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Schizophrenia (SZ) is a severe neuropsychiatric disorder associated with disrupted connectivity within the thalamic-cortico-cerebellar network. Resting-state functional connectivity studies have reported thalamic hypoconnectivity with the cerebellum and prefrontal cortex as well as thalamic hyperconnectivity with sensory cortical regions in SZ patients compared with healthy comparison participants (HCs). However, fundamental questions remain regarding the clinical significance of these connectivity abnormalities.
Resting state seed-based functional connectivity was used to investigate thalamus to whole brain connectivity using multi-site data including 183 SZ patients and 178 matched HCs. Statistical significance was based on a voxel-level FWE-corrected height threshold of p < 0.001. The relationships between positive and negative symptoms of SZ and regions of the brain demonstrating group differences in thalamic connectivity were examined.
HC and SZ participants both demonstrated widespread positive connectivity between the thalamus and cortical regions. Compared with HCs, SZ patients had reduced thalamic connectivity with bilateral cerebellum and anterior cingulate cortex. In contrast, SZ patients had greater thalamic connectivity with multiple sensory-motor regions, including bilateral pre- and post-central gyrus, middle/inferior occipital gyrus, and middle/superior temporal gyrus. Thalamus to middle temporal gyrus connectivity was positively correlated with hallucinations and delusions, while thalamus to cerebellar connectivity was negatively correlated with delusions and bizarre behavior.
Thalamic hyperconnectivity with sensory regions and hypoconnectivity with cerebellar regions in combination with their relationship to clinical features of SZ suggest that thalamic dysconnectivity may be a core neurobiological feature of SZ that underpins positive symptoms.
Psychotic symptoms are common in children and adolescents and may be early manifestations of liability to severe mental illness (SMI), including schizophrenia. SMI and psychotic symptoms are associated with impairment in executive functions. However, previous studies have not differentiated between ‘cold’ and ‘hot’ executive functions. We hypothesized that the propensity for psychotic symptoms is specifically associated with impairment in ‘hot’ executive functions, such as decision-making in the context of uncertain rewards and losses.
In a cohort of 156 youth (mean age 12.5, range 7–24 years) enriched for familial risk of SMI, we measured cold and hot executive functions with the spatial working memory (SWM) task (total errors) and the Cambridge Gambling Task (decision-making), respectively. We assessed psychotic symptoms using the semi-structured Kiddie Schedule for Affective Disorders and Schizophrenia interview, Structured Interview for Prodromal Syndromes, Funny Feelings, and Schizophrenia Proneness Instrument – Child and Youth version.
In total 69 (44.23%) youth reported psychotic symptoms on one or more assessments. Cold executive functioning, indexed with SWM errors, was not significantly related to psychotic symptoms [odds ratio (OR) 1.36, 95% confidence interval (CI) 0.85–2.17, p = 0.204). Poor hot executive functioning, indexed as decision-making score, was associated with psychotic symptoms after adjustment for age, sex and familial clustering (OR 2.37, 95% CI 1.25–4.50, p = 0.008). The association between worse hot executive functions and psychotic symptoms remained significant in sensitivity analyses controlling for general cognitive ability and cold executive functions.
Impaired hot executive functions may be an indicator of risk and a target for pre-emptive early interventions in youth.
Ten ice-sheet models are used to study sensitivity of the Greenland and Antarctic ice sheets to prescribed changes of surface mass balance, sub-ice-shelf melting and basal sliding. Results exhibit a large range in projected contributions to sea-level change. In most cases, the ice volume above flotation lost is linearly dependent on the strength of the forcing. Combinations of forcings can be closely approximated by linearly summing the contributions from single forcing experiments, suggesting that nonlinear feedbacks are modest. Our models indicate that Greenland is more sensitive than Antarctica to likely atmospheric changes in temperature and precipitation, while Antarctica is more sensitive to increased ice-shelf basal melting. An experiment approximating the Intergovernmental Panel on Climate Change’s RCP8.5 scenario produces additional first-century contributions to sea level of 22.3 and 8.1 cm from Greenland and Antarctica, respectively, with a range among models of 62 and 14 cm, respectively. By 200 years, projections increase to 53.2 and 26.7 cm, respectively, with ranges of 79 and 43 cm. Linear interpolation of the sensitivity results closely approximates these projections, revealing the relative contributions of the individual forcings on the combined volume change and suggesting that total ice-sheet response to complicated forcings over 200 years can be linearized.
Optimizing magnetic field sensors made by piezoelectric-magnetostrictive composites is a trade off between several parameters. Whereas large structures will cause in principle high electrical currents the mechanical coupling will lead to shear losses and therefore limit the sensitivity of the sensor and make it impossible to measure small magnetic fields. In very small structures the shear losses will decrease but the imperfections in the interfaces become more important and the typically small currents will be disturbed by, e.g., surface conductivity of the piezoelectric material and are thus difficult to measure. The best compromise is a mesoscale sensor which has relatively small losses due to shearing but still high enough electrical currents to work as a good sensor. We will present a setup which allows the use free standing ZnO micro rods as piezoelectric core material which are surrounded by a magnetostrictive layer. Since no clamping is necessary the expansion and contraction of the material is not hindered by a matrix material. The tuning of the relative layer thicknesses can be easily optimized by changing the thickness of the magnetostrictive layer so that an optimum can be achieved for different ZnO micro rods. For the growth of the ZnO a newly developed process will be presented which allows the growth of a large variety of single crystals with different aspect ratios up to needles with several millimeters in length.
Nanocomposite films containing Au nanoparticles embedded in a
polymer matrix were prepared by vapour phase co-deposition of Au and
polymers (Teflon AF and Poly(
-methylstyrene)) in high vacuum. The
microstructure of the composite materials as well as metal content strongly
depend on the condensation coefficient of the Au atoms, the deposition rates
of the components, the substrate temperature, and the type of polymer
matrix. The condensation coefficient, which varies between 0.03 and 1, was
determined from energy dispersive X-ray spectrometer (EDX) and surface
profilometry. It is shown that the microstructure of nanocomposites (size,
size distribution, and interparticle separation of metal clusters), which
was determined by transmission electron microscopy, can be controlled by the
deposition parameters and the choice of polymer matrix. The optical
absorption in the visible region due to the particle plasmon resonance has a
strong dependence on the metal filling factor. The correlation between the
microstructure of nanocomposites and optical properties, studied using
UV-Vis spectroscopy, was also established. Further more, the electrical
properties of the composites were studied as a function of the metal volume
fraction. It was observed that the nanocomposite films exhibit a percolation
threshold at a metal volume fraction of 0.43 and 0.20 for gold nanoclusters
in Teflon AF and Poly(α-methylstyrene), respectively.
GaN films grown on SiC (0001) by MBE at various substrate temperatures (600° - 750° C) were characterized by RHEED, STM, x-ray diffraction, AFM and TEM. This work focuses on the TEM analysis of the films' features, such as stacking faults and dislocations, which are related to the substrate temperature. There are several basal plane stacking faults in the form of cubic inclusions for samples grown at low temperatures compared to those grown at high temperatures. The dislocation density is greatest for the film grown at 600°C, and it steadily decreases with increasing growth temperatures. Despite the presence of various defects, x-ray analysis shows that the GaN films are of high quality. The double crystal rocking curve full width at half maximum (FWHM) for the GaN (0002) peak is less than 2 arc-minutes for all of the films we measured and it decreases with increasing growth temperature.
Exposure of wurtzite GaN films grown on Si-polar 6H-SiC(0001) to magnesium during molecular beam epitaxy (MBE) has been studied. In the nitrogen rich regime of MBE growth, GaN films are known to grow with rough morphology. We observe on GaN(0001) that small doses of Mg act as a surfactant, smoothing out this roughness. An interpretation of this surfactant behavior is given in terms of electron counting arguments for the surface reconstructions. Previously, we have reported that larger doses of Mg lead to inversion of the Ga-polar GaN film to produce N-polar GaN. Several Mg-related reconstructions of the resulting GaN(000 ) surface are reported.
A confocal scanning Raman microscope was constructed for spectroscopy and microscopy of biological samples (Fig. 1). The microscope contains an illumination system in which a focused krypton laser beam, of which the 647.1 nm line is used to reduce damage, is scanned over the sample using a scanning mirror which moves around two orthogonal axes. Raman scattered light is collected by a water immersion objective which directs the light on the scanning mirror. Spectral analysis takes place in a monochromator with two exit ports: one for spectroscopical purposes the other one for imaging. An image is made by scanning the light, present in the Raman band passed by the monochromator, over a CCD using a second scanning mirror which moves synchronously with the first mirror. The spatial resolution is of the order of 0.3 × 0.3 × 1.2 μm3 (x,y,z).
With this microscope we studied the following samples:
One of the major features of scanning probe microscopy is the ability to produce high-resolution images in air and in liquid. This makes these microscopes potentially very useful for the study of biological materials. Indeed the number of reports that use these microscopes, especially the atomic force microscope (AFM), has increased exponentially in the past decade. However, in order to become a routine apparatus that is able to image live processes at a scale of a few nanometers, the instrumentation of the AFM has to be improved. First of all, under normal operation, the movement of the tip across the surface of fragile biological structures such as cell membranes, often results in movement or even destruction of the object. Secondly, the lack of specificity of the AFM makes it difficult to identify the observed structures. Other problems include the low imaging speed and problems associated with the tip-sample convolution. Here we will report on attempts to improve the first two points: sample destruction and specificity.
It has become clear recently that for operation in air the so-called tapping mode AFM is much more gentle for the sample than the standard operation mode.
Cryo-electron microscopy and image analysis techniques make it possible to study structural and functional relationships of macromolecular complexes that currently are not easily examined with crystallographic techniques. We have recorded images of frozen-hydrated human rhinovirus serotype-14 (HRV-14) complexed with a neutralizing, monoclonal, antibody fragment (Fab-17Ia; Fig. 1 A); and HRV-16 complexed with the amino-terminal, two-domain fragment (D1D2) of its cellular receptor (intercellular adhesion molecule-1, ICAM-1; Fig. 1B). Three-dimensional reconstructions (Figs. 2A,B) were calculated to ∽3nm resolution from 35 and 44 images of each complex, respectively. The HRV-14/Fab structure clearly identified the footprint of the Fab on the surface of the virion. The HRV-16/D1D2 reconstruction presents, for the first time, the three-dimensional structure of a complete virus complexed with its cellular receptor.
We report a comparison of the characteristics of germanium- silicon base heterojunction bipolar transistors fabricated using mesa- etched and ion- implanted processes. The base currents of both device structures are dominated by peripheral currents associated with the plasma- SiO2 covered junction edge. After an implant damage anneal at 800 or 900 C, the ion- implanted process exhibited the lowest base currents. There was no evidence of strained layer relaxation even for the 900 C anneal.
The evolution of the carbon abundance at the surface of both components of a mass-exchanging (Algol-type) binary is examined (fig. 1). Distinction is made between case B and case AB (fig. 2) of mass transfer, in view of the different timescales involved. In the mass accreting component thermohaline mixing is adopted when matter with decreasing hydrogen abundance is deposited on the surface.
It is shown that at the surface of the loser a very low C-abundance is present, while at the surface of the gainer different regimes occur. On the average the expected C-abundance on the gainer is clearly lower than the observed solar value, but far above the value at the surface of the loser. The variation in time during the mass-exchange process is compared to the values, derived from observation of several Algol-type systems.
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