bluuebunny/crossref_metadata_2025 huggingface dataset:
Beyond Afghanistan NATO's Partnership with Central Asia and South Caucasus: A Tangled Partnership?
Authors: Bağbaşlıoğlu Arif
Published: October 2013

This article examines how the Alliance's partnership policy has changed in Central Asia and South Caucasus since the 1990s and aims to clarify to what extent NATO's new partnership policy can affect its relations with these countries. NATO–Russian relations and the Afghanistan operation are evaluated as the main drivers of this process. The target date of the withdrawal of the ISAF combat mission in December 2014, set at the Lisbon Summit 2010, as well as the shifting of the focus of long-term US foreign policy to the Asia-Pacific region and the US aim of balancing China's influence in this region increase the necessity for the Alliance to redefine its future policy towards Central Asia and South Caucasus. The article claims these developments have caused the need to treat Russia more as a partner than a potential competitor in constituting the policy towards Central Asia and South Caucasus. Furthermore the article claims there is no possibility for new Alliance expansion in this part of the world in the short to medium term.
Russia and Egypt: Conflicts in the Political Elite and Protest Movements in 2011–2012
Authors: Isaev Gumer
Published: October 2013

This article describes some reasons that initiated protest movements in Russia and Egypt in 2011. The author thinks that the conflict in the political elite made was an important background that made thousands of people take to the streets of the cities. Russian and Egyptian political systems, that seem to be so different, had much in common in fact: hidden struggle between conservative «people of force» and liberals. The situation was aggravated by the coming elections and consequences of the international economic crisis. The research is based on Russian and Egyptian Media materials.
The Pendulum Moves from Europe to Asia. Modernizing Siberia and the Far East. Economic and Security Issues
Authors: Malle Silvana , Cooper Julian
Published: October 2013

Under the current Presidency of Putin two main areas of concern are discernible: the modernization of defence industry and the accelerated development of Siberia and, in particular, the Far East. To a certain extent, development programmes prioritized within increasingly tight budget constraints overlap, since important sections of the defence industry are located beyond the Urals. In response to China's rapidly increasing economic and military strength, there is a need both to modernise infrastructure in order to boost trade opportunities eastward and to enhance and diversify industrial capabilities, a task in which the defence industry has a role to play.

The article examines the policy and financial implications of the current shift eastwards. Resistance to policy changes is strong. Private investments will need strong encouragement while the role of the state needs to increase in the short-medium term. Nationalism and ideological inclinations add to a lively policy debate often marked by harsh tones. This major turn in strategy needs to entail a certain degree of decentralization as specific long-term projects are hardly manageable from Moscow. The existing structures are manifestly inadequate. While the need for a special authority endowed with the necessary powers for coordination and control of branch and territorial projects is discussed, the appropriate balance between the representation of regional interests and federal development plans is unclear.

The article argues that more could be done to stimulate the regional powers to assume their own responsibility in selecting the most suitable projects consistent with federal priorities, offering good administrative services and, when necessary, tax incentives. While establishing nation-wide economic goals, federal government should be more receptive to local demands, while strengthening its command over security issues. Mutually supportive and respectful interaction between regional and federal bodies would improve the ability to assess in an informed way opportunities and constraints for growth and better discriminate among alternative projects on the basis of their respective outturn, feasibility and cost.
TNFα‐induced miR‐130 resulted in adipocyte dysfunction during obesity‐related inflammation
Authors: Kim Chongtae , Lee Heejin , Cho Yoon Mi , Kwon Oh-Joo , Kim Wook , Lee Eun Kyung
Published: October 2013

Adipocytes are continuously stimulated by proinflammatory cytokines such as TNFα, which cause adipocyte dysfunction by facilitating the inflammatory response. Although miR‐130 was reported to be an important regulator of adipogenesis by targeting PPARγ mRNA, little is known about the mechanisms regulating miR‐130 expression during the proinflammatory response. Here, we examined miR‐130 levels in white adipose tissue (WAT) from high‐fat diet (HFD) mice and TNFα‐stimulated adipocytes. Primary transcripts of miR‐130 were increased after TNFα stimulation, indicating that induction of miR‐130 during the pro‐inflammatory response is regulated by a transcriptional event. A chromatin immunoprecipitation assay showed that p65 binding to the promoter regions of miR‐130 was enhanced after TNFα treatment. Taken together, our findings suggest that induction of miR‐130 by TNFα is responsible for adipocyte dysfunction.
Interleukin‐32δ interacts with IL‐32β and inhibits IL‐32β‐mediated IL‐10 production
Authors: Kang Jeong-Woo , Park Yun Sun , Lee Dong Hun , Kim Man Sub , Bak Yesol , Park Su Ho , Ham Sun Young , Yang Young , Hong Jin Tae , Yoon Do-Young
Published: October 2013

There is growing evidence for multifunctional properties of IL‐32. We previously demonstrated that IL‐32β upregulates IL‐10 production through the association with PKCδ. In this study, we examined the effects of other IL‐32 isoforms on IL‐10 production. We found that IL‐32δ decreased IL‐10 production and investigated the inhibitory mechanism of IL‐32δ. We showed that IL‐32δ suppressed IL‐32β binding to PKCδ by interacting with IL‐32β. The inhibitory effect of IL‐32δ on IL‐32β association with PKCδ was further verified by immuno‐fluorescence staining. The co‐localization of IL‐32β and PKCδ around the nuclear membrane was disrupted by IL‐32δ. Our data therefore indicate that IL‐32δ plays an inhibitory role against IL‐32β function, which also suggests that IL‐32 may be regulated by its own isoform.
Crystal structures of the human histone H4K20 methyltransferases SUV420H1 and SUV420H2
Authors: Wu Hong , Siarheyeva Alena , Zeng Hong , Lam Robert , Dong Aiping , Wu Xian-Hui , Li Yanjun , Schapira Matthieu , Vedadi Masoud , Min Jinrong
Published: October 2013

SUV420H1 and SUV420H2 are two highly homologous enzymes that methylate lysine 20 of histone H4 (H4K20), a mark that has been implicated in transcriptional regulation. In this study, we present the high‐resolution crystal structures of human SUV420H1 and SUV420H2 in complex with SAM, and report their substrate specificity. Both methyltransferases have a unique N‐terminal domain and Zn‐binding post‐SET domain, and prefer the monomethylated histone H4K20 as a substrate in vitro. No histone H4K20 trimethylation activity was detected by our radioactivity‐based assay for either enzyme, consistent with the presence of a conserved serine residue that forms a hydrogen bond with the target lysine side‐chain and limits the methylation level.
The crystal structure of novel chondroitin lyase ODV‐E66, a baculovirus envelope protein
Authors: Kawaguchi Yoshirou , Sugiura Nobuo , Kimata Koji , Kimura Makoto , Kakuta Yoshimitsu
Published: October 2013

Chondroitin lyases have been known as pathogenic bacterial enzymes that degrade chondroitin. Recently, baculovirus envelope protein ODV‐E66 was identified as the first reported viral chondroitin lyase. ODV‐E66 has low sequence identity with bacterial lyases at <12%, and unique characteristics reflecting the life cycle of baculovirus. To understand ODV‐E66's structural basis, the crystal structure was determined and it was found that the structural fold resembled that of polysaccharide lyase 8 proteins and that the catalytic residues were also conserved. This structure enabled discussion of the unique substrate specificity and the stability of ODV‐E66 as well as the host specificity of baculovirus.
Genetic disruption of protein phosphatase 5 in mice prevents high‐fat diet feeding‐induced weight gain
Authors: Grankvist N. , Honkanen R.E. , Sjöholm Å. , Ortsäter H.
Published: October 2013

The role of serine/threonine protein phosphatase 5 (PP5) in the development of obesity and insulin resistance associated with high‐fat diet‐feeding (HFD) was examined using PP5‐deficient mice (Ppp5c
−/−). Despite similar caloric intake, Ppp5c
−/− mice on HFD gained markedly less weight and did not accumulate visceral fat compared to wild‐type littermates (Ppp5c
+/+). On a control diet, Ppp5c
−/− mice had markedly improved glucose control compared to Ppp5c
+/+ mice, an effect diminished by HFD. However, even after 10 weeks of HFD glucose control in Ppp5c
−/− mice was similar to that observed in Ppp5c
+/+ mice on the control diet. Thus, PP5 deficiency confers protection against HFD‐induced weight gain in mice.
A rare KCNE1 polymorphism, D85N, as a genetic modifier of long QT syndrome
Authors: Hasegawa Kanae , Ohno Seiko , Itoh Hideki , Makiyama Takeru , Aiba Takeshi , Nakano Yasutaka , Shimizu Wataru , Matsuura Hiroshi , Makita Naomasa , Horie Minoru
Published: October 2013

Background

The gene KCNE1 encodes the β‐subunit of cardiac voltage‐gated K+ channels and causes long QT syndrome (LQTS). LQTS is characterized by the prolongation of QT interval and lethal arrhythmias such as torsade de pointes (TdP). A KCNE1 polymorphism, D85N, has been shown to modify the phenotype of LQTS through a loss‐of‐function effect on both KCNQ1 and KCNH2 channels when co‐expressed and reconstituted in a heterologous expression system.

Methods

A screening for the D85N polymorphism was performed in 355 LQTS families with mutations in KCNQ1, KCNH2, or SCN5A. Among the probands who had a heterozygous status with the polymorphism, we focused on a family with a KCNH2 mutation (E58K), a N‐terminal missense mutation, and examined the clinical significance of this polymorphism. We also conducted biophysical assays to analyze the effect of the polymorphism in mammalian cells.

Results

In 355 probands, we found 14 probands (3.9%) who had a heterozygous compound status with the D85N polymorphism. In the family with a KCNE1‐D85N polymorphism and a KCNH2‐E58K mutation, the proband and her daughter carried both the KCNH2 mutation and the KCNE1‐D85N polymorphism. They experienced repetitive syncope and TdP. Two sons of the proband had either KCNH2‐E58K mutation or KCNE1‐D85N, but were asymptomatic. Biophysical assays of KCNE1‐D85N with KCNH2‐E58K variants produced a larger reduction in the reconstituted IKr currents compared to co‐expression with wild‐type KCNE1.

Conclusions

The KCNE1‐D85N polymorphism modified the clinical features of LQTS patients.
Forecasting GDP growth with financial market data in Finland: Revisiting stylized facts in a small open economy during the financial crisis
Authors: Kuosmanen Petri , Vataja Juuso
Published: October 2013

This paper examines the ability of financial variables to predict future economic growth above and beyond past economic activity in a small open economy in the euro area. We aim to clarify potential differences in forecasting economic activity during different economic circumstances.

Our results from Finland suggest that the proper choice of forecasting variables is related to general economic conditions. During steady economic growth, the preferred choice for a financial indicator is the short‐term interest rate combined with past values of output growth. However, during economic turbulence, the traditional term spread and stock returns are more important in forecasting GDP growth. The time‐varying predictive content of the financial variables may be utilized by applying regime‐switching nonlinear forecasting models. We propose a novel application using the negative term spread and observed recession as signals to switch between regimes. This procedure yields a significant improvement in forecasting performance at the one‐year forecast horizon.
Timing of glacier fluctuations and trigger mechanisms in eastern Qinghai–Tibetan Plateau during the late Quaternary
Authors: Ou XianJiao , Lai ZhongPing , Zhou ShangZhe , Zeng LanHua
Published: October 2013

It is highly debated whether glacial advances on the Qinghai–Tibetan Plateau (QTP) occurred as a response to temperature cooling, or whether they were forced by an increase in moisture brought by the intensive Indian summer monsoon. We here report a case study investigating this issue. Multiple moraine series in the Yingpu Valley, Queer Shan ranges of the Hengduan Mountains, and eastern QTP, provide an excellent archive for examining the timing and trigger mechanism of glacier fluctuations. Twenty-seven optically stimulated luminescence (OSL) samples of glacial sediments were collected from this valley. The quartz OSL ages show that the moraine series of Y-1, I, M and O were formed during the Late Holocene, Late Glacial, the global Last Glacial Maximum (LGM) and Marine Oxygen Isotope Stage (MIS) 3 (likely mid-MIS-3). The youngest Y-2 moraines probably formed during the Little Ice Age (LIA). The oldest H moraines formed before MIS-3. We found that glacial advances during the late Quaternary at the Yingpu Valley responded to cold stages or cold events rather than episodes of enhanced summer monsoon and moisture. As a result, glaciers in the monsoonal Hengduan Mountains were mainly triggered by changes in temperature. Millennial time scale temperature oscillations might have caused the multiple glacial advances.
Non‐negative matrix factorisation based on fuzzy K nearest neighbour graph and its applications
Authors: Ye Jun , Jin Zhong
Published: October 2013

Non‐negative matrix factorisation (NMF) has been widely used in pattern recognition problems. For the tasks of classification, however, most of the existing variants of NMF ignore both the discriminative information and the local geometry of data into the factorisation. The actual conditions of the problems will be affected by the change of the environmental factors to affect the recognition accuracy. In order to overcome these drawbacks, the authors regularised NMF by intra‐class and inter‐class fuzzy K nearest neighbour graphs, leading to NMF‐FK‐NN in this study. By introducing two novel fuzzy K nearest neighbour graphs, NMF‐FK‐NN can contract the intra‐class neighbourhoods and expand the inter‐class neighbourhoods in the decomposition. This method not only exploits the discriminative information and uses the geometric structure in the data effectively, but also reduces the influence of the external factors to improve recognition effect. In the factorisation, the authors minimised the approximation error whilst contracting intra‐class fuzzy neighbourhoods and expanding inter‐class fuzzy neighbourhoods. The authors develop simple multiplicative updates for NMF‐FK‐NN and present monotonic convergence results. Experiments of the text clustering on the CLUTO toolkit and face recognition on ORL and YALE datasets show the effectiveness of our proposed method.
Pixel‐wise skin colour detection based on flexible neural tree
Authors: Xu Tao , Wang Yunhong , Zhang Zhaoxiang
Published: October 2013

Skin colour detection plays an important role in image processing and computer vision. Selection of a suitable colour space is one key issue. The question that which colour space is most appropriate for pixel‐wise skin colour detection is not yet concluded. In this study, a pixel‐wise skin colour detection method is proposed based on the flexible neural tree (FNT) without considering the problem of selecting a suitable colour space. A FNT‐based skin model is constructed by using large skin data sets which identifies the important components of colour spaces automatically. Experimental results show improved accuracy and false positive rates (FPRs). The structure and parameters of FNT are optimised via genetic programming and particle swarm optimisation algorithms, respectively. In the experiments, nine FNT skin models are constructed and evaluated on features extracted from RGB, YCbCr, HSV and CIE‐Lab colour spaces. The Compaq and ECU datasets are used for constructing FNT‐based skin model and evaluating its performance compared with other skin detection methods. Without extra processing steps, the authors method achieves state of the art performance in skin pixel classification and better performance in terms of accuracy and FPRs.
Resonant electromagnetic scattering in anisotropic layered media
Authors: Shipman Stephen P. , Welters Aaron T.
Published: October 2013

The resonant excitation of an electromagnetic guided mode of a slab structure by exterior radiation results in anomalous scattering behavior, including sharp energy-transmission anomalies and field amplification around the frequency of the slab mode. In the case of a periodically layered ambient medium, anisotropy serves to couple the slab mode to radiation. Exact expressions for scattering phenomena are proved by analyzing a pole of the full scattering matrix as it moves off the real frequency axis into the lower half complex plane under a detuning of the wavevector parallel to the slab. The real pole is the frequency of a perfect (infinite Q) guided mode, which becomes lossy as the frequency gains an imaginary part. This work extends results of Shipman and Venakides to evanescent source fields and two-dimensional parallel wavevector and demonstrates by example how the latter allows one to control independently the width and central frequency of a resonance by varying the angle of incidence of the source field. The analysis relies on two nondegeneracy conditions of the complex dispersion relation for slab modes (relating poles of the scattering matrix to wavevector), which were assumed in previous works and are proved in this work for layered media. One of them asserts that the dispersion relation near the wavevector κ and frequency ω of a perfect guided mode is the zero set of a simple eigenvalue ℓ(κ, ω), and the other relates ∂ℓ/∂ω to the total energy of the mode, thereby implying that this derivative is nonzero.
Interfacial thermal conductance-rheology nexus in metal-contacted nanocomposites
Authors: Seshadri Indira , Borca-Tasciuc Theo , Keblinski Pawel , Ramanath Ganpati
Published: October 2013

Tailoring high interfacial thermal conductance is crucial for many applications and is often challenging even for interfaces comprised of high thermal conductivity materials. Here, we report the correlation between the rheological behavior of a gold-nanowire-filled polydimethylsiloxane nanocomposite and its interface thermal conductance with copper. At a critical filler fraction, an abrupt increase in the nanocomposite thermal conductivity is accompanied by a liquid-solid transition and a multifold decrease in interface conductance. These concurrent changes are attributed to nanowire percolation network formation and pre-cure polymer gelation that inhibits the formation of conformal void-free interfaces. These findings will be important for designing processing sequences to realize high thermal conductance interfaces.
New bifurcations in the simplest passive walking model
Authors: Li Qingdu , Tang Song , Yang Xiao-Song
Published: October 2013

This paper uncovers several new stable periodic gaits in the simplest passive walking bipedal model proposed in the literature. It is demonstrated that the model has period-3 to period-7 gaits beside the period-1 gaits found by Garcia et al. By simulations, this paper shows that each of these new gaits leads to chaos via period-doubling bifurcation and loses its stability by cyclic-fold bifurcation. This interesting phenomenon suggests a series of new bifurcation scenarios that have not been observed before. To confirm the new gaits and their bifurcations, this paper presents computer assisted proofs on the existence and stability of each periodic gait and its period-doubling gaits with the interval Newton method. To verify that the routes indeed lead to chaos, computer-assisted proofs are also given by means of topological horseshoes theory.
Adsorption and reaction of acetylene on clean and oxygen-precovered Pd(100) studied with high-resolution X-ray photoelectron spectroscopy
Authors: Höfert O. , Lorenz M. P. A. , Streber R. , Zhao W. , Bayer A. , Steinrück H.-P. , Papp C.
Published: October 2013

We investigated the adsorption and thermal evolution of acetylene on clean Pd(100) and Pd(100) precovered with 0.25 ML oxygen. The measurements were performed in situ by fast XPS at the synchrotron radiation facility BESSY II. On Pd(100) acetylene molecularly adsorbs at 130 K. Upon heating transformation to a CCH species occurs around 390 K along with the formation of a completely dehydrogenated carbon species. On the oxygen-precovered surface partial CCH formation already occurs upon adsorption at 130 K, and the dehydrogenation temperature and the stability range of CCH are shifted to lower temperatures by ∼200 K.
The future scalability of pH-based genome sequencers: A theoretical perspective
Authors: Go Jonghyun , Alam Muhammad A.
Published: October 2013

Sequencing of human genome is an essential prerequisite for personalized medicine and early prognosis of various genetic diseases. The state-of-art, high-throughput genome sequencing technologies provide improved sequencing; however, their reliance on relatively expensive optical detection schemes has prevented wide-spread adoption of the technology in routine care. In contrast, the recently announced pH-based electronic genome sequencers achieve fast sequencing at low cost because of the compatibility with the current microelectronics technology. While the progress in technology development has been rapid, the physics of the sequencing chips and the potential for future scaling (and therefore, cost reduction) remain unexplored. In this article, we develop a theoretical framework and a scaling theory to explain the principle of operation of the pH-based sequencing chips and use the framework to explore various perceived scaling limits of the technology related to signal to noise ratio, well-to-well crosstalk, and sequencing accuracy. We also address several limitations inherent to the key steps of pH-based genome sequencers, which are widely shared by many other sequencing platforms in the market but remained unexplained properly so far.
Long-pulse beam acceleration of MeV-class H− ion beams for ITER NB accelerator
Authors: Umeda N. , Kashiwagi M. , Taniguchi M. , Tobari H. , Watanabe K. , Dairaku M. , Yamanaka H. , Inoue T. , Kojima A. , Hanada M.
Published: October 2013

In order to realize neutral beam systems in International Thermonuclear Experimental Reactor whose target is to produce a 1 MeV, 200 A/m2 during 3600 s D− ion beam, the electrostatic five-stages negative ion accelerator so-called “MeV accelerator” has been developed at Japan Atomic Energy Agency. To extend pulse length, heat load of the acceleration grids was reduced by controlling the ion beam trajectory. Namely, the beam deflection due to the residual magnetic field of filter magnet was suppressed with the newly developed extractor with a 0.5 mm off-set aperture displacement. The new extractor improved the deflection angle from 6 mrad to 1 mrad, resulting in the reduction of direct interception of negative ions from 23% to 15% of the total acceleration power, respectively. As a result, the pulse length of 130 A/m2, 881 keV H− ion beam has been successfully extended from a previous value of 0.4 s to 8.7 s. This is the first long pulse negative ion beam acceleration over 100 MW/m2.
Dust-acoustic shock waves in a charge varying electronegative magnetized dusty plasma with nonthermal ions: Application to Halley Comet plasma
Authors: Tribeche Mouloud , Bacha Mustapha
Published: October 2013

Weak dust-acoustic waves (DAWs) are addressed in a nonthermal charge varying electronegative magnetized dusty plasmas with application to the Halley Comet. A weakly nonlinear analysis is carried out to derive a Korteweg-de Vries-Burger equation. The positive ion nonthermality, the obliqueness, and magnitude of the magnetic field are found to modify the dispersive and dissipative properties of the DA shock structure. Our results may aid to explain and interpret the nonlinear oscillations that may occur in the Halley Comet Plasma.
Particle-in-cell simulations on spontaneous thermal magnetic field fluctuations
Authors: Simões F. J. R. , Pavan J. , Gaelzer R. , Ziebell L. F. , Yoon P. H.
Published: October 2013

In this paper an electromagnetic particle code is used to investigate the spontaneous thermal emission. Specifically we perform particle-in-cell simulations employing a non-relativistic isotropic Maxwellian particle distribution to show that thermal fluctuations are related to the origin of spontaneous magnetic field fluctuation. These thermal fluctuations can become seed for further amplification mechanisms and thus be considered at the origin of the cosmological magnetic field, at microgauss levels. Our numerical results are in accordance with theoretical results presented in the literature.
Rectification in mesoscopic alternating current-gated semiconductor devices
Authors: Giblin S. P. , Kataoka M. , Fletcher J. D. , See P. , Janssen T. J. B. M. , Griffiths J. P. , Jones G. A. C. , Farrer I. , Ritchie D. A.
Published: October 2013

We analyse the rectified dc currents resulting when a three-terminal semiconductor device with gate-dependent conductance is driven with an ac gate voltage. The rectified currents exhibit surprisingly complex behaviour as the dc source-drain bias voltage, the dc gate voltage, and the amplitude of the ac gate voltage are varied. We obtain good agreement between our data and a model based on simple assumptions about the stray impedances on the sample chip, over a wide frequency range. Secondly, we evaluate the small rectified currents flowing in tunable-barrier electron pumps operated in the pinched-off regime. These currents are at most 10−12 of the pumped current for a pump current of 100 pA. This result is encouraging for the development of tunable-barrier pumps as metrological current standards. Our method is applicable to many types of experiment which involve ac gating of a non-linear device, and where an undesirable rectified contribution to the measured signal is present.
First results of the ITER-relevant negative ion beam test facility ELISE (invited)
Authors: Fantz U. , Franzen P. , Heinemann B. , Wünderlich D.
Published: October 2013

An important step in the European R&D roadmap towards the neutral beam heating systems of ITER is the new test facility ELISE (Extraction from a Large Ion Source Experiment) for large-scale extraction from a half-size ITER RF source. The test facility was constructed in the last years at Max-Planck-Institut für Plasmaphysik Garching and is now operational. ELISE is gaining early experience of the performance and operation of large RF-driven negative hydrogen ion sources with plasma illumination of a source area of 1 × 0.9 m2 and an extraction area of 0.1 m2 using 640 apertures. First results in volume operation, i.e., without caesium seeding, are presented.
Hydrodynamic instability in the open system of the iodate–arsenous acid reaction
Authors: Pópity-Tóth Éva , Pimienta Véronique , Horváth Dezső , Tóth Ágota
Published: October 2013

Hydrodynamic instability arising in horizontally propagating vertical chemical fronts leading to the formation of a single stable convection roll is investigated experimentally in the iodate–arsenous acid reaction for various stoichiometry. In the presence of a free surface, the tilted reaction front becomes more elongated due to the evaporation of the surface active iodine and the decrease in the surface tension during the reaction. The experimental conditions are then identified where Marangoni instability represents the driving force for the distortion of the reaction front at the surface.
Divalent pseudoatoms for modeling Si(100) surfaces
Authors: Gamoke Benjamin C. , Das Ujjal , Hratchian Hrant P. , Raghavachari Krishnan
Published: October 2013

An accurate first-principles treatment of complex systems, such as surfaces, continues to be a major challenge in computational chemistry. A popular approach to treat such systems is the use of cluster models, where a moderately sized model system is constructed by excising a cluster from the extended surface. This requires cutting chemical bonds, creating dangling bonds on the cluster boundary atoms that can introduce unphysical errors. Pseudobond, pseudoatom, and quantum capping potential approaches have been developed to treat such systems using a boundary “design-atom” subject to an appropriately fitted effective potential. However, previous approaches have been developed only for truncation of a single covalent bond. They may not be adequate for many important problems involving surface chemistry or materials chemistry, where multiple covalent bonds are severed between layers. In this paper, we have extended the pseudoatom formulation for divalent silicon, which can be employed to describe accurate Si(100) surface chemistry. The effective core potential parameters of our pseudoatom are obtained by fitting to geometrical parameters and atomic charges of molecules containing Si–Si and Si–O bonds, making our pseudoatom robust for applicability in different bonding environments. We calibrate the performance of our pseudoatom approach in small molecules and surface models, and also discuss its ability to describe heteroatomic bonds using multiple theoretical methods.
Neutron spin evolution through broadband current sheet spin flippers
Authors: Stonaha P. , Hendrie J. , Lee W. T. , Pynn Roger
Published: October 2013

Controlled manipulation of neutron spin is a critical tool for many neutron scattering techniques. We have constructed current-sheet, neutron spin flippers for use in Spin Echo Scattering Angle Measurement (SESAME) that comprise pairs of open-faced solenoids which introduce an abrupt field reversal at a shared boundary. The magnetic fields generated by the coils have been mapped and compared with both an analytical approximation and a numerical boundary integral calculation. The agreement is generally good, allowing the former method to be used for rapid calculations of the Larmor phase acquired by a neutron passing through the flipper. The evolution of the neutron spin through the current sheets inside the flipper is calculated for various geometries of the current-carrying conductors, including different wire shapes, arrangements, and common imperfections. The flipping efficiency is found to be sensitive to gaps between wires and between current sheets. SESAME requires flippers with high fields and flipping planes inclined to the neutron beam. To avoid substantial neutron depolarization, such flippers require an interdigitated arrangement of wires.
MCTDH study on vibrational states of the CO/Cu(100) system
Authors: Meng Qingyong , Meyer Hans-Dieter
Published: October 2013

Full (6D) and reduced (4D and 2D) dimensional multiconfiguration time-dependent Hartree (MCTDH) calculations for the vibrational fundamentals and overtones of the CO/Cu(100) system are carried out using the recently reported [R. Marquardt, F. Cuvelier, R. A. Olsen, E. J. Baerends, J. C. Tremblay, and P. Saalfrank, J. Chem. Phys. 132, 074108 (2010)] SAP potential energy surface (PES). To efficiently perform MCTDH calculations with the Heidelberg package (http://mctdh.uni-hd.de), the SAP-PES is first refitted in a sum-of-products form. Then extensive MCTDH calculations are carefully performed including thorough convergence checks to ensure the accuracy of our results. Full dimensional improved-relaxations and/or block-improved-relaxations are then performed to obtain vibrational ground and excited states of CO/Cu(100). In addition, we investigate the frustrated rotation (R mode) and vertical CO–Cu stretch (S mode), as well as C–O stretch, using a 4D Hamiltonian, which includes the distance between CO and the surface, z, bond length of CO, r, and orientation angles of CO, θ, and ϕ. The complement of this 4D Hamiltonian, a 2D Hamiltonian including only x and y coordinates, is used to alternatively calculate the states of frustrated translation (T mode). The comparison of reduced- with full-dimensional results show that the couplings between the R or S mode and the T mode do not influence the fundamentals and overtones of the R and S modes, however, do considerably influence those of the T mode. For the fundamental of the T mode, the 6D calculation yields an energy of 25.09 cm−1, a value closer to the experimental result of 31.8 cm−1 [A. P. Graham, F. Hofmann, J. P. Toennies, G. P. Williams, C. J. Hirschmugl, and J. Ellis, J. Chem. Phys. 108, 7825–7834 (1998)] than previously reported 19.6 cm−1 [R. Marquardt, F. Cuvelier, R. A. Olsen, E. J. Baerends, J. C. Tremblay, and P. Saalfrank, J. Chem. Phys. 132, 074108 (2010)] although both investigations are based on the SAP-PES. On the other hand, the present calculations give similar results for the fundamentals of the S mode and C–O stretch to previous ones [R. Marquardt, F. Cuvelier, R. A. Olsen, E. J. Baerends, J. C. Tremblay, and P. Saalfrank, J. Chem. Phys. 132, 074108 (2010)]. Furthermore, for the lateral T and R modes, the present calculations give the same excitation pattern. Our calculations also show that the couplings between the R mode and surface are weaker than those between the T mode and surface.
A Tesla-type repetitive nanosecond pulse generator for solid dielectric breakdown research
Authors: Zhao Liang , Pan Ya Feng , Su Jian Cang , Zhang Xi Bo , Wang Li Min , Fang Jin Peng , Sun Xu , Lui Rui
Published: October 2013

A Tesla-type repetitive nanosecond pulse generator including a pair of electrode and a matched absorption resistor is established for the application of solid dielectric breakdown research. As major components, a built-in Tesla transformer and a gas-gap switch are designed to boost and shape the output pulse, respectively; the electrode is to form the anticipated electric field; the resistor is parallel to the electrode to absorb the reflected energy from the test sample. The parameters of the generator are a pulse width of 10 ns, a rise and fall time of 3 ns, and a maximum amplitude of 300 kV. By modifying the primary circuit of the Tesla transformer, the generator can produce both positive and negative pulses at a repetition rate of 1-50 Hz. In addition, a real-time measurement and control system is established based on the solid dielectric breakdown requirements for this generator. With this system, experiments on test samples made of common insulation materials in pulsed power systems are conducted. The preliminary experimental results show that the constructed generator is capable to research the solid dielectric breakdown phenomenon on a nanosecond time scale.
Facilitation and correlation of flow in metallic supercooled liquid
Authors: Zhang Meng , Liu Lin , Wu Yue
Published: October 2013

Elucidation of the flow mechanism of the supercooled liquid near the glass transition temperature Tg is crucial for understanding the nature of glass transition. Dynamic facilitation between adjacent flow events in the supercooled liquid is believed to be crucial in the process of glass transition. In this work, it is shown that shear dilatation-based dynamic facilitation plays an important role in the supercooled liquid state of Zr58.5Cu15.6Al10.3Ni12.8Nb2.8, as revealed by the observed strain rate softening in the stress-strain curves above Tg = 684 K. Interestingly, along with strain rate softening, damped oscillations in the stress-strain curve emerge below 713 K, suggesting large-scale correlation between flow events as temperature approaches Tg. Such oscillations are absent above 713 K although strain rate softening remains even at 733 K. Analysis indicates that facilitation and correlation are both crucial for the flow of metallic supercooled liquid approaching Tg.
Ionization potentials of semiconductors from first-principles
Authors: Jiang Hong , Shen Yu-Chen
Published: October 2013

The ionization potential is the key to determine the absolute positions of valence and conduction bands of a semiconductor with respect to the vacuum level, which play a crucial role in physical and chemical properties of surfaces and interfaces. In spite of its far-reaching significance, theoretical determination of ionization potentials has not attained as much attention as that of band gaps. In this work, a set of prototypical semiconductors are considered to establish the performance of the state-of-the-art first-principles approaches. We have shown that in general Kohn-Sham density functional theory with local density approximation or generalized gradient approximation (LDA/GGA) significantly underestimates the ionization potentials of semiconductors. When the quasi-particle correction from many-body perturbation theory in the GW approximation is taken into account, the agreement between theory and experiment can be greatly improved. We have made a critical comparison between two GW correction schemes, one taking into account the GW correction to the valence band maximum (VBM) of the bulk system, and the other based on the assumption that the LDA/GGA gives correct band gap center (BGC). Our study shows that the VBM scheme is better founded theoretically and leads to closer agreement with experiment practically than the BGC scheme. For semiconductors with shallow semicore states, for which the band gaps from the GW approach also exhibit significant errors, there is still significant discrepancy between GW and experiment, indicating the necessity to go beyond the standard GW approach for these materials.
Operational experience with the Argonne National Laboratory Californium Rare Ion Breeder Upgrade facility and electron cyclotron resonance charge breeder
Authors: Vondrasek R. , Clark J. , Levand A. , Palchan T. , Pardo R. , Savard G. , Scott R.
Published: October 2013

The Californium Rare Ion Breeder Upgrade (CARIBU) of the Argonne National Laboratory Argonne Tandem Linac Accelerator System (ATLAS) facility provides low-energy and accelerated neutron-rich radioactive beams to address key nuclear physics and astrophysics questions. A 350 mCi 252Cf source produces fission fragments which are thermalized and collected by a helium gas catcher into a low-energy particle beam with a charge of 1+ or 2+. An electron cyclotron resonance (ECR) ion source functions as a charge breeder in order to raise the ion charge sufficiently for acceleration in the ATLAS linac. The ECR charge breeder has achieved stable beam charge breeding efficiencies of 10.1% for 23Na7+, 17.9% for 39K10+, 15.6% for 84Kr17+, and 12.4% for 133Cs27+. For the radioactive beams, a charge breeding efficiency of 11.7% has been achieved for 143Cs27+ and 14.7% for 143Ba27+. The typical breeding times are 10 ms/charge state, but the source can be tuned such that this value increases to 100 ms/charge state with the best breeding efficiency corresponding to the longest breeding times—the variation of efficiencies with breeding time will be discussed. Efforts have been made to characterize and reduce the background contaminants present in the ion beam through judicious choice of q/m combinations. Methods of background reduction are being investigated based upon plasma chamber cleaning and vacuum practices.
Commissioning and operation of the deuteron injector for PKUNIFTY project
Authors: Ren H. T. , Peng S. X. , Lu P. N. , Zhao J. , Zhou Q. F. , Song Z. Z. , Yuan Z. X. , Yu J. X. , Guo Z. Y. , Chen J. E.
Published: October 2013

PKUNIFTY (PeKing University Neutron Imaging FaciliTY), a thermal neutron imaging facility based on a 2 MeV RFQ accelerator, has been constructed at Peking University. Its deuteron injector, which consists of a 2.45 GHz permanent magnet electron cyclotron resonance (PMECR) deuteron ion source and a two-solenoid low energy beam transport (LEBT), aims at producing and delivering 50 mA, 50 keV deuteron beam with a duty factor of 10% (1 ms, 100 Hz). In the preliminary tests of RFQ accelerator, the ECR ion source and LEBT are required to operate at various duty factors (from 1% to 10%). The deuteron ion source has been tested with different pulse widths for this reason. In order to optimize the transmission parameters, the beam current at the exit of RFQ as a function of solenoids tuning and steering magnets tuning are carefully studied. The beam emittance at the entrance of RFQ has been measured with space charge compensation by different argon gas (RG) pressure from 1.6 × 10−4 Pa to 4.7 × 10−3 Pa. The measuring results show the best compensating pressure is 3.5 × 10−3 Pa with a minimal normalized rms emittance of 0.12 pi mm mrad. During the commissioning, we found the purity of deuteron gas is an important factor which severely affects ECR discharge and plasma intensity inside the ion source chamber. The detailed experimental results obtained during the commissioning are discussed in this paper.
Study of sublevel population mixing effects in hydrogen neutral beams
Authors: Polosatkin S. V. , Ivanov A. A. , Listopad A. A. , Shikhovtsev I. V.
Published: October 2013

Intensity of hydrogen Balmer-alpha line is sensitive to distribution of populations of sublevels of excited state due to difference of radiative decay branching ratio for sublevels with different orbital quantum number. Since these sublevels are degenerate transitions between sublevels and mixing of its population may be caused by very weak action of environment. A beam of fast hydrogen atoms is a system in which these fine effects of population mixing can be observed. Experimental data of Hα line radiation intensities in hydrogen neutral beams are compared with calculations assumed different models of sublevel population. The comparison most probably point out that population mixing effects cause transitions from long-lived 3s to 3p sublevel with corresponding changes in Hα radiation intensities. Discussed effects may influence to results of Doppler-shift spectroscopy measurements of the neutral beam parameters such as species and impurities content and neutralizing efficiency.
Killing symmetries in $\mathcal {H}$H-spaces with Λ
Authors: Chudecki Adam , Przanowski Maciej
Published: October 2013

All Killing symmetries in complex $\mathcal {H}$H-spaces with Λ in terms of the Plebański-Robinson-Finley coordinate system are found. All $\mathcal {H}$H-metrics with Λ admitting a null Killing vector are explicitly given. It is shown that the problem of non-null Killing vector reduces to looking for solution of the Boyer-Finley-Plebański (Toda field) equation.
Large scale behavior of a two-dimensional model of anisotropic branched polymers
Authors: Knežević Milan , Knežević Dragica
Published: October 2013

We study critical properties of anisotropic branched polymers modeled by semi-directed lattice animals on a triangular lattice. Using the exact transfer-matrix approach on strips of quite large widths and phenomenological renormalization group analysis, we obtained pretty good estimates of various critical exponents in the whole high-temperature region, including the point of collapse transition. Our numerical results suggest that this collapse transition belongs to the universality class of directed percolation.
On-the-fly ab intito calculations of anharmonic vibrational frequencies: Local-monomer theory and application to HCl clusters
Authors: Mancini John S. , Bowman Joel M.
Published: October 2013

We present an on-the-fly quantum mechanical method to obtain anharmonic vibrational frequencies for molecular clusters. The basis for the method is the local-monomer model, a “divide and conquer” approach to theoretical spectroscopy, previously applied using full-dimensional surfaces [Y. Wang and J. M. Bowman, J. Chem. Phys. 134, 154510 (2011)]. The model consists of performing a local normal-mode analysis for each monomer in a cluster in the field of the surrounding monomers. Anharmonic vibrational frequencies are then determined for each monomer by numerically solving the Schrödinger equation in terms of the local coordinates using ab initio energies obtained directly. Residual monomer-monomer coupling is accounted for using the Hückel-coupling extension [Y. Wang and J. M. Bowman, J. Chem. Phys. 136, 144113 (2012)]. In addition to the direct local-monomer approach, we propose and demonstrate a composite ab initio technique to reduce computational costs for calculating the anharmonic frequencies of large clusters. This technique utilizes two ab initio methods, a lower level of theory to compute geometries and perform harmonic analyses and a subsequent higher level of theory to compute the energies used in the anharmonic frequency calculations. We demonstrate the on-the-fly approach on hydrogen chloride clusters ranging in size from the dimer to the hexamer. Comparisons of the theoretical frequencies are made to previous experiments. We find the method to be an effective and computationally efficient approach to compute anharmonic frequencies.
On the solvability of the quantum Rabi model and its 2-photon and two-mode generalizations
Authors: Zhang Yao-Zhong
Published: October 2013

We study the solvability of the time-independent matrix Schrödinger differential equations of the quantum Rabi model and its 2-photon and two-mode generalizations in Bargmann Hilbert spaces of entire functions. We show that the Rabi model and its 2-photon and two-mode analogs are quasi-exactly solvable. We derive the exact, closed-form expressions for the energies and the allowed model parameters for all the three cases in the solvable subspaces. Up to a normalization factor, the eigenfunctions for these models are given by polynomials whose roots are determined by systems of algebraic equations.
Consecutive Rosochatius deformations of the Neumann system
Authors: Xia Baoqiang , Zhou Ruguang
Published: October 2013

Consecutive Rosochatius deformations of the Neumann system are investigated. It is first shown that different realizations of a classical sl(2) Gaudin magnet model yield different integrable Hamiltonian systems. Then an algorithm of constructing infinitely many symplectic realizations of sl(2) algebra from a known one is presented and thus the Neumann system can be deformed consecutively. The second Rosochatius deformation of the Neumann system is taken as an illustrative example to show that the deformed systems admit separations of variables and may be linearized on the Jacobi variety.
Experimental inelastic neutron scattering spectrum of hydrogen hexagonal clathrate-hydrate compared with rigorous quantum simulations
Authors: Celli Milva , Powers Anna , Colognesi Daniele , Xu Minzhong , Bačić Zlatko , Ulivi Lorenzo
Published: October 2013

We have performed high-resolution inelastic neutron scattering (INS) measurements on binary hydrogen clathrate hydrates exhibiting the hexagonal structure (sH). Two samples, differing only in the ortho/para fraction of hydrogen, were prepared using heavy water and methyl tert-butyl ether as the promoter in its perdeuterated form. The INS spectrum of the translation-rotation (TR) excitations of the guest H2 molecule was obtained by subtracting the very weak signal due to the D2O lattice modes. By means of a subtraction procedure, it has been possible to obtain separately the spectra of caged p-H2 and o-H2. sH clathrates are comprised of three distinct types of cages, two of which, differing in shape and size, are each occupied by one H2 molecule only. Both contribute to the measured INS spectrum which is, therefore, rather complex and challenging to assign unambiguously. To assist with the interpretation, the INS spectra are calculated accurately utilizing the quantum methodology which incorporates the coupled five-dimensional TR energy levels and wave functions of the H2 molecule confined in each type of nanocage. The computed INS spectra are highly realistic and reflect the complexity of the coupled TR dynamics of the guest H2 in the anisotropic confining environment. The simulated INS spectra of p-H2 and o-H2 in the small and medium cages are compared with the experimental data, and are indispensable for their interpretation.