bluuebunny/crossref_metadata_2025 huggingface dataset:
Neuroplastizität und Lernen über die Lebensspanne
Authors: Kaufmann Liane , von Aster Michael , Lipka Marlies , Kaufmann Liane
Published: October 2014

Die noch relativ jungen und rasant zunehmenden Erkenntnisse zur Neuroplas-tizität sind nicht nur für Grundlagenforscher relevant (im Sinne eines sozusagen “reinen” Erkenntnisgewinns), sondern sie haben auch immense Bedeutung für die klinische Praxis. Sie lassen uns anschaulich erkennen, was im Gehirn beim Wahrnehmen, Denken, Fühlen und Handeln vor sich geht, und wie sich das Gehirn in Abhängigkeit von Übung und Erfahrung verändert. Dies hat durchaus Auswirkungen auf die Behandlung von psychischen und neurologischen Stö-rungen und stärkt im wahrsten Sinne des Wortes lern-therapeutische Konzepte. Die praktischen Implikationen dieser teilweise sehr spezifi schen und (neuro) physiologisch ausgerichteten Forschungsbefunde haben unser Verständnis von der Funktionsweise des menschlichen Gehirns dramatisch verändert und die Entwicklung neuer und effektiver Behandlungsmaßnahmen auch von altersbe-dingten und erworbenen Hirnfunktionsstörungen angeregt. Das Wissen darum, dass Lernprozesse mit tiefgreifenden Veränderungen auf neurofunktionel-ler und -struktureller Ebene einhergehen, hat unser klinisches Störungs- und Verursachungsverständnis verändert und das Bewusstsein über umwelt- und erfahrungsbedingte Einfl üsse und die restaurativen Möglichkeiten von Hirn-funktionen und -strukturen in den psychiatrischen Fächern ebenso gestärkt wie in den neurologischen. Bahnbrechend sind hier zum Beispiel jene Befunde, die zeigen, dass im Rahmen von neurologischen oder neuropsychiatrischen Erkrankungen erworbene Hirnfunktionsstörungen mit gezielten Lernanreizen – z. B. kognitivem Training oder Neurostimulation – entgegengewirkt werden kann (z. B. Hofer et al., 2014 ). Obwohl solche neuen Befunde vielversprechend sind und als Grundstein für die Entwicklung neuer Behandlungs indikationen und -methoden betrachtet werden können, gibt es noch viele offene Fragen wie jene nach den genauen Wirkmechanismen beispielsweise der Neurosti-mulation. Ebenfalls lückenhaft ist auch noch unser Verständnis der neuropro-tektiven Faktoren: das sind jene Faktoren, die als potentielle Schutzmechanis-men die neuronale Funktionsfähigkeit über die Lebensspanne erhalten. Die anwendungsbezogenen Disziplinen verdanken der Neuroplastizitätsforschung schon heute zahlreiche belebende Impulse, und man darf gespannt sein auf zukünftige Erkenntnisse. Mit der vorliegenden Schwerpunktausgabe von “Ler-nen und Lernstörungen” möchten wir unseren Lesern dieses spannende For-schungsgebiet näherbringen und ihre Neugier auf innovative Behandlungsme-thoden stimulieren.

In diesem Sinne wünschen wir anregende Lesestunden!
Lerntherapie zur Prävention von funktionalem Analphabetismus
Authors: Löffler Cordula
Published: October 2014

Laut der 2011 veröffentlichten Ergebnisse der leo. – Level-One Studie sind in Deutschland 14,5 % der Menschen im erwerbsfähigen Alter von funktionalem Analphabetismus betroffen ( Grotlüschen & Rieckmann, 2012 ), mehr als die Hälfte von ihnen spricht Deutsch als Erstsprache. Diese funktionalen Analphabeten können nach Definition der Studie maximal auf der Satzebene Lesen und Schreiben, die Textebene erreichen sie nicht. Da der Prozentsatz an Betroffenen in allen durch die Studie erfassten Altersstufen etwa gleich ist, kann man davon ausgehen, dass die schulische Prävention von funktionalem Analphabetismus bis heute nicht funktioniert; zu viele Schülerinnen und Schüler verlassen die Schule ohne hinreichende Kenntnis der Schriftsprache. Eine individuelle Förderung ist in der Schule aus unterschiedlichen Gründen oft nicht möglich, eine Individualisierung kann in einer Lerntherapie erfolgen. Die Biographieforschung zum funktionalen Analphabetismus zeigt, dass die Betroffenen häufig aus Familien stammen, in denen zur Unterstützung schulischer Probleme keine zielführenden Handlungsmuster zur Verfügung stehen. Eltern sehen sich oft nicht in der Lage, die für eine Lerntherapie notwendigen Schritte einzuleiten. Die Möglichkeit, Lerntherapie in Anspruch zu nehmen, sollte aber grundsätzlich allen bedürftigen Kindern zur Verfügung stehen und in unserem Bildungssystem fest verankert sein.
Cellular Origin and Regulation of D-and L-Serine in in Vitro and in Vivo Models of Cerebral Ischemia
Authors: Abe Takato , Suzuki Masataka , Sasabe Jumpei , Takahashi Shinichi , Unekawa Miyuki , Mashima Kyoko , Iizumi Takuya , Hamase Kenji , Konno Ryuichi , Aiso Sadakazu , Suzuki Norihiro
Published: October 2014

D-Serine is known to be essential for the activation of the N-methyl-D-aspartate (NMDA) receptor in the excitation of glutamatergic neurons, which have critical roles in long-term potentiation and memory formation. D-Serine is also thought to be involved in NMDA receptor-mediated neurotoxicity. The deletion of serine racemase (SRR), which synthesizes D-Serine from L-Serine, was recently reported to improve ischemic damage in mouse middle cerebral artery occlusion model. However, the cell type in which this phenomenon originates and the regulatory mechanism for D-/L-Serine remain elusive. The D-/L-Serine content in ischemic brain increased until 20 hours after recanalization and then leveled off gradually. The results of in vitro experiments using cultured cells suggested that D-Serine is derived from neurons, while L-Serine seems to be released from astroglia. Immunohistochemistry studies of brain tissue after cerebral ischemia showed that SRR is expressed in neurons, and 3-phosphoglycerate dehydrogenase (3-PGDH), which synthesizes L-Serine from 3-phosphoglycerate, is located in astrocytes, supporting the results of the in vitro experiments. A western blot analysis showed that neither SRR nor 3-PGDH was upregulated after cerebral ischemia. Therefore, the increase in D-/L-Serine was not related to an increase in SRR or 3-PGDH, but to an increase in the substrates of SRR and 3-PGDH.
Hierarchical Multivariate Covariance Analysis of Metabolic Connectivity
Authors: Carbonell Felix , Charil Arnaud , Zijdenbos Alex P , Evans Alan C , Bedell Barry J ,   for the Alzheimer's Disease Neuroimaging Initiative
Published: October 2014

Conventional brain connectivity analysis is typically based on the assessment of interregional correlations. Given that correlation coefficients are derived from both covariance and variance, group differences in covariance may be obscured by differences in the variance terms. To facilitate a comprehensive assessment of connectivity, we propose a unified statistical framework that interrogates the individual terms of the correlation coefficient. We have evaluated the utility of this method for metabolic connectivity analysis using [18F]2-fluoro-2-deoxyglucose (FDG) positron emission tomography (PET) data from the Alzheimer's Disease Neuroimaging Initiative (ADNI) study. As an illustrative example of the utility of this approach, we examined metabolic connectivity in angular gyrus and precuneus seed regions of mild cognitive impairment (MCI) subjects with low and high β-amyloid burdens. This new multivariate method allowed us to identify alterations in the metabolic connectome, which would not have been detected using classic seed-based correlation analysis. Ultimately, this novel approach should be extensible to brain network analysis and broadly applicable to other imaging modalities, such as functional magnetic resonance imaging (MRI).
Quantitative Rates of Brain Glucose Metabolism Distinguish Minimally Conscious from Vegetative State Patients
Authors: Stender Johan , Kupers Ron , Rodell Anders , Thibaut Aurore , Chatelle Camille , Bruno Marie-Aurélie , Gejl Michael , Bernard Claire , Hustinx Roland , Laureys Steven , Gjedde Albert
Published: October 2014

The differentiation of the vegetative or unresponsive wakefulness syndrome (VS/UWS) from the minimally conscious state (MCS) is an important clinical issue. The cerebral metabolic rate of glucose (CMRglc) declines when consciousness is lost, and may reveal the residual cognitive function of these patients. However, no quantitative comparisons of cerebral glucose metabolism in VS/UWS and MCS have yet been reported. We calculated the regional and whole-brain CMRglc of 41 patients in the states of VS/UWS ( n=14), MCS ( n=21) or emergence from MCS (EMCS, n=6), and healthy volunteers ( n=29). Global cortical CMRglc in VS/UWS and MCS averaged 42% and 55% of normal, respectively. Differences between VS/UWS and MCS were most pronounced in the frontoparietal cortex, at 42% and 60% of normal. In brainstem and thalamus, metabolism declined equally in the two conditions. In EMCS, metabolic rates were indistinguishable from those of MCS. Ordinal logistic regression predicted that patients are likely to emerge into MCS at CMRglc above 45% of normal. Receiver-operating characteristics showed that patients in MCS and VS/UWS can be differentiated with 82% accuracy, based on cortical metabolism. Together these results reveal a significant correlation between whole-brain energy metabolism and level of consciousness, suggesting that quantitative values of CMRglc reveal consciousness in severely brain-injured patients.
Quantitative Insight in Utilizing Circulating Angiogenic Factors as Biomarkers for Antiangiogenic Therapy: Systems Pharmacology Approach
Authors: Sharan S , Woo S
Published: October 2014

Circulating angiogenic factors (CAF) like vascular endothelial growth factor (VEGF), placental growth factor (PlGF), and sVEGFR2 have potential as biomarkers for antiangiogenic therapy. The interpretation of changes in CAF is complicated by the dynamic nature of the tumor and host cells emanating CAF in response to VEGF pathway inhibition. We developed a systems pharmacology model of anti‐VEGF agents to investigate CAF modulation by tumor and host cells, and the relationship between overall CAF changes in response to sunitinib and antitumor efficacy. This model distinguishes between the tumor cells’ contributions from tumor‐independent response to therapy and total plasma CAF correlating with antitumor activity. Altered VEGF is more likely to serve as a useful biomarker reflecting tumor responses in cancer patients whose pretreatment VEGF is higher than baseline VEGF in healthy subjects. Our findings provide a mechanistic insight into tumor modulation of angiogenic molecules, and may explain the inconsistent results found in previous biomarker studies.

CPT Pharmacometrics Syst. Pharmacol. (2014) 3, e139; doi:10.1038/psp.2014.36; published online 08 October 2014
A supramolecular nanobiological hybrid as a PET sensor for bacterial DNA isolated from Streptomyces sanglieri
Authors: Chakravarty Sudesna , Saikia Dilip , Sharma Priyanka , Adhikary Nirab Chandra , Thakur Debajit , Sarma Neelotpal Sen
Published: October 2014

A ‘turn on–off–on’ sensor for highly sensitive detection of ds DNA with an excellent ‘limit of detection’ is reported.
Direct analysis of in-gel proteins by carbon nanotubes-modified paper spray ambient mass spectrometry
Authors: Han Feifei , Yang Yuhan , Ouyang Jin , Na Na
Published: October 2014

The direct extraction, desorption and ionization of in gel-intact proteins after electrophoresis have been achieved by CNTs-modified paper spray MS at ambient conditions.
Determination of sulfonylurea herbicides in soil by ionic liquid-based ultrasonic-assisted extraction high-performance liquid chromatography
Authors: Yan Rui , Ju Fulong , Wang Haoyu , Sun Changhua , Zhang Hanqi , Shao Mingyuan , Wang Yuzhi
Published: October 2014

A high-performance liquid chromatography method for determination of sulfonylurea herbicides in soil has been developed.
Separation of planar rotamers through intramolecular hydrogen bonding in polysubstituted 5-nitrosopyrimidines
Authors: Čechová L. , Procházková E. , Císařová I. , Dračínský M. , Janeba Z.
Published: October 2014

Unique isolation of pairs of planar rotamers, planamers, as chemical species differing only in nitroso group orientation, separable through the presence of a single intramolecular hydrogen bond, is reported.
A crucial process: organic matrix and magnesium ion control of amorphous calcium carbonate crystallization on β-chitin film
Authors: Ma Yufei , Feng Qingling
Published: October 2014

ACC transformation processes occurring on chitin film mediated by a water soluble matrix or magnesium ions in aqueous solution were investigated.
A combined MD/QM and experimental exploration of conformational richness in branched oligothiophenes
Authors: Sjöqvist Jonas , González-Cano Rafael C. , López Navarrete Juan T. , Casado Juan , Ruiz Delgado M. Carmen , Linares Mathieu , Norman Patrick
Published: October 2014

Averaged IR and Raman spectra are calculated using a method based on MD sampling, showing clear improvement over Boltzmann averaging.
Polyelectrolyte-coated carbons used in the generation of blue energy from salinity differences
Authors: Ahualli S. , Jiménez M. L. , Fernández M. M. , Iglesias G. , Brogioli D. , Delgado Á. V.
Published: October 2014

Polyelectrolyte-coated carbon films are used as electrodes for energy extraction from salinity exchange.
Heterogeneous catalysis for the direct synthesis of chemicals by borrowing hydrogen methodology
Authors: Shimizu Ken-ichi
Published: October 2014

This review summarizes the recent examples of hydrogen transfer-type reactions using supported transition metal catalysts with special emphasis on the one-pot synthesis of chemicals by borrowing hydrogen methodology.
Novel iron(iii) catalyst for the efficient and selective coupling of carbon dioxide and epoxides to form cyclic carbonates
Authors: Buonerba Antonio , De Nisi Assunta , Grassi Alfonso , Milione Stefano , Capacchione Carmine , Vagin Sergei , Rieger Bernhard
Published: October 2014

“Re-cycling carbon dioxide with iron”. The synthesis of cyclic organic carbonates was accomplished by the coupling of CO2 and epoxides, using a novel air-stable and easy-to-handle iron(iii) catalyst.
Application of laser ablation (imaging) inductively coupled plasma mass spectrometry for mapping and quantifying Fe in transgenic and non-transgenic soybean leaves
Authors: Oliveira Silvana R. , Arruda Marco A. Z.
Published: October 2014

Laser ablation inductively coupled plasma mass spectrometry is used for determining Fe in leaves of transgenic (variety M 7211RR) and non-transgenic (variety MSOY 8200) soybean, grown for 21 days in a growth chamber at controlled temperature (27 ± 0.1 °C) and photoperiod (12 h).
Length-dependent translation initiation benefits the functional proteome of human cells
Authors: Guo Jieming , Lian Xinlei , Zhong Jiayong , Wang Tong , Zhang Gong
Published: October 2014

Considering translational errors, length-dependent translation initiation optimizes the energy cost for maintaining a functional proteome.
Synthesis and biological evaluation of a new class of quinazolinoneazoles as potential antimicrobial agents and their interactions with calf thymus DNA and human serum albumin
Authors: Peng Li-Ping , Nagarajan Sangaraiah , Rasheed Syed , Zhou Cheng-He
Published: October 2014

A series of quinazolinone azoles were synthesized and screened for their antimicrobial activities, and further studies of their binding behaviors with calf thymus DNA and human serum albumin were investigated.
Sustained anti-BCR-ABL activity with pH responsive imatinib mesylate loaded PCL nanoparticles in CML cells
Authors: Cortese Barbara , D'Amone Stefania , Gigli Giuseppe , Palamà Ilaria Elena
Published: October 2014

IM–chitosan complex encapsulated poly(ε-caprolactone) (PCL) nanoparticles are proposed for their potential in enabling more intelligent controlled release and enhancing chemotherapeutic efficiency of IM.
Synthesis of high surface area mixed metal oxide from the NiMgAl LDH precursor for nitro-aldol condensation reaction
Authors: Bharali Dipshikha , Devi Rasna , Bharali Pankaj , Deka Ramesh C.
Published: October 2014

NiMgAl mixed oxide catalyzes nitro-aldol condensation reaction at room temperature under solvent free conditions exhibiting 99% conversion.
Effect of pretreatment temperature on the photocatalytic activity of microwave irradiated porous nanocrystalline ZnO
Authors: Ali Tarek T. , Narasimharao Katabathini , Parkin Ivan P. , Carmalt Claire J. , Sathasivam Sanjayan , Basahel Sulaiman N. , Bawaked Salem M. , Al-Thabaiti Shaeel A.
Published: October 2014

ZnO treated at 200 °C offered high photocatalytic degradation of methyl orange (99%) in a short time (90 min). The activity can be attributed to several factors including low crystallite size, high band gap energy and porosity.
Fluidic switching in nanochannels for the control of Inchworm: a synthetic biomolecular motor with a power stroke
Authors: Niman Cassandra S. , Zuckermann Martin J. , Balaz Martina , Tegenfeldt Jonas O. , Curmi Paul M. G. , Forde Nancy R. , Linke Heiner
Published: October 2014

A DNA-based motor that employs a pronounced power stroke was investigated, and a nanofluidic device needed to operate the motor was designed, fabricated, and characterized.
Residence time distribution analysis and kinetic study of toluene photo-degradation using a continuous immobilized photoreactor
Authors: Jafarikojour Morteza , Sohrabi Morteza , Royaee Sayed Javid , Rezaei Mohammad
Published: October 2014

The photocatalytic degradation of volatile organic compounds is an innovative intensification technology.
Synthesis of a novel CuI/CuII-containing sandwich-type cluster and its catalytic electron transfer property
Authors: Xue Xiaolong , Zhao Xiaofang , Zhang Deshun , Han Zhangang , Yu Haitao , Zhai Xueliang
Published: October 2014

A six-metal {Na2CuICuII3} sandwich-type heteropolyanion shows excellent catalytic activity for electron transfer reaction of ferricyanide to ferrocyanide by thiosulphate.
Crosslinked tri-side-chain-type sulfonated poly(arylene ether ketones) with enhanced proton conductivity by a Friedel–Crafts acylation reaction
Authors: Zhang Liyuan , Qi Duo , Zhang Gang , Zhao Chengji , Na Hui
Published: October 2014

Cross-linked poly(arylene ether ketones) containing multi-pendent sulfonic groups were prepared by the Friedel–Crafts acylation reaction in order to solve the problem of high methanol crossover and maintain other high performances at the same time.
Direct arylation of heterocycles through C–H bond cleavage using metal–organic-framework Cu2(OBA)2(BPY) as an efficient heterogeneous catalyst
Authors: Truong Thanh , Nguyen Vu T. , Le Hue T. X. , Phan Nam T. S.
Published: October 2014

Cu2(OBA)2(BPY) was showed to be an efficient heterogeneous catalyst for direct C-arylation of a variety of heterocycles by iodoarenes. The optimal conditions employed tBuOLi in dioxane at elevated temperature.
Highly dispersed platinum nanoparticles supported on silica as catalyst for hydrogen production
Authors: Khdary Nezar H. , Ghanem Mohamed A.
Published: October 2014

A synthetic approach is developed to produce highly disperse, low loading (3.28 wt%) Pt nanoparticles incorporated silica (Pt-NP–S) with average diameter of 3.5 nm using economical and simple surface chemical modification and reduction processes.
Copper-catalyzed enantioselective propargylic substitution of propargylic acetates with enamines
Authors: Wang Bo , Liu Chunxiao , Guo Hongchao
Published: October 2014

With the use of chiral tridentate P,N,N ligand, copper-catalyzed enantioselective propargylic substitution of propargylic acetates with enamines has been achieved, giving the corresponding propargylic ketones in high yields and with excellent enantioselectivities.
Synergistic effects of ion pairs on the dielectric properties of diblock copolymer melts
Authors: Nakamura Issei
Published: October 2014

We study the solvation of ion pairs in diblock copolymer melts.
Improved charge transport of Nb-doped TiO2nanorods in methylammonium lead iodide bromide perovskite solar cells
Authors: Yang Mengjin , Guo Rui , Kadel Kamal , Liu Yunyan , O'Shea Kevin , Bone Richard , Wang Xuewen , He Jin , Li Wenzhi
Published: October 2014

The phase of perovskite evolves when the non-stoichiometric mixed halide precursor is baked at different temperatures. Nb-doped TiO2nanorods are superior to plain nanorods as electron transport medium in crystallized perovskite.
Monitoring layer-by-layer self-assembly process of natural polyelectrolytes by fluorescent bioconjugate with aggregation-induced emission characteristic
Authors: Jia Jingwei , Wang Zhengke , Lu Wentao , Yang Ling , Wu Qingwen , Qin Wei , Hu Qiaoling , Tang Ben Zhong
Published: October 2014

Exponential growth of multilayer films was monitored by fluorescence spectra using aggregation-induced-emission fluorogens, which is in accordance with ellipsometry results.
Mussel-inspired adhesive protein-based electrospun nanofibers reinforced by Fe(iii)–DOPA complexation
Authors: Kim Bum Jin , Kim Sangsik , Oh Dongyeop X. , Masic Admir , Cha Hyung Joon , Hwang Dong Soo
Published: October 2014

The mechanical properties of mussel-inspired electrospun nanofibers were reinforced by the Fe(III)–DOPA complex in the mussel adhesive protein, a key component for a naturally occurring high performance mussel protective coating.
An extremely rapid dip-coating method for self-assembly of octadecylphosphonic acid and its thermal stability on an aluminum film
Authors: Chen Donghan , Yin Wu Horace King , Naderi-Gohar Soheila , Wu Yiliang , Huang Yining , Nie Heng-Yong
Published: October 2014

Solution of octadecylphosphonic acid in anisole enables formation of a full-coverage monolayer on metal oxides in a matter of seconds.
Modelling of concentrating solar power plant for power system reliability studies
Authors: Gafurov Tokhir , Usaola Julio , Prodanovic Milan
Published: October 2014

Growing share of concentrating solar power (CSP) plants in power systems creates the need for including these renewable sources in power system reliability studies. As such studies analyse the grid on a global scale and start to be performed increasingly by Monte Carlo simulations, modelling of CSP production has to be reasonably simplified in order to reduce the calculation time. The model simplification also concerns the minimisation of the required specific knowledge and input data which enables power system engineers to evaluate the impact of CSP without substantial expertise in its underlying physics and by focusing on the key design parameters. There is a large variety of accurate CSP simulation programs and models, and yet neither of them offers the required simplicity. This study addresses this gap by proposing reduced models for predicting energy output of parabolic trough and central receiver systems. The calculation procedure and its underlying assumptions are presented. The adequacy of the models is demonstrated by comparing their predictions with that of the System Advisor Model for different case scenarios.
Nonorthogonal orbital based n-body reduced density matrices and their applications to valence bond theory. III. Second-order perturbation theory using valence bond self-consistent field function as reference
Authors: Chen Zhenhua , Chen Xun , Ying Fuming , Gu Junjing , Zhang Huaiyu , Wu Wei
Published: October 2014

Using the formulas and techniques developed in Papers I and II of this series, the recently developed second-order perturbation theory based on a valence bond self-consistent field reference function (VBPT2) has been extended by using the internally contracted correction wave function. This ansatz strongly reduces the size of the interaction space compared to the uncontracted wave function and thus improves the capability of the VBPT2 method dramatically. Test calculations show that internally contracted VBPT2 using only a small number of reference valence bond functions, can give results as accuracy as the VBPT2 method and other more sophisticated methods such as full configuration interaction and multireference configuration interaction.
Insights into hydrogen bonding via ice interfaces and isolated water
Authors: Shultz Mary Jane , Bisson Patrick , Vu Tuan Hoang
Published: October 2014

Water in a confined environment has a combination of fewer available configurations and restricted mobility. Both affect the spectroscopic signature. In this work, the spectroscopic signature of water in confined environments is discussed in the context of competing models for condensed water: (1) as a system of intramolecular coupled molecules or (2) as a network with intermolecular dipole-dipole coupled O–H stretches. Two distinct environments are used: the confined asymmetric environment at the ice surface and the near-isolated environment of water in an infrared transparent matrix. Both the spectroscopy and the environment are described followed by a perspective discussion of implications for the two competing models. Despite being a small molecule, water is relatively complex; perhaps not surprisingly the results support a model that blends inter- and intramolecular coupling. The frequency, and therefore the hydrogen-bond strength, appears to be a function of donor-acceptor interaction and of longer-range dipole-dipole alignment in the hydrogen-bonded network. The O–H dipole direction depends on the local environment and reflects intramolecular O–H stretch coupling.
Sum frequency generation image reconstruction: Aliphatic membrane under spherical cap geometry
Authors: Volkov Victor
Published: October 2014

The article explores an opportunity to approach structural properties of phospholipid membranes using Sum Frequency Generation microscopy. To establish the principles of sum frequency generation image reconstruction in such systems, at first approach, we may adopt an idealistic spherical cap uniform assembly of hydrocarbon molecules. Quantum mechanical studies for decanoic acid (used here as a representative molecular system) provide necessary information on transition dipole moments and Raman tensors of the normal modes specific to methyl terminal – a typical moiety in aliphatic (and phospholipid) membranes. Relative degree of localization and frequencies of the normal modes of methyl terminals make nonlinearities of this moiety to be promising in structural analysis using Sum Frequency Generation imaging. Accordingly, the article describes derivations of relevant macroscopic nonlinearities and suggests a mapping procedure to translate amplitudes of the nonlinearities onto microscopy image plane according to geometry of spherical assembly, local molecular orientation, and optical geometry. Reconstructed images indicate a possibility to extract local curvature of bilayer envelopes of spherical character. This may have practical implications for structural extractions in membrane systems of practical relevance.
Direct observation of resistive heating at graphene wrinkles and grain boundaries
Authors: Grosse Kyle L. , Dorgan Vincent E. , Estrada David , Wood Joshua D. , Vlassiouk Ivan , Eres Gyula , Lyding Joseph W. , King William P. , Pop Eric
Published: October 2014

We directly measure the nanometer-scale temperature rise at wrinkles and grain boundaries (GBs) in functioning graphene devices by scanning Joule expansion microscopy with ∼50 nm spatial and ∼0.2 K temperature resolution. We observe a small temperature increase at select wrinkles and a large (∼100 K) temperature increase at GBs between coalesced hexagonal grains. Comparisons of measurements with device simulations estimate the GB resistivity (8–150 Ω μm) among the lowest reported for graphene grown by chemical vapor deposition. An analytical model is developed, showing that GBs can experience highly localized resistive heating and temperature rise, most likely affecting the reliability of graphene devices. Our studies provide an unprecedented view of thermal effects surrounding nanoscale defects in nanomaterials such as graphene.
Hydrodynamics of normal and superfluid polar liquids. Propagation of sound
Authors: Poluektov Yu. M.
Published: October 2014

Equations for normal and superfluid liquids with spontaneous polarization are obtained by a phenomenological approach. It is shown that the propagation of sound waves in media with spontaneous polarization is accompanied by electric field oscillations. Corrections are calculated for the speeds of first and second sound in normal and superfluid polar liquids.
Effect of acoustic emission on the critical velocity for the transition to turbulent flow in He II
Authors: Gritsenko I. A. , Sheshin G. A.
Published: October 2014

The conditions for the transition from laminar to turbulent flow in superfluid 4He are investigated experimentally, and the effect of acoustic emission with variable power on the critical velocity for the transition is studied. The quartz tuning fork method is used at temperatures of 2–0.3 K. The experiments are done over a wide range of pressures, from the saturated vapor pressure to 24.8 atm. It is found that at high temperatures (T > 0.9 K) the critical velocity is determined by viscous friction and at low temperatures (T < 0.5 K) by the effect of acoustic emission, which leads to a significant increase in the critical velocity for the transition to the turbulent state. The critical velocity depends on the power of the acoustic emission and the transition to the turbulent state of the superfluid is similar to that in ordinary liquids or gases. In the absence of any effects of acoustic emission, the critical transition velocity is essentially independent of temperature and the driving power is mainly determined by ballistic scattering of thermal excitations.
Photoelectric activity of defects in La-doped layered TlInS2 crystals
Authors: Seyidov MirHasan Yu. , Suleymanov Rauf A. , Acar Elif , Odrinsky A. P. , Mammadov T. G. , Nadjafov A. I. , Aliyeva V. B.
Published: October 2014

Photoelectric relaxation spectroscopy (photoinduced current relaxation spectroscopy, PICTS) is used to study pure and La-doped single crystals of TlInS2. The characteristics of electrically active defects are determined including the capture cross section for charge carriers, the thermal activation energy, and the temperature interval within which the charge state of a defect varies. The pyroelectric properties of TlInS2:La are studied. The defect responsible for the anomalies in the pyrocurrent is identified.
Averaged effective pinning potential in YBCO single crystals near Tc
Authors: Monarkha V. Yu. , Sivakov A. G. , Timofeev V. P.
Published: October 2014

The dynamics of magnetic flux trapped in low dc magnetic fields (of the order of the Earth's field) was for the first time studied experimentally in single-crystal YBCO samples with unidirectional twin boundaries in the temperature range near Tc (0.8 < T/Tc < 0.99). Strong pinning in the system of unidirectional planar defects was demonstrated, and a significant deviation from monotonous behavior was established for the averaged effective pinning potential Up(T) for the trapped flux of low density. In order to compare different methods of Jc determination, the field dependences of the magnetization loop width M(H), which are related to the effective pinning and Jc, were obtained, and resistive measurements on microbridges made from the same single crystals were carried out.
Blip decomposition of the path integral: Exponential acceleration of real-time calculations on quantum dissipative systems
Authors: Makri Nancy
Published: October 2014

The real-time path integral representation of the reduced density matrix for a discrete system in contact with a dissipative medium is rewritten in terms of the number of blips, i.e., elementary time intervals over which the forward and backward paths are not identical. For a given set of blips, it is shown that the path sum with respect to the coordinates of all remaining time points is isomorphic to that for the wavefunction of a system subject to an external driving term and thus can be summed by an inexpensive iterative procedure. This exact decomposition reduces the number of terms by a factor that increases exponentially with propagation time. Further, under conditions (moderately high temperature and/or dissipation strength) that lead primarily to incoherent dynamics, the “fully incoherent limit” zero-blip term of the series provides a reasonable approximation to the dynamics, and the blip series converges rapidly to the exact result. Retention of only the blips required for satisfactory convergence leads to speedup of full-memory path integral calculations by many orders of magnitude.
Low-temperature plastic deformation and strain-hardening of nanocrystalline titanium
Authors: Moskalenko V. A. , Smirnov A. R. , Smolyanets R. V.
Published: October 2014

Patterns of plastic deformation of nanocrystalline (NC) technical grade VT1-0 titanium, are studied in quasi-static tensile experiments, with the average size of the grain d, ranging from 35 nm to 2 μm, at the temperature interval 4.2 K < T < 395 K. The wide range of grain size, and grain size distribution, was made possible by cryomechanical grain fragmentation, which involves rolling at liquid nitrogen temperature, and subsequent annealing. At temperatures of T ≲ 30 K, smooth deformation curves become wavy, and as the temperature is continually lowered to Tjump ≈ 22 K, they become jagged. A correlation is found between the relative amplitude of the stress jump Δσ/σ and the rate of strain hardening θ = (∂σ/∂e)ė. A significant increase in plasticity is observed, especially noticeable at temperatures T ≲140 K, if a small fraction (≈15%) of submicron-sized grains is present. This is explained by a combination of dynamic grain growth under the influence of tensile stress, and nanotwinning activated in submicron grains. At cryogenic temperatures, abnormal grain growth favors nanotwinning during deformation. In nanometer-sized grains (d ≲ 50 nm), twinning is not observed.
Effect of a potential softness on the solid-liquid transition in a two-dimensional core-softened potential system
Authors: Dudalov D. E. , Tsiok E. N. , Fomin Yu. D. , Ryzhov V. N.
Published: October 2014

In the present paper, using a molecular dynamics simulation, we study a nature of melting of a two-dimensional (2D) system of classical particles interacting through a purely repulsive isotropic core-softened potential which is used for the qualitative description of the anomalous behavior of water and some other liquids. We show that the melting scenario drastically depends on the potential softness and changes with increasing the width of the smooth repulsive shoulder. While at small width of the repulsive shoulder the melting transition exhibits what appears to be weakly first-order behavior, at larger values of the width a reentrant-melting transition occurs upon compression for not too high pressures, and in the low density part of the 2D phase diagram melting is a continuous two-stage transition, with an intermediate hexatic phase in accordance with the Kosterlitz-Thouless-Halperin-Nelson-Young scenario. On the other hand, at high density part of the phase diagram one first-order transition takes place. These results may be useful for the qualitative understanding the behavior of water confined between two hydrophobic plates.
On the origin of the two-dimensional electron gas at AlGaN/GaN heterojunctions and its influence on recessed-gate metal-insulator-semiconductor high electron mobility transistors
Authors: Bakeroot B. , You S. , Wu T.-L. , Hu J. , Van Hove M. , De Jaeger B. , Geens K. , Stoffels S. , Decoutere S.
Published: October 2014

It is commonly accepted that interface states at the passivation surface of AlGaN/GaN heterostructures play an important role in the formation of the 2DEG density. Several interface state models are cited throughout literature, some with discrete levels, others with different kinds of distributions, or a combination of both. The purpose of this article is to compare the existing interface state models with both direct and indirect measurements of these interface states from literature (e.g., through the hysteresis of transfer characteristics of Metal-Insulator-Semiconductor High Electron Mobility Transistors (MISHEMTs) employing such an interface in the gate region) and Technology Computer Aided Design (TCAD) simulations of 2DEG densities as a function of the AlGaN thickness. The discrepancies between those measurements and TCAD simulations (also those commonly found in literature) are discussed. Then, an alternative model inspired by the Disorder Induced Gap State model for compound semiconductors is proposed. It is shown that defining a deep border trap inside the insulator can solve these discrepancies and that this alternative model can explain the origin of the two dimensional electron gas in combination with a high-quality interface that, by definition, has a low interface state density.
Acoustic scattering from microfibers of Parylene C
Authors: Chindam Chandraprakash , Lakhtakia Akhlesh , Awadelkarim Osama O. , Orfali Wasim
Published: October 2014

The acoustic scattering characteristics of ∼10 μm-long microfibers of Parylene C embedded in water were investigated, towards the eventual goal of designing polymeric sculptured thin films for biomedical applications. The chosen microfibers were upright circular-cylindrical, slanted circular-cylindrical, chevronic, and helical in shape. A combination of numerical and analytical techniques was adopted to examine the scattering of plane waves in a spectral regime spanning the lower few eigenfrequencies of the microfibers. Certain maximums in the spectrums of the forward and back scattering efficiencies arise from the phenomenon of creeping waves. The same phenomenon affects the total scattering efficiency in some instances. The spectrums of all efficiencies exhibit the geometric symmetry of a microfiber in relation to the direction of propagation of the incident plane wave. Similarities in the shapes of the slanted circular-cylindrical and the chevronic microfibers are reflected in the spectrums of their scattering efficiencies. A highly compliant microfiber has shorter and broader peaks than a less compliant microfiber in the spectrums of the total scattering efficiency. The proper design of polymeric sculptured thin films will benefit from the knowledge gained of the directions of maximum scattering from individual microfibers.
Lie group analysis of a generalized Krichever-Novikov differential-difference equation
Authors: Levi Decio , Ricca Eugenio , Thomova Zora , Winternitz Pavel
Published: October 2014

The symmetry algebra of the differential-difference equation \documentclass[12pt]{minimal}\begin{document}$\dot{u}_n = N/D$\end{document}u̇n=N/D with D = un+1 − un−1 and N = P(un)un+1un−1 + Q(un)(un+1 + un−1) + R(un), where P, Q, and R are arbitrary analytic functions is shown to have the dimension 1 ⩽ dimL ⩽ 5. When P, Q, and R are specific second order polynomials in un (depending on 6 constants) this is the integrable discretization of the Krichever–Novikov equation. We find 3 cases when the arbitrary functions are not polynomials and the symmetry algebra satisfies dimL = 2. These cases are shown not to be integrable. The symmetry algebras are used to reduce the equations to purely difference ones. The symmetry group is also used to impose periodicity un+N = un and thus to reduce the differential-difference equation to a system of N coupled ordinary three points difference equations.
Sum frequency and second harmonic generation from the surface of a liquid microjet
Authors: Smolentsev Nikolay , Chen Yixing , Jena Kailash C. , Brown Matthew A. , Roke Sylvie
Published: October 2014

The use of a liquid microjet as a possible source of interest for Second Harmonic Generation (SHG) and Sum Frequency Generation (SFG) spectroscopy is examined. We measured non-resonant SHG scattering patterns from the air/water interface of a microjet of pure water and observe a strong enhancement of the SHG signal for certain scattering angles. These enhancements can be explained by the optical properties and the shape of the liquid microjet. SFG experiments at the surface of a liquid microjet of ethanol in air show that it is also possible to measure the coherent vibrational SFG spectrum of the ethanol/air interface in this way. Our findings are useful for future far-UV or X-ray based nonlinear optical surface experiments on liquid jets. In addition, combined X-ray photoelectron spectroscopy and SHG/SFG measurements are feasible, which will be very useful in improving our understanding of the molecular foundations of electrostatic and chemical surface properties and phenomena.
High-stability cryogenic scanning tunneling microscope based on a closed-cycle cryostat
Authors: Hackley Jason D. , Kislitsyn Dmitry A. , Beaman Daniel K. , Ulrich Stefan , Nazin George V.
Published: October 2014

We report on the design and operation of a cryogenic ultra-high vacuum (UHV) scanning tunneling microscope (STM) coupled to a closed-cycle cryostat (CCC). The STM is thermally linked to the CCC through helium exchange gas confined inside a volume enclosed by highly flexible rubber bellows. The STM is thus mechanically decoupled from the CCC, which results in a significant reduction of the mechanical noise transferred from the CCC to the STM. Noise analysis of the tunneling current shows current fluctuations up to 4% of the total current, which translates into tip-sample distance variations of up to 1.5 picometers. This noise level is sufficiently low for atomic-resolution imaging of a wide variety of surfaces. To demonstrate this, atomic-resolution images of Au(111) and NaCl(100)/Au(111) surfaces, as well as of carbon nanotubes deposited on Au(111), were obtained. Thermal drift analysis showed that under optimized conditions, the lateral stability of the STM scanner can be as low as 0.18 Å/h. Scanning Tunneling Spectroscopy measurements based on the lock-in technique were also carried out, and showed no detectable presence of noise from the closed-cycle cryostat. Using this cooling approach, temperatures as low as 16 K at the STM scanner have been achieved, with the complete cool-down of the system typically taking up to 12 h. These results demonstrate that the constructed CCC-coupled STM is a highly stable instrument capable of highly detailed spectroscopic investigations of materials and surfaces at the atomic scale.
Resistive switching phenomena in TiOx nanoparticle layers for memory applications
Authors: Goren Emanuelle , Ungureanu Mariana , Zazpe Raul , Rozenberg Marcelo , Hueso Luis E. , Stoliar Pablo , Tsur Yoed , Casanova Fèlix
Published: October 2014

Electrical characteristics of a Co/ TiOx/Co resistive memory device, fabricated by two different methods, are reported. In addition to crystalline TiO2 layers fabricated via conventional atomic layer deposition (ALD), an alternative method has been examined, where TiOx nanoparticle layers were fabricated via sol-gel. The different devices have shown different hysteresis loops with a unique crossing point for the sol-gel devices. A simple qualitative model is introduced to describe the different current-voltage behaviours by suggesting only one active metal-oxide interface for the ALD devices and two active metal-oxide interfaces for the sol-gel devices. Furthermore, we show that the resistive switching behaviour could be easily tuned by proper interface engineering and that despite having a similar active material, different fabrication methods can lead to dissimilar resistive switching properties.
Design of a self-aligned, wide temperature range (300 mK-300 K) atomic force microscope/magnetic force microscope with 10 nm magnetic force microscope resolution
Authors: Karcı Özgür , Dede Münir , Oral Ahmet
Published: October 2014

We describe the design of a wide temperature range (300 mK-300 K) atomic force microscope/magnetic force microscope with a self-aligned fibre-cantilever mechanism. An alignment chip with alignment groves and a special mechanical design are used to eliminate tedious and time consuming fibre-cantilever alignment procedure for the entire temperature range. A low noise, Michelson fibre interferometer was integrated into the system for measuring deflection of the cantilever. The spectral noise density of the system was measured to be ∼12 fm/√Hz at 4.2 K at 3 mW incident optical power. Abrikosov vortices in BSCCO(2212) single crystal sample and a high density hard disk sample were imaged at 10 nm resolution to demonstrate the performance of the system.
Effective and accurate approach for modeling of commensurate–incommensurate transition in krypton monolayer on graphite
Authors: Ustinov E. A.
Published: October 2014

Commensurate–incommensurate (C-IC) transition of krypton molecular layer on graphite received much attention in recent decades in theoretical and experimental researches. However, there still exists a possibility of generalization of the phenomenon from thermodynamic viewpoint on the basis of accurate molecular simulation. Recently, a new technique was developed for analysis of two-dimensional (2D) phase transitions in systems involving a crystalline phase, which is based on accounting for the effect of temperature and the chemical potential on the lattice constant of the 2D layer using the Gibbs–Duhem equation [E. A. Ustinov, J. Chem. Phys. 140, 074706 (2014)]. The technique has allowed for determination of phase diagrams of 2D argon layers on the uniform surface and in slit pores. This paper extends the developed methodology on systems accounting for the periodic modulation of the substrate potential. The main advantage of the developed approach is that it provides highly accurate evaluation of the chemical potential of crystalline layers, which allows reliable determination of temperature and other parameters of various 2D phase transitions. Applicability of the methodology is demonstrated on the krypton–graphite system. Analysis of phase diagram of the krypton molecular layer, thermodynamic functions of coexisting phases, and a method of prediction of adsorption isotherms is considered accounting for a compression of the graphite due to the krypton–carbon interaction. The temperature and heat of C-IC transition has been reliably determined for the gas–solid and solid–solid system.
Ion temperature gradient driven turbulence with strong trapped ion resonance
Authors: Kosuga Y. , Itoh S.-I. , Diamond P. H. , Itoh K. , Lesur M.
Published: October 2014

A theory to describe basic characterization of ion temperature gradient driven turbulence with strong trapped ion resonance is presented. The role of trapped ion granulations, clusters of trapped ions correlated by precession resonance, is the focus. Microscopically, the presence of trapped ion granulations leads to a sharp (logarithmic) divergence of two point phase space density correlation at small scales. Macroscopically, trapped ion granulations excite potential fluctuations that do not satisfy dispersion relation and so broaden frequency spectrum. The line width from emission due only to trapped ion granulations is calculated. The result shows that the line width depends on ion free energy and electron dissipation, which implies that non-adiabatic electrons are essential to recover non-trivial dynamics of trapped ion granulations. Relevant testable predictions are summarized.
Equation of state of dense plasmas: Orbital-free molecular dynamics as the limit of quantum molecular dynamics for high-Z elements
Authors: Danel J.-F. , Blottiau P. , Kazandjian L. , Piron R. , Torrent M.
Published: October 2014

The applicability of quantum molecular dynamics to the calculation of the equation of state of a dense plasma is limited at high temperature by computational cost. Orbital-free molecular dynamics, based on a semiclassical approximation and possibly on a gradient correction, is a simulation method available at high temperature. For a high-Z element such as lutetium, we examine how orbital-free molecular dynamics applied to the equation of state of a dense plasma can be regarded as the limit of quantum molecular dynamics at high temperature. For the normal mass density and twice the normal mass density, we show that the pressures calculated with the quantum approach converge monotonically towards those calculated with the orbital-free approach; we observe a faster convergence when the orbital-free approach includes the gradient correction. We propose a method to obtain an equation of state reproducing quantum molecular dynamics results up to high temperatures where this approach cannot be directly implemented. With the results already obtained for low-Z plasmas, the present study opens the way for reproducing the quantum molecular dynamics pressure for all elements up to high temperatures.