Carrier-envelope phase control of femtosecond mode-locked lasers and direct optical frequency synthesis

We stabilized the carrier-envelope phase of the pulses emitted by a femtosecond mode-locked laser by using the powerful tools of frequency-domain laser stabilization. We confirmed control of the pulse-to-pulse carrier-envelope phase using temporal cross correlation. This phase stabilization locks the absolute frequencies emitted by the laser, which we used to perform absolute optical frequency measurements that were directly referenced to a stable microwave clock.     

Bright coherent ultrahigh harmonics in the keV x-ray regime from mid-infrared femtosecond lasers

High-harmonic generation (HHG) traditionally combines ~100 near-infrared laser photons to generate bright, phase-matched, extreme ultraviolet beams when the emission from many atoms adds constructively. Here, we show that by guiding a mid-infrared femtosecond laser in a high-pressure gas, ultrahigh harmonics can be generated, up to orders greater than 5000, that emerge as a bright supercontinuum that spans the entire electromagnetic spectrum from the ultraviolet to more than 1.6 kilo-electron volts, allowing, in principle, the generation of pulses as short as 2.5 attoseconds. The multiatmosphere gas pressures required for bright, phase-matched emission also support laser beam self-confinement, further enhancing the x-ray yield. Finally, the x-ray beam exhibits high spatial coherence, even though at high gas density the recolliding electrons responsible for HHG encounter other atoms during the emission process.     

Self-mode-locking of quantum cascade lasers with giant ultrafast optical nonlinearities

We report on the generation of picosecond self-mode-locked pulses from midinfrared quantum cascade lasers, at wavelengths within the important molecular fingerprint region. These devices are based on intersubband electron transitions in semiconductor nanostructures, which are characterized by some of the largest optical nonlinearities observed in nature and by picosecond relaxation lifetimes. Our results are interpreted with a model in which one of these nonlinearities, the intensity-dependent refractive index of the lasing transition, creates a nonlinear waveguide where the optical losses decrease with increasing intensity. This favors the generation of ultrashort pulses, because of their larger instantaneous intensity relative to continuous-wave emission.     

Femtosecond pulse sequences used for optical manipulation of molecular motion

Optical control over elementary molecular motion is enhanced with timed sequences of femtosecond (10(-15) second) pulses produced by pulse-shaping techniques. Appropriately timed pulse sequences are used to repetitively drive selected vibrations of a crystal lattice, in a manner analogous to repetitively pushing a child on a swing with appropriate timing to build up a large oscillation amplitude. This process corresponds to repetitively "pushing" molecules along selected paths in the lattice. Amplification of selected vibrational modes and discrimination against other modes are demonstrated. Prospects for more extensive manipulation of molecular and collective behavior and structure are clearly indicated.     

马铃薯芽粗提物对粘虫的作用方式研究

试验采用虫体浸渍法研究了‘庄薯3号’马铃薯在有光照和无光照条件下生芽经不同极性溶剂提取所得粗提物对粘虫5龄幼虫的杀虫作用.结果表明:有光、无光鲜芽、干芽用不同极性溶剂提取,以无光干芽乙酸乙酯粗提物对粘虫幼虫的触杀作用为最强,稀释5倍液的校正死亡率可达52.0%;无光干芽丙酮粗提物具有较强的触杀作用,粘虫校正死亡率为18.67%;有光干芽甲醇粗提物等大多数粗提物具有一定或很弱的触杀作用,粘虫校正死亡率在10.0%以下;有光干芽乙醇、丙酮、石油醚粗提物则无触杀作用;无光干芽乙酸乙酯粗提物对粘虫的胃毒作用很弱,校正死亡率仅为4.26%;无光干芽乙酸乙酯粗提物对粘虫具有很强的生长发育抑制作用,处理后6d的生长发育抑制率为67.12%.     

Mutations in diphtheria toxin separate binding from entry and amplify immunotoxin selectivity

Monoclonal antibodies linked to toxic proteins (immunotoxins) can selectively kill some tumor cells in vitro and in vivo. However, reagents that combine the full potency of the native toxins with the high degree of cell type selectivity of monoclonal antibodies have not previously been designed. Two heretofore inseparable activities on one polypeptide chain of diphtheria toxin and ricin account for the failure to construct optimal reagents. The B chains (i) facilitate entry of the A chain to the cytosol, which allows immunotoxins to efficiently kill target cells, and (ii) bind to receptors present on most cells, which imparts to immunotoxins a large degree of non-target cell toxicity. This report identifies point mutations in the B polypeptide chain of diphtheria toxin that block binding but allow cytosol entry. Three mutants of diphtheria toxin have 1/1,000 to 1/10,000 the toxicity and 1/100 to 1/8,000 the binding activity of diphtheria toxin. Linking of either of two of the inactivated mutant toxins (CRM103, Phe508; CRM107, Phe390, Phe525) to a monoclonal antibody specific for human T cells reconstitutes full target-cell toxicity--indistinguishable from that of the native toxin linked to the same antibody--without restoring non-target cell toxicity. This separation of the entry function from the binding function generates a uniquely potent and cell type-specific immunotoxin that retains full diphtheria toxin toxicity, yet is four to five orders of magnitude less toxic than the native toxin is to nontarget cells.     

基于高SBS阈值的HNLF产生高重复频率超短光脉冲

基于光纤中的四波混频(FWM)产生高重复频率超短光脉冲的原理,并为抑制光纤中的受激Brillouin散射(SBS),采用非均匀掺杂高SBS阈值非线性光纤,通过FWM对双拍频信号进行整形压缩,实验上获得了100GHz的高重复率超短光脉冲序列,进而分析了入纤功率对输出光脉冲的影响。     

蓖麻花序提取物对粘虫的杀虫活性及其作用机理研究

研究了蓖麻花序提取物对粘虫的杀虫活性、作用方式及其作用机理,结果表明,蓖麻花序不同极性溶剂提取物对粘虫的触杀作用以乙醇提取物最强,校正死亡率为16.9%;拒食作用以乙酸乙酯提取物最强,拒食率为41.5%;胃毒作用以乙酸乙酯提取物最强,其次为石油醚提取物,死亡率分别为42.5%和41.5%;生长发育抑制作用以石油醚提取物最强,3、4、5、6,7 d后生长发育抑制率分别为66.88%、66.98%、59.39%、55.63%和38.66%.乙醇提取物不同极性溶剂萃取物的触杀作用以石油醚萃取物最强,校正死亡率可达53.1%.石油醚萃取物对Na+-k+-ATP酶的活性具一定的抑制作用.     

Prolactin: evidence that it is separate from growth hormone in human blood

A highly sensitive bioassay has been developed for prolactin, which uses a mammalian end organ and which is capable of measuring the hormone in unextracted human plasma. High prolactin activity, largely neutralizable with antiserum to human growth hormone, is stimulated along with high immunoassayable growth hormone by insulin-induced hypoglycemia. High prolactin activity, not neutralizable with antiserum to growth hormone, exists with low concentrations of plasma growth hormone in postpartum patients and patients with galactorrhea.     

贝加尔唐松草提取物对粘虫的杀虫活性及其作用机理研究

研究了贝加尔唐松草提取物对粘虫的杀虫活性及其作用机理.结果表明,贝加尔唐松草不同极性溶剂提取物对粘虫的触杀作用以甲醇提取物最强,校正死亡率为17.0%;胃毒作用以甲醇提取物最强,其次为石油醚提取物,校正死亡率分别为40.0%和20.0%;不同极性溶剂提取物无杀卵和拒食作用.甲醇提取物不同极性溶剂萃取物的触杀作用以乙酸乙酯萃取物最强,校正死亡率可达73.9%.乙酸乙酯萃取物对Na+-K+-ATP酶的活性具有一定的抑制作用.     

Ammonia synthesis from first-principles calculations

The rate of ammonia synthesis over a nanoparticle ruthenium catalyst can be calculated directly on the basis of a quantum chemical treatment of the problem using density functional theory. We compared the results to measured rates over a ruthenium catalyst supported on magnesium aluminum spinel. When the size distribution of ruthenium particles measured by transmission electron microscopy was used as the link between the catalyst material and the theoretical treatment, the calculated rate was within a factor of 3 to 20 of the experimental rate. This offers hope for computer-based methods in the search for catalysts.     

红蓼种子萃取物对黏虫的作用机理

测定了红蓼种子乙酸乙酯萃取物对黏虫5龄幼虫体内5种酶活性的影响,结果表明,红蓼种子乙酸乙酯萃取物对黏虫幼虫体内Na+-K+-ATP酶的活性具有一定的抑制作用,而对其他几种酶活性没有明显作用。     

玉米幼胚离体培养幼苗分化的影响因素研究

用6个玉米基因型的幼胚进行离体培养幼苗分化试验,从培养基种类、基因型和细胞质效应、激动素、分化前最后一次继代培养基中2,4 D质量浓度、蔗糖质量浓度等6个方面分析了幼苗分化的影响因素.结果表明,N6和MS两种基本培养基之间以及激动素6 BA和KT之间对幼苗分化的影响没有明显差别,6 BA质量浓度和其余4个因素对幼苗的分化都有较大影响.87-1×郑22在幼苗分化中是较为理想的组合,分化培养基中6 BA质量浓度为1mg·L-1,蔗糖质量浓度为50g·L-1,分化前最后1次继代培养基中2,4 D质量浓度为1mg·L-1时,有利于幼苗的分化.     

Lunar surface: composition inferred from optical properties

The optical characteristics (intensity, polarization, spectrum, and albedo) of the moon surface are compared with those of rock and meteorite powders. The only materials whose optical properties match those of the lunar surface are basic rocks containing lattice iron but little or no free iron, and then only after irradiation of these rocks by a simulated solar wind. Optical properties of chondritic meteorite powders differ from those of the moon in significant respects. The lunar crust is probably not chondritic, but is similar in composition to terrestrial iron-rich basalts. These results are independent of those from the Surveyor V alpha-scattering experiment and, in addition, provide a basis for extrapolating the Surveyor V analysis to other areas of the moon. The Surveyor V experiment has thus confirmed the value of earth-based optical techniques for the study of the structure and composition of the surfaces of other planets.     

马铃薯茎叶和果实粗提物对粘虫触杀作用研究

采用虫体浸渍法测定了马铃薯品种庄薯3号盛花期、收获期茎叶和青果不同溶剂粗提物对粘虫5龄幼虫的触杀效果。结果表明,马铃薯青果乙酸乙酯粗提物对粘虫幼虫具有很强的触杀作用,稀释5倍液的校正死亡率可达59．5％;丙酮粗提物具有一定的触杀作用,校正死亡率为10．0％。青果的甲醇、乙醇和石油醚粗提物及盛花期、收获期茎叶的甲醇、乙醇、丙酮、石油醚和乙酸乙酯粗提物触杀作用很弱或无触杀作用。     

皂角提取物的杀虫活性及其对粘虫的作用方式研究

本文采用虫体浸渍法和夹毒叶碟法等室内生测方法研究了皂角提取物的杀虫活性及其对粘虫的作用方式。结果表明,皂角85%乙醇提取物对粘虫(Mythimna separate)五龄幼虫具有很强的触杀作用,在76 g/L浓度下的校正死亡率为70%;对菜粉蝶(Pieris rapae)三龄幼虫具有很强的拒食作用,在380 g/L浓度下的拒食率高达100%;对朱砂叶螨(Tetranychus cinnabarinus)具有一定的触杀作用,在3.8 g/L浓度下的校正死亡率为33.4%。皂角85%乙醇提取物对粘虫的作用方式表现为很强的触杀作用、较强的拒食(拒食率为67.38%)和胃毒作用(校正死亡率为42.87%)、很强的生长发育抑制作用(处理后3d的生长发育抑制率为100%),而无杀卵、杀蛹、熏蒸、麻醉和内吸作用。     

The optical resonances in carbon nanotubes arise from excitons

Optical transitions in carbon nanotubes are of central importance for nanotube characterization. They also provide insight into the nature of excited states in these one-dimensional systems. Recent work suggests that light absorption produces strongly correlated electron-hole states in the form of excitons. However, it has been difficult to rule out a simpler model in which resonances arise from the van Hove singularities associated with the one-dimensional band [corrected] structure of the nanotubes. Here, two-photon excitation spectroscopy bolsters the exciton picture. We found binding energies of approximately 400 millielectron volts for semiconducting single-walled nanotubes with 0.8-nanometer diameters. The results demonstrate the dominant role of many-body interactions in the excited-state properties of one-dimensional systems.