bluuebunny/crossref_metadata_2025 huggingface dataset:
The African rain forest – main characteristics of changes in vegetation and climate from the Upper Cretaceous to the Quaternary
Authors: Maley Jean
Published: April 2012

Synopsis

This chapter sets out to give a historical overview of the African rain forest from its origins, towards the end of the Cretaceous period. The areas around the Gulf of Guinea, in particular from Ivory Coast to Nigeria and especially Cameroon, Gabon and Congo, appear to have been already occupied at this time by wet tropical forest formations mainly composed of Angiosperms which were then becoming established. In the course of the Tertiary period the combined effect of the equator being situated further north than now and the development of the Antarctic ice cap favoured the development of wet tropical conditions over a large part of North Africa which in turn led to the extension of tropical forest to various sites on the shores of the Tethys Sea. There were probably at this time common taxa and similar vegetation patterns stretching from the Gulf of Guinea to the Tethys Sea.

Towards the end of the Tertiary, the equator reached its present position and the northern hemisphere ice caps appeared, and these phenomena resulted in the disappearance of the forest formations spread across the north of Africa, and the concentration of these formations near the equatorial zone around the Gulf of Guinea and in the Congo–Zaïre basin. From 800 000 years ago onwards the marked glacial variations at middle and high latitudes in both hemispheres, with a periodicity of about 100 000 years determined by the orbital variations of the earth around the sun, lowered temperatures in equatorial areas and brought arid climates at times of maximum glacial extension. The most arid periods resulted in the fragmentation of the forest cover, and the forest biotopes and their biodiversity were preserved in a series of refugia. The lowering of temperatures also resulted in the extension of montane flora to low altitudes, with migration of montane flora and fauna between main mountain ranges. These compounded phenomena of isolation and migration, probably involving genie exchange, must have resulted in numerous speciation phenomena. Subsequently, such montane flora or fauna became isolated on mountain areas during periods of maximum warming, in the last instance in the course of the Holocene, when a vast forest cover became re-established from Guinea westwards, and to the East as far as the Lake Victoria area. The phases of maximum fragmentation, which appear to have been connected with only the coldest periods – in the last instance during the second part of isotopic stages 6 (fromc.160 to 130 000 years) and 2 (fromc.24 to 12000 years BP) – relate to less than 10% of the last 800 000 years, and the phases of maximum forest extension would likewise appear to be less than 10% of the period. The remaining 80–90% of the time relates to ‘intermediate situations’ which varied from period to period, and these intermediate extension situations seem to have been the norm over the larger part of the Quaternary, rather than the present situation which is closer to a situation of maximum extension.
The Advowson: The History and Development of a Most Peculiar Property
Authors: Smith Peter M.
Published: April 2012

The right of patronage has for many centuries played a most significant role in the life of the English Church. In many ways it is a remarkable concept. What could be more spiritual than the right to present a clerk who is to have the care of the souls of a parish to the bishop for admission and institution? Yet from around the twelfth century this right has been regarded in England as a piece of secular property, and disputes concerning this right cognisable in the common-law courts. Coke tells us that it is an ‘incorporeall inheritance’, or, to use a more modern term, an ‘incorporeal hereditament’, which is real property capable of devolving to heirs on intestacy and yet takes no tangible form: an invisible right which gives substantial power to those who possess it.
Black Sea nitrogen cycling and the preservation of phytoplankton δ15N signals during the Holocene
Authors: Fulton James M. , Arthur Michael A. , Freeman Katherine H.
Published: April 2012

The stable isotopic compositions of bulk, clay‐bound, organic, and compound‐specific nitrogen were determined for mid to late Holocene Black Sea sediments from a set of box and gravity cores. The data demonstrate that cyanobacterial N2fixation provided ∼55% of phytoplankton‐derived N preserved in the top 1–2 cm of the sediments. Prior to widespread agricultural and industrial development in the catchment, N2fixation was more prominent, providing 70–80% of phytoplankton N. Organic and clay‐bound nitrogen fractions record different down‐coreδ15N trends that reflect phytoplankton and detrital sources, respectively, and in samples with low organic matter content, the clay‐bound fraction comprises up to 38% of bulk nitrogen. Compared with bulk samples, pyropheophytina (Pphe a), which is a chlorophyll a (Chl a) degradation product, provides a more accurate record of changing phytoplankton δ15N values during the Holocene. An examination of the δ15NPphe a values in light of published and new estimates of the isotopic difference between biomass and Chl a suggests that most of the preserved Pphe a was derived from eukaryotic algae, not cyanobacteria. We infer from these data that cyanobacterial biomass is rapidly recycled in the photic zone, with 15N‐depleted NH4+ released during heterotrophy and assimilated by other phytoplankton. A conceptual model for N2 fixation in the Black Sea is presented, drawing upon water column nutrient and hydrographic data as well as regional climate variability to explain the proposed temporal variability in N2 fixation.
Novel inversion approach to constrain plume sedimentation from tephra deposit data: Application to the 17 June 1996 eruption of Ruapehu volcano, New Zealand
Authors: Klawonn Malin , Wolfe Cecily J. , Frazer L. Neil , Houghton Bruce F.
Published: April 2012

We introduce a new inversion approach to constrain eruption source parameters and the distribution of tephra sedimentation from a weak plume. Our model is parameterized as a set of point sources along the plume base, whose trajectory is constrained by satellite and photographic images. Each point source releases tephra that is dispersed according to an advection‐diffusion equation. This dispersion process is expressed as a system of linear equations with nonlinear dependence on diffusivity and wind speed. We employ inversion techniques to estimate the tephra mass released by each point source as well as diffusivity, stabilizing the inversion by regularization. We apply our method to the Ruapehu eruption on 17 June, 1996 in New Zealand, which was characterized by a strongly wind‐advected plume that can be studied via tephra isomass measurements and particle size distributions at 119 locations. We demonstrate that the approach is feasible by performing analyses with real and synthetic data at a single grain size, and gain insight into the effects of data gaps, presence of noise, and nonlinear parameters on the inversion results. The best fit value of diffusivity yields tephra fallout that decreases steadily with distance to vent, and the predicted deposit is a good fit to the field measurements. This study illustrates the potential of a direct inversion approach to constrain diffusivity, as well as to recover the tephra fallout, without assuming a physical model for mass transport inside the plume.
Assessing the oceanic control on the amplitude of sea surface cooling induced by tropical cyclones
Authors: Vincent Emmanuel M. , Lengaigne Matthieu , Vialard Jérôme , Madec Gurvan , Jourdain Nicolas C. , Masson Sébastien
Published: April 2012

Tropical cyclones (TCs) induce sea surface cooling that feeds back negatively on their intensity. Previous studies indicate that the cooling magnitude depends on oceanic conditions as well as TC characteristics, but this oceanic control has been poorly documented. We investigate the oceanic influence on TC‐induced cooling using a global ocean model experiment that realistically samples the ocean response to more than 3,000 TCs over the last 30 years. We derive a physically grounded oceanic parameter, the Cooling Inhibition index (CI), which measures the potential energy input required to cool the ocean surface through vertical mixing, and hence accounts for the pre‐storm upper‐ocean stratification resistance to TC‐induced cooling. The atmospheric control is described using the wind power index (WPi), a proxy of the kinetic energy transferred to the ocean by a TC, which accounts for both the effects of maximum winds and translation speed. The cooling amplitude increases almost linearly with WPi. For a given WPi, the cooling amplitude can however vary by an order of magnitude: a strong wind energy input can either result in a 0.5°C or 5°C cooling, depending on oceanic background state. Using an oceanic parameter such as CI in addition to wind energy input improves statistical hindcasts of the cold wake amplitude by ∼40%. Deriving an oceanic parameter based on the potential energy required to cool the ocean surface through vertical mixing is thus a promising way to better account for ocean characteristics in TCs studies.
Precipitating radiation belt electrons and enhancements of mesospheric hydroxyl during 2004–2009
Authors: Andersson Monika E. , Verronen Pekka T. , Wang Shuhui , Rodger Craig J. , Clilverd Mark A. , Carson Bonar R.
Published: April 2012

Energetic particle precipitation leads to enhancement of odd hydrogen (HOx) below 80 km altitude through water cluster ion chemistry. Using measurements from the Microwave Limb Sounder (MLS/Aura) and Medium Energy Proton and Electron Detector (MEPED/POES) between 2004–2009, we study variations of nighttime OH caused by radiation belt electrons at geomagnetic latitudes 55–65°. For those months with daily mean 100–300 keV electron count rate exceeding 150 counts/s in the outer radiation belt, we find a strong correlation (r ≥ 0.6) between OH mixing ratios at 70–78 km (0.046–0.015 hPa) and precipitating electrons. Correlations r ≥ 0.35, corresponding to random chance probability p ≤ 5%, are observed down to52 km (0.681 hPa), while no clear correlation is observed at altitudes below. This suggests that the fluxes of ≥3 MeV electrons were not high enough to cause observable changes in OH mixing ratios. At 75 km, in about 34% of the 65 months analyzed we find a correlation r ≥ 0.35. Although similar results are obtained for both hemispheres in general, in some cases the differences in atmospheric conditions make the OH response more difficult to detect in the South. Considering the latitude extent of electron forcing, we find clear effects on OH at magnetic latitudes 55–72°, while the lower latitudes are influenced much less. Because the time period 2004–2009 analyzed here coincided with an extended solar minimum, and the year 2009 was anomalously quiet, it is reasonable to assume that our results provide a lower‐limit estimation of the importance of energetic electron precipitation at the latitudes considered.
The first cosmic ray albedo proton map of the Moon
Authors: Wilson Jody K. , Spence Harlan E. , Kasper Justin , Golightly Michael , Bern Blake J. , Mazur Joe E. , Townsend Lawrence W. , Case Anthony W. , Dixon Looper Mark , Zeitlin Cary , Schwadron Nathan A.
Published: April 2012

Neutrons emitted from the Moon are produced by the impact of galactic cosmic rays (GCRs) within the regolith. GCRs are high‐energy particles capable of smashing atomic nuclei in the lunar regolith and producing a shower of energetic protons, neutrons and other subatomic particles. Secondary particles that are ejected out of the regolith become “albedo” particles. The neutron albedo has been used to study the hydrogen content of the lunar regolith, which motivates our study of albedo protons. In principle, the albedo protons should vary as a function of the input GCR source and possibly as a result of surface composition and properties. During the LRO mission, the total detection rate of albedo protons between 60 MeV and 150 MeV has been declining since 2009 in parallel with the decline in the galactic cosmic ray flux, which validates the concept of an albedo proton source. On the other hand, the average yield of albedo protons has been increasing as the galactic cosmic ray spectrum has been hardening, consistent with a disproportionately stronger modulation of lower energy GCRs as solar activity increases. We construct the first map of the normalized albedo proton emission rate from the lunar surface to look for any albedo variation that correlates with surface features. The map is consistent with a spatially uniform albedo proton yield to within statistical uncertainties.
New particle formation and growth in biomass burning plumes: An important source of cloud condensation nuclei
Authors: Hennigan Christopher J. , Westervelt Daniel M. , Riipinen Ilona , Engelhart Gabriella J. , Lee Taehyoung , Collett Jeffrey L. , Pandis Spyros N. , Adams Peter J. , Robinson Allen L.
Published: April 2012

Experiments were performed in an environmental chamber to characterize the effects of photo‐chemical aging on biomass burning emissions. Photo‐oxidation of dilute exhaust from combustion of 12 different North American fuels induced significant new particle formation that increased the particle number concentration by a factor of four (median value). The production of secondary organic aerosol caused these new particles to grow rapidly, significantly enhancing cloud condensation nuclei (CCN) concentrations. Using inputs derived from these new data, global model simulations predict that nucleation in photo‐chemically aging fire plumes produces dramatically higher CCN concentrations over widespread areas of the southern hemisphere during the dry, burning season (Sept.–Oct.), improving model predictions of surface CCN concentrations. The annual indirect forcing from CCN resulting from nucleation and growth in biomass burning plumes is predicted to be −0.2 W m−2, demonstrating that this effect has a significant impact on climate that has not been previously considered.
Reactive greenhouse gas scenarios: Systematic exploration of uncertainties and the role of atmospheric chemistry
Authors: Prather Michael J. , Holmes Christopher D. , Hsu Juno
Published: April 2012

Knowledge of the atmospheric chemistry of reactive greenhouse gases is needed to accurately quantify the relationship between human activities and climate, and to incorporate uncertainty in our projections of greenhouse gas abundances. We present a method for estimating the fraction of greenhouse gases attributable to human activities, both currently and for future scenarios. Key variables used to calculate the atmospheric chemistry and budgets of major non‐CO2greenhouse gases are codified along with their uncertainties, and then used to project budgets and abundances under the new climate‐change scenarios. This new approach uses our knowledge of changing abundances and lifetimes to estimate current total anthropogenic emissions, independently and possibly more accurately than inventory‐based scenarios. We derive a present‐day atmospheric lifetime for methane (CH4) of 9.1 ± 0.9 y and anthropogenic emissions of 352 ± 45 Tg/y (64% of total emissions). For N2O, corresponding values are 131 ± 10 y and 6.5 ± 1.3 TgN/y (41% of total); and for HFC‐134a, the lifetime is 14.2 ± 1.5 y.
Tropical cyclone track forecasts using JMA model with ECMWF and JMA initial conditions
Authors: Yamaguchi Munehiko , Nakazawa Tetsuo , Aonashi Kazumasa
Published: April 2012

The JMA's Global Spectral Model (JMA/GSM) was run from the initial conditions of ECMWF, which are available in the YOTC data set, to distinguish between TC track prediction errors attributable to the initial conditions and those attributable to the NWP model. The average position error was reduced by about 10% by replacing the initial conditions, and in some cases, the predictions were significantly improved. In these cases, the low wavenumber component of the ECMWF analysis was found to account for most of the improvement. In addition, the observed tracks were captured by the JMA Typhoon Ensemble Prediction System (TEPS), which deals with initial condition uncertainties. In some cases, however, the replacement of the initial conditions did not improve the prediction even when the ECMWF forecast was accurate. In these cases, TEPS could not capture the observed track either, implying the need for dealing with uncertainties associated with the NWP model.
Moisture flux convergence in regional and global climate models: Implications for droughts in the southwestern United States under climate change
Authors: Gao Yanhong , Leung L. Ruby , Salathé Eric P. , Dominguez Francina , Nijssen Bart , Lettenmaier Dennis P.
Published: April 2012

The water cycle of the southwestern United States (SW) is dominated by winter storms that maintain a positive annual net precipitation. Analysis of the control and future climate from four pairs of regional and global climate models (RCMs and GCMs) shows that the RCMs simulate a higher fraction of transient eddy moisture fluxes because the hydrodynamic instabilities associated with flow over complex terrain are better resolved. Under global warming, this enables the RCMs to capture the response of transient eddies to increased atmospheric stability that allows more moisture to converge on the windward side of the mountains by blocking. As a result, RCMs simulate enhanced transient eddy moisture convergence in the SW compared to GCMs, although both robustly simulate drying due to enhanced moisture divergence by the divergent mean flow in a warmer climate. This enhanced convergence leads to reduced susceptibility to hydrological change in the RCMs compared to GCMs.
Detection of Rossby wave breaking and its response to shifts of the midlatitude jet with climate change
Authors: Barnes Elizabeth A. , Hartmann Dennis L.
Published: April 2012

A Rossby wave breaking identification method is presented which searches for overturning of absolute vorticity contours on pressure surfaces. The results are compared to those from an analysis of isentropic potential vorticity, and it is demonstrated that both yield similar wave breaking distributions. As absolute vorticity is easily obtained from most model output, we present wave breaking frequency distributions from the ERA‐Interim data set, thirteen general circulation models (GCMs) and a barotropic model. We demonstrate that a poleward shift of the Southern Hemisphere midlatitude jet is accompanied by a decrease in poleward wave breaking in both the barotropic model and all GCMs across multiple climate forcing scenarios. In addition, it is shown that while anticyclonic wave breaking shifts poleward with the jet, cyclonic wave breaking shifts less than half as much and reaches a poleward limit near 60 degrees S. Comparison of the observed distribution of Southern Hemisphere wave breaking with those from the GCMs suggests that wave breaking on the poleward flank of the jet has already reached its poleward limit and will likely become less frequent if the jet migrates any further poleward with climate change.
Tracking colloid transport in real pore structures: Comparisons with correlation equations and experimental observations
Authors: Li Zhelong , Zhang Dongxiao , Li Xiqing
Published: April 2012

Accurate prediction of colloid transport in porous media under environmentally relevant conditions requires incorporation of complex pore geometries into particle trajectory simulations. Advances in pore structure characterization and numeric flow simulations have the potential to take real pore geometries into account. In this work, a scheme was developed to extract pore structures (grain radii and center positions) from X‐ray microtomography images of glass beads. Lattice Boltzmann flow simulations were performed to derive flow fields in pore spaces. On the basis of the derived flow fields, particle tracking was carried out in the absence of an energy barrier to deposition and under a wide range of colloid size and flow conditions. Simulated depositions agree reasonably well with predictions by applicable correlation equations and experimental observations at groundwater flow regimes, indicating that the particle tracking algorithm is able to simulate colloid trajectories in porous media with reasonable accuracy in the absence of an energy barrier and may also be able to do so in the presence of an energy barrier (which is more environmentally relevant). The simulated depositions are much greater than both predicted and experimentally observed values at high fluid velocities (>1 × 10−3 m s−1). Simulations under selected unfavorable conditions at groundwater flow regimes indicated that temporary retention of colloids by low‐flow zones in pore spaces could play a predominant role in colloid removal at low ionic strengths. As the ionic strength increases (deposition condition becomes less unfavorable), the contribution of temporary retention to overall removal decreases.
Mitotic spindle orientation can direct cell fate and bias Notch activity in chick neural tube
Authors: Das Raman M , Storey Kate G
Published: April 2012

Inheritance of apical membrane is proposed to maintain vertebrate neural stem cell proliferation. However, evidence for this is contradictory. Using direct clonal analysis and live imaging in chick neural tube, we show that divisions that separate apical and basal components generate an apical daughter, which becomes a neuron, and a basal daughter, which rapidly re‐establishes apico‐basal polarity and divides again. Using a recently described real‐time reporter of Notch activity, we confirm progenitor status and demonstrate that division orientation can influence Notch signalling. In addition, we reveal loss of apical complex proteins on neuronal differentiation onset, suggesting that removal of this inherited complex is part of the neuronal differentiation mechanism. These findings reconcile contradictory data, link asymmetric division to Notch signalling dynamics and identify apical complex loss as a new step towards neuronal differentiation.
Delivering Minocycline into Brain Endothelial Cells with Liposome-Based Technology
Authors: Xing Changhong , Levchenko Tatyana , Guo Shuzhen , Stins Monique , Torchilin Vladimir P , Lo Eng H
Published: April 2012

Minocycline has been proposed as a way to blunt neurovascular injury from matrix metalloproteinases (MMPs) during stroke. However, recent clinical trials suggest that high levels of minocycline may have deleterious side-effects. Here, we showed that very high minocycline concentrations damage endothelial cells via calpain/caspase pathways. To alleviate this potential cytotoxicity, we encapsulated minocycline in liposomes. Low concentrations of minocycline could not reduce tumor necrosis factor α (TNF α)-induced MMP-9 release from endothelial cells. But low concentrations of minocycline-loaded liposomes significantly reduced TNF α-induced MMP-9 release. This study provides proof-of-concept that liposomes may be used to deliver lower levels of minocycline for targeting MMPs in cerebral endothelium.
Detection of Retinal Glial Cell Activation in Glaucoma by Time Domain Optical Coherence Tomography
Authors: Grieshaber M. C. , Moramarco F. , Schoetzau A. , Flammer J. , Orguel S.
Published: April 2012

Background: Activated retinal astrocytes and Müller cells (ARAM) have been found in glaucoma patients. This study investigated whether presumed ARAM can be detected by optical coherence tomography (OCT), and assessed their relationship to the retinal nerve fiber layer (RNFL) thickness.

Patients and Methods: Single-center observational study involving 35 age-matched healthy controls and 19 patients with primary open-angle glaucoma (POAG) between 45 − 82 years of age. Presumed ARAM was defined as patchy, discrete glittering but transparent changes of the macula. The retina was documented by red-free photography to assess distribution of ARAM, and compared to the RNFL thickness measured around the fovea by OCT. A linear mixed effects model was used to detect a difference between eyes with ARAM versus eyes without ARAM.

Results: ARAM was not found in healthy subjects. The mean RNFL around the fovea was not significantly thicker in healthy controls (34.01 SD ± 22.24) than in POAG patients with ARAM (30.86 microns SD ± 15.09; p = 0.36) or without ARAM (33.19 microns SD ± 19.87; p = 0.46). Furthermore, the median RNFL thickness was similar to the control group (29 microns) but slightly thinner in POAG patients (each 27 microns with ARAM and without ARAM). In a subgroup analysis of POAG patients with ARAM, the within subject standard deviation of RNFL was significantly lower in areas with ARAM (SD 10.12) than in areas without ARAM (SD 17.30) (p < 0.001).

Conclusions: Although the mean and median RNFL thickness was comparable between the groups, the variability of the RNFL thickness was significantly lower in areas with ARAM than in areas without ARAM suggesting that ARAM may mask RNFL loss in POAG patients.
Recording of Amplitude-Integrated Electroencephalography, Oxygen Saturation, Pulse Rate, and Cerebral Blood Flow during Massage of Premature Infants
Authors: Rudnicki Jacek , Boberski Marek , Butrymowicz Ewa , Niedbalski Paweł , Ogniewski Paweł , Niedbalski Marek , Niedbalski Zbigniew , Podraza Wojciech , Podraza Hanna
Published: April 2012

Objective Stimulation of the nervous system plays an important role in brain function and psychomotor development of children. Massage can benefit premature infants, but has limitations.

Study Design The authors conducted a study to verify the direct effects of massage on amplitude-integrated electroencephalography (aEEG), oxygen saturation (SaO2), and pulse analyzed by color cerebral function monitor (CCFM) and cerebral blood flow assessed by the Doppler technique.

Results The amplitude of the aEEG trend during massage significantly increased. Massage also impacted the dominant frequency δ waves. Frequency significantly increased during the massage and return to baseline after treatment. SaO2 significantly decreased during massage. In four premature infants, massage was discontinued due to desaturation below 85%. Pulse frequency during the massage decreased but remained within physiological limits of greater than 100 beats per minute in all infants. Doppler flow values in the anterior cerebral artery measured before and after massage did not show statistically significant changes. Resistance index after massage decreased, which might provide greater perfusion of the brain, but this difference was not statistically significant.

Conclusion Use of the CCFM device allows for monitoring of three basic physiologic functions, namely aEEG, SaO2, and pulse, and increases the safety of massage in preterm infants.
The orbital-specific-virtual local coupled cluster singles and doubles method
Authors: Yang Jun , Chan Garnet Kin-Lic , Manby Frederick R. , Schütz Martin , Werner Hans-Joachim
Published: April 2012

We extend the orbital-specific-virtual tensor factorization, introduced for local Møller-Plesset perturbation theory in Ref. [J. Yang, Y. Kurashige, F. R. Manby and G. K. L. Chan, J. Chem. Phys. 134, 044123 (2011)10.1063/1.3528935], to local coupled cluster singles and doubles theory (OSV-LCCSD). The method is implemented by modifying an efficient projected-atomic-orbital local coupled cluster program (PAO-LCCSD) described recently, [H.-J. Werner and M. Schütz, J. Chem. Phys. 135, 144116 (2011)10.1063/1.3641642]. By comparison of both methods we find that the compact representation of the amplitudes in the OSV approach affords various advantages, including smaller computational time requirements (for comparable accuracy), as well as a more systematic control of the error through a single energy threshold. Overall, the OSV-LCCSD approach together with an MP2 correction yields small domain errors in practical calculations. The applicability of the OSV-LCCSD is demonstrated for molecules with up to 73 atoms and realistic basis sets (up to 2334 basis functions).
Impact ionization scattering model based on the random-k approximation for GaAs, InP, InAlAs, and InGaAs
Authors: Dolgos Denis , Schenk Andreas , Witzigmann Bernd
Published: April 2012

The inclusion of momentum conservation and the evaluation of the double Coulomb transition matrix elements render the calculation of the impact ionization scattering rates with first principle approaches computationally expensive and their numerical implementation laborious. Despite the positive assessment of Kane’s random-k approximation, the impact ionization rates and the secondary carrier energies for the III-V semiconductors GaAs, InP, In0.52Al0.48As, and In0.53Ga0.47As have not been provided to the charge transport modeling community in terms of analytical fit functions yet. We provide the impact ionization scattering rates as modified Keldysh formulas and the secondary carrier energies as straight line fits. The band structure computation is based on the empirical pseudopotential method.
Contribution of dislocation dipole structures to the acoustic nonlinearity
Authors: Cash W. D. , Cai W.
Published: April 2012

The ultrasonic nonlinearity created by dislocations in crystals is investigated using two-dimensional dislocation dynamics (DD) simulations. An analytic model of the acoustic nonlinearity parameter, β, of an isolated dislocation dipole is derived using a quasi-static loading assumption. β is predicted to be strongly dependent on the glide stress acting on the dipole, which is not captured by existing models. The technique is extended to an infinite dipole train and an infinite Taylor lattice. β is shown to arise only under the presence of a glide stress. These results contradict the existing model that predicts β of these dipole arrangements to be independent of stress. The analytical models are shown to agree with two-dimensional DD simulations for glide stresses well below the critical stress that causes dissolution of the dipole structure. Several finite sections of the Taylor lattice are modeled with DD and are found to have anomalous scaling behaviors.
Nonadiabatic Ehrenfest molecular dynamics within the projector augmented-wave method
Authors: Ojanperä Ari , Havu Ville , Lehtovaara Lauri , Puska Martti
Published: April 2012

We derive equations for nonadiabatic Ehrenfest molecular dynamics within the projector augmented-wave (PAW) formalism. The discretization of the electrons is time-dependent as the augmentation functions depend on the positions of the nuclei. We describe the implementation of the Ehrenfest molecular dynamics equations within the real-space PAW method. We demonstrate the applicability of our method by studying the vibration of NaCl, the torsional rotation of H2C=\documentclass[12pt]{minimal}\begin{document}${\rm NH}_2^+$\end{document}NH2+ in both the adiabatic and the nonadiabatic regimes, and the hydrogen bombardment of C40H16.
Pico calorimeter for detection of heat produced in an individual brown fat cell
Authors: Inomata Naoki , Toda Masaya , Sato Masaaki , Ishijima Akihiko , Ono Takahito
Published: April 2012

A pico calorimeter with a highly sensitive sensor for detecting heat from a biological cell is developed and evaluated, and also the heat detection of a single brown fat cell has been demonstrated. The measurement principle relies on resonant frequency tracking of a resonator in temperature variation due to the heat from the sample; the resonator is placed in vacuum, and heat is conducted from the sample in the microfluidic channel via a heat guide. This configuration can prevent heat loss from the resonator to the surroundings and damping in water. The heat resolution of the fabricated sensor is 5.2 pJ. Heat emissions from single cells are detected as pulsed or continuous in the absence and presence of stimulation, respectively.
Effect of timing of exposure to vasectomised rams and ewe lamb body condition score on the breeding performance of ewe lambs
Authors: Cave L. M. , Kenyon P. R. , Morris S. T.
Published: April 2012

The aims of this study were to examine the effects of exposing Romney ewe lambs (8–9 months of age) to vasectomised rams across three studies in the February–March period and to determine the influence of body condition score (CS) in two of the studies on their reproductive performance. In all studies, ewe lambs exposed to vasectomised rams had greater (P < 0.05) conception rates to the first 17 days of breeding by 6–12 percentage points. However, Studies 2 and 3 indicated that exposing ewe lambs to vasectomised rams did not increase (P > 0.05) the percentage of ewe lambs conceiving over a 34-day breeding period, nor did it increase the number of fetuses per ewe lamb presented for breeding. The results of Study 1 suggest that there is a limit to how early in the year ewe lambs can be exposed to vasectomised rams. In Study 2, a greater (P < 0.05) percentage of Teased CS 2.0 or 2.5+ ewe lambs conceived during the first 17 days of breeding than those which were Unteased. This effect was not observed (P > 0.05) in CS 1.5 ewe lambs. In Study 3, a greater (P < 0.05) percentage of CS 2.5+ ewe lambs conceived over the 34-day breeding period than ewe lambs of lower CS. In Studies 2 and 3, ewe lambs with a CS of 2.5+ had a greater (P < 0.05) number of fetuses per ewe lamb presented for breeding than CS 1.5 ewe lambs. In conclusion, exposing ewe lambs to vasectomised rams in the late February or March period increased the proportion of ewe lambs successfully bred in the first 17 days of breeding. Further achieving higher CS and heavier liveweights of ewe lambs at breeding should result in improved reproductive performance.
Genetic variation in sulfur, calcium, magnesium, manganese and trace metal content of Merino wool and correlations with brightness, yellowness and photostability
Authors: Hatcher S. , King A. L. , Millington K. R.
Published: April 2012

Genetic parameters (heritability, phenotypic and genetic correlations) were estimated for sulfur (S), calcium (Ca), magnesium (Mg), manganese (Mn) and trace metal content (i.e. Cu, copper; Fe, iron; Zn, zinc) of yearling (11 months, n = 387) and adult (23 months, n = 274) fleeces from the 2007 and 2008 cohorts of Merino progeny (including both ewes and wethers) born into the Sheep CRC Information Nucleus. There was significant genetic variation in S and all metals. Ninety percent of the variation in S and Zn content of yearling wool was genetic, while heritability estimates for the remaining metals were all higher than 0.28 except for Cu (h2 = 0.17 ± 0.11) and Mn (h2 = 0.03 ± 0.12) in yearling fleeces and Cu (h2 = 0.14 ± 0.18) in adult fleeces. Ca and Mg were very highly correlated both phenotypically (0.95 ± 0.01 as yearlings and adults) and genetically (0.95 ± 0.07 as yearlings). There were also strong genetic correlations between yearling and adult Ca and adult Mn (0.85 ± 0.22 and 0.88 ± 0.10), Mg and Mn (0.92 ± 0.10) and between yearling S and adult Zn (0.67 ± 0.22) and adult S and adult Zn (0.60 ± 0.22) suggesting similar genetic mechanisms controlling the biochemical pathways of incorporation of each pair of elements into the fibre. There were significant phenotypic correlations between certain elements and the brightness, yellowness and photostability of wool. Taken together across the yearling and adult measurements, the phenotypic and genetic correlations suggest that wool with higher concentrations of Ca and Mg would tend to be less bright, yellower and less photostable than wool with lower concentrations of these metals. Wool with higher concentrations of Mn would tend to have a similar impact to Ca and Mg on brightness, clean colour and photostability. Fe was also associated with less bright wool, however wool with a high Fe content would tend to be whiter but with a propensity to yellow following UVB exposure.
Engagement of β-arrestin by transactivated insulin-like growth factor receptor is needed for V2 vasopressin receptor-stimulated ERK1/2 activation
Authors: Oligny-Longpré Geneviève , Corbani Maithé , Zhou Joris , Hogue Mireille , Guillon Gilles , Bouvier Michel
Published: April 2012

G protein-coupled receptors (GPCRs) have been shown to activate the mitogen-activated protein kinases, ERK1/2, through both G protein-dependent and -independent mechanisms. Here, we describe a G protein-independent mechanism that unravels an unanticipated role for β-arrestins. Stimulation of the V2 vasopressin receptor (V2R) in cultured cells or in vivo in rat kidney medullar collecting ducts led to the activation of ERK1/2 through the metalloproteinase-mediated shedding of a factor activating the insulin-like growth factor receptor (IGFR). This process was found to be both Src- and β-arrestin–dependent. Whereas Src was found to act upstream of the metalloproteinase activation and be required for the release of the IGFR-activating factor, β-arrestins were found to act downstream of the IGFR transactivation. Unexpectedly, the engagement of β-arrestins by the IGFR but not by the V2R was needed to promote the vasopressin-stimulated ERK1/2 activation, indicating that a pool of β-arrestins distinct from those β-arrestins recruited to the V2R acts downstream of the receptor tyrosine kinase to activate ERK1/2. Such a dual site of action for β-arrestins helps explain the pleiotropic actions of this scaffolding protein. Given the role that V2R-stimulated ERK1/2 plays in kidney cell proliferation, this transactivation mechanism may have important implications for renal pathophysiology. Still, the role of β-arrestins downstream of a transactivation event is not limited to the V2R, because we observed a similar involvement for an unrelated GPCR (the platelet-activating factor receptor), indicating that it may be a general mechanism shared among GPCRs.
Summer temperature variability and long-term survival among elderly people with chronic disease
Authors: Zanobetti Antonella , O'Neill Marie S. , Gronlund Carina J. , Schwartz Joel D.
Published: April 2012

Time series studies show that hot temperatures are associated with increased death rates in the short term. In light of evidence of adaptation to usual temperature but higher deaths at unusual temperatures, a long-term exposure relevant to mortality might be summertime temperature variability, which is expected to increase with climate change. We investigated whether the standard deviation (SD) of summer (June–August) temperatures was associated with survival in four cohorts of persons over age 65 y with predisposing diseases in 135 US cities. Using Medicare data (1985–2006), we constructed cohorts of persons hospitalized with chronic obstructive pulmonary disease, diabetes, congestive heart failure, and myocardial infarction. City-specific yearly summer temperature variance was linked to the individuals during follow-up in each city and was treated as a time-varying exposure. We applied a Cox proportional hazard model for each cohort within each city, adjusting for individual risk factors, wintertime temperature variance, yearly ozone levels, and long-term trends, to estimate the chronic effects on mortality of long-term exposure to summer temperature SD, and then pooled results across cities. Mortality hazard ratios ranged from 1.028 (95% confidence interval, 1.013– 1.042) per 1 °C increase in summer temperature SD for persons with congestive heart failure to 1.040 (95% confidence interval, 1.022–1.059) per 1 °C increase for those with diabetes. Associations were higher in elderly persons and lower in cities with a higher percentage of land with green surface. Our data suggest that long-term increases in temperature variability may increase the risk of mortality in different subgroups of susceptible older populations.
ParA-like protein uses nonspecific chromosomal DNA binding to partition protein complexes
Authors: Roberts Mark A. J. , Wadhams George H. , Hadfield Katie A. , Tickner Susan , Armitage Judith P.
Published: April 2012

Recent data have shown that plasmid partitioning Par-like systems are used by some bacterial cells to control localization of protein complexes. Here we demonstrate that one of these homologs, PpfA, uses nonspecific chromosome binding to separate cytoplasmic clusters of chemotaxis proteins upon division. Using fluorescent microscopy and point mutations, we show dynamic chromosome binding and Walker-type ATPase activity are essential for cluster segregation. The N-terminal domain of a cytoplasmic chemoreceptor encoded next toppfAis also required for segregation, probably functioning as a ParB analog to control PpfA ATPase activity. An orphan ParA involved in segregating protein clusters therefore uses a similar mechanism to plasmid-segregating ParA/B systems and requires a partner protein for function. Given the large number of genomes that encode orphan ParAs, this may be a common mechanism regulating segregation of proteins and protein complexes.
Disruption of the 5-lipoxygenase pathway attenuates atherogenesis consequent to COX-2 deletion in mice
Authors: Yu Zhou , Crichton Irene , Tang Soon Yew , Hui Yiqun , Ricciotti Emanuela , Levin Mark D. , Lawson John A. , Puré Ellen , FitzGerald Garret A.
Published: April 2012

Suppression of cyclooxygenase 2 (COX-2)–derived prostacyclin (PGI
2
) is sufficient to explain most elements of the cardiovascular hazard from nonsteroidal antinflammatory drugs (NSAIDs). However, randomized trials are consistent with the emergence of cardiovascular risk during chronic dosing with NSAIDs. Although deletion of the PGI
2
receptor fosters atherogenesis, the importance of COX-2 during development has constrained the use of conventional knockout (KO) mice to address this question. We developed mice in which COX-2 was deleted postnatally, bypassing cardiorenal defects exhibited by conventional KOs. When crossed into ApoE-deficient hyperlipidemic mice, COX-2 deletion accelerated atherogenesis in both genders, with lesions exhibiting leukocyte infiltration and phenotypic modulation of vascular smooth muscle cells, as reflected by loss of α-smooth muscle cell actin and up-regulation of vascular cell adhesion molecule-1. Stimulated peritoneal macrophages revealed suppression of COX-2–derived prostanoids and augmented 5-lipoxygenase product formation, consistent with COX-2 substrate rediversion. Although deletion of the 5-lipoxygenase activating protein (FLAP) did not influence atherogenesis, it attenuated the proatherogeneic impact of COX-2 deletion in hyperlipidemic mice. Chronic administration of NSAIDs may increasingly confer a cardiovascular hazard on patients at low initial risk. Promotion of atherogenesis by postnatal COX-2 deletion affords a mechanistic explanation for this observation. Coincident inhibition of FLAP may offer an approach to attenuating such a risk from NSAIDs.
Tuning DNA-amphiphile condensate architecture with strongly binding counterions
Authors: Radhakrishnan A. V. , Ghosh S. K. , Pabst G. , Raghunathan V. A. , Sood A. K.
Published: April 2012

Electrostatic self-assembly of colloidal and nanoparticles has attracted a lot of attention in recent years, since it offers the possibility of producing novel crystalline structures that have the potential to be used as advanced materials for photonic and other applications. The stoichiometry of these crystals is not constrained by charge neutrality of the two types of particles due to the presence of counterions, and hence a variety of three-dimensional structures have been observed depending on the relative sizes of the particles and their charge. Here we report structural polymorphism of two-dimensional crystals of oppositely charged linear macroions, namely DNA and self-assembled cylindrical micelles of cationic amphiphiles. Our system differs from those studied earlier in terms of the presence of a strongly binding counterion that competes with DNA to bind to the micelle. The presence of these counterions leads to novel structures of these crystals, such as a square lattice and a

superlattice of an underlying hexagonal lattice, determined from a detailed analysis of the small-angle diffraction data. These lower-dimensional equilibrium systems can play an important role in developing a deeper theoretical understanding of the stability of crystals of oppositely charged particles. Further, it should be possible to use the same design principles to fabricate structures on a longer length-scale by an appropriate choice of the two macroions.
Role of the Bering Strait on the hysteresis of the ocean conveyor belt circulation and glacial climate stability
Authors: Hu Aixue , Meehl Gerald A. , Han Weiqing , Timmermann Axel , Otto-Bliesner Bette , Liu Zhengyu , Washington Warren M. , Large William , Abe-Ouchi Ayako , Kimoto Masahide , Lambeck Kurt , Wu Bingyi
Published: April 2012

Abrupt climate transitions, known as Dansgaard-Oeschger and Heinrich events, occurred frequently during the last glacial period, specifically from 80–11 thousand years before present, but were nearly absent during interglacial periods and the early stages of glacial periods, when major ice-sheets were still forming. Here we show, with a fully coupled state-of-the-art climate model, that closing the Bering Strait and preventing its throughflow between the Pacific and Arctic Oceans during the glacial period can lead to the emergence of stronger hysteresis behavior of the ocean conveyor belt circulation to create conditions that are conducive to triggering abrupt climate transitions. Hence, it is argued that even for greenhouse warming, abrupt climate transitions similar to those in the last glacial time are unlikely to occur as the Bering Strait remains open.
H
2
O
2
activates G protein, α 12 to disrupt the junctional complex and enhance ischemia reperfusion injury
Authors: Yu Wanfeng , Beaudry Sarah , Negoro Hideyuki , Boucher Ilene , Tran Mei , Kong Tianqing , Denker Bradley M.
Published: April 2012

The epithelial cell tight junction separates apical and basolateral domains and is essential for barrier function. Disruption of the tight junction is a hallmark of epithelial cell damage and can lead to end organ damage including renal failure. Herein, we identify Gα12 activation by H
2
O
2
leading to tight junction disruption and demonstrate a critical role for Gα12 activation during bilateral renal ischemia/reperfusion injury. Madin–Darby canine kidney (MDCK) cells with inducible Gα12 (Gα12-MDCK) and silenced Gα12 (shGα12-MDCK) were subjected to ATP depletion/repletion and H
2
O
2
/catalase as models of tight junction disruption and recovery by monitoring transepithelial resistance. In ATP depleted cells, barrier disruption and recovery was not affected by Gα12, but reassembly was accelerated by Gα12 depletion. In contrast, silencing of Gα12 completely protected cells from H
2
O
2
-stimulated barrier disruption, a response that rapidly occurred in control cells. H
2
O
2
activated Src and Rho, and Src inhibition (by PP2), but not Rho (by Y27632), protected cells from H
2
O
2
-mediated barrier disruption. Immunofluorescent and biochemical analysis showed that H
2
O
2
led to increased tyrosine phosphorylation of numerous proteins and altered membrane localization of tight junction proteins through Gα12/Src signaling pathway. Gα12 and Src were activated in vivo during ischemia/reperfusion injury, and transgenic mice with renal tubular QLα12 (activated mutant) expression were delayed in recovery and showed more extensive injury. Conversely, Gα12 knockout mice were nearly completely protected from ischemia/reperfusion injury. Taken together, these studies reveal that ROS stimulates Gα12 to activate injury pathways and identifies a therapeutic target for ameliorating ROS mediated injury.