bluuebunny/crossref_metadata_2025 huggingface dataset:
Chaotic masking for securing RFID systems against relay attacks
Authors: Malek Behzad , Miri Ali
Published: June 2012

The relay attack is a simple yet effective attack against most radio‐frequency identification (RFID) authentication systems. Because of the minimalist design of an RFID system, a lightweight authentication scheme must be designed to provide a strong level of security for low‐cost RFID tags. In this work, we propose a simple but secure masking scheme that counters the relay attack in RFID systems. Our scheme is the first solution based on the chaos suppression theory. We have exploited the chaotic characteristics of a dynamic Lorenz controller to distinguish a legitimate RFID reader from a proxy reader in the relay attack. We also show that the proposed approach is practical using simulation results. Copyright © 2012 John Wiley & Sons, Ltd.
Determination of Physical and Chemical Properties of Electric Arc Furnace Dusts for the Purposes of Their Utilization
Authors: Lis Teresa , Nowacki Krzysztof
Published: June 2012

Electric arc furnace dusts are among the most environment polluting wastes. Numerous utilization technologies have been developed for dusts containing up to 4% of Zn and more than 20% of Zn. However, the remaining part of steelmaking dusts are the most problematic ones, as they are mostly dumped generating costs and posing serious environmental threats. This paper provides an analysis of the potential utilization options for dusts containing ca. 10% of zinc generated in a single electric steelmaking shop. Physical and chemical properties of dusts have been determined and examined, and furthermore, results of the studies on the EAFD utilization in production of cement clinker and industrial glass have been discussed. It has been found that a particularly beneficial feature of the production technology proposed is that the iron content exceeds 30%. The influence of the dusts used on the functional properties of the products obtained has been established as well as the environmental impact of the processes and products in question and the dust mass possible to be utilized in the production technology proposed have been determined.
The climate benefit of Swedish ethanol: present and prospective performance
Authors: Börjesson Pål , Ahlgren Serina , Berndes Göran
Published: June 2012

Biofuels are introduced in the transportation sector as a means to reduce the sectorŉs greenhouse gas (GHG) emissions. European and other national and global standardization schemes for biofuels also include certain minimum GHG emission reduction among the requirements to be met. Assessments of the GHG performance of biofuels are complex due to the complexities of physical, chemical, and biological conversion processes, feedstock diversity, and variability in site‐specific environmental conditions. Differences may also arise in analytical approaches, including in how direct and indirect land use change is accounted for. Current production of first‐generation ethanol in Sweden, based on wheat, causes relatively low GHG emissions, whereas a future expansion may cause increased emissions from changes in land use and less optimal utilization of by‐products. Such negative impacts may be avoided by an introduction and expansion of second‐generation ethanol based on lignocellulosic feedstock (e.g., straw, short rotation coppice, and forest residues), which eventually could become the major feedstock in ethanol production. This transition to low, indirect impact ethanol systems creates an opening for a significant expansion of ethanol in the transport sector without compromising the sizeable climate benefits and sustainable resource exploitation.

This article is categorized under:

Bioenergy > Science and Materials

Bioenergy > Systems and Infrastructure

Bioenergy > Climate and Environment
GreenATP: APPortunities to catalyze local to global positive tipping points through collaborative innovation networks
Authors: Totten Michael P.
Published: June 2012

Humanity's unceasing ingenuity is generating vast economic gain for billions of people with goods unavailable to even kings and queens throughout most of history. Unfortunately, this economic growth has triggered unprecedented security challenges of global and historical magnitude: more absolute poor than any time in human history, the sixth largest extinction spasm of life on earth, climate destabilization with mega‐catastrophic consequences, and multi‐trillion dollar wars over access to energy. These multiple, inextricably interwoven challenges have low probability of being solved if decision makers maintain the strong propensity to think and act as if life is linear, has no carrying capacity limits, uncertainty is controllable, the future free of surprises, planning is predictable and compartmentalized into silos, and Gaussian distributions are taken as the norm while fat‐tail futures are ignored. Although the future holds irreducible uncertainties, it is not fated. The emergence of Internet availability to one‐third of humanity and access by most of humanity within a decade has spawned the Web analogue of a ‘Cambrian explosion’ of speciation in knowledge applications. Among the most prodigious have been collaboration innovation networks (COINs) reflecting a diversity of ‘genome’ types, facilitating a myriad of collective intelligence crowd‐swarming phenomena (Malone T, Laubacher R, Dellarocas C. The Collective Intelligence Genome. MIT Sloan Management Review, Spring; 2010, Vol. 51). COINs are essential tools for accelerating and scaling transformational solutions (positive tipping points) to the wicked problems confronting humanity. Web COINs enable acceleration of multiple‐benefit innovations and solutions to these problems that permeate the nested clusters of linked nonlinear complex adaptive systems comprising the global biosphere and socioeconomy [Raford N. How to build a collective intelligence platform to crowdsource almost anything. Available at: http:news.noahraford.com. (Accessed November 30, 2011)]. The Web initiative, GreenATP, illustrates this opportunity.

This article is categorized under:

Energy and Climate > Economics and Policy
On Tris(dithiocarbamato)‐Chromium(III), Cr(S2CNH2)3
Authors: Teske Christoph Ludwig , Bensch Wolfgang
Published: June 2012

Scarab blue crystals of the title compound were precipitated from aqueous solutions of CrIII salts by adding an excess of ammoniumdithiocarbamate solution. The compound crystallizes in the trigonal space group R$\bar{3}$ (No. 148) with a = 13.2694(8), c = 11.2542(7) Å and γ = 120°. The crystal structure consists of a three‐dimensional hydrogen‐bonded network of six Cr(S2CNH2)3 molecules per unit cell. The CrS6 polyhedron is twisted with trigonal antiprismatic arrangement and approximate D3 symmetry. Thermal decomposition starts at T ≈ 185 °C followed by several simultaneous decomposition reactions. The residue is a mixture of Cr2S3 and deficient sulfur chromium sulfides.
Syntheses, Crystal Structures and Thermal Behavior of Five New Complexes Containing 2, 4, 6‐Trifluorobenzoate as Ligand
Authors: Lamann Rainer , Hülsen Michael , Dolg Michael , Ruschewitz Uwe
Published: June 2012

Five new complexes containing 2, 4, 6‐trifluorobenzoateas ligand have been synthesized and structurally characterized, namely Li(C6F3H2COO)(H2O) (P21, Z = 2, 1),Cs(C6F3H2COO)(C6F3H2COOH) (P21/c, Z = 4, 2),Cu(C6F3H2COO)2(H2O)2 (P$\bar{1}$, Z = 1, 3), Cu(C6F3H2COO)2(MeOH) (P21/c. Z = 4, 4) and Ag(C6F3H2COO)(H2O) (C2/c, Z = 8, 5). 1–3 and 5 are coordination polymers forming strands (1, 3, 5) or corrugated layers (2). In 1 and 2 the benzoate ligand acts as a bridging ligand, whereas in 3 and 5 the benzoate ligand is not bridging and the molecular units are interconnected by bridging water molecules. In 4 and 5, dimeric Cu2 and Ag2 units, respectively, are formed with short M···M contacts. The dimeric units in 4 resemble the well‐known paddlewheel structural motif. In 5 these dimeric units are further connected by bridging water molecules, whereas in 4 only very weak F···H interactions connect the dimeric units. DTA/TG experiments on 1, 3 and 4 reveal that in a first step solvent molecules (H2O, MeOH) are unquestionably released. In 1–5 the torsion angles of the carboxylate group with respect to the aromatic ring deviate significantly from zero. These results are in very good agreement with the results of quantum chemical calculations of free 2, 4, 6‐trifluorobenzoic acid and its dimer at the DFT and RI‐MP2 level of theory.
Comparable Postoperative Morbidity and Mortality After Laparoscopic and Open Emergent Restorative Colectomy: Outcomes From the ACS NSQIP
Authors: Ballian Nikiforos , Weisensel Natalie , Rajamanickam Victoria , Foley Eugene F. , Heise Charles P. , Harms Bruce A. , Kennedy Gregory D.
Published: June 2012

Background

Laparoscopic surgery is safe and effective in the management of common abdominal emergencies. However, there is currently a lack of data about its use for emergency colorectal surgery. We hypothesized that laparoscopy can improve the postoperative outcomes of emergency restorative colon resection.

Methods

Adult patients undergoing emergent open and laparoscopic colon resection with primary anastomosis were retrieved from the American College of Surgeons National Surgical Quality Improvement Program database for the years 2005 to 2008 inclusive. Demographic and operative characteristics, laboratory values, and postoperative outcomes were compared between patients undergoing laparoscopic and open colon resection using univariate analyses, multivariate logistic regression, and propensity score analyses.

Results

A total of 341 laparoscopic (9.6 %) and 3211 (90.4 %) open colon resections were included. Patients undergoing laparoscopic surgery had a significantly lower prevalence of co‐morbidities and better postoperative outcomes. On multivariate analysis, laparoscopic surgery was an independent predictor of a longer operating time (p < 0.001) and shorter total (p = 0.013) and postoperative (p = 0.004) hospital stays, but it did not affect the need for intraoperative blood transfusion (p = 0.488), the 30‐day reoperation rates (p = 0.969), or mortality (p = 0.417). After adjusted propensity score analysis, postoperative morbidity (p = 0.833) and mortality (p = 0.568) were comparable in patients undergoing laparoscopic and open surgery.

Conclusions

On a national scale, laparoscopic emergent colon resections are being performed in a small number of patients, who have favorable co‐morbidity characteristics and improved postoperative outcomes. Laparoscopic emergent colon resection with primary anastomosis has postoperative morbidity and mortality rates comparable to those seen with the open approach, and it reduces the total and postoperative length of hospital stay.
Factors Associated with Psychological Distress among Women of African Descent at High Risk for BRCA Mutations
Authors: Cukier Yael R. , Thompson Hayley S. , Sussner Katarina , Forman Andrea , Jandorf Lina , Edwards Tiffany , Bovbjerg Dana H. , Schwartz Marc D. , Valdimarsdottir Heiddis B.
Published: June 2012

Little is known about psychological distress among women of African descent who are at high risk for a BRCA mutation. This is a group for whom breast cancer risk reduction is critical due to the group's high rates of breast cancer mortality. Distress is important to consider as it may reduce the potential benefit of genetic counseling and negatively affect decision making related to risk reduction. The goals of the current study were to examine breast cancer‐specific distress and depressive symptoms in women of African descent at who are at high risk for a BRCA mutation and to identify background factors associated with these outcomes. Participants were 148 high‐risk African American and Caribbean women who were part of a larger study that offered participants BRCA counseling at no cost. Participants completed the Impact of Events Scale, which assessed breast cancer‐specific distress, and the Center of Epidemiological Studies‐Depression Scale, which assessed depressive symptoms. Results of analyses revealed that almost half of the sample achieved scores indicating high and clinically significant breast cancer‐specific distress, while almost one‐third had clinically significant depression scores. Results further showed that low income was significantly associated with cancer‐specific distress, while having a cancer diagnosis was significantly associated with depressive symptoms. These results underscore the need for targeted psychological support throughout the genetic risk assessment process for this particular high‐risk group.
Design and Evaluation of a Decision Aid for Inviting Parents to Participate in a Fragile X Newborn Screening Pilot Study
Authors: Bailey Donald B. , Lewis Megan A. , Harris Shelly L. , Grant Tracey , Bann Carla , Bishop Ellen , Roche Myra , Guarda Sonia , Barnum Leah , Powell Cynthia , Therrell Bradford L.
Published: June 2012

The major objectives of this project were to develop and evaluate a brochure to help parents make an informed decision about participation in a fragile X newborn screening study. We used an iterative development process that drew on principles of Informed Decision Making (IDM), stakeholder input, design expertise, and expert evaluation. A simulation study with 118 women examined response to the brochure. An independent review rated the brochure high on informational content, guidance, and values. Mothers took an average of 6.5 min to read it and scored an average of 91.1 % correct on a knowledge test. Most women rated the brochure as high quality and trustworthy. When asked to make a hypothetical decision about study participation, 61.9 % would agree to screening. Structural equation modeling showed that agreement to screening and decisional confidence were associated with perceived quality and trust in the brochure. Minority and white mothers did not differ in perceptions of quality or trust. We demonstrate the application of IDM in developing a study brochure. The brochure was highly rated by experts and consumers, met high standards for IDM, and achieved stated goals in a simulation study. The IDM provides a model for consent in research disclosing complicated genetic information of uncertain value.
Quality of life: international and domestic students studying medicine in New Zealand
Authors: Henning Marcus A. , Kr¨ageloh Christian , Moir Fiona , Doherty Iain , Hawken Susan J.
Published: June 2012

International students form a significant proportion of students studying within universities in Western countries. The quality of life perceptions of international medical students in comparison with domestic medical students has not been well documented. There is some evidence to suggest that international medical students may have different educational and social experiences in relation to their domestic peers. This study investigates the levels of quality of life experienced by international and domestic students studying medicine. A total of 548 medical students completed the abbreviated version of the World Health Organization Quality of Life questionnaire. The focus of the analysis was to evaluate differences between international and domestic students in their early clinical years. The responses were analysed using multivariate analysis of variance methods. International medical students are experiencing lower social and environmental quality of life compared with domestic peers. International medical students in New Zealand have expressed quality of life concerns, which likely have an impact on their academic achievement, feelings of wellness, acculturation, and social adaptation. The findings reinforce the need for creating stronger social networks and accessible accommodation, as well as developing systems to ensure safety, peer mentorship and student support.
Holocene dune formation at Ash Meadows National Wildlife Area, Nevada, USA
Authors: Lancaster Nicholas , Mahan Shannon A.
Published: June 2012

Small isolated dune fields in the northern Mojave Desert are important centers of biodiversity and archaeological occupation sites. Currently dunes at Ash Meadows, Nevada, are stabilized by vegetation and are experiencing erosion of their upwind margins, indicating a negative sediment budget. New OSL ages from dunes at Ash Meadows indicate continuous eolian accumulation from 1.5 to 0.8 ka, with further accumulation around 0.2 ka. Prior studies (e.g., Mehringer and Warren, 1976) indicate periods of dune accumulation prior to 3.3 ka; 1.9–1 ka; and after 0.9 ka. These periods of eolian accumulation are largely synchronous with those identified elsewhere in the Mojave Desert. The composition of the Ash Meadows dunes indicates their derivation from regional fluvial sources, most likely during periods when axial washes were active as a result of enhanced winter precipitation.
Mountain glaciation and paleoclimate reconstruction in the Picos de Europa (Iberian Peninsula, SW Europe)
Authors: Serrano Enrique , González-Trueba Juan José , González-García María
Published: June 2012

Geomorphic mapping and stratigraphic analysis of a lake core document the late Quaternary glacial history of the Central and Eastern Massifs of the Picos de Europa, northwestern Spain. The distribution of glacial deposits indicates that at their most advanced positions glaciers occupied 9.1 km2, extended as far as 7 km down-valley and had an estimated equilibrium-line altitude (ELA) ranging between 1666 and 1722 m. Radiocarbon dating of sediment deposited in a lake dammed by moraines of this advance show that the maximum glacial extent was prior to 35,280 ± 440 cal yr BP. This advance was followed by two subsequent but less extensive late Pleistocene advances, recorded by multiple moraines flanking both massifs and sedimentary characteristics in the lake deposits. The last recognized glacial episode is the 19th-century maximum extent of small Little Ice Age glaciers in the highest cirques above 2200 m.
Disguised Protectionism and Linkages to the GATT/WTO
Authors: Kim Moonhawk
Published: June 2012

Member states of the GATT/WTO have linked some issue-areas outside trade to the institution and did so with varying depths. At the same time they have chosen not to link other issue-areas. What accounts for this variation? The author argues that states establish a legalized linkage between the GATT/WTO and an issue-area outside it when they are uncertain about the possibilities of disguised protectionism. Such uncertainty exists under two conditions: when diversity in regulations in an issue-area across states generates a large adverse impact on trade (negative externalities) but that diversity can be justified at the international level for (1) having an independent objective apart from hampering trade and (2) when there are few alternative policies to achieve that objective (legitimacy). States establish a highly legalized linkage in these situations to reduce the uncertainty and minimize disguised protectionism. By contrast, when regulatory diversity exhibits low legitimacy, states establish only a weakly legalized linkage. In the absence of meaningful externalities, they do not establish any linkages. The author evaluates this argument in two ways. He provides an overview of eleven issue-areas about which there have been some debates or conflicts about linkages to the GATT/WTO. In addition, he carries out in-depth case studies of three issue-areas—labor standards, environmental standards, and health safety standards. The findings of this article contribute to a better understanding of international institutions and cooperation as well as of the evolution of the multilateral trade institution.
Surface circulation in the Alborán Sea (western Mediterranean) inferred from remotely sensed data
Authors: Renault L. , Oguz T. , Pascual A. , Vizoso G. , Tintore J.
Published: June 2012

In this study, for the first time at regional scale, the combined use of remote sensing data (altimetry and sea surface temperature records) provides a description of the persistent, recurrent and transient circulation regimes of the Alborán Sea circulation. The analysis of 936 altimeter‐derived weekly absolute dynamic topography (ADT) and surface geostrophic current maps for 1993–2010 reveals the presence of a dominant annual signal and of two interannual modes of variability. The winter‐spring phase is characterized by two stable gyral scale features; the well‐known Western Anticyclonic Gyre within the western area and the Central Cyclonic Gyre, a new structure not identified in former studies, occupying the central and eastern parts of the Alborán Sea. A double anticyclonic gyre regime constitutes the stable circulation system of the summer–autumn period when the Eastern Anticyclonic Gyre is formed within the eastern Alborán basin. In this case, the Central Cyclonic Gyre is narrower and located closer to the Western Anticyclonic Gyre. They represent two stable states of the system, robust at the decadal time scale, whereas transient changes reflect perturbations on these stable states and are mainly observed at an interannual scale. The circulation variability and the gyral features development may be dynamically linked to the corresponding changes of the Gibraltar transport rates.
Too early to infer a global NPP decline since 2000
Authors: Ahlström Anders , Miller Paul A. , Smith Benjamin
Published: June 2012

The global terrestrial carbon cycle plays a pivotal role in regulating the atmospheric composition of greenhouse gases. It has recently been suggested that the upward trend in net primary production (NPP) seen during the 1980's and 90's has been replaced by a negative trend since 2000 induced by severe droughts mainly on the southern hemisphere. Here we compare results from an individual‐based global vegetation model to satellite‐based estimates of NPP and top‐down reconstructions of net biome production (NBP) based on inverse modelling of observed CO2 concentrations and CO2 growth rates. We find that simulated NBP exhibits considerable covariation on a global scale with interannual fluctuations in atmospheric CO2. Our simulations also suggest that droughts in the southern hemisphere may have been a major driver of NPP variations during the past decade. The results, however, do not support conjecture that global terrestrial NPP has entered a period of drought‐induced decline.
Observations of the structure of turbulent mixing across the Kuroshio
Authors: Kaneko Hitoshi , Yasuda Ichiro , Komatsu Kosei , Itoh Sachihiko
Published: June 2012

The mean structure of turbulence intensity across the Kuroshio in spring is presented by compositing microstructure profiles on a stream coordinate. The composite mean of turbulent energy dissipation rate
was high near fronts on both cyclonic and anticyclonic sides. On the cyclonic side,
> 10−8 W kg−1 (vertical diffusivity of > 3 × 10−5 m2 s−1) was observed in the region of strong vertical shear of geostrophic velocity. Depth‐averaged
within the depth range 50–150 m (150–250 m) was significantly higher at 0 to 50 km (−25 to 50 km) compared with >50 km from the axis. Although lower than on the cyclonic side,
at depths of 50–150 m on the anticyclonic side near the front was again enhanced. On this side, the total vertical shear of horizontal velocity was strong, whereas the geostrophic shear was weak.
Progressive microscopic damage associated with fault growth
Authors: Tamarkin T. , Ougier‐Simonin A. , Zhu Wenlu
Published: June 2012

It is known that microstuctural damage precedes macroscopic fracture in rocks during brittle failure. The quantitative relationship between the grain‐scale damage and fault growth is not yet clearly understood, partly due to the unstable nature of the faulting process. A lateral relaxation path was devised so that a rock sample can be deformed to failure by increasing differential stress along with decreasing effective mean stress. Porous rocks subjected to such a loading path exhibit a rather stable fault growth. Microstructural damage was analyzed on samples deformed to various post‐yielding stages before macroscopic faulting emerges. The intensity of microcracking is strain rate and effective pressure dependent. At peak stress, no spatial correlation among the regions with high crack intensities was observed. Beyond peak stress, the overall crack intensity increases and the regions with high crack intensities coalesce to form a macroscopic fracture. These results provide constraints for a better understanding of fault rupture.
Arctic Ocean freshwater: How robust are model simulations?
Authors: Jahn A. , Aksenov Y. , de Cuevas B. A. , de Steur L. , Häkkinen S. , Hansen E. , Herbaut C. , Houssais M.‐N. , Karcher M. , Kauker F. , Lique C. , Nguyen A. , Pemberton P. , Worthen D. , Zhang J.
Published: June 2012

The Arctic freshwater (FW) has been the focus of many modeling studies, due to the potential impact of Arctic FW on the deep water formation in the North Atlantic. A comparison of the hindcasts from ten ocean‐sea ice models shows that the simulation of the Arctic FW budget is quite different in the investigated models. While they agree on the general sink and source terms of the Arctic FW budget, the long‐term means as well as the variability of the FW export vary among models. The best model‐to‐model agreement is found for the interannual and seasonal variability of the solid FW export and the solid FW storage, which also agree well with observations. For the interannual and seasonal variability of the liquid FW export, the agreement among models is better for the Canadian Arctic Archipelago (CAA) than for Fram Strait. The reason for this is that models are more consistent in simulating volume flux anomalies than salinity anomalies and volume‐flux anomalies dominate the liquid FW export variability in the CAA but not in Fram Strait. The seasonal cycle of the liquid FW export generally shows a better agreement among models than the interannual variability, and compared to observations the models capture the seasonality of the liquid FW export rather well. In order to improve future simulations of the Arctic FW budget, the simulation of the salinity field needs to be improved, so that model results on the variability of the liquid FW export and storage become more robust.
Impact of Indian Ocean Dipole and El Niño/Southern Oscillation wind‐forcing on the Wyrtki jets
Authors: Gnanaseelan C. , Deshpande Aditi , McPhaden Michael J.
Published: June 2012

Interannual variability of the Wyrtki jets is studied in the context of Indian Ocean Dipole (IOD) and El Niño and Southern Oscillation (ENSO) wind‐forcing using a three dimensional numerical ocean model and observations. The boreal fall (October–November) Wyrtki jet is more significantly affected than the boreal spring (April–May) Wyrtki jet since both the IOD and ENSO tend to peak toward the end of the calendar year. Various statistical methods are used in an attempt to separate the impacts of the IOD and ENSO on these jets, with emphasis on the fall jet. The first two modes of an Empirical Orthogonal Function (EOF) decomposition account for about 90% and 85% of variability in zonal currents and wind stress respectively along the equator in the Indian Ocean, but EOF analysis does not cleanly separate out IOD and ENSO forcing and response. Partial correlation analysis reveals that IOD wind‐forcing and zonal equatorial current response are stronger on average than for ENSO and extend further west across the basin. Composite analysis of IOD only, ENSO only, and combined IOD and ENSO years provides a complementary definition of the relative contributions of these two phenomena on Wyrtki jet variability and in general is consistent with the results of the partial correlation analysis.
Dynamics of some piecewise smooth Fermi-Ulam models
Authors: de Simoi Jacopo , Dolgopyat Dmitry
Published: June 2012

We find a normal form which describes the high energy dynamics of a class of piecewise smooth Fermi-Ulam ping pong models. Depending on the value of a single real parameter, the dynamics can be either hyperbolic or elliptic. In the first case, we prove that the set of orbits undergoing Fermi acceleration has zero measure but full Hausdorff dimension. We also show that for almost every orbit, the energy eventually falls below a fixed threshold. In the second case, we prove that, generically, we have stable periodic orbits for arbitrarily high energies and that the set of Fermi accelerating orbits may have infinite measure.
Fermi acceleration in time-dependent rectangular billiards due to multiple passages through resonances
Authors: Itin A. P. , Neishtadt A. I.
Published: June 2012

We consider a slowly rotating rectangular billiard with moving boundaries and use canonical perturbation theory to describe the dynamics of a billiard particle. In the process of slow evolution, certain resonance conditions can be satisfied. Correspondingly, phenomena of scattering on a resonance and capture into a resonance happen in the system. These phenomena lead to destruction of adiabatic invariance and to unlimited acceleration of the particle.
Third-order superintegrable systems separable in parabolic coordinates
Authors: Popper I. , Post S. , Winternitz P.
Published: June 2012

In this paper, we investigate superintegrable systems which separate in parabolic coordinates and admit a third-order integral of motion. We give the corresponding determining equations and show that all such systems are multi-separable and so admit two second-order integrals. The third-order integral is their Lie or Poisson commutator. We discuss how this situation is different from the Cartesian and polar cases where new potentials were discovered which are not multi-separable and which are expressed in terms of Painlevé transcendents or elliptic functions.
Incorporation, valence state, and electronic structure of Mn and Cr in bulk single crystal β–Ga2O3
Authors: Lovejoy T. C. , Chen Renyu , Yitamben E. N. , Shutthanadan V. , Heald S. M. , Villora E. G. , Shimamura K. , Zheng S. , Dunham S. T. , Ohuchi F. S. , Olmstead M. A.
Published: June 2012

Single crystals of transition metal (TM) doped β–Ga2O3, a wide gap semiconductor system of interest for transparent conductive oxide and diluted magnetic semiconductor applications, have been studied in the dilute, non-interacting limit (≤0.06 cation %). Based on optical absorption, particle induced x-ray emission, and Rutherford backscattering measurements, Mn does not incorporate as well as Cr, and Mn degrades the crystal quality. Using superconducting quantum interference device (SQuID) magnetometry, a Brillouin type paramagnetic magnetization is observed for Mn or Cr doped crystals with an effective number of Bohr magnetons per TM ion of 5.88 ± 0.1 or 3.95 ± 0.1, respectively. A trace ferromagnetic signal is consistent with a very small concentration of secondary phases in the Mn-doped crystal. The position of the edge in x-ray absorption near edge structure (XANES) measurements suggests that the Cr takes the 3+ valence, while a mixture of Mn2+ and Mn3+ are present; based on the absence of a prominent pre-edge feature in the XANES, both TM predominantly occupy an octahedral site in β–Ga2O3. Density functional theory (DFT) results, optical absorption and SQuID data are consistent with this assignment. While the Cr-doped crystal is conductive, the Mn-doped crystal is insulating, which is consistent with the Mn2+/Mn3+ mixed valence, assuming the Fermi level is pinned mid-gap at the Mn 2+/3+ transition level, which is predicted by DFT to be 1.8 eV above the valence band maximum.
Direct experimental observation of binary agglomerates in complex plasmas
Authors: Chaudhuri M. , Nosenko V. , Knapek C. , Konopka U. , Ivlev A. V. , Thomas H. M. , Morfill G. E.
Published: June 2012

A defocusing imaging technique has been used as a diagnostic to identify binary agglomerates (dimers) in complex plasmas. Quasi-two-dimensional plasma crystal consisting of monodisperse spheres and binary agglomerates has been created where the agglomerated particles levitate just below the spherical particles without forming vertical pairs. Unlike spherical particles, the defocused images of binary agglomerates show distinct, stationary/periodically rotating interference fringe patterns. The results can be of fundamental importance for future experiments on complex plasmas.
Spin torque switching and scaling in synthetic antiferromagnet free layers with in-plane magnetization
Authors: Devolder T. , Ito K.
Published: June 2012

We study the field-induced and the current-induced switching of synthetic antiferromagnet free layers with in-plane magnetization. In practical cases, the energy barrier relevant for the thermal stability depends mainly on the magneto-crystalline anisotropies of the layers. We derive the spin-flop and the direct overwrite fields and their dependence on the asymmetry of the thickness of the two layers of the SyF. This is used to explain why the SyF magnetizations are much more robust to external fields than the anisotropy would tell. We then calculate the spin-torque instability threshold current densities for the acoustical and the optical excitations of the SyF, taking into account that there are spin torques acting on the two layers of the SyF. The acoustical excitation has the lowest instability current. Based on these findings, we finally discuss the scaling of SyF free layers by combining thermal stability requirements and dielectric breakdown avoidance constraints. Scaling can be conducted with either the aim of minimizing the write current or with the aim of minimizing the free layer surface. An absolute minimum of write current can be reached for relatively large cells (166×166 nm2) provided a zero effective magnetization is induced by a proper choice of the free layer thicknesses. Depending on how close the technology can reliably approach to the thickness yielding the easy axis reorientation transition while keeping bulk damping, this current minimum could in principle be as low as 14 μA in the macrospin approximation. If in contrast one aims at small free layer surfaces, then the present CoFeB alloy-based technology cannot reach dimensions below 90×90 nm2.
Assessing the accuracy of quantum Monte Carlo and density functional theory for energetics of small water clusters
Authors: Gillan M. J. , Manby F. R. , Towler M. D. , Alfè D.
Published: June 2012

We present a detailed study of the energetics of water clusters (H2O)n with n ⩽ 6, comparing diffusion Monte Carlo (DMC) and approximate density functional theory (DFT) with well converged coupled-cluster benchmarks. We use the many-body decomposition of the total energy to classify the errors of DMC and DFT into 1-body, 2-body and beyond-2-body components. Using both equilibrium cluster configurations and thermal ensembles of configurations, we find DMC to be uniformly much more accurate than DFT, partly because some of the approximate functionals give poor 1-body distortion energies. Even when these are corrected, DFT remains considerably less accurate than DMC. When both 1- and 2-body errors of DFT are corrected, some functionals compete in accuracy with DMC; however, other functionals remain worse, showing that they suffer from significant beyond-2-body errors. Combining the evidence presented here with the recently demonstrated high accuracy of DMC for ice structures, we suggest how DMC can now be used to provide benchmarks for larger clusters and for bulk liquid water.
Properties inheritance in metallic glasses
Authors: Hua Wang Wei
Published: June 2012

It is widely accepted that the structural features of a metallic glass inherits from its liquid state. The survey of the elastic, plastic, mechanical and physical properties, and glass transition of various metallic glasses indicates that metallic glasses can inherit their properties from their solvent components (or base components). It is found that the elastic properties are mainly determined by the weakest solvent-solvent bonds in metallic glasses, and the plastic events and glass transition prefer to be initiated in the regions with high density of weak solvent-solvent bonds and propagate toward the regions with less density of solvent-solvent bonds in metallic glasses. Some physical properties of the metallic glasses are found to be determined by the electronic structure of the solvent components. The properties inheritance allows new understanding of the glassy structure as well as the properties and structure relationship in metallic glasses, and also indicates the hierarchical atomic bands and inhomogeneous microstructure in metallic glasses which is helpful for understanding the mechanisms of plastic and elastic deformations and glass transition in metallic glasses.
High optical quality polycrystalline indium phosphide grown on metal substrates by metalorganic chemical vapor deposition
Authors: Zheng Maxwell , Yu Zhibin , Joon Seok Tae , Chen Yu-Ze , Kapadia Rehan , Takei Kuniharu , Aloni Shaul , Ager Joel W. , Wu Ming , Chueh Yu-Lun , Javey Ali
Published: June 2012

III–V semiconductor solar cells have demonstrated the highest power conversion efficiencies to date. However, the cost of III-V solar cells has historically been too high to be practical outside of specialty applications. This stems from the cost of raw materials, need for a lattice-matched substrate for single-crystal growth, and complex epitaxial growth processes. To address these challenges, here, we explore the direct non-epitaxial growth of thin poly-crystalline films of III-Vs on metal substrates by using metalorganic chemical vapor deposition. This method minimizes the amount of raw material used while utilizing a low cost substrate. Specifically, we focus on InP which is known to have a low surface recombination velocity of carriers, thereby, making it an ideal candidate for efficient poly-crystalline cells where surface/interface properties at the grain boundaries are critical. The grown InP films are 1-3 μm thick and are composed of micron-sized grains that generally extend from the surface to the Mo substrate. They exhibit similar photoluminescence peak widths and positions as single-crystalline InP, as well as excellent crystallinity as examined through TEM and XRD analyses. This work presents poly-InP as a promising absorber layer for future photovoltaics.
Trench-filled cellular parylene electret for piezoelectric transducer
Authors: Feng Yue , Hagiwara Kei , Iguchi Yoshinori , Suzuki Yuji
Published: June 2012

Cellular ferroelectrets with charged voids are promising for piezoelectric transducers, but the long-term stability or reproducibility due to the conventional “stochastic” fabrication and the corona charging methods is of concern. We microfabricated a high-density cellular piezoelectret with high-aspect-ratio polymer structures based on the trench-filled parylene technology. Vertical walls of the parylene structures are charged using soft x-ray to realize uniform artificial dipoles, of which moments could vary along with parylene structural deformation driven by the inertia of a seismic mass. Charge and voltage sensitivities of 9600 pC/N and 960 V/N with respect to the in-plane resonant oscillation have been achieved at 149 Hz, respectively.
Magnetic Schottky diode exploiting spin polarized transport in Co/p-Si heterostructure
Authors: Sarkar A. , Adhikari R. , Das A. K.
Published: June 2012

Magnetic Schottky heterojunction fabricated from Co/p-Si is investigated. The diode showed proper rectifying property at all temperatures and evolution of a giant positive junction magnetoresistance is observed at temperatures below 50 K. Based on a simplified band structure, the spin polarization of the device is determined to be ∼31% at 10 K. A phenomenological model is proposed to explain the observed spintronic behavior of the device.
Three-state resistive switching in CoFe2O4/Pb(Zr0.52Ti0.48)O3/ZnO heterostructure
Authors: Li Ziwei , Zhou Mingxiu , Ding Wangfeng , Zhou Hang , Chen Bo , Wan Jian-Guo , Liu Jun-Ming , Wang Guanghou
Published: June 2012

The heterostructural film combining multiferroic CoFe2O4/Pb(Zr0.52Ti0.48)O3 bilayer with semiconductor ZnO layer was prepared. Three-state resistive switching was demonstrated by time-dependent current measurements under different stimuli combination of voltage pulse and magnetic bias. The asymmetry diodelike current-voltage, capacitance-voltage, and polarization-voltage loops, which seriously depend on magnetic bias, were observed. We revealed that three-state resistive switching was dominated by the changes in the charge carriers in the heterostructure, which were modulated by the magnetoelectric coupling between ferromagnetic and ferroelectric layers and interface polarization coupling between ferroelectric and semiconductor layers. This work provides promising candidates for developing advanced switchable devices with multifunctional memory.
Nanophotonic detection of side-coupled nanomechanical cantilevers
Authors: Sauer V. T. K. , Diao Z. , Freeman M. R. , Hiebert W. K.
Published: June 2012

A silicon nanophotonic Mach-Zehnder interferometer (MZI) is used to detect the mechanical resonance of a cantilever external to a nanophotonic waveguide. Small cantilever devices, below the cut-off for waveguide supported modes, are fabricated ∼140 nm away from one MZI arm. Cantilever resonant frequencies up to 60 MHz are measured with mechanical quality factors around 20 000 and signal to noise ratios up to 1000. Phase-locked loop frequency stability measurements indicate a mass sensitivity of 2 zg in an example cantilever of 0.5 pg mass. An interferometric transduction mechanism is confirmed, and the system is shown to work effectively in all-optical operation.
Fabrication and luminescent properties of core-shell InGaN/GaN multiple quantum wells on GaN nanopillars
Authors: Chang J.-R. , Chang S.-P. , Li Y.-J. , Cheng Y.-J. , Sou K.-P. , Huang J.-K. , Kuo H.-C. , Chang C.-Y.
Published: June 2012

Core-shell InGaN/GaN multiple quantum wells (MQWs) on GaN nanopillars were fabricated by top-down etching followed by epitaxial regrowth. The regrowth formed hexagonal sidewalls and pyramids on the nanopillars. The cathodoluminescence of MQWs blue shifts as the location moves from top to bottom on both the pillar sidewalls and pyramid facets, covering a spectral linewidth of about 100 nm. The MQWs on the pillar sidewalls have a higher InN fraction than those on the pyramid facets. The photoluminescent wavelength is stable over two orders of carrier density change due to the smaller quantum confined Stark effect on the nanopillar facets.
First-principles calculations of mechanical and electronic properties of silicene under strain
Authors: Qin Rui , Wang Chun-Hai , Zhu Wenjun , Zhang Yalin
Published: June 2012

We perform first-principles calculations of mechanical and electronic properties of silicene under strains. The in-plane stiffness of silicene is much smaller than that of graphene. The yielding strain of silicene under uniform expansion in the ideal conditions is about 20%. The homogeneous strain can introduce a semimetal-metal transition. The semimetal state of silicene, in which the Dirac cone locates at the Fermi level, can only persist up to tensile strain of 7% with nearly invariant Fermi velocity. For larger strains, silicene changes into a conventional metal. The work function is found to change significantly under biaxial strain. Our calculations show that strain tuning is important for applications of silicene in nanoelectronics.
Strength and bonding nature of superhard Z-carbon from first-principle study
Authors: Qin Jiaqian , Hou Zhufeng , Zhang Xinyu
Published: June 2012

Z-carbon is a candidate structure proposed recently for the cold-compressed phase of carbon. We have studied the mechanical properties of Z-carbon by performing the first-principles density functional calculations. The single-crystal elastic constants calculations show that Z-carbon is mechanically stable. The predicted bulk and shear moduli of Z-carbon are comparable to diamond and cubic BN, suggesting that Z-carbon can be a superhard material. We also obtained the ideal tensile and shear strengths for Z-carbon through deformation from the elastic regime to structural instability. The failure modes under tensile deformation were explored carefully based on the calculated charge density distribution and bonding evolution.
Crystal structure and biochemical studies of the trans-acting polyketide enoyl reductase LovC from lovastatin biosynthesis
Authors: Ames Brian D. , Nguyen Chi , Bruegger Joel , Smith Peter , Xu Wei , Ma Suzanne , Wong Emily , Wong Steven , Xie Xinkai , Li Jesse W.-H. , Vederas John C. , Tang Yi , Tsai Shiou-Chuan
Published: June 2012

Lovastatin is an important statin prescribed for the treatment and prevention of cardiovascular diseases. Biosynthesis of lovastatin uses an iterative type I polyketide synthase (PKS). LovC is a trans-acting enoyl reductase (ER) that specifically reduces three out of eight possible polyketide intermediates during lovastatin biosynthesis. Such trans-acting ERs have been reported across a variety of other fungal PKS enzymes as a strategy in nature to diversify polyketides. How LovC achieves such specificity is unknown. The 1.9-Å structure of LovC reveals that LovC possesses a medium-chain dehydrogenase/reductase (MDR) fold with a unique monomeric assembly. Two LovC cocrystal structures and enzymological studies help elucidate the molecular basis of LovC specificity, define stereochemistry, and identify active-site residues. Sequence alignment indicates a general applicability to trans-acting ERs of fungal PKSs, as well as their potential application to directing biosynthesis.
p85β phosphoinositide 3-kinase subunit regulates tumor progression
Authors: Cortés Isabel , Sánchez-Ruíz Jesús , Zuluaga Susana , Calvanese Vincenzo , Marqués Miriam , Hernández Carmen , Rivera Teresa , Kremer Leonor , González-García Ana , Carrera Ana C.
Published: June 2012

PIK3R2
encodes a ubiquitous regulatory subunit (p85β) of PI3K, an enzyme that generates 3-polyphosphoinositides at the plasma membrane. PI3K activation triggers cell survival and migration. We found that p85β expression is elevated in breast and colon carcinomas and that its increased expression correlates with PI3K pathway activation and tumor progression. p85β expression induced moderate PIP
3
generation at the cell membrane and enhanced cell invasion. In accordance, genetic alteration of
pik3r2
expression levels modulated tumor progression in vivo. Increased p85β expression thus represents a cellular strategy in cancer progression.
Gonads directly regulate growth in teleosts
Authors: Bhatta Sandip , Iwai Toshiharu , Miura Chiemi , Higuchi Masato , Shimizu-Yamaguchi Sonoko , Fukada Haruhisa , Miura Takeshi
Published: June 2012

In general, there is a relationship between growth and reproduction, and gonads are known to be important organs for growth, but direct evidence for their role is lacking. Here, using a fish model, we report direct evidence that gonads are endocrine organs equal to the pituitary in controlling body growth. Gonadal loss of function, gain of function, and rescue of growth were investigated in tilapia. Gonadectomy experiments were carried out in juvenile males and females. Gonadectomy significantly retarded growth compared with controls; however, this retardation was rescued by the implantation of extirpated gonads. Because gonads express growth hormone, it is possible that gonads control body growth through the secretion of growth hormone and/or other endocrine factors. We propose that gonads are integral players in the dynamic regulation of growth in teleosts.