On blocking rules for the bootstrap with dependent data

We address the issue of optimal block choice in applicationsof the block bootstrap to dependent data. It is shown that optimalblock size depends significantly on context, being equal ton^1/3, n^1/4 and n^1/5 in the cases of variance or bias estimation,estimation of a onesided distribution function, and estimationof a two-sided distribution function, respectively. A clearintuitive explanation of this phenomenon is given, togetherwith outlines of theoretical arguments in specific cases. Itis shown that these orders of magnitude of block sizes can beused to produce a simple, practical rule for selecting blocksize empirically. That technique is explored numerically.     

Electromyographic correlates of the transition from aerobic to anaerobic metabolism in treadmill running

This study analysed the changes in electromyographic (EMG) activity of the vastus lateralis, biceps femoris and gastrocnemius muscles during incremental treadmill running. The changes in EMG were related to the lactate and ventilatory thresholds. Ten trained subjects participated in the study. Minute ventilation, oxygen consumption, carbon dioxide expired and the fraction of oxygen in the expired gas were recorded continuously. Venous blood samples were collected at each exercise intensity and analysed for lactate concentration. The EMG were recorded at the end of each exercise intensity using surface electrodes. The EMG were quantified through integration (iEMG) and by calculating the mean power frequency (MPF). The iEMG measurements were characterized by a breakpoint in the vastus lateralis and/or gastrocnemius muscles in eight of the subjects tested. However, the results indicated that blood lactate concentrations had already begun to increase in a nonlinear fashion before the iEMG breakpoint had been surpassed. Consequently, the occurence of the lactate threshold cannot be attributed solely to the change in motor unit recruitment or rate coding patterns demonstrated by the iEMG breakpoint. The ventilatory threshold was shown to be a far more reliable and convenient noninvasive predictor of the lactate threshold in comparison with EMG techniques. In conclusion, the EMG measurements used in this study (i.e. iEMG and MPF) were not considered to be viable noninvasive determinants of the aerobic-anaerobic transition phase in treadmill running.     

生物组织散射元平均间距估计的一种新方法

生物组织散射元平均间中划描述生物组织微观结构特性和生物组织超微散射特性的重要参数。本文在对生物组织超声背向散射随机模的基础上,提出了基于生物组织超声背向散射信号突变点检测的工用射元平均间距估计的新方法。该方法是生物组织超声散射分析的有效方法。     

云南普通马矮型马蛋白多态性及其品种分化关系

本文运用蛋白电泳技术对来自云南省文山州马关县和麻栗坡县的２１匹普通马和１４匹矮型马进行了分析。共分析遗传座位４４个,其中有１０个座位检测到多态性。根据分子钟假说和相应的公式,推算两者的分歧时间约为１８．５万年。     

Evaluation of mean skin temperature formulas by infrared thermography

 To study the reliabiliity of formulas for calculating mean skin temperature (T _sk), values were computed by 18 different techniques and were compared with the mean of 10,841 skin temperatures measured by infrared thermography. One hundred whole-body infrared thermograms were scanned in ten resting males while changing the air temperature from 40° C to 4° C. Local, regional average and mean skin temperatures were obtained using an image processing system. The agreement frequency, defined as the percentage of the calculated T _sk values which agreed with the corresponding infrared thermographic T _sk within ±0.2° C, ranged for with the various formulas from 7% to 80%. In many sites, the local skin temperature did not coincide with the regional average skin temperature. When the local skin temperatures which showed the highest percentage similarity to the regional average skin temperature within ±0.4° C were applied to the formula, the agreement frequency was markedly improved for all formulas. However, the agreement frequency was not affected by changing the weighting factors from specific constants to individually measured values of regional surface area. By applying the physiologically reliable accuracy range of ±0.2° C in the moderate and ±0.4° C in the cool condition, agreement frequencies of at least 95% were observed in formulas involving seven or more skin temperature measurement sites, including the hand and foot. We conclude that calculation of a reliable mean skin temperature must involve more than seven skin temperature measurement sites regardless of ambient temperature. Optimal sites for skin temperature measurement are proposed for various formulas. Received: 2 December 1996 / Accepted: 25 June 1997     

Differential cardiovascular effects mediated by mu and kappa opiate receptors in hindbrain nuclei

To further investigate the role of opioid peptides and specific opiate receptor subtypes in central cardiovascular regulation by hindbrain nuclei, mu (D-Ala²,MePhe⁴,Gly-ol⁵ enkephalin, DAGO), delta (D-Ala²,D-Leu⁵ enkephalin, DADL) or kappa (MRZ 2549) agonists were microinjected into hindbrain nuclei of spontaneously or artificially respired, pentobarbital-anesthetized rats. In the nucleus tractus solitarius (NTS), DAGO and DADL (0.3 nmol) elicited pressor responses and tachycardia. MRZ (3.0–16 nmol) depressed blood pressure in spontaneously breathing rats, but accelerated heart rate in artificially ventilated animals. Blood pressure and heart rate of spontaneously breathing animals were not altered following nucleus ambiguus (NA) injection of DAGO or DADL (0.3 nmol), but were elevated in artificially respired animals; MRZ (3.0–10 nmol) injected into the NA depressed blood pressure in both groups. These data suggest that in the absence of respiratory depression, NTS and NA mu receptors mediate pressor responses and tachycardia; kappa receptors in the NA mediate a decrease in blood pressure but cardioacceleration in the NTS.     

Community dynamics of evergreen broadleaf forests in southwestern Japan. I. Wind damaged trees and canopy gaps in an evergreen oak forest

The rates of treefall and canopy opening in the evergreen oak forest in southwestern Japan were determined by studying the number and size distribution of overstory trees, wind damaged trees, and canopy gaps in a belt transect in the Kasugayama Forest Reserve in Nara City. Thirty three percent of the overstory trees wereCastanopsis cuspidata. The total area of canopy gaps was about 20% of the total land area in the study area. The ages of the gaps were determined by counting the annual rings of various kinds of trees growing in gaps. By comparing gap ages with meteorological data, it became evident that gap formation was mainly caused by strong typhoons. The mean time interval between strong typhoons visiting the forest reserve, 6.57 years, was determined by applying the MNY method to the meteorological data. The treefall rate and the mean area of canopy openings per year were 0.84 overstory trees/ha·year and 55.6 m²/ha·year, respectively. The mean residence time of the forest canopy was about 180 years.     

Trait vs. phylogenetic diversity as predictors of competition and community composition in herbivorous marine amphipods

Field studies of community assembly patterns increasingly use phylogenetic relatedness as a surrogate for traits. Recent experiments appear to validate this approach by showing effects of correlated trait and phylogenetic distances on coexistence. However, traits governing resource use in animals are often labile. To test whether feeding trait or phylogenetic diversity can predict competition and production in communities of grazing amphipods, we manipulated both types of diversity independently in mesocosms. We found that increasing the feeding trait diversity of the community increased the number of species coexisting, reduced dominance and changed food availability. In contrast, phylogenetic diversity had no effect, suggesting that whatever additional ecological information it represents was not relevant in this context. Although community phylogenetic structure in the field may result from multiple traits with potential for phylogenetic signal, phylogenetic effects on species interactions in controlled experiments may depend on the lability of fewer key traits.     

Angiotensin (1-7) contributes to nitric oxide tonic inhibition of vasopressin release during hemorrhagic shock in acute ethanol intoxicated rodents

Aims

Acute ethanol intoxication (AEI) attenuates the arginine vasopressin (AVP) response to hemorrhage leading to impaired hemodynamic counter-regulation and accentuated hemodynamic stability. Previously we identified that the ethanol-induced impairment of circulating AVP concentrations in response to hemorrhage was the result of augmented central nitric oxide (NO) inhibition. The aim of the current study was to examine the mechanisms underlying ethanol-induced up-regulation of paraventricular nucleus (PVN) NO concentration. Angiotensin (ANG) (1-7) is an important mediator of NO production through activation of the Mas receptor. We hypothesized that Mas receptor inhibition would decrease central NO concentration and thus restore the rise in circulating AVP levels during hemorrhagic shock in AEI rats.

Main methods

Conscious male Sprague–Dawley rats (300–325 g) received a 15 h intra-gastric infusion of ethanol (2.5 g/kg + 300 mg/kg/h) or dextrose prior to a fixed-pressure (~ 40 mm Hg) 60 min hemorrhage. The Mas receptor antagonist A-779 was injected through an intracerebroventricular (ICV) cannula 15 min prior to hemorrhage.

Key findings

PVN NOS activity and NO were significantly higher in AEI compared to DEX-treated controls at the completion of hemorrhage. ICV A-779 administration decreased NOS activity and NO concentration, partially restoring the rise in circulating AVP level at completion of hemorrhage in AEI rats.

Significance

These results suggest that Mas receptor activation contributes to the NO-mediated inhibitory tone of AVP release in the ethanol-intoxicated hemorrhaged host.