Large-scale structure formation for power spectra with broken scale invariance

We have simulated the formation of large-scale structure arising from COBE-normalized spectra computed by convolving a primordial double-inflation perturbation spectrum with the CDM transfer function. Due to the broken scale invariance ('BSI') characterizing the primordial perturbation spectrum, this model has less small-scale power than the (COBE-normalized) standard CDM model. The particle-mesh code (with $512^3$ cells and $256^3$ particles) includes a model for thermodynamic evolution of baryons in addition to the usual gravitational dynamics of dark matter. It provides an estimate of the local gas temperature. In particular, our galaxy-finding procedure seeks peaks in the distribution of gas that has cooled. It exploits the fact that ``cold" particles trace visible matter better than average and thus provides a natural biasing mechanism. The basic picture of large-scale structure formation in the BSI model is the familiar hierarchical clustering scenario. We obtain particle in cell statistics, the galaxy correlation function, the cluster abundance and the cluster-cluster correlation function and statistics for large and small scale velocity fields. We also report here on a semi-quantitative study of the distribution of gas in different temperature ranges. Based on confrontation with observations and comparison with standard CDM, we conclude that the BSI scenario could represent a promising modification of the CDM picture capable of describing many details of large-scale structure formation.Comment: 15 pages, Latex using mn.sty, uuencoded compressed ps-file with 15 figures by anonymous ftp to ftp://ftp.aip.de/incoming/mueller/bsi.u

Dynamical effects of the neutrino gravitational clustering at Planck angular scales

We study the CMB anisotropy induced by the non-linear perturbations in the massive neutrino density associated to the non-linear gravitational clustering proceses. Our results show that for the neutrino fraction in agreement with that indicated by the astroparticle and nuclear physics experiments and a cosmological accreting mass comparable with the mass of known clusters, the angular resolution and the sensitivity of the CMB anisotropy measurements from the Planck surveyor will allow the detection of the dynamical effects of the neutrino gravitational clustering.Comment: 40 pages and 12 figures, submitted to ApJ (14 March 2002

The Neural Correlates of Non-Spatial Working Memory in Velocardiofacial Syndrome (22q11.2 Deletion Syndrome)

Velocardiofacial syndrome (VCFS), also known as 22q11.2 deletion syndrome, is a neurogenetic disorder that is associated with both learning disabilities and a consistent neuropsychological phenotype, including deficits in executive function, visuospatial perception, and working memory. Anatomic imaging studies have identified significant volumetric reductions in the parietal lobe of individuals with VCFS, but several studies have reported that the frontal lobe is relatively preserved. We used functional magnetic resonance imaging to investigate the neural correlates of non-spatial working memory in 17 youths with VCFS, 10 of their unaffected siblings, and 10 community controls (with the same proportion of learning disabilities as the VCFS youths). Task performance of siblings tended to be more accurate than children with VCFS, who did not differ from community controls. All three-study groups recruited parietal regions that were equivalent in location and magnitude. Whereas the sibling group also recruited the dorsolateral prefrontal cortex (DLPFC), Broca\u27s area, and anterior cingulate, DLPFC activation was absent in the whole brain analyses of children with VCFS and controls. Moreover, the magnitude of frontal activation in VCFS participants was restricted relative to both siblings and controls. These findings suggest that VCFS participants exhibit frontal hypoactivation that is not attributable to performance. In addition, VCFS children and controls (many with idiopathic learning disabilities) appear to rely on phonological rehearsal to hold information on line instead of the DLPFC. Despite previous anatomic MRI reports of preserved frontal lobe volumes in VCFS therefore, these fMRI findings suggest that the frontal component of the distributed network subserving executive function and working memory may be disrupted in youth with this disorder

Velo-Cardio-Facial Syndrome

Purpose of review: Velo-cardio-facial syndrome has emerged from obscurity to become one of the most researched disorders this past decade. It is one of the most common genetic syndromes in humans, the most common contiguous gene syndrome in humans, the most common syndrome of cleft palate, and the most common syndrome of conotruncal heart malformations. Velo-cardio-facial syndrome has an expansive phenotype, a factor reflected in the wide range of studies that cover both clinical features and molecular genetics. In this review, we cover multiple areas of research during the past year, including psychiatric disorders, neuroimaging, and the delineation of clinical features. Recent findings: The identification of candidate genes for heart anomalies, mental illness, and other clinical phenotypes has been reported in the past year with a focus on TBX1 for cardiac and craniofacial phenotypes and COMT and PRODH for psychiatric disorders. The expansive phenotype of velo-cardio-facial syndrome continues to grow with new behavioral and structural anomalies reported. Treatment issues are beginning to draw attention, although most authors continue to focus on diagnostic issues. Summary: Its high population prevalence, estimated to be as common as 1:2000 has sparked a large amount of research, as has the model the syndrome serves for identifying the causes of mental illness and learning disabilities, but it is obvious that more information is needed. Intensive scrutiny of velo-cardio-facial syndrome will undoubtedly continue for many years to come with the hope that researchers will turn more of their attention to treatment and treatment outcomes

Cognitive and Psychiatric Predictors to Psychosis in Velocardiofacial Syndrome: A 3-Year Follow-Up Study

Objective: To predict prodromal psychosis in adolescents with velocardiofacial syndrome (VCFS). Method: 70 youth with VCFS, 27 siblings of youth with VCFS and 25 community controls were followed from childhood (Mean age = 11.8 years) into mid-adolescence (mean age 15.0 years). Psychological tests measuring intelligence, academic achievement, learning/memory, attention and executive functioning as well as measures of parent and clinician ratings of child psychiatric functioning were completed at both time point. Results: Major depressive disorder, oppositional defiant disorder, and generalized anxiety disorder diagnoses increased in the VCFS sample. With very low false positive rates, the best predictor of adolescent prodromal psychotic symptoms was parent ratings of childhood odd/eccentric symptoms and child performance on a measure of executive functioning, the Wisconsin Card Sorting Test. Conclusions: Similar to the non-VCFS prodromal psychosis literature, a combination of cognitive and psychiatric variables appears to predict psychosis in adolescence. A child with VCFS who screens positive is noteworthy and demands clinical attention

Luminosity- and morphology-dependent clustering of galaxies

How does the clustering of galaxies depend on their inner properties like morphological type and luminosity? We address this question in the mathematical framework of marked point processes and clarify the notion of luminosity and morphological segregation. A number of test quantities such as conditional mark-weighted two-point correlation functions are introduced. These descriptors allow for a scale-dependent analysis of luminosity and morphology segregation. Moreover, they break the degeneracy between an inhomogeneous fractal point set and actual present luminosity segregation. Using the Southern Sky Redshift Survey~2 (da Costa et al. 1998, SSRS2) we find both luminosity and morphological segregation at a high level of significance, confirming claims by previous works using these data (Benoist et al. 1996, Willmer et al. 1998). Specifically, the average luminosity and the fluctuations in the luminosity of pairs of galaxies are enhanced out to separations of 15Mpc/h. On scales smaller than 3Mpc/h the luminosities on galaxy pairs show a tight correlation. A comparison with the random-field model indicates that galaxy luminosities depend on the spatial distribution and galaxy-galaxy interactions. Early-type galaxies are also more strongly correlated, indicating morphological segregation. The galaxies in the PSCz catalog (Saunders et al. 2000) do not show significant luminosity segregation. This again illustrates that mainly early-type galaxies contribute to luminosity segregation. However, based on several independent investigations we show that the observed luminosity segregation can not be explained by the morphology-density relation alone.Comment: aastex, emulateapj5, 20 pages, 13 figures, several clarifying comments added, ApJ accepte

The Longitudinal Course of Attention Deficit/Hyperactivity Disorder in Velo-Cardio-Facial Syndrome

OBJECTIVE: To evaluate predictors of persistence of attention deficit/hyperactivity disorder (ADHD) in a large sample of children with velo-cardio-facial syndrome (VCFS) with and without ADHD followed prospectively into adolescence. STUDY DESIGN: Children with VCFS with (n = 37) and without (n = 35) ADHD who were on average 11 years old at the baseline assessment and 15 years old at the follow-up assessment were comprehensively assessed with structured diagnostic interviews and assessments of behavioral, cognitive, social, school, and family functioning. Control participants both with and without ADHD were also followed prospectively. RESULTS: In adolescence, 65% of children with VCFS continued to have findings consistent with ADHD. Childhood predictors of persistence were higher rates of familial ADHD, having childhood depression, having higher levels of hyperactivity, and a larger number of intrusion errors on a verbal list learning test at baseline. Approximately 15% of children with VCFS who did not have ADHD at Time 1 met diagnostic criteria for ADHD at Time 2. All of these children had subthreshold ADHD symptoms at Time 1. CONCLUSIONS: These findings prospectively confirm that persistence of ADHD into adolescence in VCFS is predicted by childhood variables that have been previously documented in the non-VCFS ADHD literature

Cortical Gyrification in Velo-Cardio-Facial (22q11.2 Deletion) Syndrome: A Longitudinal Study

Introduction: Velo-cardio-facial syndrome (VCFS) has been identified as an important risk factor for psychoses, with up to 32% of individuals with VCFS developing a psychotic illness. Individuals with VCFS thus form a unique group to identify and explore early symptoms and biological correlates of psychosis. In this study, we examined if cortical gyrification pattern, i.e. gyrification index (GI) can be a potential neurobiological marker for psychosis. Method: GIs of 91 individuals with VCFS were compared with 29 siblings and 54 controls. Further, 58 participants with VCFS, 21 siblings and 18 normal controls were followed up after 3 years and longitudinal changes in GI were compared. Additionally, we also correlated longitudinal changes in GI in individuals with VCFS with prodromal symptoms of psychosis on the Scale of Prodromal Symptoms (SOPS). Result: Individuals with VCFS had significantly lower GIs as compared to their siblings and normal controls. Longitudinal examination of GI did not reveal any significant group–time interactions between the three groups. Further, longitudinal change in GI scores in the VCFS group was negatively correlated with positive prodromal symptoms, with the left occipital region reaching statistical significance. Conclusion: The study confirms previous reports that individuals with VCFS have reduced cortical folding as compared to normal controls. However over a period of three years, there is no difference in the rate of change of GI among both individuals with VCFS and normal controls. Finally, our results suggest that neuroanatomical alterations in areas underlying visual processing may be an early marker for psychosis