bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electrical and optical studies of gap states in self-assembled molecular aggregates
Authors: Burtman V. , Hukic G. , Ndobe A. S. , Drori T. , Vardeny Z. V. 
Published: March 2007

We fabricated a variety of two-terminal devices using self-assembled monolayers (SAM) of solid-state mixtures comprised of molecular “wires” [1,4-methane-benzenedithiol (Me-BDT)] and molecular insulator “spacers” [1-pentanethiol], which were prepared at various molar concentrations ratio, r of wires/spacers, and sandwiched between two gold electrodes. The devices’ electrical transport was investigated at several r values using the bias voltage (V) dependencies of the conductance and differential conductance at various temperatures. In parallel, we also studied the UV-visible absorption and photoluminescence (PL) emission spectra of the SAM mixtures grown on silica transparent substrates. For r&gt;10−3 we found that two-dimensional (2D) Me-BDT aggregates are formed in the SAM films leading to novel properties compared to SAM films of isolated Me-BDT molecules at concentrations 10−8&lt; r&lt;10−4, which we studied before [V. Burtman, A. S. Ndobe, and Z. V. Vardeny, J. Appl. Phys. 98, 034314 (2005)]. First, an Ohmic response in the current-voltage (I-V) characteristics is obtained up to V∼0.5 V, which results in a new band in the differential conductance spectrum around V=0. Second, a new subgap absorption band is formed at ∼2.4 eV, which is related to a new yellow/red PL emission band. The novel optical and electrical properties of the 2D Me-BDT aggregates are explained by the formation of an electronic continuum band in the Me-BDT energy gap, which is caused by weak in-plane charge delocalization among the molecules forming the aggregates. To verify this model we also studied SAM molecular aggregate diodes using Al electrodes. The 1-eV difference in the electrode work function between Au and Al metals results in a pronounced EF shift with respect to the aggregate-related continuum band in the gap, and consequently, dramatically changes the device I-V characteristics.
An Investigation of
Steady-State Dynamic Response of a Sphere-Plane Contact Interface With Contact
Loss
Authors: Ma Q.
L. , Kahraman A. , Perret-Liaudet J. , Rigaud E. 
Published: March 2007

Abstract
In this study, the dynamic behavior of an elastic sphere-plane contact interface is studied analytically and experimentally. The analytical model includes both a continuous nonlinearity associated with the Hertzian contact and a clearance-type nonlinearity due to contact loss. The dimensionless governing equation is solved analytically by using multi-term harmonic balance method in conjunction with discrete Fourier transforms. The accuracy of the dynamic model and solution methods is demonstrated through comparisons with experimental data and numerical solutions for both harmonic amplitudes of the acceleration response and the phase difference between the response and the force excitation. A single-term harmonic balance approximation is used to derive a criterion for contact loss to occur. The influence of harmonic external excitation f(τ) and damping ratio ζ on the steady state response is also demonstrated.
How warm is the corporate response to climate change? Evidence from Pakistan and the UK
Authors: Jeswani Harish Kumar , Wehrmeyer Walter , Mulugetta Yacob 
Published: March 2007

AbstractIn response to growing consensus among scientists and governments to act fast to avoid dangerous impacts of climate change, many industries have started to prepare for a carbon‐constrained world. However, this response is far from being uniform. Often action is predicated on economic, technological, organizational and institutional drivers and barriers, which vary between countries and across industrial sectors. In order to understand the effectiveness of industry response, it is therefore important to analyse corporate response across different sectors in different countries.Focusing on the nine most energy‐intensive and greenhouse gas (GHG) emitting industrial sectors, this paper compares corporate responses to climate change in Pakistan and the UK. By analysing the divergence of strategies adopted by industries across different sectors in two countries, the paper examines the key factors influencing corporate adoption and implementation of GHG reduction and energy‐efficiency strategies in Pakistan and the UK. Copyright © 2007 John Wiley & Sons, Ltd and ERP Environment.
Chiral Platinum(II) Metallointercalators with Potent in vitro Cytotoxic Activity
Authors: Fisher Dianne M. , Bednarski Patrick J. , Grünert Renate , Turner Peter , Fenton Ronald R. , Aldrich‐Wright Janice R. 
Published: March 2007

AbstractFour platinum(II) metallointercalating complexes of 1,10‐phenanthroline (phen) with the chiral ancillary ligands trans‐R,R‐ and trans‐S,S‐1,2‐diaminocyclohexane (R,R‐ and S,S‐dach, respectively), and N,N′‐dimethyl‐R,R‐ and N,N′‐dimethyl‐S,S‐1,2‐diaminocyclohexane (Me2‐R,R‐dach and Me2‐S,S‐dach, respectively) have been synthesised and characterised. The crystal structure of [Pt(Me2‐S,S‐dach)(phen)](ClO4)2⋅1.5 H2O (C20H26Cl2N4O9.5Pt) has been determined; orthorhombic, space group P212121(No. 19), a=23.194(8), b=25.131(9), c=8.522(3) Å. In vitro cytotoxic assays (IC50) in the human bladder cancer cell line 5637 and in the murine leukemia L1210 cell line revealed that [Pt(S,S‐dach)(phen)](ClO4)2 (0.091 and 0.13 μM, respectively) and [Pt(R,R‐dach)(phen)](ClO4)2 (0.54 and 1.50 μM, respectively) were more cytotoxic than cisplatin (0.31 and 0.50 μM, respectively) and considerably more cytotoxic than their methylated counterparts, [Pt(Me2‐R,R‐dach)(phen)](ClO4)2 and [Pt(Me2‐S,S‐dach)(phen)](ClO4)2 (both>23 μM). Chiral discrimination for [Pt(S,S‐dach)(phen)](ClO4)2 over its R,R‐enantiomer was observed in all 13 cancer cell lines investigated. Moreover, [Pt(S,S‐dach)(phen)](ClO4)2 was more active than cisplatin in all cell lines tested and shows only partial cross‐resistance to cisplatin in two cisplatin resistant cell lines.
The shielding tensor part II: Understanding its strange effects on relaxation
Authors: Anet Frank A. L. , O'leary Daniel J. 
Published: March 2007

AbstractThe shielding tensor can be nonsymmetric and thus in general has both symmetric and antisymmetric parts. Relaxation by these two parts of the shielding tensor (chemical shift anisotropy or CSA relaxation) are reviewed and compared with relaxation by the dipole‐dipole (DD) mechanism. It is explained how T2 can be equal to (6/7)T1 or to 2T1 in limiting situations for relaxation that involves the shielding tensor. Cross‐correlation (or interference) effects between CSA and DD relaxation and the relationship between CSA and spin‐rotation relaxation are briefly reviewed.
The Hamiltonians of NMR. part I
Authors: Smith Scott A. , Palke William E. , Gerig J. T. 
Published: March 2007

AbstractNuclear magnetic resonance spectroscopy has evolved in complexity to the extent that it is often useful to carry out computer simulations of experiments as a way to refine experimental conditions, to maximize usable information, or to interpret results reliably. The starting point for such simulations is an appropriate quantum mechanical formulation. This article presents many of the physical ideas that are important in high‐resolution NMR spectroscopy and then develops expressions for the contribution of each of these to the Hamiltonian for the system under consideration. The Hamiltonians for the Zeeman interaction, scalar coupling, and the chemical shielding effect are discussed with the aim of explaining the quantum mechanics of NMR in a manner understandable to a nontheoretician. Consequently, much of the discussion is explicit and includes points skimmed over in other presentations in the literature.
Measurements of spin concentration in electron paramagnetic resonance spectroscopy preparation of standard solutions from optical absorption
Authors: Kooser Robert G. , Kirchmann Eric , Matkov Thomas 
Published: March 2007

AbstractThe detailed requirements for the accurate determination of electron spin concentration by electron paramagnetic resonance spectroscopy are examined, and the use of the dual‐sample cavity for measuring spin concentrations is reviewed. The lack of adequate solution‐phase concentration standards is examined, and a new method based on photometric titration techniques is given for determining piperidine nitroxide concentrations in polar solvents. The titration procedure is used to determine the molar absorptivity of several common piperidine nitroxides in water and in water‐methanol solutions.
The Hamiltonians of NMR. Part II
Authors: Smith Scott A. , Palke William E. , Gerig J. T. 
Published: March 2007

AbstractThe derivation of various components of the Hamiltonian operator used to describe high‐resolution NMR experiments is presented, with an emphasis on time‐dependent interactions that can produce relaxation of a spin system (dipole‐dipole, chemical shift anisotropy) or that lead to excitation of a spin system (radio‐frequency field).
Methods of single‐ and double‐selective excitation: Theory and applications. Part II
Authors: Gaggelli Elena , Valensin Gianni 
Published: March 2007

AbstractA general review of applications of selective excitation techniques is provided. The different methods for suppression of solvent signal are summarized. The theoretical basis of selective population inversion and selective polarization transfer is considered and applications are treated. Direct observation of chemical‐exchange processes is discussed for both the two‐site and the multi‐site system. Finally, the potential of selective excitation techniques for extracting structural and dynamic information from single‐ and double‐selective relaxation rates is addressed, with particular emphasis given to NMR studies of small ligands bound to macromolecules.
Introduction to transmission lines basic principles and applications of quarter‐wavelength cables and impedance matching
Authors: Traficante Daniel D. 
Published: March 2007

AbstractThe basic electrical properties of transmission lines are reviewed, and it is shown how these properties determine the characteristic impedance of the line. For resonant lines, the formation of standing waves is explained. The variation of the impedance of the line as a function of its length is shown to be caused by the standing waves of voltage and current. Various equations for the standing‐wave ratio and the concomitant power losses are derived for systems that are impedance mismatched. Applications in NMR spectroscopy include the use of transmission lines as filters, as impedance‐matching devices, and for directing pulses toward the probe and away from the preamplifier. Finally, a simple laboratory experiment demonstrates the properties of open and shorted quarter‐ and half‐wavelength cables.
Density matrix calculations of AB spectra from multipulse sequences: Quantum mechanics meets In vivo spectroscopy
Authors: Mulkern Robert , Bowers John 
Published: March 2007

AbstractLocalized in vivo spectroscopic studies are generally performed with successive, spatially orthogonal, slice‐selective radio‐frequency (rf) pulses so that the received signal is confined to a particular volume of interest. Although these techniques spatially restrict the signal, successive rf pulses applied prior to signal acquisition give rise to complex spectral modulations for coupled spin systems. Interpulse timing delays, rf flip angles, and phases all affect these modulations, which must be fully understood and appreciated if sequences are to be optimized for specific in vivo spectroscopic studies. The density matrix formalism is particularly suited for this task. Our purpose is to demonstrate how the density matrix formalism is used to study spectral modulations induced by selected multipulse sequences for an AB system.
The relationship between sensitivity and integral accuracy further comments on optimum tip angle and relaxation delay for quantitative analysis
Authors: Traficante Daniel D. , Steward Lynne R. 
Published: March 2007

AbstractAn evaluation of the relationship between signal‐to‐noise ratio (S/N) and integral accuracy, as a function of tip angle and relaxation delay, shows that the SIN decreases with increasing integral accuracy. At the expense of a slight decrease in integral accuracy, a substantial increase in SIN can be realized, and a procedure is presented for selecting the appropriate tip angle and relaxation delay.
The hamiltonians of NMR. Part IV: NMR relaxation
Authors: Smith Scott A. , Palke William E. , Gerig J. T. 
Published: March 2007

AbstractUsing the methods presented in our previous discussions of the Hamiltonians of NMR, we describe the processes that lead to relaxation of spin systems. The same nomenclature and methods of Parts I, II, and III have been used to develop a formulation of time‐dependent operators.
COSY spectra of paramagnetic macromolecules: Observability, scalar effects, cross‐correlation effects, relaxation‐allowed coherence transfer
Authors: Bertini Ivano , Piccioli Mario , Tarchi Dario , Luchinat Claudio 
Published: March 2007

Abstract1H‐1H homonuclear correlated spectroscopy (COSY) cross peaks are detected at high fields in the case of paramagnetic macromolecular systems, even between signals with linewidths of 103 hertz. Because they cannot be ascribed to J‐coupling effects, we began to look for novel or undiscovered physical phenomena. Cross correlation occurs between proton‐proton dipolar coupling and Curie spin‐nuclear spin relaxation. The effect on a dipolar coupled AX system is that each signal is made up of two overlapped components with different linewidths. The cross correlation produces antiphase coherence that generates COSY cross peaks when a 90° ‐t1 −90°‐ t2 experiment is performed, even though the phase of the cross peak with respect to a normal J‐coupling scheme is different. Here, a theoretical derivation of the effect is given. Because the observation of this cross‐correlation effect is absolutely general in paramagnetic metalloproteins, the pulse sequences that quench the effect are shown. It also is stressed that it would be desirable to quench concomitant J‐coupling effects and to detect cross peaks that result only from cross‐correlation effects; a sequence to achieve this is shown.
Tailored selective NMR excitation by projection presaturation
Authors: Singh Saryu , Deslauriers Roxanne 
Published: March 2007

AbstractSelective excitation of spins in one region in a relatively large object is important for many NMR applications in biology and medicine. For example, excitation of spins in a slice (one‐dimensional excitation) is the basis of tomographic (section) imaging and is currently used in clinical MR imaging (MRI) for diagnosing human disease. Selective excitation in two and three dimensions also is important. It is used primarily in localized in vivo MR spectroscopy (MRS) for quantifying the metabolites or energetics of a diseased tissue, but it also is used in MRI for limited field of view imaging or for improving image quality by suppression of flow and motion artifacts. We describe a technique, projection presaturation, for selectively exciting a single volume of interest (VOI) or for simultaneous excitation of multiple VOIs, the shape and size of which can be tailored in one, two, or three dimensions. Projection presaturation has advantages over commonly used techniques: It is conformal; it provides maximum sensitivity; it is accurate even in the presence of T1 variation, tip‐angle errors (deviation from the desired tip‐angle caused by mistuning or inhomogeneity of the radio frequency transmit field), and off‐resonance effects (variation in the resonance frequency caused by Bo inhomogeneity and chemical shifts); and it is suitable for shortT2 species. Several applications of the method in MRI and MRS are described and discussed.
Introduction to EPR imaging using magnetic‐field gradients
Authors: Eaton Gareth R. , Eaton Sandra S. 
Published: March 2007

AbstractElectron paramagnetic resonance (EPR) imaging studies the location of paramagnetic centers in a sample and the characteristics of the spins at each location. This article introduces techniques in which magnetic‐field gradients are used to encode spatial information in one‐dimensional spatial, two‐dimensional spatial‐spatial, two‐dimensional spectralspatial. And three‐dimensional spectral‐spatial‐spatial images. Examples from continuous‐wave and spin‐echo EPR imaging are presented.
Adiabatic slice‐selective rf pulses and a single‐shot adiabatic localization pulse sequence
Authors: Slotboom J. , Bovée W. M. M. J. 
Published: March 2007

AbstractThe localization quality of frequency‐selective adiabatic radio frequency (rf) pulses is subtantially less affected by rf inhomogeneity than is the localization of amplitude‐modulated pulses. For this reason, adiabatic pulses are popular for use in experiments carried out with rf coils that produce inhomogeneous rf fields. Starting with the Schrodinger equation, the Bloch equations are derived, neglecting relaxation. The adiabatic principle is introduced, and it is demonstrated that accurate adiabatic localization is possible with simple schemes for amplitude and frequency modulation. Adiabatic pulses perform well only in an rf amplitude range limited by a lower and an upper bound. Phase‐compensated, slice‐selective adiabatic 2π pulses are used in a variant of the single‐shot localization method, SADLOVE, for which a theoretical quantitative model of the localization performance is derived. A simple variant of the VERSE method to reduce the rf pulse energy of adiabatic pulses is presented.
Expression of caveolin‐1 in mucoepidermoid carcinoma of the salivary glands: Correlation with vascular endothelial growth factor, microvessel density, and clinical outcome
Authors: Shi Lu , Chen Xin‐Ming , Wang Li , Zhang Lu , Chen Zhi 
Published: March 2007

AbstractBACKGROUND.Caveolin‐1, which has been proposed as a candidate tumor suppressor, plays a regulatory role in several signaling pathways. The importance of caveolin‐1 in endothelial cells in angiogenesis has been confirmed. The clinicopathologic significance of caveolin‐1 expression and its correlation with angiogenesis remains unknown in mucoepidermoid carcinoma (MEC) of the salivary glands.METHODS.Based on an immunohistochemical study, the expression levels of caveolin‐1 and vascular endothelial growth factor (VEGF) and the intratumoral microvessel density (MVD) (labeled by CD34) in 75 patients with MEC were investigated, and correlations with clinicopathologic variables were evaluated statistically.RESULTS.The expression rates of both caveolin‐1 and VEGF were 54.7% (41 of 75 tumors). MVD varied from 9 to 56 (24.45 ± 10.72)/×200. Caveolin‐1 expression was correlated inversely with duration of tumor, clinical stage, histologic grade, and MVD (P = .027, P = .011, P = .04, and P = .025; respectively). VEGF expression was associated positively with MVD (P = .000). Advanced clinical stage, higher grade, and tumors that originated from minor salivary glands exhibited higher MVD (P = .029, P = .002, and P = .008, respectively). The presence of clinical symptoms, male gender, advanced clinical stage, higher grade, increased MVD, and down‐regulated caveolin‐1 were correlated significantly with the development of recurrent disease, as indicated by a shorter disease‐free interval (P < .05). Both univariate and multivariate analyses indicated that clinical stage, histologic grade, and MVD were independent prognostic factors (P < .05). The presence of clinical symptoms and the down‐regulation of caveolin‐1 were identified as negative prognostic predictors in the univariate analysis (P < .05) but did not achieve significance in the multivariate analysis (P > .05).CONCLUSIONS.The current results suggest that caveolin‐1 may function as a tumor suppressor in MEC of the salivary glands. Reduced expression of caveolin‐1 and increased MVD may indicate a poor prognosis for certain patients. Cancer 2007. © 2007 American Cancer Society.
Evidence for activation of KIT, PDGFRα, and PDGFRβ receptors in the Ewing sarcoma family of tumors
Authors: Bozzi Fabio , Tamborini Elena , Negri Tiziana , Pastore Elisa , Ferrari Andrea , Luksch Roberto , Casanova Michela , Pierotti Marco A. , Bellani Franca Fossati , Pilotti Silvana 
Published: March 2007

AbstractBACKGROUND.The Ewing sarcoma family of tumors (ESFT) is one of the most common malignant neoplasms of children and adolescents, characterized by nonrandom translocations involving the Ewing sarcoma (EWS) gene. Over the years the adoption of intensive multimodality treatment approaches has led to a gradual improvement in the survival of patients with ESFT. The prognosis is still unsatisfactory for high‐risk patients, however, and novel therapeutic approaches are desirable. The aim of the study was to investigate the expression/activation of KIT, PDGFRα, and PDGFRβ receptor tyrosine kinases (RTKs) as potential therapeutic targets in ESFT.METHODS.RNA and proteins were extracted from 20 frozen ESFT specimens to ascertain the state activation of KIT, PDGFRα, and PDGFRβ.RESULTS.No mutations were found, whereas the cognate ligands were detected in all cases by polymerase chain reaction (PCR). The expression and activation of KIT, PDGFRα, and PDGFRβ were confirmed by quantitative PCR, immunohistochemistry, and immunoprecipitation and/or Western blot analysis. In particular, when compared with a protein pool obtained from normal adult tissues, PDGFRβ showed a greater protein expression and/or a stronger phosphorylation signal.CONCLUSIONS.The results are consistent with an autocrine/paracrine loop activation of the KIT, PDGFRα, and PDGFRβ receptors and suggest a rationale for the use of RTK inhibitors, either alone or in combination with chemotherapy. Cancer 2007. © 2007 American Cancer Society.
Stress analysis on stentless quadrileaflet pericardial mitral valve
Authors: Kuai Xingcheng , Zhang Jing , Ren Biqiao , Liu Feng , Gong Guangfu , Zeng Yanjun 
Published: March 2007

AbstractThe finite‐element method (FEM) has become an applicable method to analyse the stress distribution of bioprosthetic valves. However, most of the stress analyses performed in the past have been on bioprosthetic aortic valves. No public reports are available on the numerical simulation of stress analysis for stentless quadrileaflet pericardial mitral valves up to date. This study applied FEM to investigate the mechanical behaviours of a modified stentless quadrileaflet pericardial mitral valve. The finite‐element model includes the material non‐linearity, large deformation and the contact condition of leaflets. The results showed that the deformed shapes of valve in the numerical simulation are quite similar to ones observed in the hydrodynamic experiment in vitro, the stress distribution is relatively uniform and the magnitudes of stresses are in a reasonable range. It can be concluded that the finite‐element model in this paper is reasonable and feasible, and the numerical results can be used to evaluate the biomechanical performance of this valve. Copyright © 2007 John Wiley & Sons, Ltd.