bluuebunny/crossref_metadata_2025 huggingface dataset:
Reflection of attosecond x-ray free electron laser pulses
Authors: Hau-Riege Stefan P. , Chapman Henry N.
Published: January 2007

In order to utilize hard x-ray free electron lasers (XFEL’s) when they are extended to attosecond pulse lengths, it is necessary to choose optical elements with minimal response time. Specular grazing-incidence optics made of low-Z materials are popular candidates for reflectors since they are likely to withstand x-ray damage and provide sufficiently large reflectivities. Using linear-optics reflection theory, we calculated the transient reflectivity of a delta-function electric pulse from a homogenous semi-infinite medium as a function of angle of incidence for s- and p-polarized light. We specifically considered the pulse response of beryllium, diamond, silicon carbide, and silicon, all of which are of relevance to the XFEL’s that are currently being built. We found that the media emit energy in a damped oscillatory way, and that the impulse-response times are shorter than 0.3fs for normal incidence. For grazing incidence, the impulse-response time is substantially shorter, making grazing-incidence mirrors a good choice for deep subfemtosecond reflective optics.
Method for measuring the three-dimensional distribution of a fluorescent dye in a cell membrane
Authors: Yamamoto Kazuya , Ishimaru Ichirou , Fujii Yoshiki , Yasokawa Toshiki , Kuriyama Shigeki , Masaki Tsutomu , Takegawa Kaoru , Tanaka Naotaka
Published: January 2007

This letter reports on a method for accurately determining the component distribution in a cell membrane over the entire cell surface. This method involves exciting a fluorescent-dyed cell membrane using evanescent light and scanning the entire cell surface by rotating the cell using a noncontact technique, namely, proximal two-beam optical tweezers. To position the cell membrane in the thin evanescent field, the authors designed an optical system capable of precisely positioning the focal position. Using this method, they were able to measure the surface distribution of glycoprotein labeled by lectin in a breast cancer cell membrane.
Time-resolved thermal characterization of semiconductor lasers
Authors: Lanco L. , Ducci S. , Likforman J.-P. , Filloux P. , Marcadet X. , Calligaro M. , Leo G. , Berger V.
Published: January 2007

The authors propose and demonstrate a simple nondestructive technique that allows characterizing precisely the thermal properties of semiconductor lasers. The method consists of performing transmission measurements with a probe beam end fire coupled into one of the waveguide facets. Fabry-Perot oscillations occur as the cavity temperature varies, allowing for a time-resolved characterization of heating and dissipation processes. This leads to a very accurate knowledge of the thermal behavior of a third-order-mode semiconductor laser proposed for intracavity nonlinear processes.
Effects of anisotropy, aspect ratio, and nonstraightness of carbon nanotubes on thermal conductivity of carbon nanotube composites
Authors: Deng Fei , Zheng Quan-Shui , Wang Li-Feng , Nan Ce-Wen
Published: January 2007

Simple models for the thermal conductivity enhancements in carbon nanotube (CNT) composites are presented as analytical functions of volume fraction, anisotropic thermal conductivities, aspect ratio, nonstraightness, and interfacial thermal resistance of the CNTs. The model predictions agree very well with the measured thermal conductivities of CNT composites available in the literature. It is shown that using CNTs with higher aspect and straightness ratios is an efficient means to get much better thermal conductivity enhancements for CNT composites. The models are further extended to account the effects of either the random or aligned orientation of CNTs and the interaction among CNTs on thermal conductivity of CNT composites.
Transparent amorphous indium zinc oxide thin-film transistors fabricated at room temperature
Authors: Song Ju-Il , Park Jae-Soung , Kim Howoon , Heo Young-Woo , Lee Joon-Hyung , Kim Jeong-Joo , Kim G. M. , Choi Byeong Dae
Published: January 2007

The authors report on transparent thin-film transistors using amorphous indium zinc oxides for an active channel layer and gate-source-drain electrodes fabricated by rf magnetron sputtering at room temperature. The conducting properties of the amorphous indium zinc oxides were controlled by oxygen partial pressures in the sputtering ambient. An amorphous AlOx served as the gate dielectric oxide. Devices were realized that display a threshold voltage of 1.1V and an on/off ratio of ∼106 operated as a n-type enhancement mode with saturation mobility of 0.53cm2∕Vs. The devices showed optical transmittance about 80% in the visible range.
Pressure sensitivity of adiabatic shear banding in metals
Authors: Hanina E. , Rittel D. , Rosenberg Z.
Published: January 2007

Adiabatic shear banding (ASB) is a dynamic failure mode characterized by large plastic strains in a narrow localized band. ASB occurs at high strain rates (ε̇⩾103s−1), under adiabatic conditions leading to a significant temperature rise inside the band [H. Tresca, Annales du Conservatoire des Arts et Métiers 4, (1879); Y. L. Bai and B. Dodd, Adiabatic Shear Localization-Occurrence, Theories, and Applications (Pergamon, Oxford, 1992); M. A. Meyers, Dynamic Behavior of Materials (Wiley, New York, 1994).; and J. J. Lewandowski and L. M. Greer, Nat. Mater. 5, 15 (2006)]. Large hydrostatic pressures are experienced in many dynamic applications involving ASB formation (e.g., ballistic penetration, impact, and machining). The relationship between hydrostatic pressure and ASB development remains an open question, although its importance has been often noted. This letter reports original experimental results indicating a linear relationship between the (normalized) dynamic deformation energy and the (normalized) hydrostatic pressure.
Pulsed-laser deposited LiNi0.8Co0.15Al0.05O2 thin films for application in microbatteries
Authors: Ramana C. V. , Zaghib K. , Julien C. M.
Published: January 2007

Li Ni 0.8 Co 0.15 Al 0.05 O 2 thin films were prepared by pulsed-laser deposition at varying growth conditions. It was found that the growth and microstructure of the films is highly dependent on the target composition, deposition temperature, and the reactive atmosphere during laser ablation. The x-ray diffraction and Raman spectroscopic measurements indicated the high-structural quality of the grown LiNi0.8Co0.15Al0.05O2 thin films. A phase diagram mapping the effect of temperature on the microstructure of LiNi0.8Co0.15Al0.05O2 thin films has been proposed. The measurements of charge-discharge profiles of Li microcells using the LiNi0.8Co0.15Al0.05O2 films grown at 450°C demonstrate their possible applications in microbatteries. A stable capacity of 98μAh∕cm2μm was obtained in the potential range of 4.2–2.5V for LiNi0.8Co0.15Al0.05O2 films grown at 450°C.
Cooperative quantum cutting in one-dimensional (YbxGd1−x)Al3(BO3)4:Tb3+ nanorods
Authors: Zhang Q. Y. , Yang C. H. , Pan Y. X.
Published: January 2007

Near-infrared (NIR) quantum cutting (QC) involving the emission of two NIR photons per absorbed photon via a cooperative downconversion mechanism in one-dimensional (1D) (YbxGd1−x)Al3(BO3)4:Tb3+ nanorods has been demonstrated. The authors have analyzed the measured luminescence spectra and decay lifetimes and proposed a mechanism to rationalize the QC effect. Upon excitation of Tb3+ with a blue-visible photon at 485nm, two NIR photons could be emitted by Yb3+ through an efficient cooperative energy transfer from Tb3+ to two Yb3+ with optimal quantum efficiency as great as 196%. The development of 1D Tb3+–Yb3+ QC nanomaterials could open up a possibility to realize high efficiency silicon-based solar cells by means of downconversion of the green-to-ultraviolet part of the solar spectrum to ∼1000nm photons with a twofold increase in the photon number.
Hysteretic ac loss of superconducting strips simultaneously exposed to ac transport current and phase-different ac magnetic field
Authors: Mawatari Yasunori , Kajikawa Kazuhiro
Published: January 2007

A simple analytical expression is presented for hysteretic ac loss Q of a superconducting strip simultaneously exposed to an ac transport current I0cosωt and a phase-different ac magnetic field H0cos(ωt+θ0). On the basis of the critical state model, the authors calculate Q for small current amplitude I0⪡Ic, for small magnetic field amplitude H0⪡Ic∕2πa, and for arbitrary phase difference θ0, where Ic is the critical current and 2a is the width of the strip. The resulting expression for Q=Q(I0,H0,θ0) is a simple biquadratic function of both I0 and H0, and Q becomes maximum (minimum) when θ0=0 or π (θ0=π∕2).
Lithium ion sources for investigations of fast ion transport in magnetized plasmas
Authors: Zhang Y. , Boehmer H. , Heidbrink W. W. , McWilliams R. , Leneman D. , Vincena S.
Published: January 2007

In order to study the interaction of ions of intermediate energies with plasma fluctuations, two plasma immersible lithium ion sources, based on solid-state thermionic emitters (Li aluminosilicate) were developed. Compared to discharge based ion sources, they are compact, have zero gas load, small energy dispersion, and can be operated at any angle with respect to an ambient magnetic field of up to 4.0kG. Beam energies range from 400eVto2.0keV with typical beam current densities in the 1mA∕cm2 range. Because of the low ion mass, beam velocities of 100–300km∕s are in the range of Alfvén speeds in typical helium plasmas in the large plasma device.
Low-voltage electroluminescence of europium in zinc oxide thin films
Authors: Lima S. A. M. , Davolos M. R. , Quirino W. G. , Legnani C. , Cremona M.
Published: January 2007

Europium(III)-containing zinc oxide thin films (1, 5, 8, and 10at.%) were prepared from Pechini’s solution and used as active layers in thin-film electroluminescent devices. By applying a low bias steady state voltage (10–50V) it was possible to observe electroluminescence of the device. By increasing the rate Eu3+∕Zn2+ the relative intensity of emission from the dopand Eu3+ ions increases, while the relative intensity of emission from the zinc oxide (ZnO) matrix decreases. This leads to ZnO:Eu3+ (10at.%) thin-film electroluminescent devices with low-voltage operation and high pure color.
Characterization and application of single fluorescent nanodiamonds as cellular biomarkers
Authors: Fu Chi-Cheng , Lee Hsu-Yang , Chen Kowa , Lim Tsong-Shin , Wu Hsiao-Yun , Lin Po-Keng , Wei Pei-Kuen , Tsao Pei-Hsi , Chang Huan-Cheng , Fann Wunshain
Published: January 2007

Type Ib diamonds emit bright fluorescence at 550–800 nm from nitrogen-vacancy point defects, (N-V)
0
and (N-V)
−
, produced by high-energy ion beam irradiation and subsequent thermal annealing. The emission, together with noncytotoxicity and easiness of surface functionalization, makes nano-sized diamonds a promising fluorescent probe for single-particle tracking in heterogeneous environments. We present the result of our characterization and application of single fluorescent nanodiamonds as cellular biomarkers. We found that, under the same excitation conditions, the fluorescence of a single 35-nm diamond is significantly brighter than that of a single dye molecule such as Alexa Fluor 546. The latter photobleached in the range of 10 s at a laser power density of 10
4
W/cm
2
, whereas the nanodiamond particle showed no sign of photobleaching even after 5 min of continuous excitation. Furthermore, no fluorescence blinking was detected within a time resolution of 1 ms. The photophysical properties of the particles do not deteriorate even after surface functionalization with carboxyl groups, which form covalent bonding with poly
l
-lysines that interact with DNA molecules through electrostatic forces. The feasibility of using surface-functionalized fluorescent nanodiamonds as single-particle biomarkers is demonstrated with both fixed and live HeLa cells.
Small-molecule agonists for the glucagon-like peptide 1 receptor
Authors: Knudsen Lotte Bjerre , Kiel Dan , Teng Min , Behrens Carsten , Bhumralkar Dilip , Kodra János T. , Holst Jens J. , Jeppesen Claus B. , Johnson Michael D. , de Jong Johannes Cornelis , Jorgensen Anker Steen , Kercher Tim , Kostrowicki Jarek , Madsen Peter , Olesen Preben H. , Petersen Jacob S. , Poulsen Fritz , Sidelmann Ulla G. , Sturis Jeppe , Truesdale Larry , May John , Lau Jesper
Published: January 2007

The peptide hormone glucagon-like peptide (GLP)-1 has important actions resulting in glucose lowering along with weight loss in patients with type 2 diabetes. As a peptide hormone, GLP-1 has to be administered by injection. Only a few small-molecule agonists to peptide hormone receptors have been described and none in the B family of the G protein coupled receptors to which the GLP-1 receptor belongs. We have discovered a series of small molecules known as ago-allosteric modulators selective for the human GLP-1 receptor. These compounds act as both allosteric activators of the receptor and independent agonists. Potency of GLP-1 was not changed by the allosteric agonists, but affinity of GLP-1 for the receptor was increased. The most potent compound identified stimulates glucose-dependent insulin release from normal mouse islets but, importantly, not from GLP-1 receptor knockout mice. Also, the compound stimulates insulin release from perfused rat pancreas in a manner additive with GLP-1 itself. These compounds may lead to the identification or design of orally active GLP-1 agonists.
Smelling home can prevent dispersal of reef fish larvae
Authors: Gerlach Gabriele , Atema Jelle , Kingsford Michael J. , Black Kerry P. , Miller-Sims Vanessa
Published: January 2007

Many marine fish and invertebrates show a dual life history where settled adults produce dispersing larvae. The planktonic nature of the early larval stages suggests a passive dispersal model where ocean currents would quickly cause panmixis over large spatial scales and prevent isolation of populations, a prerequisite for speciation. However, high biodiversity and species abundance in coral reefs contradict this panmixis hypothesis. Although ocean currents are a major force in larval dispersal, recent studies show far greater retention than predicted by advection models. We investigated the role of animal behavior in retention and homing of coral reef fish larvae resulting in two important discoveries: (
i
) Settling larvae are capable of olfactory discrimination and prefer the odor of their home reef, thereby demonstrating to us that nearby reefs smell different. (
ii
) Whereas one species showed panmixis as predicted from our advection model, another species showed significant genetic population substructure suggestive of strong homing. Thus, the smell of reefs could allow larvae to choose currents that return them to reefs in general and natal reefs in particular. As a consequence, reef populations can develop genetic differences that might lead to reproductive isolation.
Negative feedback loop in T cell activation through IκB kinase-induced phosphorylation and degradation of Bcl10
Authors: Lobry Camille , Lopez Tatiana , Israël Alain , Weil Robert
Published: January 2007

Activation of the transcription factor NF-κB after stimulation through antigen receptors is important for lymphocyte differentiation, activation, proliferation, and protection against apoptosis. Much progress has been made in understanding the molecular events leading to NF-κB activation, but how this activation is eventually down-regulated is less well understood. Recent studies have indicated that Bcl10 functions downstream of lymphocyte antigen receptors to promote the activation of the IκB kinase complex leading to the phosphorylation and degradation of the IκB inhibitors of NF-κB. Bcl10 has also been implicated in the pathogenesis of mucosa-associated lymphoid tissue lymphoma, possibly in association with its nuclear localization. Here, we provide evidence that the IκB kinase complex phosphorylates Bcl10 after T cell antigen receptor stimulation and causes its proteolysis via the β-TrCP ubiquitin ligase/proteasome pathway. These findings document a negative regulatory activity of the IKK complex and suggest that Bcl10 degradation is part of the regulatory mechanisms that precisely control the response to antigens. Mutants of Bcl10 in the IKK phosphorylation site are resistant to degradation, accumulate in the nucleus, and lead to an increase in IL-2 production after T cell antigen receptor stimulation.
Inducible expression of the proallergic cytokine thymic stromal lymphopoietin in airway epithelial cells is controlled by NFκB
Authors: Lee Hai-Chon , Ziegler Steven F.
Published: January 2007

The epithelial-derived cytokine thymic stromal lymphopoietin (TSLP) is important for the initiation of allergic airway inflammation through a dendritic cell-mediated T helper 2 response. To identify the factors that control TSLP expression, we examined the ability of inflammatory mediators to regulate TSLP production in human airway epithelial cells. We found that both IL-1β and TNF-α were capable of inducing rapid TSLP production in primary human bronchial airway epithelial cells. We further characterized the human TSLP gene promoter, using two human epithelial cell lines, 16HBEo−and A549, and showed that IL-1β- and TNF-α-mediated human TSLP promoter activation in these cells was mediated by an upstream NFκB site. Mutation of this NFκB site abolished activation, as did overexpression of a dominant-negative version of IκB kinase (IKK)β (a kinase acting on IκB, the inhibitor of NFκB). Interestingly, human TSLP mRNA levels were also increased after exposure to Toll-like receptor (TLR) 2, TLR8, and TLR9 ligands, further supporting an important role for NFκB in TSLP gene regulation. Similarly, analysis of the mouse TSLP gene promoter revealed the presence of a similarly situated NFκB site that was also critical for IL-1β-inducible expression of mouse TSLP. Taken together, these results demonstrate that the inflammatory mediators IL-1β and TNF-α regulate human TSLP gene expression in an NFκB-dependent manner.
Instant effect of soluble antigen on effector T cells in peripheral immune organs during immunotherapy of autoimmune encephalomyelitis
Authors: Odoardi Francesca , Kawakami Naoto , Li Zhaoxia , Cordiglieri Chiara , Streyl Kristina , Nosov Mikhail , Klinkert Wolfgang E. F. , Ellwart Joachim W. , Bauer Jan , Lassmann Hans , Wekerle Hartmut , Flügel Alexander
Published: January 2007

i.v. infusion of native autoantigen or its altered peptide variants is an important therapeutic option for the treatment of autoimmune diseases, because it selectively targets the disease-inducing T cells. To learn more about the mechanisms and kinetics of this approach, we visualized the crucial initial effects of i.v. infusion of peptides or intact protein on GFP-tagged autoaggressive CD4+effector T cells using live-video and two-photonin situimaging of spleens in living animals. We found that the time interval between i.v. injection of intact protein to first changes in T cell behavior was extremely short; within 10 min after protein application, the motility of the T cells changed drastically. They slowed down and became tethered to local sessile stromal cells. A part of the cells aggregated to form clusters. Within the following 20 min, IFN-γ mRNA was massively (>100-fold) up-regulated; surface IL-2 receptor and OX-40 (CD 134) increased 1.5 h later. These processes depleted autoimmune T cells in the blood circulation, trapping the cells in the peripheral lymphoid organs and thus preventing them from invading the CNS. This specific blockage almost completely abrogated CNS inflammation and clinical disease. These findings highlight the speed and efficiency of antigen recognitionin vivoand add to our understanding of T cell-mediated autoimmunity.
Plants and people from the Early Neolithic to Shang periods in North China
Authors: Lee Gyoung-Ah , Crawford Gary W. , Liu Li , Chen Xingcan
Published: January 2007

An assemblage of charred plant remains collected from 26 sites in the Yiluo valley of North China as part of an archaeological survey spans the period from the sixth millennium to 1300 calibrated calendrical years (cal) B.C. The plant remains document a long sequence of crops, weeds, and other plants in the country. The results also demonstrate the effectiveness of sediment sampling as part of an archaeological survey. Ten accelerator mass spectrometer (AMS) radiocarbon dates on crop remains inform an assessment of the sequence of agricultural development in the region. Foxtail millet (
Setaria italica
subsp.
italica
) was grown during the Early Neolithic period and was the principal crop for at least four millennia. Broomcorn millet (
Panicum miliaceum
) was significantly less important throughout the sequence. Rice (
Oryza sativa
) was introduced by 3000 cal B.C. but apparently was not an important local crop. Wheat became a significant crop between 1600 and 1300 cal B.C. The weed flora diversified through time and were dominated by annual grasses, some of which were probably fodder for domesticated animals. The North China farming tradition that emphasized dry crops (millets, wheat, and legumes) with some rice appears to have been established at the latest by the Early Shang (Erligang; 1600–1300 B.C.) period.
In the regulation of cytochrome P450 genes, phenobarbital targets LKB1 for necessary activation of AMP-activated protein kinase
Authors: Blättler Sharon M. , Rencurel Franck , Kaufmann Michel R. , Meyer Urs A.
Published: January 2007

Transcriptional activation of cytochrome P450 (CYP) genes and various drug metabolizing enzymes by the prototypical inducer phenobarbital (PB) and many other drugs and chemicals is an adaptive response of the organism to exposure to xenobiotics. The response to PB is mediated by the nuclear receptor constitutive androstane receptor (CAR), whereas the chicken xenobiotic receptor (CXR) has been characterized as the PB mediator in chicken hepatocytes. Our previous results suggested an involvement of AMP-activated protein kinase (AMPK) in the molecular mechanism of PB induction. Here, we show that the mechanism of AMPK activation is related to an effect of PB-type inducers on mitochondrial function with consequent formation of reactive oxygen species (ROS) and phosphorylation of AMPK by the upstream kinase LKB1. Gain- and loss-of-function experiments demonstrate that LKB1-activated AMPK is necessary in the mechanism of drug induction and that this is an evolutionary conserved pathway for detoxification of exogenous and endogenous chemicals. The activation of LKB1 adds a proximal target to the so far elusive sequence of events by which PB and other drugs induce the transcription of multiple genes.
A blasticidin S-resistant
Plasmodium falciparum
mutant with a defective plasmodial surface anion channel
Authors: Hill David A. , Pillai Ajay D. , Nawaz Fatima , Hayton Karen , Doan Lanxuan , Lisk Godfrey , Desai Sanjay A.
Published: January 2007

Erythrocytes infected with malaria parasites exhibit marked increases in permeability to organic and inorganic solutes. The plasmodial surface anion channel (PSAC), an unusual voltage-dependent ion channel induced on the host membrane after infection, may play a central role in these permeability changes. Here, we identified a functional PSAC mutant through
in vitro
selection with blasticidin S. Resistance to blasticidin S was generated during culture and correlated with significant reductions in permeability to multiple solutes, consistent with uptake via a common pathway. Single channel recordings revealed marked changes in PSAC gating with the addition of a subconductance state not present in wild-type channels. The channel's selectivity profile and pharmacology also were significantly altered. Eventual loss of the mutant phenotype upon removal of selective pressure and slower growth of mutant parasites suggest that PSAC serves an important role in intracellular parasite survival. These findings provide solid evidence for the uptake of diverse solutes via PSAC and implicate one or more parasite genes in expression of this channel.
RETRACTED: Metabolic regulation of SIRT1 transcription via a HIC1:CtBP corepressor complex
Authors: Zhang Qinghong , Wang Su-Yan , Fleuriel Capucine , Leprince Dominique , Rocheleau Jonathan V. , Piston David W. , Goodman Richard H.
Published: January 2007

The Sir2 histone deacetylases are important for gene regulation, metabolism, and longevity. A unique feature of these enzymes is their utilization of NAD
+
as a cosubstrate, which has led to the suggestion that Sir2 activity reflects the cellular energy state. We show that SIRT1, a mammalian Sir2 homologue, is also controlled at the transcriptional level through a mechanism that is specific for this isoform. Treatment with the glycolytic blocker 2-deoxyglucose (2-DG) decreases association of the redox sensor CtBP with HIC1, an inhibitor of SIRT1 transcription. We propose that the reduction in transcriptional repression mediated by HIC1, due to the decrease of CtBP binding, increases SIRT1 expression. This mechanism allows the specific regulation of SIRT1 in response to nutrient deprivation.
Linking sandeel consumption and the likelihood of starvation in harbour porpoises in the Scottish North Sea: could climate change mean more starving porpoises?
Authors: MacLeod Colin D , Santos M. Begoña , Reid Robert J , Scott Beth E , Pierce Graham J
Published: January 2007

Sandeels are known to be negatively affected by climate change in a number of ways. This study investigated whether these changes are affecting the harbour porpoise (
Phocoena phocoena
), a species which consumes sandeels. Porpoise diet was examined in spring (March–May), a critical time of year for survival when sandeels are important prey, from 1993 to 2001 to provide baseline information on the proportion of sandeels consumed. When data from spring 2002 and 2003 were compared to these baseline data, the diet was found to be substantially different, with a significant and substantially smaller proportion of sandeels being consumed in March and May. There were also differences in the number of porpoises starving between the two time periods (33% in spring 2002 and 2003 died of starvation, but only 5% in the baseline period). This suggests that a lower proportion of sandeels in the diet of porpoises in spring increases the likelihood of starvation. Therefore, we suggest that the negative effects of climate change on sandeel availability may have serious negative effects on harbour porpoise populations in the North Sea by increasing the likelihood of starvation in spring.
The forces exerted by aquatic suction feeders on their prey
Authors: Wainwright Peter C , Day Steven W
Published: January 2007

Successful prey capture by aquatic suction feeders depends on the ability of the predator to generate a flow of water external to the mouth that overcomes any movements and forces that the prey uses to resist the suction flow. Elucidating the nature and magnitude of these forces is a key to understanding what limits suction feeding performance. We identify three potential forces produced by the suction flow field: drag, acceleration reaction and the fluid pressure gradient. Using a mathematical model parametrized with empirical data from feeding bluegill,Lepomis macrochirus, we explore the relative magnitude of these forces under three encounter scenarios with a 5 mm diameter, spherical prey: an immobile mid-water prey; a similar prey that executes an escape response; and a prey item that grips a substratum. Contrary to the almost exclusive emphasis on drag in the suction feeding literature, it made a minor contribution to the total forces in all three cases. In all three scenarios, the pressure gradient is the largest of the three forces. These results are important because previous researchers have emphasized drag and have not explicitly recognized a role for the pressure gradient force in suction feeding. The simulations suggest previously unrecognized mechanisms that suction feeders can use to enhance the forces that they exert, by increasing the steepness of the pressure gradient that the prey item is exposed to. This can be accomplished either by increasing the rate of increase in fluid velocity or by restricting the size of the mouth aperture, which creates a steeper spatial gradient in pressure.
Towards electrically conductive, self-healing materials
Authors: Williams Kyle A , Boydston Andrew J , Bielawski Christopher W
Published: January 2007

A novel class of organometallic polymers comprising
N
-heterocyclic carbenes and transition metals was shown to have potential as an electrically conductive, self-healing material. These polymers were found to exhibit conductivities of the order of 10
−3
 S cm
−1
and showed structurally dynamic characteristics in the solid-state. Thin films of these materials were cast onto silicon wafers, then scored and imaged using a scanning electron microscopy (SEM). The scored films were subsequently healed via thermal treatment, which enabled the material to flow via a unique depolymerization process, as determined by SEM and surface profilometry. A method for incorporating these features into a device that exhibits electrically driven, self-healing functions is proposed.
On modifications of Newton's second law and linear continuum elastodynamics
Authors: Milton Graeme W , Willis John R
Published: January 2007

In this paper, we suggest a new perspective, where Newton's second law of motion is replaced by a more general law which is a better approximation for describing the motion of seemingly rigid macroscopic bodies. We confirm a finding of Willis that the density of a body at a given frequency of oscillation can be anisotropic. The relation between the force and the acceleration is non-local (but causal) in time. Conversely, for every response function satisfying these properties, and having the appropriate high-frequency limit, there is a model which realizes that response function. In many circumstances, the differences between Newton's second law and the new law are small, but there are circumstances, such as in specially designed composite materials, where the difference is enormous. For bodies which are not seemingly rigid, the continuum equations of elastodynamics govern behaviour and also need to be modified. The modified versions of these equations presented here are a generalization of the equations proposed by Willis to describe elastodynamics in composite materials. It is argued that these new sets of equations may apply to all physical materials, not just composites. The Willis equations govern the behaviour of the average displacement field whereas one set of new equations governs the behaviour of the average-weighted displacement field, where the weighted displacement field may attach zero weight to ‘hidden’ areas in the material where the displacement may be unobservable or not defined. From knowledge of the average-weighted displacement field, one obtains an approximate formula for the ensemble averaged energy density. Two other sets of new equations govern the behaviour when the microstructure has microinertia, i.e. where there are internal spinning masses below the chosen scale of continuum modelling. In the first set, the average displacement field is assumed to be observable, while in the second set an average-weighted displacement field is assumed to be observable.
The
N
-vortex problem on a rotating sphere. III. Ring configurations coupled to a background field
Authors: Newton Paul K , Sakajo Takashi
Published: January 2007

We study the evolution of
N
-point vortices in ring formation embedded in a background flowfield that initially corresponds to solid-body rotation on a sphere. The evolution of the point vortices is tracked numerically as an
embedded
dynamical system along with the
M
contours which separate strips of constant vorticity. The full system is a discretization of the Euler equations for incompressible flow on a rotating spherical shell, hence a ‘barotropic’ model of the one-layer atmosphere. We describe how the coupling creates a mechanism by which energy is exchanged between the ring and the background, which ultimately serves to break up the structure. When the centre-of-vorticity vector associated with the ring is initially misaligned with the axis of rotation of the background field, it sets up the propagation of Rossby waves around the sphere which move retrograde to the solid-body rotation. These waves pass energy to the ring (in the case when the solid-body field and the ring initially co-rotate) or extract energy from the ring (when the solid-body field and the ring initially counter-rotate), hence the Hamiltonian and the centre-of-vorticity vector associated with the
N
-point vortices are no longer conserved as they are for the one-way coupled model described by Newton & Shokraneh. In the first case, energy is transferred to the ring, the length of the centre-of-vorticity vector increases, while its tip spirals in a clockwise manner towards the North Pole. The ring stays relatively intact for short times, but ultimately breaks-up on a longer time-scale. In the latter case, energy is extracted from the ring, the length of the centre-of-vorticity vector decreases while its tip spirals towards the North Pole and the ring loses its coherence more quickly than in the co-rotating case. The special case where the ring is initially oriented so that its centre-of-vorticity vector is perpendicular to the axis of rotation is also examined as it shows how the coupling to the background field breaks this symmetry. In this case, both the length of the centre-of-vorticity vector and the Hamiltonian energy of the ring achieve a local maximum at roughly the same time.
Maternal nutrition affects reproductive output and sex allocation in a lizard with environmental sex determination
Authors: Warner Daniel A , Lovern Matthew B , Shine Richard
Published: January 2007

Life-history traits such as offspring size, number and sex ratio are affected by maternal feeding rates in many kinds of animals, but the consequences of variation in maternal diet quality (rather than quantity) are poorly understood. We manipulated dietary quality of reproducing female lizards (Amphibolurus muricatus; Agamidae), a species with temperature-dependent sex determination, to examine strategies of reproductive allocation. Females maintained on a poor-quality diet produced fewer clutches but massively (twofold) larger eggs with lower concentrations of yolk testosterone than did conspecific females given a high-quality diet. Although all eggs were incubated at the same temperature, and yolk steroid hormone levels were not correlated with offspring sex, the nutrient-deprived females produced highly male-biased sex ratios among their offspring. These responses to maternal nutrition generate a link between sex and offspring size, in a direction likely to enhance maternal fitness if large body size enhances reproductive success more in sons than in daughters (as seems plausible, given the mating system of this species). Overall, our results show that sex determination in these animals is more complex, and responsive to a wider range of environmental cues, than that suggested by the classification of ‘environmental sex determination’.
Surviving with low genetic diversity: the case of albatrosses
Authors: Milot Emmanuel , Weimerskirch Henri , Duchesne Pierre , Bernatchez Louis
Published: January 2007

Low genetic diversity is predicted to negatively impact species viability and has been a central concern for conservation. In contrast, the possibility that some species may thrive in spite of a relatively poor diversity has received little attention. The wandering and Amsterdam albatrosses (Diomedea exulansandDiomedea amsterdamensis) are long-lived seabirds standing at an extreme along the gradient of life strategies, having traits that may favour inbreeding and low genetic diversity. Divergence time of the two species is estimated at 0.84 Myr ago from cytochromebdata. We tested the hypothesis that both albatrosses inherited poor genetic diversity from their common ancestor. Within the wandering albatross, per cent polymorphic loci and expected heterozygosity at amplified fragment length polymorphisms were approximately one-third of the minimal values reported in other vertebrates. Genetic diversity in the Amsterdam albatross, which is recovering from a severe bottleneck, was about twice as low as in the wandering albatross. Simulations supported the hypothesis that genetic diversity in albatrosses was already depleted prior to their divergence. Given the generally high breeding success of these species, it is likely that they are not suffering much from their impoverished diversity. Whether albatrosses are unique in this regard is unknown, but they appear to challenge the classical view about the negative consequences of genetic depletion on species survival.
Did the perils of abdominal obesity affect depiction of feminine beauty in the sixteenth to eighteenth century British literature? Exploring the health and beauty link
Authors: Singh Devendra , Renn Peter , Singh Adrian
Published: January 2007

‘Good gene’ mate selection theory proposes that all individuals share evolved mental mechanisms that identify specific parts of a woman's body as indicators of fertility and health. Depiction of feminine beauty, across time and culture, should therefore emphasize the physical traits indicative of health and fertility. Abdominal obesity, as measured by waist size, is reliably linked to decreased oestrogen, reduced fecundity and increased risk for major diseases. Systematic searches of British literature across the sixteenth, seventeenth and eighteenth centuries reveal that a narrow waist is consistently described as beautiful. Works in ancient Indian and Chinese literature similarly associate feminine attractiveness with a narrow waist. Even without the benefit of modern medical knowledge, both British and Asian writers knew intuitively the biological link between health and beauty.
Big-brained birds survive better in nature
Authors: Sol Daniel , Székely Tamás , Liker András , Lefebvre Louis
Published: January 2007

Big brains are hypothesized to enhance survival of animals by facilitating flexible cognitive responses that buffer individuals against environmental stresses. Although this theory receives partial support from the finding that brain size limits the capacity of animals to behaviourally respond to environmental challenges, the hypothesis that large brains are associated with reduced mortality has never been empirically tested. Using extensive information on avian adult mortality from natural populations, we show here that species with larger brains, relative to their body size, experience lower mortality than species with smaller brains, supporting the general importance of the cognitive buffer hypothesis in the evolution of large brains.
Neural networks for perceptual processing: from simulation tools to theories
Authors: Gurney Kevin
Published: January 2007

Neural networks are modelling tools that are, in principle, able to capture the input–output behaviour of arbitrary systems that may include the dynamics of animal populations or brain circuits. While a neural network model is useful if it captures phenomenologically the behaviour of the target system in this way, its utility is amplified if key mechanisms of the model can be discovered, and identified with those of the underlying system. In this review, we first describe, at a fairly high level with minimal mathematics, some of the tools used in constructing neural network models. We then go on to discuss the implications of network models for our understanding of the system they are supposed to describe, paying special attention to those models that deal with neural circuits and brain systems. We propose that neural nets are useful for brain modelling if they are viewed in a wider computational framework originally devised by Marr. Here, neural networks are viewed as an intermediate mechanistic abstraction between ‘algorithm’ and ‘implementation’, which can provide insights into biological neural representations and their putative supporting architectures.
Sensory ecology and perceptual allocation: new prospects for neural networks
Authors: Phelps Steven M
Published: January 2007

Sensory ecology provides a conceptual framework for considering how animals ought to design sensory systems to capture meaningful information from their environments. The framework has been particularly successful at describing how one should allocate sensory receptors to maximize performance on a given task. Neural networks, in contrast, have made unique contributions to understanding how ‘hidden preferences’ can emerge as a by-product of sensory design. The two frameworks comprise complementary techniques for understanding the design and the evolution of sensation. This article reviews empirical literature from multiple modalities and levels of sensory processing, considering vision, audition and touch from the viewpoints of sensory ecology and neuroethology. In the process, it presents modifications of extant neural network algorithms that would allow a more effective integration of these diverse approaches. Together, the reviewed literature suggests important advances that can be made by explicitly formulating neural network models in terms of sensory ecology, by incorporating neural costs into models of perceptual evolution and by exploring how such demands interact with historical forces.
Holocene fire and occupation in Amazonia: records from two lake districts
Authors: Bush Mark B , Silman Miles R , de Toledo Mauro B , Listopad Claudia , Gosling William D , Williams Christopher , de Oliveira Paulo E , Krisel Carolyn
Published: January 2007

While large-scale pre-Columbian human occupation and ecological disturbance have been demonstrated close to major Amazonian waterways, less is known of sites in terra firme settings. Palaeoecological analyses of two lake districts in central and western Amazonia reveal long histories of occupation and land use. At both locations, human activity was centred on one of the lakes, while the others were either lightly used or unused. These analyses indicate that the scale of human impacts in these terra firme settings is localized and probably strongly influenced by the presence of a permanent open-water body. Evidence is found of forest clearance and cultivation of maize and manioc. These data are directly relevant to the resilience of Amazonian conservation, as they do not support the contention that all of Amazonia is a ‘built landscape’ and therefore a product of past human land use.
Perceptions of Disability as Related to Medical and Social Factors
Authors: LoBianco Anthony F. , Sheppard‐Jones Kathy
Published: January 2007

This study addressed self‐perception of disability and the belief that others perceive one to have a disability. Factors from the medical and social models of disability were tested to determine if social factors still play a role in such perceptions when controlling for medical factors. Cross‐sectional data from the 1994–1995 National Health Interview Study on Disability (NHIS‐D) provided a stratified random sample of 25,805 noninstitutionalized adults. Logistic regression models were used to demonstrate that even controlling for medical factors (e.g., particular disabling conditions and restrictions in activities of daily living), social and vocational factors were significant predictors of disability perception. Ramifications for the theoretical study of disability, social psychology, and disability policy are discussed.
Effects of Two Selection Batteries on Decoy Effects in Job‐Finalist Choice1
Authors: Slaughter Jerel E.
Published: January 2007

The decoy effect occurs when manipulation of an inferior option influences preferences between two superior options. Although this phenomenon has been demonstrated for choices among job finalists, it has not been tested in situations in which candidates enter the final stage of selection on uneven ground. The results of the present investigation suggest that information from the first stage of selection interacts with manipulation of the decoy's characteristics to influence choice. Specifically, the frequency with which the targeted option was chosen for a job depended on whether the target was also the highest ranked candidate entering the final stage of selection. Results also suggest significant effects of nondominated decoys on choice. Practical implications and suggestions for future research are discussed.
Stigma and Discrimination in Health‐Care Provision to Drug Users: The Role of Values, Affect, and Deservingness Judgments
Authors: Skinner Natalie , Feather N. T. , Freeman Toby , Roche Ann
Published: January 2007

This study examined the role of values, affect, and deservingness judgments in health professionals' views of patients with stigmatized conditions (e.g., drug dependence). Participants were 277 nurses who responded to a survey containing 2 scenarios of a nurse providing high‐ or low‐quality care to a patient with a condition related to prolonged use of alcohol or heroin. Affective responses to the patient were more positive for nurses with higher self‐transcendence values, and more negative for nurses with higher conservation values. Deservingness judgments were predicted by positive and negative affect toward the patient, but not by attributions of responsibility for drug use. Deservingness judgments emerged as strong predictors of nurses' satisfaction with the provision of high‐ or low‐quality care. The findings imply that the deservingness judgments made by nurses reflected strong entitlement norms concerning the provision of proper care for patients that were independent of patients' perceived responsibility for their condition.
Synergistic growth inhibition by acyclic retinoid and vitamin K2 in human hepatocellular carcinoma cells
Authors: Kanamori Toh , Shimizu Masahito , Okuno Masataka , Matsushima‐Nishiwaki Rie , Tsurumi Hisashi , Kojima Soichi , Moriwaki Hisataka
Published: January 2007

Hepatocellular carcinoma (HCC) is one of the most prevalent cancers worldwide. However, effective chemopreventive and chemotherapeutic agents for this cancer have not yet been developed. In clinical trials acyclic retinoid (ACR) and vitamin K2 (VK2) decreased the recurrence rate of HCC. In the present study we examined the possible combined effects of ACR or another retinoid 9‐cis retinoic acid (9cRA) plus VK2 in the HuH7 human HCC cell line. We found that the combination of 1.0 µM ACR or 1.0 µM 9cRA plus 10 µM VK2 synergistically inhibited the growth of HuH7 cells without affecting the growth of Hc normal human hepatocytes. The combined treatment with ACR plus VK2 also acted synergistically to induce apoptosis in HuH7 cells. Treatment with VK2 alone inhibited phosphorylation of the retinoid X receptor (RXR)α protein, which is regarded as a critical factor for liver carcinogenesis, through inhibition of Ras activation and extracellular signal‐regulated kinase phosphorylation. Moreover, the inhibition of RXRα phosphorylation by VK2 was enhanced when the cells were cotreated with ACR. The combination of retinoids plus VK2 markedly increased both the retinoic acid receptor responsive element and retinoid X receptor responsive element promoter activities in HuH7 cells. Our results suggest that retinoids (especially ACR) and VK2 cooperatively inhibit activation of the Ras/MAPK signaling pathway, subsequently inhibiting the phosphorylation of RXRα and the growth of HCC cells. This combination might therefore be effective for the chemoprevention and chemotherapy of HCC. (Cancer Sci 2007; 98: 431–437)