bluuebunny/crossref_metadata_2025 huggingface dataset:
The Thermodynamics of Translesion DNA Synthesis Past Major Adducts of Enantiomeric Analogues of Antitumor Cisplatin
Authors: Malina Jaroslav , Novakova Olga , Natile Giovanni , Brabec Viktor
Published: February 2012

The PtII‐coordination complex [PtCl2(DAB)] (DAB=2,3‐diaminobutane) belongs to a class of cytotoxic cisplatin analogues that contain chiral diamine ligands. Enantiomeric pairs of these compounds have attracted particular interest because they have different effects on different DNA conformations, which, in turn, influences the binding of damaged‐DNA‐processing enzymes that control downstream effects of the adducts, and thus exhibit different biological activities of the enantiomers. Herein, we studied the translesion synthesis across the major 1,2‐d(GG) intrastrand cross‐link formed by the R,R and S,S enantiomers of [Pt(DAB)]2+ in the TGGT sequence by using the enzyme that catalyzes the polymerization of deoxyribonucleotides into a DNA strand. We also employed differential scanning calorimetry (DSC) to measure the thermodynamic changes associated with replication‐bypass past 1,2‐d(GG) adducts of the [Pt(DAB)]2+ enantiomers. In the sequence TGGT, the 1,2‐d(GG) intrastrand cross‐links that were formed by the enantiomeric pairs of [Pt(DAB)]2+ inhibited DNA polymerization in a chirality‐dependent manner. The thermodynamic data helped to understand the effect of the alterations in thermodynamic stability of DNA caused by the Pt‐d(GG) adducts upon DNA polymerization across these lesions. Moreover, these data can possibly explain the influence of these alterations on the ability of many DNA polymerases to bypass adducts of antitumor platinum drugs. These results also highlighted the usefulness of DSC in evaluating the impact of DNA adducts of platinum‐coordinated compounds on the processing of these lesions by damaged‐DNA processing‐enzymes.
Bayesian imputation of non‐chosen attribute values in revealed preference surveys
Authors: Washington Simon , Ravulaparthy Srinath , Rose John M. , Hensher David , Pendyala Ram
Published: February 2012

Obtaining attribute values of non‐chosen alternatives in a revealed preference context is challenging because non‐chosen alternative attributes are unobserved by choosers, chooser perceptions of attribute values may not reflect reality, existing methods for imputing these values suffer from shortcomings, and obtaining non‐chosen attribute values is resource intensive. This paper presents a unique Bayesian (multiple) Imputation Multinomial Logit model that imputes unobserved travel times and distances of non‐chosen travel modes based on random draws from the conditional posterior distribution of missing values. The calibrated Bayesian (multiple) Imputation Multinomial Logit model imputes non‐chosen time and distance values that convincingly replicate observed choice behavior. Although network skims were used for calibration, more realistic data such as supplemental geographically referenced surveys or stated preference data may be preferred. The model is ideally suited for imputing variation in intrazonal non‐chosen mode attributes and for assessing the marginal impacts of travel policies, programs, or prices within traffic analysis zones. Copyright © 2012 John Wiley & Sons, Ltd.
Proteoglycans in stem cells
Authors: Gasimli Leyla , Linhardt Robert J. , Dordick Jonathan S.
Published: February 2012

The remarkable promise of pluripotent and multipotent stem cells (SCs) imparts tremendous optimism for advancement of regenerative medicine, developmental biology, and drug discovery. Perhaps the greatest challenge is to finely direct, control, and command their differentiation. As those processes are managed on many levels, including genomic, transcriptomic, and epigenomic, examination of all of these components will yield powerful tools for manipulation of SCs. Carbohydrates surround all cells, including SCs as a glycocalyx. Of particular interest is the class of carbohydrates known as proteoglycans (PGs), which are a diverse group of glycoconjugates consisting of core protein with one or more glycosaminoglycan (GAG) chains attached. They are primarily located in the extracellular matrix as well as at cell surfaces, where they are bound or anchored to the membrane through their core proteins. GAG chains are linear, anionic, and highly heterogeneous carbohydrates consisting of repeating disaccharides. PGs facilitate interaction of cells with the extracellular environment by interacting with chemokines, growth factors, and other signaling molecules. Core proteins are involved in many signaling pathways, both individually, as well as through attached proteins via GAG‐mediated interactions. These essential and accessible functions make PGs an excellent target for manipulating SCs and guiding their fate. Studying the role of PGs in cell development will yield valuable insight into the mechanism of SC differentiation and suggest approaches toward directing those pathways. Such studies may also help identify valuable markers for distinguishing between various cell populations during differentiation.
Role of the planar cell polarity gene CELSR1 in neural tube defects and caudal agenesis
Authors: Allache Redouane , De Marco Patrizia , Merello Elisa , Capra Valeria , Kibar Zoha
Published: February 2012

BACKGROUND

Neural tube defects (NTDs), including anencephaly and spina bifida, have a complex etiology. Defects in the planar cell polarity (PCP) signaling pathway have been strongly associated with NTDs in animal models and human cohorts. In this genetic study, we examined the core PCP gene CELSR1 in NTDs and caudal agenesis cases to determine whether mutations at this gene predispose to these defects.

METHODS

We sequenced the coding region and the exon‐intron junctions of CELSR1 in a cohort of 473 patients affected with various forms of open and closed NTDs (412) or caudal agenesis (61). Novel and rare variants (<1%) were genotyped in a cohort of 639 ethnically‐matched individuals. The effect of novel missense mutations absent in controls and in public databases on protein function was predicted in silico.

RESULTS

We identified in our cohort one nonsense mutation in exon 1 of CELSR1 that truncates the majority of the protein in one patient with NTD and one in‐frame 12 bp deletion that removes a putative PKC phosphorylation “SSR” motif in one caudal agenesis patient. We also detected a total of 13 novel missense variants in 12 patients (11 NTDs and 1 caudal agenesis) that were predicted to be pathogenic in silico.

CONCLUSIONS

We detected novel CELSR1 mutations predicted to be pathogenic in 2.9% of our NTD cohort and 3.3% of our caudal agenesis cohort. Our findings implicate CELSR1 as a risk factor for NTDs or caudal agenesis and provide additional evidence for a pathogenic role of PCP signaling in these malformations. Birth Defects Research (Part A), 2012. © 2012 Wiley Periodicals, Inc.
Nhs: Network‐based hierarchical segmentation for cryo‐electron microscopy density maps
Authors: Burger Virginia , Chennubhotla Chakra
Published: February 2012

Cryo‐electron microscopy (cryo‐EM) experiments yield low‐resolution (3–30 Å) 3D‐density maps of macromolecules. These density maps are segmented to identify structurally distinct proteins, protein domains, and subunits. Such partitioning aids the inference of protein motions and guides fitting of high‐resolution atomistic structures. Cryo‐EM density map segmentation has traditionally required tedious and subjective manual partitioning or semisupervised computational methods, whereas validation of resulting segmentations has remained an open problem in this field. We introduce a network‐based hierarchical segmentation (Nhs) method, that provides a multi‐scale partitioning, reflecting local and global clustering, while requiring no user input. This approach models each map as a graph, where map voxels constitute nodes and weighted edges connect neighboring voxels. Nhs initiates Markov diffusion (or random walk) on the weighted graph. As Markov probabilities homogenize through diffusion, an intrinsic segmentation emerges. We validate the segmentations with ground‐truth maps based on atomistic models. When implemented on density maps in the 2010 Cryo‐EM Modeling Challenge, Nhs efficiently and objectively partitions macromolecules into structurally and functionally relevant subregions at multiple scales. © 2012 Wiley Periodicals, Inc. Biopolymers 97: 732–741, 2012.
Enhanced arsenate uptake in Saccharomyces cerevisiae overexpressing the Pho84 phosphate transporter
Authors: Shen Michael W.Y. , Shah Dhawal , Chen Wilfred , Da Silva Nancy
Published: February 2012

Arsenate is a major toxic constituent in arsenic‐contaminated water supplies. Saccharomyces cerevisiae was engineered as a potential biosorbent for enhanced arsenate accumulation. The phosphate transporter, Pho84p, known to import arsenate, was overexpressed using a 2μ‐based vector carrying PHO84 under the control of the late‐phase ADH2 promoter. Arsenate uptake was then evaluated using a resting cell system. In buffer solutions containing high arsenate concentrations (12,000 and 30,000 ppb), the engineered strains internalized up to 750 μg of arsenate per gram of cells, a 50% improvement over control strains. Increasing the cell mass 2.5‐fold yielded a proportional increase in the volumetric arsenate uptake, while maintaining the same level of specific uptake. At high levels of arsenate, loss from the intact cells to the medium was observed with time; knockouts of two known arsenic extrusion genes, ACR3 and FPS1, did not prevent this loss. At trace level concentrations (120 ppb), rapid and total arsenate removal was observed. The presence of 50 μM phosphate reduced uptake by approximately 15% in buffer containing 80 μM (6,000 ppb) arsenate. At trace levels of arsenate (70 ppb), the phosphate reduced the initial rate of uptake, but not the total amount removed. PHO84 mRNA levels were nearly 30 times higher in the engineered strains relative to the control strains. Uptake may no longer be a limiting factor in the engineered system and further increases should be possible by upregulating the downstream reduction and sequestration pathways. © 2012 American Institute of Chemical Engineers Biotechnol. Prog., 2012
Encapsulation of hemoglobin inside liposomes surface conjugated with poly(ethylene glycol) attenuates their reactions with gaseous ligands and regulates nitric oxide dependent vasodilation
Authors: Rameez Shahid , Guzman Nicole , Banerjee Uddyalok , Fontes Jorge , Paulaitis Michael E. , Palmer Andre F. , Patel Rakesh P. , Honavar Jaideep
Published: February 2012

Acellular hemoglobin (Hb)‐based O2 carriers (HBOCs) are being investigated as red blood cell (RBC) substitutes for use in transfusion medicine. However, commercial acellular HBOCs elicit both vasoconstriction and systemic hypertension which hampers their clinical use. In this study, it is hypothesized that encapsulation of Hb inside the aqueous core of liposomes should regulate the rates of NO dioxygenation and O2 release, which should in turn regulate its vasoactivity. To test this hypothesis, poly(ethylene glycol) (PEG) conjugated liposome‐encapsulated Hb (PEG‐LEHs) dispersions were prepared using human and bovine Hb. In this study, the rate constants for O2 dissociation, CO association, and NO dioxygenation were measured for free Hb and PEG‐LEH dispersions using stopped‐flow UV–visible spectroscopy, while vasoactivity was assessed in rat aortic ring strips using both endogenous and exogenous sources of NO. It was observed that PEG‐LEH dispersions had lower O2 release and NO dioxygenation rate constants compared with acellular Hbs. However, no difference was observed in the CO association rate constants between free Hb and PEG‐LEH dispersions. Furthermore, it was observed that Hb encapsulation inside vesicles prevented Hb dependent inhibition of NO‐mediated vasodilation. In addition, the magnitude of the vasoconstrictive effects of Hb and PEG‐LEH dispersions correlated with their respective rates of NO dioxygenation and O2 release. Overall, this study emphasizes the pivotal role Hb encapsulation plays in regulating gaseous ligand binding/release kinetics and the vasoactivity of Hb. © 2012 American Institute of Chemical Engineers Biotechnol. Prog., 2012
High‐throughput methods for miniaturization and automation of monoclonal antibody purification processes
Authors: Treier Katrin , Hansen Sigrid , Richter Carolin , Diederich Patrick , Hubbuch Jürgen , Lester Philip
Published: February 2012

In the last decade, high‐throughput downstream process development techniques have entered the biopharmaceutical industry. As chromatography is the standard downstream purification method, several high‐throughput chromatographic methods have been developed and applied including miniaturized chromatographic columns for utilization on liquid handling stations. These columns were used to setup a complete downstream process on a liquid handling station for the first time. In this article, a monoclonal antibody process was established in lab‐scale and miniaturized afterwards. The scale‐down methodology is presented and discussed. Liquid handling in miniaturized single and multicolumn processes was improved and applicability was demonstrated by volume balances. The challenges of absorption measurement are discussed and strategies were shown to improve volume balances and mass balances in 96‐well microtiter plates. The feasibility of miniaturizing a complete downstream process was shown. In the future, analytical bottlenecks should be addressed to gain the full benefit from miniaturized complete process development. © 2012 American Institute of Chemical Engineers Biotechnol. Prog., 2012
Surgical anatomy of the superior gluteal nerve and landmarks for its localization during minimally invasive approaches to the hip
Authors: Apaydin Nihal , Kendir Simel , Loukas Marios , Tubbs R. Shane , Bozkurt Murat
Published: February 2012

The superior gluteal nerve (SGN) is vulnerable to damage during total hip arthroplasty and various pelvic surgeries. Recently introduced minimally invasive approaches to the hip show promise for less muscle trauma compared to conventional approaches. However, the risk of damaging the SGN has not been well documented for such alternative approaches. Therefore, we aimed to investigate the anatomic course of the SGN and to define anatomical landmarks that may be used by surgeons during minimally invasive approaches to the hip. Twenty‐eight gluteal regions from 14 formalin‐fixed cadavers were dissected and the course and the distances of the SGN and its branches to the tip of the greater trochanter (GT) were measured. The landmarks for standardizing the course of the SGN included the posterior inferior iliac spine (PIIS), GT, and a line (PIIS‐GT) connecting these two points. The exit of the SGN was found to be at the medial one third of the PIIS‐GT line and 5.4 cm from the GT. Two branching patterns were noted. The branches of the SGN were distributed lateral to the PIIS‐GT line. On the basis of our study, the safe zone for the SGN was smaller than previously reported. Posterior, lateral, or anterolateral minimally invasive approaches to the hip should take into account the point of exit of the SGN and the area of distribution of its branches. A minimally invasive anterolateral approach may particularly compromise branches to the tensor fasciae latae muscle. Localization of the SGN and its branches using the anatomic landmarks defined in this study may decrease surgical morbidity. Clin. Anat. 26:614–620, 2013. © 2012 Wiley Periodicals, Inc.
Acid‐Catalyzed Decomposition of the Benzyl Nitrite Intermediate in HNO3‐Mediated Aerobic Oxidation of Benzyl Alcohol
Authors: Aellig Christof , Neuenschwander Ulrich , Hermans Ive
Published: February 2012

Benzyl nitrite (PhCH2ONO) was previously identified as the pivotal intermediate in the HNO3‐mediated oxidation of benzyl alcohol. Its acid‐catalyzed decomposition yields benzaldehyde and HNO, the precursor of undesirable N2O. Most likely, an analogous mechanism is responsible for the formation of N2O during the oxidation of cyclohexanol and cyclohexanone to adipic acid, the largest industrial source of this important greenhouse gas. In this paper, the decomposition of benzyl nitrite is studied in more detail, allowing the kinetic isotope effect and the influence of substituents to be determined. A linear Evans–Polanyi correlation between the measured Arrhenius activation energies and the computed reaction energies was established. Furthermore, the differences in the reactivities of the substituted benzyl nitrites are reflected in the oxidation of the corresponding alcohols, and also affect the rate‐determining step in the overall mechanism. The results of this study corroborate the importance of the nitrite intermediate in HNO3‐based oxidation technology.
Highly Efficient Extraction and Oxidative Desulfurization System Using Na7H2LaW10O36⋅32 H2O in [bmim]BF4 at Room Temperature
Authors: Xu Junhua , Zhao Shen , Chen Wei , Wang Miao , Song Yu‐Fei
Published: February 2012

Highly efficient, deep desulfurization of model oil containing dibenzothiophene (DBT), benzothiophene (BT), or 4,6‐dimethyldibenzothiophene (4,6‐DMDBT) has been achieved under mild conditions by using an extraction and catalytic oxidative desulfurization system (ECODS) in which a lanthanide‐containing polyoxometalate Na7H2LnW10O36⋅32 H2O (LnW10; Ln=Eu, La) acts as catalyst, [bmim]BF4 (bmim=1‐butyl‐3‐methylimidazolium) as extractant, and H2O2 as oxidant. Sulfur removal follows the order DBT>4,6‐DMDBT>BT at 30 °C. DBT can be completely oxidized to the corresponding sulfone in 25 min under mild conditions, and the LaW10/[bmim]BF4 system could be recycled for ten times with only slight decrease in activity. Thus, LaW10 in [bmim]BF4 is one of the most efficient systems for desulfurization using ionic liquids as extractant reported so far.
Solvation of Na+, K+, and Their Dimers in Helium
Authors: An der Lan Lukas , Bartl Peter , Leidlmair Christian , Jochum Roland , Denifl Stephan , Echt Olof , Scheier Paul
Published: February 2012

Helium atoms bind strongly to alkali cations which, when embedded in liquid helium, form so‐called snowballs. Calculations suggest that helium atoms in the first solvation layer of these snowballs form rigid structures and that their number (n) is well defined, especially for the lighter alkalis. However, experiments have so far failed to accurately determine values of n. We present high‐resolution mass spectra of Na+Hen, K+Hen, Na2+Hen and K2+Hen, formed by electron ionization of doped helium droplets; the data allow for a critical comparison with several theoretical studies. For sodium and potassium monomers the spectra indicate that the value of n is slightly smaller than calculated. Na2+Hen displays two distinct anomalies at n=2 and n=6, in agreement with theory; dissociation energies derived from experiment closely track theoretical values. K2+Hen distributions are fairly featureless, which also agrees with predictions.
π‐Electron‐System‐Layered Polymer: Through‐Space Conjugation and Properties as a Single Molecular Wire
Authors: Morisaki Yasuhiro , Ueno Shizue , Saeki Akinori , Asano Atsushi , Seki Shu , Chujo Yoshiki
Published: February 2012

[2.2]Paracyclophane‐based through‐space conjugated oligomers and polymers were prepared, in which poly(p‐arylene–ethynylene) (PAE) units were partially π‐stacked and layered, and their properties in the ground state and excited state were investigated in detail. Electronic interactions among PAE units were effective through at least ten units in the ground state. Photoexcited energy transfer occurred from the stacked PAE units to the end‐capping PAE moieties. The electrical conductivity of the polymers was estimated using the flash‐photolysis time‐resolved microwave conductivity (FP‐TRMC) method and investigated together with time‐dependent density functional theory (TD‐DFT) calculations, showing that intramolecular charge carrier mobility through the stacked PAE units was a few tens of percentage larger than through the twisted PAE units.
Velocity Distribution and Variations in Gas Pressure in Crosswise Flow through Tanks
Authors: Surek Dominik
Published: February 2012

In der verfahrenstechnischen Industrie werden vielfach Behälter mit großem Volumen von 250 – 1000 m3 benötigt, die von großen Gasvolumenströmen bis zu 150 000 m3h–1 bei Geschwindigkeiten von 0,347 – 1,0 m s–1 durchströmt werden. Die Gaszu‐ und ‐abströmung muss dabei über je ein bis zwei Ein‐ und Austrittsstutzen mit Durchmessern von 1,20 – 2,0 m erfolgen. Im Behälter soll mit Rücksicht auf eine chemische oder katalytische Reaktion eine konstante Strömungsgeschwindigkeit herrschen. Im vorliegenden Beitrag wird gezeigt, wie eine Gasverteilerplatte für einen quer angeströmten Behälter oder Katalysator mit einer differentiellen Querschnittsverteilung für die Durchströmfläche entworfen und berechnet werden kann, die eine nahezu konstante Strömungsgeschwindigkeit im Behälter gewährleistet, ohne den Durchströmwiderstand zu erhöhen.
Orthotropic active strain models for the numerical simulation of cardiac biomechanics
Authors: Rossi Simone , Ruiz‐Baier Ricardo , Pavarino Luca F. , Quarteroni Alfio
Published: February 2012

A model for the active deformation of cardiac tissue considering orthotropic constitutive laws is introduced and studied. In particular, the passive mechanical properties of the myocardium are described by the Holzapfel‐Ogden relation, whereas the activation model is based on the concept of active strain. There, an incompatible intermediate configuration is considered, which entails a multiplicative decomposition between active and passive deformation gradients. The underlying Euler–Lagrange equations for minimizing the total energy are written in terms of these deformation factors, where the active part is assumed to depend, at the cell level, on the electrodynamics and on the specific orientation of the cardiomyocytes. The active strain formulation is compared with the classical active stress model from both numerical and modeling perspectives. The well‐posedness of the linear system derived from a generic Newton iteration of the original problem is analyzed, and different mechanical activation functions are considered. Taylor–Hood and MINI finite elements are used in the discretization of the overall mechanical problem. The results of several numerical experiments show that the proposed formulation is mathematically consistent and is able to represent the main features of the phenomenon, while allowing savings in computational costs. Copyright © 2012 John Wiley & Sons, Ltd.
STED Microscopy and its Applications: New Insights into Cellular Processes on the Nanoscale
Authors: Müller Tobias , Schumann Christian , Kraegeloh Annette
Published: February 2012

For about a decade, superresolution fluorescence microscopy has been advancing steadily, maturing from the proof‐of‐principle stage to routine application. Of the various techniques, STED (stimulated emission depletion) microscopy was the first to break the diffraction barrier. Today, it is a prominent and versatile form of superresolution light microscopy. STED microscopy has shed a sharper light on numerous topics in cell biology, but also in material sciences. Both disciplines extend into the nanometer range, making detailed studies of structural and functional relationships difficult or even impossible to achieve using diffraction‐limited microscopy. With recent advancements like spectral multiplexing or live‐cell imaging, STED microscopy makes nanoscale materials and components of the cell accessible for fluorescence‐based investigations. With multicolor superresolution imaging, even the interactions between biological and engineered nanostructures can be studied in detail. This review gives an introduction into the working principle of STED microscopy, provides a detailed overview of recent advancements and new techniques implemented for use with STED microscopy and shows how these have been applied in the life sciences and nanotechnologies.
Social Relationships and Social Roles
Authors: Champion Lorna
Published: February 2012

This review draws attention to the broad and diverse theoretical underpinnings of interpersonal psychotherapy (IPT). A plea is made for greater attention to the theoretical influences on IPT in forming our understanding of the techniques and processes and to establish indicators of successful outcome as well as for whom the treatment is most suitable. The paper takes a lifespan perspective that considers the implications of social factors for the different age groups to which IPT has been shown to be effective in the treatment of depression. The main thrust of the paper considers the potential importance of social theory, particularly the research on life events and social support. It is argued that it is these social aspects and particularly a focus on the use of the patient's wider social network that distinguishes IPT from other evidence‐based short‐term therapies. Copyright © 2012 John Wiley & Sons, Ltd.

Key Practitioner Message

Interpersonal psychotherapy draws on a broad and diverse range of theoretical influences.

The study of the theory underpinning IPT can inform assessment, technique and process in the practice of IPT.

Knowledge of aspects of the research on life events and social support is particularly relevant not only for the assessment phase but also for the middle and termination phases.

Attention to the theory behind IPT can usefully inform future research on IPT particularly what may determine successful or unsuccessful outcome of this short‐term treatment.
The influence of crystallization conditions on the onset of dendritic growth of calcium carbonate
Authors: Beck R. , Andreassen J.‐P.
Published: February 2012

Understanding the crystallization of calcium carbonate is relevant in numerous fields like biomineralization, geology and industrial applications where calcium carbonate forms. In order to enhance the knowledge about the formation of calcium carbonate with focus on the vaterite polymorph, in this work calcium carbonate has been crystallized in aqueous solutions at temperatures from 5 °C to 90 °C. Special attention has been directed to higher temperatures for which the effect of the initial supersaturation on the resulting crystal morphologies and the onset of dendritic growth have been studied. In analogy to snow crystal formation, it has been found that in a certain temperature range hexagonal plate‐like crystals form at low supersaturation whereas dendritic patterns start to appear at higher supersaturation. The symmetrical branches characteristic for dendritic growth get less pronounced as the temperature is decreased. The results reported here related to the interdependence between supersaturation, crystal morphology and growth mechanisms, can be used in future works to predict particle formation and to design crystal architectures. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Determination of optical parameters of Ga0.75In0.25Se layered crystals
Authors: Isik M. , Gasanly N. M.
Published: February 2012

The optical properties of the Ga0.75In0.25Se crystals have been investigated by means of transmission and reflection measurements in the wavelength range of 380–1100 nm. The analysis of the results performed at room temperature revealed the presence of optical indirect transtions with band gap energy of 1.89 eV. The variation of the band gap energy as a function of temperature was also studied in the temperature range of 10–300 K. The rate of change of band gap energy (γ = –6.2 × 10–4 eV/K) and absolute zero value of the band gap (Egi(0) = 2.01 eV) were reported. The wavelength dependence of the refractive index was analyzed using Wemple and DiDomenico, Sellmeier and Cauchy models to find the oscillator energy, dispersion energy, oscillator strength and zero‐frequency refractive index values. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The Behavior of Dust Particles Near Langmuir Probe
Authors: Ramazanov T. S. , Bastykova N. Kh. , Ussenov Y. A. , Kodanova S. K. , Dzhumagulova K. N. , Dosbolayev M. K.
Published: February 2012

In the present work the dynamics of dust particles near electric probe in gas discharge at different pressures was studied. Trajectories of dust particles near electric probe with taking into account of the ion drag force and neutral friction force were calculated numerically. The comparisons between experimental and calculated results showed the good agreement (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Generalized Linear Mixing Rule for Classical Coulomb Mixtures
Authors: Chugunov A. I.
Published: February 2012

It is shown that the Coulomb energy U of fully ionized ionic mixture can be written as a sum over partial contributions of ion species j: U = T Σj Nju (Γj, yj) (generalized linear mixing rule). In contrast to the traditional linear mixing rule ULM = T Σj NjuOCP(Γj), applicable for strong coupling, the partial contribution function u depends not only on Γj, but on an additional parameter yj = (rD/rDOCP)2 also. Here rD and rDOCP are Debye radiuses in the mixture and in the one component plasma at coupling parameter Γj, correspondingly. The parameter yj does not depend on a specific composition of the mixture, but on the Debye radius rD only, making function u (Γj, yj) universal. The generalized linear mixing rule can be applied at any coupling parameter, if ionic mixture is not crystallized. It reproduces results of the Debye‐Hückel theory at weak coupling and traditional linear mixing rule at strong coupling. It can be easily applied to the complicated mixtures, composed of a large number of ion species. Since yj is temperature independent, the Coulomb contribution to Helmholtz free energy of the mixture can also be presented in a form of generalized linear mixing rule (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Collective Excitations of Finite‐Temperature Nano Plasmas
Authors: Raitza T. , Broda I. , Reinholz H. , Röpke G.
Published: February 2012

Electron density fluctuations as well as current density correlations are considered for excited nano plasmas. Calculations are performed by classical MD simulations at high temperatures for expanding nearly spherical clusters of laser irradiated sodium atoms. The resonance structures observed in the frequency spectrum of the bi‐local correlation functions are analyzed. Mie modes and volume plasmon type excitations are observed as well as breathing modes. We investigate the relation between the bi‐local correlation functions of the electron density fluctuations and current density via the equation of continuity.The collective excitations are of significance for the dielectric function and further properties such as the photo absorption coefficients. Results are presented for an exemplarily taken set of parameter values of the nano plasma (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Quantum Monte Carlo Simulations of Strongly Coupled Quark‐Gluon Plasma
Authors: Filinov V. S. , Bonitz M. , Ivanov Y.B. , Levashov P.R. , Fortov V.E.
Published: February 2012

A strongly coupled quark‐gluon plasma (QGP) of constituent quasiparticles is studied by a path‐integral Monte‐Carlo method. This approach is a quantum generalization of the model developed by Gelman, Shuryak and Zahed. It is shown that this method is able to reproduce the QCD lattice equation of state, internal energy, entropy and trace anomaly (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Practical Equation of State for the Sun and Sun‐like Stars
Authors: Lin H‐H. , Däppen W.
Published: February 2012

For models of the Sun and Sun‐like stars, a high‐quality equation of state is crucial. Conversely, helio‐ and asteroseismological observations put constraints on the physical formalisms. They effectively turn the Sun and stars into laboratories for dense plasmas. For models of the Sun and Sun‐like stars, the most accurate equation of state so far has been the one developed as part of OPAL opacity project of Livermore. However, the OPAL equation of state is limited in two important respects. First, it is only available in the form of pre‐computed tables that are provided from Lawrence Livermore National Laboratory. Applications to stellar modeling require therefore interpolation, with unavoidable loss of accuracy. Second, the OPAL equation of state is proprietary and not freely available. Varying its underlying physical parameters is therefore no option for the community. We report on the most recent progress with the development of a high‐precision emulation of the OPAL equation of state that will lead to an in‐line tool for modelers (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Low‐temperature Extensions of the Virial Equation of State for Solar Modeling
Authors: Liang Y.‐C. , Mussack K. , Däppen W.
Published: February 2012

Low‐order density expansions cannot adequately describe recombination reactions. Therefore, the usefulness of an exact quantum virial expansion truncated at the order of ϱ5/2 is limited to the deeper interior of the Sun, where the plasma is nearly fully ionized. Here, intermediate steps towards full‐fledged solar modeling are presented. They are (i) a smooth numerical representation of the quantum virial expansion and (ii) the construction of a smooth transition to the low‐temperature regime (below 50,000 K), where the virial expansions breaks down due to H recombination. These technical steps are realized for a simplified H‐only plasma; the extension to He and heavier elements will be dealt with later. Ultimately, the outcome will be that solar observations can be used to test the accuracy of the virial equation of state and to compare it with current more phenomenological formalisms (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optimal power control for wireless cooperative relay networks: a cooperative game theoretic approach
Authors: Zhang Guopeng , Li Ping , Zhou Dongdai , Yang Kun , Ding Enjie
Published: February 2012

Wireless nodes operating on batteries are always assumed to be selfish to consume their energy solely to maximize their own benefits. Thus, the two network objectives, that is, system efficiency and user fairness should be considered simultaneously. To this end, we propose two game theoretic mechanisms, that is, the signal‐to‐noise ratio (SNR) game and the data‐rate game to stimulate cooperation among selfish user nodes for cooperative relaying. Considering one node could trade its transmission power for its partner's relaying directly, the strategy of a node is defined as the amount of power that it is willing to contribute for relaying purpose. In the SNR game, selfish nodes are willing to achieve SNR increases at their receivers, while in the data‐rate game the nodes are willing to achieve data‐rate gains. We prove that each of the games has a unique Nash bargaining solution. Simulation results show that the Nash bargaining solution lead to fair and efficient resource allocation for both the cooperative partner nodes in the Pareto optimal sense, that is, both the nodes could experience better performance than they work independently and the degree of cooperation of a node only depends on how much contribution its partner can make to improve its own performance. Copyright © 2012 John Wiley & Sons, Ltd.
Disposition of opioids in oral fluid: Importance of chromatography and mass spectral transitions in LC‐MS/MS
Authors: Tuyay James , Coulter Cynthia , Rodrigues Warren , Moore Christine
Published: February 2012

The use of prescription pain relievers, specifically opioids, has been increasing over the last few years. Oral fluid is easier to collect than urine, is difficult to adulterate, and is a reflection of free drug in the body, so its analysis is becoming more widespread in the monitoring of opioids. The demethylated metabolites of oxycodone, hydrocodone, and codeine are present at higher concentrations in oral fluid than oxymorphone, hydromorphone, and morphine, respectively; therefore, their detection in saliva indicates ingestion of the medication rather than diversion, and should be included in the analysis of opioids in this matrix. Since the compounds have the same nominal molecular weights, the same M + H+ precursor ions in positive electrospray mode, and potentially identical collisionally activated fragmentation patterns, the importance of chromatography to separate the various opioids as well as the selection of mass spectral transitions is critical for correct identification. A procedure for the simultaneous determination of 12 opioid related compounds in oral fluid using liquid chromatography with tandem mass spectrometry (LC‐MS/MS) is presented. The recovery of opioids from the collection device was over 80% at 20 ng/ml; intra‐day imprecision was less than 6.8%; inter‐day imprecision less than 6.2%. In authentic specimens, the predominant metabolite of oxycodone was noroxycodone; for specimens containing codeine, no morphine was detected; and for hydrocodone positives, norhydrocodone was detected at significantly higher levels than hydromorphone. The importance of monitoring specific mass spectral transitions and chromatographic separation is demonstrated. Copyright © 2012 John Wiley & Sons, Ltd.
Differentiation of methylbenzylpiperazines (MBPs) and benzoylpiperazine (BNZP) using GC‐MS and GC‐IRD
Authors: Abdel‐Hay Karim M. , DeRuiter Jack , Randall Clark C.
Published: February 2012

Three‐ring substituted methylbenzylpiperazines (MBPs) and their isobaric benzoylpiperazine (BNZP) have equal mass and many common mass spectral fragment ions. The mass spectrum of BNZP yields a unique benzoyl‐group containing fragment at m/z 122 and an additional major fragment at m/z 69 that allows its discrimination from the three MBP regioisomers. Perfluoroacylation of the secondary amine nitrogen of these isomeric piperazines gave mass spectra with differences in relative abundance of some fragment ions but acylation does not alter the fragmentation pathway and did not provide additional MS fragments of discrimination among these isomers.

Gas chromatography coupled with infrared detection (GC‐IRD) provides direct confirmatory data for the structural differentiation between the four isomers. The mass spectra in combination with the vapour phase IR spectra provide for specific confirmation of each of the isomeric piperazines. The underivatized and perfluoroacyl derivatives of these four piperazines were resolved on a stationary phase of 100% trifluoropropyl methyl polysiloxane (Rtx‐200). Gas chromatography coupled with time‐of‐flight mass spectrometry provides an additional means of differentiating between the isobaric MBP and BNZP which have equivalent nominal masses but are different in their elemental composition and exact masses. Copyright © 2012 John Wiley & Sons, Ltd.
Monitoring of aglycons of yew glycosides (3,5‐dimethoxyphenol, myrtenol and 1‐octen‐3‐ol) as first indicator of yew presence
Authors: Varlet V. , Augsburger M.
Published: February 2012

The toxicity of yew (Taxus spp) is well known from ancient times and is mainly due to taxins acting as inhibitors of calcium and sodium transport across the cell membrane of cardiac myocytes. The confirmation of yew taxins in body fluids can be carried out by liquid chromatography‐tandem mass spectrometry (LC‐MS/MS). However, before selecting this precise but expensive technique, an orientation test should be done to ascertain yew presence as toxic agent in the organism. As the 3,5‐dimethoxyphenol (3,5‐DMP), myrtenol and 1‐octen‐3‐ol appear as glycosidically bound volatile compounds and are very yew specific, the detection of 3,5‐DMP and the measurement of 1‐octen‐3‐ol / myrtenol concentration ratio constitute reliable indicators of yew presence in forensic cases. The detection of these compounds is easily performed by gas chromatography‐mass spectrometry (GC‐MS) (SIM) after an enzymatic hydrolysis (β‐glucosidase) allowing the release of volatile compounds from yew glycosides. Copyright © 2012 John Wiley & Sons, Ltd.
The synthesis and characterization N‐methyl‐3‐phenyl‐norbornan‐2‐amine (Camfetamine™)
Authors: Kavanagh Pierce , Angelov Daniel , O'Brien John , Power John D. , McDermott Seán D. , Talbot Brian , Fox John , O'Donnell Cora , Christie Rachel
Published: February 2012

N‐Methyl‐3‐phenyl‐norbornan‐2‐amine (N‐methyl‐3‐phenylbicyclo[2.2.1]heptan‐2‐amine, Camfetamine™) is available from a number of online legal highs/research chemicals' vendors. Although it was developed as an analeptic by Merck in the early 1960s, it was never commercialized. However, the Association of Independent Research Chemical Retailers (AIRCR), an umbrella organization for a number of online vendors, has redeveloped it for use as a recreational drug. N‐Methyl‐3‐phenyl‐norbornan‐2‐amine is closely related to fencamfamine which has been widely used as a central nervous system (CNS) stimulant and appetite suppressant. In this paper we describe the synthesis of N‐methyl‐3‐phenyl‐norbornan‐2‐amine, its characterization and interpretations of its electron impact, and electrospray ionization mass spectra. Copyright © 2012 John Wiley & Sons, Ltd.
A validated HPLC method for the simultaneous determination of naftidrofuryl oxalate and its degradation product (metabolite), naftidrofuryl acid: applications to pharmaceutical tablets and biological samples
Authors: Sabry Suzy M. , Belal Tarek S. , Barary Magda H. , Ibrahim Mohammed E. A.
Published: February 2012

A simple, sensitive, and selective reverse phase‐high performance liquid chromatography (RP‐HPLC) method was developed and validated for the simultaneous determination of naftidrofuryl oxalate (NF) and its hydrolytic degradation product (metabolite), naftidrofuryl acid (NFA). Chromatographic separation was achieved on Spheri‐5 RP‐C8 (5 µm) (220 × 4.6 mm i.d.) column using a mobile phase composed of acetonitrile, 0.05 M sodium acetate and triethylamine (40 : 60 : 0.1, by volume) adjusted to pH 5.5 using glacial acetic acid. The mobile phase was pumped at flow rate 1.5 ml/min. The UV detector was set at 225 nm and quantification of the analytes was based on measuring the peak areas. The method was proved to be accurate and precise with linearity ranges of 0.1–25 and 0.2–25 µg ml‐1 for NF and NFA, respectively. The limits of detection were 0.03 and 0.04 µg ml‐1 for NF and NFA, respectively. The method was applied to serve three goals: (1) stability‐indicating assay of the parent drug NF in its pharmaceutical formulation, (2) determination of the degradation product NFA down to a level of 0.005% in the presence of large excess of the parent drug, and (3) drug monitoring of naftidrofuryl and its metabolite, naftidrofuryl acid, in human plasma/urine samples taken from a healthy volunteer treated with 200 mg oral dose of naftidrofuryl oxalate. The proposed method proved to be accurate, precise, and reliable in all these application fields. Copyright © 2012 John Wiley & Sons, Ltd.
A role for Drosophila Wnt‐4 in heart development
Authors: Tauc Helen M. , Mann Tabea , Werner Kathrin , Pandur Petra
Published: February 2012

In vertebrates, different Wnt‐signaling pathways are required in a temporally coordinated manner to promote cardiogenesis. In Drosophila, wingless holds an essential role in heart development. Among the known Drosophila Wnts is DWnt4, the function of which has been studied in various developmental processes except for heart development. We re‐evaluated the expression pattern of DWnt4 during embryogenesis and show that transcripts are not restricted to the dorsal ectoderm but are also present in the cardiogenic mesoderm. Moreover, we detect DWnt4 mRNA transcripts in myocardial cells by stage 16. The heart phenotype in DWnt4 mutant embryos is characterized by various degrees of disrupted expression of different cardiac markers. Overexpression of Dwnt4 also affects heart marker expression, which can be partially rescued by simultaneous inhibition of PKC. Our data reveal a role for DWnt4 in cardiogenesis; however, integration of DWnt4 with other known signaling pathways that function in heart development still awaits further investigation. genesis 50:466–481, 2012. © 2012 Wiley Periodicals, Inc.
Lanthanide Loaded Zeolites, Clays, and Mesoporous Silica Materials as MRI Probes
Authors: Peters Joop A. , Djanashvili Kristina
Published: February 2012

Zeolites, clays, and mesoporous silica materials offer the possibility to be loaded with Ln3+ ions either by means of ion exchange of the cations that are balancing the negative charge of the framework or by grafting of Ln3+ chelates to the framework. In this Microreview, the structures of the materials used up to now are described and related to their stabilities and relaxometric behavior. The possible exploitation of the unique features of these materials as both positive and negative MRI contrast agents in multimodal probes and in theranostics are discussed.
Synthesis of Enantiopure 7‐Substituted Azepane‐2‐carboxylic Acids as Templates for Conformationally Constrained Peptidomimetics
Authors: Cini Elena , Bifulco Giuseppe , Menchi Gloria , Rodriquez Manuela , Taddei Maurizio
Published: February 2012

The introduction of a cyclic amino acid in a peptide is one of the best methods to rigidify a strand. A general approach towards a new class of seven‐membered ring amino acids is described starting from (S)‐tribenzyl glutamic acid γ‐aldehyde, which reacts with β‐keto phosphonates to generate the Horner–Wadsworth–Emmons product. In the presence of H2 and a Pd catalyst, a four‐step process occurs involving double‐bond hydrogenation, hydrogenolysis of three benzyl protecting groups, imine formation, and reductive amination to produce the 7‐substituted azepane carboxylic acid in good overall yield and with good to excellent diastereomeric ratios. An amino function can be introduced in the 7‐position as an additional orthogonal chemical handle for readily generating diversity on the cyclic amino acid scaffold by using a β‐keto phosphonate derived from amino acids. A cyclic RGD (Arg‐Gly‐Asp) pentapeptide analogue containing this new class of noncoded amino acids was also prepared by microwave‐assisted cyclization, showing a promising activity as αvβ3 integrin inhibitor.
Basicity of Phosphanes and Diphosphanes in Acetonitrile
Authors: Haav Kristjan , Saame Jaan , Kütt Agnes , Leito Ivo
Published: February 2012

Phosphanes are widely used in organic chemistry. Their basicity is important in determining their behavior in solutions of different acidity. We report a study of the basicities of various mono‐ and diphosphanes in acetonitrile, some of them of significant practical interest (BINAP, BIPHEP). The basicities of the studied phosphanes in acetonitrile are in the pKa range of 4–16. From the results, the relationship between the structure and basicity of the phosphanes has been analyzed and compared with that of amines of similar structure. A remarkably stronger change in basicity can be observed in the amines in comparison with the phosphanes when alkyl groups are replaced by aryl groups. This is mainly caused by resonance between the aryl group and the lone pair of the basicity center, which is strong in the case of the nitrogen atom and weak in the case of the phosphorus atom. The results of the basicity measurements of the diphosphanes in this work has led to two tentative conclusions: (1) there is no intramolecular hydrogen bond in protonated diphosphanes with an alkyl backbone, and (2) there may be a weak intramolecular hydrogen bond in protonated diphosphanes with an aromatic backbone.