A critical review of advanced analytical techniques for water-soluble organic matter from atmospheric aerosols

Water-soluble organic matter (WSOM) from air particles plays a potentially important role in the climate system, yet little is known about its molecular composition and physico-chemical properties. During the past decade, the rapidly-evolving field of analytical instrumentation has produced sophisticated tools capable of providing molecular level information on this organic-aerosol fraction.This article presents a critical review of the major applications of these advanced analytical methods in WSOM analysis. We emphasize off-line methods relying on nuclear magnetic resonance and infrared spectroscopies, and high-resolution mass spectrometry. We also discuss the most prominent analytical methods for near real-time measurements of particulate WSOM. We address the limitations of advanced off-line and on-line instrumental techniques, and, finally, outline the major challenges ahead to improve the current knowledge on the chemical structures of aerosol WSOM.     

From large analogical instruments to small digital black boxes: 40 years of progress in mass spectrometry and its role in proteomics. Part II 1985–2000

This is the continuation of a personal retrospective on the developments that since 1965 have given shape to Mass Spectrometry (MS) and taken it from a position of simply playing a role in Protein Chemistry to becoming an indispensable tool in Proteomics, all within a 40‐year span. Part I covered the period from 1965 to 1984. This second part reviews the Mass Spectrometry timeline of events from 1985 to 2000, stopping at various time points where MS made significant contributions to protein chemistry or where the development of new instrumentation for MS represented a major advance for peptide and protein work. Major highlights in the field and their significance for peptide and protein characterization such as the advent and practical consequences of electrospray ionization (ESI) and matrix‐assisted laser desorption/ionization (MALDI) are covered, including work done with triple quads, the development of time‐of‐flight (TOF) instruments and new ion traps and going on to the more recent work on the full characterization of the Proteome with ion traps, TOF instruments and new ionization and tagging techniques for protein sequencing. Copyright © 2009 John Wiley & Sons, Ltd.     

Phase-changing sacrificial layers in microfluidic devices: adding another dimension to separations

The use of polymers in microchip fabrication affords new opportunities for the development of powerful, miniaturized separation techniques. One method in particular, the use of phase-changing sacrificial layers, allows for simplified designs and many additional features to the now standard fabrication of microchips. With the possibility of adding a third dimension to the design of separation devices, various means of enhancing analysis now become possible. The application of phase-changing sacrificial layers in microchip analysis systems is discussed, both in terms of current uses and future possibilities. Figure Phase-changing sacrificial materials enable multilayer microfluidic device layouts     

Fast two‐dimensional detection for X‐ray photon correlation spectroscopy using the PILATUS detector

The first X‐ray photon correlation spectroscopy experiments using the fast single‐photon‐counting detector PILATUS (Paul Scherrer Institut, Switzerland) have been performed. The short readout time of this detector permits access to intensity autocorrelation functions describing dynamics in the millisecond range that are difficult to access with charge‐coupled device detectors with typical readout times of several seconds. Showing no readout noise the PILATUS detector enables measurements of samples that either display fast dynamics or possess only low scattering power with an unprecedented signal‐to‐noise ratio.     

Dielectrophoretic cell trapping for improved surface plasmon resonance imaging sensing

The performance of conventional surface plasmon resonance (SPR) biosensors can be limited by the diffusion of the target analyte to the sensor surface. This work presents an SPR biosensor that incorporates an active mass‐transport mechanism based on dielectrophoresis and electroosmotic flow to enhance analyte transport to the sensor surface and reduce the time required for detection. Both these phenomena rely on the generation of AC electric fields that can be tailored by shaping the electrodes that also serve as the SPR sensing areas. Numerical simulations of electric field distribution and microparticle trajectories were performed to choose an optimal electrode design. The proposed design improves on previous work combining SPR with DEP by using face‐to‐face electrodes, rather than a planar interdigitated design. Two different top‐bottom electrode designs were experimentally tested to concentrate firstly latex beads and secondly biological cells onto the SPR sensing area. SPR measurements were then performed by varying the target concentrations. The electrohydrodynamic flow enabled efficient concentration of small objects (3 μm beads, yeasts) onto the SPR sensing area, which resulted in an order of magnitude increased SPR response. Negative dielectrophoresis was also used to concentrate HEK293 cells onto the metal electrodes surrounded by insulating areas, where the SPR response was improved by one order of magnitude.     

A kHz heat‐load shutter for white‐beam experiments at synchrotron sources

A heat‐load shutter capable of frequencies from one to several tens of kHz and window times from 10 µs up to 1 ms is described. In the current configuration the water‐cooled shutter absorbs ～99% of the heat generated by the white beam. It has been successfully used for extended periods synchronized with a Jülich pulse‐selector operating at 946 Hz. The temperature of the pulse‐selector remained constant during a three‐day continuous operation. Flexibility is provided by the interchangeability of the chopper disc.     

Diagnosis of negative hydrogen ions and rovibrational distribution of H<Subscript>2</Subscript> molecule in non-thermal plasmas

Rovibrational excited hydrogen molecule plays an important role for the production of H^- ions. The correlation between H^- ion density and rovibrational distribution of H₂ molecules has been investigated in dielectric barrier discharge hydrogen plasmas via optical emission spectrometry and molecular beam mass spectrometry. The relative vibrational distribution of molecular hydrogen in the electronic ground state has been determined by the best fitting to the Fulcher-α band emission lines. It is shown that the ratio of the Q_(0-0)(1) to Q_(1-1)(1) line is very suitable and simple for the diagnosis of vibrational temperature in the range of 1500 to 7500 K. At certain discharge conditions (ac 40 kHz, 14 kV), the vibrational temperature decreases from 3600 to 2400 K as the pressure increases from 100 to 200 Pa and the negative ions density near the ground electrode also decreases as the pressure increases. Both the hydrogen ions density and the vibrational temperature increase with the increasing of discharge voltage. It is found that the evolution of negative atomic hydrogen ions density greatly depends on the vibrational temperature.     

Antenna pattern for four gravitational wave antennas

Summary The antenna pattern is analysed for four widely spaced cryogenic gravitational wave antennas which are expected to begin operating in coincidence during 1987. Using reasonable assumptions for senstivity, the four-antenna pattern is shown to give between 50% and 80% sky coverage for circularly polarized radiation under the minimum-detection criterion of two-way coincidence. One-hundred percent sky coverage can be achieved if one antenna is reoriented, but this is at the expense of reduced probability for 3-way coincidences.     

A ballon-borne experiment for observations of the near-infrared cosmological background

Summary We present here a ballon-borne experiment to measure the near-infrared cosmological background in the (1÷5) μm range. The instrument, a liquid helium cooled telescope (250 mm,F/2), was built in the infrared laboratory of Istituto TE.S.R.E./C.N.R.-Bologna (Italy) collaboration with the Haverford College (PA-U.S.A.). It will be launched from the NSBF base of Palestine (Texas-U.S.A.) in May 1989. To speed up publication, the proofs were not sent to the authors and were supervised by the Scientific Committee.     

磁共振快速T/R开关驱动器研制

在磁共振T/R开关和主动失谐线圈中广泛使用PIN管,由外部驱动器向PIN管提供驱动电源,控制其导通或截止,从而达到开关切换和线圈失谐的目的.因此,驱动器的性能直接影响T/R开关和线圈的性能.该工作提出了一种新的T/R开关驱动器设计方案.电路中门控信号与驱动电源互相隔离,同时包含了场效应管死区调整电路,提高了电路稳定性和灵活性.该电路开关切换时间可达500 ns,驱动电压和电流理论上分别可达400 V和10 A以上,具有快速、驱动能力强等特点.可用于快速T/R开关和主动失谐线圈的驱动、缩短死时间、减小发射线圈和接收线圈间的耦合.