bluuebunny/crossref_metadata_2025 huggingface dataset:
Characteristics of large‐scale wave structure observed from African and Southeast Asian longitudinal sectors
Authors: Tulasi Ram S. , Yamamoto M. , Tsunoda R. T. , Chau H. D. , Hoang T. L. , Damtie B. , Wassaie M. , Yatini C. Y. , Manik T. , Tsugawa T.
Published: February 2014

The spatial large‐scale wave structure (LSWS) at the base of F layer is the earliest manifestation of seed perturbation for Rayleigh‐Taylor instability, hence, found to play a deterministic role in the development of Equatorial Plasma Bubbles (EPBs). Except for a few case studies, a comprehensive investigation has not been conducted on the characteristics of LSWS because of the complexity involved in detecting the LSWS, particularly, in spatial domain. In this scenario, a comprehensive study is carried out, for the first time, on the spatial and temporal characteristics of LSWS observed in spatial domain over African and Southeast Asian longitudinal sectors during the year 2011. The observations indicate that these wave structures can be detected a few degrees west of E region sunset terminator and found to grow significantly at longitudes past the sunset terminator. The phase fronts of these spatial structures are found to align with the geomagnetic field () lines over a latitudinal belt for at least 5−6° (~500–600 km) centered on dip equator. The zonal wavelengths of these structures are found to vary from 100 to 700 km, which is consistent with the earlier reports, and the EPBs were consistently observed when the amplitudes of LSWS were grown to sufficient strengths. These results would provide better insights on the underlying physical processes involved in excitation of LSWS in terms of important roles being played by E region electrical loading and polarization electric fields induced via spatially varying dynamo current due to neutral wind perturbations associated with atmospheric gravity waves.
Evaluation of ionospheric profilers using topside sounding data
Authors: Verhulst T. , Stankov S. M.
Published: February 2014

An operational system for deducing and imaging the vertical distribution of the electron density in the local ionosphere has been recently developed. The electron density profile is deduced from combined ground‐based measurements of the total electron content, ionospheric vertical incidence soundings, and empirically obtained values of the O+‐H+ ion transition height. The topside profile is permitted to take one of several forms: Exponential, Chapman, or Epstein. An evaluation of the above mentioned ionospheric profilers is needed in order to determine which one of them provides the best representation of the current ionospheric conditions. For this purpose, we use electron density profiles obtained from ionograms recorded by the topside sounders onboard the Alouette and ISIS satellites. Every profile has been fitted with each of the above mentioned theoretical ionospheric profilers and the corresponding approximation errors calculated. The results have been analyzed with respect to local time, geomagnetic latitude, season, magnetic and solar activity, ion transition height, and the ionospheric density peak characteristics. It has been found that, in the majority of cases, the best fit is provided by the exponential profiler, followed by the Chapman profiler. Also, while some influence of the underlying physical drivers on the topside electron density profile is detected, it is the use of ionospheric characteristics that offers more reliable selection criteria for the most appropriate profiler.
The rapid and precise computation of GPS slant total delays and mapping factors utilizing a numerical weather model
Authors: Zus Florian , Dick Galina , Douša Jan , Heise Stefan , Wickert Jens
Published: February 2014

In a previous study we developed an elegant technique to compute the signal travel time delay due to the neutral atmosphere, also known as slant total delay (STD), between a Global Positioning System (GPS) satellite and a ground‐based receiver utilizing data from a numerical weather model (NWM). Currently, we make use of NWM data from the Global Forecast System (GFS) because short‐range forecasts are easily accessible. In this study we introduce some modifications which double the speed of our algorithm without altering its precision; on an ordinary PC (using a single core) we compute about 2000 STDs per second with a precision of about 1 mm. The data throughput and precision are independent of the vacuum elevation (azimuth) angle of the receiver satellite link. Hence, the algorithm allows the computation of STDs in a mesobeta‐scale NWM with an unprecedented speed and precision. A practical by‐product of the algorithm is introduced as well; the Potsdam Mapping Factors (PMFs), which are generated by fast direct mapping utilizing short‐range GFS forecasts. In fact, it appears that the PMFs make the application of parameterized mapping in GPS processing obsolete.
Ray entity based postprocessing of ray‐tracing data for continuous modeling of radio channel
Authors: Mataga Nikola , Zentner Radovan , Mucalo Ana Katalinić
Published: February 2014

Ray‐tracing data are usually given as angles of arrival and departure, transmitter and receiver coordinates, ray length and delay, received power level, and polarity. Usually, these values are given in raw data with some resolution that covers the area of interest where the simulation is performed. There are two main drawbacks of such approach: first, a huge amount of storage capacity is typically needed and second, although the area of interest is covered by a certain resolution, it is nearly impossible to interpolate between sample points and new time, and memory consuming simulations are necessary in order to increase the resolution of the simulations. This paper addresses the two mentioned drawbacks of ray tracing, suggesting a procedure based on the concept of ray entities both to enable continuous interpolation of ray‐tracing data and reduce the memory needed for storing data. Ray entity is a set of rays that all undergo the same series of propagation phenomena (direct ray, diffraction, reflection, or scattering) on the same objects (building walls or edges). The method is given and illustrated for reflection and diffraction phenomena, and diffuse scattering was not included, but discussion is easily extended to this propagation type as well. The paper gives detailed statistics of entities' length and rays' count per simulated receiver point in few illustrative examples and provides an insight on how to interpolate angles of arrival and departure, ray length, and received power level in order to provide a continuous description of the radio environment.
Keogram analysis of ENA images at Saturn
Authors: Carbary J. F. , Mitchell D. G.
Published: February 2014

Keograms are constructed from azimuthal profiles of energetic hydrogen atoms (25–55 keV) from Saturn's magnetosphere. The keograms exhibit linear structures or “tracks” that reveal prograde rotational motion of features or “blobs” in the energetic neutral atom (ENA) images. From polynomial fits, the first derivatives of these tracks are used to estimate the rotational speeds of the blobs. The total blob speed consists of plasma convective drift plus gradient drift, so the convective speed can be approximated by subtracting the gradient drift of the protons from which the ENA derive. This subtraction gives plasma convection speeds that are ~28°/h at ~5 RS and decrease to a constant ~21°/h between 10 RS and 20 RS, which are consistently below corotation (~33.3°/h) and in substantial agreement with estimates of plasma convection made in situ. The speeds also show a local time dependence, decreasing as much as 4–6°/h as the blobs move from midnight through noon to midnight.
Crime Type, Perceived Stereotypicality, and Memory Biases: A Contextual Model of Eyewitness Identification
Authors: Osborne Danny , Davies Paul G.
Published: February 2014

The fallibility of eyewitness identifications is well documented. Nevertheless, research has yet to assess the possibility that the type of crime committed systematically influences who eyewitnesses mistakenly identify. We address this oversight by presenting a contextual model of eyewitness identification (CMEI). The CMEI asserts that discrete crimes automatically activate distinct stereotypes about a perpetrator's appearance. Depending on the congruence between these stereotypes and the perpetrator's actual appearance, eyewitnesses will remember the perpetrator as appearing more (or less) representative of his or her group (i.e., higher or lower on perceived stereotypicality). Estimator and system variables are posited to affect identifications at different stages of the identification process. The literatures on stereotype activation, perceived stereotypicality, and stereotype‐consistent memory biases are reviewed to support the CMEI. Our conceptual integration provides a model of eyewitness identification that explains when mistaken identifications are likely to occur and who they are likely to affect. Copyright © 2014 John Wiley & Sons, Ltd.
Exploiting Memristive BiFeO3 Bilayer Structures for Compact Sequential Logics
Authors: You Tiangui , Shuai Yao , Luo Wenbo , Du Nan , Bürger Danilo , Skorupa Ilona , Hübner René , Henker Stephan , Mayr Christian , Schüffny René , Mikolajick Thomas , Schmidt Oliver G. , Schmidt Heidemarie
Published: February 2014

Resistive switching devices are considered as one of the most promising candidates for the next generation memories and nonvolatile logic applications. In this paper, BiFeO3:Ti/BiFeO3 (BFTO/BFO) bilayer structures with optimized BFTO/BFO thickness ratio which show symmetric, bipolar, and nonvolatile resistive switching with good retention and endurance performance, are presented. The resistive switching mechanism is understood by a model of flexible top and bottom Schottky‐like barrier heights in the BFTO/BFO bilayer structures. The resistive switching at both positive and negative bias make it possible to use both polarities of reading bias to simultaneously program and store all 16 Boolean logic functions into a single cell of a BFTO/BFO bilayer structure in three logic cycles.
Colloidal Bi2S3Nanocrystals: Quantum Size Effects and Midgap States
Authors: Aresti Mauro , Saba Michele , Piras Roberto , Marongiu Daniela , Mula Guido , Quochi Francesco , Mura Andrea , Cannas Carla , Mureddu Mauro , Ardu Andrea , Ennas Guido , Calzia Vasco , Mattoni Alessandro , Musinu Anna , Bongiovanni Giovanni
Published: February 2014

Among solution‐processed nanocrystals containing environmentally benign elements, bismuth sulfide (Bi2S3) is a very promising n‐type semiconductor for solar energy conversion. Despite the prompt success in the fabrication of optoelectronic devices deploying Bi2S3nanocrystals, the limited understanding of electronic properties represents a hurdle for further materials developments. Here, two key materials science issues for light‐energy conversion are addressed: bandgap tunability via the quantum size effect, and photocarrier trapping. Nanocrystals are synthesized with controlled sizes varying from 3 to 30 nm. In this size range, bandgap tunability is found to be very small, a few tens of meV. First principles calculations show that a useful blueshift, in the range of hundreds of meV, is achieved in ultra‐small nanocrystals, below 1.5 nm in size. Similar conclusions are envisaged for the class of pnictide chalcogenides with a ribbon‐like structure [Pn4Ch6]n(Pn = Bi, Sb; Ch = S, Se). Time‐resolved differential transmission spectroscopy demonstrates that only photoexcited holes are quickly captured by intragap states. Photoexcitation dynamics are consistent with the scenario emerging in other metal–chalcogenide nanocrystals: traps are created in metal‐rich nanocrystal surfaces by incomplete passivation by long fatty acid ligands. In large nanocrystals, a lower bound to surface trap density of one trap every sixteen Bi2S3units is found.
A Review of Organic and Inorganic Biomaterials for Neural Interfaces
Authors: Fattahi Pouria , Yang Guang , Kim Gloria , Abidian Mohammad Reza
Published: February 2014

Recent advances in nanotechnology have generated wide interest in applying nanomaterials for neural prostheses. An ideal neural interface should create seamless integration into the nervous system and performs reliably for long periods of time. As a result, many nanoscale materials not originally developed for neural interfaces become attractive candidates to detect neural signals and stimulate neurons. In this comprehensive review, an overview of state‐of‐the‐art microelectrode technologies provided first, with focus on the material properties of these microdevices. The advancements in electro­active nanomaterials are then reviewed, including conducting polymers, carbon nanotubes, graphene, silicon nanowires, and hybrid organic‐inorganic nanomaterials, for neural recording, stimulation, and growth. Finally, technical and scientific challenges are discussed regarding biocompatibility, mechanical mismatch, and electrical properties faced by these nanomaterials for the development of long‐lasting functional neural interfaces.
Glycogen synthase kinase 3 beta gene structural variants as possible risk factors of bipolar depression
Authors: Ronai Zsolt , Kovacs‐Nagy Reka , Szantai Eszter , Elek Zsuzsanna , Sasvari‐Szekely Maria , Faludi Gabor , Benkovits Judit , Rethelyi Janos M. , Szekely Anna
Published: February 2014

The glycogen synthase kinase 3B (GSK3B) is an important target protein of several antidepressants, such as lithium, a mood stabilizer. Recent studies associated structural variations of the GSK3B gene to bipolar disorder (BP), although replications were not conclusive. Here we present data on copy number variations (CNVs) of the GSK3B gene probing the 9th exon region in 846 individuals (414 controls, 172 patients with major depressive disorder (MDD) and 260 with BP). A significant accumulation (odds ratio: 5.5, P = 0.00051) of the amplified exon 9 region was found in patients (22 out of 432) compared to controls (4 of 414). Analyzing patient subgroups, GSK3B structural variants were found to be risk factors of BP particularly (P = 0.00001) with an odds ratio of 8.1 while no such effect was shown in the MDD group. The highest odds (19.7 ratio) for bipolar disorder was observed in females with the amplified exon 9 region. A more detailed analysis of the identified GSK3B CNV by a set of probes covering the GSK3B gene and the adjacent NR1I2 and C3orf15 genes showed that the amplified sequences contained 3′ (downstream) segments of the GSK3B and NR1I2 genes but none of them involved the C3orf15 gene. Therefore, the copy number variation of the GSK3B gene could be described as a complex set of structural variants involving partial duplications and deletions, simultaneously. In summary, here we confirmed significant association of the GSK3B CNV and bipolar disorder pointing out that the copy number and extension of the CNV varies among individuals. © 2014 Wiley Periodicals, Inc.
Health Is not always written in bone: Using a modern comorbidity index to assess disease load in paleopathology
Authors: van Schaik Katherine , Vinichenko Dmitry , Rühli Frank
Published: February 2014

Paleopathology has revealed much about disease in the past but is usually limited to conditions with osteological manifestations; this often excludes acute soft tissue infections and causes of death for most individuals in the past and present. Our understanding of the evolution of disease is essential for contextualizing and predicting the epidemiological shifts that are happening in modern society, as high rates of infectious disease coexist alongside high rates of chronic disease in rates unlike those observed previously in human history. Moreover, many physiological states not previously classified as “disease” (obesity) have become pathologized, influencing our conception of disease and what defines health. By using the Galler Collection, a pre‐antibiotic and pre‐chemotherapeutic osteological series with modern autopsy records, our research quantifies disease burden of the past using the Charlson Index (CI), a modern comorbidity index of disease severity. Galler Collection remains and autopsy records were scored with the Charlson Index to correlate bone findings with soft tissue findings, and statistical analysis was performed for cumulative scores and absolute diagnosis counts, with patients stratified by sex and cause of death (pneumonia or cancer). Osteological diagnosis counts were more predictive of soft‐tissue autopsy disease counts than were associated cumulative CI scores. Diagnosis counts and CI scores for osteological data were more closely related to associated soft tissue data for cancer patients than for pneumonia patients. This research indicates how interdisciplinary paleopathological analysis assists in making more reliable assessments of health and mortality in the past, with implications for trending and predicting future epidemiological shifts. Am J Phys Anthropol 154:215–221, 2014. © 2014 Wiley Periodicals, Inc.
Predictive factors to differentiate between allergic and nonallergic rhinitis in children
Authors: Topal Erdem , Bakirtas Arzu , Yılmaz Ozlem , Karagöl Ilbilge Hacer Ertoy , Arslan Umut , Arga Mustafa , Demirsoy Mehmet Sadik , Turktas Ipek
Published: February 2014

Background

Although symptoms and signs of allergic rhinitis (AR) and nonallergic rhinitis (NAR) are similar, treatment and follow‐up are different. We aimed to find predictive factors that can be used in primary health care to differentiate AR from NAR.

Methods

We made a retrospective analysis of cases aged 6–18 years old who were diagnosed as having chronic rhinitis within a 1‐year period. Skin‐prick tests were done and severity of rhinitis symptoms was recorded on a visual analog scale in all patients.

Results

There were 472 cases whose medical records were complete and included in the analysis. The median age was 11 (interquartile range [IQR], 5) years. AR was diagnosed in 363 patients (76.9%) and was different from NAR with respect to: median age (p = 0.042), seasonality of the symptoms (p = 0.002), persistent symptoms (p = 0.003), moderate/severe according to visual analogue scale (VAS) score (p = 0.017), conjunctivitis (p < 0.001), parental history of AR (p = 0.026), rhinorrhea (p < 0.001), sneezing (p = 0.005), mucosal pallor (p = 0.004), and response to antihistamines (p = 0.035). All parameters with a significance of p < 0.1 between AR and NAR were included in logistic regression analysis. Seasonality, sneezing, moderate/severe rhinitis, and response to antihistamines were identified as significant independent parameters to differentiate AR from NAR.

Conclusion

Features of rhinitis patients with seasonality, sneezing, moderate/severe rhinitis, and response to antihistamines may help in differentiation of AR from NAR at the primary care level.
Heteroatom‐freie Arencobalt‐ und Areneisen‐Katalysatoren für Hydrierungen
Authors: Gärtner Dominik , Welther Alice , Rad Babak Rezaei , Wolf Robert , Jacobi von Wangelin Axel
Published: February 2014

75 Jahre nach der Entdeckung der Hydroformylierung erleben Cobalt‐Katalysatoren eine Renaissance in Hydrierungen. Wir haben Arenmetallate untersucht, in denen die niedervalente Metallspezies nicht durch Heteroatom‐Liganden, sondern durch einfache π‐Kohlenwasserstoffe stabilisiert ist. Kaliumbis(anthracen)cobaltat 1 und ‐ferrat 2 sind synthetische Vorstufen für quasi‐“nackte” anionische Metallspezies. Eine Aggregation wird durch (labile) Koordination der in Hydrierungen vorhandenen π‐Akzeptoren (Olefine, Arene, Carbonylverbindungen) effektiv unterdrückt. Kinetische Studien, NMR‐Spektroskopie und Vergiftungsexperimente in Alkenhydrierungen bestätigen die Bildung eines homogenen Katalysators aus 1, der durch Ligandenaustausch gebildet und durch Koordination an Alkene stabilisiert wird. Das zugrundeliegende Katalysatorkonzept ist komplementär zur Verwendung von Komplexen mit Heteroatom‐Donorliganden in reduktiven Prozessen.
Interaction with the Surrounding Water Plays a Key Role in Determining the Aggregation Propensity of Proteins
Authors: Chong Song‐Ho , Ham Sihyun
Published: February 2014

Understanding the molecular determinants of the relative propensities of proteins to aggregate in a cellular environment is a central issue for treating protein‐aggregation diseases and developing peptide‐based therapeutics. Despite the expectation that protein aggregation can largely be attributed to direct protein–protein interactions, a crucial role the surrounding water in determining the aggregation propensity of proteins both in vitro and in vivo was identified. The overall protein hydrophobicity, defined solely by the hydration free energy of a protein in its monomeric state sampling its equilibrium structures, was shown to be the predominant determinant of protein aggregation propensity in aqueous solution. Striking discrimination of positively and negatively charged residues by the surrounding water was also found. This effect depends on the protein net charge and plays a crucial role in regulating the solubility of the protein. These results pave the way for the design of aggregation‐resistant proteins as biotherapeutics.
Direct Catalytic Enantio‐ and Diastereoselective Mannich Reaction of Isocyanoacetates and Ketimines
Authors: Ortín Irene , Dixon Darren J.
Published: February 2014

A catalytic asymmetric synthesis of imidazolines with a fully substituted β‐carbon atom by a Mannich‐type addition/cyclization reaction of isocyanoacetate pronucleophiles and N‐diphenylphosphinoyl ketimines has been developed. When a combination of a cinchona‐derived aminophosphine precatalyst and silver oxide was employed as a binary catalyst system, good reactivity, high diastereoselectivities (up to 99:1 d.r.), and excellent enantioselectivities (up to 99 % ee) were obtained for a range of substrates.
Supercapacitive Swing Adsorption of Carbon Dioxide
Authors: Kokoszka Berenika , Jarrah Nina K. , Liu Cong , Moore David T. , Landskron Kai
Published: February 2014

An electrical effect, the supercapacitive swing adsorption (SSA) effect is reported, which allows for reversible adsorption and desorption of carbon dioxide by capacitive charge and discharge of electrically conducting porous carbon materials. The SSA effect can be observed when an electrically conducting, nanoporous carbon material is brought into contact with carbon dioxide gas and an aqueous electrolyte. Charging the supercapacitor electrodes initiates the spontaneous organization of electrolyte ions into an electric double layer at the surface of each porous electrode. The presence of this double layer leads to reversible, selective uptake and release of the CO2 as the supercapacitor is charged and discharged.
Dual Stimuli‐Responsive Self‐Assembled Supramolecular Nanoparticles
Authors: Stoffelen Carmen , Voskuhl Jens , Jonkheijm Pascal , Huskens Jurriaan
Published: February 2014

Supramolecular nanoparticles (SNPs) encompass multiple copies of different building blocks brought together by specific noncovalent interactions. The inherently multivalent nature of these systems allows control of their size as well as their assembly and disassembly, thus promising potential as biomedical delivery vehicles. Here, dual responsive SNPs have been based on the ternary host–guest complexation between cucurbit[8]uril (CB[8]), a methyl viologen (MV) polymer, and mono‐ and multivalent azobenzene (Azo) functionalized molecules. UV switching of the Azo groups led to fast disruption of the ternary complexes, but to a relatively slow disintegration of the SNPs. Alternating UV and Vis photoisomerization of the Azo groups led to fully reversible SNP disassembly and reassembly. SNPs were only formed with the Azo moieties in the trans and the MV units in the oxidized states, respectively, thus constituting a supramolecular AND logic gate.
Monitoring Conformational Changes in the NDM‐1 Metallo‐β‐lactamase by 19F NMR Spectroscopy
Authors: Rydzik Anna M. , Brem Jürgen , van Berkel Sander S. , Pfeffer Inga , Makena Anne , Claridge Timothy D. W. , Schofield Christopher J.
Published: February 2014

The New Delhi metallo‐β‐lactamase (NDM‐1) is involved in the emerging antibiotic resistance problem. Development of metallo‐β‐lactamases (MBLs) inhibitors has proven challenging, due to their conformational flexibility. Here we report site‐selective labeling of NDM‐1 with 1,1,1‐trifluoro‐3‐bromo acetone (BFA), and its use to study binding events and conformational changes upon ligand–metal binding using 19F NMR spectroscopy. The results demonstrate different modes of binding of known NDM‐1 inhibitors, including L‐ and D‐captopril by monitoring the changing chemical environment of the active‐site loop of NDM‐1. The method described will be applicable to other MBLs and more generally to monitoring ligand‐induced conformational changes.
The Formation and Self‐Assembly of Long Prebiotic Oligomers Produced by the Condensation of Unactivated Amino Acids on Oxide Surfaces
Authors: Martra Gianmario , Deiana Chiara , Sakhno Yuriy , Barberis Ilvis , Fabbiani Marco , Pazzi Marco , Vincenti Marco
Published: February 2014

In situ IR and mass spectrometry evidence for the catalytic formation on SiO2 and TiO2 surfaces of glycine oligomers (poly‐Gly) up to 16 units long by successive feeding with monomers from the vapor phase is presented. Parallel experiments carried out on hydroxyapatite resulted in the unreactive adsorption of Gly, thus indicating that the oligomerization was specifically catalyzed by the surfaces of SiO2 and TiO2. Furthermore, the poly‐Gly moved on the surface when contacted with H2O vapor and formed self‐assembled aggregates containing both helical and β‐sheet‐like structural motifs. These results indicate that polypeptides formed by the condensation of amino acids adsorbed on a mineral surface can evolve into structured supramolecular assemblies.
Defect‐Controlled Electronic Properties in AZn2Sb2 Zintl Phases
Authors: Pomrehn Gregory S. , Zevalkink Alex , Zeier Wolfgang G. , van de Walle Axel , Snyder G. Jeffrey
Published: February 2014

Experimentally, AZn2Sb2 samples (A=Ca, Sr, Eu, Yb) are found to have large charge carrier concentrations that increase with increasing electronegativity of A. Using density functional theory (DFT) calculations, we show that this trend can be explained by stable cation vacancies and the corresponding finite phase width in A1−xZn2Sb2 compounds.
Antibody–Drug Conjugates: An Emerging Concept in Cancer Therapy
Authors: Chari Ravi V. J. , Miller Michael L. , Widdison Wayne C.
Published: February 2014

Traditional cancer chemotherapy is often accompanied by systemic toxicity to the patient. Monoclonal antibodies against antigens on cancer cells offer an alternative tumor‐selective treatment approach. However, most monoclonal antibodies are not sufficiently potent to be therapeutically active on their own. Antibody–drug conjugates (ADCs) use antibodies to deliver a potent cytotoxic compound selectively to tumor cells, thus improving the therapeutic index of chemotherapeutic agents. The recent approval of two ADCs, brentuximab vedotin and ado‐trastuzumab emtansine, for cancer treatment has spurred tremendous research interest in this field. This Review touches upon the early efforts in the field, and describes how the lessons learned from the first‐generation ADCs have led to improvements in every aspect of this technology, i.e., the antibody, the cytotoxic compound, and the linker connecting them, leading to the current successes. The design of ADCs currently in clinical development, and results from mechanistic studies and preclinical and clinical evaluation are discussed. Emerging technologies that seek to further advance this exciting area of research are also discussed.
Heteroatom‐Free Arene‐Cobalt and Arene‐Iron Catalysts for Hydrogenations
Authors: Gärtner Dominik , Welther Alice , Rad Babak Rezaei , Wolf Robert , Jacobi von Wangelin Axel
Published: February 2014

75 years after the discovery of hydroformylation, cobalt catalysts are now undergoing a renaissance in hydrogenation reactions. We have evaluated arene metalates in which the low‐valent metal species is—conceptually different from heteroatom‐based ligands—stabilized by π coordination to hydrocarbons. Potassium bis(anthracene)cobaltate 1 and ‐ferrate 2 can be viewed as synthetic precursors of quasi‐“naked” anionic metal species; their aggregation is effectively impeded by (labile) coordination to the various π acceptors present in the hydrogenation reactions of unsaturated molecules (alkenes, arenes, carbonyl compounds). Kinetic studies, NMR spectroscopy, and poisoning studies of alkene hydrogenations support the formation of a homogeneous catalyst derived from 1 which is stabilized by the coordination of alkenes. This catalyst concept complements the use of complexes with heteroatom donor ligands for reductive processes.
Enantioselective Synthesis of Boron‐Substituted Quaternary Carbon Stereogenic Centers through NHC‐Catalyzed Conjugate Additions of (Pinacolato)boron Units to Enones
Authors: Radomkit Suttipol , Hoveyda Amir H.
Published: February 2014

The first examples of Lewis base catalyzed enantioselective boryl conjugate additions (BCAs) that generate products containing boron‐substituted quaternary carbon stereogenic centers are disclosed. Reactions are performed in the presence of 1.0–5.0 mol % of a readily accessible chiral accessible N‐heterocyclic carbene (NHC) and commercially available bis(pinacolato)diboron; cyclic or linear α,β‐unsaturated ketones can be used and rigorous exclusion of air or moisture is not necessary. The desired products are obtained in 63–95 % yield and 91:9 to >99:1 enantiomeric ratio (e.r.). The special utility of the NHC‐catalyzed approach is demonstrated in the context of an enantioselective synthesis of natural product antifungal (−)‐crassinervic acid.
A Quantitative Relaxometric Version of the ELISA Test for the Measurement of Cell Surface Biomarkers
Authors: Alberti Diego , van't Erve Mark , Stefania Rachele , Ruggiero Maria Rosaria , Tapparo Marta , Geninatti Crich Simonetta , Aime Silvio
Published: February 2014

Quantitative measurement of marker expression in diseased cells is still a topic of considerable interest and different methodologies are currently under intense scrutiny. This work aims at developing an in vitro diagnostic method based on the release of paramagnetic species from relaxometrically “silent” liposomes operated by the action of a phospholipase A2 (PLA2) previously targeted to the epitope of interest. The released paramagnetic species causes an increase of the longitudinal water proton relaxation rate proportional to the number of PLA2 bound to the cell outer surface. The sensitivity of the herein proposed method, named R‐ELISA, was attempted in the detection of folate receptor expression on human ovarian cancer cells by functionalizing PLA2 with folic acid. Receptor/cell number of 8.3×105 has been measured on IGROV‐1 cells. The R‐ELISA assay can detect nanomolar cell suspension receptor concentrations and has been validated by well‐established spectrofluorimetric procedures.
Pressure‐Induced Intersite BiM (M=Ru, Ir) Valence Transitions in Hexagonal Perovskites
Authors: Huang Zixin , Auckett Josie E. , Blanchard Peter E. R. , Kennedy Brendan J. , Miiller Wojciech , Zhou Qingdi , Avdeev Maxim , Johnson Mark R. , Zbiri Mohamed , Garbarino Gaston , Marshall William G. , Gu Qinfen , Ling Chris D.
Published: February 2014

Pressure‐induced charge transfer from Bi to Ir/Ru is observed in the hexagonal perovskites Ba3+nBiM2+nO9+3n (n=0,1; M=Ir,Ru). These compounds show first‐order, circa 1 % volume contractions at room temperature above 5 GPa, which are due to the large reduction in the effective ionic radius of Bi when the 6s shell is emptied on oxidation, compared to the relatively negligible effect of reduction on the radii of Ir or Ru. They are the first such transitions involving 4d and 5d compounds, and they double the total number of cases known. Ab initio calculations suggest that magnetic interactions through very short (ca. 2.6 Å) MM bonds contribute to the finely balanced nature of their electronic states.
Diamond: Electronic Ground State of Carbon at Temperatures Approaching 0 K
Authors: Grochala Wojciech
Published: February 2014

The relative stability of graphite and diamond is revisited with hybrid density functional theory calculations. The electronic energy of diamond is computed to be more negative by 1.1 kJ mol−1 than that of graphite at T=0 K and in the absence of external pressure. Graphite gains thermodynamic stability over diamond at 298 K only because of the differences in the zero‐point energy, specific heat, and entropy terms for both polymorphs.
Comparison of preparation methods for iron–alumina oxygen carrier and its reduction kinetics with hydrogen in chemical looping combustion
Authors: Zhao Haibo , Mei Daofeng , Ma Jinchen , Zheng Chuguang
Published: February 2014

Seven preparation methods, namely sol‐gel, co‐precipitation, hydrothermal synthesis, low heating solid‐state reaction, freeze granulation, combustion synthesis, and mechanical mixing, were used to synthesize Fe2O3/Al2O3 oxygen carrier for chemical looping combustion. A comprehensive physicochemical characterization (i.e. productivity, crushing strength, crystalline characteristics, microstructure, and chemical reactivity with hydrogen) was carried out, and the effects of preparation methods and processes on the oxygen carrier performance were explored. Taking into consideration various physicochemical indices, the sol‐gel method and the freeze granulation method were preferred for oxygen carrier preparation. Following that, a critical chemical reaction in in situ gasification chemical looping combustion, the reduction reaction between oxygen carrier and hydrogen, was clarified in terms of reaction kinetics through the non‐isothermal kinetics analysis and the double extrapolation method. Temperature programmed reduction experiments of the sol‐gel‐derived Fe2O3/Al2O3 particle and hydrogen were performed using a chemisorption analyzer. The reduction mechanisms and kinetics parameters for the two‐stage reaction (reduced from Fe2O3 to Fe3O4 and then from Fe3O4 to FeAl2O4) were determined. In the first stage, the reduction reaction is described by the surface reaction model with an order of 2; on the other hand, the conversion from Fe3O4 to FeAl2O4 is dominated by the nucleation and nuclei growth process. © 2014 Curtin University of Technology and John Wiley & Sons, Ltd.
Acrylonitrile–butadiene–styrene/poly(vinyl acetate)/nanosilica mixed matrix membrane for He/CH4 separation
Authors: Bandehali Samaneh , Kargari Ali , Moghadassi Abdolreza , Saneepur Hamidreza , Ghanbari Davood
Published: February 2014

In the present work, the separation of He/CH4 through different polymeric membranes has been considered. In this regard, composite flat sheet membranes are prepared from blending acrylonitrile–butadiene–styrene (ABS) with different amounts of poly(vinyl acetate) (PVAc) (0–40 wt%). Gas permeability/selectivity analyses as well as the pressure effects were studied for the prepared membranes. The results demonstrated that the ABS/PVAc (20 wt%) membrane revealed higher permselectivity. Afterwards, novel mixed matrix membranes were prepared by incorporating 1–5 wt% SiO2 nanoparticles into the ABS/PVAc (20 wt%). Additionally, further modification was carried out with the addition of styrene–butadiene–rubber (SBR) (5–15 wt%). The primary results of the prepared mixed matrix membranes showed a significant increase in the He permeability together with a decrease in He/CH4 selectivity by incorporating the SiO2 nanoparticles into the blend membranes. Finally, with the introduction of SBR, the (He permeability) selectivity was enhanced from (6.30 Barrer) 45 for the neat ABS/PVAc (20 wt%) to (42.39 Barrer) 51.88 for the ABS/PVAc (20 wt%)/SiO2 (3 wt%)/SBR (15 wt%) membrane. © 2014 Curtin University of Technology and John Wiley & Sons, Ltd.
Synthesis and characterization of fluorene‐based polybenzimidazole copolymer for gas separation
Authors: Han Jun Young , Lee Ju Yeon , Kim Hyoung‐Juhn , Kim Man‐Ho , Han Su Gyeong , Jang Jong Hyun , Cho Eun Ae , Yoo Sung Jong , Henkensmeier Dirk
Published: February 2014

The purpose of this study is to develop new cardo‐polybenzimidazole (CPBI) copolymers containing cardo fluorene, with improved gas permeability, specifically oxygen permeability. The characteristics of these copolymers are investigated by Fourier transform infrared spectroscopy, nuclear magnetic resonance, 1H and 13C), thermo‐gravimetric analysis, and wide‐angle X‐ray diffraction. These membranes fabricated from copolymers have relatively high oxygen diffusion coefficients, determined using gas permeation. In particular, the CPBI‐co91 (synthesized by using the monomers ratio containing dibenzoic acid = 9 : 1) membrane have oxygen permeability coefficient (PO2) of 10.69 Barrer, theoretical selectivity of 5.4 for oxygen to nitrogen, and O2 diffusion coefficient of 9.64 × 10−8 cm2/s. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40521.
Synthesis of end‐functionalized poly(N‐isopropyl acrylamide) with zinc porphyrin and its photocatalytic activity under visible light
Authors: Qiu Nannan , Li Yanhui , Han Shuangli , Satoh Toshifumi , Kakuchi Toyoji , Duan Qian
Published: February 2014

A series of well‐defined linear poly(N‐isopropyl acrylamide) with an asymmetrical zinc(II) porphyrin (ZnPor–PAM) end group was synthesized by atom transfer radical polymerization, wherein 5,10,15,20‐tetra(p‐bromopropanoyloxyethylphenyl) zinc porphyrin tripropionate was used as the initiator and CuBr/tris(2‐dimeoethyl)amine was used as the catalyst system. The structure of the ZnPor–PAM was characterized by Fourier transform infrared spectroscopy and 1H‐NMR. In addition, the polydispersity index (PDI) obtained by gel permeation chromatography indicated that the molecular weight distribution was narrow; thus, the polymerization was well controlled (1.05 < PDI < 1.21). Because of the incorporation of hydrophobic porphyrin, the lower critical solution temperature of ZnPor–PAM was lower than that of the N‐isopropyl acrylamide homopolymer. Most interestingly, the ZnPor–PAM possessed remarkable photocatalytic activity for the oxidative degradation of methylene blue in the presence of hydrogen peroxide under visible‐light radiation. Moreover, ZnPor–PAM could be reused through the uncomplicated procedure, which exploited the thermoresponsive properties of ZnPor–PAM without any significant loss in activity. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40523.
PROSTAGLANDIN MEDIATES DOWN‐REGULATION OF PHENOLOXIDASE ACTIVATION OF Spodoptera exigua VIA PLASMATOCYTE‐SPREADING PEPTIDE‐BINDING PROTEIN
Authors: Park Jiyeong , Kim Yonggyun
Published: February 2014

Insect immunity is innate and highly efficient to defend against various pathogens. However, uncontrolled excessive immune responses would be highly detrimental and energy‐consuming processes. An insect cytokine, plasmatocyte‐spreading peptide (SePSP), induces hemocyte‐spreading behavior as well as activates phenoloxidase (PO) in the beet armyworm, Spodoptera exigua. A hemocyte transcriptome of S. exigua contains a partial sequence of a putative PSP‐binding protein (SePSP‐BP1). SePSP‐BP1 was expressed in most larval stages except in the last instar. However, a bacterial challenge induced SePSP‐BP1 expression in the last instar especially in hemocytes and fat body. Injecting a double‐stranded RNA specific to SePSP‐BP1 (dsPSP‐BP1) suppressed the induction of SePSP‐BP1 expression in response to bacterial challenge. The larvae treated with dsPSP‐BP1 suffered high mortality to infection of nonpathogenic bacteria due to uncontrolled high PO activity. SePSP significantly induced PO activity. The eicosanoid synthesis inhibitor, dexamethasone (DEX), inhibited SePSP‐mediated PO activation. However, treatment with prostaglandin E2 (PGE2) induced a transient increase of PO activity under DEX treatment. Treatment of dsPSP decreased the duration of PO activation induced by PGE2, while treatment of dsPSP‐BP1 increased the induced period. These results suggest that prostaglandin mediates PSP signals in both upregulation of PO activity and its subsequent downregulation via SePSP‐BP1.
Cr3+:SrGa12O19: A Broadband Near‐Infrared Long‐Persistent Phosphor
Authors: Xu Ju , Chen Daqin , Yu Yunlong , Zhu Wenjuan , Zhou Jiangchong , Wang Yuansheng
Published: February 2014

Cr3+‐doped SrGa12O19 is demonstrated to be a broadband near‐infrared (650–950 nm) long‐persistent phosphor whose luminescence can last for more than 2 h after ultraviolet irradiation is stopped. Detailed analysis of the photoluminescence and thermoluminescence spectra and of the persistent decay behavior of the Cr3+‐doped SrGa12O19 samples indicate that the persistent energy transfer from the SrGa12O19 host to the Cr3+ ions and the filling and release of electrons into and from the shallow and deep traps through the conduction band is responsible for the long‐persistent phosphorescence.
Consequences of Block Sequence on the Orthogonal Folding of Triblock Copolymers
Authors: Hosono Nobuhiko , Stals Patrick J. M. , Palmans Anja R. A. , Meijer E. W.
Published: February 2014

ABA‐ and BAB‐type triblock copolymers possessing pendant, self‐assembling motifs in the A and B blocks were synthesized, with 2‐ureidopyrimidinone (UPy) and benzene‐1,3,5‐tricarboxamide (BTA) for the A and B block, respectively. They were investigated to assess if and how the polymer’s microstructure influences the self‐assembly behavior of the supramolecular motifs and, as a result, the single‐chain folding process. BAB‐type triblock copolymers were synthesized via atom transfer radical polymerization (ATRP) with molecular weights ranging from 30 to 120 kg mol−1; the BTA and UPy motifs were attached using a post‐functionalization approach. The ABA‐type triblock copolymers were available from previous work. In highly dilute solutions, both types of triblock copolymers fold into single‐chain polymeric nanoparticles (SCPNs) via thermally induced BTA self‐assembly and photo‐triggered UPy dimerization. Chain collapse induced by intramolecular UPy dimerization was evaluated using size‐exclusion chromatography (SEC). The BTA self‐assembly was monitored by circular dichroism (CD) spectroscopy. The microstructures of SCPNs were visualized by atomic force microscopy (AFM). SEC analysis indicated a more loose packing for the BAB‐type folded nanoparticles than for the ABA‐type ones, which implies that topological differences in the polymer architecture do affect the folding behavior, although only slightly. The facile synthetic protocol developed here provides topologically different triblock architectures and opens up the area for single‐chain folding technology that is applicable in artificial enzymatic systems with compartmentalized domains.
Inhibitory effect of ciprofloxacin on β‐glucuronidase‐mediated deconjugation of mycophenolic acid glucuronide
Authors: Kodawara Takaaki , Masuda Satohiro , Yano Yoshitaka , Matsubara Kazuo , Nakamura Toshiaki , Masada Mikio
Published: February 2014

The interaction between mycophenolate (MPA) and quinolone antibiotics such as ciprofloxacin is considered to reduce the enterohepatic recycling of MPA, which is biotransformed in the intestine from MPA glucuronide (MPAG) conjugate excreted via the biliary system; however, the molecular mechanism underlying this biotransformation of MPA is still unclear. In this study, an in vitro system was established to evaluate β‐glucuronidase‐mediated deconjugation and to examine the influence of ciprofloxacin on the enzymatic deconjugation of MPAG and MPA resynthesis. Resynthesis of MPA via deconjugation of MPAG increased in a time‐dependent manner from 5 to 60 min in the presence of β‐glucuronidase. Ciprofloxacin and phenolphthalein‐β‐d‐glucuronide (PhePG), a typical β‐glucuronidase substrate, significantly decreased the production of MPA from MPAG in the β‐glucuronidase‐mediated deconjugation system. In addition, enoxacin significantly inhibited the production of MPA from MPAG, while levofloxacin and ofloxacin had no inhibitory effect on MPA synthesis. Pharmacokinetic analysis revealed that ciprofloxacin showed a dose‐dependent inhibitory effect on MPA production from MPAG via β‐glucuronidase with a half‐maximal inhibitory concentration (IC50) value of 30.4 µm. While PhePG inhibited the β‐glucuronidase‐mediated production of MPA from MPAG in a competitive manner, ciprofloxacin inhibited MPA synthesis via noncompetitive inhibition. These findings suggest that the reduction in the serum MPA concentration during the co‐administration of ciprofloxacin is at least in part due to the decreased enterohepatic circulation of MPA because of noncompetitive inhibition of deconjugation of MPAG by intestinal β‐glucuronidase. Copyright © 2014 John Wiley & Sons, Ltd.
Occupational exposure to intermediate frequency and extremely low frequency magnetic fields among personnel working near electronic article surveillance systems
Authors: Roivainen Päivi , Eskelinen Tuomo , Jokela Kari , Juutilainen Jukka
Published: February 2014

Cashiers are potentially exposed to intermediate frequency (IF) magnetic fields at their workplaces because of the electronic article surveillance (EAS) systems used in stores to protect merchandise against theft. This study aimed at investigating occupational exposure of cashiers to IF magnetic fields in Finnish stores. Exposure to extremely low frequency (ELF) magnetic fields was also evaluated because cashiers work near various devices operating with 50 Hz electric power. The peak magnetic flux density was measured for IF magnetic fields, and was found to vary from 0.2 to 4 µT at the cashier's seat. ELF magnetic fields from 0.03 to 4.5 µT were found at the cashier's seat. These values are much lower than exposure limits. However, according to the International Commission on Non‐Ionizing Radiation Protection (ICNIRP) occupational reference levels for IF magnetic fields (141 µT for the peak field) were exceeded in some cases (maximum 189 µT) for short periods of time when cashiers walked through the EAS gates. As the ICNIRP reference levels do not define any minimum time for exposure, additional investigations are recommended to determine compliance with basic restrictions. Even if the basic restrictions are not exceeded, persons working near EAS devices represent an exceptional group of workers with respect to exposure to electromagnetic fields. This group could serve as a basis for epidemiological studies addressing possible health effects of IF magnetic fields. Compliance with the reference levels for IF fields was evaluated using both broadband measurement of peak fields and the ICNIRP summation rule for multiple frequencies. The latter was generally more conservative, and the difference between the two methods was large (>10‐fold) for EAS systems using a 58 kHz signal with complex waveform. This indicates that the ICNIRP multiple frequency rule can be unnecessarily conservative when measuring complex waveforms. Bioelectromagnetics. 35:245–250, 2014. © 2014 Wiley Periodicals, Inc.