Correlation of the expansion segments in mammalian rRNA with the fine structure of the 80 S ribosome; a cryoelectron microscopic reconstruction of the rabbit reticulocyte ribosome at 21 A resolution

Samples of 80 S ribosomes from rabbit reticulocytes were subjected to electron cryomicroscopy combined with angular reconstitution. A three-dimensional reconstruction at 21 A resolution was obtained, which was compared with the corresponding (previously published) reconstruction of Escherichia coli 70 S ribosomes carrying tRNAs at the A and P sites. In the region of the intersubunit cavity, the principal features observed in the 70 S ribosome (such as the L1 protuberance, the central protuberance and A site finger in the large subunit) could all be clearly identified in the 80 S particle. On the other hand, significant additional features were observed in the 80 S ribosomes on the solvent sides and lower regions of both subunits. In the case of the small (40 S) subunit, the most prominent additions are two extensions at the base of the particle. By comparing the secondary structure of the rabbit 18 S rRNA with our model for the three-dimensional arrangement of E. coli 16 S rRNA, these two extensions could be correlated with the rabbit expansion segments (each totalling ca 170 bases) in the regions of helix 21, and of helices 8, 9 and 44, respectively. A similar comparison of the secondary structures of mammalian 28 S rRNA and E. coli 23 S rRNA, combined with preliminary modelling studies on the 23 S rRNA within the 50 S subunit, enabled the additional features in the 60 S subunit to be sub-divided into five groups. The first (corresponding to a total of ca 335 extra bases in helices 45, 98 and 101) is located on the solvent side of the 60 S subunit, close to the L7/L12 area. The second (820 bases in helices 25 and 38) is centrally placed on the solvent side of the subunit, whereas the third group (totaling 225 bases in helices 18/19, 27/29, 52 and 54) lies towards the L1 side of the subunit. The fourth feature (80 bases in helices 78 and 79) lies within or close to the L1 protuberance itself, and the fifth (560 bases in helix 63) is located underneath the L1 protuberance on the interface side of the 60 S subunit.     

An investigation of unilateral cerebral pathology with equated verbal and visual-spatial tasks.

Ss with left cerebral damage perform significantly different on certain tasks so as to be distinguishable from Ss with right cerebral damage. In this instance, verbal and visual-spatial paired associations were learned. The results indicated that control Ss (no known cerebral damage) showed no difference on either task, but patients with right cerebral damage (R) did significantly poorer on visual-spatial learning than verbal learning; patients with left cerebral damage (L) did just the reverse. Percent of accuracy of diagnosis of Rs as R, and Ls as L was marred by the factor of age. Measures of perseveration were less clearcut than error scores. From Psyc Abstracts 36:04:4JG82S. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Limited-Dose Electron Microscopy Reveals the Crystallinity of Fibrous C–S–H Phases

Using electron diffraction, we demonstrate that the fibrous calcium–silicate–hydrates (C–S–H) of tricalciumsilicate (C₃S) hydration possess a crystalline structure. The crystalline nature was revealed by limiting the electron dose, which is common in electron microscopy of biomacromolecules. Compared with room temperature, the fading of the electron diffraction patterns at −175°C occurs at an electron dose that is about one order of magnitude higher. A combination of low-dose and cryo-protection methods offers the possibility to investigate the structures of water-containing cement phases by high-resolution electron microscopy in a close-to-native state.     

One billion transistors, one uniprocessor, one chip

Billion-transistor processors will be much as they are today, just bigger, faster and wider (issuing more instructions at once). The authors describe the key problems (instruction supply, data memory supply and an implementable execution core) that prevent current superscalar computers from scaling up to 16- or 32-instructions per issue. They propose using out-of-order fetching, multi-hybrid branch predictors and trace caches to improve the instruction supply. They predict that replicated first-level caches, huge on-chip caches and data value speculation will enhance the data supply. To provide a high-speed, implementable execution core that is capable of sustaining the necessary instruction throughput, they advocate a large, out-of-order-issue instruction window (2,000 instructions), clustered (separated) banks of functional units and hierarchical scheduling of ready instructions. They contend that the current uniprocessor model can provide sufficient performance and use a billion transistors effectively without changing the programming model or discarding software compatibility     

Absence of an Odd-Error Signal Mechanism in Human Accommodation

Experiments have been designed to demonstrate that the human accommodative system operates with an even-error signal mechanism under restricted monocular viewing conditions. Retinal blur is such an even-error input signal and, thus, these experimental results add to the evidence considering blur as the effective input signal in accommodation. The random 50 percent erroneous initial direction of movement is a null experimental result which should be robust to a variety of experimental artifacts that may have contaminated previously published results.     

A multiple-stage screening procedure for the identification of childhood anxiety disorders.

Examined the usefulness of a multiple-stage screening procedure in the identification of youth experiencing elevated levels of anxiety. 758 children in Grades 4–7 completed a 3-stage screening procedure. During the 1st and 2nd stages, Ss completed the Revised Children's Manifest Anxiety Scale; the 3rd stage involved a clinical interview with the S based on the Schedule for Affective Disorders and Schizophrenia for School-Age Children. Results were similar to those found when the procedure was used to identify children with depression. Nearly 18% of the original sample was identified in the 1st stage. Of the 124 children who completed the 2nd stage, over 69% met the cutoff criteria for the 3rd stage interview, where 41% of that subset exhibited an anxiety disorder. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Temperature-jump experiments on thin lipid membranes in the presence of valinomycin

Temperature jump relaxation experiments on planar lipid membranes in the presence of valinomycin were performed using the absorption of a strong light flash as an energy source for the generation of the T-jump. The relaxation of the current carried by valinomycin/Rb+ complexes was measured. The results were interpreted on the basis of a transport model which was also analyzed by voltage jump relaxation experiments. The study shows that the application of the T-jump technique provides valuable information about transport kinetics as well as the dynamics of the membrane structure. At the given experimental conditions the relaxation of the current is believed to reflect a temperature-dependent transition of the membrane to a new conformational state of low order. The relaxation could be resolved with the present technique only at low temperatures and for membranes of high microviscosity.     

The limited value of cophenetic correlation as a clustering criterion

A common procedure for evaluating hierarchical cluster techniques is to compare the input data, in terms of for example a matrix of similarities or dissimilarities, with the output hierarchy expressed in matrix form. If an ordinary product-moment correlation is used for this comparison, the technique is known as that of cophenetic correlations, frequently used by numerical taxonomists. A high correlation between the input similarities and the output dendrogram has been regarded as a criterion of a successful classification. This paper contains a Monte Carlo study of the characteristics of the cophenetic correlation and a related measure of agreement which have been both interpreted in terms of generalized variance for some different hierarchical cluster algorithms. The generalized variance criterion chosen for this study is Wilk's lambda, whose sampling distribution under the null hypothesis of identical group centroids is used in this context to define the degree of separation between clusters. Thus, a probabilistic approach is introduced into the evaluation procedure. With the above definition of presence of clusters, use of the cophenetic correlation and related measures of agreement as criteria of goodness-of-fit is shown to be quite misleading in most cases. This is due to their large variability for low separation of clusters.