995 research outputs found
Splitting of macroscopic fundamental strings in flat space and holographic hadron decays
In this review article we present the calculation of the splitting rate in
flat space of a macroscopic fundamental string either intersecting at a generic
angle a Dp-brane or lying on it. The result is then applied, in the context of
the string/gauge theory correspondence, to the study of exclusive decay rates
of large spin mesons into mesons. As examples, we discuss the cases of N=4 SYM
with a small number of flavors, and of QCD-like theories in the quenched
approximation. In the latter context, explicit analytic formulas are given for
decay rates of mesons formed either by heavy quarks or by massless quarks.Comment: 17 pages, 3 figures. Invited review for Modern Physics Letters
GFINDer: Genome Function INtegrated Discoverer through dynamic annotation, statistical analysis, and mining
Statisticalandclustering analyses ofgeneexpression results from high-density microarray experiments produce lists of hundreds of genes regulated differentially, or with particular expression profiles, in the conditions under study. Independent of the microarray platforms and analysis methods used, these lists must be biologically interpreted to gain a better knowledge of the patho-physiological phenomena involved. To this end, numerous biological annotations are available within heterogeneous and widely distributed databases. Although several tools have been developed for annotating lists of genes, most of them do not give methods for evaluating the relevance of the annotations provided, or for estimating the functional bias introduced by the gene set on the array used to identify the gene list considered. We developed Genome Functional INtegrated Discoverer (GFINDer ), a web server able to automatically provide large-scale lists of user-classified genes with functional profiles biologically characterizing the different gene classes in the list. GFINDer automatically retrieves annotations of several functional categories from different sources, identifies the categories enriched in each class of a user-classified gene list and calculates statistical significance values for each category. Moreover, GFINDer enables the functional classification of genes according to mined functional categories and the statistical analysis is of the classifications obtained, aiding better interpretationof microarray experiment results. GFINDer is available online at http://www.medinfopoli.polimi.it/GFINDer/
Flavor brane on the baryonic branch of moduli space
We study an extra flavor in the cascading SU((k+1)M)xSU(k M) gauge theory by
adding probe D7-brane to the geometry. By finding a solution to the
kappa-symmetry equation we establish that the D7-brane is mutually
supersymmetric with the background everywhere on the baryonic branch of moduli
space. We also discuss possible applications of this result.Comment: 15 pages; v2 typo corrected, references adde
Wilson Loop, Regge Trajectory and Hadron Masses in a Yang-Mills Theory from Semiclassical Strings
We compute the one-loop string corrections to the Wilson loop, glueball Regge
trajectory and stringy hadron masses in the Witten model of non supersymmetric,
large-N Yang-Mills theory. The classical string configurations corresponding to
the above field theory objects are respectively: open straight strings, folded
closed spinning strings, and strings orbiting in the internal part of the
supergravity background. For the rectangular Wilson loop we show that besides
the standard Luescher term, string corrections provide a rescaling of the field
theory string tension. The one-loop corrections to the linear glueball Regge
trajectories render them nonlinear with a positive intercept, as in the
experimental soft Pomeron trajectory. Strings orbiting in the internal space
predict a spectrum of hadronic-like states charged under global flavor
symmetries which falls in the same universality class of other confining
models.Comment: 52 pages, latex 3 times, v3: references adde
A Link between Parental Psychopathology and Preschool Depression: Take Care of Parents to Take Care of Children
There is a lot of evidence in the literature showing that early-onset depression determines an emotional and cognitive vulnerability for psychiatric disorders in subsequent years.
Aims: The first aim of this outcome research was to analyze the impact of parental support treatment in a sample of depressed preschool children divided into two groups of comparison (under-reactive and over-reactive) through evolution in the Clinical Global Impression (CGI). The second aim was to analyze the correlation between the presence of parental psychopathology and the severity of children's disorders.
Methods: Our clinical sample consisted of 32 preschool-age children with a final diagnosis of MDD. The children's assessment included a psychiatric assessment to establish a diagnosis of MDD, confirmed by means of a semi-structured interview, which was administered again one month after the end of parental treatment. All the parents began a six-month parent training treatment conducted by experienced child psychiatrists, whereas children were not treated. During this period, the Clinical Global Impression Scale (CGI) was filled out monthly in order to observe the evolution of the children's disorders.
Results: Post-hoc tests showed a significant difference from before the treatment to after the treatment only in the over-reactive group (p = 0.00). Regarding parental psychiatric disorders, in the over-reactive group, only 3 children had no parents with psychopathology. In the under-reactive group, no child lacked a parent with psychopathology.
Conclusion: Parent training treatment seems to be a valid intervention to improve preschool depression, especially in over-reactive groups, and to prevent dysfunctional parental styles connected to parental psychopathology
MRI and Clinical Biomarkers Overlap between Glaucoma and Alzheimer’s Disease
glaucoma is the leading cause of blindness worldwide. It is classically associated with structural and functional changes in the optic nerve head and retinal nerve fiber layer, but the damage is not limited to the eye. The involvement of the central visual pathways and disruption of brain network organization have been reported using advanced neuroimaging techniques. the brain structural changes at the level of the areas implied in processing visual information could justify the discrepancy between signs and symptoms and underlie the analogy of this disease with neurodegenerative dementias, such as alzheimer’s disease, and with the complex group of pathologies commonly referred to as “disconnection syndromes.” this review aims to summarize the current state of the art on the use of advanced neuroimaging techniques in glaucoma and alzheimer’s disease, highlighting the emerging biomarkers shared by both diseases
Synergic strategies to improve the PBF-LB/M processability of a cracking-sensitive alloy
The Powder Bed Fusion-Laser Beam\Metals (PBF-LB\M) is a promising additive manufacturing process
that can be used to directly produce functional components with a complex shape for a wide variety
of applications. However, the layer-by-layer scanning and high cooling rates result in a high thermal gra-
dient and thus, in thermally induced stresses. The stresses developed during the additive process could
lead to undesirable cracking and delamination phenomena that can seriously affect the performance of
the final component. The alloy composition can exacerbate crack and delamination formation, however,
the need to expand the portfolio of high-strength materials processable for PBF-LB\M makes the resolu-
tion of these undesirable phenomena a primary challenge in the additive manufacturing field. This works
aims to systematically investigate some strategies to make processable non-standard compositions. As no
standard compositions, the promising pre-alloyed AlSi10Cu8Mg composition was chosen for the present
work. Based on the results obtained from a condition of severe delamination, the synergetic use of appro-
priate process parameters and support structures can lead to crack-free and fully dense specimens also
when platform heating is not allowed. The developed approach could also be applied to adapt other
cracking-sensitive alloys for PBF-LB\M production
Deformations of calibrated D-branes in flux generalized complex manifolds
We study massless deformations of generalized calibrated cycles, which
describe, in the language of generalized complex geometry, supersymmetric
D-branes in N=1 supersymmetric compactifications with fluxes. We find that the
deformations are classified by the first cohomology group of a Lie algebroid
canonically associated to the generalized calibrated cycle, seen as a
generalized complex submanifold with respect to the integrable generalized
complex structure of the bulk. We provide examples in the SU(3) structure case
and in a `genuine' generalized complex structure case. We discuss cases of
lifting of massless modes due to world-volume fluxes, background fluxes and a
generalized complex structure that changes type.Comment: 52 pages, added references, added comment on ellipticity in appendix
B, made minor changes according to instructions referee JHE
Supersymmetric D-branes and calibrations on general N=1 backgrounds
We study the conditions to have supersymmetric D-branes on general {\cal N}=1
backgrounds with Ramond-Ramond fluxes. These conditions can be written in terms
of the two pure spinors associated to the SU(3)\times SU(3) structure on
T_M\oplus T^\star_M, and can be split into two parts each involving a different
pure spinor. The first involves the integrable pure spinor and requires the
D-brane to wrap a generalised complex submanifold with respect to the
generalised complex structure associated to it. The second contains the
non-integrable pure spinor and is related to the stability of the brane. The
two conditions can be rephrased as a generalised calibration condition for the
brane. The results preserve the generalised mirror symmetry relating the type
IIA and IIB backgrounds considered, giving further evidence for this duality.Comment: 23 pages. Some improvements and clarifications, typos corrected and
references added. v3: Version published in JHE
Open String Wavefunctions in Warped Compactifications
We analyze the wavefunctions for open strings in warped compactifications,
and compute the warped Kahler potential for the light modes of a probe D-brane.
This analysis not only applies to the dynamics of D-branes in warped
backgrounds, but also allows to deduce warping corrections to the closed string
Kahler metrics via their couplings to open strings. We consider in particular
the spectrum of D7-branes in warped Calabi-Yau orientifolds, which provide a
string theory realizations of the Randall-Sundrum scenario. We find that
certain background fluxes, necessary in the presence of warping, couple to the
fermionic wavefunctions and qualitatively change their behavior. This modified
dependence of the wavefunctions are needed for consistency with supersymmetry,
though it is present in non-supersymmetric vacua as well. We discuss the
deviations of our setup from the RS scenario and, as an application of our
results, compute the warping corrections to Yukawa couplings in a simple model.
Our analysis is performed both with and without the presence of D-brane
world-volume flux, as well as for the case of backgrounds with varying dilaton.Comment: 52 pages, refs. added, minor correction
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