Investigation of a cylindrical chemosorptive denuder for sampling and phase separation of toluene diisocyanate aerosols

A cylindrical chemosorptive denuder in series with a glass fibre filter has been evaluated for sampling toluene diisocyanate (TDI) aerosols. The sampler is designed for measuring personal exposure to diisocyanates. Several denuder coatings and derivatising reagents were investigated. Dimethylpolysiloxane (SE-30) and 5% phenyl dimethylpolysiloxane (SE-54) with either dibutylamine (DBA) or dipentylamine (DPeA) as derivatising reagents yielded the lowest vapour breakthrough (the amount (%) of the vapour that passes through the denuder), close to values predicted by theory. Immobilisation of the SE-30 denuder coating by in-situ cross-linking yielded comparable results. With an SE-30/DBA-coated denuder operating within an airflow range of 100–500 mL min^–1, the phase separation was shown to be consistent with theoretical predictions derived by use of the Gormley–Kennedy equation. This provides a means of calculating the vapour breakthrough and correcting experimentally obtained values with regard to vapour–particulate phase distribution, suggesting that the denuder can provide accurate phase-distribution measurements. The SE-30/DBA denuder can be used over a concentration range spanning nearly six orders of magnitude. Its capacity is sufficient to perform 15-min exposure measurements of a TDI aerosol with air concentrations as high as 1,700 g m^–3, 40 times higher than the Swedish occupational exposure limit (OEL). At the other end of the range, the estimated limit of detection (LOD) was less than 2 ng m^–3 for both the vapour and the aerosol phases when LC–ESI–MS–MS was used for chemical analysis.Electronic Supplementary Material Supplementary material for this article is available at     

圆柱类构件超声相控阵聚焦模型

在利用平面相控阵超声换能器对圆柱类构件检测时,受曲界面结构引起的入射波和回波时延的影响,扫描声束的波阵面产生弯曲,在利用传统迭代遍历算法计算延迟时间时效率低,无法发挥相控阵换能器检测优势。针对上述问题,建立了一种基于圆柱类构件特征和耦合介质特性的超声相控阵扫描成像的聚焦模型。该模型基于换能器、耦合介质、圆柱类构件材料特性和几何关系以及声线模型和折射定律,建立了耦合介质及被检构件的声速、曲面曲率半径、阵列与曲面间的距离等关联的延迟时间聚焦控制模型。利用该模型计算出的延时时间,对各阵元发射时间进行控制,从而实现扫描声束的聚焦。该文以液体和有机玻璃制介质楔块为例,对圆柱钢曲面的相控阵声束聚焦进行了仿真实验,结果表明该文方法计算效率显著提升,同时声束可以在预设位置实现聚焦,验证了该模型在计算效率上的优势与有效性。     

Searching for gravitational waves with the LIGO and Virgo interferometers

The first generation of ground-based interferometric gravitational wave detectors, LIGO, GEO, and Virgo, have operated and taken data at their design sensitivities over the last few years. The data has been examined for the presence of gravitational wave signals. Presented here is a comprehensive review of the most significant results. The network of detectors is currently being upgraded and extended, providing a large likelihood for observations. These future prospects will also be discussed.     

The Skorohod integral and the derivative operator of functional of a cylindrical Brownian motion

The paper presents a definition of the Skorohod integral of operator-valued processes and the derivative operator for functional of a cylindrical Brownian motionW on a Hilbert space. The method is based on the chaos expansions in terms of multiple Wiener integrals ofW.This research was partially supported by the U.S. Air Force Office of Scientific Research Contract No. F49620 85C 0144. The research of V. Pérez-Abreu was also supported by CONACYT Grant D111-904237.     

Temperature Evolution During Radiative Gravitational Collapse

We investigate the evolution of the temperature profile of a Friedmann-like collapsing sphere undergoing dissipative gravitational collapse in the form of a radial heat flux. We further consider the behavior of the star close to quasi-static equilibrium (weak heat flux approximation) and show that relaxational effects cannot be ignored. It is explicitly shown that extended irreversible thermodynamics predict a higher temperature at all interior points of the stellar configuration compared to the Eckart theory. These results carry over to the weak heat flux approximation with the magnitude of the temperature being lower than the full radiating model. The stability of the model after its departure from equilibrium is studied by considering the behavior of the control parameter throughout the stellar interior.     

Electrostatic potential in cylindrical dielectric media using the image charge method

We derive a simple analytical expression for the electric potential produced by a point charge in a cylindrical pore with relative permittivity different from that of the surrounding medium. The interface between the pore and the surrounding media may contain electric charge or be electrically neutral. The expression reduces to the known solutions when the surrounding dielectric medium is identical to the pore or an electric conductor. We discuss the convergence of the series expansion and numerically evaluate the electrostatic potential inside the cylindrical pore. The calculated potential shows the effect of the dielectric permittivity difference of the media. The results demonstrate that the expression can be implemented in a numerical dynamic simulation of charged systems in cylindrical geometry. We also give an expression for the case when the source charge is in the medium outside the cylinder.     

柱面微通道板的制备及其性能研究

针对未来空间天文学应用的超分辨率光谱成像仪器的需求,对低噪声柱面微通道板（MCP）的制备方法及其性能进行了研究. 提出了一种将光学抛光与热成型相结合的新的柱面MCP制备方法,利用不含放射性元素的低噪声MCP玻璃,制备出曲率半径为400mm、尺寸为30mm′46mm、长径比为80:1、通道直径12.5mm、通道间距15mm的柱面MCP,并将其与感应电荷楔条形阳极（WSA）组成光子计数探测器,对其暗计数率、分辨率进行了检测,暗计数率约为0.1counts/cm2×s.     

On the theory of the condensed states of heteropolymers

The collapse (globulization) of an ideal heteropolymer chain under the action of an external attractive field is considered. The problem of the collapse of different types of primary structures, including mobile, periodic, large-block, and statistical structures, is formulated. It is shown that for a random heteropolymer, the mathematical image of the globular state is the chain-length independence of the probability distribution of a random thermal distribution function of the end monomer coordinates. The free energy per monomer of a chain in a globular state and local densities of monomers of all types are shown to be a self-averaging quantities. An exactly solvable model is proposed for a globule formed by a statistical heteropolymer chain. In this model, different types of monomers are attracted to different centers by linear elastic forces with identical elastic constants. The modulus of elasticity is obtained for a heteropolymer globule with respect to the attraction of different types of monomers in different directions. It is shown that this modulus is higher for a short-periodic polymer than for a statistical one.     

Spherical gravitational collapse with photon emission and a generalized Schwarzchild interior solution

The general dynamical equations for perfect fluid filled spheres with an outward flux of photons are derived. The vital role played by the energy density of the free gravitational field in accelerating photon production has been emphasized. It is pointed out that even when the material energy density is finite, the energy density of the free gravitational field can take infinitely large values resulting in vanishing surface area of the star. A generalized Schwarzschild interior solution with conformally flat geometry but with photon emission has been obtained. It is pointed out that the interior conformal coordinate system bears a strong resemblance to the exterior Krushkal coordinates. It is shown that for spherical star the invariant velocity of the fluid particles, falling towards the centre, is proportional to its radius suggesting that the outer envelopes collapse at a faster rate than the core part. It is shown that the interior radiating solution can be matched with generalized Schwarzchild exterior solution.     

Why Matter Occupies so Large a Volume？

The paper represents a rigorous treatment of the underlying quantum theory, not just in words but providing the underlying technical details, as to why matter occupies so large a volume and its intimate connection with the Pauli exclusion principle, as more and more matter is put together, as well as of the contraction or shrinkage of ＂bosonic matter＂, upon collapse, for which the Panli exclusion is abolished. From the derived explicit bounds of integrals of powers of the particle number densities, explicit bounds on probabilities of the occurrences of the events just described are extracted. These probabilities lead one to infer the change of the ＂size＂ or extension of such matter, upon expansion or contraction, respectively, as their content is increased.