irrigation), and in trees under two levels of deficit irrigation (DI60, 61% ETc; DI30, 29% ETc). Time courses of Q and TDV measured on days of contrasting weather and soil water conditions were analysed to evaluate the usefulness of both methods to assess the crop water status. We calculated the daily tree water consumption (Ep) from Q measurements. For both DI treatments we calculated a signal intensity by dividing daily Ep values of each DI tree by those of the FI tree (SI−Ep). We did the same with the maximum daily shrinkage (MDS) values (SI−MDS). Neither SI−Ep nor SI−MDS rendered useful information for assessing the crop water needs. On the contrary, the daily difference for maximum trunk diameter (MXTD) between each of the DI trees and the FI tree (DMXTD) clearly indicated the onset and severity of water stress. A similar analysis with the Ep values, from which DEp values were derived, showed the effect of water stress on the water consumption of the trees. We concluded that the simultaneous use of DMXTD and DEp values provides more detailed information to assess water needs in mature olive orchards than the use of Q or TDV records alone. 相似文献
8.
Robert H. Kennedy 《International Review of Hydrobiology》1999,84(6):557-566
The relationship between phosphorus retention (RP) and water residence time (RT) was assessed for selected U.S. Army Corps of Engineers reservoirs and found to be influenced by areal phosphorus loading rate (PL). For reservoirs with high PL (>15 gm/m2/yr), RP increased markedly with modest increases in RT. Reservoirs with lower values of PL exhibited less dramatic responses in RP to changes in RT. The water quality management implications of this are great since reservoirs for which marked changes in RP can occur with modest changes in RT are potential management loci within a drainage basin. 相似文献
9.
Zachary F. Kohl Michael S. Hedrick Stanley S. Hillman 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2013,183(7):921-932
Amphibian pulmonary and systemic vascular circuits are arranged in parallel, with potentially important consequences for resistance (R) to blood flow. The contribution of the parallel anatomic arrangement to total vascular R (R T), independent of blood viscosity, is unknown. We measured pulmonary (R P) and systemic (R S) vascular R with an in situ Ringer’s solution perfusion technique using anesthetized anuran and urodele species to determine: (1) relative contributions of vascular anatomy and blood viscosity to R T; (2) distensibility index (%Δ flow kPa?1) of the pulmonary and systemic vascular circuits; and (3) interspecific correlates of variation in these parameters with red blood cell size, cardiac power output, and aerobic capacities. R P was lower than R S in anurans, while R P of the urodeles was greater than R S and significantly greater than anuran R P. Anuran R T was lowest and did not vary interspecifically, whereas urodele R T was significantly greater than anuran, and varied interspecifically. Pulmonary and systemic circuit distensibility differences may explain cardiac shunt patterns in toads with changes in cardiac output from rest to activity. When blood viscosity was taken into account, vascular resistance accounted for about 25 % of R T while blood viscosity accounted for the remaining 75 %. Owing to lower R T, terrestrial anuran species required lower cardiac power outputs when moving fluid through their vasculature compared to aquatic species. These results indicate that physical characteristics of the vasculature can account for interspecific differences in cardiovascular physiology and suggest a co-evolution of cardiac and vascular anatomy among amphibians. 相似文献
10.
The relationship between pulmonary artery pressure (P
LA) and oxygen saturation of mixed venous blood (S
V
) has been studied in subjects (1750 men and 1026 women) subdivided into 12 groups. Functional relationships have been found
between P
LA and S
V
, P
LA = f(S
V
), and S
V
= f(P
LA), which were estimated using direct measurement of P
LA and S
V
for each group. These factors have been found to obey the following dependences: P
LA = f(S
V
) and P
LA = a(S
V
)−b
, where b = −0.2284a + 0.6564 in men and b = −0.285a + 1.2947 in women; S
V
= f(P
LA) and S
V
= c(P
LA)−d
, where d = −0.25131Ln(c) + 1.0212; R
2 = 0.8993 in men and d = −1.9645Ln(c) + 2.852; and R
2 = 0.9674 in women. Each group occupies a position on the curves specified by the equations. Subjects with the diagnosis of
a functional heart murmur and patients with congenital aortic valve stenosis were grouped together to form the so-called normal
group characterized by specific P
LA = f(S
V
) and S
V
= f(P
LA) dependences. Male patients with coronary heart disease were also included in the normal group. An equation was derived to
relate P
LA caused by different reasons with the corresponding saturation of mixed venous blood. In the case of the changing saturation
of mixed venous blood, this equation gives the corresponding value of P
LA. Equilibrium between systemic and pulmonary circulations is established through interdependent changes in the physiological
indices of blood circulation and gas exchange in humans. 相似文献
11.
Roberto L. Salomn Kathy Steppe Kristine Y. Crous Nam Jin Noh David S. Ellsworth 《Plant, cell & environment》2019,42(7):2151-2164
To quantify stem respiration (RS) under elevated CO2 (eCO2), stem CO2 efflux (EA) and CO2 flux through the xylem (FT) should be accounted for, because part of respired CO2 is transported upwards with the sap solution. However, previous studies have used EA as a proxy of RS, which could lead to equivocal conclusions. Here, to test the effect of eCO2 on RS, both EA and FT were measured in a free‐air CO2 enrichment experiment located in a mature Eucalyptus native forest. Drought stress substantially reduced EA and RS, which were unaffected by eCO2, likely as a consequence of its neutral effect on stem growth in this phosphorus‐limited site. However, xylem CO2 concentration measured near the stem base was higher under eCO2, and decreased along the stem resulting in a negative contribution of FT to RS, whereas the contribution of FT to RS under ambient CO2 was positive. Negative FT indicates net efflux of CO2 respired below the monitored stem segment, likely coming from the roots. Our results highlight the role of nutrient availability on the dependency of RS on eCO2 and suggest stimulated root respiration under eCO2 that may shift vertical gradients in xylem [CO2] confounding the interpretation of EA measurements. 相似文献
12.
《Journal of electromyography and kinesiology》2014,24(3):394-403
Unexpected loading of the spine is a risk factor for low back pain. The trunk neuromuscular and kinematics responses are likely influenced by the perturbation itself as well as initial trunk conditions. The effect of four parameters (preload, sudden load, initial trunk flexed posture, initial abdominal antagonistic activity) on trunk kinematics and back muscles reflex response were evaluated. Twelve asymptomatic subjects participated in sudden forward perturbation tests under six distinct conditions. Preload did not change the reflexive response of back muscles and the trunk displacement; while peak trunk velocity and acceleration as well as the relative load peak decreased. Sudden load increased reflex response of muscles, trunk kinematics and loading variables. When the trunk was initially flexed, back muscles latency was delayed, trunk velocity and acceleration increased; however, reflex amplitude and relative trunk displacement remained unchanged. Abdominal antagonistic preactivation increased reflexive response of muscles but kinematics variables were not affected. Preload, initial flexed posture and abdominal muscles preactivation increased back muscles preactivity. Both velocity and acceleration peaks of the trunk movement decreased with preload despite greater total load. In contrast, they increased in the initial flexed posture and to some extent when abdominal muscles were preactivated demonstrating the distinct effects of pre-perturbation variables on trunk kinematics and risk of injury. 相似文献
13.
The objective of this study was to evaluate the thermoregulatory responses, acid-basic and electrolytic equilibrium of locally adapted goats under natural heat conditions in a semi-arid region. Ten (10) Canindé goats aged between 2 and 3 years, non-lactating, non-pregnant and having a body weight (BW) of 22.90 ± 2.70 kg were used in this study. Air temperature (AT) and relative humidity (RH) were measured, and the radiant heat load (RHL) was subsequently calculated. Rectal temperature (RT), respiratory rate (RR), sweating rate (SR) and heat shock (S) were recorded at 1-h intervals for 24 continuous hours. Hydrogen potential (pH), partial pressure of carbon dioxide (PCO2), partial pressure of oxygen (PO2), bicarbonate (HCO3), base excess (BE), total carbon dioxide concentration (TCO2), oxygen saturation (SO2), sodium (Na+) and potassium (K+) were recorded at three moments during the day (5 a.m.; 1 p.m.; 6 p.m.). There were also significant differences between the means of hours of the day for AT and RH. RR was the thermoregulatory response which most closely followed RHL, with important elevations in the periods between 10 a.m. to noon. It was observed that the goats activated their SR mechanism before RR, more precisely between the hours of 9 a.m. and 1 p.m. The acid-base and electrolytic equilibrium for the goats which showed great association with the first components contributed the most to the total variation of the data. The most important variables in the adaptive profile of these animals in order of importance were: SO2, PO2, RR, RT, SR, HCO3, BE, TCO2 and pH. An association between all variables grouped in each period was observed, where the thermoregulatory responses in the periods of 5 a.m. and 6 p.m. were closer than when compared to 1 p.m., showing a physiological return to the initial state. Therefore, the variation in thermoregulatory responses, acid-base and electrolytic equilibrium indicated that the goats have the ability to recover after a challenging environmental condition. 相似文献
14.
Slips are frequently the cause of fall-related injuries. Identifying modifiable biomechanical requirements for successful recovery is a key prerequisite to developing task-specific fall preventive training programs. The purpose of this study was to quantify the biomechanical role of the upper extremities during the initial phase of a slip resulting in trunk motion primarily in the sagittal plane. Two groups of adults were examined: adults over age 65 who fell and adults aged 18–40 who avoided falling after slipping. We hypothesized that rapid shoulder flexion could significantly reduce trunk extension velocity, that adults who slipped would implement this as a fall avoidance strategy, and that younger adults who avoided falling would use this strategy more effectively than older adults who fell. The kinematics of the 12 younger adults and eight older adults were analyzed using a three-segment conservation of momentum model developed to represent the trunk, head, and upper extremities. The model was used to estimate the possible contribution of the upper extremities to reducing trunk extension velocity. The model showed that upper extremity motion can significantly reduce trunk extension velocity. Although the upper extremities significantly reduced the trunk extension velocity of both young and older adults (p<0.027), the reduction found for the young adults, 13.6±11.4%, was significantly larger than that of the older adults (5.8±3.4%, p=0.045). Given the potential for trunk extension velocity to be reduced by rapid shoulder flexion, fall prevention interventions focused on slip-related falls may benefit from including upper extremity motion as an outcome whether through conventional or innovative strategies. 相似文献
15.
The local dynamic stability of trunk movements, quantified using the maximum Lyapunov exponent (λmax), can provide important information on the neuromuscular control of spine stability during movement tasks. Although previous research has displayed the promise of this technique, all studies were completed with healthy participants. Therefore the goal of this study was to compare the dynamic stability of spine kinematics and trunk muscle activations, as well as antagonistic muscle co-contraction, between athletes with and without low back pain (LBP). Twenty interuniversity varsity athletes (10 LBP, 10 healthy controls) were recruited to participate in the study. Each participant completed a repetitive trunk flexion task at 15 cycles per minute, both symmetrically and asymmetrically, while trunk kinematics and muscular activity (EMG) were monitored. The local dynamic stability of low back EMG was significantly higher (lower λmax) in healthy individuals (p=0.002), whereas the dynamic stability of kinematics, the dynamic stability of full trunk system EMG, and the amount of antagonistic co-contraction were significantly higher when moving asymmetrically (p<0.05 for all variables). Although non-significant, kinematic and trunk system EMG stability also tended to be impaired in LBP participants, whereas they also tended to co-contract their antagonist muscles more. This study provides evidence that Lyapunov analyses of kinematic and muscle activation data can provide insight into the neuromuscular control of spine stability in back pain participants. Future research will repeat these protocols in patients with higher levels of pain, with hopes of developing a tool to assess impairment and treatment effectiveness in clinical and workplace settings. 相似文献
16.
This study documents intra-session and inter-day reproducibility (coefficient of variation [V%]) and single measurement reliability (intra-class correlations [RI]; standard error of a single measurement [SEM%] [95% confidence limits]) of indices of neuromuscular performance elicited during peripheral nerve magnetic stimulation. Twelve adults (five men and seven women) completed 3 assessment sessions on 3 days, during which multiple assessments of knee flexor volitional and magnetically-evoked indices of electromechanical delay (EMDV; EMDE), rate of force development (RFDV; RFDE), peak force (PFV; PTFE), and compound muscle action potential latency (LATE) and amplitude (AMPE) were obtained. Results showed that magnetically-evoked indices of neuromuscular performance offered statistically equivalent levels of measurement reproducibility (V%: 4.3–31.2%) and reliability (RI: 0.98–0.51) compared to volitional indices (V%: 3.7–25.2%; RI: 0.98–0.64), which support the efficacy of both approaches to assessment and the indices PFV, EMDV, EMDE and LATE offer the greatest practical utility for assessing neuromuscular performance. 相似文献
17.
Chia-Hui Wu Chia-Wen Pen Pei-Yun Wang Shau-Wei Tsai 《Applied microbiology and biotechnology》2013,97(4):1581-1587
In the Candida antarctica lipase B-catalyzed hydrolysis of (R,S)-azolides derived from (R,S)-N-protected proline in water-saturated methyl tert-butyl ether (MTBE), high enzyme activity with excellent enantioselectivity (V S V R ?1 ?>?100) for (R,S)-N-Cbz-proline 1,2,4-triazolide (1) and (R,S)-N-Cbz-proline 4-bromopyrazolide (2) was exploited in comparison with their corresponding methyl ester analog (3). Changing of the substrate structure, water content, solvent, and temperature was found to have profound influences on the lipase performance. On the basis of enzyme activity and enantioselectivity and solvent boiling point, the best reaction condition of using 1 as the substrate in water-saturated MTBE at 45 °C was selected and further employed for the successful resolution of (R,S)-N-Cbz-pipecolic 1,2,4-triazolide (5) and (R,S)-N-Boc-nipecotic 1,2,4-triazolide (9). Moreover, more than 89.1 % recovery of remained (R)-1 is obtainable in five cycles of enzyme reusage, when pH 7 phosphate buffers were employed as the extract at 4 °C. 相似文献
18.
A quantitative light and electron microscope study of developing and degenerating mycorrhizal arbuscules of Glomus fasciculatum in Zea mays was carried out in order to estimate three parameters during the colonization cycle. These were: 1) Vv(f,c), the fraction of the host cell volume occupied by a volume of fungus; 2) Vv(cy,c), the fraction of the host cell volume occupied by host cytoplasm; 3) Sv(pr,c), the surface-area-to-volume ratio of the host protoplast to the whole host cell. Uninfected cortical cells had an Sv(pr,c) of 0.13 μm2/μm3. As the fungus penetrates the cell wall, the protoplast invaginates, causing a decrease in protoplast volume and an increase in protoplast Sv. The Sv(pr,c) of a cell containing a mature arbuscule is 1.275 μm2/μm3. Because of the shrinkage of the protoplast, the Sv of the protoplast to its own volume rather than the original cell volume is 2.55 μm2/μm3, or almost a 20-fold increase. Total cell size is unaffected. When the arbuscule is mature, the fungus occupies 42% of the cell, with 24% as 1-μm-diam branches, and 18% as trunk. Arbuscular branch formation progresses at a linear rate and is the most important factor in causing the increased host Sv. The correlation coefficient for Vv(br,c) the volume fraction for arbuscular branches, vs. Sv(pr,c) is r = 0.932 (P < 0.001). Degeneration of the arbuscule is marked by a rapid decrease in branches, host Sv, and host cytoplasm. The trunk develops and degenerates at a slower rate than the branches. 相似文献
19.
Glauber S.F. da SilvaHumberto Giusti Luiz G.S. BrancoMogens L. Glass 《Journal of thermal biology》2011,36(8):521-526
The control of pulmonary ventilation in South American lungfish Lepidosiren paradoxa is poorly understood. Interactions between temperature and hypoxia are particularly relevant due to large seasonal variations of its habitat. Therefore, we tested the hypothesis that the ventilatory responses to aerial hypoxia of Lepidosiren are highly dependent on ambient temperature. We used a pneumotachograph to measure pulmonary ventilation (VE), tidal volume (VT) and respiratory frequency (fR) during normoxic (21% O2) and hypoxic (12%, 10% and 7% O2) conditions at two temperatures (25 and 35 °C). Blood gases, arterial PO2 (PaO2), arterial PCO2 (PaCO2) and arterial pH (pHa) were also evaluated. At 25 °C, VE increased significantly at 10% and 7% hypoxic levels when compared to the control value (21% O2). At 35 °C, all hypoxic levels elicited a significant increase of VE relative to control values. VE is augmented mostly by increases of respiratory frequency (fR), and there were significant interactions (p<0.001) between aerial hypoxia and temperature. PaCO2 increased from ∼22 mmHg (normoxic value at 25 °C) to ∼32 mmHg (normoxic value at 35 °C). Concomitantly, the pHa decreased from 7.51 (25 °C) to 7.38 (35 °C). Hypoxia-induced hyperventilation caused a reduction in PaCO2 and an increase in pHa, which were more pronounced at 35 °C than at 25 °C, reflecting an increased hyperventilation under the high temperature. In conclusion, the magnitude of ventilatory response is highly temperature-dependent in L. paradoxa, which is important for an animal experiencing large seasonal variations. 相似文献
20.
Galip Seckin Turan YilmazAytac Guven Ahmet YuceerMesut Basibuyuk Cagatayhan B. Ersu 《Ecological Engineering》2011,37(3):523-528
This study investigates the predictive ability of gene-expression programming (GEP) in the estimation of methane yield (Ym) and effluent substrate (Se) produced by two anaerobic filters. The modeling study was carried out using the data obtained from two upflow anaerobic filters - one mesophilic (35 °C) and one thermophilic (55 °C) - operated for the treatment of paper-mill wastewater under varying organic loadings. The GEP model was composed of three inputs, hydraulic retention time (Thr), organic loading rate (Rol), and influent substrate (Si), and one output, either Se or Ym. The Stover-Kincannon model was also used for data analysis and to evaluate the prediction ability. Three statistical criteria, root mean square error (RMSE), determination coefficient (R2), and Akaike's information criteria (AIC), were the means used for comparison. The results showed that the GEP approach predicted the performance of both anaerobic filters much better than the Stover-Kincannon model. 相似文献