Mild concussive head injury results in increased brain substance P immunoreactivity

The document attached has been archived with permission from the Medimond International Proceedings Division. An external link to the publisher’s web site is included.The neuroinflammatory neuropeptide substance P (SP) has been implicated in oedema development following traumatic brain injury. Whether the neuropeptide plays a role in concussive head injury is unknown. Accordingly, we have used a newly developed model of mild head injury in rats to characterise the release of SP following concussive brain injury. Following brain trauma, there was no evidence of motor or cognitive deficits over the ensuing 3 weeks. Despite this, increased SP immunoreactivity was present in perivascular axons, some pyramidal neurones and astrocytes when compared to sham animals. Our findings suggest that concussive brain injury predisposes an individual to diffuse brain swelling, which may have implications in the management of sports related concussion.J.J. Donkin, I. Cernak, K.M. Rodgers and R. Vinkhttp://www.medimond.com/proceedings/moreinfo/20040912.ht

Relative judgement is relatively difficult: evidence against the role of relative judgement in absolute identification

A variety of processes have been put forward to explain absolute identification performance. One difference between current models of absolute identification is the extent to which the task involves accessing stored representations in long-term memory (e.g. exemplars in memory, Kent & Lamberts, Journal of Experimental Psychology: Learning Memory and Cognition, 31, 289–305, 2005) or relative judgement (comparison of the current stimulus to the stimulus on the previous trial, Stewart, Brown & Chater, Psychological Review, 112, 881–911, 2005). In two experiments we explored this by tapping into these processes. In Experiment 1 participants completed an absolute identification task using eight line lengths whereby a single stimulus was presented on each trial for identification. They also completed a matching task aimed at mirroring exemplar comparison in which eight line lengths were presented in a circular array and the task was to report which of these matched a target presented centrally. Experiment 2 was a relative judgement task and was similar to Experiment 1 except that the task was to report the difference (jump-size) between the current stimulus and that on the previous trial. The absolute identification and matching data showed clear similarities (faster and more accurate responding for stimuli near the edges of the range and similar stimulus-response confusions). In contrast, relative judgment performance was poor suggesting relative judgement is not straightforward. Moreover, performance as a function of jump-size differed considerably between the relative judgement and absolute identification tasks. Similarly, in the relative judgement task, predicting correct stimulus identification based on successful relative judgement yielded the reverse pattern of performance observed in the absolute identification task. Overall, the data suggest that relative judgement does not underlie absolute identification and that the task is more likely reliant on an exemplar comparison process

First cohomology groups for finite groups of Lie type in defining characteristic

Let G be a finite group of Lie type, defined over a field k of characteristic p > 0 . We find explicit bounds for the dimensions of the first cohomology groups for with coefficients in simple kG-modules. We proceed by bounding the number of composition factors of Weyl modules for simple algebraic groups independently of P and using this to deduce bounds for the 1-cohomology of simple algebraic groups. If γl denotes the (finite) maximum of the dimensions of the 1-cohomology groups over all Lie groups of rank l we find bounds for the growth rate of the sequence. {γl}We show that log γl is O(l3log l

Precision Gauge Unification from Extra Yukawa Couplings

We investigate the impact of extra vector-like GUT multiplets on the predicted value of the strong coupling. We find in particular that Yukawa couplings between such extra multiplets and the MSSM Higgs doublets can resolve the familiar two-loop discrepancy between the SUSY GUT prediction and the measured value of alpha_3. Our analysis highlights the advantages of the holomorphic scheme, where the perturbative running of gauge couplings is saturated at one loop and further corrections are conveniently described in terms of wavefunction renormalization factors. If the gauge couplings as well as the extra Yukawas are of O(1) at the unification scale, the relevant two-loop correction can be obtained analytically. However, the effect persists also in the weakly-coupled domain, where possible non-perturbative corrections at the GUT scale are under better control.Comment: 26 pages, LaTeX. v6: Important early reference adde

Super duality and irreducible characters of ortho-symplectic Lie superalgebras

We formulate and establish a super duality which connects parabolic categories $O$ between the ortho-symplectic Lie superalgebras and classical Lie algebras of $BCD$ types. This provides a complete and conceptual solution of the irreducible character problem for the ortho-symplectic Lie superalgebras in a parabolic category $O$, which includes all finite-dimensional irreducible modules, in terms of classical Kazhdan-Lusztig polynomials.Comment: 30 pages, Section 5 rewritten and shortene

Electroweak Symmetry Breaking in the DSSM

We study the theoretical and phenomenological consequences of modifying the Kahler potential of the MSSM two Higgs doublet sector. Such modifications naturally arise when the Higgs sector mixes with a quasi-hidden conformal sector, as in some F-theory GUT models. In the Delta-deformed Supersymmetric Standard Model (DSSM), the Higgs fields are operators with non-trivial scaling dimension 1 < Delta < 2. The Kahler metric is singular at the origin of field space due to the presence of quasi-hidden sector states which get their mass from the Higgs vevs. The presence of these extra states leads to the fact that even as Delta approaches 1, the DSSM does not reduce to the MSSM. In particular, the Higgs can naturally be heavier than the W- and Z-bosons. Perturbative gauge coupling unification, a large top quark Yukawa, and consistency with precision electroweak can all be maintained for Delta close to unity. Moreover, such values of Delta can naturally be obtained in string-motivated constructions. The quasi-hidden sector generically contains states charged under SU(5)_GUT as well as gauge singlets, leading to a rich, albeit model-dependent, collider phenomenology.Comment: v3: 40 pages, 3 figures, references added, typos correcte

The Conformal Sector of F-theory GUTs

D3-brane probes of exceptional Yukawa points in F-theory GUTs are natural hidden sectors for particle phenomenology. We find that coupling the probe to the MSSM yields a new class of N = 1 conformal fixed points with computable infrared R-charges. Quite surprisingly, we find that the MSSM only weakly mixes with the strongly coupled sector in the sense that the MSSM fields pick up small exactly computable anomalous dimensions. Additionally, we find that although the states of the probe sector transform as complete GUT multiplets, their coupling to Standard Model fields leads to a calculable threshold correction to the running of the visible sector gauge couplings which improves precision unification. We also briefly consider scenarios in which SUSY is broken in the hidden sector. This leads to a gauge mediated spectrum for the gauginos and first two superpartner generations, with additional contributions to the third generation superpartners and Higgs sector.Comment: v2: 51 pages, 2 figures, remark added, typos correcte

Algebra of the observables in the Calogero model and in the Chern-Simons matrix model

The algebra of observables of an N-body Calogero model is represented on the S_N-symmetric subspace of the positive definite Fock space. We discuss some general properties of the algebra and construct four different realizations of the dynamical symmetry algebra of the Calogero model. Using the fact that the minimal algebra of observables is common to the Calogero model and the finite Chern-Simons (CS) matrix model, we extend our analysis to the CS matrix model. We point out the algebraic similarities and distinctions of these models.Comment: 24 pages, misprints corrected, reference added, final version, to appear in PR

Interaction effects on common measures of sensitivity:Choice of measure, type I error, and power

Here we use simulation to assess previously unaddressed problems in the assessment of statistical interactions in detection and recognition tasks. The proportion of hits and false-alarms made by an observer on such tasks is affected by both their sensitivity and bias, and numerous measures have been developed to separate out these two factors. Each of these measures makes different assumptions regarding the underlying process and different predictions as to how false-alarm and hit rates should covary. Previous simulations have shown that choice of an inappropriate measure can lead to inflated type I error rates, or reduced power, for main effects, provided there are differences in response bias between the conditions being compared. Interaction effects pose a particular problem in this context. We show that spurious interaction effects in analysis of variance can be produced, or true interactions missed, even in the absence of variation in bias. Additional simulations show that variation in bias complicates patterns of type I error and power further. This under-appreciated fact has the potential to greatly distort the assessment of interactions in detection and recognition experiments. We discuss steps researchers can take to mitigate their chances of making an error