bluuebunny/crossref_metadata_2025 huggingface dataset:
Strong UV absorption and emission from L-cysteine capped monodispersed gold nanoparticles
Authors: Sarangi S. N. , Hussain A. M. P. , Sahu S. N.
Published: August 2009

We report a synthesis of L-cysteine capped monodispersed gold (Au) nanoparticles (NPs) with size ∼2.0 nm exhibiting a strong surface plasmon resonance optical absorption at 3.13 eV, which is blueshifted by 1.01 eV compared to the uncapped Au NPs of size 20.0 nm. A strong fluorescence (FL) of the capped Au NPs appears at 3.25 eV, whereas the uncapped Au NPs do not show any FL in this range. The L-cysteine concentration has been optimized to achieve one of the strongest ultraviolet absorption and luminescence. The capping of Au NPs has been confirmed by Fourier transform infra red measurement.
An extended high pressure-temperature phase diagram of NaBH4
Authors: George Lyci , Drozd Vadym , Couvy Helene , Chen Jiuhua , Saxena Surendra K.
Published: August 2009

We have studied the structural stability of NaBH4 under pressures up to 17 GPa and temperatures up to 673 K in a diamond anvil cell and formed an extended high P-T phase diagram using combined synchrotron x-ray diffraction and Raman spectroscopy. Even though few reports on phase diagram of NaBH4 are found in current literature, up to our knowledge this is the first experimental work using diamond anvil cell in a wide pressure/temperature range. Bulk modulus, its temperature dependence, and thermal expansion coefficient for the ambient cubic phase of NaBH4 are found to be 18.76(1) GPa, −0.0131 GPa K−1, and 12.5×10−5+23.2×10−8 T/K, respectively. We have also carried out Raman spectroscopic studies at room temperature up to 30 GPa to reinvestigate the phase transitions observed for NaBH4. A comparative symmetry analysis also has been carried out for different phases of NaBH4.
Molecular dynamics study of thermal-driven methane hydrate dissociation
Authors: English Niall J. , Phelan Gráinne M.
Published: August 2009

Nonequilibrium molecular dynamics simulations have been performed to investigate the thermal-driven breakup of both spherical methane hydrate nanocrystallites (with radii of approximately 18 and 21 Å) and planar methane hydrate interfaces in liquid water at 280–340 K. The melting temperatures of each cluster were estimated, and dissociation was observed to be strongly dependent on temperature, with higher dissociation rates at larger overtemperatures vis-a-vis melting. For the 18 and 21 Å radius nanocrystals, breakup was also seen to be dependent on cluster size, and different methane compositions (85%, 95%, and 100% of maximum theoretical occupation) in the planar case also lead to slight differences in the initial dissociation rate. In all cases, the diffusion of the methane into the surrounding liquid water was found to be an important step limiting the overall rate of breakup. A simple coupled mass and heat transfer model has been devised for both the spherical and planar hydrate systems that explains these findings, and distinguishes between the role of the overall thermal driving force and methane diffusional mass transfer in controlling the break-up rate.
Control of the molecular orientation of a 2,2′-bithiophene-9,9-dioctylfluorene copolymer by laser annealing and subsequent enhancement of the field effect transistor characteristics
Authors: Kubota Korefumi , Kato Takuji , Adachi Chihaya
Published: August 2009

We controlled the orientation of a 2,2′-bithiophene-9,9-dioctylfluorene (F8T2) copolymer spin-coated film on a polycarbonate substrate using a laser-annealing technique and demonstrated an enhancement of the field-effect transistor characteristics. We used a semiconductor laser, having a lasing wavelength of λ=405 nm, with a small spot size of 400 nm. Using polarizing optical microscopy and x-ray diffraction analysis, we confirmed enhancement of the orientation of the molecular chains of F8T2, along the laser scanning direction. Following laser annealing, the field-effect hole mobility resulted in a value of μ=1.6×10−3 cm2/V s, which is about three times higher than that of the unannealed sample.
Control morphology of nanostructures with electric field
Authors: Park Jonghyun , Lu Wei
Published: August 2009

We showed that the morphology of nanostructures on a dielectric substrate may be tuned by electric field. The collective action of surface energy, interface energy between nanostructures and the substrate, and electrostatic energy defines a thermodynamic force that drives surface diffusion. The evolution is characterized by a quick adjustment of the dihedral angle at the triple junction, followed by an extrusion of a thin layer from the edges, and subsequent significant overall morphology change through long range mass transport. A high voltage can induce instability of the extrusion, causing the formation of a pattern of tiny islands.
A luminal flavoprotein in endoplasmic reticulum-associated degradation
Authors: Riemer Jan , Appenzeller-Herzog Christian , Johansson Linda , Bodenmiller Bernd , Hartmann-Petersen Rasmus , Ellgaard Lars
Published: August 2009

The quality control system of the endoplasmic reticulum (ER) discriminates between native and nonnative proteins. The latter are degraded by the ER-associated degradation (ERAD) pathway. Whereas many cytosolic and membrane components of this system are known, only few luminal players have been identified. In this study, we characterize ERFAD (ER flavoprotein associated with degradation), an ER luminal flavoprotein that functions in ERAD. Upon knockdown of ERFAD, the degradation of the ERAD model substrate ribophorin 332 is delayed, and the overall level of polyubiquitinated cellular proteins is decreased. We also identify the ERAD components SEL1L, OS-9 and ERdj5, a known reductase of ERAD substrates, as interaction partners of ERFAD. Our data show that ERFAD facilitates the dislocation of certain ERAD substrates to the cytosol, and we discuss the findings in relation to a potential redox function of the protein.
Op18 reveals the contribution of nonkinetochore microtubules to the dynamic organization of the vertebrate meiotic spindle
Authors: Houghtaling Benjamin R. , Yang Ge , Matov Alexandre , Danuser Gaudenz , Kapoor Tarun M.
Published: August 2009

Accuracy in chromosome segregation depends on the assembly of a bipolar spindle. Unlike mitotic spindles, which have roughly equal amounts of kinetochore microtubules (kMTs) and nonkinetochore microtubules (non-kMTs), vertebrate meiotic spindles are predominantly comprised of non-kMTs, a large subset of which forms an antiparallel “barrel” array at the spindle equator. Though kMTs are needed to drive chromosome segregation, the contributions of non-kMTs are more mysterious. Here, we show that increasing the concentration of Op18/stathmin, a component of the chromosome-mediated microtubule formation pathway that directly controls microtubule dynamics, can be used to deplete non-kMTs in the vertebrate meiotic spindle assembled in
Xenopus
egg extracts. Under these conditions, kMTs and the spindle pole-associated non-kMT arrays persist in smaller spindles. In excess Op18, distances between sister kinetochores, an indicator of tension across centromeres, remain unchanged, even though kMTs flux poleward with a ≈30% slower velocity, and chromosomes oscillate more than in control metaphase spindles. Remarkably, kinesin-5, a conserved motor protein that can push microtubules apart and is required for the assembly and maintenance of bipolar meiotic spindles, is not needed to maintain spindle bipolarity in the presence of excess Op18. Our data suggest that non-kMTs in meiotic spindles contribute to normal kMT dynamics, stable chromosome positioning, and the establishment of proper spindle size. We propose that without non-kMTs, metaphase meiotic spindles are similar to mammalian mitotic spindles, which balance forces to maintain metaphase spindle organization in the absence of extensive antiparallel microtubule overlap at the spindle equator or a key mitotic kinesin.
Mutation of
p107
exacerbates the consequences of
Rb
loss in embryonic tissues and causes cardiac and blood vessel defects
Authors: Berman Seth D. , West Julie C. , Danielian Paul S. , Caron Alicia M. , Stone James R. , Lees Jacqueline A.
Published: August 2009

The retinoblastoma tumor-suppressor protein, pRb, is a member of the pocket protein family that includes p107 and p130. These proteins have well-defined roles in regulating entry into and exit from the cell cycle and also have cell cycle–independent roles in facilitating differentiation. Here we investigate the overlap between pocket protein's function during embryonic development by using conditional mutant alleles to generate
Rb;p107
double-mutant embryos (DKOs) that develop in the absence of placental defects. These DKOs die between e13.5 and e14.5, much earlier than either the conditional
Rb
or the germline
p107
single mutants, which survive to birth or are largely viable, respectively. Analyses of the e13.5 DKOs shows that
p107
mutation exacerbates the phenotypes resulting from pRb loss in the central nervous system and lens, but not in the peripheral nervous system. In addition, these embryos exhibit novel phenotypes, including increased proliferation of blood vessel endothelial cells, and heart defects, including double-outlet right ventricle (DORV). The DORV is caused, at least in part, by a defect in blood vessel endothelial cells and/or heart mesenchymal cells. These findings demonstrate novel, overlapping functions for pRb and p107 in numerous murine tissues.
A 3D structure model of the melibiose permease of Escherichia coli represents a distinctive fold for Na
+
symporters
Authors: Yousef Mohammad S. , Guan Lan
Published: August 2009

The melibiose permease of
Escherichia coli
(MelB) catalyzes the coupled stoichiometric symport of a galactoside with a cation (either Na
+
, Li
+
, or H
+
), using free energy from the downhill translocation of one cosubstrate to catalyze the accumulation of the other. Here, we present a 3D structure model of MelB threaded through a crystal structure of the lactose permease of
E. coli
(LacY), manually adjusted, and energetically minimized. The model contains 442 consecutive residues (≈94% of the polypeptide), including all 12 transmembrane helices and connecting loops, with no steric clashes and superimposes well with the template structure. The electrostatic surface potential calculated from the model is typical for a membrane protein and exhibits a characteristic ring of positive charges around the periphery of the cytoplasmic side. The 3D model indicates that MelB consists of two pseudosymmetrical 6-helix bundles lining an internal hydrophilic cavity, which faces the cytoplasmic side of the membrane. Both sugar and cation binding sites are proposed to lie within the internal cavity. The model is consistent with numerous previous mutational, biochemical/biophysical characterizations as well as low-resolution structural data. Thus, an alternating access mechanism with sequential binding is discussed. The proposed overall fold of MelB is different from the available crystal structures of other Na
+
-coupled transporters, suggesting a distinctive fold for Na
+
symporters.
Distinct populations of quiescent and proliferative pancreatic β-cells identified by HOTcre mediated labeling
Authors: Hesselson Daniel , Anderson Ryan M. , Beinat Marine , Stainier Didier Y. R.
Published: August 2009

Pancreatic β-cells are critical regulators of glucose homeostasis, and they vary dramatically in their glucose stimulated metabolic response and levels of insulin secretion. It is unclear whether these parameters are influenced by the developmental origin of individual β-cells. Using HOTcre, a Cre-based genetic switch that uses heat-induction to precisely control the temporal expression of transgenes, we labeled two populations of β-cells within the developing zebrafish pancreas. These populations originate in distinct pancreatic buds and exhibit gene expression profiles suggesting distinct functions during development. We find that the dorsal bud derived β-cells are quiescent and exhibit a marked decrease in insulin expression postembryonically. In contrast, ventral bud derived β-cells proliferate actively, and maintain high levels of insulin expression compared with dorsal bud derived β-cells. Therapeutic strategies to regulate β-cell proliferation and function are required to cure pathological states that result from excessive β-cell proliferation (e.g., insulinoma) or insufficient β-cell mass (e.g., diabetes mellitus). Our data reveal the existence of distinct populations of β-cells in vivo and should help develop better strategies to regulate β-cell differentiation and proliferation.
The physical basis for increases in precipitation extremes in simulations of 21st-century climate change
Authors: O'Gorman Paul A. , Schneider Tapio
Published: August 2009

Global warming is expected to lead to a large increase in atmospheric water vapor content and to changes in the hydrological cycle, which include an intensification of precipitation extremes. The intensity of precipitation extremes is widely held to increase proportionately to the increase in atmospheric water vapor content. Here, we show that this is not the case in 21st-century climate change scenarios simulated with climate models. In the tropics, precipitation extremes are not simulated reliably and do not change consistently among climate models; in the extratropics, they consistently increase more slowly than atmospheric water vapor content. We give a physical basis for how precipitation extremes change with climate and show that their changes depend on changes in the moist-adiabatic temperature lapse rate, in the upward velocity, and in the temperature when precipitation extremes occur. For the tropics, the theory suggests that improving the simulation of upward velocities in climate models is essential for improving predictions of precipitation extremes; for the extratropics, agreement with theory and the consistency among climate models increase confidence in the robustness of predictions of precipitation extremes under climate change.
High pressure chemistry in the H
2
-SiH
4
system
Authors: Wang Shibing , Mao Ho-kwang , Chen Xiao-Jia , Mao Wendy L.
Published: August 2009

Understanding the behavior of hydrogen-rich systems at extreme conditions has significance to both condensed matter physics, where it may provide insight into the metallization and superconductivity of element one, and also to applied research areas, where it can provide guidance for designing improved hydrogen storage materials for transportation applications. Here we report the high-pressure study of the SiH
4
-H
2
binary system up to 6.5 GPa at 300 K in a diamond anvil cell. Raman measurements indicate significant intermolecular interactions between H
2
and SiH
4
. We found that the H
2
vibron frequency is softened by the presence of SiH
4
by as much as 40 cm
−1
for the fluid with 50 mol% H
2
compared with pure H
2
fluid at the same pressures. In contrast, the Si-H stretching modes of SiH
4
shift to higher frequency in the mixed fluid compared with pure SiH
4
. Pressure-induced solidification of the H
2
-SiH
4
fluid shows a binary eutectic point at 72(±2) mol% H
2
and 6.1(±0.1) GPa, above which the fluid crystallizes into a mixture of two nearly end-member solids. Neither solid has a pure end-member composition, with the silane-rich solid containing 0.5–1.5 mol% H
2
and the hydrogen-rich solid containing 0.5–1 mol% SiH
4
. These two crystalline phases can be regarded as doped hydrogen-dominant compounds. We were able to superpressurize the sample by 0.2–0.4 GPa above the eutectic before complete crystallization, indicating extended metastability.
Zona Occludens-2 Is Critical for Blood–Testis Barrier Integrity and Male Fertility
Authors: Xu Jianliang , Anuar Farhana , Mohamed Ali Safiah , Ng Mei Yong , Phua Dominic C.Y. , Hunziker Walter
Published: August 2009

Tight junction integral membrane proteins such as claudins and occludin are tethered to the actin cytoskeleton by adaptor proteins, notably the closely related zonula occludens (ZO) proteins ZO-1, ZO-2, and ZO-3. All three ZO proteins have recently been inactivated in mice. Although ZO-3 knockout mice lack an obvious phenotype, animals deficient in ZO-1 or ZO-2 show early embryonic lethality. Here, we rescue the embryonic lethality of ZO-2 knockout mice by injecting ZO-2(−/−) embryonic stem (ES) cells into wild-type blastocysts to generate viable ZO-2 chimera. ZO-2(−/−) ES cells contribute extensively to different tissues of the chimera, consistent with an extraembryonic requirement for ZO-2 rather than a critical role in epiblast development. Adult chimera present a set of phenotypes in different organs. In particular, male ZO-2 chimera show reduced fertility and pathological changes in the testis. Lanthanum tracer experiments show a compromised blood–testis barrier. Expression levels of ZO-1, ZO-3, claudin-11, and occludin are not apparently affected. ZO-1 and occludin still localize to the blood–testis barrier region, but claudin-11 is less well restricted and the localization of connexin-43 is perturbed. The critical role of ZO-2 for male fertility and blood–testis barrier integrity thus provides a first example for a nonredundant role of an individual ZO protein in adult mice.
Structural and Spatial Determinants Regulating TC21 Activation by RasGRF Family Nucleotide Exchange Factors
Authors: Calvo Fernando , Crespo Piero
Published: August 2009

RasGRF family guanine nucleotide exchange factors (GEFs) promote guanosine diphosphate (GDP)/guanosine triphosphate (GTP) exchange on several Ras GTPases, including H-Ras and TC21. Although the mechanisms controlling RasGRF function as an H-Ras exchange factor are relatively well characterized, little is known about how TC21 activation is regulated. Here, we have studied the structural and spatial requirements involved in RasGRF 1/2 exchange activity on TC21. We show that RasGRF GEFs can activate TC21 in all of its sublocalizations except at the Golgi complex. We also demonstrate that TC21 susceptibility to activation by RasGRF GEFs depends on its posttranslational modifications: farnesylated TC21 can be activated by both RasGRF1 and RasGRF2, whereas geranylgeranylated TC21 is unresponsive to RasGRF2. Importantly, we show that RasGRF GEFs ability to catalyze exchange on farnesylated TC21 resides in its pleckstrin homology 1 domain, by a mechanism independent of localization and of its ability to associate to membranes. Finally, our data indicate that Cdc42-GDP can inhibit TC21 activation by RasGRF GEFs, demonstrating that Cdc42 negatively affects the functions of RasGRF GEFs irrespective of the GTPase being targeted.
Quantifying cancer progression with conjunctive Bayesian networks
Authors: Gerstung Moritz , Baudis Michael , Moch Holger , Beerenwinkel Niko
Published: August 2009

Motivation: Cancer is an evolutionary process characterized by accumulating mutations. However, the precise timing and the order of genetic alterations that drive tumor progression remain enigmatic.

Results: We present a specific probabilistic graphical model for the accumulation of mutations and their interdependencies. The Bayesian network models cancer progression by an explicit unobservable accumulation process in time that is separated from the observable but error-prone detection of mutations. Model parameters are estimated by an Expectation-Maximization algorithm and the underlying interaction graph is obtained by a simulated annealing procedure. Applying this method to cytogenetic data for different cancer types, we find multiple complex oncogenetic pathways deviating substantially from simplified models, such as linear pathways or trees. We further demonstrate how the inferred progression dynamics can be used to improve genetics-based survival predictions which could support diagnostics and prognosis.

Availability: The software package ct-cbn is available under a GPL license on the web site cbg.ethz.ch/software/ct-cbn

Contact:  moritz.gerstung@bsse.ethz.ch
Inhibition of Inflammatory Gene Expression in Keratinocytes Using a Composition Containing Carnitine, Thioctic Acid and Saw Palmetto Extract
Authors: Chittur Sridar , Parr Brian , Marcovici Geno
Published: August 2009

Chronic inflammation of the hair follicle (HF) is considered a contributing factor in the pathogenesis of androgenetic alopecia (AGA). Previously, we clinically tested liposterolic extract of Serenoa repens (LSESr) and its glycoside, β‐sitosterol, in subjects with AGA and showed a highly positive response to treatment. In this study, we sought to determine whether blockade of inflammation using a composition containing LSESr as well as two anti‐inflammatory agents (carnitine and thioctic acid) could alter the expression of molecular markers of inflammation in a well‐established in vitro system. Using a well‐validated assay representative of HF keratinocytes, specifically, stimulation of cultured human keratinocyte cells in vitro, we measured changes in gene expression of a spectrum of well‐known inflammatory markers. Lipopolysaccharide (LPS) provided an inflammatory stimulus. In particular, we found that the composition effectively suppressed LPS‐activated gene expression of chemokines, including CCL17, CXCL6 and LTB(4) associated with pathways involved in inflammation and apoptosis. Our data support the hypothesis that the test compound exhibits anti‐inflammatory characteristics in a well‐established in vitro assay representing HF keratinocyte gene expression. These findings suggest that 5‐alpha reductase inhibitors combined with blockade of inflammatory processes could represent a novel two‐pronged approach in the treatment of AGA with improved efficacy over current modalities.
Haemodynamic and arrhythmic effects of moderately cold (22°C) water immersion and swimming in patients with stable coronary artery disease and heart failure
Authors: Schmid Jean‐Paul , Morger Cyrill , Noveanu Markus , Binder Ronald K. , Anderegg Matthias , Saner Hugo
Published: August 2009

Aims

Data on moderately cold water immersion and occurrence of arrhythmias in chronic heart failure (CHF) patients are scarce.

Methods and results

We examined 22 male patients, 12 with CHF [mean age 59 years, ejection fraction (EF) 32%, NYHA class II] and 10 patients with stable coronary artery disease (CAD) without CHF (mean age 65 years, EF 52%). Haemodynamic effects of water immersion and swimming in warm (32°C) and moderately cold (22°C) water were measured using an inert gas rebreathing method. The occurrence of arrhythmias during water activities was compared with those measured during a 24 h ECG recording. Rate pressure product during water immersion up to the chest was significantly higher in moderately cold (P = 0.043 in CHF, P = 0.028 in CAD patients) compared with warm water, but not during swimming. Rate pressure product reached 14200 in CAD and 12 400 in CHF patients during swimming. Changes in cardiac index (increase by 5–15%) and oxygen consumption (increase up to 20%) were of similar magnitude in moderately cold and warm water. Premature ventricular contractions (PVCs) increased significantly in moderately cold water from 15 ± 41 to 76 ± 163 beats per 30 min in CHF (P = 0.013) but not in CAD patients (20 ± 33 vs. 42 ± 125 beats per 30 min, P = 0.480). No ventricular tachycardia was noted.

Conclusion

Patients with compensated CHF tolerate water immersion and swimming in moderately cold water well. However, the increase in PVCs raises concerns about the potential danger of high‐grade ventricular arrhythmias.
Addressing the Dilemmas of Measuring Amylose in Rice
Authors: Fitzgerald Melissa A. , Bergman Christine J. , Resurreccion Adoracion P. , Möller Jürgen , Jimenez Rosario , Reinke Russell F. , Martin Margrit , Blanco Pedro , Molina Federico , Chen Ming‐Hsuan , Kuri Victoria , Romero Marissa V. , Habibi Fatemeh , Umemoto Takayuki , Jongdee Supanee , Graterol Eduardo , Reddy K. Radhika , Bassinello Priscila Zaczuk , Sivakami Rajeswari , Rani N. Shobha , Das Sanjukta , Wang Ya Jane , Indrasari Siti Dewi , Ramli Asfaliza , Ahmad Rauf , Dipti Sharifa S. , Xie Lihong , Lang Nguyen Thi , Singh Pratibha , Toro Dámaso Castillo , Tavasoli Fatemeh , Mestres Christian
Published: August 2009

Amylose content is a parameter that correlates with the cooking behavior of rice. It is measured at the earliest possible stages of rice improvement programs to enable breeders to build the foundations of appropriate grain quality during cultivar development. Amylose is usually quantified by absorbance of the amylose‐iodine complex. The International Network for Quality Rice (INQR) conducted a survey to determine ways that amylose is measured, reproducibility between laboratories, and sources of variation. Each laboratory measured the amylose content of a set of 17 cultivars of rice. The study shows that five different versions of the iodine binding method are in use. The data show that repeatability was high within laboratories but reproducibility between laboratories was low. The major sources of variability were the way the standard curve was constructed and the iodine binding capacity of the potato amylose used to produce the standard. Reproducibility is much lower between laboratories using a standard curve of potato amylose alone compared with those using calibrated rice cultivars. This study highlights the need to standardize the way amylose is measured, and presents research avenues for doing so.
Tocopherol and Tocotrienol Content in Commercial Wheat Mill Streams
Authors: Engelsen Merete M⊘ller , Hansen Åse
Published: August 2009

The content of tocopherols and tocotrienols, collectively known as vitamin E (tocols), was determined in fractions of roller‐milled wheat grains. The results showed that vitamin E components are present in all major flour fractions of wheat, but that the vitamin E content and composition differed significantly between fractions. The total content of vitamin E, calculated as alpha‐tocopherol equivalents, changed from 16.1 mg α‐TE/g in wheat grain to 12.2 mg α‐TE/g in roller‐milled wheat flour. The germ fraction had the highest content of tocopherols, and the content of α‐tocopherol (195.2 μg/g) was 16 times higher (on average) than in any other fraction. The content of tocotrienols was distributed more uniform in the wheat grain with the highest content in the bran fractions, and the content of β‐tocotrienol was higher than the content of α‐tocopherol in all milling fractions except the wheat germ. The content of β‐tocotrienol was 24.1 μg/g in wheat grain, 25.3–31.0 μg/g in the bran fractions, and 14.3–21.9 μg/g in the fractions of endosperm. Overall, germ and fine bran fractions represent good sources of vitamin E and might be used in breadmaking.
Aerodynamic effects of flexibility in flapping wings
Authors: Zhao Liang , Huang Qingfeng , Deng Xinyan , Sane Sanjay P.
Published: August 2009

Recent work on the aerodynamics of flapping flight reveals fundamental differences in the mechanisms of aerodynamic force generation between fixed and flapping wings. When fixed wings translate at high angles of attack, they periodically generate and shed leading and trailing edge vortices as reflected in their fluctuating aerodynamic force traces and associated flow visualization. In contrast, wings flapping at high angles of attack generate stable leading edge vorticity, which persists throughout the duration of the stroke and enhances mean aerodynamic forces. Here, we show that aerodynamic forces can be controlled by altering the trailing edge flexibility of a flapping wing. We used a dynamically scaled mechanical model of flapping flight (Re≈ 2000) to measure the aerodynamic forces on flapping wings of variable flexural stiffness (EI). For low to medium angles of attack, as flexibility of the wing increases, its ability to generate aerodynamic forces decreases monotonically but its lift-to-drag ratios remain approximately constant. The instantaneous force traces reveal no major differences in the underlying modes of force generation for flexible and rigid wings, but the magnitude of force, the angle of net force vector and centre of pressure all vary systematically with wing flexibility. Even a rudimentary framework of wing veins is sufficient to restore the ability of flexible wings to generate forces at near-rigid values. Thus, the magnitude of force generation can be controlled by modulating the trailing edge flexibility and thereby controlling the magnitude of the leading edge vorticity. To characterize this, we have generated a detailed database of aerodynamic forces as a function of several variables including material properties, kinematics, aerodynamic forces and centre of pressure, which can also be used to help validate computational models of aeroelastic flapping wings. These experiments will also be useful for wing design for small robotic insects and, to a limited extent, in understanding the aerodynamics of flapping insect wings.
The application of Fermat's principle for imaging anisotropic and inhomogeneous media with application to austenitic steel weld inspection
Authors: Connolly George D. , Lowe Michael J. S. , Temple J. Andrew G. , Rokhlin Stanislav I.
Published: August 2009

Ultrasonic inspection in anisotropic and inhomogeneous media has long presented a challenge because of the complex steering of ultrasonic paths. An approach is presented in which the true geometry of a previously used austenitic steel weld model is distorted so that, from one viewing location, all ultrasound travels in straight lines with a constant isotropic velocity. The mapping from the real space to this distorted space is accomplished using Fermat’s theorem of least travel time applied through ray tracing. Applications specific to inspection design and data interpretation for manual ultrasonic inspection of welds in austenitic steel plates are given. Validation of some intermediate results is provided using finite element analysis.
Coevolution of adaptive technology, maladaptive culture and population size in a producer–scrounger game
Authors: Lehmann Laurent , Feldman Marcus W.
Published: August 2009

Technology (i.e. tools, methods of cultivation and domestication, systems of construction and appropriation, machines) has increased the vital rates of humans, and is one of the defining features of the transition from Malthusian ecological stagnation to a potentially perpetual rising population growth. Maladaptations, on the other hand, encompass behaviours, customs and practices that decrease the vital rates of individuals. Technology and maladaptations are part of the total stock of culture carried by the individuals in a population. Here, we develop a quantitative model for the coevolution of cumulative adaptive technology and maladaptive culture in a ‘producer–scrounger’ game, which can also usefully be interpreted as an ‘individual–social’ learner interaction. Producers (individual learners) are assumed to invent new adaptations and maladaptations by trial-and-error learning, insight or deduction, and they pay the cost of innovation. Scroungers (social learners) are assumed to copy or imitate (cultural transmission) both the adaptations and maladaptations generated by producers. We show that the coevolutionary dynamics of producers and scroungers in the presence of cultural transmission can have a variety of effects on population carrying capacity. From stable polymorphism, where scroungers bring an advantage to the population (increase in carrying capacity), to periodic cycling, where scroungers decrease carrying capacity, we find that selection-driven cultural innovation and transmission may send a population on the path of indefinite growth or to extinction.
Longicorn beetle that vectors pinewood nematode carries manyWolbachiagenes on an autosome
Authors: Aikawa Takuya , Anbutsu Hisashi , Nikoh Naruo , Kikuchi Taisei , Shibata Fukashi , Fukatsu Takema
Published: August 2009

Monochamus alternatusis the longicorn beetle notorious as a vector of the pinewood nematode that causes the pine wilt disease. When two populations ofM. alternatuswere subjected to diagnostic polymerase chain reaction (PCR) detection of fourWolbachiagenes, only theftsZgene was detected from one of the populations. TheWolbachia ftsZgene persisted even after larvae were fed with a tetracycline-containing diet for six weeks. The inheritance of theftsZgene was not maternal but biparental, exhibiting a typical Mendelian pattern. TheftsZgene titres in homozygoticftsZ+insects were nearly twice as high as those in heterozygoticftsZ+insects. Exhaustive PCR surveys revealed that 31 and 30 of 214Wolbachiagenes examined were detected from the two insect populations, respectively. Many of theseWolbachiagenes contained stop codon(s) and/or frame shift(s). Fluorescentin situhybridization confirmed the location of theWolbachiagenes on an autosome. On the basis of these results, we conclude that a largeWolbachiagenomic region has been transferred to and located on an autosome ofM. alternatus. The discovery of massive gene transfer fromWolbachiatoM. alternatuswould provide further insights into the evolution and fate of laterally transferred endosymbiont genes in multicellular host organisms.
Cooperative breeding in South American hunter–gatherers
Authors: Hill Kim , Hurtado A. Magdalena
Published: August 2009

Evolutionary researchers have recently suggested that pre-modern human societies habitually practised cooperative breeding and that this feature helps explain human prosocial tendencies. Despite circumstantial evidence that post-reproductive females and extra-pair males both provide resources required for successful reproduction by mated pairs, no study has yet provided details about the flow of food resources by different age and sex categories to breeders and offspring, nor documented the ratio of helpers to breeders. Here, we show in two hunter–gatherer societies of South America that each breeding pair with dependent offspring on average obtained help from approximately 1.3 non-reproductive adults. Young married males and unmarried males of all ages were the main food providers, accounting for 93–100% of all excess food production available to breeding pairs and their offspring. Thus, each breeding pair with dependants was provisioned on average by 0.8 adult male helpers. The data provide no support for the hypothesis that post-reproductive females are the main provisioners of younger reproductive-aged kin in hunter–gatherer societies. Demographic and food acquisition data show that most breeding pairs can expect food deficits owing to foraging luck, health disabilities and accumulating dependency ratio of offspring in middle age, and that extra-pair provisioning may be essential to the evolved human life history.
Prelife catalysts and replicators
Authors: Ohtsuki Hisashi , Nowak Martin A.
Published: August 2009

Life is based on replication and evolution. But replication cannot be taken for granted. We must ask what there was prior to replication and evolution. How does evolution begin? We have proposed prelife as a generative system that produces information and diversity in the absence of replication. We model prelife as a binary soup of active monomers that form random polymers. ‘Prevolutionary’ dynamics can have mutation and selection prior to replication. Some sequences might have catalytic activity, thereby enhancing the rates of certain prelife reactions. We study the selection criteria for these prelife catalysts. Their catalytic efficiency must be above certain critical values. We find a maintenance threshold and an initiation threshold. The former is a linear function of sequence length, and the latter is an exponential function of sequence length. Therefore, it is extremely hard to select for prelife catalysts that have long sequences. We compare prelife catalysis with a simple model for replication. Assuming fast template-based elongation reactions, we can show that replicators have selection thresholds that are independent of their sequence length. Our calculation demonstrates the efficiency of replication and provides an explanation of why replication was selected over other forms of prelife catalysis.
Hosts as ecological traps for the vector of Lyme disease
Authors: Keesing F. , Brunner J. , Duerr S. , Killilea M. , LoGiudice K. , Schmidt K. , Vuong H. , Ostfeld R. S.
Published: August 2009

Vectors of infectious diseases are generally thought to be regulated by abiotic conditions such as climate or the availability of specific hosts or habitats. In this study we tested whether blacklegged ticks, the vectors of Lyme disease, granulocytic anaplasmosis and babesiosis can be regulated by the species of vertebrate hosts on which they obligately feed. By subjecting field-caught hosts to parasitism by larval blacklegged ticks, we found that some host species (e.g. opossums, squirrels) that are abundantly parasitized in nature kill 83–96% of the ticks that attempt to attach and feed, while other species are more permissive of tick feeding. Given natural tick burdens we document on these hosts, we show that some hosts can kill thousands of ticks per hectare. These results indicate that the abundance of tick vectors can be regulated by the identity of the hosts upon which these vectors feed. By simulating the removal of hosts from intact communities using empirical models, we show that the loss of biodiversity may exacerbate disease risk by increasing both vector numbers and vector infection rates with a zoonotic pathogen.
First record of a pterosaur landing trackway
Authors: Mazin Jean-Michel , Billon-Bruyat Jean-Paul , Padian Kevin
Published: August 2009

The terrestrial progression of pterosaurs, the flying reptiles of the Mesozoic Era, has been debated for over two centuries. The recent discovery of quadrupedal pterodactyloid pterosaur tracks from Late Jurassic sediments near Crayssac, France, shows that the hindlimbs moved parasagittally, as in mammals, birds and other dinosaurs, and the hypertrophied forelimbs could make tracks both close to the body wall and far outside it. Their manus tracks are unique in form, position and kinematics, which would be expected because the forelimbs were used for flight. Here, we report the first record of a pterosaur landing track, which differs substantially from typical walking trackways. The individual landed on both hind feet in parallel fashion, dragged its toes slightly as it left the track, landed again almost immediately and placed the hindfeet parallel again, then placed its forelimbs on the ground, took another short step with both hindlimbs and adjusted its forelimbs, and then began to walk off normally. The trackway shows that pterosaurs stalled to land, a reflection of their highly developed capacity for flight control and manoeuverability.
A short-armed dromaeosaurid from the Jehol Group of China with implications for early dromaeosaurid evolution
Authors: Zheng Xiaoting , Xu Xing , You Hailu , Zhao Qi , Dong Zhiming
Published: August 2009

Recent discoveries of basal dromaeosaurids from the Early Cretaceous Jiufotang and Yixian formations of Liaoning, China, add significant new information about the transition from non-avian dinosaurs to avians. Here we report on a new dromaeosaurid,Tianyuraptor ostromigen. et sp. nov., from the Early Cretaceous Yixian Formation of western Liaoning, China, based on a nearly complete skeleton.Tianyuraptorpossesses several features only seen in other Liaoning dromaeosaurids, although to a less developed degree, and it also exhibits features unknown in Laurasian dromaeosaurids but present in the Gondwanan dromaeosaurids and basal avialans, thus reducing the morphological gap between these groups.Tianyuraptorpossesses a comparatively small furcula and proportionally short forelimbs. This lies in stark contrast to the possible capacity for flight in the microraptorines, which have proportionally long and robust forelimbs and large furculae. The presence of such striking differences between the Early Cretaceous Jehol dromaeosaurids reveals a great diversity in morphology, locomotion and ecology early in dromaeosaurid evolution.
Determinants of echolocation call frequency variation in the Formosan lesser horseshoe bat (Rhinolophus monoceros)
Authors: Chen Shiang-Fan , Jones Gareth , Rossiter Stephen J.
Published: August 2009

The origin and maintenance of intraspecific variation in vocal signals is important for population divergence and speciation. Where vocalizations are transmitted by vertical cultural inheritance, similarity will reflect co-ancestry, and thus vocal divergence should reflect genetic structure. Horseshoe bats are characterized by echolocation calls dominated by a constant frequency component that is partly determined by maternal imprinting. Although previous studies showed that constant frequency calls are also influenced by some non-genetic factors, it is not known how frequency relates to genetic structure. To test this, we related constant frequency variation to genetic and non-genetic variables in the Formosan lesser horseshoe bat (Rhinolophus monoceros). Recordings of bats from across Taiwan revealed that females called at higher frequencies than males; however, we found no effect of environmental or morphological factors on call frequency. By comparison, variation showed clear population structure, with frequencies lower in the centre and east, and higher in the north and south. Within these regions, frequency divergence was directional and correlated with geographical distance, suggesting that call frequencies are subject to cultural drift. However, microsatellite clustering analysis showed that broad differences in constant frequency among populations corresponded to discontinuities in allele frequencies resulting from vicariant events. Our results provide evidence that the processes shaping genetic subdivision have concomitant consequences for divergence in echolocation call frequency.
Live-Cell Imaging Reveals Periarbuscular Membrane Domains and Organelle Location in Medicago truncatula Roots during Arbuscular Mycorrhizal Symbiosis
Authors: Pumplin Nathan , Harrison Maria J.
Published: August 2009

In the arbuscular mycorrhizal symbiosis, the fungal symbiont colonizes root cortical cells, where it establishes differentiated hyphae called arbuscules. As each arbuscule develops, the cortical cell undergoes a transient reorganization and envelops the arbuscule in a novel symbiosis-specific membrane, called the periarbuscular membrane. The periarbuscular membrane, which is continuous with the plant plasma membrane of the cortical cell, is a key interface in the symbiosis; however, relatively little is known of its composition or the mechanisms of its development. Here, we used fluorescent protein fusions to obtain both spatial and temporal information about the protein composition of the periarbuscular membrane. The data indicate that the periarbuscular membrane is composed of at least two distinct domains, an “arbuscule branch domain” that contains the symbiosis-specific phosphate transporter, MtPT4, and an “arbuscule trunk domain” that contains MtBcp1. This suggests a developmental transition from plasma membrane to periarbuscular membrane, with biogenesis of a novel membrane domain associated with the repeated dichotomous branching of the hyphae. Additionally, we took advantage of available organelle-specific fluorescent marker proteins to further evaluate cells during arbuscule development and degeneration. The three-dimensional data provide new insights into relocation of Golgi and peroxisomes and also illustrate that cells with arbuscules can retain a large continuous vacuolar system throughout development.
Discovery and Characterization of a Novel Lachrymatory Factor Synthase inPetiveria alliaceaand Its Influence on Alliinase-Mediated Formation of Biologically Active Organosulfur Compounds
Authors: Musah Rabi A. , He Quan , Kubec Roman
Published: August 2009

A novel lachrymatory factor synthase (LFS) was isolated and purified from the roots of the Amazonian medicinal plant Petiveria alliacea. The enzyme is a heterotetrameric glycoprotein comprised of two α-subunits (68.8 kD each), one γ-subunit (22.5 kD), and one δ-subunit (11.9 kD). The two α-subunits are glycosylated and connected by a disulfide bridge. The LFS has an isoelectric point of 5.2. It catalyzes the formation of a sulfine lachrymator, (Z)-phenylmethanethial S-oxide, only in the presence of P. alliacea alliinase and its natural substrate, S-benzyl-l-cysteine sulfoxide (petiveriin). Depending on its concentration relative to that of P. alliacea alliinase, the LFS sequesters, to varying degrees, the sulfenic acid intermediate formed by alliinase-mediated breakdown of petiveriin. At LFS:alliinase of 5:1, LFS sequesters all of the sulfenic acid formed by alliinase action on petiveriin, and converts it entirely to (Z)-phenylmethanethial S-oxide. However, starting at LFS:alliinase of 5:2, the LFS is unable to sequester all of the sulfenic acid produced by the alliinase, with the result that sulfenic acid that escapes the action of the LFS condenses with loss of water to form S-benzyl phenylmethanethiosulfinate (petivericin). The results show that the LFS and alliinase function in tandem, with the alliinase furnishing the sulfenic acid substrate on which the LFS acts. The results also show that the LFS modulates the formation of biologically active thiosulfinates that are downstream of the alliinase in a manner dependent upon the relative concentrations of the LFS and the alliinase. These observations suggest that manipulation of LFS-to-alliinase ratios in plants displaying this system may provide a means by which to rationally modify organosulfur small molecule profiles to obtain desired flavor and/or odor signatures, or increase the presence of desirable biologically active small molecules.
The Role of Specific Tomato Volatiles in Tomato-Whitefly Interaction
Authors: Bleeker Petra M. , Diergaarde Paul J. , Ament Kai , Guerra José , Weidner Monique , Schütz Stefan , de Both Michiel T.J. , Haring Michel A. , Schuurink Robert C.
Published: August 2009

Bemisia tabaci (whitefly) infestations and the subsequent transfer of viruses are the cause of severe losses in crop production and horticultural practice. To improve biological control of B. tabaci, we investigated repellent properties of plant-produced semiochemicals. The mix of headspace volatiles, collected from naturally repellent wild tomato accessions, influenced B. tabaci initial choice behavior, indicating a role for plant semiochemicals in locating host plants. A collection of wild tomato accessions and introgression lines (Solanum pennellii LA716 × Solanum lycopersicum ‘Moneyberg’) were extensively screened for attractiveness to B. tabaci, and their headspace profiles were determined by means of gas chromatography-mass spectrometry. Correlation analysis revealed that several terpenoids were putatively involved in tomato-whitefly interactions. Several of these candidate compounds conferred repellence to otherwise attractive tomato plants when applied to the plant's branches on paper cards. The sesquiterpenes zingiberene and curcumene and the monoterpenes p-cymene, α-terpinene, and α-phellandrene had the strongest effects in free-choice bioassays. These terpenes also elicited a response of receptors on the insect's antennae as determined by electroantennography. Conversely, the monoterpene β-myrcene showed no activity in both assays. B. tabaci apparently uses, besides visual cues, specific plant volatile cues for the initial selection of a host. Altering whitefly choice behavior by manipulation of the terpenoid composition of the host headspace may therefore be feasible.