bluuebunny/crossref_metadata_2025 huggingface dataset:
Aerosol relationships to warm season clouds and rainfall at monthly scales over east China: Urban land versus ocean
Authors: Jin Menglin , Shepherd J. Marshall
Published: December 2008

This paper provides a prototype study on combining the advanced satellite observations of rainfall, clouds, and aerosols to examine their interrelationships. Monthly satellite observations from the Tropical Rainfall Measuring Mission (TRMM) and Moderate Resolution Imaging Spectroradiometer (MODIS) for July (2000–2005) were analyzed to assess how urban aerosols affect cloud droplet size and cumulative rainfall over the eastern China mainland and the China Sea, respectively. It seems that aerosol effects may be more evident on clouds than on convective rainfall: high correlation coefficients between aerosol optical thickness (AOT) and water cloud droplet size are observed, while only a weak aerosol‐rainfall relationship is detectable during light rainfall cases (i.e., rainfall rate < 2.5 mm/d) and that is most likely for warm rain clouds only. In addition, aerosols affect clouds more significantly over ocean than over land. Over the ocean, at the monthly scale, the aerosol‐cloud relationship is evident: the cloud effective radius decreases as aerosol optical thickness (AOT) increases. However, over land, cloud effective radius does not show an apparent relationship with aerosol processes, which indicates that aerosols are not the only physical process affecting clouds. Dynamic processes related to factors like urban land cover may play at least an equally critical role in cloud formation.
Plume‐in‐grid modeling of atmospheric mercury
Authors: Vijayaraghavan Krish , Karamchandani Prakash , Seigneur Christian , Balmori Rochelle , Chen Shu‐Yun
Published: December 2008

An existing plume‐in‐grid model for ozone and particulate matter, which provides an explicit treatment of stack plumes embedded within a three‐dimensional grid‐based Eulerian air quality model, is extended to include a comprehensive treatment of mercury (Hg) processes. The model is applied to the continental United States to investigate the subgrid‐scale effects associated with Hg emissions from large elevated point sources on atmospheric Hg concentrations and deposition. The top thirty Hg‐emitting power plants in the U.S. were selected for explicit plume‐in‐grid treatment. Two new processes are included in the Hg chemical mechanism: the gas‐phase adsorption of reactive gaseous mercury (RGM) on atmospheric particulate matter and the reduction of RGM to elemental Hg by sulfur dioxide. The plume‐in‐grid treatment results in improved performance for Hg wet deposition over a purely Eulerian grid‐based model, partial correction of overpredictions of wet deposition downwind of coal‐fired power plants in the northeastern U.S., and decreases of approximately 10% in simulated dry and wet deposition over large parts of the eastern U.S., with larger decreases near the plants selected for plume‐in‐grid treatment. On average, 23% of ambient RGM is modeled to adsorb on atmospheric particulate matter.
First observations of SO2 above Venus' clouds by means of Solar Occultation in the Infrared
Authors: Belyaev D. , Korablev O. , Fedorova A. , Bertaux J.‐L. , Vandaele A.‐C. , Montmessin F. , Mahieux A. , Wilquet V. , Drummond R.
Published: December 2008

Solar Occultation in the Infrared (SOIR) is a part of the Spectroscopy for Investigation of Characteristics of the Atmosphere of Venus (SPICAV)/SOIR occultation experiment on board Venus Express dedicated to the study of gaseous and aerosol vertical structure of Venus' mesosphere. SOIR is an echelle spectrometer with acoustooptic selection of diffraction orders operating in the wavelengths range of 2.2–4.3 μm at high spectral resolution (λ/Δλ ∼ 20,000). Detection of minor constituents such as CO, H2O, HDO, HCl, HF, and SO2, at altitudes between 65 and 130 km has been demonstrated. We report results from a series of six occultations with observations of the 4‐μm SO2 band at latitudes 69°–88°N and 23°–30°N. It is the first time when the vertical distribution of SO2 is retrieved above the clouds with the help of solar occultation direct method. The sulfur dioxide transmission spectrum is measured on a background of strong CO2 absorption. Each retrieved vertical profile of SO2 is characterized by few points; the mixing ratio of SO2 being ∼0.1 ppm with scale height 1 ± 0.4 km for polar measurements (evening observations) and ∼1 ppm with scale height 3 ± 1 km at low latitudes (morning observations) at the altitude of about 70 km. Upper limits of <∼0.05 ppm are established around 75 km.
Petrogenesis of high‐phosphorous Wishstone Class rocks in Gusev Crater, Mars
Authors: Usui Tomohiro , McSween Harry Y. , Clark Benton C.
Published: December 2008

The Spirit rover has analyzed a wide variety of alkaline volcanic rocks in Gusev Crater. Among them are Wishstone Class tephrites with unusually high P2O5 (>5 wt %) abundances. To obtain the chemical compositions of rock interiors, we extrapolated a trend defined by brushed and abraded surface compositions. The extrapolation analysis suggests the high‐P2O5 tephrite signature is not attributable to secondary aqueous alteration but represents an igneous rock composition. Assessment of the compositional trend also suggests that merrillite is the phosphate mineral in Wishstone Class. Modified CIPW norm calculations using merrillite instead of apatite show that Wishstone Class rocks are silica saturated (hypersthene‐olivine normative) and alkaline. The high‐P2O5 whole rock compositions plot above solubility curves of merrillite in a diagram of P2O5 versus aluminosity, suggesting that mechanical admixture of merrillite is required. A source supplying merrillite cannot be a common silicate magma; instead, it could be a carbonatitic melt or a highly fractionated residual melt (jotunite) after anorthosite crystallization. Comparison with Earth analogs suggests that the Wishstone Class is akin to alkaline basalts in the eastern Snake River Plain, with regard to its chemistry, texture, and geologic context. These alkaline basalts are interpreted to originate from mantle metasomatized by CO2‐fluids and highly alkaline melts in the wake of the Yellowstone hot spot. Thus, we propose that the Wishstone Class represents a silica‐saturated alkaline suite that has mechanically mixed xenocrystic merrillites, probably during explosive volcanic eruption; the merrillites crystallized from carbonate‐rich magma produced by melting of a CO2‐bearing Martian mantle.
Considerations for measuring pressure head and water content in inclined boreholes
Authors: Hinnell A. C. , Ferré T. P. A.
Published: December 2008

Angled boreholes have been proposed to improve water content and pressure head monitoring in deep vadose zones by reducing the impact of the borehole on measurements by placing sensors below undisturbed soil. However, the borehole casing distorts the flow field, which may impact measurements made with sensors placed on or in the boreholes. We examined a wide range of soil types, background fluxes, and casing radii and angles of inclination to predict the error in water content and pressure head measurements that arise due to this flow disruption under unit gradient flow. We found that placing pressure head and water content sensors 110° and 120° from the top of the borehole, respectively, minimizes the effects of flow perturbation. Under some conditions, it may be possible to use the perturbation of the flow field caused by the casing to estimate hydraulic parameter values.
An analysis of India's Future Attractiveness as an Offshore Destination for IT and IT-Enabled Services
Authors: Joshi Kailash , Mudigonda Srikanth
Published: December 2008

Offshoring of services will shape the economic landscape for the coming decades, and present opportunities and challenges for individuals, organizations, and countries. Many countries are jostling in the global services marketplace to take advantage of the emerging opportunities. The success of an organization's offshoring initiative depends critically on the selection of a right destination; a wrong choice may result in a failure and impose significant costs. This paper presents a framework to assess the attractiveness of a target country, which identifies various motivating, inhibiting, and facilitating factors that may influence its attractiveness. The framework is used to analyze the future attractiveness of India, a topic that continues to be debated. The relative attractiveness of other potential competitors for offshoring of services is also discussed. Contrary to other analysts’ opinions, we conclude that India is likely to sustain its leading position for a long time in the services sector, and that it is likely to emerge as a global hub for the delivery of services, analogous to China's role in the manufacturing sector.
Anxiety and Psychological Security in Offshoring Relationships: The Role and Development of Trust as Emotional Commitment
Authors: Kelly Séamas , Noonan Camilla
Published: December 2008

In this paper we focus on the neglected role of anxiety and psychological security in organizational life, specifically in the context of the organization and development of offshoring relationships that extend across time and geography. In contrast with much of the literature on offshoring (and inter-organizational relationships more generally), which tends to take a very conventional rational decision-making perspective on the phenomenon in question, we emphasize the less tangible, emotional dimensions. In particular, we are concerned with understanding the processes by which clients, who have little or no previous experience of offshoring, may develop and sustain adequate levels of psychological security to enable them to bracket risk and productively engage in such unfamiliar and alien work arrangements. To this end, we draw on Anthony Giddens’ distinctive, non-cognitivist conception of trust, supplemented by other important contributions in the area, to explore the processes by which a sense of psychological security and stability is achieved in the face of the quotidian anxieties provoked by engagement in these contemporary modes of global organizing. Our synthesized theoretical framework is developed and illustrated in the context of an ongoing, in-depth, longitudinal study of the evolution of an Ireland-India information systems offshoring relationship. By tracing the dynamics of this relationship over an 18-month period, we examine the practices (or ‘relationship work’) through which trust is produced, and suggest that different mechanisms can be discerned at different (albeit overlapping) stages of the relationship. In the earlier phase, the emphasis is on the role played by care and attentiveness in producing a sense of trust in the qualities of the supplier. As the relationship develops, however, the emphasis shifts to the production of a stable collaborative order. Here, we focus on the micro-political dynamics of such processes and draw attention to three important tactical interventions (brokerage, signaling, and the ‘third man’). We conclude by arguing that the sense of trust that was carefully cultivated in the earlier phase of the relationship provided a crucial foundation, which not only facilitated the subsequent development of a stable collaborative order but, most noticeably, helped contain a serious crisis that beset the project in December 2006.
Country Attractiveness for Offshoring and Offshore Outsourcing: Additional Considerations
Authors: Kotlarsky Julia , Oshri Ilan
Published: December 2008

In this article, we review aspects relating to the attractiveness of India for information technology offshore - outsourcing. Our starting point is that, indeed, India will remain competitive in the short-medium term. However, more importantly, we move on to argue that country attractiveness is becoming a less important issue. We consider an alternative approach to analyze country attractive in which the client's strategic intent behind going offshore and the vendor's global dispersedness and its local knowledge define the attractiveness of the firm's offshoring strategy.
An Exploratory Study on IS Capabilities and Assets in a Small-to-Medium Software Enterprise
Authors: Butler Tom , Murphy Ciaran
Published: December 2008

There is a dearth of research on the capabilities of innovative small-to-medium software enterprises (SMSEs). Understanding how SMSEs build and apply business and information systems (IS) capabilities is important, as such firms account for over 90% of software enterprises operating in Europe and the US. This paper elaborates and applies dynamic capability theory to explore and help understand the web of conditions and factors that shaped and influenced business and IS capability development and application in one European SMSE. Drawing on the overarching theory of dynamic capabilities, a theoretical model is presented that posits relationships among (1) a firm's past activities; (2) its integration, learning and reconfiguration, and transformation capabilities; (3) its financial, complementary, locational, and technological asset positions; and (4) the products and services that result, and which are of value to an SMSE's customers. The paper refines and elaborates the model by describing and enumerating the business and IS capabilities, assets, and products and services of the SMSE under study. To properly assess whether this firm's products and services were of value to its customers, research was also conducted at two customer sites in Ireland and the US, in addition to the investigation at the primary research site in Dublin. The study therefore informs both practitioners’ and researchers’ understandings of this complex and under-researched phenomenon: for practitioners, it highlights the characteristics required to build innovative software solutions; for researchers, it illustrates the patterns and regularities associated with the development and application of business and IS capabilities.
Quantum Monte Carlo formulation of volume polarization in dielectric continuum theory
Authors: Amovilli Claudio , Filippi Claudia , Floris Franca Maria
Published: December 2008

We present a novel formulation based on quantum Monte Carlo techniques for the treatment of volume polarization due to quantum mechanical penetration of the solute charge density in the solvent domain. The method allows to accurately solve Poisson’s equation of the solvation model coupled with the Schrödinger equation for the solute. We demonstrate the performance of the approach on a representative set of solutes in water solvent and give a detailed analysis of the dependence of the volume polarization on the solute cavity and the treatment of electron correlation.
Real-time imaging of acoustic waves on a bulk acoustic resonator
Authors: Fujikura Takashi , Matsuda Osamu , Profunser Dieter M. , Wright Oliver B. , Masson Jeremy , Ballandras Sylvain
Published: December 2008

Time resolved images of acoustic waves in the 100 MHz–2.2 GHz range are obtained for an electrically excited thin-film bulk acoustic wave resonator by means of an ultrafast optical technique. Electrical pulses, synchronized to ultrashort laser pulses, piezoelectrically excite the device, and synchronous near-infrared laser pulses interferometrically detect surface motion. The frequency dispersion is extracted using spatiotemporal Fourier transforms, revealing both longitudinal and surface acoustic modes.
Tuning in-plane and out-of-plane exchange biases in Ni80Fe20/Cr-oxide bilayers
Authors: Lin K.-W. , Guo J.-Y.
Published: December 2008

The exchange bias effects of NiFe/Cr-oxide bilayers were studied. Results have shown that NiFe/Cr-oxide bilayers exhibited an exchange bias loop shift when field cooled to 5 K. A strong linear dependence of ferromagnetic NiFe and antiferromagnetic Cr2O3 thicknesses on the exchange bias field Hex was observed. The largest interfacial exchange energy Eint∼5.4×10−2 erg/cm2 was found in bilayers with the thickest Cr2O3 layer indicating that stronger interface exchange coupling is enabled by thicker Cr2O3 layers. In addition, Hex decreased linearly with increasing %O2/Ar ratio, reflecting that ion-beam bombardment tends to degrade the Cr2O3 surface spin structures. We also find that annealing the Cr-oxide layer yields both a structural phase transformation and improved crystallinity, giving rise to stronger exchange bias behavior. Further, the coexistence of in-plane as well as out-of-plane exchange biases was observed in a NiFe/annealed Cr2O3/Al2O3(0001) bilayer. This clearly indicates that by using the single crystal Al2O3(0001) substrate together with a rapid thermal annealing process, the antiferromagnet Cr2O3 spins are tilted toward the out-of-plane direction and thus exhibit this unusual exchange bias behavior.
Scalable time-correlated photon counting system with multiple independent input channels
Authors: Wahl Michael , Rahn Hans-Jürgen , Röhlicke Tino , Kell Gerald , Nettels Daniel , Hillger Frank , Schuler Ben , Erdmann Rainer
Published: December 2008

Time-correlated single photon counting continues to gain importance in a wide range of applications. Most prominently, it is used for time-resolved fluorescence measurements with sensitivity down to the single molecule level. While the primary goal of the method used to be the determination of fluorescence lifetimes upon optical excitation by short light pulses, recent modifications and refinements of instrumentation and methodology allow for the recovery of much more information from the detected photons, and enable entirely new applications. This is achieved most successfully by continuously recording individually detected photons with their arrival time and detection channel information (time tagging), thus avoiding premature data reduction and concomitant loss of information. An important property of the instrumentation used is the number of detection channels and the way they interrelate. Here we present a new instrument architecture that allows scalability in terms of the number of input channels while all channels are synchronized to picoseconds of relative timing and yet operate independent of each other. This is achieved by means of a modular design with independent crystal-locked time digitizers and a central processing unit for sorting and processing of the timing data. The modules communicate through high speed serial links supporting the full throughput rate of the time digitizers. Event processing is implemented in programmable logic, permitting classical histogramming, as well as time tagging of individual photons and their temporally ordered streaming to the host computer. Based on the time-ordered event data, any algorithms and methods for the analysis of fluorescence dynamics can be implemented not only in postprocessing but also in real time. Results from recently emerging single molecule applications are presented to demonstrate the capabilities of the instrument.
Cation ordering in epitaxial lead zirconate titanate films
Authors: Zhang L. C. , Vasiliev A. L. , Misirlioglu I. B. , Ramesh R. , Alpay S. P. , Aindow M.
Published: December 2008

Electron diffraction and atom location by channeling enhanced microanalysis were used to show that epitaxial PbZr0.2Ti0.8O3 films grown on (001) SrTiO3 substrates by pulsed laser deposition exhibit long-range order on the tetravalent cation sublattice parallel to the film/substrate interface. This ordering gives two distinct tetravalent cation sites, one Zr lean and one Zr rich, and results in a superlattice with a tetragonal unit cell with lattice parameters a0≈√2aPZT and c0≈aPZT. Since such ordered states are inherently unstable in homovalent perovskite solutions, it is inferred that the ordering arises in response to the lattice misfit and could constitute an additional relaxation mode.
Multilayer stacking technique for holographic polymer dispersed liquid crystals
Authors: Shriyan Sameet K. , Rai Kashma K. , Bellingham Alyssa , Fontecchio Adam K.
Published: December 2008

We demonstrate an alternate method of stacking holographic polymer dispersed liquid crystal (HPDLC) reflection gratings on substrates coated with indium tin oxide on both sides allowing independent switching of each grating in the stack. Successive layers of the stack are formed by switching existing layers, while exposing the subsequent layer to an interference pattern. Wavefront analysis based on wavefront propagation through HPDLC with electric field on and off is used to substantiate the improvement in the reflection efficiency of the layers in the stack. Results show an optical path length reduction due to elimination of substrate layers at each grating.
Spin-wave confinement in rolled-up ferromagnetic tubes
Authors: Mendach Stefan , Podbielski Jan , Topp Jesco , Hansen Wolfgang , Heitmann Detlef
Published: December 2008

We investigate the spin-wave dispersion in rolled-up Permalloy microtubes based on self-rolling strained semiconductor layers. Using microwave absorption spectroscopy we find that these structures exhibit a characteristic spin-wave mode spectrum. The magnetization and spin-wave resonance at zero external magnetic field is determined by curvature induced dynamic demagnetization fields. At high magnetic fields transverse to the tube axis, the three-dimensional shape anisotropy of the tube results in spin-wave confinement in well-defined regions along the tube perimeter.
Effect of substituted side chain on donor-acceptor conjugated copolymers
Authors: Cho Shinuk , Seo Jung Hwa , Kim Sun Hee , Song Suhee , Jin Youngeup , Lee Kwanghee , Suh Hongsuk , Heeger Alan J.
Published: December 2008

The effects of substitute side chain (alkyl or alkoxy) on optical and electrical properties of low-band-gap conjugated copolymers were investigated using poly(2,7-dihydroindeno[2,1-a]indene-co-4,7-di-2-thienyl-2,1,3-benzothiadiazole), poly(2,7-dihydroindeno[2,1-a]indene-co-4,7-bis(4-hexyl-2-thienyl)-2,1,3-benzothiadiazole) (PININE-DHTBT), and poly(2,7-dihydroindeno[2,1-a]indene-co-4,7-bis[3-(hexyloxy)-2-thienyl]-2,1,3-benzothiadiazole) (PININE-DHOTBT). Alkyl introduced PININE-DHTBT exhibits blueshifted absorption spectrum, while alkoxy introduced PININE-DHOTBT exhibits redshifted absorption spectrum. Because of steric hindrance of alkyl or alkoxy side chain, highest occupied molecular orbitals of PININE-DHTBT and PININE-DHOTBT highly localized on donor segments, thereby decreasing hole mobilities of PININE-DHTBT and PININE-DHOTBT. Consequently, despite the spectral advantage of PININE-DHOTBT for photovoltaic cells, the actual solar cell property of PININE-DHOTBT was not enhanced.
Optical far-field and near-field observations of the strong angular dispersion in a lithium niobate photonic crystal superprism designed for double (passive and active) demultiplexer applications
Authors: Diziain Séverine , Amet Julien , Baida Fadi I. , Bernal Maria-Pilar
Published: December 2008

We report on a lithium niobate photonic crystal (PC) superprism device designed for double demultiplexer applications. In fact, the strong angular beam steering cannot only be reached by passively tuning the wavelength but it can also be actively controlled by the Pockels effect enhanced due to the slow light phenomenon. The performance of the passive device is demonstrated by measuring its transmission properties. Optical far field and near-field experiments, corroborated by two-dimensional finite difference time domain (2D-FDTD) calculations, exhibit an angular dispersion of 1.5°/nm. A value as high as 4.3°/nm is expected by improving the PC design as supported by 2D-FDTD simulation.
The observation of comblike transmission spectrum from a tapered single mode fiber tip
Authors: Li Y. , Bao X.
Published: December 2008

Tapered fiber tips are fabricated by the fast stretching of a heated single mode fiber until it breaks. As the fiber tip diameter decreases, the propagation mode converts from the single core mode to a few cladding modes. The cladding modes are then emitted from the fiber tip and interfere with each other in the near field. Along the propagation direction, the optical field is found to be modulated due to multibeam interferences. Interestingly, broadband transmission spectrums show equidistant comblike peaks. A tunable spatial filter based on a fiber tip is realized to reshape a broadband light source.
Structurally diverse natural products that cause potassium leakage trigger multicellularity in
Bacillus subtilis
Authors: López Daniel , Fischbach Michael A. , Chu Frances , Losick Richard , Kolter Roberto
Published: December 2008

We report a previously undescribed quorum-sensing mechanism for triggering multicellularity in
Bacillus subtilis. B. subtilis
forms communities of cells known as biofilms in response to an unknown signal. We discovered that biofilm formation is stimulated by a variety of small molecules produced by bacteria—including the
B. subtilis
nonribosomal peptide surfactin—that share the ability to induce potassium leakage. Natural products that do not cause potassium leakage failed to induce multicellularity. Small-molecule-induced multicellularity was prevented by the addition of potassium, but not sodium or lithium. Evidence is presented that potassium leakage stimulates the activity of a membrane protein kinase, KinC, which governs the expression of genes involved in biofilm formation. We propose that KinC responds to lowered intracellular potassium concentration and that this is a quorum-sensing mechanism that enables
B. subtilis
to respond to related and unrelated bacteria.
A regulatory interplay between miR-27a and Runx1 during megakaryopoiesis
Authors: Ben-Ami Oren , Pencovich Niv , Lotem Joseph , Levanon Ditsa , Groner Yoram
Published: December 2008

The transcription factor Runx1 is a key regulator of definitive hematopoiesis in the embryo and the adult. Lineage-specific expression of Runx1 involves transcription and post-transcription control through usage of alternative promoters and diverse 3′UTR isoforms, respectively. We identified and mapped microRNA (miR) binding sites on Runx1 3′UTR and show that miR-27a, miR-9, miR-18a, miR-30c, and miR-199a* bind and post-transcriptionally attenuate expression of Runx1. miR-27a impacts on both the shortest (0.15 kb) and longest (3.8 kb) 3′UTRs and, along with additional miRs, might contribute to translation attenuation of Runx1 mRNA in the myeloid cell line 416B. Whereas levels of Runx1 mRNA in 416B and the B cell line 70Z were similar, the protein levels were not. Large amounts of Runx1 protein were found in 70Z cells, whereas only minute amounts of Runx1 protein were made in 416B cells and overexpression of Runx1 in 416B induced terminal differentiation associated with megakaryocytic markers. Induction of megakaryocytic differentiation in K562 cells by 12-o-tetradecanoylphorbol-13-acetate markedly increased miR-27a expression, concomitantly with binding of Runx1 tomiR-27aregulatory region. The data indicate that miR-27a plays a regulatory role in megakaryocytic differentiation by attenuating Runx1 expression, and that, during megakaryopoiesis, Runx1 and miR-27a are engaged in a feedback loop involving positive regulation of miR-27a expression by Runx1.
Folding energy landscape and network dynamics of small globular proteins
Authors: Hori Naoto , Chikenji George , Berry R. Stephen , Takada Shoji
Published: December 2008

The folding energy landscape of proteins has been suggested to be funnel-like with some degree of ruggedness on the slope. How complex the landscape, however, is still rather unclear. Many experiments for globular proteins suggested relative simplicity, whereas molecular simulations of shorter peptides implied more complexity. Here, by using complete conformational sampling of 2 globular proteins, protein G and src SH3 domain and 2 related random peptides, we investigated their energy landscapes, topological properties of folding networks, and folding dynamics. The projected energy surfaces of globular proteins were funneled in the vicinity of the native but also have other quite deep, accessible minima, whereas the randomized peptides have many local basins, including some leading to seriously misfolded forms. Dynamics in the denatured part of the network exhibited basin-hopping itinerancy among many conformations, whereas the protein reached relatively well-defined final stages that led to their native states. We also found that the folding network has the hierarchic nature characterized by the scale-free and the small-world properties.
Voltage- and [ATP]-dependent Gating of the P2X2 ATP Receptor Channel
Authors: Fujiwara Yuichiro , Keceli Batu , Nakajo Koichi , Kubo Yoshihiro
Published: December 2008

P2X receptors are ligand-gated cation channels activated by extracellular adenosine triphosphate (ATP). Nonetheless, P2X2 channel currents observed during the steady-state after ATP application are known to exhibit voltage dependence; there is a gradual increase in the inward current upon hyperpolarization. We used a Xenopus oocyte expression system and two-electrode voltage clamp to analyze this “activation” phase quantitatively. We characterized the conductance–voltage relationship in the presence of various [ATP], and observed that it shifted toward more depolarized potentials with increases in [ATP]. By analyzing the rate constants for the channel's transition between a closed and an open state, we showed that the gating of P2X2 is determined in a complex way that involves both membrane voltage and ATP binding. The activation phase was similarly recorded in HEK293 cells expressing P2X2 even by inside-out patch clamp after intensive perfusion, excluding a possibility that the gating is due to block/unblock by endogenous blocker(s) of oocytes. We investigated its structural basis by substituting a glycine residue (G344) in the second transmembrane (TM) helix, which may provide a kink that could mediate “gating.” We found that, instead of a gradual increase, the inward current through the G344A mutant increased instantaneously upon hyperpolarization, whereas a G344P mutant retained an activation phase that was slower than the wild type (WT). Using glycine-scanning mutagenesis in the background of G344A, we could recover the activation phase by introducing a glycine residue into the middle of second TM. These results demonstrate that the flexibility of G344 contributes to the voltage-dependent gating. Finally, we assumed a three-state model consisting of a fast ATP-binding step and a following gating step and estimated the rate constants for the latter in P2X2-WT. We then executed simulation analyses using the calculated rate constants and successfully reproduced the results observed experimentally, voltage-dependent activation that is accelerated by increases in [ATP].
Identification of Regulatory Phosphorylation Sites in a Cell Volume– and Ste20 Kinase–dependent ClC Anion Channel
Authors: Falin Rebecca A. , Morrison Rebecca , Ham Amy-Joan L. , Strange Kevin
Published: December 2008

Changes in phosphorylation regulate the activity of various ClC anion transport proteins. However, the physiological context under which such regulation occurs and the signaling cascades that mediate phosphorylation are poorly understood. We have exploited the genetic model organism Caenorhabditis elegans to characterize ClC regulatory mechanisms and signaling networks. CLH-3b is a ClC anion channel that is expressed in the worm oocyte and excretory cell. Channel activation occurs in response to oocyte meiotic maturation and swelling via serine/threonine dephosphorylation mediated by the type I phosphatases GLC-7α and GLC-7β. A Ste20 kinase, germinal center kinase (GCK)-3, binds to the cytoplasmic C terminus of CLH-3b and inhibits channel activity in a phosphorylation-dependent manner. Analysis of hyperpolarization-induced activation kinetics suggests that phosphorylation may inhibit the ClC fast gating mechanism. GCK-3 is an ortholog of mammalian SPAK and OSR1, kinases that bind to, phosphorylate, and regulate the cell volume–dependent activity of mammalian cation-Cl− cotransporters. Using mass spectrometry and patch clamp electrophysiology, we demonstrate here that CLH-3b is a target of regulatory phosphorylation. Concomitant phosphorylation of S742 and S747, which are located 70 and 75 amino acids downstream from the GCK-3 binding site, are required for kinase-mediated channel inhibition. In contrast, swelling-induced channel activation occurs with dephosphorylation of S747 alone. Replacement of both S742 and S747 with glutamate gives rise to kinase- and swelling-insensitive channels that exhibit activity and biophysical properties similar to those of wild-type CLH-3b inhibited by GCK-3. Our studies provide novel insights into ClC regulation and mechanisms of cell volume signaling, and provide the foundation for studies aimed at defining how conformational changes in the cytoplasmic C terminus alter ClC gating and function in response to intracellular signaling events.
Regulated RNA Editing and Functional Epistasis inShakerPotassium Channels
Authors: Ingleby Lindsey , Maloney Rachel , Jepson James , Horn Richard , Reenan Robert
Published: December 2008

Regulated point modification by an RNA editing enzyme occurs at four conserved sites in the Drosophila Shaker potassium channel. Single mRNA molecules can potentially represent any of 24 = 16 permutations (isoforms) of these natural variants. We generated isoform expression profiles to assess sexually dimorphic, spatial, and temporal differences. Striking tissue-specific expression was seen for particular isoforms. Moreover, isoform distributions showed evidence for coupling (linkage) of editing sites. Genetic manipulations of editing enzyme activity demonstrated that a chief determinant of Shaker editing site choice resides not in the editing enzyme, but rather, in unknown factors intrinsic to cells. Characterizing the biophysical properties of currents in nine isoforms revealed an unprecedented feature, functional epistasis; biophysical phenotypes of isoforms cannot be explained simply by the consequences of individual editing effects at the four sites. Our results unmask allosteric communication across disparate regions of the channel protein and between evolved and regulated amino acid changes introduced by RNA editing.
Molecular Basis for Cation Selectivity in Claudin-2–based Paracellular Pores: Identification of an Electrostatic Interaction Site
Authors: Yu Alan S.L. , Cheng Mary H. , Angelow Susanne , Günzel Dorothee , Kanzawa Sanae A. , Schneeberger Eveline E. , Fromm Michael , Coalson Rob D.
Published: December 2008

Paracellular ion transport in epithelia is mediated by pores formed by members of the claudin family. The degree of selectivity and the molecular mechanism of ion permeation through claudin pores are poorly understood. By expressing a high-conductance claudin isoform, claudin-2, in high-resistance Madin-Darby canine kidney cells under the control of an inducible promoter, we were able to quantitate claudin pore permeability. Claudin-2 pores were found to be narrow, fluid filled, and cation selective. Charge selectivity was mediated by the electrostatic interaction of partially dehydrated permeating cations with a negatively charged site within the pore that is formed by the side chain carboxyl group of aspartate-65. Thus, paracellular pores use intrapore electrostatic binding sites to achieve a high conductance with a high degree of charge selectivity.
The Frozen Ark Project: the role of zoos and aquariums in preserving the genetic material of threatened animals
Authors: CLARKE A. G.
Published: December 2008

The earth currently suffers from a bout of animal extinctions. The Frozen Ark Project is acting internationally in preserving the genetic resources of threatened wild species before they become extinct. Modern techniques make preservation of this material easier, and costs of sequencing genomes have declined drastically during the past 10 years. The project is vital because the extinction of a species results in the loss of not only the animal but also the genetic information accumulated over millions of years of evolution. It will give us the ability to invigorate conservation‐breeding programmes and conserve material of practical value in the form of tissues, viable somatic cells, gametes, eggs and embryos. The Frozen Ark is not considered a substitute for saving the animals themselves but an essential ‘back‐up’ to this activity. International collaboration between the world's zoos, aquariums, museums and universities is developing to achieve this conservation effort of last resort. Zoos and aquariums are crucial to the project because they increasingly hold the last individuals of the most threatened species.
Planning for a sustainable Emmen Zoo
Authors: LANDMAN W. , VISSCHER D.
Published: December 2008

A new zoo is being developed in Emmen. Six worlds of nature and culture will be presented to the visitors, immersing them in various ecosystems. Laying out and constructing a whole new zoo makes it possible to utilize the most modern developments in the field of sustainability. This is particularly important as Emmen Zoo is committed to reducing its environmental impact over the next 50 years to 5% of the level established in 1997, which can be achieved if the environmental impact is halved every 10 years. In this article, we present the aims of the new Emmen Zoo in relation to water purification and utilization, renewable‐energy use and the treatment of waste products.
Early introduction of hand‐reared Gorillas Gorilla gorilla to conspecifics at Barcelona Zoo: general procedures and three case studies
Authors: ABELLÓ M. T. , COLELL M.
Published: December 2008

The purpose of this paper is to describe the early introduction protocols developed for four (1.3) hand‐reared Gorillas Gorilla gorilla that were introduced to conspecifics at Barcelona Zoo. The introduction process for each was initiated when the infants were <1 year old. The introductions began in 1999 and ended in 2001, and the difficulties faced while carrying out such procedures were novel at that time. The protocols had to be improved following the assay error results. In the first instance, the infant Gorillas were introduced into their family group of two hand‐reared adult ♀♀ and a silverback. However, the development conditions and rearing inexperience of the adult ♀♀ resulted in failure to nurture the young. The ♀♀ did not protect or take care of the infants well enough to keep them safe. Appropriate maternal behaviours did not develop in the adults, although some social contacts between the adults and young were observed during the process. However, a silverback managed to kill a 6 month‐old ♂ infant after a slide‐gate malfunction. The three ♀ infants were successfully integrated into a group of conspecifics but not into their family group.
A study into the mother–pup relationship in three California sea lionZalophus californianusmothers and pups at Barcelona Zoo
Authors: SORIANO A. I. , GONZÁLEZ R. , MATÉ C.
Published: December 2008

The limited number of studies into maternal care in captivity carried out on California sea lionsZalophus californianusindicates that it is necessary to study their biology and behaviour in greater depth to improve management conditions and participate in the conservation of their genetic information and habitat. This study involved three adult ♀♀, two primiparous mothers and one that had already given birth, and their pups. The study period occurred from July to November 2003. Sampling was focused but data were collected continuously in 10 minute observation sessions. Twenty‐four observation sessions were carried out for each individual, resulting in a total of 4 hours of observational data per animal evenly divided over three periods of the day (morning, midday and afternoon). The mother–pup location and play behaviours were not observed in the experienced mother; however, she spent more time in lactation than the primiparous mothers and her pup was more inactive. The use of space was similar for the three mother–pup pairs. The primiparous mothers started, received and finished more episodes with their pups than the experienced mother, which interacted with her pup more in the afternoon. The experienced mother's pup received more aggressive vocalizations than the primiparous mothers' pups.
Experiments in Active Control of Stall on an Aeroengine Gas Turbine
Authors: Freeman C. , Wilson A. G. , Day I. J. , Swinbanks M. A.
Published: December 2008

This paper describes work carried out between 1989 and 1994 to investigate the application of “Active Stall Control” to a Rolls-Royce Viper turbojet. The results demonstrate that stall control is feasible and can increase the stable operating range by up to 25 percent of pressure rise. Stall disturbances were detected using rings of high response pressure transducers positioned at different axial planes along the compressor, and processed using a PC-based data acquisition and control system. Actuation was provided by six hydraulically operated sleeve valves positioned to recirculate air over all or part of the compressor. Stall was artificially induced using combinations of in-bleed into the combustor outer casing, fuel spiking, hot gas ingestion, and inlet pressure spoiling, thus replicating many of the transient conditions commonly observed to make a compressor prone to stall. Results are compared from a number of stall control strategies including those demonstrated at low speed by Paduano et al. (1993) and Day (1993). Best results were obtained with detection of nonaxisymmetric disturbances coupled with axisymmetric control action. A control system of this type is demonstrated to be capable of extending the stable engine operating range at all speeds and with each method of inducing stall.
Viscous Throughflow Modeling of Axial Compressor Bladerows Using a Tangential Blade Force Hypothesis
Authors: Gallimore S. J.
Published: December 2008

This paper describes the modeling of axial compressor blade rows in an axisymmetric viscous throughflow method. The basic method, which has been reported previously, includes the effects of spanwise mixing, using a turbulent diffusion model, and endwall shear within the throughflow calculation. The blades are modeled using a combination of existing two-dimensional blade performance predictions for loss and deviation away from the annulus walls and a novel approach using tangential blade forces in the endwall regions. Relatively simple assumptions about the behavior of the tangential static pressure force imposed by the blades allow the secondary deviations produced by tip clearance flows and the boundary layer flows at fixed blade ends to be calculated in the axisymmetric model. Additional losses are assigned in these regions based on the calculated deviations. The resulting method gives realistic radial distributions of loss and deviation across the whole span at both design and off-design operating conditions, providing a quick method of estimating the magnitudes of these effects in the preliminary design process. Results from the method are compared to measured data in low and high-speed compressors and multistage three-dimensional viscous CFD predictions.
Effect of Squealer Tip on Rotor Heat Transfer and Efficiency
Authors: Ameri A. A. , Steinthorsson E. , Rigby D. L.
Published: December 2008

Calculations were performed to simulate the tip flow and heat transfer on the GE-E3 first-stage turbine, which represents a modern gas turbine blade geometry. Cases considered were a smooth tip, 2 percent recess, and 3 percent recess. In addition, a two-dimensional cavity problem was calculated. Good agreement with experimental results was obtained for the cavity calculations, demonstrating that the k–ω turbulence model used is capable of representing flows of the present type. In the rotor calculations, two dominant flow structures were shown to exist within the recess. Also areas of large heat transfer rate were identified on the blade tip and the mechanisms of heat transfer enhancement were discussed. No significant difference in adiabatic efficiency was observed for the three tip treatments investigated.
Unsteady Total Temperature Measurements Downstream of a High-Pressure Turbine
Authors: Buttsworth D. R. , Jones T. V. , Chana K. S.
Published: December 2008

An experimental technique for the measurement of flow total temperature in a turbine facility is demonstrated. Two thin film heat transfer gases located at the stagnation point of fused quartz substrates are operated at different temperatures in order to determine the flow total temperature. With this technique, no assumptions regarding the magnitude of the convective heat transfer coefficient are made. Thus, the probe can operate successfully in unsteady compressible flows of arbitrary composition and high free-stream turbulence levels without a heat transfer law calibration. The operation of the total temperature probe is first demonstrated using a small wind tunnel facility. Based on results from the small wind tunnel tests, it appears that the probe total temperature measurements are accurate to within ±1 K. Experiments using the probe downstream of a high-pressure turbine stage are than described. Both high and low-frequency components of the flow total temperature can be accurately resolved with the present technique. The probe measures a time-averaged flow total temperature that is in good agreement with thermocouple measurements made downstream of the rotor. Frequencies as high as 182 kHz have been detected in the spectral analysis of the heat flux signals from the total probe. Through comparison with fast-response aerodynamic probe measurements, it is demonstrated that the current measurement location, the total temperature fluctuations arise mainly due to the isentropic extraction of work by the turbine. The present total temperature probe is demonstrated to be an accurate, robust, fast-response device that is suitable for operation in a turbomachinery environment.
Effects of Very High Free-Stream Turbulence on the Jet–Mainstream Interaction in a Film Cooling Flow
Authors: Kohli A. , Bogard D. G.
Published: December 2008

Dispersion of coolant jets in a film cooling flow field is the result of a highly complex interaction between the film cooling jets and the mainstream. Understanding this complex interaction, particularly near the injection location, is critical for improving the predictive capabilities of existing film cooling models, especially when very high free-stream turbulence levels exist. This study uses a high-Frequency-response temperature sensor to investigate the mean and fluctuating thermal field of a film cooling flow for two vastly different free-stream turbulence levels (0.5 and 20 percent). The high-frequency-response temperature sensor provides new information about the film cooling flow in terms of actual rms levels (Θ′), probability density functions (pdf’s), and frequency spectra of the thermal field. Results are presented for both free-stream conditions using round hosed inclined at 35 deg, at a momentum flux ration of I = 0.156 and density ratio of DR = 1.05. The mean thermal field results show severe degradation of the film cooling jet occurs with very high free-stream turbulence levels. Temperature rms results indicate levels as high as Θ′ = 0.25 exist at the jet-mainstream interface. More information is provided by the temperature pdf’s, which are able to identify differences in the jet-mainstream interaction for the two free stream conditions. With small free-stream turbulence, strong intermittent flow structures generated at the jet-mainstream interface disperse the jet by moving hot main stream fluid into the coolant core, and ejecting coolant fluid into the mainstream. When the free stream has large scales and very high turbulence levels, the jet-mainstream interface is obliterated by large-scale turbulent structures originating from the free stream, which completely penetrate the coolant jet, causing very rapid dispersion of the film cooling jet.