bluuebunny/crossref_metadata_2025_split huggingface dataset:
Laser Excited Expanding Small Clusters: Single Time Distribution Functions
Authors: Raitza T. , Reinholz H. , Röpke G. , Morozov I. , Suraud E. 
Published: October 2009

AbstractThe time evolution of laser excited small clusters such as Na309 is investigated using a classical MD simulation code. Results for the electron phase space distribution are analyzed. We are interested intime dependent density and temperature profiles. The question of local thermal equilibrium is addressed comparing the simulated profiles with predictions from equilibrium statistical physics. Once the local thermal equilibrium is established, the time evolution of collective modes of the excited electron system can be investigated. For this, a restricted MD simulation scheme has been developed (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electron Dynamics in Tight‐Binding Approximation ‐ the Influence of Thermal Anharmonic Lattice Excitations
Authors: Chetverikov A. P. , Ebeling W. , Velarde M.G. 
Published: October 2009

AbstractWe study here several basic problems of the quantum mechanics of electrons which are embedded into a onedimensional (1D) nonlinear, thermally excited lattice. Our approach uses the tight‐binding model for the dynamics of the electrons. Through coupling terms in the Hamiltonian the electron quantum dynamics is connected with the classical dynamics of the lattice endowed with Morse interactions. First it is shown that the electron forms bound states with the solitonic excitations in the lattice. These so‐called solectrons may move with supersonic speed. Then we study the effects of interference of solectrons with solitons. Finally we study the interference between thermal excitations on tunneling between two minima (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Energy Distribution of Electrons Expelled from Relativistically Intense Laser Beam
Authors: Galkin A.L. , Egorov V.A. , Kalashnikov M.P. , Korobkin V.V. , Romanovsky M.Yu. , Shiryaev O.B. , Trofimov V.A. 
Published: October 2009

AbstractMotions of electrons driven by the fields of relativistically intense laser pulses are studied. The treatment is based on the numerical solution of the relativistic Newton's equation with the Lorentz force. It is demonstrated that an electron can be accelerated by a relativistically intense optical field up to a considerable part of the energy of its oscillation within the pulse. Energy spectra of the electrons scattered by an optical field are used to estimate the absolute value of the laser pulse intensity (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electric Field Fluctuations in the Systems of the Charged Particles with Exchange Interaction
Authors: Belyi V.V. , Kukharenko Yu.A. 
Published: October 2009

AbstractThe quantum plasma of Bose and Fermi particles is considered. A scheme of equation linearization for density matrix with the exchange interaction taken in account is proposed and the equation solution is found. An expression for Hartree‐ Fock dielectric permeatability with the exchange interaction is obtained. This interaction is taken into account in the exchange scattering amplitude. With the use of obtained solutions the non‐equilibrium spectral function of electric field fluctuations in presence of exchange interaction and medium polarization is found. It is shown that in the state of thermodynamic equilibrium a Fluctuation‐Dissipation Theorem holds. An expression for the system's response to an external electric field in presence of exchange interaction is given (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fast Electron Generation by Coulomb Scattering on Spatially Correlated Ions in a Strong Laser Field
Authors: Bauch S. , Bonitz M. 
Published: October 2009

AbstractElectrons colliding with spatially fixed ions in strong laser fields are investigated by solving the time‐dependent Schrödinger equation. Considering first simple one‐dimensional model systems, the mechanisms and energy spectra of fast electrons are analyzed, starting from collisions on a single ion. By using these electrons as projectiles for a second and third collision, the maximum possible energy obtained can be significantly increased. We then generalize the analysis to 2D systems where additional angular degrees of freedom lead to a drastic loss of efficiency. This problem can be overcome by introducing external confinements, which allow to focus the electrons and increase the intensity of high‐energy electrons (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Resonant Penetration of Intense Femtosecond Laser Pulses Through Plasma of Ultra‐Thin Foils
Authors: Bordyukh N.V. , Krainov V.P. 
Published: October 2009

AbstractSimple analytic expression for the transmission coefficient as a function of foil thickness d describing penetration of intense femtosecond laser pulse through ultra‐thin foils with the thickness of the order of 100 nm has been derived using the Maxwell‐Vlasov‐Boltzmann equation. It is found that the transmission of laser radiation stops on the skin depth c/ωp, but sharp and narrow resonances take place at the foil thickness d > c/ωp where the there is no laser reflection (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Generation of Zeptosecond Electromagnetic Pulses by Electrons Under their Interaction with Femtosecond Laser Pulses
Authors: Galkin A.L. , Korobkin V.V. , Romanovsky M.Yu. , Shiryaev O.B. 
Published: October 2009

AbstractThe motions of electrons driven by the fields of relativistically intense laser pulses are analyzed for the linear polarization. The treatment is based on the numerical solution of the relativistic Newton's equation with the Lorentz force for laser beams with Gaussian transverse intensity distribution. The electromagnetic radiation of an electron interacting with a laser pulse is also studied. It is shown that: laser fields accelerate electrons both in the transverse and longitudinal directions and the electron radiation comprises short pulses having zeptosecond (and even subzeptosecond) durations (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical Properties of the e–e+ Plasma Generated in the Focal Spot of a High‐Intensity Laser
Authors: Blaschke D. B. , Ilyine S. V. , Panferov A.D. , Röpke G. , Smolyansky S. A. 
Published: October 2009

AbstractWe discuss the high frequency conductivity and absorption coefficient of an quasiparticle electron ‐ positron plasma (EPP) created from the vacuum in a strong nonstationary electric field (nonstationary Schwinger mechanism), e.g., in the focus spot of two counterpropagating laser beams. The consideration is based on a strong nonperturbative approach. It is shown that the basic contribution here is due to vacuum polarization effects. For subcritical linearly polarised fields, we obtain the general expression for the induced conductivity and the absorption coefficient, which is investigated in a wide range of frequencies from the optical to the γ‐ray region. Some experimental consequences of the high absorptivity of the quasiparticle EPP are discussed (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
ABCG2‐associated resistance to Hoechst 33342 and topotecan in a murine cell model with constitutive expression of side population characteristics
Authors: Smith Paul J. , Furon Emeline , Wiltshire Marie , Campbell Lee , Feeney Graham P. , Snyder Ronald D. , Errington Rachel J. 
Published: October 2009

AbstractDrug resistant tumor “side‐populations,” enriched in cancer stem cells and identified by reduced accumulation of Hoechst 33342 under ABCG2‐mediated efflux, may compromise therapeutic outcome. Side‐population cells have predicted resistance to minor groove ligands, including the DNA topoisomerase I poison topotecan. We have used a stable Hoechst 33342‐resistant murine L cell system (HoeR415) to study resistance patterns, removing the need for SP isolation before microarray analysis of gene expression and the tracking of cell cycle dynamics and cytotoxicity. The majority of HoeR415 cells displayed a side‐population phenotype comparable with that of the side‐population resident in the ABCG2 over‐expressing A549 lung cancer cell line. Photo‐crosslinking showed direct protection against minor groove ligand residence on DNA, driven by ABCG2‐mediated efflux and not arising from any binding competition with endogenous polyamines. The covalent minor‐groove binding properties of the drug FCE24517 (tallimustine) prevented resistance suggesting a mechanism for overcoming SP‐related drug resistance. Hoechst 33342‐resistant murine cells showed lower but significant crossresistance to topotecan, again attributable to enhanced ABCG2 expression, enabling cells to evade S‐phase arrest. Hoechst 33342/TPT‐resistant cells showed limited ancillary gene expression changes that could modify cellular capacity to cope with chronic stress including over‐expression of Aldh1a1 and Mgst1, but under‐expression of Plk2 and Nnt. There was no evidence to link the putative stem cell marker ALDH1A1 with any augmentation of the TPT resistance phenotype. The study has implications for the patterns of drug resistance arising during tumor repopulation and the basal resistance to minor groove‐binding drugs of tumor side‐populations. © 2009 International Society for Advancement of Cytometry
Flow cytometry without alignment of collection optics
Authors: Sitton Greg , Srienc Friedrich 
Published: October 2009

AbstractThis study describes the performance of a new waveguide flow cell constructed from Teflon AF® (TFC) and the potential use of fiber optic splitters to replace collection objectives and dichroic mirrors. The TFC has the unique optical property that the refractive index of the polymer is lower than water and therefore, water filled TFC behaves and functions as a liquid core waveguide. Thus, as cells flow through the TFC and are illuminated by a laser orthogonal to the flow direction, scattered and fluorescent light is directed down the axis of the TFC to a fiber optic. The total signal in the fiber optic is then split into multiple fibers by fiber optic splitters to enable measurement of signal intensities at different wavelengths. Optical filters are placed at the terminus of each fiber before measurement of specific wavelengths by a PMT. The constructed system was used to measure DNA content of CHO and yeast cells. Polystyrene beads were used for alignment and to assess the performance of the system. Polystyrene beads were observed to produce light scattering signals with unique bimodal characteristics dependent on the direction of flow relative to the collecting fiber optic. © 2009 International Society for Advancement of Cytometry
Fundamentals of electrochemical detection techniques for CE and MCE
Authors: Kubáň Pavel , Hauser Peter C. 
Published: October 2009

AbstractThe electroanalytical techniques of amperometry, conductometry and potentiometry match well with the instrumental simplicity of CE. Indeed, all three detection approaches have been reported for electrophoretic separations. However, the characteristics of the three methods are quite distinct and these are not related to the optical methods more commonly employed. A detailed discussion of the underlying principles of each is given. The issue of possible effects of the separation voltage on the electrochemical detection techniques is considered in depth, and approaches to the elimination of such interferences are also discussed for each case.
Detection of hormone active chemicals using genetically engineered yeast cells and microfluidic devices with interdigitated array electrodes
Authors: Ino Kosuke , Kitagawa Yusuke , Watanabe Tsuyoshi , Shiku Hitoshi , Koide Masahiro , Itayama Tomoaki , Yasukawa Tomoyuki , Matsue Tomokazu 
Published: October 2009

AbstractEndocrine disruptors that act like hormones in the endocrine system might have toxic effects. Therefore, it is important to develop a portable device that can detect hormone active chemicals in samples rapidly and easily. In this study, a microfluidic device was developed for the detection of hormone active chemicals using genetically engineered yeast cells. The yeast cells were used as biosensors since they were genetically engineered to respond to the presence of hormone active chemicals by synthesizing β‐galactosidase (β‐gal). For achieving further sensitivity, we incorporated interdigitated array (IDA) electrodes (width, 1.2 μm; gap, 0.8 μm) with 40 electrode fingers into the analytical chamber of the microfluidic device. The yeast cells precultured with a hormone active chemical, 17β‐estradiol (E2), were trapped from the main channel of the device to the analytical camber by electrophoresis. After trapping in the analytical chamber, we performed electrochemical detection of β‐gal induced in the yeast cells with the IDA electrodes. Actually, electrochemical detection was performed on p‐aminophenol that was converted from p‐aminophenyl‐β‐D‐galactopyranoside with β‐gal. The electrochemical signals from the yeast cells precultured with 17β‐estradiol were successfully detected with the device. Furthermore, the inhibitory effects of antagonists such as tamoxifen were also detected electrochemically by using the device. Thus, the present microfluidic device can be used for highly sensitive detection of hormone active chemicals.
Chemoselective ligand patterning of electroactive surfaces using microfluidics
Authors: Westcott Nathan P. , Yousaf Muhammad N. 
Published: October 2009

AbstractTo generate model substrates for cell adhesion, we have developed two different biocompatible strategies based on self‐assembled monolayers (SAMs) of alkanethiolates on gold terminated with latent ketones and aldehydes. Under spatial control, the hydroquinone and alcohol‐terminated SAMs can be oxidized to allow for oxyamine ligand patterning on the surface with microfluidic cassettes. These immobilization strategies were characterized by electrochemistry, fluorescence, and utilizing a cell adhesive peptide, cell patterns were generated.
Improving MCE with electrochemical detection using a bubble cell and sample stacking techniques
Authors: Guan Qian , Henry Charles S. 
Published: October 2009

AbstractTwo efforts to improve the sensitivity and limits of detection for MCE with electrochemical detection are presented here. One is the implementation of a capillary expansion (bubble cell) at the detection zone to increase the exposed working electrode surface area. Bubble cell widths were varied from 1× to 10× the separation channel width (50 μm) to investigate the effects of electrode surface area on detection sensitivity, LOD, and separation efficiency. Improved detection sensitivity and decreased detection limits were obtained with increased bubble cell width, and LODs of dopamine and catechol detected in a 5× bubble cell were 25 and 50 nM, respectively. Meanwhile, fluorescent imaging results demonstrated ∼8 and ∼12% loss in separation efficiency in 4× and 5× bubble cell, respectively. Another effort at reducing the LOD involves using field amplified sample injection for gated injection and field amplified sample stacking for hydrodynamic injection. Stacking effects are shown for both methods using amperometric detection and pulsed amperometric detection. The LODs of dopamine in a 4× bubble cell were 8 and 20 nM using field amplified sample injection and field amplified sample stacking, respectively. However, improved LODs were not obtained for anionic analytes using either stacking technique.
Prenatal sonographic diagnosis of short umbilical cord in a dichorionic twin with normal fetal anatomy
Authors: Sherer David M. , Dalloul Mudar , Ajayi Olusegun , Kheyman Mila , Sokolovski Margarita , Abulafia Ovadia 
Published: October 2009

AbstractShort umbilical cords are associated with fetal anomalies, often including those with decreased or absent fetal movement, fetal akinesia/hypokinesia sequence, and restrictive dermopathies and aneuploidy. In normal fetuses, abnormally short umbilical cords have been associated with an increased risk of umbilical vessel hematomas, thrombosis, rupture, thrombocytopenia, cord compression, variable fetal heart rate decelerations, instrumental and operative deliveries, and fetal demise. We report a 24‐year‐old gravida 2, para 0 with a concordant dichorionic twin gestation, at 26 weeks' gestation, in whom sonography depicted fetuses with normal‐appearing anatomy as well as short umbilical cord of the 1st twin. Increased fetal surveillance was conducted. Following delivery at 36 weeks' gestation, the presence of a short umbilical cord of the 1st twin measuring 19 cm was confirmed. Systematic review of the literature confirms that this is the first report of prenatal diagnosis of a short umbilical cord in an otherwise normal fetus. © 2009 Wiley Periodicals, Inc. J Clin Ultrasound 2010
Scrotal sonography revisited
Authors: Carkaci Selin , Ozkan Efe , Lane Deanna , Yang Wei T. 
Published: October 2009

AbstractSonography is the imaging modality of choice for the scrotum because it is simple, relatively inexpensive, and quick. Recent technological advances and transducer improvements have led to exquisite high‐resolution detail in gray‐scale as well as Doppler imaging. The purposes of this pictorial essay are to review the anatomy and embryology of the scrotal contents and to review the various scrotal and extrascrotal pathologic conditions, including acute scrotum, pediatric and adult testicular and extratesticular scrotal neoplasms, traumatic lesions, and miscellaneous other scrotal lesions. © 2009 Wiley Periodicals, Inc. J Clin Ultrasound 2010
Subcutaneous lipoma compressing the common peroneal nerve and causing palsy: Sonographic diagnosis
Authors: Hsu Yi‐Chih , Shih Yen‐Yu I. , Gao Hong‐Wei , Huang Guo‐Shu 
Published: October 2009

AbstractThe compression of peripheral nerves by benign fatty tumors has rarely been reported in the literature. We present the case of a patient who had a subcutaneous lipoma in the region of the knee that caused common peroneal nerve palsy and appeared to compress the nerve on sonography. The surgical removal of subcutaneous lipoma allowed complete recovery. © 2009 Wiley Periodicals, Inc. J Clin Ultrasound 2010
Mass spectrometry as a tool for characterization of N,N‐dialkylaminoethane‐ 2‐thiols—precursors and degradation products of chemical warfare agents
Authors: Papoušková Barbora , Bednář Petr , Stýskala Jakub , Hlaváč Jan , Barták Petr , Lemr Karel 
Published: October 2009

AbstractN,N‐dialkylaminoethane‐2‐thiols belong to the group of precursors and degradation products of chemical warfare agents (CWAs). These compounds were analyzed by means of electrospray ionization‐multiple stage mass spectrometry (ion trap) and proposed fragments were confirmed by accurate mass measurement using a QqTOF system. The fragmentation pathways of studied compounds and the products of oxidation (formation of ‐S‐S‐ linkage) were described. Some minor interesting processes, such as rearrangement of SH group, were observed and proved. A new µLC/MS method, based on ion‐pairing chromatography, was developed. Trifluoroacetic acid was employed as an ion‐pairing agent to increase the low retention of compounds of interest in the reverse‐phase system. The technique was compared with the UPLC/MS method, allowing fast analysis of all the studied thiols as well as an explorative control of originated disulfides. Copyright © 2009 John Wiley & Sons, Ltd.
Ablation of articular cartilage with an erbium:YAG laser: An ex vivo study using porcine models under real conditions—ablation measurement and histological examination
Authors: Meister Jörg , Franzen René , Gavenis Karsten , Zaum Martin , Stanzel Sven , Gutknecht Norbert , Schmidt‐Rohlfing Bernhard 
Published: October 2009

AbstractBackground and ObjectivesThe use of an erbium:YAG laser in arthroscopic surgery has the advantage of a precise treatment of soft tissue. Due to the high absorption in water, the laser energy is perfectly matched to smoothing the hydrous, fibrillated articular cartilage surface. In minimal invasive surgery, the workspace is filled with aqueous liquids for enlargement. This appears contrary to the absorption characteristics of erbium:YAG laser radiation in water. The purpose of this study was to evaluate the ablated volume per pulse of cartilage lesions and the potential side effects including thermal damage and tissue necrosis.Study Design/Materials and MethodsTwenty‐four osteochondral specimens of porcine knee joints were irradiated with an Er:YAG laser completely submerged in water, with distances to the cartilage surface of 1, 3 and 5 mm and pulse durations of 75 and 100 microseconds. To keep a constant peak power of approximately 6 kW, pulse energies of 450 and 580 mJ were used at a pulse repetition rate of 15 Hz. After a histological preparation, ablated volumes, depths, and widths of the cuts were investigated. Additionally, laser protocols were correlated with different markers of cartilage tissue damage and apoptosis.ResultsAblation could be observed for every measurement. The influence of the distance showed a statistical significance (P < 0.001) for the volume, depth, and width of the cuts. For the pulse duration, statistical significance (P < 0.001) was found only for the volume and the depth. We observed no loss of proteoglycan or collagen type II. The total cell number, cell morphology, and number of apoptotic cells in an area close to the cutting edge and in a corresponding unaffected area of the same specimens revealed no differences regardless of the applied protocol.ConclusionThe use of an Er:YAG laser demonstrates the successful application in liquid environments for cartilage removal without any damage of the surrounding tissue. Lasers Surg. Med. 41:674–685, 2009. © 2009 Wiley‐Liss, Inc.
Synthesis of Amorphous Hydrophobic Telechelic Hydrocarbon Diols via ADMET Polymerization
Authors: Schwendeman John E. , Wagener Kenneth B. 
Published: October 2009

AbstractAmorphous, hydrophobic telechelic hydrocarbon diols were synthesized using acyclic diene metathesis (ADMET) polymerization. These diols can be used in hydrolysis and UV resistant polyurethanes. The hydrocarbon backbone is based on a mimic of an ethylene/isobutylene polymer, made by the ADMET polymerization of a gem‐dimethyl substituted α,ω‐diene followed by hydrogenation of the polymer's repeat unit unsaturation. Chain termination reactants (CTR's) having one, three, and nine methylene “spacers,” respectively, between their olefin and alcohol precursor group were used to cap the polymer chain ends to yield 2.0 functional telechelics. Use of the medium length CTR in a polymerization–depolymerization scheme, resulted in amorphous (Tg = −56 °C) telechelic diols with good molecular weight control.magnified image
Synthesis of Supported Nickel Diimine Catalysts for Ethylene Slurry Polymerization
Authors: Choi Yiyoung , Soares João B. P. 
Published: October 2009

AbstractEthylene slurry polymerizations were performed using supported nickel diimine catalysts. The effects of catalyst structure and polymerization conditions on catalyst activity, polymer particle morphology, and polymer properties were investigated. Covalently attached supported nickel diimine catalysts activated with ethyl aluminum sesquichloride (EASC) have high activities and made polymers with spherical morphology. Compared with the equivalent homogeneous catalysts, the covalently attached supported catalysts produced polyethylene with higher melting temperatures, higher molecular weights, and broader molecular weight distributions. Borates used as internal activator during the synthesis of these supported catalysts successfully activated the nickel diimine complexes.magnified image