bluuebunny/crossref_metadata_2025 huggingface dataset:
Lagrangian Formulation of the Phonon Field Equations
Authors: Levine Arnold D.
Published: May 2005

The equations of motion of lattice vibrations are formulated with the action principle as a starting point. Aa a result, one obtains, in addition to the equations of motion, the conservation laws for energy and momentum. The latter are contained in a set of finite difference equations. Boundary conditions on the field variables must be specified over a region equal to one lattice spacing in order for the entire procedure to be meaningful. The quantized version of the theory can be constructed in a conventional way, and the commutators of the field variables exhibit a set of periodically spaced singularities. In this way we construct a field which is nonlocal with respect to its dependence on space variables, but is local with respect to its time dependence.
Dyadic Analysis of Space-Time Congruences
Authors: Estabrook Frank B. , Wahlquist Hugo D.
Published: May 2005

A physical 3-vector and dyadic formalism for the treatment of general relativistic problems is derived, by systematic introduction of a proper tetrad field. The method is especially appropriate when there exists a physically or geometrically preferred timelike congruence; all quantities in the formalism are then shown to have immediate physical interpretation as proper local observables. A complete and nonredundant set of equations for the analysis of timelike congruences is developed in this operational language. Application is made to some simple examples involving local observations, and the direct measurement of the Riemann tensor discussed.
Complex Lorentz Group with a Real Metric: Group Structure
Authors: Barut A. O.
Published: May 2005

In the attempts to connect the Lorentz group and the internal symmetry group of fundamental particles, a 16-parameter connected, noncompact group of rank 4 is studied in detail. The subgroup structure, Lie algebra and its complex extension (which is A3 in Cartan's notation),little groups, the inhomogeneous groups, and the group invariants are discussed.
Conditions for the Existence of Closed Solutions by the Normal Ordering Method
Authors: Marburger J. H.
Published: May 2005

It is shown that the normal ordering method of solving boson operator equations leads to closed solutions of the Schrödinger and density operator equations only in certain cases. In particular, a necessary condition for the existence of solutions of the form π{exp [G(ai+, ai)]} with G a finite multinomial is that the Hamiltonian be of the general form H = Σi,j(cijai+ai + c̃ijaiaj + c̃ij*ai+aj+) + Σi(ciai + ci*ai+) + c. Approximate solutions may be obtained for the density operator for arbitrary Hamiltonians.
The Implications of Unitarity on Possible Higher Symmetries
Authors: Muzinich I. J.
Published: May 2005

Using the covariant spinor formalism for higher-spin particles, it is shown that the only combination of the internal symmetry group and the Lorentz group that is compatible with the unitarity condition is the direct product. Three theorems are proved which severely limit the type of symmetries that are consistent with the unitarity condition.
Exchange of Massive Particles in the Bethe-Salpeter Equation
Authors: Rosner Jonathan L.
Published: May 2005

The high-energy behavior of the absorptive part A(s) of the forward scattering amplitude in the gφ3 ladder-graph approximation can be obtained from a homogeneous integral equation. If A(s)grows as sα, α is the highest characteristic value of this equation. When the mass μ of the exchanged particles is nonzero, the high-g behavior of α is radically different from that in the case of scalar photon exchange. For small g, α = −1 + g2a − g4b +  ..., where a is independent of μ. The dependence of b on μ has been calculated.
Rigid Motions in Einstein Spaces
Authors: Wahlquist Hugo D. , Estabrook Frank B.
Published: May 2005

The dyadic formulation of general relativity is used systematically to discuss rigid congruences in Einstein space-time. For space-time of uniform curvature, the quotient space metrics of rotating and accelerating rigid bodies are obtained. For Einstein space-time of nonuniform curvature, all irrotational, nonisometric, rigid motions are explicitly displayed. They have one degree of freedom,and occur only in degenerate static metrics of Class B. Rotating rigid congruences in Einstein space-timeof nonuniform curvature are shown to have no degrees of freedom. Their evolution is in fact found to be governed by a complete set of 14 first-order total differential equations, linear in the time derivatives of the dyadic variables. Such rotating motions are shown further to be constrained by a set of algebraic conditions, and the implication of this for the validity of the Herglotz-Noether theorem in Einstein space-time is discussed.
A 2000-Channel Analyzer for Neutron Spectroscopy
Authors: Hahn J. , Havens W. W.
Published: May 2005

A 2000-channel time-of-flight analyzer for neutron spectroscopy is described. The analyzer is designed for use with pulsed accelerators operating at approximately 60 cps. Channel widths of 0.1 μsec and a Head time of 0.8 μsec are obtained. A fast electrostatic memory is used to record data with a minimum of dead time, and a slower larger capacity magnetic drum memory is used to read out the electrostatic memory and accumulate data between bursts. The electrostatic memory system which was developed at Columbia University is described in detail.
Effect of Gaseous Impurities on BF3 Proportional Counters
Authors: Aponte J. Davila , Korff S. A.
Published: May 2005

The effect which SiF4, SO2, and SF6 have on the plateau and the pulse size distribution of a proportional counter were investigated. SiF4 was tested at three pressures, 30, 45, and 60 cm, of BF3 and its effect was found to be independent of the counter pressure for the range of value considered. From the variation in the plateau, the attachment probability for SiF4 was calculated to be h = 1.485×10−5 and its cross section for attachment to be σa = 5.12×10−20 cm2. The amount of these gases permitted, without the counter being affected beyond the limits of tolerance which are set up, were found to be 0.04% for SiF4, 0.01% for SO2, and 2.0×10−6% for SF6.
Method of Butt Welding Small Thermocouples 0.001 to 0.010 Inch in Diameter
Authors: Stover Clifford M.
Published: May 2005

A method of butt welding thermocouples 0.001 to 0.010 in, in diameter is described. The thermocouple wires are positioned in a micro-manipulator, and a controlled welding pulse is applied to them. This welding method provides uniform upset welds through a simple production technique.
Efficient Neutron Detector with a Stable Energy Threshold
Authors: Miller Douglas , Hobbie Russell K.
Published: May 2005

The principle of a range telescope has been iterated to achieve a neutron detector with 2% efficiency at 125 Mev. The energy threshold is variable, yet its stability is high enough for precise asymmetry measurements. The logic of the counter introduces several economies in instrumentation.
Transistorized Precision Ratemeter
Authors: Giannelli G. , Mandl V.
Published: May 2005

A linear ratemeter based on a special circuit with a saturated-core blocking oscillator is described. This circuit feeds a capacitance with a calibrated quantity of electric charge for every input pulse. The instrument is characterized by an absolute zero stability, a good linearity, and independence from temperature.
Gating System for Photographic Printout of Counts in Neurophysiological Research
Authors: Eisenberg L. , Ratliff F.
Published: May 2005

An electronic gating system is described which enables the photographing of an instantaneous numeral display of either the time of arrival of nerve impulses, or the time interval between successive impulses, superimposed on the oscilloscope trace of the impulses. The electronic circuitry is based on commercially available decade counters modified for the gating facility.
Interpolation of Platinum Resistance Thermometers, 20° to 273.15°K
Authors: Corruccini Robert J.
Published: May 2005

A numerical method for interpolating the resistance-temperature relation of a platinum resistance thermometer is given. Calibration at three points such as 20°, 90°, and 273°K is required. The interpolation is then carried out by reference to the complete resistance-temperature relations of two other slightly different thermometers. Limited tests suggest that it is possible to achieve a temperature scale in this way using commercially available thermometers that is reproducible within 0.001 deg, provided the Callendar-van Dusen constants and the residual resistance ratio are sufficiently restricted.
Simple Transducer Type Magnetic Balance
Authors: Vickery R. C. , Sexton W. C.
Published: May 2005

A modified Sucksmith balance is described in which a displacement transducer, linked to a flat spiral spring,replaces the conventional optical system. Voltage output from the transducer may be metered or read by oscillograph. A furnace-cryostat assembly associated with the balance head is also described.
Automatic Vacuum Control in the 760 to 1 × 10−8 Torr Range
Authors: Linner L. R. , George R. I. , McQuistan R. B.
Published: May 2005

A control system is described with which it is possible to regulate the pressure in a vacuum system over the range of 1 atm to less than 1 × 10−8 torr within ±5% of the desired pressure. An electrical signal, arising because of a deviation from the prescribed pressure, is used through a servo system, to pulse sequentially solenoid valves which control pumping speed and leak rate. Subsequent to initial adjustments, operation for extended periods is possible without operator attention.
Influence of pit-trap type on the interpretation of fauna diversity
Authors: Thompson Scott A. , Thompson Graham G. , Withers Philip C.
Published: May 2005

We compare bias in the interpretation of sampled reptile and mammal assemblages caught using 20-L PVC buckets and PVC pipes (150 mm by 600 mm deep) when used as pit-traps. We report on 16 632 pipe- and 16 632 bucket-nights of pit-trap data collected over 11 survey periods spread over 2.5 years around Ora Banda in Western Australia. Buckets caught more reptiles and more of the common ‘small’ and ‘medium’-sized reptiles, whereas pipes caught more mammals and the larger of the small trappable mammals. The trappability of some families of reptiles and some mammal species differs between buckets and pipes. We conclude that different pit-trap types provide a bias in the interpretation of the sampled fauna assemblage. Differences in the interpretation of vertebrate faunal diversity were accentuated by low trapping effort but attenuated by high trapping effort. We recommend that both buckets and pipes be employed as pit-traps during fauna surveys (as well as alternatives such as funnel traps) to more fully document fauna assemblages being surveyed.
Evaluation of trapping-web designs
Authors: Lukacs Paul M. , Anderson David R. , Burnham Kenneth P.
Published: May 2005

The trapping web is a method for estimating the density and abundance of animal populations. A Monte Carlo simulation study is performed to explore performance of the trapping web for estimating animal density under a variety of web designs and animal behaviours. The trapping performs well when animals have home ranges, even if the home ranges are large relative to trap spacing. Webs should contain at least 90 traps. Trapping should continue for 5–7 occasions. Movement rates have little impact on density estimates when animals are confined to home ranges. Estimation is poor when animals do not have home ranges and movement rates are rapid. The trapping web is useful for estimating the density of animals that are hard to detect and occur at potentially low densities.
Effect of lights on activity levels of forest bats: increasing the efficiency of surveys and species identification
Authors: Adams Maria D. , Law Bradley S. , French Kris O.
Published: May 2005

We investigated the effects of insect-attracting ultraviolet lights on activity of forest bats (Microchiroptera) with the prediction that lights would increase our indices of bat activity and improve species identification of recorded echolocation calls. Insect aggregations were created on forest tracks (n = 9) near Kioloa, New South Wales, using three vertically stratified insect light traps. Bat echolocation calls were recorded using a ground-based vertically oriented Anabat II detection system. Bat activity and foraging rates were higher at lit points than at unlit points, particularly when the lights were operated in full darkness. More species were identified at lit points and the sampling time required to identify the second to the fifth new species was 3.3–4.6 times shorter with lights. The presence of lights resulted in a greater number of bat passes more than five pulses in length, which was associated with an increased ability to identify passes to species level. Our study demonstrates that the use of lights in forest-based echolocation surveys can improve bat species inventories, particularly in communities where overlap in call characteristics among species is common.
Release of oxidized plastocyanin from photosystem I limits electron transfer between photosystem I and cytochromeb6fcomplexin vivo
Authors: Finazzi Giovanni , Sommer Frederik , Hippler Michael
Published: May 2005

We used fast absorbance spectroscopy to investigatein vivobinding dynamics and electron transfer between plastocyanin (pc) and photosystem I (PSI), and cytochrome (cyt)foxidation kinetics inChlamydomonas reinhardtiimutants in which either the binding or the release of pc from PSI was diminished. Under single flash-excitation conditions, electron flow between PSI and the cyt complex was not affected by a 5-fold lowering of the binding affinity of pc to PSI, as induced by a mutation replacing the tryptophan-651 of the PsaA subunit by a serine residue (PsaA-W651S). On the other hand, electron flow from PSI to the cytb6fcomplex was very sensitive to a 2- to 3-fold decrease in the rate of pc release from PSI, obtained by replacing the glutamic acid residue 613 of the PsaB subunit with glutamine (PsaB-E613N). Thus, our data indicate that under these experimental conditions the release of oxidized pc limits electron transfer between cytb6fcomplex and PSIin vivo.
Quantum dynamics of complex molecular systems
Authors: Miller William H.
Published: May 2005

This Perspective presents a broad overview of the present status of theoretical capabilities for describing quantum dynamics in molecular systems with many degrees of freedom, e.g., chemical reactions in solution, clusters, solids, or biomolecular environments.
How sequence defines structure: A crystallographic map of DNA structure and conformation
Authors: Hays Franklin A. , Teegarden Amy , Jones Zebulon J. R. , Harms Michael , Raup Dustin , Watson Jeffrey , Cavaliere Emily , Ho P. Shing
Published: May 2005

The fundamental question of how sequence defines conformation is explicitly answered if the structures of all possible sequences of a macromolecule are determined. We present here a crystallographic screen of all permutations of the inverted repeat DNA sequence d(CCnnn
N
6
N
7
N
8
GG), where
N
6
,
N
7
, and
N
8
are any of the four naturally occurring nucleotides. At this point, 63 of the 64 possible permutations have been crystallized from a defined set of solutions. When combined with previous work, we have assembled a data set of 37 single-crystal structures from 29 of the sequences in this motif, representing three structural classes of DNA (B-DNA, A-DNA, and four-stranded Holliday junctions). This data set includes a unique set of amphimorphic sequence, those that crystallize in two different conformations and serve to bridge the three structural phases. We have thus constructed a map of DNA structures that can be walked through in single nucleotide steps. Finally, the resulting data set allows us to dissect in detail the stabilization of and conformational variations within structural classes and identify significant conformational deviations within a particular structural class that result from sequence rather than crystal or crystallization effects.
Exogenous nitric oxide reduces glucose transporters translocation and lactate production in ischemic myocardium
in vivo
Authors: Lei Biao , Matsuo Ken , Labinskyy Volodymyr , Sharma Naveen , Chandler Margaret P. , Ahn Anna , Hintze Thomas H. , Stanley William C. , Recchia Fabio A.
Published: May 2005

Nitric oxide (NO) inhibits myocardial glucose transport and metabolism, although the underlying mechanism(s) and functional consequences of this effect are not clearly understood. We tested the hypothesis that NO inhibits the activation of AMP-activated protein kinase (AMPK) and translocation of cardiac glucose transporters (GLUTs; GLUT-4) and reduces lactate production. Ischemia was induced in open-chest dogs by a 66% flow reduction in the left anterior descending coronary artery (LAD). During ischemia, dogs were untreated (control) or treated by direct LAD infusion of (
i
) nitroglycerin (NTG) (0.5 μg·kg
–1
·min
–1
); (
ii
) 8-Br-cGMP (50 μg·kg
–1
·min
–1
); or (
iii
) NO synthase inhibitor
l
-nitro-argininemethylester (40 μg·kg
–1
·min
–1
;
n
= 9 per group). Cardiac substrate oxidation was measured with isotopic tracers. There were no differences in myocardial blood flow or oxygen delivery among groups; however, at 45 min of ischemia, the activation of AMPK was significantly less in NTG (77 ± 12% vs. nonischemic myocardium) and 8-Br-cGMP (104 ± 13%), compared with control (167 ± 17%). Similarly, GLUT-4 translocation was significantly reduced in NTG (74 ± 7%) and 8-Br-cGMP (120 ± 11%), compared with control (165 ± 17%). Glucose uptake and lactate output were 30% and 60% lower in NTG compared with control. Inhibition of NO synthesis stimulated glucose oxidation (67% increase compared with control) but did not affect AMPK phosphorylation, GLUT-4 translocation and glucose uptake. Contractile function in the ischemic region was significantly improved by NTG and
l
-nitro-argininemethylester. In conclusion, in ischemic myocardium an NO donor inhibits glucose uptake and lactate production via a reduction in AMPK stimulation of GLUT-4 translocation, revealing a mechanism of metabolic modulation and myocardial protection activated by NO donors.
A common haplotype in the complement regulatory gene factor H (
HF1/CFH
) predisposes individuals to age-related macular degeneration
Authors: Hageman Gregory S. , Anderson Don H. , Johnson Lincoln V. , Hancox Lisa S. , Taiber Andrew J. , Hardisty Lisa I. , Hageman Jill L. , Stockman Heather A. , Borchardt James D. , Gehrs Karen M. , Smith Richard J. H. , Silvestri Giuliana , Russell Stephen R. , Klaver Caroline C. W. , Barbazetto Irene , Chang Stanley , Yannuzzi Lawrence A. , Barile Gaetano R. , Merriam John C. , Smith R. Theodore , Olsh Adam K. , Bergeron Julie , Zernant Jana , Merriam Joanna E. , Gold Bert , Dean Michael , Allikmets Rando
Published: May 2005

Age-related macular degeneration (AMD) is the most frequent cause of irreversible blindness in the elderly in developed countries. Our previous studies implicated activation of complement in the formation of drusen, the hallmark lesion of AMD. Here, we show that factor H (HF1), the major inhibitor of the alternative complement pathway, accumulates within drusen and is synthesized by the retinal pigmented epithelium. Because previous linkage analyses identified chromosome 1q25-32, which harbors the factor H gene (
HF1
/
CFH
), as an AMD susceptibility locus, we analyzed
HF1
for genetic variation in two independent cohorts comprised of ≈900 AMD cases and 400 matched controls. We found association of eight common
HF1
SNPs with AMD; two common missense variants exhibit highly significant associations (I62V, χ
2
= 26.1 and
P
= 3.2 × 10
-7
and Y402H, χ
2
= 54.4 and
P
= 1.6 × 10
-13
). Haplotype analysis reveals that multiple
HF1
variants confer elevated or reduced risk of AMD. One common at-risk haplotype is present at a frequency of 50% in AMD cases and 29% in controls [odds ratio (OR) = 2.46, 95% confidence interval (1.95-3.11)]. Homozygotes for this haplotype account for 24% of cases and 8% of controls [OR = 3.51, 95% confidence interval (2.13-5.78)]. Several protective haplotypes are also identified (OR = 0.44-0.55), further implicating HF1 function in the pathogenetic mechanisms underlying AMD. We propose that genetic variation in a regulator of the alternative complement pathway, when combined with a triggering event, such as infection, underlie a major proportion of AMD in the human population.
Identification and analysis of vnd/NK-2 homeodomain binding sites in genomic DNA
Authors: Wang Lan-Hsiang , Chmelik Rebecca , Tang Derek , Nirenberg Marshall
Published: May 2005

Vnd/NK-2 homeodomain affinity column chromatography was used to purify
Drosophila
DNA fragments bound by the vnd/NK-2 homeodomain. Sequencing the selected genomic DNA fragments led to the identification of 77
Drosophila
DNA fragments that were grouped into 42 vnd/NK-2 homeodomain-binding loci. Most loci were within upstream or intronic regions, especially first introns. Nineteen of the
Drosophila
DNA fragments cloned correspond to one locus, termed Clone A, which is 312 bp in length and contains five vnd/NK-2 homeodomain core consensus binding sites, 5′-AAGTG, and is part of the first intron of the
Beadex
gene. We further analyzed the interactions between Clone A and vnd/NK-2 homeodomain protein by mobility-shift assay, DNase I footprinting, methylation interference, and ethylation interference. The DNase I footprinting analysis of Clone A with vnd/NK-2 homeodomain protein revealed three strong binding sites and one weak binding site between 15 and 130 bp of Clone A. We also analyzed binding of the vnd/NK-2 homeodomain to the 5′-flanking sequence of
vnd
/
NK-2
genomic DNA. The DNase I footprinting result showed that there are two strong binding sites and five weak binding sites in the fragment between -385 and -675 bp from the transcription start site of the
vnd
/
NK-2
gene.
Genomewide production of multipurpose alleles for the functional analysis of the mouse genome
Authors: Schnütgen Frank , De-Zolt Silke , Van Sloun Petra , Hollatz Melanie , Floss Thomas , Hansen Jens , Altschmied Joachim , Seisenberger Claudia , Ghyselinck Norbert B. , Ruiz Patricia , Chambon Pierre , Wurst Wolfgang , von Melchner Harald
Published: May 2005

A type of retroviral gene trap vectors has been developed that can induce conditional mutations in most genes expressed in mouse embryonic stem (ES) cells. The vectors rely on directional site-specific recombination systems that can repair and reinduce gene trap mutations when activated in succession. After the gene traps are inserted into the mouse genome, genetic mutations can be produced at a particular time and place in somatic cells. In addition to their conditional features, the vectors create multipurpose alleles amenable to a wide range of postinsertional modifications. Here we have used these directional recombination vectors to assemble the largest library of ES cell lines with conditional mutations in single genes yet assembled, presently totaling 1,000 unique genes. The trapped ES cell lines, which can be ordered from the German Gene Trap Consortium, are freely available to the scientific community.
Background gamma rhythmicity and attention in cortical local circuits: A computational study
Authors: Börgers Christoph , Epstein Steven , Kopell Nancy J.
Published: May 2005

We describe a simple computational model, based on generic features of cortical local circuits, that links cholinergic neuromodulation, gamma rhythmicity, and attentional selection. We propose that cholinergic modulation, by reducing adaptation currents in principal cells, induces a transition from asynchronous spontaneous activity to a “background” gamma rhythm (resembling the persistent gamma rhythms evoked
in vitro
by cholinergic agonists) in which individual principal cells participate infrequently and irregularly. We suggest that such rhythms accompany states of preparatory attention or vigilance and report simulations demonstrating that their presence can amplify stimulus-specific responses and enhance stimulus competition within a local circuit.
Balance of actively generated contractile and resistive forces controls cytokinesis dynamics
Authors: Zhang Wendy , Robinson Douglas N.
Published: May 2005

Cytokinesis, the fission of a mother cell into two daughter cells, is a simple and dramatic cell shape change. Here, we examine the dynamics of cytokinesis by using a combination of microscopy, dynamic measurements, and genetic analysis. We find that cytokinesis proceeds through a single sequence of shape changes, but the kinetics of the transformation from one shape to another differs dramatically between strains. We interpret the measurements in a simple and quantitative manner by using a previously uncharacterized analytic model. From the analysis, wild-type cytokinesis appears to proceed through an active, extremely regulated process in which globally distributed proteins generate resistive forces that slow the rate of furrow ingression. Finally, we propose that, in addition to myosin II, a Laplace pressure, resulting from material properties and the geometry of the dividing cell, generates force to help drive furrow ingression late in cytokinesis.
The importance of antennae for pea aphid wing induction in the presence of natural enemies
Authors: Kunert G. , Weisser W.W.
Published: May 2005

The pea aphid Acyrthosiphon pisum Harris has been shown to produce an increasing proportion of winged morphs among its offspring when exposed to natural enemies, in particular hoverfly larvae, lacewing larvae, adult and larval ladybirds and aphidiid parasitoids. While these results suggest that wing induction in the presence of predators and parasitoids is a general response of the pea aphid, the cues and mechanisms underlying this response are still unclear. Tactile stimuli and the perception of chemical signals as well as visual signals are candidates for suitable cues in the presence of natural enemies. In this paper the hypothesis that the aphids' antennae are crucial for the wing induction in the presence of natural enemies is tested. Antennae of pea aphids were ablated and morph production was scored when aphids were reared either in the presence or the absence of predatory lacewing larvae over a six-day period. Ablation of antennae resulted in a drastic drop in the proportion of winged morphs among the offspring, both in the presence and the absence of a predator whereas predator presence increased wing induction in aphids with intact antennae, as reported in previous experiments. The results show that antennae are necessary for wing induction in the presence of natural enemies. Critical re-examination of early work on the importance of aphid antennae and tactile stimuli for wing induction suggests that a combination of tactile and chemical cues is likely to be involved not only in predator-induced wing formation but also for wing induction in response to factors such as crowding in the aphid colony.
The effect of environmentally induced changes in the bark of young conifers on feeding behaviour and reproductive development of adult Hylobius abietis (Coleoptera: Curculionidae)
Authors: Wainhouse D. , Staley J. , Johnston J. , Boswell R.
Published: May 2005

Young plants of Sitka spruce, Scots and Corsican pine were subject to high and low light, and high and low nitrogen treatments in a polyhouse experiment. The effect of treatments on resin duct size and nitrogen concentration in stem bark was determined together with feeding by Hylobius abietis Linnaeus on the stems of ‘intact’ plants and on ‘detached’ stems cut from the plant. Resin duct size was largest on Corsican pine and smallest on Sitka spruce and inherent variation in duct size between the three conifer species appears to determine the pattern of weevil feeding between species. Resin ducts and the flow of resin from them protect the stems of young conifers from weevil feeding not by affecting the total amount of bark eaten but by limiting the depth of feeding and so protecting the inner phloem and cambium. Shallow feeding may increase the likelihood of effective wound repair. Duct size was positively related to plant growth and in particular increased with bark thickness. Overall, ducts were largest in the high light treatment although species differed in their response to the treatment. It is suggested that the effects of plant size, growing conditions and transplantation on susceptiblilty to attack by H. abietis, reported in various studies, may be due to underlying variation in resin duct size or flow rate. The effect on weevils of super-ficial feeding on stems is to increase the time for reproductive maturation by reducing consumption of the inner bark which has a higher nitrogen content.
How host larval age, and nutrition and density of the parasitoid Dinarmus basalis (Hymenoptera: Pteromalidae) influence control of Acanthoscelides obtectus (Coleoptera: Bruchidae)
Authors: Schmale I. , Wäckers F.L. , Cardona C. , Dorn S.
Published: May 2005

Choice of the targeted host developmental stage, regulation of parasitoid numbers released and introduction of food supplements are operational factors with a potential to influence the level of biological control. In a closed laboratory storage system maintained over two generations of the host, the impact of these three parameters on the control potential of the parasitoid Dinarmus basalis Rondani was investigated for high populations of larvae of Acanthoscelides obtectus (Say) feeding inside dry common bean seeds Phaseolus vulgaris. The beans were already infested with immature bruchids at the beginning of the storage period to simulate harvest conditions, characterized in a previous study. Treatments resulted in a reduction of 48–75% of the bruchid population within 16 weeks of storage. The best timing of parasitoid release was at the simulated harvest, as later releases reduced the bruchid population only by about half this percentage. Host feeding is postulated to be the key factor involved in the observed difference. The effect of increasing the number of parasitoids strongly depended on host age and food supplement. Addition of vials with honey had no direct effect on the bruchid population or on the parasitoid progeny. The ecological significance of these findings and implications for biological control are discussed.
Intestinal perception: mechanisms and assessment
Authors: Azpiroz Fernando
Published: May 2005

Physiological stimuli in the gut induce regulatory reflexes to accomplish the digestive process, but are normally not perceived. However, under some circumstances, gut stimuli may activate perception pathways and induce conscious sensations. Experimental evidence gathered during the past decade suggests that patients with functional gut disorders and unexplained abdominal symptoms may have a sensory dysfunction of the gut, so that physiological stimuli would induce symptoms. Assessment of visceral sensitivity is still poorly developed, but in analogy to somatosensory testing, differential stimulation of visceral afferents may be achieved by a combination of stimulation techniques, which may help to characterize sensory dysfunctions. Visceral afferent input is modulated by a series of mechanisms at different levels of the brain–gut axis, and conceivably, a dysfunction of these regulatory mechanisms could cause hyperalgesia. The sensory dysfunction in functional patients seems to be associated with altered reflex activity, and both mechanisms may interact to produce the symptoms. Evidence of a gut sensory–reflex dysfunction as a common pathophysiological mechanism in different functional gastrointestinal disorders would suggest that they are different forms of the same process, and that the clinical manifestations depend on the specific pathways affected.
Modulation of gut mucosal biofilms
Authors: Kleessen Brigitta , Blaut Michael
Published: May 2005

Non-digestible inulin-type fructans, such as oligofructose and high-molecular-weight inulin, have been shown to have the ability to alter the intestinal microbiota composition in such a way that members of the microbial community, generally considered as health-promoting, are stimulated. Bifidobacteria and lactobacilli are the most frequently targeted organisms. Less information exists on effects of inulin-type fructans on the composition, metabolism and healthrelated significance of bacteria at or near the mucosa surface or in the mucus layer forming mucosa-associated biofilms. Using rats inoculated with a human faecal flora as an experimental model we have found that inulin-type fructans in the diet modulated the gut microbiota by stimulation of mucosa-associated bifidobacteria as well as by partial reduction of pathogenicSalmonella enterica subsp. entericaserovar Typhimurium and thereby benefit health. In addition to changes in mucosal biofilms, inulin-type fructans also induced changes in the colonic mucosa stimulating proliferation in the crypts, increasing the release of mucins, and altering the profile of mucin components in the goblet cells and epithelial mucus layer. These results indicate that inulin-type fructans may stabilise the gut mucosal barrier. Dietary supplementation with these prebiotics could offer a new approach to supporting the barrier function of the mucosa.
Application of inulin-type fructans in animal feed and pet food
Authors: Verdonk J. M. A. J. , Shim S. B. , van Leeuwen P. , Verstegen M. W. A.
Published: May 2005

The inulin-type fructans are non-digestible oligosaccharides that are fermented in the gastrointestinal tract of farm animals and pets. This review focuses on the various effects of inulin-type fructans in pigs, poultry, calves and companion animals. Effects of the inulin-type fructans on gut microflora, digestion and availability of nutrients, gut morphology, fermentation characteristics and animal performance are discussed. Inulin-type fructans can support animal performance and health by affecting nutrient digestion, gut microflora and gut morphology, although results vary depending on composition of the basal diet, inclusion level, type of fructan, adaptation period and experimental hygienic conditions.
Inulin, oligofructose and immunomodulation
Authors: Watzl Bernhard , Girrbach Stephanie , Roller Monika
Published: May 2005

Diet is known to modulate immune functions in multiple ways and to affect host resistance to infections. Besides the essential nutrients, non-essential food constituents such as non-digestible carbohydrates may also have an impact on the immune system, especially in the area of the gut-associated lymphoid tissue (GALT). Recent data now provide first evidence that prebiotics such as inulin/oligofructose (IN/OF) modulate functions of the immune system. In animal studies IN/OF primarily activated immune cells in Peyer's patches including IL-10 production and natural killer (NK) cell cytotoxicity. Other immune functions modulated by IN/OF included the concentration of secretory IgA in ileum and caecum, splenic NK cell cytotoxicity as well as splenocyte cytokine production. In different tumour models, a lower incidence of tumours was observed, which in the case of colonic tumours was associated with enhanced NK cell cytotoxicity in the GALT. Few human studies so far have investigated the effects of IN/OF alone or in combination with other dietary supplements on immunocompetence. Supplementation of IN/OF resulted in minor changes of systemic immune functions such as decrease in phagocytic activity. No data are available on the effects of IN/OF on the GALT in man. The mechanisms of the reported effects of IN/OF on the immune system are currently investigated and include: (i) direct effects of lactic acid-producing bacteria or bacterial constituents on immune cells; (ii) the production of SCFA and binding to SCFA receptors on leucocytes. In conclusion, the current data suggest that IN/OF primarily modulate immune parameters in the GALT, but splenocytes are also activated by IN/OF. Human studies are needed to find out whether IN/OF have the potential to modulate systemic immunity in wellnourished individuals and to lower the risk of diseases such as colon cancer.
Development and simulated validation of a food-frequency questionnaire for the Colombian population
Authors: Bautista Leonelo E , Herrán Oscar F , Pryer Jane A
Published: May 2005

Objective

To develop a food-frequency questionnaire (FFQ) useful for ranking of nutrient intakes.

Design

Subjects consuming their regular diet completed 7 days of weighed intake registry (7-WIR). Foods for the FFQ were selected by stepwise multiple regression. The FFQ was then completed for each subject using data on individual food consumption from the 7-WIR. The correlation and agreement between the extrapolated FFQ and the 7-WIR data were assessed using Spearman's rank correlation coefficients (rS) and Bland and Altman's limits of agreement (LOA).

Setting

Bucaramanga, Colombia.

Subjects

We studied 97 randomly selected 20–40-year-old subjects.

Results

Sixty foods were selected for the FFQ. The 7-WIR and the extrapolated FFQ intake estimates correlated well. rS was 0.58 for energy, 0.53 for carbohydrate, 0.50 for total fat, and 0.48 for protein. For micronutrients, rS varied from 0.46 (manganese) to 0.71 (vitamin B12). FFQ average intake estimates were 83%, 80%, 86.2% and 86.4% of 7-WIR estimates for energy, carbohydrate, total fat and protein, respectively. LOA for these nutrients ranged between 45% and 165%. FFQ micronutrient intakes were on average 96% (median) of those from the 7-WIR, and the median lower and upper LOA were 50% and 203%. However, there was no indication that the degree of agreement varied with the level of intake.

Conclusions

According to our simulated validation, this FFQ may be useful to rank subjects by nutrient intake. Its validity against standard independent measurements and its applicability to other subsets of the Colombian population should be carefully considered.
Mechanical vibrations from tadpoles' flapping tails transform salamander's carnivorous morphology
Authors: Michimae Hirofumi , Nishimura Kinya , Wakahara Masami
Published: May 2005

Some prey or predator organisms exhibit striking rapid morphological plastic changes with distinct morphology under the condition of predator or prey presence. Remote chemicals propagating from the inducing agents are the prevalent induction cues for most examples of induction of distinct morphs. Sonic and visual cues, as well as chemical cues, are known as triggers for induction of behavioural plasticity. Here we show that hydraulic vibration originating from flapping tails of anuran tadpoles is a key cue in relation to induction of a distinct carnivorous morphology, a broad-headed morph, in larval salamander
Hynobius retardatus
, which is able to efficiently capture and handle prey. This result was further supported by the fact that simple mechanical vibrations of tail-like vinyl fins were able to induce the morph without any biological cues. Induction of the morph triggered by hydraulic vibration provides a novel concept for understanding the proximate mechanisms of induction of morphological changes.
‘Genome gating’; polarized intranuclear trafficking of influenza virus RNPs
Authors: Elton Debra , Amorim Maria Joao , Medcalf Liz , Digard Paul
Published: May 2005

Many viruses exploit cellular polarity to constrain the assembly and release of progeny virions to a desired surface. Influenza virus particles are released only from the apical surface of epithelial cells and this polarization is partly owing to specific targeting of the viral membrane proteins to the apical plasma membrane. The RNA genome of the virus is transcribed and replicated in the nucleus, necessitating nuclear export of the individual ribonucleoprotein (RNP) segments before they can be incorporated into budding virus particles. We show that the process of polarized virus assembly begins in the nucleus with the RNPs adopting a novel asymmetric distribution at the inner nuclear membrane prior to their export to the cytoplasm. The viral nucleoprotein, the major protein component of RNPs, displays the same polarized intranuclear distribution in the absence of other influenza virus components, suggesting the existence of a hitherto unrecognized polarity within the mammalian cell nucleus.
Resolving the nanoscale adhesion of individual gecko spatulae by atomic force microscopy
Authors: Huber Gerrit , Gorb Stanislav N , Spolenak Ralph , Arzt Eduard
Published: May 2005

Animals that cling to walls and walk on ceilings owe this ability to micron and nanoscale attachment elements. The highest adhesion forces are encountered in geckoes, which have developed intricate hierarchical structures consisting of toes (millimetre dimensions), lamella (400–600 μm size), setae (micron dimensions) and spatulae (∼200 nm size). Adhesion forces of setae on different substrates have previously been measured by a micro-electromechanical system technique. Here we report the first successful experiments in which the force–displacement curves were determined forindividualspatulae by atomic force microscopy. The adhesion force for these smallest elements of the gecko's attachment system is reproducibly found to be about 10 nN. This method sheds new light on the nanomechanisms of attachment and will help in the rational design of artificial attachment systems.
Sperm competition, mating rate and the evolution of testis and ejaculate sizes: a population model
Authors: Parker G.A , Ball M.A
Published: May 2005

There are various ways to estimate ejaculate expenditure. Ejaculate size or sperm number (
s
) is an absolute number of units of ejaculate. Relative ejaculate expenditure (
E
) is the expenditure on the ejaculate as the proportion of the total expenditure on all aspects of the mating, including finding and acquiring a female, and so on. Relative testis size or gonadosomatic index (
σ
) is testes mass divided by body mass; it is assumed to reflect the product of mating rate (
M
) and ejaculate mass (
s
). In a new model, where mating rate, sperm competition and sperm allocation interact, and where the female's inter-clutch interval is assumed to be independent of
s
or
M
, we show that
σ
is directly proportional to the mean
E
for a species; across species
σ
and
E
increase monotonically with sperm competition. However, the relation between
s
and sperm competition across species depends on the range of sperm competition (low risk or high intensity):
s
increases with sperm competition at low risk levels, but decreases with sperm competition at high intensity levels. This situation arises because
s
∝
E
/
M
; both
E
and
M
increase with sperm competition, but
E
increases differently with sperm competition in its two ranges.
Latest European coelacanth shows Gondwanan affinities
Authors: Cavin Lionel , Forey Peter L , Buffetaut Eric , Tong Haiyan
Published: May 2005

The last European fossil occurrence of a coelacanth is from the Mid-Cretaceous of the English Chalk (Turonian, 90 million years ago). Here, we report the discovery of a coelacanth from Late Cretaceous non-marine rocks in southern France. It consists of a left angular bone showing structures that imply close phylogenetic affinities with some extinct Mawsoniidae. The closest relatives are otherwise known from Cretaceous continental deposits of southern continents and suggest that the dispersal of freshwater organisms from Africa to Europe occurred in the Late Cretaceous.
Increasing search rate over time may cause a slower than expected increase in prey encounter rate with increasing prey density
Authors: Ruxton Graeme D
Published: May 2005

A previous experiment with birds searching for caterpillars in an aviary demonstrated a highly counterintuitive result, that the rate at which a forager encounters prey does not increase linearly with prey density. Here, I demonstrate that if search rate increases over time then this can produce exactly the observed type of behaviour. Further, I argue that declining perception of predation risk over time in the absence of reinforcement, coupled with a trade-off between anti-predator vigilance and searching ability (both widely reported in field and laboratory studies), could generate such a change in search rate over time. Hence, if my hypothesis is correct, the previous experimental results could have considerable generality, and invite reconsideration of our mathematical descriptions of predator–prey interactions.
Efficient quadrature of highly oscillatory integrals using derivatives
Authors: Iserles Arieh , Nørsett Syvert P
Published: May 2005

In this paper, we explore quadrature methods for highly oscillatory integrals. Generalizing the method of stationary phase, we expand such integrals into asymptotic series in inverse powers of the frequency. The outcome is two families of methods, one based on a truncation of the asymptotic series and the other extending an approach implicit in the work of

Filon (Filon 1928
Proc. R. Soc. Edinb.
49
, 38–47)

. Both kinds of methods approximate the integral as a linear combination of function values and derivatives, with coefficients that may depend on frequency. We determine asymptotic properties of these methods, proving, perhaps counterintuitively, that their performance drastically improves as frequency grows. The paper is accompanied by numerical results that demonstrate the potential of this set of ideas.
On the distribution of elastic forces in disordered structures and materials. II A statistical mechanics theory
Authors: Ngan A.H.W
Published: May 2005

Based on computer simulated results in prototypical examples of granular packings and random open-cell foams in part I of the present study, a theoretical framework based on statistical physics concepts is developed in this work to describe the internal force distributions in random materials under external loadings. The theory involves the use of an entropy functional to represent the effect of structural randomness on the force distribution, and this is assumed to remain constant during energy minimization in the search of equilibrium states. The theory accurately predicts the form of the force distributions obtained by computer simulations up to an unknown parameter, which is analogous to the temperature in a thermal system. The predicted internal force distributions can be used to construct failure surfaces based on a first-yield criterion.
Stability results for constrained calculus of variations problems: an analysis of the twisted elastic loop
Authors: Hoffman Kathleen A
Published: May 2005

Problems with a variational structure are ubiquitous throughout the physical sciences and have a distinguished scientific history. Constrained variational problems have been much less studied, particularly the theory of stability, which determines which solutions are physically realizable. In this paper, we develop stability exchange results appropriate for parameter-dependent calculus of variations problems with two particular features: either the parameter appears in the boundary conditions, or there are isoperimetric constraints. In particular, we identify an associated distinguished bifurcation diagram, which encodes the direction of stability exchange at folds. We apply the theory to a twisted elastic loop, which can naturally be formulated as a calculus of variations problem with both isoperimetric constraints and parameter-dependent boundary conditions. In combination with a perturbation expansion that classifies certain pitchfork bifurcations as sub- or super-critical, the distinguished diagram for the twisted loop provides a classification of the stability properties of all equilibria. In particular, an unanticipated sensitive dependence of stability properties on the ratio of twisting to bending stiffness is revealed.