Topical Review: Impact of Central Vision Loss on Navigation and Obstacle Avoidance while Walking.

SIGNIFICANCE: Individuals with central vision loss are at higher risk of injury when walking and thus may limit trips outside the home. Understanding the mobility challenges associated with central vision loss (CVL) can lead to more effective interventions.A systematic literature review focusing on mobility in CVL was conducted. Using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses method, 2424 articles were identified in 4 databases (PsycINFO, APA PsycArticles, PubMed, and Web of Science). To be included within this review, the study methodology needed to be related to the three components of walking: (1) navigation, defined as the ability to reach a target destination; (2) obstacle avoidance, defined as the ability to avoid collisions with obstacles located at various heights and directions; and (3) street crossing, defined as the ability to both navigate a path and avoid collisions in a traffic environment. The methodology also needed to be empirical. Case studies, unstructured observational studies, studies based on self-report, research proposals, and existing systematic reviews were excluded. Titles, abstracts, and full text of identified articles were screened, yielding 26 articles included in the review. Results showed that, in many tasks, individuals with CVL can accomplish a level of performance comparable with individuals with normal vision. Differences between normal and impaired vision were due to either age or how the groups completed the task. For example, individuals with CVL could cross a street successfully but did so less safely (i.e., smaller safety margins) than individuals with normal vision. To identify new interventions for CVL, future research should focus on the differences in the mechanisms underlying mobility between individuals with normal and impaired vision rather than solely on performance differences.

Neural correlates of sustained attention and cognitive control in depression and rumination: An ERP study.

Attention problems and risk for depression are often associated with a trait tendency towards rumination. Although theorists have linked rumination to deficits in attention, the nature of its effect on cognitive control, and how it may interact with depression remains unclear. Therefore, this study explored cognitive control in depression and two forms of rumination (brooding and reflection) associated with passive and analytic responses to negative mood, respectively. An electrophysiological Go/NoGo vigilance task was used to measure N2 and P3 event related potentials (ERPs) associated with the recruitment of cognitive resources and inhibition of motor responses in the task, respectively. Participants continuous levels of depressive symptoms and trait levels of each form of rumination were also obtained by self-report. Consistent with prior research, significantly larger mean amplitudes in the N2 and P3 ranges were observed in NoGo versus Go trials. A significant interaction between reflection and depression on P3 amplitudes was observed, indicating that at high levels of reflection, as depression increased P3 amplitudes to NoGo trials also increased. Levels of depression and reflection were not significantly associated with accuracy or reaction time in the task. No significant interactions between depression and brooding, or main effect of brooding was observed on any task measure. Thus, high levels of reflection may uniquely and negatively impact the efficiency that cognitive resources are applied during goal directed behavior in depression. Results are discussed in relation to cognitive models of depression and rumination.

Drastic fluorine effect: complete reversal of the selectivity in the Au-catalyzed hydroalkoxylation reaction of fluorinated haloalkynes.

The gold-catalyzed hydration reaction of haloalkynes is highly regioselective producing 2-halomethylketones as the sole products. Herein, we document a drastic fluorine effect where the reaction of 1-halo-3,3-difluoroalkynes as substrates leads to a complete reversal of selectivity and produces 3,3-difluoroesters as the unique products.

Regioselective Gold-Catalyzed Hydration of CF3- and SF5-alkynes.

The regioselective gold-catalyzed hydration of CF3- and SF5-alkynes is described. The corresponding trifluoromethylated and pentasulfanylated ketones are obtained in up to 91% yield as single regioisomers showcasing the use of CF3 and SF5 as highly efficient directing groups in this reaction. Notably, this transformation represents the first use of CF3- and SF5-alkynes in gold catalysis.

Highly regioselective gold-catalyzed formal hydration of propargylic gem-difluorides.

Herein, we report a highly regioselective gold-catalyzed formal hydration of propargylic gem-difluorides. Not only does this transformation provide access to versatile fluorinated building blocks that were difficult or hardly possible to access beforehand, but it also represents a rare case of a highly regioselective gold-catalyzed hydroalkoxylation of internal alkynes and puts forward the utility of the difluoromethylene unit as a directing group in catalysis.

Exploiting a Difference in Leaving Group Ability: An Approach to ß-Substituted Monofluoroalkenes Using gem-Chlorofluoropropenes.

The superior nucleofuge character of chlorine over fluorine was taken advantage of in the selective SN2' substitution reaction of gem-chlorofluoropropenes, allowing for the clean formation of ß-substituted monofluoroalkenes under metal-free conditions. Numerous N-, S-, O-, and C-nucleophiles behaved nicely in this system. Further synthetic transformations of selected monofluoroalkenes were also accomplished.