Feature and rule selection in categorization tasks.

The process by which stimuli are assigned to categories has been traditionally conceptualized as bottom-up. Accordingly, stimulus features are supposed to be the fundamental units of analysis, and categorization to be accomplished on the basis of feature category correlations (cue validities). Alternatively, top-down processes are invoked, in which case one begins with a given categorization rule and then assigns stimuli to categories on that basis. Bottom-up and top-down views share a fundamental weakness, namely, they are unable to specify how features or rules, respectively, are acquired. This difficulty can be overcome if it is assumed that the process starts with neither features nor rules, but with stimuli. Then, as a result of experience with stimuli belonging to different categories, the cognitive system discovers and uses locally constructed features that maximally discriminate between the categories at hand. According to this view, the relationship between a target and a contrast category is the main factor affecting what subjects learn about each. Two experiments were conducted to explore this hypothesis. Both experiments support the notion that the relationship between the target and contrast category significantly determines which critical features are extracted as being defining of either category. In particular, it determines the level of generality of these features. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Within-story recalls and the retention of ideas in prose processing.

Examined the facilitatory effect of within-story recalls on later recalls as a function of the interval elapsed between presentation of a to-be-recalled idea and its 1st recall, using 75 undergraduates. Results show that (1) specific ideas contained in a prose passage were forgotten rapidly during story presentation, (2) only those ideas that were successfully recalled during story presentation were likely to be recalled on later tests, and (3) the probability of a later recall given a successful within-story recall increased with retention interval. Findings suggest that frequent test questions, interspersed while listening to or reading an expository passage, were most beneficial for long-term retention. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Death-effector filaments: novel cytoplasmic structures that recruit caspases and trigger apoptosis

The death-effector domain (DED) is a critical protein interaction domain that recruits caspases into complexes with members of the TNF-receptor superfamily. Apoptosis can also be induced by expressing certain DED-containing proteins without surface receptor cross-linking. Using Green Fluorescent Protein to examine DED-containing proteins in living cells, we show that these proteins cause apoptosis by forming novel cytoplasmic filaments that recruit and activate pro-caspase zymogens. Formation of these filaments, which we term death-effector filaments, was blocked by coexpression of viral antiapoptotic DED-containing proteins, but not by bcl-2 family proteins. Thus, formation of death-effector filaments allows a regulated intracellular assembly of apoptosis-signaling complexes that can initiate or amplify apoptotic stimuli independently of receptors at the plasma membrane.     

Analysis of the evolution of microcreep during physical aging and mechanical deformation in poly(methyl methacrylate) using a microstructural model

The evolution of poly(methyl methacrylate) (PMMA) during physical aging at 90°C is followed by torsional microcreep tests. On the aged specimen a longitudinal stress is applied which induces a strain of 5 percent after 30 days of creep. The torsional microcreep tests are performed during the longitudinal creep in order to compare the structure evolution of PMMA caused by straining with its evolution measured during aging. The microcreep, for the first 800s, follows a reversible logarithmic law. In this stage the mobile defects achieve their activated form which is perfectly reversible when unloaded. The physical aging reduces this logarithmic part of microcreep. This is due to the decrease of either the number or the volume of the mobile defects. Beyond a critical elongation ? = 1 percent, the longitudinal straining has just the opposite influence, i.e., the logarithmic part of microcreep increases. This critical elongation ? = 1 percent corresponds to the beginning of the steady state longitudinal creep. The transient that precedes this steady state has no detectable influence on the structure of the specimen.     

Effects of the level of asphyxia during delivery on viability at birth and early postnatal vitality of newborn pigs

Newborn pigs (n = 117) were used to provide information on the relationships of degree of asphyxia during delivery, viability at birth, and some striking aspects of postnatal vitality including survival, interval between birth and first udder contact and between birth and first suckling, rectal temperature at 24 h of life (RT24), and growth rate over the first 10 d of life. The degree of asphyxia at birth was estimated from cord blood pCO2, pH, and lactate levels. Onset of respiration, heart rate, skin color, and attempts to stand during the first minute after birth were used to estimate the viability score. Neonatal asphyxia, i.e., decreased blood pH and increased blood pCO2 and lactate, was associated with the production of unusually high levels of catecholamines. The degree of asphyxia increased with late position in the birth order (P < .01) and was higher in piglets born posteriorly (P < 0.5). Further, the average blood pCO2 within a litter increased (P < .05) with litter size. The was an inverse relationship between the degree of asphyxia and the viability score (P < .001). Highly viable piglets reached the udder more rapidly (P < .001) and had a higher RT24 (P < .001) than those of low viability. Plasma glucose concentrations increased with blood pCO2 and plasma epinephrine concentrations (P < .001). Neonatal asphyxia reduced postnatal vitality by delaying the first contact with the udder (P < .03) and was associated with a lower RT24 (P < .05), growth rate (P < .001), and survival over 10 d (P < 0.06). These variables, i.e., interval between birth and first udder contact, RT24, and growth rate, were correlated with birth weight (P < .001); RT24 was also shown to decrease (P < .001) with the time taken to reach the udder. Overall, results suggest that piglet suffering from asphyxia during delivery are less viable at birth and less prone to adapt to extrauterine life.     

Galanin positively modulates prolactin secretion in normal women

It is widely accepted that, in man, galanin, a neuropeptide, has a clear GH-releasing effect while its stimulatory influence on PRL secretion is matter of debate. To clarify this point, in 6 normal young women (23-35 yr) in their early follicular phase, we studied the effect of galanin (pGAL, 80 pmol/kg. min infused i.v. over 60 min) on both basal and arginine (ARG, 0.5 g/kg i.v. in 30 min), TRH (400 micrograms i.v. as a bolus at 0 min) or metoclopramide (MCP, 10 mg i.v. as a bolus at 0 min)-stimulated PRL secretion. GAL infusion failed to significantly increase basal PRL levels (peak vs baseline: 12.2 +/- 3.6 vs 8.7 +/- 1.2 micrograms/L) but counteracted the spontaneous PRL decrease observed during saline infusion (AUC: 1216.6 +/- 282.1 vs 672.0 +/- 94.5 micrograms.min/L; p < 0.05). GAL infusion clearly enhanced the PRL response to TRH (AUC: 5806.3 +/- 743.0 vs 3952.1 +/- 423.9 micrograms.min/L, p < 0.05) and ARG (AUC: 3676.8 +/- 382.6 vs 2638.9 +/- 287.0 micrograms.min/L, p < 0.05), respectively. On the other hand, GAL failed to modify the MCP-induced PRL response (AUC: 15409.5 +/- 2085.3 vs 14,787.9 +/- 2045.5 micrograms.min/L). The PRL response to MCP was higher than that to TRH (p < 0.01) which, in turn, was higher than that to ARG (p < 0.01). During GAL infusion, the PRL response to TRH or ARG remained lower (p < 0.01) than that after MCP administration. Thus, in conclusion, present data demonstrate that in normal women galanin enhances the PRL response to ARG and TRH but fails to modify that induced by dopamine receptor blockade with metoclopramide. Based on evidence that the inhibition of central dopaminergic activity inhibits the lactotrope responsiveness to dopaminergic antagonists or TRH, it is unlikely that galanin influences PRL secretion via inhibition of dopaminergic tone.     

PVC membrane potentiometric sensor based on 5-pyridino-2,8-dithia[9](2,9)-1,10-phenanthroline-phane for selective determination of neodymium(III)

Spectrofluorometric studies on the binding properties of 5-pyridino-2,8-dithia[9](2,9)-1,10-phenanthrolinephane (L) toward La3+, Sm3+, Gd3+, Yb3+, and Nd3+ in methanol solution revealed the occurrence of both 1:1 and 2:1 (ligand/metal) complexation with a stability order of Nd3+ > Yb3+ > Gd3+ > Sm3+ > La3+. Consequently, L was used as a suitable neutral ionophore for the preparation of a novel polymeric membrane-selective electrode for Nd3+ ion. The electrode exhibited a Nernstian response over a wide concentration range (1.0 x 10(-6)-1.0 x 10(-2) M) with a low limit of detection of 7.9 x 10(-7) M. The electrode possesses a fast response time of <5 s and can be used for at least 9 weeks without observing any considerable deviation. The proposed electrode revealed a very good selectivity for Nd3+ over a wide variety of alkali, alkaline earth, transition, and heavy metal ions, including members of the lanthanide family other than Nd3+. The potentiometric response of the electrode is independent of the pH of test solution in the pH range 4.0-6.5. The proposed electrode was successfully applied to the recovery of Nd3+ ion from tap water samples and, also, as an indicator electrode, in potentiometric titration of neodymium(III) ions.     

Improved algorithm for calculations of Rayleigh-scattering optical depth in standard atmospheres

Precise calculations of the total Rayleigh-scattering optical depth have been performed at 88 wavelengths ranging from 0.20 to 4.00 microm for the six well-known standard atmosphere models by integrating the volume Rayleigh-scattering coefficient along the vertical atmospheric path from sea level to a 120-km height. The coefficient was determined by use of an improved algorithm based on the Ciddor algorithm [Appl. Opt. 35, 1566 (1996)], extended by us over the 0.20-0.23-microm wavelength range to evaluate the moist air refractive index as a function of wavelength, air pressure, temperature, water-vapor partial pressure, and CO2 volume concentration. The King depolarization factor was also defined taking into account the moisture conditions of air. The results indicate that the influence of water vapor on Rayleigh scattering cannot be neglected at tropospheric altitudes: for standard atmospheric conditions represented in terms of the U.S. Standard Atmosphere (1976) model, the relative variations produced by water vapor in the Rayleigh scattering parameters at a 0.50-microm wavelength turn out to be equal to -0.10% in the moist air refractivity at sea level (where the water-vapor partial pressure is equal to approximately 7.8 hPa), -0.04% in the sea-level King factor, -0.24% in the sea-level Rayleigh-scattering cross section, and -0.06% in the Rayleigh-scattering optical depth.