bluuebunny/crossref_metadata_2025 huggingface dataset:
Paleoseismology of the North Anatolian Fault at Güzelköy (Ganos segment, Turkey): Size and recurrence time of earthquake ruptures west of the Sea of Marmara
Authors: Meghraoui Mustapha , Aksoy M. Ersen , Akyüz H. Serdar , Ferry Matthieu , Dikbaş Aynur , Altunel Erhan
Published: March 2012

The Ganos fault is the westernmost segment of the North Anatolian Fault that experienced the Mw = 7.4 earthquake of 9 August 1912. The earthquake revealed 45‐km‐long of surface ruptures inland, trending N70°E, and 5.5 m of maximum right lateral offset near Güzelköy. The long‐term deformation of the fault is clearly expressed by several pull‐apart basins and sag ponds, pressure and shutter ridges and offset streams. In parallel with detailed geomorphologic investigations, we measured co‐seismic and cumulative displacements along the fault, and selected the Güzelköy site for paleoseismology. A microtopographic survey at the site yields 10.5 ± 0.5 m and 35.4 ± 1.5 m cumulative lateral offsets of stream channels and geomorphologic features. Seven paleoseismic parallel and cross‐fault trenches document successive faulting events and provide the timing of past earthquakes on the Ganos fault segment. Radiocarbon dating of successive colluvial wedges in trench T1, and the fresh scarplet above (probably 1912 surface rupture) indicate the occurrence of three faulting events since the 14th century. Parallel trenches (3, 5, 6 and 7) expose paleo‐channels and show a cumulative right‐lateral offset of 16.5 ± 1.5 m next to the fault, and 21.3 ± 1.5 m total channel deflection. Radiocarbon dating of past channel units and fault scarp‐related colluvial deposits imply an average 17 +/− 5 mm/year slip rate and 323 ± 142 years recurrence interval of large earthquakes during the last 1000 years on the Ganos fault. The succession of past faulting events and inferred slip rate west of the Marmara Sea provide more constraint on the long‐term faulting behavior in the seismic gap of the North Anatolian Fault and may contribute to a better seismic hazard assessment in the Istanbul region.
Morphological features of tweeks and nighttime D region ionosphere at tweek reflection height from the observations in the low‐latitude Indian sector
Authors: Maurya Ajeet K. , Singh Rajesh , Veenadhari B. , Kumar Sushil , Cohen M. B. , Selvakumaran R. , Pant P. , Singh A. K. , Siingh D. , Inan U. S.
Published: March 2012

A total of 19,308 tweeks recorded during April 2007 to March 2008, at Allahabad, a low‐latitude station in the Indian sector, has been used to study seasonal occurrence which shows maximum tweek occurrence of about 63% during summer season and about 19% and 18% occurrences during equinox and winter seasons. Maximum occurrence of tweeks during summer season is consistent with the larger number of lightnings detected by World Wide Lightning Location Network in the Indian and Asia Oceania regions during summer as compared to that during equinox and winter. Seasonally, tweek (ionospheric) reflection height in the premidnight (18:00‐00:00 LT) during winter is less as compared to that during equinox and summer. Annual (seasonal average) variation of the mean ionospheric reflection height shows a gradual increase in the reflection height from about 19:30 to 04:30 LT. The annual average of postmidnight (00:00–06:00 LT) reflection height is about 5 km higher as compared to that in the premidnight. Our initial results on the variability in the ionospheric reflection height under pure nighttime propagation (21:00–03:00 LT) on magnetically quiet days show a day‐to‐day variability of up to 8 km. Theoretically calculated attenuation of the Earth‐ionosphere waveguide for first six tweek modes in the early and late night periods (21:00–00:00 LT; 00:00–03:00 LT) is less compared to that in the dusk (18:00–21:00 LT) period. The higher attenuation in the dusk period and most of the tweeks in the dawn period traveling partially under daytime conditions explain the lower occurrence of tweeks in these periods.
A global comparison of O+ upward flows at 850 km and outflow rates at 6000 km during nonstorm times
Authors: Redmon R. J. , Peterson W. K. , Andersson L. , Denig W. F.
Published: March 2012

There has been recent progress in understanding the sources and consequences of energetic O+ in the ring current and other regions of the magnetosphere. Various energization mechanisms that depend on geomagnetic activity, altitude, magnetic local time, and relative position within the auroral oval acting on O+ have been proposed. Our understanding of the altitude and magnetic local time variation of these processes has not proceeded as rapidly, however. Contemporary magnetosphere models now include species‐dependent dynamics. These models will benefit from improved spatial and altitudinal knowledge of O+ energization processes. Here we present a global view of O+ upward flows observed at DMSP (850 km) compared to outflow rates observed by Polar (5000–7000 km) during nonstorm times in the framework of dynamic auroral boundary coordinates. This study considers observational proxies for heating and energization mechanisms and shows that these proxies set useful boundaries on their efficacy. This study indicates that during nonstorm times (1) energization between 850 km and 5000–7000 km is predominantly transverse, (2) the efficiency of ion energization is often not focused at the boundaries of the auroral zone, and (3) auroral zone acceleration above DMSP is relatively more important in the cusp than at midnight.
Inner magnetosphere currents during the CIR/HSS storm on July 21–23, 2009
Authors: Ganushkina N. Y. , Dubyagin S. , Kubyshkina M. , Liemohn M. , Runov A.
Published: March 2012

Modeling results of the configuration of the inner magnetosphere current systems, namely, the ring current and the near‐Earth tail current, during the July 21–23, 2009 CIR/HSS storm event are presented. We use two different modeling approaches, magnetic field modeling and particle modeling. We perform the magnetospheric magnetic field modeling with several standard and one modified Tsyganenko models, and the particle modeling with the Inner Magnetosphere Particle Transport and Acceleration Model (IMPTAM). It is found that the magnitudes of current densities in the inner magnetosphere computed with IMPTAM are comparable to those of computed with the TS05 magnetic field model. The model ring current, being asymmetric during the storm main phase did not show a duskward shift of its peak. It is shown with both modeling approaches that the incorporation of near‐Earth tail currents in the calculations of model Dst (SymH in the present paper) index is crucial, as there is significant current beyond 6.6 RE in the simulation results. A discrepancy is found between the SymH contributions from various currents as defined by the TS05 modules and from current streamline tracing through these same currents. We conclude that the method to calculate the contributions of different current systems to the model Dst using the global magnetospheric magnetic field models should be Biot‐Savart integration inside the regions, which contain the current systems, not using the magnetic field from the model representations of current modules.
A statistical study of low latitude F region irregularities at Brazilian longitudinal sector response to geomagnetic storms during post‐sunset hours in solar cycle 23
Authors: Sun Y. Y. , Liu J. Y. , Lin C. H.
Published: March 2012

Effects of intense geomagnetic storms (Dst index < −100) to low latitude F region irregularities in the post‐sunset hours are statistically studied by the total electron content (TEC) phase fluctuation observations obtained from the ground‐based global positioning system (GPS) receivers in the Brazilian longitude sector during a 7.5‐year period of 1 April 1998–31 October 2005. Results show that the low latitude irregularities are significantly suppressed during the main and recovery phases of the intense geomagnetic storms in the months (September–March) that normally have high irregularity activity. In contrast, the post‐sunset triggering signatures are pronounced in the low irregularity activity season (April–August) during storms. To further understand the storm‐produced behaviors in the low latitude F region irregularity in the post‐sunset hours, the relationship between the intensity of GPS phase fluctuations and the occurrence time of the of IMF Bz turnings is examined and discussed.
Improving empirical aftershock modeling based on additional source information
Authors: Bach C. , Hainzl S.
Published: March 2012

Several mechanisms are proposed to underlie earthquake triggering including static stress interactions and dynamic stress transfer. Significant differences of these mechanisms are particularly expected in the spatial distribution of aftershocks. However, testing the different hypotheses is challenging because it requires the consideration of the large uncertainties involved in stress calculations as well as the appropriate consideration of secondary aftershock triggering which is related to stress changes induced by smaller pre‐ and aftershocks. In order to evaluate the forecast capability of different mechanisms, we take the effect of smaller‐magnitude earthquakes into account by using the epidemic type aftershock sequence (ETAS) model where the spatial probability distribution of direct aftershocks, if available, is correlated to alternative source information and mechanisms. We test surface shaking, rupture geometry, and slip distributions. As an approximation of the shaking level, we use ShakeMap data which are available in near real‐time after a main shock and thus could be used for first‐order forecasts of the spatial aftershock distribution. Alternatively, we test the use of empirical decay laws related to minimum fault distance and Coulomb stress change calculations based on published and random slip models. For comparison, we analyze the likelihood values of the different model combinations in the case of several well‐known aftershock sequences (1992 Landers, 1999 Hector Mine, 2004 Parkfield). Our test shows that the fault geometry is the most valuable information for improving aftershock forecasts. Furthermore, we find that static stress maps can additionally improve the forecasts of off‐fault aftershock locations, while the integration of ground shaking data could not upgrade the results significantly.
Hydroecological model predictions indicate wetter and more diverse soil water regimes and vegetation types following floodplain restoration
Authors: Booth Eric G. , Loheide Steven P.
Published: March 2012

Transitions between aquatic and terrestrial ecosystems represent zones where soil moisture is a dominant factor influencing vegetation composition. Niche models based on hydrological and vegetation observations can be powerful tools for guiding management of these zones, especially when they are linked with physically based hydrological models. Floodplain restoration represents a unique opportunity to utilize such a predictive vegetation tool when a site's hydrology is altered to create a wetter environment. A variably saturated groundwater flow model was developed and used to simulate the soil moisture regime across a floodplain in Wisconsin where post‐settlement alluvium was removed with the intent of increasing regionally threatened wetland plant species. Hydrological niche models based on simultaneous observations of vegetation composition and surface effective saturation were used to predict probability of presence for two plant species (Carex vulpinoidea (fox sedge) and Elymus canadensis(Canada wildrye)) and wetland indicator score (a composite indicator of relative frequency of species in five habitat categories) based on simulated surface effective saturation. The vegetation predictions following restoration are more wetland‐species dominant overall. However, zones of the study site where a confining layer is present that decouples groundwater from the near‐surface soil zone tend to be drier following restoration due to restricted upward groundwater flow and less soil water storage above the confining layer. As reflected by an increase in the interquartile range in the predicted wetland indicator score, this restoration technique may increase the site‐scale spatial diversity of plant community types while simultaneously accomplishing the goal of increasing wetland plant species occurrence.
Collecting winter data on U.S. Coast Guard icebreakers
Authors: Oyserman Ben O. , Woityra William C. , Bullerjahn George S. , Beall Benjamin F. N. , McKay Robert Michael L.
Published: March 2012

Winter research and monitoring of icebound rivers, lakes, and coastal seas to date has usually involved seagoing civilian scientists leading survey efforts. However, because of poor weather conditions and a lack of safe research platforms, scientists collecting data during winter face some difficult and often insurmountable problems. To solve these problems and to further research and environmental monitoring goals, new partnerships can be formed through integrating efforts of the U.S. Coast Guard (USCG) with citizen science initiatives. USCG and a research group at Ohio's Bowling Green State University are entering the third year of such a partnership, in which icebreaking operations in Lake Erie using USCG Cutter Neah Bay support volunteer data collection. With two additional USCG vessels joining the program this winter season, the partnership serves as a timely and useful model for worldwide environmental research and monitoring through citizen science and government collaboration.
National Science Foundation proposed budget could see another increase
Authors: Showstack Randy
Published: March 2012

President Barack Obama's proposed budget for the U.S. National Science Foundation (NSF) for fiscal year (FY) 2013 would provide the agency with $7.37 billion, a $340 million increase, 4.8% above the FY 2012 estimated budget under which NSF has been operating. NSF has fared well during previous budget cycles, and the Obama administration's budget document for FY 2013 states that “NSF plays a critical role in the implementation of the President's Plan for Science and Technology.” With federal agencies operating under tighter budgets in a difficult financial climate, NSF director Subra Suresh said the budget includes substantial increases for core programs, frontier science, education, and human resources. “I am confident that NSF merits the $7.4 billion the president proposed. I'm optimistic Congress will approve the budget,” Suresh said at a 13 February NSF budget briefing.
NOAA budget would boost satellite funding but cut some key areas
Authors: Showstack Randy
Published: March 2012

The White House's proposed fiscal year (FY) 2013 budget for the National Oceanic and Atmospheric Administration (NOAA), announced on 13 February, looks favorable at first glance. The administration's request calls for $5.1 billion, an increase of $153 million (3.1%) above the FY 2012 estimated budget. However, the increase for NOAA satellites is $163 million, which means that other areas within the agency would be slated for decreased funding, including programs within the National Ocean Service (NOS), National Marine Fisheries Service (NMFS), National Weather Service (NWS), and some NOAA education programs. The proposed overall budget for the agency “reflects the overarching importance of weather satellites to public safety, to national security, and to the economy,” NOAA director Jane Lubchenco said at a 16 February briefing, noting that difficult choices were made regarding the budget. “Due to significant resources required for our weather satellites and the economic conditions in the country, other parts of our budget have been reduced, in some cases quite significantly,” she said. She added that the imperative to fund both the Joint Polar Satellite System (JPSS) and geostationary satellites in FY 2013 “imposes serious constraints on the rest of NOAA's budget.”
Climate science in a postnormal context
Authors: Krauss Werner , von Storch Hans
Published: March 2012

Postnormal Science: The Case of Climate Research; Hamburg, Germany, 4–6 May 2011 Climate research has left the narrow confines of pure science and has entered the public arena. At a workshop organized by Helmholtz Research Centre Geesthacht and the KlimaCampus, University of Hamburg, experts from the cultural, social, and natural sciences discussed the current state of climate science through the lens of “postnormal science” (see, e.g., S. O. Funtowicz and J. R. Ravetz, “Science for the postnormal age,” Futures,25, 739–755, 1993). Science turns postnormal when facts are uncertain, stakes are high, values are disputed, and decisions are urgent. During the workshop, situations and practices in climate research were identified and discussed to provide a solid empirical basis for a more realistic definition of climate science.
Marine‐hydrokinetic energy and the environment: Observations, modeling, and basic processes
Authors: Foufoula‐Georgiou Efi , Guala Michele , Sotiropoulos Fotis
Published: March 2012

Research at the Interface of Marine Hydrokinetic Energy and the Environment: A Workshop; Minneapolis, Minnesota, 5–7 October 2011 Marine and hydrokinetic (MHK) energy harvesting technologies convert the kinetic energy of waves and water currents into power to generate electricity. Although these technologies are in early stages of development compared to other renewable technologies, such as solar and wind energy, they offer electricity consumers situated near coastlines or inland rivers an alternative energy technology that can help meet renewable portfolio standards. However, the potential environmental impacts of MHK energy are far from well understood, both in general principles and in site‐specific cases. As pressure for new MHK energy licenses builds, accelerated research in providing the scientific understanding of harnessing the natural power of water for renewable energy at a competitive cost and without harming the environment becomes a priority.
AGU signs memorandum of agreement with Asia Oceania Geosciences Society
Authors: McEntee Chris
Published: March 2012

AGU has taken the latest step in building strategic alliances with partner groups by signing a memorandum of agreement with the Asia Oceania Geosciences Society (AOGS). This agreement is based on the common interests of our members and will allow us to strengthen our respective organizations by

exchanging information on key programs and initiatives;

expanding membership of both our organizations through possible joint programs;

offering additional educational opportunities, professional services, and student programs; and

extending benefits to members of both organizations.
The planet in a pebble: A journey into Earth's deep history
Authors: Natland James H.
Published: March 2012

An old idea in America is that the perfect educator could sit on one end of a log, with a pupil on the other end, and simply by dint of knowledge, organization, and verve be able to teach that student anything. Picture now a log of driftwood on a beach in Wales. The educator takes one end, and we—any of us, but mainly someone not too well versed in geology—take the other end. He is about to clue us in. He picks up a pebble, a beach cobble, and begins.
Associating tornado occurrence with environmental parameters
Authors: Balcerak Ernie
Published: March 2012

Tornado prediction on monthly scales could be improved if tornadoes could be associated with predictable environmental parameters. Tippett et al. sought to identify atmospheric parameters associated with monthly tornado activity to create an index that could provide a basis for extended‐range forecasts of monthly tornado activity. They analyzed U.S. tornado data from 1979 through 2010 and atmospheric parameters including convective precipitation and other factors. They were able to create an index that captures the spatial distribution, seasonal variation, and year‐to‐year variability of tornado occurrence. (Geophysical Research Letters, doi:10.1029/2011GL050368, 2012)
Modulation of T‐cell function by type I interferon
Authors: Tough David F
Published: March 2012

Production of type I interferon (IFN‐α/β) is a common cellular response to virus infection. IFN‐α/β has a dual role in combating infection, triggering innate antiviral mechanisms and stimulating the generation of an adaptive immune response. This review focuses on the effects of IFN‐α/β on one particular immune cell type, the T cell, and the impact of IFN‐α/β‐mediated signalling in T cells on the immune response. The critical role of T‐cell responsiveness to IFN‐α/β for the generation of productive T‐cell responses after infections with certain viruses in vivo is discussed in the context of in vitro experiments investigating the mechanisms by which IFN‐α/β modifies T‐cell function. These studies reveal complex effects of IFN‐α/β on T cells, with the consequences of exposure to IFN‐α/β depending on the context of other signals received by the T cell.
Disruptive Strategies for Removing Drug Discovery Bottlenecks
Authors: Ekins Sean , Waller Chris , Bradley Mary , Williams Antony
Published: March 2012

Drug Discovery is shifting focus from the industry to outside partners and in the process creating new bottlenecks, suggesting the need for a more disruptive overhaul. Technologies like high throughput screening (HTS) have moved to a larger number of academic and institutional laboratories in the US, with little apparent coordination or consideration of the outputs and creating a translational gap. While there have been collaborative public private partnerships in Europe to share pharmaceutical data, the USA has lagged behind. Sharing precompetitive computational models may be the next frontier to provide more confidence in the quality of the leads produced and attract investment. We suggest there needs to be an awareness of what research is going on in the screening centers, more collaboration and coordination. These efforts will shift the focus to finding the best researchers to fund and require a rethink of how to reward their collaborative efforts.
Docking studies to explore novel inhibitors against human beta-site APP cleaving enzyme (BACE-1) involved in Alzheimer’s disease
Authors: Anjum Mobeen S , Munikumar Manne , Umamaheswari Amineni
Published: March 2012

Alzheimer’s disease (AD) is one of the most prominent neurodegenerative disorders, particularly in elder persons over 65 age. It is characterized by progressive cognitive deterioration together with declining activities. Amyloid precursor protein (APP) cleaves at A-beta (Aβ) peptide by rate limiting factor of Beta-site APP cleaving enzyme (BACE-1) in amyloidogenic pathway. Elevated level of BACE-1 leads to the accumulation of an insoluble form of Aβ peptides (Senile Plaques), an important hallmark in the pathogenesis of Alzheimer disease. Five published inhibitors of BACE-1, thiazolidinediones, rosiglitazone, pioglitazone, Sc7 and tartaric acid are available with poor pharmacological properties and intolerable side effects. Therefore, a computational approach was undertaken to design novel inhibitors against human BACE-1. The crystal structure of human BACE-1 was retrieved from the protein data bank and optimized by applying OPLS force field in Maestro v9.2. An ASINEX database (115,000 ligands) was downloaded and compounds were prepared using LigPrep. The optimized ligand dataset was docked into the BACE-1 through sequential application of Glide HTVS, SP and XP methods that penalizes more stringently for minor steric classes subsequently. Finally, seven leads were reported and ranked based on XPGscore with better binding affinity and good pharmacological properties compared with existing inhibitors. Six leads were proposed for human BACE-1. Among the six, lead 1, with XPGscore -8.051Kcal/mol, would be intriguing for rational drug design against Alzheimer’s disease and would be highly encouraging for future Alzheimer’s therapy if tested in animal models.
Note: Optical trigger device with sub-picosecond timing jitter and stability
Authors: Kodet Jan , Prochazka Ivan
Published: March 2012

We are presenting the design, construction, and overall performance of the optical trigger device. This device generates an electrical signal synchronously to the detected ultra-short optical pulse. The device was designed for application in satellite laser ranging and laser time transfer experiments, time correlated photon counting and similar experiments, where picosecond timing resolution and detection delay stability are required. It consists of the ultrafast optical detector, signal discriminator, output pulse forming circuit, and output driver circuits. It was constructed as a single compact device to optimize their matching and maintain stability. The detector consists of an avalanche photodiode–-both silicon and germanium types may be used to cover the wavelength range of 350–1550 nm. The analogue signal of this photodiode is sensed by the ultrafast comparator with 8 GHz bandwidth. The ps clock distribution circuit is used to generate the fast rise/fall time output pulses of pre-set length. The trigger device timing performance is excellent: the random component of the timing jitter is typically 880 fs, the temperature dependence of the detection delay was measured to be 370 fs/K. The systematic error contribution depends on the laser used and its stability. The sub-ps values have been obtained for various laser sources.
Effects of low-frequency repetitive transcranial magnetic stimulation on event-related potential P300
Authors: Torii Tetsuya , Sato Aya , Iwahashi Masakuni , Iramina Keiji
Published: March 2012

The present study analyzed the effects of repetitive transcranial magnetic stimulation (rTMS) on brain activity. P300 latency of event-related potential (ERP) was used to evaluate the effects of low-frequency and short-term rTMS by stimulating the supramarginal gyrus (SMG), which is considered to be the related area of P300 origin. In addition, the prolonged stimulation effects on P300 latency were analyzed after applying rTMS. A figure-eight coil was used to stimulate left-right SMG, and intensity of magnetic stimulation was 80% of motor threshold. A total of 100 magnetic pulses were applied for rTMS. The effects of stimulus frequency at 0.5 or 1 Hz were determined. Following rTMS, an odd-ball task was performed and P300 latency of ERP was measured. The odd-ball task was performed at 5, 10, and 15 min post-rTMS. ERP was measured prior to magnetic stimulation as a control. Electroencephalograph (EEG) was measured at Fz, Cz, and Pz that were indicated by the international 10–20 electrode system. Results demonstrated that different effects on P300 latency occurred between 0.5–1 Hz rTMS. With 1 Hz low-frequency magnetic stimulation to the left SMG, P300 latency decreased. Compared to the control, the latency time difference was approximately 15 ms at Cz. This decrease continued for approximately 10 min post-rTMS. In contrast, 0.5 Hz rTMS resulted in delayed P300 latency. Compared to the control, the latency time difference was approximately 20 ms at Fz, and this delayed effect continued for approximately 15 min post-rTMS. Results demonstrated that P300 latency varied according to rTMS frequency. Furthermore, the duration of the effect was not similar for stimulus frequency of low-frequency rTMS.
Sensitivity enhancement of a giant magnetoresistance alternating spin-valve sensor for high-field applications
Authors: Yoon Seungha , Jang Youngman , Nam Chunghee , Lee Seungkyo , Kwon Joonhyun , Na Kyungmin , Lee Kisu , Cho B. K.
Published: March 2012

We introduce a CoFe/Tb multilayer film as a sensing layer of alternating giant magnetoresistance (GMR) spin-valve sensors for use in a high-field measurements. The CoFe/Tb sensing layer has lower in-plane anisotropy than a single CoFe sensing layer and allows the alternating GMR sensor to show a high sensitivity, ∼0.4 MR[%]/kOe, when the sensing layer structure is [CoFe(1.92 nm)/Tb(1.22 nm)] × 2. This sensitivity is about four times larger than previously reported values. In addition, it was found that the working range of the sensor could be easily tuned by varying the CoFe thickness in the reference layer. Therefore, this study is encouraging not only for GMR alternating spin-valve sensor applications, but also for the development of tunneling magnetoresistance based alternating sensor applications with considerably higher sensitivities.
Field and current induced asymmetric domain wall motion in a giant magnetoresistance spin-valve stripe with a circular ring
Authors: Yoon Seungha , Jang Youngman , Kim Kab-Jin , Moon Kyoung-Woong , Kim Jaegwan , Nam Chunghee , Choe Sug-Bong , Cho B. K.
Published: March 2012

Giant magnetoresistance (GMR) signals and the magneto-optic Kerr effect (MOKE) are combined to investigate the asymmetric domain wall (DW) motion in a GMR spin-valve stripe consisting of a wire and a circular ring. In the propagation of a tail-to-tail DW, the left-hand side, top-half ring, bottom-half ring, and the right-hand side are reversed in sequence. However, in the propagation of a head-to-head DW, the left-hand side, bottom half-ring, right-hand side, and top-half ring are switched in sequence. In addition, the critical current density for DW depinning shows asymmetric behavior. For tail-to-tail DW depinning, the critical current density of negative current pulses are lower than that of current pulses in the positive direction, and vice versa for head-to-head DW depinning.
Switching behavior of lithographically fabricated nanomagnets for logic applications
Authors: Li Peng , Csaba Gyorgy , Sankar Vijay K. , Ju Xueming , Lugli Paolo , Hu X. Sharon , Niemier Michael , Porod Wolfgang , Bernstein Gary H.
Published: March 2012

The switching behavior and the magnetization states of non-interacting Supermalloy (Ni79Fe16Mo5) nanomagnet arrays were studied by magnetic measurements and micromagnetic simulations. The switching-field distribution of the easy-axis hysteresis loop of the nanomagnets was broadened due to lithographic shape variations and thermal fluctuations. When cooled to a low temperature (100 K), the switching-field distribution of the loop was reduced and its squareness ratio became higher. We found strong remanent magnetization along the hard axes of the nanomagnets, indicating the presence of metastable states and end-domain states. An oscillating field with amplitude of 30 Oe was sufficient to destabilize these metastable states; however, a high oscillating field (amplitude > 250 Oe) is required to reduce the remanence to zero.
Controlled synthesis of superparamagnetic iron-oxide nanoparticles by phase transformation
Authors: Laurenzi Mark A. , Carpenter Everett E.
Published: March 2012

A synthesis procedure for generating a uniform distribution of iron-oxide nanoparticles from an amorphous precursor is reported. The investigation suggests no evidence of the formation of unwanted surface oxide layers, internal stress, and multiple phases. This is likely because the physical properties of the diffusion fields surrounding the nanoparticles are self-limiting by Fe(II) depletion. Inside the diffusion field surrounding the nucleation site, decreasing Fe(II) concentration results in a decrease in the diffusion rate that continues to decrease until self-limiting kinetic arrest occurs. The initial Fe(II) concentration is established by reducing a system abundant in Fe(III) by means of exposure to CO/CO2 gas at high temperature.
Spin current injection by spin Seebeck and spin pumping effects in yttrium iron garnet/Pt structures
Authors: da Silva G. L. , Vilela-Leão L. H. , Rezende S. M. , Azevedo A.
Published: March 2012

It is reported an investigation of pure spin current injection in Pt strips deposited on yttrium iron garnet (YIG) films by means of the spin pumping (SPE) and spin Seebeck (SSE) effects. Both effects were characterized by measuring the DC voltage created along the Pt strips by means of the inverse spin Hall effect (VISHE). SPE and SSE are simultaneously activated by exciting the ferromagnetic resonance (FMR) of the YIG film at the same time that a temperature gradient is created along the sample length. While the FMR signal is little affected by the temperature gradient, the voltage measured at the Pt strip placed at the lower temperature end exhibits a very challenging behavior. The voltage excited by the FMR uniform mode increases by six times as the temperature difference (ΔT) between the two ends of the YIG slab changes from 0 to 12 K. In contrast the VISHE generated by other magnetostatic spin-wave modes decreases to zero as ΔT varies from 0 to 12 K.
Magnetic field effect on growth, arsenic uptake, and total amylolytic activity on mesquite (Prosopis juliflora x P. velutina) seeds
Authors: Flores-Tavizón Edith , Mokgalaka-Matlala Ntebogeng S. , Elizalde Galindo José T. , Castillo-Michelle Hiram , Peralta-Videa Jose R. , Gardea-Torresdey Jorge L.
Published: March 2012

Magnetic field is closely related to the cell metabolism of plants [N. A. Belyavskaya, Adv. Space Res. 34, 1566 (2004)]. In order to see the effect of magnetic field on the plant growth, arsenic uptake, and total amylolytic activity of mesquite (Prosopis juliflora x P. velutina) seeds, ten sets of 80 seeds were selected to be oriented with the long axis parallel or randomly oriented to an external magnetic field. The external magnetic field magnitude was 1 T, and the exposition time t = 30 min. Then, the seeds were stored for three days in a plastic bag and then sown on paper towels in a modified Hoagland’s nutrient solution. After three days of germination in the dark and three days in light, seedlings were grown hydroponically in modified Hoagland’s nutrient solution (high PO42−) containing 0, 10, or 20 ppm of arsenic as As (III) and (V). The results show that the germination ratios, growth, elongation, arsenic uptake, and total amylolytic activity of the long axis oriented mesquite seeds were much higher than those of the randomly oriented seeds. Also, these two sets of seeds showed higher properties than the ones that were not exposed to external magnetic field.
Magnetic and optical properties of monosized Eu-doped ZnO nanocrystals from nanoemulsion
Authors: Yoon Hayoung , Hua Wu Jun , Hyun Min Ji , Sung Lee Ji , Ju Jae-Seon , Keun Kim Young
Published: March 2012

We report the synthesis and characterization of monosized Eu-doped ZnO nanocrystals via a nanoemulsion process as a function of the doping ratio. The structure, optical, and magnetic properties of the nanocrystals are investigated by XRD, TEM, PL spectrometry, and physical property measurement system. The nanocrystals as prepared show high crystallinity and tight particle size distributions with the diameters of ∼ 10 nm. The doped samples clearly exhibit the 5D0→7FJ transition emission due to the presence of the Eu3+ ions. Meanwhile, the magnetic responses demonstrate the temperature dependence and change with dopant concentration.
DNA conformation in nanochannels: Monte Carlo simulation studies using a primitive DNA model
Authors: Chang Rakwoo , Jo Kyubong
Published: March 2012

We have performed canonical ensemble Monte Carlo simulations of a primitive DNA model to study the conformation of 2.56 ∼ 21.8 μm long DNA molecules confined in nanochannels at various ionic concentrations with the comparison of our previous experimental findings. In the model, the DNA molecule is represented as a chain of charged hard spheres connected by fixed bond length and the nanochannels as planar hard walls. System potentials consist of explicit electrostatic potential along with short-ranged hard-sphere and angle potentials. Our primitive model system provides valuable insight into the DNA conformation, which cannot be easily obtained from experiments or theories. First, the visualization and statistical analysis of DNA molecules in various channel dimensions and ionic strengths verified the formation of locally coiled structures such as backfolding or hairpin and their significance even in highly stretched states. Although the folding events mostly occur within the region of ∼0.5 μm from both chain ends, significant portion of the events still take place in the middle region. Second, our study also showed that two controlling factors such as channel dimension and ionic strength widely used in stretching DNA molecules have different influence on the local DNA structure. Ionic strength changes local correlation between neighboring monomers by controlling the strength of electrostatic interaction (and thus the persistence length of DNA), which leads to more coiled local conformation. On the other hand, channel dimension controls the overall stretch by applying the geometric constraint to the non-local DNA conformation instead of directly affecting local correlation. Third, the molecular weight dependence of DNA stretch was observed especially in low stretch regime, which is mainly due to the fact that low stretch modes observed in short DNA molecules are not readily accessible to much longer DNA molecules, resulting in the increase in the stretch of longer DNA molecules.
Instability of a transverse liquid rivulet on an inclined plane
Authors: Diez Javier A. , González Alejandro G. , Kondic Lou
Published: March 2012

This work concentrates on the stability of a viscous liquid rivulet positioned across an inclined plane under partial wetting conditions. The study is performed within the framework of lubrication approximation by employing a slip model. Both normal and parallel components of gravity are considered. We find the stability regions for given area of the cross section of the rivulet, A, plane inclination angle, α, and static contact angle, θ0, characterizing the wettability of the substrate. For α’s smaller than some critical angle, α*, a static solution exists. This solution is characterized by rear/front contact angles given by θ0 ± δ. The linear stability analysis of this solution is performed using an efficient pseudo-spectral Chebyshev method. We analyze the effects of A, θ0, and α on the predictions of the model, such as the dominant wavelength, the maximum growth rate, and the behavior of the most unstable perturbation mode. To verify them, we also carry out experiments with silicone oils spreading on a coated glass substrate for several different fluid volumes and inclination angles. We find very good agreement between the wavelength of maximum growth rate given by the theory and the average distance between the drops after rivulet breakup. An analysis of finite size effects shows that the inclusion of normal gravity effects leads to a better agreement between theoretical and experimental results.
Diffusion and viscosity of liquid tin: Green-Kubo relationship-based calculations from molecular dynamics simulations
Authors: Mouas Mohamed , Gasser Jean-Georges , Hellal Slimane , Grosdidier Benoît , Makradi Ahmed , Belouettar Salim
Published: March 2012

Molecular dynamics (MD) simulations of liquid tin between its melting point and 1600 °C have been performed in order to interpret and discuss the ionic structure. The interactions between ions are described by a new accurate pair potential built within the pseudopotential formalism and the linear response theory. The calculated structure factor that reflects the main information on the local atomic order in liquids is compared to diffraction measurements. Having some confidence in the ability of this pair potential to give a good representation of the atomic structure, we then focused our attention on the investigation of the atomic transport properties through the MD computations of the velocity autocorrelation function and stress autocorrelation function. Using the Green-Kubo formula (for the first time to our knowledge for liquid tin) we determine the macroscopic transport properties from the corresponding microscopic time autocorrelation functions. The selfdiffusion coefficient and the shear viscosity as functions of temperature are found to be in good agreement with the experimental data.
A perspective on paper-based microfluidics: Current status and future trends
Authors: Li Xu , Ballerini David R. , Shen Wei
Published: March 2012

“Paper-based microfluidics” or “lab on paper,” as a burgeoning research field with its beginning in 2007, provides a novel system for fluid handling and fluid analysis for a variety of applications including health diagnostics, environmental monitoring as well as food quality testing. The reasons why paper becomes an attractive substrate for making microfluidic systems include: (1) it is a ubiquitous and extremely cheap cellulosic material; (2) it is compatible with many chemical/biochemical/medical applications; and (3) it transports liquids using capillary forces without the assistance of external forces. By building microfluidic channels on paper, liquid flow is confined within the channels, and therefore, liquid flow can be guided in a controlled manner. A variety of 2D and even 3D microfluidic channels have been created on paper, which are able to transport liquids in the predesigned pathways on paper. At the current stage of its development, paper-based microfluidic system is claimed to be low-cost, easy-to-use, disposable, and equipment-free, and therefore, is a rising technology particularly relevant to improving the healthcare and disease screening in the developing world, especially for those areas with no- or low-infrastructure and limited trained medical and health professionals. The research in paper-based microfluidics is experiencing a period of explosion; most published works have focused on: (1) inventing low-cost and simple fabrication techniques for paper-based microfluidic devices; and (2) exploring new applications of paper-based microfluidics by incorporating efficient detection methods. This paper aims to review both the fabrication techniques and applications of paper-based microfluidics reported to date. This paper also attempts to convey to the readers, from the authors’ point of view the current limitations of paper-based microfluidics which require further research, and a few perspective directions this new analytical system may take in its development.
Kinetics of the sulfur oxidation on palladium: A combined in situ x-ray photoelectron spectroscopy and density-functional study
Authors: Gotterbarm Karin , Luckas Nicola , Höfert Oliver , Lorenz Michael P. A. , Streber Regine , Papp Christian , Viñes Francesc , Steinrück Hans-Peter , Görling Andreas
Published: March 2012

We studied the reaction kinetics of sulfur oxidation on the Pd(100) surface by in situ high resolution x-ray photoelectron spectroscopy and ab initio density functional calculations. Isothermal oxidation experiments were performed between 400 and 500 K for small amounts (∼0.02 ML) of preadsorbed sulfur, with oxygen in large excess. The main stable reaction intermediate found on the surface is SO4, with SO2 and SO3 being only present in minor amounts. Density-functional calculations depict a reaction energy profile, which explains the sequential formation of SO2, SO3, and eventually SO4, also highlighting that the in-plane formation of SO from S and O adatoms is the rate limiting step. From the experiments we determined the activation energy of the rate limiting step to be 85 ± 6 kJ mol−1 by Arrhenius analysis, matching the calculated endothermicity of the SO formation.
On the triplet ground state of tetrahedral X4 clusters (X = Li, Na, K, Cu)
Authors: Verdicchio Marco , Evangelisti Stefano , Leininger Thierry , Monari Antonio
Published: March 2012

The lowest electronic state of distorted tetrahedral X4 clusters (with X = Li, Na, K, Cu) is studied at coupled-cluster level using high-quality atomic basis sets. The ground state is found to have a triplet spin symmetry for this kind of geometry and for all the considered atomic species. The equilibrium geometries correspond to Jahn-Teller-distorted oblate tetrahedra having D2d symmetry, and tetrahedric structures are local minima on the potential-energy surfaces for the triplet states. Their energies lie between 0.2 eV (for the K4 cluster) and 0.9 eV (for Cu4) above the absolute minimum of the corresponding systems, which is a spin singlet having a rhombus geometry.
Open-system Kohn-Sham density functional theory
Authors: Zhou Yongxi , Ernzerhof Matthias
Published: March 2012

A simple model for electron transport through molecules is provided by the source-sink potential (SSP) method [F. Goyer, M. Ernzerhof, and M. Zhuang, J. Chem. Phys. 126, 144104 (2007)10.1063/1.2715932]. In SSP, the boundary conditions of having an incoming and outgoing electron current are enforced through complex potentials that are added to the Hamiltonian. Depending on the sign of the imaginary part of the potentials, current density is generated or absorbed. In this way, a finite system can be used to model infinite molecular electronic devices. The SSP has originally been developed for the Hückel method and subsequently it has been extended [F. Goyer and M. Ernzerhof, J. Chem. Phys. 134, 174101 (2011)10.1063/1.3581096] to the Hubbard model. Here we present a step towards its generalization for first-principles electronic structure theory methods. In particular, drawing on our earlier work, we discuss a new generalized density functional theory for complex non-Hermitian Hamiltonians. This theory enables us to combine SSP and Kohn-Sham theory to obtain a method for the description of open systems that exchange current density with their environment. Similarly, the Hartree-Fock method is extended to the realm of non-Hermitian, SSP containing Hamiltonians. As a proof of principle, we present the first applications of complex-density functional theory (CODFT) as well as non-Hermitian Hartree-Fock theory to electron transport through molecules.
Coarse-grain model of the benzene ring with para-substituents in the molecule
Authors: Neverov Vladimir S. , Komolkin Andrei V.
Published: March 2012

A new two-site coarse-grain model of the benzene ring with substituents in the para-position is proposed for use with multiscale simulations. The model uses a modified Lennard-Jones potential and introduces an additional shifting parameter to the description of the atom-atom interactions. Furthermore, the model separates sets of parameters of Van-der-Waals interactions into inter- and intramolecular. The shifting parameter is specified separately for each pair of atom types for both inter- and intramolecular interactions. The model itself consists of two superatoms. It allows for high speed calculations, “remembers” the benzene ring orientation in multiscale simulations, and can be used together with well-known sets of “united atoms” potentials. This model was tested on p-xylene, 1-ethyl-4-methylbenzene, and 1-methyl-4-propylbenzene. Structural properties for all three substances in the full-atomic model, the “united atoms” model, and the suggested coarse-grained model are discussed. The results demonstrate that the local structure derived from the coarse-grained model is very similar to that derived from the “united atoms” model.