Aggregated indices for trends in eutrophication of different types of fresh water in the Netherlands

As in many European countries, eutrophication of surface waters is a key problem in the Netherlands, caused by high concentrations of nitrogen (N) and phosphorus (P). For implementation of the EU Water Framework Directive (WFD) in the Netherlands, surface water types have been identified and for each water type environmental quality standard concentrations (EQS) were determined for both nutrients. With these standards, a new method was developed to quantify trends in water quality with respect to eutrophication on a national scale for the period 1990–2010. Firstly, monitoring data were aggregated to seven classes of surface water. Next, for each water class and each nutrient, a Nutrient Index was developed to express the degree of exceedance of EQS (distance-to-target method). The Nutrient Index for N shows a minor exceedance of EQS as well as an improvement in all water types; for P, the index shows a major exceedance in small stagnant waters throughout the 1990–2010 period, whereas in major rivers and lakes levels were close to EQS. Thirdly, the indices for seven surface water classes were aggregated to one index for each nutrient, and finally to a national Eutrophication Index combining N and P. This Eutrophication Index integrates all monitoring data and shows an improvement in the period 1990–2003 and stabilization since 2004.     

The scaling or ontogeny of human gait kinetics and walk-run transition: The implications of work vs. peak power minimization

A simple model is developed to find vertical force profiles and stance durations that minimize either limb mechanical work or peak power demands during bipedal locomotion. The model predicts that work minimization is achieved with a symmetrical vertical force profile, consistent with previous models and observations of adult humans, and data for 487 participants (predominantly 11–18 years old) required to walk at a range of speeds at a Science Fair. Work minimization also predicts the discrete walk-run transition, familiar for adult humans. In contrast, modeled peak limb mechanical power demands are minimized with an early skew in vertical ground reaction force that increases with speed, and stance durations that decrease steadily with speed across the work minimizing walk-run transition speed. The peak power minimization model therefore predicts a continuous walk-run gait transition that is quantitatively consistent with measurements of younger children (1.1–4.7 years) required to locomote at a range of speeds but free to select their own gaits.     

A collisional model of the energetic cost of support work qualitatively explains leg sequencing in walking and galloping, pseudo-elastic leg behavior in running and the walk-to-run transition

Terrestrial legged locomotion requires repeated support forces to redirect the body's vertical velocity component from down to up. We assume that the redirection is accomplished by impulsive leg forces that cause small-angle glancing collisions of a point-mass model of the animal. We estimate the energetic costs of these collisions by assuming a metabolic cost proportional to positive muscle work involved in generating the impulses. The cost of bipedal running estimated from this collisional model becomes less than that of walking at a Froude number (v2/gl) of about 0.7. Two strategies to reduce locomotion costs associated with the motion redirection are: (1) having legs simulate purely elastic springs, as is observed in human running; and (2) sequencing the leg forces during the redirection phase; examples of this sequencing are the ba-da-dump pattern of a horse gallop and having push-off followed by heel-strike in human walking.     

蝉的变音调复合声和发声机制的分析

蛙鸣蝉(Meimuna opalifera (Walk).ab.punctata Kato)的自然鸣声为“ji…guái”的重复单变调复合声.“ji”为主音频约4800Hz的准单音;“guái”的波形和主音频呈明显的演变,优势主频约2100Hz和2800Hz的变音调声.鸟鸣蝉(Meimuna opalifera (Walk)var.formosana Kato)的自然鸣声由重复的“jiū…ruǎ”和“jiū…gū…”合成的双变调复合声.“jiū”为基频和主频分别约625Hz和2100—2300Hz的准单音;“ruǎ”的波形和主音频呈明显的演变,基音和优势主频分别约575—625Hz和1550—1750Hz的变音调声.“gū”为优势主频约625Hz的准单音.变音调复合声不仅与腹部运动有关,而主要取决于发声肌的收缩特性和发声膜肋结构的振动特性.     

Optimal foot shape for a passive dynamic biped

Passive walking dynamics describe the motion of a biped that is able to "walk" down a shallow slope without any actuation or control. Instead, the walker relies on gravitational and inertial effects to propel itself forward, exhibiting a gait quite similar to that of humans. These purely passive models depend on potential energy to overcome the energy lost when the foot impacts the ground. Previous research has demonstrated that energy loss at heel-strike can vary widely for a given speed, depending on the nature of the collision. The point of foot contact with the ground (relative to the hip) can have a significant effect: semi-circular (round) feet soften the impact, resulting in much smaller losses than point-foot walkers. Collisional losses are also lower if a single impulse is broken up into a series of smaller impulses that gradually redirect the velocity of the center of mass rather than a single abrupt impulse. Using this principle, a model was created where foot-strike occurs over two impulses, "heel-strike" and "toe-strike," representative of the initial impact of the heel and the following impact as the ball of the foot strikes the ground. Having two collisions with the flat-foot model did improve efficiency over the point-foot model. Representation of the flat-foot walker as a rimless wheel helped to explain the optimal flat-foot shape, driven by symmetry of the virtual spoke angles. The optimal long period foot shape of the simple passive walking model was not very representative of the human foot shape, although a reasonably anthropometric foot shape was predicted by the short period solution.     

Effects of size on vervet (Cercopithecus aethiops) gait parameters: a longitudinal approach

Changes in the values of certain locomotor parameters were analyzed over a range of speeds for five immature vervet monkeys sampled at 6 month intervals over approximately a 3 year period. Lateral and diagonal sequence walking gaits and transverse and rotary gallops were commonly used. The monkeys switched from walking to galloping at long cycle durations for their mass, although, as a group, their transition speeds were in agreement with data from other mammals. However, for individual monkeys, transition speed was not consistently dependent on body mass. Cycle and stance durations generally increased with increasing size at each speed for each animal, with the greatest increases occurring at slower speeds. Swing durations increased slightly with size. For any particular individual, speed was highly predictable from cycle (or stance) duration and body mass (or age). However, the multiple regression equations for each animal were significantly different from each other, suggesting that no single equation is satisfactory for all of the individuals within a species.     

The effects of alignment of an articulated ankle-foot orthosis on lower limb joint kinematics and kinetics during gait in individuals post-stroke

Mechanical tuning of an ankle-foot orthosis (AFO) is important in improving gait in individuals post-stroke. Alignment and resistance are two factors that are tunable in articulated AFOs. The aim of this study was to investigate the effects of changing AFO ankle alignment on lower limb joint kinematics and kinetics with constant dorsiflexion and plantarflexion resistance in individuals post-stroke. Gait analysis was performed on 10 individuals post-stroke under four distinct alignment conditions using an articulated AFO with an ankle joint whose alignment is adjustable in the sagittal plane. Kinematic and kinetic data of lower limb joints were recorded using a Vicon 3-dimensional motion capture system and Bertec split-belt instrumented treadmill. The incremental changes in the alignment of the articulated AFO toward dorsiflexion angles significantly affected ankle and knee joint angles and knee joint moments while walking in individuals post-stroke. No significant differences were found in the hip joint parameters. The alignment of the articulated AFO was suggested to play an important role in improving knee joint kinematics and kinetics in stance through improvement of ankle joint kinematics while walking in individuals post-stroke. Future studies should investigate long-term effects of AFO alignment on gait in the community in individuals post-stroke.     

Concurrent validity of the Microsoft Kinect for assessment of spatiotemporal gait variables

Spatiotemporal characteristics of gait such as step time and length are often associated with overall physical function in clinical populations, but can be difficult, time consuming and obtrusive to measure. This study assessed the concurrent validity of overground walking spatiotemporal data recorded using a criterion reference – a marker-based three-dimensional motion analysis (3DMA) system – and a low-cost, markerless alternative, the automated skeleton tracking output from the Microsoft Kinect™ (Kinect). Twenty-one healthy adults performed normal walking trials while being monitored using both systems. The outcome measures of gait speed, step length and time, stride length and time and peak foot swing velocity were derived using supervised automated analysis. To assess the agreement between the Kinect and 3DMA devices, Bland–Altman 95% bias and limits of agreement, percentage error, relative agreement (Pearson's correlation coefficients: r) overall agreement (concordance correlation coefficients: r_c) and landmark location linearity as a function of distance from the sensor were determined. Gait speed, step length and stride length from the two devices possessed excellent agreement (r and r_c values >0.90). Foot swing velocity possessed excellent relative (r=0.93) but only modest overall (r_c=0.54) agreement. Step time (r=0.82 and r_c=0.23) and stride time (r=0.69 and r_c=0.14) possessed excellent and modest relative agreement respectively but poor overall agreement. Landmark location linearity was excellent (R²=0.991). This widely available, low-cost and portable system could provide clinicians with significant advantages for assessing some spatiotemporal gait parameters. However, caution must be taken when choosing outcome variables as some commonly reported variables cannot be accurately measured.     

Optimal shear cushion stiffness at different gait speeds

The present study quantified the effects of different shear cushion stiffness on the time to peak posterior shear force (TPPSF), peak posterior shear force (PPSF), average posterior loading rate (APLR), and maximum posterior loading rate (MPLR) at different locomotion speeds using a custom-made sliding platform, as well as to identify the optimal stiffness of shear cushion. Twelve male collegiate students (heel-strikers) performed walking at 1.5 m/s, jogging at 2.5 m/s, and running at 3.5 m/s. A custom-made sliding platform was used to provide the different shear cushion conditions. The shear cushion conditions were fixed (a fixed platform; control group), stiff (K = 2746 N/m), medium stiff (K = 2256 N/m), medium soft (K = 1667 N/m), and soft (K = 1079 N/m). The results showed that all cushion conditions produced sliding displacement and delayed the TPPSF during walking, jogging, and running compared with fixed condition. The APLR and MPLR were lowest under medium soft condition during walking, while the PPSF was similar between medium soft and soft conditions. For jogging and running, the PPSF as well as APLR and MPLR were the lowest under medium stiff condition except the maximum PLR was similar among stiff, medium stiff, and medium soft conditions during running. In conclusion, shear cushion produces appropriate sliding displacement and effectively delays the TPPSF to provide the musculoskeletal system additional time to absorb the impact and reduce loading. The present study demonstrates optimal stiffness of shear cushion at different traveling speeds and suggests that a shear cushion system can be applied in future designs of cushion structures.     

Know when to walk away: contingent movement and the evolution of cooperation

Models of the evolution of cooperation suggest that an important characteristic of successful strategies is the ability to respond contingently to the social environment. A number of mechanisms by which this can be accomplished have been suggested, some of which require relatively complex information processing systems. This research explores relaxing the requirements on information processing while preserving the evolvability of a cooperative strategy. The agent-based computer simulations reported here show that 'Walk Away,' a behavioral rule of extremely limited complexity (move after partner defects), can outperform more complex strategies under a number of conditions. Previous simulations of exit strategies have not examined the effect of implicit and explicit movement costs, different error rates, or the simultaneous presence of TFT and PAVLOV. The simulations reported here establish that the Walk Away strategy resists invasion and can invade a population of defectors at a lower initial frequency than any other strategy. The Walk Away strategy was successful, despite its simplicity, because it exploited aspects of the physical and social environment.     

Confidence Intervals and Tests of Hypotheses on Variance Components in an Unbalanced Two-fold Nested Design

Confidence intervals and tests of hypotheses on variance components are required in studies that employ a random effects design. The unbalanced random two-fold nested design is considered in this paper and confidence intervals are proposed for the variance components σ2/A and σ2/B. Computer simulation is used to show that even in very unbalanced designs, these intervals generally maintain the stated confidence coefficient. The hypothesis test for σ2/A based on the lower bound of the recommended confidence interval is shown to be better than previously proposed approximate tests.     

一类具有随机周期移民扰动的非线性人口发展方程随机周期解的存在唯一性

本文给出了一类具有随机周期移民扰动的非线性m增生人口发展方程随机周期解的存在性和唯一性结论。     

应用随机PCR方法鉴定一株真养产碱杆菌

采用随机引物PCR技术从新建细胞培养室空气中获得一段长414bp的片段,通过克隆测序及序列分析,结果表明所测序列与真养产碱杆菌主要参考菌株的同源性分别高达79%-83%,由其推导的氨基酸序列与真养产碱杆菌主要参考菌株的同源性高达86.4%-89.1%,从而确定所分离菌株为真养产碱杆菌。     

Mean Figures and Mean Shapes Applied to Biological Figure and Shape Distributions in the Plane

Fundamental propositions for mean figures and mean shapes in the plane are proved by using complex numbers. A test of equality of two figure or shape distributions is introduced and applied to data from larvae of mussels and from saurian heads.     

Hadamard randomization: a valid restriction of random permuted blocks

Random permuted blocks can result in treatment imbalance if entry to the trial stops in mid‐block. This paper presents a restriction of this method of randomization. The restriction avoids severe treatment imbalance but gives unbiased estimators of the treatment difference and its variance.     

ENSO事件的发生对马尾松毛虫发生的影响

迈过对２０多年来ＥＮＳＯ事件的发生与马尾松毛虫发生关系的研究．探讨全球气侯异常对马尾松毛虫发生和种群发展动态的影响．结果表明：在厄尔尼诺或反厄尔尼诺事件的当年,连江县马尾松毛虫书为中到大发生年;南方涛动｜ΣＳＯＩ｜≤０．９的当年,为马尾松毛虫大发生年;在南方涛动０．９＜｜ΣＳＯＩ｜＜１．９的当年,为马尾松毛虫轻发生年．     

应用抗病毒抗体表位筛选的多肽文库的构建

1985年,Sndth在《科学》杂志上提出构建"融合噬菌体",即在这种丝状病毒的包膜蛋白上表达融合蛋白[1]．1990年,Scott和Smith山利用这种表面表达载体建立了随机多肽文库,可以很方便地筛选出抗体及其他功能蛋白的强结合配基[2]．我们建立了十二肽的随机多肽库,将从中筛选出抗HIV-gP160抗体的抗独特型多肽．1材料和方法1．1质粒、菌株和培养墓噬菌粒成h血四、大肠杆菌XLI-Blue和辅助噬菌体VCSM13由军事医学科学院微生物流行病研究所王海涛教授惠赠．SB液体培养基：30gtmptone,20g酵母膏,10gMops溶于IL去离子水中,调pH7．0．枝…     

Prediction of multi-locus inbreeding coefficients and relation to linkage disequilibrium in random mating populations

An algorithm to predict the level of identity by descent simultaneously at multiple loci is presented, which can in principle be extended to any number of loci. The model assumes a random mating population, with random association of haplotypes. The relationship is shown between coefficients of multi-locus identity or non-identity by descent and moments of multi-locus linkage disequilibrium. Thus, these moments can be computed from the multilocus identity or, using algorithms derived previously to predict the disequilibria moments, vice-versa. The results can be applied to predict multi-locus identity in, for example, gene mapping.