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Schizophrenia is associated with robust hippocampal volume deficits but subregion volume deficits, their associations with cognition, and contributing genes remain to be determined.
Hippocampal formation (HF) subregion volumes were obtained using FreeSurfer 6.0 from individuals with schizophrenia (n = 176, mean age ± s.d. = 39.0 ± 11.5, 132 males) and healthy volunteers (n = 173, mean age ± s.d. = 37.6 ± 11.3, 123 males) with similar mean age, gender, handedness, and race distributions. Relationships between the HF subregion volume with the largest between group difference, neuropsychological performance, and single-nucleotide polymorphisms were assessed.
This study found a significant group by region interaction on hippocampal subregion volumes. Compared to healthy volunteers, individuals with schizophrenia had significantly smaller dentate gyrus (DG) (Cohen's d = −0.57), Cornu Ammonis (CA) 4, molecular layer of the hippocampus, hippocampal tail, and CA 1 volumes, when statistically controlling for intracranial volume; DG (d = −0.43) and CA 4 volumes remained significantly smaller when statistically controlling for mean hippocampal volume. DG volume showed the largest between group difference and significant positive associations with visual memory and speed of processing in the overall sample. Genome-wide association analysis with DG volume as the quantitative phenotype identified rs56055643 (β = 10.8, p < 5 × 10−8, 95% CI 7.0–14.5) on chromosome 3 in high linkage disequilibrium with MOBP. Gene-based analyses identified associations between SLC25A38 and RPSA and DG volume.
This study suggests that DG dysfunction is fundamentally involved in schizophrenia pathophysiology, that it may contribute to cognitive abnormalities in schizophrenia, and that underlying biological mechanisms may involve contributions from MOBP, SLC25A38, and RPSA.
The nearby radio galaxy M87 offers a unique opportunity for exploring the connection between γ-ray production and jet formation at an unprecedented linear resolution. However, the origin and location of the γ-rays in this source is still elusive. Based on previous radio/TeV correlation events, the unresolved jet base (radio core) and the peculiar knot HST-1 at >120 pc from the nucleus are proposed as candidate site(s) of γ-ray production. Here we report our intensive, high-resolution radio monitoring observations of the M87 jet with the VLBI Exploration of Radio Astrometry (VERA) and the European VLBI Network (EVN) from February 2011 to October 2012. During this period, an elevated level of the M87 flux is reported at TeV with VERITAS. We detected a remarkable flux increase in the radio core with VERA at 22/43 GHz coincident with the VHE activity. Meanwhile, HST-1 remained quiescent in terms of its flux density and structure at radio. These results strongly suggest that the TeV γ-ray activity in 2012 originates in the jet base within 0.03 pc (projected) from the central supermassive black hole.
Legionnaires' disease (LD) is a major cause of severe community-acquired pneumonia but the source and mode of transmission are not always apparent, especially in sporadic cases. We hypothesized that LD can be acquired from the air-conditioning systems of motor cars. Swabs were taken from the evaporator compartments of the air-conditioning system of scrapped cars. Healthy subjects who were mainly employees of regional transportation companies were tested for antibody to Legionella pneumophila serogroups 1–6; they also completed a questionnaire. Legionella species were detected in 11/22 scrapped cars by the loop-mediated isothermal amplification method. The prevalence of microplate agglutination titres ⩾1:32 was significantly higher in subjects who sometimes used car air-conditioning systems. Although we did not prove a direct link between Legionella spp. in the car evaporator and LD, our findings point to a potential risk of car air-conditioning systems in LD, which needs further investigation.
We propose and demonstrate Bonding-in-Solution Technique (BiST) for encapsulation of liquid in MEMS devices. Liquid encapsulation enables innovative MEMS devices with various functions, such as hydraulic displacement amplification and scanning mirrors. Interfusion of air bubbles and leakage of the encapsulated liquid must be averted not to deteriorate device performances. Several liquid encapsulation processes have been proposed, such as parylene deposition and polymer thermal bonding. However, they involve vacuum and/or thermal processes and cannot be applied to volatile liquids. In BiST, two structural layers are passively aligned and brought into contact in solution, where the encapsulation cavities are uniformly filled up with the liquid without air bubbles. A UV-curable resin is used as an adhesive that does not require heat or vacuum environment but UV to bond the two layers. The detail processes of BiST are (a)UV-curable adhesive resin is coated onto the bonding surface of a structural layer. The layer contains not only encapsulating cavities but also concave-shaped structures for the following passive alignment. (b) The other layer with convex-shaped structures is brought into contact in solution, when the two layers are passively aligned by matching concave and convex structures. (c) UV light is irradiated and the two layers are permanently bonded while the contact is maintained by the jig. We successfully achieved encapsulation of DI water and glycerin in PDMS and silicon structural layers. No liquid remains in the bonding interface. Since conventional aligners are not applicable to BiST, we experimentally evaluated the accuracy of the passive alignment process in solution that makes use of matching concave and convex structures. We used a PDMS layer with cylinders (concave) and a silicon layer with cavities (convex) to evaluate the alignment in BiST. The height and depth of the cylinders and cavities are designed such that the PDMS cylinders elastically deform when the two layers are brought into contact. The elastic averaging enables the passive alignment of the two layers. We investigated the bonding accuracy with respect to the number of pairs of concave/convex structures and the height of PDMS cylinders while in contact. The bonding accuracy improved as the number of pairs increased while the height of PDMS cylinders did not show a correlation. The alignment accuracy of 5μm in BiST was achieved with 12 pairs of the concave/convex structures. The ultimate goal of our research is to develop innovative MEMS devices with encapsulated liquid, such as a hydraulic displacement amplification mechanism applicable to a tactile display. Glycerin was encapsulated by largely-deformable-PDMS thin membranes and silicon cavities by using BiST. The displacement at the input was successfully amplified at the output associated with the ratio of the cross-sectional areas.
A systematic investigation of the effect of annealing time and temperature on the incubation period for spontaneous morphology change (SMC) in electrodeposited copper metallization is reported. The incubation time is greatly reduced at higher temperatures. At each temperature, the remaining incubation time at room temperature was found to decrease approximately linearly with increasing annealing time. An Arhennius plot of the measured rates of decrease showed good linearity and yielded a value of 0.48 eV for the activation energy. This is consistent with a vacancy diffusion mechanism for the process occurring during the incubation period and supports our proposed mechanism for SMC.
We summarize the characteristic defect structures associated with gradual-degradation, rapiddegradation, catastrophic (mirror-facet) optical damage (COD), electric static discharge (ESD) and electric overstress (EOS) damages to provide a defect-map for device failure mode analysis. The generation mechanisms of these lattice defects are discussed which pinpoint the weak links in the device structures.
Tungsten (W) films were deposited onto InP in a cold wall, rapid thermal low-pressure chemical vapor deposition (RT-LPCVD) reactor, from a tungsten hexafluoride (WF6) gas reduced by hydrogran (H2). W films of thickness 50 to 450 nm were deposited in the temperature range of 350° to 550°C, pressure range of 0.5 to 4.5 Torr and deposition rates up to 4 nm/sec with an apparent activation energy of about 1.12 eV. The film stress varied depending upon the deposition pressure, from low compressive for deposition at 0.5 Torr to moderate tensile for deposition at about 4.5 Torr. The films were aged at temperatures as high as 300°C for about 800 hr and exhibited an excellent mechanical stability. Post-deposition sintering of the W films at temperatures up to 600°C led to reduction of the resistivity with a minimum value of about 55μΩ-crn as a result of heating at 500°C. Conditions for both selective and blanket deposition were defined, and a dry etching process for further geometrical definitions of the films was developed, providing etch rates of 40 to 50 nm·sec-1. This report reflects the first attempt to deposit W films onto III-V semiconductor at a very high rate by means of RT-LPCVD.
The viability of forming an ohmic contact to InGaAs/InP structures by means of a load-locked RT-LP(MO)CVD integrated process, was demonstrated. The wafer was loaded into the reactor chamber and was exposed to a sequence of dry and in-situ processes which led to the formation of an ohmic contact. After an in-situ cleaning of the wafer through a thermal cycle at 500°C under a flow of tertiarybutylphosphine (TBP), which provided the needed free hydrogen for a mild etching of the surface, however with an over pressure of P to eliminate surface degradation, a layer of silicon oxide (SiOx ) was rapid thermal chemical vapor deposited (RT-CVD) onto the InGaAs/InP sample via a rapid thermal cycle (500°C,30 s) in a low pressure O2 and 2% diluted SiH4. Dry etching of 50–150 μm wide contact stripes was carried out using a contact stencil mask by an electron-cyclotron resonance (ECR) dry etching. Subsequently the wafer was reloaded through the load-lock to the main chamber and a TiNx layer were selectively deposited into the via-holes and processed to provide an ohmic contact to the InGaAs/InP substrate. Finally, a blanket deposition of conducting cap layer was realized by means of RT-LP(MO)CVD. This work provides a solid demonstration to the feasibility of the single-wafer-integrated-process (SWIP) as an approach to replace the batch process traditionally used for manufacturing the InP-based optoelectronic devices.
Low resistance Pt/Ti nonalloy contacts to GaAs, GaP, In As, InGaAs, and In Alas have been studied using Rutherford Backscattering. The samples were studied by comparing an as deposited structure to samples annealed at temperatures between 300°C and 600°C for 30 s. For all samples intermixing of the Pt and Ti was observed to start at 350°C. The Ti/HI-V semiconductor interface mixing was strongest for As when it was present, but In and Ga also strongly intermixed for anneals of 4S0°C and above.
Pt/Ti contact to variety of binary III-V and related ternary semiconductor materials were established. These contacts were formed by electron beam evaporation and subsequent rapid thermal processing in order to sinter the metal-semiconductor systems. The contacts to p-type InAs, GaAs, In0.53Ga0.43As, In0.52Al0.4As and Ga0.7Al0.3As were ohmic, as a result of heating at temperatures of 450°C or higher. The Pt/Ti contacts to InP and GaP displayed Schottky behavior as-deposited and preserved the rectifying nature through heat treatments, regardless of the processing conditions. The electrical properties and the microstructure evolution in these 7 systems is discussed in this paper.
Significantly improved flux-pinning has been achieved in bulk YBa2Cu3O7-δ superconductor (‘123’ compound) containing fine-scale defects (<~50 A thick). The measured Jc(magn.) of ~l05 A/cm2 at 77K, H = 0.9T is about ten times higher than the typical values for bulk Y-Ba-Cu-O. The improved structure was produced by rapid decomposition at 920°C of the YBa2Cu4O8 (‘124’) precursor.
Recently it was reported that high quality, 10–100 μm thick, single-crystalline Si films were formed on oxidized single-crystalline Si wafers by the lateral epitaxial growth over oxide (LEGO) process. Although this recrystallization process is reliable and reproducible, periodic regions of dislocations in the otherwise relatively dislocation-free Si film were not well understood. In this paper, therefore, the film stress and defect properties are investigated in detail, and devices made in recrystallized wafers are compared with devices in conventional wafer structures. Stress levels were found to be too low to cause defects, with TEM data suggesting an impurity mechanism (SiO2 precipitation) for small dislocation loops and slight crystalline misorientation for long dislocation lines in the periodic, defective areas. Device results confirmed that LEGO is a viable alternative to the dielectric isolation (DI) technology.
Ultrafine copper particles were prepared by the thermal decomposition of a copper formate-poly(2-vinylpyridine) complex. At temperatures above 125°C, a redox reaction occurs where Cu+2 is reduced to copper metal and formate is oxidized to CO2 and H2. The decomposition reaction was studied by thermogravimetric analysis, differential scanning calorimetry and mass spectrometry. Copper concentrations up to 23 wt% have been incorporated into the polymer by this technique. The presence of the polymeric ligand induces the redox reaction to occur at a temperature 80°C lower than in uncomplexed copper formate. Incorporation of the reducing agent (formate anion) into the polymer precursor enables the redox reaction to occur in the solid state. Films of the polymer precursor were prepared and the formation of metallic copper particles were studied by visible and infrared spectroscopy, x-ray diffraction techniques, and transmission electron microscopy. Results from these measurements indicate that spherical copper particles with an average diameter of 35angstrom are isolated within the polymer matrix. The particles are thermodynamically stable at temperatures up to the decomposition of the polymer matrix (≈350 °C), but oxidize rapidly upon exposure air.
Two problems facing MOCVD grown GaAs-on-Si are firstly, scale up to 3” and greater wafer diameter with acceptably uniform layer thicknesses and electrical and optical properties, and secondly the achievement of adequate device isolation through the use of buffer layers of low doping density (≤1014 cm−3). We have investigated the thickness uniformity and 300K photoluminescence intensity of 3” Ø, MOCVD grown GaAs layers on Si substrates by whole wafer mapping of these parameters, and correlate the variations found with the gas flow direction during deposition of the GaAs. We have overcome the high background doping densities (n =5−20 × 1015 cm2) in the material by a buried Be implant (1−5 × 1012 at 120 keV) followed by 850°C, 3 sec annealing. This provides adequate isolation for MESFETS and we fabricated such devices with gm's of 160-175 mS mm−1 using our standard process. These values are similar to homoepitaxial MESFETS fabricated in the same way.
The transport Jc of the polycrystalline YBa2Cu3O7-δ superconductor seems to be dominated by weak links between high Jc regions as evidenced by low Jc values and their strong field dependence. The possible effects of thermal expansion-contraction and the tetragonal-orthorhombic transformation on the weak links and the Jc values were investigated by repeated thermal cycling of sintered pellets between -196°C and various high temperatures (600–850°C) using a furnace heating and cooling in an oxygen atmosphere. While more than a five-fold decrease in Jc from -400 to -70 A/cm2 (at 77K in zero field) is observed after 5 temperature cycles between -196'C and 850°C, only a slight decrease (to -370 Atm2) is noticed after 5 cycles between -196*C to 600°C, the temperature span of which is not all that much smaller than the former cycles. Transmission electron microscopy analysis clearly indicates that the drastic deterioration in Jc by repeated phase transformation is caused by increased amount of microcracks on (001) basal planes near the grain boundaries. The results will be discussed in terms of the large thermal expansion anisotropy of this layer-structured compound.
Correlations between observed defect structures and the orientation of planes involved in grain boundary (GB) formation in single phase, near ideal density orthorhombic Ba2YCu3O7−x are presented. Coherent boundaries involving only a low energy network of dislocations at the interface are associated with boundaries not involving the (001) basal plane, while basal-plane-faced GBs are highly defective. These results are interpreted using a model for local stress based on the known anisotropie thermal contraction of the material during cooling from sintering temperatures. Scanning Auger microscopy of in situ fractured surfaces demonstrates that there is preferential segregation of carbon at the GBs as well.
We report ion scattering and TEM investigations of the first layers of GaAs grown on clean Si(111). Based on observations of pure Ga cluster growth on As terminated Si(111) we propose a model for GaAs growth on Si, where Ga atoms are mobile and tend to cluster, but are immobilized by arriving As. These results establish conditions necessary for uniform film growth of GaAs/Si at the important film/substrate interface.
A technique for observing both plan view and cross sections of a specimen directly in a transmission electron microscope (TEM) without relying on a tedious thinning operation was developed. This technique involves cleaving a specimen perpendicular to the plane, so that the thin (electron transparent) section of the cleaved edge can be directly imaged by TEM. The only limitations of this technique are that a specimen must be readily criacked or cleaved and that, since the transparent region is often bounded by a 90° corner, the extent of electron transparent region is somewhat localized. Nevertheless, the technique has the advantages of the ease of specimen preparation, and the absence of contamination or damage introduced in other conventional thinning methods. The geometry of the cleaved specimen is also suitable for reflection electron microscopy.
The recent discovery of the YBa2Cu3O7-δ type high Tc superconductors stimulated worldwide R&D interest in this field. However, the relatively low critical current density (Jc) in the polycrystalline, bulk superconductors (as well as its significant deterioration in weak magnetic fields) has been a major roadblock to the rapid technical advancement toward applications. In this paper, we investigated the effect of processing and microstructural control on Jc of the superconductor. Improved Jc values of -3100 A/cm2 at 77K with somewhat reduced field dependence have been obtained through appropriate microstructural modifications.