bluuebunny/crossref_metadata_2025 huggingface dataset:
When are multiobjective calibration trade‐offs in hydrologic models meaningful?
Authors: Kollat J. B. , Reed P. M. , Wagener T.
Published: February 2012

This paper applies a four‐objective calibration strategy focusing on peak flows, low flows, water balance, and flashiness to 392 model parameter estimation experiment (MOPEX) watersheds across the United States. Our analysis explores the influence of model structure by analyzing how the multiobjective calibration trade‐offs for two conceptual hydrologic models, the Hydrology Model (HYMOD) and the Hydrologiska Byråns Vattenbalansavdelning (HBV) model, compare for each of the 392 catchments. Our results demonstrate that for modern multiobjective calibration frameworks to identify any meaningful measure of model structural failure, users must be able to carefully control the precision by which they evaluate their trade‐offs. Our study demonstrates that the concept of epsilon‐dominance provides an effective means of attaining bounded and meaningful hydrologic model calibration trade‐offs. When analyzed at an appropriate precision, we found that meaningful multiobjective trade‐offs are far less frequent than prior literature has suggested. However, when trade‐offs do exist at a meaningful precision, they have significant value for supporting hydrologic model selection, distinguishing core model deficiencies, and identifying hydroclimatic regions where hydrologic model prediction is highly challenging.
China cuts energy intensity, but overall energy growth continues, report notes
Authors: Showstack Randy
Published: February 2012

A new report states that China has cut its energy intensity—defined as energy use per unit of economic output—by 19.1% from 2006 to 2010, reversing the previous upward trend. However, energy use and carbon emissions in the country continue to grow sharply, according to the Climate Policy Initiative's (CPI)Annual Review of Low‐Carbon Development in China: 2010, the second of such reports. China nearly hit its goal of a 20% target reduction in energy intensity during that time period, which spanned the country's eleventh Five‐Year Period (FYP) for social and economic development, but during that same period energy‐related growth in carbon dioxide (CO2) emissions in China increased by 33.6%, from 5.15 billion tons to 6.88 billion tons, said Qi Ye, CPI's Beijing office director, at a 2 February briefing held at the Brookings Institution in Washington, D. C.
U.N. report on sustainable development goals
Authors: Showstack Randy
Published: February 2012

A new United Nations report on sustainable development includes broad recommendations to protect water and other resources, preserve ecosystems, ensure universal access to sustainable energy, increase resources for adaptation and disaster risk reduction, scale up efforts to achieve the Millennium Development Goals for cutting poverty and reducing inequalities, establish price signals that value sustainability, and strengthen the interface between policy and science. The 30 January report, “Resilient people, resilient planet: A future worth choosing,” states, “Today our planet and our world are experiencing the best of times, and the worst of times. The world is experiencing unprecedented prosperity, while the planet is under unprecedented stress.” The report goes on to say that the current global development model is “unsustainable” and that by 2030 the world will need at least 50% more food, 45% more energy, and 30% more water.
Ian S. E. Carmichael (1930–2011)
Authors: Lange Rebecca
Published: February 2012

Ian S. E. Carmichael, who had a highly imaginative research career and was legendary for his successful mentoring of graduate students, died in Berkeley, Calif., on 26 August 2011. Ian applied thermodynamic theory, experiment, and the ground truth of fieldwork to the study of magmatic rocks. Throughout the arc of his career, he played a critical role in transforming igneous petrology from a discipline that was largely descriptive to one that is rigorously quantitative. Ian was born in London on 29 March 1930 and was educated at Westminster School. He spent 2 years in the British Army (as a parachutist and a second lieutenant in the Corps of Royal Engineers), where he saw service in Egypt, Palestine, and Sudan. He obtained his B.A. and M.A. in geology at Cambridge University in 1954 and then traveled to Canada, where he prospected for copper and wintered in the Arctic. Ian returned to England and obtained his Ph.D. in 1958 at Imperial College London. His thesis, on Thingmuli volcano in eastern Iceland, addressed one of the most contentious issues in Earth science at the time (before the days of isotope geochemistry and plate tectonics), namely, the origin of silicic magma from basalt in the absence of preexisting continental crust. The problem went to the heart of crustal evolution.
Honors
Authors: Anonymous
Published: February 2012

James Yoder, vice president for academic programs and dean at the Woods Hole Oceanographic Institution, Woods Hole, Mass., has been selected as a fellow of the Oceanography Society (TOS) “for his innovative and visionary application of satellite ocean color technologies to interdisciplinary oceanography and his extraordinary service to oceanography.” TOS also has three new councilors. Blanche Meeson of NASA Goddard Space Flight Center, Greenbelt, Md., is TOS's education councilor; Janet Sprintall, Scripps Institution of Oceanography, La Jolla, Calif., is TOS's councilor for physical biology; and Deborah Steinberg, Virginia Institute of Marine Sciences, Gloucester Point, is biological oceanography councilor.
Environment Canada cuts threaten the future of science and international agreements
Authors: Thompson Anne M. , Salawitch Ross J. , Hoff Raymond M. , Logan Jennifer A. , Einaudi Franco
Published: February 2012

In August 2011, 300 Environment Canada scientists and staff working on environmental monitoring and protection learned that their jobs would be terminated, and an additional 400‐plus Environment Canada employees received notice that their positions were targeted for elimination. These notices received widespread coverage in the Canadian media and international attention in Nature News. Environment Canada is a government agency responsible for meteorological services as well as environmental research. We are concerned that research and observations related to ozone depletion, tropospheric pollution, and atmospheric transport of toxic chemicals in the northern latitudes may be seriously imperiled by the budget cuts that led to these job terminations. Further, we raise the questions being asked by the international community, scientists, and policy makers alike: First, will Canada be able to meet its obligations to the monitoring and assessment studies that support the various international agreements inTable 1? Second, will Canada continue to be a leader in Arctic research.
Scientific drilling in the Indian Ocean
Authors: Exon Neville , Pandey Dhananjai , Gallagher Stephen
Published: February 2012

Indian Ocean IODP Workshop; Goa, India, 17–18 October 2011 An Indian Ocean Integrated Ocean Drilling Program (IODP) Workshop was hosted by the National Centre for Antarctic and Ocean Research. With no scientific ocean drilling in the Indian Ocean for nearly a decade, this region remains a major gap in understanding global geoscientific processes, past and present, and their implications for the future.
Pushing the size limits of radiocarbon analysis
Authors: Smittenberg Rienk H. , Bernasconi Stefano M. , Szidat Soenke
Published: February 2012

An International Workshop on Small‐Scale Radiocarbon Analysis; Zurich, Switzerland, 13–16 September 2011 Besides being an important dating tool, radiocarbon (14C) analysis is also used increasingly in carbon cycle studies and environmental sciences. New developments in accelerator mass spectrometry (AMS) and sample introduction methods have allowed the downscaling of required sample sizes to a few micrograms of pure carbon. Modern techniques also make it possible to separate individual organic compounds for radiocarbon measurement, which allows targeting very specific sources of carbon out of mixed and complex matrices. These developments have created new opportunities for the use of 14C in scientific fields where its application had previously been limited by sample size. However, this has also presented new challenges with respect to sample preparation and assessment of uncertainties caused by contamination and instrumental background.
Gischig receives 2011 Natural Hazards Focus Group Award for Graduate Research
Authors: Anonymous
Published: February 2012

Valentin Gischig has been awarded the AGU Natural Hazards Focus Group Award for Graduate Research, given annually to a recent Ph.D. recipient for outstanding contributions to natural hazards research. Gischig's thesis is entitled “Kinematics and failure mechanisms of the Randa rock slope instability (Switzerland).” He presented an invited talk and was formally presented with the award at the 2011 AGU Fall Meeting, held 5–9 December in San Francisco, Calif. Gischig received his M.Sc. in geophysics and glaciology at Eidgenössiche Technische Hochschule (ETH) Zürich, in Switzerland, in 2007. In 2011 he attained a Ph.D. in engineering geology/rock mechanics/landslide analysis under the supervision of Simon Loew, Jeffrey R. Moore, Florian Amann, and Keith F. Evans at ETH Zürich. Gischig is currently conducting postdoctoral research at ETH Zürich. His research interests include landslides, induced seismicity in enhanced geothermal systems, and coupled processes in rock mechanics.
Sea ice controls variability in microseismicity
Authors: Schultz Colin
Published: February 2012

When an ocean wave swells, the sudden change in water column mass sends a pressure wave down to the ocean bottom. If the wave lasts long enough to strike the shore, its kinetic energy is transferred to the rock. Both processes induce microseismicity—low‐powered seismic waves with periods of between 1 and 20 seconds—which is picked up by seismic monitoring stations as regular background motions of the Earth. The observed amplitude of the microseismic signal varies with the distance from the source and shows pronounced seasonality because big winter storms kick up larger waves.
Dusty plasma around Enceladus affects Saturn's magnetosphere
Authors: Balcerak Ernie
Published: February 2012

Scientists have been puzzled by periodic bursts of radiation, known as the Saturn kilometric radiation (SKR), that occur in the planet's magnetosphere. These emissions occur at a rate that is close to, but not quite the same as, the rate at which the planet rotates. New observations from the Cassini Spacecraft's flybys of Saturn's moon Enceladus in 2008 are revealing new details about the plasma environment around Enceladus and how it may affect Saturn's magnetosphere. These observations could also shed some light on the SKR rotation rate.
Bark beetle outbreaks affect regional carbon cycle
Authors: Balcerak Ernie
Published: February 2012

Bark beetle outbreaks can kill a large number of trees—in fact, insect outbreaks affect an area similar in size to that affected by forest fires annually across North America. Trees absorb carbon dioxide, so bark beetle outbreaks can significantly affect regional carbon dynamics. In general, immediately after an outbreak, carbon uptake by trees decreases. Dead trees become snags, which may fall to the ground several or more years after the outbreak. After snags fall, decomposition increases. Carbon uptake begins to recover years to decades after a bark beetle outbreak. There have been few studies of biogeochemical cycling following outbreaks, and those studies have shown a variety of effects in different forests.
ALAS1 gene expression is down-regulated by Akt-mediated phosphorylation and nuclear exclusion of FOXO1 by vanadate in diabetic mice
Authors: Oliveri Leda M. , Davio Carlos , Batlle Alcira M. del C. , Gerez Esther N.
Published: February 2012

Porphyrias are diseases caused by partial deficiencies of haem biosynthesis enzymes. Acute porphyrias are characterized by a neuropsychiatric syndrome with intermittent induction of hepatic ALAS1 (δ-aminolaevulinate synthase 1), the first and rate-limiting enzyme of the haem pathway. Acute porphyria attacks are usually treated by the administration of glucose; its effect is apparently related to its ability to inhibit ALAS1 by modulating insulin plasma levels. It has been shown that insulin blunts hepatocyte ALAS1 induction, by disrupting the interaction of FOXO1 (forkhead box O1) and PGC-1α (peroxisome-proliferator-activated receptor γ co-activator 1α). We evaluated the expression of ALAS1 in a murine model of diabetes and determined the effects of the insulinomimetic vanadate on the enzyme regulation to evaluate its potential for the treatment of acute porphyria attacks. Both ALAS1 mRNA and protein content were induced in diabetic animals, accompanied by decreased Akt phosphorylation and increased nuclear FOXO1, PGC-1α and FOXO1–PGC-1α complex levels. Vanadate reversed ALAS1 induction, with a concomitant PI3K (phosphoinositide 3-kinase)/Akt pathway activation and subsequent reduction of nuclear FOXO1, PGC-1α and FOXO1–PGC-1α complex levels. These findings support the notion that the FOXO1–PGC-1α complex is involved in the control of ALAS1 expression and suggest further that a vanadate-based therapy could be beneficial for the treatment of acute porphyria attacks.
Pref-1 in brown adipose tissue: specific involvement in brown adipocyte differentiation and regulatory role of C/EBPδ
Authors: Armengol Jordi , Villena Josep A. , Hondares Elayne , Carmona María C. , Sul Hei Sook , Iglesias Roser , Giralt Marta , Villarroya Francesc
Published: February 2012

Pref-1 (pre-adipocyte factor-1) is known to play a central role in regulating white adipocyte differentiation, but the role of Pref-1 in BAT (brown adipose tissue) has not been analysed. In the present study we found that Pref-1 expression is high in fetal BAT and declines progressively after birth. However, Pref-1-null mice showed unaltered fetal development of BAT, but exhibited signs of over-activation of BAT thermogenesis in the post-natal period. In C/EBP (CCAAT/enhancer-binding protein) α-null mice, a rodent model of impaired fetal BAT differentiation, Pref-1 was dramatically overexpressed, in association with reduced expression of the Ucp1 (uncoupling protein 1) gene, a BAT-specific marker of thermogenic differentiation. In brown adipocyte cell culture models, Pref-1 was mostly expressed in pre-adipocytes and declined with brown adipocyte differentiation. The transcription factor C/EBPδ activated the Pref-1 gene transcription in brown adipocytes, through binding to the proximal promoter region. Accordingly, siRNA (small interfering RNA)-induced C/EBPδ knockdown led to reduced Pref-1 gene expression. This effect is consistent with the observed overexpression of C/EBPδ in C/EBPα-null BAT and high expression of C/EBPδ in brown pre-adipocytes. Dexamethasone treatment of brown pre-adipocytes suppressed Pref-1 down-regulation occurring throughout the brown adipocyte differentiation process, increased the expression of C/EBPδ and strongly impaired expression of the thermogenic markers UCP1 and PGC-1α [PPARγ (peroxisome-proliferator-activated receptor γ) co-activator-α]. However, it did not alter normal fat accumulation or expression of non-BAT-specific genes. Collectively, these results specifically implicate Pref-1 in controlling the thermogenic gene expression program in BAT, and identify C/EBPδ as a novel transcriptional regulator of Pref-1 gene expression that may be related to the specific role of glucocorticoids in BAT differentiation.
The influence of the extraction voltage on the energetic electron population of an electron cyclotron resonance ion source plasma
Authors: Stiebing K. E. , Schächter L. , Dobrescu S.
Published: February 2012

An influence of the extraction voltage on the high energy slope of bremsstrahlung radiation spectra has been reported in ECRIS experiments, which is not well understood so far. In order to provide more detailed data on this effect, we have measured bremsstrahlung radiation spectra accompanying especially the evolution of highly charge ions (i.e., by monitoring the Ar14+ charge state) as the extraction voltage is changed from 0 to 20 kV, in dedicated experiments at the Frankfurt 14 GHz-ECRIS.
Deuteron injector for Peking University Neutron Imaging Facility project
Authors: Ren H. T. , Peng S. X. , Lu P. N. , Zhou Q. F. , Yuan Z. X. , Zhao J. , Zhang M. , Song Z. Z. , Yu J. X. , Guo Z. Y. , Chen J. E.
Published: February 2012

The deuteron injector developed for the PKUNIFTY (Peking University Neutron Imaging Facility) has been installed and commissioned at Peking University (PKU). The injector system must transfer 50 keV 50 mA of D+ ion beam to the entrance of the 2 MeV radio frequency quadrupole (RFQ) with 10% duty factor (1 ms, 100 Hz). A compact 2.45 GHz permanent magnet electron cyclotron resonance (PMECR) ion source and a 1.36 m long low energy beam transport (LEBT) line using two solenoids was developed as the deuteron injector. A ϕ5 mm four-quadrant diaphragm was used to simulate the entrance of RFQ electrodes. The beam parameters are measured after this core with an emittance measurement unit (EMU) and a bending magnet for ion fraction analysis at the end of injector. During the commissioning, 77 mA of total deuteron beam was extracted from PMECR and 56 mA of pure D+ beam that passed through the ϕ5 mm four-quadrant diaphragm was obtained at the position of RFQ entrance with the measured normalized rms emittance 0.12–0.16π mm mrad. Ion species analysis results show that the deuteron fraction is as high as 99.5%. All of the parameters satisfy PKUNIFTY's requirements. In this paper, we will describe the deuteron injector design and report the commissioning results as well as the initial operation.
Optimization of negative ion current in a compact microwave driven upper hybrid resonance multicusp plasma source
Authors: Sahu D. , Bhattacharjee S. , Singh M. J. , Bandyopadhyay M. , Chakraborty A.
Published: February 2012

Performance of a microwave driven upper hybrid resonance multicusp plasma source as a volume negative ion source is reported. Microwaves are directly launched into the plasma chamber predominantly in the TE11 mode. The source is operated at different discharge conditions to obtain the optimized negative H− ion current which is ∼33 μA (0.26 mA/cm2). Particle balance equations are solved to estimate the negative ion density, which is compared with the experimental results. Future prospects of the source are discussed.
Beam injection improvement for electron cyclotron resonance charge breeders
Authors: Lamy T. , Angot J. , Sortais P. , Thuillier T. , Galatà A.
Published: February 2012

The injection of a 1+ beam into an electron cyclotron resonance (ECR) charge breeder is classically performed through a grounded tube placed on its axis at the injection side. This tube presents various disadvantages for the operation of an ECR charge breeder. First experiments without a grounded tube show a better use of the microwave power and a better charge breeding efficiency. The optical acceptance of the charge breeder without decelerating tube allows the injection of high intensity 1+ ion beams at high energy, allowing metals sputtering inside the ion source. The use of this method for refractory metallic ion beams production is evaluated.
Study on the beam transport from the Bio-Nano ECRIS
Authors: Uchida T. , Minezaki H. , Oshima K. , Racz R. , Muramatsu M. , Asaji T. , Kitagawa A. , Kato Y. , Biri S. , Yoshida Y.
Published: February 2012

The beam transport of N+ ion and C60+ ion in the Bio-Nano ECRIS with min-B configuration was investigated based on the ion beam profiles. The N+ beam could be focused under the low-beam current conditions. Also the C60+ beam could be focused in spite of the large space-charge effect which will lead the divergence of the beam. We confirmed that our beam transport system works well even for the C60+ ion beam. We estimated the highest C60+ beam current with the focused beam profile by comparing the N+ ion beam.
Forty years of surface plasma source development
Authors: Dudnikov Vadim
Published: February 2012

The cesiation effect, a significant enhancement of negative ion emission from a gas discharge with decrease of co-extracted electron current below negative ion current, was observed for the first time on July 1, 1971 by placing into the discharge a compound with 1 mg of cesium. Subsequent developments of surface plasma sources (SPS) for highly efficient negative ion production caused by the interaction of plasma particles with electrodes on which the adsorbed cesium reduced the surface work function are described. In the last 40 years, the intensity of negative ion beams has increased by cesiation up to 104 times from 3 mA to tens of amperes. Here, the main attention is concentrated on earlier SPS developments because recent results are well known and widely available.
Correlation between the plasma parameters and the extracted current density in the volume-production based sources of negative hydrogen ions
Authors: Lishev St. , Shivarova A. , Tarnev Kh.
Published: February 2012

Unified description of a volume-production based source of negative hydrogen ions, including its three regions—the driver, the plasma expansion through the magnetic filter, and the extraction of the ions at the position of the first electrode of the extraction system—is presented within a two-dimensional fluid plasma model. The results display the crucial role of the potential of the first electrode of the extraction system and show that the optimized conditions for the source operation should ensure proper balance between the local and non-local processes in the discharge. The role of the material of the plasma electrode is also discussed.
Study of surface effects on CoCu nanogranular alloys by ferromagnetic resonance
Authors: García Prieto A. , Fdez-Gubieda M. L. , Lezama L. , Orue I.
Published: February 2012

Room temperature ferromagnetic resonance measurements have been performed on Co5Cu95 melt-spun nanogranular alloys. Results on the ratio of the orbital-to-spin magnetic moment have been compared to previous results obtained by x-ray magnetic circular dichroism, explaining the differences in terms of the degree of magnetic saturation of the samples. Finally, the ferromagnetic resonance results have been related to the giant magnetoresistance (GMR) response of the samples at each stage of annealing, which has been interpreted as a sign of the interfacial origin of the GMR phenomenon.
Study on rare-earth–doped type-I germanium clathrates
Authors: Zhu Xiaohui , Chen Ning , Liu Lihua , Li Yang
Published: February 2012

The synthesis of rare-earth clathrates RExBa8−xGa16Ge30 is a challenging task. The Group IV clathrates with rare-earth doping are hardly to be experimentally prepared, except Eu clathrate. In the current study, the first-principle method based on the density functional theory was implemented. The effects of the various RE elements doping on the binding energy and chemical reaction drive energy were studied by optimizing the phase structure. The energy calculations suggest that it is difficult to synthesize RE clathrates without Ga doping. The function of Ga doping is to effectively increase the drive chemical reaction in order to synthesize the clathrates. The simulation shows that, besides Eu, other rare-earth elements, such as Sm, Nd, and Yb can also enter cage lattice in the considering of drive energy, thus making it possible to synthesize the (RE,Ba)8Ge30Ga16 clathrates.
Thermal issues and their effects on heat-assisted magnetic recording system (invited)
Authors: Xu B. X. , Liu Z. J. , Ji R. , Toh Y. T. , Hu J. F. , Li J. M. , Zhang J. , Ye K. D. , Chia C. W.
Published: February 2012

Compared to the conventional magnetic recording, the big difference in the heat-assisted magnetic recording (HAMR) is the introduction of the thermal energy. It is necessary to study the thermal effects on the HAMR system which includes the head, the media, the head and disk interface (HDI) and data recording and reproducing performance. In this paper, the key thermal issues in the HAMR system and their effects on the recording performances are analyzed and discussed. In the HAMR head, the heat sources are analyzed, and their effects on the temperature increase of the HAMR head are studied. The thermal profile of the media generated by the near field transducer is a determinant for achieving high density. Based on the measured thermal parameters of the medium materials, the thermal profiles of the medium at different medium parameters are studied. The results indicate that the boundary thermal resistance and the insulation of the grains are very important factors for obtaining small thermal spot sizes. The recording performances at a variety of temperatures are analyzed by the simulation of a micro-magnetic modeling. In the HDI, one of the key challenges is if the lubricant film can suffer the dynamic high temperature working environment. The lubricant thermal response for the dynamic high temperature working environment is characterized.
Modeling and analysis of a magnetically levitated synchronous permanent magnet planar motor
Authors: Kou Baoquan , Zhang Lu , Li Liyi , Zhang Hailin
Published: February 2012

In this paper, a new magnetically levitated synchronous permanent magnet planar motor (MLSPMPM) driven by composite-current is proposed, of which the mover is made of a copper coil array and the stator are magnets and magnetic conductor. The coil pitch τt and permanent magnet pole pitch τp satisfy the following relationship 3nτt = (3n ± 1)τp. Firstly, an analytical model of the planar motor is established, flux density distribution of the two-dimensional magnet array is obtained by solving the equations of the scalar magnetic potential. Secondly, the expressions of the electromagnetic forces induced by magnetic field and composite current are derived. To verify the analytical model and the electromagnetic forces, finite element method (FEM) is used for calculating the flux density and electromagnetic forces of the MLSPMPM. And the results from FEM are in good agreement with the results from the analytical equations. This indicates that the analytical model is reasonable.
Circulating currents in a metallic ring with two quantum dots
Authors: Anda E. V. , Chiappe G. , Louis E.
Published: February 2012

We analyze a system constituted by two single level quantum dots embedded in a metallic ring connected to external electrodes. The energy levels of the dots are controlled by an external gate potential. Additionally, the external electrodes are under the effect of an external applied potential. In these conditions, a circulating current appears in the ring. We show that this current appears when the gate potential is such that the electron-hole symmetry is broken. The direction of circulation depends upon the sign of the external potential and which dot has greater energy. The maximum value of this current is very sensitive to the gate and applied potentials, but it remains finite as the connection between the leads and the ring goes to zero. Therefore, although the circulating current is directly related to the applied potential, it demands a negligible current from the leads. The current is shown to be independent of the ring length, as opposed to the case of a persistent current induced by a magnetic field. It is not a nanoscopic phenomenon, and, as a consequence, it can be orders of magnitude larger than a typical persistent current in a metallic ring.
On convergent series representations of Mellin-Barnes integrals
Authors: Friot Samuel , Greynat David
Published: February 2012

Multiple Mellin-Barnes integrals are often used for perturbative calculations in particle physics. In this context, the evaluation of such objects may be performed through residues calculations which lead to their expression as multiple power series and logarithms of the parameters involved in the problem under consideration. However, in most of the cases, several convergent series representations exist for a given integral. These series converge in different regions of values of the parameters, and it is not obvious to obtain them. For twofold integrals, we present a method which allows to derive straightforwardly and systematically: First, different sets of poles which correspond to different convergent double series representations of a given integral, second the regions of convergence of all these series (without an a priori full knowledge of their general term), and third the general term of each series (this may be performed, if necessary, once the relevant domain of convergence has been found). This systematic procedure is illustrated with some integrals which appear, among others, in the calculation of the two-loop hexagon Wilson loop in $\mathcal {N} = 4$N=4 SYM theory. Mellin-Barnes integrals of higher dimension are also considered.
A reconstruction of cubic rs-ZnO on MgO (200) substrate through (100) plane of w-ZnO:rs-ZnO for transparent electronic application
Authors: Bobade Santosh M.
Published: February 2012

ZnO crystallizes in various crystallographic forms. While, the zinc blende (zb) and the rock salt (rs) structure of ZnO occur at high pressure, wurtzite (w) ZnO is the observed structure under ambient conditions. Interestingly, the high pressure polymorph of ZnO, cubic rs-ZnO oxide is presented on MgO (200) substrate at ordinary condition of temperature and pressure. The lattice constant of rs-ZnO is observed to be 4.203 Å identical to that for MgO. The possible configurational path for the hexagonal to cubic transformation is proposed. The compression of w-ZnO along c-axis, movement of Zn or O sub-lattice along [1¯10] direction and (110) plane appears to drive the transition. It has also been observed that rs-ZnO on MgO substrate is stable for certain maximum thickness (150 nm). It may be possible to stabilize the cubic phase at lower temperature and smaller thickness level.
Origin of 2.7 μm luminescence and energy transfer process of Er3+: 4I11/2→4I13/2 transition in Er3+/Yb3+ doped germanate glasses
Authors: Xu Rongrong , Tian Ying , Hu Lili , Zhang Junjie
Published: February 2012

An investigation of spectroscopic property and energy transfer process of Er3+ doped and Er3+/Yb3+ co-doped germanate glasses is presented. The emission cross section of the 4I11/2 → 4I13/2 transition of Er3+ doped germanate glass is calculated to be 1.2 × 10−20 cm2. The microparameter of energy transfer from Yb3+:2 F5/2 to Er3+:4I11/2 is calculated to be 2.74 × 10−39 cm6/s, and that is not phonon dependent in the quasiresonant process. The intensity of the emission around 2.7 μm is enhanced obviously when Er3+ co-doped with Yb3+. The excited-state relaxation process of Er3+ is adequately described by a combination of the Judd-Ofelt model and the energy-gap law. With the exception of 4I13/2 and 4I11/2 levels, multiphonon relaxation is dominant for all excited states, making it possible to efficiently pump the 1.55 μm 4I13/2 → 4I15/2 and 2.7 μm 4I13/2 → 4I11/2 emission by excitation of Yb3+:2F5/2 and Er3+:4I11/2 at 980 nm.
Cell viability studies and operation in cellular culture medium of n-type organic field-effect transistors
Authors: Barra M. , Viggiano D. , Di Capua R. , Di Girolamo F. , Santoro F. , Taglialatela M. , Cassinese A.
Published: February 2012

The possibility of the fabrication of organic devices suitable to be applied in bio-sensing fields depends largely on the availability of organic compounds displaying robust electrical properties even in aqueous solutions and effective biocompatibility features. In this paper, we report about the good cellular biocompatibility and the electrical response stability in an ionic medium of n-type organic transistors based on the recently developed PDI-8CN2 oligomer. The biocompatibility has been tested by analyzing the adhesion and viability of two different cell lines, human epithelial HeLa cells and murine neuronal F11 cells, on PDI-8CN2 films grown by organic molecular beam deposition (OMBD) on SiO2 substrates. The effect of film thickness on cell attachment was also tested. Uncoated SiO2 substrates were used as control surfaces and sexithiophene (T6) as device testing control. Moreover, the possible toxicity of –CN groups of PDI-8CN2 was tested on HeLa cell cultures, using PDI-8 and T6 molecules as controls. Results showed that, although at high concentration these organic compounds are toxic in solution, if they are presented in form of film, cell lines can attach and grow on them. The electrical response stability of PDI-8CN2 transistors in a cellular culture medium characterized by high concentrations of ionic species has been also investigated. For this purpose, low-voltage operation devices with VGS ranging from −5 V to 5 V, able to strongly reduce the influence of Faradaic currents coming from the electrical operation in an highly ionic environment, have been fabricated on 35 nm thick SiO2 layers and electrically characterized. These results are useful to experimentally define the main critical issues to be further addressed for the fabrication of reliable bio-sensors based on organic transistors.
Do ultradiscrete systems with parity variables satisfy the singularity confinement criterion?
Authors: Mimura N. , Isojima S. , Murata M. , Satsuma J. , Ramani A. , Grammaticos B.
Published: February 2012

Ultradiscrete singularity confinement test, which is an integrability detector for ultradiscrete equations with parity variables, is applied to various ultradiscrete equations. The ultradiscrete equations exhibit singularity structures analogous to those of the discrete counterparts. Exact solutions to linearisable ultradiscrete equations are also constructed to explain the singularity structures.
Drawing graphene nanoribbons on SiC by ion implantation
Authors: Tongay S. , Lemaitre M. , Fridmann J. , Hebard A. F. , Gila B. P. , Appleton B. R.
Published: February 2012

We describe a straightforward technique for selective graphene growth and nanoribbon production onto 4H- and 6H-SiC. The technique presented is as easy as ion implanting regions where graphene layers are desired followed by annealing to 100 °C below the graphitization temperature (TG) of SiC. We find that ion implantation of SiC lowers the TG, allowing selective graphene growth at temperatures below the TG of pristine SiC and above TG of implanted SiC. This results in an approach for patterning device structures ranging from a couple tens of nanometers to microns in size without using conventional lithography and chemical processing.
Theoretical description of thermal lens spectrometry in micro space
Authors: Liu Mingqiang , Korte Dorota , Franko Mladen
Published: February 2012

For thermal lens spectrometry in micro space, temperature distributions in the sample under continuous-wave modulated excitations of either laser or incoherent light source (ILS) are for the first time deduced with respective considerations of different experimental parameters, such as flow of the sample, excitation beam divergence, effects of top/bottom layers adjacent to the sample, and sidewall effects. On the basis of the temperature distributions, thermal lens (TL) models are built based on the Fresnel diffraction theory. Numerical simulations of the influence of the above factors on the TL signal are made for different detection schemes in search of higher detection sensitivity. We were able to predict the optimum probe beam offset as a function of the flow of the sample, the optimum detection scheme to minimize the effects of fluctuation of the flow velocity and/or excitation beam radius, the optimum excitation beam radius for a given sample length, and propose a three-layer system in an ILS-excited thermal lens microscope for sensitivity enhancement of up to 10 times.
Optical properties of a periodic array of slit-groove
Authors: Wang Guo-dong , Huang Cheng-ping , Zhang Yi , Wang Qian-jin , Zhu Yong-yuan
Published: February 2012

The optical properties of a periodic slit-groove array perforated in a metal film have been studied experimentally and theoretically. Due to the interplay between periodic slits and periodic grooves, a switching from transmission minimum to maximum and the appearance of an additional dip were experimentally observed. To understand the effect, two different theoretical methods, i.e., the phenomenological method and analytical (coupled-mode) method, for studying the peculiar optical properties have been adopted. The results may provide us with new insights into underlying physics of interaction between the sub-wavelength objects and electromagnetic waves.
Existence and concentration of ground states for Schrödinger-Poisson equations with critical growth
Authors: He Xiaoming , Zou Wenming
Published: February 2012

In this paper, we study the existence and concentration behavior of ground state solutions for a class of Schrödinger-Poisson equation with a parameter ɛ > 0. Under some suitable conditions on the nonlinearity f and the potential V, we prove that for ε small, the equation has a ground state solution concentrating around global minimum of the potential V in the semi-classical limit. Also, the exponential decay of the ground state solutions is studied.
Electronic spectroscopy of jet-cooled YbNH3
Authors: Tonge Nicola M. , Rusher Cassandra A. , Bhalla Nitika , Varriale Luigi , Ellis Andrew M.
Published: February 2012

We report the first spectroscopic study of a complex consisting of a rare earth atom in combination with ammonia. Using two-color resonance-enhanced multiphoton ionization (REMPI) spectroscopy, the lowest energy electronic transition of YbNH3 has been found in the near-infrared. The spectrum arises from a spin-forbidden transition between the 1A1 ground electronic state and the lowest 3E excited electronic state. The transition is metal centered and approximately correlates with the Yb 6s6p 3P ← 6s2 1S transition. The observation of clear spin-orbit structure in the spectrum confirms the C3v symmetry of YbNH3. Vibrational structure is also observed in the REMPI spectrum, which is dominated by excitation of the Yb–N stretching vibration.
Electric field-perturbation measurement of the interaction between two laser-induced plasmas
Authors: Sánchez-Aké C. , Bredice F. , Villagrán-Muniz M.
Published: February 2012

The interaction between two ns-laser-induced plasmas in air at the early-stage of expansion has been analyzed by using a method based on the direct measurement of the perturbation of an externally applied electric field. In this experimental method, the plasmas were produced by focusing two laser beams between the plates of a parallel-plane-charged capacitor. These plasmas produce a perturbation in the electric field of the capacitor which can be measured as a voltage change across a resistor connected to the ground plate. It was found that for delays shorter than 5 ns, the interaction between plasmas is mainly due to the interaction of the dipole-charge distribution of each plasma. For longer time delays, the shielding effect was dominant.
Stretch-induced plasmonic anisotropy of self-assembled gold nanoparticle mats
Authors: Millyard Matthew G. , Min Huang Fu , White Richard , Spigone Elisabetta , Kivioja Jani , Baumberg Jeremy J.
Published: February 2012

Close-packed monolayers of 20 nm Au nanoparticles are self-assembled at hexane/water interfaces and transferred to elastic substrates. Stretching the resulting nanoparticle mats provides active and reversible tuning of their plasmonic properties, with a clear polarization dependance. Both uniaxial and biaxial strains induce strong blue shifts in the plasmonic resonances. This matches theoretical simulations and indicates that plasmonic coupling at nanometer scale distances is responsible for the observed spectral tuning. Such stretch-tunable metal nanoparticle mats can be exploited for the development of optical devices, such as flexible colour filters and molecular sensors.
Solid-state source of atomic oxygen for low-temperature oxidation processes: Application to pulsed laser deposition of TiO2:N films
Authors: Ojima Daiki , Chiba Tetsuya , Shima Kazunari , Hiramatsu Hidenori , Hosono Hideo , Hayashi Katsuro
Published: February 2012

An atomic oxygen (AO) source has been redesigned to coordinate with a pulsed laser deposition system and used to grow nitrogen-doped TiO2 films by deposition of TiN and simultaneous irradiation of the substrate with AO. The AO source uses an incandescently heated thin tube of zirconia as an oxygen permeation media to generate pure AO of low kinetic energy. The emission flux is calibrated using a silver-coated quartz crystal microbalance. The thin shape of the probe and transverse emission geometry of this emission device allow the emission area to be positioned close to the substrate surface, enhancing the irradiation flux at the substrate. AO irradiation is crucial for formation of TiO2 phases via oxidation of the deposited TiN laser plume, and is effective for decrease of the substrate temperature for crystallization of anatase phase to as low as around 200 °C.
An excited state paired interacting orbital method
Authors: Kawata Isao , Nitta Hiroya
Published: February 2012

A new method for analyzing and visualizing the molecular excited states, named “excited state paired interacting orbital (EPIO),” is proposed. The method is based both on the paired interacting orbital (PIO) proposed by Fujimoto and Fukui [J. Chem. Phys. 60, 572 (1974)] and the natural transition orbital (NTO) by Martin [J. Chem. Phys. 118, 4775 (2003)10.1063/1.1558471]. Within the PIO method, orbital interactions between the two fragmented molecules are represented practically only by a few pairs of fragment orbitals. The NTO method is a means of finding a compact orbital representation for the electronic transitions in the excited states. With the method, electronic transitions are expressed by a few particle-hole orbital pairs and a clear picture on the electronic transitions is obtained. EPIO method is designed to have both properties of the preceding two methods: electronic transitions in composite molecular systems can be expressed with a few pairs of EPIOs which are constructed with fragmented molecular orbitals (MOs). Excited state characters, such as charge transfer and local excitations, are analyzed by using EPIOs with their generation probabilities. Thus, the present method gives us clear information on the composition of MOs which play an important role in the molecular excitation processes, e.g., optical processes.
Vibronic coupling simulations for linear and nonlinear optical processes: Theory
Authors: Silverstein Daniel W. , Jensen Lasse
Published: February 2012

A comprehensive vibronic coupling model based on the time-dependent wavepacket approach is derived to simulate linear optical processes, such as one-photon absorbance and resonance Raman scattering, and nonlinear optical processes, such as two-photon absorbance and resonance hyper-Raman scattering. This approach is particularly well suited for combination with first-principles calculations. Expressions for the Franck-Condon terms, and non-Condon effects via the Herzberg-Teller coupling approach in the independent-mode displaced harmonic oscillator model are presented. The significance of each contribution to the different spectral types is discussed briefly.
Thickness effects on the texture development of fluorine-doped SnO2 thin films: The role of surface and strain energy
Authors: Consonni V. , Rey G. , Roussel H. , Bellet D.
Published: February 2012

Polycrystalline fluorine-doped SnO2 thin films have been grown by ultrasonic spray pyrolysis with a thickness varying in the range of 40 to 600 nm. A texture transition from ⟨110⟩ to ⟨100⟩ and ⟨301⟩ crystallographic orientations has experimentally been shown by x-ray diffraction measurements as film thickness is increased, showing that a process of abnormal grain growth has occurred. The texture effects are considered within a thermodynamic approach, in which the minimization of total free energy constitutes the driving force for grain growth. For very small film thickness, it is found that the ⟨110⟩ preferred orientation is due to surface energy minimization, as the (110) planes have the lowest surface energy in the rutile structure. In contrast, as film thickness is increased, the ⟨100⟩ and ⟨301⟩ crystallographic orientations are progressively predominant, owing to elastic strain energy minimization in which the anisotropic character is considered in the elastic biaxial modulus. A texture map is eventually determined, revealing the expected texture as a function of elastic strain and film thickness.
Iron-phthalocyanine molecular junction with high spin filter efficiency and negative differential resistance
Authors: Huang Jing , Xu Ke , Lei Shulai , Su Haibin , Yang Shangfeng , Li Qunxiang , Yang Jinlong
Published: February 2012

We investigate the spin transport properties of iron-phthalocyanine (FePc) molecule sandwiched between two N-doped graphene nanoribbons (GNRs) based on the density functional theory and nonequilibrium Green's function methods. Our calculated results clearly reveal that the FePc molecular junction has high spin-filter efficiency as well as negative differential resistance (NDR). The zero-bias conductance through FePc molecule is dominated by the spin-down electrons, and the observed NDR originates from the bias-dependent effective coupling between the FePc molecular orbitals and the narrow density of states of electrodes. The remarkable high spin-filter efficiency and NDR are robust regardless of the edge shape and the width of GNRs, and the N-doping site in GNRs. These predictions indicate that FePc junction holds great promise in molecular electronics and spintronics applications.
InGaN/GaN multiple-quantum-well light-emitting diodes grown on Si(111) substrates with ZrB2(0001) buffer layers
Authors: Blake Adam H. , Caselli Derek , Durot Christopher , Mueller Jason , Parra Eduardo , Gilgen Joseph , Boley Allison , Smith David J. , Tsong Ignatius S. T. , Roberts John C. , Piner Edwin , Linthicum Kevin , Cook James W. , Koleske Daniel D. , Crawford Mary H. , Fischer Arthur J.
Published: February 2012

Multiple-quantum-well light-emitting diode (LED) structures of InGaN/GaN were grown by metalorganic chemical vapor deposition on Si(111) substrates via ZrB2(0001) buffer layers and a GaN template comprising composite AlxGa1-xN (where x lies in the range from 0 to 1) transition layers to minimize cracking due to thermal expansion mismatch between Si and GaN. Photoluminescence and electroluminescence results from the LED structures compared favorably with similar measurements obtained on identical LED structures grown on sapphire substrates. However, in spite of all the precautions taken, cracking was still present in the LED structures. Scanning electron microscopy and transmission electron microscopy in plan-view and cross-section geometries were conducted on the LED structures to examine the presence and the influence of various defects such as microvoids, micropipes, and threading dislocations on the mechanism of cracking. Our results suggest that the crack network propagates from microvoids on the surface of the LED structure. The formation of microvoids appears to originate from imperfections in the epitaxial ZrB2(0001) buffer layer.
Depletion of nitrogen-vacancy color centers in diamond via hydrogen passivation
Authors: Stacey A. , Karle T. J. , McGuinness L. P. , Gibson B. C. , Ganesan K. , Tomljenovic-Hanic S. , Greentree A. D. , Hoffman A. , Beausoleil R. G. , Prawer S.
Published: February 2012

We show reduction in the emission from nitrogen-vacancy (NV) centers in single crystal diamond due to exposure to hydrogen plasmas ranging from 700 °C to 1000 °C. Significant fluorescence reduction was observed beneath the exposed surface to 80 μm depth after ∼10 min and did not recover after post-annealing in vacuum for 7 h at 1100 °C. We attribute the fluorescence reduction to the formation of nitrogen-vacancy-hydrogen centers by the plasma-induced diffusion of hydrogen. These results have important implications for the formation of NV centers for quantum applications, whilst also providing experimental evidence of long range hydrogen diffusion through intrinsic high-purity diamond.