bluuebunny/crossref_metadata_2025 huggingface dataset:
Strong variable linear polarization in the cool active star II Peg
Authors: Rosén Lisa , Kochukhov Oleg , Wade Gregg A.
Published: August 2014

Magnetic fields of cool active stars are currently studied polarimetrically using only circular polarization observations. This provides limited information about the magnetic field geometry since circular polarization is only sensitive to the line-of-sight component of the magnetic field. Reconstructions of the magnetic field topology will therefore not be completely trustworthy when only circular polarization is used. On the other hand, linear polarization is sensitive to the transverse component of the magnetic field. By including linear polarization in the reconstruction the quality of the reconstructed magnetic map is dramatically improved. For that reason, we wanted to identify cool stars for which linear polarization could be detected at a level sufficient for magnetic imaging. Four active RS CVn binaries, II Peg, HR 1099, IM Peg, and σ Gem were observed with the ESPaDOnS spectropolarimeter at the Canada-France-Hawaii Telescope. Mean polarization profiles in all four Stokes parameters were derived using the multi-line technique of least-squares deconvolution (LSD). Not only was linear polarization successfully detected in all four stars in at least one observation, but also, II Peg showed an extraordinarily strong linear polarization signature throughout all observations. This qualifies II Peg as the first promising target for magnetic Doppler imaging in all four Stokes parameters and, at the same time, suggests that other such targets can possibly be identified.
Activity on a Li-rich giant: DI Psc revisited
Authors: Kriskovics Levente , Kővári Zsolt , Vida Krisztián , Oláh Katalin
Published: August 2014

We present a new Doppler imaging study for the Li-rich single K-giant DI Psc. Surface temperature maps are reconstructed for two subsequent rotation cycles. From the time evolution of the spot distribution antisolar-type differential rotation pattern is revealed. We show marks of non-uniform Li-abundance as well. The possible connection between the current evolutionary phase of the star and its magnetic activity is briefly discussed.
Search for surface magnetic fields in Mira stars: first results on χ Cyg
Authors: Lèbre Agnès , Aurière Michel , Fabas Nicolas , Gillet Denis , Herpin Fabrice , Petit Pascal , Konstantinova-Antova Renada
Published: August 2014

So far, surface magnetic fields have never been reported on Mira stars, while observational facilities allowing detection and measurement of weak surface fields through the Zeeman effect have become available. Then, in order to complete the knowledge of the magnetic field and of its influence during the transition from Asymptotic Giant Branch (AGB) to Planetary Nebulae (PN) stages, we have undertaken a search for magnetic fields at the surface of Miras. We present the first spectropolarimetric observations (performed with the Narval instrument at Télescope Bernard Lyot-TBL, Pic du Midi, France) of the S-type Mira star χ Cyg. We have detected a polarimetric signal in the Stokes V spectra and we have established its Zeeman origin. We claim that it is likely to be related to a weak magnetic field present at the photospheric level and in the lower part of the stellar atmosphere. The origin of this magnetic field is discussed in the framework of shock waves periodically propagating throughout the atmosphere of a Mira.
Magnetic fields around AGB stars and Planetary Nebulae
Authors: Vlemmings W. H. T.
Published: August 2014

Stars with a mass up to a few solar masses are one of the main contributors to the enrichment of the interstellar medium in dust and heavy elements. However, while significant progress has been made, the process of the mass-loss responsible for this enrichment is still not exactly known and forces beyond radiation pressure might be required. Often, the mass lost in the last phases of the stars life will become a spectacular planetary nebula. The shaping process of often strongly a-spherical PNe is equally elusive. Both binaries and magnetic fields have been suggested to be possible agents although a combination of both might also be a natural explanation.

Here I review the current evidence for magnetic fields around AGB and post-AGB stars pre-Planetary Nebulae and PNe themselves. Magnetic fields appear to be ubiquitous in the envelopes of apparently single stars, challenging current ideas on its origin, although we have found that binary companions could easily be hidden from view. There are also strong indications of magnetically collimated outflows from post-AGB/pre-PNe objects supporting a significant role in shaping the circumstellar envelope.
Improving productive efficiency in hospitals: findings from a review of the international evidence
Authors: Rumbold Benedict E. , Smith Judith A. , Hurst Jeremy , Charlesworth Anita , Clarke Aileen
Published: August 2014

At present, health systems across Europe face the same challenges: a changing demographic profile, a rise in multi-morbidity and long-term conditions, increasing health care costs, large public debts and other legacies of an economic downturn. In light of these concerns, this article provides an overview of the international evidence on how to improve productive efficiency in secondary care settings. Updating and expanding upon a recent review of the literature by Hurst and Williams (2012), we set out evidence on potential interventions in the policy environment, hospital management, and operational processes. We conclude with five key lessons for policy makers and practitioners on how to improve productive efficiency within hospital settings, and identify several gaps in the existing evidence base.
A metal–ion-responsive adhesive material via switching of molecular recognition properties
Authors: Nakamura Takashi , Takashima Yoshinori , Hashidzume Akihito , Yamaguchi Hiroyasu , Harada Akira
Published: August 2014

Common adhesives stick to a wide range of materials immediately after they are applied to the surfaces. To prevent indiscriminate sticking, smart adhesive materials that adhere to a specific target surface only under particular conditions are desired. Here we report a polymer hydrogel modified with both β-cyclodextrin (βCD) and 2,2′-bipyridyl (bpy) moieties (βCD–bpy gel) as a functional adhesive material responding to metal ions as chemical stimuli. The adhesive property of βCD–bpy gel based on interfacial molecular recognition is expressed by complexation of metal ions to bpy that controlled dissociation of supramolecular cross-linking of βCD–bpy. Moreover, adhesion of βCD–bpy gel exhibits selectivity on the kinds of metal ions, depending on the efficiency of metal–bpy complexes in cross-linking. Transduction of two independent chemical signals (metal ions and host–guest interactions) is achieved in this adhesion system, which leads to the development of highly orthogonal macroscopic joining of multiple objects.
Epiphytic leafy liverworts diversified in angiosperm-dominated forests
Authors: Feldberg Kathrin , Schneider Harald , Stadler Tanja , Schäfer-Verwimp Alfons , Schmidt Alexander R. , Heinrichs Jochen
Published: August 2014

Recent studies have provided evidence for pulses in the diversification of angiosperms, ferns, gymnosperms and mosses as well as various groups of animals during the Cretaceous revolution of terrestrial ecosystems. However, evidence for such pulses has not been reported so far for liverworts. Here we provide new insight into liverwort evolution by integrating a comprehensive molecular dataset with a set of 20 fossil age constraints. We found evidence for a relative constant diversification rate of generalistic liverworts (Jungermanniales) since the Palaeozoic, whereas epiphytic liverworts (Porellales) show a sudden increase of lineage accumulation in the Cretaceous. This difference is likely caused by the pronounced response of Porellales to the ecological opportunities provided by humid, megathermal forests, which were increasingly available as a result of the rise of the angiosperms.
Novel ultra-low temperature co-fired microwave dielectric ceramic at 400 degrees and its chemical compatibility with base metal
Authors: Di Zhou , Li-Xia Pang , Ze-Ming Qi , Biao-Bing Jin , Xi Yao
Published: August 2014

A novel NaAgMoO4 material with spinel-like structure was synthesized by using the solid state reaction method and the ceramic sample was well densified at an extreme low sintering temperature about 400°C. Rietveld refinement of the crystal structure was performed using FULLPROF program and the cell parameters are a = b = c = 9.22039 Å with a space group F D −3 M (227). High performance microwave dielectric properties, with a permittivity ~7.9, a Qf value ~33,000 GHz and a temperature coefficient of resonant frequency ~−120 ppm/°C, were obtained. From X-ray diffraction (XRD) and Energy Dispersive Spectrometer (EDS) analysis of the co-fired sample, it was found that the NaAgMoO4 ceramic is chemically compatible with both silver and aluminum at the sintering temperature and this makes it a promising candidate for the ultra-low temperature co-fired ceramics technology. Analysis of infrared and THz spectra indicated that dielectric polarizability at microwave region of the NaAgMoO4 ceramic was equally contributed by ionic displasive and electronic polarizations. Its small microwave dielectric permittivity can also be explained well by the Shannon's additive rule.
The newly identified migration inhibitory protein regulates the radial migration in the developing neocortex
Authors: Zhang Suxiang , Kanemitsu Yoshitaka , Fujitani Masashi , Yamashita Toshihide
Published: August 2014

Neuronal migration is a crucial process in the organization of the developing cerebral cortex. Although a number of positive regulatory mechanisms of radial migration have been identified, negative cell-autonomous mechanisms have yet to be fully described. Here we report a newly identified Migration Inhibitory Protein (MINP, formerly known as 2900011O08Rik) that negatively regulates radial migration. MINP mRNA was specifically detected in the central and peripheral nervous system and especially enriched in the cerebral cortex. MINP immunoreactivity co-localized with the neuronal marker Tuj1 and was detected in the cytoplasm of post-mitotic neurons. To elucidate the function of MINP in the developing brain, we performed in utero electroporation of MINP siRNA, MINP shRNA, or MINP-overexpressing vectors into mouse cortices and carried out in vivo migration assays. Whereas knockdown of MINP did not alter neuronal morphology, the radial migration was found accelerated by MINP knockdown and reduced by MINP overexpression. This migration phenotype was also confirmed in vitro, indicating that MINP regulates neuronal migration in a cell-autonomous fashion. Furthermore, downregulation of MINP affected microtubule stability by interacting with tubulin that is a potential mechanism involved in the regulation of neuronal migration.
A zero-background fluorescent probe for Hg2+ designed via the “covalent-assembly” principle
Authors: Song Linlin , Lei Zuhai , Zhang Baoyan , Xu Zhiping , Li Zhong , Yang Youjun
Published: August 2014

We herein report a novel fluorescent probe for Hg2+ based on the deprotection of 1,3-dithiolane, via the covalent assembly principle.
A low temperature, isothermal gas-phase system for conversion of methane to methanol over Cu–ZSM-5
Authors: Sheppard T. , Hamill C. D. , Goguet A. , Rooney D. W. , Thompson J. M.
Published: August 2014

A low temperature, recyclable process for partial methane oxidation is described over Cu–ZSM-5 using NO as the oxidant.
Promising two-photon probes for in vivo detection of β amyloid deposits
Authors: Murugan N. Arul , Zaleśny Robert , Kongsted Jacob , Nordberg Agneta , Ågren Hans
Published: August 2014

A novel relationship between the charge-transfer descriptor, Δr, and two-photon absorption cross-sections in NIRF probes.
Luminescent materials containing multiple benzoxaphosphole units
Authors: Wu Shanshan , Rheingold Arnold L. , Protasiewicz John D.
Published: August 2014

A series of bisbenzoxaphospholes and a trisbenzoxaphosphole have been prepared and characterized.
Preparation of highly substituted (β-acylamino)acrylates via iron-catalyzed alkoxycarbonylation of N-vinylacetamides with carbazates
Authors: Ding Ran , Zhang Qiu-Chi , Xu Yun-He , Loh Teck-Peng
Published: August 2014

A simple and efficient iron-catalyst system was applied for the synthesis of various (β-acylamino)acrylate derivatives under mild reaction conditions.
An alternative strategy to construct Fe(ii)-based MOFs with multifarious structures and magnetic behaviors
Authors: Li Qipeng , Tian Chongbin , Zhang Huabin , Qian Jinjie , Du Shaowu
Published: August 2014

An alternative strategy using cyclopentadienyliron dicarbonyl dimer as an iron source has been applied to construct six new Fe(ii)-based MOFs (1–6). The successful preparation of1–6may provide an alternative and useful approach for the synthesis of Fe(ii)-based MOFs in the future.
Tip-enhanced Raman spectroscopic measurement of stress change in the local domain of epitaxial graphene on the carbon face of 4H-SiC(000–1)
Authors: Suzuki Toshiaki , Itoh Tamitake , Vantasin Sanpon , Minami Satoshi , Kutsuma Yasunori , Ashida Koji , Kaneko Tada-aki , Morisawa Yusuke , Miura Takeshi , Ozaki Yukihiro
Published: August 2014

We measured TERS spectra of epitaxial graphene on the carbon face of 4H-SiC(000–1) and compared them with the corresponding normal Raman spectra.
A theoretical study of the L3 pre-edge XAS in Cu(ii) complexes
Authors: Mangione G. , Sambi M. , Nardi M. V. , Casarin M.
Published: August 2014

L2,3 spectra of Cu(ii) complexes have been simulated by means of time dependent DFT. Besides the agreement between theory and experiment, the adopted approach provided further insights into the use of the Cu(ii) L3-edge intensity and position to investigate the Cu–ligand symmetry-restricted covalency and the ligand-field strength.
Direct observation of OH formation from stabilised Criegee intermediates
Authors: Novelli A. , Vereecken L. , Lelieveld J. , Harder H.
Published: August 2014

The first direct observation of OH radicals from syn-CH3CHOO Criegee intermediates decomposition suggests it affects tropospheric chemistry and ambient OH measurements.
Mechanistic aspects of thioflavin-T self-aggregation and DNA binding: evidence for dimer attack on DNA grooves
Authors: Biancardi A. , Biver T. , Burgalassi A. , Mattonai M. , Secco F. , Venturini M.
Published: August 2014

Simultaneous intercalation and groove-binding is infrequent: here, under dye excess, the TFT dimer binds to grooves of TFT-intercalated DNA.
Biological metals and metal-targeting compounds in major neurodegenerative diseases
Authors: Barnham Kevin J. , Bush Ashley I.
Published: August 2014

Metals are functionally essential, but redistribute in neurodegenerative disease where they induce protein aggregates, catalyze radical formation, and lose bioavailability.
Uranium incorporation into aluminum-substituted ferrihydrite during iron(ii)-induced transformation
Authors: Massey Michael S. , Lezama-Pacheco Juan S. , Michel F. Marc , Fendorf Scott
Published: August 2014

Uranium retention processes (adsorption, precipitation, and incorporation into host minerals) exert strong controls on U mobility in the environment, and understanding U retention is therefore crucial for predicting the migration of U within surface and groundwater.
Toward structural femtosecond chemical dynamics: imaging chemistry in space and time
Authors: Minitti Michael P. , Budarz James M. , Kirrander Adam , Robinson Joseph , Lane Thomas J. , Ratner Daniel , Saita Kenichiro , Northey Thomas , Stankus Brian , Cofer-Shabica Vale , Hastings Jerome , Weber Peter M.
Published: August 2014

We aim to observe a chemical reaction in real time using gas-phase X-ray diffraction. In our initial experiment at the Linac Coherent Light Source (LCLS), we investigated the model system 1,3-cyclohexadiene (CHD) at very low vapor pressures. This reaction serves as a benchmark for numerous transformations in organic synthesis and natural product biology. Excitation of CHD by an ultraviolet optical pulse initiates an electrocyclic reaction that transforms the closed ring system into the open-chain structure of 1,3,5-hexatriene. We describe technical points of the experimental method and present first results. We also outline an approach to analyze the data involving nonlinear least-square optimization routines that match the experimental observations with predicted diffraction patterns calculated from trajectories for nonadiabatic vibronic wave packets.
Organic semiconductor distributed feedback laser pixels for lab-on-a-chip applications fabricated by laser-assisted replication
Authors: Liu Xin , Prinz Stephan , Besser Heino , Pfleging Wilhelm , Wissmann Markus , Vannahme Christoph , Guttmann Markus , Mappes Timo , Koeber Sebastian , Koos Christian , Lemmer Uli
Published: August 2014

The integration of organic semiconductor distributed feedback (DFB) laser sources into all-polymer chips is promising for biomedical or chemical analysis. However, the fabrication of DFB corrugations is often expensive and time-consuming. Here, we apply the method of laser-assisted replication using a near-infrared diode laser beam to efficiently fabricate inexpensive poly(methyl methacrylate) (PMMA) chips with spatially localized organic DFB laser pixels. This time-saving fabrication process enables a pre-defined positioning of nanoscale corrugations on the chip and a simultaneous generation of nanoscale gratings for organic edge-emitting laser pixels next to microscale waveguide structures. A single chip of size 30 mm × 30 mm can be processed within 5 min. Laser-assisted replication allows for the subsequent addition of further nanostructures without a negative impact on the existing photonic components. The minimum replication area can be defined as being as small as the diode laser beam focus spot size. To complete the fabrication process, we encapsulate the chip in PMMA using laser transmission welding.
Elucidation of epithelial–mesenchymal transition-related pathways in a triple-negative breast cancer cell line model by multi-omics interactome analysis
Authors: Pauling Josch K. , Christensen Anne G. , Batra Richa , Alcaraz Nicolas , Barbosa Eudes , Larsen Martin R. , Beck Hans C. , Leth-Larsen Rikke , Azevedo Vasco , Ditzel Henrik J. , Baumbach Jan
Published: August 2014

Network features discriminate between epithelial and mesenchymal phenotype in a triple-negative breast cancer cell line model.
Flow-scanning optical tomography
Authors: Pégard Nicolas C. , Toth Marton L. , Driscoll Monica , Fleischer Jason W.
Published: August 2014

We present a 3D tomography technique for in vivo observation of microscopic samples.
Fine-tuning of ferrocene redox potentials towards multiplex DNA detection
Authors: Marsh Barrie J. , Hampton Lauren , Goggins Sean , Frost Christopher G.
Published: August 2014

Rational tuning of ferrocene redox potential is achieved by modulation of the hydrophobicity and correlated to c log P.
Plasmonic effect of spray-deposited Au nanoparticles on the performance of inverted organic solar cells
Authors: Chaturvedi Neha , Swami Sanjay Kumar , Dutta Viresh
Published: August 2014

Au nanoparticles are deposited on an ITO substrate using an electric field-assisted spray process. Different sizes of nanoparticles can be deposited by applying DC voltage during the spray deposition. A maximum of 3.6% PCE is achieved by using the ITO/Au/ZnO/P3HT:PCBM/Ag device structure.
PdnAg(4−n) and PdnPt(4−n) clusters on MgO (100): a density functional surface genetic algorithm investigation
Authors: Heard Christopher J. , Heiles Sven , Vajda Stefan , Johnston Roy L.
Published: August 2014

Global optimisation of catalytically relevant noble metal mono and bimetallic clusters is performed directly on an MgO substrate with DFT. Charge is distributed locally upon the cluster, providing a means to atomically control binding and reaction sites, as found for CO molecules on Pd/Ag/Pt.
Organophosphorus-catalyzed diaza-Wittig reaction: application to the synthesis of pyridazines
Authors: Bel Abed Hassen , Mammoliti Oscar , Bande Omprakash , Van Lommen Guy , Herdewijn Piet
Published: August 2014

The elaboration of the first organophosphorus-catalyzed diaza-Wittig reaction is reported.
Enhanced drug toxicity by conjugation of platinum drugs to polymers with guanidine containing zwitterionic functional groups that mimic cell-penetrating peptides
Authors: Abd Karim Khairil Juhanni , Utama Robert H. , Lu Hongxu , Stenzel Martina H.
Published: August 2014

Inspired by the Ringsdorf model, statistical copolymers with solubility enhancers, platinum drugs and groove binders were compared.
Room temperature, open-flask C–H arylation of electron-deficient heteroarenes with triazenes: rapid synthesis of heterobiaryls
Authors: Wang Rui , Falck John R.
Published: August 2014

Aryl triazenes were coupled with heteroarenes via C–H functionalization to produce heterobiaryls in moderate to good yields at ambient temperature.
CoxFe3−xO4 hierarchical nanocubes as peroxidase mimetics and their applications in H2O2 and glucose detection
Authors: Yang Wenshu , Hao Jinhui , Zhang Zhe , Lu Baoping , Zhang Bailin , Tang Jilin
Published: August 2014

A facile approach was proposed for the synthesis of hierarchical CoxFe3−xO4 (CF) nanocubes, using Prussian Blue (PB) as precursor. Then, an efficient and simple colorimetric biosensor for H2O2 and glucose was fabricated using CF nanocubes as peroxidase mimetic.
A new, facile method to prepare hybrid calcium poly(styrene-phenylvinylphosphonate)–phosphate materials for a superior performance catalyst support
Authors: Huang Jing , Tang Mei , Li Chang Ming
Published: August 2014

Various pores or channels produced by modification of the PS-PVPA chain could contribute to significant impact on the excellent catalytic activity.
The hydrolysis mechanism of polyglycolic acid under tensile mechanical loading: a density functional theory study
Authors: Ju Shin-Pon , Huang Wei-Chun , Chen Chien-Chia
Published: August 2014

The hydrolysis mechanisms of polyglycolic acid (PGA) under tensile mechanical loading were studied by the density functional theory (DFT) calculations for illustrating the enhancement of PGA hydrolysis by external mechanical loading found in previous experimental studies (Iran. Polym. J., 2008, 17(9), 691–701).
Nano-sized layered manganese oxide in a poly-L-glutamic acid matrix: a biomimetic, homogenized, heterogeneous structural model for the water-oxidizing complex in photosystem II
Authors: Najafpour Mohammad Mahdi , Ghobadi Mohadeseh Zarei , Sedigh Davood Jafarian , Haghighi Behzad
Published: August 2014

Here, we report a nano-sized layered Mn–Ca oxide in poly-L-glutamic acid as a structural model for a biological water-oxidizing site in plants, algae and cyanobacteria.
Hierarchical nanostructured FeS2 hollow microspheres for lithium-ion batteries
Authors: Wang Yourong , Qian Xiaofang , Zhou Wei , Liao Hantao , Cheng Siqing
Published: August 2014

The as-obtained FeS2 hollow microsphere electrode delivered excellent cycling stability and electrochemical performance after the first cycle at ambient temperature.
A facile method to prepare composite and porous polyphosphazene membranes and investigation of their properties
Authors: Hu Lei , Zhang Aiqing , Liu Kai , Lei Shan , Ou Guangxin , Cheng Xinjian
Published: August 2014

Polyphosphazene/SiO2 composite membranes and porous polyphosphazene membranes were prepared and their properties were studied in detail.
Copper(ii)-catalyzed cleavage of carbon–carbon triple bond to synthesize 1,2,3-triesterindolizines
Authors: Sun Jinwei , Hu Huayou , Wang Fuyao , Wu Hui , Liu Yun
Published: August 2014

An efficient Cu(ii)-catalyzed carbon–carbon triple bond cleavage protocol for the synthesis of 1,2,3-triesterindolizines via the reaction of pyridines with butynedioates has been developed.
Employment of nanomaterials in polymerase chain reaction: insight into the impacts and putative operating mechanisms of nano-additives in PCR
Authors: Yuce Meral , Kurt Hasan , Mokkapati Venkata R. S. S. , Budak Hikmet
Published: August 2014

The latest developments in the field of nanomaterial-assisted PCR are evaluated with a focus on putative operating mechanisms.
Hydrothermally prepared chromia-alumina (xCr/Al2O3) catalysts with hierarchical structure for propane dehydrogenation
Authors: Lang Wan-Zhong , Hu Chang-Long , Chu Lian-Feng , Guo Ya-Jun
Published: August 2014

Propane dehydrogenation was investigated over a series of chromia-alumina (xCr/Al2O3) catalysts containing 2.5–10 wt% chromium (Cr), synthesizedviaa hydrothermal synthesis method.
Electrospun nanofibers with a core–shell structure of silicon nanoparticles and carbon nanotubes in carbon for use as lithium-ion battery anodes
Authors: Hieu Nguyen Trung , Suk Jungdon , Kim Dong Wook , Park Jun Seo , Kang Yongku
Published: August 2014

Core–shell Si–CNT@C nanofibers as anodes in LIBs can minimize the volume change and improve the conductivity, enhancing the battery performance.
Uniform nanoparticle coating of cellulose fibers during wet electrospinning
Authors: Zheng Yingying , Miao Jianjun , Maeda Noriko , Frey David , Linhardt Robert J. , Simmons Trevor J.
Published: August 2014

This work outlines a newly developed method that allows electrospun cellulose fibers to be coated with nanoparticles during dry-jet wet electrospinning. Fibers coated with Mg(OH)2 nanoparticles exhibited flame retardant properties, whereas fibers containing Mg(OH)2 nanoparticles exhibited accelerated burning.
High temperature structural stability, electrical properties and chemical reactivity of NdBaCo2−xMnxO5+δ (0 ≤ x ≤ 2) for use as cathodes in solid oxide fuel cells
Authors: Broux Thibault , Bahout Mona , Hanlon James M. , Hernandez Olivier , Paofai Serge , Berenov Andrey , Skinner Stephen J.
Published: August 2014

TGA for NdBaCo2−xMnxO5+δ in air with heating/cooling at 2 °C min−1 and an intermediate step at 800 °C for 6 h.
Magnetic molecularly imprinted polymers (MMIPs) for carbazole derivative release in targeted cancer therapy
Authors: Parisi Ortensia Ilaria , Morelli Catia , Puoci Francesco , Saturnino Carmela , Caruso Anna , Sisci Diego , Trombino Giovanna Elvi , Picci Nevio , Sinicropi Maria Stefania
Published: August 2014

Magnetic Molecularly Imprinted Polymers (MMIPs) are synthesized with the aim to prepare novel devices for 9H-carbazole derivative sustained delivery in targeted cancer therapy.
Growing gold nanoparticles on a flexible substrate to enable simple mechanical control of their plasmonic coupling
Authors: Cataldi Ugo , Caputo Roberto , Kurylyak Yuriy , Klein Gérard , Chekini Mahshid , Umeton Cesare , Bürgi Thomas
Published: August 2014

A macroscopic mechanical strain can be used to control the coupling and therefore the electromagnetic field at the nanoscale.
Adenylate cyclase-centred microdomains
Authors: Cooper Dermot M. F. , Tabbasum Valentina G.
Published: August 2014

Recent advances in the AC (adenylate cyclase)/cAMP field reveal overarching roles for the ACs. Whereas few processes are unaffected by cAMP in eukaryotes, ranging from the rapid modulation of ion channel kinetics to the slowest developmental effects, the large number of cellular processes modulated by only three intermediaries, i.e. PKA (protein kinase A), Epacs (exchange proteins directly activated by cAMP) and CNG (cyclic nucleotide-gated) channels, poses the question of how selectivity and fine control is achieved by cAMP. One answer rests on the number of differently regulated and distinctly expressed AC species. Specific ACs are implicated in processes such as insulin secretion, immunological responses, sino-atrial node pulsatility and memory formation, and specific ACs are linked with particular diseased conditions or predispositions, such as cystic fibrosis, Type 2 diabetes and dysrhythmias. However, much of the selectivity and control exerted by cAMP lies in the sophisticated properties of individual ACs, in terms of their coincident responsiveness, dynamic protein scaffolding and organization of cellular microassemblies. The ACs appear to be the centre of highly organized microdomains, where both cAMP and Ca2+, the other major influence on ACs, change in patterns quite discrete from the broad cellular milieu. How these microdomains are organized is beginning to become clear, so that ACs may now be viewed as fundamental signalling centres, whose properties exceed their production of cAMP. In the present review, we summarize how ACs are multiply regulated and the steps that are put in place to ensure discrimination in their signalling. This includes scaffolding of targets and modulators by the ACs and assembling of signalling nexuses in discrete cellular domains. We also stress how these assemblies are cell-specific, context-specific and dynamic, and may be best addressed by targeted biosensors. These perspectives on the organization of ACs uncover new strategies for intervention in systems mediated by cAMP, which promise far more informed specificity than traditional approaches.
Structures of lipoyl synthase reveal a compact active site for controlling sequential sulfur insertion reactions
Authors: Harmer Jenny E. , Hiscox Martyn J. , Dinis Pedro C. , Fox Stephen J. , Iliopoulos Andreas , Hussey James E. , Sandy James , Van Beek Florian T. , Essex Jonathan W. , Roach Peter L.
Published: August 2014

Lipoyl cofactors are essential for living organisms and are produced by the insertion of two sulfur atoms into the relatively unreactive C–H bonds of an octanoyl substrate. This reaction requires lipoyl synthase, a member of the radical S-adenosylmethionine (SAM) enzyme superfamily. In the present study, we solved crystal structures of lipoyl synthase with two [4Fe–4S] clusters bound at opposite ends of the TIM barrel, the usual fold of the radical SAM superfamily. The cluster required for reductive SAM cleavage conserves the features of the radical SAM superfamily, but the auxiliary cluster is bound by a CX4CX5C motif unique to lipoyl synthase. The fourth ligand to the auxiliary cluster is an extremely unusual serine residue. Site-directed mutants show this conserved serine ligand is essential for the sulfur insertion steps. One crystallized lipoyl synthase (LipA) complex contains 5′-methylthioadenosine (MTA), a breakdown product of SAM, bound in the likely SAM-binding site. Modelling has identified an 18 Å (1 Å=0.1 nm) deep channel, well-proportioned to accommodate an octanoyl substrate. These results suggest that the auxiliary cluster is the likely sulfur donor, but access to a sulfide ion for the second sulfur insertion reaction requires the loss of an iron atom from the auxiliary cluster, which the serine ligand may enable.
Modeling direct interband tunneling. I. Bulk semiconductors
Authors: Pan Andrew , Chui Chi On
Published: August 2014

Interband tunneling is frequently studied using the semiclassical Kane model, despite uncertainty about its validity. Revisiting the physical basis of this formula, we find that it neglects coupling to other bands and underestimates transverse tunneling. As a result, significant errors can arise at low and high fields for small and large gap materials, respectively. We derive a simple multiband tunneling model to correct these defects analytically without arbitrary parameters. Through extensive comparison with band structure and quantum transport calculations for bulk InGaAs, InAs, and InSb, we probe the accuracy of the Kane and multiband formulas and establish the superiority of the latter. We also show that the nonlocal average electric field should be used when applying either of these models to nonuniform potentials. Our findings are important for efficient analysis and simulation of bulk semiconductor devices involving tunneling.
Ab initio multiple cloning algorithm for quantum nonadiabatic molecular dynamics
Authors: Makhov Dmitry V. , Glover William J. , Martinez Todd J. , Shalashilin Dmitrii V.
Published: August 2014

We present a new algorithm for ab initio quantum nonadiabatic molecular dynamics that combines the best features of ab initio Multiple Spawning (AIMS) and Multiconfigurational Ehrenfest (MCE) methods. In this new method, ab initio multiple cloning (AIMC), the individual trajectory basis functions (TBFs) follow Ehrenfest equations of motion (as in MCE). However, the basis set is expanded (as in AIMS) when these TBFs become sufficiently mixed, preventing prolonged evolution on an averaged potential energy surface. We refer to the expansion of the basis set as “cloning,” in analogy to the “spawning” procedure in AIMS. This synthesis of AIMS and MCE allows us to leverage the benefits of mean-field evolution during periods of strong nonadiabatic coupling while simultaneously avoiding mean-field artifacts in Ehrenfest dynamics. We explore the use of time-displaced basis sets, “trains,” as a means of expanding the basis set for little cost. We also introduce a new bra-ket averaged Taylor expansion (BAT) to approximate the necessary potential energy and nonadiabatic coupling matrix elements. The BAT approximation avoids the necessity of computing electronic structure information at intermediate points between TBFs, as is usually done in saddle-point approximations used in AIMS. The efficiency of AIMC is demonstrated on the nonradiative decay of the first excited state of ethylene. The AIMC method has been implemented within the AIMS-MOLPRO package, which was extended to include Ehrenfest basis functions.
On the spin separation of algebraic two-component relativistic Hamiltonians: Molecular properties
Authors: Li Zhendong , Xiao Yunlong , Liu Wenjian
Published: August 2014

The idea for separating the algebraic exact two-component (X2C) relativistic Hamiltonians into spin-free (sf) and spin-dependent terms [Z. Li, Y. Xiao, and W. Liu, J. Chem. Phys. 137, 154114 (2012)] is extended to both electric and magnetic molecular properties. Taking the spin-free terms (which are correct to infinite order in α ≈ 1/137) as zeroth order, the spin-dependent terms can be treated to any desired order via analytic derivative technique. This is further facilitated by unified Sylvester equations for the response of the decoupling and renormalization matrices to single or multiple perturbations. For practical purposes, explicit expressions of order α2 in spin are also given for electric and magnetic properties, as well as two-electron spin-orbit couplings. At this order, the response of the decoupling and renormalization matrices is not required, such that the expressions are very compact and completely parallel to those based on the Breit-Pauli (BP) Hamiltonian. However, the former employ sf-X2C wave functions, whereas the latter can only use nonrelativistic wave functions. As the sf-X2C terms can readily be interfaced with any nonrelativistic program, the implementation of the \documentclass[12pt]{minimal}\begin{document}$\mathcal {O}(\alpha ^2)$\end{document}O(α2) spin-orbit corrections to sf-X2C properties requires only marginal revisions of the routines for evaluating the BP type of corrections.
Charge carrier recombination channels in the low-temperature phase of organic-inorganic lead halide perovskite thin films
Authors: Wehrenfennig Christian , Liu Mingzhen , Snaith Henry J. , Johnston Michael B. , Herz Laura M.
Published: August 2014

The optoelectronic properties of the mixed hybrid lead halide perovskite CH3NH3PbI3−xClx have been subject to numerous recent studies related to its extraordinary capabilities as an absorber material in thin film solar cells. While the greatest part of the current research concentrates on the behavior of the perovskite at room temperature, the observed influence of phonon-coupling and excitonic effects on charge carrier dynamics suggests that low-temperature phenomena can give valuable additional insights into the underlying physics. Here, we present a temperature-dependent study of optical absorption and photoluminescence (PL) emission of vapor-deposited CH3NH3PbI3−xClx exploring the nature of recombination channels in the room- and the low-temperature phase of the material. On cooling, we identify an up-shift of the absorption onset by about 0.1 eV at about 100 K, which is likely to correspond to the known tetragonal-to-orthorhombic transition of the pure halide CH3NH3PbI3. With further decreasing temperature, a second PL emission peak emerges in addition to the peak from the room-temperature phase. The transition on heating is found to occur at about 140 K, i.e., revealing significant hysteresis in the system. While PL decay lifetimes are found to be independent of temperature above the transition, significantly accelerated recombination is observed in the low-temperature phase. Our data suggest that small inclusions of domains adopting the room-temperature phase are responsible for this behavior rather than a spontaneous increase in the intrinsic rate constants. These observations show that even sparse lower-energy sites can have a strong impact on material performance, acting as charge recombination centres that may detrimentally affect photovoltaic performance but that may also prove useful for optoelectronic applications such as lasing by enhancing population inversion.
Particle dynamics and rapid trapping in electro-osmotic flow around a sharp microchannel corner
Authors: Zehavi Matan , Yossifon Gilad
Published: August 2014

We study here the curious particle dynamics resulting from electro-osmotic flow around a microchannel junction corner whose dielectric walls are weakly polarizable. The hydrodynamic velocity field is obtained via superposition of a linear irrotational term associated with the equilibrium zeta potentials of both the microchannel and particle surfaces and the nonlinear induced-charge electro-osmotic flow which originates from the interaction of the externally applied electric field on the charge cloud it induces at the solid-liquid interface. The particle dynamics are analyzed by considering dielectrophoretic forces via the addition of a mobility term to the flow field in the limit of Stokes drag law. The former, non-divergence free term is responsible for migration of particles towards the sharp microchannel junction corner, where they can potentially accumulate. Experimental observations of particle trapping for various applied electric fields and microparticle size are rationalized in terms of the growing relative importance of the dielectrophoretic force and induced-charge contributions to the global velocity field with increasing intensity of the externally applied electric field.
Magnetic ordered structure dependence of magnetic refrigeration efficiency
Authors: Tamura Ryo , Tanaka Shu , Ohno Takahisa , Kitazawa Hideaki
Published: August 2014

We have investigated the relation between magnetic ordered structure and magnetic refrigeration efficiency in the Ising model on a simple cubic lattice using Monte Carlo simulations. The magnetic entropy behaviors indicate that the protocol, which was first proposed in [Tamura et al., Appl. Phys. Lett. 104, 052415 (2014)], can produce the maximum isothermal magnetic entropy change and the maximum adiabatic temperature change in antiferromagnets. Furthermore, the total amount of heat transfer under the proposed protocol reaches a maximum. The relation between measurable physical quantities and magnetic refrigeration efficiency is also discussed.
Improved electrical mobility in highly epitaxial La:BaSnO3 films on SmScO3(110) substrates
Authors: Wadekar P. V. , Alaria J. , O'Sullivan M. , Flack N. L. O. , Manning T. D. , Phillips L. J. , Durose K. , Lozano O. , Lucas S. , Claridge J. B. , Rosseinsky M. J.
Published: August 2014

Heteroepitaxial growth of BaSnO3 and Ba1−xLaxSnO3 (x = 7%) lanthanum doped barium stannate thin films on different perovskite single crystal (SrTiO3 (001) and SmScO3 (110)) substrates has been achieved by pulsed laser deposition under optimized deposition conditions. X-ray diffraction measurements indicate that the films on either of these substrates are relaxed due to the large mismatch and present a high degree of crystallinity with narrow rocking curves and smooth surface morphology while analytical quantification by proton induced X-ray emission confirms the stoichiometric La transfer from a polyphasic target, producing films with measured La contents above the bulk solubility limit. The films show degenerate semiconducting behavior on both substrates, with the observed room temperature resistivities, Hall mobilities, and carrier concentrations of 4.4 mΩ cm, 10.11 cm2 V−1 s−1, and 1.38 × 1020 cm−3 on SmScO3 and 7.8 mΩ cm, 5.8 cm2 V−1 s−1, and 1.36 × 1020 cm−3 on SrTiO3 ruling out any extrinsic contribution from the substrate. The superior electrical properties observed on the SmScO3 substrate are attributed to reduction in dislocation density from the lower lattice mismatch.
Magnetic shielding of Hall thrusters at high discharge voltages
Authors: Mikellides Ioannis G. , Hofer Richard R. , Katz Ira , Goebel Dan M.
Published: August 2014

A series of numerical simulations and experiments have been performed to assess the effectiveness of magnetic shielding in a Hall thruster operating in the discharge voltage range of 300–700 V (Isp ≈ 2000–2700 s) at 6 kW, and 800 V (Isp ≈ 3000) at 9 kW. At 6 kW, the magnetic field topology with which highly effective magnetic shielding was previously demonstrated at 300 V has been retained for all other discharge voltages; only the magnitude of the field has been changed to achieve optimum thruster performance. It is found that magnetic shielding remains highly effective for all discharge voltages studied. This is because the channel is long enough to allow hot electrons near the channel exit to cool significantly upon reaching the anode. Thus, despite the rise of the maximum electron temperature in the channel with discharge voltage, the electrons along the grazing lines of force remain cold enough to eliminate or reduce significantly parallel gradients of the plasma potential near the walls. Computed maximum erosion rates in the range of 300–700 V are found not to exceed 10−2 mm/kh. Such rates are ∼3 orders of magnitude less than those observed in the unshielded version of the same thruster at 300 V. At 9 kW and 800 V, saturation of the magnetic circuit did not allow for precisely the same magnetic shielding topology as that employed during the 6-kW operation since this thruster was not designed to operate at this condition. Consequently, the maximum erosion rate at the inner wall is found to be ∼1 order of magnitude higher (∼10−1 mm/kh) than that at 6 kW. At the outer wall, the ion energy is found to be below the sputtering yield threshold so no measurable erosion is expected.
Detailed characteristics of intermittent current pulses due to positive corona
Authors: Liu Yang , Cui Xiang , Lu Tiebing , Wang Zhenguo , Li Xuebao , Xiang Yu , Wang Xiaobo
Published: August 2014

In order to get detailed characteristics of intermittent current pulses due to positive corona such as the repetition rate of burst-pulse trains, the peak value ratio of the primary pulse to the secondary pulse, the number of pulses per burst, and the interval of the secondary pulses, a systematic study was carried out in a coaxial conductor-cylinder electrode system with the conductor electrode being set with a discharge point. Empirical formulae for the number of pulses per burst and the interval of the secondary pulses are first presented. A theoretical model based on the motion of the space-charge clouds is proposed. Analysis with the model gives explanations to the experimental results and reveals some new insights into the physical mechanism of positive intermittent corona.
Infrared thermal emission from a two-dimensional array of plasmonic spheres
Authors: Zimmerman Ian , Liang Min , Xin Hao
Published: August 2014

We explore in numerical simulation the degree to which the thermal emission in the mid-infrared (IR) range can be controlled using a lattice of plasmonic spheres. While it has been shown that a great deal of spectral control can be achieved using a single sphere, obviously no directional control exists. We propose gaining this additional directional control over the thermal emission by designing a 2D lattice of resonant spheres. In this paper, we demonstrate that directional control as well as additionally spectral control over the thermal emission is achieved with this method. We do this by simulating a 2D layer of spheres composed of SiO2 cores and a SiC shells with a polaritonic resonance in the mid-IR. We then analyze how changing the lattice geometry affects the thermal emission characteristics of the ensemble of spheres. We show that for closely spaced spheres, modest directional control is possible with the additional benefit of some spectral control. When the spheres are spaced farther apart, Bragg scattering allows for more directional control, however, the spectrum of the emission is mostly governed by the properties of a single sphere.
Delineating the magnetic field line escape pattern and stickiness in a poloidally diverted tokamak
Authors: Martins Caroline G. L. , Roberto M. , Caldas I. L.
Published: August 2014

We analyze a Hamiltonian model with five wire loops that delineates magnetic surfaces of tokamaks with poloidal divertor. Non-axisymmetric magnetic perturbations are added by external coils, similar to the correction coils that have been installed or designed in present tokamaks. To show the influence of magnetic perturbations on the field line escape, we integrate numerically the field line differential equations and obtain the footprints and deposition patterns on the divertor plate. Moreover, we show that the homoclinic tangle describes the deposition patterns in the divertor plate, agreeing with results observed in sophisticated simulation codes. Additionally, we show that while chaotic lines escape to the divertor plates, some of them are trapped, for many toroidal turns, in complex structures around magnetic islands, embedded in the chaotic region, giving rise to stickiness evidences characteristic of chaotic Hamiltonian systems. Finally, we introduce a random collisional term to the field line mapping to investigate stickiness alterations due to particle collisions. Within this model, we conclude that, even reduced by collisions, the observed trapping still influences the field line transport. The results obtained for our numerical estimations indicate that the reported trapping may affect the transport in present tokamaks.
Single-crystal CdTe solar cells with Voc greater than 900 mV
Authors: Duenow J. N. , Burst J. M. , Albin D. S. , Kuciauskas D. , Johnston S. W. , Reedy R. C. , Metzger W. K.
Published: August 2014

We fabricated single-crystal CdTe photovoltaic devices in a heterojunction structure with an In-doped CdS window layer and ZnO/Al-doped ZnO front contact. By replacing the polycrystalline absorber layer of a CdTe solar cell with a single crystal, we were able to achieve open-circuit voltage (Voc) as high as 929 mV. Simulations and measurements indicate that increased minority-carrier lifetime and carrier concentration can explain this high Voc. Cu and Na both introduce transient effects in single-crystal CdTe similar to those observed in polycrystalline CdTe, suggesting that Group I dopants pose stability problems that are linked fundamentally to their defect chemistry in CdTe, regardless of the presence of grain boundaries.
Eliminating anchor loss in optomechanical resonators using elastic wave interference
Authors: Zhang Mian , Luiz Gustavo , Shah Shreyas , Wiederhecker Gustavo , Lipson Michal
Published: August 2014

Optomechanical resonators suffer from the dissipation of mechanical energy through the necessary anchors enabling the suspension of the structure. Here, we show that such structural loss in an optomechanical oscillator can be almost completely eliminated through the destructive interference of elastic waves using dual-disk structures. We also present both analytical and numerical models that predict the observed interference of elastic waves. Our experimental data reveal unstressed silicon nitride (Si3N4) devices with mechanical Q-factors up to 104 at mechanical frequencies of f = 102 MHz (fQ = 1012) at room temperature.