Harold H. Kelley (1921-2003).

This obituary reports the death of Harold Harding Kelley, Professor Emeritus of Psychology at University of California (1921-2003). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparison of 2D simultaneous multi-slice and 3D GRASE readout schemes for pseudo-continuous arterial spin labeling of cerebral perfusion at 3 T

Objective

In this perfusion magnetic resonance imaging study, the performances of different pseudo-continuous arterial spin labeling (PCASL) sequences were compared: two-dimensional (2D) single-shot readout with simultaneous multislice (SMS), 2D single-shot echo-planar imaging (EPI) and multishot three-dimensional (3D) gradient and spin echo (GRASE) sequences combined with a background-suppression (BS) module.

Materials and methods

Whole-brain PCASL images were acquired from seven healthy volunteers. The performance of each protocol was evaluated by extracting regional cerebral blood flow (rCBF) measures using an inline morphometric segmentation prototype. Image data postprocessing and subsequent statistical analyses enabled comparisons at the regional and sub-regional levels.

Results

The main findings were as follows: (i) Mean global CBF obtained across methods was were highly correlated, and these correlations were significantly higher among the same readout sequences. (ii) Temporal signal-to-noise ratio and gray-matter-to-white-matter CBF ratio were found to be equivalent for all 2D variants but lower than those of 3D-GRASE.

Discussion

Our study demonstrates that the accelerated SMS readout can provide increased acquisition efficiency and/or a higher temporal resolution than conventional 2D and 3D readout sequences. Among all of the methods, 3D-GRASE showed the lowest variability in CBF measurements and thus highest robustness against noise.

     

Collaborative writing in multiple discourse contexts

Research in computer-supported writing has traditionally compared electronic communication with oral, face-to-face communication to identify the benefits and weaknesses of each, as if they entailed dichotomous choices. In this article, we challenge that view and argue instead that any form of communication and its educational usefulness is shaped by the situation in which it is used, the backgrounds and goals of the participants, the institutional and technological setup, and the intended purpose of the medium. Three modes of communication in one graduate course are examined — oral discussion, synchronous written discussion on a local area network, and asynchronous written postings on an email list set up for the class. It was found that patterns of participation, topic introduction, and topic development differed across the three communication modes, but that the three were interwoven with each other and embedded within the larger classroom context and forms of knowledge creation in the class. Thus, rather than examining different communication media separately, researchers interested in understanding computer-supported collaborative writing need to look at how different media are used to create a meta-medium, which is established by the discourse community involved.     

Advanced Characterization and Optimization of NiOx:Cu-SAM Hole-Transporting Bi-Layer for 23.4% Efficient Monolithic Cu(In,Ga)Se2-Perovskite Tandem Solar Cells

The performance of five hole-transporting layers (HTLs) is investigated in both single-junction perovskite and Cu(In, Ga)Se₂ (CIGSe)-perovskite tandem solar cells: nickel oxide (NiO_x,), copper-doped nickel oxide (NiO_x:Cu), NiO_x+SAM, NiO_x:Cu+SAM, and SAM, where SAM is the [2-(3,-6Dimethoxy-9H-carbazol-9yl)ethyl]phosphonic acid (MeO-2PACz) self-assembled monolayer. The performance of the devices is correlated to the charge-carrier dynamics at the HTL/perovskite interface and the limiting factors of these HTLs are analyzed by performing time-resolved and absolute photoluminescence ((Tr)PL), transient surface photovoltage (tr-SPV), and X-ray/UV photoemission spectroscopy (XPS/UPS) measurements on indium tin oxide (ITO)/HTL/perovskite and CIGSe/HTL/perovskite stacks. A high quasi-Fermi level splitting to open-circuit (QFLS-V_oc) deficit is detected for the NiO_x-based devices, attributed to electron trapping and poor hole extraction at the NiO_x-perovskite interface and a low carrier effective lifetime in the bulk of the perovskite. Simultaneously, doping the NiO_x with 2% Cu and passivating its surface with MeO-2PACz suppresses the electron trapping, enhances the holes extraction, reduces the non-radiative interfacial recombination, and improves the band alignment. Due to this superior interfacial charge-carrier dynamics, NiO_x:Cu+SAM is found to be the most suitable HTL for the monolithic CIGSe-perovskite tandem devices, enabling a power-conversion efficiency (PCE) of 23.4%, V_oc of 1.72V, and a fill factor (FF) of 71%, while the remaining four HTLs suffer from prominent V_oc and FF losses.     

Iterative global and local methods of image restoration

Most of the reconstruction algorithms smooth out the edges of the reconstructed images but iterative total variation regularization and local adaptive methods preserve the edge information without any prior knowledge about the image geometric details. The restoration performance of the proposed algorithms for image deblurring is compared in terms of the mean squared error. Computer simulation results are provided and discussed.     

Reinforcement learning to adjust parametrized motor primitives to new situations

Humans manage to adapt learned movements very quickly to new situations by generalizing learned behaviors from similar situations. In contrast, robots currently often need to re-learn the complete movement. In this paper, we propose a method that learns to generalize parametrized motor plans by adapting a small set of global parameters, called meta-parameters. We employ reinforcement learning to learn the required meta-parameters to deal with the current situation, described by states. We introduce an appropriate reinforcement learning algorithm based on a kernelized version of the reward-weighted regression. To show its feasibility, we evaluate this algorithm on a toy example and compare it to several previous approaches. Subsequently, we apply the approach to three robot tasks, i.e., the generalization of throwing movements in darts, of hitting movements in table tennis, and of throwing balls where the tasks are learned on several different real physical robots, i.e., a Barrett WAM, a BioRob, the JST-ICORP/SARCOS CBi and a Kuka KR?6.     

Hot carrier reliability of RF N- LDMOS for S Band radar application

This paper presents an innovative reliability bench specifically dedicated to high RF power device lifetime tests under pulse conditions for radar application. A base-station dedicated LDMOS transistor has been chosen for RF lifetests and a complete device electric characterization has been performed. A whole review of its critical electrical parameters after accelerated ageing tests is proposed and discussed. This study tend to explain the physical degradation mechanisms occurred during RF life-tests by means of 2D ATLAS-SILVACO simulations. Finally, the paper demonstrates that N-LDMOS degradation is linked to hot carriers generated interface states (traps) and trapped electrons, which results in a build up of negative charge at Si/SiO2 interface. More interface states are created at low temperature due to a located maximum impact ionization rate at the gate edge.     

Biorthogonal Loop-Subdivision Wavelets

We present a biorthogonal wavelet construction for Loop subdivision, based on the lifting scheme. Our wavelet transform uses scaling functions that are recursively defined by Loop subdivision for arbitrary manifold triangle meshes. We orthogonalize our wavelets with respect to local scaling functions. This way, the wavelet analysis computes locally a least squares fit when reducing the resolution and converting geometric detail into sparse wavelet coefficients. The contribution of our approach is local computation of both, wavelet analysis and synthesis in linear time. We provide numerical examples supporting the stability of our scheme.     

Different metabolic and absorption patterns of betaine in response to dietary intake of whole-wheat grain, wheat aleurone or rye aleurone in catheterized pigs

In the present study, a novel method of measuring the uptake of nutrients by 1H NMR spectroscopy was performed to determine dietary effects. Six pigs catheterized in the portal vein and mesenteric artery were fed breads made from whole-wheat grain (WWG), wheat aleurone flour (WAF; 19?% aleurone of bread) or rye aleurone flour (RAF; 15?% aleurone of bread) in a repeated 3?×?3 crossover design. Three meals were provided daily (at 0, 5 and 10?h), and each period comprised of 1?week. Portal and arterial blood samples were collected at fasting (?30?min) on day 4–7, and on day 7, pooled blood samples were collected at 0–2.5, 2.5–5, 5–7.5 and 7.5–10?h after first (0?h) daily meal. Using the arterial-venous difference and ANOVA–simultaneous component analysis, plasma betaine was found to accumulate during the experimental period. On day 7, plasma betaine concentrations was 20–40?% higher than when feeding the WAF diet compared with RAF and WWG (P?=?0.001), whereas the content of betaine in the WAF diet was about twice as high. The arterial-venous difference showed a tendency (P?=?0.078) for the diet–time interaction of betaine absorption in the absorption phases but there was no diet effect (P?=?0.31), which indicates a steady-state absorption has been reached on day 7. Furthermore, high plasma betaine levels correlated with low plasma creatine of endogenous origin. In conclusion, the explorative method revealed that the plasma concentration and absorption of betaine were differentially modified by the diets.