bluuebunny/crossref_metadata_2025 huggingface dataset:
Channel profiles around Himalayan river anticlines: Constraints on their formation from digital elevation model analysis
Authors: Robl Jörg , Stüwe Kurt , Hergarten Stefan
Published: June 2008

We present a comparison between measured and numerically modeled channel profiles of rivers in two important drainage basins of Central Nepal: the Kali‐Gandaki and the Arun drainage basins. Modeled channel profiles are based on a simple stream power approach using best fit exponents defining the nonlinearities in the relative contributions of local channel gradient and water flux to erosion rate. Our analysis of the stream power in the whole river network confirms the work of other authors that a 50‐ to 80‐km‐wide zone, roughly corresponding to the High Himalayan topography, is subjected to rapid rock uplift. We suggest a model where the uplift of this zone is driven by erosion and isostatic response, so that centers of maximum uplift are located within the main channels of the north–south draining rivers. We also suggest that the rate of uplift slows down with increasing distance to the main channels. Such a spatial distribution of the uplift leads ultimately to the formation of river anticlines as observed along all major Himalayan rivers. We propose that the formation of river anticlines along south draining Himalayan rivers was accelerated by a sudden increase of the drainage area and discharge when the rivers captured orogen‐parallel drainages on the north side of the range. This may follow successive headward cutting into the Tibetan Plateau. The model is confirmed by differences between main channels and east–west running tributaries. Time‐dependent numerical models predict that capture events cause strongly elevated erosion rates in the main channel.
Paleozoic structural controls on shortening transfer in the Subandean foreland thrust system, Ene and southern Ucayali basins, Peru
Authors: Espurt Nicolas , Brusset Stéphane , Baby Patrice , Hermoza Wilber , Bolaños Rolando , Uyen Dennys , Déramond Joachim
Published: June 2008

The Neogene evolution of the Ene and southern Ucayali basins of the Subandes has been controlled by two stacked thrust wedges that differ in terms of tectonic styles. The lower thrust wedge is formed by deep‐seated décollements within the basement related to thick‐skinned foreland structures inherited from an Early Carboniferous thrust system. Seismic reflection data show that this Paleozoic compressional system has been eroded and unconformably covered by Late Carboniferous clastic sediments. It generated an irregular Paleozoic sedimentary architecture controlling the Neogene thrust propagation. The upper thin‐skinned thrust wedge developed within this Paleozoic sedimentary series and constitutes the Subandean zone. Cross‐section balancing shows an along‐strike homogenous horizontal shortening of ∼56 km (∼30%) across the Ene−southern Ucayali thrust system. This amount of shortening was vertically partitioned onto the two stacked thrust wedges. The N‐S thickness variations of the Paleozoic sedimentary prism controlled the eastward propagation of the upper thrust wedge. The southern thickening of the Paleozoic series generated major décollements and the shortening excess is of 7 km (16%) in comparison to the north. Consequently, the northern lack of shortening onto the upper thrust wedge was transferred to the Early Carboniferous compressional structures of the lower thrust wedge. We suggest that this vertical partitioning of the shortening was accommodated by a regional oblique ramp: the Tambo transfer zone. This geometrical analysis of the Ene−southern Ucayali thrust system provides new perspectives for future hydrocarbon exploration in this region.
Spring frost risk in a changing climate
Authors: Rigby J. R. , Porporato Amilcare
Published: June 2008

While both the mean and variance of daily temperature are forecasted to increase in future climate scenarios, studies of spring frost risk to vegetation have relied on changes in mean temperature to understand frost risk in these scenarios. We present a probabilistic model of spring frost risk based on the stochastic‐crossing properties of a coupled temperature‐phenology model in which the mean, variance, and autocorrelation structure of spring temperature may be controlled through independent parameters. The model results show that frost risk to vegetation is as sensitive to increases in daily temperature variance (which increases frost risk) as to increases in the mean temperature (which decreases frost risk).
Potential for non‐destructive astrochemistry using the ExoMars PanCam
Authors: Storrie‐Lombardi Michael C. , Muller J.‐P. , Fisk M. R. , Griffiths A. D. , Coates A. J.
Published: June 2008

We investigate the utility of adding a 365 nm ultraviolet (UV) light source to the ExoMars panoramic camera (PanCam) scheduled for launch in 2013. The modification makes it feasible to monitor rover drill cuttings for aromatic organic molecules and provide constraints on polycyclic aromatic hydrocarbons (PAH) as a function of depth to the 2‐meter limit of the ExoMars drill. This non‐destructive triage allows prioritized deployment of organic detection experiments requiring sample destruction and/or expenditure of non‐replaceable resources. Utilizing the Beagle 2 PanCam backup filter wheel fitted with original blue (440 nm), green (530 nm), and red (670 nm) filters we captured fluorescent images following 365 nm excitation of 3‐, 4‐ and 5‐ring PAH species doped on Mars analog peridotite grains. We demonstrate a detection limit for pyrene of 1.5 μg in granular peridotite doped at pyrene levels of 50 ± 5 ppm for camera‐to‐target distance of 1 meter.
Kant and the Brain: A New Empirical Hypothesis
Authors: Palmer Linda
Published: June 2008

Immanuel Kant's three great Critiques stand among the bulkier monuments of Enlightenment thought. The first is best known; the last had until recently been rather less studied. But his final Critique contains, I contend, a remarkable development of his theory of how human beings create and use systems of knowledge. While Kant was not himself concerned with the neuronal substrates of cognition, I argue this development yields a novel empirical hypothesis susceptible of experimental investigation. Here I present the Kantian motivation and describe experimental work aimed at testing predictions arising from the new hypothesis.
Does the Experimental Scientist Have a “Theory of Mind”?
Authors: Belmonte Matthew K.
Published: June 2008

The concept of a “theory of mind” was widely used in developmental and evolutionary psychology and neuroscience in the wake of Premack and Woodruff's 1978 article “Does the Chimpanzee Have a Theory of Mind?” and Baron-Cohen, Leslie, and Frith's 1985 follow-up “Does the Autistic Child Have a ‘Theory of Mind?’” The subsequent confluence of cognitive science and narrative theory brought “theory of mind” to literary critics. Only a very small set of people, however, have read both the neuropsychological and the literary texts on “theory of mind”; as a result of this lack of interdisciplinary expertise, the term has acquired subtly differing senses in the literary and neuroscientific communities. Because of this terminological slippage, neuroscientists and literary critics who argue in terms of “theory of mind” may believe that they are speaking with each other when they actually are speaking past each other. If proponents of cognitive literary theory are to realize the interdisciplinary fusion to which we aspire, then we must ensure that we speak in the same idiom.
Arsenic doped zinc oxide
Authors: Volbers N. , Lautenschläger S. , Leichtweiss T. , Laufer A. , Graubner S. , Meyer B. K. , Potzger K. , Zhou Shengqiang
Published: June 2008

As-doping of zinc oxide has been approached by ion implantation and chemical vapor deposition. The effect of thermal annealing on the implanted samples has been investigated by using secondary ion mass spectrometry and Rutherford backscattering∕channeling geometry. The crystal damage, the distribution of the arsenic, the diffusion of impurities, and the formation of secondary phases is discussed. For the thin films grown by vapor deposition, the composition has been determined with regard to the growth parameters. The bonding state of arsenic was investigated for both series of samples using x-ray photoelectron spectroscopy.
Combined macro- and microrheometer for use with Langmuir monolayers
Authors: Walder Robert , Schmidt Christoph F. , Dennin Michael
Published: June 2008

A Langmuir monolayer trough that is equipped for simultaneous microrheology and standard rheology measurements has been constructed. The central elements are the trough itself with a full range of optical tools accessing the air-water interface from below the trough and a portable knife-edge torsion pendulum that can access the interface from above. The ability to simultaneously measure the mechanical response of Langmuir monolayers on very different length scales is an important step for our understanding of the mechanical response of two-dimensional viscoelastic networks.
A lattice Monte Carlo simulation of the FePt alloy using a first-principles renormalized four-body interaction
Authors: Misumi Yuji , Masatsuji Satoru , Sahara Ryoji , Ishii Soh , Ohno Kaoru
Published: June 2008

Although a lattice Monte Carlo method provides an effective, simple, and fast way to study thermodynamic properties of substitutional alloys, it cannot treat by itself the off-lattice effects, such as thermal vibrations and local distortions. Therefore, even if the interaction among atoms at lattice points is calculated accurately by means of first-principles calculations, the lattice Monte Carlo simulation overestimates the order-disorder phase transition temperature. In this paper, we treat this problem in the investigation of the FePt alloy, which has recently attracted considerable interest in its magnetic properties. We apply a simple version of the potential renormalization theory to determine the interaction among atoms, including partly the off-lattice effects by means of first-principles calculations. Then, we use the interaction to perform a lattice Monte Carlo simulation of the FePt alloy on a fcc lattice. From the results, we find that the transition temperature obtained after the present renormalization procedure becomes closer to the experimental value.
Visibility study of graphene multilayer structures
Authors: Teo Guoquan , Wang Haomin , Wu Yihong , Guo Zaibing , Zhang Jun , Ni Zhenhua , Shen Zexiang
Published: June 2008

The visibility of graphene sheets on different types of substrates has been investigated both theoretically and experimentally. Although single layer graphene is observable on various types of dielectrics under an optical microscope, it is invisible when it is placed directly on most of the semiconductor and metallic substrates. We show that coating of a resist layer with optimum thickness is an effective way to enhance the contrast of graphene on various types of substrates and makes single layer graphene visible on most semiconductor and metallic substrates. Experiments have been performed to verify the results on quartz and NiFe-coated Si substrates. The results obtained will be useful for fabricating graphene-based devices on various types of substrates for electronics, spintronics, and optoelectronics applications.
Growth and optical investigation of self-assembled InGaN quantum dots on a GaN surface using a high temperature AlN buffer
Authors: Wang Q. , Wang T. , Bai J. , Cullis A. G. , Parbrook P. J. , Ranalli F.
Published: June 2008

InGaN quantum dots (QDs) with a high density up to 9×1010/cm2 have been obtained on a surface of high quality GaN grown using high temperature AlN as a buffer layer on sapphire substrates. X-ray diffraction measurements indicate that the full width at half maximum of rocking curve of the GaN in (0002) direction has been reduced to as narrow as 61 arc sec. The growth of the InGaN QDs has been found to be different from the formation of other III–V semiconductor QDs in the conventional Stranski–Krastanov mode. Too high NH3 flow rate leads to the InGaN QDs in a large diameter up to 50 nm with a density of ∼1010/cm2, while too low NH3 flow rate results in disappearance of the InGaN QDs. The growth mechanism for the InGaN QDs due to the change in NH3 flow rate has been discussed. The optical properties of the InGaN QDs have been investigated. A stimulated emission from the InGaN multiple QD layers has been observed under an optical pumping with a low threshold at room temperature. The influence of thickness of the GaN barrier and growth temperature for the GaN barrier on InGaN QDs has been investigated, in combination with optical pumping measurements. Our results indicate that both the thickness of the GaN barrier and growth temperature for the GaN barrier should be carefully chosen. Otherwise, either the formation of the InGaN QDs can be prevented or the InGaN QDs that have been formed can be destroyed.
Compact two-dimensional coarse-positioner for scanning probe microscopes
Authors: Gupta Anjan K. , Sinha Rajiv Shankar , Singh Reetesh Kumar
Published: June 2008

We report on the design and fabrication of a compact two-dimensional xy-positioner for scanning probe microscopes. This positioner uses three piezoelectric bimorphs in flexing or length-change mode by appropriate selection of electrodes and voltage polarities. One end of these bimorphs is fixed to a rectangular metal frame while on each of the free ends two sapphire disks are fixed which can slide against the polished plates of a platform movable in the xy-plane. For moving the platform by one step, the bimorphs are deformed sequentially in one mode and they are brought back to their undeformed state simultaneously. The motion of the positioner has been tested with an optical microscope and a homemade scanning tunneling microscope.
Coherent spin dynamics in Permalloy-GaAs hybrids at room temperature
Authors: Hohage P. E. , Nannen J. , Halm S. , Bacher G. , Wahle M. , Fischer S. F. , Kunze U. , Reuter D. , Wieck A. D.
Published: June 2008

Time-resolved Kerr rotation is used to study the coherent evolution of spin states in Permalloy-GaAs hybrid structures up to room temperature. Varying the width, distance and orientation of the nanopatterned Permalloy wires allow us to control the degree of frequency shift of the coherent electron spin precession due to the local magnetic fringe field in a wide range. Analytical fringe field calculations describe the measured data at room temperature quite well.
Efficient GaN slab vertical light-emitting diode covered with a patterned high-index layer
Authors: Kim Sun-Kyung , Cho Hyun Kyong , Bae Duk Kyu , Lee Jeong Soo , Park Hong-Gyu , Lee Yong-Hee
Published: June 2008

We demonstrate the enhancement of light extraction from a wide-area (500×500μm2) GaN slab light-emitting diode (LED) that results from covering it with a TiO2-patterned layer. To fabricate this device, a Cu supporter is electroplated onto the p-GaN face followed by detaching the sapphire substrate with a laser lift-off process. At the standard current of 60mA, the wall-plug efficiency of the TiO2-patterned LED is ∼14.8%, i.e., the efficiency is enhanced by a factor of ∼1.8 over that of nonpatterned LEDs. Our three-dimensional finite-difference time-domain computations confirm that this output increases with the index of the patterned layer.
Strong orange/red electroluminescence from hydrogenated polymorphous silicon carbon light-emitting devices
Authors: Stenger I. , Abramov A. , Barthou C. , Nguyen-Tran Th. , Frigout A. , Roca i Cabarrocas P.
Published: June 2008

We report on electroluminescent P-I-N diodes containing silicon nanocrystals embedded in an amorphous silicon carbon matrix as emitting material. The as-deposited devices mostly contain amorphous Si nanoparticles and emit weakly in the IR. After a forming process consisting of the application of a high current density to the structure, the intensity of the electroluminescence increases by a factor of 30 and shifts to the red. The forming process is characterized by electroluminescence measurements and the induced crystallization of the nanoparticles is evidenced by Raman scattering spectroscopy measurements. These results are interpreted as a metal induced crystallization.
Comparison of the effective conductivity between composites reinforced by graphene nanosheets and carbon nanotubes
Authors: Xie S. H. , Liu Y. Y. , Li J. Y.
Published: June 2008

Both graphene nanosheets and carbon nanotubes have exceptional electric and thermal conductivities, rendering them excellent candidates as second-phase fillers in composite materials to substantially enhance their effective conductivities. Their markedly different geometries, however, can have significant effect on the effective conductivities of composites, which we investigate using an effective medium approximation. It is demonstrated that graphene nanosheet is more effective in conductivity enhancement than carbon nantubes, and both fillers lead to substantially higher conductivity and much reduced percolation threshold in composites. The effects of conductivity anisotropy and interfacial resistance are also discussed.
Understanding of martensitic (TiCu)-based bulk metallic glasses through deformation behavior of a binary Ti50Cu50 martensitic alloy
Authors: Kim K. B. , Song K. A. , Zhang X. F. , Yi S.
Published: June 2008

A binary Ti50Cu50 martensitic alloy having similar atomic clusters to (TiCu)-based martensitic bulk metallic glasses presents a large plastic strain of 18.04% with high fracture strength of 1705MPa. Detailed microstructural investigations point out that martensite embedded in γ-TiCu matrix is effective to dissipate localization of the shear stress thus leading to rotational propagation, interaction, and multiplication of the shear bands. Furthermore, the propagation of microcracks formed by local stress transition during deformation is hindered by the martensite.
Facultative autogamy in Cyrtopodium polyphyllum (Orchidaceae) through a rain-assisted pollination mechanism
Authors: Pansarin Ludmila Mickeliunas , Pansarin Emerson Ricardo , Sazima Marlies
Published: June 2008

Cyrtopodium includes ~42 species, among which is Cyrtopodium polyphyllum (Vell.) Pabst ex F. Barros that occurs in a rainforest in south-eastern Brazil. Its non-rewarding flowers, which attract Centridini bees by deceit, are rain-assisted self-pollinated, a phenomenon rarely found in orchids and other plant families. In addition, self-pollination has never been reported in Cyrtopodiinae and data on the pollination of South American orchids are scarce. Flowers were observed at different times of the day, on both sunny and rainy days, to record floral morphology, visitors and the effects of rainfall on flowers. On rainy days, water accumulates on the stigma and dissolves the adhesive substance of the stigmatic surface. A viscous drop thus forms, which contacts the pollinarium. When evaporation makes the viscous drop shrink, the drop moves the pollinarium with the anther onto the stigmatic surface and promotes self-pollination. Fruit set in natural habitat was low, with 2.4% at one study site, where a similar value (2.2%) was recorded in flowers self-pollinated by rain. In C. polyphyllum, facultative self-pollination assisted by rain is thus an important strategy that guarantees fruit set when pollinator’s visits are scarce, which is common in species pollinated by deceit.
Using video image analysis to count hens in cages and reduce egg breakage on collection belts
Authors: Cronin G. M. , Borg S. S. , Dunn M. T.
Published: June 2008

Stock people working in modern cage layer sheds spend more than half their daily work time directly checking hens to monitor health and welfare. In addition, mechanical egg collection belts must be checked for potential blockages that may result in cracked or broken eggs during the collection process. These are important tasks in the profitable management of modern multi-tier cage systems. However, where the upper tiers of cages are above stockperson eye level, the effectiveness of humans to perform these tasks accurately may be questioned. We investigated whether video image analysis (VIA, the ability of a computer to ‘see’) could automatically perform two common tasks – that of counting the number of hens per cage and scanning the egg collection belt to identify foreign (non-egg) objects. Cameras were attached to the robotic feeder that moved along the front of the cages. Views of the interior of the cages and the egg collection belt were recorded on digital video as the robotic feeder moved. Two VIA prototypes were evaluated, initially at the research institute and subsequently at a commercial farm. Using the respective automatic detection algorithms that were developed for the research, 79% of targets (hen legs) in cages were correctly counted, while 95% of foreign objects on the egg collection belt were detected. The results demonstrate that VIA can be used to monitor egg belts for potential blockages, and has potential as technology to count hens.
Putting Merino weaner management recommendations to the test
Authors: Edwards J. E. Hocking , Gould R. M. , Copping K. J.
Published: June 2008

Merino weaner survival is poor under normal traditional management practices. Data from four trials conducted between 2001 and 2005 were used to assess the effectiveness of current industry recommendations to achieve 95% survival rates of Merino weaners. There was very little difference between 2001 and 2003 in survival of Merino weaners despite average weaning weight ranging from 20 to 24 kg between years. The recommended target weaning weight of 23 kg does not always appear to be a good predictor of survival. However, a target of 45% mature liveweight at pasture senescence achieved the industry recommendation of 95% weaner survival. Merino weaners were fed over the summer–autumn period to reach 40 kg liveweight by the time green feed became available. Weaner survival reached 93% compared with 89% survival to hogget shearing in weaners managed under normal growth paths. Furthermore, twice as many ewe weaners died in the traditional feeding program compared with the well fed ewe weaners. Differences in mortality between feeding levels in the wether weaners was less than that observed in the ewe weaners. Flock average growth rates were not useful indicators of weaner survival and there was no relationship between Merino ram estimated breeding values for weaning weight and the survival of the progeny.
An evaluation of slaughter age on the profitability of intensive slaughter ostrich production
Authors: Jordaan J. W. , Brand T. S. , Bhiya C. , Aucamp B. B.
Published: June 2008

The traditional slaughter ostrich production system evolved mainly around two aspects: producing the optimum skin size and attaining the ideal shape of follicle on the skin. Over time the practice of slaughtering ostriches at 14 months of age proved to be the ideal system and became the standard in the ostrich industry. With a gradual increase in demand for ostrich meat in the past decade, the meat yielded by a 14-month-old bird provided additional income to the producer. However, the cost of feed can affect profitability and, especially so, for a production system over a 14-month period. In addition to increasing feed costs, evidence exists of an increasing risk of skin damage over long production periods, affecting income negatively. A study at the Kromme Rhee experimental farm near Stellenbosch in South Africa investigated slaughter age regimes at 8.5 months, 10.5 months, 12.5 months, 14.5 months and 16.5 months. Data on feed intake and yields of cold carcass, crust skin size, skin grade and total feathers revealed significant differences (P < 0.01) at different slaughter ages. This paper attempts to assess the effect of different slaughter age regimes on the profitability of intensive slaughter ostrich production. Values predicted from a regression analysis were imputed into a gross margin budget analysis and discounted over a 5-year planning period to compare profitability over the long-term. Income was highest at the 14.5-month slaughter system but gross margin of the 10.5-month slaughter age system was highest, with the 8.5-month system second. Changes in the slaughter age regimes in the ostrich industry may increase efficiency in production systems.
Genotype and age effects on sheep meat production. 5. Lean meat and fat content in the carcasses of Australian sheep genotypes at 20-, 30- and 40-kg carcass weights
Authors: Ponnampalam E. N. , Butler K. L. , Hopkins D. L. , Kerr M. G. , Dunshea F. R. , Warner R. D.
Published: June 2008

Lean meat and fat content of Australian sheep genotypes were compared at 20-, 30- and 40-kg carcass weights. Sheep comprised Poll Dorsetgrowth × Border Leicester Merino (PDg × BLM), Poll Dorsetgrowth × Merino (PDg × M), Poll Dorsetmuscling × Merino (PDm × M), Border Leicester × Merino (BL × M) and Merino × Merino (M × M) genotypes. Lambs were raised as a mixed flock under grazing and slaughtered at 4, 8, 14 and 22 months of age with each slaughter time involving ~150 mixed sex animals. At 24 h after slaughter, chilled carcasses were halved along the backbone and the right sides were used for determination of lean, fat and ash percentages using dual energy X-ray absorptiometry. Within a particular age group and genotype, animals growing at faster rates and reaching heavier carcass weights had lower carcass lean meat content than slower growing animals. Merino carcasses weighing 20 and 30 kg had similar levels of lean meat to PD × M genotypes, which was greater than that from the BL × M genotype. Second-cross PD × BLM carcasses weighing 20 kg at 4 months and 30 kg at 8 months had similar carcass fat and lean percentages to 20-kg Merino carcasses at 8 months and first-cross PD × M carcasses weighing 30 kg at 14 months, respectively. At 40-kg carcass weight, 22-month-old Merinos had similar levels of leanness to carcasses from 22-month-old PD × M animals and carcasses from 14-month-old second-cross PD × BLM animals. Carcass lean meat content decreased with increasing carcass weight and first- cross BL × M animals had the lowest carcass lean across all weight categories. There was a major acceleration in carcass fatness between 14 and 22 months associated with a reduction in muscle deposition. Results indicate that age of the animal should be taken into account when carcass lean and fat contents are compared at a particular carcass weight. Merinos will achieve weight/composition specifications at least equally well to crossbreds but will take longer with a likely increase in production costs.
Benefits obtained from cattle by smallholder farmers: a case study of Limpopo Province, South Africa
Authors: Stroebel A. , Swanepoel F. J. C. , Nthakheni N. D. , Nesamvuni A. E. , Taylor G.
Published: June 2008

A survey of livestock production systems was conducted in the Vhembe District, located between 22°85′ latitude and 30°71′ longitude in the Limpopo Province of South Africa. The objective of the study was to investigate the benefits obtained from, and key functions of, cattle production, as well as related breeding objectives in smallholder livestock production in the Limpopo Province of South Africa. Data were collected by means of a general survey questionnaire and a participatory rural appraisal (PRA) exercise. The results indicate that almost 60% of farmers own < 10 cattle. Female animals constituted the largest component of the herd (55.02%). Although the bull : cow ratio was extremely high (1 : 3.7), the calving rate was low at 35.60%, with an extremely high herd mortality of 15.70% and a low off-take of 8.70%. In a pairwise ranking, the benefits obtained from cattle by smallholder livestock farmers are as follows: selling and meat consumption (4), wealth, status and savings (3), socio-cultural activities (2) and draught power (1). The ‘cattle complex’, where cattle are kept for prestige and status, is still appropriate, but cattle also make significant contributions in respect to selling and meat consumption, and arable inputs such as draft and fertiliser. It is concluded that benefits obtained from cattle form the basis of decision-making by smallholder cattle owners with respect to livestock production.
Nutrients and their duration of enrichment influence periphyton cover and biomass in rural and urban streams
Authors: Elsdon Travis S. , Limburg Karin E.
Published: June 2008

Although it is well known that land use affects nutrient dynamics and algal growth in streams, the responses to different durations of nutrient supply are poorly understood. The associations of benthic (periphyton-dominated) biomass with concentrations of dissolved nitrogen and phosphorus in rural and urban streams in New York were quantified. Biomass was significantly greater (2-fold) in the urban compared with the rural stream, which was associated with differences in dissolved nutrients. Experimental field enrichment of nutrient concentrations and duration of exposure altered benthic periphyton. Increasing nutrients by 60–99% of ambient concentrations increased periphyton percentage cover and biomass. Periphyton abundance also increased with increasing duration of exposure to nutrients (2, 4 and 8 weeks); however, short-term pulses of nutrients (2 weeks) had no significant effect in the rural stream. These results indicate that effective management of nutrient delivery, by reducing time periods of high nutrient load, will minimise impacts to benthic environments.
Ephrins as negative regulators of adult neurogenesis in diverse regions of the central nervous system
Authors: Jiao Jian-wei , Feldheim David A. , Chen Dong Feng
Published: June 2008

In the central nervous system (CNS) of adult mammals, neurogenesis occurs in only two restricted areas, the subgranular zone (SGZ) of the hippocampus and the subventricular zone (SVZ). Isolation of multipotent progenitor cells from other CNS regions suggests that their neurogenic potential is dictated by local environmental cues. Here, we report that astrocytes in areas outside of the SGZ and SVZ of adult mice express high levels of ephrin-A2 and -A3, which present an inhibitory niche, negatively regulating neural progenitor cell growth. Adult mice lacking both ephrin-A2 and -A3 display active ongoing neurogenesis throughout the CNS. These findings suggest that neural cell replacement therapies for neurodegeneration or injury in the adult CNS may be achieved by manipulating ephrin signaling pathways.
A catalytic di-heme
bis
-Fe(IV) intermediate, alternative to an Fe(IV)=O porphyrin radical
Authors: Li Xianghui , Fu Rong , Lee Sheeyong , Krebs Carsten , Davidson Victor L. , Liu Aimin
Published: June 2008

High-valent iron species are powerful oxidizing agents in chemical and biological catalysis. The best characterized form of an Fe(V) equivalent described in biological systems is the combination of a
b
-type heme with Fe(IV)=O and a porphyrin or amino acid cation radical (termed Compound I). This work describes an alternative natural mechanism to store two oxidizing equivalents above the ferric state for biological oxidation reactions. MauG is an enzyme that utilizes two covalently bound
c
-type hemes to catalyze the biosynthesis of the protein-derived cofactor tryptophan tryptophylquinone. Its natural substrate is a monohydroxylated tryptophan residue present in a 119-kDa precursor protein. An EPR-silent di-heme reaction intermediate of MauG was trapped. Mössbauer spectroscopy revealed the presence of two distinct Fe(IV) species. One is consistent with an Fe(IV)=O (ferryl) species (δ = 0.06 mm/s, Δ
E
Q
= 1.70 mm/s). The other is assigned to an Fe(IV) heme species with two axial ligands from protein (δ = 0.17 mm/s, Δ
E
Q
= 2.54 mm/s), which has never before been described in nature. This
bis
-Fe(IV) intermediate is remarkably stable but readily reacts with its native substrate. These findings broaden our views of how proteins can stabilize a highly reactive oxidizing species and the scope of enzyme-catalyzed posttranslational modifications.
Double-quantum resonances and exciton-scattering in coherent 2D spectroscopy of photosynthetic complexes
Authors: Abramavicius Darius , Voronine Dmitri V. , Mukamel Shaul
Published: June 2008

A simulation study demonstrates how the nonlinear optical response of the Fenna–Matthews–Olson photosynthetic light-harvesting complex may be explored by a sequence of laser pulses specifically designed to probe the correlated dynamics of double excitations. Cross peaks in the 2D correlation plots of the spectra reveal projections of the double-exciton wavefunctions onto a basis of direct products of single excitons. An alternative physical interpretation of these signals in terms of quasiparticle scattering is developed.
The ubiquitin ligase Nedd4-1 is dispensable for the regulation of PTEN stability and localization
Authors: Fouladkou Fatemeh , Landry Tamara , Kawabe Hiroshi , Neeb Antje , Lu Chen , Brose Nils , Stambolic Vuk , Rotin Daniela
Published: June 2008

PTEN
is a tumor suppressor frequently mutated in cancer. Recent reports implicated Nedd4-1 as the E3 ubiquitin ligase for PTEN that regulates its stability and nuclear localization. We tested the physiological role of Nedd4-1 as a PTEN regulator by using cells and tissues derived from two independently generated strains of mice with their
Nedd4-1
gene disrupted. PTEN stability and ubiquitination were indistinguishable between the wild-type and Nedd4-1-deficient cells, and an interaction between the two proteins could not be detected. Moreover, PTEN subcellular distribution, showing prominent cytoplasmic and nuclear staining, was independent of Nedd4-1 presence. Finally, activation of PKB/Akt, a major downstream target of cytoplasmic PTEN activity, and the ability of PTEN to transactivate the Rad51 promoter, a measure of its nuclear function, were unaffected by the loss of Nedd4-1. Taken together, our results fail to support a role for Nedd4-1 as the E3 ligase regulating PTEN stability and subcellular localization.
Endocannabinoid signaling controls pyramidal cell specification and long-range axon patterning
Authors: Mulder Jan , Aguado Tania , Keimpema Erik , Barabás Klaudia , Ballester Rosado Carlos J. , Nguyen Laurent , Monory Krisztina , Marsicano Giovanni , Di Marzo Vincenzo , Hurd Yasmin L. , Guillemot Francois , Mackie Ken , Lutz Beat , Guzmán Manuel , Lu Hui-Chen , Galve-Roperh Ismael , Harkany Tibor
Published: June 2008

Endocannabinoids (eCBs) have recently been identified as axon guidance cues shaping the connectivity of local GABAergic interneurons in the developing cerebrum. However, eCB functions during pyramidal cell specification and establishment of long-range axonal connections are unknown. Here, we show that eCB signaling is operational in subcortical proliferative zones from embryonic day 12 in the mouse telencephalon and controls the proliferation of pyramidal cell progenitors and radial migration of immature pyramidal cells. When layer patterning is accomplished, developing pyramidal cells rely on eCB signaling to initiate the elongation and fasciculation of their long-range axons. Accordingly, CB
1
cannabinoid receptor (CB
1
R) null and pyramidal cell-specific conditional mutant (CB
1
R
f/f,NEX-Cre
) mice develop deficits in neuronal progenitor proliferation and axon fasciculation. Likewise, axonal pathfinding becomes impaired after
in utero
pharmacological blockade of CB
1
Rs. Overall, eCBs are fundamental developmental cues controlling pyramidal cell development during corticogenesis.
Direct observation of fast protein conformational switching
Authors: Ishikawa Haruto , Kwak Kyungwon , Chung Jean K. , Kim Seongheun , Fayer Michael D.
Published: June 2008

Folded proteins can exist in multiple conformational substates. Each substate reflects a local minimum on the free-energy landscape with a distinct structure. By using ultrafast 2D-IR vibrational echo chemical-exchange spectroscopy, conformational switching between two well defined substates of a myoglobin mutant is observed on the ≈50-ps time scale. The conformational dynamics are directly measured through the growth of cross peaks in the 2D-IR spectra of CO bound to the heme active site. The conformational switching involves motion of the distal histidine/E helix that changes the location of the imidazole side group of the histidine. The exchange between substates changes the frequency of the CO, which is detected by the time dependence of the 2D-IR vibrational echo spectrum. These results demonstrate that interconversion between protein conformational substates can occur on very fast time scales. The implications for larger structural changes that occur on much longer time scales are discussed.
Relationship of Influenza Vaccination Declination Statements and Influenza Vaccination Rates for Healthcare Workers in 22 US Hospitals
Authors: Polgreen Philip M. , Septimus Edward J. , Parry Michael F. , Beekmann Susan E. , Cavanaugh Joseph E. , Srinivasan Arjun , Talbot Thomas R.
Published: June 2008

The use of declination statements was associated with a mean increase of 11.6% in influenza vaccination rates among healthcare workers at 22 hospitals. In most hospitals, there were no negative consequences for healthcare workers who refused to sign the forms, and most policies were implemented along with other interventions designed to increase vaccination rates.
Economic Burden of Surgical Site Infections at a European University Hospital
Authors: Weber Walter P. , Zwahlen Marcel , Reck Stefan , Feder-Mengus Chantal , Misteli Heidi , Rosenthal Rachel , Brandenberger Daniel , Oertli Daniel , Widmer Andreas F. , Marti Walter R.
Published: June 2008

Objective.

To quantify the economic burden of in-hospital surgical site infections (SSIs) at a European university hospital.

Design.

Matched case-control study nested in a prospective observational cohort study.

Setting.

Basel University Hospital in Switzerland, where an average of 28,000 surgical procedures are performed per year.

Methods.

All in-hospital occurrences of SSI associated with surgeries performed between January 1, 2000, and December 31, 2001, by the visceral, vascular, and traumatology divisions at Basel University Hospital were prospectively recorded. Each case patient was matched to a control patient by age, procedure code, and National Nosocomial Infection Surveillance System risk index. The case-control pairs were analyzed for differences in cost of hospital care and in provision of specialized care.

Results.

A total of 6,283 procedures were performed:187 SSIs were detected in inpatients, 168 of whom were successfully matched with a control patient. For case patients, the mean additional hospital cost was SwF19,638 (95% confidence interval [CI], SwF8,492–SwF30,784); the mean additional postoperative length of hospital stay was 16.8 days (95% CI, 13–20.6 days); and the mean additional in-hospital duration of antibiotic therapy was 7.4 days (95% CI, 5.1–9.6 days). Differences were primarily attributable to organ space SSIs (n = 76).

Conclusions.

Ina European university hospital setting, SSIs are costly and constitute a heavy and potentially preventable burden on both patients and healthcare providers.
Study on Interaction Between Two Parallel Plates with Iteration Method in Functional Theory
Authors: Zhou Ming , Wang Zheng-wu , Xu Zu-min
Published: June 2008

By introducing the functional theory into the calculation of electric double layer (EDL) interaction, the interaction energies of two parallel plates were calculated respectively at low, moderate, and high potentials. Compared with the results of two existing methods, Debye-Huckel and Langmuir methods, which are applicable just to the critical potentials and perform poorly in the intermediate potential, the functional approach not only has much simpler expression of the EDL interaction energy, but also performs well in the entire range of potentials.
Growth and Chemical Thermodynamics Analysis of SiC Film on Si Substrate by Heating Polystyrene/Silica Bilayer Method
Authors: Li Yun , Wang Yu-xia , Chen Zheng , Wang Jian-wen , Zou You-ming
Published: June 2008

SiC films were prepared by modified heating polystyrene/silica bilayer method on Si (111) substrate in normal pressure flowing Ar ambient at 1300C. The films were investigated by Fourier transform infrared absorption, X-ray diffraction, and scanning electron microscopy measurements. The chemical thermodynamics process is discussed. The whole reaction can be separated into four steps. The carburizing of SiO is the key step of whole reaction. The main reaction-sequence is figured out based on Gibbs free energy and equilibrium constant. Flowing Ar is necessary to continue the progress of whole reaction by means of carrying out accumulating gaseous resultants. The film is very useful for application in a variety of MOS-based devices for its silica/SiC/Si(111) structure, in which the silica layer can be removed thoroughly by the standard RCA cleaning process.
The Meiosis-Specific Sid2p-related Protein Slk1p Regulates Forespore Membrane Assembly in Fission Yeast
Authors: Yan Hongyan , Ge Wanzhong , Chew Ting Gang , Chow Jeng Yeong , McCollum Dannel , Neiman Aaron M. , Balasubramanian Mohan K.
Published: June 2008

Cytokinesis in all organisms involves the creation of membranous barriers that demarcate individual daughter cells. In fission yeast, a signaling module termed the septation initiation network (SIN) plays an essential role in the assembly of new membranes and cell wall during cytokinesis. In this study, we have characterized Slk1p, a protein-kinase related to the SIN component Sid2p. Slk1p is expressed specifically during meiosis and localizes to the spindle pole bodies (SPBs) during meiosis I and II in a SIN-dependent manner. Slk1p also localizes to the forespore membrane during sporulation. Cells lacking Slk1p display defects associated with sporulation, leading frequently to the formation of asci with smaller and/or fewer spores. The ability of slk1Δ cells to sporulate, albeit inefficiently, is fully abolished upon compromise of function of Sid2p, suggesting that Slk1p and Sid2p play overlapping roles in sporulation. Interestingly, increased expression of the syntaxin Psy1p rescues the sporulation defect of sid2-250 slk1Δ. Thus, it is likely that Slk1p and Sid2p play a role in forespore membrane assembly by facilitating recruitment of components of the secretory apparatus, such as Psy1p, to allow membrane expansion. These studies thereby provide a novel link between the SIN and vesicle trafficking during cytokinesis.
Transcriptional Regulation of Serine/Threonine Kinase-15 (STK15) Expression by Hypoxia and HIF-1
Authors: Klein Alexandra , Flügel Daniela , Kietzmann Thomas
Published: June 2008

The serine/threonine kinase-15 (STK15) acts as a cell cycle regulator being overexpressed in various tumors. One mechanism that could contribute to overexpression of STK15 is tumor hypoxia where hypoxia-inducible factor-1 (HIF-1) is a major regulator of transcription. Therefore, we analyzed whether hypoxia and HIF-1 could contribute to overexpression of STK15. We found that hypoxia increased STK15 expression and STK15 promoter activity in HepG2 tumor cells. Overexpression of HIF-1α induced STK15 gene transcription, whereas HIF-1α siRNA and overexpression of prolyl hydroxylase 2 (PHD-2), a negative regulator of HIF-1α, reversed this effect. In addition, site-directed mutagenesis experiments and chromatin immunoprecipitation revealed that from the three putative hypoxia responsive elements (HRE) within the STK15 promoter only HRE-2 was functional and bound HIF-1. Further, siRNA against STK15 inhibited proliferation of HepG2 cells induced by hypoxia. These results show that STK15 gene transcription can be regulated by hypoxia and HIF-1 via HRE-2 of the STK15 promoter. Thus, tumor hypoxia may trigger overexpression of STK15 observed in various tumors.
E2F6 Inhibits Cobalt Chloride-Mimetic Hypoxia-induced Apoptosis through E2F1
Authors: Yang Wei-Wei , Shu Bo , Zhu Yi , Yang Huang-Tian
Published: June 2008

E2F6, a potent transcriptional repressor, plays important roles in cell cycle regulation. However, roles of E2F6 in hypoxia-induced apoptosis are unknown. Here, we demonstrated biological functions of E2F6 in hypoxia-induced apoptosis and regulatory pathways. During hypoxia (CoCl2, 800 μM)-induced human embryonic kidney 293 cell apoptosis, E2F6 expression was down-regulated with concurrent increases in E2F1 expression and transactivation. E2F6 overexpression abrogated hypoxia-induced apoptosis and alteration of E2F1. Conversely, specific knockdown of E2F6 by small interfering RNA had opposite effects. Chromatin immunoprecipitation assay confirmed that E2F6 regulated E2F1 expression through the transrepression of E2F1 promoter. Interestingly, E2F1 transactivation and apoptosis induced by hypoxia in cells stably expressing E2F1 were inhibited by E2F6 overexpression, suggesting that the inhibitory effects of E2F6 are not only mediated by the repression of E2F1 promoter. This was confirmed by E2F6-inhibited transactivation of E2F1 and apoptosis via competing with E2F1 for DNA binding sites evidenced by the different behaviors of E2F6ΔC (C-terminal deletion) and E2F6.E68 (mutant DNA binding site) and by the lack of association of E2f6 with E2F1 protein. Moreover, hypoxia up-regulated expression of E2F1-responsive proapoptotic gene apoptosis protease-activating factor 1 was repressed by E2F6 overexpression. Together, these findings demonstrate a novel role of E2F6 in control of hypoxia-induced apoptosis through regulation of E2F1.
Reflections on Alfred D. Chandler, Jr.
Authors: Galambos Louis
Published: June 2008

Once, long ago, I was teaching business and economic history at Rice University in Houston, Texas. Alas,my academic career was stalled in the early 1960s. A distinguished Yale professor had kept the revised manuscript of my dissertation sitting on his desk for a year without reading it or submitting a report to the press. Meanwhile, I had just learned that editors do not want to publish fifty-page academic articles. I was having a wonderful time teaching the talented students at Rice, but it was not at all clear that I was not soon going to be looking for a different job and maybe a different profession.
Inheritance of L1014F and M918T sodium channel mutations associated with pyrethroid resistance in
Myzus persicae
Authors: Eleftherianos Ioannis , Foster Stephen P , Williamson Martin S , Denholm Ian
Published: June 2008

Two amino acid substitutions (L1014F and M918T) in the voltage-gated sodium channel confer target-site resistance to pyrethroid insecticides in the peach potato aphid,
Myzus persicae
. Pyrethroid-resistant and -susceptible
M. persicae
clones with various combinations of these mutations were crossed under laboratory conditions, and the genotypes of aphid progeny were analysed by direct DNA sequencing of the IIS4–S6 region of the sodium channel gene. Segregation patterns showed that in aphids heterozygous for both L1014F and M918T, both mutations were present in the same resistance allele. Despite these mutations appearing largely recessive in other pest species, such aphids exhibited strong resistance to pyrethroids in leaf-dip bioassays. These results have important implications for the spread and management of pyrethroid resistance in field populations.