bluuebunny/crossref_metadata_2025 huggingface dataset:
Opioid Addiction and Suicidality
Authors: Krausz Michael , Degkwitz Peter , Haasen Christian , Verthein Uwe
Published: January 2011

The prevalence of suicide attempts among opioid addicts is reported to lie between 8% and 17%, with some studies reporting an even higher rate among special groups of addicts. Yet there is insufficient knowledge about which addicts have a higher risk of suicide and which other factors seem to be involved in the constellation leading to the suicide attempt; the study of different subgroups of addicts is thus necessary. This paper reports a study on suicide attempts among a sample population in a detoxification unit and another group undergoing codeine maintenance treatment. There was a high rate of suicide attempts among both groups (23% of those in the detoxification unit and 28% of those maintained on codeine), but treating physicians tended to underestimate suicidality. The results lead to the conclusion that among a subgroup of addicts suicidality plays a larger role; a greater emphasis should thus be placed on the underlying psychopathology and the treatment needed.
Transcriptional and antagonistic responses of Pseudomonas fluorescens Pf0-1 to phylogenetically different bacterial competitors
Authors: Garbeva Paolina , Silby Mark W , Raaijmakers Jos M , Levy Stuart B , de Boer Wietse
Published: January 2011

The ability of soil bacteria to successfully compete with a range of other microbial species is crucial for their growth and survival in the nutrient-limited soil environment. In the present work, we studied the behavior and transcriptional responses of soil-inhabiting Pseudomonas fluorescens strain Pf0-1 on nutrient-poor agar to confrontation with strains of three phylogenetically different bacterial genera, that is, Bacillus, Brevundimonas and Pedobacter. Competition for nutrients was apparent as all three bacterial genera had a negative effect on the density of P. fluorescens Pf0-1; this effect was most strong during the interaction with Bacillus. Microarray-based analyses indicated strong differences in the transcriptional responses of Pf0-1 to the different competitors. There was higher similarity in the gene expression response of P. fluorescens Pf0-1 to the Gram-negative bacteria as compared with the Gram-positive strain. The Gram-negative strains did also trigger the production of an unknown broad-spectrum antibiotic in Pf0-1. More detailed analysis indicated that expression of specific Pf0-1 genes involved in signal transduction and secondary metabolite production was strongly affected by the competitors’ identity, suggesting that Pf0-1 can distinguish among different competitors and fine-tune its competitive strategies. The results presented here demonstrate that P. fluorescens Pf0-1 shows a species-specific transcriptional and metabolic response to bacterial competitors and provide new leads in the identification of specific cues in bacteria–bacteria interactions and of novel competitive strategies, antimicrobial traits and genes.
Sequence variability of the pattern recognition receptor Mermaid mediates specificity of marine nematode symbioses
Authors: Bulgheresi Silvia , Gruber-Vodicka Harald R , Heindl Niels R , Dirks Ulrich , Kostadinova Maria , Breiteneder Heimo , Ott Joerg A
Published: January 2011

Selection of a specific microbial partner by the host is an all-important process. It guarantees the persistence of highly specific symbioses throughout host generations. The cuticle of the marine nematode Laxus oneistus is covered by a single phylotype of sulfur-oxidizing bacteria. They are embedded in a layer of host-secreted mucus containing the mannose-binding protein Mermaid. This Ca2+-dependent lectin mediates symbiont aggregation and attachment to the nematode. Here, we show that Stilbonema majum—a symbiotic nematode co-occurring with L. oneistus in shallow water sediment—is covered by bacteria phylogenetically distinct to those covering L. oneistus. Mermaid cDNA analysis revealed extensive protein sequence variability in both the nematode species. We expressed three recombinant Mermaid isoforms, which based on the structural predictions display the most different carbohydrate recognition domains (CRDs). We show that the three CRDs (DNT, DDA and GDA types) possess different affinities for L. oneistus and S. majum symbionts. In particular, the GDA type, exclusively expressed by S. majum, displays highest agglutination activity towards its symbionts and lowest towards its L. oneistus symbionts. Moreover, incubation of L. oneistus in the GDA type does not result in complete symbiont detachment, whereas incubation in the other types does. This indicates that the presence of particular Mermaid isoforms on the nematode surface has a role in the attachment of specific symbionts. This is the first report of the functional role of sequence variability in a microbe-associated molecular patterns receptor in a beneficial association.
ADRB2 and LEPR Gene Polymorphisms: Synergistic Effects on the Risk of Obesity in Japanese
Authors: Pereira Tiago V. , Mingroni‐Netto Regina C. , Yamada Yoshiji
Published: January 2011

The objective of the present study was to validate a recently reported synergistic effect between variants located in the leptin receptor (LEPR) gene and in the β‐2 adrenergic receptor (ADRB2) gene on the risk of overweight/obesity. We studied a middle‐aged/elderly sample of 4,193 nondiabetic Japanese subjects stratified according gender (1,911 women and 2,282 men). The LEPR Gln223Arg (rs1137101) variant as well as both ADRB2 Arg16Gly (rs1042713) and Gln27Glu (rs1042714) polymorphisms were analyzed. The primary outcome was the risk of overweight/obesity defined as BMI ≥25 kg/m2, whereas secondary outcomes included the risk of a BMI ≥27 kg/m2 and BMI as a continuous variable. None of the studied polymorphisms showed statistically significant individual effects, regardless of the group or phenotype studied. Haplotype analysis also did not disclose any associations of ADRB2 polymorphisms with BMI. However, dimensionality reduction‐based models confirmed significant interactions among the investigated variants for BMI as a continuous variable as well as for the risk of obesity defined as BMI ≥27 kg/m2. All disclosed interactions were found in men only. Our results provide external validation for a male specific ADRB2–LEPR interaction effect on the risk of overweight/obesity, but indicate that effect sizes associated with these interactions may be smaller in the population studied.
Copy Number Variations at the Prader‐Willi Syndrome Region on Chromosome 15 and associations with Obesity in Whites
Authors: Chen Yuan , Liu Yong‐Jun , Pei Yu‐Fang , Yang Tie‐Lin , Deng Fei‐Yan , Liu Xiao‐Gang , Li Ding‐You , Deng Hong‐Wen
Published: January 2011

Obesity is a serious health problem with strong genetic determination. Copy number variation (CNV) is a common type of genomic variant associated with some complex human diseases. However, it is not clear how CNVs contribute to the etiology of obesity. In this study, we examined 1,000 unrelated US whites to search for CNVs that may predispose to obesity. We focused our analyses on the Prader‐Willi syndrome (PWS) critical region (chromosome 15q11–q13), because the PWS region is a hotspot for CNV generation and obesity is one of the major clinical manifestations for chromosome abnormalities at this region. We constructed a map containing 39 CNVs at the PWS critical region with CNV occurrence rates higher than 1%. Among them, three CNVs were significantly associated with body fat mass (P < 0.05), with a higher copy number (CN) associated with an increase of 5.08–9.77 kg in body fat mass. These three CNVs are close to two known PWS genes, NDN (necdin homolog) and C15orf2 (chromosome 15 open reading frame 2), and partially overlap with another obesity gene PWRN1 (Prader‐Willi region nonprotein‐coding RNA 1). Interestingly, our recently published whole genome association scan study using the same sample by examining single‐nucleotide polymorphisms (SNPs) did not find any significant associations at these CNV regions, suggesting the importance of examining both CNVs and SNPs for better understanding of genetic basis of obesity. Further studies are warranted to validate these CNVs and their importance to obesity.
A wavelet transform algorithm for peak detection and application to powder x-ray diffraction data
Authors: Gregoire John M. , Dale Darren , van Dover R. Bruce
Published: January 2011

Peak detection is ubiquitous in the analysis of spectral data. While many noise-filtering algorithms and peak identification algorithms have been developed, recent work [P. Du, W. Kibbe, and S. Lin, Bioinformatics 22, 2059 (2006); A. Wee, D. Grayden, Y. Zhu, K. Petkovic-Duran, and D. Smith, Electrophoresis 29, 4215 (2008)] has demonstrated that both of these tasks are efficiently performed through analysis of the wavelet transform of the data. In this paper, we present a wavelet-based peak detection algorithm with user-defined parameters that can be readily applied to the application of any spectral data. Particular attention is given to the algorithm's resolution of overlapping peaks. The algorithm is implemented for the analysis of powder diffraction data, and successful detection of Bragg peaks is demonstrated for both low signal-to-noise data from theta–theta diffraction of nanoparticles and combinatorial x-ray diffraction data from a composition spread thin film. These datasets have different types of background signals which are effectively removed in the wavelet-based method, and the results demonstrate that the algorithm provides a robust method for automated peak detection.
Guided ion beam and theoretical study of the reactions of Au+ with H2, D2, and HD
Authors: Li Fengxia , Hinton Christopher S. , Citir Murat , Liu Fuyi , Armentrout P. B.
Published: January 2011

Reactions of the late third-row transition metal cation Au+ with H2, D2, and HD are examined using guided ion beam tandem mass spectrometry. A flow tube ion source produces Au+ in its 1S (5d10) electronic ground state level. Corresponding state-specific reaction cross sections for forming AuH+ and AuD+ as a function of kinetic energy are obtained and analyzed to give a 0 K bond dissociation energy of D0(Au+–H) = 2.13 ± 0.11 eV. Quantum chemical calculations at the B3LYP/HW+/6-311+G(3p) and B3LYP/Def2TZVPP levels performed here show good agreement with the experimental bond energy. Theory also provides the electronic structures of these species and the reactive potential energy surfaces. We also compare this third-row transition metal system with previous results for analogous reactions of the first-row and second-row congeners, Cu+ and Ag+. We find that Au+ has a stronger M+–H bond, which can be explained by the lanthanide contraction and relativistic effects that alter the relative size of the valence s and d orbitals. Results from reactions with HD provide insight into the reaction mechanism and indicate that ground state Au+ reacts largely via a direct mechanism, in concordance with the behavior of the lighter group 11 metal ions, but includes more statistical behavior than these metals as well.
Photodissociation of protonated leucine-enkephalin in the VUV range of 8–40 eV
Authors: Bari S. , Gonzalez-Magaña O. , Reitsma G. , Werner J. , Schippers S. , Hoekstra R. , Schlathölter T.
Published: January 2011

Until now, photodissociation studies on free complex protonated peptides were limited to the UV wavelength range accessible by intense lasers. We have studied photodissociation of gas-phase protonated leucine–enkephalin cations for vacuum ultraviolet (VUV) photons energies ranging from 8 to 40 eV. We report time-of–flight mass spectra of the photofragments and various photofragment-yields as a function of photon energy. For sub-ionization energies our results are in line with existing studies on UV photodissociation of leucine–enkephalin. For photon energies exceeding 10 eV we could identify a new dissociation scheme in which photoabsorption leads to a fast loss of the tyrosine side chain. This loss process leads to the formation of a residual peptide that is remarkably cold internally.
Electron ionization of methane: The dissociation of the methane monocation and dication
Authors: Ward Michael D. , King Simon J. , Price Stephen D.
Published: January 2011

Time-of-flight mass spectrometry and two-dimensional coincidence techniques have been used to determine, for the first time, the relative precursor-specific partial ionization cross sections following electron–methane collisions. Precursor-specific partial ionization cross sections quantify the contribution of single, double, and higher levels of ionization to the partial ionization cross section for forming a specific ion (e.g. CH+) following electron ionization of methane. Cross sections are presented for the formation of H+, H2+, C+, CH+, CH2+, and CH3+, relative to CH4+, at ionizing electron energies from 30 to 200 eV. We can also reduce our dataset to derive the relative partial ionization cross sections for the electron ionization of methane, for comparison with earlier measurements. These relative partial ionization cross sections are in good agreement with recent determinations. However, we find that there is significant disagreement between our partial ionization cross sections and those derived from earlier studies. Inspection of the values of our precursor-specific partial ionization cross sections shows that this disagreement is due to the inefficient collection of energetic fragment ions in the earlier work. Our coincidence experiments also show that the lower energy electronic states of CH42+ populated by electron double ionization of CH4 at 55 eV are the same (ground 3T1, first excited 1E1) as those populated by 40.8 eV photoionization. The 3T1 state dissociating to form CH3+ + H+ and CH2+ + H2+ and the 1E1 to form CH2+ + H+ and CH+ + H+. At this electron energy, we also observe population of the first excited triplet state of CH42+ (3T2) which dissociates to both CH2+ + H+ + H and CH+ + H+ + H2.
Quantum and classical study of surface characterization by three-dimensional helium atom scattering
Authors: Moix Jeremy M. , Pollak Eli , Allison William
Published: January 2011

Exact time-dependent wavepacket calculations of helium atom scattering from model symmetric, chiral, and hexagonal surfaces are presented and compared with their classical counterparts. Analysis of the momentum distribution of the scattered wavepacket provides a convenient method to obtain the resulting energy and angle resolved scattering distributions. The classical distributions are characterized by standard rainbow scattering from corrugated surfaces. It is shown that the classical results are closely related to their quantum counterparts and capture the qualitative features appearing therein. Both the quantum and classical distributions are capable of distinguishing between the structures of the three surfaces.
Broadband inversion for MAS NMR with single-sideband-selective adiabatic pulses
Authors: Pell Andrew J. , Kervern Gwendal , Emsley Lyndon , Deschamps Michaël , Massiot Dominique , Grandinetti Philip J. , Pintacuda Guido
Published: January 2011

We explain how and under which conditions it is possible to obtain an efficient inversion of an entire sideband family of several hundred kHz using low-power, sideband-selective adiabatic pulses, and we illustrate with some experimental results how this framework opens new avenues in solid-state NMR for manipulating spin systems with wide spinning-sideband (SSB) manifolds. This is achieved through the definition of the criteria of phase and amplitude modulation for designing an adiabatic inversion pulse for rotating solids. In turn, this is based on a framework for representing the Hamiltonian of the spin system in an NMR experiment under magic angle spinning (MAS). Following earlier ideas from Caravatti et al. [J. Magn. Reson. 55, 88 (1983)], the so-called “jolting frame” is used, which is the interaction frame of the anisotropic interaction giving rise to the SSB manifold. In the jolting frame, the shift modulation affecting the nuclear spin is removed, while the Hamiltonian corresponding to the RF field is frequency modulated and acquires a spinning-sideband pattern, specific for each crystallite orientation.
Inclined slot-excited annular electron cyclotron resonance plasma source for hyperthermal neutral beam generation
Authors: You H.-J. , Kim D.-W. , Koo M. , Jang S.-O. , Jung Y.-H. , Hong S.-H. , Lee B.-J.
Published: January 2011

An inclined slot-excited antenna (ISLAN) electron cyclotron resonance (ECR) plasma source is newly designed and constructed for higher flux hyperthermal neutral beam (HNB) generation. The developed ISLAN source is modified from vertical slot-excited antenna (VSLAN) source in two aspects: one is the use of inclined slots instead of vertical slots, and the other is a cusp magnetic field configuration rather than a toroidal configuration. Such modifications allow us to have more uniform arrangement of slots and magnets, then enabling plasma generation more uniform and thinner. Moreover, ECR plasma allows higher ionization rate, enabling plasma density higher even in submillitorr pressures, therefore decreasing the collision rate and/or the reionization rate of the reflected atoms while passing through the plasma, and eventually getting higher flux of HNBs. In this paper, we report the design features and the plasma characteristics of the ISLAN source by doing plasma measurements and electromagnetic simulations. It was found that ISLAN source can be a high potential source for larger flux HNB generation; the source was found to give higher plasma densities and better uniformities than inductively coupled plasma source, particularly in low pressure ranges. Also, it is important that using ISLAN gives easier matching and better stability, i.e., ISLAN shows similar field patterns and good plasma symmetries irrespective of the variations of the mean diameter of the ring resonator and/or the presence of a limiter or a reflector, and the operating pressures.
Decomposition of excited electronic state s-tetrazine and its energetic derivatives
Authors: Guo Yuanqing , Bhattacharya Atanu , Bernstein Elliot R.
Published: January 2011

Decomposition of excited electronic state s-tetrazine and its energetic derivatives, such as 3-amino-6-chloro-1,2,4,5-tetrazine-2,4-dioxide (ACTO), and 3,3′-azobis (6-amino-1,2,4,5-tetrazine)-mixed N-oxides (DAATO3.5), is investigated through laser excitation and resonance enhanced multi photon ionization techniques. The N2 molecule is detected as an initial product of the s-tetrazine decomposition reaction, through its two photon, resonance absorption transitions [a″ 1Σg+ (v′ = 0) ← X 1Σg+ (v″ = 0)]. The suggested mechanism for this reaction is a concerted triple dissociation yielding rotationally cold (∼20 K) ground electronic state N2 and 2 HCN molecules. The comparable decomposition of excited electronic state ACTO and DAATO3.5 yields an NO product with a cold rotational (∼20 K) but a hot vibrational (∼1200 K) distribution. Thus, tetrazine and its substituted energetic materials ACTO and DAATO3.5 evidence different decomposition mechanisms upon electronic excitation. N2O is excluded as a potential intermediate precursor of the NO product observed from these two s-tetrazine derivatives through direct determination of its decomposition behavior. Calculations at the CASMP2/CASSCF level of theory predict a concerted triple dissociation mechanism for generation of the N2 product from s-tetrazine, and a ring contraction mechanism for the generation of the NO product from the energetic s-tetrazine derivatives. Relaxation from Sn evolves through a series of conical intersections to S0, upon which surface the dissociation occurs in both mechanisms. This work demonstrates that the substituents on the tetrazine ring change the characteristics of the potential energy surfaces of the derivatives, and lead to a completely different decomposition pathway from s-tetrazine itself. Moreover, the N2 molecule can be excluded as an initial product from decomposition of these excited electronic state energetic materials.
Improved hybrid functional for solids: The HSEsol functional
Authors: Schimka Laurids , Harl Judith , Kresse Georg
Published: January 2011

We introduce the hybrid functional HSEsol. It is based on PBEsol, a revised Perdew–Burke–Ernzerhof functional, designed to yield accurate equilibrium properties for solids and their surfaces. We present lattice constants, bulk moduli, atomization energies, heats of formation, and band gaps for extended systems, as well as atomization energies for the molecular G2-1 test set. Compared to HSE, significant improvements are found for lattice constants and atomization energies of solids, but atomization energies of molecules are slightly worse than for HSE. Additionally, we present zero-point anharmonic expansion corrections to the lattice constants and bulk moduli, evaluated from ab initio phonon calculations.
Hydrophobic treatment of organics against glass employing nonequilibrium atmospheric pressure pulsed plasmas with a mixture of CF4 and N2 gases
Authors: Inui Hirotoshi , Takeda Keigo , Ishikawa Kenji , Yara Takuya , Uehara Tsuyoshi , Sekine Makoto , Hori Masaru
Published: January 2011

A hydrophobic organics surface selectively against glass was realized by employing nonequilibrium atmospheric-pressure pulsed plasmas with a mixture of CF4 and N2 gases. The organic surface was drastically altered to have a high hydrophobicity, while the glass surface itself remained hydrophilic after the plasma treatment with the addition of a small amount of CF4 to the N2 gas. After 100 CF4/N2 plasma treatments, no thin film deposition was observed on the organic material. To investigate the characteristics of the CF4/N2 plasma, the exhaust gas from the plasma was measured by using ion attachment mass spectroscopy (IAMS). The IAMS spectrum indicated that the amounts of CF3 and F radicals were increased drastically with increasing addition of CF4. A mechanism of the selective surface modification was clarified on a result of surface chemical bonding with the gas phase.
State-to-state reactive scattering in six dimensions using reactant–product decoupling: OH + H2 → H2O + H (J = 0)
Authors: Cvitaš Marko T. , Althorpe Stuart C.
Published: January 2011

We extend to full dimensionality a recently developed wave packet method [M. T. Cvitaš and S. C. Althorpe, J. Phys. Chem. A 113, 4557 (2009)] for computing the state-to-state quantum dynamics of AB + CD → ABC + D reactions and also increase the computational efficiency of the method. This is done by introducing a new set of product coordinates, by applying the Crank–Nicholson approximation to the angular kinetic energy part of the split-operator propagator and by using a symmetry-adapted basis-to-grid transformation to evaluate integrals over the potential energy surface. The newly extended method is tested on the benchmark OH + H\documentclass[12pt]{minimal}\begin{document}$_2$\end{document}2 → H\documentclass[12pt]{minimal}\begin{document}$_2$\end{document}2O + H reaction, where it allows us to obtain accurately converged state-to-state reaction probabilities (on the Wu–Schatz–Fang–Lendvay–Harding potential energy surface) with modest computational effort. These methodological advances will make possible efficient calculations of state-to-state differential cross sections on this system in the near future.
A study of electron affinities using the initiator approach to full configuration interaction quantum Monte Carlo
Authors: Cleland D. M. , Booth George H. , Alavi Ali
Published: January 2011

For the atoms with Z ⩽ 11, energies obtained using the “initiator” extension to full configuration interaction quantum Monte Carlo (i-FCIQMC) come to within statistical errors of the FCIQMC results. As these FCIQMC values have been shown to converge onto FCI results, the i-FCIQMC method allows similar accuracy to be achieved while significantly reducing the scaling with the size of the Slater determinant space. The i-FCIQMC electron affinities of the Z ⩽ 11 atoms in the aug-cc-pVXZ basis sets are presented here. In every case, values are obtained to well within chemical accuracy [the mean absolute deviation (MAD) from the relativistically corrected experimental values is 0.41 \documentclass[12pt]{minimal}\begin{document}$mE_h$\end{document}mEh], and significantly improve on coupled cluster with singles, doubles and perturbative triples [CCSD(T)] results. Since the only remaining source of error is basis set incompleteness, we have investigated using CCSD(T)-F12 contributions to correct the i-FCIQMC results. By doing so, much faster convergence with respect to basis set size may be achieved for both the electron affinities and the FCIQMC ionization potentials presented in a previous paper. With this F12 correction, the MAD can be further reduced to 0.13 \documentclass[12pt]{minimal}\begin{document}$mE_h$\end{document}mEh for the electron affinities and 0.31 \documentclass[12pt]{minimal}\begin{document}$mE_h$\end{document}mEh for the ionization potentials.
Interactions of Mz–X complexes (M = Cu, Ag, and Au; X = He, Ne, and Ar; and z = ±1)
Authors: Tong Xiao-Fei , Yang Chuan-Lu , Wang Mei-Shan , Ma Xiao-Guang , Wang De-Hua
Published: January 2011

The coupled cluster singles and doubles method with perturbative treatment of triple excitations is applied to calculate the potentials of Mz–X complexes (M = Cu, Ag, and Au; X = He, Ne, and Ar; and z = ±1). The bond functions and the basis set superposition errors are considered to obtain accurate interaction energies. The potential energy curves of all complexes are obtained. The vibrational energy levels and the spectroscopic parameters for these complexes are determined. The analytical potential energy functions are also fitted based on the potential energies.
Critical thickness for extrinsic contributions to the dielectric and piezoelectric response in lead zirconate titanate ultrathin films
Authors: Bastani Yaser , Schmitz-Kempen Thorsten , Roelofs Andreas , Bassiri-Gharb Nazanin
Published: January 2011

Highly (100)-textured Pb(Zr0.53Ti0.47)O3 films (Lotgering factors ≥90%) with thicknesses ranging from 20 to 260 nm were grown on platinized Si substrates using sol-gel deposition. Ferroelectric hysteresis, low field dielectric permittivity, and nonlinear dielectric response as well as converse longitudinal piezoelectric response (d33,f) of the ultrathin films were studied at 1 kHz. The measurements revealed the existence of a critical film thickness, ∼50 nm, below which the extrinsic contributions to the dielectric response are almost completely suppressed. Piezoelectric response of the films also showed a significant (∼50%) drop at the same critical thickness. Due to the columnar microstructure of these films the critical dimension of the ferroelectric is represented by the thickness rather than the lateral grain size, where the latter is invariant across the samples. The critical thickness led also to a deviation of the thickness dependence of the dielectric permittivity from the in-series capacitors model frequently representing “interfacial dead layers.” The critical size is attributed to significant reduction in domain wall population and/or mobility in films thinner than ∼50 nm.
Conductance switching in diarylethenes bridging carbon nanotubes
Authors: Ashraf M. K. , Bruque Nicolas A. , Tan Jeremy L. , Beran Gregory J. O. , Lake Roger K.
Published: January 2011

The recently reported photoswitching of diarylethene derivative molecules bridging carbon nanotube (CNT) contacts is theoretically analyzed. The short lifetime of the lowest unoccupied molecular orbital (LUMO) indicates that neither the open nor closed form of the molecule can be photoexcited into a charge-neutral excited state for any appreciable length of time preventing photochromic ring opening. Analysis of the highest occupied molecular orbital (HOMO) and LUMO lifetimes also suggests that photoexcitation results in oxidation of the molecules. This either reduces the quantum yield of photochromic ring closing, or it gives rise to the possibility of oxidative ring closing. Analysis of the resistance values and energy levels indicates that the HOMO energy levels of the closed isomers relevant for transport must lie within a few \documentclass[12pt]{minimal}\begin{document}$k_BT$\end{document}kBT of the CNT Fermi level. For armchair contacts, the change in resistance with isomer or substituent group is the result of shifts in the energy level of the molecular HOMO. The coupling of the molecular HOMO to the CNT contacts is insensitive to the isomer type or substituent group. For zigzag CNTs, the conductance is dominated by surface states at the Fermi level on the cut ends of the CNTs so that the conductance is relatively insensitive to the isomer type, and the conductance switching ratio is low. Multiple bridging molecules can interact coherently, resulting in energy splitting, shifting, and interference that cause a nonlinear change in conductance with increasing numbers of molecules. Instead of a factor of 3 increase in conductance expected for three independent channels, a factor of \documentclass[12pt]{minimal}\begin{document}$10^3$\end{document}103 increase in conductance is obtained for three bridging molecules.
Ultrafast photofragmentation dynamics of molecular iodine driven with timed XUV and near-infrared light pulses
Authors: Krikunova Maria , Maltezopoulos Theophilos , Wessels Philipp , Schlie Moritz , Azima Armin , Wieland Marek , Drescher Markus
Published: January 2011

Photofragmentation dynamics of molecular iodine was studied as a response to the joint illumination with femtosecond 800 nm near-infrared and 13 nm extreme ultraviolet (XUV) pulses delivered by the free-electron laser facility FLASH. The interaction of the molecular target with two light pulses of different wavelengths but comparable pulse energy elucidates a complex intertwined electronic and nuclear dynamics. To follow distinct pathways out of a multitude of reaction channels, the recoil of created ionic fragments is analyzed. The delayed XUV pulse provides a way of following molecular photodissociation of \documentclass[12pt]{minimal}\begin{document}${\rm I}_{2}$\end{document}I2 with a characteristic time-constant of (55 ± 10) fs after the laser-induced formation of antibonding states. A preceding XUV pulse, on the other hand, preferably creates a 4d\documentclass[12pt]{minimal}\begin{document}$^{-1}$\end{document}−1 inner-shell vacancy followed by the fast Auger cascade with a revealed characteristic time constant \documentclass[12pt]{minimal}\begin{document}$\tau _{\rm A2}=(23\pm 11)$\end{document}τA2=(23±11) fs for the second Auger decay transition. Some fraction of molecular cationic states undergoes subsequent Coulomb explosion, and the evolution of the launched molecular wave packet on the repulsive Coulomb potential was accessed by the laser-induced postionization. A further unexpected photofragmentation channel, which relies on the collective action of XUV and laser fields, is attributed to a laser-promoted charge transfer transition in the exploding molecule.
Quantum reaction boundary to mediate reactions in laser fields
Authors: Kawai Shinnosuke , Komatsuzaki Tamiki
Published: January 2011

Dynamics of passage over a saddle is investigated for a quantum system under the effect of time-dependent external field (laser pulse). We utilize the recently developed theories of nonlinear dynamics in the saddle region, and extend them to incorporate both time-dependence of the external field and quantum mechanical effects of the system. Anharmonic couplings and laser fields with any functional form of time dependence are explicitly taken into account. As the theory is based on the Weyl expression of quantum mechanics, interpretation is facilitated by the classical phase space picture, while no “classical approximation” is involved. We introduce a quantum reactivity operator to extract the reactive part of the system. In a model system with an optimally controlled laser field for the reaction, it is found that the boundary of the reaction in the phase space, extracted by the reactivity operator, is modulated with time by the effect of the laser field, to “catch” the system excited in the reactant region, and then to “release” it into the product region. This method provides new insights in understanding the origin of optimal control of chemical reactions by laser fields.
Characterizing interfacial friction in bis(2-ethylhexyl) sodium sulfosuccinate reverse micelles from photoisomerization studies of carbocyanine derivatives
Authors: Gangamallaiah V. , Dutt G. B.
Published: January 2011

Photoisomerization of two carbocyanine derivatives has been examined in bis(2-ethylhexyl) sodium sulfosuccinate (AOT) reverse micelles to understand the factors that govern this process in the interfacial region of organized assemblies. To this effect, fluorescence lifetimes and quantum yields of 3,3′-diethyloxadicarbocyanine iodide and merocyanine 540 have been measured in AOT/isooctane/water and AOT/cyclohexane/water reverse micellar systems as a function of the mole ratio of water to the surfactant, W. The nonradiative rate constants, which have been identified as the rates of photoisomerization for these solutes, were obtained from the experimentally measured parameters. The steady rise and subsequent saturation observed in the nonradiative rate constants upon increasing W has been rationalized in terms of micellar packing. An inverse correlation has been obtained between the nonradiative rate constants and the critical packing parameter, indicating that the interfacial friction experienced by the solute molecule is essentially described by this parameter.
Opening of simultaneous photonic and phononic band gap in two-dimensional square lattice periodic structure
Authors: Bria D. , Assouar M. B. , Oudich M. , Pennec Y. , Vasseur J. , Djafari-Rouhani B.
Published: January 2011

We discuss two points related to the simultaneous existence of phononic and photonic band gaps in a two-dimensional crystal constituted by a square array of holes drilled in a matrix. In a first part, using the case of a sapphire sample in the microwave range, we show that in addition to the phononic gap, an absolute photonic gap may be obtained making use of the high values as well as the anisotropy of the dielectric matrix elements in the microwave regime. In a second part, using the case of silicon in the telecom frequency range, we demonstrate that absolute photonic and phononic gaps may be obtained by making a combination of two crystals having slightly different filling factors. The calculations of the band structures and transmission coefficients were mainly computed using the finite difference time domain method.
Scalar scattering model of highly textured transparent conducting oxide
Authors: Lin Chien-Chung , Liu Wei-Lin , Hsieh Chi-Ying
Published: January 2011

Amorphous silicon solar cell is one of the most well developed solar energy solutions. In order to increase the energy conversion efficiency, light-trapping is necessary to the cell structure. Light trapping can be achieved by a textured transparent conducting oxide (TCO) layer and one of the critical factors of textured TCO is its haze value, which characterizes the scattering capability of the TCO. Recently several highly textured TCOs were presented with high haze at near IR region, where the haze of textured interfaces traditionally suffered from reduced scattering. However, suitable modeling is not established yet. In this work, we use scalar scattering theory and Kirchhoff approximation to solve haze value of complex surfaces analytically. Different from original Rayleigh scattering expression, this model illustrates intricacy between the surface roughness, correlation length, and the separation between different groups of height distributions. The resulting analytical formulation can be applied successfully not only in regular monotonically decaying spectral hazes but also various nonmonotonically shaped ones, meanwhile it retains important physical factors which can be useful for process evaluation.
Dislocation contribution to acoustic nonlinearity: The effect of orientation-dependent line energy
Authors: Cash W. D. , Cai W.
Published: January 2011

Dislocation dynamics (DD) simulations are used to investigate the acoustic nonlinearity created by dislocations in crystals. The acoustic nonlinearity parameter, β, is quantitatively predicted for a single dislocation bowing in its glide plane between pinning points under a quasistatic loading assumption using DD simulations. The existing model using a constant line energy assumption fails to capture the correct behavior of β for edge dislocations in materials with a nonzero Poisson’s ratio. A strong dependence of β on the orientation of Burgers vector relative to the line direction of the dislocation is shown by the DD simulations. A new model using an orientation-dependent line energy is derived for the cases of initially pure edge and screw dislocations. The model is shown to agree with the DD simulations over a range of Poisson’s ratio and static stresses.
Boundary scattering effects during electron thermalization in nanoporous gold
Authors: Hopkins Patrick E. , Serrano Justin R. , Phinney Leslie M. , Li Hongqi , Misra Amit
Published: January 2011

We study the electron relaxation processes in nanoporous Au structures using pump-probe thermoreflectance. Using a modified two temperature model, we determine that the electron Fermi relaxation time is unaffected by the ligament size and is an athermal process that is constant with laser pulse excitation, yet the electron-phonon relaxation is affected by boundary scattering and is dependent on electron temperature. The increased, temperature dependent electron-phonon coupling measurements can be explained by electron-boundary scattering and electron-electron scattering that alters the rate of electron equilibration with the surrounding media. These results lend insight into electron relaxation processes in high surface area nanostructures.
Lowest weight representations of super Schrödinger algebras in one dimensional space
Authors: Aizawa N.
Published: January 2011

Lowest weight modules, in particular, Verma modules over the \documentclass[12pt]{minimal}\begin{document}$ {\cal N} = 1, 2$\end{document}N=1,2 super Schrödinger algebras in (1 + 1) dimensional spacetime are investigated. The reducibility of the Verma modules is analyzed via explicitly constructed singular vectors. The classification of the irreducible lowest weight modules is given for both massive and massless representations. A vector field realization of the \documentclass[12pt]{minimal}\begin{document}$ {\cal N} = 1, 2$\end{document}N=1,2 super Schrödinger algebras is also presented.
Diffuse discharge, runaway electron, and x-ray in atmospheric pressure air in an inhomogeneous electrical field in repetitive pulsed modes
Authors: Shao Tao , Zhang Cheng , Niu Zheng , Yan Ping , Tarasenko Victor F. , Baksht Evgenii Kh. , Burahenko Alexander G. , Shut’ko Yuliya V.
Published: January 2011

This letter reports on experimental studies of a pulsed discharge in an inhomogeneous electric field at a pressure of 1 atm for varying voltage pulse parameters. The amplitude of voltage pulses applied to point-to-plane and point-to-point gaps was 12–140 kV and the full width at half maximum was 1–40 ns. It is shown that in a wide range of experimental conditions, a diffuse discharge is ignited due to preionization of the gap by runaway electrons and x-rays. With all gaps, the runaway electrons are produced in response to electric field amplification near the electrodes and in the gap.
Theoretical and experimental studies of surface plasmons excited at metal-uniaxial dielectric interface
Authors: Wang Xiaolei , Wang Pei , Chen Junxue , Lu Yonghua , Ming Hai , Zhan Qiwen
Published: January 2011

In this letter, surface plasmons (SPs) excited at the metal-uniaxial dielectric interface are investigated both theoretically and experimentally. The dispersion relations of SPs are derived for the cases where the optical axis of uniaxial medium is parallel the interface or in the incident plane perpendicular to the interface. The theoretical predictions are verified by a Kretschmann–Raether [W. L. Barnes, A. Dereux, and T. W. Ebbesen, Nature (London) 424, 824 (2003)] configuration with azobenzene polymer as photoinduced uniaxial medium. The attenuated total reflection spectra clearly show that the dependence of the SPs propagation properties on the orientations of optical axis, which is consistent with the theoretical analysis. The results of this study provide a useful approach to modulate SPs through adjusting the azobenzene molecular orientation.
Voltage-induced recovery of dielectric breakdown (high current resistance switching) in HfO2
Authors: El Kamel F. , Gonon P. , Vallée C. , Jousseaume V. , Grampeix H.
Published: January 2011

Metal/HfO2/Pt stacks (where the metal is Au, Ag, Co, Ni, Cr, or In) are voltage stressed to induce a high-to-low resistive transition. No current compliance is applied during stressing (except the 100 mA limit of the voltage source). As a consequence very high conductance states are reached after switching, similar to a hard breakdown. Samples conductance after breakdown can reach up to 0.1 S, depending on the metal electrode. Despite the high postbreakdown conductance level, the samples are able to recover an insulating state by further voltage biasing (“high current resistance switching”).
Reversibly phototunable TiO2 photonic crystal modulated by Ag nanoparticles’ oxidation/reduction
Authors: Liu Jian , Li Mingzhu , Zhou Jinming , Ye Changqing , Wang Jingxia , Jiang Lei , Song Yanlin
Published: January 2011

We report a reversibly phototunable photonic crystal system whose reflectance at the stop band position can be modulated by alternating UV/visible (UV/Vis) irradiation. The phototunable system consists of Ag nanoparticles and TiO2 photonic crystal. The stop bands intensity of Ag loaded TiO2 photonic crystals were found to be dependent on the redox states of Ag nanoparticles. The quasi “on” and “off” states of the stop band were reversibly modulated by the Ag nanoparticles’ oxidation/reduction through alternating UV/Vis light irradiation.
Field effect mobility model in organic thin film transistor
Authors: Li Ling , Chung Kwan-Soo , Jang Jin
Published: January 2011

An analytical model is presented here for the field effect mobility in organic thin-film transistors. It is developed rigorously using the variable range hopping theory, the Gaussian density of states distribution function and the transistor model. Based on the proposed model, a variety of temperature and gate voltage dependencies of the field effect mobility can be well described. Good agreement between the calculation and recent experimental data is also observed.
Accurate extraction of ΔI/I due to random telegraph noise in gate edge current of high-k n-type metal-oxide-semiconductor field-effect transistors under accumulation mode
Authors: Lee Ju-Wan , Park Chan Hyeong , Shin Hyungcheol , Park Byung-Gook , Lee Jong-Ho
Published: January 2011

Random telegraph noise (RTN) in the gate edge current under accumulation mode is studied in high-k gate dielectric n-type metal-oxide-semiconductor field-effect transistors (nMOSFETs). The RTN in the gate edge current is originated by a trap which exists in the gate dielectric between the gate and the drain (or source). The gate edge current is separated from the total gate tunneling current. The gate edge and the gate-induced drain leakage currents are also separated from the source or drain current. Accurate ΔI/I in the gate edge currents is extracted by separating the gate edge current from the total gate current. We propose a schematic model based on accurate ΔI/I, elucidating the generation of the RTN in the gate edge current.
Capturing Lightness between Contours
Authors: Vergeer Mark , van Lier Rob
Published: January 2011

Homogeneously coloured bars may exhibit lightness differences at the intersections. A well-known example is the Hermann grid illusion, where crossing white bars on a black background show dark patches at the crossings. Jung (1973, Handbook of Sensory Physiology volume VII/3, pp 1 – 152) found that the dark patches persist when thin outlines are drawn at the intersections, and are even visible in foveal vision. Recently, it has been shown that making distortions to the contours of a Hermann grid-like configuration results in the disappearance of the illusory dark spots (Geier et al, 2008 Perception37 651 – 665). We show that thin outlines at the crossings of the distorted Hermann grid induce lightness differences in the same direction as in the original Hermann grid illusion, even in foveal vision and in displays consisting of two crossing bars. Our experiments reveal that the induced lightness differences are independent of the luminance polarity and shape of the contours at the intersection. We suggest that the effect results from lateral inhibition and an additional spreading and capturing of these differences between luminance contours. A similar capturing between collinear contours may play a role in peripheral vision in the original Hermann grid.
Some Organometallic Chemistry of Tetracyanoethene: CN-displacement and Cycloaddition Reactions with Alkynyl - Transition Metal Complexes and Related Chemistry
Authors: Bruce Michael I.
Published: January 2011

The highly electron-deficient cyanocarbons tetracyanoethene (tcne) and, to a lesser extent, tetracyanoquinodimethane (tcnq), display a fascinating chemistry with transition metal substrates. In particular, the [2 + 2]-cycloadditions of the cyanocarbons with alkynyl- or poly-ynyl–metal complexes have been extensively studied by the author’s group. These reactions proceed via polar adducts to give σ-cyclobutenyl complexes, which then undergo facile ring-opening (retro-electrocyclic) reactions to form the corresponding butadienyl derivatives. In some cases, further reactions can occur by displacement of weakly bound ligands from the metal centre. The subsequent chemistry of these derivatives has been only cursorily investigated, while related studies of organic analogues have produced molecules with interesting electronic and optical properties.
Anomalies in the Stereoselectivity of the Petasis Reaction Using Styrenyl Boronic Acids
Authors: Churches Quentin I. , Johnson James K. , Fifer Nathan L. , Hutton Craig A.
Published: January 2011

The Petasis three-component coupling reaction of N-benzylphenylglycinol, glyoxylic acid, and styrenylboronic acids allows for the efficient synthesis of functionalized homoarylalanine derivatives. The reactions were shown to proceed in high yield but low selectivity, regardless of the nature of the substituent on the styrenylboronic acid component. Anomalies in the stereoselectivity of these reactions compared with previously reported results have been traced to the source of the organoboronic acid. Asymmetric dihydroxylation of the unsaturated amino acid derivatives enables a highly efficient route to dihydroxyhomoarylalanine derivatives.