DNA-directed immobilization of horseradish peroxidase onto porous SiO2optical transducers

ABSTRACT: Multifunctional porous Si nanostructure is designed to optically monitor enzymatic activity of Horseradish Peroxidase. First, an oxidized PSi optical nanostructure, a Fabry-Perot thin film, is synthesized and is used as the optical transducer element. Immobilization of the enzyme onto the nanostructure is performed through DNA-Directed Immobilization. Preliminary studies demonstrate high enzymatic activity levels of the immobilized Horseradish Peroxidase, while maintaining its specificity. The catalytic activity of the enzymes immobilized within the porous nanostructure is monitored in real time by reflective interferometric Fourier transform spectroscopy. We show that we can easily regenerate the surface for consecutive biosensing analysis by mild de-hybridization conditions.     

Kinetics of interaction of HIV fusion protein (gp41) with lipid membranes studied by real-time AFM imaging

One of the most important steps in the process of viral infection is a fusion between cell membrane and virus, which is mediated by the viral envelope glycoprotein. The study of activity of the glycoprotein in the post-fusion state is important for understanding the progression of infection. Here we present a first real-time kinetic study of the activity of gp41 (the viral envelope glycoprotein of human immunodeficiency virus—HIV) and its two mutants in the post-fusion state with nanometer resolution by atomic force microscopy (AFM). Tracking the changes in the phosphatidylcholine (PC) and phosphatidylcholine–phosphatidylserine (PC:PS) membrane integrity over one hour by a set of AFM images revealed differences in the interaction of the three types of protein with zwitterionic and negatively charged membranes. A quantitative analysis of the slow kinetics of hole formation in the negatively charged lipid bilayer is presented. Specifically, analysis of the rate of roughness change for the three types of proteins suggests that they exhibit different types of kinetic behavior.     

Perspective taking and synchronous argumentation for learning the day/night cycle

Changing practices in schools is a very complex endeavor. This paper is about new practices we prompted to foster collaboration and critical reasoning in science classrooms: the presentation of pictures representing different perspectives, small group synchronous argumentation, and moderation of synchronous argumentation. A CSCL tool helped in supporting synchronous argumentation through graphical representations of argumentative moves. We checked the viability of these practices in science classrooms. To do so, we investigated whether these practices led to conceptual learning, and undertook interactional analyses to study the behaviors of students and teachers. Thirty-two Grade 8 students participated in a series of activities on the day/night cycle. Learning was measured by the correctness of knowledge, the extent to which it was elaborated, the mental models that emerged from the explanations, the knowledge integration in explanations, and their simplicity. We showed that participants could learn the day/night cycle concept, as all measures of learning improved. For some students, it even led to conceptual change. However, the specific help provided by teachers during collective argumentation did not yield additional learning. The analysis of protocols of teacher-led collective argumentation indicated that although the teachers’ help was needed, some teachers had difficulties monitoring these synchronous discussions. We conclude that the next step of the design-research cycle should be devoted to (a) the development of new tools directed at helping teachers facilitate synchronous collective argumentation, and to (b) activities including teachers, designers, and researchers for elaborating new strategies to use these tools to improve the already positive learning outcomes from synchronous argumentation.     

Parenting of adult children in an Israeli sample: Parents are always parents.

This qualitative study examines the role of parents with regard to their adult children, by exploring parents' experiences, meanings, and the underlying psychological processes of their parental role. In-depth interviews with healthy Israeli parents (N = 23) aged 56 to 69 explored their perceptions about their parental role. Narrative analysis techniques focused on the content and on the form of the narratives were applied. Five important internal dialectic dimensions emerged: emotional connection and separation; the child as narcissistic extension of the parent and the parent's desire to let the child individuate; growing importance of familial connections and the perceived generation gap; parents' balancing personal needs and the children's needs, and finally, maintaining a hierarchical stance and an equal stance. The results are integrated into the developing theory of intergenerational ambivalence, suggesting a dialectical configuration for the role of parent to adult children. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The moving learner: Object manipulation in virtual reality improves vocabulary learning

A challenging aspect of foreign language acquisition is learning new vocabulary. Research has demonstrated the benefits of motor action to vocabulary learning, though these findings are rarely translated into teaching and learning practices. In this work, we present a novel paradigm for vocabulary learning in a virtual reality environment, capitalizing on the prominent advantages of this technology as an ‘embodied learning’ tool. Hebrew-speaking adults explored a virtual room and learned the Finnish names of 40 daily objects. Every participant learned the new object names under three conditions: (1) Watch-only: watching the object without performing any movement (2) performing an irrelevant movement or (3) performing a manipulation movement that implied its habitual use. Participants completed a word–picture matching test after each training block, as well as additional word–picture matching and recall tests a week after the initial training session. The overall results demonstrate improved comprehension rates for items that were learned in the manipulation movement condition compared to the irrelevant movement condition, both in the initial learning session and 1 week following it. These initial findings suggest that VR technology may indeed hold the potential to offer a more authentic, multisensory and motor context to efficient foreign language learning.     

The pushes and pulls of close relationships: Attachment insecurities and relational ambivalence.

Attachment theorists have emphasized that attachment-anxious individuals are ambivalent in their relational tendencies, wishing to be close to their relationship partners but also fearing rejection. Here we report 6 studies examining the contribution of attachment anxiety and experimentally induced relational contexts (both positive and negative) to explicit and implicit manifestations of (a) attitudinal ambivalence toward a romantic partner and (b) motivational ambivalence with respect to the goals of relational closeness and distance. Attachment-anxious individuals exhibited strong attitudinal ambivalence toward a romantic partner, assessed by both explicit and implicit measures. They also exhibited strong motivational ambivalence regarding closeness (both explicit and implicit), and this motivational conflict was intensified in relational contexts that encouraged either approach or avoidance tendencies. Participants who scored relatively high on avoidant attachment proved to be implicitly ambivalent about distance issues but mainly in negative relational contexts. Several alternative interpretations of the results were considered and ruled out. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Construction and Characterization of Porous SiO2/Hydrogel Hybrids as Optical Biosensors for Rapid Detection of Bacteria

The use of a new class of hybrid nanomaterials as label‐free optical biosensors for bacteria detection (E. coli K12 as a model system) is demonstrated. The hybrids combine a porous SiO₂ (PSiO₂) optical nanostructure (a Fabry–Pérot thin film) used as the optical transducer element and a hydrogel. The hydrogel, polyacrylamide, is synthesized in situ within the nanostructure inorganic host and conjugated with specific monoclonal antibodies (IgGs) to provide the active component of the biosensor. The immobilization of the IgGs onto the hydrogel via a biotin‐streptavidin system is confirmed by fluorescent labeling experiments and reflective interferometric Fourier transform spectroscopy (RIFTS). Additionally, the immobilized IgGs maintain their immunoactivity and specificity when attached to the sensor surface. Exposure of these modified‐hybrids to the target bacteria results in “direct cell capture” onto the biosensor surface. These specific binding events induce predictable changes in the thin‐film optical interference spectrum of the hybrid. Preliminary studies demonstrate the applicability of these biosensors for the detection of low bacterial concentrations in the range of 10³–10⁵ cell mL^?1 within minutes.     

Microstructure and Tensile Properties of Sn-1Ag-0.5Cu Solder Alloy Bearing Al for Electronics Applications

This work investigates the effects of 0.1?wt.% and 0.5?wt.% Al additions on bulk alloy microstructure and tensile properties as well as on the thermal behavior of Sn-1Ag-0.5Cu (SAC105) lead-free solder alloy. The addition of 0.1?wt.% Al reduces the amount of Ag₃Sn intermetallic compound (IMC) particles and leads to the formation of larger ternary Sn-Ag-Al IMC particles. However, the addition of 0.5?wt.% Al suppresses the formation of Ag₃Sn IMC particles and leads to a large amount of fine Al-Ag IMC particles. Moreover, both 0.1?wt.% and 0.5?wt.% Al additions suppress the formation of Cu₆Sn₅ IMC particles and lead to the formation of larger Al-Cu IMC particles. The 0.1?wt.% Al-added solder shows a microstructure with coarse ??-Sn dendrites. However, the addition of 0.5?wt.% Al has a great effect on suppressing the undercooling and refinement of the ??-Sn dendrites. In addition to coarse ??-Sn dendrites, the formation of large Sn-Ag-Al and Al-Cu IMC particles significantly reduces the elastic modulus and yield strength for the SAC105 alloy containing 0.1?wt.% Al. On the other hand, the fine ??-Sn dendrite and the second-phase dispersion strengthening mechanism through the formation of fine Al-Ag IMC particles significantly increases the elastic modulus and yield strength of the SAC105 alloy containing 0.5?wt.% Al. Moreover, both 0.1?wt.% and 0.5?wt.% Al additions worsen the elongation. However, the reduction in elongation is much stronger, and brittle fracture occurs instead of ductile fracture, with 0.5?wt.% Al addition. The two additions of Al increase both solidus and liquidus temperatures. With 0.5?wt.% Al addition the pasty range is significantly reduced and the differential scanning calorimetry (DSC) endotherm curve gradually shifts from a dual to a single endothermic peak.     

Direction of influence between posttraumatic and depressive symptoms during prolonged exposure therapy among children and adolescents.

Objective: Our objective in the present study was to examine the temporal sequencing of posttraumatic and depressive symptoms during prolonged exposure therapy for posttraumatic stress disorder (PTSD) among children and adolescents. Method: Participants were 73 children and adolescents (56.2% female) between the ages of 8 and 18. Participants completed self-report measures of posttraumatic stress and depression prior to every session. Measures included the Child PTSD Symptom Scale, Beck Depression Inventory, and Children's Depression Inventory. Results: Multilevel mediational analyses indicated reciprocal relations during treatment: Changes in posttraumatic symptoms led to changes in depressive symptoms and vice versa. Posttraumatic symptoms accounted for 64.1% of the changes in depression, whereas depressive symptoms accounted for 11.0% of the changes in posttraumatic stress. Conclusions: Prolonged exposure therapy may work primarily by reducing posttraumatic stress, which in turn reduces depression. (PsycINFO Database Record (c) 2011 APA, all rights reserved)