Computational approaches to motor control.

This review will focus on four areas of motor control which have recently been enriched both by neural network and control system models: motor planning, motor prediction, state estimation and motor learning. We will review the computational foundations of each of these concepts and present specific models which have been tested by psychophysical experiments. We will cover the topics of optimal control for motor planning, forward models for motor prediction, observer models of state estimation arid modular decomposition in motor learning. The aim of this review is to demonstrate how computational approaches, as well as proposing specific models, provide a theoretical framework to formalize the issues in motor control.

水飞蓟原生质体培养形成愈伤组织及组织培养再生植株

本论文对药用植物水飞蓟Silybum marianum Gaertn 进行了原生质体培养和组织培养的研究，获得如下结果： 1、以水飞蓟叶片愈伤组织为材料，系统地研究了植物材料生理状态，酶液配比及酶的浓度、酶解时间长短等对原生质体产率的影响。探讨了原生质体培养过程中材料的生理状态、激素、附加物及培养方法对于原生质体分裂频率的影响，还比较分析了培养后期不加液及加各种细胞培养液对原生质体来源的细胞团的影响，最后进行了愈伤组织分化的诱导。选取继代一年的水飞蓟叶愈伤组织转代十天后挑选愈伤组织表面生长旺盛的细胞层置于Onozuka R-103% Macerozyme R-10 0.8%的CPW混合酶液（PH 5.6～5.3）中，30℃下酶解5小时后所得原生质体产率最高。适合于水飞蓟原生质体培养的基本培养基为TCCW烟草原生质体培养基~[18]。用低融点琼脂糖（0.3%）平板培养法培养得到的分裂频率显著高于液体浅层法。在培养基中加入羟脯氨酸（100mg/l）和谷氨酰胺（200mg/l）可促进原生质体分裂。在飞蓟原生质体培养中能获得最高分裂频率（35.4%）的激素组合为2.4-D、1mg/l Kn0.5mg/l。在培养过程中每隔二周必须加液，否则细胞团褐化并全部死亡，同时要求降低细胞培养液的Kn浓度（由0.5mg/l、降到0.1mg/l）才能使细胞团继续长大。从水飞蓟原生质体培养得到的愈伤组织色浅黄，结构疏松，转至MS附加NAA0.8mg/l、6－BA 2mg/l、水解酪蛋白200mg/l的固体培养基上愈伤组织表面出现许多绿色芽点，但尚未得到再生植株。 2、以萌发两周后的水飞蓟种子无菌苗为材料，切取下胚轴于MS附加NAA0.8mg/l、6－BA0.5mg/l、水解酪蛋白200mg/l的固体培养基上诱导出愈伤组织，再转入MS附加NAA0.8mg/l、6－BA2mg/l、水解酪蛋白200mg/l的分化培养基后，愈伤组织表面分化出芽，再生苗的频率为75%，然后移至MS附加NAA0.5mg/l、IBA0.1mg/l、水解酪蛋白200mg/l的培养基上分化出大量的根，并得到了大量健壮的植株。

Trends in counts of manatees Trichechus manatus latirostris from 1987 to 2006 in waters of Sarasota County, Florida, USA

To demonstrate the utility of distributional surveys for assessing relative abundance and trends in counts for a discrete area of coastline, aerial survey data from Sarasota County, Florida, USA, were analyzed for the years 1987 to 2006. The study area was divided into 3 regions: the Sarasota Bay Region (SBR; N = 353 surveys), Lemon Bay (N = 368), and the Myakka River (N = 209). Manatee counts varied significantly across seasons (p < 0.0001) for all 3 regions. Manatees within Sarasota County utilized open bays primarily in the warmer months. Such usage may have been influenced by resource availability. Conversely, usage of the Myakka River peaked in winter months when manatees seek warm-water refugia such as Warm Mineral Spring. Marginal means for yearly counts within Lemon Bay and the SBR increased significantly, beginning midway through the survey period (1996) until the early 2000s. In contrast, mean yearly counts within the Myakka River decreased over this time period. After record lows in 2003 for Lemon Bay and the Myakka River, and a considerable decline in 2004 for the SBR, mean yearly counts for all 3 regions showed an increasing trend over the remaining 2 yr of the study. Greater protection of manatee habitat and availability of forage coincided with the increase in numbers of manatees using Sarasota County waters during the 1990s, and the subsequent decline in numbers may be indicative of the increase in mortality in recent years due to watercraft collisions and severe red tide events.

Age and growth estimates of the winter skate (Leucoraja ocellata) in the western Gulf of Maine

Age and growth estimates for the winter skate (Leucoraja ocellata) were estimated from vertebral band counts on 209 fish ranging in size from 145 to 940 mm total length (TL). An index of average percent error (IAPE) of 5.8% suggests that our aging method represents a precise approach to the age assessment of L. ocellata. Marginal increments were significantly different between months (Kruskal-Wallis P<0.001) and a distinct trend of increasing monthly increment growth began in July. Estimates of von Bertalanffy growth parameters suggest that females attain a slightly larger asymptotic TL (L∞=1374 mm) than males (L∞=1218 mm) and grow more slowly (k=0.059 and 0.074, respectively). The oldest ages obtained for the winter skate were 19 years for males and 18 years for females, which corresponded to total lengths of 932 mm and 940 mm, respectively. The results indicate that the winter skate exhibits the characteristics that have made other elasmobranch populations highly susceptible to exploitation by commercial fisheries.

Recruitment season, size, and age of young American eels (Anguilla rostrata) entering an estuary near Beaufort, North Carolina

Net catches from 1985–86 to 1994–95 at Pivers Island, North Carolina, indicated that glass-eel stage American eels (Anguilla rostrata) were recruited to the estuary from November to early May, with peak numbers in January, February, and March. There was no declining trend in recruitment over the years of sampling. Except for one year, there was no clear seasonal decrease in mean length. But shorter glass eels were older than longer glass eels, as judged by age within the glass eel growth zone of the otolith, suggesting that smaller fish took longer to arrive. The mean age of glass eels collected from the lower estuary and a freshwater site 9.5 km upriver differed by 8.4 d (36.2 vs. 44.6, respectively). Outer increments (30–35) of the otolith growth zone of glass eels from North Carolina were significantly wider than corresponding increments of otoliths from New Brunswick. Mean total ages of North Carolina, New Jersey, and New Brunswick elvers were 175.4, 201.2, and 209.3 d, corresponding to mean lengths of 55.9, 60.9, and 58.1 mm TL, respectively. The mean durations of glass-eel growth zones (44.6, 62.3, and 69.8) were in close agreement with those from previous studies, but total ages were not. This suggested that perhaps some finer (leptocephalus stage) increments were not detected by light microscopy, differences occurred in seasonal increment deposition, or absorption of the otolith material may have taken place during metamorphosis, rendering the aging of larvae inaccurate. Judging from the long recruitment period and seasonal uniformity in both mean age and length found in our study, the spawning period of American eels may be somewhat more protracted than previously considered.

Atmospheric circulation patterns associated with tree growth anomalies in the central and southern Sierra Nevada mountains [abstract]

EXTRACT (SEE PDF FOR FULL ABSTRACT): In this work, I examine patterns of atmospheric circulation associated with tree growth anomalies at mid-to-high latitudes (2000-3500 meters).