482 research outputs found
Non-Abelian discrete gauge symmetries in 4d string models
We study the realization of non-Abelian discrete gauge symmetries in 4d field
theory and string theory compactifications. The underlying structure
generalizes the Abelian case, and follows from the interplay between gaugings
of non-Abelian isometries of the scalar manifold and field identifications
making axion-like fields periodic. We present several classes of string
constructions realizing non-Abelian discrete gauge symmetries. In particular,
compactifications with torsion homology classes, where non-Abelianity arises
microscopically from the Hanany-Witten effect, or compactifications with
non-Abelian discrete isometry groups, like twisted tori. We finally focus on
the more interesting case of magnetized branes in toroidal compactifications
and quotients thereof (and their heterotic and intersecting duals), in which
the non-Abelian discrete gauge symmetries imply powerful selection rules for
Yukawa couplings of charged matter fields. In particular, in MSSM-like models
they correspond to discrete flavour symmetries constraining the quark and
lepton mass matrices, as we show in specific examples.Comment: 58 pages; minor typos corrected and references adde
Brief Report: AIP Mutation in Pituitary Adenomas in the 18th Century and Today
From New England Journal of Medicine, Volume 364, issue 1, p.43-50. Copyright © (2011) Massachusetts Medical Society. Reprinted with permission.Gigantism results when a growth hormone–secreting pituitary adenoma is present
before epiphyseal fusion. In 1909, when Harvey Cushing examined the skeleton of
an Irish patient who lived from 1761 to 1783,1-3 he noted an enlarged pituitary
fossa. We extracted DNA from the patient’s teeth and identified a germline mutation
in the aryl hydrocarbon–interacting protein gene (AIP). Four contemporary
Northern Irish families who presented with gigantism, acromegaly, or prolactinoma
have the same mutation and haplotype associated with the mutated gene. Using
coalescent theory, we infer that these persons share a common ancestor who lived
about 57 to 66 generations earlier
Effects of the Behavior of two natural enemies to reduce populations of (heliothis zea) in the Corn Corn crop
La presencia de plagas en el cultivo del MaĂz en su etapa de choclo ha causado pĂ©rdidas econĂłmicas en el PerĂş. El estudio surge como objetivo: Evaluar la efectividad de dos predadores en estudio en control de Heliothis zea. en el cultivo de maĂz, comparar la efectividad de dos enemigos naturales del Heliothis zea; Para ello se seleccionaron tres lotes de maĂz variedad San JerĂłnimo, en etapas de floraciĂłn, maduraciĂłn para evaluar porcentajes de predacion de insectos en estudio fenolĂłgicas, Las observaciones en campo se realizĂł cada 10 dĂas, teniendo presencia de predadores de Orius insidiosus (Hemiptera: Anthocoridae). Los estados inmaduros del mazorquero (Heliothis zea). Se evaluaron en tres etapas floraciĂłn, fructificaciĂłn y maduraciĂłn. Los resultados encontrados de predacion Coleomegilla maculata y Orius insidiosus, La etapa de floraciĂłn el C. maculata tiene un 13.71 % en los diferentes estados del Heliothis zea, siendo menor porcentaje 12.71 % de Orius insidiosus esto se debe a que C. maculata tiene mayor actividad en estadios larvales, La etapa de maduraciĂłn C. maculata alcanza 24.71 % y Orius insidiosus 26.71%. El porcentaje de predacion de insectos en estudio mostraron mayor actividad predatora el Orius insidiosus, C. maculata y Orius insidiosus en la etapa de floraciĂłn del cultivo de maĂz.The presence of pests in the cultivation of maize in its choclo stage has caused economic losses in Peru. The study aims to: Evaluate the effectiveness of two predators under study in control of Heliothis zea. in maize cultivation, compare the effectiveness of two natural enemies of Heliothis zea; For this purpose, three batches of maize variety Saint Jerome were selected, in flowering stages, maturation to evaluate percentages of predation of insects in phenological study, Observations in the field was made every 10 days, having the presence of predators of Orius insidiosus (Hemiptera: Anthocoridae). The immature states of the mazorquero (Heliothis zea). They were evaluated in three stages flowering, fruiting and maturation. The results found from predation Coleomegilla maculata and Orius insidiosus, the flowering stage C. maculata has 13.71 % in the different states of Heliothis zea, being less percentage 12.71 % of Orius insidiosus this is because C. maculata has greater activity in larval stages, the maturation stage C. maculata reaches 24.71 % and Orius insidiosus 26.71%. The percentage of predation of insects under study showed increased predatory activity in Orius insidiosus, C. maculata and Orius insidiosus at the flowering stage of maize cultivation
The Formation and Evolution of the First Massive Black Holes
The first massive astrophysical black holes likely formed at high redshifts
(z>10) at the centers of low mass (~10^6 Msun) dark matter concentrations.
These black holes grow by mergers and gas accretion, evolve into the population
of bright quasars observed at lower redshifts, and eventually leave the
supermassive black hole remnants that are ubiquitous at the centers of galaxies
in the nearby universe. The astrophysical processes responsible for the
formation of the earliest seed black holes are poorly understood. The purpose
of this review is threefold: (1) to describe theoretical expectations for the
formation and growth of the earliest black holes within the general paradigm of
hierarchical cold dark matter cosmologies, (2) to summarize several relevant
recent observations that have implications for the formation of the earliest
black holes, and (3) to look into the future and assess the power of
forthcoming observations to probe the physics of the first active galactic
nuclei.Comment: 39 pages, review for "Supermassive Black Holes in the Distant
Universe", Ed. A. J. Barger, Kluwer Academic Publisher
RNAseq Analyses Identify Tumor Necrosis Factor-Mediated Inflammation as a Major Abnormality in ALS Spinal Cord
ALS is a rapidly progressive, devastating neurodegenerative illness of adults that produces disabling weakness and spasticity arising from death of lower and upper motor neurons. No meaningful therapies exist to slow ALS progression, and molecular insights into pathogenesis and progression are sorely needed. In that context, we used high-depth, next generation RNA sequencing (RNAseq, Illumina) to define gene network abnormalities in RNA samples depleted of rRNA and isolated from cervical spinal cord sections of 7 ALS and 8 CTL samples. We aligned \u3e50 million 2X150 bp paired-end sequences/sample to the hg19 human genome and applied three different algorithms (Cuffdiff2, DEseq2, EdgeR) for identification of differentially expressed genes (DEG’s). Ingenuity Pathways Analysis (IPA) and Weighted Gene Co-expression Network Analysis (WGCNA) identified inflammatory processes as significantly elevated in our ALS samples, with tumor necrosis factor (TNF) found to be a major pathway regulator (IPA) and TNFα-induced protein 2 (TNFAIP2) as a major network “hub” gene (WGCNA). Using the oPOSSUM algorithm, we analyzed transcription factors (TF) controlling expression of the nine DEG/hub genes in the ALS samples and identified TF’s involved in inflammation (NFkB, REL, NFkB1) and macrophage function (NR1H2::RXRA heterodimer). Transient expression in human iPSC-derived motor neurons of TNFAIP2 (also a DEG identified by all three algorithms) reduced cell viability and induced caspase 3/7 activation. Using high-density RNAseq, multiple algorithms for DEG identification, and an unsupervised gene co-expression network approach, we identified significant elevation of inflammatory processes in ALS spinal cord with TNF as a major regulatory molecule. Overexpression of the DEG TNFAIP2 in human motor neurons, the population most vulnerable to die in ALS, increased cell death and caspase 3/7 activation. We propose that therapies targeted to reduce inflammatory TNFα signaling may be helpful in ALS patients
Formation of Supermassive Black Holes
Evidence shows that massive black holes reside in most local galaxies.
Studies have also established a number of relations between the MBH mass and
properties of the host galaxy such as bulge mass and velocity dispersion. These
results suggest that central MBHs, while much less massive than the host (~
0.1%), are linked to the evolution of galactic structure. In hierarchical
cosmologies, a single big galaxy today can be traced back to the stage when it
was split up in hundreds of smaller components. Did MBH seeds form with the
same efficiency in small proto-galaxies, or did their formation had to await
the buildup of substantial galaxies with deeper potential wells? I briefly
review here some of the physical processes that are conducive to the evolution
of the massive black hole population. I will discuss black hole formation
processes for `seed' black holes that are likely to place at early cosmic
epochs, and possible observational tests of these scenarios.Comment: To appear in The Astronomy and Astrophysics Review. The final
publication is available at http://www.springerlink.co
Analyzing the Number of Common Integration Sites of Viral Vectors – New Methods and Computer Programs
Vectors based on Îł-retroviruses or lentiviruses have been shown to stably express therapeutical transgenes and effectively cure different hematological diseases. Molecular follow up of the insertional repertoire of gene corrected cells in patients and preclinical animal models revealed different integration preferences in the host genome including clusters of integrations in small genomic areas (CIS; common integrations sites). In the majority, these CIS were found in or near genes, with the potential to influence the clonal fate of the affected cell. To determine whether the observed degree of clustering is statistically compatible with an assumed standard model of spatial distribution of integrants, we have developed various methods and computer programs for Îł-retroviral and lentiviral integration site distribution. In particular, we have devised and implemented mathematical and statistical approaches for comparing two experimental samples with different numbers of integration sites with respect to the propensity to form CIS as well as for the analysis of coincidences of integration sites obtained from different blood compartments. The programs and statistical tools described here are available as workspaces in R code and allow the fast detection of excessive clustering of integration sites from any retrovirally transduced sample and thus contribute to the assessment of potential treatment-related risks in preclinical and clinical retroviral gene therapy studies
Serologic evidence of human orthopoxvirus infections in Sierra Leone
<p>Abstract</p> <p>Background</p> <p>Orthopoxviruses, including variola virus, vaccinia virus, and monkeypox virus, have previously been documented in humans in West Africa, however, no cases of human orthopoxvirus infection have been reported in the region since 1986. We conducted a serosurvey to determine whether human exposure to orthopoxviruses continues to occur in eastern Sierra Leone.</p> <p>Findings</p> <p>To examine evidence of exposure to orthopoxviruses in the Kenema District of Sierra Leone, we collected and tested sera from 1596 persons by IgG ELISA and a subset of 313 by IgM capture ELISA. Eleven persons born after the cessation of smallpox vaccination had high orthopoxvirus-specific IgG values, and an additional 6 persons had positive IgM responses. No geographic clustering was noted.</p> <p>Conclusions</p> <p>These data suggest that orthopoxviruses continue to circulate in Sierra Leone. Studies aimed at obtaining orthopoxvirus isolates and/or genetic sequences from rodents and symptomatic humans in the area are indicated.</p
Gravitational Waves from Gravitational Collapse
Gravitational wave emission from the gravitational collapse of massive stars
has been studied for more than three decades. Current state of the art
numerical investigations of collapse include those that use progenitors with
realistic angular momentum profiles, properly treat microphysics issues,
account for general relativity, and examine non--axisymmetric effects in three
dimensions. Such simulations predict that gravitational waves from various
phenomena associated with gravitational collapse could be detectable with
advanced ground--based and future space--based interferometric observatories.Comment: 68 pages including 13 figures; revised version accepted for
publication in Living Reviews in Relativity (http://www.livingreviews.org
The Formation of the First Massive Black Holes
Supermassive black holes (SMBHs) are common in local galactic nuclei, and
SMBHs as massive as several billion solar masses already exist at redshift z=6.
These earliest SMBHs may grow by the combination of radiation-pressure-limited
accretion and mergers of stellar-mass seed BHs, left behind by the first
generation of metal-free stars, or may be formed by more rapid direct collapse
of gas in rare special environments where dense gas can accumulate without
first fragmenting into stars. This chapter offers a review of these two
competing scenarios, as well as some more exotic alternative ideas. It also
briefly discusses how the different models may be distinguished in the future
by observations with JWST, (e)LISA and other instruments.Comment: 47 pages with 306 references; this review is a chapter in "The First
Galaxies - Theoretical Predictions and Observational Clues", Springer
Astrophysics and Space Science Library, Eds. T. Wiklind, V. Bromm & B.
Mobasher, in pres
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