Lower N-Acetyl-Aspartate Levels in Prefrontal Cortices in Pediatric Bipolar Disorder: A (1)H Magnetic Resonance Spectroscopy Study

Objective: The few studies applying single-voxel(1)H spectroscopy in children and adolescents with bipolar disorder (BD) have reported low N-acetyl-aspartate (NAA) levels in the dorsolateral prefrontal cortex (DLPFC), and high myo-inositol / phosphocreatine plus creatine (PCr+Cr) ratios in the anterior cingulate. The aim of this study was to evaluate NAA, glycerophosphocholine plus phosphocholine (GPC+PC) and PCr+Cr in various frontal cortical areas in children and adolescents with BD. We hypothesized that NAA levels within the prefrontal cortex are lower in BD patients than in healthy controls, indicating neurodevelopmental alterations in the former. Method: We studied 43 pediatric patients with DSM-IV BD (19 female, mean age 13.2 +/- 2.9 years) and 38 healthy controls (79 female, mean age 13.9 +/- 2.7 years). We conducted multivoxel in vivo (1)H spectroscopy measurements at 1.5 Tesla using a long echo time of 272 ms to obtain bilateral metabolite levels from the medial prefrontal cortex (MPFC), DLPFC (white and gray matter), cingulate (anterior and posterior), and occipital lobes. We used the nonparametric Mann-Whitney U test to compare neurochemical levels between groups. Results: In pediatric BD patients, NAA and GPC+PC levels in the bilateral MPFC, and PCr+Cr levels in the left MPFC were lower than those seen in the controls. In the left DLPFC white matter, levels of NAA and PCr+Cr were also lower in BD patients than in controls. Conclusions: Lower NAA and PCr+Cr levels in the PFC of children and adolescents with BD may be indicative of abnormal dendritic arborization and neuropil, suggesting neurodevelopmental abnormalities. J. Am. Acad. Child Adolesc. Psychiatry, 2011;50(1):85-94.University of Texas Health Science Center at San Antonio (UTHSCSA) General Clinical Research Center (GCRC)[M01-RR-01346]UTHSCSA Krus Endowed Chair in PsychiatryCoordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES) Foundation of BrazilFundacao de Amparo a Pesquisa de Sao Paulo, Brazil (FAPESP)Conselho Nacional de Desenvolvimento Cientifico e Tecnologico, Brazil (CNPq)National Alliance for Research on Schizophrenia and Depression (NARSAD)American Psychiatric Association/AstraZenecaOrtho-McNeil Janssen and Shire Inc.PfizerGlaxoSmithKlineRepligen[MH 01736][MH 69774][MH 068662][RR 020571

Effect of Degassing and Grain Refinement on Hot Tearing Tendency in Al8Si3Cu Alloy

The effect of melt quality on hot tearing susceptibility of Al8Si3Cu alloy was examined under six different conditions, by using a traditional T-shaped mold. Grain refinement was carried out by two different modifiers: AlTi5B1 and Al3B. For each test, samples were cast before and after degassing of melt. Therefore, a new hot tearing tendency index was developed by both bifilm calculations and porosity that occurred in the middle of T-zone of casting parts. Results indicated that hot tearing of cast aluminum alloys was a complex phenomenon, and bifilms play a major role, especially by compensating for shrinkage and consequently contributing to the inconsistencies in results

Hot tearing susceptibility of Mg-5Nd-xZn alloys

Magnesium-neodynium-zinc (Mg-Nd-Zn) alloys are promising candidates as creep resistant alloys. Further, Nd is a rare earth (RE) addition with lower solid solubility and a relatively lower cost. Hence, the use of such alloys may result in a feasible and cost effective alternative for enhancing Mg alloy use in high temperature applications. Nevertheless, studies on the castability of Mg-Nd-Zn alloys are lacking. As such, the aim of this research was to investigate the hot tearing susceptibility of Mg-5Nd-xZn (x= 0, 3, 5, 7 wt%) alloys during permanent mold casting. Specifically, a constrained-rod casting mold equipped with a load cell was used to characterize hot tearing severity and determine the onset temperature of hot tearing. The onset solid fraction of hot tearing was subsequently determined via thermodynamic software. The results suggest that hot tearing severity increased initially with addition of Zn (up to 5 wt%), but then decreased with further addition to 7 wt%. This was likely attributed to both the low onset solid fraction of hot tearing (i.e. 0.5) recorded for this alloy, which enabled enhanced feeding and opportunity to heal developing hot tears, as well as the divorced eutectic structure observed which may have facilitated late stage feeding of eutectic liquid and hence limit the alloy's susceptibility to hot tearing