Effect of prior knowledge on good and poor readers' memory of text.

We investigated how prior knowledge influences the amount of short-term nonverbal and verbal memory and long-term retention in students of high and low ability in reading comprehension. Sixty-four junior high students were divided into four equal-sized groups on the basis of preassessed reading ability (high and low) and preassessed amount of existing prior knowledge about baseball (high and low). Each subject silently read an account of a half inning of a baseball game. After reading, each subject recalled the account nonverbally by moving figures and verbally by retelling the story. After an interpolated task, they summarized the game and sorted passage sentences for idea importance. There was a significant main effect for prior knowledge on all measures. No interactions between prior knowledge and ability were found. These results delineate the powerful effect of prior knowledge. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Learning to transform time series with a few examples

We describe a semi-supervised regression algorithm that learns to transform one time series into another time series given examples of the transformation. This algorithm is applied to tracking, where a time series of observations from sensors is transformed to a time series describing the pose of a target. Instead of defining and implementing such transformations for each tracking task separately, our algorithm learns a memoryless transformation of time series from a few example input-output mappings. The algorithm searches for a smooth function that fits the training examples and, when applied to the input time series, produces a time series that evolves according to assumed dynamics. The learning procedure is fast and lends itself to a closed-form solution. It is closely related to nonlinear system identification and manifold learning techniques. We demonstrate our algorithm on the tasks of tracking RFID tags from signal strength measurements, recovering the pose of rigid objects, deformable bodies, and articulated bodies from video sequences. For these tasks, this algorithm requires significantly fewer examples compared to fully-supervised regression algorithms or semi-supervised learning algorithms that do not take the dynamics of the output time series into account.     

Distributed control of systems over discrete Groups

This paper discusses distributed controller design and analysis for distributed systems with arbitrary discrete symmetry groups. We show how recent results for designing controllers for spatially interconnected systems, based on semidefinite programming, are applicable to a much larger class of interconnection topologies. We also show how to exploit the structure of the symmetry group to produce a hierarchy of decreasingly conservative analysis and synthesis conditions.     

Inorganic-melt-catalysed hydrogenation of phenanthrene

The hydrogenation of the coal model compound phenanthrene was investigated using a molten hydroxide-carbonate catalyst. The rate of catalysed hydrogenation was found to be approximately an order of magnitude greater than the uncatalysed reaction. Batch experiments were conducted at 20.7 MPa hydrogen pressure in a 1-l top-stirred autoclave at 480 °C for reaction times up to 1 h. Spinning-band distillation and gas-liquid chromatography coupled with mass spectrometry were used to separate and identify reaction products. Principal hydrogenation products were 9,10 dihydrophenanthrene and 1,2,3,4-tetrahydrophenanthrene. In addition, substituted naphthalenes and biphenyls were formed by hydrocracking of these two compounds. A similar product distribution was reported by others for an investigation of the thermal high-pressure hydrogenolysis of phenanthrene. The rate of the thermal reaction, however, was considerably lower.     

Power Performance of AlGaN/GaN HEMTs Grown on SiC by Ammonia-MBE at 4 and 10 GHz

In this letter, we report on the microwave power and efficiency performance of AlGaN/GaN high-electron mobility transistors (HEMTs) grown by ammonia molecular beam epitaxy (ammonia-MBE) on SiC substrates. At 4 GHz, an output power density of 11.1 W/mm with an associated power-added efficiency (PAE) of 63% was measured at V _ds = 48 V on passivated devices. At 10 GHz, an output power density of 11.2 W/mm with a PAE of 58% was achieved for V _ds = 48 V. These results are the highest reported power performance for AlGaN/GaN HEMTs grown by ammonia-MBE and the first reported for ammonia-MBE on SiC substrates.     

Single‐Phase Filamentary Cellular Breakdown Via Laser‐Induced Solute Segregation

Nanosecond melting and quenching of materials offers a pathway to novel structures with unusual properties. Impurity‐rich silicon processed using nanosecond‐pulsed‐laser‐melting is known to produce nanoscale features in a process referred to as “cellular breakdown” due to destabilization of the planar liquid/solid interface. Here, atom probe tomography combined with electron microscopy is applied to show that the morphology of cellular breakdown in these materials is significantly more complex than previously documented. Breakdown into a complex, branching filamentary structure topped by a few nm of a cell‐like layer is observed. Single‐phase diamond cubic silicon highly supersaturated with at least 10% atomic Co and no detectable silicides is reported within these filaments. In addition, the unprecedented spatio‐chemical accuracy of the atom probe allows to investigate nanosecond formation dynamics of this complex material. Previously reported properties of these materials can now be reconsidered in light of their true composition, and this class of inhomogeneous metastable alloys in silicon can be explored with confidence.     

RNA sequence determinants for aminoglycoside binding to an A-site rRNA model oligonucleotide

The codon-anticodon interaction on the ribosome occurs in the A site of the 30 S subunit. Aminoglycoside antibiotics, which bind to ribosomal RNA in the A site, cause misreading of the genetic code and inhibit translocation. Biochemical studies and nuclear magnetic resonance spectroscopy were used to characterize the interaction between the aminoglycoside antibiotic paromomycin and a small model oligonucleotide that mimics the A site of Escherichia coli 16 S ribosomal RNA. Upon chemical modification, the RNA oligonucleotide exhibits an accessibility pattern similar to that of 16 S rRNA in the 30 S subunit. In addition, the oligonucleotide binds specifically aminoglycoside antibiotics. The antibiotic binding site forms an asymmetric internal loop, caused by non-canonical base-pairs. Nucleotides that are important for binding of paromomycin were identified by performing quantitative footprinting on oligonucleotide sequence variants and include the C1407.G1494 base-pair, and A.U base-pair at positions 1410/1490, and nucleotides A1408, A1493 and U1495. The asymmetry of the internal loop, which requires the presence of a nucleotide in position 1492, is also crucial for antibiotic binding. Introduction into the oligonucleotide of base changes that are known to confer aminoglycoside resistance in 16 S rRNA result in weaker binding of paromomycin to the oligonucleotide. Oligonucleotides homologous to eukaryotic rRNA sequences show reduced binding of paromomycin, suggesting a physical origin for the species-specific action of aminoglycosides.     

Distribution of normal and abnormal fluid collections in the glenohumeral joint: implications for MR arthrography

OBJECTIVE: This study determined levels of cathepsin D activity in tissue components of normal human ovary to establish a basis for comparison with human ovarian adenocarcinomas. METHODS: Cathepsin D activity per mg tissue, per microgram protein, and per microgram DNA was determined in human ovarian tissues (cortex, follicle, corpus luteum, corpus albicans) from patients of various ages and during the menstrual cycle. Levels of cathepsin D activity were also determined in ovarian adenocarcinomas and other pathologic tissues. RESULTS: Cathepsin D levels (per mg tissue) were significantly greater (P < .001) in ovarian follicle and corpus luteum compared with cortex. Although there was not a clear correlation between enzyme activity in the cortex and day of the menstrual cycle or patient age, levels of enzyme activity appeared to decrease with each parameter. Cathepsin D levels per mg tissue in ovarian adenocarcinoma were 40% higher than in postmenopausal ovarian cortex, but the difference was not statistically significant. CONCLUSION: The diversity of cathepsin D levels in normal ovarian tissue compartments indicates that specific tissues must be used in comparisons with ovarian tumors.     

Characterization of Non-Alloyed Ohmic Contacts to Si-Implanted AlGaN/GaN Heterostructures for High-Electron Mobility Transistors

This paper reports results of a study of non-alloyed ohmic contacts on Si-implanted AlGaN/GaN heterostructures, obtained from current–voltage characteristics of transfer-length method (TLM) test structures. It is shown that the measured contact resistance from the Ti/Au/Ni metal contacts, deposited on Si-implanted regions, to the two-dimensional electron gas channel at the AlGaN/GaN heterointerface of the non-implanted region, is formed by three different components: (i) contact resistance between the metal␣and the semiconductor (0.60 ± 0.16 Ω mm), (ii) resistance of the implanted region (0.62 ± 0.03 Ω mm) and (iii) an additional resistance (0.72 ± 0.24 Ω mm) giving a total value of 1.9 ± 0.3 Ω mm. The specific ohmic contact resistance was determined to be (2.4 ± 0.5) × 10⁻⁵ Ω cm².