Pericyclic Organometallic Reactions. Substituent Effects on Cycloadditions and Rearrangements of (η4-cycloheptatriene)Fe(CO)3 Derivatives

The mechanism of the reactions of (η⁴-cycloheptatrien-1-al)Fe(CO)₃ and its ethyleneglycol acetal with tetracyanoethylene (TCNE) was studied. The aldehyde undergoes a fast reversible 3+2 cycloaddition involving the free aldehyde-substituted double bond, and a slow irreversible 3+2 cycloaddition at the coordinated site. The latter, σ,π-allylic complex undergoes a slow interconversion with the corresponding 5 +2 isomer via the pericyclic [3,3]-sigmahaptotropic rearrangement. In contrast, the acetal reacts with TCNE at the free acetal-substituted double bond to give a single kinetic 3+2 adduct, which, under thermodynamic conditions, undergoes a [4,4]-sigmahaptotropic rearrangement to the 6 + 2 adduct. The reaction kinetics was followed by ¹H NMR. The effect of substituents on the reaction course is discussed, and the detailed mechanism of both the cycloadditions and rearrangements is described.     

Perception of density by pedestrians on urban paths: an experiment in virtual reality

This paper presents a virtual reality experiment in a controlled visualization laboratory. The study explores the impact of morphology on the perceived density by participants along pedestrian paths. The issue addressed is the intensification of existing urban centres, where over-crowding may diminish their viability. The basic hypothesis is that increased visibility in a given urban space will be evaluated with a lower perceived density, and in some cases, a preferred view will decrease the participant’s perceived density. This research can contribute to future research and practice for the planning and design of sustainable urban environments for the benefit of pedestrian users.     

Neurochemical Alterations in Social Anxiety Disorder (SAD): A Systematic Review of Proton Magnetic Resonance Spectroscopic Studies

(1) Objective: Considering that current knowledge of mechanisms involved in the molecular pathogenesis of Social Anxiety Disorder (SAD) is limited, we conducted a systematic review to evaluate cumulative data obtained by Proton Magnetic Resonance Spectroscopic (¹H MRS) studies. (2) Methods: A computer-based literature search of Medline, EMBASE, PsycInfo, and ProQuest was performed. Only cross-sectional studies using ¹H MRS techniques in participants with SAD and healthy controls (HCs) were selected. (3) Results: The search generated eight studies. The results indicated regional abnormalities in the ‘fear neurocircuitry’ in patients with SAD. The implicated regions included the anterior cingulate cortex (ACC), dorsomedial prefrontal cortex (dmPFC), dorsolateral prefrontal cortex (dlPFC), insula, occipital cortex (OC), as well as the subcortical regions, including the thalamus, caudate, and the putamen. (4) Conclusions: The evidence derived from eight studies suggests that possible pathophysiological mechanisms of SAD include impairments in the integrity and function of neurons and glial cells, including disturbances in energy metabolism, maintenance of phospholipid membranes, dysregulations of second messenger systems, and excitatory/inhibitory neurocircuitry. Conducting more cross-sectional studies with larger sample sizes is warranted given the limited evidence in this area of research.     

Effects of surface microtopography on the assembly of the osteoclast resorption apparatus

Bone degradation by osteoclasts depends on the formation of a sealing zone, composed of an interlinked network of podosomes, which delimits the degradation lacuna into which osteoclasts secrete acid and proteolytic enzymes. For resorption to occur, the sealing zone must be coherent and stable for extended periods of time. Using titanium roughness gradients ranging from 1 to 4.5 µm R_a as substrates for osteoclast adhesion, we show that microtopographic obstacles of a length scale well beyond the range of the ‘footprint’ of an individual podosome can slow down sealing-zone expansion. A clear inverse correlation was found between ring stability, structural integrity and sealing-zone translocation rate. Direct live-cell microscopy indicated that the expansion of the sealing zone is locally arrested by steep, three-dimensional ‘ridge-like barriers’, running parallel to its perimeter. It was, however, also evident that the sealing zone can bypass such obstacles, if pulled by neighbouring regions, extending through flanking, obstacle-free areas. We propose that sealing-zone dynamics, while being locally regulated by surface roughness, are globally integrated via the associated actin cytoskeleton. The effect of substrate roughness on osteoclast behaviour is significant in relation to osteoclast function under physiological and pathological conditions, and may constitute an important consideration in the design of advanced bone replacements.     

Networking strategies of young biotechnology firms in Israel

This article examines the factors involved in the network development process in young biotechnology firms in Israel. The findings show that this process occurs as a result of the firm’s existing network and networking resources, as well as of exposure and activation routines that are implemented by the firm and targeted for the network development process. Exposure routines refer to the frequency at which the firm uses existing tools, such as partnering events, conferences, and publications. Activation routines refer to the extent to which the firm uses its networking resources for the benefit of the networking process.     

CK2 Phosphorylation Is Required for Regulation of Syntaxin 1A Activity in Ca2+-Triggered Release in Neuroendocrine Cells

The polybasic juxtamembrane region (5RK) of the plasma membrane neuronal SNARE, syntaxin1A (Syx), was previously shown by us to act as a fusion clamp in PC12 cells, as charge neutralization of 5RK promotes spontaneous and inhibits Ca²⁺-triggered release. Using a Syx-based FRET probe (CSYS), we demonstrated that 5RK is required for a depolarization-induced Ca⁺²-dependent opening (close-to-open transition; CDO) of Syx, which involves the vesicular SNARE synaptobrevin2 and occurs concomitantly with Ca²⁺-triggered release. Here, we investigated the mechanism underlying the CDO requirement for 5RK and identified phosphorylation of Syx at Ser-14 (S14) by casein kinase 2 (CK2) as a crucial molecular determinant. Thus, following biochemical verification that both endogenous Syx and CSYS are constitutively S14 phosphorylated in PC12 cells, dynamic FRET analysis of phospho-null and phospho-mimetic mutants of CSYS and the use of a CK2 inhibitor revealed that the S14 phosphorylation confers the CDO requirement for 5RK. In accord, amperometric analysis of catecholamine release revealed that the phospho-null mutant does not support Ca²⁺-triggered release. These results identify a functionally important CK2 phosphorylation of Syx that is required for the 5RK-regulation of CDO and for concomitant Ca²⁺-triggered release. Further, also spontaneous release, conferred by charge neutralization of 5RK, was abolished in the phospho-null mutant.     

Family processes as pathways from income to young children's development.

A variety of family processes have been hypothesized to mediate associations between income and young children's development. Maternal emotional distress, parental authoritative and authoritarian behavior (videotaped mother-child interactions), and provision of cognitively stimulating activities (Home Observation for Measurement of the Environment [HOME] scales) were examined as possible mediators in a sample of 493 White and African American low-birth-weight premature infants who were followed from birth through age 5. Cognitive ability was assessed by standardized test, and child behavior problems by maternal report, when the children were 3 and 5 years of age. As expected, family income was associated with child outcomes. The provision of stimulating experiences in the home mediated the relation between family income and both children's outcomes; maternal emotional distress and parenting practices mediated the relation between income and children's behavior problems. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Copolymerization of styrene with vinyl monomers substituted by nitrile and sulfonyl groups

Two trisubstituted vinyl monomers, 2-phenylsulfonyl (crotonitrile) and 2-phenylsulfonyl (cinnamonitrile) were synthesized and characterized by proton NMR, IR, ¹³C-NMR, and mass spectroscopy. Both monomers were copolymerized with styrene by free-radical initiation. The copolymerization parameters of both systems were determined, and the mutual reactivity of the monomers of the two systems is discussed. The new copolymers were characterized by proton NMR and IR spectroscopy, melting range, T_g, and intrinsic viscosity. The influence of the chemical structures of the two comonomers on these two latter properties of the copolymers is discussed.