Glass physics: from fundamentals to applications

The European Physical Journal E -     

Hydrogel-based encapsulation of biological, functional tissue: fundamentals, technologies and applications

Replacing dysfunctional endocrine cells or tissues (e.g. islets, parathyroid tissue) by functional, foreign material without using immunosuppressives could soon become reality. Immunological reactions are avoided by encapsulating cells/tissues in hydrogel (e.g. alginate) microcapsules, preventing interaction of the enclosed material with the host’s immune system while permitting the unhindered passage of nutrients, oxygen and secreted therapeutic factors. Detailed investigations of the physical, physico-chemical and immunological parameters of alginate-based microcapsules have led recently to the development of a novel class of cell-entrapping microcapsules that meet the demands of biocompatibility, long-term integrity and function. This together with the development of ‘good medical practice’ microfluidic chip technology and of advanced cryopreservation technology for generation and storage of immunoisolated transplants will bring cell-based therapy to clinics and the market. PACS  82.35.Pq; 87.19.Xx     

固体发动机羽烟的激光透过率测试

为获得羽烟对激光透过率的影响,用烟箱法对2种配方的缩比发动机羽烟在1.06 μm、10.6 μm激光波段的透过率进行测试.采用1.064 μm激光调制发射、接收、数据采集系统对1.06 μm激光波段烟雾透过率测试;用黑体、光谱辐射计、数据采集系统可测出2 μm ～13 μm 的光学透过率,从中提出10.6 μm激光波段烟雾透过率,得到不同推进剂配方、不同烟雾浓度情况下10.6 μm光波和1.06 μm光波的烟雾透过率测试数据.烟箱1.8 m烟道上的测试数据表明:配方2推进剂优于配方1推进剂,10.6 μm光波的烟雾透过率96%～97%大于1.06 μm光波的烟雾透过率92%～93%.     

Pulsed intense electron beams generated in transient hollow cathodedischarges: fundamentals and applications

For the commercial application of pulsed power, material processing with intense pulsed particle beams is a very interesting subject. Recently, high-voltage (1-70 kV), low-pressure (1-100 Pa) transient hollow-cathode discharges turned out to be sources for pulsed intense electron beam generation suitable for this application. The remarkable parameters of these electron beams-beam currents of 50-1000 A (10-30% of the maximum discharge current) with a high energy component (mean energy of about 0.25-0.75 of maximum applied voltage) of 20-70% of the maximum beam current, power density up to 10 W/cm², beam diameters of 0.1-3 mm, beam charge efficiency of 3-5%-captured the attention not only of the scientific community in the last decade. The electron beam is emitted during the early phases of the discharge, and only weak dependence of the high energetic peak of the beam current was found on the external capacity, which determine the development of the later high-current phases. However, the beam parameters depend on the breakdown voltage, gas pressure, and discharge geometry (including self-capacity). In this paper, the characteristics of the pulsed intense electron beams generated in two configurations-multigap pseudosparks and preionization-controlled open-ended hollow-cathode transient discharges (PCOHC)-are described. Such electron beams already were used successfully in a variety of pulsed power applications in material processing, deposition of superconducting (YBaCuO) and diamond-like thin films, microlithography, electron sources for accelerators, and intense point-like X-ray sources, and some preliminary experiments revealed new potential applications such as pumping of short-wavelength laser active media. These pulsed electron beams could be used further in any kind of pulsed power applications that require high-power density, small or high electron energy, and small-beam diameters     

Broadband THz emission from gas plasmas induced by femtosecond optical pulses: From fundamentals to applications

We review the generation of broadband THz radiation from femtosecond photo‐induced gas plasmas, with an emphasis on the highly efficient “AC‐bias” case where the plasma is generated and driven by a superposition of fundamental and second‐harmonic optical fields. The dependence on experimental parameters such as pulse energy, air pressure, polarization and focusing are presented, and compared to the predictions from semi‐quantitative models for the THz generation process, namely (i) a microscopic photocurrent model and (ii) a four‐wave mixing model. We also employ these models to the case of few‐cycle pulses, where the observed THz emission is related directly to the carrier‐envelope phase of the pulses, and hence provides a mechanism with which to measure this phase.}     

Nonlinear response of ultrasound contrast agent microbubbles:From fundamentals to applications

Modelling and biomedical applications of ultrasound contrast agent(UCA) microbubbles have attracted a great deal of attention. In this review, we summarize a series of researches done in our group, including(i) the development of an all-in-one solution of characterizing coated bubble parameters based on the light scattering technique and flow cytometry;(ii) a novel bubble dynamic model that takes into consideration both nonlinear shell elasticity and viscosity to eliminate the dependences of bubble shell parameters on bubble size;(iii) the evaluation of UCA inertial cavitation threshold and its relationship with shell parameters; and(iv) the investigations of transfection efficiency and the reduction of cytotoxicity in gene delivery facilitated by UCAs excited by ultrasound exposures.     

激光外差探测超声位移的原理、方法和实验

本文介绍了激光外差探测超声位移的原理，用布喇格声光衍射盒作为激光移频，锁相环作调相信号解调等方法组成的外差干涉探测装置和实验结果，并分析了空间准直性对激光外差干涉信噪比的影响以及减小探测极限和抑制噪声的途径。     

Laser frequency locking by direct measurement of detuning

We present a new method of laser frequency locking in which the feedback signal is directly proportional to the detuning from an atomic transition, even at detunings many times the natural linewidth of the transition. Our method is a form of sub-Doppler polarization spectroscopy, based on measuring two Stokes parameters (I2 and I3) of light transmitted through a vapor cell. It extends the linear capture range of the lock loop by as much as an order of magnitude and provides frequency discrimination equivalent to or better than those of other commonly used locking techniques.     

Laser applications in nuclear physics: Present and future

The use of lasers for nuclear physics research is widespread and growing rapidly. The major impact in nuclear structure research has come from nuclear size and shape determinations for nuclei far from stability via high resolution isotope shift measurements. In addition, systematic data on nuclear magnetic and quadrupole moments have been obtained via the hyperfine splitting resolved in laser fluorescence studies of atomic spectra in both stable and unstable systems. The tunability, high intensity and inherent polarization of laser light can be used to polarize atomic nuclei for nuclear reaction studies. The rapid efficient polarization of unstable nuclei with lasers also presents opportunities for new research in nuclear physics. In this paper the physics of the laser interaction for the studies indicated will be introduced. Some examples of work completed and in progress will be presented primarily from on-line laser studies at charged particle accelerators. Extensions of current research, particularly with respect to possible studies of short-lived nuclei, are discussed and the synergistic effects of certain advances in quantum electronics and nuclear physics described.     

Laser heating in the diamond cell: techniques and applications

Very high temperatures (>2000 K) at megabar presures (∼100 GPa) can be achieved by classic shock compression experiments and in laser-heated diamond cells, which have evolved to a formidable tool for accurately characterizing material properties at controlled pressure and temperature conditions of the Earth's lower mantle and core. The diamond cell has great potential for future development and broad application but due to the small sample dimensions there are strict experimental requirements for obtaining reliable data, some of which are described in the present paper. Results for measuring melting temperatures of iron at very high pressure, which constrain the temperature in the Earth's centre, are reviewed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Laser spectroscopy 9. Prospects and applications

This concluding article in the series discusses the prospects of realizing the ultimate parameters — spectral resolving power and sensitivity — and some fields of application — nuclear physics, chemical kinetics and molecular physics, quantum metrology — of laser spectroscopy.     

Laser shock processing: a review of the physics and applications

Developed since the beginning of the 1970s in the United States (Battelle, Columbus), laser shock processing (LSP) is being extensively studied in France in order to improve the mechanical properties of metallic surfaces of dense or porous materials. This paper reviews the considerable data on LSP which has been obtained in recent years and provides an exhaustive account of current trends concerning the physics, the mechanics and the applications involved. After presenting some general and specific data regarding the physical principles of laser shock (laser system, plasma physics, pressure generation, physical limits) and mechanical effects induced (experimental and theoretical) on different materials, the efficiency of the process is illustrated through two potential industrial applications linked with modifications of surface states: fatigue and wear resistance of metals. Experience with LSP applications shows that, because it uses safe surface geometries and provides greater affected depths, LSP is about to emerge as a real alternative to classical treatments.     

Laser frequency modulation noise measurement by recirculating delayed self-heterodyne method

I propose and demonstrate the use of the recirculating delayed self-heterodyne (DSH) method for measuring FM noise power spectral densities (PSDs), which are the most fundamental measure characterizing the spectral purity of laser sources. By analyzing the DSH beat signals with 1, 10, and 160?km delays, the FM noise PSD of a narrow-linewidth fiber laser is evaluated for Fourier frequency range between 10?Hz and 100?kHz, which exhibits flicker noise as the dominant contribution.