生物材料玻璃化保存方法研究进展

生物材料的玻璃化保存技术一直是低温生物学领域的研究热点,提高冷却速率是实现玻璃化保存的一条途径。介绍了常用玻璃化保存方法的操作方法,分析比较了其冷却速率和保存效果,并提出了一种新颖的玻璃化保存法。     

Rheological microscopy: local mechanical properties from microrheology

We demonstrate how tracer microrheology methods can be extended to study submicron scale variations in the viscoelastic response of soft materials; in particular, a semidilute solution of lambda-DNA. The polymer concentration is depleted near the surfaces of the tracer particles, within a distance comparable to the polymer correlation length. The rheology of this microscopic layer alters the tracers' motion and can be precisely quantified using one- and two-point microrheology. Interestingly, we found this mechanically distinct layer to be twice as thick as the layer of depleted concentration, likely due to solvent drainage through the locally perturbed polymer structure.     

Rheological properties of dense granular flows

Recent progresses in understanding the behavior of dense granular flows are presented. After presenting a bulk rheology of granular materials, I focus on the new developments to account for non-local effects, and on ongoing research concerning the surface rheology and the evolution of mechanical properties for heterogeneous systems.     

Rheological properties of a vesicle suspension

The rheological properties of a vesicle suspension have been investigated in the limit of strong flows destroying the stationary form of vesicles. The dependence of the effective viscosity of the suspension on the velocity gradient and the properties of vesicles has been obtained for the case of the plane flow. In particular, it has been shown that the effective viscosity of the suspension can strongly depend on its initial state. The effect of thermal fluctuations on the rheological properties of the suspension has been analyzed.     

Piezoelectricity in polymers and biological materials

The piezoelectric effect in polymers is usually explained in terms of the uniaxial orientation of the polymer crystallites and the classical piezoelectric property of these crystallites. Polarization caused by stress gradient seems to be necessary to the understanding of the geometrical relationship between stress and polarization. Studies of the temperature variation of the complex piezoelectric modulus have revealed a new type of relaxation phenomenon, which is closely related to elastic and dielectric relaxation. The possibility of a polymer piezoelectric transducer has been demonstrated by a microphone using an elongated film of poly-γ-methyl-L-glutamate. The physiological significance of piezoelectricity in biological polymers, such as its correlation with the growth mechanism of bone and with the sense of a mechanical stimulus, is worth further investigation.     

Rheological properties of water-based magnetic fluid and its emulsion

Field-induced rheological properties were studied for pure magnetic fluids (MFs) and 5% MF–cetyltrimethylammonium bromide (CTABr) emulsion for varying CTABr concentration (0–0.1 M) at different temperatures. The zero-field rheological study for 5% MF–CTABr emulsion shows maximum viscosity for 0.01 M CTABr concentrations. In-field viscosity results for 0.01 M CTABr–MF emulsion shows nearly 10 times more change in viscosity than the pure fluid, indicating the interaction between micelles and magnetic particles.     

Review of air-coupled ultrasonic materials characterization

This article presents a review of air-coupled ultrasonics employed in the characterization or nondestructive inspection of industrial materials. Developments in air-coupled transduction and electronics are briefly treated, although the emphasis here is on methods of characterization and inspection, and in overcoming limitations inherent in the use of such a tenuous sound coupling medium as air. The role of Lamb waves in plate characterization is covered, including the use of air-coupled acoustic beams to measure the elastic and/or viscoelastic properties of a material. Air-coupled acoustic detection, when other methods are employed to generate high-amplitude sound beams is also reviewed. Applications to civil engineering, acoustic tomography, and the characterization of both paper and wood are dealt with here. A brief summary of developments in air-coupled acoustic arrays and the application of air-coupled methods in nonlinear ultrasonics complete the review. In particular, the work of Professor Bernard Hosten and his collaborators at Bordeaux is carefully examined.     

Bioactive coatings of porous materials: Fabrication and properties

The methods for producing implants based on a metal matrix with a bioactive coating are described. Porous titanium and titanium nickelide obtained by ion-plasma sputtering are selected as the metal substrate. The bioactive coating is formed from an aqueous suspension of hydroxyapatite. Various methods of deposition are proposed such as vacuum impregnation, its combination with centrifugation, and exposure to ultrasound. Their comparative estimation is given. The surface morphology of the samples is studied by electron microscopy; the characteristics of the surface are estimated by the Brunauer?Emmett?Teller method.     

Polarized optical scattering signatures from biological materials

The polarization of laser light backscattered from biological samples has been measured over the wavelength range 350-850 nm. Incident circular, linearly polarized, and unpolarized light produces significant spectral features in the case of samples containing chlorophyll such as leaves and cyanobacteria. Polarization scattering signatures are observed around the chlorophyll ‘red edge’ that may have diagnostic value in the search for life signatures from extrasolar planets.     

Elastic properties of magnetic materials

This review discusses the theoretical aspects of magnetoelastic coupling with emphasis on the magnetic perturbation of elastic properties. The basic theory of magnetostriction is set out with application to ferromagnets, ferrimagnets and antiferromagnets, and is followed by a discussion of the physical origin of the magnetoelastic coupling coefficients in both localized and itinerant magnetic systems. Magnetic contributions to elastic compliance are then discussed and sound velocity anomalies near magnetic phase transitions investigated, including the cooperative Jahn-Teller limit for which the acoustic mode itself drives a structural transition even when magnetic ordering does not occur. The review concludes with discussion of magnetoelastic (or mixed magnon-phonon) waves in low temperature magnetically ordered phases and with a study of local striction phenomena in magnetically dilute materials. The latter leads to a recognition of internal rearrangement modes which may also be present in concentrated magnetic systems, and which may or may not couple significantly to bulk homogenous strain.     

Remote time-resolved filament-induced breakdown spectroscopy of biological materials

We report, for what we believe to be the first time, on the feasibility of remote time-resolved filament-induced breakdown spectroscopy (FIBS) of biological materials. The fluorescence from egg white and yeast powder, induced by femtosecond laser pulse filamentation in air, was detected in the backward direction with targets located 3.5 m away from the detection system. The remarkably distinct spectra of egg white and yeast allow us to propose that this technique, time-resolved FIBS, could be potentially useful for remote detection and identification of harmful biological agents.     

Thermal properties of two-dimensional materials

Two-dimensional(2D) materials, such as graphene, phosphorene, and transition metal dichalcogenides(e.g., Mo S2 and WS2), have attracted a great deal of attention recently due to their extraordinary structural, mechanical, and physical properties. In particular, 2D materials have shown great potential for thermal management and thermoelectric energy generation. In this article, we review the recent advances in the study of thermal properties of 2D materials. We first review some important aspects in thermal conductivity of graphene and discuss the possibility to enhance the ultra-high thermal conductivity of graphene. Next, we discuss thermal conductivity of Mo S2 and the new strategy for thermal management of Mo S2 device. Subsequently, we discuss the anisotropic thermal properties of phosphorene. Finally, we review the application of 2D materials in thermal devices, including thermal rectifier and thermal modulator.     

Molecular depth profiling of organic and biological materials

Atomic depth profiling using secondary ion mass spectrometry, SIMS, is common in the field micro-electronics; however, the generation of molecular information as a function of sample depth is difficult due to the accumulation of damage both on and beneath the sample surface. The introduction of polyatomic ion beams such as SF₅ and C₆₀ have raised the possibility of overcoming this problem as they deposit the majority of their energy in the upper surface of the sample resulting in increased sputter yields but with a complimentary reduction in sub-surface damage accumulation. In this paper we report the depth profile analysis of the bio-polymer polycaprolactone, PCL, using the polyatomic ions and and the monoatomic Au⁺. Results are compared to recent analysis of a similar sample using . depth profiling of cellulose is also demonstrated, an experiment that has been reported as unsuccessful when attempted with implications for biological analysis are discussed.     

Review of particle properties: Particle data group

This review of the properties of leptons, mesons, and baryons is an updating of Review of Particle Properties, Particle Data Group [Rev. Mod. Phys. 48 (1976) No. 2, Part II; and Supplement, Phys. Lett. 68B (1977) 1]. Data are evaluated, listed, averaged, and summarized in tables. Numerous tables, figures, and formulae of interest to particle physicists are also included. A data booklet is available.     

聚苯乙烯/纳米铝复合材料的流变特性及纺丝研究

为有效制得Z箍缩氘代聚苯乙烯/纳米铝(DPS/AlNPs)导电丝阵材料,采用PS中掺入AlNPs制备PS/AlNPs复合材料纤维进行模拟研究。研究了温度及剪切速率等因素对PS/AlNPs复合材料流变性能的影响、复合材料熔体的结构变化及流动状态与可纺性能的关系,以及PS/AlNPs纤维的形貌、热稳定性能和力学性能。结果表明：PS/AlNPs熔体属于典型剪切变稀型非牛顿流体,熔体的表观粘度与温度呈现负相关,240~260 ℃时复合材料的非牛顿指数介于0.462~0.546,结构黏度系数介于1.8~2.1,黏流活化能介于77.2~104.6 kJ·mol^-1,具有良好的可纺性。PS/AlNPs纤维表面光滑,对AlNPs粒子包覆良好且对其抗氧化非常有利,其中当AlNPs质量分数为1%时纤维的断裂伸长率突出、掺量为5%时其断裂强度较高。     

Review of photorefractive materials: an application to laser beam cleanup

Nonlinear photorefractive materials are well suited to record dynamic volume holograms using the wave mixing of coherent laser beams. The photo-induced index modulation is due to a space charge field which modulates the crystal refractive index. The basic phenomena and beam interactions are reviewed for different types of materials operating in the visible and near infrared. In particular, we outline their ability to amplify a low intensity signal beam due to the intensity transfer of a spatially multimode pump beam. We apply this interaction to the cleanup of a multimode large core fiber amplifier. This class of nonlinear materials contribute to extending the performances of laser sources for advanced applications of photonics. To cite this article: L. Lombard et al., C. R. Physique 8 (2007).     

Review of particle properties

This review of the properties of leptons, mesons, and baryons is an updating of Review of Particle Properties, Particle Data Group [Rev. Mod. Phys. 45, No. 2, Part II, Supplement (1973)]. Data are evaluated, listed, averaged, and summarized in tables.