Holonomy groups of pseudo-quaternionic-K\"ahlerian manifolds of non-zero scalar curvature

The holonomy group $G$ of a pseudo-quaternionic-K\"ahlerian manifold of signature $(4r,4s)$ with non-zero scalar curvature is contained in \Sp(1)\cdot\Sp(r,s) and it contains \Sp(1). It is proved that either $G$ is irreducible, or $s=r$ and $G$ preserves an isotropic subspace of dimension $4r$, in the last case, there are only two possibilities for the connected component of the identity of such $G$. This gives the classification of possible connected holonomy groups of pseudo-quaternionic-K\"ahlerian manifolds of non-zero scalar curvature.Comment: 7 pages; Dedicated to Dmitri Vladimirovich Alekseevsky at the occasion of his 70th birthda

Producing Human Therapeutic Proteins in Plastids

Plastid transformation technology is set to become a major player in the production of human therapeutic proteins. Protein expression levels that can be achieved in plant plastids are hundreds of times greater than the expression levels generally obtained via nuclear transformation. Plastids can produce human proteins that are properly folded and are biologically active. Effective protein purification strategies and strategies that can achieve inducible plastid gene expression are being developed within the system. Plastid transformation technology has been extended to edible plant species, which could minimize down-stream processing costs and raises the possibility of “edible protein therapies”. The system is limited by the fact that plastid-produced proteins are not glycosylated and that, at the moment, it can be difficult to predict protein stability within the plastid. The high level of protein expression that can be obtained in plastids could make it possible to produce high-value therapeutic proteins in plants on a scale that could be accommodated in contained glasshouse facilities and still be economically viable. Growing plastid-transformed plants under contained conditions, and coupled with the level of bio-safety conferred by maternal inheritance of plastid transgenes, would address many of the social and environmental concerns relating to plant based production of human therapeutic proteins

An ontology model for clinical documentation templates

Thesis (S.M.)--Harvard-MIT Division of Health Sciences and Technology, 2005.Includes bibliographical references (leaves 46-47).There are various kinds of clinical documents used in a hospital or clinic setting. With the emergence of Electronic Medical Records, efforts are being made to computerize these documents in a structured fashion in order to enable decision support. With structured data entry, because each fact about the patient is stored discretely and can be retrieved separately, information can be organized and presented in different ways, depending on the needs of the user. A typical structured clinical document contains a range of findings recorded by a physician, nurse or other care. These findings can be thought of as discrete pieces of information, called observations. These observations can be grouped together to form observation sets that can be placed under relevant headers within the document. When building information systems that support structured clinical documentation, these observations and sets are created and stored in catalogs. My thesis addresses the issue of building an ontology model for clinical documentation that supports the creation and management of an observations catalog, observation sets catalog and a clinical document catalog. The ontology can be used as an organizational tool for efficient maintenance of these catalogs. By tagging observations and observation sets with relevant attributes, it is possible to generate intelligent displays of data that are more flexible and dynamic.by Joyce George.S.M

The high temperature expansion of the classical XYZXYZ chain

We present the $\beta$-expansion of the Helmholtz free energy of the classical $XYZ$ model, with a single-ion anisotropy term and in the presence of an external magnetic field, up to order $\beta^{12}$. We compare our results to the numerical solution of Joyce's [Phys. Rev. Lett. 19, 581 (1967)] expression for the thermodynamics of the $XXZ$ classical model, with neither single-ion anisotropy term nor external magnetic field. This comparison shows that the derived analytical expansion is valid for intermediate temperatures such as $kT/J_x \approx 0.5$. We show that the specific heat and magnetic susceptibility of the spin-2 antiferromagnetic chain can be approximated by their respective classical results, up to $kT/J \approx 0.8$, within an error of 2.5%. In the absence of an external magnetic field, the ferromagnetic and antiferromagnetic chains have the same classical Helmholtz free energy. We show how this two types of media react to the presence of an external magnetic field

Asymptotically cylindrical 7-manifolds of holonomy G_2 with applications to compact irreducible G_2-manifolds

We construct examples of exponentially asymptotically cylindrical Riemannian 7-manifolds with holonomy group equal to G_2. To our knowledge, these are the first such examples. We also obtain exponentially asymptotically cylindrical coassociative calibrated submanifolds. Finally, we apply our results to show that one of the compact G_2-manifolds constructed by Joyce by desingularisation of a flat orbifold T^7/\Gamma can be deformed to one of the compact G_2-manifolds obtainable as a generalized connected sum of two exponentially asymptotically cylindrical SU(3)-manifolds via the method given by the first author (math.DG/0012189).Comment: 36 pages; v2: corrected trivial typos; v3: some arguments corrected and improved; v4: a number of improvements on presentation, paritularly in sections 4 and 6, including an added picture

Cosmological Magnetic Fields from Primordial Helicity

Primordial magnetic fields may account for all or part of the fields observed in galaxies. We consider the evolution of the magnetic fields created by pseudoscalar effects in the early universe. Such processes can create force-free fields of maximal helicity; we show that for such a field magnetic energy inverse cascades to larger scales than it would have solely by flux freezing and cosmic expansion. For fields generated at the electroweak phase transition, we find that the predicted wavelength today can in principle be as large as 10 kpc, and the field strength can be as large as 10^{-10} G.Comment: 13 page

A Way to Reopen the Window for Electroweak Baryogenesis

We reanalyse the sphaleron bound of electroweak baryogenesis when allowing deviations to the Friedmann equation. These modifications are well motivated in the context of brane cosmology where they appear without being in conflict with major experimental constraints on four-dimensional gravity. While suppressed at the time of nucleosynthesis, these corrections can dominate at the time of the electroweak phase transition and in certain cases provide the amount of expansion needed to freeze out the baryon asymmetry without requiring a strongly first order phase transition. The sphaleron bound is substantially weakened and can even disappear so that the constraints on the higgs and stop masses do not apply anymore. Such modification of cosmology at early times therefore reopens the parameter space allowing electroweak baryogenesis which had been reduced substantially given the new bound on the higgs mass imposed by LEP. In contrast with previous attempts to turn around the sphaleron bound using alternative cosmologies, we are still considering that the electroweak phase transition takes place in a radiation dominated universe. The universe is expanding fast because of the modification of the Friedmann equation itself without the need for a scalar field and therefore evading the problem of the decay of this scalar field after the completion of the phase transition and the risk that its release of entropy dilutes the baryon asymmetry produced at the transition.Comment: 19 pages, 3 figures; v2: minor changes, remark added at end of section 5 and in caption of figure 1; v3: references added, version to be publishe

Macrophage Ontogeny Underlies Differences in Tumor-Specific Education in Brain Malignancies.

Extensive transcriptional and ontogenetic diversity exists among normal tissue-resident macrophages, with unique transcriptional profiles endowing the cells with tissue-specific functions. However, it is unknown whether the origins of different macrophage populations affect their roles in malignancy. Given potential artifacts associated with irradiation-based lineage tracing, it remains unclear if bone-marrow-derived macrophages (BMDMs) are present in tumors of the brain, a tissue with no homeostatic involvement of BMDMs. Here, we employed multiple models of murine brain malignancy and genetic lineage tracing to demonstrate that BMDMs are abundant in primary and metastatic brain tumors. Our data indicate that distinct transcriptional networks in brain-resident microglia and recruited BMDMs are associated with tumor-mediated education yet are also influenced by chromatin landscapes established before tumor initiation. Furthermore, we demonstrate that microglia specifically repress Itga4 (CD49D), enabling its utility as a discriminatory marker between microglia and BMDMs in primary and metastatic disease in mouse and human

Electronic structure investigation of CeB6 by means of soft X-ray scattering

The electronic structure of the heavy fermion compound CeB6 is probed by resonant inelastic soft X-ray scattering using photon energies across the Ce 3d and 4d absorption edges. The hybridization between the localized 4f orbitals and the delocalized valence-band states is studied by identifying the different spectral contributions from inelastic Raman scattering and normal fluorescence. Pronounced energy-loss structures are observed below the elastic peak at both the 3d and 4d thresholds. The origin and character of the inelastic scattering structures are discussed in terms of charge-transfer excitations in connection to the dipole allowed transitions with 4f character. Calculations within the single impurity Anderson model with full multiplet effects are found to yield consistent spectral functions to the experimental data.Comment: 9 pages, 4 figures, 1 table, http://link.aps.org/doi/10.1103/PhysRevB.63.07510

Risk analysis of animal–vehicle crashes: a hierarchical Bayesian approach to spatial modelling

Driving along any rural road within Western Australia involves some level of uncertainty about encountering an animal whether it is wildlife, farm stock or domestic. This level of uncertainty can vary depending on factors such as the surrounding land use, water source, geometry of the road, speed limits and signage. This paper aims to model the risk of animal–vehicle crashes (AVCs) on a segmented highway. A hierarchical Bayesian model involving multivariate Poisson lognormal regression is used in establishing the relationship between AVCs and the contributing factors. Findings of this study show that farming on both sides of a road, a mixture of farming and forest roadside vegetation and roadside vegetation have significant positive effect on AVCs, while speed limits and horizontal curves indicate a negative effect. AVCs consist of both spatial- and segment-specific contributions, even though the spatial random error does not dominate model variability. Segment 15 is identified as the highest risk segment and its nearby segments also exhibit high risk