Understanding of the electrochemical properties of graphene, especially the electron transfer kinetics of a redox reaction between the graphene surface and a molecule, in comparison to graphite or ...other carbon-based materials, is essential for its potential in energy conversion and storage to be realized. Here we use voltammetric determination of the electron transfer rate for three redox mediators, ferricyanide, hexaammineruthenium, and hexachloroiridate (Fe(CN)6 3–, Ru(NH3)6 3+, and IrCl6 2–, respectively), to measure the reactivity of graphene samples prepared by mechanical exfoliation of natural graphite. Electron transfer rates are measured for varied number of graphene layers (1 to ca. 1000 layers) using microscopic droplets. The basal planes of mono- and multilayer graphene, supported on an insulating Si/SiO2 substrate, exhibit significant electron transfer activity and changes in kinetics are observed for all three mediators. No significant trend in kinetics with flake thickness is discernible for each mediator; however, a large variation in kinetics is observed across the basal plane of the same flakes, indicating that local surface conditions affect the electrochemical performance. This is confirmed by in situ graphite exfoliation, which reveals significant deterioration of initially, near-reversible kinetics for Ru(NH3)6 3+ when comparing the atmosphere-aged and freshly exfoliated graphite surfaces.
Type 2 diabetes is a metabolic disease categorized primarily by reduced insulin sensitivity, β-cell dysfunction, and elevated hepatic glucose production. Treatments reducing hyperglycemia and the ...secondary complications that result from these dysfunctions are being sought after. Two distinct pathways encourage glucose transport activity in skeletal muscle, ie, the contraction-stimulated pathway reliant on Ca(2+)/5'-monophosphate-activated protein kinase (AMPK)-dependent mechanisms and an insulin-dependent pathway activated via upregulation of serine/threonine protein kinase Akt/PKB. Metformin is an established treatment for type 2 diabetes due to its ability to increase peripheral glucose uptake while reducing hepatic glucose production in an AMPK-dependent manner. Peripheral insulin action is reduced in type 2 diabetics whereas AMPK signaling remains largely intact. This paper firstly reviews AMPK and its role in glucose uptake and then focuses on a novel mechanism known to operate via an insulin-dependent pathway. Inositol hexakisphosphate (IP6) kinase 1 (IP6K1) produces a pyrophosphate group at the position of IP6 to generate a further inositol pyrophosphate, ie, diphosphoinositol pentakisphosphate (IP7). IP7 binds with Akt/PKB at its pleckstrin homology domain, preventing interaction with phosphatidylinositol 3,4,5-trisphosphate, and therefore reducing Akt/PKB membrane translocation and insulin-stimulated glucose uptake. Novel evidence suggesting a reduction in IP7 production via IP6K1 inhibition represents an exciting therapeutic avenue in the treatment of insulin resistance. Metformin-induced activation of AMPK is a key current intervention in the management of type 2 diabetes. However, this treatment does not seem to improve peripheral insulin resistance. In light of this evidence, we suggest that inhibition of IP6K1 may increase insulin sensitivity and provide a novel research direction in the treatment of insulin resistance.
Microbial cells buried in subseafloor sediments comprise a substantial portion of Earth's biosphere and control global biogeochemical cycles; however, the rate at which they use energy (i.e., power) ...is virtually unknown. Here, we quantify organic matter degradation and calculate the power utilization of microbial cells throughout Earth's Quaternary-age subseafloor sediments. Aerobic respiration, sulfate reduction, and methanogenesis mediate 6.9, 64.5, and 28.6% of global subseafloor organic matter degradation, respectively. The total power utilization of the subseafloor sediment biosphere is 37.3 gigawatts, less than 0.1% of the power produced in the marine photic zone. Aerobic heterotrophs use the largest share of global power (54.5%) with a median power utilization of 2.23 × 10
watts per cell, while sulfate reducers and methanogens use 1.08 × 10
and 1.50 × 10
watts per cell, respectively. Most subseafloor cells subsist at energy fluxes lower than have previously been shown to support life, calling into question the power limit to life.
We conduct a statistical analysis of 2,094 reconnection events in Saturn's near‐equatorial magnetotail previously identified in Cassini magnetometer data from intervals during 2006 and 2009/2010. ...These consist of tailward propagating plasmoids and planetward propagating dipolarizations, with approximately twice as many plasmoids as dipolarizations. We organize these by three related planetary period oscillation (PPO) phase systems, the northern and southern PPO phases relative to noon, the same phases retarded by a radial propagation delay, and the local retarded phases that take account of the azimuth (local time) of the observation. Clear PPO modulation is found for both plasmoid and dipolarization events, with local retarded phases best organizing the event data with the modulation in event frequency propagating across the tail as the PPO systems rotate. This indicates that the events are localized in azimuth, rather than simultaneously affecting much of the tail width. Overall, events occur preferentially by factors of ~3 at northern and southern phases where the tail current sheet is expected locally to be thinnest in the PPO cycle, with field lines contracting back from their maximum radial displacement, compared with the antiphase conditions. Separating the events into those representing the start of independent reconnection episodes, occurring at least 3 hr after the last, and events in subsequent clusters, shows that the above phases are predominantly characteristic of the majority cluster events. The phases at the start of independent reconnection episodes are typically ~60° earlier.
Key Points
We analyze a catalogue of 2,094 reconnection events in Saturn's magnetotail and organize them according to northern and southern PPO phases
Events are best organized by local PPO phases rather than global phases, implying that reconnection is more locally than globally triggered
Events are best organized by phases where the tail current sheet should be locally thin and the field lines near maximum radial displacement
Robotic technology is one of the most recent technological changes in coronary artery bypass graft (CABG) operations. The current analysis was conducted to identify trends in the use and outcomes of ...robotic-assisted CABG (RA-CABG).
A retrospective analysis was performed using data from The Society of Thoracic Surgeons Adult Cardiac Surgery Database between 2006 and 2012. Patient and site-level characteristics were compared between traditional CABG and RA-CABG. Operative death, postoperative length of stay, and postoperative complications were compared between the two groups.
The number of sites using RA-CABG remained relatively constant during the study period (from 148 in 2006 to 151 in 2012). The volume of RA-CABG as a percentage of the total CABG procedures increased slightly from 0.59% (872 RA-CABG of 127,717 total CABG) in 2006 to 0.97% (1,260 RA-CABG of 97,249 total CABG) in 2012. The RA-CABG patients were significantly younger (64 vs 65 years, p < 0.0001), had fewer comorbidities, and had lower rates of cardiopulmonary bypass use (22.4% vs 80.4%, p < 0.0001). RA-CABG patients had significantly lower unadjusted major complication rates (10.2% vs 13.5%, p < 0.0001), including postoperative renal failure (2.2% vs 2.9%, p < 0.0001), and shorter length of stay (4 vs 5 days, p < 0.0001). The difference in operative death was not significant (odds ratio, 1.10; 95% confidence interval, 0.92 to 1.30, p = 0.29).
RA-CABG use remained relatively stagnant during the analysis period despite lower rates of major perioperative complications and no difference in operative deaths. Additional analysis is needed to fully understand the role that robotic technology will play in CABG operations in the future.
The association between gait speed and cognition has been reported; however, there is limited knowledge about the temporal associations between gait slowing and cognitive decline among cognitively ...normal individuals.
The Mayo Clinic Study of Aging is a population-based study of Olmsted County, Minnesota, United States, residents aged 70-89 years. This analysis included 1,478 cognitively normal participants who were evaluated every 15 months with a nurse visit, neurologic evaluation, and neuropsychological testing. The neuropsychological battery used nine tests to compute domain-specific (memory, language, executive function, and visuospatial skills) and global cognitive z-scores. Timed gait speed (m/s) was assessed over 25 feet (7.6 meters) at a usual pace. Using mixed models, we examined baseline gait speed (continuous and in quartiles) as a predictor of cognitive decline and baseline cognition as a predictor of gait speed changes controlling for demographics and medical conditions.
Cross-sectionally, faster gait speed was associated with better performance in memory, executive function, and global cognition. Both cognitive scores and gait speed declined over time. A faster gait speed at baseline was associated with less cognitive decline across all domain-specific and global scores. These results were slightly attenuated after excluding persons with incident mild cognitive impairment or dementia. By contrast, baseline cognition was not associated with changes in gait speed.
Our study suggests that slow gait precedes cognitive decline. Gait speed may be useful as a reliable, easily attainable, and noninvasive risk factor for cognitive decline.
We report a fatal infection in a 65-year-old immunocompromised male patient caused by pan-triazole-resistant Aspergillus fumigatus containing a TR
/L98H genetic mutation linked to agricultural ...fungicide use. Clinical and environmental surveillance of triazole-resistant A. fumigatus is needed in the United States to prevent spread and guide healthcare and agricultural practices.
Donation after Cardiac Death (DCD) is an increasingly important source of kidney transplants, but because of concerns of ischemic injury during the agonal phase, many centers abandon donation if ...cardiorespiratory arrest has not occurred within 1 h of controlled withdrawal of life‐supporting treatment (WLST). We report the impact on donor numbers and transplant function using instead a minimum ‘cut‐off’ time of 4 h. The agonal phase of 173 potential DCD donors was characterized according to the presence or absence of: acidemia; lactic acidosis; prolonged (>30 min) hypotension, hypoxia or oliguria, and the impact of these characteristics on 3‐ and 12‐month transplant outcome evaluated by multivariable regression analysis. Of the 117 referrals who became donors, 27 (23.1%) arrested more than 1 h after WLST. Longer agonal‐phase times were associated with greater donor instability, but surprisingly neither agonal‐phase instability nor its duration influenced transplant outcome. In contrast, 3‐ and 12‐month eGFR in the 190 transplanted kidneys was influenced independently by donor age, and 3‐month eGFR by cold ischemic time. DCD kidney numbers are increased by 30%, without compromising transplant outcome, by lengthening the minimum waiting time after WLST from 1 to 4 h.
Donation after cardiac death kidney numbers are increased by 30%, without compromising transplant outcome, by lengthening the minimum waiting time after withdrawal of life‐supporting treatment from 1 to 4 hours.
We used magnetic resonance imaging and cortical matching algorithms to map gray matter density (GMD) in 176 normal individuals ranging in age from 7 to 87 years. We found a significant, nonlinear ...decline in GMD with age, which was most rapid between 7 and about 60 years, over dorsal frontal and parietal association cortices on both the lateral and interhemispheric surfaces. Age effects were inverted in the left posterior temporal region, where GMD gain continued up to age 30 and then rapidly declined. The trajectory of maturational and aging effects varied considerably over the cortex. Visual, auditory and limbic cortices, which are known to myelinate early, showed a more linear pattern of aging than the frontal and parietal neocortices, which continue myelination into adulthood. Our findings also indicate that the posterior temporal cortices, primarily in the left hemisphere, which typically support language functions, have a more protracted course of maturation than any other cortical region.
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