Spherically Symmetric Quantum Horizons

Isolated horizon conditions specialized to spherical symmetry can be imposed directly at the quantum level. This answers several questions concerning horizon degrees of freedom, which are seen to be related to orientation, and its fluctuations at the kinematical as well as dynamical level. In particular, in the absence of scalar or fermionic matter the horizon area is an approximate quantum observable. Including different kinds of matter fields allows to probe several aspects of the Hamiltonian constraint of quantum geometry that are important in inhomogeneous situations.Comment: 4 pages, RevTeX

The production of Mexican rhotics by Haitian Creole speakers in Tijuana Mexico: a sociophonetic approach

This study investigates the production of the Spanish /ɾ-r/ (e.g., [ˈpɛ.ɾo] ‘but’ vs. [ˈpɛ.ro] \u27dog\u27) contrast by 30 multi-lingual Haitian Creole speakers learning Spanish, living in Tijuana, Mexico. Specifically, it (a) tests the Speech Learning Model (Flege, 1995) regarding the ease of acquisition of \u27new sounds\u27 (i.e. the Spanish rhotics), (b) examines the effect of orthography and (c) investigates the role of social factors, namely language attitude and education on the production of the Spanish rhotics. An acoustic analysis of 2396 tokens show that despite Flege\u27s predictions, the [r] and the [ɾ] are difficult for the learners to produce, albeit the latter is easier than the former. Developmental patterns, transfer and target-like production of the /ɾ/ and the /r/ are reported. The results also indicate a novel effect of orthography, where the grapheme and the digraph trigger an asymmetrical effect in the learners\u27 productions. Moreover, the results presented a trend, where the more educated learners had less difficulty with the production of the /r/. Furthermore, all learners reported a positive attitude towards Spanish, which may explain why there was not a significant correlation between language attitude and the production of the /ɾ-r/ contrast. The findings make an important contribution to the field of L2 and speech learning because of the various factors that have been considered in the study

Fine Structure of Spermiogenesis in the Tick Amblyomma Hebraeum (Acari: Ixodidae): Late Stages of Differentiation and Structure of the Mature Spermatozoon

Spermatids of Amblyomma hebraeum were examined by light and electron microscopy. These large, elongate, tubular cells are pointed at one end and truncate at the other. Each is composed of an outer sheath and an inner cord. The outer sheath lining and the inner cord surface are composed of cellular processes joined at the truncate end of the sperm cell. The nucleus is in the outer sheath. The semispherical apex of the inner cord is covered by numerous bulbous expansions. The final stage of spermiogenesis is the simultaneous evagination of the inner cord at the pointed end and invagination of the outer sheath at the truncate end of the cell. The mature spermatozoon, ca. 200 μm long and consisting of the inner cord added to the former outer sheath, is clavate anteriorly and caudate posteriorly, where the nucleus is located. The mature spermatozoon contains β-glycogen particles and large peripheral granules. A prominent acrosomal complex associated with the nucleus is observed in the aging spermatozoon. The cellular processes and/or the fibrillar granular cytoplasm may have a role in sperm movemen

Delivery of an anti-HIV-1 ribozyme into HIV-infected cells via cationic liposomes

Cationic liposome-mediated intracellular delivery of a fluorescein-labeled chimeric DNA-RNA ribozyme targeted to the HIV-1 5\u27 LTR was investigated, using THP-1, THP-1/HIV-1(IIIB) or HeLa/LAV cells. Different fluorescence patterns were observed when the cells were exposed to Lipofectamine, Lipofectin or DMRIE:DOPE (1:1) complexed to the ribozyme. With Lipofectamine intense cell-associated fluorescence was found. Incubation with Lipofectin resulted in less intense diffuse fluorescence, while with DMRIE an intense but sporadic fluorescence was observed. Differentiated THP-1/HIV-1(IIIB) cells were more susceptible to killing by liposome-ribozyme complexes than THP-1 cells. Under non-cytotoxic conditions (a 4-h treatment) complexes of 5, 10 or 15 μM Lipofectin or DOTAP:DOPE (1:1) and ribozyme, at lipid:ribozyme ratios of 8:1 or 4:1, did not affect p24 production in THP-1/HIV-1(IIIB) cells in spite of the intracellular accumulation of the ribozyme. A 24-h exposure of THP-1/HIV-1(IIIB) cells to 5 μM Lipofectin or DOTAP:DOPE (1:1) complexed with either the functional or a modified control ribozyme reduced virus production by approximately 30%. Thus, the antiviral effect of the liposome-complexed ribozyme was not sequence-specific. In contrast, the free ribozyme at a relatively high concentration inhibited virus production by 30%, while the control ribozyme was ineffective, indicating a sequence-specific effect. Both Lipofectin and DOTAP complexed with ribozyme were toxic at 10 and 15 μM after a 24-h treatment. A 4-h treatment of HeLa/LAV cells with Lipofectin at 5, 10 or 15 μM was not toxic to the cells, but also did not inhibit p24 production. In contrast, treatment of HeLa CD4+ cells immediately after infection with HIV-1(IIIB) at the same lipid concentrations and lipid:ribozyme ratios was cytotoxic. Our results indicate that the delivery of functional ribozyme into cells by cationic liposomes is an inefficient process and needs extensive improvement before it can be used in ex vivo and in vivo applications. Copyright (C) 1998 Elsevier Science B.V

Relationships of diversity, disparity, and their evolutionary rates in squirrels (Sciuridae)

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/111786/1/evo12642.pd

Structural and functional-annotation of an equine whole genome oligoarray

<p>Abstract</p> <p>Background</p> <p>The horse genome is sequenced, allowing equine researchers to use high-throughput functional genomics platforms such as microarrays; next-generation sequencing for gene expression and proteomics. However, for researchers to derive value from these functional genomics datasets, they must be able to model this data in biologically relevant ways; to do so requires that the equine genome be more fully annotated. There are two interrelated types of genomic annotation: structural and functional. Structural annotation is delineating and demarcating the genomic elements (such as genes, promoters, and regulatory elements). Functional annotation is assigning function to structural elements. The Gene Ontology (GO) is the <it>de facto </it>standard for functional annotation, and is routinely used as a basis for modelling and hypothesis testing, large functional genomics datasets.</p> <p>Results</p> <p>An Equine Whole Genome Oligonucleotide (EWGO) array with 21,351 elements was developed at Texas A&M University. This 70-mer oligoarray was designed using the approximately 7× assembled and annotated sequence of the equine genome to be one of the most comprehensive arrays available for expressed equine sequences. To assist researchers in determining the biological meaning of data derived from this array, we have structurally annotated it by mapping the elements to multiple database accessions, including UniProtKB, Entrez Gene, NRPD (Non-Redundant Protein Database) and UniGene. We next provided GO functional annotations for the gene transcripts represented on this array. Overall, we GO annotated 14,531 gene products (68.1% of the gene products represented on the EWGO array) with 57,912 annotations. GAQ (GO Annotation Quality) scores were calculated for this array both before and after we added GO annotation. The additional annotations improved the <it>meanGAQ </it>score 16-fold. This data is publicly available at <it>AgBase </it><url>http://www.agbase.msstate.edu/</url>.</p> <p>Conclusion</p> <p>Providing additional information about the public databases which link to the gene products represented on the array allows users more flexibility when using gene expression modelling and hypothesis-testing computational tools. Moreover, since different databases provide different types of information, users have access to multiple data sources. In addition, our GO annotation underpins functional modelling for most gene expression analysis tools and enables equine researchers to model large lists of differentially expressed transcripts in biologically relevant ways.</p

Quantum geometry and the Schwarzschild singularity

In homogeneous cosmologies, quantum geometry effects lead to a resolution of the classical singularity without having to invoke special boundary conditions at the singularity or introduce ad-hoc elements such as unphysical matter. The same effects are shown to lead to a resolution of the Schwarzschild singularity. The resulting quantum extension of space-time is likely to have significant implications to the black hole evaporation process. Similarities and differences with the situation in quantum geometrodynamics are pointed out.Comment: 31 pages, 1 figur

Degenerate Configurations, Singularities and the Non-Abelian Nature of Loop Quantum Gravity

Degenerate geometrical configurations in quantum gravity are important to understand if the fate of classical singularities is to be revealed. However, not all degenerate configurations arise on an equal footing, and one must take into account dynamical aspects when interpreting results: While there are many degenerate spatial metrics, not all of them are approached along the dynamical evolution of general relativity or a candidate theory for quantum gravity. For loop quantum gravity, relevant properties and steps in an analysis are summarized and evaluated critically with the currently available information, also elucidating the role of degrees of freedom captured in the sector provided by loop quantum cosmology. This allows an outlook on how singularity removal might be analyzed in a general setting and also in the full theory. The general mechanism of loop quantum cosmology will be shown to be insensitive to recently observed unbounded behavior of inverse volume in the full theory. Moreover, significant features of this unboundedness are not a consequence of inhomogeneities but of non-Abelian effects which can also be included in homogeneous models.Comment: 28 pages, 1 figure; v2: extended discussion of singularity removal and summar