Development of an X-band Photoinjector at SLAC

As part of a National Cancer Institute contract to develop a compact source of monoenergetic X-rays via Compton backscattering, we have completed the design and construction of a 5.5 cell Photoinjector operating at 11.424 GHz. Successful completion of this project will result in the capability of generating a monoenergetic X-ray beam, continuously tunable from 20 - 85 KeV. The immediate goal is the development of a Photoinjector producing 7 MeV, 0.5 nC, sub-picosecond electron bunches with normalized RMS emittances of approximately 1 pi-mm-mR at repetition rates up to 60 Hz. This beam will then be further accelerated to 60 MeV using a 1.05 m accelerating structure. This Photoinjector is somewhat different than the traditional 1.5 cell design both because of the number of cells and the symmetrically fed input coupler cell. Its operating frequency is also unique. Since the cathode is non-removable, cold-test tuning was somewhat more difficult than in other designs. We will present results of "bead-drop" measurements used in tuning this structure. Initial beam measurements are currently in progress and results will be presented as well as results of RF conditioning to high gradients at X-band. Details of the RF system, emittance-compensating solenoid, and cathode laser system as well as PARMELA simulations will also be presented.Comment: 3 pages, 6 figures, 1 Table, LINAC 200

Extraction efficiency of drifting electrons in a two-phase xenon time projection chamber

We present a measurement of the extraction efficiency of quasi-free electrons from the liquid into the gas phase in a two-phase xenon time-projection chamber. The measurements span a range of electric fields from 2.4 to 7.1 kV/cm in the liquid xenon, corresponding to 4.5 to 13.1 kV/cm in the gaseous xenon. Extraction efficiency continues to increase at the highest extraction fields, implying that additional charge signal may be attained in two-phase xenon detectors through careful high-voltage engineering of the gate-anode region

Genetic Correlates of Brain Aging on MRI and Cognitive Test Measures: A Genome-Wide Association and Linkage Analysis in the Framingham Study

BACKGROUND: Brain magnetic resonance imaging (MRI) and cognitive tests can identify heritable endophenotypes associated with an increased risk of developing stroke, dementia and Alzheimer's disease (AD). We conducted a genome-wide association (GWA) and linkage analysis exploring the genetic basis of these endophenotypes in a community-based sample. METHODS: A total of 705 stroke- and dementia-free Framingham participants (age 62 +9 yrs, 50% male) who underwent volumetric brain MRI and cognitive testing (1999–2002) were genotyped. We used linear models adjusting for first degree relationships via generalized estimating equations (GEE) and family based association tests (FBAT) in additive models to relate qualifying single nucleotide polymorphisms (SNPs, 70,987 autosomal on Affymetrix 100K Human Gene Chip with minor allele frequency ≥ 0.10, genotypic call rate ≥ 0.80, and Hardy-Weinberg equilibrium p-value ≥ 0.001) to multivariable-adjusted residuals of 9 MRI measures including total cerebral brain (TCBV), lobar, ventricular and white matter hyperintensity (WMH) volumes, and 6 cognitive factors/tests assessing verbal and visuospatial memory, visual scanning and motor speed, reading, abstract reasoning and naming. We determined multipoint identity-by-descent utilizing 10,592 informative SNPs and 613 short tandem repeats and used variance component analyses to compute LOD scores. RESULTS: The strongest gene-phenotype association in FBAT analyses was between SORL1 (rs1131497; p = 3.2 × 10-6) and abstract reasoning, and in GEE analyses between CDH4 (rs1970546; p = 3.7 × 10-8) and TCBV. SORL1 plays a role in amyloid precursor protein processing and has been associated with the risk of AD. Among the 50 strongest associations (25 each by GEE and FBAT) were other biologically interesting genes. Polymorphisms within 28 of 163 candidate genes for stroke, AD and memory impairment were associated with the endophenotypes studied at p < 0.001. We confirmed our previously reported linkage of WMH on chromosome 4 and describe linkage of reading performance to a marker on chromosome 18 (GATA11A06), previously linked to dyslexia (LOD scores = 2.2 and 5.1). CONCLUSION: Our results suggest that genes associated with clinical neurological disease also have detectable effects on subclinical phenotypes. These hypothesis generating data illustrate the use of an unbiased approach to discover novel pathways that may be involved in brain aging, and could be used to replicate observations made in other studies.National Institutes of Health National Center for Research Resources Shared Instrumentation grant (ISI0RR163736-01A1); National Heart, Lung, and Blood Institute's Framingham Heart Study (N01-HC-25195); National Institute of Aging (5R01-AG08122, 5R01-AG16495); National Institute of Neurological Disorders and Stroke (5R01-NS17950

Calibration of a two-phase xenon time projection chamber with a 37^{37}Ar source

We calibrate a two-phase xenon detector at 0.27 keV in the charge channel and at 2.8 keV in both the light and charge channels using a $^{37}$Ar source that is directly released into the detector. We map the light and charge yields as a function of electric drift field. For the 2.8 keV peak, we calculate the Thomas-Imel box parameter for recombination and determine its dependence on drift field. For the same peak, we achieve an energy resolution, $E_{\sigma}/E_{mean}$, between 9.8% and 10.8% for 0.1 kV/cm to 2 kV/cm electric drift fields.Comment: 12 pages, 7 figure

Autophagy gene haploinsufficiency drives chromosome instability, increases migration, and promotes early ovarian tumors.

Autophagy, particularly with BECN1, has paradoxically been highlighted as tumor promoting in Ras-driven cancers, but potentially tumor suppressing in breast and ovarian cancers. However, studying the specific role of BECN1 at the genetic level is complicated due to its genomic proximity to BRCA1 on both human (chromosome 17) and murine (chromosome 11) genomes. In human breast and ovarian cancers, the monoallelic deletion of these genes is often co-occurring. To investigate the potential tumor suppressor roles of two of the most commonly deleted autophagy genes in ovarian cancer, BECN1 and MAP1LC3B were knocked-down in atypical (BECN1+/+ and MAP1LC3B+/+) ovarian cancer cells. Ultra-performance liquid chromatography mass-spectrometry metabolomics revealed reduced levels of acetyl-CoA which corresponded with elevated levels of glycerophospholipids and sphingolipids. Migration rates of ovarian cancer cells were increased upon autophagy gene knockdown. Genomic instability was increased, resulting in copy-number alteration patterns which mimicked high grade serous ovarian cancer. We further investigated the causal role of Becn1 haploinsufficiency for oncogenesis in a MISIIR SV40 large T antigen driven spontaneous ovarian cancer mouse model. Tumors were evident earlier among the Becn1+/- mice, and this correlated with an increase in copy-number alterations per chromosome in the Becn1+/- tumors. The results support monoallelic loss of BECN1 as permissive for tumor initiation and potentiating for genomic instability in ovarian cancer

Systems of education governance and cultures of justice in Ireland, Scotland and Pakistan

This chapter compares the issue of cultures of justice in the systems of education governance in three education systems: Ireland, Scotland and Pakistan. The focus for the comparison are the current policies which shape the regulation of education. These policies were reviewed to identify key issues relating to social justice and equality, decision-making and accountability. From the analysis of each system, three central issues were identified: firstly, the improvement of a state education system; secondly, the degree of decentralisation and centralisation in governance structures and thirdly, the expectations placed on school leaders. The chapter concludes by discussing the tensions between the drive for system improvement and opportunities for school leaders to build strategies to address issues of inequality in schools

Interactivity Mitigates the Impact of Working Memory Depletion on Mental Arithmetic Performance

Doing long sums in the absence of complementary actions or artefacts is a multi-step procedure that quickly taxes working memory; congesting the phonological loop further handicaps performance. In the experiment reported here, participants completed long sums either with hands down?the low interactivity condition?or by moving numbered tokens?the high interactivity condition?while they repeated ?the? continuously, loading the phonological loop, or not. As expected, interactivity and articulatory suppression substantially affected performance; critically, the effect of articulatory suppression was stronger in the low than in the high interactivity condition. In addition, independent measure of mathematics anxiety predicted the impact of articulatory suppression on performance only in the low (not high) interactivity condition. These findings suggest that interactivity augmented overall or systemic working memory resources and diminished the effect of mathematics anxiety, underscoring the importance of characterizing the properties of the system as it is configured by the dynamic agent-environment coupling

Flow induced vibration within centrifugal gas compressors

The purpose of this study is to determine the effects of aerodynamically forced disturbances occurring in the impeller channels of centrifugal gas compressors. These disturbances are induced at the diffuser inlet when the tips of the impeller blades pass in front of the tips of the diffuser vanes, thereafter propagating into the impeller channels. In these channels, the disturbance waves can be amplified enough to cause severe structural damage to the walls. Theory was developed and coded into a Fortran program that gave the steady and unsteady (disturbance) properties at all points within the impeller channel above the inducer region and in the region between the impeller and the diffuser. The results revealed that keeping all design variables constant and changing only the ratio of diffuser vanes to impeller blades, greatly influenced the amplitude of the disturbances within the impeller channels. Consequently, with the program developed here, the optimum ratio of diffuser vanes to impeller blades can be determined without testing. This is one major finding, but it is obvious that the program will give valuable insight into many compressor design changes