bluuebunny/crossref_metadata_2025 huggingface dataset:
Protein degradation in bovine milk caused byStreptococcus agalactiae
Authors: Åkerstedt Maria , Wredle Ewa , Lam Vo , Johansson Monika
Published: August 2012

Streptococcus(Str.)agalactiaeis a contagious mastitis bacterium, often associated with cases of subclinical mastitis. Different mastitis bacteria have been evaluated previously from a diagnostic point of view, but there is a lack of knowledge concerning their effect on milk composition. Protein composition is important in achieving optimal yield and texture when milk is processed to fermented products, such as cheese and yoghurt, and is thus of great economic value. The aim of thisin vitrostudy was to evaluate protein degradation mainly caused by exogenous proteases originating from naturally occurringStr. agalactiae. The samples were incubated at 37°C to imitate degradation caused by the bacteria in the udder. Protein degradation caused by different strains ofStr. agalactiaewas also investigated. Protein degradation was observed to occur whenStr. agalactiaewas added to milk, but there were variations between strains of the bacteria. Caseins, the most economically important proteins in milk, were degraded up to 75% in milk inoculated withStr. agalactiaein relation to sterile ultra-high temperature (UHT) milk, used as control milk. The major whey proteins, α-lactalbumin and β-lactoglobulin, were degraded up to 21% in relation to the sterile control milk. These results suggest that different mastitis bacteria but also different strains of mastitis bacteria should be evaluated from a milk quality perspective to gain knowledge about their ability to degrade the economically important proteins in milk.
Strange non-chaotic attractors in quasi-periodically forced circle maps: Diophantine forcing
Authors: JÄGER T.
Published: August 2012

We study parameter families of quasi-periodically forced (qpf) circle maps with Diophantine frequency. Under certain $\mathcal {C}^1$-open conditions concerning their geometry, we prove that these families exhibit non-uniformly hyperbolic behaviour, often referred to as the existence of strange non-chaotic attractors, on parameter sets of positive measure. This provides a nonlinear version of results by Young on quasi-periodic $\mathrm {SL}(2,\mathbb {R})$-cocycles and complements previous results in this direction which hold for sets of frequencies of positive measure, but did not allow for an explicit characterization of these frequencies. As an application, we study a qpf version of the Arnold circle map and show that the Arnold tongue corresponding to rotation number $1/2$collapses on an open set of parameters. The proof requires to perform a parameter exclusion with respect to some twist parameter and is based on the multiscale analysis of the dynamics on certain dynamically defined critical sets. A crucial ingredient is to obtain good control on the parameter dependence of the critical sets. Apart from the presented results, we believe that this step will be important for obtaining further information on the behaviour of parameter families like the qpf Arnold circle map.
Research on the SBS mediums used in high peak power laser system and their selection principle
Authors: Guo X.Y. , Hasi W.L.J. , Zhong Z.M. , Jin C.Y. , Lin D.Y. , He W.M. , Lu Z.W.
Published: August 2012

In this paper, we designed an experiment to research the properties for the stimulated Brillouin scattering (SBS) medium of perfluorocarbon-compounds (PFCs) and perfluoropolyether (PFPE), then we proposed that the selection principle of the high load capacity SBS medium can be used in the high peak power SBS system. The results showed that, for PFCs, perfluorinated hydrocarbons (FC-72) has the highest optical breakdown threshold (OBT); for PFPE, the medium with average molecular weight (AMW) less than 1000 has small medium absorption coefficient (AC) and high OBT, for AMW, greater than 1000, the medium AC becomes high and the OBT becomes low. Further research shows that, for PFPE series SBS medium, the AC increases and the OBT decreases gradually with increasing of AMW. We find some SBS mediums can work stably under high peak power pump, which lays a good foundation for the application of SBS technology in a high-power laser system.
Operating characteristics of intense electron beam accelerator at different load conditions
Authors: Cheng Xin-Bing , Liu Jin-Liang , Hong Zhi-Qiang , Qian Bao-Liang
Published: August 2012

As the development of the pulsed power technology, high voltage pulse transformer (HVPT) is usually used instead of Marx generator as a charging device for the pulse forming line (PFL) of intense electron-beam accelerator (IEBA), and which make the IEBA compact. However, during the operation of the IEBA, the HVPT may be destroyed for the failure of electrical insulation and the over-voltage. So in this paper, the output voltage characteristics of IEBA, characteristics of the voltage at the output terminal of HVPT at four kinds of load conditions are analyzed, including load matching, load short, load open, and surface flashover in the vacuum chamber. It is found that load short, load open, and surface flashover in vacuum chamber will affect the voltage at the output terminal of HVPT, and an oscillation wave could be formed, which affect the electrical insulation of HVPT and decrease the lifetime of HVPT. Meanwhile, the waveform of the load voltage is also modified, especially at the conditions of load open and surface flashover in vacuum chamber. When the load is open, the amplitude of the output main pulse of IEBA is twice the charging voltage of BPFL. However, the amplitude of the output pulse of IEBA is modified by the voltage at the output terminal of HVPT, and the resistance of main switch channel has a great effect on the amplitude of the load voltage. When surface flashover occurs in the vacuum chamber, the pulse duration of the output voltage will be decreased. So, during the operation of IEBA, load short, load open and surface flashover in vacuum chamber should be avoided.
Sensor fusion-based dynamic positioning of ships using Extended Kalman and Particle Filtering
Authors: Rigatos Gerasimos G.
Published: August 2012

The paper examines the problem of dynamic ship positioning with the use of Kalman Filter- and Particle Filter-based sensor fusion algorithms. The proposed approach enables to estimate accurately the ship's state vector by fusing the vessel's position and heading measurements coming from on-board sensors together with distance measurements coming from sensors located at the coast (e.g. radar). The estimated state vector is used in turn, in a control loop, to regulate the horizontal position and heading of the vessel. The performance of dynamic positioning of the ship based on Kalman and Particle Filtering is evaluated through simulation experiments.
Epidemiological analysis of critically ill adult patients with pandemic influenza A(H1N1) in South Korea
Authors: HONG S. B. , CHOI E. Y. , KIM S. H. , SUH G. Y. , PARK M. S. , LEE M. G. , LIM J. , LEE H. K. , KIM S. C. , KIM S. J. , KIM K. U. , KWAK S. H. , KOH Y.
Published: August 2012

A total of 245 patients with confirmed 2009 H1N1 influenza were admitted to the intensive-care units of 28 hospitals (South Korea). Their mean age was 55·3 years with 68·6% aged >50 years, and 54·7% male. Nine were obese and three were pregnant. One or more comorbidities were present in 83·7%, and nosocomial acquisition occurred in 14·3%. In total, 107 (43·7%) patients received corticosteroids and 66·1% required mechanical ventilation. Eighty (32·7%) patients died within 30 days after onset of symptoms and 99 (40·4%) within 90 days. Multivariate logistic regression analysis showed that the clinician's decision to prescribe corticosteroids, older age, Sequential Organ Failure Assessment score and nosocomial bacterial pneumonia were independent risk factors for 90-day mortality. In contrast with Western countries, critical illness in Korea in relation to 2009 H1N1 was most common in older patients with chronic comorbidities; nosocomial acquisition occurred occasionally but disease in obese or pregnant patients was uncommon.
Elastic waves in layered media: Two-scale homogenization approach
Authors: SHELUKHIN V. V. , ISAKOV A. E.
Published: August 2012

Using the two-scale convergence approach, we derive equations which govern transversal time-harmonic waves through a layered medium taking the form of a poroelastic composite saturated with a viscous fluid. To improve convergence, we construct a corrector. We study how wave speed and attenuation time depend on porosity and frequency. We prove that the Darcy permeability and the acoustic permeability in the Biot equations do not coincide.
International donor agencies’ incentive structures and foreign aid effectiveness
Authors: MONKAM NARA F.
Published: August 2012

This paper examines in depth one of the potential causes of the low performance of foreign aid; in particular, the role incentive structures within international donor agencies could play in leading to ‘a push’ to disburse money. This pressure to disburse money is termed as the ‘Money-Moving Syndrome’ (MMS). The theoretical analysis in this paper relies on the principal–agent theory to explore how donor agencies' institutional incentive systems may affect the characteristics of an optimal and efficient incentive contract and thus give rise to the MMS. The basic framework of the principal–agent theory was innovatively adapted to fit the organizational settings of donor agencies. The model concludes that the extent to which a performance measure based on the amount of aid allocated within a specific period of time would lead to the MMS and affect aid effectiveness depends on the level of ‘institutional imperatives’, the degree of aid agency's accountability for effectiveness, the level of corruption in recipient countries and the degree of difficulty to evaluate development activities.
Cooperative transnationalism in contemporary Europe: Europeanization and political opportunities for LGBT mobilization in the European Union
Authors: Ayoub Phillip M.
Published: August 2012

This article builds on previous research on Europeanization and political opportunity structures (POS) for mobilization, to explore the processes of transnational LGBT (Lesbian, Gay, Bisexual, and Transgender) mobilization in the European Union (EU). In the case of LGBT activism, European integration affects contentious politics by altering POS – both vertically and horizontally – for mobilization and changing the tactics of LGBT activism. Using the cases of Germany and Poland to trace cross-border connections between norm entrepreneur and target state, the findings suggest that LGBT activism relies on transnational resources – primarily, social spaces and organizational capacity – that are scarce in many member states but readily available in others. These horizontal opportunities among member states, alongside top-down vertical ones provided by Brussels, serve as mobilizing structures that bring together distinct groups of international actors. Europeanization also alters the tactics that transnational actors use when engaging with authorities in the target state. Employing socialization mechanisms that highlight appropriate behavior, actors tactically frame their demands in a European discourse by associating the issue of LGBT acceptance with democratic responsibilities as members of the EU community.
How Object Shape Affects Visual Metaphor Processing
Authors: van Weelden Lisanne , Maes Alfons , Schilperoord Joost , Swerts Marc
Published: August 2012

In order to interpret novel metaphoric relations, we have to construct ad hoc categories under which the metaphorically related concepts can be subsumed. Shape is considered to be one of the primary vehicles of object categorization. Accordingly, shape might play a prominent role in interpreting visual metaphors (i.e., two metaphorically related objects depicted in one visual array). This study explores the role of object shape in visual metaphor interpretation of 10- to 12-year-olds. The experiment shows that participants can produce more correspondences between similarly shaped objects as compared to dissimilarly shaped objects and that they need less thinking time to do so. These findings suggest that similarity in shape facilitates the process of interpreting visual metaphors.
The Joys of Spring
Authors: Riby Leigh M.
Published: August 2012

This study used Vivaldi’s Four Seasons, an extraordinary example of program music, to explore the consequence of music exposure on cognitive event-related potentials (ERPs). Seventeen participants performed a three-stimulus visual odd-ball task while ERPs were recorded. Participants were required to differentiate between a rare target stimulus (to elicit a memory updating component; P3b), a rare novel stimulus (to elicit a novelty attention component; P3a), and a frequent nontarget stimulus. During task performance participants listened to the four concertos: Spring, Summer, Autumn, and Winter in comparison to a silent control condition. Additionally, the three movements of each concerto have a fast, slow, fast structure that enabled examination of the impact of tempo. The data revealed that “Spring,” particularly the well-recognized, vibrant, emotive, and uplifting first movement, had the ability to enhance mental alertness and brain measures of attention and memory.
Nonlinear spatiotemporal evolution of whistler mode chorus waves in Earth's inner magnetosphere
Authors: Summers Danny , Omura Yoshiharu , Miyashita Yu , Lee Dong‐Hun
Published: August 2012

We analyze the nonlinear evolution of whistler mode chorus waves propagating along a magnetic field line from their equatorial source. We solve wave evolution equations off the equator for the wave magnetic field amplitude and wave frequency, subject to boundary conditions at the equator comprising model “chorus equations” that describe the generation of a seed chorus element. The electron distribution function is assumed to evolve adiabatically along a field line. The wave profiles exhibit nonlinear convective growth followed by saturation. Convective growth is due to nonlinear wave trapping, and the saturation process is partly due to a combination of adiabatic effects and a decreasing resonant current with latitude. Notwithstanding computationally expensive full‐scale kinetic simulations, our study appears to be the first to analyze the nonlinear evolution and saturation of whistler mode waves off the equator.
GOCI, the world's first geostationary ocean color observation satellite, for the monitoring of temporal variability in coastal water turbidity
Authors: Choi Jong‐Kuk , Park Young Je , Ahn Jae Hyun , Lim Hak‐Soo , Eom Jinah , Ryu Joo‐Hyung
Published: August 2012

The primary advantage of the Geostationary Ocean Color Imager (GOCI), the world's first geostationary ocean color observation satellite, over other ocean color satellite imagers is that it can obtain data every hour during the daytime, allowing ocean monitoring in near real time. Here, we investigated temporal variation in turbidity along a coastal region. To estimate suspended sediment concentrations (SSC), water samples and radiometric data were collected from waters in the Mokpo coastal area, located along the west coast of Korea. GOCI images acquired on the same day as the samples were used to generate a map of turbidity and to estimate the differences in SSC displayed in each image. Hourly GOCI images successfully identified the temporal variation in turbidity, which is mainly driven by the tidal cycle. A hydrodynamic model also showed that the GOCI‐derived turbidity variation was reliable. This study shows that the GOCI can be effectively used to monitor the temporal dynamics of the turbidity of coastal waters, i.e., sediment movements driven by the tidal cycle along the west coast of the Korean Peninsula.
Simulation of in‐cloud icing events on Mount Washington with the GEM‐LAM
Authors: Yang Jing , Jones Kathleen F. , Yu Wei , Morris Robert
Published: August 2012

In‐cloud icing on structures such as transmission lines and wind turbines is an important consideration both for design and operations. It often occurs in coastal areas and over high terrain, where there are virtually no systematic observations. The regional mesoscale model GEM‐LAM of the Canadian Meteorological Center (CMC) was used to model three historical icing events on Mount Washington, where observational data were available. These three events are representative of the most frequent low level wind directions for seven available observation periods. A newly developed sophisticated two‐moment microphysics scheme (Milbrandt‐Yau) is used in GEM‐LAM. The simulated cloud properties and other meteorological data are compared with near surface observational data. Simulation results from the 1‐km resolution run agree best with the observations, with an average RMSE (root mean square error) of 1.6°C for near surface temperature, 4.6 m s−1 for wind speed, 0.23 g m−3 for liquid water content, and 5.8 μm for the median volume droplet diameter. These simulated meteorological fields and cloud properties were used as inputs to a cylindrical sleeve icing model. The modeled icing rate from the GEM‐LAM simulated fields follows the temporal evolution of the observed one with average RMSE of 1.53 g m−1 min−1 compared to an average measured icing rate of 1.98 g m−1 min−1 for all the three cases.
Assimilating Doppler radar radial velocity and reflectivity observations in the weather research and forecasting model by a proper orthogonal‐decomposition‐based ensemble, three‐dimensional variational assimilation method
Authors: Pan Xiaoduo , Tian Xiangjun , Li Xin , Xie Zhenghui , Shao Aimei , Lu Chunyan
Published: August 2012

Doppler radar observations with high spatial and temporal resolution can effectively improve the description of small‐scale structures in the initial condition and enhance the mesoscale and microscale model skills of numerical weather prediction (NWP). In this paper, Doppler radar radial velocity and reflectivity are simultaneously assimilated into a weather research and forecasting (WRF) model by a proper orthogonal‐decomposition‐based ensemble, three‐dimensional variational assimilation method (referred to as PODEn3DVar), which therefore forms the PODEn3DVar‐based radar assimilation system (referred to as WRF‐PODEn3DVar). The main advantages of WRF‐PODEn3DVar over the standard WRF‐3DVar are that (1) the PODEn3DVar provides flow‐dependent covariances through the evolving ensemble of short‐range forecasts, and (2) the PODEn3DVar analysis can be obtained directly without an iterative process, which significantly simplifies the assimilation. Results from real data assimilation experiments with the WRF model show that WRF‐PODEn3DVar simulation yields better rainfall forecasting than radar retrieval, and radar retrieval is better than the standard WRF‐3DVar assimilation, probably because of the flow‐dependence character embedded in the WRF‐PODEn3DVar.
The signature of ozone depletion on tropical temperature trends, as revealed by their seasonal cycle in model integrations with single forcings
Authors: Polvani Lorenzo M. , Solomon Susan
Published: August 2012

The effect of ozone depletion on temperature trends in the tropical lower stratosphere is explored with an atmospheric general circulation model, and directly contrasted to the effect of increased greenhouse gases and warmer sea surface temperatures. Confirming and extending earlier studies we find that, over the second half of the 20th Century, the model's lower‐stratospheric cooling caused by ozone depletion is several times larger than that induced by increasing greenhouse gases. Moreover, our model suggests that the response to different forcings is highly additive. Finally we demonstrate that when ozone depletion alone is prescribed in the model, the seasonal cycle of the resultant cooling trends in the lower stratosphere is quite similar to that recently reported in satellite and radiosonde observations: this constitutes strong, new evidence for the key role of ozone depletion on tropical lower‐stratospheric temperature trends.
Climate extremes and climate change: The Russian heat wave and other climate extremes of 2010
Authors: Trenberth Kevin E. , Fasullo John T.
Published: August 2012

A global perspective is developed on a number of high impact climate extremes in 2010 through diagnostic studies of the anomalies, diabatic heating, and global energy and water cycles that demonstrate relationships among variables and across events. Natural variability, especially ENSO, and global warming from human influences together resulted in very high sea surface temperatures (SSTs) in several places that played a vital role in subsequent developments. Record high SSTs in the Northern Indian Ocean in May 2010, the Gulf of Mexico in August 2010, the Caribbean in September 2010, and north of Australia in December 2010 provided a source of unusually abundant atmospheric moisture for nearby monsoon rains and flooding in Pakistan, Colombia, and Queensland. The resulting anomalous diabatic heating in the northern Indian and tropical Atlantic Oceans altered the atmospheric circulation by forcing quasi‐stationary Rossby waves and altering monsoons. The anomalous monsoonal circulations had direct links to higher latitudes: from Southeast Asia to southern Russia, and from Colombia to Brazil. Strong convection in the tropical Atlantic in northern summer 2010 was associated with a Rossby wave train that extended into Europe creating anomalous cyclonic conditions over the Mediterranean area while normal anticyclonic conditions shifted downstream where they likely interacted with an anomalously strong monsoon circulation, helping to support the persistent atmospheric anticyclonic regime over Russia. This set the stage for the “blocking” anticyclone and associated Russian heat wave and wild fires. Attribution is limited by shortcomings in models in replicating monsoons, teleconnections and blocking.
Analysis of ELF electromagnetic field pulses recorded by the Hylaty station coinciding with terrestrial gamma‐ray flashes
Authors: Kulak A. , Mlynarczyk J. , Ostrowski M. , Kubisz J. , Michalec A.
Published: August 2012

Terrestrial gamma‐ray flashes (TGFs) were registered the first time by the NASA's Compton Gamma Ray Observatory. The physical mechanism of TGF generation is not fully known, but there is a consensus among researchers that the radiation is produced by bremsstrahlung of relativistic electrons in the thunderstorm regions of the atmosphere. Therefore, TGFs have been linked to positive‐polarity intracloud lightning discharges, strong positive cloud‐to‐ground discharges or upward discharges from a thundercloud top. The currently operating Fermi Gamma‐ray Space Telescope is equipped with a Gamma‐ray Burst Monitor that can detect terrestrial gamma‐ray flashes. It opens up a new possibility to search for lightning discharges responsible for TGFs. Ground‐based lightning monitoring systems in the ELF, LF and VLF ranges can be used for that purpose. The ELF systems are especially useful, since they provide a large monitoring range of several thousand kilometers for strong atmospheric discharges (charge moments above several tens of C km). In this paper we have described the data analysis method for ELF electromagnetic field pulses and applied it to study our first examples of TGFs registered by Fermi GBM coinciding with ELF pulses recorded by the Hylaty ELF station located in the Carpathian Mountains in Poland. Using our ELF electromagnetic wave propagation model we have evaluated charge moments for the two registered events to be 320 and 110 C km and provided upper limits for the remaining events.
Solar‐Storm/Lunar Atmosphere Model (SSLAM): An overview of the effort and description of the driving storm environment
Authors: Farrell W. M. , Halekas J. S. , Killen R. M. , Delory G. T. , Gross N. , Bleacher L. V. , Krauss‐Varben D. , Travnicek P. , Hurley D. , Stubbs T. J. , Zimmerman M. I. , Jackson T. L.
Published: August 2012

On 29 April 1998, a coronal mass ejection (CME) was emitted from the Sun that had a significant impact at Earth. The terrestrial magnetosphere became more electrically active during the storm passage. Less explored is the effect of such a storm on an exposed rocky body like our Moon. The solar‐storm/lunar atmosphere modeling effort (SSLAM) brings together surface interactions, exosphere, plasma, and surface charging models all run with a common driver – the solar storm and CME passage occurring from 1 to 4 May 1998. We present herein an expanded discussion on the solar driver during the 1–4 May 1998 period that included the passage of an intense coronal mass ejection (CME) that had >10 times the solar wind density and had a compositional component of He++ that exceeded 20%. During this time, the plasma mass flux to the exposed lunar surface increased by over 20 times compared to the nominal solar wind, to a value near 10−13 kg/m2‐s. Over a two day CME passage by the Moon, this amount approaches 300 tons of added mass to the Moon in the form of individual proton and helium ions. Such an increase in ion flux should have a profound impact on sputtering loss rates from the surface, since this process scales as the mass, energy, and charge state of the incident ion. Associated loss processes were addressed by SSLAM and will be discussed herein.
A Numerical Investigation of Quasi-static Conditions for Granular Media
Authors: Modenese C. , Utili S. , Houlsby G.T.
Published: August 2012

A numerical campaign by means of the Discrete Element Method (DEM) was carried out in order to investigate the accuracy of the assumption of quasi-static (QS) conditions in DEM experiments. The dimensionless inertial number, , was considered in order to assess the inertia of the system at both the peak and critical states of the material. DEM triaxial tests were run in a 3D periodic cell at increasing inertial number (e.g. loading rate). The classical Hert-Mindlin no-slip solution was employed at the contact level and grains were assigned with realistic properties of silica sands. Furthermore, a realistic wide particles size distribution was adopted.

Macroscopic observations show that the QS limit is not approached even for very small inertial numbers, i.e. I≈10−5, in contrast with the threshold identified by Roux and Combe (2010), i.e. I≤10−3. Nevertheless, the rate dependency of the mechanical response should be interpreted as a result of local dynamic effects (micro-inertial effects) rather than an indication of a time-dependent behaviour. Interestingly, such behaviour was only visible at very small strains, i.e. less than 3%, suggesting that different mechanisms may dominate at the particulate level at different stages of shearing.

The combined influence of inertia and confining stress was then studied in detail at the critical state. Results show that the influence of the applied pressure is non-negligible on the critical void ratio. Nevertheless, the opposite and counterintuitive behaviour is exhibited (i.e. higher void ratios for higher pressures) when a constant inertial number I≤10−3 is adopted. A modified definition of limiting inertial number, proportional to the speed of sound, is proposed which appears to produce results in agreement with the principles of critical state theory.
Retracted Article: Polycaprolactone composites with TiO2 for potential nanobiomaterials: tunable properties using different phases
Authors: Gupta Kamal K. , Kundan Akshay , Mishra Pradeep K. , Srivastava Pradeep , Mohanty Sujata , Singh Narendra K. , Mishra Abhinay , Maiti Pralay
Published: August 2012

TiO2 nanoparticles of different phases play a key role in property alteration of nanocomposite fibers.
Hypothalamic glycogen synthase kinase 3β has a central role in the regulation of food intake and glucose metabolism
Authors: Benzler Jonas , Ganjam Goutham K. , Krüger Manon , Pinkenburg Olaf , Kutschke Maria , Stöhr Sigrid , Steger Juliane , Koch Christiane E. , Ölkrug Rebecca , Schwartz Michael W. , Shepherd Peter R. , Grattan David R. , Tups Alexander
Published: August 2012

GSK3β (glycogen synthase kinase 3β) is a ubiquitous kinase that plays a key role in multiple intracellular signalling pathways, and increased GSK3β activity is implicated in disorders ranging from cancer to Alzheimer's disease. In the present study, we provide the first evidence of increased hypothalamic signalling via GSK3β in leptin-deficient Lepob/ob mice and show that intracerebroventricular injection of a GSK3β inhibitor acutely improves glucose tolerance in these mice. The beneficial effect of the GSK3β inhibitor was dependent on hypothalamic signalling via PI3K (phosphoinositide 3-kinase), a key intracellular mediator of both leptin and insulin action. Conversely, neuron-specific overexpression of GSK3β in the mediobasal hypothalamus exacerbated the hyperphagia, obesity and impairment of glucose tolerance induced by a high-fat diet, while having little effect in controls fed standard chow. These results demonstrate that increased hypothalamic GSK3β signalling contributes to deleterious effects of leptin deficiency and exacerbates high-fat diet-induced weight gain and glucose intolerance.
In vitro reconstitution of RNA primer removal in Archaea reveals the existence of two pathways
Authors: Henneke Ghislaine
Published: August 2012

Using model DNA substrates and purified recombinant proteins from Pyrococcus abyssi, I have reconstituted the enzymatic reactions involved in RNA primer elimination in vitro. In my dual-labelled system, polymerase D performed efficient strand displacement DNA synthesis, generating 5′-RNA flaps which were subsequently released by Fen1, before ligation by Lig1. In this pathway, the initial cleavage event by RNase HII facilitated RNA primer removal of Okazaki fragments. In addition, I have shown that polymerase B was able to displace downstream DNA strands with a single ribonucleotide at the 5′-end, a product resulting from a single cut in the RNA initiator by RNase HII. After RNA elimination, the combined activities of strand displacement DNA synthesis by polymerase B and flap cleavage by Fen1 provided a nicked substrate for ligation by Lig1. The unique specificities of Okazaki fragment maturation enzymes and replicative DNA polymerases strongly support the existence of two pathways in the resolution of RNA fragments.
Buckling instability of squeezed droplets
Authors: Elfring Gwynn J. , Lauga Eric
Published: August 2012

Motivated by recent experiments, we consider theoretically the compression of droplets pinned at the bottom on a surface of finite area. We show that if the droplet is sufficiently compressed at the top by a surface, it will always develop a shape instability at a critical compression. When the top surface is flat, the shape instability occurs precisely when the apparent contact angle of the droplet at the pinned surface is π, regardless of the contact angle of the upper surface, reminiscent of a past work on liquid bridges and sessile droplets as first observed by Plateau. After the critical compression, the droplet transitions from a symmetric to an asymmetric shape. The force required to deform the droplet peaks at the critical point then progressively decreases the indicative of catastrophic buckling. We characterize the transition in droplet shape using illustrative examples in two dimensions followed by perturbative analysis as well as numerical simulation in three dimensions. When the upper surface is not flat, the simple apparent contact angle criterion no longer holds, and a detailed stability analysis is carried out to predict the critical compression.
Surface treatment method for 1/f noise suppression in reactively sputtered nickel oxide film
Authors: Kim Dong Soo , Park Seung-Man , Lee Hee Chul
Published: August 2012

A surface treatment method combined with O2 plasma treatment and Ar+ bombardment is proposed for 1/f noise suppression in a reactively sputtered NiO film as a micro-bolometer sensing material. The 1/f noise power spectral density on a sample prepared by the proposed surface treatment method prior to the contact formation is suppressed to a level roughly 18 times lower than that on an untreated sample. The improved noise characteristic can be ascribed to the cooperative effects of the two steps in the proposed surface treatment method. In its effects, the oxygen plasma treatment is supposed to increase the Ni3+ component on the surface of the NiO film, which in turn increases the hole concentration on the surface. Additional Ar+ bombardment is expected to remove contaminants on the surface of the NiO film, leading to a low contact resistance.
Oxygen partial pressure dependence of the SiC oxidation process studied by in-situ spectroscopic ellipsometry
Authors: Kouda Keiko , Hijikata Yasuto , Yagi Shuhei , Yaguchi Hiroyuki , Yoshida Sadafumi
Published: August 2012

The oxygen partial pressure dependence of the Silicon carbide (SiC) oxidation process was investigated using in-situ spectroscopic ellipsometry at oxygen partial pressures between 1 and 0.02 atm for 4 H-SiC (0001) Si- and (000−1) C-faces. Analyses of the interface structure between the oxide and SiC indicate that the interface layer has a modified SiC-like structure around 1 nm thick accompanied by oxide growth; the structure and thickness do not change after an oxide growth of about 7 nm. The oxide thickness dependence of the growth rate at sub-atmospheric oxygen pressures is similar to that at 1 atm pressure, that is, just after oxidation starts, the growth rate rapidly decreases as the oxidation proceeds. After an oxide growth of about 7 nm thick, the deceleration of the growth rate suddenly changes to a gentle slope. The thickness at which deceleration changes depends slightly on both the oxygen partial pressure and surface polarity of the SiC substrate. The origins of these two deceleration stages, i.e., rapid and gentle decelerations, are discussed from their pressure dependencies based on the SiC oxidation model taking into account the interfacial emission of Si and C atoms. The formation and structures of the interface layers are also discussed in relation to the oxidation mechanisms.
A numerical electromagnetic linear dispersion relation for Maxwellian ring-beam velocity distributions
Authors: Umeda Takayuki , Matsukiyo Shuichi , Amano Takanobu , Miyoshi Yoshizumi
Published: August 2012

A positive slope in a velocity distribution function perpendicular to the ambient magnetic field, such as due to a loss cone or ring velocity distribution, can become a free energy source for the excitation of various plasma waves. Since there exists no analytic expression for integrals of Maxwellian ring velocity distribution functions, their linear properties have previously been studied using several approximations or modeled distributions. In this paper, a numerical method for analyzing the linear dispersion relation for Maxwellian ring-beam velocity distributions is developed. The obtained linear properties are confirmed by direct comparison with full particle simulation results.
1H relaxation dispersion in solutions of nitroxide radicals: Effects of hyperfine interactions with 14N and 15N nuclei
Authors: Kruk D. , Korpała A. , Kowalewski J. , Rössler E. A. , Moscicki J.
Published: August 2012

1H relaxation dispersion of decalin and glycerol solutions of nitroxide radicals, 4-oxo-TEMPO-d16-15N and 4-oxo-TEMPO-d16-14N was measured in the frequency range of 10 kHz–20 MHz (for 1H) using STELAR Field Cycling spectrometer. The purpose of the studies is to reveal how the spin dynamics of the free electron of the nitroxide radical affects the proton spin relaxation of the solvent molecules, depending on dynamical properties of the solvent. Combining the results for both solvents, the range of translational diffusion coefficients, 10−9–10−11 m2/s, was covered (these values refer to the relative diffusion of the solvent and solute molecules). The data were analyzed in terms of relaxation formulas including the isotropic part of the electron spin – nitrogen spin hyperfine coupling (for the case of 14N and 15N) and therefore valid for an arbitrary magnetic field. The influence of the hyperfine coupling on 1H relaxation of solvent molecules depending on frequency and time-scale of the translational dynamics was discussed in detail. Special attention was given to the effect of isotope substitution (14N/15N). In parallel, the influence of rotational dynamics on the inter-molecular (radical – solvent) electron spin – proton spin dipole-dipole coupling (which is the relaxation mechanism of solvent protons) was investigated. The rotational dynamics is of importance as the interacting spins are not placed in the molecular centers. It was demonstrated that the role of the isotropic hyperfine coupling increases for slower dynamics, but it is of importance already in the fast motion range (10−9m2/s). The isotope effects is small, however clearly visible; the 1H relaxation rate for the case of 15N is larger (in the range of lower frequencies) than for 14N. It was shown that when the diffusion coefficient decreases below 5 × 10−11 m2/s electron spin relaxation becomes of importance and its role becomes progressively more significant when the dynamics slows done. As far as the influence of the rotational dynamics is concerned, it was show that this process is of importance not only in the range of higher frequencies (like for diamagnetic solutions) but also at low and intermediate frequencies.
Molecular vibrations-induced quantum beats in two-dimensional electronic spectroscopy
Authors: Butkus Vytautas , Valkunas Leonas , Abramavicius Darius
Published: August 2012

Quantum beats in nonlinear spectroscopy of molecular aggregates are often attributed to electronic phenomena of excitonic systems, while nuclear degrees of freedom are commonly included into models as overdamped oscillations of bath constituents responsible for dephasing. However, molecular systems are coupled to various high-frequency molecular vibrations, which can cause the spectral beats hardly distinguishable from those created by purely electronic coherences. Models containing damped, undamped, and overdamped vibrational modes coupled to an electronic molecular transition are discussed in this paper in context of linear absorption and two-dimensional electronic spectroscopy. Analysis of different types of bath models demonstrates how do vibrations map onto two-dimensional spectra and how the damping strength of the coherent vibrational modes can be resolved from spectroscopic signals.
Existence domains of arbitrary amplitude nonlinear structures in two-electron temperature space plasmas. I. Low-frequency ion-acoustic solitons
Authors: Maharaj S. K. , Bharuthram R. , Singh S. V. , Lakhina G. S.
Published: August 2012

Using the Sagdeev pseudopotential technique, the existence of large amplitude ion-acoustic solitons is investigated for a plasma composed of ions, and hot and cool electrons. Not only are all species treated as adiabatic fluids but the model for which inertial effects of the hot electrons is neglected whilst retaining inertia and pressure for the ions and cool electrons has also been considered. The focus of this investigation has been on identifying the admissible Mach number ranges for large amplitude nonlinear ion-acoustic soliton structures. The lower Mach number limit yields a minimum velocity for the existence of ion-acoustic solitons. The upper Mach number limit for positive potential solitons is found to coincide with the limiting value of the potential (positive) beyond which the ion number density ceases to be real valued, and ion-acoustic solitons can no longer exist. Small amplitude solitons having negative potentials are found to be supported when the temperature of the cool electrons is negligible.
Effect of molecular rotation on enantioseparation
Authors: Jacob Andreas , Hornberger Klaus
Published: August 2012

Recently, several laser schemes have been proposed to separate racemic mixtures of enantiomers by splitting a molecular beam into subbeams consisting of molecules of definite chirality [Y. Li, C. Bruder, and C. P. Sun, Phys. Rev. Lett. 99, 130403 (2007)10.1103/PhysRevLett.99.130403; X. Li and M. Shapiro, J. Chem. Phys. 132, 194315 (2010)10.1063/1.3429884]. These ideas rely on laser-induced effective gauge potentials in an adiabatic basis which lead to a chirality dependent force on the center-of-mass. However, the effect of molecular rotation has been neglected in these studies. Accounting for the full molecular quantum state we find that the potentials from the adiabatic dressed state approach cannot be recovered once the molecular orientation dynamics is included, even in the rotational ground state. This affects substantially the ability to perform enantioseparation in the above mentioned setups.
Relaxation of electronic excitations in CaF2 nanoparticles
Authors: Vistovskyy V. V. , Zhyshkovych A. V. , Mitina N. E. , Zaichenko A. S. , Gektin A. V. , Vasil’ev A. N. , Voloshinovskii A. S.
Published: August 2012

The luminescence properties of CaF2 nanoparticles with various sizes (20–140 nm) are studied upon the excitation by VUV and x-ray quanta in order to reveal the influence of ratio of mean free path and thermalization length of charge carriers and nanoparticle size on the self-trapped exciton luminescence. The luminescence intensity for exciting quantum energies corresponding to optical creation of exciton and to the range of electronic excitation multiplication is not so sensitive to nanoparticle size as for quanta with energy of Eg < hν < 2Eg. The dependences of luminescence intensity on nanoparticle size at the excitation by quanta of various energies are discussed in terms of electron-phonon and electron-electron scattering lengths and energy losses on surface defects.
Electronic states of Ge/Si nanocrystals with crescent-shaped Ge-cores
Authors: Neupane Mahesh R. , Lake Roger K. , Rahman Rajib
Published: August 2012

Ge/Si nanocrystals can serve as charge storage sites in a nanocrystal memory by providing a hole quantum-well in the Ge region. The electronic states of realistically shaped Ge/Si nanocrystals with crescent-shaped Ge-cores are calculated to determine the hole confinement energies, effective masses, barrier heights, and thermionic lifetimes. As the Ge crescent thickness increases from 1 nm to 3.5 nm, the hole confinement energy decreases from 0.52 to 0.28 eV, the barrier height to escape into the Si valence band increases from 0.25 to 0.51 eV, and the resulting thermionic hole lifetime increases from 10−9 to 10−5 s. The nanocrystals are modeled with an atomistic, 20-band sp3d5s* tight-binding model including spin-orbit coupling as implemented in NEMO3D. Geometry relaxation and strain are included using the valence-force-field model with Keating potentials.
Efficiency determination of an electrostatic lunar dust collector by discrete element method
Authors: Afshar-Mohajer Nima , Wu Chang-Yu , Sorloaica-Hickman Nicoleta
Published: August 2012

Lunar grains become charged by the sun’s radiation in the tenuous atmosphere of the moon. This leads to lunar dust levitation and particle deposition which often create serious problems in the costly system deployed in lunar exploration. In this study, an electrostatic lunar dust collector (ELDC) is proposed to address the issue and the discrete element method (DEM) is used to investigate the effects of electrical particle-particle interactions, non-uniformity of the electrostatic field, and characteristics of the ELDC. The simulations on 20-μm-sized lunar particles reveal the electrical particle-particle interactions of the dust particles within the ELDC plates require 29% higher electrostatic field strength than that without the interactions for 100% collection efficiency. For the given ELDC geometry, consideration of non-uniformity of the electrostatic field along with electrical interactions between particles on the same ELDC geometry leads to a higher requirement of ∼3.5 kV/m to ensure 100% particle collection. Notably, such an electrostatic field is about 103 times less than required for electrodynamic self-cleaning methods. Finally, it is shown for a “half-size” system that the DEM model predicts greater collection efficiency than the Eulerian-based model at all voltages less than required for 100% efficiency. Halving the ELDC dimensions boosts the particle concentration inside the ELDC, as well as the resulting field strength for a given voltage. Though a lunar photovoltaic system was the subject, the results of this study are useful for evaluation of any system for collecting charged particles in other high vacuum environment using an electrostatic field.
Development of an optically pumped atomic magnetometer using a K-Rb hybrid cell and its application to magnetocardiography
Authors: Ito Yosuke , Ohnishi Hiroyuki , Kamada Keigo , Kobayashi Tetsuo
Published: August 2012

We have developed an optically pumped atomic magnetometer using a hybrid cell of K and Rb. The hybrid optical pumping technique can apply dense alkali-metal vapor to the sensor head and leads to high signal intensity. We use dense Rb vapor as probed atoms, and achieve a sensitivity of approximately 100 fTrms/Hz1/2 around 10 Hz. In this case, the sensitivity is limited by the system noise, and the magnetic linewidth is narrower than that for direct Rb optical pumping. We demonstrated magnetocardiography using the magnetometer and obtained clear human magnetocardiograms.
The effect of PECVD plasma decomposition on the wettability and dielectric constant changes in silicon modified DLC films for potential MEMS and low stiction applications
Authors: Ogwu A. A. , Okpalugo T. I. T. , McLaughlin J. A. D.
Published: August 2012

We have carried out investigations aimed at understanding the mechanism responsible for a water contact angle increase of up to ten degrees and a decrease in dielectric constant in silicon modified hydrogenated amorphous carbon films compared to unmodified hydrogenated amorphous carbon films. Our investigations based on surface chemical constituent analysis using Raman spectroscopy, x-ray photoelectron spectroscopy (XPS), SIMS, FTIR, contact angle / surface energy measurements and spectroscopic ellipsometry suggests the presence of hydrophobic chemical entities on the surface of the films. This observation is consistent with earlier theoretical plasma chemistry predictions and observed Raman peak shifts in the films. These surface hydrophobic entities also have a lower polarizability than the bonds in the un-modified films thereby reducing the dielectric constant of the silicon modified films measured by spectroscopic ellipsometry. Ellipsometric dielectric constant measurement is directly related to the surface energy through Hamaker's constant. Our current finding is expected to be of benefit to understanding stiction, friction and lubrication in areas that range from nano-tribology to microfluidics.
Bias-induced migration of ionized donors in amorphous oxide semiconductor thin-film transistors with full bottom-gate and partial top-gate structures
Authors: Mativenga Mallory , Hwang Tae-Ha , Jang Jin
Published: August 2012

Bias-induced charge migration in amorphous oxide semiconductor thin-film transistors (TFTs) confirmed by overshoots of mobility after bias stressing dual gated TFTs is presented. The overshoots in mobility are reversible and only occur in TFTs with a full bottom-gate (covers the whole channel) and partial top-gate (covers only a portion of the channel), indicating a bias-induced uneven distribution of ionized donors: Ionized donors migrate towards the region of the channel that is located underneath the partial top-gate and the decrease in the density of ionized donors in the uncovered portion results in the reversible increase in mobility.
Fernique-type inequalities and moduli of continuity for anisotropic Gaussian random fields
Authors: Meerschaert Mark , Wang Wensheng , Xiao Yimin
Published: August 2012

This paper is concerned with sample path properties of anisotropic Gaussian random fields. We establish Fernique-type inequalities and utilize them to study the global and local moduli of continuity for anisotropic Gaussian random fields. Applications to fractional Brownian sheets and to the solutions of stochastic partial differential equations are investigated.