Calcium carbonate concretions formed by the decomposition of organic matter

Bacterial decomposition of butterfish and smelts in small sealed jars containing seawater and other solutions, for periods ranging from 65 to 205 days, results in a large increase in concentrations of dissolved bicarbonate, carbonate, and ammonia (plus volatile amines). Accompanying this is a rise in pH and the precipitation of Ca(++) ion from solution. The Ca(++) is not precipitated as CaCO(3) but instead as a mixture of calcium fatty acid salts or soaps with from 14 to 18 carbon atoms. This can be explained by the thermodynamic instability of CaCO(3) relative to Ca soaps in the presence of excess free fatty acid. It is suggested that some ancient CaCO(3) concretions, especially those enclosing fossils of soft-bodied organisms, may have formed rapidly after death in the form of natural Ca soap (adipocere) which was later converted to CaCO(3).     

Ultralow thermal conductivity in disordered, layered WSe2 crystals

The cross-plane thermal conductivity of thin films of WSe2 grown from alternating W and Se layers is as small as 0.05 watts per meter per degree kelvin at room temperature, 30 times smaller than the c-axis thermal conductivity of single-crystal WSe2 and a factor of 6 smaller than the predicted minimum thermal conductivity for this material. We attribute the ultralow thermal conductivity of these disordered, layered crystals to the localization of lattice vibrations induced by the random stacking of two-dimensional crystalline WSe2 sheets. Disordering of the layered structure by ion bombardment increases the thermal conductivity.     

用成本现值法分析超低等林区公路

本文对新近在南方林区出现的超低等林区公路,用成本现值法进行了经济分析,导出了一套可以用于方案比较与决策的通用公式,举了一个实例,并作了敏感性分析。     

A low-temperature thermal process for the decomposition of water

The following three reactions, each of which has been shown to proceed at the temperature indicated above the arrow, are suggested as a cycle for the thermal decomposition of water:     

喹诺酮类(吡哌酸、诺氟沙星)药物的热分解特性研究

分别采用差示扫描量热法(DSC)、热重法(TG)和微分热重法(DTG),研究了喹诺酮类(吡哌酸、诺氟沙星)抗菌药的热分解动力学过程,计算了其热分解动力学参数——活化能(E),分析了其热分解机理,并剖析了喹诺酮类药物有机结构上的差异。     

一株氧化木糖无色杆菌对Cd的固定作用

【目的】研究一株氧化木糖无色杆菌LAX2对镉(Cd)的碳酸盐矿化作用及其对Cd污染稻田土壤的修复效果。【方法】将LAX2接种于含0~40mg/L Cd2+的牛肉膏蛋白胨液体培养基中,测定LAX2对Cd的耐受性。在LAX2发酵液中加入0.1mol/L CdCl2放置12h,利用X-射线衍射、红外光谱、扫描电镜和能谱对菌株LAX2矿化固结Cd的产物特征进行分析,并通过水稻盆栽试验验证菌株LAX2对Cd污染土壤的修复效果。【结果】菌株LAX2对Cd2+的耐受能力较强,当溶液中Cd2+质量浓度达35 mg/L时,其生长不受明显影响;但当Cd2+质量浓度为40mg/L时,LAX2生长受到明显抑制。矿化产物特征分析结果表明,菌株LAX2可通过碳酸盐矿化作用将Cd矿化为呈小颗粒团聚体的CdCO3晶体。Cd污染稻田土壤经菌株LAX2发酵液、无菌发酵液和菌体细胞修复后,水稻根部Cd含量分别下降了35.3%,19.4%和12.5%,茎叶Cd含量分别降低了26.7%,15.6%和8.4%,水稻籽粒中Cd含量分别降低了28.7%,16.4%和7.5%,土壤有效态Cd含量分别下降了56.9%,34.5%和21.0%。【结论】菌株LAX2可通过碳酸盐矿化作用固结土壤中的有效态Cd,从而减少水稻对Cd的吸收。     

Atomic-scale control of friction by actuation of nanometer-sized contacts

Stiction and wear are demanding problems in nanoelectromechanical devices, because of their large surface-to-volume ratios and the inapplicability of traditional liquid lubricants. An efficient way to switch friction on and off at the atomic scale is achieved by exciting the mechanical resonances of the sliding system perpendicular to the contact plane. The resulting variations of the interaction energy reduce friction below 10 piconewtons in a finite range of excitation and load, without any noticeable wear. Without actuation, atomic stick-slip motion, which leads to dissipation, is observed in the same range. Even if the normal oscillations require energy to actuate, our technique represents a valuable way to minimize energy dissipation in nanocontacts.     

Anisotropic origin of transform faults

Transform faults appear in the process of stretching during freezing of the surface films on liquid wax. These films are composed of a warp yarn of wax fibers with optical anisotropy. This fabric is absent in materials that fail to produce transform faults. The mechanical anisotropy of these wax films (with high tensile strength and low shear strength in the direction of spreading) is responsible for the initiation of the transform faults. It is suggested that the anisotropy of the ocean upper mantle recorded seismically may likewise be responsible for the creation of the ridge-ridge transform faults in the oceans.     

Deformation on nearby faults induced by the 1999 Hector Mine earthquake

Interferometric Synthetic Aperture Radar observations of surface deformation due to the 1999 Hector Mine earthquake reveal motion on several nearby faults of the eastern California shear zone. We document both vertical and horizontal displacements of several millimeters to several centimeters across kilometer-wide zones centered on pre-existing faults. Portions of some faults experienced retrograde (that is, opposite to their long-term geologic slip) motion during or shortly after the earthquake. The observed deformation likely represents elastic response of compliant fault zones to the permanent co-seismic stress changes. The induced fault displacements imply decreases in the effective shear modulus within the kilometer-wide fault zones, indicating that the latter are mechanically distinct from the ambient crustal rocks.     

Nanoscale friction varied by isotopic shifting of surface vibrational frequencies

Friction converts kinetic energy at sliding interfaces into lattice vibrations, but the detailed mechanisms of this process remain unresolved. Atomic force microscopy measurements reveal that changing the mass of the terminating atoms on a surface, and thus their vibrational frequencies, affects nanoscale friction substantially. We compared hydrogen- and deuterium-terminated single-crystal diamond and silicon surfaces, and in all cases the hydrogenated surface exhibited higher friction. This result implies that the lower natural frequency of chemisorbed deuterium reduces the rate at which the tip's kinetic energy is dissipated. This discovery is consistent with a model describing energy transfer to adsorbates from a moving surface.     

Mutation caused by human phagocytes

Histidine-requiring mutants of Salmonella typhimurium TA100 were incubated with human peripheral blood leukocytes. More of these bacteria reverted to histidine independence than controls not incubated with cells. Phagocyte-rich suspensions were mutagenic, while heat-killed cells, lymphocytes, or mixed blood leukocytes of a patient with chronic granulomatous disease were not. Production of reactive oxygen metabolites could explain the capacity of phagocytes to induce mutation.     

人工组合复合菌系分解木质纤维素特征研究

为研究人工组合复合菌系降解木质纤维素的效果以及降解过程中微生物群落变化特征。首先对天然复合菌系PLC-8进行分离纯化,随后将筛选出的5株细菌和2株真菌进行组合,构建3种简化的复合菌系,分别为F1、F2和F3。随后,设计秸秆降解试验,利用DGGE方法测定3种复合菌在分解纤维素过程中微生物群落的变化特征,并进行相关的理化分析。结果表明：人工组合复合菌系F3分解木质纤维素的能力最强,在分解木质纤维素30d内秸秆平均减重率为39.80%,半纤维素下降52.64%,纤维素下降25.8%,木质素下降6.26%。在第15天时纤维素内切酶、纤维素外切酶、滤纸酶、β-葡萄糖苷酶、木聚糖酶的活性已经达到整个分解过程的最高值,分别为0.09、0.08、0.09、0.07和0.11U/mL。复合菌系F3能够自我调节pH,从而改变溶液的pH从微酸性至微碱性,F3的微生物群落呈现出真菌-细菌稳定共存的状态,并且能够长时间保持稳定。因此,人工组合复合菌系F3是稳定、高效的木质纤维素降解复合菌系。     

Disruption of hibernation caused by hypothalamic lesions

Lesions were made in the preoptic-anterior hypothalamic area or ventromedial nucleus of ground squirrels (Citellus tridecemlineatus). Four squirrels, two with preoptic damage and two obese hyperphagics, entered hibernation within 1 to 3 days. They all died after 11 to 12 days, shortly after all normal hibernating squirrels had awakened. Seven squirrels with preoptic damage, rendered hypothermic before being placed in the cold, died within 2 to 6 days.     

Visual disappearances caused by form similarity

Three forms were scaled for similarity by two groups of observers, who used different methods. A third group reported the duration of disappearances observed for each pair of forms. Duration of total disappearance increased with an increase in form-pair similarity. Neural overlap can explain the similarity judgments; cell fatigue, the disappearances.     

Surface self-organization caused by dislocation networks

We report a new mechanism of self-organization that can lead to robust surface ordering. We have quantitatively analyzed the thermal motion of holes created by sulfur atoms in a silver monolayer on a ruthenium surface, which we observed in real time with scanning tunneling microscopy. We find that the stability of the array of holes is determined by the arrangement and structure of misfit dislocations in the film.