A new 48 d.o.f. quadrilateral shell element with variable-order polynomial and rational B-spline geometries with rigid body modes

A 48 degrees-of-freedom (d.o.f.) quadrilateral thin elastic shell finite element using variable-order polynomial functions, B-spline functions and rational B-spline functions to model the shell surface is developed. This development may allow the stiffness formulation of the shell element to be linked to the geometry data bases created by computer aided design systems. The displacement functions are that of bicubic Hermitian polynomials. The displacement functions and d.o.f. are expressed and investigated in both the curvilinear and Cartesian forms. The cuivilinear form is simpler and can provide the proper solution for a certain class of shell problems. For certain highly curved shells such as bellows, however, the curvilinear form fails to properly model some rigid body modes even with either the explicit inclusion of rigid body terms or the high order displacement functions. It is suggested in this study that such difficulty can be circumvented and the rigid body modes can be properly included if a Cartesian form is used for displacement functions. The strain–displacement equations are expressed in curvilinear co-ordinates. Thus, the Cartesian displacement functions require a transformation to curvilinear displacement at each numerical integration point. Examples include a pinched cylinder, a translational shell under central load, a uniformly loaded hypar shell, a pressurized ovel shell, a semi-toroidal bellows and a U-shaped bellows. For the first four examples, geometric modellings consist of polynomials of second-order (subparametric), third-order (isoparametric), and fourth and fifth-order (both superparametric) as well as B-spline functions of fourth- and fifth-order. The geometries of the pinched cylinder, the semi-toroidal bellows, and the U-shaped bellows were modelled exactly using rational B-spline functions. All the results obtained are in good agreement with alternative existing solutions.     

Ribosomes: protein synthesis in slow motion

Using image reconstruction methods, electron microscopists can now visualize ribosomes at resolutions so high that the changes in the positions of ribosome-bound tRNAs which occur during protein synthesis can be seen.     

Discrimination of frequency glides with superimposed random glides in level

These experiments were designed to test the hypothesis that glides in frequency are detected and discriminated by monitoring changes in excitation level on the low-frequency side of the excitation pattern. Thresholds were measured for detecting an increase in the extent of a frequency glide, for various standard extents (transition spans). The center frequency of each stimulus was roved, to prevent subjects from using the start or endpoint frequencies of the stimuli as cues. The level was either fixed at 70 dB SPL, or changed linearly in dB/s by an amount that varied randomly in extent and direction, keeping the level at the midpoint of the glide at 70 dB SPL. These random changes in level were intended to disrupt cues based on monitoring changes in excitation level on one side of the excitation pattern. For some conditions, performance was too good to be explained by subjects monitoring the start or endpoint frequencies of the stimuli. Performance was also too good to be explained in terms of the discrimination of changes in excitation level on one side of the excitation pattern. Thresholds, expressed as a proportion of the equivalent rectangular bandwidth (ERB) of the auditory filter, did not vary greatly with center frequency (0.5, 2, or 6 kHz), suggesting that discrimination did not depend strongly on information derived from phase locking. Glide duration (50 or 400 ms) and glide direction (upward or downward) also had little effect. Thresholds increased with increasing standard transition span, when that span was increased beyond 0.5 ERB. It is concluded that changes in glide extent per se can be discriminated, but this is not done by monitoring just one side of the excitation pattern.     

An investigation of the high-avidity antibody response to glycoprotein 120 of human immunodeficiency virus type 1

The avidity of antibodies for antigens can be measured by determining what remains bound after exposing the antibody-antigen complex to a chaotropic agent such as urea. This method has been gaining popularity for assessing the immune response to the human immunodeficiency virus type 1 (HIV-1) surface glycoprotein gp120 (or its counterpart from simian immunodeficiency virus), during natural infection or after subunit vaccination. High-avidity antibodies have been considered to be a possible correlate of protection. We have examined the avidity assay to determine what it, in fact, measures. First, we studied the development of the anti-gp120 response in seroconverting individuals. Urea elution reduced the polyclonal anti-gp120 titers by 3- to 10-fold. After allowing for the consequent reduction in assay sensitivity, there was no obvious change in the rate of development of the high-avidity and unfractionated antibody responses. Furthermore, in the one individual who developed a strong autologous, virus-neutralizing response, the appearance of neutralizing antibodies and high-avidity antibodies did not coincide. Antibodies to the V3 loop, when present, comprised a major fraction of the polyclonal response that survives urea elution. We next examined the effect of urea elution on the binding to gp120 of a panel of monoclonal antibodies (MAbs). Urea treatment preferentially eluted MAbs to discontinuous rather than continuous epitopes, independent of their affinities. Furthermore, these patterns of epitope stability were unaltered by the presence of polyclonal anti-gp120 antibodies. As most broadly neutralizing anti-gp120 antibodies recognize discontinuous epitopes, this skewing effect must be taken into account when interpreting studies using polyclonal sera.     

In vitro corrosion behavior and microstructure examination of a gallium-based restorative

Concerns of mercury toxicity have led to the development of gallium-based restorative materials to replace dental amalgam. A new gallium-based dental restorative, Galloy, was compared with a high-copper amalgam, Permite, for anodic polarization behavior in deoxygenated Ringer's solution and by immersion testing in normal Ringer's solution at 37 degrees C. Corrosion products were analyzed using energy dispersive X-ray spectrometry and transmission electron diffraction. The data from both sources were consistent with the presence of alpha-Ga2O3 and SnO2 as the primary corrosion products of Galloy. Anodic polarization behavior of Galloy- and Permite-coupled specimens suggests that coupling Galloy with the more noble Permite amalgam may cause accelerated electrochemical corrosion and that Galloy is more corrosion prone than Permite.     

Organization of neural inputs to the suprachiasmatic nucleus in the rat

The circadian timing of the suprachiasmatic nucleus (SCN) is modulated by its neural inputs. In the present study, we examine the organization of the neural inputs to the rat SCN using both retrograde and anterograde tracing methods. After Fluoro-Gold injections into the SCN, retrogradely labeled neurons are present in a number of brain areas, including the infralimbic cortex, the lateral septum, the medial preoptic area, the subfornical organ, the paraventricular thalamus, the subparaventricular zone, the ventromedial hypothalamic nucleus, the posterior hypothalamic area, the intergeniculate leaflet, the olivary pretectal nucleus, the ventral subiculum, and the median raphe nuclei. In the anterograde tracing experiments, we observe three patterns of afferent termination within the SCN that correspond to the photic/raphe, limbic/hypothalamic, and thalamic inputs. The median raphe projection to the SCN terminates densely within the ventral subdivision and sparsely within the dorsal subdivision. Similarly, areas that receive photic input, such as the retina, the intergeniculate leaflet, and the pretectal area, densely innervate the ventral SCN but provide only minor innervation of the dorsal SCN. A complementary pattern of axonal labeling, with labeled fibers concentrated in the dorsal SCN, is observed after anterograde tracer injections into the hypothalamus and into limbic areas, such as the ventral subiculum and infralimbic cortex. A third, less common pattern of labeling, exemplified by the paraventricular thalamic afferents, consists of diffuse axonal labeling throughout the SCN. Our results show that the SCN afferent connections are topographically organized. These hodological differences may reflect a functional heterogeneity within the SCN.     

Fetoplacental vascular tone during fetal circuit acidosis and acidosis with hypoxia in the ex vivo perfused human placental cotyledon

OBJECTIVES: Our purpose was to determine the effects of acidosis and acidosis-hypoxia on fetoplacental perfusion pressure and its response to angiotensin II. STUDY DESIGN: Perfused cotyledons from 14 placentas were studied with either an acidotic fetal circuit perfusate (n = 7) or an acidotic-hypoxic fetal circuit perfusate (n = 7). Each cotyledon's fetal vasculature was initially perfused under standard conditions and bolus injected with 1 x 10(-10) moles of angiotensin II. Fetoplacental perfusate was then replaced with either an acidotic medium (pH 6.90 to 7.00 and Po2 516 to 613 mm Hg) or an acidotic-hypoxic medium (pH 6.90 to 7.00 and Po2 20 to 25 mm Hg) followed by an angiotensin II injection. The vasculature was subsequently recovered with standard perfusate and again injected with angiotensin II. Perfusion pressures within each group were compared by one-way analysis of variance, and results were expressed as mean pressure +/- SEM. RESULTS: Resting fetoplacental perfusion pressure did not change when the fetal circuit perfusate was made acidotic (28 +/- 1 mm Hg vs 25 +/- 2 mm Hg) or acidotic-hypoxic (26 +/- 2 mm Hg vs 25 +/- 2 mm Hg). The maximal fetoplacental perfusion pressure achieved in response to angiotensin II did not differ with an acidotic perfusate (41 +/- 2 mm Hg vs 38 +/- 1 mm Hg) or with an acidotic-hypoxic perfusate (39 +/- 2 mm Hg vs 36 +/- 2 mm Hg). CONCLUSIONS: In the perfused placental cotyledon fetoplacental perfusion pressure and pressor response to angiotensin II are not affected by fetal circuit acidosis or acidosis-hypoxia. This suggests that neither fetal acidosis nor fetal acidosis combined with hypoxia has a direct effect on fetoplacental vascular tone.     

On the relationship between reading, listening and speaking: it's different for people's names

Two experiments are reported that tested predictions derived from the framework of face, object, and word recognition proposed by Valentine, Brennen, and Brédart (1996). The findings were as follows: (1) Production of a celebrity's name in response to seeing the celebrity's face primed a subsequent familiarity decision to the celebrity's printed name. The degree of repetition priming observed was as great as that observed when a familiarity decision to the printed name was repeated in the prime and test phases of the experiment. (2) Making a familiarity decision to an auditory presentation of a celebrity's name primed a familiarity decision to the same celebrity's name presented visually. The magnitude of cross-modality priming was as great as the magnitude of within-modality repetition priming. This result for people's names contrasted with the effects observed in lexical decision tasks, in which no reliable cross-modality priming was observed. The results cannot be accounted for by previous models of face and name processing. They show a marked contrast between processing people's names and processing words. The results support the framework proposed by Valentine et al. (1996). The implications for models of speech production, perception, and reading are discussed, together with the potential of the methodology to elucidate our understanding of proper name processing.     

Phase II study of mitoguazone, cyclophosphamide, doxorubicin, vincristine and prednisone for patients with diffuse histologic subtypes of non-Hodgkin's lymphoma: an Eastern Cooperative Oncology Group Study (PE481)

Mitoguazone, an investigational agent with significant activity in advanced lymphoma, was added to a modified CHOP regimen (COPA) in an effort to improve the activity of standard therapy in 66 previously untreated patients with stages II-IV lymphoma and diffuse histology of intermediate or high grade other than lymphoblastic in this phase II pilot study. The regimen was well tolerated and the complete response rate in diffuse large cell lymphoma was 55%. Sixty-five percent of all complete responders were in complete response for at least one year. Despite these excellent results. it is unlikely that the addition of mitoguazone improved results compared with those obtained with standard therapy alone, since similar results have been frequently reported with the latter.