Cell interactions in the sea urchin embryo studied by fluorescence photoablation

In many organisms, interactions between cells play a critical role in the specification of cell fates. In the sea urchin embryo, primary mesenchyme cells (PMCs) regulate the developmental program of a subpopulation of secondary mesenchyme cells (SMCs). The timing of this cell interaction was analyzed by means of a fluorescence photoablation technique, which was used to specifically ablate PMCs at various stages of development. In addition, the PMCs were microinjected into PMC-depleted recipient embryos at different developmental stages and their effect on SMC fate was examined. The critical interaction between PMCs and SMCs was brief and took place late in gastrulation. Before that time, SMCs were insensitive to the suppressive signals transmitted by the PMCs.     

Potato late blight caused by Phytophthora infestans: From molecular interactions to integrated management strategies

Over 170 years after the infamous Irish Potato Famine,potato late blight (PLB) caused by Phytophthora infestans remains the single most devastating disease of global potato production,causing up to 10 billion USD in yield loss and management costs.Through decades of research,growers and agronomists in the?eld as well as laboratory scientists have made signi?cant progress in understanding the molecular pathogenesis process of this critical pathosystem and effective management strategies to contro...     

Venus: mapping the surface reflectivity by radar interferometry

The surface reflectivity of Venus obtained by radar interferometry at a wavelength of 3.8 centimeters has been mapped for a region extending approximately from -80 degrees to 0 degrees in longitude (Carpenter's definition) and from -50 degrees to +40 degrees in latitude. The map is free from the twofold range-Doppler ambiguity because the interferometer fringe pattern makes possible the separation of two points of equal range and Doppler shift. The map presents many new features and clearly delineates features already observed. Most notably, the map shows large circular regions of significantly lower reflectivity than their surroundinigs.     

Wind velocities on venus: vector determination by radio interferometry

To determine the wind directions and speeds on Venus, as each Pioneer probe fell to the surface we tracked its motion in three dimensions using a combination of Doppler and long-baseline radio interferometric methods. Preliminary results from this tracking, coupled with results from test observations of other spacecraft, enable us to estimate the uncertainties of our eventual determinations of the velocity vectors of the probes with respect to Venus. For altitudes below about 65 kilometers and with time-averaging over 100-second intervals, all three components of the velocity should have errors of the order of 0.3 meter per second or less.     

A magnetic nanoprobe technology for detecting molecular interactions in live cells

Technologies to assess the molecular targets of biomolecules in living cells are lacking. We have developed a technology called magnetism-based interaction capture (MAGIC) that identifies molecular targets on the basis of induced movement of superparamagnetic nanoparticles inside living cells. Efficient intracellular uptake of superparamagnetic nanoparticles (coated with a small molecule of interest) was mediated by a transducible fusogenic peptide. These nanoprobes captured the small molecule's labeled target protein and were translocated in a direction specified by the magnetic field. Use of MAGIC in genome-wide expression screening identified multiple protein targets of a drug. MAGIC was also used to monitor signal-dependent modification and multiple interactions of proteins.     

Identification of diapause-associated proteins in migratory locust,Locusta migratoria L. (Orthoptera: Acridoidea) by label-free quantification analysis

Maternal photoperiodic response is a key factor that affects offspring diapause in migratory locust, Locusta migratoria L. (Orthoptera: Acridoidea). Although many aspects of insect diapause have been studied, little is known about the molecular mechanisms of maternal photoperiodic response that influence diapause regulation. To gain insight into the possible mechanisms of maternal photoperiod influence on diapause regulation, proteomics data by label-free quantification analysis were generated from non-diapause and diapause eggs. A total of 175 proteins were differentially expressed between diapause and non-diapause eggs. Among them, 24 proteins were upregulated, and 151 proteins were downregulated. Gene Ontology (GO) analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichments were performed on all differentially expressed proteins (DEPs) and showed that peroxisome, insect hormone biosynthesis, and longevity regulating pathway may be related to diapause of migratory locust. Furthermore, we used qRT-PCR to verify some results of the proteomic analysis. Proteins such as hexamerin-like protein 4, juvenile hormone epoxide hydrolase 1 (JHEH1), cytochrome P450 and heat shock protein (HSP) 20.7 were predicted to be involved in diapause. This study provides an important reference for future research that will explore the mechanisms of diapause induced by maternal effects in migratory locust.     

Transcontinental baselines and the rotation of the Earth measured by radio interferometry

Nine separate very-long-baseline interferometry (VLBI) experiments, carried out in 1972 and 1973 with radio telescopes 3900 kilometers apart, yielded values for the baseline length with a root-mean-square deviation about the mean of less than 20 centitneters. The corresponding fractional spread is about five parts in 10(8). Changes in universal time and in polar motion were also detertnined accurately from these data; the root-mean-square scatter of these results with respect to those based on optical methods were 2.9 milliseconds and 1.3 meters, respectively. Solid-earth tides were apparently detected, but no useful estimate of their amplituide was extracted.     

Real-time, very-long-baseline interferometry based on the use of a communications satellite

The Hermes satellite, a joint Canadian-American program, has been used to provide a communication channel between radio telescopes in West Virginia and Ontario, for very-long-baseline interferometry (VLBI). This system makes possible instantaneous correlation of the data as well as a sensitivity substantially better than that of earlier VLBI systems, by virtue of a broader observational bandwidth. With the use of a geostationary communications satellite it is possible to eliminate the tape recorders and the most troublesome part of the postobservational data processing. A further possibility is the development of a phase-coherent interferometer.     

Spectral line interferometry with independent time standards at stations separated by 845 kilometers

An upper limit of 0.02 second of arc has been determined for a hydroxyl radical (OH) emission region associated with the radio source W3, with the use of a Michelson interferometer consisting of two radio telescopes 845 kilometers apart. Timing was provided at the stations by independent atomic frequency standards. The 1665-megahertz radiation was translated to video frequency and recorded digitally on magnetic tapes which were later processed by computer, yielding fringe phase and amplitude as a function of frequency over the received bandwidth.     

A reversible, unidirectional molecular rotary motor driven by chemical energy

With the long-term goal of producing nanometer-scale machines, we describe here the unidirectional rotary motion of a synthetic molecular structure fueled by chemical conversions. The basis of the rotation is the movement of a phenyl rotor relative to a naphthyl stator about a single bond axle. The sense of rotation is governed by the choice of chemical reagents that power the motor through four chemically distinct stations. Within the stations, the rotor is held in place by structural features that limit the extent of the rotor's Brownian motion relative to the stator.     

Localization, interactions, and the metal-insulator transition

Recent advances in our understanding of electronic conduction have pointed up deficiencies in traditional thinking. For a metal at a sufficiently low temperature, it is known both theoretically and experimentally that the conventional picture in terms of the Boltzmann theory breaks down. Improved understanding of both electron localization and the effects of electron-electron interactions in a disordered medium has led to experimentally verifiable predictions. These effects have an important influence on the nature of the metal-insulator transition.     

Blood pressure responses of wild giraffes studied by radio telemetry

Blood pressure was telemetered from transducers chronically implanted in the carotid arteries of two adult, wild, male giraffes captured and released near Kiboko, Kenya. Cerebral perfusion pressure ranged from 280/180 mm-Hg while the animal was lying with its head on the ground to 125/75 mm-Hg when it was standing erect; it varied between these levels during spontaneous activity such as walking, grazing, and running.     

氮吸附法分析生物质焦孔隙结构

采用氮吸附法对4种生物质焦(稻壳、树叶、玉米秆、棉花秆)的孔隙结构进行测量,结果表明,不同种类焦样的比表面积和孔径分布有明显差别,树叶的比表面积最大,为242.21 m2·g-1,玉米秆的比表面积最小,为0.81 m2·g-1.850℃时,稻壳、树叶、玉米秆焦样的孔径分布曲线在微孔和中孔范围各有一个分布峰,而棉花秆焦样的孔径分布曲线只在中孔范围内出现一个分布峰.热解温度是影响孔隙结构的一个重要因素,在高温条件下,同步热解得到的焦样的比表面积较大,微孔较多.在本研究中,600℃、850℃的稻壳焦样和850℃的树叶焦样具有较大的比表面积,比较适合做吸附剂.     

Electronic structure of mott insulators studied by inelastic X-ray scattering

The electronic structure of Mott insulators continues to be a major unsolved problem in physics despite more than 50 years of research. Well-developed momentum-resolved spectroscopies such as photoemission or neutron scattering cannot probe the full Mott gap. High-resolution resonant inelastic x-ray scattering revealed dispersive charge excitations across the Mott gap in a high-critical temperature parent cuprate (Ca(2)CuO(2)Cl(2)), shedding light on the anisotropy of the Mott gap. These charge excitations across the Mott gap can be described within the framework of the Hubbard model.     

DNA conformation, dynamics, and interactions in solution

The conformation and dynamics of the d(CGCGAATTCGCG) duplex, its analogs containing mismatched base pairs and helix interruptions, and its complexes with actinomycin and Netropsin, bound separately and simultaneously, have been investigated by nuclear magnetic resonance spectroscopy in aqueous solution. Structural information has been deduced from chemical shift and nuclear Overhauser effect parameters, while the kinetics have been probed from line width and saturation recovery experiments on proton and phosphorus markers at the individual base pair level. These studies lead to an improved understanding of the role of nucleic acid sequence on the structure, flexibility, and conformational interconversions in the duplex state. The nuclear magnetic resonance measurements readily identify helix modification and antibiotic binding sites on the nucleic acid and estimate the extent to which the observed conformational and dynamic perturbations are transmitted to adjacent base pair regions.     

利用核磁共振技术研究热处理中密度纤维板的吸水性

基于时域核磁共振技术,对3个热处理温度(120、170和220℃)下MDF(中密度纤维板)的吸水性进行了研究,并利用X射线衍射技术,辅助揭示不同样品吸水性差异的机理。结果表明,170℃处理MDF吸水过程中吸水率、自由水和结合水含量最低;220℃热处理MDF的纤维素结晶区被破坏,原有的空隙结构被改变,吸水率、自由水和结合水含量最高。     

Coherent atomic motions in a nanostructure studied by femtosecond X-ray diffraction

Reversible structural changes of a nanostructure were measured nondestructively with subpicometer spatial and subpicosecond temporal resolution via x-ray diffraction (XRD). The spatially periodic femtosecond excitation of a gallium arsenide/aluminum gallium arsenide superlattice results in coherent lattice motions with a 3.5-picosecond period, which was directly monitored by femtosecond x-ray pulses at a 1-kilohertz repetition rate. Small changes (DeltaR/R = 0.01) of weak Bragg reflexes (R = 0.005) were detected. The phase and amplitude of the oscillatory XRD signal around a new equilibrium demonstrate that displacive excitation of the zone-folded acoustic phonons is the dominant mechanism for strong excitation.     

镁、锰、活性炭和石灰及其交互作用对小麦镉吸收的影响

采用盆栽试验,研究了在镉污染土壤上施用石灰、硫酸镁、硫酸锰和活性炭不同用量以及交互作用对小麦生长和吸收重金属镉的影响。研究结果表明,在试验条件下施用适量的硫酸镁、硫酸锰或与石灰配合能明显提高小麦籽粒产量,单施石灰或与活性炭配合施用降低了小麦籽粒产量;与对照(CK)相比, 所有处理秸秆产量均下降。施用硫酸镁能显著降低小麦籽粒和秸秆中Cd浓度,且随用量的增加而增大。低量硫酸锰能有效降低小麦籽粒和秸秆中Cd浓度,高量反而增加小麦对Cd的吸收。石灰、活性炭单独施用或配合施用都能明显减少小麦对Cd的吸收,但籽/杆中Cd比却随石灰用量的增加呈明显的上升趋势。叶面喷施硫酸镁对降低小麦吸收镉的效果与土施相当,但叶面喷施硫酸锰却比土施硫酸锰显著降低了小麦籽粒中的镉浓度与吸收量。硫酸镁与硫酸锰,或石灰、硫酸镁和硫酸锰3种物质配合施用,对小麦籽粒镉浓度和吸收量的降低表现出明显的正交互作用,对抑制小麦体内镉从秸秆向籽粒的转移具有显著效果。