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Vibrio parahaemolyticus, a kind of biofilm-forming foodborne bacterium, presents formidable challenges to the effectiveness of antimicrobial agents. Increasingly, the safety of chemical antimicrobials has aroused the widespread attention of the public. The development of the novel nature antimicrobial agents has become critical for controlling biofilm-related pollution and infections. In this paper, we investigated the antibacterial activity of Lactobacillus paracasei L10, and evaluated the inhibition and eradication effects of the cell-free supernatant (CFS) of the strain on V. parahaemolyticus biofilms in detail. We found that the CFS exhibited marked antibacterial activity against all tested pathogenic bacteria. In co-cultural assay, L. paracasei L10 could notably reduce cell viability in both plankton and biofilm of V. parahaemolyticus and this antagonism effect in biofilm was greater than that in planktonic state. Meanwhile, the growth of V. parahaemolyticus was completely inhibited when 6% (v/v) of the CFS was added, and the supernatant also showed a concentration-dependent manner to inhibit and eradicate the biofilms of V. parahaemolyticus while decreased the metabolic activity of the biofilm in the same way. Moreover, the fluorescence microscopic and confocal laser scanning microscopy images confirmed the anti-biofilm activity of the CFS. This study elucidates that L. paracasei L10 displays a significant anti-biofilm effect on V. parahaemolyticus and the mechanism of its antagonism merits further study, which provides theoretical support for further development and application of L. paracasei L10 as anti-biofilm agents.

The smart cleaning ability of cotton fabrics is realized by cross-linking thermo-responsive random copolymer to the cotton. Poly(2-(2-methoxyethoxy)ethoxyethyl methacrylate-co-ethylene glycol methacrylate), denoted as P(MEO2MA-co-EGMA), is synthesized from 2-(2-methoxyethoxy)ethoxyethyl methacrylate (MEO2MA) and ethylene glycol methacrylate (EGMA) with a molar ratio of 17 : 3. Its dilute aqueous solution (1 mg mL−1) presents a lower critical solution temperature (LCST) of 38 °C. Furthering increase the solution concentration, the LCST shifts towards lower temperature. By applying citric acid as a cross-linker, P(MEO2MA-co-EGMA) is successfully immobilized onto cotton fabrics. The obtained cotton fabrics also possess thermo-responsive property with a LCST at 37 °C. The smart cleaning ability is confirmed by single fiber cleaning experiments using a confocal microscope. It is observed that the cleaning ability of the cotton with cross-linked P(MEO2MA-co-EGMA) can be prominently enhanced at low temperature (below LCST). In addition, due to the low glass transition temperature of P(MEO2MA-co-EGMA) (−26 °C), the polymer is in a gel state at room temperature and will not negatively impact fabric softness. P(MEO2MA-co-EGMA) is a promising candidate for preparing textiles with smart cleaning ability and great fabric hand.

Reasonably fabricating ordered structures of ionic polymers is very important for the development of novel func- tional materials. By combining the ions and liquid cry stalline polymer, we successfully designed and synthesized a series of novel combined main-chain/side-chain ionic liquid crystalline polymer (MCSC-ILCPs) containing imidazolium groups and different counter-anions, poly (2,5-bis{(6-(4-butoxy-4!-imidazolium biphenyl)hexyl)oxycarbonyl}styrene salts) poly(BImBHCS-X) with the following types of counter-anions (Br", BF4", PF6" and TFSI"). Combined technologies con- firmed the chemical structures of the monomers and polymers with imidazolium cation and different counter-anions. Dif- ferential scanning calorimetry (DSC), polarized light microscopy (PLM) and one- and two-dimensional wide-angle X-ray diffraction (1D and 2D WAXD) results illustrated that the LC structures and the transitions of ordered structures depended on the nature of the counter-anion employed. The polymers with Br" and BF4" counter-anions exhibited smectic A (SmA) LC behavior below the isotropic temperature. The another one, poly(BImBHCS-TFSI) with the large volume of the TFSI" anion destroyed the packing of the LC ordered structure resulting in an amorphous structure. The photophysical properties of the polymers prepared can be adjusted by tuning the ionic interaction of the polymers by switching the counter-anion.

Graphene Oxide (GO) was prepared from natural graphite and treated with different types and various amounts of cationic surfactants to form the intercalation nanocomposites. The resulting specimens were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectrum (FT-IR), X-ray diffraction (XRD), and Thermogravimetric analysis (TGA). X-ray diffraction patterns revealed that the interlamellar spacing strongly depended on the mole mass ratios between GO to cationic surfactants and the alkyl chain length of surfactants. In addition, a model was proposed to illustrate the procedure of cetyltrimethylammonium chloride (CTAC)-GO intercalation, and the angles of inclination between the alkyl chains and GO planes were calculated based on the model.

Polycrystalline Cu2ZnSnS4 (CZTS) films were deposited on ITO conductive glass substrates by one-step pulsed laser deposition. The influence of laser pulse energy on the microstructure and optical properties was investigated. The results indicate that all the films are rich in Sn, poor in S and well crystallized with dominant (1 1 2) preferred orientation. At laser pulse energies of 130, 165 and 180 mJ, SnS2 impurity phase exists in CZTS films, which is probably the reason for their larger bandgaps (1.61–1.67 eV) compared with that of a stoichiometric CZTS film (around 1.50 eV). While at the laser pulse energy of 150 mJ, an attractive Cu-poor and Zn-rich, large grain size and single-phase CZTS film can be obtained. In such a film, excess Cu vacancies reduce the valence band maximum (VBM) of CZTS, leading to the blue shift of its bandgap (1.60 eV).

Monitoring erosion progress of biodegradable drug carrying polymer coated on coronary drug eluting stents (DES) is largely hindered because of the small amount of coating material as well as the irregular profile of coating, both of which make the monitoring using traditional methods highly challenging. In our study, electrochemical impedance spectroscopy (EIS), a widely used method in the study of metal corrosion, was used to address the challenges traditional methods face. In vitro, remained mass and molecular weight drop data of film-like poly(lactide-co-glycolide) (PLGA) samples due to degradation were monitored using traditional mass loss measurement and size exclusion chromatography (SEC) methods. The obtained data were compared to the changes of capacitance and impedance measured by EIS from PLGA-coated stainless slices with an equivalent electrical circuit model. The results showed that the changes of the resistance and capacitance obtained by EIS, which indicates transformations of PLGA coating, can be correlated to the degradation measured by traditional methods, such as SEC. Furthermore, EIS method was applied to monitor and evaluate the erosion progress of a real stent with PLGA coating. Our results suggested that EIS method can accurately monitor real-time erosion process of thin polymer coatings on DES in situ. © 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 103B: 691–699, 2015.

Three zinc (II) complexes of the amino acid Schiff base were synthesized by the one step reaction of amino acid with aldehyde, zinc acetate in solvent-free. The compositions and structures of the complexes were characterized by elemental analyses, FTIR, XRD, TG-DSC. The compositions of the complexes are ZnL•nH2O (L = sal-leu, sal-ala, van-leu; sal = salicylaldehyde; van = vanillic aldehyde; leu = leucine; ala = alanine). Infrared spectra of the complexes indicate that the Schiff base ligands are formed, zinc ion is coordinated to the Schiff base ligands as terdentate with O, O and N donors from carboxylic, phenolic and imino groups respectively, the coordination numbers of zinc ion is four. The possible pyrolysis reactions in the thermal decomposition process of the complexes, the experimental and calculated percentage mass loss are also given.

Copper electrocrystallisation on a glassy carbon electrode from acid sulphate electrolytes in the presence of different concentrations of 3-mercapto-1-propanesulphonate sodium salt (MPS) and its combinations with chloride ions (Cl) or/and polyethylene glycol (PEG) have been investigated by utilising chronoamperometry (CA) technique and scanning electronic microscopy (SEM). The CA and SEM results indicate that copper nucleation follows instantaneous nucleation with three-dimensional growth (3DI) from all baths at the deposition potentials studied. With increasing MPS concentration, copper nucleation rate and nuclei number density N increase in the MPS, MPS–Cl and MPS–PEG–Cl baths, but decrease in the MPS–PEG bath.

Copper electrodeposition and nucleation on a glassy carbon electrode from acid sulfate electrolytes in the presence of 3-mercapto-1-propanesulfonate sodium salt (MPS) and its combinations with chloride ions (Cl) or/and polyethylene glycol (PEG) were investigated by utilizing cyclic voltammetry (CV), chronoamperometry (CA) and scanning electron microscopy (SEM). CV results indicate that MPS and MPS–PEG inhibit whereas MPS–Cl and MPS–PEG–Cl accelerate copper deposition. CA and SEM results suggest that copper nucleation follows an instantaneous nucleation mechanism with three-dimensional growth from all baths at the studied deposition potentials. The copper nucleation rate and nuclei number density are increased greatly in the MPS–Cl and MPS–PEG–Cl baths.

Four ethylenediamine-N,N,N′,N′-tetraacetate complexes with Sb(III)-M-Sb(III) polynuclear structure (M=Co(II), La(III), Nd(III), Dy(III)) are synthesized. [Sb2-μ4-(EDTA)2Co(H2O)2]·5.15H2O is characterized by single crystal X-ray diffraction. The crystal structure of [Sb2-μ4-(EDTA)2Co(H2O)2]·5.15H2O belongs to monoclinic system, space group P21/n, lattice parameters: a=6.9969(2), b=20.8705(4), c=10.8106(2) A, β=90.031(1)°, V=1578.66(6) A3, Z=2, M r=1007.76, D c=2.120 g cm−3, F(000)=1001, μ=2.323 mm−1, the final R=0.0235 and wR=0.0629 for 3480 observed reflections (I>2σ(I)). The powder X-ray diffraction patterns of the complexes are also measured. Elemental analyses, FTIR spectra, TG-DSC and DTA of [Sb2(EDTA)2Ln]NO3·nH2O are performed. FTIR spectra reveal that the antimony and other metallic ions were connected through the carboxylate bridges. The thermal analysis can demonstrate the complex formation of the antimony, other metallic ions and EDTA. The possible pyrolysis reactions in the thermal decomposition process of the complexes, the experimental and calculated percentage mass losses are also given.

International audience; Two odd-odd nuclei from the A ~ 100 and A ~ 130 regions, namely ^102Rh and ^134Pr have been studied in search for chiral doublet bands via ^94Zr(^11B,3n)^102Rh and ^119Sn(^19F,4n)^134Pr reactions, respectively. Two nearly degenerate bands built on the pig_9/2 ⊗ vh_11/2 configuration have been identified in ^102Rh and on the pig_11/2 ⊗ vh_11/2 configuration for ^134Pr. Lifetimes of excited nuclear states were measured using Dopplershift attenuation method and recoil distance Doppler-shift method. The deexciting gamma rays were registered by the Indian National Gamma Array for ^102Rh and using the EUROBALL IV detector array with an inner Bismuth Germanate (BGO) ball for ^134Pr, respectively. Polarization and angular correlation measurements have been performed to establish the spin and parity assignments for these bands. The derived reduced transition probabilities are compared to the predicitons of the two quasiparticles + triaxial rotor and interacting boson fermion-fermion models.

The thiourea complexes of antimony and bismuth triiodide were synthesized by a direct reaction of antimony and bismuth triiodide with thiourea powder at room temperature. The formula of the complex is MI3[SC(NH2)2]3(M=Sb, Bi). The crystal structure of the complexes belongs to monoclinic system and the lattice parameters are a=1.4772 nm, b=1.6582 nm, c=2.0674 nm and β=90.81° for SbI3(SC(NH2)2)3 and a=1.4009 nm, b=2.0170 nm, c=2.0397 nm and β=90.84° for BiI3[SC(NH2)2]3. The infrared spectra reveal that the trivalent antimony or bismuth ion is coordinated by the nitrogen atom, not the sulfur atom of the thiourea. Thermal analysis shows that there are two times structure rearrangements or phase transformation in the complexes from 100 to 170°C.

Static and ultrafast infrared spectroscopy have been used to measure absorption spectra and vibrational energy relaxation (VER) times for the antisymmetric stretching vibrational band of azide, N(3)(-), in formamide-containing reverse micelles (RMs). RMs were formed in n-heptane using the surfactant AOT, sodium bis(2-ethylhexyl) sulfosuccinate. The VER times were found to be significantly longer than in bulk formamide. The VER times became longer as the molar ratio of formamide to AOT, omega(F), was decreased. Decreasing omega(F) also resulted in substantial blue shifts of the azide static absorption band compared to the frequency in bulk formamide. The omega(F) dependent studies are consistent with expected size trends, where a larger RM results in more bulklike polar solvent and faster VER rates. These results are in contrast to aqueous AOT RMs where VER times were indistinguishable from those in the bulk and the static spectral shifts were much smaller. The differences between the static and dynamic behavior in aqueous and formamide RMs are related to differences in structural changes upon confinement in RMs.

Twenty chiral isochromene derivatives have been chromatographed on native and derivatized cyclodextrin stationary phases using HPLC. The most effective CSPs for the enantioresolution of these analytes in the reverse phase mode are the hydroxypropyl-β-cyclodextrin (Cyclobond RSP), the 2,3-dimethyl-β-cyclodextrin (Cyclobond DM), and the γ-cyclodextrin (Cyclobond II) stationary phases. The α-cyclodextrin (Cyclobond III), β-cyclodextrin (Cyclobond I), acetyl-β-cyclodextrin (Cyclobond AC), S-1-naphthylethyl carbamate-β-cyclodextrin (Cyclobond SN), and 3,5-dimethylphenyl carbamate-β-cyclodextrin (Cyclobond DMP) stationary phases also show enantioselectivities for some analytes. No enantioseparations were observed in the polar organic mode and only a few separations were found in the normal phase mode. The Cyclobond RSP CSP provided the best overall separations of these analytes in the reverse phase mode. The pH of the mobile phase and the nature of organic modifiers have little effect on the enantioresolution. The substituents on the isochromene ring greatly affect the chiral recognition.

Ultrafast infrared spectroscopy has been used to measure vibrational energy relaxation (VER) and reorientation (Tr) times for the high frequency vibrational bands of potassium ferrocyanide and ferricyanide (CN stretches), and sodium nitroprusside (SNP, CN, and NO stretches) in water and several other solvents. Relatively short VER times (4-43 ps) are determined for the hexacyano species and for the NO band of SNP, but the CN band of SNP relaxes much more slowly (55-365 ps). The solvent dependence of the VER times is similar for all the solutes and resembles what has been previously observed for triatomic molecular ions [Li et al., J. Chem. Phys. 98, 5499 (1993)]. Anisotropy decay times are also measured from the polarization dependence of the transient absorptions. The Tr times determined for SNP are different for the different vibrational bands; for the nondegenerate NO mode of nitroprusside (SNP) they are much longer (>15 ps), correlate with solvent viscosity, and are attributed to overall molecular rotation. The short Tr (

Vibrational energy relaxation (VER) and reorientation times have been measured by ultrafast polarization infrared spectroscopy for the antisymmetric stretching ν3 band of free azide ion and NaN3, MgN3+, and CaN3+ ion pairs in dimethyl sulfoxide solutions. The ν3 absorption bands are shifted to higher frequency in the ion pairs relative to the unassociated, dissolved anion, but VER times of the ion pairs are similar, all in the range of 11–18 ps. The reorientation times of the ion pairs are longer (>20 ps) than for free azide (6 ± 2 ps), as expected based on their structures. Ab initio calculations were performed to help interpret the experimental results.

Reorientation and vibrational energy relaxation times have been measured by ultrafast transient polarization IR spectroscopy for the antisymmetric stretching band in the 2000–2200 cm−1 region of pseudohalide ions, N3−, NCO−, and NCS−, confined in nanosize water pools of reverse micelles (RMs). The RMs are composed of nonionic nonylphenyl poly-oxyethylene surfactant in cyclohexane. Vibrational energy relaxation times (T1) of the NCO− and NCS− ions are about three times longer in small RMs compared to bulk water, similar to our earlier results on the N3− ion [J. Chem. Phys. 118, 7074 (2003)]. The longer T1 times are attributed to the reduced interaction between the ions and water molecules due to confinement effects and hydration of the surfactant headgroups by water molecules. Reorientation times (TR) of the N3− and NCS− ions are found to be more than one order of magnitude longer in small RMs than in bulk H2O. The observed longer TR times support the notion that water molecules inside RMs have very restri...

Vibrational energy relaxation (VER) times have been measured by ultrafast infrared spectroscopy near 2000 cm−1 for the antisymmetric stretching ν3 band of azide ion in water pools of nonionic reverse micelles (RM). The water pool radii were varied in the 1–3 nm range by adjusting the water-to-surfactant molar ratio, ω=[H2O]/[surfactant]. Compared to the value measured in this work for bulk water (0.81±0.06 ps), the VER decay times are about three times longer (2.5±0.2 ps) for the smallest RM studied (ω=1) and become shorter with increasing ω and RM size but do not reach the bulk value at the largest ω studied. Solvent shifts of the azide vibrational band in RMs have been previously reported [Langmuir 18, 7401 (2002)], and in a manner similar to the VER rates, tend toward the bulk water value with increasing ω. Studies of the VER dynamics of azide ion in RMs are used to investigate confinement effects on solvation and to explore the effects of continuously modifying the solute–solvent interaction by varyin...

The photodissociation dynamics of the 3s Rydberg state of three ketones (CH3CO–R, R=C2H5, C3H7, and iso-C4H9) and the ensuing dissociation of the nascent acetyl radical following 195 nm excitation were investigated by ultrafast photoionization spectroscopy. The 3s state the lifetimes of these ketones are similar (2.5–2.9 ps), though lifetimes of the acetyl radical range from 8.6 ps for CH3CO–C2H5, 15 ps for CH3CO–C3H7, to 23 ps for CH3CO–(iso-C4H9), which suggests that for larger R more vibrational degrees of freedom compete for the excess energy so that less energy is partitioned into the internal energy of the acetyl radical.

The antisymmetric stretching band of the ν3 vibration of azide ion was studied in nanosize water droplets confined in reverse micelles by Fourier transform infrared spectroscopy. In reverse micelle...

New hexamethylenetetramine complexes of antimony and bismuth trichloride were synthesized through a solid phase reaction of hexamethylenetetramine and antimony or bismuth trichloride. The formula of the complex is MCl3(C6H12N4)2⋅H2O (M=Sb, Bi).The crystal structure of the complexes belongs to monoclinic system and the lattice parameters: a=1.249 nm, b=1.4583 nm, c=1.6780 nm andβ=91.78° for SbCl3(C6H12N4)2⋅H2O and a=1.3250 nm, b=1.3889 nm, c=1.7449 nm and β=98.94° for BiCl3(C6H12N4)2⋅H2O. Far-infrared spectra reveal that the antimony or bismuth ion is coordinated by the nitrogen atom of the hexamethylenetetramine. The thermal analysis also demonstrates the complex formation between the antimony or bismuth ion and hexamethylenetetramine. The intermediate and final residues in the thermal decomposition process have been analyzed to check the pyrolysis reaction.

The primary events in the photosynthetic retinal protein bacteriorhodopsin (bR) are reviewed in light of photophysical and photochemical experiments with artificial bR in which the native retinal polyene is replaced by a variety of chromophores. Focus is on retinals in which the “critical” C13=C14 bond is locked with respect to isomerization by a rigid ring structure. Other systems include retinal oxime and non-isomerizable dyes noncovalently residing in the binding site. The early photophysical events are analyzed in view of recent pump–probe experiments with sub-picosecond time resolution comparing the behavior of bR pigments with those of model protonated Schiff bases in solution. An additional approach is based on the light-induced cleavage of the protonated Schiff base bond that links retinal to the protein by reacting with hydroxylamine. Also described are EPR experiments monitoring reduction and oxidation reactions of a spin label covalently attached to various protein sites. It is concluded that in bR the initial relaxation out of the Franck–Condon (FC) state does not involve sub-stantial C13=C14 torsional motion and is considerably catalyzed by the protein matrix. Prior to the decay of the relaxed fluorescent state (FS or I state), the protein is activated via a mechanism that does not require double bond isomerization. Most plausibly, it is a result of charge delocalization in the excited state of the polyene (or other) chromophores. More generally, it is concluded that proteins and other macromolecules may undergo structural changes (that may affect their chemical reactivity) following optical excitation of an appropriately (covalently or non-covalently) bound chromophore. Possible relations between the light-induced changes due to charge delocalization, and those associated with C13=C14 isomerization (that are at the basis of the bR photocycle), are discussed. It is suggested that the two effects may couple at a certain stage of the photocycle, and it is the combination of the two that drives the cross-membrane proton pump mechanism.

Transforming growth factor beta (TGFbeta)1 induced dephosphorylation of pRb at multiple serine and threonine residues including Ser249/Thr252, Thr373, Ser780, and Ser807/811 in MV4-11 cells. Likewise, TGFbeta1 caused the dephosphorylation of p130, while inhibiting accumulation of p107 protein. Phosphorylated pRb was detected to bind E2F-1 and E2F-3, which appears to be a major form of pRb complexes in actively cycling cells. TGFbeta1 significantly downregulated pRb-E2F-1 and pRb-E2F-3 complexes as a result of inhibition of E2F-1 and E2F-3. In contrast, complexes of E2F-4 with pRb and with p130 were increased markedly upon TGFbeta1 treatment, whereas p107 associated E2F-4 was dramatically decreased. In agreement with these results, p130-E2F-4 DNA binding activity was dominant in TGFbeta1 treated cells, whereas p107-E2F-4 DNA binding activity was only found in proliferating cells. Our data strongly suggest that inhibition of E2Fs and differential regulation of pRb family-E2F-4 complexes are linked to TGFbeta1-induced growth inhibition. E2F-4 is switched from p107 to p130 and pRb when cells are arrested in G1 phase by TGFbeta1.

The dynamics of the interaction of the Rydberg E(1Σ+) state and the valence state V(1Σ+) of HBr and DBr were investigated using a reflectron time-of-flight mass spectrometer coupled with a femtosecond laser system. Interrogation of the state formed by the avoided crossing of the Rydberg and valence states revealed dynamic behavior that was different for the two isotopes. Pump–probe experiments on HBr showed no change in the lifetime over the range of pump wavelengths of 256.7–254.7 nm. However, the lifetime of DBr decreased as the pump wavelength was tuned bluer. Tunneling is involved in the evolution of the population in photoexcited Rydberg state to the ion-pair state.

Excited state electron transfer at the adsorbate/metal interface represents a key step in molecular electronic devices. The dynamics of such processes are governed by ultrafast energy relaxation which can be probed directly by time-resolved two-photon photoemission (2PPE). Using 2PPE spectroscopy we investigate the energetics and lifetimes of the unoccupied electronic states of C6F6 adsorbed on Cu(111) as a model system for electron transfer at organic/metal interfaces. With increasing C6F6 layer thickness we find a pronounced decrease in the energetic position of the lowest unoccupied state, which is accompanied by a strong increase in its lifetime as well as a decrease in the effective electron mass. The frequently employed dielectric continuum model which describes delocalized (quantum well) states within adsorbate layers does not give a consistent explanation of these findings. By adsorption of Xe overlayers onto C6F6/Cu(111) we can show that, even for one monolayer of C6F6, the excited state must be localized predominantly inside the C6F6 layer and thus originates from a molecular state (presumably an antibonding σ* orbital). With increasing coverage this state becomes more delocalized within the adsorbate layer, which reduces the coupling to the metal substrate and thus enhances the excited state lifetime.

A reflectron-time-of-flight mass spectrometer (RTOFMS) coupled with a femtosecond multiphoton ionization technique is used to study the combined metastable and collision-induced dissociation of sulfur dioxide clusters and mixed sulfur dioxide-water clusters. From the dissociation patterns, the general structural arrangement of the clusters is clearly identified: (SO2)m·+ clusters have a SO2·+ core solvated by SO2 molecules; [SO(SO2)n]·+ and [S(SO2)n+1]·+ have a structure of SO·+ · (SO2)n and (SO)2·+ · (SO2)n, respectively. For [HSO2(SO2)]+ clusters, the ion core is HSO2+. H3SO3+ appears to have two isomeric structures: one HSO2+ · H2O, the other H3O+ · SO2.

The study of the interaction of femtosecond laser radiation with matter, especially clusters, has blossomed in recent years due to advances in laser technology. One aspect of this interaction is Coulomb explosion. This effect occurs when the repulsive energy of like charges, known as Coulomb repulsion, overcomes the cluster’s total cohesive energy, causing the cluster to disintegrate into charged fragments. In this study, the interactions of methyl iodide clusters, formed in a supersonic expansion using argon and helium as carrier gases, were investigated at 795 nm using a Ti:Sapphire femtosecond laser. The resulting atomic and cluster ions were analyzed in a reflection time-of-flight mass spectrometer. The focus of these studies was the elucidation of the effects of carrier gas and laser wavelength on the laser-cluster interactions leading to Coulomb explosion. To achieve these goals, the effects of different carrier gases, laser power, cluster distribution, and the resulting Coulomb explosion energies w...

Because of the dispute in the literature over the dissociation rate and energy partitioning of the acetone molecule upon photoexcitation to the S1 state (π*←n) and 3s Rydberg state (3s←n), we have remeasured the lifetime of acetone (also d6-acetone) on the S1 and 3s surfaces by a femtosecond time-resolved multiphoton ionization technique, coupled with a reflectron time-of-flight mass spectrometer. The measured dissociation rate of acetone on the S1 surface is prompt, and the acetyl radical is long lived. The lifetime of acetone on the 3s surface is measured to be 3.2±0.4 ps (6.0±0.5 ps for d6-acetone). The dissociation rate of acetyl is approximately 1.7 ps (2.5 ps for d3-acetyl) from the curve fitting. This agrees well with the Rice–Ramsperger–Kassel–Marcus theory predicted lifetime of 1.0 ps (1.9 ps for d3-acetyl) when the internal excitation energy of the acetyl radical is treated by a statistical-adiabatic-impulsive model.

The photodissociation dynamics of methyl iodide clusters using λ=270 nm as pump and λ=405 nm as probe are studied using a femtosecond two color pump–probe laser arrangement combined with a reflectron time-of-flight (RTOF) mass spectrometer. This enables the A state and 10s Rydberg state of methyl iodide to be accessed with the pump beam. Of particular interest is a comparison of the femtosecond dynamics of the methyl iodide monomer with the clustered species. Clocking of the monomer dissociation shows a transient which is indicative of a fast C–I bond breakage as is to be expected upon excitation of methyl iodide into the fast dissociating A state, or into the predissociative 10s Rydberg state. Clusters, however, show a very different pump–probe transient composed of a fast decay and a subsequent dip in ion signal followed by a rise for pump–probe delay times greater than 2 ps. The cluster ion signal shows an enhancement for pump probe delay times up to 70 ps. The results are interpreted in terms of the e...

The dissociation pathways of (HCl)2+ are studied by a molecular beam-femtosecond multiphoton ionization technique, and via ab initio calculations at the MP2/6-31G(d,p) level and using Gaussian-2 theory. Results indicate, besides the commonly accepted proton-transferred HClH+Cl structure, a hydrogen-peroxide-like structure, (HCl–ClH)+, also exists and appears to be more stable. Their interconversion involves a barrier of 0.24 eV. A new dissociation product, Cl2+, is observed and shown to come from an intracluster reaction of the HCl dimer cation. Dissociations of the (HCl)2+ into H2Cl+ and HCl+ channels are preferred at low internal excitations, whereas dissociations into Cl2+ and HCl2+ require higher excitation energies.

The unimolecular dissociation dynamics of selected alkene cluster ions (ethene, propene, 1-butene, trans-2-butene, and cis-2-butene) and their fast fragment ions has been investigated using a reflectron time-of-flight mass spectrometer. These ions were prepared by the supersonic expansion of a premixed sample gas containing 20% alkene in Ar, followed by multiphotoionization (MPI) using a Ti:sapphire femtosecond laser. From the unimolecular decomposition patterns of all the ions investigated, we conclude that after photoionization a radical cation initiated intracluster polymerization takes place in these cluster ions. But, due to steric hindrance, it does not continue indefinitely as the cluster size increases. For ethene, pentamerization can be observed, and for propene, trimerization; while in the case of the three isomeric butenes, 1-butene is partially trimerized and only dimerization is observed in 2-butene.

Photo-assisted MOCVD has been applied to the fabrication of thick film YBa 2 Cu 3 O 7− x for wires and tapes. The application of photo-irradiation as the sole source of energy for the MOCVD reaction has resulted in extremely rapid growth rates for YBCO films with high superconducting performance. Typical YBCO films of thickness >1 μ m exhibit J c ∽1×10 6 A cm −2 and T c >90 K on single crystal oxide substrates. Such films have now been integrated to metal substrates including both single crystal Ni(100) and roll-textured nickel foil. YBCO films grown on these substrates with CeO 2 and YSZ buffer layers show J c >3×10 5 A cm −2 for films of >1 μ m thickness grown in 2–4 min time. Such performance for thick films made in such a short time is promising for YBCO wire fabrication with optimization of the photo-assisted MOCVD process expected to yield J c >1×10 6 A cm −2 for 1–5 μ m thick YBCO films on flexible nickel substrates.

Mixed NO/H 2 O-clusters are produced by merging a beam of pure NO-clusters, formed by supersonic expansion in a pulsed nozzle, with water vapor in a pickup source. After ionization with 400 nm light from a femtosecond laser system, a mixed NO/H 2 O-cluster series of pure protonated water clusters H + (H 2 O) n (with n up to 20) is observed which shows an obvious intensity maximum for cluster size n = 4. Other experimental findings are reported herein on the metastable decay of ionized mixed NO/H 2 O-clusters. Taken together, the results establish that reactions occurring at degrees of hydration corresponding to n ⩾ 4 lead to the production of the protonated hydrates and the concomitant formation of HNO 2 . In this study special attention is paid to NO + (H 2 O) n ions because these ions are considered to be an important precursor for the production of proton hydrates in the ionosphere.

Neutron diagnostics have become a significant means to study energetic particles in high power auxiliary heating plasmas on the Experimental Advanced Superconducting Tokamak (EAST). Several kinds of neutron diagnostic systems have been implemented for time-resolved measurements of D-D neutron flux, fluctuation, emission profile, and spectrum. All detectors have been calibrated in laboratory, and in situ calibration using 252Cf neutron source in EAST is in preparation. A new technology of digitized pulse signal processing is adopted in a wide dynamic range neutron flux monitor, compact recoil proton spectrometer, and time of flight spectrometer. Improvements will be made continuously to the system to achieve better adaptation to the EAST’s harsh γ-ray and electro-magnetic radiation environment.

Previous studies have yielded contradictory results about interrelations between endotoxin and endothelium-derived relaxing factor (EDRF). We tested the hypothesis that in vivo endotoxemia inhibits basal and/or agonist-mediated release of EDRF and nitric oxide (NO). EDRF bioactivity, NO production, and NO synthase (NOS) activity were measured in aorta from guinea pigs following 16 h of Escherichia coli endotoxemia (4 mg/kg endotoxin i.p.). Endothelium-dependent relaxation of aortic rings was studied under standard isometric conditions. Endotoxemia resulted in an 89% reduction in basal EDRF bioactivity and a 62% reduction in basal NO production in perfused aorta. EDRF bioactivity and NO production in response to the receptor-dependent agonists acetylcholine and ADP were significantly reduced in perfused aorta from endotoxemic animals. In contrast, endotoxin did not significantly inhibit EDRF bioactivity and NO production by the receptor-independent agonist A-23187. Aortic rings from endotoxemic animals likewise showed decreased vasodilator responses to acetylcholine and ADP but not to A-23187. Inducible (Ca2+ independent) NOS activity was not significantly different in control and endotoxin-treated animals. These findings indicate that prolonged endotoxemia resulted in diminution of release of EDRF, consistent with the interpretation that endotoxemia decreases basal and agonist-stimulated EDRF bioactivity and NO production with loss of endothelium-dependent vasodilator reserves during gram-negative sepsis.

C 60 films up to 1000 A in thickness have been grown by room-temperature sublimation onto Si(100) and Si(111) substrates that have been prepared with surfaces passivated against dangling bonds. X-ray diffraction measurements reveal that films deposited on such substrates have a high degree of (111)-textured crystallinity which is absent in films deposited on untreated Si. Examination of surface topographies with tapping mode atomic force microscopy shows a thickness-dependent increase in roughness which is greater for the treated samples. Our results are placed in context with respect to what is presently known about the growth of C 60 films on a variety of substrates. Implications for possible device applications will also be discussed.

Rutherford backscattering spectrometry (RBS) was used to measure the titanium concentration profile for hydrogen-reduced, vacuum-reduced, and as-received, stoichiometric rutile. These profiles give the degree of reduction, specifically, the extent of oxygen deficiency, as a function of depth below the sample surface. Using forward-recoil spectrometry (FRES), the hydrogen-reduced rutile was found to contain more bulk and near-surface hydrogen than the as-received, stoichiometric rutile. This observation provides additional evidence for a hydrogen-diffusion model for the reduction of rutile in a hydrogen environment.

The voltage, V(x) and reversible capacity, xmax of Li/LixC6 electrochemical cells depends on the choice of carbon used as the electrode. We have developed a structural model for disordered carbons and a corresponding structure refinement program for powder X-ray data which allows accurate quantification of the structural parameters (lattice constants, basal plane particle size, probability of turbostratic disorder, etc.) describing disordered carbons. The structural model is used to fit the diffraction patterns of hard and soft carbons, treated at different temperatures, and the structural parameters are then obtained. The structural data is then correlated to V(x) and xmax to determine how the carbon structure influences the intercalation of lithium. We are able to understand, qualitatively, the variation in both xmax and V(x) with heat treatment temperature and with the types of disorder present in the two classes of carbon. V(x) and xmax are also measured for lithium intercalation in boron substituted carbon (B0.05C0.95). We are able to make general statements about which classes of carbons are most suitable as anodes in lithium ion cells and give some suggestions for future research directions.

A silica optical fiber was imaged using an atomic force microscope (AFM) in both contact and tapping mode. The fiber surface contains fragments of low-modulus, viscoelastic polymer after the coating was mechanically removed. While scanning in the contact mode resulted in tip-induced irreversible damage of the polymer, the tapping mode AFM generated reproducible images of the surface topography. It is shown that tapping mode AFM can reduce the contact force significantly, estimated to be as low as a tenth of a nanonewton, even in ambient conditions. This is facilitated by oscillating the tip (i.e. the cantilever) in the vicinity of the surface with an amplitude of up to ∼ 100 nm, which would eliminate capture of the tip by the surface fluid layer. Since the tip is no longer continuously in contact with the surface, both tip and sample degradations are minimized. The example presented herein demonstrates the utility of the tapping mode A AFM; evidence is provided which supports the proposed bonding mechanism at the polymer/silica interface.

This paper shows that the intercalation of Li in WO[sub 3] depends on how the WO[sub 3] host is made. Electrochemical intercalation and deintercalation of Li into WO[sub 3] films caused two reversible phase transitions in a range of 0 [lt] x [lt] 0.5 in Li[sub x] WO[sub 3] films. The same studies on commercial WO[sub 3] powders showed no evidence for these phases and an irreversible phase transition to an amorphous phase instead. The authors prepared WO[sub 3] by heating H[sub 2]WO[sub 4] powders at various temperatures. The reversible Li intercalation seen in the film was reproduced in WO[sub 3] powder made by heating H[sub 2]WO[sub 4] at low temperature (e.g., 400[degrees]C), but WO[sub 3] powder made by heating H[sub 2]WO[sub 4] at high temperatures (e.g., 900[degrees]C) showed the same behavior as the commercial powder. The authors believe the differences in the proton or oxygen content of the materials may be responsible for these differences.

We report studies of the electrochemical intercalation of lithium in ${\mathrm{WO}}_{3}$ powder and in polycrystalline evaporated ${\mathrm{WO}}_{3}$ films. Electrochemical cells with beryllium x-ray windows were used to study the structure changes in the ${\mathrm{WO}}_{3}$ host in situ. Rietveld profile refinement was used to analyze the x-ray-diffraction patterns of ${\mathrm{Li}}_{\mathit{x}}$${\mathrm{WO}}_{3}$ after correcting for the absorption of the beryllium window. Upon the intercalation of Li, the monoclinic structure of ${\mathrm{WO}}_{3}$ proceeds to higher and higher symmetry. First a first-order phase transition to a tetragonal phase with x\ensuremath{\sim}0.1 in ${\mathrm{Li}}_{\mathit{x}}$${\mathrm{WO}}_{3}$ occurs. Then another first-order phase transition to a cubic phase with x\ensuremath{\sim}0.36 occurs. The cubic phase can accommodate further Li, up to a maximum of about x=0.5. All the phase transitions can be reversed, although some hysteresis is observed; upon complete deintercalation, monoclinic ${\mathrm{WO}}_{3}$ is recovered. We report the structural changes, prove that the transitions are first order, and give a phase diagram for ${\mathrm{Li}}_{\mathit{x}}$${\mathrm{WO}}_{3}$ as a function of x. Our results suggest that the formation of the tetragonal phase upon intercalation of Li in ${\mathrm{WO}}_{3}$ is responsible for the electrochromatic properties of crystalline ${\mathrm{Li}}_{\mathit{x}}$${\mathrm{WO}}_{3}$, and that conventional interpretations that ignore the existence of this phase are most likely in error.

An approach for the localization and characterization of electrically active defects in multicrystalline silicon and of artefacts in photovoltaic devices is presented. The essential idea of the method is the noninvasive magnetic detection of photocurrents generated in the sample by local illumination. Magnetic imaging with high spatial and magnetic resolution is performed by scanning the sample under investigation and synchronously measuring the magnetic field of the photocurrents using highly sensitive superconducting quantum interference device magnetometers. The technique enables the nondestructive and nonpolluting detection and investigation of electrically active grain boundaries in multicrystalline silicon wafers. Results obtained from photovoltaic devices show that typical, performance-limiting defects can be localized, as they cause distinct features in the magnetic field topography.

We adopt a system theoretic approach and explore the model of retinal ganglion cells as linear filters followed by a maximum-likelihood Bayesian predictor. We evaluate the model by using cross-validation, i.e., first the model parameters are estimated using a training set, and then the prediction error is computed (by comparing the stochastic rate predicted by the model with the rate code of the response) for a test set. As in system identification theory, we present spatially uniform stimuli to the retina, whose temporal intensity is drawn independently from a Gaussian distribution, and we simultaneously record the spike trains from multiple neurons. The optimal linear filter for each cell is obtained by maximizing the mutual information between the filtered stimulus values and the output of the cell (as measured in terms of a stochastic rate code). Our results show that the model presented in this paper performs well on the test set, and it outperforms the identity Bayesian model and the traditional linear model. Moreover, in order to reduce the number of optimal filters needed for prediction, we cluster the cells based on the filters' shapes, and use the cluster consensus filters to predict the firing rates of all neurons in the same class. We obtain almost the same performance with these cluster filters. These results provide hope that filter-based retinal prosthetics might be an effective and feasible idea.