Development and calibration of mirrors and gratings for the soft x-ray materials science beamline at the Linac Coherent Light Source free-electron laser

This work discusses the development and calibration of the x-ray reflective and diffractive elements for the Soft X-ray Materials Science (SXR) beamline of the Linac Coherent Light Source (LCLS) free-electron laser (FEL), designed for operation in the 500 to 2000 eV region. The surface topography of three Si mirror substrates and two Si diffraction grating substrates was examined by atomic force microscopy (AFM) and optical profilometry. The figure of the mirror substrates was also verified via surface slope measurements with a long trace profiler. A boron carbide (B4C) coating especially optimized for the LCLS FEL conditions was deposited on all SXR mirrors and gratings. Coating thickness uniformity of 0.14 nm root mean square (rms) across clear apertures extending to 205 mm length was demonstrated for all elements, as required to preserve the coherent wavefront of the LCLS source. The reflective performance of the mirrors and the diffraction efficiency of the gratings were calibrated at beamline 6.3.2 at the Advanced Light Source synchrotron. To verify the integrity of the nanometer-scale grating structure, the grating topography was examined by AFM before and after coating. This is to our knowledge the first time B4C-coated diffraction gratings are demonstrated for operation in the soft x-ray region.     

Examining alcohol outcome expectancies in laboratory and naturalistic bar settings: A within-subject experimental analysis.

Using a within-subject design, this study investigated the situational-specificity hypothesis, namely that alcohol outcome expectancies (AOEs), subjective evaluations of AOEs, and the speed with which AOEs are accessed from memory vary as a function of environmental setting. Thirty-nine undergraduates (20 women), of legal drinking age, responded to the Comprehensive Effects of Alcohol questionnaire (K. Fromme, E. Stroot, & D. Kaplan, 1993) that was presented on a laptop computer in 2 counterbalanced contexts: a laboratory setting and an on-campus bar. Response latencies served as dependent measures for memory accessibility. Consistent with previous research (A.-M. Wall, S. A. McKee, & R. E. Hinson, 2000), evidence in support of the situational-specificity hypothesis was found. Specifically, environmental context influenced undergraduates' expectations concerning alcohol's effects and subjective evaluations of AOEs, as well as the speed with which specific AOEs were accessed from memory. Overall, these findings suggest the need for greater attention to situational variation in AOEs. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Solid Freeform Fabrication of Aqueous Alumina–Poly(vinyl alcohol) Gelcasting Suspensions

Solid freeform fabrication of aqueous alumina–poly(vinyl alcohol) (Al₂O₃–PVA) gel-casting suspensions was conducted using a computer-controlled extrusion apparatus fitted with a two-nozzle delivery system. The impact of casting parameters on the shear rate profiles experienced during deposition was evaluated via conventional flow analysis and computer simulations. In addition, the influence of these parameters on line resolution/uniformity, printability, and as-cast component properties was studied using laser profilometry, optical microscopy, and scanning electron microscopy. Continuous printablity was achieved for tip diameters ranging from 0.254 to 1.370 mm for all mixing rates and suspension compositions studied. Printed lines were uniform with good edge definition, and line dimensions were independent of mixing rate for these process conditions. The Al₂O₃ volume fraction (φ_Al2O3) in the as-deposited layers depended on casting conditions and cross-linking agent concentration, where (φ_Al2O3 increased with decreased tip diameter and increased cross-linking agent concentration. The free-formed Al₂O₃ components exhibited uniform particle packing, with minimal macrodefects (e.g., slumping or staircasing) and no discernable microdefects (e.g., bubbles or cracking).     

The characterization and interpretation of ductile fracture mechanisms in AL2024-T351 using X-ray and focused ion beam tomography

This paper describes an experimental investigation into the mechanism of ductile fracture in the aluminum alloy AL2024-T351 using a combination of synchrotron X-ray and focused ion beam tomography. Microstructural features that influence fracture at the micro- and nanoscale were characterized in virgin material in three-dimensions. The nature and volume fraction of ductile damage was then quantified as a function of distance below the fracture surfaces of tested notched and fatigue pre-cracked laboratory specimens. In both specimens the ductile fracture process initiates with the brittle fracture of large irregular intermetallic particles at low levels of plastic strain. With increasing plasticity, the resulting voids grow and combine with pre-existing porosity to increase the overall void volume fraction. Once a critical void volume fraction is attained, final failure occurs by the fracture or decohesion of dispersoids from the matrix, initiating a second population of nanoscale voids, which interlinks the larger voids. The critical void volume fraction for coalescence and the distribution of ductile damage below the fracture surface is markedly different between blunt-notched and pre-cracked specimens, with notched specimens exhibiting a significantly lower critical void volume fraction and a more extensive distribution of ductile damage below the fracture surface than is observed in pre-cracked specimens. This observation, related to the gradients in stress triaxiality and plastic strain in each specimen type, has important implications for the calibration of ductile damage mechanics models against notched-specimen data and their use to predict crack behavior in engineering structures.     

Paradoxical effects of interprofessional briefings on OR team performance

Our recent research has found that structured preoperative team briefings can reduce communication failures, improve the knowledge and practice of operating room (OR) team members, and garner broad support from surgeons, nurses, and anesthesiologists. However, we have also encountered challenges and unexpected, negative effects. Using qualitative analysis of fieldnotes from 302 preoperative team briefings, we identified five paradoxical findings: team briefings could mask knowledge gaps, disrupt positive communication, reinforce professional divisions, create tension, and perpetuate a problematic culture. Fifteen percent of the briefings exhibited only these paradoxical effects without any apparent utility. We describe these paradoxical findings and analyze them in relation to educational, functional, structural, and cultural factors. This analysis is instructive not only for re-engineering the briefing process, but also for revealing dynamics that may continue to impede optimal interprofessional performance.     

Identification and distribution of photoreceptor subtypes in the neotenic tiger salamander retina

The neotenic tiger salamander retina is a major model system for the study of retinal physiology and circuitry, yet there are unresolved issues regarding the organization of the photoreceptors and the photoreceptor mosaic. The rod and cone subtypes in the salamander retina were identified using a combination of morphological and immunocytochemical markers for specific rod and cone opsin epitopes. Because the visual pigment mechanisms present in the tiger salamander retina are well characterized and the antibodies employed in these studies are specific for particular rod and cone opsin epitopes, we also were able to identify the spectral class of the various rod and cone subtypes. Two classes of rods corresponding to the "red" and "green" rods previously reported in amphibian retinas were identified. In serial semithin section analyses, rods and cones comprised 62.4+/-1.4% and 37.6+/-1.4% of all photoreceptors, respectively. One rod type comprising 98.0+/-0.7% of all rods showed the immunological and morphological characteristics of "red" rods, which are maximally sensitive to middle wavelengths. The second rod subtype comprised 2.0+/-0.7% of all rods and possessed the immunological and morphological characteristics of "green" rods, which are maximally sensitive to short wavelengths. By morphology four cone types were identified, showing three distinct immunological signatures. Most cones (84.8+/-1.5% of all cones), including most large single cones, the accessory and principal members of the double cone, and some small single cones, showed immunolabeling by antisera that recognize long wavelength-sensitive cone opsins. A subpopulation of small single cones (8.4+/-1.7% of all cones) showed immunolabeling for short wavelength-sensitive cone opsin. A separate subpopulation of single cones which included both large and small types (6.8+/-1.4% of all cones) was identified as the UV-Cone population and showed immunolabeling by antibodies that recognize rod opsin epitopes. Analysis of flatmounted retinas yielded similar results. All photoreceptor types appeared to be distributed in all retinal regions. There was no obvious crystalline organization of the various photoreceptor subtypes in the photoreceptor mosaic.     

Induction of the chemokine beta peptides, MIP-1 alpha and MIP-1 beta, by lipopolysaccharide is differentially regulated by immunomodulatory cytokines gamma-IFN, IL-10, IL-4, and TGF-beta

The macrophage occupies a central role in the host response to invasion, exerting its control over the developing inflammatory response largely through the elaboration of an assortment of endogenous mediators including many cytokines. The beta chemokine peptides, macrophage inflammatory protein [MIP]-1 alpha and MIP-1 beta, are two such effectors markedly up-regulated in macrophages following exposure to bacterial lipopolysaccharide (LPS). These highly homologous peptides, like the other members of the beta chemokine family, exhibit diverse but partially overlapping biological activity profiles, suggesting that the cellular participants and intensity of an inflammatory response may in part be regulated by selective expression of these chemokines. Studies reported here demonstrate that, in contrast to the "balanced" MIP-1 alpha/MIP-1 beta chemokine responses of LPS-stimulated macrophage cultures in vitro, circulating levels of MIP-1 beta are significantly higher than those of MIP-1 alpha following LPS administration in vivo. Further studies have revealed that several immunomodulatory cytokines known to be up-regulated in vivo as a consequence of exposure to an invasive stimulus (gamma-IFN, IL-10, IL-4, and transforming growth factor [TGF]-beta) down-regulated the LPS-induced release of MIP-1 alpha by macrophages in vitro, but spared the MIP-1 beta response. This altered pattern of secretion may explain, at least in part, the high circulating levels of MIP-1 beta relative to MIP-1 alpha observed in vivo in response to LPS challenge.     

Randomized Controlled Trial for Behavioral Smoking and Weight Control Treatment: Effect of Concurrent Versus Sequential Intervention.

The authors compared simultaneous versus sequential approaches to multiple health behavior change in diet, exercise, and cigarette smoking. Female regular smokers (N = 315) randomized to 3 conditions received 16 weeks of behavioral smoking treatment, quit smoking at Week 5, and were followed for 9 months after quit date. Weight management was omitted for control and was added to the 1st 8 weeks for early diet (ED) and the final 8 weeks for late diet (LD). ED lacked lasting effect on weight gain, whereas LD initially lacked but gradually acquired a weight-suppression effect that stabilized (p = .004). Behavioral weight control did not undermine smoking cessation and, when initiated after the smoking quit date, slowed the rate of weight gain, supporting a sequential approach. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A Personalization Effect in Multimedia Learning: Students Learn Better When Words Are in Conversational Style Rather Than Formal Style.

Students received a personalized or nonpersonalized version of a narrated animation explaining how the human respiratory system works. The narration for the nonpersonalized version was in formal style, whereas the narration for the personalized version was in conversational style in which "the" was changed to "your" in 12 places. In 3 experiments, students who received the personalized version scored significantly higher on transfer tests but not on retention tests than did students who received the nonpersonalized version. The results are consistent with a cognitive theory of multimedia learning in which personalization causes students to actively process the incoming material. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Fabrication of interpenetrating polymer network to enhance the biological activity of synthetic hydrogels

A three dimensional porous hydrogel with suitable biological and mechanical properties are required for bone tissue engineering. Hydrogels of poly(lactic-ethylene oxide fumarate) (PLEOF), crosslinked with poly(ethylene glycol)-diacrylate (PEG-da) have desirable mechanical properties, however, their application for bone regeneration is limited due to the lack of cell motif sites within their structure. The aim of this study was to incorporate a naturally derived polymer such as gelatin into PLEOF hydrogels to promote their biological properties. Interpenetrating polymer network (IPN) was used as an efficient technique to acquire uniform mixture of these two polymers. Additionally gas foaming agents were used to create pores with average diameter of 250 μm in these IPN hydrogels. The concentrations of PEG-da and gelatin were optimized to tune the mechanical strength and degradation properties of these hydrogels. A compression modulus of 500 kPa was achieved for hydrogel fabricated with 400 mg/ml PLEOF, 200 mg/ml PEG-da and 150 mg/ml gelatin. The addition of gelatin to PLEOF elevated the compression modulus by two-fold and decreased the energy loss by 40%. The result of protein analysis demonstrated that IPN substantially enhanced the retention of physically crosslinked gelatin in the 3D structure of hydrogel. More than 50% of gelatin was retained in IPN hydrogel after two weeks of incubation in simulated physiological environment. Preserving gelatin in the hydrogel structure provides cell motif sites for a longer period of time, which is desirable for uniform cell proliferation. In vitro studies showed that primary human osteoblast cells adhered and proliferated in PLEOF-gelatin hydrogel. These results demonstrated the potential of using this IPN hydrogel for bone tissue engineering.