Supermirror hard-x-ray telescope

The practical use of a grazing x-ray telescope is demonstrated for hard-x-ray imaging as hard as 40 keV by means of a depth-graded d-spacing multilayer, a so-called supermirror. Platinum-carbon multilayers of 26 layer pairs in three blocks with a different periodic length d of 3-5 nm were designed to enhance the reflectivity in the energy range from 24 to 36 keV at a grazing angle of 0.3 deg. The multilayers were deposited on thin-replica-foil mirrors by a magnetron dc sputtering system. The reflectivity was measured to be 25%-30% in this energy range; 20 mirror shells thus deposited were assembled into the tightly nested grazing-incidence telescope. The focused hard-x-ray image was observed with a newly developed position-sensitive CdZnTe solid-state detector. The angular resolution of this telescope was found to be 2.4 arc min in the half-power diameter.     

Push-to-Talk Social Talk

This paper presents an exploratory study of college-age students using two-way, push-to-talk cellular radios. We describe the observed and reported use of cellular radio by the participants. We discuss how the half-duplex, lightweight cellular radio communication was associated with reduced interactional commitment, which meant the cellular radios could be used for a wide range of conversation styles. One such style, intermittent conversation, is characterized by response delays. Intermittent conversation is surprising in an audio medium, since it is typically associated with textual media such as instant messaging. We present design implications of our findings.     

Numerical Modeling of Geofoam Embankments

In 2001, the Utah Department of Transportation completed a 4-year $1.4 billion I-15 reconstruction project in Salt Lake City, Utah. This project included widespread use of expanded polystyrene geofoam as lightweight embankment at important utility crossings and where close proximity to existing buildings necessitated minimizing consolidation settlement. This paper presents construction and long-term monitoring results for some of these embankments with numerical modeling of the field measurements. Fast Lagrangian Analysis of Continua, a finite-difference program, was used to estimate the complex stress distribution and the displacements (i.e., strain) that developed in select geofoam embankments. The writers used a bilinear elastic model to produce reasonable estimates of gap closure, block seating, and the subsequent elastic compression of the geofoam embankment at higher stress levels. Such estimations are important for modeling and designing geofoam embankments and potential connections with other systems. The calculation of the complex stress distribution and displacements that develops in a geofoam embankment has application to settlement, lateral earth pressure against retaining and buried walls, slope stability, and seismic design of geofoam embankments.     

Gratitude as moral sentiment: Emotion-guided cooperation in economic exchange.

Economic exchange often pits options for selfish and cooperative benefit against one another. Decisions favoring communal profit at the expense of self-interest have traditionally been thought to stem from strategic control aimed at tamping down emotional responses centered on immediate resource acquisition. In the present article, evidence is provided to argue against this limited view of the role played by emotion in shaping prosociality. Findings demonstrate that the social emotion gratitude functions to engender cooperative economic exchange even at the expense of greater individual financial gains. Using real-time inductions, increased gratitude is shown to directly mediate increased monetary giving within the context of an economic game, even where such giving increases communal profit at the expense of individual gains. Moreover, increased giving occurred regardless of whether the beneficiary was a known individual or complete stranger, thereby removing the possibility that it stemmed from simple awareness of reciprocity constraints. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Characterizing interactions between anxious mothers and their children.

The present study assessed interactions between anxious mothers and their children, using observational techniques to elucidate potential mechanisms of anxiety transmission. Results revealed that anxious mothers were less warm and positive in their interactions with their children, less granting of autonomy, and more critical and catastrophizing in comparison with normal control mothers. Maternal anxiety status appeared to be the primary predictor of maternal warmth during interactions. Child anxiety status was most predictive of maternal granting of autonomy behavior. Maternal behaviors exhibited during interactions were the most salient predictors of child anxiety. Interventions focusing on family interactions that take into account the contributions of both members of the dyad may be more effective in curbing transmission than interventions that solely address maternal or child symptomatology. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

99mTc-HMPAO SPECT of the brain in mild to moderate traumatic brain injury patients: compared with CT--a prospective study

Single photon emission computed tomography (SPECT) with Technetium-99m hexamethyl propylenamine oxime (Tc-99m-HMPAO) was used in 20 patients with mild to moderate traumatic brain injury (TBI) to evaluate the effects of brain trauma on regional cerebral blood flow (rCBF). SPECT scan was compared with CT scan in 16 patients. SPECT showed intraparenchymal differences in rCBF more often than lesions diagnosed with CT scans (87.5% vs. 37.5%). In five of six patients with lesions in both modalities, the area of involvement was relatively larger on SPECT scans than on CT scans. Contrecoup changes were seen in five patients on SPECT alone, two patients with CT alone and one patient had contrecoup lesions on CT and SPECT. Of the eight patients (50%) with skull fractures, seven (43.7%) had rCBF findings on SPECT scan and five (31.3%) demonstrated decrease in rCBF in brain underlying the fracture. All these patients with fractures had normal brain on CT scans. Conversely, extra-axial lesions and fractures evident on CT did not visualize on SPECT, but SPECT demonstrated associated changes in rCBF. Although there is still lack of clinical and pathological correlation, SPECT appears to be a promising method for a more sensitive evaluation of axial lesions in patients with mild to moderate TBI.     

Nucleus accumbens dopamine modulates response rate but not response timing in an interval timing task.

While previous work has demonstrated that systemic dopamine manipulations can modulate temporal perception by altering the speed of internal clock processes, the neural site of this modulation remains unclear. Based on recent research suggesting that changes in incentive salience can alter the perception of time, as well as work showing that nucleus accumbens (NAc) shell dopamine (DA) levels modulate the incentive salience of discriminative stimuli that predict instrumental outcomes, we assessed whether microinjections of DA agents into the NAc shell would impact temporal perception. Rats were trained on either a 10-s or 30-s temporal production procedure and received intra-NAc shell microinfusions of sulpiride, amphetamine, and saline. Results showed that NAc DA modulations had no effect on response timing, but intra-NAc shell sulpiride microinfusions significantly decreased response rates relative to saline and amphetamine. Our findings therefore suggest that neither NAc shell DA levels, nor the resultant changes in incentive salience signaled by this structure, impact temporal control. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

The influence of matrix microstructure

The low-cycle and high-cycle fatigue behavior and cyclic response of naturally aged and artificially aged 2219/TiC/15_p and unreinforced 2219 Al were investigated utilizing plastic strain-controlled and stress-controlled testing. The cyclic response of both the reinforced and un-reinforced materials was similar for all plastic strain amplitudes tested except that the saturation stress level for the composite was always greater than that of the unreinforced material. The cyclic response of the naturally aged materials exhibited cyclic hardening and, in some cases, cyclic softening, while the cyclic response for the artificially aged materials showed no evidence of either cyclic hardening or softening. The higher ductility of the unreinforced material made it more resistant to fatigue failure at high strains, and thus, at a given plastic strain, it had longer fatigue life. It should be noted that the tensile ductilities of the 2219/TiC/15_p were significantly higher than those previously reported for 2XXX-series composites. During stress-controlled test-ing at stresses below 220 MPa, the presence of TiC particles lead to an improvement in fatigue life. Above 220 MPa, no influence of TiC reinforcement on fatigue life could be detected. In both the composite and unreinforced materials, the low-cycle and high-cycle fatigue lives were found to be virtually independent of matrix microstructure. G.M. VYLETEL, formerly Graduate Student, Department of Materials Science and Engineering, The University of Michigan D.C. VAN AKEN, formerly Assistant Professor, Department of Materials Science and Engineering, The University of Michigan     

Secondary Prestressing Moments in Rehabilitated Posttensioned Bridges

Typical rehabilitation procedures for posttensioned slab bridges involve removing concrete from the top surface of the bridge, replacing corroded reinforcement, and resurfacing with new concrete. These permanently change primary and thus secondary prestressing moments. Continuous posttensioned bridges often rely on secondary prestressing moments to counteract dead and live load moments over interior supports and thus changes caused by rehabilitation impact serviceability and, particularly, ultimate limit states. An analysis procedure is derived for computing the changes in prestressing moments caused by rehabilitation. The impact of rehabilitation on a two-span continuous voided-slab bridge is evaluated considering rehabilitation schemes where both spans are rehabilitated simultaneously,?or where one span is completely rehabilitated before work commences on the other. Rehabilitation creates concentrated primary prestressing moments at the exterior supports and at interfaces between solid and voided regions that reduce or even reverse the secondary moment at the interior support. The two-span scheme virtually eliminates secondary prestressing moments and, contrary to intuition, the span-by-span scheme has a markedly greater impact.     

Mechanical Model for Unbonded Seven-Wire Tendon with Symmetric Wire Breaks

A mechanical model for unbonded seven-wire tendons with broken wires that accounts for the effects of interwire friction and contact forces between the tendon and surrounding concrete is derived. The model is an essential tool for predicting the response, and reliability, of unbonded posttensioned concrete structures containing corroded tendons with broken wires. For the case where the broken wires are symmetrically arranged around the tendon cross section, the model predicts: (1) the strain variation with distance from the break in the broken and unbroken wires; (2) the affected length, where strains in the broken wires are less than those in the unbroken wires; and (3) the prestress force remaining after wire breaks occur. The affected length has practical significance because techniques used in practice to detect wire breaks will fail if performed outside the affected length. Experimental data obtained using a novel strongback beam confirm the response predicted by the model and indicate the coefficient of interwire friction is 0.164 for uncorroded tendons.