ALBERT

Beschreibung: Author Posting. © American Institute of Physics, 2017. This article is posted here by permission of American Institute of Physics for personal use, not for redistribution. The definitive version was published in Physics Today 70, no. 11 (2017): 78, doi:10.1063/PT.3.3773.

Beschreibung: With only a minimal flapping, the wandering albatross can circumnavigate the globe. During its peregrinations over the Southern Ocean, the seabird exploits wind shear—the gradient of wind speed—to extract energy for its sustained flight. That same maneuver, called dynamic soaring, is used by pilots of radio-controlled gliders. In flights that take advantage of the shear associated with wind blowing over mountain ridges, the gliders reach air speeds of an astonishing 500 mph. Engineers are currently developing autonomous unmanned vehicles that can use the technique to supplement different sources of energy for sustained flight over the oceans. Possible applications include environmental monitoring, surveillance, and search and rescue.

Beschreibung: 2018-11-01

Beschreibung: The Green's function (GF) for the scalar wave equation is numerically constructed by an advanced geometric ray-tracing method based on the eikonal approximation related to the semiclassical propagator. The underlying theory is first briefly introduced, and then it is applied to acoustics and implemented in a ray-tracing-type numerical simulation. The so constructed numerical method is systematically used to calculate the sound field in a rectangular (cuboid) room, yielding also the acoustic modes of the room. The simulated GF is rigorously compared to its analytic approximation. Good agreement is found, which proves the devised numerical approach potentially useful also for low frequency acoustic modeling, which is in practice not covered by geometrical methods.

Beschreibung: by Gibran Hemani, Kate Tilling, George Davey Smith

Beschreibung: by Darragh P. O’Brien, Dominique Durand, Alexis Voegele, Véronique Hourdel, Marilyne Davi, Julia Chamot-Rooke, Patrice Vachette, Sébastien Brier, Daniel Ladant, Alexandre Chenal Once translocated into the cytosol of target cells, the catalytic domain (AC) of the adenylate cyclase toxin (CyaA), a major virulence factor of Bordetella pertussis , is potently activated by binding calmodulin (CaM) to produce supraphysiological levels of cAMP, inducing cell death. Using a combination of small-angle X-ray scattering (SAXS), hydrogen/deuterium exchange mass spectrometry (HDX-MS), and synchrotron radiation circular dichroism (SR-CD), we show that, in the absence of CaM, AC exhibits significant structural disorder, and a 75-residue-long stretch within AC undergoes a disorder-to-order transition upon CaM binding. Beyond this local folding, CaM binding induces long-range allosteric effects that stabilize the distant catalytic site, whilst preserving catalytic loop flexibility. We propose that the high enzymatic activity of AC is due to a tight balance between the CaM-induced decrease of structural flexibility around the catalytic site and the preservation of catalytic loop flexibility, allowing for fast substrate binding and product release. The CaM-induced dampening of AC conformational disorder is likely relevant to other CaM-activated enzymes.

Beschreibung: by The PLOS ONE Staff

Beschreibung: by Federico Devalle, Alex Roxin, Ernest Montbrió Recurrently coupled networks of inhibitory neurons robustly generate oscillations in the gamma band. Nonetheless, the corresponding Wilson-Cowan type firing rate equation for such an inhibitory population does not generate such oscillations without an explicit time delay. We show that this discrepancy is due to a voltage-dependent spike-synchronization mechanism inherent in networks of spiking neurons which is not captured by standard firing rate equations. Here we investigate an exact low-dimensional description for a network of heterogeneous canonical Class 1 inhibitory neurons which includes the sub-threshold dynamics crucial for generating synchronous states. In the limit of slow synaptic kinetics the spike-synchrony mechanism is suppressed and the standard Wilson-Cowan equations are formally recovered as long as external inputs are also slow. However, even in this limit synchronous spiking can be elicited by inputs which fluctuate on a time-scale of the membrane time-constant of the neurons. Our meanfield equations therefore represent an extension of the standard Wilson-Cowan equations in which spike synchrony is also correctly described.

Beschreibung: by Carlos Díaz-Venegas, Daniel C. Schneider, Mikko Myrskylä, Neil K. Mehta Diabetes affects mortality and cognitive functioning. It is not known how diabetes influences life expectancy (LE) with and without cognitive impairment. We seek to examine age at onset of cognitive impairment and life expectancy (LE) with and without cognitive impairment by diabetes status among middle- and older-aged Americans. Data come from the U.S. Health and Retirement Study 2000–2012 linked to the National Death Index (N = 13,687). We use multinomial regression models stratified by gender and controlling for age, education and race/ethnicity to estimate diabetes-status specific transition probabilities, then use a Markov chain matrix population model to calculate age at onset of cognitive impairment and LE with and without cognitive impairment by diabetes status at age 50. LE at age 50 was 27.6 (men) and 32.1 (women). From age 50, those with diabetes had a first incidence of cognitive impairment 3 (men) and 4 (women) years earlier than those without. Diabetes reduced total LE by 5–7 years and cognitively healthy LE by 4–6 years. Those with diabetes lived one year less in a cognitively impaired state than those without. Over 80% of the lower LE associated with diabetes is attributable to the loss of cognitively-healthy years. Those with diabetes have a shorter LE with cognitive impairment because of higher mortality. In analyses by educational attainment, education was strongly protective of cognitive health, yet diabetes was associated with lower age of cognitive impairment onset and fewer cognitive healthy years lived in all educational groups. The excess mortality because of diabetes may be decreasing. If the mortality decline is not coupled with a comparable decline in the risk of cognitive impairment, the population level burden of impaired cognition may grow larger.

Beschreibung: by Zhijun Zhong, Yinan Tian, Yuan Song, Lei Deng, Junxian Li, Zhihua Ren, Xiaoping Ma, Xiaobin Gu, Changliang He, Yi Geng, Guangneng Peng

Beschreibung: by Emily Booth Warren, Aidan Edward Aicher, Joshua Patrick Fessel, Christine Konradi Mitochondrial DNA (mtDNA), the discrete genome which encodes subunits of the mitochondrial respiratory chain, is present at highly variable copy numbers across cell types. Though severe mtDNA depletion dramatically reduces mitochondrial function, the impact of tissue-specific mtDNA reduction remains debated. Previously, our lab identified reduced mtDNA quantity in the putamen of Parkinson’s Disease (PD) patients who had developed L-DOPA Induced Dyskinesia (LID), compared to PD patients who had not developed LID and healthy subjects. Here, we present the consequences of mtDNA depletion by ethidium bromide (EtBr) treatment on the bioenergetic function of primary cultured neurons, astrocytes and neuron-enriched cocultures from rat striatum. We report that EtBr inhibition of mtDNA replication and transcription consistently reduces mitochondrial oxygen consumption, and that neurons are significantly more sensitive to EtBr than astrocytes. EtBr also increases glycolytic activity in astrocytes, whereas in neurons it reduces the expression of mitochondrial creatine kinase mRNA and levels of phosphocreatine. Further, we show that mitochondrial creatine kinase mRNA is similarly downregulated in dyskinetic PD patients, compared to both non-dyskinetic PD patients and healthy subjects. Our data support a hypothesis that reduced striatal mtDNA contributes to energetic dysregulation in the dyskinetic striatum by destabilizing the energy buffering system of the phosphocreatine/creatine shuttle.

Beschreibung: by Feng He, Kun Wang, David B. Hannaway, Xianglin Li Leymus chinensis (Trin.) is the dominant vegetation type in eastern Eurasian temperate grasslands but is decreasing due to the combined pressure of reduced precipitation and overgrazing. This study evaluated the separate and combined effects of precipitation and defoliation on net primary productivity (NPP) and composition of a L . chinensis steppe to promote the sustainable development of temperate grasslands through improved management practices. The effects of three precipitation gradients (precipitation unchanged, reduced by 50%, and increased by 50%) and two clipping intensities (clipping once or twice per year) were examined on NPP and composition of the L . chinensis community using a 7-year in situ controlled trial at the Guyuan State Key Monitoring and Research Station of Grassland Ecosystem in China. The results showed that: (1) a 50% reduction in natural precipitation significantly decreased NPP; a 50% increase in precipitation did not significantly increase NPP, but it decreased the importance value of L . chinensis because more water promoted the growth of competing species. (2) Clipping twice per year increased NPP, but the increase was from the dry matter of other species (DMO) component, and not from the dry matter of L . chinensis . (3) The standardized coefficients of a regression model (β) for DMO, NPP, and the importance value of L . chinensis were 0.685, 0.532, and −0.608 for precipitation, and 0.369, 0.419, and −0.276 for clipping mode, respectively. This study demonstrated that variation in precipitationis the key driver of NPP and composition of a L . chinensis steppe under the precipitation range and clipping intensities evaluated. This improved understanding of the effects of precipitation and clipping on NPP and composition will allow for improved, sustainable management of L . chinensis temperate grassland steppes.