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Ni-Catalyzed Arylboration of Unactivated Alkenes: Scope and Mechanistic Studies
No full textA method for the Ni-catalyzed arylboration of unactivated monosubstituted, 1,1-disubstituted, and trisubstituted alkenes is disclosed. The reaction is notable in that it converts highly substituted alkenes, aryl bromides, and diboron reagents to products that contain a quaternary carbon and a synthetically versatile carbon–boron bond with control of stereoselectivity and regioselectivity. In addition, the method is demonstrated to be useful for the synthesis of saturated nitrogen heterocycles, which are important motifs in pharmaceutical compounds. Finally, due to the unusual reactivity demonstrated, the mechanistic details of the reaction were studied with both computational and experimental techniques
Inverse association between changes in energetic cost of walking and vertical accelerations in non-metastatic breast cancer survivors
No full textPurpose: With accelerometry, the utility to detect changes in physical activity are predicated on the assumption that walking energetics and gait mechanics do not change. The present work examined associations between changes (∆) in walking energetics, exercise self-efficacy, and several accelerometer-derived metrics. Methods Secondary analyses were performed among a sub-sample ( = 29) of breast cancer survivors participating in a larger randomized trial. During 4 min of treadmill walking (0.89 m s, 0% grade), indirect calorimetry quantified steady-state energy expenditure (EE), wherein, participants were fitted with a heart rate monitor and hip-worn triaxial accelerometer. Exercise self-efficacy was measured using a 9-item questionnaire, while vector magnitude (VM) and individual planes (e.g., mediolateral, vertical, and anteroposterior) of the movement were extracted for data analyses. Evaluations were made at baseline and after 3 months. Results From baseline to 3 months, the energetic cost of walking (kcals min) significantly decreased by an average of − 5.1% ( = 0.001; = 0.46). Conversely, VM significantly increased ( = 0.007; = 0.53), exclusively due to greater vertical accelerations (acc) (+ 5.7 ± 7.8 acc; = 0.001; = 0.69). Changes in vertical accelerations were inversely and positively associated with ∆walking EE ( = − 0.37; = 0.047) and ∆exercise self-efficacy ( = 0.39; = 0.034), respectively. Conclusion: Hip-worn accelerometers do not appear well-suited to correctly detect changes in ease of walking as evidenced by reduced energetic cost. Further research should determine if a divergence between measured EE and vertical accelerations could contribute to erroneous inferences in free-living physical activity
Gut microbiota diversity is associated with cardiorespiratory fitness in post-primary treatment breast cancer survivors
No full textPrevious studies have not adequately considered the influence of adiposity and activity-related energy expenditure (AEE) on gut microbe diversity. We determined associations of gut microbiota diversity with measures of cardiorespiratory fitness while accounting for the potential effects of %body fat and free-living AEE. Cancer treatment uniquely triggers multiple physiologic shifts detrimental to overall health. Though previous research indicates a link between gut microbiota and cardiorespiratory fitness, it is unclear whether these findings are due to potential underlying effects %body fat or free-living activity energy expenditure (AEE). Microbe composition of fecal specimens from 37 breast cancer survivors were determined using 16S microbiome analyses. Individual-sample microbiota diversity (α-diversity) and between-sample community differences (β-diversity) were examined. Peak oxygen uptake (V̇O) was estimated from a graded exercise test (GXT) consistent with the modified-Naughton protocol, in which, exercise terminates at 85% age-predicted heart rate max (HR). AEE was measured over 10-days using doubly-labeled water wherein %body fat was calculated from total body water. Pearson correlations revealed α-diversity indices (Chao1, Observed Species, PD Whole Tree, Shannon) positively associated with V̇O (r = 0.34 to 0.51; p < 0.05) whereas %HR during Stages 1–4 of the GXT ( = −0.34 to −0.50; < 0.05) and %body fat ( = −0.32 to −0.41; < 0.05) were negatively associated with the same α-diversity indices. Multiple linear regression models showed V̇O accounted for 22% and 26% of the variance in taxonomic richness (Observed Species) and phylogenic diversity after adjustment for %body fat and menopausal status. Unweighted UniFrac (β-diversity) was significant for several outcomes involving cardiorespiratory fitness and significant taxa comparisons were found. Associations between gut microbiota and free-living AEE were not found. Results from the present work suggest cardiorespiratory fitness, not physical activity, is a superior correlate of gut microbiota diversity
On Activities and Affordances for Mobile Learning
No full textAcross the articles in this special issue, there is a clear and important focus on how people learn through mobility, which allows them to move across contexts as they learn. This commentary considers ways mobile technologies can support learning with a focus on understanding the affordances to of the mobile technologies develop new learning practices that could not be accomplished without this technology. With this in mind, we return to the definition of mobile learning that suggests mobile learning is learning across multiple contexts, through social interaction, using personal electronic devices that can immediately capture information about, or provide information to the user. To explore how to implement this definition in truly powerful ways, we suggest explicitly unpacking this into its four component parts, so that we can explore and discuss the unique affordances of mobile learning: (1) multiple contexts, (2) social interactions, (3) content interactions, and (4), capturing information and providing information to users in real-time. We further suggest a 5th element, which is the synergies among these different dimensions. We conclude with the challenges in doing research in mobile learning environments and the need to understand both how and what people learn in such environments
Observation of a Degenerate Fermi Gas Trapped by a Bose-Einstein Condensate
No full textWe report on the formation of a stable quantum degenerate mixture of fermionic Li and bosonic Cs in an optical trap by sympathetic cooling near an interspecies Feshbach resonance. New regimes of quantum degenerate Bose-Fermi mixtures are identified. With moderate attractive interspecies interactions, we show that a degenerate Fermi gas of Li can be fully confined in a Cs Bose-Einstein condensate without external potentials. For stronger attraction where mean-field collapse is expected, no such instability is observed. Potential mechanisms to explain this phenomenon are discussed
Hawaiian picture-winged Drosophila exhibit adaptive population divergence along a narrow climatic gradient on Hawaii Island
No full textAnthropogenic influences on global processes and climatic conditions are increasingly affecting ecosystems throughout the world. Hawaii Island’s native ecosystems are well studied and local long‐term climatic trends well documented, making these ecosystems ideal for evaluating how native taxa may respond to a warming environment. This study documents adaptive divergence of populations of a Hawaiian picture‐winged Drosophila, D. sproati, that are separated by only 7 km and 365 m in elevation. Representative laboratory populations show divergent behavioral and physiological responses to an experimental low‐intensity increase in ambient temperature during maturation. The significant interaction of source population by temperature treatment for behavioral and physiological measurements indicates differential adaptation to temperature for the two populations. Significant differences in gene expression among males were mostly explained by the source population, with eleven genes in males also showing a significant interaction of source population by temperature treatment. The combined behavior, physiology, and gene expression differences between populations illustrate the potential for local adaptation to occur over a fine spatial scale and exemplify nuanced response to climate change
Surface states and arcless angles in twisted Weyl semimetals
No full textFermi arc states are features of Weyl semimetal (WSM) surfaces which are robust due to the topological character of the bulk band structure. We demonstrate that Fermi arcs may undergo profound restructurings when surfaces of different systems with a well-defined twist angle are tunnel coupled. The twisted WSM interface supports a moiré pattern which may be approximated as a periodic system with a large real-space unit cell. States bound to the interface emerge, with interesting consequences for the magneto-oscillations expected when a magnetic field is applied perpendicular to the system surfaces. As the twist angle passes through special “arcless angles,” for which open Fermi arc states are absent at the interface, Fermi loops of states with no connection to bulk states appear. Such states have interesting resonance signatures in the optical conductivity of the system in a magnetic field perpendicular to the interface. These signatures are independent of the bulk thickness or disorder
Patterns of polysubstance use and simultaneous co-use in high risk young adults
No full textBackground: Polysubstance use (PSU) is associated with worse prognosis and poorer physical and mental health compared to single substance use. The current study provides information about PSU patterns by examining a diverse range of alcohol/substance use behaviors ranging from low-level experimentation to indicators of severe abuse. In addition, the current study, for the first time, examines how simultaneous co-use of multiple substances cluster with other more commonly studied PSU behaviors. Methods: Latent Class Analysis was used to identify patterns of substance use, in a sample of young-adults (n = 2098), using 25 items from the Semi-Structured Assessment for the Genetics of Alcoholism (SSAGA-II) including: items assessing severity of problems with alcohol, cannabis, stimulants, opiates, and sedatives; items assessing # of lifetime uses; items assessing simultaneous co-use of all combinations of substances. Then the association of class membership and age, antisocial and impulsive personality, experience seeking, anxiety, and neuroticism was examined using Multinomial Regression. Results: Fit indices (i.e. AIC, SSABIC, and entropy) and interpretability of classes supported a five-class solution: "Low Problems" (32% of sample), "Alcohol Primary" (11%), "Alcohol and Cannabis" (25%), "Moderate PSU" (23%), and "Severe PSU" (9%). Simultaneous co-use behaviors discriminated between lower and higher severity groups. Externalizing personality constructs robustly predicted membership in the "Moderate" and "Severe" PSU classes compared to the "Alcohol Primary" class. Conclusions: PSU patterns followed an additive pattern of use with lower severity classes using alcohol/cannabis and more severe classes using other illicit substances in addition. Co-use items provided valuable information about PSU severity