bluuebunny/crossref_metadata_2025 huggingface dataset:
An experiment for the investigation of forces on microparticles in ion beams
Authors: Schneider Viktor , Trottenberg Thomas , Teliban Iulian , Kersten Holger
Published: January 2010

A novel experiment for the study of forces on microparticles in ion beams is presented. A broad beam ion source provides a vertically upward directed beam wherein 100 μm hollow glass spheres are injected. The particles are illuminated by a diode laser and recorded with a charge-coupled device camera. From the trajectories the acceleration and the net force on the particles are determined. Information on energetic neutral atoms is achieved, which is not accessible by electrostatic methods.
Vacuum space charge effect in laser-based solid-state photoemission spectroscopy
Authors: Graf J. , Hellmann S. , Jozwiak C. , Smallwood C. L. , Hussain Z. , Kaindl R. A. , Kipp L. , Rossnagel K. , Lanzara A.
Published: January 2010

We report a systematic measurement of the space charge effect observed in the few-picosecond laser pulse regime in laser-based solid-state photoemission spectroscopy experiments. The broadening and the shift of a gold Fermi edge as a function of spot size, laser power, and emission angle are characterized for pulse lengths of 6 ps and 6 eV photon energy. The results are used as a benchmark for an N-body numerical simulation and are compared to different regimes used in photoemission spectroscopy. These results provide an important reference for the design of time- and angle-resolved photoemission spectroscopy setups and next-generation light sources.
Heteroepitaxial growth of SnO2 thin films on SrTiO3 (111) single crystal substrate by laser molecular beam epitaxy
Authors: Ke C. , Yang Z. , Zhu W. , Pan J. S. , Karamat S.
Published: January 2010

SnO 2 films with a thickness around 150 nm were deposited on the (111) surface of a SrTiO3 single crystal substrate by laser molecular beam epitaxy technique in a temperature range 600–750 °C and oxygen pressure from 10−3 to 1 Pa, respectively. The growth behavior was in situ monitored by reflection high-energy electron diffraction, and the epitaxial relations were further investigated by ex situ x-ray diffraction measurement in different geometries. All the films were confirmed to be highly (200) oriented showing good crystalline quality, despite the large lattice mismatch between SnO2 and SrTiO3. Based on the crystallographic model and structure analysis, six equivalent directions in the SrTiO3 (111) surface for the nucleation of SnO2 were discovered, which confirmed the existence of sixfold symmetrical domains in the SnO2 epilayer. Additionally, the optical dielectric function of the SnO2/SrTiO3 epitaxial film was simulated by the Tauc–Lorentz–Drude model in the UV-vis-NIR region.
Constrained ferroelectric domain orientation in (BiFeO3)m(SrTiO3)n superlattice
Authors: Ranjith R. , Mangalam R. V. K. , Boullay Ph. , David A. , Lepetit M. B. , Lüders U. , Prellier W. , Da Costa A. , Ferri A. , Desfeux R. , Vincze Gy. , Radi Zs. , Aruta C.
Published: January 2010

Ferroelectric domains were investigated using piezoresponse force microscopy in superlattices composed of multiferroic BiFeO3 and SrTiO3 layers. Compared to single BiFeO3 thin films, a reduction in the domains size and a suppression of the in-plane orientation of domains are observed in a superlattice of (BiFeO3)4(SrTiO3)8, suggesting a constrained ferroelectric domain orientation along the out-of-plane ⟨001⟩ direction. Such modification of domain size and orientation in BiFeO3-based heterostructures could play a vital role on engineering the domains and domain wall mediated functional properties necessary for device applications.
A study on the temperature dependence of the threshold switching characteristics of Ge2Sb2Te5
Authors: Lee Suyoun , Jeong Doo Seok , Jeong Jeung-hyun , Zhe Wu , Park Young-Wook , Ahn Hyung-Woo , Cheong Byung-ki
Published: January 2010

We investigated the temperature dependence of the threshold switching characteristics of a memory-type chalcogenide material, Ge2Sb2Te5. We found that the threshold voltage (Vth) decreased linearly with temperature, implying the existence of a critical conductivity of Ge2Sb2Te5 for its threshold switching. In addition, we investigated the effect of bias voltage and temperature on the delay time (tdel) of the threshold switching of Ge2Sb2Te5 and described the measured relationship by an analytic expression which we derived based on a physical model where thermally activated hopping is a dominant transport mechanism in the material.
Performance of a CsBr coated Nb photocathode at room temperature
Authors: Maldonado Juan R. , Pianetta Piero , Dowell David H. , Smedley John , Kneisel Peter
Published: January 2010

Experiments performed on Nb substrates coated with thin films of CsBr indicate a substantial enhancement of 150 to 800 times of the photoyield at 257 nm relative to the uncoated substrates. Results are presented for several power density illuminations and sample thickness. Further enhancement of photoyield was observed when the laser illumination was interrupted for a short time in samples with 5–10 nm thick CsBr coatings.
Natural frequencies of C60, C70, and C80 fullerenes
Authors: Sakhaee-Pour A. , Vafai A.
Published: January 2010

This letter adopts an atomistic modeling approach to study free vibrational characteristics of C60, C70, and C80 fullerenes. In this regard, we use the molecular structural mechanics consisting of equivalent structural beams to calculate the nonzero natural frequencies. The simulation results indicate that the first natural frequency of the fullerene is in the order terahertz and decreases nonlinearly with respect to the number of the carbon atoms.
A general few-projection method for tomographic reconstruction of samples consisting of several distinct materials
Authors: Myers Glenn R. , Thomas C. David L. , Paganin David M. , Gureyev Timur E. , Clement John G.
Published: January 2010

We present a method for tomographic reconstruction of objects containing several distinct materials, which is capable of accurately reconstructing a sample from vastly fewer angular projections than required by conventional algorithms. The algorithm is more general than many previous discrete tomography methods, as: (i) a priori knowledge of the exact number of materials is not required; (ii) the linear attenuation coefficient of each constituent material may assume a small range of a priori unknown values. We present reconstructions from an experimental x-ray computed tomography scan of cortical bone acquired at the SPring-8 synchrotron.
Effect of osteogenesis imperfecta mutations in tropocollagen molecule on strength of biomimetic tropocollagen-hydroxyapatite nanocomposites
Authors: Dubey Devendra K. , Tomar Vikas
Published: January 2010

Osteogenesis Imperfecta (OI) is a genetic disorder that affects cellular synthesis of Type-I collagen fibrils and causes extreme bone fragility. This study reports the effects of OI mutations in Tropocollagen (TC) molecules on strength of model Tropocollagen-Hydroxyapatite biomaterials with two different mineral [hydroxyapatite (HAP)] distributions using three dimensional atomistic simulations. Results show that the effect of TC mutations on the strength of TC-HAP biomaterials is insignificant. Instead, change in mineral distribution showed significant impact on the overall strength of TC-HAP biomaterials. Study suggests that TC mutations manifest themselves by changing the mineral distribution during hydroxyapatite growth and nucleation period.
Ghost transmission: How large basis sets can make electron transport calculations worse
Authors: Herrmann Carmen , Solomon Gemma C. , Subotnik Joseph E. , Mujica Vladimiro , Ratner Mark A.
Published: January 2010

The Landauer approach has proven to be an invaluable tool for calculating the electron transport properties of single molecules, especially when combined with a nonequilibrium Green’s function approach and Kohn–Sham density functional theory. However, when using large nonorthogonal atom-centered basis sets, such as those common in quantum chemistry, one can find erroneous results if the Landauer approach is applied blindly. In fact, basis sets of triple-zeta quality or higher sometimes result in an artificially high transmission and possibly even qualitatively wrong conclusions regarding chemical trends. In these cases, transport persists when molecular atoms are replaced by basis functions alone (“ghost atoms”). The occurrence of such ghost transmission is correlated with low-energy virtual molecular orbitals of the central subsystem and may be interpreted as a biased and thus inaccurate description of vacuum transmission. An approximate practical correction scheme is to calculate the ghost transmission and subtract it from the full transmission. As a further consequence of this study, it is recommended that sensitive molecules be used for parameter studies, in particular those whose transmission functions show antiresonance features such as benzene-based systems connected to the electrodes in meta positions and other low-conducting systems such as alkanes and silanes.
Mixing kinematics of moderate Reynolds number flows in a T-channel
Authors: Thomas Susan , Ameel Tim , Guilkey James
Published: January 2010

An experimental study of water flow in a T-shaped channel with rectangular cross section (20×20 mm2 inlet ID and 20×40 mm2 outlet ID) has been conducted for a Reynolds number Re range based on inlet geometry of Re=56–422. Dynamical conditions and T-channel geometry of the current study are applicable to the microscale. This study supports a large body of numerical work, and resolution and the interrogation region are extended beyond previous experimental studies. Laser induced fluorescence (LIF) permits a detailed look at the flow fields that evolve in the outlet channel over the broad range of Re where realistic T-channels operate. Scalar structures previously unresolved in the literature are presented. Unsteady flow regimes numerically predicted to occur at higher Re are characterized, and simultaneous planar and discrete-point LIF measurements relate the development of oscillatory behavior in the outlet channel to flow structure in the junction. Further, the development of an unsteady symmetric topology at higher Re, which negatively affects mixing, is presented, and mechanisms behind the wide range of mixing qualities predicted for this regime are explained. Characteristics of steady and unsteady flows are tracked with Re to elucidate mixing behavior on a fundamental level. Practical conclusions for experimental mixing in a T-channel are extracted.
Screening-controlled morphologies of Yukawa crystals
Authors: Cioslowski Jerzy , Grzebielucha Ewa
Published: January 2010

Asymptotic expressions for the energies of Yukawa crystals, valid at the Coulomb and hard-sphere (i.e., the weak-screening and strong-screening) limits, are derived. Careful analysis of these limits elucidates the origin of the observed structural transitions that interconnect distinct particle configurations. Whereas the Coulomb limits are characterized by prominent shell structures, their hard-sphere counterparts obtain from tight packings of impenetrable spheres that minimize radii of gyration. Interestingly, these packings are not identical with fragments of regular close-packing lattices. In crystals of more than seven particles, the limiting configurations usually possess distinct point-group symmetries and thus are mutually incompatible. This incompatibility constitutes the driving force for the structural transitions and precludes smooth interpolation of the energies in question. As demonstrated by the examples of the eight- and eleven-particle species, the overall picture of structural transitions (which involve either catastrophes or level crossings) and Yukawa crystal morphologies is much more complex than that revealed by monitoring of shell occupancies alone.
Structural degradation mechanism of multiwalled carbon nanotubes in electrically treated field emission
Authors: Baik Chan-Wook , Lee Jeonghee , Choi Jun Hee , Jung Insun , Choi Hye Ran , Jin Yong Wan , Kim Jong Min
Published: January 2010

Carbon nanotubes in printed field emission arrays are known to be often damaged during field emission. A high-resolution transmission electron microscopy and Raman scattering spectra suggest that the degraded structure is mainly determined by electrical treatment conditions. A nonstationary alternating-current treatment has caused emitters to be thicker and fewer with loss of crystallinity but improved the emission brightness and uniformity, while a direct-current treatment has shown little influence. The experimental observations can be quantitatively explained by the analytical estimation on the apex radius as well as the work function using the Seppen–Katamuki chart from the Fowler–Nordheim characteristics.
Observation of negative differential resistance in DNA molecular junctions
Authors: Kang Ning , Erbe Artur , Scheer Elke
Published: January 2010

The mechanically controllable break junction technique is used to study charge transport through suspended DNA molecules. The current-voltage (I-V) characteristics in an aqueous solution display series of negative differential resistance (NDR) and hysteresis behavior. Under high-vacuum conditions, the peak positions of NDR shift to lower voltage, and the amplitude is reduced dramatically. The observed NDR behavior is consistent with the polarization mechanism in DNA molecular junctions, which demonstrates a change in the coupling of the molecular level to a polaron mode under different environment.
Strong localization effect in magnetic two-dimensional hole systems
Authors: Wurstbauer U. , Knott S. , Zolotaryov A. , Schuh D. , Hansen W. , Wegscheider W.
Published: January 2010

We report an extensive study of the magnetotransport properties of magnetically doped two-dimensional hole systems. Inverted manganese modulation doped InAs quantum wells with localized manganese ions providing a magnetic moment of S=5/2 were grown by molecular beam epitaxy. Strong localization effect found in low-field magnetotransport measurements on these structures can either be modified by the manganese doping density or by tuning the two-dimensional hole density p via field effect. The data reveal that the ratio between p and manganese ions inside or in close vicinity to the channel enlarges the strong localization effect. Moreover, asymmetric broadening of the doping layer due to manganese segregation is significantly influenced by strain in the heterostructure.
Adsorption of the heteronuclear AB diblock copolymers confined in the slitlike pores
Authors: Kim Soon-Chul , Seong Baek-Seok
Published: January 2010

A density functional perturbative theory, which is based on both the modified fundamental measure theory for the spheres and the Wertheim’s first-order perturbation theory for the chain connectivity, has been proposed for investigating the structure of the heteronuclear AB diblock copolymers. It has been applied for studying the adsorption of the heteronuclear AB diblock copolymers confined in the hard slit pores and the walls via the Lennard-Jones (3-9) potential. The theoretical calculation shows that the structure of the confined heteronuclear AB diblock copolymer are strongly affected by the size ratio of the beads composed of the block as well as the chain lengths of the blocks composed of the copolymer. The surface-binding potential, which has different affinity with regard to the walls, plays an important role for the structure and phase behaviors of the heteronuclear AB diblock copolymer such as the selective adsorption of the homogeneous AB diblock copolymer immersed in the solvent.
Field-theoretic simulations in the Gibbs ensemble
Authors: Riggleman Robert A. , Fredrickson Glenn H.
Published: January 2010

Calculating phase diagrams and measuring the properties of multiple phases in equilibrium is one of the most common applications of field-theoretic simulations. Such a simulation often attempts to simulate two phases in equilibrium with each other in the same simulation box. This is a computationally demanding approach because it is necessary to perform a large enough simulation so that the interface between the two phases does not affect the estimate of the bulk properties of the phases of interest. In this paper, we describe an efficient method for performing field-theoretic simulations in the Gibbs ensemble, a familiar construct in particle-based simulations where two phases in equilibrium with each other are simulated in separate simulation boxes. Chemical and mechanical equilibrium is maintained by allowing the simulation boxes to swap both chemical species and volume. By fixing the total number of each chemical species and the total volume, the Gibbs ensemble allows for the efficient simulation of two bulk phases at equilibrium in the canonical ensemble. After providing the theoretical framework for field-theoretic simulations in the Gibbs ensemble, we demonstrate the method on two two-dimensional model polymer test systems in both the mean-field limit (self-consistent field theory) and in the fluctuating field theory.
Dewatering of microalgal cultures: A major bottleneck to algae-based fuels
Authors: Uduman Nyomi , Qi Ying , Danquah Michael K. , Forde Gareth M. , Hoadley Andrew
Published: January 2010

Microalgae dewatering is a major obstruction to industrial-scale processing of microalgae for biofuel production. The dilute nature of harvested microalgal cultures creates a huge operational cost during dewatering, thereby, rendering algae-based fuels less economically attractive. Currently there is no superior method of dewatering microalgae. A technique that may result in a greater algal biomass may have drawbacks such as a high capital cost or high energy consumption. The choice of which harvesting technique to apply will depend on the species of microalgae and the final product desired. Algal properties such as a large cell size and the capability of the microalgae to autoflocculate can simplify the dewatering process. This article reviews and addresses the various technologies currently used for dewatering microalgal cultures along with a comparative study of the performances of the different technologies.
Deciphering Faces: Quantifiable Visual Cues to Weight
Authors: Coetzee Vinet , Chen Jingying , Perrett David I , Stephen Ian D
Published: January 2010

Body weight plays a crucial role in mate choice, as weight is related to both attractiveness and health. People are quite accurate at judging weight in faces, but the cues used to make these judgments have not been defined. This study consisted of two parts. First, we wanted to identify quantifiable facial cues that are related to body weight, as defined by body mass index (BMI). Second, we wanted to test whether people use these cues to judge weight. In study 1, we recruited two groups of Caucasian and two groups of African participants, determined their BMI and measured their 2-D facial images for: width-to-height ratio, perimeter-to-area ratio, and cheek-to-jaw-width ratio. All three measures were significantly related to BMI in males, while the width-to-height and cheek-to-jaw-width ratios were significantly related to BMI in females. In study 2, these images were rated for perceived weight by Caucasian observers. We showed that these observers use all three cues to judge weight in African and Caucasian faces of both sexes. These three facial cues, width-to-height ratio, perimeter-to-area ratio, and cheek-to-jaw-width ratio, are therefore not only related to actual weight but provide a basis for perceptual attributes as well.
Linking knowledge with action in the pursuit of sustainable water-resources management
Authors: Jacobs Katharine , Lebel Louis , Buizer James , Addams Lee , Matson Pamela , McCullough Ellen , Garden Po , Saliba George , Finan Timothy
Published: January 2010

Managing water for sustainable use and economic development is both a technical and a governance challenge in which knowledge production and sharing play a central role. This article evaluates and compares the role of participatory governance and scientific information in decision-making in four basins in Brazil, Mexico, Thailand, and the United States. Water management institutions in each of the basins have evolved during the last 10–20 years from a relatively centralized water-management structure at the state or national level to a decision structure that involves engaging water users within the basins and the development of participatory processes. This change is consistent with global trends in which states increasingly are expected to gain public acceptance for larger water projects and policy changes. In each case, expanded citizen engagement in identifying options and in decision-making processes has resulted in more complexity but also has expanded the culture of integrated learning. International funding for water infrastructure has been linked to requirements for participatory management processes, but, ironically, this study finds that participatory processes appear to work better in the context of decisions that are short-term and easily adjusted, such as water-allocation decisions, and do not work so well for longer-term, high-stakes decisions regarding infrastructure. A second important observation is that the costs of capacity building to allow meaningful stakeholder engagement in water-management decision processes are not widely recognized. Failure to appreciate the associated costs and complexities may contribute to the lack of successful engagement of citizens in decisions regarding infrastructure.
Rescue of defective G protein–coupled receptor function in vivo by intermolecular cooperation
Authors: Rivero-Müller Adolfo , Chou Yen-Yin , Ji Inhae , Lajic Svetlana , Hanyaloglu Aylin C. , Jonas Kim , Rahman Nafis , Ji Tae H. , Huhtaniemi Ilpo
Published: January 2010

G protein–coupled receptors (GPCRs) are ubiquitous mediators of signaling of hormones, neurotransmitters, and sensing. The old dogma is that a one ligand/one receptor complex constitutes the functional unit of GPCR signaling. However, there is mounting evidence that some GPCRs form dimers or oligomers during their biosynthesis, activation, inactivation, and/or internalization. This evidence has been obtained exclusively from cell culture experiments, and proof for the physiological significance of GPCR di/oligomerization in vivo is still missing. Using the mouse luteinizing hormone receptor (LHR) as a model GPCR, we demonstrate that transgenic mice coexpressing binding-deficient and signaling-deficient forms of LHR can reestablish normal LH actions through intermolecular functional complementation of the mutant receptors in the absence of functional wild-type receptors. These results provide compelling in vivo evidence for the physiological relevance of intermolecular cooperation in GPCR signaling.
Detecting and understanding combinatorial mutation patterns responsible for HIV drug resistance
Authors: Zhang Jing , Hou Tingjun , Wang Wei , Liu Jun S.
Published: January 2010

We propose a systematic approach for a better understanding of how HIV viruses employ various combinations of mutations to resist drug treatments, which is critical to developing new drugs and optimizing the use of existing drugs. By probabilistically modeling mutations in the HIV-1 protease or reverse transcriptase (RT) isolated from drug-treated patients, we present a statistical procedure that first detects mutation combinations associated with drug resistance and then infers detailed interaction structures of these mutations. The molecular basis of our statistical predictions is further studied by using molecular dynamics simulations and free energy calculations. We have demonstrated the usefulness of this systematic procedure on three HIV drugs, (Indinavir, Zidovudine, and Nevirapine), discovered unique interaction features between viral mutations induced by these drugs, and revealed the structural basis of such interactions.
Vertical silicon nanowires as a universal platform for delivering biomolecules into living cells
Authors: Shalek Alex K. , Robinson Jacob T. , Karp Ethan S. , Lee Jin Seok , Ahn Dae-Ro , Yoon Myung-Han , Sutton Amy , Jorgolli Marsela , Gertner Rona S. , Gujral Taranjit S. , MacBeath Gavin , Yang Eun Gyeong , Park Hongkun
Published: January 2010

A generalized platform for introducing a diverse range of biomolecules into living cells in high-throughput could transform how complex cellular processes are probed and analyzed. Here, we demonstrate spatially localized, efficient, and universal delivery of biomolecules into immortalized and primary mammalian cells using surface-modified vertical silicon nanowires. The method relies on the ability of the silicon nanowires to penetrate a cell’s membrane and subsequently release surface-bound molecules directly into the cell’s cytosol, thus allowing highly efficient delivery of biomolecules without chemical modification or viral packaging. This modality enables one to assess the phenotypic consequences of introducing a broad range of biological effectors (DNAs, RNAs, peptides, proteins, and small molecules) into almost any cell type. We show that this platform can be used to guide neuronal progenitor growth with small molecules, knock down transcript levels by delivering siRNAs, inhibit apoptosis using peptides, and introduce targeted proteins to specific organelles. We further demonstrate codelivery of siRNAs and proteins on a single substrate in a microarray format, highlighting this technology’s potential as a robust, monolithic platform for high-throughput, miniaturized bioassays.
Tracking footprints of artificial selection in the dog genome
Authors: Akey Joshua M. , Ruhe Alison L. , Akey Dayna T. , Wong Aaron K. , Connelly Caitlin F. , Madeoy Jennifer , Nicholas Thomas J. , Neff Mark W.
Published: January 2010

The size, shape, and behavior of the modern domesticated dog has been sculpted by artificial selection for at least 14,000 years. The genetic substrates of selective breeding, however, remain largely unknown. Here, we describe a genome-wide scan for selection in 275 dogs from 10 phenotypically diverse breeds that were genotyped for over 21,000 autosomal SNPs. We identified 155 genomic regions that possess strong signatures of recent selection and contain candidate genes for phenotypes that vary most conspicuously among breeds, including size, coat color and texture, behavior, skeletal morphology, and physiology. In addition, we demonstrate a significant association betweenHAS2and skin wrinkling in the Shar-Pei, and provide evidence that regulatory evolution has played a prominent role in the phenotypic diversification of modern dog breeds. Our results provide a first-generation map of selection in the dog, illustrate how such maps can rapidly inform the genetic basis of canine phenotypic variation, and provide a framework for delineating the mechanistic basis of how artificial selection promotes rapid and pronounced phenotypic evolution.
Symbolic use of marine shells and mineral pigments by Iberian Neandertals
Authors: Zilhão João , Angelucci Diego E. , Badal-García Ernestina , d’Errico Francesco , Daniel Floréal , Dayet Laure , Douka Katerina , Higham Thomas F. G. , Martínez-Sánchez María José , Montes-Bernárdez Ricardo , Murcia-Mascarós Sonia , Pérez-Sirvent Carmen , Roldán-García Clodoaldo , Vanhaeren Marian , Villaverde Valentín , Wood Rachel , Zapata Josefina
Published: January 2010

Two sites of the Neandertal-associated Middle Paleolithic of Iberia, dated to as early as approximately 50,000 years ago, yielded perforated and pigment-stained marine shells. At Cueva de los Aviones, three umbo-perforated valves of
Acanthocardia
and
Glycymeris
were found alongside lumps of yellow and red colorants, and residues preserved inside a
Spondylus
shell consist of a red lepidocrocite base mixed with ground, dark red-to-black fragments of hematite and pyrite. A perforated
Pecten
shell, painted on its external, white side with an orange mix of goethite and hematite, was abandoned after breakage at Cueva Antón, 60 km inland. Comparable early modern human-associated material from Africa and the Near East is widely accepted as evidence for body ornamentation, implying behavioral modernity. The Iberian finds show that European Neandertals were no different from coeval Africans in this regard, countering genetic/cognitive explanations for the emergence of symbolism and strengthening demographic/social ones.
The transition state for peptide bond formation reveals the ribosome as a water trap
Authors: Wallin Göran , Åqvist Johan
Published: January 2010

Recent progress in elucidating the peptide bond formation process on the ribosome has led to notion of a proton shuttle mechanism where the 2'-hydroxyl group of the P-site tRNA plays a key role in mediating proton transfer between the nucleophile and leaving group, whereas ribosomal groups do not actively participate in the reaction. Despite these advances, the detailed nature of the transition state for peptidyl transfer and the role of several trapped water molecules in the peptidyl transferase center remain major open questions. Here, we employ high-level quantum chemical
ab initio
calculations to locate and characterize global transition states for the reaction, described by a molecular model encompassing all the key elements of the reaction center. The calculated activation enthalpy as well as structures are in excellent agreement with experimental data and point to feasibility of an eight-membered “double proton shuttle” mechanism in which an auxiliary water molecule, observed both in computer simulations and crystal structures, actively participates. A second conserved water molecule is found to be of key importance for stabilizing developing negative charge on the substrate oxyanion and its presence is catalytically favorable both in terms of activation enthalpy and entropy. Transition states calculated both for six- and eight-membered mechanisms are invariably late and do not involve significant charge development on the attacking amino group. Predicted kinetic isotope effects consistent with this picture are similar to those observed for uncatalyzed ester aminolysis reactions in solution.
Compositional phrasal verbs with up
Authors: Machonis Peter A.
Published: January 2010

This study examines a corpus of 300 compositional phrasal verbs in English using the particle up. Whereas frozen phrasal verbs clearly do not have the same meaning without the particle and must be listed in the lexicon grammar of idiomatic expressions (e.g., break up the audience “cause to laugh”), compositional phrasal verbs merely add an aspectual element to the simple verb, and particle usage might be better analyzed as a property of the simple verb. Although this meaning is difficult to characterize precisely, it generally indicates direction (ride up the elevator), completion (open up the store), intensity (hype up the book), or combinations (polish up the silverware, completion and intensity). These properties are added to the table of compositional phrasal verbs. Optional particle usage can also identify the meaning of a potentially ambiguous simple verb. For example, the simple verb call “phone” can take the particle up but not out, while the simple verb call “announce” can take the particle out but not up. The simple verb tables, however, will become enormously complex when all English particles (fifteen different particles according to B. Fraser 1976) are taken into account.
Can Payments for Watershed Services Help Finance Biodiversity Conservation? A Spatial Analysis of Highland Guatemala
Authors: Pagiola Stefano , Zhang Wei , Colom Ale
Published: January 2010

Payments for environmental services (PES) are a promising mechanism for conservation. PES could either provide additional funding for protected areas, pay land users to conserve biodiversity outside protected areas, or both. PES require a secure long-term source of financing to work effectively. Obtaining payments directly for biodiversity conservation is difficult, however. In most cases, water users are the most likely source, either directly or indirectly. Thus the potential for PES to help conserve biodiversity depends, in a large measure, on the degree to which areas of interest for conservation of water services overlap with areas of interest for conservation of biodiversity. This paper examines the extent of such an overlap in the case of highland Guatemala. The results show that this potential varies substantially within the country, with some biodiversity conservation priority areas having very good potential for receiving payments, and others little or none. Overall, about a quarter of all biodiversity conservation priority areas have potential for receiving payments. Thus PES are far from being a silver bullet for biodiversity conservation, but they can make a meaningful contribution to this objective.
Protecting Developing Countries' Forests: Enforcement in Theory and Practice
Authors: Robinson Elizabeth J. Z. , Kumar Ajay M. , Albers Heidi J.
Published: January 2010

This paper relates the key findings of the optimal economic enforcement literature to practical issues of enforcing forest and wildlife management access restrictions in developing countries. Our experiences, particularly from Tanzania and eastern India, provide detail of the key pragmatic issues facing those responsible for protecting natural resources. We identify large gaps in the theoretical literature that limit its ability to inform practical management, including issues of limited funding and cost recovery, multiple tiers of enforcement and the incentives facing enforcement officers, and conflict between protected area managers and rural people's needs.
Household Consumption and Natural Resource Management around National Parks in Zambia
Authors: Bandyopadhyay Sushenjit , Tembo Gelson
Published: January 2010

Game Management Areas in Zambia aim to combine nature conservation with economic empowerment of rural households. This study determines the impact of community-based wildlife management and participation in related community institutions on household welfare. The results indicate that the gains from living in Game Management Areas and from participating in natural resource management are large but unevenly distributed. Only Game Management Areas with limited alternative livelihoods exhibit significant consumption benefits. However, the gains accrue mainly to the relatively well off, while the poor do not gain even if they participate. The results also show that infrastructure development does not necessarily translate into household level consumption gains in the short run. The design of community-based natural resource management programmes needs to respond to the inherent diversity among both the national parks and the community members. There is a need to address impediments to effective participation by the majority of the community members.
Genetic and pharmacological targeting of activin receptor-like kinase 1 impairs tumor growth and angiogenesis
Authors: Cunha Sara I. , Pardali Evangelia , Thorikay Midory , Anderberg Charlotte , Hawinkels Lukas , Goumans Marie-José , Seehra Jasbir , Heldin Carl-Henrik , ten Dijke Peter , Pietras Kristian
Published: January 2010

Members of the transforming growth factor β (TGF-β) family have been genetically linked to vascular formation during embryogenesis. However, contradictory studies about the role of TGF-β and other family members with reported vascular functions, such as bone morphogenetic protein (BMP) 9, in physiological and pathological angiogenesis make the need for mechanistic studies apparent. We demonstrate, by genetic and pharmacological means, that the TGF-β and BMP9 receptor activin receptor-like kinase (ALK) 1 represents a new therapeutic target for tumor angiogenesis. Diminution of ALK1 gene dosage or systemic treatment with the ALK1-Fc fusion protein RAP-041 retarded tumor growth and progression by inhibition of angiogenesis in a transgenic mouse model of multistep tumorigenesis. Furthermore, RAP-041 significantly impaired the in vitro and in vivo angiogenic response toward vascular endothelial growth factor A and basic fibroblast growth factor. In seeking the mechanism for the observed effects, we uncovered an unexpected signaling synergy between TGF-β and BMP9, through which the combined action of the two factors augmented the endothelial cell response to angiogenic stimuli. We delineate a decisive role for signaling by TGF-β family members in tumor angiogenesis and offer mechanistic insight for the forthcoming clinical development of drugs blocking ALK1 in oncology.
CD8 T cell response and evolutionary pressure to HIV-1 cryptic epitopes derived from antisense transcription
Authors: Bansal Anju , Carlson Jonathan , Yan Jiyu , Akinsiku Olusimidele T. , Schaefer Malinda , Sabbaj Steffanie , Bet Anne , Levy David N. , Heath Sonya , Tang Jianming , Kaslow Richard A. , Walker Bruce D. , Ndung’u Thumbi , Goulder Philip J. , Heckerman David , Hunter Eric , Goepfert Paul A.
Published: January 2010

Retroviruses pack multiple genes into relatively small genomes by encoding several genes in the same genomic region with overlapping reading frames. Both sense and antisense HIV-1 transcripts contain open reading frames for known functional proteins as well as numerous alternative reading frames (ARFs). At least some ARFs have the potential to encode proteins of unknown function, and their antigenic properties can be considered as cryptic epitopes (CEs). To examine the extent of active immune response to virally encoded CEs, we analyzed human leukocyte antigen class I–associated polymorphisms in HIV-1 gag, pol, and nef genes from a large cohort of South Africans with chronic infection. In all, 391 CEs and 168 conventional epitopes were predicted, with the majority (307; 79%) of CEs derived from antisense transcripts. In further evaluation of CD8 T cell responses to a subset of the predicted CEs in patients with primary or chronic infection, both sense- and antisense-encoded CEs were immunogenic at both stages of infection. In addition, CEs often mutated during the first year of infection, which was consistent with immune selection for escape variants. These findings indicate that the HIV-1 genome might encode and deploy a large potential repertoire of unconventional epitopes to enhance vaccine-induced antiviral immunity.
Single cell optical transfection
Authors: Stevenson David J. , Gunn-Moore Frank J. , Campbell Paul , Dholakia Kishan
Published: January 2010

The plasma membrane of a eukaryotic cell is impermeable to most hydrophilic substances, yet the insertion of these materials into cells is an extremely important and universal requirement for the cell biologist. To address this need, many transfection techniques have been developed including viral, lipoplex, polyplex, capillary microinjection, gene gun and electroporation. The current discussion explores a procedure called optical injection, where a laser field transiently increases the membrane permeability to allow species to be internalized. If the internalized substance is a nucleic acid, such as DNA, RNA or small interfering RNA (siRNA), then the process is called optical transfection. This contactless, aseptic, single cell transfection method provides a key nanosurgical tool to the microscopist—the intracellular delivery of reagents and single nanoscopic objects. The experimental possibilities enabled by this technology are only beginning to be realized. A review of optical transfection is presented, along with a forecast of future applications of this rapidly developing and exciting technology.
Medication use as a risk factor for inpatient falls in an acute care hospital: a case‐crossover study
Authors: Shuto Hideki , Imakyure Osamu , Matsumoto Junichi , Egawa Takashi , Jiang Ying , Hirakawa Masaaki , Kataoka Yasufumi , Yanagawa Takashi
Published: January 2010

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

• Benzodiazepines, antidepressants, antipsychotic agents, anti‐arrhythmic agents, opioid analgesics and antihypertensive agents including α‐receptor antagonists and β‐receptor antagonists, but not angiotensin II receptor antagonists, have been implicated as risk factors for falls among community dwelling elderly people, and those in aged care hospitals and nursing homes.

WHAT THIS STUDY ADDS

• Using a case‐crossover design, the study's findings provide the first evidence suggesting that newly initiating treatment using an angiotensin II receptor antagonist, candesartan, or etizolam, biperiden and zopiclone may be potential risk factors for falls in acute hospitals.

AIMS The present study aimed to evaluate the associations between medication use and falls and to identify high risk medications that acted as a trigger for the onset of falls in an acute care hospital setting.

METHODS We applied a case‐crossover design wherein cases served as their own controls and comparisons were made within each participant. The 3‐day period (days 0 to −2) and the 3‐day periods (days −6 to −8, days −9 to −11 and days −12 to −14) before the fall event were defined as the case period and the control periods, respectively. Exposures to medications were compared between the case and control periods. Odds ratios (OR) and 95% confidence intervals (CI) for the onset of falls with respect to medication use were computed using conditional logistic regression analyses.

RESULTS A total of 349 inpatients who fell during their hospitalization were recorded on incident report forms between March 2003 and August 2005. The initial use of antihypertensive, antiparkinsonian, anti‐anxiety and hypnotic agents as medication classes was significantly associated with an increased risk of falls, and these ORs (95% CI) were 8.42 (3.12, 22.72), 4.18 (1.75, 10.02), 3.25 (1.62, 6.50) and 2.44 (1.32, 4.51), respectively. The initial use of candesartan, etizolam, biperiden and zopiclone was also identified as a potential risk factor for falls.

CONCLUSIONS Medical professionals should be aware of the possibility that starting a new medication such as an antihypertensive agent, including candesartan, and antiparkinsonian, anti‐anxiety and hypnotic agents, may act as a trigger for the onset of a fall.
Rapid isolation of translocation breakpoints in chronic myeloid and acute promyelocytic leukaemia
Authors: Bartley Paul A. , Martin‐Harris Michael H. , Budgen Bradley J. , Ross David M. , Morley Alexander A.
Published: January 2010

Isolation and sequencing of the translocation breakpoint in chronic myeloid leukaemia‐(CML) and acute promyelocytic leukaemia (APML) may help to elucidate the mechanism of translocation and provide a molecular marker for monitoring of minimal residual disease. Amplification across the translocation breakpoint was performed in samples from 91 patients with CML and 15 patients with APML using single‐tube multiplex polymerase chain reaction (PCR) involving 308 primers for CML and 40 primers for APML. Nonspecific amplification was removed by a modification of PCR, termed sequential hybrid primer PCR (SHP‐PCR), which involved two sequential rounds of PCR, each of which used a low concentration of a specially designed hybrid primer. The resultant amplified material was sequenced. The method as finally developed was simple quick and robust. The translocation breakpoint was successfully isolated and sequenced in all 106 samples. The strategy of highly multiplexed PCR followed by SHP‐PCR is thus an effective method for isolating the translocation breakpoint in CML and APML. It may also be applicable to other haematological disorders characterised by translocation, deletion or inversion.
A prostacyclin agonist with thromboxane inhibitory activity for airway allergic inflammation in mice
Authors: Hayashi M. , Koya T. , Kawakami H. , Sakagami T. , Hasegawa T. , Kagamu H. , Takada T. , Sakai Y. , Suzuki E. , Gelfand E. W. , Gejyo F.
Published: January 2010

Background
ONO‐1301 is a novel drug that acts as a prostacyclin agonist with thromboxane A2 (TxA2) synthase inhibitory activity. We investigated the effect of ONO‐1301 on development of airway allergic inflammation.

Methods
Mice sensitized and challenged to ovalbumin (OVA) received ONO‐1301, OKY‐046 (TxA2 synthase inhibitor), beraprost, a prostacyclin receptor (IP) agonist, ONO‐1301 plus CAY10449 (selective IP antagonist) or vehicle during the challenge period. Twenty‐four hours after the OVA challenge, airway hyperresponsiveness (AHR) to methacholine was assessed and bronchoalveolar lavage was performed. Lung specimens were excised for goblet cell staining and analysis of lung dendritic cells (DCs). Bone marrow‐derived dendritic cells (BMDCs) were generated, in the presence or absence of drugs, for analysis of DC function.

Results
Mice that received ONO‐1301 showed significantly lower AHR, airway eosinophilia, T‐helper type 2 cytokine levels, mucus production and lung DCs numbers than vehicle‐treated mice. These effects of ONO‐1301 were mostly reversed by CAY10449. BMDCs treated with ONO‐1301 alone showed lower DC functions, such as expression of costimulatory factors or stimulation to spleen T cells.

Conclusions
These data suggest that ONO‐1301 may suppress AHR and airway allergic inflammation through modulation of DCs, mainly mediated through the IP receptor. This agent may be effective as an anti‐inflammatory drug in the treatment of asthma.

Cite this as: M. Hayashi, T. Koya, H. Kawakami, T. Sakagami, T. Hasegawa, H. Kagamu, T. Takada, Y. Sakai, E. Suzuki, E. W. Gelfand and F. Gejyo, Clinical & Experimental Allergy, 2010 (40) 317– 326.
Airway smooth muscle proliferation and survival is not modulated by mast cells
Authors: Kaur D. , Hollins F. , Saunders R. , Woodman L. , Sutcliffe A. , Cruse G. , Bradding P. , Brightling C.
Published: January 2010

Background
Airway smooth muscle (ASM) hyperplasia and mast cell localization within the ASM bundle are important features of asthma. The cause of this increased ASM mass is uncertain and whether it is a consequence of ASM–mast cell interactions is unknown.

Objective
We sought to investigate ASM proliferation and survival in asthma and the effects of co‐culture with mast cells.

Methods
Primary ASM cultures were derived from 11 subjects with asthma and 12 non‐asthmatic controls. ASM cells were cultured for up to 10 days in the presence or absence of serum either alone or in co‐culture with the human mast cell line‐1, unstimulated human lung mast cells (HLMC) or IgE/anti‐IgE‐activated HLMC. Proliferation was assessed by cell counts, CFSE assay and thymidine incorporation. Apoptosis and necrosis were analysed by Annexin V/propidium iodide staining using flow cytometry and by assessment of nuclear morphology using immunofluorescence. Mast cell activation was confirmed by the measurement of histamine release.

Results
Using a number of techniques, we found that ASM proliferation and survival was not significantly different between cells derived from subjects with or without asthma. Co‐culture with mast cells did not affect the rate of proliferation or survival of ASM cells.

Conclusion
Our findings do not support a role for increased airway smooth proliferation and survival as the major mechanism driving ASM hyperplasia in asthma.

Cite this as: D. Kaur, F. Hollins, R. Saunders, L. Woodman, A. Sutcliffe, G. Cruse, P. Bradding and C. Brightling, Clinical & Experimental Allergy, 2010 (40) 279– 288.