bluuebunny/crossref_metadata_2025 huggingface dataset:
Statistical inference for ratiometric imaging of excitable cells: a self‐organizing state‐space model
Authors: Iwahashi Ryouhei , Tateno Takashi
Published: November 2012

Concentrations of free intracellular calcium ions ([Ca2+]i) in excitable cells are often measured using indicator dyes, such as fura‐2. Of note, however, these indicator dyes are divalent metal ion chelators that affect intrinsic changes in [Ca2+]i. To examine whether indicator dyes alter calcium signaling, we estimated [Ca2+]i using a novel statistical inference method that examines fluorescence signals and the calcium current through the cell membrane. We first constructed a model of transient [Ca2+]i, which was then translated into a state‐space model with such state variables as [Ca2+]i, endogenous calcium buffer, and calcium indicators. Then, a self‐organizing state‐space model was defined by augmenting a state vector with unknown parameters from the original state‐space model. In the model, some unknown parameters were estimated with the original state vector. Next, we used a recursive Bayesian estimation to obtain a set of state vectors and the unknown parameters associated with a set of observation vectors. To calculate the recursive Bayesian estimation, we used a sequential Monte Carlo method, which is referred to as a particle filter method. To verify the effectiveness of the proposed method, we carried out experiments with a set of test data from a model with known parameters. The results show that our proposed method properly estimated the temporal profiles of [Ca2+]i, the indicator dye concentration, and certain model parameters in a noisy environment. © 2012 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.
The Protonation of Acetamide and Thioacetamide in Super­acidic Solutions: Crystal Structures of [H3CC(OH)NH2]+AsF6– and [H3CC(SH)NH2]+AsF6–
Authors: Axhausen Joachim , Ritter Cornelia , Lux Karin , Kornath Andreas
Published: November 2012

Acetamide and thioacetamide react with the superacid solutions HF/MF5 (M = As, Sb) under formation of the corresponding salts [H3CC(OH)NH2]+MF6– and [H3CC(SH)NH2]+MF6– (M = As, Sb), respectively. The reaction of DF/AsF5 with acetamide and thioacetamide lead to the corresponding deuterated salts [H3CC(OD)ND2]+AsF6– and [H3CC(SD)ND2]+AsF6–, respectively. The salts are characterized by vibrational and NMR spectroscopy, and in the case of [H3CC(OH)NH2]+AsF6– and [H3CC(SH)NH2]+AsF6– also by single‐crystal X‐ray analyses. The [H3CC(OH)NH2]+AsF6– (1) salt crystallizes in the triclinic space group P$\bar{1}$ with two formula units per unit cell, and the [H3CC(SH)NH2]+AsF6– (2) salt crystallizes in the monoclinic space group P21/c with four formula units per unit cell. In both crystal structures three‐dimensional networks are observed which are formed by intra‐ and intermolecular N–H···F and O–H···F or S–H···F hydrogen bonds, respectively. For the vibrational analyses, quantum chemically calculated spectra of the cations [H3CC(OH)NH2·3HF]+ and [H3CC(SH)NH2·2HF]+ are considered.
Probing the charged Higgs boson at the LHC in the CP-violating type-II 2HDM
Authors: Basso L. , Lipniacka A. , Mahmoudi F. , Moretti S. , Osland P. , Pruna G. M. , Purmohammadi M.
Published: November 2012

Abstract

We present a phenomenological study of a CP-violating two-Higgs-doublet Model with type-II Yukawa couplings at the Large Hadron Collider (LHC). In the light of recent LHC data, we focus on the parameter space that survives the current and past experimental constraints as well as theoretical bounds on the model. Once the phenomeno-logical scenario is set, we analyse the scope of the LHC in exploring this model through the discovery of a charged Higgs boson produced in association with a W boson, with the former decaying into the lightest neutral Higgs and a second W state, altogether yielding a
$ b\bar{b}{W^{+}}{W^{-}} $
signature, of which we exploit the W
+
W
− semileptonic decays.
From black holes to quivers
Authors: Manschot Jan , Pioline Boris , Sen Ashoke
Published: November 2012

Abstract

Middle cohomology states on the Higgs branch of supersymmetric quiver quantum mechanics — also known as pure Higgs states — have recently emerged as possible microscopic candidates for single-centered black hole micro-states, as they carry zero angular momentum and appear to be robust under wall-crossing. Using the connection between quiver quantum mechanics on the Coulomb branch and the quantum mechanics of multi-centered black holes, we propose a general algorithm for reconstructing the full moduli-dependent cohomology of the moduli space of an arbitrary quiver, in terms of the BPS invariants of the pure Higgs states. We analyze many examples of quivers with loops, including all cyclic Abelian quivers and several examples with two loops or non-Abelian gauge groups, and provide supporting evidence for this proposal. We also develop methods to count pure Higgs states directly.
Returns on Lifetime Investments in Children in Egypt
Authors: Cunningham Solveig A. , Yount Kathryn M. , Engelman Michal , Agree Emily
Published: November 2012

Parental expectations about the companionship and assistance they will receive in later life from their children are key considerations in family formation decisions. We explore patterns of parents’ investment and the support and contact they receive from adult children in Egypt, where fertility is falling and sources of support at all life stages are in flux. Using data from a survey of older adults in Ismailia governorate, we consider parents’ past investments in childbearing, child survival, and children’s education and marriage, as well as recent assistance to adult children via housing, care for grandchildren, gifts, and money. The returns from children considered include economic assistance, instrumental support, and visits. Most parental investments are associated with frequent visits from children. The assistance children provide to parents is gendered: sons tend to provide economic transfers, whereas daughters tend to provide instrumental help. A greater number of surviving children is most strongly associated with parents’ receipt of multiple types of later-life returns. Investments in children’s education and marriage are not associated with assistance, but recent assistance to children—especially economic transfers and provision of housing—is associated with receiving instrumental assistance from adult children.
The Hague Convention: Who is Protecting the Child?
Authors: Tetley Carmen
Published: November 2012

The Hague Convention of 25 October 1980 on the Civil Aspects of International Child Abduction is a multilateral treaty that seeks to protect children from the harmful effects of abduction and retention across international boundaries by providing a procedure to bring about their prompt return. The ‘Child Abduction Section’ provides information about the operation of the Convention and the work of the Hague Conference in monitoring its implementation and promoting international co-operation in the area of child abduction. There are currently 58 member countries and 22 non-member countries. Australia signed the Convention five years after its introduction. The Family Law (Child Abduction) Regulations 1986 enshrined in Australian law the principles espoused in the Convention which came into force in 1987. The Regulations are to:

(a)

secure the prompt return of children wrongfully removed to or retained in any contracting state, and

(b)

ensure that rights of custody and access under the law of one contracting state are effectively respected in the other contracting states.

This paper shows that the failure of Family Courts to take account of the effects of their actions on the development and best interests of children whose return is secured can add to the psychological abuse of those who were removed from their home countries to avoid sexual abuse and violence. It suggests that the exceptions in the regulations that allow a child to remain in the new country with the primary caregiver are being ignored.
Family, Courts and Media Discourses: The Contested Spaces of Time, and the Politics of the Protection of Children
Authors: Schulz Pamela D.
Published: November 2012

This article, which is built on media discourse analysis, provides an insight into how public opinion on the work of courts has developed into a discourse of disapproval. The discourse of time is often used to evaluate the work of courts and tends to meet with disapproval when related to sentencing and when the Family Court fails to deliver equal parental access to children. The Family Court is also the subject of discourses of fear within the media, with stories often focusing on child abuse and horror stories of neglect designed to attract and recruit an audience to media outlets. In addition, the discourses facing the Family Court are now firmly tied to time as a major aspect of decision-making. Because of this contested view, child protection may be reduced to a secondary perspective. This paper recommends a change to discourses surrounding courts by all parties in order to facilitate better understanding.
‘It's Quite a Journey’: Australian Parents’ Experience of Adopting Older Children from Overseas Orphanages
Authors: Alessia Kate , Roufeil Louise
Published: November 2012

Intercountry adoption, often of children post-infancy, is one way of forming a family in Australia. However, few studies have invited Australian parents who have incorporated older children into their family to tell their story. Fathers are under-represented in studies of parenting generally and adoptive parenting specifically.

As part requirement for a clinical psychology dissertation, with ethics approval from the relevant university, 28 parents (13 fathers and 15 mothers) were interviewed about their experiences of adopting children over the age of 24 months from orphanages in China, Ethiopia, India and Thailand. Although parents’ experiences and recollections were diverse, almost all parents had been confronted by difficult child behaviours, at least initially. Contrary to previous research, the child's gender, age or duration of institutional care did not appear related to parental experience.

Six major themes emerged from parent interviews: (1) the long wait and intense emotions of adoption; (2) disparity between expectations and reality; (3) recognition of children's difficult past experiences; (4) parenting as a path to self-discovery; (5) the perception of needing to present as coping; and (6) unmet needs. Mothers blamed themselves for their children's behavioural problems, rather than attributing difficulties to children's previous adverse life events. Both mothers and fathers were reluctant to use support services because they felt scrutinised and feared repercussions, and those who sought assistance generally found professionals ill-informed and unhelpful. Parents made recommendations about how the adoptive parenting process could be improved and expressed a strong desire for more information, both pre- and post-placement.
Father Absence: Exploring the Experiences of Young People in Regional Western Australia
Authors: Kostos Janette , Flynn Catherine
Published: November 2012

This article describes the experiences of four young people aged 18 to 25 years whose fathers were absent during their adolescent years. The study, located in regional Western Australia, sought to investigate how young people experience father absence, their needs and preferences in regard to any help seeking, and their evaluation of the effectiveness of supports used. Participants were found to share a combination of risk factors which were linked to negative psychosocial outcomes. Problems identified by young people included no one to talk to about problems and a lack of available services. Participants disclosed involvement in substance use, school misconduct and anti-social behaviour, and all reported early home leaving. Male and female participants reported using similar coping styles and a hierarchy of preference in help-seeking was found with friends and family preferred over counselling. Counselling was considered helpful when offered online or via drop-in services not requiring an appointment. Ethical constraints, however, were found to limit young people's participation in research.
Temporal variation of Mexiconema cichlasomae (Nematoda: Daniconematidae) in the Mayan cichlid fish Cichlasoma urophthalmus and its intermediate host Argulus yucatanus from a tropical coastal lagoon
Authors: MAY-TEC A. L. , PECH D. , AGUIRRE-MACEDO M. L. , LEWIS J. W. , VIDAL-MARTÍNEZ V. M.
Published: November 2012

The aim of the present investigation was to determine whether temporal variation in environmental factors such as rainfall or temperature influence long-term fluctuations in the prevalence and mean abundance of the nematode Mexiconema cichlasomae in the cichlid fish Cichlasoma uropthalmus and its crustacean intermediate host, Argulus yucatanus. The study was undertaken in a tropical coastal lagoon in the Yucatan Peninsula (south-eastern Mexico) over an 8-year period. Variations in temperature, rainfall and monthly infection levels for both hosts were analysed using time series and cross-correlations to detect possible recurrent patterns. Infections of M. cichlasomae in A. yucatanus showed annual peaks, while in C. urophthalmus peaks were bi-annual. The latter appear to be related to the accumulation of several generations of this nematode in C. urophthalmus. Rainfall and temperature appear to be key environmental factors in influencing temporal variation in the infection of M. cichlasomae over periods longer than a year together with the accumulation of larval stages throughout time.
Application of an automated ribosomal intergenic spacer analysis database for identification of cultured Antarctic fungi
Authors: Slemmons Caleb , Johnson Gregory , Connell Laurie B.
Published: November 2012

We utilized an automated ribosomal intergenic spacer analysis (ARISA) method as a more rapid alternative to classical morphological/nutritional identification and a less expensive alternative to sequencing for identification and grouping of isolates in culture-based fungal abundance studies. This method is well suited for the study of culturable Antarctic soil fungal communities where both abundance and diversity are relatively low. We optimized template concentration and verified the effect of primer selection from eight commonly used fungal polymerase chain reaction primers on ARISA chromatographs for 46 fungal species commonly isolated from south Victoria Land. A database of Antarctic fungal electropherograms was produced containing each of the species and was used as the first step in a tiered system for species identification. In addition, isolates containing more than one species were identified, allowing isolates not in the database to be sequenced for further analysis. This method unambiguously identified 78% of the fungal taxa in this study and we were able to rapidly determine which isolates should be subjected to further analysis by DNA sequencing. Using this approach, the cost of analysis for abundance studies can be greatly reduced compared to DNA sequencing of each isolate.
Unemployable Workers? Comparing the Context and Contract in Voluntary Work and Regular Jobs
Authors: Andreassen Tone Alm
Published: November 2012

In welfare societies, disability pensions or incapacity benefits provide income security to people who, due to health problems or disability, are assessed as being unemployable. However, it is sometimes possible for people on disability pensions to work, for instance on a voluntary basis in and on behalf of associations of disabled people. This article applies perspectives on employability and discusses whether voluntary workers, like representatives of associations of disabled people, could have been employed in the ordinary labour market or whether there are definite characteristics of voluntary work which allow their capacity for work to be utilised.
Individual Differences in the Behavioral Immune System and the Emergence of Cultural Systems
Authors: Clay Russ , Terrizzi John A. , Shook Natalie J.
Published: November 2012

Cultural variation may be evoked through the interaction between domain-specific psychological mechanisms and environmental conditions (Gangestad, Haselton, & Buss, 2006 ). One such constellation of mechanisms is the behavioral immune system, a cluster of psychological processes evolved to promote disease-avoidance ( Schaller, 2006 ). Previous research demonstrated that higher levels of both historic and contemporary pathogen prevalence are predictive of collectivism across geopolitical regions ( Fincher, Thornhill, Murray, & Schaller, 2008 ). Across two studies, we demonstrate that individual differences in behavioral immune system reactivity (e.g., disgust sensitivity, germ aversion) are associated with variable endorsement of a vertical collectivist cultural orientation and differential value priorities, which are indicative of cultural differences. These findings provide support at an individual level for the proposition of evoked culture.
Statistical characterization of short wind waves from stereo images of the sea surface
Authors: Mironov A. S. , Yurovskaya M. V. , Dulov V. A. , Hauser D. , Guérin C. A.
Published: November 2012

We propose a methodology to extract short‐scale statistical characteristics of the sea surface topography by means of stereo image reconstruction. The possibilities and limitations of the technique are discussed and tested on a data set acquired from an oceanographic platform at the Black Sea. A validation is made with simultaneous in situ measurements as well as results from the literature. We show that one‐ and two‐point properties of the short‐scale roughness can be well estimated without resorting to an interpolation procedure or an underlying surface model. We obtain the first cumulants of the probability distribution of small‐scale elevations and slopes as well as related structure functions. We derive an empirical parametrization for the skewness function that is of primary importance in analytical scattering models from the sea surface.
Application of a roughness‐length representation to parameterize energy loss in 3‐D numerical simulations of large rivers
Authors: Sandbach S. D. , Lane S. N. , Hardy R. J. , Amsler M. L. , Ashworth P. J. , Best J. L. , Nicholas A. P. , Orfeo O. , Parsons D. R. , Reesink A. J. H. , Szupiany R. N.
Published: November 2012

Recent technological advances in remote sensing have enabled investigation of the morphodynamics and hydrodynamics of large rivers. However, measuring topography and flow in these very large rivers is time consuming and thus often constrains the spatial resolution and reach‐length scales that can be monitored. Similar constraints exist for computational fluid dynamics (CFD) studies of large rivers, requiring maximization of mesh‐ or grid‐cell dimensions and implying a reduction in the representation of bedform‐roughness elements that are of the order of a model grid cell or less, even if they are represented in available topographic data. These “subgrid” elements must be parameterized, and this paper applies and considers the impact of roughness‐length treatments that include the effect of bed roughness due to “unmeasured” topography. CFD predictions were found to be sensitive to the roughness‐length specification. Model optimization was based on acoustic Doppler current profiler measurements and estimates of the water surface slope for a variety of roughness lengths. This proved difficult as the metrics used to assess optimal model performance diverged due to the effects of large bedforms that are not well parameterized in roughness‐length treatments. However, the general spatial flow patterns are effectively predicted by the model. Changes in roughness length were shown to have a major impact upon flow routing at the channel scale. The results also indicate an absence of secondary flow circulation cells in the reached studied, and suggest simpler two‐dimensional models may have great utility in the investigation of flow within large rivers.
Angular anisotropy of satellite observations of land surface temperature
Authors: Vinnikov Konstantin Y. , Yu Yunyue , Goldberg Mitchell D. , Tarpley Dan , Romanov Peter , Laszlo Istvan , Chen Ming
Published: November 2012

Satellite‐based time series of land surface temperature (LST) have the potential to be an important tool to diagnose climate changes of the past several decades. Production of such a time series requires addressing several issues with using asynchronous satellite observations, including the diurnal cycle, clouds, and angular anisotropy. Here we evaluate the angular anisotropy of LST using one full year of simultaneous observations by two Geostationary Operational Environment Satellites, GOES‐EAST and GOES‐WEST, at the locations of five surface radiation (SURFRAD) stations. We develop a technique to convert directionally observed LST into direction‐independent equivalent physical temperature of the land surface. The anisotropy model consists of an isotropic kernel, an emissivity kernel (LST dependence on viewing angle), and a solar kernel (effect of directional inhomogeneity of observed temperature). Application of this model reduces differences of LST observed from two satellites and between the satellites and surface ground truth ‐ SURFRAD station observed LST. The techniques of angular adjustment and temporal interpolation of satellite observed LST open a path for blending together historical, current, and future observations of many geostationary and polar orbiters into a homogeneous multi‐decadal data set for climate change research.
ELF/VLF wave generation from the beating of two HF ionospheric heating sources
Authors: Cohen M. B. , Moore R. C. , Golkowski M. , Lehtinen N. G.
Published: November 2012

It is well established that Extremely Low Frequency (ELF, 0.3–3 kHz) and Very Low Frequency (VLF, 3–30 kHz) radio waves can be generated via modulated High Frequency (HF, 3–10 MHz) heating of the lower ionosphere (60–100 km). The ionospheric absorption of HF power modifies the conductivity of the lower ionosphere, which in the presence of natural currents such as the auroral electrojet, creates an ‘antenna in the sky.’ We utilize a theoretical model of the HF to ELF/VLF conversion and the ELF/VLF propagation, and calculate the amplitudes of the generated ELF/VLF waves when two HF heating waves, separated by the ELF/VLF frequency, are transmitted from two adjacent locations. The resulting ELF/VLF radiation pattern exhibits a strong directional dependence (as much as 15 dB) that depends on the physical spacing of the two HF sources. This beat wave source can produce signals 10–20 dB stronger than those generated using amplitude modulation, particularly for frequencies greater than 5–10 kHz. We evaluate recent suggestions that beating two HF waves generates ELF/VLF waves in the F‐region (>150 km), and conclude that those experimental results may have misinterpreted, and can be explained strictly by the much more well established D region mechanism.
Adiabatic acceleration of suprathermal electrons associated with dipolarization fronts
Authors: Pan Qingjiang , Ashour‐Abdalla Maha , El‐Alaoui Mostafa , Walker Raymond J. , Goldstein Melvyn L.
Published: November 2012

Recent observations in the inner magnetotail have shown rapid and significant flux increases (usually an order of magnitude of increase within seconds) of suprathermal electrons (tens of keV to hundreds of keV) associated with earthward moving dipolarization fronts. To explain where and how these suprathermal electrons are produced during substorm intervals, two types of acceleration models have been suggested by previous studies: acceleration that localizes near the reconnection site and acceleration that occurs during earthward transport. We perform an analytical analysis of adiabatic acceleration to show that the slope of source differential fluxes is critical for understanding adiabatic flux enhancements during earthward transport. Observationally, two earthward propagating dipolarization fronts accompanied by energetic electron flux enhancements observed by the THEMIS spacecraft have been analyzed; in each event the properties of dipolarization fronts in the inner magnetosphere (XGSM ≈ −10RE) were well correlated with those further down the tail (XGSM ≈ −15RE or XGSM ≈ −20RE). Coupled with theoretical analysis, this enables us to estimate the relative acceleration that occurred as the electrons propagated earthward between the two spacecraft. During the two events studied, the differential fluxes of supra thermal electrons had steep energy spectra with power law indices of −4 to −6.These spectra were much steeper than those at lower energy, as well as those of the supra thermal electrons observed before the fronts arrived. A compression factor of 1.5 as the electrons propagated earthward induced a flux increase of suprathermal electrons by a factor of 7 to 17. Provided these steep spectra, we demonstrate that adiabatic acceleration from the betatron and Fermi mechanisms simultaneously operating can account for these flux increases. Since both analytical analysis and data from the two events show that adiabatic acceleration during earthward transport does not significantly change the power law indices, the steep spectra were likely to be traced back to their source region, presumably near the reconnection site.
Objective calibration of regional climate models
Authors: Bellprat O. , Kotlarski S. , Lüthi D. , Schär C.
Published: November 2012

Climate models are subject to high parametric uncertainty induced by poorly confined model parameters of parameterized physical processes. Uncertain model parameters are typically calibrated in order to increase the agreement of the model with available observations. The common practice is to adjust uncertain model parameters manually, often referred to as expert tuning, which lacks objectivity and transparency in the use of observations. These shortcomings often haze model inter‐comparisons and hinder the implementation of new model parameterizations. Methods which would allow to systematically calibrate model parameters are unfortunately often not applicable to state‐of‐the‐art climate models, due to computational constraints facing the high dimensionality and non‐linearity of the problem. Here we present an approach to objectively calibrate a regional climate model, using reanalysis driven simulations and building upon a quadratic metamodel presented by Neelin et al. (2010) that serves as a computationally cheap surrogate of the model. Five model parameters originating from different parameterizations are selected for the optimization according to their influence on the model performance. The metamodel accurately estimates spatial averages of 2 m temperature, precipitation and total cloud cover, with an uncertainty of similar magnitude as the internal variability of the regional climate model. The non‐linearities of the parameter perturbations are well captured, such that only a limited number of 20–50 simulations are needed to estimate optimal parameter settings. Parameter interactions are small, which allows to further reduce the number of simulations. In comparison to an ensemble of the same model which has undergone expert tuning, the calibration yields similar optimal model configurations, but leading to an additional reduction of the model error. The performance range captured is much wider than sampled with the expert‐tuned ensemble and the presented methodology is effective and objective. It is argued that objective calibration is an attractive tool and could become standard procedure after introducing new model implementations, or after a spatial transfer of a regional climate model. Objective calibration of parameterizations with regional models could also serve as a strategy toward improving parameterization packages of global climate models.
Constraining the influence of natural variability to improve estimates of global aerosol indirect effects in a nudged version of the Community Atmosphere Model 5
Authors: Kooperman Gabriel J. , Pritchard Michael S. , Ghan Steven J. , Wang Minghuai , Somerville Richard C. J. , Russell Lynn M.
Published: November 2012

Natural modes of variability on many timescales influence aerosol particle distributions and cloud properties such that isolating statistically significant differences in cloud radiative forcing due to anthropogenic aerosol perturbations (indirect effects) typically requires integrating over long simulations. For state‐of‐the‐art global climate models (GCM), especially those in which embedded cloud‐resolving models replace conventional statistical parameterizations (i.e., multiscale modeling framework, MMF), the required long integrations can be prohibitively expensive. Here an alternative approach is explored, which implements Newtonian relaxation (nudging) to constrain simulations with both pre‐industrial and present‐day aerosol emissions toward identical meteorological conditions, thus reducing differences in natural variability and dampening feedback responses in order to isolate radiative forcing. Ten‐year GCM simulations with nudging provide a more stable estimate of the global‐annual mean net aerosol indirect radiative forcing than do conventional free‐running simulations. The estimates have mean values and 95% confidence intervals of −1.19 ± 0.02 W/m2 and −1.37 ± 0.13 W/m2for nudged and free‐running simulations, respectively. Nudging also substantially increases the fraction of the world's area in which a statistically significant aerosol indirect effect can be detected (66% and 28% of the Earth's surface for nudged and free‐running simulations, respectively). One‐year MMF simulations with and without nudging provide global‐annual mean net aerosol indirect radiative forcing estimates of −0.81 W/m2 and −0.82 W/m2, respectively. These results compare well with previous estimates from three‐year free‐running MMF simulations (−0.83 W/m2), which showed the aerosol‐cloud relationship to be in better agreement with observations and high‐resolution models than in the results obtained with conventional cloud parameterizations.
Nutrients as the dominant control on the spread of anoxia and euxinia across the Cenomanian‐Turonian oceanic anoxic event (OAE2): Model‐data comparison
Authors: Monteiro F. M. , Pancost R. D. , Ridgwell A. , Donnadieu Y.
Published: November 2012

The Cenomanian‐Turonian oceanic anoxic event (OAE2) is characterized by large perturbations in the oxygen and sulfur cycles of the ocean, potentially resulting from changes in oxygen supply (via oxygen solubility and ocean circulation) and in marine productivity. We assess the relative impact of these mechanisms, comparing model experiments with a new compilation of observations for seafloor dysoxia/anoxia and photic zone euxinia. The model employed is an intermediate‐complexity Earth system model which accounts for the main ocean dynamics and biogeochemistry of the Cretaceous climate. The impact of higher temperature and marine productivity is evaluated in the model as a result of higher atmospheric carbon dioxide and oceanic nutrient concentrations. The model shows that temperature is not alone able to reproduce the observed patterns of oceanic redox changes associated with OAE2. Observations are reproduced in the model mainly via enhanced marine productivity due to higher nutrient content (responsible for 85% of the change). Higher phosphate content could have been sustained by increased chemical weathering and phosphorus regeneration from anoxic sediments, which in turn induced an enhanced nitrogen nutrient content of the ocean via nitrogen fixation. The model also shows that the presence of seafloor anoxia, as suggested by black‐shale deposition in the proto‐North Atlantic Ocean before the event, might be the result of the silled shape and lack of deep‐water formation of this basin at the Late Cretaceous. Overall our model‐data comparison shows that OAE2 anoxia was quasi‐global spreading from 5% of the ocean volume before the event to at least 50% during OAE2.
Paleozoic to early Cenozoic cooling and exhumation of the basement underlying the eastern Puna plateau margin prior to plateau growth
Authors: Insel N. , Grove M. , Haschke M. , Barnes J. B. , Schmitt A. K. , Strecker M. R.
Published: November 2012

Constraining the pre‐Neogene history of the Puna plateau is crucial for establishing the initial conditions that attended the early stage evolution of the southern extent of the Andean plateau. We apply high‐ to low‐temperature thermochronology data from plutonic rocks in northwestern Argentina to quantify the Paleozoic, Mesozoic and early Tertiary cooling history of the Andean crust. U‐Pb crystallization ages of zircons indicate that pluton intrusion occurred during the early mid‐Ordovician (490–470 Ma) and the late Jurassic (160–150 Ma). Lower‐temperature cooling histories from40Ar/39Ar analyses of K‐feldspar vary substantially. Basement rocks underlying the western Puna resided at temperatures below 200°C (<6 km depth) since the Devonian (∼400 Ma). In contrast, basement rocks underlying the southeastern Puna were hotter (∼200–300°C) throughout the Paleozoic and Jurassic and cooled to temperatures of <200°C by ∼120 Ma. The southeastern Puna basement records a rapid cooling phase coeval with active extension of the Cretaceous Salta rift at ∼160–100 Ma that we associate with tectonic faulting and lithospheric thinning. The northeastern Puna experienced protracted cooling until the late Cretaceous with temperatures <200°C during the Paleocene. Higher cooling rates between 78 and 55 Ma are associated with thermal subsidence during the postrift stage of the Salta rift and/or shortening‐related flexural subsidence. Accelerated cooling and deformation during the Eocene was focused within a narrow zone along the eastern Puna/Eastern Cordillera transition that coincides with Paleozoic/Mesozoic structural and thermal boundaries. Our results constrain regional erosion‐induced cooling throughout the Cenozoic to have been less than ∼150°C, which implies total Cenozoic denudation of <6–4 km.
The dynamic action of SecA during the initiation of protein translocation
Authors: Gold Vicki A. M. , Whitehouse Sarah , Robson Alice , Collinson Ian
Published: November 2012

The motor ATPase SecA drives protein secretion through the bacterial Sec complex. The PPXD (pre-protein cross-linking domain) of the enzyme has been observed in different positions, effectively opening and closing a clamp for the polypeptide substrate. We set out to explore the implicated dynamic role of the PPXD in protein translocation by examining the effects of its immobilization, either in the position occupied in SecA alone with the clamp held open or when in complex with SecYEG with the clamp closed. We show that the conformational change from the former to the latter is necessary for high-affinity association with SecYEG and a corresponding activation of ATPase activity, presumably due to the PPXD contacting the NBDs (nucleotide-binding domains). In either state, the immobilization prevents pre-protein transport. However, when the PPXD was attached to an alternative position in the associated SecYEG complex, with the clamp closed, the transport capability was preserved. Therefore large-scale conformational changes of this domain are required for the initiation process, but not for translocation itself. The results allow us to refine a model for protein translocation, in which the mobility of the PPXD facilitates the transfer of pre-protein from SecA to SecYEG.
Invited Article: Attosecond photonics: Synthesis and control of light transients
Authors: Hassan M. Th. , Wirth A. , Grguraš I. , Moulet A. , Luu T. T. , Gagnon J. , Pervak V. , Goulielmakis E.
Published: November 2012

Ultimate control over light entails the capability of crafting its field waveform. Here, we detail the technological advances that have recently permitted the synthesis of light transients confinable to less than a single oscillation of its carrier wave and the precise attosecond tailoring of their fields. Our work opens the door to light field based control of electrons on the atomic, molecular, and mesoscopic scales.
Monitoring the in-situ oxide growth on uranium by ultraviolet-visible reflectance spectroscopy
Authors: Schweke Danielle , Maimon Chen , Chernia Zelig , Livneh Tsachi
Published: November 2012

We demonstrate the in-situ monitoring of oxide growth on U-0.1 wt. % Cr by means of UV-visible reflectance spectroscopy in the thickness range of ∼20-150 nm. Two different approaches are presented: In the “modeling approach,” we employ a model for a metallic substrate covered by a dielectric layer, while taking into account the buildup of oxygen gradient and surface roughness. Then, we fit the simulated spectra to the experimental one. In the “extrema analysis,” we derive an approximated analytical expression, which relates the oxide thickness to the position of the extrema in the reflectance spectra based on the condition for optical interference of the reflected light. Good agreement is found between the values extracted by the two procedures. Activation energy of ∼21 kcal/mole was obtained by monitoring the oxide growth in the temperature range of 22-90 °C. The upper bound for the thickness determination is argued to be mostly dictated by cracking and detachment processes in the formed oxide.
Microstructural evolution of thin film vanadium oxide prepared by pulsed-direct current magnetron sputtering
Authors: Motyka M. A. , Gauntt B. D. , Horn M. W. , Dickey E. C. , Podraza N. J.
Published: November 2012

Vanadium oxide (VOx) thin films have been deposited by pulsed-DC magnetron sputtering using a metallic vanadium target in a reactive argon and oxygen environment. While the process parameters (power, total pressure, oxygen-to-argon ratio) remained constant, the deposition time was varied to produce films between 75 ± 6 and 2901 ± 30 Å thick, which were then optically and electrically characterized. The complex dielectric function spectra (ε = ε1 + iε2) of the films from 0.75 to 5.15 eV were extracted by ex situ, multiple-angle spectroscopic ellipsometry (SE) measurements for the series of varied thickness VOx samples. Significant changes in ε and resistivity occur as a function of thickness, indicating the correlations exist between the electrical and the optical properties over this spectral range. In addition, in situ measurements via real time SE (RTSE) were made on the film grown to the largest thickness to track optical property and structural variations during growth. RTSE was also used to characterize changes in the film occurring after growth was completed, namely during post sputtering in the presence of argon and oxygen while the sample is shielded, and atmospheric exposure. RTSE indicates that the exposure of the film to the argon and oxygen environment, regardless of the shutter isolating the target, causes up to 200 Å of the top surface of the deposited film to become more electrically resistive as evidenced by variations in ε. Exposure of the VOx thin film to atmospheric conditions introduces a similar change in ε, but this change occurs throughout the bulk of the film. A combination of these observations with RTSE results indicates that thinner, less ordered VOx films are more susceptible to drastic changes due to atmospheric exposure and that microstructural variations in this material ultimately control its environmental stability.
Modelling spherical explosions with turbulent mixing and post-detonation
Authors: Saurel Richard , Huber Gregory , Jourdan Georges , Lapébie Emmanuel , Munier Laurent
Published: November 2012

This paper addresses post detonation modelling in spherical explosions. One of the challenges is thus related to compressible turbulent mixing layers modelling. A one-dimensional flow model is derived consisting in a reduced two-phase compressible flow model with velocity drift. To reduce the number of model parameters, the stiff velocity relaxation limit is considered. A semi-discrete analysis is used resulting in a specific artificial viscosity formulation embedded in the diffuse interface model of Kapila et al. [Phys. Fluids 13(10), 3002–3024 (2001)]10.1063/1.1398042. Thanks to the velocity non-equilibrium model and semi discrete formulation, the model fulfils the second law of thermodynamics in the global sense and uses a single parameter. Multidimensional mixing layer effects occurring at gas-gas unstable interfaces are thus summarized as artificial viscosity effects. Model's predictions are compared against experimental measurements of mixing layer growth in shock tubes at moderate initial pressure ratios as well as fireball radius evolutions in air explosions at high initial pressure ratios. Also, pressure signals recorded at various stations are compared, showing excellent agreement for the leading shock wave as well as the secondary one. With the help of various experiments in the low and high initial pressure ratios bounds, estimates for the interpenetration parameter are given.
Distortion of ethyne on formation of a π complex with silver chloride: C2H2⋯Ag–Cl characterised by rotational spectroscopy and ab initio calculations
Authors: Stephens Susanna L. , Mizukami Wataru , Tew David P. , Walker Nicholas R. , Legon Anthony C.
Published: November 2012

C2H2⋯Ag–Cl was formed from ethyne and AgCl in the gas phase and its rotational spectrum observed by both the chirped-pulse and Fabry-Perot cavity versions of Fourier-transform microwave spectroscopy. Reaction of laser-ablated silver metal with CCl4 gave AgCl which then reacted with ethyne to give the complex. Ground-state rotational spectra of the six isotopologues 12C2H2⋯107Ag35Cl, 12C2H2⋯109Ag35Cl, 12C2H2⋯107Ag37Cl, 12C2H2⋯109Ag37Cl, 13C2H2⋯107Ag35Cl, and 13C2H2⋯109Ag35Cl were analysed to yield rotational constants A0, B0, and C0, centrifugal distortion constants ΔJ, ΔJK, and δJ, and Cl nuclear quadrupole coupling constants χaa(Cl) and χbb(Cl) −χcc(Cl). A less complete analysis was possible for 12C2D2⋯107Ag35Cl and 12C2D2⋯109Ag35Cl. Observed principal moments of inertia were interpreted in terms of a planar, T-shaped geometry of C2v symmetry in which the AgCl molecule lies along a C2 axis of ethyne and the Ag atom forms a bond to the midpoint (*) of the ethyne π bond. r0 and $r_{\rm m}^{(1)} $rm(1) geometries and an almost complete rs-geometry were established. The ethyne molecule distorts on complex formation by lengthening of the C≡C bond and movement of the two H atoms away from the C≡C internuclear line and the Ag atom. The $r_{\rm m}^{(1)} $rm(1) bond lengths and angles are as follows: r(*⋯Ag) = 2.1800(3) Å, r(C–C) = 1.2220(20) Å, r(Ag–Cl) = 2.2658(3) Å and the angle H–C≡* has the value 187.79(1)°. Ab initio calculations at the coupled-cluster singles and doubles level of theory with a perturbative treatment of triples (F12*)/cc-pVTZ yield a re geometry in excellent agreement with the experimental $r_{\rm m}^{(1)} $rm(1)version, including the ethyne angular distortion.
Impact ionization and carrier multiplication in graphene
Authors: Pirro Luca , Girdhar Anuj , Leblebici Yusuf , Leburton Jean-Pierre
Published: November 2012

We develop a model for carrier generation by impact ionization in graphene, which shows that this effect is non-negligible because of the vanishing energy gap, even for carrier transport in moderate electric fields. Our theory is applied to graphene field effect transistors for which we parameterize the carrier generation rate obtained previously with the Boltzmann formalism [A. Girdhar and J. Leburton, Appl. Phys. Lett. 99, 229903 (2011)] to include it in a self-consistent scheme and compute the transistor I-V characteristics. Our model shows that the drain current exhibits an “up-kick” at high drain biases, which is consistent with recent experimental data. We also show that carrier generation affects the electric field distribution along the transistor channel, which in turn reduces the carrier velocity.
Fisher information for inverse problems and trace class operators
Authors: Nordebo S. , Gustafsson M. , Khrennikov A. , Nilsson B. , Toft J.
Published: November 2012

This paper provides a mathematical framework for Fisher information analysis for inverse problems based on Gaussian noise on infinite-dimensional Hilbert space. The covariance operator for the Gaussian noise is assumed to be trace class, and the Jacobian of the forward operator Hilbert-Schmidt. We show that the appropriate space for defining the Fisher information is given by the Cameron-Martin space. This is mainly because the range space of the covariance operator always is strictly smaller than the Hilbert space. For the Fisher information to be well-defined, it is furthermore required that the range space of the Jacobian is contained in the Cameron-Martin space. In order for this condition to hold and for the Fisher information to be trace class, a sufficient condition is formulated based on the singular values of the Jacobian as well as of the eigenvalues of the covariance operator, together with some regularity assumptions regarding their relative rate of convergence. An explicit example is given regarding an electromagnetic inverse source problem with “external” spherically isotropic noise, as well as “internal” additive uncorrelated noise.
Driving mechanism of exchange bias and magnetic anisotropy in multiferroic polycrystalline BiFeO3/permalloy bilayers
Authors: Hauguel Tony , Pogossian Souren P. , Dekadjevi David T. , Spenato David , Jay Jean-Philippe , Ben Youssef Jamal
Published: November 2012

Magnetization reversal processes of Permalloy exchange coupled with thin polycrystalline antiferromagnetic multiferroic BiFeO3 films were investigated. The BiFeO3 critical thickness and the interfacial exchange energy are comparable with similar epitaxially grown systems. However, the coercive field dependence on multiferroic thickness presents an atypical behaviour. This system shows induced unidirectional, uniaxial, and biquadratic-like behaviour with misalignment of magnetic easy axis with respect to pinning field direction.
pH controlled staining of CD4+ and CD19+ cells within functionalized microfluidic channel
Authors: Mortato Mariangela , Blasi Laura , Barbarella Giovanna , Argentiere Simona , Gigli Giuseppe
Published: November 2012

Herein proposed is a simple system to realize hands-free labeling and simultaneous detection of two human cell lines within a microfluidic device. This system was realized by novel covalent immobilization of pH-responsive poly(methacrylic acid) microgels onto the inner glass surface of an assembled polydimethylsiloxane/glass microfluidic channel. Afterwards, selected thiophene labeled monoclonal antibodies, specific for recognition of CD4 antigens on T helper/inducer cells and CD19 antigens on B lymphocytes cell lines, were encapsulated in their active state by the immobilized microgels. When the lymphocytes suspension, containing the two target subpopulations, was flowed through the microchannel, the physiological pH of the cellular suspension induced the release of the labeled antibodies from the microgels and thus the selective cellular staining. The selective pH-triggered staining of the CD4- and CD19-positive cells was investigated in this preliminary experimental study by laser scanning confocal microscopy. This approach represents an interesting and versatile tool to realize cellular staining in a defined module of lab-on-a-chip devices for subsequent detection and counting.