35 research outputs found
On the trispectrum as a gaussian test for cosmology
In the standard model for structure formation, bound objects originate from
the gravitational collapse of small perturbations arising from quantum
fluctuations with random phases. In other scenarios, based on defects,
structures are seeded by localized energy density. In principle, it is possible
to differentiate between these models on the basis of their statistical
properties; only in the former case is the initial density field an
almost-perfect random gaussian field. In this paper, we investigate the use of
the trispectrum of the galaxy density field, which is the connected four-point
function in Fourier space, as a discriminant between gaussian and non-gaussian
models. It has the advantage of having only weak non-linear growth. We define a
related statistic which, as a test of the gaussian hypothesis, is
independent of cosmology, the power spectrum and biasing, in real space, and
which is, in principle, a measure of the departure from gaussian statistics.
For galaxy redshift surveys, the statistic depends on cosmology and bias only
through the potentially observable parameter . We compute the expected
errors on the estimate of , and demonstrate with numerical simulations
that it can be a useful discriminant of models, with the important proviso that
any bias is linear on large scales. Whether it is the most effective method is
uncertain and depends on the nature of the departure from gaussianity.Comment: to appear in ApJ, 28 pages, 5 figure
Auto-aggressive metallic mercury injection around the knee joint: a case report
<p>Abstract</p> <p>Background</p> <p>Accidental or intentional subcutaneous and/or intramuscular injection of metallic mercury is an uncommon form of poisoning. Although it does not carry the same risk as mercury vapour inhalation, it may cause destructive early and late reactions.</p> <p>Case Presentation</p> <p>Herein we present the case of a 29-year-old male patient who developed an obsessive-compulsive disorder causing auto-aggressive behaviour with injection of elemental mercury and several other foreign bodies into the soft tissues around the left knee about 15 years before initial presentation. For clinical examination X-rays and a CT-scan of the affected area were performed. Furthermore, blood was taken to determine the mercury concentration in the blood, which showed a concentration 17-fold higher than recommended. As a consequence, the mercury depots and several foreign bodies were resected marginally.</p> <p>Conclusion</p> <p>Blood levels of mercury will decrease rapidly following surgery, especially in combination with chelating therapy. In case of subcutaneous and intramuscular injection of metallic mercury we recommend marginal or wide excision of all contaminated tissue to prevent migration of mercury and chronic inflammation. Nevertheless, prolonged clinical and biochemical monitoring should be performed for several years to screen for chronic intoxication.</p
Effects of Imatinib Mesylate (Gleevec) on Human Islet NF-kappaB Activation and Chemokine Production In Vitro
Imatinib Mesylate (Gleevec) is a drug that potently counteracts diabetes both in humans and in animal models for human diabetes. We have previously reported that this compound in human pancreatic islets stimulates NF-κB signaling and islet cell survival. The aim of this study was to investigate control of NF-κB post-translational modifications exerted by Imatinib and whether any such effects are associated with altered islet gene expression and chemokine production in vitro.Human islets were either left untreated or treated with Imatinib for different timepoints. IκB-α and NF-κB p65 phosphorylation and methylation were assessed by immunoblot analysis. Islet gene expression was assessed using a commercial Pathway Finder microarray kit and RT-PCR. Islet chemokine production was determined by flow cytometric bead array analysis.Human islet IκB-α and Ser276-p65 phosphorylation were increased by a 20 minute Imatinib exposure. Methylation of p65 at position Lys221 was increased after 60 min of Imatinib exposure and persisted for 3 hours. Microarray analysis of islets exposed to Imatinib for 4 hours revealed increased expression of the inflammatory genes IL-4R, TCF5, DR5, I-TRAF, I-CAM, HSP27 and IL-8. The islet release of IL-8 was augmented in islets cultured over night in the presence of Imatinib. Following 30 hours of Imatinib exposure, the cytokine-induced IκB-α and STAT1 phosphorylation was abolished and diminished, respectively. The cytokine-induced release of the chemokines MIG and IP10 was lower in islets exposed to Imatinib for 30 hours.Imatinib by itself promotes a modest activation of NF-κB. However, a prolonged exposure of human islets to Imatinib is associated with a dampened response to cytokines. It is possible that Imatinib induces NF-κB preconditioning of islet cells leading to lowered cytokine sensitivity and a mitigated islet inflammation
Effects of Scale-Dependent Non-Gaussianity on Cosmological Structures
The detection of primordial non-Gaussianity could provide a powerful means to
test various inflationary scenarios. Although scale-invariant non-Gaussianity
(often described by the formalism) is currently best constrained by
the CMB, single-field models with changing sound speed can have strongly
scale-dependent non-Gaussianity. Such models could evade the CMB constraints
but still have important effects at scales responsible for the formation of
cosmological objects such as clusters and galaxies. We compute the effect of
scale-dependent primordial non-Gaussianity on cluster number counts as a
function of redshift, using a simple ansatz to model scale-dependent features.
We forecast constraints on these models achievable with forthcoming data sets.
We also examine consequences for the galaxy bispectrum. Our results are
relevant for the Dirac-Born-Infeld model of brane inflation, where the
scale-dependence of the non-Gaussianity is directly related to the geometry of
the extra dimensions.Comment: 43 pages, 9 figures; references added, submitted to JCAP; typo
corrected in Table 1, minor changes to the tex