bluuebunny/crossref_metadata_2025 huggingface dataset:
Fitting the Higgs to natural SUSY
Authors: D’Agnolo Raffaele Tito , Kuflik Eric , Zanetti Marco
Published: March 2013

Abstract

We present a fit to the 2012 LHC Higgs data in different supersymmetric frameworks using naturalness as a guiding principle. We consider the MSSM and its D-term and F -term extensions that can raise the tree-level Higgs mass. When adding an extra chiral superfield to the MSSM, three parameters are needed determine the tree-level couplings of the lightest Higgs. Two more parameters cover the most relevant loop corrections, that affect the hγγ and hgg vertexes. Motivated by this consideration, we present the results of a five parameters fit encompassing a vast class of complete supersymmetric theories. We find meaningful bounds on singlet mixing and on the mass of the pseudoscalar Higgs m
A as a function of tan β in the MSSM. We show that in the (m
A
, tan β) plane, Higgs couplings measurements are probing areas of parameter space currently inaccessible to direct searches. We also consider separately the two cases in which only loop effects or only tree-level effects are sizable. In the former case we study in detail stops’ and charginos’ contributions to Higgs couplings, while in the latter we show that the data point to the decoupling limit of the Higgs sector. In a particular realization of the decoupling limit, with an approximate PQ symmetry, we obtain constraints on the heavy scalar Higgs mass in a general type-II Two Higgs Doublet Model.
Guidelines for Surgeons on Establishing Projects in Low‐Income Countries
Authors: Grimes Caris E. , Maraka Jane , Kingsnorth Andrew N. , Darko Rudolph , Samkange Christopher A. , Lane Robert H. S.
Published: March 2013

Background

There is increasing interest by surgeons in high‐income countries to support colleagues in low‐income countries to improve the provision of surgical care, particularly in rural areas. Such interest may be demonstrated by single individuals, short‐term surgical missions, or establishment of partnerships. Such altruistic efforts may cause problems unless properly planned and carried out.

Methods

We reviewed the available literature and consulted widely to establish consensus guidelines for any surgeon considering participating in an initiative to improve surgical care in low‐income countries.

Results

A series of recommendations is presented. These include ensuring that projects are appropriate, that there is an emphasis on training local healthcare providers in all aspects of perioperative care, that outcomes are monitored, and that initiatives work with local and regional training programs.

Conclusions

With adherence to these recommendations, we hope that future partnerships and missions can maximize their effectiveness and minimize the risks of potential harm done.
The melody of the immature brain
Authors: Sieben K. , Hartung H. , Wolff A. , Hanganu-Opatz I.
Published: March 2013

The periodicity of brain activity became ob­vious even after the first attempt to capture it, with Hans Berger noting in 1929 that the “electroencephalogram represents a con­tinuous curve with continuous oscillations”. This rhythmicity of neural activity, the ‘melo­dy’ of the brain, has since gained interest as an energy-efficient strategy for the organisa­tion and communication both within and be­tween brain regions. While it is now known that these oscillations actively contribute to sensory perception and cognition in the adult brain, their function during development is still largely unknown. Recent experimental data revealed the ability of immature human and rodent brain to generate various patterns of electrical activity. Their properties and un­derlying mechanisms may vary among dif­ferent brain areas. However, these early pat­terns of activity seem to facilitate the refine­ment of cortical maps involved in sensory perception as well as mnemonic and execu­tive processing. Here we review recent stud­ies, which characterize the early oscillatory activity and demonstrate its impact on brain development.
Addressing barriers to safe abortion
Authors: Culwell Kelly R. , Hurwitz Manuelle
Published: March 2013

The latest World Health Organization data estimate that the total number of unsafe abortions globally has increased to 21.6 million in 2008. There is increasing recognition by the international community of the importance of the contribution of unsafe abortion to maternal mortality. However, the barriers to delivery of safe abortion services are many. In 68 countries, home to 26% of the world's population, abortion is prohibited altogether or only permitted to save a woman's life. Even in countries with more liberal abortion legal frameworks, additional social, economic, and health systems barriers and the stigma surrounding abortion prevent adequate access to safe abortion services and postabortion care. While much has been achieved to reduce the barriers to comprehensive abortion care, much remains to be done. Only through the concerted action of public, private, and civil society partners can we ensure that women have access to services that are safe, affordable, confidential, and stigma free.
Servitization: Disentangling the impact of service business model innovation on manufacturing firm performance
Authors: Kastalli Ivanka Visnjic , Van Looy Bart
Published: March 2013

As manufacturing businesses operate in an ever more competitive, global economy where products are easily commoditized, innovating by adding services to the core product offering has become a popular strategy. Contrary to the economic benefits expected, recent findings pinpoint implementation hurdles that lead to a potential performance decline, the so‐called ‘servitization paradox’. In this paper, we analyze this paradox by disentangling the value creation and value appropriation processes of 44 national subsidiaries of a global manufacturing firm turned product‐service provider, in the 2001–2007 period. Our findings show that the firm under study is able to successfully transcend the inherent substitution of products by services and to enact complementary sales dynamics between the two activities. Moreover, labor‐intensive services such as maintenance, which imply higher levels of customer proximity, further enhance product sales. Empirical results also reveal a positive yet non‐linear relationship between the scale of service activities and profitability: while initial levels of servicing result in a steep increase in profitability, a period of relative decline is observed before the positive relationship between the scale of services and profitability re‐emerges. These findings suggest the presence of initial short‐term gains but also indicate the existence of a ‘profitability’ hurdle; profitable growth seems feasible only to the extent that investments in service capability are translated into economies of scale. In helping to clarify the performance implications of service innovation, our findings suggest pathways to sustainable growth through servitization for manufacturing firms.
1-REGULAR CAYLEY GRAPHS OF VALENCY 7
Authors: LI JING JIAN , ZHANG GENG RONG , LING BO
Published: March 2013

A graph $\mit{\Gamma} $ is called $1$-regular if $ \mathsf{Aut} \mit{\Gamma} $ acts regularly on its arcs. In this paper, a classification of $1$-regular Cayley graphs of valency $7$ is given; in particular, it is proved that there is only one core-free graph up to isomorphism.
Genetic structure ofLycorma delicatula(Hemiptera: Fulgoridae) populations in Korea: implication for invasion processes in heterogeneous landscapes
Authors: Park Marana , Kim Kyung-Seok , Lee Joon-Ho
Published: March 2013

Lycorma delicatula(White) was identified in 2004 as an invasive pest in South Korea, where it causes serious damage to vineyard crops. To investigate the population structure and dispersal pattern ofL. delicatulain South Korea, we estimated the population genetic structure and gene flow among nine locations across the country using seven microsatellite markers. AlthoughL. delicatulaspread throughout most of its geographical range in South Korea within 5–7 years following invasion, its populations show evidence of genetic structuring across the range with a low but significant globalFST(genetic differentiation across all populations) of 0.0474. Bayesian-based clustering analysis indicates the presence of at least three genetically unique populations in South Korea, including populations in northeastern South Korea, which show a distinct genetic background. However, isolation by distance suggests that populations in South Korea have not yet reached genetic equilibrium. Estimates of the historical rate of gene flow (Nem) indicate that relatively high rates of flow have been maintained among populations within the western region, which may indicate recent range expansion. A population assignment test using the first-generation migrant detection method suggested that long-distance dispersal ofL. delicatulamay have occurred over large areas of South Korea. More complex dispersal patterns may have occurred duringL. delicatulainvasion of heterogeneous landscapes in South Korea.
INTRA-CORPORATE CONSPIRACY: AN INTRIGUING PROSPECT
Authors: Witting Christian
Published: March 2013

This paper considers whether unlawful means conspiracy might have a role to play in extending liability from insolvent companies to those who stand behind them. A reason for thinking that the tort might have such a role is that, where an agreement to injure exists, liability can be found not only in those who commit unlawful acts but in any other persons who take steps to further the conspiracy. The paper argues, furthermore, that courts should accept that unlawful means conspiracy might be committed between even the smallest company and its controlling shareholder. This would strengthen the propositions that the company is a separate legal person with its own rights and responsibilities and that it is competent to deal with all comers, including its controller.
Padma Kant Shukla 1950–2013
Authors: BINGHAM ROBERT , ELIASSON BENGT , MENDONCA TITO , STENFLO LENNART
Published: March 2013

Professor Padma Kant Shukla passed away on the 26th of January in New Delhi, India, just after receiving the prestigious Hind Rattan (Jewel of India) Award. He was born in the village Tulapur, Uttar Pradesh (UP), India and was educated there. After his Ph.D. in Physics from Banaras Hindu University in Varanasi, he obtained his second doctorate degree in Theoretical Plasma Physics from Umea University under the supervision of one of us (Lennart Stenflo). He worked at the Faculty of Physics & Astronomy, Ruhr-University Bochum, Germany since January 1973, where he was a permanent faculty member and Professor of International Affairs, a position that was created for him to honour his international accomplishments and reputation.
Asking the Right Questions: Remembering David Montgomery
Authors: Fujita-Rony Dorothy
Published: March 2013

David and Marty Montgomery had enormous influence over my life and intellectual work, in ways that I continue to discover on a daily basis. I first heard about David in the early 1980s when I started Yale College because he was well known for being a wonderful lecturer. When I went to college, we were deep in the middle of Reagan's first term as president. Those were conservative times. Many of us undergraduates had no direct memories of the Civil Rights Movement, the Vietnam War, or the political unrest of the late 1960s and looked forward to becoming lawyers or working on Wall Street. Someone recommended that I take David Montgomery's class because he was a well-known professor. So along with a few hundred of my classmates, I trooped along to the Lindsley-Chit 101 classroom. I do not remember much of those initial lectures, but I do remember how David had great stage presence as he strode around the stage and told us stories about everyday people who fought for workers' rights.
When the Plumber(s) Come to Fix a Country: Doing Labor History in Brazil
Authors: French John D. , Fortes Alexandre
Published: March 2013

Those with a sharp tongue might say that labor historians in contemporary Brazil operate in the shadows or, to be more accurate, the shadow cast by the success of Latin America's most famous trade unionist, who served as president from 2002–2010. The field's growth in the number and quality of practitioners, as well as the breadth of their ambitions, cannot be separated from the memorable metalworkers' strikes of 1979 and 1980, the subsequent defeat of the military dictatorship in 1985, and the construction of a militant trade unionism and the radical Workers' Party that ran Luiz Inácio Lula da Silva for president in five successive elections between 1989 and 2006.
Taking Stock: Labor History during the Past Fifty Years
Authors: Kirk Neville
Published: March 2013

This essay has two aims. The first is to provide a critical overview of the nature and development of labor history in selected places during the past fifty years. The second is to offer a critical evaluation of the recent “transnational turn” in labor history and its likely future development. Although reference is made to the global context and to labor history beyond national borders, my main focus rests upon the development of labor history in parts of the Americas and the countries of Britain, Ireland, Germany, India, Japan, and Australia.
An Enlightening Decade? New Histories of 1970s’ Britain
Authors: Black Lawrence
Published: March 2013

The 1970s have made something of a comeback recently–in terms of interest, if not always reputation. This is partly because it was an unfashionable, “lost” decade, possessed of a depressing image in the shadows of its immediate neighbors and because the present economic crisis has made its difficulties relevant and brought them closer. The decade is ripe for revisionism, as well as for seeking lessons. And what ultimately emerges is not just an arc towards neoliberalism but a more fragmented picture, liberating in many respects–and which demands historians come to terms with the grim decline long associated with the decade.
BOUNDARY ANGULAR DERIVATIVES OF GENERALIZED SCHUR FUNCTIONS
Authors: BOLOTNIKOV VLADIMIR , WANG TENGYAO , WEISS JOSHUA M.
Published: March 2013

Characterization of generalized Schur functions in terms of their Taylor coefficients was established by Krein and Langer [‘Über einige Fortsetzungsprobleme, die eng mit der Theorie hermitescher Operatoren im Raume${\Pi }_{\kappa } $zusammenhängen. I. Einige Funktionenklassen und ihre Darstellungen’,Math. Nachr. 77(1977), 187–236]. We establish a boundary analogue of this characterization.
HYPERCOMMUTING VALUES IN ASSOCIATIVE RINGS WITH UNITY
Authors: DE FILIPPIS VINCENZO , SCUDO GIOVANNI
Published: March 2013

Let $K$ be a commutative ring with unity, $R$ an associative $K$-algebra of characteristic different from $2$ with unity element and no nonzero nil right ideal, and $f({x}_{1} , \ldots , {x}_{n} )$ a multilinear polynomial over $K$. Assume that, for all $x\in R$ and for all ${r}_{1} , \ldots , {r}_{n} \in R$ there exist integers $m= m(x, {r}_{1} , \ldots , {r}_{n} )\geq 1$ and $k= k(x, {r}_{1} , \ldots , {r}_{n} )\geq 1$ such that $\mathop{[{x}^{m} , f({r}_{1} , \ldots , {r}_{n} )] }\nolimits_{k} = 0$. We prove that: (1) if $\text{char} (R)= 0$ then $f({x}_{1} , \ldots , {x}_{n} )$ is central-valued on $R$; and (2) if $\text{char} (R)= p\gt 2$ and $f({x}_{1} , \ldots , {x}_{n} )$ is not a polynomial identity in $p\times p$ matrices of characteristic $p$, then $R$ satisfies ${s}_{n+ 2} ({x}_{1} , \ldots , {x}_{n+ 2} )$ and for any ${r}_{1} , \ldots , {r}_{n} \in R$ there exists $t= t({r}_{1} , \ldots , {r}_{n} )\geq 1$ such that ${f}^{{p}^{t} } ({r}_{1} , \ldots , {r}_{n} )\in Z(R)$, the center of $R$.
Anodal transcranial direct current stimulation increases brain intracellular pH and modulates bioenergetics
Authors: Rae Caroline D. , Lee Vincent H.-C. , Ordidge Roger J. , Alonzo Angelo , Loo Colleen
Published: March 2013

Transcranial direct current stimulation is an emerging treatment for brain disorders but its mode of action is not well understood. We applied 10 min 1 mA anodal transcranial direct current stimulation (tDCS) inside the bore of a 3 T MRI scanner to the left dorsolateral prefrontal cortex of 13 healthy volunteers (aged 19–28 yr) in a blinded, sham-controlled, cross-over design. Brain bioenergetics were measured from the left temporo-frontal region using 31P magnetic resonance spectroscopy before, during and for 20 min following tDCS. Brain pH rose during tDCS and remained elevated afterwards. Phosphomonoesters were significantly decreased while inorganic phosphate (Pi) also fell. Partial-least squares discriminant analysis of the data revealed two significantly different subject groups: one where phosphocreatine (PCr), ATP and Pi fell along with a larger increase in pH and one where PCr and ATP increased along with a smaller increase in pH and a slower and more sustained decrease in Pi. Group membership was predicted by baseline pH and ATP. We interpreted the effects of tDCS as driving two biochemical processes: cellular consumption of ATP causing hydrolysis of PCr via the creatine kinase reaction driving the increase in pH; synthesis of ATP and PCr by mitochondria with concomitant drop in Pi and phosphomonoester levels.
Hierarchical molecular tagging to resolve long continuous sequences by massively parallel sequencing
Authors: Lundin Sverker , Gruselius Joel , Nystedt Björn , Lexow Preben , Käller Max , Lundeberg Joakim
Published: March 2013

Here we demonstrate the use of short-read massive sequencing systems to in effect achieve longer read lengths through hierarchical molecular tagging. We show how indexed and PCR-amplified targeted libraries are degraded, sub-sampled and arrested at timed intervals to achieve pools of differing average length, each of which is indexed with a new tag. By this process, indices of sample origin, molecular origin and degree of degradation is incorporated in order to achieve a nested hierarchical structure, later to be utilized in the data processing to order the reads over a longer distance than the sequencing system originally allows. With this protocol we show how continuous regions beyond 3000 bp can be decoded by an Illumina sequencing system and we illustrate the potential applications by calling variants of the lambda genome, analysing TP53 in cancer cell lines and targeting a variable canine mitochondrial region.
The Role of Fat Grafting in the Treatment of Posttraumatic Maxillofacial Deformities
Authors: Arcuri Francesco , Brucoli Matteo , Baragiotta Nicola , Stellin Livia , Giarda Mariangela , Benech Arnaldo
Published: March 2013

Purpose

The first autologous adipose tissue grafting was performed by Neuber in 1893 with an open approach. In the early 1980s, Illouz and Fournier introduced closed liposuction. In the 1990s, Coleman published a new method of atraumatic fat transplantation. Recently, immunohistochemical studies of the extracellular matrix of the lipoaspirate showed the presence of adipose-derived stem cells. The purpose of this study is to describe the role of fat grafting in the management of posttraumatic facial deformities.

Methods

The study population was composed of all patients who underwent facial fat grafting between March 2008 and November 2010 as a secondary reconstructive procedure after an initial unsatisfactory treatment of the skeletal fractures. We analyzed the postoperative morphological changes by comparing the grafted side of the face to the contralateral side with the aid of a software package.

Results

Nineteen patients were surgically treated with fat transplantation for facial asymmetry due to a pathological postoperative healing of the soft tissue. Clinical examination and software analysis showed adequate postoperative facial balance without major complications.

Conclusion

Fat grafting is a very powerful tool to correct posttraumatic maxillofacial deformities and to ensure a long-term follow-up. Although we have achieved excellent clinical results in our reconstructive clinical cases, we are convinced that more complex prospective studies, enriched by long-term radiological controls, are needed to fully understand the biological behavior of the transplanted fat in the posttraumatic face.
Nanowire-filled polymer composites with ultrahigh thermal conductivity
Authors: Balachander Nikhil , Seshadri Indira , Mehta Rutvik J. , Schadler Linda S. , Borca-Tasciuc Theo , Keblinski Pawel , Ramanath Ganpati
Published: March 2013

Realizing high thermal conductivity nanocomposites is a challenge because of difficulties in incorporating high fractions of uniformly dispersed nanofillers and countering low filler-matrix interfacial conductance. Here, we obviate these issues by using <3 vol. % gold nanowire fillers to obtain a 30-fold increase in polydimethylsiloxane thermal conductivity that is 6-fold higher than any nanocomposite at low nanofiller loadings and exceeds theoretical predictions. The nanowire diameter and aspect ratio are keys to obtaining cold-welded networks that enhance thermal conductivity while fostering low modulus and electrical conductivity. Such nanowire nanocomposites are attractive for many applications in electronics, packaging, and energy devices.
Vibration-vibration and vibration-translation energy transfer in H2-H2 collisions: A critical test of experiment with full-dimensional quantum dynamics
Authors: dos Santos S. Fonseca , Balakrishnan N. , Forrey R. C. , Stancil P. C.
Published: March 2013

Quantum scattering calculations of vibration-vibration (VV) and vibration-translation (VT) energy transfer for non-reactive H2-H2 collisions on a full-dimensional potential energy surface are reported for energies ranging from the ultracold to the thermal regime. The efficiency of VV and VT transfer is known to strongly correlate with the energy gap between the initial and final states. In H2(v = 1, j = 0) + H2(v = 0, j = 1) collisions, the inelastic cross section at low energies is dominated by a VV process leading to H2(v = 0, j = 0) + H2(v = 1, j = 1) products. At energies above the opening of the v = 1, j = 2 rotational channel, pure rotational excitation of the para-H2 molecule leading to the formation of H2(v = 1, j = 2) + H2(v = 0, j = 1) dominates the inelastic cross section. For vibrationally excited H2 in the v = 2 vibrational level colliding with H2(v = 0), the efficiency of both VV and VT process is examined. It is found that the VV process leading to the formation of 2H2(v = 1) molecules dominates over the VT process leading to H2(v = 1) + H2(v = 0) products, consistent with available experimental data, but in contrast to earlier semiclassical results. Overall, VV processes are found to be more efficient than VT processes, for both distinguishable and indistinguishable H2-H2 collisions confirming room temperature measurements for v = 1 and v = 2.
Isotope effects on the photodesorption processes of X2O (X = H,D) and HOD ice
Authors: Koning J. , Kroes G. J. , Arasa C.
Published: March 2013

To investigate the isotope effects on the photodesorption processes of X2O (X = H,D) ice, molecular dynamics calculations have been performed on the ultraviolet photodissociation of an H2O or a D2O molecule in an H2O or a D2O amorphous ice surface, and on HOD photodissociation in an H2O amorphous ice surface, where the photodissociated molecules were located in the top four or five monolayers at ice temperatures of 10, 20, 30, 60, and 90 K. Three photodesorption processes can occur upon X2O photodissociation: X atom photodesorption, OX radical photodesorption, and X2O (or HOD) molecule photodesorption. X2O (or HOD) photodesorption can occur after recombination of X and OX, or after an energetic X atom photofragment kicks a surrounding X2O molecule from the ice surface. Isotope effects are observed for the X atom and the OX radical photodesorption as well as for the kick-out photodesorption. However, no isotope effects were noticeable for the photodesorption of recombined X2O molecules. The average D atom photodesorption probabilities are about a factor 0.9 smaller than those for the H atom, regardless of the isotope of the surrounding ice system. Also, the kick-out mechanism is more likely to occur if a D photofragment is created upon dissociation than if an H atom is created. These observations can be explained by more efficient energy transfer from the D atom to water molecules than from the H atom. Reasoning based on the X2O phonon frequencies associated with the librational modes and energy transfer efficiencies explain why the OX radical photodesorption probabilities are noticeably larger if the OX radical desorbs from a D2O ice system than from an H2O ice system. Also, the OX radical photodesorption is more probable upon dissociation of DOX (X = H,D) than upon dissociation of HOX (X = H,D), because the initial kinetic energy of the OX radical is larger if the dissociation products are D + OX than H + OX. The branching ratio of \documentclass[12pt]{minimal}\begin{document}$\frac{\rm{OD}}{\rm{OH}}$\end{document} OD OH desorption following photodissociation of an HOD molecule in ice (about 1.0) is much lower than the \documentclass[12pt]{minimal}\begin{document}$\frac{\rm{OD}}{\rm{OH}}$\end{document} OD OH branching ratio in gas-phase HOD photodissociation. This may lead to differences in isotope fractionation in OH(g) formation in dense and diffuse clouds in the interstellar medium.
Theory of k→⋅π→+U formalism for diluted magnetic semiconductors: Application to p-type Sn1−xGdxTe
Authors: Tripathi G. S. , Dash K. , Behera S. N. , Nayak S. K. , Entel P.
Published: March 2013

We develop a k→⋅π→+U formalism, where k→ is the carrier wave vector and π→ is the momentum operator in the presence of the spin-orbit interaction, within the effective mass representation of Luttinger and Kohn, which includes an effective magnetic field arising out of the mean field treated Hubbard onsite Coulomb repulsion. An effective equation of motion is obtained in the Luttinger-Kohn basis. As distinguished from hitherto used ordinary perturbation techniques in k→⋅π→ formalism, we use a Green's function perturbation technique to derive the energy of a carrier in this formalism. We apply the formalism to look for possibilities of a ferromagnetic transition in the diluted magnetic p-type Sn1−xGdxTe based on the Stoner criterion. The carrier electronic structure developed for p-SnTe using the k→⋅π→ method is extended to p-type Sn1−xGdxTe. The Fermi energy, density of states, effective g-factor, and the effective mass are calculated as functions of hole density. Our results show that there could be a hole-induced transition to a ferromagnetic state at high hole concentrations and low temperatures in the dilute limit of Gd impurities.
Anharmonic Rice-Ramsperger-Kassel-Marcus (RRKM) and product branching ratio calculations for the partially deuterated protonated water dimers: Dissociation and isomerization
Authors: Song Di , Su Hongmei , Kong Fan-ao , Lin Sheng-Hsien
Published: March 2013

Partially deuterated protonated water dimers, H2O·H+·D2O, H2O·D+·HDO, and HDO·H+·HDO, as important intermediates of isotopic labeled reaction of H3O+ + D2O, undergo direct dissociation and indirect dissociation, i.e., isomerization before the dissociation. With Rice-Ramsperger-Kassel-Marcus theory and ab initio calculations, we have computed their dissociation and isomerization rate constants separately under the harmonic and anharmonic oscillator models. On the basis of the dissociation and isomerization rate constants, branching ratios of two primary products, [HD2O+]/[H2DO+], are predicted under various kinetics models with the harmonic or anharmonic approximation included. The feasible kinetics model accounting for experimental results is shown to include anharmonic effect in describing dissociation, while adopting harmonic approximation for isomerization. Thus, the anharmonic effect is found to play important roles affecting the dissociation reaction, while isomerization rates are shown to be insensitive to whether the anharmonic or harmonic oscillator model is being applied.
Temperature and pressure dependent geometry optimization and elastic constant calculations for arbitrary symmetry crystals: Applications to MgSiO3 perovskites
Authors: Wen Bin , Shao Tianjiao , Melnik Roderick , Kawazoe Yoshiyuki , Tian Yongjun
Published: March 2013

To optimize lattice parameters for arbitrary symmetry crystals under high temperature and high pressure conditions, a new “geometry optimization method for arbitrary symmetry crystals” has been proposed in this work. By minimizing non-equilibrium Gibbs energy functions for a series of deformed crystal configurations, the components of deformation tensors have been obtained, and allowing the optimized crystal lattice parameters to be determined. Based on our method and Zhao's method, a new method for calculating high temperature and high pressure elastic constants in arbitrary symmetry crystals has been deduced. To verify the effectiveness of the new method, the high temperature and high pressure lattice parameters and elastic constants of orthorhombic symmetry MgSiO3 pv have been studied, and a good agreement between calculated and experimental results has been obtained.
Transparent p-CuI/n-ZnO heterojunction diodes
Authors: Schein Friedrich-Leonhard , von Wenckstern Holger , Grundmann Marius
Published: March 2013

Transparent and electrically conducting p-type copper(I)-iodide thin-films form highly rectifying p-CuI/n-ZnO diodes. Sputtered copper thin films on glass were transformed into polycrystalline γ-CuI by exposing them to iodine vapor. The electrical parameters extracted from Hall effect are p=5×1018 cm−3, μh,Hall=6 cm2/Vs, and ρ=0.2 Ωcm for hole concentration, mobility, and electrical resistivity, respectively. Heterostructures consisting of p-CuI and pulsed-laser deposited n-ZnO were fabricated on a-plane sapphire substrates. The p-CuI/n-ZnO diode exhibits a current rectification ratio of 6×106 at ±2 V and an ideality factor of η=2.14.
Short desynchronization episodes prevail in synchronous dynamics of human brain rhythms
Authors: Ahn Sungwoo , Rubchinsky Leonid L.
Published: March 2013

Neural synchronization is believed to be critical for many brain functions. It frequently exhibits temporal variability, but it is not known if this variability has a specific temporal patterning. This study explores these synchronization/desynchronization patterns. We employ recently developed techniques to analyze the fine temporal structure of phase-locking to study the temporal patterning of synchrony of the human brain rhythms. We study neural oscillations recorded by electroencephalograms in α and β frequency bands in healthy human subjects at rest and during the execution of a task. While the phase-locking strength depends on many factors, dynamics of synchrony has a very specific temporal pattern: synchronous states are interrupted by frequent, but short desynchronization episodes. The probability for a desynchronization episode to occur decreased with its duration. The transition matrix between synchronized and desynchronized states has eigenvalues close to 0 and 1 where eigenvalue 1 has multiplicity 1, and therefore if the stationary distribution between these states is perturbed, the system converges back to the stationary distribution very fast. The qualitative similarity of this patterning across different subjects, brain states and electrode locations suggests that this may be a general type of dynamics for the brain. Earlier studies indicate that not all oscillatory networks have this kind of patterning of synchronization/desynchronization dynamics. Thus, the observed prevalence of short (but potentially frequent) desynchronization events (length of one cycle of oscillations) may have important functional implications for the brain. Numerous short desynchronizations (as opposed to infrequent, but long desynchronizations) may allow for a quick and efficient formation and break-up of functionally significant neuronal assemblies.
Operation of a titanium nitride superconducting microresonator detector in the nonlinear regime
Authors: Swenson L. J. , Day P. K. , Eom B. H. , Leduc H. G. , Llombart N. , McKenney C. M. , Noroozian O. , Zmuidzinas J.
Published: March 2013

If driven sufficiently strongly, superconducting microresonators exhibit nonlinear behavior including response bifurcation. This behavior can arise from a variety of physical mechanisms including heating effects, grain boundaries or weak links, vortex penetration, or through the intrinsic nonlinearity of the kinetic inductance. Although microresonators used for photon detection are usually driven fairly hard in order to optimize their sensitivity, most experiments to date have not explored detector performance beyond the onset of bifurcation. Here, we present measurements of a lumped-element superconducting microresonator designed for use as a far-infrared detector and operated deep into the nonlinear regime. The 1 GHz resonator was fabricated from a 22 nm thick titanium nitride film with a critical temperature of 2 K and a normal-state resistivity of 100 μΩ cm. We measured the response of the device when illuminated with 6.4 pW optical loading using microwave readout powers that ranged from the low-power, linear regime to 18 dB beyond the onset of bifurcation. Over this entire range, the nonlinear behavior is well described by a nonlinear kinetic inductance. The best noise-equivalent power of 2×10−16 W/Hz1/2 at 10 Hz was measured at the highest readout power, and represents a ∼10 fold improvement compared with operating below the onset of bifurcation.
Shape memory metamaterials with tunable thermo-mechanical response via hetero-epitaxial integration: A molecular dynamics study
Authors: Guda Vishnu Karthik , Strachan Alejandro
Published: March 2013

We show that nanoscale epitaxial superlattices (SLs) can be used to engineer the energy landscape that governs the martensitic transformation in shape memory alloys and tune their thermo-mechanical response. We demonstrate the approach using large-scale molecular dynamics simulations of a SL material consisting of alternate layers of a shape memory Ni-rich NiAl alloy and NiAl B2 alloy. The non-martensitic NiAl alloy was chosen to reduce the energy barrier that separates the martensite and austenite phases of the SL and its incorporation leads to a reduction in the thermal hysteresis of the transition. This is a desirable feature in applications involving actuation and our approach represents a generally applicable and powerful avenue to engineer desired behavior in mechanically active materials.
Enhancement of laser to x-ray conversion with a low density gold target
Authors: Shang Wanli , Yang Jiamin , Dong Yunsong
Published: March 2013

X-ray emission from laser-plasma interaction is an important x-ray source, and improving laser to x-ray conversion is imperative for various applications. The laser to x-ray conversion efficiency (CE) was simulated for gold targets with different initial densities. Using a 0.1 g/cm3 Au layer target, an x-ray conversion efficiency of 50.8% was obtained, which was 1.34 times of the 37.9% for the solid density target. It has been shown that the enhancement of the x-ray conversion efficiency is caused by the increase of absorption from the incident laser and reduction of ion kinetic energy due to the initial low density of the gold target.
Ballistic electron transport properties across the manganese/silicon interface
Authors: Friend B. E. , Wolter E. , Kidd T. E. , Stollenwerk A. J.
Published: March 2013

Ballistic electron transmission is used to investigate electron transport across the Au/Mn/Si and Au/Si interfaces. The Au/Mn/Si spectra exhibit multiple threshold voltages above the Schottky barrier. The energetic spacing of these threshold voltages is found to vary with Mn thickness. These features are believed to be the result of resonant transport. Transmission calculations match the experimental data exceedingly well, but only when one accounts for reflections at the Au/Mn interface. Interestingly, scattering at the Mn/Si interface is over an order of magnitude less than at the Au/Si interface, suggesting a better matching of available states at the Mn/Si interface.
Nitrogen passivation at GaAs:Al2O3 interfaces
Authors: Guo Yuzheng , Lin Liang , Robertson John
Published: March 2013

The effects of nitrogen passivation at interfaces between III–V semiconductors and high dielectric constant oxides are calculated using the GaAs:Al2O3 interface as a model. Nitrogen replaces As from interface sites. The N-N dimer is found to be unstable and breaks into N dangling bonds. The N dangling bond has states lying well below the bulk valence band edge, away from the band gap, due to the electronegativity of nitrogen. Thus nitrogen is an effective passivant because it removes the states of two candidate species away from the gap.
Age splitting of the La(Fe1−xSix)13Hy first order magnetocaloric transition and its thermal restoration
Authors: Zimm Carl B. , Jacobs Steven A.
Published: March 2013

The La(Fe1−xSix)13Hy system has a first order ferromagnetic phase transition with a large magnetocaloric effect for 0.11 < x < 0.13. Such materials produced the highest currently published cooling power of a magnetic refrigerator. Adjusting the H content, y allows selection of any Curie point Tc from ∼200 K to 330 K, but hydrogen-unsaturated material (y < 1.6) with a first order transition exhibits an unusual instability. If La(Fe1−xSix)13Hy is held within a few K of its initial Tc, an initially single magnetic transition, with a sharp differential scanning calorimetry peak, gradually splits into two transitions separated by a large temperature interval. The ultimate splitting interval depends almost linearly on (1.6-y) and Tc. If the material is held more than 10 K above or below Tc, an initially sharp transition is retained, and a split transition is restored to its original sharp single transition. The recovery rate increases with temperature. For temperatures above 320 K, the recovery rate is rapid enough to allow overnight recovery of magnetocaloric material that is in a split state. This method was employed to maintain high performance of La(Fe1−xSix)13Hy in a magnetic refrigerator. In order to verify that the recovery process involves the macroscopic movement of hydrogen within the solid, a portion of 0.2 mm diameter particle material with a split transition was ground into particles of 0.05 mm diameter. The unground 0.2 mm particles and the ground 0.05 mm particles were held at 13 K above Tc. The 0.3 mm particles recovered their initial single transition, but the 0.05 mm particles, when examined as a group, retained their split line, presumably because they had been separated into particles with differing total hydrogen fraction y.
Interrelationship between the shear modulus of a metallic glass, concentration of frozen-in defects, and shear modulus of the parent crystal
Authors: Makarov A. S. , Khonik V. A. , Mitrofanov Yu. P. , Granato A. V. , Joncich D. M. , Khonik S. V.
Published: March 2013

The Interstitialcy theory assumes that major structural defects defining the properties of glass are similar to dumbbell interstitials in crystalline metals. Within the framework of this approach, we showed that at a constant defect concentration, the temperature coefficient of the shear modulus of glass equals to that of the parent crystal, in agreement with the theory. Relaxation of the defect system leads to either positive or negative variation of this coefficient, depending on the sign of defect concentration change. A full map of the defect concentration for initial, relaxed, and quasi-equilibrium states of a Pd-based glass is presented.
Ultrahigh dielectric constant composites based on the oleic acid modified ferroferric oxide nanoparticles and polyvinylidene fluoride
Authors: Wang Tingting , Li Weiping , Luo Laihui , Zhu Yuejin
Published: March 2013

We studied the dielectric properties of the percolative composites based on polyvinylidene fluoride and oleic acid modified ferroferric oxide nanoparticles. It demonstrates that surface modification not only can prevent the aggregation of the nanoparticles but also can greatly increase the dielectric constant of the composites. The space charge polarization at the interfaces between modified nanoparticles and polymers results in huge enhancement of dielectric constant. The maximum of dielectric constant is up to 24 105 at 100 Hz and the dielectric loss is still controlled in the range of 0–2.5. These composites can be used as the dielectric materials of super-capacitors.
Organic transistor and inverter based on assembly of organic nanowires achieved by optimizing surface morphology
Authors: Yadav Sarita , Sharma Akanksha , Ghosh Subhasis
Published: March 2013

We have demonstrated that assemblies of organic nanowires can be grown on Si and SiO2 substrates by controlling growth parameters. At higher growth temperatures, anisotropic growth dominates over isotropic growth, resulting in surface morphologies consisting of nanowire-like elongated grains. These elongated grains provide better π-π stacking, leading to higher carrier mobility and better performance of organic transistors. Using this approach, we have demonstrated organic inverter using complementary semiconducting materials, p-type copper phthalocyanine and n-type copper hexadecafluoro phthalocyanine. These results indicate that small organic molecule-based nanowires are promising candidates for future organic based microelectronics.
Optical endpoint detection for plasma reduction of graphene oxide
Authors: Kim MaengJun , Kahng Yung Ho , Kim Yong Jae , kumar T. Prem , Park KwangMook , Lee Kwanghee , Jang Jae-Hyung
Published: March 2013

The plasma reduction process for the production of reduced graphene oxide (rGO) requires precise process control in order to avoid the degradation of electrical characteristics. We report that the reduction status of the graphene oxides could be determined by monitoring the optical emission intensity at 844.6 nm. Properties of the rGO samples processed with various plasma exposure times were characterized by X-ray photoelectron spectroscopy, Raman spectroscopy, atomic force microscopy, and 4-point probe measurements. Optimum electrical performance and surface morphology were obtained from the sample for which the reduction process was stopped when the emission intensity at 844.6 nm began to decrease.
Oxygen segregation at coherent grain boundaries of cubic boron nitride
Authors: Chen Chunlin , Lv Shuhui , Wang Zhongchang , Saito Mitsuhiro , Shibata Naoya , Taniguchi Takashi , Ikuhara Yuichi
Published: March 2013

Segregation of even a trace amount of impurities to grain boundaries (GBs) can often modify properties of polycrystalline materials. Here, we demonstrate, by a combined study of advanced transmission electron microscopy with atomistic first-principles calculations to two coherent Σ9 and Σ3 GBs of cubic boron nitride (BN), that the two GBs are inclined to trap oxygen, which induces notable electronic states at Fermi level in the forbidden band gap of bulk BN and lowers the GB adhesion energies significantly. Such GB weakening by oxygen segregation is attributed to the lessened charge transfer between grains and more ionic bonding nature at GB.
Impacts of level of utilisation by grazing on an Astrebla (Mitchell grass) grassland in north-western Queensland between 1984 and 2010. 2. Plant species richness and abundance
Authors: Orr D. M. , Phelps D. G.
Published: March 2013

The occurrence of interstitial species in Astrebla grasslands in Australia are influenced by grazing and seasonal rainfall but the interactions of these two influences are complex. This paper describes three studies aimed at determining and explaining the changes in plant species richness and abundance of the interstitial species in a long-term sheep utilisation experiment in an Astrebla grassland in northern Queensland. In the first study, increasing utilisation increased the frequency of Dactyloctenium radulans (Button grass) and Brachyachne convergens (Downs couch) and reduced that of Streptoglossa adscendens (Mint bush). In the second study, seasonal rainfall variation between 1984 and 2009 resulted in large annual differences in the size of the seed banks of many species, but increasing utilisation consistently reduced the seed bank of species such as Astrebla spp. and S. adscendens and increased that of species such as B. convergens, D. radulans, Amaranthus mitchellii (Boggabri) and Boerhavia sp. (Tar vine). In the third study, the highest species richness occurred at the lightest utilisation because of the presence of a range of palatable forbs, especially legumes. Species richness was reduced as utilisation increased. Species richness in the grazing exclosure was low and similar to that at the heaviest utilisation where there was a reduction in the presence of palatable forb species. The pattern of highest species richness at the lightest grazing treatment was maintained across three sampling times, even with different amounts of seasonal rainfall, but there was a large yearly variation in both the density and frequency of many species. It was concluded that the maintenance of highest species richness at the lightest utilisation was not aligned with other data from this grazing experiment which indicated that the maximum sustainable wool production occurred at moderate utilisation.
Assessment of fire selectivity in relation to land cover and topography: a comparison between Southern European countries
Authors: Oliveira Sandra , Moreira Francisco , Boca Roberto , San-Miguel-Ayanz Jesús , Pereira José M. C.
Published: March 2013

Land cover distribution is one of the factors that influence fire behaviour and its consequences in the landscape. The relation between land cover type and fire was investigated at a broad scale, in order to analyse land cover differences in fire proneness. The selection ratio for nine different land cover categories was calculated for the fire perimeters mapped in Southern Europe between 2000 and 2008. The results obtained were then compared per country and region. The fire proneness of topographic classes and its potential association with land cover types were also assessed. At a broad scale, shrublands and grasslands were the most preferred by fire, whereas artificial surfaces and agricultural areas were less fire prone. Forests showed intermediate values of selection ratio. Principal components and cluster analysis identified three regions with significant differences among them: the Mediterranean area, the Balkans and Turkey–Cyprus. Slopes >25% and with a north aspect were also less susceptible to burning. The identification of common land cover and topographic characteristics allows for the application of common management strategies in Southern Europe, coupled with particular measures adjusted to the conditions that are country- and region-specific.