A liquid-solution-phase synthesis of crystalline silicon

A liquid-solution-phase technique for preparing submicrometer-sized silicon single crystals is presented. The synthesis is based on the reduction of SiCl(4) and RSiCl(3) (R = H, octyl) by sodium metal in a nonpolar organic solvent at high temperatures (385 degrees C) and high pressures (> 100 atmospheres). For R = H, the synthesis produces hexagonal-shaped silicon single crystals ranging from 5 to 3000 nanometers in size. For R = octyl, the synthesis also produces hexagonal-shaped silicon single crystals; however, the size range is controlled to 5.5 +/- 2.5 nanometers.     

alpha-Hydroxy and alpha-amino acids under possible Hadean, volcanic origin-of-life conditions

To test the theory of a chemoautotrophic origin of life in a volcanic, hydrothermal setting, we explored mechanisms for the buildup of bio-organic compounds by carbon fixation on catalytic transition metal precipitates. We report the carbon monoxide-dependent formation of carbon-fixation products, including an ordered series of alpha-hydroxy and alpha-amino acids of the general formula R-CHA-COOH (where R is H, CH3,C2H5,orHOCH2 and A is OH or NH2) by carbon fixation at 80 degrees to 120 degrees C, catalyzed by nickel or nickel,iron precipitates with carbonyl, cyano, and methylthio ligands as carbon sources, with or without sulfido ligands. Calcium or magnesium hydroxide was added as a pH buffer. The results narrow the gap between biochemistry and volcanic geochemistry and open a new gateway for the exploration of a volcanic, hydrothermal origin of life.     

化学镀镍-铜-镍导电涤纶织物的性能研究

通过化学镀镍和化学镀铜组合工艺制备了电磁屏蔽导电涤纶织物,镀层由镍/铜/镍三层金属层组成.重点研究了镀层重量和织物型号等因素对镀层抗氧化能力、电磁屏蔽效能的影响.结果表明:镍作为铜镀层防护层,其上量越多,抗腐蚀和氧化能力越强.铜金属上量越多,表而电阻越小,电磁屏蔽效果越好,当铜上量约20g·cm~(-2)时,表面电阻显著下降.另外织物的编制密度对电磁屏蔽效能也有影响,编制密度越大,电磁屏蔽效能略有上升.     

Fine particles produced from automotive emissions-control catalysts

High concentrations of metal-containing condensation nuclei have been thermally induced from stabilized catalysts containing chromium, copper, and nickel under conditions closely resembling those found in automobile exhaust. Commercial and developmental catalyst formulations have been found to emit fine particles under a broad range of controlled conditions at temperatures ranging from 185 degrees to 800 degrees C, in filtered air, in a mixture of 3 percent carbon monoxide in molecular nitrogen, and in the product stream of a pulsed flame combustor.     

两种硅化物对甜瓜白粉病的抑制机理研究

 以玉金香甜瓜为试验材料，研究不同硅化物对白粉病的抑制机理。结果表明，2种硅化物处理均能显著降低甜瓜幼苗白粉病的严重度，以硅酸钠降低的幅度最大。经20 mmol·L-1硅酸钠处理后和接种白粉菌后，甜瓜POD活性显著高于对照；GLU活性也于硅酸钠处理后120 h和接种白粉菌后120 h，显著高于对照。经SEM-EDX分析显示硅酸钠处理，其硅在叶面气孔和表皮层沉积明显提高。纳米氧化硅处理对POD酶活性没有明显影响，但硅的沉积特点与硅酸钠处理相似。     

Zeolite effect on heavy metal content in grey forest soil in conditions of technogenic pollution

The effect of Khotynetz deposit zeolite on the content of lead, nickel and copper in the grey forest soil with copper content above MAC, lead and nickel two times more than background concentrations has been investigated. Under applying zeolite in doze 8–16 t/ha the content of mobile compounds of these elements was reduced significantly; zeolite doze increasing more than 16 t/ha did not provide essential reduction of mobility.     

New phases of c60 synthesized at high pressure

The fullerene C(60) can be converted into two different structures by high pressure and temperature. They are metastable and revert to pristine C(60) on reheating to 300 degrees C at ambient pressure. For synthesis temperatures between 300 degrees and 400 degrees C and pressures of 5 gigapascals, a nominal face-centered-cubic structure is produced with a lattice parameter a(o) = 13.6 angstroms. When treated at 500 degrees to 800 degrees C at the same pressure, C(60) transforms into a rhombohedral structure with hexagonal lattice parameters of a(o) = 9.22 angstroms and c(o) = 24.6 angstroms. The intermolecular distance is small enough that a chemical bond can form, in accord with the reduced solubility of the pressure-induced phases. Infrared, Raman, and nuclear magnetic resonance studies show a drastic reduction of icosahedral symmetry, as might occur if the C(60) molecules are linked.     

碳酸钙原位沉积对单根竹纤维拉伸性能的影响

采用离子溶液原位反应法,研究了不同反应温度下碳酸钙在竹纤维上的沉积情况及其对单根竹纤维拉伸性能的影响。结果表明:温度对附着在竹纤维表面的碳酸钙晶粒尺寸及形貌有明显影响,随着温度的升高,碳酸钙由分散性较好的不规则四面体单晶逐渐团聚生长为球形或椭球形;25℃下碳酸钙粒径较均匀,附着量最高,纳米碳酸钙颗粒填充了纤维上的微孔。所有附着碳酸钙的单根竹纤维拉伸性能均有所改善,这可能与填充的碳酸钙颗粒承受纤维孔隙传递的应力有关。CaCO3沉积情况对竹单根纤维力学性能的影响显著,25℃条件下改性慈竹纤维的拉伸强度和弹性模量最高,与未改性纤维相比,分别提高了30.50%和32.71%。     

Bacterial Sulfate Reduction Above 100{degrees}C in Deep-Sea Hydrothermal Vent Sediments

The currently known upper temperature limit for growth of organisms, shared by a number of archaebacteria, is 110 degrees C. However, among the sulfate-reducing bacteria, growth temperatures of greater than 100 degrees C have not been found. A search for high-temperature activity of sulfate-reducing bacteria was done in hot deep-sea sediments at the hydrothermal vents of the Guaymas Basin tectonic spreading center in the Gulf of California. Radiotracer studies revealed that sulfate reduction can occur at temperatures up to 110 degrees C, with an optimum rate at 103 degrees to 106 degrees C. This observation expands the upper temperature limit of this process in deep-ocean sediments by 20 degrees C and indicates the existence of an unknown group of hyperthermophilic bacteria with a potential importance for the biogeochemistry of sulfur above 100 degrees C.     

Search for organic and volatile inorganic compounds in two surface samples from the chryse planitia region of Mars

Two surface samples collected from the Chryse Planitia region of Mars were heated to temperatures up to 500 degrees C, and the volatiles that they evolved were analyzed with a gas chromatograph-mass spectrometer. Only water and carbon dioxide were detected. This implies that organic compounds have not accumulated to the extent that individual components could be detected at levels of a few parts in 10(9) by weight in our samples. Proposed mechanisms for the accumulation and destruction of organic compounds are discussed in the light of this limit.     

Geomicrobiology of deep-sea hydrothermal vents

During the cycling of seawater through the earth's crust along the mid-ocean ridge system, geothermal energy is transferred into chemical energy in the form of reduced inorganic compounds. These compounds are derived from the reaction of seawater with crustal rocks at high temperatures and are emitted from warm (相似文献   

Ice nucleation by alcohols arranged in monolayers at the surface of water drops

Monolayers of aliphatic long-chain alcohols induced nucleation of ice at temperatures approaching 0 degrees C, in contrast with water-soluble alcohols, which are effective antifreeze agents. The corresponding fatty acids, or alcohols with bulky hydrophobic groups, induce freezing at temperatures as much as 12 degrees C lower. The freezing point induced by the amphiphilic alcohols was sensitive not only to surface area per molecule but, for the aliphatic series (C(n)H(2n + 1)OH), to chain length and parity. The freezing point for chains with n odd reached an asymptotic temperature of 0 degrees C for an upper value of n = 31; for n even the freezing point reached a plateau of -8 degrees C for n in the upper range of 22 to 30. The higher freezing point induced by the aliphatic alcohols is due to formation of ordered clusters in the uncompressed state as detected by grazing incidence synchrotron x-ray diffraction measurements. The diffraction data indicate a close lattice match with the ab layer of hexagonal ice.     

硅素分期施用对土壤镉形态和水稻镉累积的影响

为了探明硅素运筹对土壤-水稻(Oryza sativa L.)体系中Cd迁移的影响,探索缓解Cd污染土壤中水稻吸收和积累Cd的最佳施硅时期和施硅比例,采用盆栽实验,以稻田土壤为供试土壤,外源添加氯化镉模拟Cd含量为100 mg·kg~(-1)的污染土壤,在施硅总量(56 mg·kg~(-1)土壤)不变的基础上设置基施硅素(C1)、基肥和拔节期硅素1∶1分期施用(C2)和拔节期施硅素(C3)3种处理,以不施硅(CK)为对照,研究硅素分期施用对土壤Cd的形态以及水稻对Cd的吸收、转运和累积的影响。结果表明:与CK相比,C2和C3处理水稻成熟期土壤中Cd含量增加19.4%(P0.05)、18.9%(P0.05),C2和C3土壤可交换态Cd含量降低27.3%(P0.05)、27.1%(P0.05),而土壤残渣态Cd含量分别增加97.7%(P0.05)、111.3%(P0.05)。成熟期各施硅处理水稻的根和糊粉层中Cd含量显著增加,而茎、叶和精米中Cd含量明显降低,其中C1、C2和C3精米的Cd含量分别比CK降低13.8%(P0.05)、35.1%(P0.05)和27.9%(P0.05),茎、叶、精米的Cd转移系数和富集系数也显著降低,而根的Cd富集系数显著升高。此外,本研究还发现土壤各形态Cd含量与水稻根和精米中Cd累积量有着显著的相关关系。综上表明,C2和C3成熟期土壤Cd的有效性显著降低,残渣态Cd显著增加,Cd从土壤向稻株中的转移受到抑制,水稻吸收的Cd大部分累积在根部,降低Cd向地上部各器官的迁移,从而导致精米Cd含量和累积量明显降低,其中C2处理更利于整个生育期土壤可还原态Cd含量的减少和抽穗期土壤中可氧化态Cd含量的增加,利于抽穗前水稻生长发育。C2处理施硅效果好,值得推荐。     

Reversible switching of hydrogel-actuated nanostructures into complex micropatterns

Responsive behavior, which is intrinsic to natural systems, is becoming a key requirement for advanced artificial materials and devices, presenting a substantial scientific and engineering challenge. We designed dynamic actuation systems by integrating high-aspect-ratio silicon nanocolumns, either free-standing or substrate-attached, with a hydrogel layer. The nanocolumns were put in motion by the "muscle" of the hydrogel, which swells or contracts depending on the humidity level. This actuation resulted in a fast reversible reorientation of the nanocolumns from tilted to perpendicular to the surface. By further controlling the stress field in the hydrogel, the formation of a variety of elaborate reversibly actuated micropatterns was demonstrated. The mechanics of the actuation process have been assessed. Dynamic control over the movement and orientation of surface nanofeatures at the micron and submicron scales may have exciting applications in actuators, microfluidics, or responsive materials.     

Regulation of body temperature in the blue-tongued lizard

Lizards (Tiliqua scincoides) regulated their internal body temperature by moving back and forth between 15 degrees and 45 degrees C environments to maintain colonic and brain temperatures between 30 degrees and 37 degrees C. A pair of thermodes were implanted across the preoptic region of the brain stem, and a reentrant tube for a thermocouple was implanted in the brain stem. Heating the brain stem to 41 degrees C activated the exit response from the hot environment at a colonic temperature 1 degrees to 2 degrees C lower than normal, whereas cooling the brain stem to 25 degrees C delayed the exit from the hot environment until the colonic temperature was 1 degrees to 2 degrees C higher than normal. The behavioral thermoregulatory responses of this ectotherm appear to be activated by a combination of hypothalamic and other body temperatures.     

Body-centered cubic iron-nickel alloy in Earth's core

Cosmochemical, geochemical, and geophysical studies provide evidence that Earth's core contains iron with substantial (5 to 15%) amounts of nickel. The iron-nickel alloy Fe(0.9)Ni(0.1) has been studied in situ by means of angle-dispersive x-ray diffraction in internally heated diamond anvil cells (DACs), and its resistance has been measured as a function of pressure and temperature. At pressures above 225 gigapascals and temperatures over 3400 kelvin, Fe(0.9)Ni(0.1) adopts a body-centered cubic structure. Our experimental and theoretical results not only support the interpretation of shockwave data on pure iron as showing a solid-solid phase transition above about 200 gigapascals, but also suggest that iron alloys with geochemically reasonable compositions (that is, with substantial nickel, sulfur, or silicon content) adopt the bcc structure in Earth's inner core.     

Liquid water in frozen tissue: study by nuclear magnetic resonance

Nuclear magnetic resonance (NMR) spectroscopy was used to examine the behavior and extent of liquid water in postrigor-frozen tissue of cod at temperatures below 0 degrees C. A liquid-water phase persists in the tissue down to about -70 degrees C; the extent of the phase decreases rapidly between 0 degrees and -10 degrees C and slowly at lower temperatures. That the NMR absorption peak of the liquid water increases in width, with decreasing temperature, suggests loss of mobility or structuring of the phase. A technique for introducing geometrically uniform cores of muscle into the probe of the high-resolution spectrometer permits quantitative determinations of liquid water.     

High-temperature cubic boron nitride p-N junction diode made at high pressure

A p-n junction diode of cubic boron nitride was made by growing an n-type crystal epitaxially on a p-type seed crystal at a pressure of 55 kilobars and a temperature of about 1700 degrees C. A temperature-difference solvent method was used for the crystal growth, and beryllium and silicon were doped as acceptors and donors, respectively. Formation of the p-n junction was clearly confirmed at 1 bar by rectification characteristics and by existence of a space charge layer of the junction as observed by electron beam induced current measurement. This diode operated at 530 degrees C.     

Organic Compounds in Meteorites: They may have formed in the solar nebula, by catalytic reactions of carbon monoxide, hydrogen, and ammonia

Organic compounds in meteorites seem to have formed by catalytic reactions of CO, H2, and NH3 in the solar nebula, at 360 degrees to 400 degrees K and (4 to 10) x 10-6 atm. The onset of these reactions was triggered by the formation of suitable catalysts (magnetite, hydrated silicates) at these temperatures. These reactions may be a source of prebiotic carbon compounds on the inner planets, and interstellar molecules.     

Starch accumulation associated with growth reduction at low temperatures in a tropical plant

Growth of Digitaria decumbens is severely reduced by night temperatures of 10 degrees C or below. Ultra-structure of leaves and chemical analyses show a high starch content in chloroplasts of plants illuminated and kept at a temperature of 30 degrees C. This starch disappears after a period in the dark at 30 degrees C, but it remains if the temperature during the dark period is 10 degrees C. The inhibition or slowing of starch translocation out of chloroplasts appears to account for reduced photo-synthesis and growth at low night temperatures.