bluuebunny/crossref_metadata_2025 huggingface dataset:
The (in)compatibility of morpheme orders and lexical categories and its historical implications
Authors: Berg Thomas
Published: September 2008

English testifies to a remarkable pattern of lexical gaps. In quite a few cases, particlestem nouns (e.g.the income) and adjectives (e.g.incoming) exist in the current language whereas their corresponding verbs (e.g.*to income) do not. Verbs with the opposite morpheme order (e.g.to come in) are, of course, attested. Since most relevant nouns and adjectives are derivatives of verbs, the word-class shift must either have entailed an inversion of the morphemes, or the verbs must have dropped out of the language. A diachronic analysis does indeed reveal that particle-stem verbs have a lower ‘life-expectancy’ than the corresponding nouns and adjectives. This difference is claimed to follow from differing degrees of compatibility between word classes and morpheme orders. The criterion of syntacticity shows particle-stem nouns and stem-particle verbs to be internally consistent but stem-particle nouns and particle-stem verbs to be inconsistent. This inconsistency gives rise to the observed historical instability of particle-stem verbs. While also disfavoured in this framework, the currency of stem-particle nouns (e.g.the handout) can be attributed to a conspiracy of several facilitatory effects which tend to override the arguments against this word type. The fact that linguistic units may fall into disuse necessitates certain revisions of the notion of optimality as the backbone of Optimality Theory.
On the origin of auxiliarydo
Authors: Garrett Andrew
Published: September 2008

Prevailing theories link the English periphrastic auxiliary verbdohistorically with Old and Middle English causativedo.I argue that these and other accounts are inconsistent with modern dialect evidence and an analysis of the historical record suggested by that evidence. The primary source of periphrasticdowas a habitual aspect marker which itself arose from the reinterpretation of bare object nominalizations as infinitive verbs.1
THE EUTHYPHRO DILEMMA
Authors: Mawson T. J.
Published: September 2008

Is something good because God wills it, or does God will it because it is good? This lies at the heart of our debate on “Good without God”. Here Tim Mawson explains how he thinks the theist can solve it.
GOOD WITHOUT GOD
Authors: Norman Richard
Published: September 2008

In the fifth of our articles on “Good without God”, Richard Norman explains why he believes we can be good without God.
THE TWO ADAM SMITHS
Authors: Cam Philip
Published: September 2008

Philip Cam argues that we need to rise above Smith's fixation on self-interest in economic affairs.
Vertical aerosol profiles from Raman polarization lidar observations during the dry season AMMA field campaign
Authors: Heese Birgit , Wiegner Matthias
Published: September 2008

Lidar measurements of the vertical distribution of optical particle properties were performed in January 2006 in the frame of the dry season field experiment of the African Monsoon Multidisciplinary Analyses (AMMA). The measurements were conducted at a remote site in West Africa in the Sahel region just south of the Saharan desert to investigate the influence of particles on the West African monsoon. The portable Raman polarization lidar system POLIS of the University of Munich was operated each forenoon and during selected nights. These measurements are the first Raman and depolarization lidar measurements taken in the Sahel. The particle depolarization ratio and the extinction coefficient profiles allow the characterization of the particles and the distinction between Saharan dust particles and biomass burning aerosol (BBA). The origin of this aerosol was investigated by trajectory analyses. The profiles show a varying dust layer in the lowermost troposphere during the whole period. Above the dust layer a broad layer of BBA reaching up to an altitude of 5 km was frequently observed. The extinction coefficient in the dust layer was between 0.2 and 0.4 km−1 at 355 nm, and the particle depolarization was around 25%. In the BBA layer the extinction coefficient was lower with values between 0.1 and 0.2 km−1, and the particle depolarization ratio was below 10%. Lidar ratio values around 55 sr were found for the dust layer and around 75 sr for the BBA layer. From previous observations, lidar ratios between 40 and 80 sr were expected for BBA.
Interval‐based statistical validation of operational seasonal forecasts in Spain conditioned to El Niño–Southern Oscillation events
Authors: Sordo C. , Frías M. D. , Herrera S. , Cofiño A. S. , Gutiérrez J. M.
Published: September 2008

As opposed to the tropics, operational seasonal forecasting systems have shown little or no skill in European midlatitudes. In this paper we explore the potential source of predictability in this region given by El Niño–Southern Oscillation (ENSO) events; in particular we analyze winter rainfall in Spain. First, we apply a simple statistical method to assess the teleconnections between rainfall records in 123 gauges over Spain and ENSO events during the last 40 years. A significant teleconnection for dry winter episodes is found associated with La Niña events, extending the results obtained in previous studies. Then, we adapt the statistical method to perform operational seasonal forecasts validation conditioned to ENSO events; in particular we consider a state‐of‐the‐art operational model, the System2 from ECMWF. The validation method defines a forecast interval to account for the ensemble spread, and applies a simple skill measure based on the proportion of hits (observations falling into the forecast interval) compared with a random forecast. As a result, we uncover the significant skill of operational seasonal predictions for reproducing the dry winter episodes associated with La Niña events (a window of opportunity for operational seasonal forecast in midlatitudes). Finally, the results are improved using statistical downscaling methods and some sensitivity studies are conducted. The analysis presented in this paper can be extended to other regions under the influence of any seasonal predictability‐driving factor.
Composition‐resolved size distributions of volcanic aerosols in the Mt. Etna plumes
Authors: Martin R. S. , Mather T. A. , Pyle D. M. , Power M. , Allen A. G. , Aiuppa A. , Horwell C. J. , Ward E. P. W.
Published: September 2008

Particle size distributions for soluble and insoluble species in Mt. Etna's summit plumes were measured across an extended size range (10 nm < d < 100 μm) using a combination of techniques. Automated scanning electron microscopy (QEMSCAN) was used to chemically analyze many thousands of insoluble particles (collected on pumped filters) allowing the relationships between particle size, shape, and composition to be investigated. The size distribution of fine silicate particles (d < 10 μm) was found to be lognormal, consistent with formation by bursting of gas bubbles at the surface of the magma. The compositions of fine silicate particles were found to vary between magmatic and nearly pure silica; this is consistent with depletion of metal ions by reactions in the acidic environment of the gas plume and vent. Measurements of the size, shape and composition of fine silicate particles may potentially offer insights into preemission, synemission, and postemission processes. The mass flux of fine silicate particles from Mt. Etna released during noneruptive volcanic degassing in 2004 and 2005 was estimated to be ∼7000 kg d−1. Analysis of particles in the range 0.1 < d/μm < 100 by ion chromatography shows that there are persistent differences in the size distributions of sulfate aerosols between the two main summit plumes. Analysis of particles in the range 0.01 μm < d < 0.1 μm by scanning transmission electron microscopy (STEM) shows that there are significant levels of nanoparticles in the Mt. Etna plumes although their compositions remain uncertain.
An analysis of the vertical structure of the atmosphere and the upper‐level meteorology and their impact on surface ozone levels in Houston, Texas
Authors: Rappenglück Bernhard , Perna Ryan , Zhong Shiyuan , Morris Gary A.
Published: September 2008

Despite emission reductions, Houston continues to be designated as a nonattainment area for ozone (O3) by the Environmental Protection Agency. Upper‐level synoptic maps and information about the vertical structure of the lower troposphere obtained by in situ measurements were analyzed to characterize ozone exceedances in which peak 8‐h average concentration exceeded 85 ppb during the Texas Air Quality Study‐II in August–September 2006. Cluster analysis of meteorological conditions showed that the highest background surface O3 concentrations occurred under northerly or easterly flow regimes at 850 hPa, coinciding with the advection of dry continental air. Exceedance days in September 2006 occurred almost exclusively in postfrontal environments. These frontal passages are associated with shifts in wind direction and may lead to increases in background O3 from 30 ppbv (marine) to 60–70 ppbv (continental) throughout the lower troposphere. Several factors are identified to be important for 8‐h average ozone peaks in Houston under well‐developed land‐sea‐bay breeze conditions, including (1) the presence of easterly winds advecting industrial emissions from the Ship Channel, and (2) the presence of persistent large‐scale northerly flows aloft advecting elevated continental background ozone levels that are eventually entrained into lower layers through the growth of the convective planetary boundary layer.
Frequency and temperature dependence in electromagnetic properties of Martian analog minerals
Authors: Stillman David , Olhoeft Gary
Published: September 2008

Ground‐penetrating radar (GPR) has the potential to image the Martian subsurface to give geological context to drilling targets, investigate stratigraphy, and locate subsurface water. GPR depth of penetration depends strongly on the electromagnetic (EM) properties (complex dielectric permittivity, complex magnetic permeability, and DC resistivity) of the subsurface. These EM properties in turn depend on the mineralogical composition of the subsurface and are sensitive to temperature. In this study, the EM properties of Martian analog samples were measured versus frequency (1 MHz‐1 GHz) and at Martian temperatures (180–300 K). Results from the study found the following: gray hematite has a large temperature‐dependent dielectric relaxation, magnetite has a temperature‐independent magnetic relaxation, and JSC Mars‐1 has a broad temperature‐dependent dielectric relaxation most likely caused by absorbed water. Two orbital radars, MARSIS and SHARAD, are currently investigating the subsurface of Mars. On the basis of the results of our measurements, the attenuation rate of gray hematite is 0.03 and 0.9 dB/m, magnetite is 0.04 and 1.1 dB/m, and JSC Mars‐1 is 0.015 and 0.09 dB/m at MARSIS and SHARAD frequencies, respectively, and at the average Martian temperature of 213 K. With respect to using GPR for subsurface investigation on Mars, absorbed water will be a larger attenuator of radar energy as high concentrations of magnetite and gray hematite are not found globally on Mars.
Constraining model transient climate response using independent observations of solar‐cycle forcing and response
Authors: Tung Ka Kit , Zhou Jiansong , Camp Charles D.
Published: September 2008

The phenomenon of 11‐year solar cycles has a well‐measured forcing, and the response in surface temperature is confirmed using multiple datasets, including reanalysis (NCEP/NCAR and ERA‐40) and blended in situ land‐ocean data (GISS and HadCRUT3). Missing coverage in the historical in situ station data reduces the amplitude of the response compared to the geographically complete reanalysis data, but all extracted signals are statistically robust. A transient climate sensitivity parameter can be defined once forcing and response are known. The coupled atmosphere‐ocean models participating in the 4th Assessment Report (AR4) of the Intergovernmental Panel on Climate Change (IPCC) span a large range in their transient climate response (TCR). Using observational results on the response to the 11‐year solar variation, we derive a constraint for the TCR. It is seen that, compared with our derived constraint, most models assessed by IPCC AR4 have too low a TCR, even lower than that derived from the station data.
Formation of artificial ionospheric ducts
Authors: Milikh G. M. , Papadopoulos K. , Shroff H. , Chang C. L. , Wallace T. , Mishin E. V. , Parrot M. , Berthelier J. J.
Published: September 2008

It is well known that strong electron heating by a powerful HF‐facility can lead to the formation of electron and ion density perturbations that stretch along the magnetic field line. Those density perturbations can serve as ducts for ELF waves, both of natural and artificial origin. This paper presents the first experimental evidence of plasma modifications associated with ion outflows due to HF heating. The experiments were conducted using the HAARP heater during times that the DEMETER satellite flying at an altitude of approximately 670 km was close to the magnetic zenith of HAARP. The DEMETER satellite has provided in situ measurements of the ion temperature and composition. The experimental results are compared with the numerical model of inter‐hemispheric artificial ducts, and it is found that they are in qualitative agreement.
A new source of auroral infrared emission observed by TIMED/SABER
Authors: Mertens Christopher J. , Fernandez Jose R. , Xu Xiaojing , Evans David S. , Mlynczak Martin G. , Russell James M.
Published: September 2008

We demonstrate for the first time that O2+ + NO charge transfer produces NO+(v). This mechanism identifies a new source of auroral infrared emission at 4.3 μm, which provides a major step forward in understanding auroral processes and a new context for understanding previously observed auroral enhancements in O2(b1Σg+) and O2(a1Δg) bands. The charge transfer process is identified by comparing physics‐based model simulations with NO+(v) volume emission rates derived from SABER 4.3 μm limb emission measurements.
Transient layers in the topside ionosphere of Mars
Authors: Kopf A. J. , Gurnett D. A. , Morgan D. D. , Kirchner D. L.
Published: September 2008

Radar soundings from the MARSIS instrument on board the Mars Express spacecraft have shown that distinct layers can occur in the topside ionosphere of Mars, well above the main photo‐ionization layer. These layers appear as cusps, or sometimes steps, in plots of the time delay as a function of frequency. Usually only one topside layer is observed, typically at altitudes from 180 to 240 km. However, occasionally an additional layer occurs at even higher altitudes. The layers are transient features and are present about 60% of the time near the subsolar point, decreasing with increasing solar zenith angle to less than 5% at the terminator and the nightside. The transient nature of the layers suggests that they are produced by a dynamical process, most likely involving an interaction with the solar wind in the upper levels of the ionosphere.
A multi‐model study of the hemispheric transport and deposition of oxidised nitrogen
Authors: Sanderson M. G. , Dentener F. J. , Fiore A. M. , Cuvelier C. , Keating T. J. , Zuber A. , Atherton C. S. , Bergmann D. J. , Diehl T. , Doherty R. M. , Duncan B. N. , Hess P. , Horowitz L. W. , Jacob D. J. , Jonson J.‐E. , Kaminski J. W. , Lupu A. , MacKenzie I. A. , Mancini E. , Marmer E. , Park R. , Pitari G. , Prather M. J. , Pringle K. J. , Schroeder S. , Schultz M. G. , Shindell D. T. , Szopa S. , Wild O. , Wind P.
Published: September 2008

Fifteen chemistry‐transport models are used to quantify, for the first time, the export of oxidised nitrogen (NOy) to and from four regions (Europe, North America, South Asia, and East Asia), and to estimate the uncertainty in the results. Between 12 and 24% of the NOx emitted is exported from each region annually. The strongest impact of each source region on a foreign region is: Europe on East Asia, North America on Europe, South Asia on East Asia, and East Asia on North America. Europe exports the most NOy, and East Asia the least. East Asia receives the most NOy from the other regions. Between 8 and 15% of NOx emitted in each region is transported over distances larger than 1000 km, with 3–10% ultimately deposited over the foreign regions.
Viewing perspective in energetic neutral atom intensity
Authors: Zheng Yihua , Lui Anthony T. Y. , Fok Mei‐Ching
Published: September 2008

Through interspacecraft comparison of energetic neutral oxygen (ENO) intensity from two different vantage points provided by IMAGE and Geotail, Lui et al. (2005) showed that viewing perspective plays a very important role in the observed ENO intensity level during a magnetic storm period. Motivated by the findings of Lui et al. (2005), we investigate how viewing perspective influences energetic neutral atom emissions from a modeling perspective. The main results of this paper are that (1) our simulation results, based upon O+ ion fluxes from the Comprehensive Ring Current Model and the subsequent ENO calculation, reproduce the total differential ENO intensity obtained from two spacecraft to a reasonable degree and (2) further analysis of our results indicates that pitch angle anisotropy in ring current ion flux, a crucial physical quantity in ring current dynamics, is one major contributor to the difference in energetic neutral atom intensity from different viewing perspectives.
Vertical distribution and radiative effects of mineral dust and biomass burning aerosol over West Africa during DABEX
Authors: Johnson B. T. , Heese B. , McFarlane S. A. , Chazette P. , Jones A. , Bellouin N.
Published: September 2008

This paper presents measurements of the vertical distribution of aerosol extinction coefficient over West Africa during the Dust and Biomass‐burning Aerosol Experiment (DABEX)/African Monsoon Multidisciplinary Analysis dry season Special Observing Period Zero (AMMA‐SOP0). In situ aircraft measurements from the UK FAAM aircraft have been compared with two ground‐based lidars (POLIS and ARM MPL) and an airborne lidar on an ultralight aircraft. In general, mineral dust was observed at low altitudes (up to 2 km), and a mixture of biomass burning aerosol and dust was observed at altitudes of 2–5 km. The study exposes difficulties associated with spatial and temporal variability when intercomparing aircraft and ground measurements. Averaging over many profiles provided a better means of assessing consistent errors and biases associated with in situ sampling instruments and retrievals of lidar ratios. Shortwave radiative transfer calculations and a 3‐year simulation with the HadGEM2‐A climate model show that the radiative effect of biomass burning aerosol was somewhat sensitive to the vertical distribution of aerosol. In particular, when the observed low‐level dust layer was included in the model, the absorption of solar radiation by the biomass burning aerosols increased by 10%. We conclude that this absorption enhancement was caused by the dust reflecting solar radiation up into the biomass burning aerosol layer. This result illustrates that the radiative forcing of anthropogenic absorbing aerosol can be sensitive to the presence of natural aerosol species.
Structural insight into the inhibition of tubulin by vinca domain peptide ligands
Authors: Cormier Anthony , Marchand Matthieu , Ravelli Raimond B G , Knossow Marcel , Gigant Benoît
Published: September 2008

The tubulin vinca domain is the target of widely different microtubule inhibitors that interfere with the binding of vinblastine. Although all these ligands inhibit the hydrolysis of GTP, they affect nucleotide exchange to variable extents. The structures of two vinca domain antimitotic peptides—phomopsin A and soblidotin (a dolastatin 10 analogue)—bound to tubulin in a complex with a stathmin‐like domain show that their sites partly overlap with that of vinblastine and extend the definition of the vinca domain. The structural data, together with the biochemical results from the ligands we studied, highlight two main contributors in nucleotide exchange: the flexibility of the tubulin subunits' arrangement at their interfaces and the residues in the carboxy‐terminal part of the β‐tubulin H6–H7 loop. The structures also highlight common features of the mechanisms by which vinca domain ligands favour curved tubulin assemblies and destabilize microtubules.
The zinc‐binding protein Hot13 promotes oxidation of the mitochondrial import receptor Mia40
Authors: Mesecke Nikola , Bihlmaier Karl , Grumbt Barbara , Longen Sebastian , Terziyska Nadia , Hell Kai , Herrmann Johannes M
Published: September 2008

A disulphide relay system mediates the import of cysteine‐containing proteins into the intermembrane space of mitochondria. This system consists of two essential proteins, Mia40 and Erv1, which bind to newly imported proteins by disulphide transfer. A third component, Hot13, was proposed to be important in the biogenesis of cysteine‐rich proteins of the intermembrane space, but the molecular function of Hot13 remained unclear. Here, we show that Hot13, a conserved zinc‐binding protein, interacts functionally and physically with the import receptor Mia40. It improves the Erv1‐dependent oxidation of Mia40 both in vivo and in vitro. As a consequence, in mutants lacking Hot13, the import of substrates of Mia40 is impaired, particularly in the presence of zinc ions. In mitochondria as well as in vitro, Hot13 can be functionally replaced by zinc‐binding chelators. We propose that Hot13 maintains Mia40 in a zinc‐free state, thereby facilitating its efficient oxidation by Erv1.
Carbons and Carbon-Supported Catalysts in Hydroprocessing
Authors: Furimsky Edward
Published: September 2008

Carbon materials have, in recent years, been attracting attention as potential supports in heterogeneous catalysis. In 2006, the number of articles dealing with various types of catalysts supported on carbon approached 1000, however only a fraction of those were devoted to hydroprocessing catalysts, despite the fact that interest in carbons as supports for hydroprocessing catalysts began more than two decades ago. This unique book is a comprehensive summary of recent research in the field and covers all areas of carbons and carbon materials. The potential application of carbon supports, particularly those of carbon black (CB) and activated carbon (AC) in hydroprocessing catalysis are covered extensively in the book. Novel carbon materials such as carbon fibers and carbon nano tubes (CNT) are also covered, including the more recent developments in the use of fullerenes in hydroprocessing applications - an area with little published research. Although the primary focus of this book is on carbons and carbon supported catalysts, it also identifies the difference in the effect of carbon supports compared with the oxidic supports, particularly that of y-AL2O3. Although many books claim to have the same objective, this publication is unique as the difference in catalyst activity and stability was estimated using both model compounds and real feeds under variable conditions. The conditions applied during the preparation of carbon supported catalysts are also comprehensively covered and include various methods of pretreatment of carbon supports to enhance catalyst performance. The model compounds results consistently show higher hydrodesulfurization and hydrodeoxygenation activities of carbon supported catalysts than that of the y-Al2O3 supported catalysts. Also, the deactivation of the former catalysts by coke deposition was much less evident. Importantly, in this book, most of the model compounds studies on hydrodesulfurization and hydrodeoxygenation were conducted in the absence of nitrogen compounds, as the poisoning effects of such compounds on hydroprocessing reactions are well known. Non-conventional metals (e.g., Pt, Pd, Ru, Rh, Re and Ir) supported on carbon supports are also studied in this book as catalysts for hydroprocessing of model feeds and real feeds. The book shows that these catalysts are much more active than conventional metals containing catalysts however the high cost of these metals prevents commercial utilization of these catalysts. Kinetics of hydroprocessing reactions, as well as kinetics of deactivation over carbon supported catalysts are also investigated under a wide range of experimental conditions and the y-Al2O3 supported catalysts have been included for comparison. This book, unique in its field, indicates the future potential of carbon supported catalysts during hydroprocessing, particularly in deep hydrodesulfurization and hydrodemetallization.
Chemical mapping of chemical conversion in heterogeneous catalytic reactors using MRI
Authors: Gladden Lynn F. , Mantle Michael D. , Sederman Andrew J.
Published: September 2008

Magnetic Resonance Imaging (MRI) is an emerging measurement technique for the study of chemical reactions in situ within reactor environments. Whilst MRI is now well established as a tool to image gas, liquid and even some solids flows in reactors, the ability to perform spatially resolved spectroscopic measurements is still in its infancy. Here we introduce the basic concepts of MRI and then introduce two pulse sequences which are finding increasing use in application to studying catalytic processes. First, we outline the Rapid Acquisition with Relaxation Enhancement (RARE) pulse sequence which provides sub-second image acquisition times thereby enabling unsteady-state processes to be imaged. Second, Single-Point Ramped Imaging with T1-Enhancment (SPRITE) is described; this technique is particularly useful for studying systems characterised by short nuclear spin relaxation times, and has been used to map coke distribution in reactors. The four main strategies for obtaining chemical resolution in MRI data are then outlined, these methods being relaxation time contrast, chemical shift imaging, volume selective spectroscopy and natural abundance 13C imaging. Examples of all these techniques in application to catalytic systems are given. In particular, the advent of natural abundance 13C imaging is identified as a method which may open up substantial opportunities for chemical mapping of a wide range of heterogeneous catalytic conversions in the reactor environment.
Signalling cascades integrating light-enhanced nitrate metabolism
Authors: Lillo Cathrine
Published: September 2008

In higher plants, light is crucial for regulation of nitrate uptake, translocation and assimilation into organic compounds. Part of this metabolism is tightly coupled to photosynthesis because the enzymes involved, nitrite reductase and glutamate synthase, are localized to the chloroplasts and receive reducing power from photosynthetic electron transport. However, important enzymes in nitrate acquisition and reduction are localized to cellular compartments other than chloroplasts and are also up-regulated by light, i.e. transporters in cell and organellar membranes and nitrate reductase in the cytosol. This review describes the different light-dependent signalling cascades regulating nitrate metabolism at the transcriptional as well as post-transcriptional level, and how reactions in different compartments of the cell are co-ordinated. Essential players in this network are phytochrome and HY5 (long hypocotyls 5)/HYH (HY5 homologue)-dependent signalling pathways, the energy-related AMPK (AMP-activated protein kinase) protein kinase homologue SNRK1 (sucrose non-fermenting kinase 1-related kinase), chloroplastic thioredoxins and the prokaryotically originated PII protein. A complex light-dependent network of regulation emerges, which appears to be necessary for optimal nitrogen assimilation and for avoiding the accumulation of toxic intermediates and side products, such as nitrite and reactive oxygen compounds.
Diaphragm electromyography using an oesophageal catheter: current concepts
Authors: Luo Yuan Ming , Moxham John , Polkey Michael I.
Published: September 2008

The usefulness of diaphragm electromyography recorded from an oesophageal electrode depends on a reliable signal which is free of artefact. The diaphragm EMG (electromyogram) recorded from chest wall surface electrodes may be unreliable because of signal contamination from muscle activity other than the diaphragm. Initially, the oesophageal electrode catheter for human studies had only one electrode pair, which could be difficult to position accurately and was influenced by a change in lung volume. Recently, a multipair oesophageal electrode has been developed which allows a high-quality EMG to be recorded. In the present review, the progress of oesophageal electrode design is outlined. The effects of signal contamination, electrode movement and particularly the effect of change in lung volume on the diaphragm EMG are discussed. The diaphragm EMG, recorded from a multipair oesophageal electrode, is useful to assess neural respiratory drive and diaphragm function in different groups of patients with respiratory disease, including patients with neuromuscular disease and sleep-disordered breathing, and those in the intensive care unit. When combined with cervical and cranial magnetic stimulation, an oesophageal electrode can be used to partition the central respiratory response time and phrenic nerve conduction time.
Electronic spectra of 7-azaindole/ammonia clusters and their photochemical reactivity
Authors: Koizumi Yuna , Jouvet Christophe , Norihiro Tsuji , Ishiuchi Shun-ichi , Dedonder-Lardeux Claude , Fujii Masaaki
Published: September 2008

The S1-S0 electronic spectra of 7-azaindole-(NH3)n clusters (n=1–3) were measured by mass-selected two-color resonance-enhanced multiphoton ionization spectroscopy. The laser-induced fluorescence spectrum obtained by monitoring the UV fluorescence shows well-structured vibrational bands for the monomer and 7-azaindole-(NH3)1,2 clusters, while no signals appear for the 7-azaindole-(NH3)3 cluster. The action spectrum obtained by monitoring visible emission shows no signal for all species, which suggests little reactivity for excited-state proton/hydrogen transfer. From the observed and calculated IR spectra, the geometry of 7-azaindole-(NH3)1,2 was concluded to be a hydrogen-bonded bridge form, which is similar to the photochemically reactive 7-hydroxyquinoline-(NH3)3 cluster. The difference in the photochemical reactivity is discussed on the basis of excited-state quantum chemical calculations.
Computing the free energy of molecular solids by the Einstein molecule approach: Ices XIII and XIV, hard-dumbbells and a patchy model of proteins
Authors: Noya E. G. , Conde M. M. , Vega C.
Published: September 2008

The recently proposed Einstein molecule approach is extended to compute the free energy of molecular solids. This method is a variant of the Einstein crystal method of Frenkel and Ladd [J. Chem. Phys. 81, 3188 (1984)]. In order to show its applicability, we have computed the free energy of a hard-dumbbell solid, of two recently discovered solid phases of water, namely, ice XIII and ice XIV, where the interactions between water molecules are described by the rigid nonpolarizable TIP4P/2005 model potential, and of several solid phases that are thermodynamically stable for an anisotropic patchy model with octahedral symmetry which mimics proteins. Our calculations show that both the Einstein crystal method and the Einstein molecule approach yield the same results within statistical uncertainty. In addition, we have studied in detail some subtle issues concerning the calculation of the free energy of molecular solids. First, for solids with noncubic symmetry, we have studied the effect of the shape of the simulation box on the free energy. Our results show that the equilibrium shape of the simulation box must be used to compute the free energy in order to avoid the appearance of artificial stress in the system that will result in an increase in the free energy. In complex solids, such as the solid phases of water, another difficulty is related to the choice of the reference structure. As in some cases there is no obvious orientation of the molecules; it is not clear how to generate the reference structure. Our results will show that, as long as the structure is not too far from the equilibrium structure, the calculated free energy is invariant to the reference structure used in the free energy calculations. Finally, the strong size dependence of the free energy of solids is also studied.
Effects of quench rates on the short- and medium-range orders of amorphous silicon carbide: A molecular-dynamics study
Authors: Xue Kun , Niu Li-Sha , Shi Hui-Ji
Published: September 2008

Amorphous silicon carbide (a-SiC) networks generated from melted SiC at various quench rates (from 1014 to 5×1011 K/s) are studied with Tersoff potential based molecular-dynamics simulations. With the decreasing quench rates, dramatic changes are observed in chemical order, as well as in its topological orders over both short and medium ranges. The corresponding modification of topological short-range order is manifested not only by improvement of the characteristic tetrahedral configuration, but also by variation in the spatial distributions of the homonuclear bonds. On the other hand, the corresponding development over medium range gives rise to a more compact and more homogeneous structure. The essential mechanisms determining the atomic arrangements on both length scales are further explored. It is reasonable to argue that chemical order, as a function of the quench rate, should be mainly responsible for the topological features of a-SiC.
Analytical calculations of wake field generated by microwave pulses in a plasma filled waveguide for electron acceleration
Authors: Malik Hitendra K.
Published: September 2008

Analytical expressions are obtained for the longitudinal field (wake field), density perturbation, and the potential behind microwave pulse propagating in a plasma filled rectangular waveguide with the pulse duration half of the electron plasma period. A feasibility study on wake field is carried out with rectangular pulse and its combination with Gaussian and triangular pulses under the effects of microwave pulse parameters and waveguide dimensions. It is inferred that the wake field in the waveguide cannot be attained when the length of rectangular microwave pulse is exactly equal to the plasma wavelength. A 1 ns short rectangular pulse with intensity of 250 kW/cm2 at the frequency of 5.03 GHz can excite the wake field of 1.0 MV/m in a waveguide with width of 6 cm and height of 4 cm. However, enhanced field is obtained when rectangular-triangular pulse (combination of rectangular and triangular pulses) is used. The field of wake gets weakened at higher microwave frequency and larger dimensions of the waveguide for other fixed parameters. However, a larger field is achieved when the pulse length of the microwave pulses is made shorter and/or intensity of the pulses is increased. A comparative study of the pulses shows that better results can be obtained with rectangular pulse (rectangular-Gaussian pulse: combination of rectangular and Gaussian pulses) if the microwave of shorter pulse duration (higher intensity) is available.
Time-resolved thermal mirror method: A theoretical study
Authors: Sato F. , Malacarne L. C. , Pedreira P. R. B. , Belancon M. P. , Mendes R. S. , Baesso M. L. , Astrath N. G. C. , Shen J.
Published: September 2008

A general and complete theoretical model of the time-resolved thermal mirror method for the measurement of thermo-optical-mechanical properties of solid materials is developed. The laser-induced temperature profile in a sample and its thermoelastic surface displacement are derived. The center intensity of a probe beam at the detector plane is calculated using the Fresnel diffraction theory. Additionally, simplified models for high and low optical absorption samples are presented, and the suitability of the simplified models is also analyzed. The influence of experimental parameters on the sensitivity of the thermal mirror method is discussed for the optimization of the experimental apparatus. The presented model and the experimental technique can be used to quantitatively determine the physical properties of transparent and opaque solids.
Core-level electronic structure of solid-phase glycine, glycyl-glycine, diglycyl-glycine, and polyglycine: X-ray photoemission analysis and Hartree–Fock calculations of their zwitterions
Authors: Chatterjee Avisek , Zhao Liyan , Zhang Lei , Pradhan Debabrata , Zhou Xiaojing , Leung K. T.
Published: September 2008

X-ray photoelectron spectroscopy (XPS) has been used to investigate the core-level electronic structures of glycine (G) and its peptides, including glycyl-glycine (GG), diglycyl-glycine (GGG), and polyglycine (poly-G), in their powder forms. Increasing the number of G units in the peptides does not change the locations of the respective C 1s, N 1s, and O 1s features corresponding to different functional groups: –COO−, –NH3+, >CH2, and –CONH–. The electronic structures of the zwitterions of these molecules have been calculated as isolated molecules and as molecules in an aqueous environment under the periodic boundary conditions by quantum-mechanical and molecular mechanics methods. In the case of glycine zwitterion, the binding energies of the C 1s, N 1s, and O 1s XPS features are found to be in reasonable accord with the respective orbital energies obtained by Hartree–Fock self-consistent-field calculations, within the context of Koopmans’ approximation. However, considerably worse agreement in the binding energies is found for the larger zwitterions (with the specific conformations considered in this work), indicating the need for higher-level calculations. The present work shows that optimizing the zwitterion in an aqueous environment under the periodic boundary conditions by molecular mechanics could be a very cost-effective approach for calculating the electronic structures of large, complex biomolecular systems.
Fully relativistic prolapse-free Gaussian basis sets: The actinides and Tl81–Ra88
Authors: de Macedo Luiz Guilherme M. , Angelotti Wagner F. D. , Sambrano Julio R. , de Souza Aguinaldo R.
Published: September 2008

In this work, four-component prolapse-free Gaussian-type functions (GTFs) suitable for molecular calculations were generated for elements from Tl (Z=81) up to No (Z=102). In order to obtain compact, stable, and reliable basis sets, the absolute values of the energy difference between the Dirac–Fock–Roothan (DFR) total energy E(DFR) and the corresponding numerical values E(NDF) obtained by Visscher and Dyall [At. Data Nucl. Data Tables67, 207 (1997)] are at millihartree order of magnitude and prolapse to be smaller than (or close to) 1mH. The resulting GTFs are the most compact explicit prolapse-free basis sets for these elements.
Surface modification of ZnO film by hydrogen peroxide solution
Authors: Tsai Chia-Hung , Wang Wei-Chin , Jenq Feng-Lin , Liu Chien-Chih , Hung Chen-I , Houng Mau-Phon
Published: September 2008

The effect of hydrogen peroxide (H2O2) treatment on the microstructure and luminescent properties of ZnO thin films has been investigated. Governed by high-resolution transmission electron microscopy and selected-area electron diffraction patterns, the oxygen radicals dissociated from H2O2 solution at room temperature and substantially changed the polycrystalline ZnO film into an insulator. In addition, the photoluminescence spectra showed that H2O2 solution had nearly no effect on the intensity of ultraviolet emission, whereas it significantly enhanced the intensity of deep-level emission. These observations strongly reveal the fact that the oxygen radicals penetrating into a ZnO film are reasonably speculated to occupy the interstitial sites to form oxygen interstitials Oi or fill the Zn vacancies to form antisite oxygen OZn defects. Because of these extra defects involved, an enhancement of the green light luminescence is significantly promoted in our ZnO samples after handling with H2O2 solution. Based on the characteristics mentioned above, our hydrogen peroxide solution treated ZnO film has the potential for applying to the light-emitting diode with metal-insulator-semiconductor structure.
Application of magnetically perturbed time-dependent density functional theory to magnetic circular dichroism. III. Temperature-dependent magnetic circular dichroism induced by spin-orbit coupling
Authors: Seth Michael , Ziegler Tom , Autschbach Jochen
Published: September 2008

A methodology for calculating the temperature-dependent magnetic circular dichroism (MCD) of open-shell molecules with time-dependent density functional theory (TDDFT) is described. The equations for the MCD of an open-shell molecule including spin-orbit coupling in the low- and high-temperature limits are reviewed. Two effects lead to the temperature-dependent MCD: the breaking of degeneracies and the perturbation of transition dipoles by spin-orbit coupling. The equations necessary to evaluate the required terms using TDDFT-derived quantities are presented. The performance of the formalism is demonstrated through application to the MCD of several molecules. The spectra of these molecules have differing properties with respect to bandwidth, temperature dependence of the MCD, and relative magnitude of the temperature-dependent and temperature-independent components of the MCD. The important features of the experimental spectra are reproduced by the calculations.
Pulse compression approach to infrared nondestructive characterization
Authors: Mulaveesala Ravibabu , Vaddi Jyani Somayajulu , Singh Pushpraj
Published: September 2008

Infrared thermography is a whole field, noncontact, and nondestructive characterization technique widely used for the investigation of subsurface features in various solid materials (conductors, semiconductors, and composites). Increased demand for greater subsurface probing in thermal nondestructive testing is often thwarted by the probing high peak power into the sample, for which narrow pulse operation is usually used. The technique of pulse compression offers a means of increasing the average power available to illuminate test specimen without any loss of the depth resolution needed for the tactical requirements. This is accomplished by transmitting a wide pulse in which the incident heat flux is frequency modulated and then, by proper signal processing methods, causing a time compression of the received signal to a much narrower pulse of high effective peak power. For the demonstration, a mild steel sample having flat bottom holes at various depths is introduced and detection capability of the proposed approach has been studied.
Theory of coherent resonance energy transfer
Authors: Jang Seogjoo , Cheng Yuan-Chung , Reichman David R. , Eaves Joel D.
Published: September 2008

A theory of coherent resonance energy transfer is developed combining the polaron transformation and a time-local quantum master equation formulation, which is valid for arbitrary spectral densities including common modes. The theory contains inhomogeneous terms accounting for nonequilibrium initial preparation effects and elucidates how quantum coherence and nonequilibrium effects manifest themselves in the coherent energy transfer dynamics beyond the weak resonance coupling limit of the Förster and Dexter (FD) theory. Numerical tests show that quantum coherence can cause significant changes in steady state donor/acceptor populations from those predicted by the FD theory and illustrate delicate cooperation of nonequilibrium and quantum coherence effects on the transient population dynamics.
Collisional energy transfer in two-component plasmas
Authors: Vranjes J. , Kono M. , Poedts S. , Tanaka M. Y.
Published: September 2008

The friction in plasmas consisting of two species with different temperatures is discussed together with the consequent energy transfer. It is shown that the friction between the two species has no effect on the ion acoustic mode in a quasineutral plasma. Using the Poisson equation instead of the quasineutrality reveals the possibility for an instability driven by the collisional energy transfer. However, the different starting temperatures of the two species imply an evolving background. It is shown that the relaxation time of the background electron-ion plasma is, in fact, always shorter than the growth rate time. Therefore the instability is unlikely to develop. The results obtained here should contribute to the definite clarification of some contradictory results obtained in the past.
Comment on “Method to analyze electromechanical stability of dielectric elastomers”[Appl. Phys. Lett. 91, 061921 (2007)]
Authors: Liu Yanju , Liu Liwu , Zhang Zhen , Shi Liang , Leng Jinsong
Published: September 2008

We would like to thank Zhao and Suo [Appl. Phys. Lett. 91, 061921 (2007)] for their insights and help on “Method to analyze electromechanical stability of dielectric elastomers;” Suo provided the theory of stability of dielectric elastomers. In this Comment, the nonlinear electromechanical theory for deformable dielectrics described in Suo’s paper is applied to analyze the stability of dielectric elastomers. Different from that given in Suo’s paper, in the current work, elastic strain energy functional with two material constants is used for the stability analysis. Dielectric materials with different values of k are analyzed, and the results seem to support Suo’s theory. These results can be applied in the design of dielectric elastomer actuator and in larger application spectrum.
Noise analysis and sensitivity enhancement in immunomagnetic nanomechanical biosensors
Authors: Icoz Kutay , Iverson Brian D. , Savran Cagri
Published: September 2008

We report noise and detection limitations in cantilever-based immunomagnetic biosensors. A differential cantilever system with sensing and control arms was used whereby the control arm was passivated with bovine serum albumin (BSA) and the sensing arm was functionalized with biotin-BSA. Streptavidin-coated magnetic beads were exposed to cantilever arms. An oscillatory magnetic field induced a magnetic force on the beads which caused a relative deflection of the sensing arm. Increasing the excitation frequency suppressed the 1∕f noise by 100-fold, resulting in a deflection resolution of 0.065Å in air.
Strain engineered Si∕SiGe resonant interband tunneling diodes with outside barriers grown on Si0.8Ge0.2 virtual substrates
Authors: Anisha R. , Jin Niu , Chung Sung-Yong , Yu Ronghua , Berger Paul R. , Thompson Phillip E.
Published: September 2008

Si-based resonant interband tunneling diodes (RITDs) grown on commercially available Si0.8Ge0.2 virtual substrates were studied. Peak-to-valley current ratios (PVCRs) were improved by utilizing strain induced band offsets to 3.5 with a peak current density (Jp) of 161A∕cm2. More specifically, a tensilely strained Si layer on the p-side and a compressively strained Si0.5Ge0.5 layer on the n-side were added to the design to form enhanced potential barriers away from the tunneling junction. The outside barriers deepen the respective hole and electron quantum wells and also block nonresonant tunneling current, which improved the PVCR significantly. However, due to the large surface roughness of the SiGe virtual substrates used in this study, the RITDs grown on Si0.8Ge0.2 substrates exhibit a smaller PVCR overall than RITDs optimized on standard Si substrates. Better performance is expected by using higher quality SiGe substrates with smaller surface roughness.
Quantification of porosity and deposition rate of nanoporous films grown by oblique-angle deposition
Authors: Poxson D. J. , Mont F. W. , Schubert M. F. , Kim J. K. , Schubert E. F.
Published: September 2008

We propose an analytic model that accurately predicts the porosity and deposition rate of nanoporous films grown by oblique-angle deposition. The model employs a single fitting parameter and takes into account geometrical factors as well as surface diffusion. We have determined the porosity and deposition rate from the measured refractive index and thickness of SiO2 and indium tin oxide nanoporous films deposited at various incident angles. Comparison of experimental data with the model reveals excellent agreement. The theoretical model allows for the predictive control of refractive index, porosity, and deposition rate for a wide range of deposition angles and materials.