193 research outputs found
Strong Sphalerons and Electroweak Baryogenesis
We analyze the spontaneous baryogenesis and charge transport mechanisms
suggested by Cohen, Kaplan and Nelson for baryon asymmetry generation in
extended versions of electroweak theory. We find that accounting for
non-perturbative chirality-breaking transitions due to strong sphalerons
reduces the baryonic asymmetry by the factor or ,
provided those processes are in thermal equilibrium.Comment: CERN-TH.7080/9
Self-gravity as an explanation of the fractal structure of the interstellar medium
The gas clouds of the interstellar medium have a fractal structure, the
origin of which has generally been thought to lie in turbulence. The energy of
turbulence could come from galactic rotation at large-scale, then cascade down
to be dissipated on small-scales by viscosity; it has been suggested that such
turbulence helps to prevent massive molecular clouds from collapsing in
response to their own gravity. Here we show that, on the contrary, self-gravity
itself may be the dominant factor in making clouds fractal. We develop a
field-theory approach to the structure of clouds, assuming them to be
isothermal, and with only gravitational interactions; we find that the observed
fractal dimension of the clouds arise naturally from this approach. Although
this result does not imply that turbulence is not important, it does
demonstrate that the fractal structure can be understood without it.Comment: Latex file, four pages and two colour figures in .cps files. To
appear in Nature, 5 September 199
Genetic contributions to visuospatial cognition in Williams syndrome: insights from two contrasting partial deletion patients
Background
Williams syndrome (WS) is a rare neurodevelopmental disorder arising from a hemizygotic deletion of approximately 27 genes on chromosome 7, at locus 7q11.23. WS is characterised by an uneven cognitive profile, with serious deficits in visuospatial tasks in comparison to relatively proficient performance in some other cognitive domains such as language and face processing. Individuals with partial genetic deletions within the WS critical region (WSCR) have provided insights into the contribution of specific genes to this complex phenotype. However, the combinatorial effects of different genes remain elusive.
Methods
We report on visuospatial cognition in two individuals with contrasting partial deletions in the WSCR: one female (HR), aged 11 years 9 months, with haploinsufficiency for 24 of the WS genes (up to GTF2IRD1), and one male (JB), aged 14 years 2 months, with the three most telomeric genes within the WSCR deleted, or partially deleted.
Results
Our in-depth phenotyping of the visuospatial domain from table-top psychometric, and small- and large-scale experimental tasks reveal a profile in HR in line with typically developing controls, albeit with some atypical features. These data are contrasted with patient JB’s atypical profile of strengths and weaknesses across the visuospatial domain, as well as with more substantial visuospatial deficits in individuals with the full WS deletion.
Conclusions
Our findings point to the contribution of specific genes to spatial processing difficulties associated with WS, highlighting the multifaceted nature of spatial cognition and the divergent effects of genetic deletions within the WSCR on different components of visuospatial ability. The importance of general transcription factors at the telomeric end of the WSCR, and their combinatorial effects on the WS visuospatial phenotype are also discussed
Acupuncture and pharmacopuncture are as effective as morphine or carprofen for postoperative analgesia in bitches undergoing ovariohysterectomy
Large scale analytic calculations in quantum field theories
We present a survey on the mathematical structure of zero- and single scale
quantities and the associated calculation methods and function spaces in higher
order perturbative calculations in relativistic renormalizable quantum field
theories.Comment: 25 pages Latex, 1 style fil
On the Integrand-Reduction Method for Two-Loop Scattering Amplitudes
We propose a first implementation of the integrand-reduction method for
two-loop scattering amplitudes. We show that the residues of the amplitudes on
multi-particle cuts are polynomials in the irreducible scalar products
involving the loop momenta, and that the reduction of the amplitudes in terms
of master integrals can be realized through polynomial fitting of the
integrand, without any apriori knowledge of the integral basis. We discuss how
the polynomial shapes of the residues determine the basis of master integrals
appearing in the final result. We present a four-dimensional constructive
algorithm that we apply to planar and non-planar contributions to the 4- and
5-point MHV amplitudes in N=4 SYM. The technique hereby discussed extends the
well-established analogous method holding for one-loop amplitudes, and can be
considered a preliminary study towards the systematic reduction at the
integrand-level of two-loop amplitudes in any gauge theory, suitable for their
automated semianalytic evaluation.Comment: 26 pages, 11 figure
Reaction rates and transport in neutron stars
Understanding signals from neutron stars requires knowledge about the
transport inside the star. We review the transport properties and the
underlying reaction rates of dense hadronic and quark matter in the crust and
the core of neutron stars and point out open problems and future directions.Comment: 74 pages; commissioned for the book "Physics and Astrophysics of
Neutron Stars", NewCompStar COST Action MP1304; version 3: minor changes,
references updated, overview graphic added in the introduction, improvements
in Sec IV.A.
The Novel Object and Unusual Name (NOUN) database: a collection of novel images for use in experimental research
Many experimental research designs require images of novel objects. Here we introduce the Novel Object and Unusual Name (NOUN) Database. This database contains 64 primary novel object images and additional novel exemplars for ten basic- and nine global-level object categories. The objects’ novelty was confirmed by both self-report and a lack of consensus on questions that required participants to name and identify the objects. We also found that object novelty correlated with qualifying naming responses pertaining to the objects’ colors. Results from a similarity sorting task (and subsequent multidimensional scaling analysis on the similarity ratings) demonstrated that the objects are complex and distinct entities that vary along several featural dimensions beyond simply shape and color. A final experiment confirmed that additional item exemplars comprise both sub- and superordinate categories. These images may be useful in a variety of settings, particularly for developmental psychology and other research in language, categorization, perception, visual memory and related domains
Longitudinal Evaluation of the Hypothalamic-Pituitary-Testicular Function in 8 Boys with Adrenal Hypoplasia Congenita (AHC) Due to NR0B1 Mutations
BACKGROUND:Boys carrying mutations in the NR0B1 gene develop adrenal hypoplasia congenita (AHC) and impaired sexual development due to the combination of hypogonadotropic hypogonadism (HH) and primary defects in spermatogenesis. METHODS:We analysed the evolution of hypothalamic-pituitary-testicular function of 8 boys with AHC due to NR0B1 mutations. Our objective was to characterize and monitor the progressive deterioration of this function. RESULTS:The first symptoms appeared in the neonatal period (n = 5) or between 6 months and 8.7 years (n = 3). Basal plasma adrenocorticotrophic hormone (ACTH) concentrations increased in all boys, whilst cortisol levels decreased in one case. The natremia was equal or below 134 mmol/L and kaliemia was over 5 mmol/L. All had increased plasma renin. In 3 of 4 patients diagnosed in the neonatal period and evaluated during the first year, the basal plasma gonadotropins concentrations, and their response to gonadotropin releasing hormone (GnRH) test (n = 2), and those of testosterone were normal. The plasma inhibin B levels were normal in the first year of life. With the exception of two cases these concentrations decreased to below the normal for age. Anti-Müllerian hormone concentrations were normal for age in all except one case, which had low concentrations before the initiation of testosterone treatment. In 3 of the 8 cases the gene was deleted and the remaining 5 cases carried frameshift mutations that are predicted to introduce a downstream nonsense mutation resulting in a truncated protein. CONCLUSIONS:The decreases in testosterone and inhibin B levels indicated a progressive loss of testicular function in boys carrying NR0B1 mutations. These non-invasive examinations can help to estimate the age of the testicular degradation and cryopreservation of semen may be considered in these cases as investigational procedure with the aim of restoring fertility
The Evolution of Compact Binary Star Systems
We review the formation and evolution of compact binary stars consisting of
white dwarfs (WDs), neutron stars (NSs), and black holes (BHs). Binary NSs and
BHs are thought to be the primary astrophysical sources of gravitational waves
(GWs) within the frequency band of ground-based detectors, while compact
binaries of WDs are important sources of GWs at lower frequencies to be covered
by space interferometers (LISA). Major uncertainties in the current
understanding of properties of NSs and BHs most relevant to the GW studies are
discussed, including the treatment of the natal kicks which compact stellar
remnants acquire during the core collapse of massive stars and the common
envelope phase of binary evolution. We discuss the coalescence rates of binary
NSs and BHs and prospects for their detections, the formation and evolution of
binary WDs and their observational manifestations. Special attention is given
to AM CVn-stars -- compact binaries in which the Roche lobe is filled by
another WD or a low-mass partially degenerate helium-star, as these stars are
thought to be the best LISA verification binary GW sources.Comment: 105 pages, 18 figure
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