26 research outputs found
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Weldability of polycrystalline aluminides. Final report
When gas-tungsten arc welded, iron aluminides form a coarse fusion zone microstructure which is susceptible to hydrogen cracking. Magnetic arc oscillation and weld pool inoculation were implemented to refine the fusion zone microstructure in iron aluminide alloy FA-129 weldments. Magnetic arc oscillation effectively refined the fusion zone microstructure, and slow strain rate tensile tests showed fine-grained microstructures to be less susceptible to hydrogen cracking. However, magnetic arc oscillation was found to be suitable only for well-controlled fabrication environments. Weld pool inoculation offers a potentially more robust refinement method. Titanium inoculation was also shown to effectively refined the fusion zone microstructure, but weldment properties were not improved using this refinement method. The effect of titanium on the size, shape and distribution of the second phase particles in the fusion zone appears to be the cause of the observed decrease in weldment properties
Fine-Scale Mapping of the 4q24 Locus Identifies Two Independent Loci Associated with Breast Cancer Risk
Background: A recent association study identified a common variant (rs9790517) at 4q24 to be associated with breast cancer risk. Independent association signals and potential functional variants in this locus have not been explored.
Methods: We conducted a fine-mapping analysis in 55,540 breast cancer cases and 51,168 controls from the Breast Cancer Association Consortium.
Results: Conditional analyses identified two independent association signals among women of European ancestry, represented by rs9790517 [conditional P = 2.51 × 10−4; OR, 1.04; 95% confidence interval (CI), 1.02–1.07] and rs77928427 (P = 1.86 × 10−4; OR, 1.04; 95% CI, 1.02–1.07). Functional annotation using data from the Encyclopedia of DNA Elements (ENCODE) project revealed two putative functional variants, rs62331150 and rs73838678 in linkage disequilibrium (LD) with rs9790517 (r2 ≥ 0.90) residing in the active promoter or enhancer, respectively, of the nearest gene, TET2. Both variants are located in DNase I hypersensitivity and transcription factor–binding sites. Using data from both The Cancer Genome Atlas (TCGA) and Molecular Taxonomy of Breast Cancer International Consortium (METABRIC), we showed that rs62331150 was associated with level of expression of TET2 in breast normal and tumor tissue.
Conclusion: Our study identified two independent association signals at 4q24 in relation to breast cancer risk and suggested that observed association in this locus may be mediated through the regulation of TET2.
Impact: Fine-mapping study with large sample size warranted for identification of independent loci for breast cancer risk
Spin asymmetries for events with high p(T) hadrons in DIS and an evaluation of the gluon polarization
Adeva B, Arik E, Arvidson A, et al. Spin asymmetries for events with high p(T) hadrons in DIS and an evaluation of the gluon polarization. Phys.Rev. D. 2004;70(1): 012002.We present a measurement of the longitudinal spin cross section asymmetry for deep-inelastic muon-nucleon interactions with two high transverse momentum hadrons in the final state. Two methods of event classification are used to increase the contribution of the photon-gluon fusion process to above 30%. The most effective one, based on a neural network approach, provides the asymmetries A(p)lN(-->)lhhX=0.030+/-0.057(stat)+/-0.010(syst) and A(d)lN(-->)lhhX=0.070+/-0.076(stat)+/-0.010(syst). From these values we derive an averaged gluon polarization DeltaG/G=-0.20+/-0.28(stat)+/-0.10(syst) at an average fraction of nucleon momentum carried by gluons =0.07
Dynamics of Telomeres and Promyelocytic Leukemia Nuclear Bodies in a Telomerase-negative Human Cell Line
Telomerase-negative tumor cells maintain their telomeres via an alternative lengthening of telomeres (ALT) mechanism. This process involves the association of telomeres with promyelocytic leukemia nuclear bodies (PML-NBs). Here, the mobility of both telomeres and PML-NBs as well as their interactions were studied in human U2OS osteosarcoma cells, in which the ALT pathway is active. A U2OS cell line was constructed that had lac operator repeats stably integrated adjacent to the telomeres of chromosomes 6q, 11p, and 12q. By fluorescence microscopy of autofluorescent LacI repressor bound to the lacO arrays the telomere mobility during interphase was traced and correlated with the telomere repeat length. A confined diffusion model was derived that describes telomere dynamics in the nucleus on the time scale from seconds to hours. Two telomere groups were identified that differed with respect to the nuclear space accessible to them. Furthermore, translocations of PML-NBs relative to telomeres and their complexes with telomeres were evaluated. Based on these studies, a model is proposed in which the shortening of telomeres results in an increased mobility that could facilitate the formation of complexes between telomeres and PML-NBs
New insights on low vitamin D plasma concentration as a potential cardiovascular risk factor
The role of Vitamin D hormone in human health and disease is still debated. Recently, growing attention has been paid to its putative role in cardiovascular system homeostasis with several studies that suggested a correlation between low vitamin D levels and increased cardiovascular risk. Several mechanisms are involved in the development of cardiovascular diseases: systemic inflammation, endothelial dysfunction, arterial hypertension and insulin resistance. In the present paper, we have revised the current literature supporting a role for vitamin D in the development of these pathogenetic processes. Finally, we have evaluated the current evidence linking vitamin D to atherosclerosis and its natural consequence, cardiovascular diseases
The silicon microstrip sensors of the ATLAS semiconductor tracker.
This paper describes the AC-coupled, single-sided, p-in-n silicon microstrip sensors used in the Semiconductor Tracker (SCT) of the ATLAS experiment at the CERN Large Hadron Collider (LHC). The sensor requirements, specifications and designs are discussed, together with the qualification and quality assurance procedures adopted for their production. The measured sensor performance is presented, both initially and after irradiation to the fluence anticipated after 10 years of LHC operation. The sensors are now successfully assembled within the detecting modules of the SCT, and the SCT tracker is completed and integrated within the ATLAS Inner Detector. Hamamatsu Photonics Ltd. supplied 92.2% of the 15,392 installed sensors, with the remainder supplied by CiS
The ATLAS semiconductor tracker end-cap module
The challenges for the tracking detector systems at the LHC are unprecedented in terms of the number of channels, the required readout
speed and the expected radiation levels. The ATLAS Semiconductor Tracker (SCT) end-caps have a total of about 3 million
electronics channels each reading out every 25 ns into its own on-chip 3:3 ms buffer. The highest anticipated dose after 10 years operation
is 1:4 1014 cm2 in units of 1 MeV neutron equivalent (assuming the damage factors scale with the non-ionising energy loss). The
forward tracker has 1976 double-sided modules, mostly of area �70 cm2, each having 2 768 strips read out by six ASICs per side. The
requirement to achieve an average perpendicular radiation length of 1.5% X0, while coping with up to 7W dissipation per module (after
irradiation), leads to stringent constraints on the thermal design. The additional requirement of 1500e equivalent noise charge (ENC)
rising to only 1800e ENC after irradiation, provides stringent design constraints on both the high-density Cu/Polyimide flex read-out
circuit and the ABCD3TA read-out ASICs. Finally, the accuracy of module assembly must not compromise the 16 mm ðrfÞ resolution
perpendicular to the strip directions or 580 mm radial resolution coming from the 40 mrad front-back stereo angle.
A total of 2210 modules were built to the tight tolerances and specifications required for the SCT. This was 234 more than the 1976 required
and represents a yield of 93%. The component flow was at times tight, but the module production rate of 40–50 per week was maintained
despite this. The distributed production was not found to be a major logistical problem and it allowed additional flexibility to take advantage
of where the effort was available, including any spare capacity, for building the end-cap modules. The collaboration that produced the ATLAS
SCT end-cap modules kept in close contact at all times so that the effects of shortages or stoppages at different sites could be rapidly resolved