bluuebunny/crossref_metadata_2025 huggingface dataset:
In vitrodetection of apoptosis using oscillating and pulsed gradient diffusion magnetic resonance imaging
Authors: Portnoy S. , Fichtner N. D. , Dziegielewski C. , Stanisz M. P. , Stanisz G. J.
Published: January 2014

Cellular apoptosis, a common pathway towards tumor regression, is induced by many radiotherapy and chemotherapy regimens. Imaging methods that can detect apoptosis may be able to assess treatment response earlier than typical tumor volume measurements. In this paper, a wide range of diffusion experiments and a simple model of diffusion in tissues were used to probe the microstructural effects of apoptosis. Experiments were conducted on acute myeloid leukemia cell pellets, where apoptosis was induced by treatment with the chemotherapeutic agent cisplatin. Seventy‐two hours following cisplatin treatment, pulsed and oscillating gradient diffusion measurements were utilized to assess effects across a broad range of structural scales.

The presence of apoptosis, which was histologically confirmed by TUNEL (terminal deoxynucleotidyl transferase UTP nick end labelling) staining, significantly changed diffusion properties. To describe these changes, the data were fit to the parallel plane model, which characterizes the effects of restricted diffusion in terms of three parameters:d, the restricted size,Dfree, the intrinsic, free diffusion coefficient of the solvent, andDrest, the long time or “restricted” diffusion coefficient. Apoptotic samples exhibited significant decreases in parametersdandDfreeand a significant increase inDrest. These changes appear consistent with the established morphological effects of apoptosis. In particular, the decrease indmay be a result of the combined effects of cell shrinkage, nuclear fragmentation and membrane blebbing, the decrease inDfreemay relate to cytosolic condensation, while the increase inDrestcan be attributed to increased membrane permeability and extracellular volume fraction. By non‐invasively detecting apoptosis, the methods reported in this study have the potential to improve upon current MRI methods for monitoring therapeutic response. Furthermore, these methods may offer sufficient specificity to differentiate between apoptosis and other modes of cell death, such as oncosis or necrosis. Copyright © 2014 John Wiley & Sons, Ltd.
The state of public affairs in Bulgaria
Authors: Mihova Meglena
Published: January 2014

This paper studies the recent post‐communist developments of linkages amongst organisations, society and government in Bulgaria.

I argue that public affairs is in a very early, embryonic stage of development. This is to a large extent due to the very slow re‐establishment of the non‐centralised market economy; this is very specific to Bulgaria compared with the rest of the Central and Eastern European countries and can be explained by the significant heritage from the communist period. Today, the economic actors in Bulgaria are represented by two extremes—a myriad of small and medium enterprises, lacking the capacity and resources to develop government relations, and a few monopolistic groups with an unclear structure and ownership, which are influencing the government policy in a non‐transparent way. Despite the exceptionally strong state tradition, the government institutions are very often paralysed by the lack of long‐term political vision. As a result, the government was and is still easily subject to external influences. However, the situation is progressively changing, although not without external pressure from the European Union and the internal pressure of foreign investors. Public affairs will therefore develop at the speed of the development of political democracy, a modern corporate culture and the establishment of economic operators with long‐term vision and interests. The profession of public affairs consultant, almost non‐existent today, will then progressively find its natural place, acting as a catalyst for the development of business–government–society linkages. Copyright © 2014 John Wiley & Sons, Ltd.
Temperature‐dependent structure and magnetism of Mn‐doped Ge nanowires
Authors: Majumdar S. , Bhaumik S. , Rana K. , Ray S. K. , Das A. K.
Published: January 2014

We report a study on the growth temperature dependent phase formation and its magnetic property in Mn‐doped Ge nanowires (NWs) fabricated at temperature (TG) varying from 600 to 900 °C using vapor–liquid–solid technique. Structural and magnetic measurements on the nanowires reveal that Mn are not homogeneously distributed in Ge‐matrix, but atomic clusters (Mn‐rich regions) are formed in lightly doped Ge matrix (GeMn‐matrix) at 600 °C. Upon increasing TG, Ge3Mn5 compound starts to nucleate in expense of atomic clusters following the migration of Mn from GeMn‐matrix. At 900 °C, only precipitates of Ge3Mn5 in cluster‐free Ge‐matrix are found.
Measuring students' continuing motivation for science learning
Authors: Fortus David , Vedder‐Weiss Dana
Published: January 2014

Continuing motivation for science learning may be manifested through engagement in extracurricular science‐related activities, which are not the result of school or other external requirements. Very few articles have appeared in the last decade on this important aspect of science learning. This article presents a survey based on seven Likert‐type items for measuring adolescents' continuing motivation for science. It describes how the survey was developed, tested, and used to explore the relations between school type, grade, and gender and adolescents' continuing motivation for science learning. Data on the continuing motivation of 2,958 Israeli 5th–8th grade students, from traditional and democratic schools, were collected and analyzed using polytomous Rasch techniques and hierarchical linear modeling. The results indicate that in both types of schools girls had lower continuing motivation for science than boys, and that while the continuing motivation of both boys and girls in traditional schools decreased between 5th and 8th grade, the continuing motivation of students in democratic schools remained constant during this period. © 2014 Wiley Periodicals, Inc. J Res Sci Teach 51: 497–522, 2014
The ecology and biodiversity of urban ponds
Authors: Hassall Christopher
Published: January 2014

Recent research has demonstrated that ponds contribute a great deal to biodiversity at a regional level as networks of habitat patches that also act as ‘stepping stones’ to facilitate the movement of species through the landscape. Similarly, a great deal of biodiversity persists in urban environments where synanthropic communities are supplemented by species that thrive in disturbed environments. Aquatic urban biodiversity appears to persist despite anthropogenic stressors: an array of anthropogenic pollutants (road salt and heavy metals), invasive species, and active mismanagement—particularly the removal of riparian vegetation. Optimizing urban ponds for different ecosystem services results in conflicting priorities over hydrological, geochemical, ecological, aesthetic, and cultural functions. The socio‐ecosystem approach to environmental management opens a path to greater incorporation of biodiversity into town planning and sustainability, while accounting for cultural attitudes to urban ecosystems. I identify a range of research needs: (1) the roles of design and location of urban ponds in influencing biodiversity, (2) the function of urban wetlands for stormwater and pollution management, and (3) public perceptions of urban ecosystems and how those perceptions are influenced by interactions with natural systems. Urban wetlands offer an important opportunity to educate the general public on natural systems and science in general using a resource that is located on their doorstep. In the face of increasing pressures on natural systems and increasing extent and intensity of urbanization, a more comprehensive appreciation of the challenges and opportunities provided by urban ponds could play a substantial role in driving sustainable urban development.

This article is categorized under:

Water and Life > Conservation, Management, and Awareness

Water and Life > Nature of Freshwater Ecosystems

Water and Life > Stresses and Pressures on Ecosystems
Synthesis and Crystal Structure of Two CuII‐benzene‐1,2,4,5‐tetracarboxylates with Three‐Dimensional Open Frameworks
Authors: Köferstein Roberto , Robl Christian
Published: January 2014

Two new three‐dimensional frameworks with zeolite‐like channels were prepared in the presence of 1,6‐diaminohexane. Cu1.5(H3N–(CH2)6–NH3)0.5[C6H2(COO)4]·5H2O (1) crystallizes in the triclinic space group P$\bar{1}$ with a = 772.56(7), b = 1110.36(7), c = 1111.98(8) pm, α = 98.720(7)°, β = 108.246(9)°, and γ = 95.559(7)°. Cu2(H3N–(CH2)6–NH3)0.5(OH)[C6H2(COO)4]·3H2O (2) crystallizes in the monoclinic space group P2/c with a = 1159.34(11), b = 1059.44(7), c = 1582.2(2) pm, and β = 106.130(11)°. The Cu2+ coordination polyhedra are connected by [C6H2(COO)4]4– anions to yield three‐dimensional frameworks with wide centrosymmetric channel‐like voids. Complex 1 reveals voids extending along [100] with diagonals of 900 pm and 300 pm, whereas in complex 2 the diagonal of the nearly rectangular crossection of the channels extending parallel to [001] is 900 pm. The negative excess charges of the frameworks are compensated by [H3N–(CH2)6–NH3]2+ cations, which occupy the voids along with water molecules. The [H3N–(CH2)6–NH3]2+ cations are not connected to Cu2+ and have served as templates.
Chemical Bonding in Zinc‐based Intermetallic Compounds with the CuTi or the CsCl Type of Structure
Authors: Alarcón Villaseca Sebastián , Kandaskalov Dmytro , Gaudry Émilie , Armbrüster Marc
Published: January 2014

The chemical bonding in the intermetallic compounds ZnPd and ZnPt with the tetragonal CuTi type of structure, and in the chemically related intermetallic compounds ZnNi, ZnCu, ZnAg, and ZnAu with the cubic CsCl type of structure, is examined applying the electron localizability approach. The analysis of the chemical bonding reveals charge transfer from zinc to the transition metal (TM), in line with the respective electronegativities. While in ZnNi, ZnCu, and ZnAg as well as ZnPd and ZnPt the Zn–TM interactions are described by multi‐center bonding and ionic interactions, mainly ionic interactions are found in the intermetallic compound ZnAu. Going from ZnNi over ZnPd to ZnPt, a gradual change from isotropic to more and more anisotropic distribution of the atomic interactions is detected, resulting in a more pronounced tetragonal distortion.
Gap junction and hemichannel‐independent actions of connexins on cell and tissue functions – An update
Authors: Zhou Jade Z. , Jiang Jean X.
Published: January 2014

Connexins, a family of transmembrane proteins, are components of both gap junction channels and hemichannels, which mediate the exchange of ions and small molecules between adjacent cells, and between the inside and outside of the cell, respectively. Substantial advancements have been made in the comprehension of the role of gap junctions and hemichannels in coordinating cellular events. In recent years, a plethora of studies demonstrate a role of connexin proteins in the regulation of tissue homeostasis that occurs independently of their channel activities. This is shown in the context of cell growth, adhesion, migration, apoptosis, and signaling. The major mechanisms of these channel‐independent activities still remain to be discovered. In this review, we provide an updated overview on the current knowledge of gap junction‐ and hemichannel‐independent functions of connexins, in particular, their effects on tumorigenesis, neurogenesis and disease development.
Human papillomavirus (HPV)‐18 E6 oncoprotein interferes with the epithelial cell polarity Par3 protein
Authors: Facciuto Florencia , Bugnon Valdano Marina , Marziali Federico , Massimi Paola , Banks Lawrence , Cavatorta Ana Laura , Gardiol Daniela
Published: January 2014

High‐risk human papillomavirus (HPV) infection is the principal risk factor for the development of cervical cancer. The HPV E6 oncoprotein has the ability to target and interfere with several PSD‐95/DLG/ZO‐1 (PDZ) domain‐containing proteins that are involved in the control of cell polarity. This function can be significant for E6 oncogenic activity because a deficiency in cell polarisation is a marker of tumour progression. The establishment and control of polarity in epithelial cells depend on the correct asymmetrical distribution of proteins and lipids at the cell borders and on specialised cell junctions. In this report, we have investigated the effects of HPV E6 protein on the polarity machinery, with a focus on the PDZ partitioning defective 3 (Par3) protein, which is a key component of tight junctions (TJ) and the polarity network. We demonstrate that E6 is able to bind and induce the mislocalisation of Par3 protein in a PDZ‐dependent manner without significant reduction in Par3 protein levels. In addition, the high‐risk HPV‐18 E6 protein promotes a delay in TJ formation when analysed by calcium switch assays. Taken together, the data presented in this study contribute to our understanding of the molecular mechanism by which HPVs induce the loss of cell polarity, with potential implications for the development and progression of HPV‐associated tumours.
Charcot‐Marie‐Tooth Disease: An Overview of Genotypes, Phenotypes, and Clinical Management Strategies
Authors: El‐Abassi Rima , England John D. , Carter Gregory T.
Published: January 2014

Charcot‐Marie‐Tooth (CMT) disease, which encompasses several hereditary motor and sensory neuropathies, is one of the most common neuromuscular disorders. Our understanding of the molecular genotypes of CMT and the resultant clinical and electrophysiological phenotypes has increased greatly in the past decade. Characterized by electrodiagnostic studies into demyelinating (type 1) and axonal (type 2) forms, subsequent genetic testing often provides an exact diagnosis of a specific subtype of CMT. These advancements have made diagnostic paradigms fairly straightforward. Still, the nature and extent of neuromuscular disability is often complex in persons with CMT, and no curative treatments are yet available. Genotypically homologous animal models of CMT have improved exploration of disease‐modifying treatments, of which molecular genetic manipulation and stem cell therapies appear to be the most promising. Research is also needed to develop better rehabilitative strategies that may limit disease burden and improve physical performance and psychosocial integration. Clinical management should be multidisciplinary, including neurologists, physiatrists, neurogeneticists, neuromuscular nurse practitioners, and orthopedists, along with physical and occupational therapists, speech‐language pathologists, orthotists, vocational counselors, social workers, and other rehabilitation clinicians. Goals should include maximizing functional independence and quality of life while minimizing disability and secondary morbidity.
Appalachian Trail Hikers’ Ability to Recognize Lyme Disease by Visual Stimulus Photographs
Authors: Knoll Judith M. , Ridgeway Andrea C. , Boogaerts Christine M. , Burket Glenn A.
Published: January 2014

Background

Lyme disease is the most common vector-borne infectious disease in North America. With nearly 2,500 Appalachian Trail (AT) hikers entering the endemic area for as long as 6 months, exposure to the disease is likely. The characteristic exanthem of erythema migrans (EM) should be a trigger for seeking medical treatment, and its recognition in this relatively isolated environment is important.

Objective

The purpose of this study was to determine the ability of AT hikers to identify EM, the exanthem of Lyme disease.

Methods

Hikers were administered a photographic stimulus in this Internal Review Board–approved pilot study. Historical hiking data, basic demographics, and self-reported treatment and diagnosis were collected.

Results

In all, 379 responses were collected by 4 researchers at 3 geographically separate locations at or proximate to the AT from June 2011 to May 2012. Fifty-four percent of respondents (206 of 379) were able to recognize the photographs of EM/Lyme disease; 46% could not. Of those who did recognize EM, 23 (6%) had seen it either on themselves or on another hiker while on the AT. A total of 37 hikers stated that they had been diagnosed with Lyme disease while hiking, and of these, 89% were treated with antibiotics. Thirteen of these 37 hikers (35%) diagnosed with Lyme disease had visualized an embedded tick. Nine percent of all respondents reported they had been diagnosed with Lyme disease by a healthcare practitioner, whether from EM, symptomatology, or by titer.

Conclusions

This study suggests that hikers are poorly able to recognize the characteristic exanthem of Lyme disease but have a high exposure risk.
Employing Geographical Principles for Sampling in State of the Art Dialectological Projects
Authors: Buchstaller Isabelle , Alvanides Seraphim
Published: January 2014

The aims of this paper are twofold. First, we locate the most effective human geographical methods for sampling across space in large-scale dialectological projects. We propose two geographical concepts as a basis for sampling decisions: Geo-demographic classification, which is a multidimensional method used for the socio-economic grouping of areas; we also develop an updated version of functional regions that can be used in sociolinguistic research. We then report on the results of a pilot project that applies these models to collect data regarding the acceptability of vernacular morphosyntactic forms in the North East of England. Following the method of natural breaks advocated for dialectology by Horvath & Horvath (2002), we interpret breaks in the probabilistic patterns as areas of dialect transitions. This study contributes to the debate about the role and limitations of spatiality in linguistic analysis. It intends to broaden our knowledge about the interfaces between human geography and dialectology.
Experimental study on the aetiology of benign paroxysmal positional vertigo due to canalolithiasis: comparison between normal and vestibular dysfunction models
Authors: Otsuka K , Negishi M , Suzuki M , Inagaki T , Yatomi M , Konomi U , Kondo T , Ogawa Y
Published: January 2014

Objectives:

Using American bullfrog models under normal conditions and under vestibular dysfunction, we investigated whether mechanical vibration applied to the ear could induce otoconial dislodgement.

Methods:

Vibration was applied to the labyrinth of the bullfrog using a surgical drill. The time required for the otoconia to dislodge from the utricular macula was measured. Vestibular dysfunction models were created and the dislodgement time was compared with the normal models. The morphology of the utricular macula was also investigated.

Results:

In the normal models, the average time for otoconial dislodgement to occur was 7 min and 36 s; in the vestibular dysfunction models, it was 2 min and 11 s. Pathological investigation revealed that the sensory hairs of the utricle were reduced in number and that the sensory cells became atrophic in the vestibular dysfunction models.

Conclusion:

The otoconia of the utricle were dislodged into the semicircular canal after applying vibration. The time to dislodgement was significantly shorter in the vestibular dysfunction models than in the normal models; the utricular macula sustained significant morphological damage.
A two-cycle prospective audit of temporal bone computed tomography scan requests: improving the clinical applicability of radiology reports
Authors: Qureishi A , Garas G , Shah J , Birchall J
Published: January 2014

Background:

Radiologists require accurate clinical information to formulate reports. This is particularly relevant to computed tomography of the temporal bone, in which previous surgery can mimic disease.

Objectives:

The information provided with temporal bone computed tomography scan requests was evaluated. The study aimed to minimise inappropriate requests and improve the clinical value of reports.

Method:

A two-cycle prospective audit was undertaken using a proforma designed on the basis of national guidelines. Following the first cycle (in which the requests and reports of 100 scans were evaluated), new guidelines and training were implemented. A follow-up audit (of 50 scans) was then performed.

Results:

Following intervention, the percentage of clinically relevant reports increased from 52 to 94 (p < 0.01), whilst unnecessary or inappropriate scan requests decreased from 11 to 2 per cent (p < 0.05).

Conclusion:

Optimising the clinical value of temporal bone computed tomography scan requests will have positive implications for patient care, time management and cost. The quality of the clinical information provided can have a significant impact on the clinical value of radiology reports, and can mean that unnecessary irradiation is avoided.
Vocabularies for human development: Arctic politics and the power of knowledge
Authors: Sinevaara-Niskanen Heidi
Published: January 2014

The Arctic Council (AC) has been accorded the status of knowledge holder and knowledge provider for the Arctic region. This paper probes the broader definition-making power of Arctic knowledge, challenging the common notion that this knowledge is value neutral. It argues that attention should be paid to the ways in which power is exercised in, and though, the various reports and assessments published under the auspices of the AC. The specific focus of the paper is human development and gender as an aspect of that development. The research analyses the Arctic Human Development Report (AHDR) in order to examine the ways in which knowledge defines human development and its agents in the Arctic. The paper draws on Foucault-inspired and feminist approaches to analyse three vocabularies of rule in particular: strength of the community, vulnerability and the need for adaptation. These vocabularies are coexistent and share an emphasis on communities. Yet, questions of gender seldom figure in them, a lack of salience that reveals the power of the partiality of knowledge. The politics of knowledge operate by placing in the foreground only certain accounts of Arctic development.
Simulations of shipping along Arctic routes: comparison, analysis and economic perspectives
Authors: Lasserre Frédéric
Published: January 2014

Arctic sea routes have for long been of interest for shipping because of much shorter distances between the Atlantic and the Pacific. Sea ice prevented real development of significant traffic, but did not prevent research from trying to assess their economic viability. With the melting of sea ice in the Arctic, this effort at modeling the profitability of Arctic shipping routes has received a new impetus. However, the conclusions of these studies vary widely, depending on the parameters chosen and their value. What can be said of these models, from 1991 until 2013, and to what extent can a model be drawn, capitalising on twenty years of simulations?
High-voltage pulse modulator based on cylindrical self-coupling saturable pulse transformer and solid-state Marx generator
Authors: Zhang Yu , Liu Jinliang
Published: January 2014

High-voltage pulse modulator has broad applications in industry. In order to pursue the qualities of compactness, solidification, and long life time, a high-voltage pulse modulator based on a helical Blumlein pulse forming line (HBPFL),a Marx generator and a self-coupling saturable pulse transformer (SPT) with fully cylindrical coaxial conductors is put forward and investigated in this paper. A new method that the fully cylindrical SPT simultaneously works as the charging pulse transformer and magnetic switch of the HBPFL is put forward and demonstrated. Traditional spark gap is substituted by the SPT to enable the features of solidification, compactness, and long life time of the modulator. Experimental results showed that the SPT had good response characteristics to short sinusoidal pulse and 100 ns-range square pulses. The fully cylindrical SPT driven by the 50–70 kV Marx generator can suppress the saturated inductance of the secondary windings to a level less than 500 nH, due to the strong reversed mutual induction between cylindrical windings after the core saturated. It also demonstrated that the pulse modulator was able to deliver a high-voltage pulse to a 160 Ω load, with amplitude of 148 kV, pulse duration of 130 ns, and pulse rise time ranging from 60 to 105 ns.
Validation of a self-administered FFQ in adults in Argentina, Chile and Uruguay
Authors: Elorriaga Natalia , Irazola Vilma E , Defagó María D , Britz Mónica , Martínez-Oakley Solange P , Witriw Alicia M , Rubinstein Adolfo L
Published: January 2014

Objective

To assess the reproducibility and validity among adults in the Southern Cone of Latin America (Argentina, Chile and Uruguay) of a self-administered FFQ to be used in the CESCAS I Study, an ongoing observational prospective cohort study to detect and follow up CVD and their risk factors, as well as in other epidemiological studies.

Design

Relative validity of the FFQ was evaluated by comparing nutrient and selected food group intakes with those from three 24 h recalls (24HR) administered over 6 months. The FFQ was administered at baseline (FFQ1) and again after 3 months (FFQ2).

Setting

Primary-care centres in Argentina, Chile and Uruguay.

Subjects

Adults (n147) aged 21–74 years.

Results

Reproducibility (FFQ1v. FFQ2): the intra-class correlation coefficients for nutrients ranged from 0·52 (potassium) to 0·74 (fat). Validity (FFQ1v. the average of three 24HR): the Pearson correlations for energy-adjusted nutrients ranged from 0·39 (thiamin and cholesterol) to 0·59 (carbohydrate). Joint classification: overall, 66 % of participants in the lowest 24HR quintile were in the lowest one or two FFQ1 quintiles, and 62 % of those in the highest 24HR quintile were in the highest one or two FFQ1 quintiles. On average, only 4 % were misclassified into extreme quintiles.

Conclusions

The FFQ version for the Southern Cone seems to present moderate to acceptable relative validity and reliability for its use in the CESCAS I Study to measure dietary exposure.
Quantification of strain and charge co-mediated magnetoelectric coupling on ultra-thin Permalloy/PMN-PT interface
Authors: Nan Tianxiang , Zhou Ziyao , Liu Ming , Yang Xi , Gao Yuan , Assaf Badih A. , Lin Hwaider , Velu Siddharth , Wang Xinjun , Luo Haosu , Chen Jimmy , Akhtar Saad , Hu Edward , Rajiv Rohit , Krishnan Kavin , Sreedhar Shalini , Heiman Don , Howe Brandon M. , Brown Gail J. , Sun Nian X.
Published: January 2014

Strain and charge co-mediated magnetoelectric coupling are expected in ultra-thin ferromagnetic/ferroelectric multiferroic heterostructures, which could lead to significantly enhanced magnetoelectric coupling. It is however challenging to observe the combined strain charge mediated magnetoelectric coupling and difficult in quantitatively distinguish these two magnetoelectric coupling mechanisms. We demonstrated in this work, the quantification of the coexistence of strain and surface charge mediated magnetoelectric coupling on ultra-thin Ni0.79Fe0.21/PMN-PT interface by using a Ni0.79Fe0.21/Cu/PMN-PT heterostructure with only strain-mediated magnetoelectric coupling as a control. The NiFe/PMN-PT heterostructure exhibited a high voltage induced effective magnetic field change of 375 Oe enhanced by the surface charge at the PMN-PT interface. Without the enhancement of the charge-mediated magnetoelectric effect by inserting a Cu layer at the PMN-PT interface, the electric field modification of effective magnetic field was 202 Oe. By distinguishing the magnetoelectric coupling mechanisms, a pure surface charge modification of magnetism shows a strong correlation to polarization of PMN-PT. A non-volatile effective magnetic field change of 104 Oe was observed at zero electric field originates from the different remnant polarization state of PMN-PT. The strain and charge co-mediated magnetoelectric coupling in ultra-thin magnetic/ferroelectric heterostructures could lead to power efficient and non-volatile magnetoelectric devices with enhanced magnetoelectric coupling.
Miniaturised silicon biosensors for the detection of triglyceride in blood serum
Authors: Veeramani Mohanasundaram Sulur , Shyam Karuppiah Prakash , Ratchagar Noel Prashant , Chadha Anju , Bhattacharya Enakshi
Published: January 2014

This paper reports on the design and fabrication of electrolyte insulator semiconductor capacitor (EISCAP) devices to detect triglycerides in the form of microreactors fabricated by bulk micromachining of silicon.
Genetically encoded self-assembly of large amyloid fibers
Authors: Ridgley D. M. , Freedman B. G. , Lee P. W. , Barone J. R.
Published: January 2014

Experimental results demonstrate that large amyloid fibers can be engineered at the DNA level, spanning four orders of magnitude.
The role of isovalency in the reactions of the cyano (CN), boron monoxide (BO), silicon nitride (SiN), and ethynyl (C2H) radicals with unsaturated hydrocarbons acetylene (C2H2) and ethylene (C2H4)
Authors: Parker D. S. N. , Mebel A. M. , Kaiser R. I.
Published: January 2014

The classification of chemical reactions based on shared characteristics is at the heart of the chemical sciences, and is well exemplified by Langmuir's concept of isovalency, in which ‘two molecular entities with the same number of valence electrons have similar chemistries’.
Pyridine imines as ligands in luminescent iridium complexes
Authors: Davies David L. , Lelj Francesco , Lowe Mark P. , Ryder Karl S. , Singh Kuldip , Singh Shalini
Published: January 2014

Biscyclometallated iridium complexes [Ir(ppz)2(X^Y)][PF6] (X^Y = pyridine imine) have been synthesised;N-alkyl complexes are emissive whilstN-aryl ones are only weakly emissive, DFT calculations shed light on the reasons for this difference.
LBP-4a improves insulin resistance via translocation and activation of GLUT4 in OLETF rats
Authors: Zhao Rui , Qiu Bing , Li Qingwang , Zhang Tao , Zhao Hui , Chen Zhibao , Cai Yaping , Ruan Hongsheng , Ge Wenzhong , Zheng Xiaoliang
Published: January 2014

Stimulation of glucose transport by LBP-4a consists of two events: PI3-Kinase-dependent translocation and p38 MAPK-dependent stimulation of the intrinsic activity of GLUT4.
A facile route to realize the copolymerization of l-lactic acid and ε-caprolactone: sulfonic acid-functionalized Brønsted acidic ionic liquids as both solvents and catalysts
Authors: Peng Qiaohong , Mahmood Khalid , Wu Ying , Wang Leli , Liang Yanyan , Shen Jianan , Liu Zhengping
Published: January 2014

Biodegradable copolymers of l-lactic acid and ε-caprolactone were prepared in SFBAILs: the effect of ILs and the mechanism.
Important reaction parameters in the synthesis of phenylphosphonic acid functionalized titania particles by reactive milling
Authors: Betke Annika , Kickelbick Guido
Published: January 2014

Surface functionalized titania particles are obtained using a high energy planetary ball mill.
A highly selective colorimetric chemosensor for detection of nickel ions in aqueous solution
Authors: Liu Xin , Lin Qi , Wei Tai-Bao , Zhang You-Ming
Published: January 2014

A highly selective colorimetric chemosensor LX was described, which could instantly detect Ni2+ without interference by other cations.
NiCo2S4 sub-micron spheres: an efficient non-precious metal bifunctional electrocatalyst
Authors: Zhang Zhongyi , Wang Xiaogang , Cui Guanglei , Zhang Aihua , Zhou Xinhong , Xu Hongxia , Gu Lin
Published: January 2014

NiCo2S4 sub-micron spheres with hierarchical architectures pave the way for transition metal thiospinels as efficient bifunctional non-precious metal electrocatalysts.
Detection of high-energy compounds using photoluminescent silicon nanocrystal paper based sensors
Authors: Gonzalez Christina M. , Iqbal Muhammad , Dasog Mita , Piercey Davin G. , Lockwood Ross , Klapötke Thomas M. , Veinot Jonathan G. C.
Published: January 2014

A silicon nanocrystal paper based sensor has been developed for the rapid, on-site detection of nitro-group containing explosive compounds.
Electrochemical study of Alamar Blue (resazurin) in aqueous solutions and room-temperature ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate at a glassy carbon electrode
Authors: Khazalpour Sadegh , Nematollahi Davood
Published: January 2014

Electrochemical behaviour of resazurin in aqueous buffered solutions and ionic liquid was studied. The orientation of adsorbed resazurin was estimated. It is found that, the orientation of the adsorbed resazurin at glassy carbon surface is edgewise.
Strain induced modification in phonon dispersion curves of monolayer boron pnictides
Authors: Jha Prafulla K. , Soni Himadri R.
Published: January 2014

In the frame work of density functional theory, the biaxial strain induced phonon dispersion curves of monolayer boron pnictides (BX, X = N, P, As, and Sb) have been investigated. The electron-ion interactions have been modelled using ultrasoft pseudopotentials while exchange-correlation energies have been approximated by the method of local density approximation in the parameterization of Perdew-Zunger. The longitudinal and transverse acoustic phonon modes of boron pnictide sheets show linear dependency on wave vector k→ while out of plane mode varies as k2. The in-plane longitudinal and out of plane transverse optical modes in boron nitride displaying significant dispersion similar to graphene. We have analyzed the biaxial strain dependent behaviour of out of plane acoustic phonon mode which is linked to ripple for four BX sheets using a model equation with shell elasticity theory. The strain induces the hardening of this mode with tendency to become more linear with increase in strain percentage. The strain induced hardening of out of plane acoustic phonon mode indicates the absence of rippling in these compounds. Our band structure calculations for both unstrained and strained 2D h-BX are consistent with previous calculations.
Dielectric properties of halloysite and halloysite-formamide intercalate
Authors: Adamczyk M. , Rok M. , Wolny A. , Orzechowski K.
Published: January 2014

Due to a high increase in electromagnetic pollution, the protection from non-ionizing electromagnetic radiation (EMR) represents an important problem of contemporary environmental science. We are searching for natural materials with the potential for EMR screening. We have discovered that hydro-halloysite has interesting properties as an EMR absorber. Unfortunately, it is a very unstable material. Drying it for even a short period of time leads to the loss of desired properties. In the paper, we have demonstrated that the intercalation of halloysite (the process of introducing guest molecules into the mineral structure) makes it possible to recover the ability to absorb an electromagnetic wave and obtain a promising material for electromagnetic field shielding applications.
Anomalous diameter dependence of thermal transport in ultra-narrow Si nanowires
Authors: Karamitaheri Hossein , Neophytou Neophytos , Kosina Hans
Published: January 2014

We present atomistic valence force field calculations of thermal transport in Si nanowires of diameters from 12 nm down to 1 nm. We show that as the diameter is reduced, the phonon density-of-states and transmission function acquire a finite value at low frequency, in contrast to approaching zero as in the bulk material. It turns out that this effect results in what Ziman described as the “problem of long longitudinal waves” [J. M. Ziman, Electrons and Phonons: The Theory of Transport Phenomena in Solids (Clarendon, Oxford, 1962)], which states that the thermal conductivity of a material increases as its length is increased due to the vanishing scattering for long-wavelength phonons. We show that this thermal transport improvement also appears in nanowires as their diameter is decreased below D = 5 nm (not only as the length increases), originating from the increase in the density of the long wavevector modes. The observation is present under ballistic transport conditions, and further enhanced with the introduction of phonon-phonon scattering. Because of this, in such ultra-narrow nanowires, as the diameter is reduced, phonon transport is dominated more and more by lower energy phonons with longer mean-free paths. We show that ∼80% of the heat is carried by phonons with energies less than 5 meV, most with mean-free paths of several hundreds of nanometers.
Spiral-like multi-beam emission via transformation electromagnetics
Authors: Tichit Paul-Henri , Burokur Shah Nawaz , de Lustrac André
Published: January 2014

Transformation electromagnetics offers an unconventional approach for the design of novel radiating devices. Here, we propose an electromagnetic metamaterial able to split an isotropic radiation into multiple directive beams. By applying transformations that modify distance and angles, we show how the multiple directive beams can be steered at will. We describe transformation of the metric space and the calculation of the material parameters. Different transformations are proposed for a possible physical realization through the use of engineered artificial metamaterials. Full wave simulations are performed to validate the proposed approach. The idea paves the way to interesting applications in various domains in microwave and optical regimes.
The effect of classical and quantum dynamics on vibrational frequency shifts of H2 in clathrate hydrates
Authors: Plattner Nuria , Meuwly Markus
Published: January 2014

Vibrational frequency shifts of H2 in clathrate hydrates are important to understand the properties and elucidate details of the clathrate structure. Experimental spectra of H2 in clathrate hydrates have been measured for different clathrate compositions, temperatures, and pressures. In order to establish reliable relationships between the clathrate structure, dynamics, and observed frequencies, calculations of vibrational frequency shifts in different clathrate environments are required. In this study, a combination of classical molecular dynamics simulations, electronic structure calculations, and quantum dynamical simulation is used to calculate relative vibrational frequencies of H2 in clathrate hydrates. This approach allows us to assess dynamical effects and simulate the change of vibrational frequencies with temperature and pressure. The frequency distributions of the H2 vibrations in the different clathrate cage types agree favorably with experiment. Also, the simulations demonstrate that H2 in the 512 cage is more sensitive to the details of the environment and to quantum dynamical effects, in particular when the cage is doubly occupied. We show that for the 512 cage quantum effects lead to frequency increases and double occupation is unlikely. This is different for the 51264 cages for which higher occupation numbers than one H2 per cage are likely.
Reduced dimension rovibrational variational calculations of the S1 state of C2H2. I. Methodology and implementation
Authors: Changala P. Bryan
Published: January 2014

The bending and torsional degrees of freedom in S1 acetylene, C2H2, are subject to strong vibrational resonances and rovibrational interactions, which create complex vibrational polyad structures even at low energy. As the internal energy approaches that of the barrier to cis-trans isomerization, these energy level patterns undergo further large-scale reorganization that cannot be satisfactorily treated by traditional models tied to local minima of the potential energy surface for nuclear motion. Experimental spectra in the region near the cis-trans transition state have revealed these complicated new patterns. In order to understand near-barrier spectroscopic observations and to predict the detailed effects of cis-trans isomerization on the rovibrational energy level structure, we have performed reduced dimension rovibrational variational calculations of the S1 state. In this paper, we present the methodological details, several of which require special care. Our calculation uses a high accuracy ab initio potential surface and a fully symmetrized extended complete nuclear permutation inversion group theoretical treatment of a multivalued internal coordinate system that is appropriate for large amplitude bending and torsional motions. We also discuss the details of the rovibrational basis functions and their symmetrization, as well as the use of a constrained reduced dimension rovibrational kinetic energy operator.
Reduced dimension rovibrational variational calculations of the S1 state of C2H2. II. The S1 rovibrational manifold and the effects of isomerization
Authors: Changala P. Bryan , Baraban Joshua H. , Stanton John F. , Merer Anthony J. , Field Robert W.
Published: January 2014

Reduced dimension variational calculations have been performed for the rovibrational level structure of the S1 state of acetylene. The state exhibits an unusually complicated level structure, for various reasons. First, the potential energy surface has two accessible conformers, trans and cis. The cis conformer lies about 2700 cm−1 above the trans, and the barrier to cis-trans isomerization lies about 5000 cm−1 above the trans minimum. The trans vibrations ν4 (torsion) and ν6 (asym. bend) interact very strongly by Darling-Dennison and Coriolis resonances, such that their combination levels and overtones form polyads with unexpected structures. Both conformers exhibit very large x36 cross-anharmonicity since the pathway to isomerization is a combination of ν6 and ν3 (sym. bend). Near the isomerization barrier, the vibrational levels show an even-odd K-staggering of their rotational levels as a result of quantum mechanical tunneling through the barrier. The present calculations address all of these complications, and reproduce the observed K-structures of the bending and C–C stretching levels with good qualitative accuracy. It is expected that they will assist with the assignment of the irregular patterns near the isomerization barrier.
Organization of polymer chains onto long, single-wall carbon nano-tubes: Effect of tube diameter and cooling method
Authors: Kumar Sunil , Pattanayek Sudip K. , Pereira Gerald G.
Published: January 2014

We use molecular dynamics simulations to investigate the arrangement of polymer chains when absorbed onto a long, single-wall carbon nano-tube (SWCNT). We study the conformation and organization of the polymer chains on the SWCNT and their dependence on the tube's diameter and the rate of cooling. We use two types of cooling processes: direct quenching and gradual cooling. The radial density distribution function and bond orientational order parameter are used to characterize the polymer chain structure near the surface. In the direct cooling process, the beads of the polymer chain organize in lamella-like patterns on the surface of the SWCNT with the long axis of the lamella parallel to the axis of the SWCNT. In a stepwise, gradual cooling process, the polymer beads form a helical pattern on the surface of a relatively thick SWCNT, but form a lamella-like pattern on the surface of a very thin SWCNT. We develop a theoretical (free energy) model to explain this difference in pattern structures for the gradual cooling process and also provide a qualitative explanation for the pattern that forms from the direct cooling process.
Slow dynamics of nanocomposite polymer aerogels as revealed by X-ray photocorrelation spectroscopy (XPCS)
Authors: Hernández Rebeca , Nogales Aurora , Sprung Michael , Mijangos Carmen , Ezquerra Tiberio A.
Published: January 2014

We report on a novel slow dynamics of polymer xerogels, aerogels, and nanocomposite aerogels with iron oxide nanoparticles, as revealed by X-ray photon correlation spectroscopy. The polymer aerogel and its nanocomposite aerogels, which are porous in nature, exhibit hyper-diffusive dynamics at room temperature. In contrast, non-porous polymer xerogels exhibit an absence of this peculiar dynamics. This slow dynamical process has been assigned to a relaxation of the characteristic porous structure of these materials and not to the presence of nanoparticles.
Interplay of point defects, extended defects, and carrier localization in the efficiency droop of InGaN quantum wells light-emitting diodes investigated using spatially resolved electroluminescence and photoluminescence
Authors: Lin Yue , Zhang Yong , Liu Zhiqiang , Su Liqin , Zhang Jihong , Wei Tongbo , Chen Zhong
Published: January 2014

We perform both spatially resolved electroluminescence (SREL) as a function of injection current and spatially resolved photoluminescence (SRPL) as a function of excitation power on InGaN quantum well blue light-emitting diodes to investigate the underlying physics for the phenomenon of the external quantum efficiency (EQE) droop. SREL allows us to study two most commonly observed but distinctly different droop behaviors on a single device, minimizing the ambiguity trying to compare independently fabricated devices. Two representative devices are studied: one with macroscopic scale material non-uniformity, the other being macroscopically uniform, but both with microscopic scale fluctuations. We suggest that the EQE–current curve reflects the interplay of three effects: nonradiative recombination through point defects, carrier localization due to either In composition or well width fluctuation, and nonradiative recombination of the extended defects, which is common to various optoelectronic devices. By comparing SREL and SRPL, two very different excitation/detection modes, we show that individual singular sites exhibiting either particularly strong or weak emission in SRPL do not usually play any significant and direct role in the EQE droop. We introduce a two-level model that can capture the basic physical processes that dictate the EQE–current dependence and describe the whole operating range of the device from 0.01 to 100 A/cm2.
Deep traps in n-type GaN epilayers grown by plasma assisted molecular beam epitaxy
Authors: Kamyczek P. , Placzek-Popko E. , Zytkiewicz Z. R. , Zielony E. , Gumienny Z.
Published: January 2014

In this study, we present the results of investigations on Schottky Au-GaN diodes by means of conventional DLTS and Laplace DLTS methods within the temperature range of 77 K–350 K. Undoped GaN layers were grown using the plasma-assisted molecular beam epitaxy technique on commercial GaN/sapphire templates. The quality of the epilayers was studied by micro-Raman spectroscopy (μ-RS) which proved the hexagonal phase and good crystallinity of GaN epilayers as well as a slight strain. The photoluminescence spectrum confirmed a high crystal quality by intense excitonic emission but it also exhibited a blue emission band of low intensity. DLTS signal spectra revealed the presence of four majority traps: two high-temperature and two low-temperature peaks. Using the Laplace DLTS method and Arrhenius plots, the apparent activation energy and capture cross sections were obtained. For two high-temperature majority traps, they were equal to E1 = 0.65 eV, σ1 = 8.2 × 10−16 cm2 and E2 = 0.58 eV, σ2 = 2.6 × 10−15 cm2 whereas for the two low-temperature majority traps they were equal to E3 = 0.18 eV, σ3 = 9.7 × 10−18 cm2 and E4 = 0.13 eV, σ4 = 9.2 × 10−18 cm2. The possible origin of the traps is discussed and the results are compared with data reported elsewhere.
Electrical properties of fullerenol C60(OH)10/Au interface
Authors: Sakaino Masamichi , Sun Yong , Morimoto Fumio
Published: January 2014

Electrical properties of the C60(OH)10/Au contact have been studied by measuring its current-voltage characteristics in the temperature range of 300–500 K. The Schottky barrier of the C60(OH)10/Au contact was confirmed to be 0.70±0.02 eV from Arrhenius plots of the current-voltage characteristics measured at various bias voltages as well as various preparation conditions of the C60(OH)10 material. Significant effect of the applied electric field on the barrier height has not been observed in the range of 0.1–2.0 MVm−1. The effects of both the charge transfer from C60 cage to OH groups and the crystallinity of the C60(OH)10 material on the Schottky barrier were discussed on the basis of x-ray photoemission spectroscopy and x-ray diffraction analyses.