bluuebunny/crossref_metadata_2025 huggingface dataset:
Trajectory Design using Differential Parameterizations
Authors: Antritter Felix , Deutscher Joachim
Published: January 2007

A trajectory for the position of an underactuated ship is considered which leads to singularities when using exact input‐output linearization. This paper shows that on the basis of a differential parameterization with a non‐flat output, such singularities can be avioded using a reparameterization of the trajectory. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Model Predictive Control Algorithm Applied To Non‐Linear Processes
Authors: Balan Radu , Maties Vistrian , Hancu Olimpiu , Stan Sergiu
Published: January 2007

Model predictive control (MPC) is an optimization‐based approach that has been successfully applied to a wide variety of control problems. In most of nonlinear strategies, the controllers are based on linear models with fixed parameters so that the vast body of linear control theory can be applied. Other solutions include the use of a nonlinear analytical model, combinations of linear empirical models, etc. This paper presents an MPC algorithm which uses on‐line simulation and rule‐based control. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The Immune Response as an Optimal Control Problem with Time‐Delays
Authors: Poppe Lisa Katrin
Published: January 2007

The treatment of a pathogenic disease process can be modeled as an optimal control problem with time‐delays in several state variables. The resulting system describes the innate immune response and consists of both ordinary differential equations and delay differential equations, where the delay is constant but disease specific. In this paper the numerical treatment and the optimal solution are discussed. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Geometric Analysis of Hamiltonian Mechanics using Connections
Authors: Schöberl Markus , Schlacher Kurt
Published: January 2007

This contribution tries to clarify the role of connections in mechanics. From a geometric point of view connections appear naturally in an intrinsic description of mechanics, such that the equations remain their structure, even though time dependent transformations are applied. The choice of connections is of course not unique and physical considerations are essential for the proper selection. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
State Dependent AIMD Algorithms and Consensus Problems
Authors: Wirth Fabian , Shorten Robert , Akar Mehmet
Published: January 2007

This papers analyses a class of nonlinear positive systems that model the dynamics of nonlinearadditive‐increase multiplicative‐decrease(AIMD) protocols. The system class covers a range of protocols that are currently used in real communication networks, such as standard TCP, and recent proposals for congestion control protocols such as Scalable TCP. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dynamical stability of a viscoelastic bar
Authors: Wójcicki Zbigniew , Brza̧kała Aneta
Published: January 2007

In the paper the dynamic stability of a simply supported viscoelastic bar of the Zener material model is investigated. The bar is subjected to a parametric excitation of a periodic nature. The physical model of the system is of the continuous type. However, the proposed approach yields a transformation of the mathematical model from the partial differential equation to an ordinary one. Such a transformation is made possible by the use of an approximation function for the bending line of the bar. This way, the system is governed by a homogeneous, ordinary differential equation of the third order with periodic coefficients. For stability studies the Floquet theory is applied. A sensitivity analysis of a parametric periodic system is discussed, i.e. the influence of stiffness and damping coefficient of the Zener model on stability of the differential equation that describes the vibration of the viscoelastic bar. Furthermore the stabilization process of an unstable parametric system was realized. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Discretisation of stabilised inverse diffusion equations
Authors: Breuß Michael
Published: January 2007

The aim of the contribution is to give a theoretical discrete framework for the so‐called staircasing phenomenon arising in discretisations of stabilised inverse diffusion equations. After defining staircasing in a rigorous fashion, we show that staircasing arises systematically depending on given data. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Trapped slender vortex filaments in statistical equilibrium
Authors: Andersen Timothy , Lim Chjan
Published: January 2007

Systems of nearly parallel, slender vortex filaments in which angular momentum is conserved are an important simplification of the Navier‐Stokes equations where turbulence can be studied in statistical equilibrium. We study the canonical Gibbs distribution based on the Klein‐Majda‐Damodaran (KMD) (Klein et al. [1995]) model and find a divergence in the mean square vortex position from that of the point vortex model of Onsager [1949] at high temperature. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Hysteresis of pulsed characteristics of field emission from nanocarbon materials
Authors: Arkhipov A. V. , Mishin M. V. , Parygin I. V.
Published: January 2007

Characteristics of pulsed‐field electron emission from nanocarbon films were investigated in experiments with a wide (1.5–5 mm) quasiplanar test gap. Parameters of the applied voltage (amplitude, shape and duration of pulsed component and d.c. bias) were varied; the maximum peak voltage value amounted to 40–45 kV. Dynamic I–V plots measured in 10–100 µs pulses combined inherent features of field emission (linearity in Fowler–Nordheim (FN) coordinates) with strong hysteresis. For the explanation of the latter, a model of emission via intermediate electron energy states is proposed. The simple quantitative model excellently agrees with the measured characteristics for different emitter samples and over a broad range of voltage parameters, but fails to simulate the phenomenon of emission efficiency boosting by fast voltage drops, also observed in the experiment. A possible mechanism of this dynamic effect may consist in the redistribution of electrons among the different field focuses at the nonuniform emitter surface under the effect of a strong nonstationary electric field. Copyright © 2007 John Wiley & Sons, Ltd.
The mobility of an alkali promoter as probed in situ during a catalytic reaction: Li in the CO oxidation on Pt
Authors: Suchorski Y. , Beben J. , Frac A. , Medvedev V. K. , Weiss H.
Published: January 2007

Fluctuations of the local ion rate of Li+ ions emitted during in situ monitoring of the catalytic CO oxidation on the nanofacets of a Pt field emitter tip with a lithium field desorption‐microscope (Li‐FDM) are utilized to study the Li surface diffusion. The ‘virtual probe‐hole’ approach, which is based on the digitization of the Li‐FDM video images, is used. This allows to analyze simultaneously the local fluctuations of ions originating from arbitrarily user‐defined probed surface regions of nanometer size. The anisotropy of the Li diffusion on the spatially inhomogeneous Pt surface is directly proved and a slowing effect of the coadsorbed CO on the Li diffusion is observed. Copyright © 2007 John Wiley & Sons, Ltd.
Calcium‐induced conformational changes in the amino‐terminal half of gelsolin
Authors: Roustan Claude , Ferjani Imen , Maciver Sutherland K. , Fattoum Abdellatif , Rebière Bertrand , Benyamin Yves
Published: January 2007

Gelsolin is an actin‐binding protein that is regulated by the occupancy of multiple calcium‐binding sites. We have studied calcium induced conformational changes in the G1–2 and G1–3 sub‐domains, and report the binding affinities for the three type II sites. A new probe for G3 has been produced and a K
d of 5 μM has been measured for calcium in the context of G1–3. The two halves of gelsolin, G1–3 and G4–6 bind weakly with or without calcium, suggesting that once separated by apoptotic proteolysis, G1–3 and G4–6 remain apart allowing G1–3 to sever actin in a calcium free manner.
In vitroeffects of ghrelin on gastric H+-K+-ATPase and pepsin activity and mRNA expression of gastrin, somatostatin, receptors for GH and IGF-1 in cultured gastric mucosal cells of weanling piglets
Authors: Du G.-M. , Liu M.-J. , Shi Z.-M. , Zhang L. , Wei X.-H. , Zhao R.-Q.
Published: January 2007

The present study was conducted to investigate the effects of ghrelin on gastric acid and pepsin secretion, as well as the mRNA expression of gastrin, somatostatin (SS) and receptors for growth hormone (GH) and insulin-like growth factor-1 (IGF-1) in gastric mucosal cells in vitro. Gastric mucosal cells were isolated from 5-week-old weanling piglets and exposed for 4 h to 3×10−2, 3×10−1, 3, 3×10 and 3×102nmol/l of h-ghrelin, respectively after 30-h incubation in DMEM/F-12. Pepsin activity in culture medium, cell viability and H+-K+-ATPase activity, as well as mRNA expression of gastrin, SS, GHR and IGF-1R in gastric mucosal cells were determined as response criteria. The experiment was repeated three times. Ghrelin significantly (P<0·05) increased H+-K+-ATPase activity of gastric mucosal cells at 3×10−1, 3 and 3×10 nmol/l of h-ghrelin. However, no significant changes were observed either in pepsin activity or the cell viability after ghrelin treatment. The mRNA expression of gastrin and SS was significantly increased in gastric mucosal cells exposed to h-ghrelin at 3×10−1and 3 nmol/l (P<0·05). H-ghrelin significantly increased IGF-1R but not GHR mRNA expression at 3×10−1, 3 and 3×10 nmol/l of h-ghrelin (P<0·05). Ghrelin acts on gastric mucosal cells from weanling piglets to regulate the H+-K+-ATPase activity and mRNA expression of gastrin, SS, and IGF-1Rin vitro.
Intermediate-term results of the Senning or Mustard procedures combined with the Rastelli operation for patients with discordant atrioventricular connections associated with discordant ventriculoarterial connections or double outlet right ventricle
Authors: Hörer Jürgen , Haas Felix , Cleuziou Julie , Schreiber Christian , Kostolny Martin , Vogt Manfred , Holper Klaus , Lange Rüdiger
Published: January 2007

Background:In patients with discordant atrioventricular and ventriculoarterial connections, anatomic repair restores the morphologically left ventricle to its role in supporting the systemic circulation. In this study, we have evaluated the outcomes in the intermediate term for this complex surgical procedure.Methods:Between December 1984 and October 2003, 4 patients underwent an atrial switch operation concomitantly with a Rastelli operation, and 2 patients underwent an atrial switch operation and a patch-plasty of the pulmonary outflow tract for anatomic repair at a mean age of 3.3 plus or minus 2.1 years. All patients had intracardiac rerouting, connecting the morphologically left ventricle to the aorta.Results:There were no hospital deaths. In 5 patients, reoperation was needed, either for baffle complications, exchange of the conduit, repair of a residual ventricular septal defect, or relief of obstruction within the left ventricular outflow tract. Death occurred in 1 patient, from cardiac failure 6 months after correction. Mean follow-up time was 6.5 plus or minus 6.4 years, with a range from 6 months to 17 years. At follow-up, 1 patient presented with moderate tricuspid insufficiency, and 1 patient with mild obstruction of the pulmonary venous pathway. The remaining 3 patients showed good left and right ventricular function, and no, or mild tricuspid and mitral insufficiency.Conclusions:Anatomic repair can be performed with low hospital mortality. Restoration of the morphologically left ventricle into the systemic circulation in patients with discordant atrioventricular and ventriculoarterial connections is a demanding approach, associated with various reoperations over time. Despite this, the approach seems to be an appropriate solution for selected patients, since the majority of the patients show good left and right ventricular function, and no, or mild tricuspid and mitral insufficiency up to 17 years after correction.
Dynamic Topology of Biological Networks
Authors: Iyengar Ravi
Published: January 2007

The mammalian cell can be represented as a large modular network that consists of a central signal network that interacts with and regulates multiple cellular machines that are responsible for phenotypic behavior. We have used graph-theory approaches to analyze signal flow through a network representing the hippocampal neuron and find that signal-induced connectivity results in the formation of many regulatory motifs. Information flow through the central signaling network is initiated by extra-cellular signals such as hormones binding to their receptors. The flow of information through the signaling network results in the appearance of regulatory motifs such as feedback loops, feedforward and bifan motifs. Within the large cellular networks, these regulatory motifs are juxtaposed next to each other in several formats such as the stacked configuration or the nested configuration. We have studied the dynamics of regulatory motifs by biochemical computation using ordinary differential equation models. Positive feedback loops can function as bistable switches. Nested feed-forward motifs can give rise to two emergent properties: coincidence detection and prolonged outputs for short inputs. Bifan motifs can control response times, with some configurations working as delays and others promoting rapid responses. Bifan motifs can also act as filters. Feed-forward motifs lead to signal prolongation and thus function as a switch to alter cell state. The functional consequences of organization of motifs within networks as well as the properties of feedback, feedforward and bifans motifs are presented.
The BPS Diploma in Advanced Pharmacology: a new training opportunity (BPS Dip Pharmacol)
Authors: Hall J M
Published: January 2007

British Journal of Pharmacology (2007) 150, 129. doi:10.1038/sj.bjp.0707112
Preclinical pharmacokinetics, pharmacodynamics and activity of a humanized anti‐CD40 antibody (SGN‐40) in rodents and non‐human primates
Authors: Kelley S K , Gelzleichter T , Xie D , Lee W P , Darbonne W C , Qureshi F , Kissler K , Oflazoglu E , Grewal I S
Published: January 2007

British Journal of Pharmacology (2007) 150, 248. doi:10.1038/sj.bjp.0707129
Pulsed measurements of the nonlinear conductance of quantum point contacts
Authors: Naser B. , Ferry D. K. , Heeren J. , Reno J. L. , Bird J. P.
Published: January 2007

The conductance of quantum point contacts (QPCs) subject to strongly nonlinear source-drain biasing is investigated with transient pulses. The authors investigations reveal the presence of a characteristic fixed point, at which the transient conductance (Gt) is bias independent. This point corresponds to the situation where the unbiased QPC is almost depopulated and can apparently be accounted for by considering the unidirectional population of QPC subbands by the transient voltage. To discuss the variations of Gt away from the fixed point, it is necessary to consider the influence of the applied bias on the QPC profile and electron-phonon scattering.
Proposals for the Study of Anomalous Perceptual Schemata
Authors: Howard I P
Published: January 2007

In this paper a distinction is made between stimulus-bound processes and descriptive processes. It is suggested that the processes underlying adaptation to prismatic displacement are partly stimulus bound, but that they also involve changes in centrally evoked schemata or descriptive processes. In any case, the general procedure of confronting a person with the consequences of discordant inputs can be generalized to the study of descriptive perceptual processes. A concept of the ideal perceiver, based on the mathematical idea of the group of transformations, is defined and some examples of perceptual descriptive processes or schemata are given that illustrate how the general confrontation procedure may be applied.
A Theory of Visual Control of Braking Based on Information about Time-to-Collision
Authors: Lee David N
Published: January 2007

A theory is presented of how a driver might visually control his braking. A mathematical analysis of the changing optic array at the driver's eye indicates that the simplest type of visual information, which would be sufficient for controlling braking and would also be likely to be easily picked up by the driver, is information about time-to-collision, rather than information about distance, speed, or acceleration/deceleration. It is shown how the driver could, in principle, use visual information about time-to-collision in registering when he is on a collision course, in judging when to start braking, and in controlling his ongoing braking. Implications of the theory for safe speeds and safe following distances are discussed, taking into account visual angular velocity detection thresholds, and some suggestions are made as to how safety on the roads might be improved.
Are Curves Detected by ‘Curvature Detectors’?
Authors: Timney Brian N , Macdonald Colin
Published: January 2007

Five experiments which attempted to evaluate the relationship between orientation and curvature selectivity in human vision are described. In the first two experiments, threshold elevation for curved gratings was measured after exposure to similar gratings, with the use of either an adaptation (experiment 1) or a masking (experiment 2) paradigm. In both experiments threshold elevation occurred which was selective for both the degree and the direction of curvature of the adapting pattern. Experiment 3 compared the effects of adapting to tilted rectilinear or vertical curved gratings upon threshold for a vertical rectilinear grating. Threshold elevation declined systematically as the adapting gratings were either tilted or made more curved. Experiment 4 measured curvature selectivity as a function of the orientation of a curved adapting grating. Threshold elevation declined as the adapting grating was tilted more, but curvature selectivity remained. Experiment 5 measured the orientation tuning for curved gratings directly. Threshold elevation declined to 50% of its maximum value at an adapting orientation of about 28°. This was constant for all values of curvature used. The results are discussed with reference to the question of whether the human visual system contains ‘curvature detectors’ or linear-contour detectors which respond to the tangents of curves.
Apparent Foveofugal Drift of Counterphase Gratings
Authors: Georgeson Mark A , Harris Michael G
Published: January 2007

Counterphase gratings, and several other stimuli which consist of equal components of motion in both directions, appeared to drift foveofugally, rather than foveopetally, when presented to the retinal periphery. This ‘foveofugal drift effect’ was demonstrated by descriptive and nulling techniques and its magnitude was shown to vary across subjects. The effect was fairly brief under continuous fixation. Several lines of evidence suggested that eye movements were not responsible for the effect. The phenomenon implies a directional asymmetry in the human visual system which may be related to our consistent exposure to expanding patterns of visual flow.
Information Used in Judging Impending Collision
Authors: Schiff William , Detwiler Mary Lou
Published: January 2007

Many subhuman species and human infants, children, and adults can use two-dimensional information of relative rate of angular-size change to anticipate collisions between the self and approaching objects or surfaces. But extant studies have not determined what information is used when subjects view simulated approach events providing two-dimensional information and three-dimensional information (distance and distance change), as well as lower-order visual information contained in real approach events. Three experiments suggest that, given these several possibilities, adults' judgments of collision time are best predicted by two-dimensional spatiotemporal values which are invariant over object sizes, distances traversed, approach velocities, and several lower-order variables such as absolute angular size. However, collision time is substantially underestimated, with absolute amount of underestimation increasing as a function of actual time-to-collision. Large constant errors and loss of judgment linearity beyond about 10 s to contact time suggest that current models of human performance based on use of time-to-collision information require modified assumptions of operator efficiency.
Tests of the Hallucinations of ‘Ruth’
Authors: Harris John , Gregory Richard L
Published: January 2007

Some tests are reported on a young woman who was believed to have unusual powers of eidetic imagery and voluntary control of vivid hallucinations. No evidence was found of abnormal eidetic ability. Measurements of detection thresholds for light of different wavelengths, while the subject tried to hallucinate various colours, suggested that the supposed hallucinations acted like coloured filters held over the eye.
Psychophysical Functions for Perceived and Remembered Distance
Authors: Bradley Drake R , Vido Diane
Published: January 2007

Two separate groups of subjects made magnitude estimations of the distances to fifteen objects (from 20 ft to 14.28 miles away) situated in a landscape. On day 1 of the experiment both groups learned the names and locations of the objects while viewing them from the top of a small mountain. On day 2 the perception group ( N = 19) judged the distances to the objects while viewing them from the top of the mountain, whereas the memory group ( N = 18) judged the distances while visualizing the landscape from memory. The data for both groups were well fit by power functions; the exponent was reliably smaller for the memory group (0.596) than for the perception group (0.811). Both groups drew maps of the landscape (reproduction task) from memory and the exponents were 0.483 and 0.514 for the memory and perception groups, respectively. The results are discussed in light of possible transformations performed on the original stimulus inputs by the sensory/perceptual and the memorial systems.
Shape Constancy and Slant Perception at Birth
Authors: Slater Alan , Morison Victoria
Published: January 2007

Two experiments are described the object of which was to investigate whether perception of shape at birth is determined solely by proximal (retinal) stimulation, or whether newborn babies have the ability to perceive objective, real shape across changes in slant. In experiment 1 looking at (ie preference for) one stimulus, a square, when paired with either of two trapeziums, was found to change in a consistent manner with changes in slant, indicating that these changes in stimulation are detected and can cause considerable changes in looking behaviour. In experiment 2 newborns were desensitized to changes in slant during familiarization trials, and subsequently strongly preferred a different shape to the familiarized shape in a new orientation. This suggests that the real shape had been perceived as invariant across the retinal changes caused by the changes in slant, and further suggests that shape constancy is an organizing feature of perception which is present at birth.
Perception and Recognition of Normal and Negative Faces: The Role of Shape from Shading and Pigmentation Cues
Authors: Kemp Richard , Pike Graham , White Peter , Musselman Alex
Published: January 2007

A face is surprisingly difficult to recognise when presented in photographic negative, and negation has also been shown to affect simple perceptual judgments about a face. Two possible explanations for this effect are examined. In the shape-from-shading explanation it is argued that negating an image results in an impossible pattern of shading, and that this disrupts the formation of a three-dimensional representation of the surface geometry of the face. In an alternative account for this effect it is suggested that identification errors occur as a consequence of changes to the apparent pigmentation of the face caused by negating the image. Three experiments are reported which are designed to test these explanations by using novel colour-image transformations in which the hue and luminance components of images are independently manipulated. The results of these studies suggest that although changes to the apparent pigmentation of a face might result in identification errors in some situations, the loss of shape-from-shading cues is a more important cause of the negation effect. The role of these two sources of information in the recognition of normal faces is also discussed.
Visual Control of Steering without Course Information
Authors: Beall Andrew C , Loomis Jack M
Published: January 2007

An analysis and experimental evidence are presented that the visual control of steering in following a straight demarcated path is possible even when information about the direction of one's travel (course) is not available. Two likely sources of optical information available to observers are considered, bearing and splay, that might be used for steering under these conditions. In an experiment involving a computer-driven driving simulator, observers attempted to steer a straight path while subjected to lateral perturbing forces. When only bearing and its time derivative, motion parallax, were available, performance fell off as expected with the optical gain of motion parallax as the preview distance of the viewing aperture was varied. When splay angle and its time derivative, splay rate, were added to the display, performance generally improved and remained relatively constant with changing distance of the viewing aperture, as expected because of the constant optical gain of splay rate. Making course information available by adding point features to both displays improved steering performance only in the motion-parallax conditions.
Spatial Hearing in Children with Visual Disabilities
Authors: Ashmead Daniel H , Wall Robert S , Ebinger Kiara A , Eaton Susan B , Snook-Hill Mary-M , Yang Xuefeng
Published: January 2007

A study is reported of the effect of early visual experience on the development of auditory space perception. The spatial hearing of thirty-five children with visual disabilities (twenty-two with congenital total blindness) was compared with that of eighteen sighted children and seventeen sighted adults. The tests provided a comprehensive assessment of spatial-hearing ability, including psychophysical estimates of spatial resolution in the horizontal, vertical, and distance dimensions, as well as measures of reaching and walking to the locations of sound sources. The spatial hearing of the children with visual disabilities was comparable to or some-what better than that of the sighted children and adults. This pattern held even when the group with visual disabilities was restricted to those children with congenital total blindness; in fact, some of those children had exceptionally good spatial hearing. These findings imply that the developmental calibration of human spatial hearing is not dependent on a history of visual experience. It seems likely that this calibration arises from the experience of changes in sound-localization cues arising from self-motion, such as turning the head or walking. As a practical matter, orientation and mobility instructors may reasonably assume that individuals with visual disabilities can use their hearing effectively in day-to-day travel situations.
Perennial legumes native to Australia — a preliminary investigation of nutritive value and response to cutting
Authors: Robinson K. , Bell L. W. , Bennett R. G. , Henry D. A. , Tibbett M. , Ryan M. H.
Published: January 2007

Six Australian native herbaceous perennial legumes (Lotus australis, Swainsona colutoides, Swainsona swainsonioides, Cullen tenax, Glycine tabacina and Kennedia prorepens) were assessed in the glasshouse for nutritive value, soluble condensed tannins and production of herbage in response to three cutting treatments (regrowth harvested every 4 and 6 weeks and plants left uncut for 12 weeks). The Mediterranean perennial legumes Medicago sativa and Lotus corniculatus were also included. Dry matter (DM) yield of some native legumes was comparable to L. corniculatus, but M. sativa produced more DM than all species except S. swainsonioides after 12 weeks of regrowth. Dry matter yield of all native legumes decreased with increased cutting frequency, indicating a susceptibility to frequent defoliation. Shoot in vitro dry matter digestibility (DMD) was high (>70%) in most native legumes, except G. tabacina (65%) and K. prorepens (55%). Crude protein ranged from 21–28% for all legumes except K. prorepens (12%). More frequent cutting resulted in higher DMD and crude protein in all species, except for the DMD of C. tenax and L. australis, which did not change. Concentrations of soluble condensed tannins were 2–9 g/kg DM in the Lotus spp., 10–18 g/kg DM in K. prorepens and negligible (<1 g/kg) in the other legumes. Of the native species, C. tenax, S. swainsonioides and L. australis showed the most promise for use as forage plants and further evaluation under field conditions is now warranted.
Comparative molecular dynamics analysis of tapasin‐dependent and ‐independent MHC class I alleles
Authors: Sieker Florian , Springer Sebastian , Zacharias Martin
Published: January 2007

MHC class I molecules load antigenic peptides in the endoplasmic reticulum and present them at the cell surface. Efficiency of peptide loading depends on the class I allele and can involve interaction with tapasin and other proteins of the loading complex. Allele HLA‐B*4402 (Asp at position 116) depends on tapasin for efficient peptide loading, whereas HLA‐B*4405 (identical to B*4402 except for Tyr116) can efficiently load peptides in the absence of tapasin. Both alleles adopt very similar structures in the presence of the same peptide. Comparative unrestrained molecular dynamics simulations on the α1/α2 peptide binding domains performed in the presence of bound peptides resulted in structures in close agreement with experiments for both alleles. In the absence of peptides, allele‐specific conformational changes occurred in the first segment of the α2‐helix that flanks the peptide C‐terminal binding region (F‐pocket) and contacts residue 116. This segment is also close to the proposed tapasin contact region. For B*4402, a shift toward an altered F‐pocket structure deviating significantly from the bound form was observed. Subsequent free energy simulations on induced F‐pocket opening in B*4402 confirmed a conformation that deviated significantly from the bound structure. For B*4405, a free energy minimum close to the bound structure was found. The simulations suggest that B*4405 has a greater tendency to adopt a peptide receptive conformation in the absence of peptide, allowing tapasin‐independent peptide loading. A possible role of tapasin could be the stabilization of a peptide‐receptive class I conformation for HLA‐B*4402 and other tapasin‐dependent alleles.
Progesterone and environmental tobacco smoke act synergistically to exacerbate the development of allergic asthma in a mouse model
Authors: Mitchell V. L. , Gershwin L. J.
Published: January 2007

Background
Asthma affects males and females differently. Females have a higher incidence than males after the onset of puberty. This suggests a hormonal component to the development of the disease. Progesterone, a female hormone, has previously been shown to illicit a T‐helper type 2 (TH2) immune response similar to that seen in allergic asthma. Previous studies performed by our laboratory have shown that exposure to environmental tobacco smoke (ETS) enhances the immune response to allergens.

Objective
To determine if the combination of exposure to ETS and progesterone would further exacerbate the immune response in a mouse model of allergic asthma.

Methods
Female mice were ovariectomized and then implanted with time‐release progesterone pellets. Mice were housed in either filtered air (FA) or ETS chambers and half were exposed to aerosolized house dust mite allergen (HDMA). Bronchoalveolar lavage was performed for cell differentials; lung and spleen cells were harvested to compare IL‐4 and IFN‐γ production by ELISPOT.

Results
Progesterone pellet implantation resulted in increased serum progesterone levels (28.3±8.43 vs. 13.5±7.22 ng/mL in placebo‐treated mice, P<0.0001). Serum total IgE levels were significantly greater in progesterone vs. non‐progesterone treated animals that were also exposed to HDMA. ETS exposure enhanced total IgE levels as well. Lung homogenate cells from HDMA/progesterone‐treated animals stimulated with Concavalin A produced significantly more IL‐4 compared with HDMA/placebo‐treated animals (200±17.6 vs. 146±17.5 spots/well, P<0.01 in ETS exposed animals and 221±28.9 vs. 167±23.4 spots/well, P<0.01 in animals housed in FA). HDMA/ETS‐treated animals had higher eosinophilia in lavage than all other groups.

Conclusion
Increased serum progesterone levels exacerbate the allergic asthmatic phenotype in a mouse model. These effects are further exacerbated by the addition of environmental tobacco smoke. Progesterone provides a major contribution to the gender differences seen in the development and elicitation of the asthmatic response.
Contrasting patterns of population subdivision and historical demography in three western Mediterranean lizard species inferred from mitochondrial DNA variation
Authors: PINHO C. , HARRIS D. J. , FERRAND N.
Published: January 2007

Pleistocene climatic oscillations were a major force shaping genetic variability in many taxa. We analyse the relative effects of the ice ages across a latitudinal gradient in the Western Mediterranean region, testing two main predictions: (i) species with historical distributions in northern latitudes should have experienced greater loss of suitable habitat, resulting in higher extinction of historical lineages than species distributed in southern latitudes, where the effects of the ice ages were not as drastic. This would be reflected in the observation of lower diversity and number of differentiated lineages in northern areas. (ii) a signature of demographic expansion following the climate amelioration should be obvious in northern species, whereas in the south evidence of long‐term effective population size stability should be observed. We used as models three species of wall lizards (Podarcis bocagei, Podarcis carbonelliandPodarcis vaucheri) that replace each other along the study area. We investigated the patterns of mitochondrial DNA diversity and subdivision and obtained demographic parameter estimates for each species. Our results suggest thatP. bocagei, the northernmost species, bears low genetic diversity, a shallow coalescent history and marks of a demographic expansion. In contrast,P. vaucheri, the species with a southernmost distribution, shows deeper coalescence events, complex geographical substructure and no evidence for population growth. The species with an intermediate distribution,P. carbonelli, shows average levels of diversity, substructure and population growth. Taken together, these results conform to our main predictions and are explained by a differential influence of the ice ages on distinct latitudes.
Aetiology of Bovine Abortion in Switzerland from 1986 to 1995 – A Retrospective Study with Emphasis on Detection ofNeospora caninumandToxoplasma gondiiby PCR
Authors: Reitt K. , Hilbe M. , Voegtlin A. , Corboz L. , Haessig M. , Pospischil A.
Published: January 2007

In a retrospective study, covering the period from 1986 to 1995, tissues of aborted fetuses were re‐examined. A total of 347 cases were tested immunohistochemically, among them samples of 223 brains were examined forNeospora caninum,Toxoplasma gondiiand Bovine Virus Diarrhoea Virus (BVDV), and 249 placentae for Chlamydiaceae. Two real‐time PCR assays, one forN. caninum, and one forT. gondii, were developed. These potential abortion‐inducing agents were detected – and confirmed by PCR, except for BVDV – in 16.1% (N. caninum), 0% (T. gondii), 9.9% (BVDV) and 0.8% (Chlamydiales) of the cases examined. Immunohistochemistry proved to be inadequate for the detection of the protozoal epitopes, whereas it was confirmed as a very useful tool for the detection of BVDV. In abortion material, PCR is considered to be more suitable for the detection of protozoa andChlamydophila abortus, an adequate sampling presupposed.
Chronic subthalamic high‐frequency deep brain stimulation in Parkinson's disease – a histopathological study
Authors: Nielsen M. S. , Bjarkam C. R. , Sørensen J. C. , Bojsen‐Møller M. , Sunde N. Aa. , Østergaard K.
Published: January 2007

This study describes the pathological findings in the brain of a patient with Parkinson's disease (PD) treated with bilateral subthalamic high‐frequency deep brain stimulation (STN DBS) for 29 months prior to death. After routine neuropathological examination, tissue blocks containing the electrode tracts, the subthalamic nucleus (STN), the substantia nigra and the pre‐frontal cortex were paraffin embedded and cut into 5‐μm‐thick serial sections and stained with several conventional staining methods and immunohistochemistry. Bilateral nigral depigmentation, cell loss and Lewy body formation confirmed the diagnosis of PD. Microscopic evaluation furthermore confirmed the location of the electrodes in the STN. The electrode tracts were surrounded by a 150‐μm‐wide glial fibrillary acidic protein (GFAP)‐positive capsule consisting of a thin collagen layer lining the lumen of the tract, whilst an area with few cells and axons constituted the capsule wall towards the surrounding normal brain tissue. The brain tissue appeared normal outside the capsule boundaries with no difference in areas of stimulation compared with areas of no stimulation. Our results correspond with previous studies performed after fewer months of STN DBS and indicate mild histopathological changes in the vicinity of the electrode tract, appearing to result from the electrode placement and not from the electrical stimulation.
A Note on Simplifying Likelihoods for Site Occupancy Models
Authors: Morgan Byron J. T. , Revell David J. , Freeman Stephen N.
Published: January 2007

Summary We show how a simple reparameterization can reduce the number of parameters that need to be estimated by numerical maximum likelihood in site occupancy models. Three examples are provided.
Combining Multiple Markers for Classification Using ROC
Authors: Ma Shuangge , Huang Jian
Published: January 2007

SummaryIn biomedical studies, it is of great interest to develop methodologies for combining multiple markers for the purpose of disease classification. The receiving operating characteristic (ROC) technique has been widely used, where classification performance can be measured with the area under the ROC curve (AUC). In this article, we study a ROC‐based method for effectively combining multiple markers for disease classification. We propose a sigmoid AUC (SAUC) estimator that maximizes the sigmoid approximation of the empirical AUC. The SAUC estimator is computationally affordable,n1/2‐consistent and achieves the same asymptotic efficiency as the AUC estimator. Inference based on the weighted bootstrap is investigated. We also propose Monte Carlo methods to assess the overall prediction performance and the relative importance of individual markers. Finite sample performance is evaluated using simulation studies and two public data sets.
Spinal cord plasticity in acquisition and maintenance of motor skills
Authors: Wolpaw J. R.
Published: January 2007

Throughout normal life, activity‐dependent plasticity occurs in the spinal cord as well as in brain. Like other central nervous system (CNS) plasticity, spinal cord plasticity can occur at numerous neuronal and synaptic sites and through a variety of mechanisms. Spinal cord plasticity is prominent early in life and contributes to mastery of standard behaviours like locomotion and rapid withdrawal from pain. Later in life, spinal cord plasticity has a role in acquisition and maintenance of new motor skills, and in compensation for peripheral and central changes accompanying ageing, disease and trauma. Mastery of the simplest behaviours is accompanied by complex spinal and supraspinal plasticity. This complexity is necessary, in order to preserve the complete behavioural repertoire, and is also inevitable, due to the ubiquity of activity‐dependent CNS plasticity. Explorations of spinal cord plasticity are necessary for understanding motor skills. Furthermore, the spinal cord's comparative simplicity and accessibility makes it a logical starting point for studying skill acquisition. Induction and guidance of activity‐dependent spinal cord plasticity will probably play an important role in realization of effective new rehabilitation methods for spinal cord injuries, cerebral palsy and other motor disorders.
Thank You for Flying the Vomit Comet
Authors: Dempsey Robert , DiLisi Gregory A. , DiLisi Lori A. , Santo Gretchen
Published: January 2007

This paper describes our flight aboard NASA's C9 “Weightless Wonder,” an aircraft that creates multiple periods of microgravity by conducting a series of parabolic maneuvers over the Gulf of Mexico. Because passengers often develop motion sickness during these parabolic maneuvers, the C9 is more affectionately known as the “Vomit Comet.” To celebrate the 2005 World Year of Physics, AAPT, APS, and NASA co-sponsored a contest in which teams of high school students and their mentors could fly an experiment aboard the Vomit Comet. If selected, students would develop their experiment and travel to Houston to serve as “ground crew” while the mentors would actually fly aboard the C9 to perform the experiment.
NON LOCAL LAGRANGIANS: THE PION
Authors: NOGUERA S.
Published: January 2007

We define a family of non local and chirally symmetric low energy lagrangians motivated by theoretical studies on Quantum Chromodynamics. These models lead to quark propagators with non trivial momentum dependencies. We define the formalism for two body bound states and apply it to the pion. We study the coupling of the photon and W bosons with special attention to the implementation of local gauge invariance. We calculate the pion decay constant recovering the Goldberger-Treiman and the Gell-Mann-Oakes-Renner relations. We recover a form of the axial current consistent with PCAC. Finally we study the pion form factor and we construct the operators involved in its parton distribution.
DEVELOPMENT OF A DUAL BURN-IN POLICY FOR SEMICONDUCTOR PRODUCTS BASED ON THE NUMBER OF DEFECTIVE NEIGHBORHOOD CHIPS
Authors: TONG SEUNG HOON , YUM BONG-JIN
Published: January 2007

Most of the previous studies on developing an optimal burn-in policy for semiconductor products only deal with the burn-in process itself and little is concerned with utilizing the information on the quality levels of chips before being subjected to burn-in. Developed in this paper is a dual burn-in policy in which the number of chips (d) which do not pass the wafer probe (WP) test and lie in the neighborhood of a reference chip is utilized as an indicator on the quality level of that reference chip. The dual burn-in policy first classifies the chips which pass the WP test into two groups using a boundary value of d, and then each group is subject to burn-in for its own duration. For a certain type of 256M DRAM product, the performance of the proposed dual burn-in policy is compared to that of the single burn-in policy in which all chips are subjected to the burn-in of the same duration without considering d. The analysis results show that, for the cases considered, the proposed dual burn-in policy is more cost-effective than the single burn-in policy, implying that the additional information from the WP test is beneficial to establishing an efficient burn-in policy in semiconductor manufacturing.
MODELING AND CHARACTERIZATION OF MULTI-CHARGE MASS SPECTRA FOR PEPTIDE SEQUENCING
Authors: CHONG KET FAH , NING KANG , LEONG HON WAI , PEVZNER PAVEL
Published: January 2007

Peptide sequencing using tandem mass spectrometry data is an important and challenging problem in proteomics. We address the problem of peptide sequencing for multi-charge spectra. Most peptide sequencing algorithms currently consider only charge one or two ions even for higher-charge spectra. We give a characterization of multi-charge spectra by generalizing existing models. Using our models, we analyzed spectra from Global Proteome Machine (GPM) [Craig R, Cortens JP, Beavis RC, J Proteome Res3:1234–1242, 2004.] (with charges 1–5), Institute for Systems Biology (ISB) [Keller A, Purvine S, Nesvizhskii AI, Stolyar S, Goodlett DR, Kolker E, OMICS6:207–212, 2002.] and Orbitrap (both with charges 1–3). Our analysis for the GPM dataset shows that higher charge peaks contribute significantly to prediction of the complete peptide. They also help to explain why existing algorithms do not perform well on multi-charge spectra. Based on these analyses, we claim that peptide sequencing algorithms can achieve higher sensitivity results if they also consider higher charge ions. We verify this claim by proposing a de novo sequencing algorithm called the greedy best strong tag (GBST) algorithm that is simple but considers higher charge ions based on our new model. Evaluation on multi-charge spectra shows that our simple GBST algorithm outperforms Lutefisk and PepNovo, especially for the GPM spectra of charge three or more.
LARGE TIME BEHAVIOR OF NUMERICAL SOLUTIONS OF SCALAR CONSERVATION LAWS
Authors: LAGOUTIÈRE FRÉDÉRIC
Published: January 2007

We study the large time behavior of entropic approximate solutions to one-dimensional, hyperbolic conservation laws with periodic initial data. Under mild assumptions on the numerical scheme, we prove the asymptotic convergence of the discrete solutions to a time- and space-periodic solution.
TIMELIKE MINIMAL SUBMANIFOLDS OF GENERAL CO-DIMENSION IN MINKOWSKI SPACE TIME
Authors: ALLEN PAUL , ANDERSSON LARS , ISENBERG JAMES
Published: January 2007

We consider the timelike minimal surface problem in Minkowski spacetimes and show local and global existence of such surfaces having arbitrary dimension ≥ 2 and arbitrary co-dimension, provided they are initially close to a flat plane.
LOCAL ENERGY DECAY FOR SOLUTIONS OF MULTI-DIMENSIONAL ISOTROPIC SYMMETRIC HYPERBOLIC SYSTEMS
Authors: SIDERIS THOMAS C. , THOMASES BECCA
Published: January 2007

The local decay of energy is established for solutions to certain linear, multidimensional symmetric hyperbolic systems, with constraints. The key assumptions are isotropy and nondegeneracy of the associated symbols. Examples are given, including Maxwell's equations and linearized elasticity. Such estimates prove useful in treating nonlinear perturbations.
In Vivo Pathology: Seeing with Molecular Specificity and Cellular Resolution in the Living Body
Authors: Contag Christopher H.
Published: January 2007

The emerging tools of in vivo molecular imaging are enabling dynamic cellular and molecular analyses of disease mechanisms in living animal models and humans. These advances have the potential to dramatically change a number of fields of study, including pathology, and to contribute to the development of regenerative medicine and stem cell therapies. The new tools of molecular imaging, which have already had a tremendous impact on preclinical studies, hold great promise for bringing important and novel information to the clinician and the patient. These approaches are likely to enable early diagnosis, rapid typing of molecular markers, immediate assessment of therapeutic outcome, and ready measures of the extent of tissue regeneration after damage. However, the full impact of these new techniques will be determined by our ability to translate them to the clinic and to develop a general strategy that integrates them with other advances in molecular diagnostics and molecular medicine.