Microstructured optical fibers as high-pressure microfluidic reactors

Deposition of semiconductors and metals from chemical precursors onto planar substrates is a well-developed science and technology for microelectronics. Optical fibers are an established platform for both communications technology and fundamental research in photonics. Here, we describe a hybrid technology that integrates key aspects of both engineering disciplines, demonstrating the fabrication of tubes, solid nanowires, coaxial heterojunctions, and longitudinally patterned structures composed of metals, single-crystal semiconductors, and polycrystalline elemental or compound semiconductors within microstructured silica optical fibers. Because the optical fibers are constructed and the functional materials are chemically deposited in distinct and independent steps, the full design flexibilities of both platforms can now be exploited simultaneously for fiber-integrated optoelectronic materials and devices.     

Micromachining a miniaturized capillary electrophoresis-based chemical analysis system on a chip

Micromachining technology was used to prepare chemical analysis systems on glass chips (1 centimeter by 2 centimeters or larger) that utilize electroosmotic pumping to drive fluid flow and electrophoretic separation to distinguish sample components. Capillaries 1 to 10 centimeters long etched in the glass (cross section, 10 micrometers by 30 micrometers) allow for capillary electrophoresis-based separations of amino acids with up to 75,000 theoretical plates in about 15 seconds, and separations of about 600 plates can be effected within 4 seconds. Sample treatment steps within a manifold of intersecting capillaries were demonstrated for a simple sample dilution process. Manipulation of the applied voltages controlled the directions of fluid flow within the manifold. The principles demonstrated in this study can be used to develop a miniaturized system for sample handling and separation with no moving parts.     

Magnetic microspheres prepared by redox polymerization used in a cell separation based on gangliosides

A facile method is described for making magnetic microspheres that bind specifically to cell surfaces, in order to separate cells magnetophoretically. Control over the sizes of the spheres is effected by using their magnetic cores as part of a redox polymerization system. The use of the microspheres is demonstrated with a separation involving C-1300 neuroblastoma cells, 10% of which express the ganglioside GM1 in their membranes. The GM1-containing cells were separated with better than 99% purity, while the deficient cells were obtained at least 98% pure. The separation, which was carried out under sterile conditions, required only 6 minutes.     

Moissanite: a window for high-pressure experiments

We achieved a pressure of 52.1 gigapascals with moissanite anvils, which have optical, thermal, electric, magnetic, and x-ray properties that rival those of diamond. The mode-softening of D(2)O toward the pressure-induced hydrogen bond symmetrization and the Raman shifts of diamond under hydrostatic and nonhydrostatic compressions were studied with moissanite anvils in the spectral regions normally obscured by diamond anvils. Moissanite anvil cells allow maximum sample volumes 1000 times larger than those allowed by diamond anvil cells and may enable the next level of advancement in high-pressure experiments.     

气相色谱法测定水中丙烯腈

[目的]建立水中丙烯腈的气相色谱测定方法。[方法]采用小体积直接进样,用DB-FFAP毛细管柱程序升温分离,氢火焰离子化检测器检测,以保留时间定性,外标法定量。[结果]该方法相对标准偏差低于5.0%,加标回收率为95.7%~101.0%,标准曲线相关系数大于0.999,检出限为0.03 mg/L。[结论]该方法适用于地表水中丙烯腈的测定。     

Laser techniques in high-pressure geophysics

Laser techniques in conjunction with the diamond-anvil cell can be used to study high-pressure properties of materials important to a wide range of problems in earth and planetary science. Spontaneous Raman scattering of crystalline and amorphous solids at high pressure demonstrates that dramatic changes in structure and bonding occur on compression. High-pressure Brillouin scattering is sensitive to the pressure variations of single-crystal elastic moduli and acoustic velocities. Laser heating techniques with the diamond-anvil cell can be used to study phase transitions, including melting, under deep-earth conditions. Finally, laser-induced ruby fluorescence has been essential for the development of techniques for generating the maximum pressures now possible with the diamond-anvil cell, and currently provides a calibrated in situ measure of pressure well above 100 gigapascals.     

Protonic diffusion in high-pressure ice VII

Near ambient pressures, molecular diffusion dominates protonic diffusion in ice. Theoretical studies have predicted that protonic diffusion will dominate at high pressures in ice. We measured the protonic diffusion coefficient for the highest temperature molecular phase of ice VII at 400 kelvin over its entire stable pressure region. The values ranged from 10(-17) to 10(-15) square meters per second at pressures of 10 to 63 gigapascals. The diffusion coefficients extrapolated to high temperatures close to the ice VII melting curve were less by a factor of 10(2) to 10(3) than a superionic criterion of approximately 10(-8) square meters per second, at which protons would diffuse freely.     

Cavitation-induced reactions in high-pressure carbon dioxide

The feasibility of ultrasound-induced in situ radical formation in liquid carbon dioxide was demonstrated. The required threshold pressure for cavitation could be exceeded at a relatively low acoustic intensity, as the high vapor pressure of CO2 counteracts the hydrostatic pressure. With the use of a dynamic bubble model, the formation of hot spots upon bubble collapse was predicted. Cavitation-induced radical formation was used for the polymerization of methyl methacrylate in CO2, yielding high-molecular-weight polymers. These results show that sonochemical reactions can be performed in dense-phase fluids, which allows the environmentally benign CO2 to replace conventional organic solvents in many reaction systems.     

Cofilin promotes actin polymerization and defines the direction of cell motility

A general caging method for proteins that are regulated by phosphorylation was used to study the in vivo biochemical action of cofilin and the subsequent cellular response. By acute and local activation of a chemically engineered, light-sensitive phosphocofilin mimic, we demonstrate that cofilin polymerizes actin, generates protrusions, and determines the direction of cell migration. We propose a role for cofilin that is distinct from its role as an actin-depolymerizing factor.     

Heart activity and high-pressure circulation in cirripedia

Pulsating hemolymph pressures of remarkable magnitude for invertebrates are prevalent in the Pacific gooseneck barnacle. Mean pressures of 250 centimeters of water are common with pulse pressures up to 70 centimeters of water. The pulsations are distinctly rhythmical and the pulsation rate is highly temperature-dependent. The results strongly suggest that in cirripeds hemolymph is circulated by muscular contractions of a functional heart.     

Linear alkane polymerization on a gold surface

In contrast to the many methods of selectively coupling olefins, few protocols catenate saturated hydrocarbons in a predictable manner. We report here the highly selective carbon-hydrogen (C-H) activation and subsequent dehydrogenative C-C coupling reaction of long-chain (>C(20)) linear alkanes on an anisotropic gold(110) surface, which undergoes an appropriate reconstruction by adsorption of the molecules and subsequent mild annealing, resulting in nanometer-sized channels (1.22 nanometers in width). Owing to the orientational constraint of the reactant molecules in these one-dimensional channels, the reaction takes place exclusively at specific sites (terminal CH(3) or penultimate CH(2) groups) in the chains at intermediate temperatures (420 to 470 kelvin) and selects for aliphatic over aromatic C-H activation.     

A high-pressure structure in curium linked to magnetism

Curium lies at the center of the actinide series and has a half-filled shell with seven 5f electrons spatially residing inside its radon core. As a function of pressure, curium exhibits five different crystallographic phases up to 100 gigapascals, of which all but one are also found in the preceding element, americium. We describe here a structure in curium, Cm III, with monoclinic symmetry, space group C2/c, found at intermediate pressures (between 37 and 56 gigapascals). Ab initio electronic structure calculations agree with the observed sequence of structures and establish that it is the spin polarization of curium's 5f electrons that stabilizes Cm III. The results reveal that curium is one of a few elements that has a lattice structure stabilized by magnetism.     

In situ observations of a high-pressure phase of H2O Ice

A previously unknown solid phase of H2O has been identified by its peculiar growth patterns, distinct pressure-temperature melting relations, and vibrational Raman spectra. Morphologies of ice crystals and their pressure-temperature melting relations were directly observed in a hydrothermal diamond-anvil cell for H2O bulk densities between 1203 and 1257 kilograms per cubic meter at temperatures between -10 degrees and 50 degreesC. Under these conditions, four different ice forms were observed to melt: two stable phases, ice V and ice VI, and two metastable phases, ice IV and the new ice phase. The Raman spectra and crystal morphology are consistent with a disordered anisotropic structure with some similarities to ice VI.     

大管径高压力气液两相管流流型转变数值模拟

流型判别是气液两相流研究的重要内容.应用适用于工业设计中大管径、高压力管道的多相流瞬态模拟软件OLGA,以空气-水为介质,对倾角为-70°～90°、内径为200 mm、压力为2.0 MPa的气液两相管流进行数值模拟,通过变换不同的气液相流量和管道倾角,研究管道内气液两相流体流型的变化.根据数值模拟所得到的1 628组数据,结合流体物性和管道倾角,回归建立了不同流型转变的判别准则经验相关式,为现场大管径、高压力气液两相流管道的流型判别提供了参考依据.     

Bismuth vanadate: a high-pressure, high-temperature crystallographic study of the ferroelastic-paraelastic transition

Lattice dimensions of bismuth vanadate have been determined under 37 different high-pressure or high-temperature conditions or a combination of these conditions. New high-pressure, high-temperature, single-crystal x-ray techniques were used to bracket the reversible monoclinic (ferroelastic) to tetragonal (paraelastic) transition.     

Enthalpy of transformation of a high-pressure polymorph of titanium dioxide to the rutile modification

The enthalpy of transformation of a high-pressure form of titanium dioxide, which has the alpha lead dioxide structure, to the rutile modification was measured by the method of "transposed temperature-drop calorimetry." For the reaction, titanium dioxide (alpha lead dioxide form) transforming to rutile, the change in the heat content is -0.76 +/- 0.17 kilocalorie per mole. From this value and the volume change (+ 2.8 percent) associated with the transformation, we estimate the equilibrium pressure at 294 degrees K to be 60 +/- 20 kilobars.     

Density maxima in high-pressure supercooled water and liquid silicon dioxide

With glass capillary pressure vessels it has been possible to study the effect of pressure on the temperature of maximum density (TMD) and on the "sharpness" of the density maximum in liquid H(2)O and D(2)O in the important but little-studied supercooled regime. A pressure of 1200 bars produces a 33 degrees C depression of the TMD in these liquids and a considerable reduction in sharpness. Comparison with the rather flat density maximum for liquid SiO(2) supports the notion that the presence or absence of density anomalies in "tetrahèdral" liquids depends on the average bridge-bond angle, which is evidently unusually large in water at normal pressure.     

Nondestructive optical measurements of a single electron spin in a quantum dot

Kerr rotation measurements on a single electron spin confined in a charge-tunable semiconductor quantum dot demonstrate a means to directly probe the spin off-resonance, thus minimally disturbing the system. Energy-resolved magneto-optical spectra reveal information about the optically oriented spin polarization and the transverse spin lifetime of the electron as a function of the charging of the dot. These results represent progress toward the manipulation and coupling of single spins and photons for quantum information processing.