bluuebunny/crossref_metadata_2025 huggingface dataset:
Nickel-based super-alloy Inconel 600 morphological modifications by high repetition rate femtosecond Ti:sapphire laser
Authors: Stasic J. , Gakovic B. , Krmpot A. , Pavlovic V. , Trtica M. , Jelenkovic B.
Published: December 2009

The interaction of Ti:sapphire laser, operating at high repetition rate of 75 MHz, with nickel-based super-alloy Inconel 600 was studied. The laser was emitting at 800 nm and ultrashort pulse duration was 160 fs. Nickel-based super-alloy surface modification was studied in a low laser energy/fluence regime of maximum 20 nJ–15 mJ/cm2, for short (10 s) and long irradiation times (range of minutes). Surface damage threshold of this material was estimated to be 1.46 nJ, i.e., 0.001 J/cm2 in air. The radiation absorbed from Ti:sapphire laser beam under these conditions generates at the surface a series of effects, such as direct material vaporization, plasma creation, formation of nano-structures and their larger aggregates, damage accumulation, etc. Laser induced surface morphological changes observed on Inconel 600 were: (1) intensive removal of surface material with crater like features; (2) material deposition at near and farther periphery and creation of nano-aggregates/nano-structures; (3) sporadic micro-cracking of the inner and outer damage area. Generally, features created on nickel-based super-alloy surface by high repetition rate femtosecond pulses are characterized by low inner/outer damage diameter of less than 11 µm/30 µm and relatively large depth on the order of 150 µm, in both low (10 s) and high (minutes) irradiation time regimes.
Recent research advances in Reinforcement Learning in Spoken Dialogue Systems
Authors: Frampton Matthew , Lemon Oliver
Published: December 2009

This paper will summarize and analyze the work of the different research groups who have recently made significant contributions in using Reinforcement Learning techniques to learn dialogue strategies for Spoken Dialogue Systems (SDSs). This use of stochastic planning and learning has become an important research area in the past 10 years, since it promises automatic data-driven optimization of the behavior of SDSs that were previously hand-coded by expert developers. We survey the most important developments in the field, compare and contrast the different approaches, and describe current open problems.
The Perils of Hybridity: Resisting the Postcolonial Perspective in A. B. Yehoshua's The Liberating Bride
Authors: Morahg Gilead
Published: December 2009

The Liberating Bride (2001) figures as the most discursive of A. B. Yehoshua's novels. It follows the comings and goings of Yochanan Rivlin, an aging Middle East scholar, as he tries to discover the untold cause of his son's failed marriage and struggles to breathe life into his own moribund study of the causes of internal violence in contemporary Algiers. The novel abounds in the minutiae of everyday life and the often inane nature of human conversation. Its progression is intermittently impeded by eruptions of social comedy and political parody. It dwells on the myriad routines of marital, familial, and social transactions and gives ample scope to arcane academic disputations. But this seemingly sprawling narrative surface generates a carefully crafted deep structure by means of which the novel conducts a wide-ranging exploration of personal and political conundrums. As in many of his previous novels, Yehoshua's practice of constructing analogies between family situations and national issues enables him to engage psychological motivations, moral considerations, and ideological determinants that affect both the private and the public spheres of life.
From Ashkenaz to Zionism: Putting Eastern European Jewish Life in (Alphabetical) Order
Authors: Veidlinger Jeffrey
Published: December 2009

The publication of the YIVO Encyclopedia of Jews in Eastern Europe is a monumental achievement. It is the type of text that can transform a discipline, providing easily accessible and reasonably accurate answers to common reference questions and summarizing the state of the field in an evenhanded and inclusive manner. As one of the nearly 450 contributors to the encyclopedia, I personally feel a great deal of pride in its outcome. The two-volume, 2,400-page encyclopedia includes more than 1,800 entries, almost 1,200 illustrations, 57 color plates, and 55 maps. Editor in chief Gershon David Hundert of McGill University has succeeded in producing, as YIVO claims, “the definitive reference work on all aspects of the history and culture of Jews in Eastern Europe from the beginnings of their settlement in the region to the present.”
עיונים היסטוריים בשאלת ההתמודדות ההלכתית של החכמים עם תרבות יוון ורומא בארץ-ישראל בימי המשנה והתלמוד
Authors: פרידהיים עמנואל
Published: December 2009

מטרת המחקר שלפנינו לבחון את התמודדותם של חכמי ארץ-ישראל עם תרבות הנכר, בעיקר התרבות היוונית-רומית, בימי המשנה והתלמוד מזווית הלכתית בראי המציאות ההיסטורית ששררה במאות הראשונות לסה"נ. התרבות היוונית והרומית הקיפה כידוע תחומים רבים ומגוונים כגון: השפה, הדת, הצבא, המשפט, האמנות הויזואלית וכיוצא באלה. רבות נכתב בספרות המחקר אודות המפגש שבין היהדות לבין התרבות ההיא לגווניה מן התקופה ההלניסטית ועד ימי ביזנטיון, כולל נקודות המגע בין עולמם של חכמים לבין היוונות במובנה הרחב. אולם, לאור היקפה של התופעה דומה שמלאכת המחקר טרם הושלמה. מאמרנו דן בהיבט ההלכתי-מעשי של תגובת החכמים מול התרבות היוונית-רומית שפגשה בהם בתחומי החיים השונים ומנסה לגלות דפוסי התמודדות עקביים שעל-פיהם הגיבו החכמים בימי המשנה והתלמוד לאור מציאות היסטורית וחברתית בלתי-יציבה ומשתנה, שבה שולבו גורמים מדיניים, חברתיים-כלכליים, דתיים ותרבותיים שעיצבו את אתגרי השעה. יוצע להלן כי איסורים והיתרים הלכתיים בעולמם של חז"ל, כלפי תופעות המפגישות בין תרבות הנכר לבין דת ישראל, מהווים שני צדדים בלתי-נפרדים של מציאות היסטורית מוגדרת, המאתגרת את אורח-החיים היהודי.
Extrinsic and intrinsic factors controlling axonal regeneration after spinal cord injury
Authors: Afshari Fardad T. , Kappagantula Sunil , Fawcett James W.
Published: December 2009

Spinal cord injury is one of the most devastating conditions that affects the central nervous system. It can lead to permanent disability and there are around two million people affected worldwide. After injury, accumulation of myelin debris and formation of an inhibitory glial scar at the site of injury leads to a physical and chemical barrier that blocks axonal growth and regeneration. The mammalian central nervous system thus has a limited intrinsic ability to repair itself after injury. To improve axonal outgrowth and promote functional recovery, it is essential to identify the various intrinsic and extrinsic factors controlling regeneration and navigation of axons within the inhibitory environment of the central nervous system. Recent advances in spinal cord research have opened new avenues for the exploration of potential targets for repairing the cord and improving functional recovery after trauma. Here, we discuss some of the important key molecules that could be harnessed for repairing spinal cord injury.
Volatile bubble growth in a decompressing magmatic system: A many‐bubble model
Authors: L'Heureux Ivan
Published: December 2009

Recently, a new model of volatile bubble growth in magma with coupling to the melt advection field was proposed. In that model, the competitive effects of the other (randomly located) bubbles on the growth dynamics were treated in a mean‐field sense. That model predicts the possibility of dynamical transitions to or from inflationary regimes, whereby the growth rate and the average bubble radius increase rapidly. We present here numerical results pertaining to a decompressing magma, in which the fluid pressure explicitly decreases at a constant rate, thus simulating the ascent of the magma from a state of low volatile supersaturation. It is seen that, as the supersaturation increases (due to decompression), the system may undergo a transition to an inflationary regime, leading to a sudden increase in vesicularity. The numerical results show that the system dynamics may exhibit an oscillatory behavior characterized by a decompression‐induced succession of transitions to and from inflationary regimes. The model also shows that a constant bubble growth rate solution exists for intermediate times. This feature is in agreement with some experimental observations reported in the literature.
Water on the Moon Confirmed
Authors: Showstack Randy
Published: December 2009

When NASA's Lunar Crater Observation and Sensing Satellite (LCROSS) and a companion rocket purposely slammed into a crater at the Moon's south pole on 9 October, some observers on Earth lamented as anticlimactic the raised plumes of material that were partially blocked by a crater ridge and were difficult to see with backyard telescopes. However, it turns out that the projectiles struck it big.

“Indeed, yes, we found water. We didn't find just a little bit; we found a significant amount,” said Anthony Colaprete, LCROSS principal investigator with the NASA Ames Research Center, Moffett Field, Calif. At a 13 November news briefing, Colaprete lifted a 2‐gallon plastic bucket and said preliminary results indicate that instruments detected about a dozen buckets' worth of water in parts of the two plumes, the first generated by the spent Centaur upper stage of the Atlas V launch vehicle at 1131 UTC and the second generated by LCROSS about 4 minutes later. NASA described the two plumes as a high‐angle plume of vapor and fine dust and a lower‐angle ejecta curtain of heavier material. LCROSS and the Centaur upper stage hit the permanently shadowed Cabeus crater.
Lies, Damned Lies, and Statistics (in Geology)
Authors: Vermeesch Pieter
Published: December 2009

According to Karl Popper's epistemology of critical rationalism, scientists should formulate falsifiable hypotheses rather than produce ad hoc answers to empirical observations. In other words, we should predict and test rather than merely explain [Popper, 1959]. Sometimes, statistical tests such as chisquare, t, or Kolmogorov‐Smirnov are used to make deductions more “objective.” Such tests are used in a wide range of geological subdisciplines [see Reimann and Filzmoser, 2000; Anderson and Johnson, 1999; Lørup et al., 1998; Sircombe and Hazelton, 2004].
AGU's Upcoming Election
Authors: Grove Timothy L.
Published: December 2009

The 2010–2012 election, which runs from 4 January 2010 to 3 February 2010, marks the first time members will be asked to elect the AGU Board of Directors, which includes the Union officers, as well as section officers of the new AGU Council. The addition of a Board of Directors is new in AGU governance. In light of this, it may be helpful for you to know a bit more about the responsibilities of the Board and the Council and the kind of characteristics we are seeking in the member volunteers who will represent you in these bodies.

The elected members of the Board of Directors are the president, president‐elect, general secretary (who also serves as treasurer), international secretary, and six members elected by the Union's membership. Up to two members may be nominated by the Union president and approved by the Board. The immediate past president, vice chair of the Council, the Development Board chair, and the executive director are ex officio, meaning they are members of the board by virtue of the positions they hold.
Nominees for AGU Section Officers, 2010–2012
Authors: Anonymous
Published: December 2009

The nominees listed below constitute the slate approved by the AGU Council for the election of officers for the next biennium. The election will run from 4 January 2010 through 3 February 2010.
Have Large Dams Altered Extreme Precipitation Patterns?
Authors: Hossain Faisal , Jeyachandran Indumathi , Pielke Roger
Published: December 2009

Dams and their impounded waters are among the most common civil infrastructures, with a long heritage of modern design and operations experience. In particular, large dams, defined by the International Commission on Large Dams (ICOLD) as having a height greater than 15 meters from the foundation and holding a reservoir volume of more than 3 million cubic meters, have the potential to vastly transform local climate, landscapes, regional economics, and urbanization patterns.

In the United States alone, about 75,000 dams are capable of storing a volume of water equaling almost 1 year's mean runoff of the nation [Graf, 1999]. The World Commission on Dams (WCD) reports that at least 45,000 large dams have been built worldwide since the 1930s. These sheer numbers raise the question of the extent to which large dams and their impounded waters alter patterns that would have been pervasive had the dams not been built.
Nonlinear Geophysics: Why We Need It
Authors: Lovejoy Shaun , Agterberg Fritz , Carsteanu Alin , Cheng Qiuming , Davidsen Joern , Gaonac'h Hélène , Gupta Vijay , L'Heureux Ivan , Liu William , Morris Stephen W. , Sharma Surjalal , Shcherbakov Robert , Tarquis Ana , Turcotte Donald , Uritsky Vladimir
Published: December 2009

Few geoscientists would deny that effects are often sensitively dependent on causes, or that their amplification is commonly so strong as to give rise to qualitatively new “emergent” properties, or that geostructures are typically embedded one within another in a hierarchy. Starting in the 1980s, a growing number felt the need to underline the absolute importance of such nonlinearity through workshops and conferences. Building on this, the European Geosciences Union (EGU) organized a nonlinear processes (NP) section in 1990; AGU established a nonlinear geophysics (NG) focus group in 1997; and both unions began collaborating on an academic journal, Nonlinear Processes in Geophysics, in 1994.
Three Cups of Tea: Building Collaborations to Assess Earthquake Hazard in Pakistan: Modern Methods in Seismic Hazard Assessment; Nagarkot, Nepal, 8–12 June 2009
Authors: Hough Susan E. , Yong Alan
Published: December 2009

The M7.6 Muzaffarabad, Pakistan, earthquake struck the Pakistani Kashmir on 8 October 2005, claiming more than 80,000 lives. The earthquake underscored two points about earthquake hazard in Pakistan: first, that it is high, and, second, that it is poorly understood. In Karachi, for example, hazard is generally considered to be low, yet this rapidly growing megacity is as close to a major strike‐slip fault system as Los Angeles is to the San Andreas fault.

The Pakistani engineering community has sought guidance from seismologists on improved characterization of seismic hazard. This requires both improved hazard assessment methodology and improved constraints on the critical inputs to seismic hazard maps, for example, assessment of fault slip rates and geological site characterization. These inputs are currently unavailable. Efforts to map seismicity and attenuation and to estimate fault slip rates have been hampered by political instability. Yet there is no shortage of intellectual energy—Pakistan boasts an eager community of trained earthquake professionals.
Mobility of icy sand packs, with application to Martian permafrost
Authors: Durham William B. , Pathare Asmin V. , Stern Laura A. , Lenferink Hendrik J.
Published: December 2009

The physical state of water on Mars has fundamental ramifications for both climatology and astrobiology. The widespread presence of “softened” Martian landforms (such as impact craters) can be attributed to viscous creep of subsurface ground ice. We present laboratory experiments designed to determine the minimum amount of ice necessary to mobilize topography within Martian permafrost. Our results show that the jammed‐to‐mobile transition of icy sand packs neither occurs at fixed ice content nor is dependent on temperature or stress, but instead correlates strongly with the maximum dry packing density of the sand component. Viscosity also changes rapidly near the mobility transition. The results suggest a potentially lower minimum volatile inventory for the impact‐pulverized megaregolith of Mars. Furthermore, the long‐term preservation of partially relaxed craters implies that the ice content of Martian permafrost has remained close to that at the mobility transition throughout Martian history.
Simulated response of North Pacific Mode Waters to global warming
Authors: Luo Yiyong , Liu Qinyu , Rothstein Lewis M.
Published: December 2009

This study investigates the response of the Mode Waters in the North Pacific to global warming based on a set of Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4) models. Solutions between a present‐day climate and a future, warmer climate are compared. Under the warmer climate scenario, the Mode Waters are produced on lighter isopycnal surfaces and are significantly weakened in terms of their formation and evolution. These changes are due to a more stratified upper ocean and thus a shoaling of the winter mixing depth resulting mainly from a reduction of the ocean‐to‐atmosphere heat loss over the subtropical region. The basin‐wide wind stress may adjust the Mode Waters indirectly through its impact on the surface heat flux and subduction process.
Weekly cycle of lightning: Evidence of storm invigoration by pollution
Authors: Bell Thomas L. , Rosenfeld Daniel , Kim Kyu‐Myong
Published: December 2009

We have examined summertime 1998–2009 U.S. lightning data from the National Lightning Detection Network (NLDN) to look for weekly cycles in lightning activity. As was found by Bell et al. (2008) for rain over the southeast U.S., there is a significant weekly cycle in afternoon lightning activity that peaks in the middle of the week there. The weekly cycle appears to be reduced over population centers. Lightning activity peaks on weekends over waters near the SE U.S. The statistical significance of weekly cycles over the western half of the country is generally small. We found no evidence of a weekly cycle of synoptic‐scale forcing that might explain these patterns. The lightning behavior is entirely consistent with the explanation suggested by Bell et al. (2008) for the cycles in rainfall and other atmospheric data from the SE U.S., that aerosols can cause storms to intensify in humid, convectively unstable environments.
Delayed Sahel rainfall and global seasonal cycle in a warmer climate
Authors: Biasutti Michela , Sobel Adam H.
Published: December 2009

Twenty‐first century projections of global rainfall and sea surface temperature in the current generation of climate models indicate a delay in the seasonal cycle in response to increasing greenhouse gases, with important implications for the regional monsoons. In particular, the rainy season of the semi‐arid African Sahel is projected to start later and become shorter. The robust agreement across models on the seasonal distribution of Sahel rainfall changes stands in contrast with large uncertainty for summertime rainfall totals there.
A study of the Weddell Sea Anomaly observed by FORMOSAT‐3/COSMIC
Authors: He Maosheng , Liu Libo , Wan Weixing , Ning Baiqi , Zhao Biqiang , Wen Jin , Yue Xin'an , Le Huijun
Published: December 2009

More than two years of COSMIC electron density profiles at low solar activities are collected to study the evolution of the Weddell Sea Anomaly (WSA), which appears as an evening enhancement in electron density during local summer. Observations show that the change in NmF2 (the F2 peak electron density) is associated with the change in hmF2 (the F2 peak height), while the latter is correlated closely with the components of the geomagnetic field. We find that (1) in the afternoon, hmF2 is more liable to rise drastically in regions with a larger ∣sin(2I)∣ value, which would occur early at certain declinations, eastward in the southern hemisphere and westward in the northern hemisphere; (2) subsequently, a larger increment of hmF2 is coincidentally followed by a stronger enhancement of NmF2 and the enhancement ends just around the local sunset; and (3) in midlatitudes, the evolution pattern of hmF2 in the evening of equinoxes and winter is similar to that in summer, albeit without a lasting NmF2 enhancement as that in summer. These features suggest that the NmF2 enhancement and the hmF2 increase could arise from the thermospheric wind effect, and solar photoionization plays a crucial role in the enhancement as well. The general midlatitude F2 layer enhancement in local summer evening is consistent with the WSA on the above features, indicating that the WSA is a manifestation, with a particular geometry of the magnetic field, of the evening enhancement induced by the winds.
Temporal variations of elemental carbon in Beijing
Authors: Han S. , Kondo Y. , Oshima N. , Takegawa N. , Miyazaki Y. , Hu M. , Lin P. , Deng Z. , Zhao Y. , Sugimoto N. , Wu Y.
Published: December 2009

Concentrations of elemental carbon (EC), carbon monoxide (CO), and carbon dioxide (CO2) were measured in Beijing between 2005 and 2006. EC was measured every hour with a semicontinuous thermal optical analyzer. The observed concentrations were rather uniform over a distance of about 50 km from the observation site. The annual average concentrations of EC and CO were 6.9 μgC m−3 and 1120 parts per billion by volume, respectively. The concentrations of these species increased with decreasing near‐surface wind speed (WS). The slopes of the CO‐CO2, EC‐CO2, and EC‐CO correlations are used to estimate major EC and CO sources. In the weak wind regime (WS ≤ 2.0 m s−1), the median EC, ΔEC/ΔCO2, and ΔEC/ΔCO (except for winter) increased in the late evening and remained high until early morning. The traffic of heavy duty diesel trucks during nighttime was about 20 times higher than that during daytime. These results indicate a dominant contribution of exhaust from diesel vehicles to the nighttime EC. In winter, the nighttime CO and ΔCO/ΔCO2 ratio were largely higher than those in the other seasons. The most likely cause is the increase in the CO emissions from the exhaust of gasoline vehicles at low temperature. The ΔEC/ΔCO2 ratio in winter was lower than that in fall, indicating no significant additional EC emissions. The diurnal variations of EC, CO, CO2, and ΔEC/ΔCO were similar between weekdays and weekends. The slopes of the CO‐CO2‐EC correlations are compared with the CO‐CO2‐EC ratios derived from a published emission inventory in the Beijing area.
Climate‐vegetation‐fire interactions and their impact on long‐term carbon dynamics in a boreal peatland landscape in northern Manitoba, Canada
Authors: Camill Philip , Barry Ann , Williams Evie , Andreassi Christian , Limmer Jacob , Solick Donald
Published: December 2009

Climate warming may increase the size and frequency of fires in the boreal biome, possibly causing greater carbon release that amplifies warming. However, in peatlands, vegetation change may also control long‐term fire and carbon accumulation, confounding simple relationships between climate, fire, and carbon accumulation. Using 17 peat cores dating to 8000 cal years B.P. from northern Manitoba, Canada, we addressed the following questions: (1) Do past climate changes correlate with shifts in peatland vegetation? (2) What is the relationship between peatland vegetation and fire severity? (3) What is the mean return interval for boreal peat fires, and how does it change across fires of different severities? (4) How does fire severity affect carbon accumulation rates? (5) Do fire and long‐term carbon accumulation change directly in response to climate or indirectly though climate‐driven changes in vegetation? We measured carbon accumulation rates, fire severity, and return intervals using macroscopic charcoal and changes in vegetation using macrofossils. Climate and vegetation changes covaried, with shifts from wetter fen to drier, forested bog communities during the Holocene Thermal Maximum (HTM). Fires became more severe following the shift to forested bogs, with fire severity peaking after 4000 cal years B.P. rather than during the HTM. Rising fire severity, in turn, was correlated with a significant decrease in carbon accumulation from ∼6000 to 2000 cal years B.P. The Medieval Warm Period and Little Ice Age affected vegetation composition and permafrost, further impacting fire and carbon accumulation. Our results indicate that long‐term changes in fire and carbon dynamics are mediated by climate‐driven changes in vegetation.
Electron spectroscopy study of the initial stages of iron phthalocyanine growth on highly oriented pyrolitic graphite
Authors: Isvoranu Cristina , Åhlund John , Wang Bin , Ataman Evren , Mårtensson Nils , Puglia Carla , Andersen Jesper N. , Bocquet Marie-Laure , Schnadt Joachim
Published: December 2009

The nature of the intermolecular and substrate bonds of iron phthalocyanine adsorbed on highly oriented pyrolitic graphite has been investigated by x-ray photoelectron spectroscopy and x-ray absorption spectroscopy. We find that the molecules grow in a highly ordered fashion with the molecules essentially plane-parallel to the surface in both the mono- and multilayers. The spectra obtained on both types of film are virtually identical, which shows that the bonds both between the adsorbate and substrate and between the molecular layers have a pure van der Waals nature. Supporting density functional theory results indicate that the layers are stabilized by weak hydrogen bonds within the molecular layers.
Cavity-controlled radiative recombination of excitons in thin-film solar cells
Authors: Vuong Luat T. , Kozyreff Gregory , Betancur Rafael , Martorell Jordi
Published: December 2009

We study the performance of photovoltaic devices when controlling the exciton radiative recombination time. We demonstrate that when high-quantum-yield fluorescent photovoltaic materials are placed within an optical cavity, the spontaneous emission of the radiative exciton is partially inhibited. The corresponding increase of the exciton lifetime results in an increase of the effective diffusion length and diffusion current. This performance maximizes when the thickness of the cell is comparable to the absorption length. We show that when typical parameter values of thin solar-cell devices are used, the efficiency may improve by as much as three times.
Enhanced performance of organic light-emitting diodes using two-dimensional zinc sulfide photonic crystals
Authors: Kim C. S. , Kim M. , Larrabee D. C. , Vurgaftman I. , Meyer J. R. , Lee S. H. , Kafafi Z. H.
Published: December 2009

The light extraction efficiency of an organic light-emitting diode (OLED) was significantly enhanced upon incorporating a photonic-crystal (PC) pattern consisting of ZnS pillars residing on top of the transparent anode-glass substrate. The luminance efficiency of the PC-OLED is enhanced by a factor of 2.1 to 2.4 depending on the periodicity of the PC structure, when compared to that of a control OLED operating under the same conditions.
Analysis of thermoreflectance signals and characterization of thermal conductivity of metal thin films
Authors: Miyake Syugo , Kita Takashi , Miyake Aya , Ikeda Ken-ichi , Takamatsu Hiroyuki
Published: December 2009

The temperature response of the thermal conductivity (λ) of metal thin films has been investigated by the thermoreflectance (TR) method. The phase lag of the TR signals depends on the thermal diffusivity when the heating area is small, while on the thermal effusivity when the heating area is large. This enables us to evaluate λ by analyzing the three-dimensional thermal propagation in the film on the substrate. We show that by analyzing the TR signals, λ of Cu–Pt alloy thin films formed on glass substrates can be estimated. The estimated λ drastically decreases with an increase in the Pt concentration. Furthermore, we discuss these results by considering the crystallographic properties of the abovementioned thin films investigated by transmission electron microscopy and x-ray diffraction.
Diffusion barrier properties of amorphous and nanocrystalline Ta films for Cu interconnects
Authors: Cao Z. H. , Hu K. , Meng X. K.
Published: December 2009

In the present paper, the diffusion barrier properties of amorphous and nanocrystalline (NC) Ta films, and the interface microstructure of Ta/Cu were investigated as a function of annealing temperature. X-ray diffraction, scanning electron microscopy, cross-sectional transmission electron microscopy, and energy-dispersive spectrometer line scans were employed to study the microstructure evolution and diffusion behavior. It was found that an amorphous layer with a thickness of ∼5 nm formed at the interface of NC Ta/Cu at 450 °C annealing, while the interface of amorphous-Ta/Cu was still abrupt. Moreover, amorphous-Ta film acts as an effective diffusion barrier up to temperatures of 650 °C, which is higher than that for NC-Ta film. The fast diffusion along grain boundaries inside NC-Ta films is suggested to be responsible for the main failure of NC-Ta film.
Influence of superimposed ultrasound on deformability of Cu
Authors: Huang H. , Pequegnat A. , Chang B. H. , Mayer M. , Du D. , Zhou Y.
Published: December 2009

The effects of superimposed ultrasonic vibration on the plastic deformation of 99.99% pure polycrystalline Cu are studied both during (temporary) and after (residual) the application of ultrasound (US) using deformability measurements acquired from an automated wire bonding machine and microhardness testing. It is found that if ultrasonic irradiation is applied during the deformation of the 100 μm diameter Cu free air balls (FABs) the Cu becomes softer with increasing US power compared to Cu FABs that are deformed without US. When comparing this temporary acoustic softening of Cu to that of Au, it is found that the amount of softening is similar between the two materials. After the US is turned off, a residual acoustic softening remains. This residual softening effect increases with increasing the US power. With residual acoustic softening, a maximum increase of 13% in deformability is measured for Cu during wire bonding compared to a maximum increase of 8% for Au during wire bonding. Stronger residual acoustic softening effects are obtained in Cu than in Au with a maximum decrease in microhardness of 19% and 9%, respectively. Dynamic annealing and dislocation theory are used to explain both the temporary and residual effects of US on the deformation of Cu and Au.
High-throughput fabrication of nanoantennae over large areas for biosensing and nanospectroscopy
Authors: Kiristopuryan Arda , Ekinci Yasin , Giannini Reto , Sahoo Pratap K. , Gorodyska Ganna , Löffler Jörg F.
Published: December 2009

We report on a simple and high-throughput method for the fabrication of gold and silver nanoparticle dimers with extremely small gaps and extending over large areas, using colloidal lithography and shadow thermal-evaporation techniques. The plasmon resonances of the individual dimers with various structural parameters were studied, as well as their coupling phenomena in the nearly touching regime. The method presented enables fabrication of efficient and low-cost plasmonics structures for applications such as surface-enhanced Raman scattering, plasmon-enhanced fluorescence, and biosensing.
Elastomeric microfluidic diode and rectifier work with Newtonian fluids
Authors: Liu John , Chen Yan , Taylor Clive R. , Scherer Axel , Kartalov Emil P.
Published: December 2009

We report on two microfluidic elastomeric autoregulatory devices—a diode and a rectifier. They exhibit physically interesting and complex nonlinear behaviors (saturation, bias-dependent resistance, and rectification) with a Newtonian fluid. Due to their autoregulatory properties, they operate without active external control. As a result, they enable increased microfluidic device density and overall system miniaturization. The demonstrated diode and rectifier would also be useful components in future microfluidic logic circuitry.
A low field technique for measuring magnetic and magnetoresistance anisotropy coefficients applied to (Ga,Mn)As
Authors: Haigh J. A. , Rushforth A. W. , King C. S. , Edmonds K. W. , Campion R. P. , Foxon C. T. , Gallagher B. L.
Published: December 2009

We demonstrate a simple, low cost, magnetotransport method for rapidly characterizing the magnetic anisotropy and anisotropic magnetoresistance of ferromagnetic devices with uniaxial magnetic anisotropy. This transport technique is the analog of magnetic susceptibility measurements of bulk material but is applicable to very small samples with low total moment. The technique is used to characterize devices fabricated from the dilute magnetic semiconductor (Ga,Mn)As. The technique allows us to probe the behavior of the parameters close to the Curie temperature, in the limit of the applied magnetic field tending to zero. This avoids the complications arising from the presence of paramagnetism.
Photonic crystal based back reflectors for light management and enhanced absorption in amorphous silicon solar cells
Authors: Curtin Benjamin , Biswas Rana , Dalal Vikram
Published: December 2009

Photonic crystal back-reflectors offer enhanced optical absorption in thin-film solar cells, without undesirable losses. We fabricated metallic photonic crystal back-reflectors using photolithography and reactive-ion etching and deposited a-Si:H solar cells. The photonic crystal has triangular lattice symmetry, a pitch of 760 nm, and was designed with rigorous simulations. Scanning electron microscopy demonstrates excellent long range periodicity and conformal a-Si:H growth. The average light absorption increases by 7%, relative to a flat reference device, with an enhancement factor approaching 6 at near-infrared wavelengths. The photonic crystal back reflector strongly diffracts light and increases optical path lengths of solar photons.
Improving microstructural quality of semipolar (112̱2) GaN on m-plane sapphire by a two-step growth process
Authors: Sun Qian , Leung Benjamin , Yerino Christopher D. , Zhang Yu , Han Jung
Published: December 2009

This letter reports a two-step growth process for improving microstructural quality of semipolar (112̱2) GaN on nitridized m-plane sapphire. The two-step growth of (112̱2) GaN, islanding growth under high pressure followed by islands coalescence under low pressure, went through a roughening-recovery process, which was found very effective in reducing the density of stacking faults and dislocations in (112̱2) GaN. The x-ray rocking curves of both on-axis and off-axis planes were narrowed down by more than 50%. The improvement of GaN quality was confirmed by a boost in blue and green optical output of semipolar (112̱2) InGaN/GaN quantum wells.
Optimal electrode shape and size for shear mode thin film acoustic wave resonators
Authors: Xu L. M. , Tang B. B. , Hu Y. T. , Fan H. , Yang J. S.
Published: December 2009

We study electrode shape and size for plates of hexagonal crystals or polarized ceramics with the sixfold axis or the poling direction parallel to the plate surfaces so that they can be excited into thickness-shear vibration by an electric field in the plate thickness direction. Electrode size and shape optimal in the sense that they satisfy the criterion of Bechmann’s number in every direction are determined.
Tailoring the magnetic anisotropy in CoRh nanoalloys
Authors: Muñoz-Navia M. , Dorantes-Dávila J. , Zitoun D. , Amiens C. , Jaouen N. , Rogalev A. , Respaud M. , Pastor G. M.
Published: December 2009

CoRh alloy nanoparticles (NPs) show nontrivial correlations between chemical and magnetic order that lead to a remarkable nonmonotonous dependence of the magnetic anisotropy energy as a function of composition. Combining experiment and theory we demonstrate how the induced 4d moments and the 3d−4d interfaces control the magnetoanisotropic behavior. New possibilities of tailoring the magnetic characteristics of NPs are thus opened.
The BlueSky smoke modeling framework
Authors: Larkin Narasimhan K. , O'Neill Susan M. , Solomon Robert , Raffuse Sean , Strand Tara , Sullivan Dana C. , Krull Candace , Rorig Miriam , Peterson Janice , Ferguson Sue A.
Published: December 2009

Smoke from fire is a local, regional and often international issue that is growing in complexity as competition for airshed resources increases. BlueSky is a smoke modeling framework designed to help address this problem by enabling simulations of the cumulative smoke impacts from fires (prescribed, wildland, and agricultural) across a region. Versions of BlueSky have been implemented in prediction systems across the contiguous US, and land managers, air-quality regulators, incident command teams, and the general public can currently obtain BlueSky-based predictions of smoke impacts for their region. A highly modular framework, BlueSky links together a variety of state-of-the-art models of meteorology, fuels, consumption, emissions, and air quality, and offers multiple model choices at each modeling step. This modularity also allows direct comparison between similar component models. This paper presents the overall model framework Version 2.5 – the component models, how they are linked together, and the results from case studies of two wildfires. Predicted results are affected by the specific choice of modeling pathway. With the pathway chosen, the modeled output generally compares well with plume shape and extent as observed by satellites, but underpredicts surface concentrations as observed by ground monitors. Sensitivity studies show that knowledge of fire behavior can greatly improve the accuracy of these smoke impact calculations.
Do bare-nosed wombat (Vombatus ursinus) mounds influence terrestrial macroinvertebrate assemblages in agricultural riparian zones?
Authors: Borchard Philip , Wright Ian A. , McArthur Clare
Published: December 2009

Riparian ecosystems contain a complex mosaic of habitat structure types that can support distinct macroinvertebrate communities. Bare-nosed wombats (Vombatus ursinus) are often an integral component of agricultural riparian systems in south-eastern Australia. In these systems, wombats construct large burrow systems and mounds in the stream banks. Wombat mound structures vary markedly from the surrounding landscape and they may influence macroinvertebrate assemblages. We examined this ecosystem-engineering role of wombats as well as the ecological variability within our agricultural riparian study sites on the possible influence on macroinvertebrate assemblages. There were no detectable effects of wombat mounds on the richness or abundance of macroinvertebrates on the soil surface. At the site level, however, macroinvertebrate assemblages were most influenced by litter depth, upper canopy cover, cattle hoof prints and slope. The ecological variables within the study sites strongly affected macroinvertebrate assemblages. These findings reflect an influence of anthropogenic impact on communities of ground-dwelling invertebrates that have been found in other studies. It is possible that a finer resolution of taxa may highlight a unique pattern of macroinvertebrate use of wombat mounds.
Mitosomes in
Entamoeba histolytica
contain a sulfate activation pathway
Authors: Mi-ichi Fumika , Yousuf Mohammad Abu , Nakada-Tsukui Kumiko , Nozaki Tomoyoshi
Published: December 2009

Hydrogenosomes and mitosomes are mitochondrion-related organelles in anaerobic/microaerophilic eukaryotes with highly reduced and divergent functions. The full diversity of their content and function, however, has not been fully determined. To understand the central role of mitosomes in
Entamoeba histolytica
, a parasitic protozoon that causes amoebic dysentery and liver abscesses, we examined the proteomic profile of purified mitosomes. Using 2 discontinuous Percoll gradient centrifugation and MS analysis, we identified 95 putative mitosomal proteins. Immunofluorescence assay showed that 3 proteins involved in sulfate activation, ATP sulfurylase, APS kinase, and inorganic pyrophosphatase, as well as sodium/sulfate symporter, involved in sulfate uptake, were compartmentalized to mitosomes. We have also provided biochemical evidence that activated sulfate derivatives, adenosine-5′-phosphosulfate and 3′-phosphoadenosine-5′-phosphosulfate, were produced in mitosomes. Phylogenetic analysis showed that the aforementioned proteins and chaperones have distinct origins, suggesting the mosaic character of mitosomes in
E. histolytica
consisting of proteins derived from α-proteobacterial, δ-proteobacterial, and ancestral eukaryotic origins. These results suggest that sulfate activation is the major function of mitosomes in
E. histolytica
and that
E. histolytica
mitosomes represent a unique mitochondrion-related organelle with remarkable diversity.
Target identification using drug affinity responsive target stability (DARTS)
Authors: Lomenick Brett , Hao Rui , Jonai Nao , Chin Randall M. , Aghajan Mariam , Warburton Sarah , Wang Jianing , Wu Raymond P. , Gomez Fernando , Loo Joseph A. , Wohlschlegel James A. , Vondriska Thomas M. , Pelletier Jerry , Herschman Harvey R. , Clardy Jon , Clarke Catherine F. , Huang Jing
Published: December 2009

Identifying the molecular targets for the beneficial or detrimental effects of small-molecule drugs is an important and currently unmet challenge. We have developed a method, drug affinity responsive target stability (DARTS), which takes advantage of a reduction in the protease susceptibility of the target protein upon drug binding. DARTS is universally applicable because it requires no modification of the drug and is independent of the mechanism of drug action. We demonstrate use of DARTS to identify known small-molecule–protein interactions and to reveal the eukaryotic translation initiation machinery as a molecular target for the longevity-enhancing plant natural product resveratrol. We envisage that DARTS will also be useful in global mapping of protein–metabolite interaction networks and in label-free screening of unlimited varieties of compounds for development as molecular imaging agents.
The glucose-responsive transcription factor ChREBP contributes to glucose-dependent anabolic synthesis and cell proliferation
Authors: Tong Xuemei , Zhao Fangping , Mancuso Anthony , Gruber Joshua J. , Thompson Craig B.
Published: December 2009

Tumor cells are metabolically reprogrammed to fuel cell proliferation. Most transformed cells take up high levels of glucose and produce ATP through aerobic glycolysis. In cells exhibiting aerobic glycolysis, a significant fraction of glucose carbon is also directed into de novo lipogenesis and nucleotide biosynthesis. The glucose-responsive transcription factor carbohydrate responsive element binding protein (ChREBP) was previously shown to be important for redirecting glucose metabolism in support of lipogenesis in nonproliferating hepatocytes. However, whether it plays a more generalized role in reprogramming metabolism during cell proliferation has not been examined. Here, we demonstrated that the expression of ChREBP can be induced in response to mitogenic stimulation and that the induction of ChREBP is required for efficient cell proliferation. Suppression of ChREBP resulted in diminished aerobic glycolysis, de novo lipogenesis, and nucleotide biosynthesis, but stimulated mitochondrial respiration, suggesting a metabolic switch from aerobic glycolysis to oxidative phosphorylation. Cells in which ChREBP was suppressed by RNAi exhibited p53 activation and cell cycle arrest. In vivo, suppression of ChREBP led to a p53-dependent reduction in tumor growth. These results demonstrate that ChREBP plays a key role both in redirecting glucose metabolism to anabolic pathways and suppressing p53 activity.
Deciding fate in adverse times: Sporulation and competence in
Bacillus subtilis
Authors: Schultz Daniel , Wolynes Peter G. , Jacob Eshel Ben , Onuchic José N.
Published: December 2009

Bacteria serve as the central arena for understanding how gene networks and proteins process information and control cellular behaviors. Recently, much effort has been devoted to the investigation of specific bacteria gene circuits as functioning modules. The next challenge is the integrative modeling of complex cellular networks composed of many such modules. A tractable integrative model of the sophisticated decision-making signal transduction system that determines the fate between sporulation and competence is presented. This model provides an understanding of how information is sensed and processed to reach an “informative” decision in the context of cell state and signals from other cells. The competence module (ComK dynamics) is modeled as a stochastic switch whose transition rate is controlled by a quorum-sensing unit. The sporulation module (Spo0A dynamics) is modeled as a timer whose clock rate is adjusted by a stress-sensing unit. The interplay between these modules is mediated via the Rap assessment system, which gates the sensing units, and the AbrB–Rok decision module, which creates an opportunity for competence within a specific window of the sporulation timer. The timer is regulated via a special repressilator-like inhibition of Spo0A* by Spo0E, which is itself inhibited by AbrB. For some stress and input signals, this repressilator can generate a frustration state with large variations (fluctuations or oscillations) in Spo0A* and AbrB concentrations, which might serve an important role in generating cell variability. This integrative framework is a starting point that can be extended to include transition into cannibalism and the role of colony organization.
Unbiased probing of the entire hepatitis C virus life cycle identifies clinical compounds that target multiple aspects of the infection
Authors: Gastaminza Pablo , Whitten-Bauer Christina , Chisari Francis V.
Published: December 2009

Over 170 million people are chronically infected by the hepatitis C virus (HCV) and at risk for dying from liver cirrhosis and hepatocellular carcinoma. Current therapy is expensive, associated with significant side effects, and often ineffective. Discovery of antiviral compounds against HCV traditionally involves a priori target identification followed by biochemical screening and confirmation in cell-based replicon assays. Typically, this results in the discovery of compounds that address a few predetermined targets and are prone to select for escape variants. To attempt to identify antiviral compounds with broad target specificity, we developed an unbiased cell-based screening system involving multiple rounds of infection in a 96-well format. Analysis of a publicly available library of 446 clinically approved drugs identified 33 compounds that targeted both known and previously unexplored aspects of HCV infection, including entry, replication, and assembly. Discovery of novel viral and cellular targets in this manner will broaden the therapeutic armamentarium against this virus, allowing for the development of drug mixtures that should reduce the likelihood of mutational escape.