bluuebunny/crossref_metadata_2025 huggingface dataset:
Lightning mapping observation of a terrestrial gamma‐ray flash
Authors: Lu Gaopeng , Blakeslee Richard J. , Li Jingbo , Smith David M. , Shao Xuan‐Min , McCaul Eugene W. , Buechler Dennis E. , Christian Hugh J. , Hall John M. , Cummer Steven A.
Published: June 2010

We report the observation with the North Alabama Lightning Mapping Array (LMA) related to a terrestrial gamma‐ray flash (TGF) detected by RHESSI on 26 July 2008. The LMA data explicitly show the TGF was produced during the initial development of a compact intracloud (IC) lightning flash between a negative charge region centered at about 8.5 km above sea level (−22°C temperature level) a higher positive region centered at 13 km, both confined to the convective core of an isolated storm in close proximity to the RHESSI footprint. After the occurrence of an LMA source with a high peak power (26 kW), the initial lightning evolution caused an unusually large IC current moment that became detectable 2 ms after the first LMA source and increased for another 2 ms, during which the burst of gamma‐rays was produced. This slowly building current moment was most likely associated with the upward leader progression, which produced an uncommonly large IC charge moment change (+90 C·km) in 3 ms while being punctuated by a sequence of fast discharge. These observations suggest that the leader development may be involved in the TGF production.
Introduction to special section on Stochastic Transport and Emergent Scaling on Earth's Surface: Rethinking geomorphic transport—Stochastic theories, broad scales of motion and nonlocality
Authors: Foufoula‐Georgiou Efi , Stark Colin
Published: June 2010

In many geomorphic transport systems, the time and length scales of motion vary widely: particles can be trapped for both short and long periods of time and they can travel large or small distances in very short intervals of time. To model such systems we need fresh conceptual and mathematical formalisms. The goal of this collection of papers is to challenge existing thinking in geomorphic transport by putting forward new ideas and theories for environmental fluxes, from particle transport in a single stream, to landslide debris mobilization, sediment and water transport on hillslopes, dynamic transport on river networks, and interpretation of sedimentary deposits over geologic time. Advanced stochastic theories of transport are proposed, the notion of nonlocal flux is introduced, and fractional advection‐diffusion equations are explored as possible models of geomorphic transport.
Introduction
Authors: Qu Ying , Li Yu-Feng , Bai Ru , Chen Chunying , Chai Zhifang
Published: June 2010

Recently metalloproteomics and/or metallomics are emerging scientific areas. Metalloproteomics is focused to investigate the distributions and compositions of all metalloproteins in a proteome, their structural and functional characterization, and their structural metal-binding moieties. Metallomics is for integrated bio-trace element science besides metalloproteomics. The intent of this book is to provide readers with a comprehensive view of application of advanced nuclear analytical techniques for metalloproteomics and metallomics. In the first chapter, we introduced the overall objective of this book. The definition and history of metallomics and metalloproteomics are included in section 1. The current applications of nuclear or nuclear-related analytical techniques in metallomics and metalloproteomics are critically outlined in sections 2 and 3, along with comparison of their overall advantages, disadvantages and main limitations. The recent advances in the application of hyphenated techniques for the species-selective determination of elements of interest (As, Cd, Cr, Fe, Hg, Pb, Se, Sn and so on) are also reviewed. Finally, an outlook on the application and further development of advanced techniques in metallomics and metalloproteomics are truely discussed. The comprehensive quantification, distribution, speciation, identification and structural characterization of metallome require high-throughput and powerful analytical techniques.
Neutron Activation Analysis
Authors: Zhang Zhiyong
Published: June 2010

Neutron activation analysis (NAA) possesses many merits such as high sensitivity, good accuracy and precision, small sampling quantity and multi-elemental analysis ability. In recent decades, conventional NAA has been combined with physical, chemical or biological separation procedures to meet the ever-increasing need for chemical species study. In this chapter, the methodology and its applications of NAA in metallomics and metalloproteomics study in biological or environmental samples are outlined.
X-ray Fluorescence
Authors: Gao Yuxi
Published: June 2010

Although X- ray fluorescence technique, in principle, belongs to an atomic method, it is often cataloged into nuclear discipline, especially those based on nuclear facilities, e.g. accelerator, isotopic sources and radiation detection spectrometry. Because of its non-destructive and multi-elemental analytical characteristic, excellent analytical sensitivity and spatial resolution under micro-beam condition where the size of the excited X-ray can be regulated with a slit or focusing system, this technique is capable of microscopic analysis, supplying information about 2D distributions of trace elements. The technique can, thus, be used for imaging of trace elements in biological and environmental specimen, also for the direct determination of trace elements in protein bands after slab-gel electrophoresis (GE), which is the benchmark for high-resolution protein separation, particularly in two-dimensional (2-D) format. Therefore, XRF is a useful technique for metallomics and meralloproteomics studies. In this chapter, the physical principles, facilities, the experimental arrangements and data processing of XRF are introduced briefly. The XRF analytical procedure and its applications in the metalloproteomics field are discussed emphatically. The outlook and challenges of the technique are also outlined.
Isotopic Techniques Combined with ICP-MS and ESI-MS
Authors: Wang Meng , Feng Weiyue , Chai Zhifang
Published: June 2010

Isotopic techniques combined with ICP-MS and ESI-MS have been successfully applied for study of proteomics and metallomics in recent years. This chapter is divided in six sections and introduces these techniques and applications. In the first two sections, the principle and instrumentation of ICP-MS and ESI-MS are summarized. The two powerful techniques are really complementary for metallomics and metalloproteomics study, because ICP-MS has a unique quantitative ability and an unmatched sensitivity for elemental detection, whereas ESI-MS can provide information on protein sequence. In the following three sections, commonly used isotopic techniques combined with ICP-MS and ESI-MS are introduced respectively, including isotopic tracer techniques, isotope dilution analysis and isotope labeling techniques for protein quantification. The unique characteristics and successful applications of these isotopic techniques are highlighted. Finally, it is concluded that isotopic techniques combined with ICP-MS and ESI-MS are very promising for metallomics and metalloproteomics and more successful advances are expected in future.
Mössbauer Spectroscopy
Authors: Qiu Yang , Chen Chunying
Published: June 2010

This chapter aims to introduce the Mössbauer effect and hyperfine structure of Mössbauer spectroscopy. Owing to its excellent energy resolution, it can provide detailed structural data of metal sites when applying to metalloproteomics studies. The main applications in the metalloprotein studies are the structural characterization of iron-containing proteins, including the iron electronic structure, coordination environment; the qualitative and quantitative changes of iron containing proteins during pathological processes or the effect of environmental factors; as well as their conformational changes and reaction dynamics. The first two sections provide an overall review of Mössbauer spectroscopy in its physical principles, facilities, Equipments, performance, data processing and application. The followed section introduces the application for elemental speciation in environmental and biological samples using Mössbauer spectroscopy. Some other nuclear related techniques for ultrafine interaction study like nuclear magnetic resonance (NMR) spectroscopy, electron paramagnetic resonance (EPR), and resonance Raman spectroscopy are also outlined for study the structure of metalloproteins. Finally, the advantages and limitations are discussed.
X-ray Absorption Spectroscopy
Authors: Li Yu-Feng , Chen Chunying
Published: June 2010

X-ray absorption spectroscopy (XAS) has been a powerful tool to probe physical and chemical structure for an atom, which includes two regions, X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS). The main object of this chapter is to give the readers a brief idea about XAS and its application, alone or combined with other techniques, in metallomics and metalloproteomics studies. This chapter is divided into five sections. After a brief introduction of X-ray-related techniques in section 1, the basic items about X-ray absorption spectroscopy (XAS) are introduced in section 2, which includes the definition of XAS, the sample preparation and measurement of XAS and how to analyze the data obtained from XAS measurement. The application of XAS in metallomics and metalloproteomics is discussed in section 3, which includes the fingerprints and quantitative speciation through XANES and structural configuration like bond distance and coordination numbers through the extended fine structure (EXAFS). Besides, the application of micro-XAS with focused beam, which can provide spatial information, is also demonstrated in this section. In section 4, the combined application of XAS with other techniques like X-ray fluorescence (XRF), protein crystallography, computational chemistry, neutron scattering, circular dichroism, nuclear magnetic resonance, Raman spectroscopy, and electron spin resonance is illustated which further extend its application in metallomics and metalloproteomics studies. Finally in section 5, an overview on the application of XAS in metallomics and metalloproteomics and its further development as an useful tools are discussed.
Nuclear-based Metallomics in Metallic Nanomaterials: Nanometallomics
Authors: Li Yu-Feng , Wang Liming , Zhang Lili , Chen Chunying
Published: June 2010

The main object of this chapter is to extend the research field of metallomic to a fast developing research area as nanoscience and technology. This chapter is divided into 6 sections. The systematic study of metallic nanomaterials, nanometallomics, is first proposed in section 1. Then the definition and research area of nanometallomics is discussed in section 2. The application of nuclear techniques in characterization, oxidation state analysis and electronic configuration of metallic nanomaterials is introduced in section 3 while the application of nuclear techniques like neutron activation analysis, ICP-MS, X-ray fluorescence analysis, and isotopic tracing techniques in the quantification and biodistribution of metallic nanomaterials is reported in section 4. In section 5, the structural analysis for bio-nano interaction is reviewed which shows X-ray absorption spectroscopy is a powerful tool in this area. Finally in section 6, the outlook of nanometallomics as an emerging research field is demonstrated. The integrated techniques provide a useful platform for the quantification, biodistribution and structural analysis of metallic nanomaterials.
A central role for polyamines in microtubule assembly in cells
Authors: Savarin Philippe , Barbet Aurélie , Delga Stéphanie , Joshi Vandana , Hamon Loïc , Lefevre Julien , Nakib Samir , De Bandt Jean-Pascal , Moinard Christophe , Curmi Patrick A. , Pastré David
Published: June 2010

Owing to preferential electrostatic adsorption of multivalent cations on highly anionic surfaces, natural multivalent polyamines and especially quadrivalent spermine can be considered as potential regulators of the complex dynamical properties of anionic MTs (microtubules). Indeed, the C-terminal tails of tubulin display many negative residues in a row which should enable the formation of a correlated liquid-like phase of multivalent counterions on its surface. Although it is known that polyamine counterions promote MT assembly in vitro, little is known about the relevance of this interaction in vivo. In the present study, we have explored the relationship between polyamine levels and MT assembly in HeLa and epithelial NRK (normal rat kidney) cells using DFMO (α-difluoromethylornithine), an irreversible inhibitor of ornithine decarboxylase, and APCHA [N-(3-aminopropyl)-N-cyclohexylamine], a spermine synthase inhibitor. Under conditions of intracellular polyamine depletion, the MT network is clearly disrupted and the MT mass decreases. Addition of spermine to polyamine-depleted cells reverses this phenotype and rapidly promotes the extensions of the MT network. Finally, we show that polyamine levels modulate the coating of MTs with MAP4 (MT-associated protein 4), an MT-stabilizing protein, and the spatial distribution of EB1 (end-binding protein 1), an MT plus-end-binding protein. In addition, polyamines favour the formation of gap junctions in NRK cells, a process which requires MT extensions at the cell periphery. The present study provides a basis for a better understanding of the role played by polyamines in MT assembly and establishes polyamine metabolism as a potential cellular target for modulating MT functions.
Human Pif1 helicase is a G-quadruplex DNA-binding protein with G-quadruplex DNA-unwinding activity
Authors: Sanders Cyril M.
Published: June 2010

Pif1 proteins are helicases that in yeast are implicated in the maintenance of genome stability. One activity of Saccharomyces cerevisiae Pif1 is to stabilize DNA sequences that could otherwise form deleterious G4 (G-quadruplex) structures by acting as a G4 resolvase. The present study shows that human Pif1 (hPif1, nuclear form) is a G4 DNA-binding and resolvase protein and that these activities are properties of the conserved helicase domain (amino acids 206–620 of 641, hPifHD). hPif1 preferentially bound synthetic G4 DNA relative to ssDNA (single-stranded DNA), dsDNA (double-stranded DNA) and a partially single-stranded duplex DNA helicase substrate. G4 DNA unwinding, but not binding, required an extended (>10 nucleotide) 5′ ssDNA tail, and in competition assays, G4 DNA was an ineffective suppressor of helicase activity compared with ssDNA. These results suggest a distinction between the determinants of G4 DNA binding and the ssDNA interactions required for helicase action and that hPif1 may act on G4 substrates by binding alone or as a resolvase. Human Pif1 could therefore have a role in processing G4 structures that arise in the single-stranded nucleic acid intermediates formed during DNA replication and gene expression.
Expression ofmiR-146a/bis associated with the Toll-like receptor 4 signal in coronary artery disease: effect of renin–angiotensin system blockade and statins onmiRNA-146a/band Toll-like receptor 4 levels
Authors: Takahashi Yuji , Satoh Mamoru , Minami Yoshitaka , Tabuchi Tsuyoshi , Itoh Tomonori , Nakamura Motoyuki
Published: June 2010

The TLR4 (Toll-like receptor 4) signal plays an important role in immunity in CAD (coronary artery disease). miR-146a/b (where miR is microRNA) regulates the TLR4 downstream molecules IRAK1 (interleukin-1-receptor-associated kinase 1) and TRAF6 (tumour-necrosis-factor-receptor-associated factor 6). It has also been reported that statins and RAS (renin–angiotensin system) inhibition and have anti-atherosclerotic properties. In the present study, we have investigated whether miR-146a/b was expressed with the TLR4 signal in CAD patients, and whether combined treatment with a statin and RAS inhibition might affect these levels. A total of 66 patients with CAD and 33 subjects without CAD (non-CAD) were enrolled. Patients with CAD were randomized to 12 months of combined treatment with atorvastatin and telmisartan [an ARB (angiotensin II receptor blocker)] or atorvastatin and enalapril [an ACEI (angiotensin-converting enzyme inhibitor)]. PBMCs (peripheral blood mononuclear cells) were obtained from peripheral blood at baseline and after 12 months. Levels of miR-146a/b, IRAK1 mRNA, TRAF6 mRNA and TLR4 mRNA/TLR4 protein were significantly higher in the CAD group than in the non-CAD group (all P<0.01). Levels of miR-146a/b were positively correlated with IRAK1 mRNA and TRAF6 mRNA levels. After 12 months of treatment, these levels were markedly decreased in the ARB and ACEI groups, with the decrease in the ARB group being greater than that in the ACEI group (all P<0.05). In our 12-month follow-up study, high levels of miR-146a and TLR4 mRNA/TLR4 protein at baseline were independent predictors of cardiac events. The present study demonstrates that combined treatment with an ARB and a statin decreases miR-146a/b and the TLR4 signal in CAD patients, possibly contributing to the anti-atherogenic effects of ARBs and statins in this disorder.
Significance of serum adiponectin levels in patients with chronic liver disease
Authors: Balmer Maria Luisa , Joneli Jeannine , Schoepfer Alain , Stickel Felix , Thormann Wolfgang , Dufour Jean-François
Published: June 2010

Adiponectin, which plays a pivotal role in metabolic liver diseases, is reduced in concentration in patients with NASH (non-alcoholic steatohepatitis). The aim of the present study was to determine adiponectin concentrations in patients with different forms and stages of chronic liver diseases. Serum adiponectin concentrations were measured in 232 fasting patients with chronic liver disease: 64 with NAFLD (non-alcoholic fatty liver disease), 123 with other chronic liver disease (e.g. viral hepatitis, n=71; autoimmune disease, n=18; alcohol-induced liver disease, n=3; or elevated liver enzymes of unknown origin, n=31) and 45 with cirrhosis. Circulating adiponectin levels were significantly lower in patients with NAFLD in comparison with patients with other chronic liver disease (4.8±3.5 compared with 10.4±6.3 μg/ml respectively; P<0.0001). Circulating adiponectin levels were significantly higher in patients with cirrhosis in comparison with patients without cirrhosis (18.6±14.5 compared with 8.4±6.1 μg/ml respectively; P<0.0001). Adiponectin concentrations correlated negatively with body weight (P<0.001), serum triacylglycerols (triglycerides) (P<0.001) and, in women, with BMI (body mass index) (P<0.001). Adiponectin concentrations correlated positively with serum bile acids (P<0.001), serum hyaluronic acid (P<0.001) and elastography values (P<0.001). Adiponectin levels were decreased in patients with NAFLD. In conclusion, adiponectin levels correlate positively with surrogate markers of hepatic fibrosis (transient elastography, fasting serum bile acids and hyaluronate) and are significantly elevated in cases of cirrhosis.
Lexical and Grammatical Associations in Sequential Bilingual Preschoolers
Authors: Kohnert Kathryn , Kan Pui Fong , Conboy Barbara T.
Published: June 2010

Purpose

The authors investigated potential relationships between traditional linguistic domains (words, grammar) in the first (L1) and second (L2) languages of young sequential bilingual preschool children.

Method

Participants were 19 children, ages 2;11 (years;months) to 5;2 (M= 4;3) who began learning Hmong as the L1 from birth and English as the L2 during early childhood. Measures were the number of different words (NDW) and mean length of utterance (MLU) produced during a story retell task and scores on picture identification, an independent measure of receptive vocabulary. Correlations were conducted to determine relationships among measures.

Results

In English, there were robust positive relationships between MLU and lexical measures (NDW, Picture Identification). In Hmong, more modest cross-domain associations were evident between lexical measures and MLU. There were positive cross-language links for NDW but more limited cross-domain correspondences between the L1 and the L2.

Conclusions

In English, relationships between words and grammar were similar to those found in previous studies with monolingual and simultaneous bilingual toddlers. Weaker cross-domain associations in the L1 may reflect participants' greater development in Hmong or typological differences between the L1 and the L2.
Perception of Phonemic Length and Its Relation to Reading and Spelling Skills in Children With Family Risk for Dyslexia in the First Three Grades of School
Authors: Pennala Riitta , Eklund Kenneth , Hämäläinen Jarmo , Richardson Ulla , Martin Maisa , Leiwo Matti , Leppänen Paavo H. T. , Lyytinen Heikki
Published: June 2010

Purpose

To examine the ability to discriminate phonemic length and the association of this ability with reading accuracy, reading speed, and spelling accuracy in Finnish children throughout Grades 1–3.

Method

Reading-disabled (RDFR,
n
= 35) and typically reading children (TRFR,
n
= 69) with family risk for dyslexia and typically reading control children (TRC,
n
= 80) were tested once in each grade of Grades 1–3 using a phonemic length discrimination task. Reading, spelling, IQ, verbal short-term memory, phonological memory, and naming speed were assessed.

Results

The RDFR group made more errors in phonemic length discrimination than the TRC group in Grades 2 and 3. After taking into account variance in verbal short-term memory, phonological memory, and naming speed, discrimination ability explained unique variance of spelling accuracy in Grades 2 and 3 and reading accuracy in Grade 3 in the RDFR group. At the individual level, in Grade 2, 31.4% of the RDFR group and 14.7% of the TRFR group performed below −1.25
SD
s in the phonemic length discrimination task.

Conclusion

Problems in phonemic length discrimination could be one of the accumulating risk factors affecting development leading to dyslexia.
Differentiating Cantonese-Speaking Preschool Children With and Without SLI Using MLU and Lexical Diversity (D)
Authors: Wong Anita M.-Y. , Klee Thomas , Stokes Stephanie F. , Fletcher Paul , Leonard Laurence B.
Published: June 2010

Purpose

In this study, the authors examined the diagnostic accuracy of a composite clinical assessment measure based on mean length of utterance (MLU), lexical diversity (D), and age (Klee, Stokes, Wong, Fletcher, & Gavin, 2004) in a second, independent sample of 4-year-old Cantonese-speaking children with and without specific language impairment (SLI).

Method

The composite measure was calculated from play-based, conversational language samples of 15 children with SLI and 14 children without SLI. Scores were dichotomized and compared to diagnostic outcomes using a reference standard based on clinical judgment supported by test scores.

Results

Eleven of 15 children with SLI and 8 of 14 children with typical language skills were correctly classified by the dichotomized composite measure. The measure’s sensitivity in this second sample was 73.3% (95% confidence interval [CI] 48%–89%); specificity was 57.1% (95% CI 33%–79%); positive likelihood ratio was 1.71 (95% CI 0.87–3.37); and negative likelihood ratio was 0.47 (95% CI 0.18–1.21).

Conclusions

The diagnostic accuracy of the composite measure was substantially lower than in the original study, suggesting that it is unlikely to be informative for clinical use in its present form. The value of replication studies is discussed.
Hydrostatic and uniaxial compression studies of 1,3,5-triamino- 2,4,6-trinitrobenzene using density functional theory with van der Waals correction
Authors: Budzevich M. M. , Landerville A. C. , Conroy M. W. , Lin Y. , Oleynik I. I. , White C. T.
Published: June 2010

Hydrostatic and uniaxial compressions of 1,3,5-triamino-2,4,6-trinitrobenzene were investigated using first-principles density functional theory with an empirical van der Waals correction. The equilibrium structural and elastic properties and the hydrostatic equation of state are in good agreement with available experimental data. Physical properties such as the principal stresses, shear stresses, band gap, and the change in energy per atom as a function of compression ratio V/V0 in the directions normal to the (100), (010), (001),(110), (101), (011), and (111) crystallographic planes were calculated, showing highly anisotropic behavior under uniaxial compressions.
Kinetics of crack growth in zirconium alloys (II): Stress dependence of the crack growth rate
Authors: Kim Young S.
Published: June 2010

Delayed hydride cracking tests were conducted on a cold-worked Zr-2.5Nb tube with hydrogen at different test temperatures ranging from 160 to 280 °C in the load increasing mode where an applied KI was increased step-wise by 0.5 MPa m1/2 from 4.5 MPa m1/2. In Stage I with a low KI being close to the threshold stress intensity factor KIH, the striation spacing or the critical hydride length lc that was larger at a lower KI sharply decreased with increasing KI and the crack growth rate (CGR) showed a rapid increase with KI, arising from a reduced hydride cracking rate by creep at a lower KI. In Stage II with KI being much larger than KIH, however, the lc was much smaller and the CGR became independent of KI, demonstrating that the hydride cracking rate becomes so high as to be unaffected by the applied KI, and diffusion-controlled hydride growth becomes a rate-controlling factor for the CGR in Stage II. This explains the constant CGR independent of KI in Stage II. It is demonstrated that the CGR of zirconium alloys is determined by the rate of a slower process between two processes of growth and cracking of hydrides.
Reduction of magnetic hysteresis loss in La0.5Pr0.5Fe11.4Si1.6Hx hydrides with large magnetocaloric effects
Authors: Zhao Jin-liang , Shen Jun , Hu Feng-xia , Li Yang-xian , Sun Ji-rong , Shen Bao-gen
Published: June 2010

Magnetic properties and magnetocaloric effects (MCEs) have been investigated in hydrogenated La0.5Pr0.5Fe11.4Si1.6Hx (x=0, 0.9, and 1.6) compounds. It is found that the Curie temperature TC can be tuned from 189 to 317 K by adjusting hydrogen content from 0 to 1.6. It is attractive that both thermal and magnetic hysteresis are remarkably reduced because of the weakness of the itinerant-electron metamagnetic transition after hydrogenation, while the large magnetic entropy change is retained. The maximal hysteresis loss at TC decreases from 17.8 to 2.3 J/kg as x increases from 0 to 1.6. For the samples with x=0, 0.9, and 1.6, the maximal values of −ΔS are 26.3, 24.1, and 22.1 J/kg K at TC, with efficient refrigeration capacities of 463, 366, and 351 J/kg for a field change of 0–5 T, respectively. Large reversible MCE and small hysteresis with considerable value of refrigeration capacity indicate the potentiality of La0.5Pr0.5Fe11.4Si1.6Hx hydrides as a candidate magnetic refrigerant around room temperature.
Spectral dependency of superconducting single photon detectors
Authors: Maingault L. , Tarkhov M. , Florya I. , Semenov A. , Espiau de Lamaëstre R. , Cavalier P. , Gol’tsman G. , Poizat J.-P. , Villégier J.-C.
Published: June 2010

We investigate the effect of varying both incoming optical wavelength and width of NbN nanowires on the superconducting single photon detectors (SSPD) detection efficiency. The SSPD are current biased close to critical value and temperature fixed at 4.2 K, far from transition. The experimental results are found to verify with a good accuracy predictions based on the “hot spot model,” whose size scales with the absorbed photon energy. With larger optical power inducing multiphoton detection regime, the same scaling law remains valid, up to the three-photon regime. We demonstrate the validity of applying a limited number of measurements and using such a simple model to reasonably predict any SSPD behavior among a collection of nanowire device widths at different photon wavelengths. These results set the basis for designing efficient single photon detectors operating in the infrared (2–5 μm range).
Magnetic alignment of plant cell microfibrils and their anisotropic elasticity
Authors: Fujimura Yuu , Sakaida Hidetaka , Iino Masaaki
Published: June 2010

The magnetic alignment of microfibrils on a single regenerated plant cell surface subjected to magnetic fields and its anisotropic cell surface area expansivity modulus (area modulus) were studied. The magnetic alignment around the equator of the cell (the polar axis parallel to the magnetic field) was confirmed by a 2-dim Fourier analysis of images from a scanning electron microscope, and these were expressed by a theoretical magnetic order parameter for anisotropic relative magnetic permeability of 3×10−27, while the microfibrils near the pole did not show any such magnetic alignment. The magnetic field anisotropically stiffened the cell surface. The stiffness around the equator was greater than that around the pole. The magnetic field dependences of the area modulus agreed with the mechanical model.
Steady-state transport characteristics of photoconductor based on dye-sensitized solar cell
Authors: Xu J. , Wang X. Q. , Lu Y. M. , Liu Z. Y. , Cai C. B.
Published: June 2010

In the present work, three photoconductors based on dye-sensitized nanocrystalline TiO2 are designed with two dye-sensitized solar cells (DSSCs) connected together using a common counter electrode but different connecting approaches for electrolytes and TiO2 film. DC steady-state transport measurements on source and drain corresponding to the photoanodes of two constituent DSSC units, respectively, show that the three photoconductive devices exhibit similar transistor characteristics, regardless of their different electronic connecting approaches. It is revealed that their transport characteristics are determined by the effective areas of the photoanode and the counter electrode, rather than the connection of electrolytes and TiO2 film. Furthermore, it is demonstrated that the dominant factor of transport behavior is the imbalanced energy band caused by the match of intrinsic potential within two constituent DSSC units. Due to unique mechanism and relatively simple fabrication process, the present phototransistors have potentials for an economical and efficient light-operated switch as well as an emerged optical communication device.
Recurrence for quenched random Lorentz tubes
Authors: Cristadoro Giampaolo , Lenci Marco , Seri Marcello
Published: June 2010

We consider the billiard dynamics in a striplike set that is tessellated by countably many translated copies of the same polygon. A random configuration of semidispersing scatterers is placed in each copy. The ensemble of dynamical systems thus defined, one for each global choice of scatterers, is called quenched random Lorentz tube. We prove that under general conditions, almost every system in the ensemble is recurrent.
Surface profile dependence of the photon coupling efficiency and enhanced fluorescence in the grating-coupled surface plasmon resonance
Authors: Hori Hironobu , Tawa Keiko , Kintaka Kenji , Nishii Junji , Tatsu Yoshiro
Published: June 2010

The fluorescence excited by the enhanced electric field of grating-coupled surface plasmon resonance was detected on biochips. The enhancement of the electric field on a metallic grating surface was calculated using the finite difference time domain method for rectangular, trapezoidal, and sinusoidal models to clarify the grating-surface profile dependence of the enhanced fluorescence. The computational results showed that the enhancement in the trapezoidal model was stronger than that in the other models, and that the groove depth dependence of the enhancement in the trapezoidal model agreed well with the experimental data. The grating surface profile, including the groove depth, was found to be an important parameter of the grating structure for it to couple effectively with light.
Effect of Ru doping on magnetoresistance and magnetocaloric effect in Bi0.4Ca0.6Mn1−xRuxO3 (≤x≤0.2)
Authors: Kumar V. Suresh , Mahendiran R.
Published: June 2010

We show that Ru doping in Bi0.4Ca0.6Mn1−xRuxO3, unlike other magnetic ions, destabilizes charge ordering and transforms the charge-ordered antiferromagnetic insulator (x=0) into a ferromagnetic metal for x≥0.1. The ferromagnetic transition temperature (TC) increases from TC=130 K for x=0.1 to 272 K for x=0.2 and the resistivity of the later compound at 10 K is eight orders of magnitude lower than that of x=0. The magnetoresistance at H=7 T has a maximum value (−98%) for x=0.05 but it decreases to −20% for x=0.2. While magnetic entropy (ΔSm) for x=0.05 is positive just above the charge ordering temperature, it changes sign with lowering temperature, and is negative over a wide temperature range for x=0.1 and 0.2. The x=0.2 sample shows the highest value of ΔSm=−1.83 J/kg K for ΔH=5 T in the series. Our results suggest that while Ru doping induces ferromagnetic clusters locally in the charge-ordered matrix for x=0.05, charge ordering is completely absent in x=0.2. The greater ability of Ru to induce long range ferromagnetism and insulator-metal transition in robust charge-ordered materials such as Bi0.4Ca0.6MnO3 is quite interesting from the point of view of fundamental physics and applications.
Nucleation of islands and continuous high-quality In2O3(001) films during plasma-assisted molecular beam epitaxy on Y-stabilized ZrO2(001)
Authors: Bierwagen Oliver , Speck James S.
Published: June 2010

The surface roughness on different length scales of In2O3(001) films is detrimental to potential semiconductor applications of this material. One type of surface roughness consists of square shaped islands with edge lengths on the micron scale. This islanding was observed in In2O3(001) films grown on Y-stabilized ZrO2(001), YSZ(001), by plasma-assisted molecular beam epitaxy under oxygen-rich and under In-rich growth conditions. Our reflection high-energy electron diffraction observations during the initial phase of the growth showed that the islanding is caused by a nucleation of the In2O3 with incomplete wetting of the substrate and not by a strain-induced breakup of the film. By systematic variation in the growth parameters Indium-to-oxygen beam flux ratio (VI/III ratio) and substrate temperature we found that the wetting of YSZ(001) by the In2O3(001) film is thermodynamically not preferred and that kinetic limitations, such as low substrate temperatures or (to a lesser extent) high VI/III ratios, were able to force nucleation of continuous films. A growth diagram was constructed that shows the parameter regions with forced or inhibited wetting. The nucleation with inhibited wetting can be applied to the formation of square shaped In2O3(001) islands whose size increases and areal density decreases with decreasing VI/III ratio. To realize continuous, smooth In2O3(001) films under In-rich conditions, a thin nucleation layer was grown at lower substrate temperature to completely wet the substrate. The bulk of the film was grown on top of this nucleation layer at higher temperature to ensure a high crystalline quality.
Simultaneous velocity and pressure measurements using luminescent microspheres
Authors: Kimura Fletcher , McCann Jesse , Khalil Gamal E. , Dabiri Dana , Xia Younan , Callis James B.
Published: June 2010

Using the technique of modified rapid lifetime determination, pressure-sensitive microspheres, known as PrSBeads, were used to make quantitative oxygen measurements over two-dimensional areas within gaseous flows. Aerosolized PrSBeads in carrier gases of varying oxygen concentrations demonstrated point measurement precisions on the order of 0.1%–1%. A charge-coupled device featuring a double image frame (DIF) feature was used to make spatially resolved pressure measurements within gas phase flows. Errors on the order of 0.5 atm for one standard deviation were demonstrated when 2×2 pixel binning (162×128 pixel overall resolution) was used, but improved to 0.003–0.005 atm with the use of 32×32 pixel binning (10×8 pixel overall resolution). Experiments demonstrate the ability to resolve the oxygen concentration differences between a N2 jet and the surrounding ambient air environment and the ability to measure instantaneous air pressure changes within a square syringe as the plunger is moved in and out. In addition, instantaneous velocity measurements of the airborne PrSBeads in a square syringe were achieved using digital particle image velocimetry at frame rates of 6.4 Hz, thus validating PrSBeads as a tool to simultaneously measure the velocity and pressure within an aerodynamic flow.
Correlation of band edge native defect state evolution to bulk mobility changes in ZnO thin films
Authors: Seo Hyungtak , Park Chan-Jun , Cho Young-Je , Kim Young-Bae , Choi Duck-Kyun
Published: June 2010

The evolution of native defect states near conduction band present in ZnO thin films is correlated with the bulk electron density and mobility changes driven by the thermal structure modification. The evolution of band edge electronic structures of ZnO thin films was studied via the spectroscopic detection of empty localized defect states in conduction band (CB) edge and occupied defect states in valence band using spectroscopic ellipsometry and x-ray photoemission spectroscopy. The energy depth of native defect states against CB edge revealed the direct correlation to Hall mobility values for ZnO thin films.
Geometric structures of Gen (n=34–39) clusters
Authors: Qin Wei , Lu Wen-Cai , Zang Qing-Jun , Zhao Li-Zhen , Chen Guang-Ju , Wang C. Z. , Ho K. M.
Published: June 2010

The structures of Gen (n=34–39) clusters were searched by a genetic algorithm using a tight-binding interatomic potential. First-principles calculations based on density functional theory were performed to further identify the lowest-energy structures. The calculated results show that Gen (n=34–39) clusters favor prolate or Y-shaped three-arm structures consisting of two or three small stable clusters (Ge6, Ge7, Ge9, or Ge10) linked by a Ge6 or Ge9 bulk unit. The calculated results suggest the transition point from prolate to Y-shaped three-arm structures appears at Ge35 or Ge36.
Dynamical insights into π1σ∗ state mediated photodissociation of aniline
Authors: King Graeme A. , Oliver Thomas A. A. , Ashfold Michael N. R.
Published: June 2010

This article reports a comprehensive study of the mechanisms of H atom loss in aniline (C6H5NH2) following ultraviolet excitation, using H (Rydberg) atom photofragment translational spectroscopy. N–H bond fission via the low lying π1σ∗ electronic state of aniline is experimentally demonstrated. The π1σ∗ potential energy surface (PES) of this prototypical aromatic amine is essentially repulsive along the N–H stretch coordinate, but possesses a shallow potential well in the vertical Franck–Condon region, supporting quasibound vibrational levels. Photoexcitation at wavelengths (λphot) in the range 293.859 nm≥λphot≥193.3 nm yields H atom loss via a range of mechanisms. With λphot resonant with the 1π1π∗←S0 origin (293.859 nm), H atom loss proceeds via, predominantly, multiphoton excitation processes, resonantly enhanced at the one photon energy by the first π1π∗ excited state (the 1π1π∗ state). Direct excitation to the first few quasibound vibrational levels of the π1σ∗ state (at wavelengths in the range 269.513 nm≥λphot≥260 nm) induces N–H bond fission via H atom tunneling through an exit barrier into the repulsive region of the π1σ∗ PES, forming anilino (C6H5NH) radical products in their ground electronic state, and with very limited vibrational excitation; the photo-prepared vibrational mode in the π1σ∗ state generally evolves adiabatically into the corresponding mode of the anilino radical upon dissociation. However, as the excitation wavelength is reduced (λphot<260 nm), N–H bond fission yields fragments with substantially greater vibrational excitation, rationalized in terms of direct excitation to 1π1π∗ levels, followed by coupling to the π1σ∗ PES via a 1π1π∗/π1σ∗ conical intersection. Changes in product kinetic energy disposal once λphot approaches ∼230 nm likely indicate that the photodissociation pathways of aniline proceed via direct excitation to the (higher) 2π1π∗ state. Analysis of the anilino fragment vibrational energy disposal—and thus the concomitant dynamics of π1σ∗ state mediated photodissociation—provides a particularly interesting study of competing σ∗←π and π∗←π absorption processes and develops our appreciation of the photochemistry of aromatic amines. It also allows revealing comparisons with simple amines (such as ammonia and methylamine) as well as the isoelectronic species, phenol. This study yields a value for the N–H bond strength in aniline, D0(H−anilino)=31630±40 cm−1.
Dielectric and ferroelectric properties in (Sr,Ni,Na)TiO3 solid solutions
Authors: Ang Chen , Yu Zhi
Published: June 2010

Solid solutions of (1-z) (Sr0.7Bi0.2◻0.1)TiO3+z(Na0.5Bi0.5)TiO3 (z=0–1) system are synthesized. Dielectric measurement reveals that two dielectric anomalies exist over the temperature range of 150–680 K. One is the dielectric peak with significant frequency dispersion below 500 K, whose nature evolves from a ferroelectric relaxor (z≤0.5) to a ferroelectric (z≥0.65) with increasing z. The other is the dielectric anomaly without frequency dispersion above 520 K, which emerges at z≥0.5, and is attributed to the “paraelectric-antiferroelectric” phase transition of (Na0.5Bi0.5)TiO3 sublattice. Ferroelectric hysteresis loops are observed for z>0.65 and a significantly high remnant polarization ∼51 μC/cm2 is obtained at z=0.9. A “core-shell” microstructure is observed by transmission electron microscopy. The physical mechanism of the evolution of the dielectric/ferroelectric properties and the microstructure of the solid solutions is discussed.
Electron attachment to amino acid clusters in helium nanodroplets: Glycine, alanine, and serine
Authors: Ferreira da Silva F. , Denifl S. , Märk T. D. , Ellis A. M. , Scheier P.
Published: June 2010

The first detailed study of electron attachment to amino acid clusters is reported. The amino acids chosen for investigation were glycine, alanine, and serine. Clusters of these amino acids were formed inside helium nanodroplets, which provide a convenient low temperature (0.37 K) environment for growing noncovalent clusters. When subjected to low energy (2 eV) electron impact the chemistry for glycine and alanine clusters was found to be similar. In both cases, parent cluster anions were the major products, which contrasts with the corresponding monomers in the gas phase, where the dehydrogenated products ([AAn-H]−, where AA=amino acid monomer) dominate. Serine clusters are different, with the major product being the parent anion minus an OH group, an outcome presumably conferred by the facile loss of an OH group from the β carbon of serine. In addition to the bare parent anions and various fragment anions, helium atoms are also observed attached to both the parent anion clusters and the dehydrogenated parent anion clusters. Finally, we present the first anion yield spectra of amino acid clusters from doped helium nanodroplets as a function of incident electron energy.
Reflectance changes during shock-induced phase transformations in metals
Authors: Stevens G. D. , Turley W. D. , Veeser L. R. , Jensen B. J. , Rigg P. A.
Published: June 2010

In performing shock wave experiments to study the characteristics of metals at high pressures, wave profiles (i.e., velocity measurements of the surface of the sample) are an established and useful way to study phase transformations. For example, a sudden change in the velocity or its slope can occur when the phase transformation induces a large volume change leading to a change in particle velocity. Allowing the shock to release into a transparent window that is in contact with the sample surface allows the study of conditions away from the shock Hugoniot. However, in cases where the wave profile is not definitive, an additional phase-transformation diagnostic is often useful. Changes in the electronic structure of the atoms in the crystal offer opportunities to develop new phase-change diagnostics. We have studied optical reflectance changes for several shock-induced phase transformations to see whether reflectance changes might be a generally applicable phase-transformation diagnostic. Shocks were produced by direct contact with explosives or with impacts from guns. Optical wavelengths for the reflectance measurements ranged from 355 to 700 nm. We studied samples of tin, iron, gallium, and cerium as each passed through a phase transformation during shock loading and, if observable, a reversion upon unloading. In addition to metals with complicated phase diagrams, we also measured dynamic, pressure-induced changes in the reflectivity of aluminum. For rapid solid-solid phase changes in tin and iron, we saw small changes in the surface scattering characteristics, perhaps from voids or rough areas frozen into the surface of the sample as it transformed to a new crystal structure. For melt in gallium and cerium, we saw changes in the wavelength dependence of the reflectance, and we surmise that these changes may result from changes in the crystal electronic structure. It appears that reflectance measurements can be a significant part of a larger suite of diagnostics to search for difficult-to-detect phase transformations.
Imaging dislocations in gallium nitride across broad areas using atomic force microscopy
Authors: Bennett S. E. , Holec D. , Kappers M. J. , Humphreys C. J. , Oliver R. A.
Published: June 2010

We have employed an atomic force microscope with a high sampling rate to image GaN samples grown using an epitaxial layer overgrowth technique and treated with silane and ammonia to enlarge the surface pits associated with threading dislocations (TDs). This allows TDs to be identified in high pixel density images tens of microns in size providing detailed information about the spatial distribution of the TDs. An automated software tool has been developed, which identifies the coordinates of the TDs in the image. Additionally, we have imaged the same sample using Kelvin probe force microscopy, again at high pixel density, providing data about the local changes in surface potential associated with hundreds of dislocations.