bluuebunny/crossref_metadata_2025 huggingface dataset:
Verification of Inter-Granular Interaction in Deformation Models by Residual Stress Measurements
Authors: Wroński S. , Wierzbanowski K. , Baczmański A. , Braham C. , Lodini A.
Published: December 2004

Deformation models are used for predictions of deformation characteristics, crystallographic textures and for interpretation of residual stress measurements. A basic element of any model is a law defining the interaction between a grain and a surrounding material. The level of interaction is very different in various models. The aim of the present work is to find the value of interaction parameter in a given material, using residual stress measurements. The estimation has been done for highly rolled steel via examination of the second order stress. In particular the “snake type” behaviour (in ϵ33 vs. sin2Ψ plot) was useful in this study.
Neutron Diffraction Studies of the Stress Effect on Texture Transformations in NiTi Shape Memory Alloys
Authors: Sittner P. , Neov D. , Lukas P. , Toebbens D.M.
Published: December 2004

Texture transformations accompanying B2 cubic to B19′ monoclinic martensitic transformation in NiTi shape memory alloy occurring upon stress-free cooling and cooling under applied compressive stress of 250 MPa were investigated by neutron diffraction. In the case of stress-free cooling, the martensite texture was found to be basically inherited from that of the parent austenite phase through the lattice correspondence between the austenite and martensite phases. In the case of cooling under stress, however, the martensite texture is different since it is strongly modified by the preferential martensite variant selection due to the compressive stress applied. It is found that the stress effect on the texture transformation can be to a first approximation rationalized by assuming that mainly the lattice correspondent variants of the martensite phase providing maximum strain into the direction and sense of load in individual crystallites form upon cooling under applied stress.
Intergranular Stress Evolution in Titanium Studied by Neutron Diffraction and Self-consistent Modelling
Authors: Oliver E.C. , Daymond M.R. , Quinta Da Fonseca J. , Withers P.J.
Published: December 2004

Neutron diffraction measurements of intergranular strain development in IMI 125 commercially pure titanium were recorded during uniaxial loading at temperatures between room temperature and 380°C. An elastoplastic self-consistent (EPSC) model was used to elucidate information about the operative deformation modes. Activation of {1012} 〈1011〉 twinning was observed to limit the build up of intergranular stresses at all temperatures.
Residual Stress Driven Creep Cracking in Type 316 Stainless Steel
Authors: Turski M. , Sherry A.H. , Bouchard P.J. , Withers P.J.
Published: December 2004

A specially designed compact tension (CT) specimen has been used to simulate reheat cracking observed in plant components operating above 500°C. The specimens were deformed in compression beyond yield and unloaded to produce high tensile residual stresses at the notch root. Test specimens were machined from an ex-service AISI Type 316H austenitic stainless steel steam header. After residual stressing, one specimen was crept for 4500 h at 550°C. Residual strains along the ligament of the specimens were measured using synchrotron and neutron diffraction techniques before and after creep. A 3D finite element (FE) model was developed and used to predict the residual stress and strain fields in the two conditions. A good correlation has been found between measurements and FE predictions before and after creep. Application of a creep ductility-exhaustion model to the specimen predicts the onset of simulated reheat crack initiation during the test. The validity of this model will be assessed on destructive examination of the specimen.
Residual Stress Analysis on AA6061 + 22 vol.% Al2O3 Rear Wheel Hubs
Authors: Giuliani Alessandra , Albertini Gianni , Fiori Fabrizio , Girardin Emmanuelle
Published: December 2004

The residual stresses in a component for automotive industry, a wheel hub made of composite material, are investigated. Forged AA6061 + Al2O3 hubs of identical shape and dimensions submitted to different thermal treatments are considered. The effects of T6 and T6-special treatments are compared. A reference forged sample without thermal treatments is also studied. Results are checked and compared with those previously obtained in simple shape demonstrators submitted to the same thermal treatments. Particular attention is given to the stresses along the radial and hoop directions, as they are expected to be critical for what concerns the in-service life of that component.
In-situ Stress Determination in Thermally-grown Iron Oxide Scales using X-Ray Diffraction of Synchrotron Radiation
Authors: Panicaud B. , Grosseau-Poussard J.L. , Renault P.O. , Dinhut J.F. , Thiaudière D. , Gailhanou M.
Published: December 2004

The development of residual stress in the iron-oxide layers growing on phosphated α-Fe in the temperature range 375–450°C was investigated by in-situ X-ray diffraction of synchrotron radiation during oxide growth. As such, the stress state in the oxide layer for very short oxidation times which corresponds to low thickness of the oxide layer (≤1 µm) has been determined. The microstructural state of the oxide layers is first presented. Then a detailed study of the residual strains in the oxide layers is undertaken. Correlations between the residual stress measurements and the evolution of the microstructural state leads to a better understanding of the oxidation behaviour of phosphated α-Fe.
Investigation of Residual Stresses in a Bimetallic Stainless Steel–Zirconium Adapter by Neutron Diffraction
Authors: Tamonov A.V. , Sumin V.V.
Published: December 2004

In this paper we present the results of residual stress measurements in a bimetallic stainless steel–zirconium adapter, which is used in some structures of RBMK reactor channels. The stresses in this component arise due to various manufacturing processes and the thermal expansion factor mismatch between the two alloys. The residual stress distribution in stainless steel was investigated. The residual stresses on three different cross sections were measured. The experiments were carried out on High Resolution Fourier Diffractometer (HRFD) and Fourier stress Diffractometer (FSD) at the pulsed reactor IBR-2 (Dubna, Russia) and on the high-resolution neutron diffractometer at power reactor LVR 15 (NPI, Rez, Czech Republic).
Complementarity of Various Diffraction Techniques Applied to Characterisation of Residual Stress in a Palladium Alloy
Authors: Carradó A. , Sprauel J.-M. , Barrallier Laurent , Lodini A.
Published: December 2004

The residual stress (RS) profile state of a palladium alloy sample, used in dentistry applications, has been determined by various diffraction techniques. An additional aim of this work was to improve different experimental methods dedicated to such RS evaluation, demonstrating that the X-ray, neutron and high-energy synchrotron X-ray diffraction (HESXRD) techniques are complementary when employed in different zones of the sample.
Neutron Diffraction Study of Fatigue Behaviors in 316LN Stainless Steel
Authors: Stoica A.D. , Wang X.-L. , Horton D.J. , Tian H. , Yang L. , Richardson J.W. , Maxey E. , Liaw P.K. , Shi D.
Published: December 2004

Time-of-flight neutron diffraction has been used to investigate deformation behaviors due to cyclic loading. A study of 316LN stainless steel shows that in the early stage of fatigue life, grain-orientation dependent intergranular stresses develop quickly and oscillate between two extreme states corresponding to the ends of a tensile or compressive half loading cycle. In the late stage, the intergranular strains vanish for tests ending in tension and remain relatively unchanged for tests ending in compression, which points to the difference in plastic behaviors during tensile and compressive loadings.
Effect of Heat Treatments on the Residual Stress State of 6061Al-15 vol%SiCw Composite
Authors: Fernández R. , Bruno G. , Lin Peng R. , González-Doncel G.
Published: December 2004

Residual stresses (RS), have been studied in extruded 6061Al-15 vol%SiCw composite by neutron diffraction in two different precipitation states, namely T6 and over-annealed treatment (OV) conditions. Quenching from solution treatment prior to ageing to achieve the T6 condition leads to macro-RS, which does not relax during ageing. Additional annealing for the OV condition does lead to total relaxation of the deviatoric term and partial relaxation of the hydrostatic term. Total relaxation of both deviatoric and hydrostatic terms, however, occurs in the unreinforced alloy. Basically, no decrease of the microscopic-RS occurs from T6 to OV condition. Whereas this may be surprising considering the large difference between aluminum matrix yield strength in T6 and in OV; this result is consistent with the small value of the deviatoric RS term in comparison to the yield stress of the alloy in the OV condition.
Creating Highly Triaxial Residual Stresses and Relaxation of the Stress Field due to Thermal Ageing
Authors: Hossain S. , Truman C.E. , Smith D.J. , Daymond M.R.
Published: December 2004

This paper presents results from an experimental and numerical study about the creation of highly triaxial residual stresses by rapid spray water quenching of solid stainless steel spheres and cylinders and the subsequent change in residual stresses due to creep. Finite element (FE) simulations predicted highly compressive residual stresses around the surface of the specimens and tensile near the centre. Neutron diffraction (ND) was used to measure the internal residual stress distribution in quenched specimens. These measurements were in good agreement with FE predictions. Simulations of creep relaxation and damage accumulation were also carried out in stainless steel specimens which had previously been water quenched and subsequently allowed to thermally age at 550°C for 3200 h.
Characterisation of Microstructure and Residual Stresses in Hydroxyapatite Coatings on Titanium Prostheses
Authors: Stanic V. , Carradó A. , Fiori F. , Albertini G. , Buslaps T.
Published: December 2004

Hydroxyapatite (HA) is one of the most used biomaterials in modern orthopaedics. It allows good chemical bonding to human bones, as it is one of its constituents. HA coatings on prostheses of different nature are currently used to improve their functional performances. Substrates of Titanium and Ti6Al4V Titanium alloy are largely used as they have good mechanical properties. However, they do not induce any osteointegration. Good mechanical properties and good osteointegration processes are achieved when Titanium base prostheses are coated with HA via plasma spray deposition. This work aims to characterise the mechanism of adhesion at the coating–substrate interface in orthopaedic prostheses. Microstructural information is obtained by using optical microscopy, electron microscopy and X-ray diffraction techniques. The residual strain and residual stress gradients close to the interface are investigated by using synchrotron radiation.
Measurement of Residual Stress in a Powder Metallurgy Aluminium–SiC Composite
Authors: Schneider L.C.R. , Fitzpatrick M.E. , Daymond M.R. , Hainsworth S.V. , Cocks A.C.F.
Published: December 2004

Powder metallurgy is a potentially attractive route for producing metal matrix composites. In order to optimize the mechanical properties and processing route, it is important to have knowledge of the internal stresses. Eight Al–SiC metal matrix composites were produced with two different aluminium matrices, two SiC dispersoids and two sintering processes. Residual strains were measured using neutron diffraction. The different sintering processes had little effect on the strains in the two phases, but differences were found for the different SiC dispersoids, with large SiC particles showing smaller strains when a pure aluminium powder was used for the matrix. For a commercial casting aluminium alloy matrix containing ∼11% Si, the measured strains were similar for both types of SiC particles. The results show that powder metallurgy is a promising route for producing metal matrix composites with controlled levels of residual stress.
Relaxation of Phase Specific Elastic Strains/stresses during Deformation of Al/Si–MMCs at Elevated Temperatures
Authors: Pyzalla A.R. , Reetz B. , Jacques A. , Feiereisen J.P. , Ferry O. , Buslaps T. , Reimers W.
Published: December 2004

Thermal and mechanical loading induces phase specific strains/stresses in metal matrix composites (MMCs). At elevated temperature part of the phase specific stresses relax. The relaxation of the phase specific residual stresses is determined by in situ experiments using white high-energy synchrotron radiation (HESR). They reveal that time- resolved strain measurements are possible and that short-time phenomena can be accessed using white HESR. The elastic strain relaxation behavior is similar for all lattice planes accessed. The influence of the temperature on the characteristic relaxation time is determined.
Residual Stresses in a Zircaloy-4 Weld
Authors: Carr D.G. , Ripley M.I. , Brown D.W. , Vogel S.C. , Holden T.M.
Published: December 2004

The macroscopic stress distribution across a Zircaloy-4 (Zr-4) GTAW weld was measured by time-of-flight neutron diffraction at the SMARTS diffractometer at Los Alamos National Laboratory. Time-of-flight diffraction enabled the measurement of strain for all the available reflections permitted by the rolling texture of the plate and its modification in the weld (melted) and heat-affected zones. Reference lattice spacings were measured on coupons cut from an adjacent section of the weld. A maximum longitudinal stress of 220 ± 40 MPa was observed along the weld centre line, compared with the plate 0.2% proof stress of 390 MPa. A maximum transverse stress of 60 ± 40 MPa was observed on the weld centre-line falling to zero at the edge of the plate.
Residual Stresses in Linear Friction Welded IMI550
Authors: Preuss M. , Quinta Da Fonseca J. , Steuwer A. , Wang L. , Withers P.J. , Bray S.
Published: December 2004

Residual stresses in linear friction welded (LFW) IMI550 have been determined by means of high energy synchrotron X-ray diffraction. Specimens were studied in the as-welded, and three different post weld heat treated conditions. Mid-thickness-mid-width line scans were recorded across the weld line in the three principal directions of the welds. For calculating the nominal residual strain the “stress-free” lattice spacing was taken from far field measurements. The separation of a chemical induced and strain induced shift of the reflection was carried out by determining the variation of the d-spacing across the weld line. This was done on thin slices cut from the centre region of a LFW sample using the biaxial sin2Ψ-technique on a collimated laboratory X-ray source. Results show large tensile stresses close to the weld line for the as-welded sample and the sample post weld heat treated at the aging temperature typical of IMI550. Moderate residual stresses were observed after increasing the post weld heat treatment (PWHT) temperature by 100 or 150°C. All conditions displayed a significant hydrostatic tensile stress field component, which is generally difficult to relieve. This work demonstrates that residual strain measurements have to be carried out using a high spatial resolution in order to resolve the sharp strain gradients apparent in LFW Titanium alloys.
Microstructure Damage in Thermal Absorbers Induced by High Energy Synchrotron Light Irradiation
Authors: Pinto H.C. , Pyzalla A.R. , Reimers W. , Buslaps T. , Honkimäki V. , Zhang L. , Dabin Y.
Published: December 2004

Aluminium plates are used as power attenuators in beamline ID15 at the ESRF. They absorb the low-energy part of the synchrotron light to reduce the heat-load on the following beamline components. Despite of many proposed design criteria, the high heat-load generated in the zone interacting with the X-rays may result in a marked deterioration of the absorber plate. Absorber plates of an old design, that failed were investigated here. Microscopy and diffraction methods revealed that the irradiated zone recrystallized during service and that its mechanical properties deteriorated. High thermal stresses built up, which were relieved by crack formation. Today a new aluminium power attenuator with an optimised cooling system is implemented, which so far is successful. This investigation shall give evidence about possible failure sources since in case of an increase in electron storage ring current, the increase in heat-load similar absorber failures shall be prevented.
Synchrotron Micro-tomography and Strain Mapping on a Fatigue Cracked Ti/SiC Fibre Composite
Authors: Sinclair R. , Tan K.T.W. , Preuss M. , Withers P.J.
Published: December 2004

High resolution synchrotron microtomography and strain mapping of individual fibres were performed at the ESRF, Grenoble, France. In this manner, the strain distributions along individual fibres have been measured in relation to matrix and fibre cracking for a fatigue cracked Ti/SiC fibre composite specimen. The interfacial shear stress distributions in the bridging fibres were derived from the fibre strains. These indicate how the extent of debonding decreases from the notch towards the crack tip. The debonding behaviour was modelled using a partial debonding shear lag model. Upon unloading the sliding of the debonded regions reversed leading to fretting wear and an associated reduction in interface shear strength near the crack relative to monotonic loading tests.
Study of Residual Stresses Introduced by Laser Shock Peening in Wide Chord Fan Blades by Neutron and Synchrotron Diffraction
Authors: King A. , Evans A.D. , Preuss M. , Withers P.J. , Woodward C.
Published: December 2004

Laser shock peening (LSP) can improve the fatigue performance of components by introducing compressive residual stresses to the surface. Residual strain has been measured in LSP’d Ti-6Al-4V fan blade root style test-pieces. Neutron diffraction (ND) has been used to measure residual strain in three orthogonal directions, which is necessary to calculate stress. This is more difficult using high energy synchrotron X-ray diffraction (SXRD) because of the characteristically low diffraction angles. Instead plane strain measurements have been made in transmission through the thickness of a sample. The out-of-plane strain was calculated using stress equilibrium arguments, and this calculation was evaluated and refined using finite element modelling. The resulting stress maps of LSP’d blade roots reveal the pattern of overlapping laser impacts. The compressive stress appears to extend more than 1 mm below the surface.
Intergranular Stress Development in Al during Dynamic Strain Ageing
Authors: Daymond M.R. , Oliver E.C.
Published: December 2004

Synchrotron x-ray diffraction has been used to study the intergranular stress development during dynamic strain aging of an Al-Mg alloy. Clear discontinuities are seen in the average lattice strains development in differently oriented grain families, occurring and macroscopic loads corresponding to plateaus in macroscopic strain. Discontinuous increases in peak width were also observed.
The primacy of affinity over clustering in regulation of adhesiveness of the integrin αLβ2
Authors: Kim Minsoo , Carman Christopher V. , Yang Wei , Salas Azucena , Springer Timothy A.
Published: December 2004

Dynamic regulation of integrin adhesiveness is required for immune cell–cell interactions and leukocyte migration. Here, we investigate the relationship between cell adhesion and integrin microclustering as measured by fluorescence resonance energy transfer, and macroclustering as measured by high resolution fluorescence microscopy. Stimuli that activate adhesion through leukocyte function–associated molecule-1 (LFA-1) failed to alter clustering of LFA-1 in the absence of ligand. Binding of monomeric intercellular adhesion molecule-1 (ICAM-1) induced profound changes in the conformation of LFA-1 but did not alter clustering, whereas binding of ICAM-1 oligomers induced significant microclustering. Increased diffusivity in the membrane by cytoskeleton-disrupting agents was sufficient to drive adhesion in the absence of affinity modulation and was associated with a greater accumulation of LFA-1 to the zone of adhesion, but redistribution did not precede cell adhesion. Disruption of conformational communication within the extracellular domain of LFA-1 blocked adhesion stimulated by affinity-modulating agents, but not adhesion stimulated by cytoskeleton-disrupting agents. Thus, LFA-1 clustering does not precede ligand binding, and instead functions in adhesion strengthening after binding to multivalent ligands.
The spindle assembly checkpoint is not essential for CSF arrest of mouse oocytes
Authors: Tsurumi Chizuko , Hoffmann Steffen , Geley Stephan , Graeser Ralph , Polanski Zbigniew
Published: December 2004

In Xenopus oocytes, the spindle assembly checkpoint (SAC) kinase Bub1 is required for cytostatic factor (CSF)-induced metaphase arrest in meiosis II. To investigate whether matured mouse oocytes are kept in metaphase by a SAC-mediated inhibition of the anaphase-promoting complex/cyclosome (APC/C) complex, we injected a dominant-negative Bub1 mutant (Bub1dn) into mouse oocytes undergoing meiosis in vitro. Passage through meiosis I was accelerated, but even though the SAC was disrupted, injected oocytes still arrested at metaphase II. Bub1dn-injected oocytes released from CSF and treated with nocodazole to disrupt the second meiotic spindle proceeded into interphase, whereas noninjected control oocytes remained arrested at metaphase. Similar results were obtained using dominant-negative forms of Mad2 and BubR1, as well as checkpoint resistant dominant APC/C activating forms of Cdc20. Thus, SAC proteins are required for checkpoint functions in meiosis I and II, but, in contrast to frog eggs, the SAC is not required for establishing or maintaining the CSF arrest in mouse oocytes.
The adhesion force of Notch with Delta and the rate of Notch signaling
Authors: Ahimou Francois , Mok Lee-Peng , Bardot Boris , Wesley Cedric
Published: December 2004

Notch signaling is repeatedly used during animal development to specify cell fates. Using atomic force microscopy on live cells, chemical inhibitors, and conventional analyses, we show that the rate of Notch signaling is linked to the adhesion force between cells expressing Notch receptors and Delta ligand. Both the Notch extracellular and intracellular domains are required for the high adhesion force with Delta. This high adhesion force is lost within minutes, primarily due to the action of Presenilin on Notch. Reduced turnover or Delta pulling accelerate this loss. These data suggest that strong adhesion between Notch and Delta might serve as a booster for initiating Notch signaling at a high rate.
Domains controlling cell polarity and proliferation in the Drosophila tumor suppressor Scribble
Authors: Zeitler Jennifer , Hsu Cynthia P. , Dionne Heather , Bilder David
Published: December 2004

Cell polarity and cell proliferation can be coupled in animal tissues, but how they are coupled is not understood. In Drosophila imaginal discs, loss of the neoplastic tumor suppressor gene scribble (scrib), which encodes a multidomain scaffolding protein, disrupts epithelial organization and also causes unchecked proliferation. Using an allelic series of mutations along with rescuing transgenes, we have identified domain requirements for polarity, proliferation control, and other Scrib functions. The leucine-rich repeats (LRR) tether Scrib to the plasma membrane, are both necessary and sufficient to organize a polarized epithelial monolayer, and are required for all proliferation control. The PDZ domains, which recruit the LRR to the junctional complex, are dispensable for overall epithelial organization. PDZ domain absence leads to mild polarity defects accompanied by moderate overproliferation, but the PDZ domains alone are insufficient to provide any Scrib function in mutant discs. We suggest a model in which Scrib, via the activity of the LRR, governs proliferation primarily by regulating apicobasal polarity.
Critical role of PIP5KIγ87 in InsP3-mediated Ca2+ signaling
Authors: Wang Ying Jie , Li Wen Hong , Wang Jing , Xu Ke , Dong Ping , Luo Xiang , Yin Helen L.
Published: December 2004

Phosphatidylinositol 4,5-bisphosphate (PIP2) is the obligatory precursor of inositol 1,4,5-trisphosphate (InsP3 or IP3) and is therefore critical to intracellular Ca2+ signaling. Using RNA interference (RNAi), we identified the short splice variant of type I phosphatidylinositol 4-phosphate 5-kinase γ (PIP5KIγ87) as the major contributor of the PIP2 pool that supports G protein–coupled receptor (GPCR)-mediated IP3 generation. PIP5KIγ87 RNAi decreases the histamine-induced IP3 response and Ca2+ flux by 70%. Strikingly, RNAi of other PIP5KI isoforms has minimal effect, even though some of these isoforms account for a larger percent of total PIP2 mass and have previously been implicated in receptor mediated endocytosis or focal adhesion formation. Therefore, PIP5KIγ87's PIP2 pool that supports GPCR-mediated Ca2+ signaling is functionally compartmentalized from those generated by the other PIP5KIs.
The interplay of osteogenesis and hematopoiesis
Authors: Kuznetsov Sergei A. , Riminucci Mara , Ziran Navid , Tsutsui Takeo W. , Corsi Alessandro , Calvi Laura , Kronenberg Henry M. , Schipani Ernestina , Robey Pamela Gehron , Bianco Paolo
Published: December 2004

The ontogeny of bone marrow and its stromal compartment, which is generated from skeletal stem/progenitor cells, was investigated in vivo and ex vivo in mice expressing constitutively active parathyroid hormone/parathyroid hormone–related peptide receptor (PTH/PTHrP; caPPR) under the control of the 2.3-kb bone-specific mouse Col1A1 promoter/enhancer. The transgene promoted increased bone formation within prospective marrow space, but delayed the transition from bone to bone marrow during growth, the formation of marrow cavities, and the appearance of stromal cell types such as marrow adipocytes and cells supporting hematopoiesis. This phenotype resolved spontaneously over time, leading to the establishment of marrow containing a greatly reduced number of clonogenic stromal cells. Proliferative osteoprogenitors, but not multipotent skeletal stem cells (mesenchymal stem cells), capable of generating a complete heterotopic bone organ upon in vivo transplantation were assayable in the bone marrow of caPPR mice. Thus, PTH/PTHrP signaling is a major regulator of the ontogeny of the bone marrow and its stromal tissue, and of the skeletal stem cell compartment.
Interdependent assembly of specific regulatory lipids and membrane fusion proteins into the vertex ring domain of docked vacuoles
Authors: Fratti Rutilio A. , Jun Youngsoo , Merz Alexey J. , Margolis Nathan , Wickner William
Published: December 2004

Membrane microdomains are assembled by lipid partitioning (e.g., rafts) or by protein–protein interactions (e.g., coated vesicles). During docking, yeast vacuoles assemble “vertex” ring-shaped microdomains around the periphery of their apposed membranes. Vertices are selectively enriched in the Rab GTPase Ypt7p, the homotypic fusion and vacuole protein sorting complex (HOPS)–VpsC Rab effector complex, SNAREs, and actin. Membrane fusion initiates at vertex microdomains. We now find that the “regulatory lipids” ergosterol, diacylglycerol and 3- and 4-phosphoinositides accumulate at vertices in a mutually interdependent manner. Regulatory lipids are also required for the vertex enrichment of SNAREs, Ypt7p, and HOPS. Conversely, SNAREs and actin regulate phosphatidylinositol 3-phosphate vertex enrichment. Though the PX domain of the SNARE Vam7p has direct affinity for only 3-phosphoinositides, all the regulatory lipids which are needed for vertex assembly affect Vam7p association with vacuoles. Thus, the assembly of the vacuole vertex ring microdomain arises from interdependent lipid and protein partitioning and binding rather than either lipid partitioning or protein interactions alone.
Persistence of apoptotic cells without autoimmune disease or inflammation in CD14−/− mice
Authors: Devitt Andrew , Parker Kate G. , Ogden Carol Anne , Oldreive Ceri , Clay Michael F. , Melville Lynsey A. , Bellamy Christopher O. , Lacy-Hulbert Adam , Gangloff Sophie C. , Goyert Sanna M. , Gregory Christopher D.
Published: December 2004

Interaction of macrophages with apoptotic cells involves multiple steps including recognition, tethering, phagocytosis, and anti-inflammatory macrophage responses. Defective apoptotic cell clearance is associated with pathogenesis of autoimmune disease. CD14 is a surface receptor that functions in vitro in the removal of apoptotic cells by human and murine macrophages, but its mechanism of action has not been defined. Here, we demonstrate that CD14 functions as a macrophage tethering receptor for apoptotic cells. Significantly, CD14−/− macrophages in vivo are defective in clearing apoptotic cells in multiple tissues, suggesting a broad role for CD14 in the clearance process. However, the resultant persistence of apoptotic cells does not lead to inflammation or increased autoantibody production, most likely because, as we show, CD14−/− macrophages retain the ability to generate anti-inflammatory signals in response to apoptotic cells. We conclude that CD14 plays a broad tethering role in apoptotic cell clearance in vivo and that apoptotic cells can persist in the absence of proinflammatory consequences.
The effective temperature in the quenching of coarsening systems to and to below
TC
Authors: Corberi Federico , Lippiello Eugenio , Zannetti Marco
Published: December 2004

We overview the general scaling behaviour of the effective temperature in
quenches of simple non-disordered systems, such as ferromagnets, to and to below
T
C. Emphasis is on the behaviour as the dimensionality is varied.
Consequences for the shape of the asymptotic parametric representation
are derived. In particular, this is always trivial in critical quenches with
T
C>0. We clarify that the
quench to T
C = 0 at the lower
critical dimensionality d
L, cannot be regarded as a critical quench. Implications for the behaviour of the exponent
a
of the ageing response function in quenches to below
T
C
are developed.
The effect of cavitation on glacier sliding
Authors: Schoof Christian
Published: December 2004

Basal sliding is one of the most important components in the dynamics of fast–flowing glaciers, but remains poorly understood on a theoretical level. In this paper, the problem of glacier sliding with cavitation over hard beds is addressed in detail. First, a bound on drag generated by the bed is derived for arbitrary bed geometries. This bound shows that the commonly used sliding law,
τ
b
=

Cu
m

b

N
n

, cannot apply to beds with bounded slopes. In order to resolve the issue of a realistic sliding law, we consider the classical Nye–Kamb sliding problem, extended to cover the case of cavitation but neglecting regelation. Based on an analogy with contact problems in elasticity, we develop a method which allows solutions to be constructed for any finite number of cavities per bed period. The method is then used to find sliding laws for irregular hard beds, and to test previously developed theories for calculating the drag generated by beds on which obstacles of many different sizes are present. It is found that the maximum drag attained is controlled by those bed obstacles which have the steepest slopes.
On a Leray–α model of turbulence
Authors: Cheskidov Alexey , Holm Darryl D. , Olson Eric , Titi Edriss S.
Published: December 2004

In this paper we introduce and study a new model for three–dimensional turbulence, the Leray–
α
model. This model is inspired by the Lagrangian averaged Navier–Stokes–
α
model of turbulence (also known Navier–Stokes–
α
model or the viscous Camassa–Holm equations). As in the case of the Lagrangian averaged Navier–Stokes–
α
model, the Leray–
α
model compares successfully with empirical data from turbulent channel and pipe flows, for a wide range of Reynolds numbers. We establish here an upper bound for the dimension of the global attractor (the number of degrees of freedom) of the Leray–
α
model of the order of (
L
/
l
d
)
12/7
, where
L
is the size of the domain and
l
d
is the dissipation length–scale. This upper bound is much smaller than what one would expect for three–dimensional models, i.e. (
L
/
l
d
)
3
. This remarkable result suggests that the Leray–
α
model has a great potential to become a good sub–grid–scale large–eddy simulation model of turbulence. We support this observation by studying, analytically and computationally, the energy spectrum and show that in addition to the usual
k
−5/3
Kolmogorov power law the inertial range has a steeper power–law spectrum for wavenumbers larger than 1/
α
. Finally, we propose a Prandtl–like boundary–layer model, induced by the Leray–
α
model, and show a very good agreement of this model with empirical data for turbulent boundary layers.
Remote detection of the pitch and orientation of a reflective diffraction grating: an optical strain gauge
Authors: Alcock R. D. , Creasey C. D. , Wileman P. , Halliwell N. A. , Coupland J. M.
Published: December 2004

Measurement of surface strain in hostile environments remains a significant metrology challenge. An elegantly simple non–contact method is to measure the change in pitch of a reflective diffraction grating bonded to the surface of interest. The grating is probed with a laser beam and the change in angular position of diffracted orders is detected as the pitch changes due to surface strain. Robust application of this technique has not been possible due to assumptions such as near–normal incidence, which were necessary in predicting the angular position of diffracted orders from the existing two–dimensional theory. This paper introduces a new three–dimensional theory of diffraction, which obviates the need for these assumptions. Importantly, the theory shows that the angular position of orders can be determined for arbitrary orientation of the grating relative to the incident probe beam. This latter development is critical for success in a practical application. It is now possible to micro–machine reflective gratings directly into a surface or surface coating and thus avoid problems with creep in the bonding material. Together with the new theory, this idea now has the potential to revolutionize how strain will be measured in the future.
Adaptation to the cost of resistance: a model of compensation, recombination, and selection in a haploid organism
Authors: Wijngaarden Pieter J. , van den Bosch Frank , Jeger Michael J. , Hoekstra Rolf F.
Published: December 2004

Populations of pathogenic organisms often evolve resistance in response to the use of pesticides or antibiotics. This rise of resistance may be followed by a fall when chemical control is suspended and resistance alleles carry a fitness cost. Another possibility is that mutations at secondary loci compensate for the cost, usually without loss of resistance. This enables resistant types to withstand invasion by the susceptible wild-type; resistance then persists in the population, which reduces the efficacy of future pesticide or antibiotic use. We examined a two-locus model of a haploid organism that adapts to the cost of resistance by a single compensatory mutation. We addressed the question how different combinations of cost and compensation and different levels of recombination affect the consequences of a single pesticide application. Resistance will become fixed in the population when the fraction of the population exposed to pesticide exceeds the cost of resistance. Compensatory mutations reduce the cost of resistance and therefore this threshold level of pesticide use. In the absence of pesticide, recombination promotes stability of equilibria. In the presence of pesticide, recombination accelerates the fixation of resistance and compensating alleles; recombination may also enable the persistence of compensated resistant types after pesticide use.
Juvenile immune system activation induces a costly upregulation of adult immunity in field cricketsGryllus campestris
Authors: Jacot Alain , Scheuber Hannes , Kurtz Joachim , Brinkhof Martin W. G.
Published: December 2004

Inducible immune defence may allow organisms a state-dependent upregulation of costly immunity in order to minimize the risk of anticipated future parasitism. The basic costs of elevated immune activity might involve a reduction in other fitness-related traits as well as an increased risk of immunopathology. In male field cricketsGryllus campestriswe experimentally investigated the condition-dependent effects of immune system activation in nymphs on immunity and physiological condition during adulthood. Following a nymphal injection of bacterial lipopolysaccharides, adult males showed significantly elevated levels of two major immune parameters, i.e. haemolymph antibacterial activity and the concentration of prophenoloxidase (proPO). By contrast, the active enzyme, phenoloxidase (PO), did not increase, suggesting a strategic long-term upregulation of the inactive proenzyme proPO only. This may help avoid the cytotoxic effects associated with high standing levels of the active enzyme. The nymphal immune insult further caused a reduction in adult haemolymph protein load, suggesting a long-term decline in overall metabolic condition. Nymphal food availability positively affected adult lysozyme activity, while PO and proPO concentrations were not affected. Our data thus suggest the long-term upregulation of immunity in response to antigenic cues as an adaptive, yet costly, invertebrate strategy to improve resistance to future parasitism.
Editorial
Authors: Hill Bill
Published: December 2004

I would like to take this opportunity to thank Professor Neill Alexander for all his hard work and critical input over the past seven years.
Proceedings B
has seen tremendous change during his tenure as Editor and he has ensured that the journal has maintained its high standards. During his tenure, submission levels have more than doubled, citation impact has improved and the international profile of the journal has never been stronger. The most significant development was the introduction of the
Biology Letters
service in 2003. The service has proved so successful that
Biology Letters
has gained independence from
Proceedings B
and is now a successful journal in its own right.

It has become recognized that the present model of a single editor making decisions on 1300 papers per annum is no longer sustainable. For this reason, the editorial management of the journal has now been restructured. In the new model, as Editor-in-Chief I will oversee a team of Associate Editors. The Associate Editors will be individually responsible for making decisions based on the recommendations of board members and referees, although I will also act as Editor for some papers and be available for Associate Editors to consult. I ask you to bear with us until the new model becomes established, but I am optimistic that it will benefit both our authors and readers. I intend to maintain the high standards of refereeing and editing achieved by Neill Alexander and the Publishing section at the Royal Society.

FUTURE PLANS

Proceedings B
has its strongest presence in organismal and population biology, particularly in evolutionary biology, behaviour and ecology. I wish to see a broadening of its coverage, but recognize that it is likely to be in complementary rather than radically different areas. Thus, I particularly welcome papers using molecular methods in areas such as evolution, ecology and systematics, and also functional analysis of, for example, behaviour. I also identify three areas in which I hope to see more submissions, namely plant biology, palaeontology and neuroscience. I welcome submissions of quality in all areas of biology, however, and papers regardless of area will be published based on their merit. I want papers to be of interest and understandable to a broad audience of biologists. They should also be succinct: the standard limit is six printed pages, and that will be exceeded (at a charge) only in cases of particular need; Web archiving is available for large datasets.

I look forward to hearing from you.

Bill Hill
The energy landscape as a unifying theme in molecular science
Authors: Wales David J.
Published: December 2004

The potential energy surface (PES) underlies most calculations of structure, dynamics and thermodynamics in molecular science. In this contribution connections between the topology of the PES and observable properties are developed for a coarse–grained model of virus capsid self–assembly. The model predicts that a thermodynamically stable, kinetically accessible icosahedral shell exists for pentameric building blocks of the right shape: not too flat and not too spiky. The structure of the corresponding PES is probably common to other systems where directed searches avoid Levinthal's paradox, such as ‘magic number’ clusters, protein folding and crystallization.
Energy landscapes and solved protein–folding problems
Authors: Wolynes Peter G.
Published: December 2004

Energy–landscape theory has led to much progress in protein folding kinetics, protein structure prediction and protein design. Funnel landscapes describe protein folding and binding and explain how protein topology determines kinetics. Landscape–optimized energy functions based on bioinformatic input have been used to correctly predict low–resolution protein structures and also to design novel proteins automatically.
Experimental configurational landscapes in aqueous solutions
Authors: Finney John L. , Bowron Daniel T.
Published: December 2004

Structures and interactions between molecules in solution are modulated by the solvent. Changes in solvent conditions can lead to structural changes and transitions such as the assembly processes seen in micelle formation and protein folding. In the case of even quite complex liquid systems, we can now explore
experimentally
the configurational energy landscapes that underlie these processes. Using an aqueous solution of an amphiphile as an example, the structural transitions induced by changes in temperature, concentration and added salt are examined at the molecular level, and some critical regions of the landscape identified. Moreover, the potentials of mean force that quantitatively describe the solvent–modulated interaction between molecules in solution can now be experimentally accessed.
What Should Default Reasoning be, by Default?
Authors: Pelletier Francis Jeffry , Elio Renée
Published: December 2004

This is a position paper concerning the role of empirical studies of human default reasoning in the formalization of AI theories of default reasoning. We note that AI motivates its theoretical enterprise by reference to human skill at default reasoning, but that the actual research does not make any use of this sort of information and instead relies on intuitions of individual investigators. We discuss two reasons theorists might not consider human performance relevant to formalizing default reasoning: (a) that intuitions are sufficient to describe a model, and (b) that human performance in this arena is irrelevant to a competence model of the phenomenon. We provide arguments against both these reasons. We then bring forward three further considerations against the use of intuitions in this arena: (a) it leads to an unawareness of predicate ambiguity, (b) it presumes an understanding of ordinary language statements of typicality, and (c) it is similar to discredited views in other fields. We advocate empirical investigation of the range of human phenomena that intuitively embody default reasoning. Gathering such information would provide data with which to generate formal default theories and against which to test the claims of proposed theories. Our position is that such data are the very phenomena that default theories are supposed to explain.
Combinatorial Semantics: Semantics for Frequent Validity
Authors: Kyburg Henry E.
Published: December 2004

In ordinary first–order logic, a valid inference in a language L is one in which the conclusion is true in every model of the language in which the premises are true. To accommodate inductive/uncertain/probabilistic/nonmonotonic inference, we weaken that demand to the demand that the conclusion be true in a large proportion of the models in which the relevant premises are true. More generally, we say that an inference is [p,q] valid if its conclusion is true in a proportion lying between p and q of those models in which the relevant premises are true. If we include a statistical variable binding operator “%” in our language, there are many quite general (and useful) things we can say about uncertain validity. A surprising result is that some of these things may conflict with Bayesian conditionalization.
AI Can Rival Control Theory for Goal Achievement in a Challenging Dynamical System
Authors: DeJong Gerald
Published: December 2004

Nonlinear dynamical systems are notoriously difficult to control. The Acrobot is an under‐actuated double pendulum in a gravitational field. Under most driving schemes the Acrobot exhibits chaotic behavior. But with careful applications of energy it is possible to gradually pump the system so as to swing it over its supporting joint. This swing‐up task is of current interest to control theory researchers.

Conventional notions of AI planning are not easily extended to domains with interacting continuously varying quantities. Such continuous domains are often dynamic; important properties change over time even when no action is taken. Noise and error propagation can preclude accurately characterizing the effects of actions or predicting the trajectory of an undisturbed system through time. A plan must be a conditional action policy or a control strategy that carefully nudges the system as it strays from a desired course. Automatically generating such plans or action strategies is the subject of this research.

An AI system successfully learns to perform the swing‐up task using an approach called explanation‐based control (EBC). The approach combines a plausible qualitative domain theory with empirical observation. Results are in some respects superior to the known control theory strategies. Of particular importance to AI is EBC's notion of a “plan” or “strategy” and its method for automatic synthesis. Experimental evidence confirms EBC's ability and generality.