Engineering complex dynamical structures: sequential patterns and desynchronization

We used phase models to describe and tune complex dynamic structures to desired states; weak, nondestructive signals are used to alter interactions among nonlinear rhythmic elements. Experiments on electrochemical reactions on electrode arrays were used to demonstrate the power of mild model-engineered feedback to achieve a desired response. Applications are made to the generation of sequentially visited dynamic cluster patterns similar to reproducible sequences seen in biological systems and to the design of a nonlinear antipacemaker for the destruction of pathological synchronization of a population of interacting oscillators.     

Cis-acting regulatory variation in the human genome

The systematic screening of the human genome for genetic variants that affect gene regulation should advance our fundamental understanding of phenotypic diversity and lead to the identification of alleles that modify disease risk. There are several challenges in localizing regulatory polymorphisms, including the wide spectrum of cis-acting regulatory mechanisms, the inconsistent effects of regulatory variants in different tissues, and the difficulty in isolating the causal variants that are in linkage disequilibrium with many other variants. We discuss the current state of knowledge and technologies used for mapping and characterizing genetic variation controlling human gene expression.     

Microcephalin, a gene regulating brain size, continues to evolve adaptively in humans

The gene Microcephalin (MCPH1) regulates brain size and has evolved under strong positive selection in the human evolutionary lineage. We show that one genetic variant of Microcephalin in modern humans, which arose approximately 37,000 years ago, increased in frequency too rapidly to be compatible with neutral drift. This indicates that it has spread under strong positive selection, although the exact nature of the selection is unknown. The finding that an important brain gene has continued to evolve adaptively in anatomically modern humans suggests the ongoing evolutionary plasticity of the human brain. It also makes Microcephalin an attractive candidate locus for studying the genetics of human variation in brain-related phenotypes.     

The limitations of a cut leaf test for assessing the frost resistance of the tuber-bearing solanums

On the basis of physiological work, a cut leaf test was developed by which the frost resistances of a range of the tuber-bearing Solanums were determined. The test, enabling the resistances of thirty cut leaves to be tested during each freeze, was so designed that any variations, which might have arisen from different levels of supercooling, were avoided. During the tests prechilled material was cooled, at a rate of 2°C/hour, to a desired temperature. At this limit the temperature was held constant until the material had been below 0°C for a period of six hours. A rapid thaw was then given and the percentage injuries of the leaves were estimated after a period of recovery. After a number of tests, at temperatures from-2 to-6°C, a numerical value, the frost killing temperature was given to each plant.The use of the test is limited, for it was shown that the resistances of a chronological series of leaves vary considerably; greatest resistance is present in the central leaves. The ranges of resistance shown by identically genetical plants is considerable; such variation might be reduced by means of controlled growth conditions.The effect of the rate of thawing upon subsequent injury was also investigated. No appreciable differences between rapidly and slowly warmed leaves were apparent, yet the latter treatment produced greater uniformity in the rise and fall of resistance as the leaf passes from youth to maturity.     

天津市种植业现代化的对策研究

经济体制改革以来,天津农业、农村经济社会有了长足发展,提前完成了党中央提出的第二步战略发展目标,基本实现小康,为农业、农村现代化建设提供了良好的经济社会环境、物质基础和物质技术条件。为落实党的十五届三中全会 决定 和江泽民同志关于 沿海发达地区要率先基本实现农业现代化"的指示精神,本文仅就天津种植业现代化的对策谈点粗浅看法。基本思路是:在加大政府组织推动和扶持力度的同时,采取 一个稳定、二个加大、三个完善、四个提高"的综合对策措施,整体推进种植业现代化进程     

Seroprevalence of Coxiella burnetii in selected populations of domestic ruminants in Newfoundland

The seroprevalence of Coxiella burnetii among cattle, sheep, and goats in Newfoundland was determined by microimmunofluorescence. Seropositivity to phase II antigen increased in sheep from 3.1% in 1997 to 23.5% in 1999-2000 (P < 0.001). Cows (24%) had antibodies to phase I antigen; goats (15.6%) had antibodies to phase II antigen. Seroprevalence of C. burnetii is increasing among sheep.     

Release of bromide following rewetting of a naturally drained acid gully mire

Abstract. Currently there is growing interest in the restoration of drained peatlands in Britain. In order to investigate some of the effects of changes in land management practices on the biogeochemistry of peatlands, a field experiment was designed to manipulate the hydrological conditions in a naturally drained acid gully mire in Mid-Wales. We report preliminary results of the effects of experimentally rewetting the mire on the hydrochemistry of bromide in the peat-water. Results show that rewetting had a dramatic effect on the concentrations of bromide, which increased substantially. Peak values approached 1 mg/dm³ in some samples following rewetting, compared with typical values < 0.05 mg/dm³ under the drained conditions. Bromide was positively and significantly correlated with Dissolved Organic Carbon (DOC) in the peat-water, which suggests that Br^- is derived from breakdown of organic matter in the reducing conditions following rewetting. The bromide mobilized by rewetting may be leached out of the system and/or re-assimilated by the wetland vegetation. Further monitoring is needed to determine whether the observed hydrochemical response of bromide to rewetting of the mire has any longer-term effects.     

COLOR FLOW DOPPLER IMAGING AND DOPPLER SPECTRAL ANALYSIS OF THE BRAIN OF NEONATAL DOGS

Doppler ultrasonography was performed on the cerebral arteries o f 19 neontal dogs.Vascular structures were identified using anatomic preparations of brains pre-injected with a radiopaque silicone rubber product and cleared using a modified tissue clearing technique. Brain sections were subsequently radiographed of examined under a steromicroscope. Color flow Doppler imagin was used to facilitate positioning of the Doppler calipers for measurement of peak systolic velocity, minimum diastolic velocity, and resistance index. Blood flow velocities in the internal carotid and middle cerebral arteries were lower when measured intransvere images than in sagittal images. The rostral cerebral arteries could be measured using either plane but values obtained from different locations or using different methods of measurement were statistically different. Blood flow velocities generally increased during the first month after birth. Arterial signals were diphasic with flow throughout diastole. Resistance indices most often were between 0.6 and 0.7 and did not exceed 0.86.