Electromechanical Piezoresistive Sensing in Suspended Graphene Membranes

Monolayer graphene exhibits exceptional electronic and mechanical properties, making it a very promising material for nanoelectromechanical (NEMS) devices. Here, we conclusively demonstrate the piezoresistive effect in graphene in a nano-electromechanical membrane configuration that provides direct electrical readout of pressure to strain transduction. This makes it highly relevant for an important class of nano-electromechanical system (NEMS) transducers. This demonstration is consistent with our simulations and previously reported gauge factors and simulation values. The membrane in our experiment acts as a strain gauge independent of crystallographic orientation and allows for aggressive size scalability. When compared with conventional pressure sensors, the sensors have orders of magnitude higher sensitivity per unit area.Comment: 20 pages, 3 figure

Synthetic fluid inclusions in natural quartz. IV. Chemical analyses of fluid inclusions by SEM/EDA: Evaluation of method

The compositions of individual synthetic fluid inclusions in the systems NaCl-KCl, NaCl-CaCl2 and NaCl-KCl-CaCl2 have been semi-quantitatively determined by energy dispersive analysis of precipitates produced during thermal decrepitation. Inclusions containing known mixtures of 20 wt.% total salinity were synthesized by healing fractures in natural quartz at 600-700[deg]C and 5-7 kbars for 7-10 days. The two-phase, daughter-free inclusions homogenized at 170-250[deg]C, began to decrepitate after about 100[deg] of overheating and by 360-420[deg]C a significant number of decrepitates had formed on the polished surface. Peak heights generated by EDA (raster mode) of these decrepitates were standardized using both single and mixed salt standards evaporated to dryness in a vacuum. Although the mixed salt standards better approximated the decrepitate compositions, difficulties were encountered in producing micronscale homogeneity and the single salts yielded more reliable results.Eight different solutions of 20-23 wt.% total salinity were run and in all the samples the average compositions of 10-20 discrete, single inclusion decrepitates fell with 6 wt.% (0.2 to 5.2) of the actual composition, suggesting that the decrepitates were chemically representative of their precursor inclusions. However, not all decrepitates analyzed provided similarly accurate results. Electron mapping revealed that fracture-aligned decrepitates were often chemically inhomogeneous and thus had to be avoided. A sample decrepitated at 500[deg]C yielded spurious results suggesting that chloride volatility may become a significant problem when temperatures in excess of 450[deg]C are required for decrepitation. Decrepitates with diameters between 10 and 30 [mu]m yielded more consistent and accurate results than smaller or larger decrepitates on the same samples.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/27326/1/0000349.pd

Passive and active suicidal ideation in a population-based sample of older adults: Associations with polygenic risk scores of relevance for suicidal behavior

Introduction: There are few studies investigating genetic factors related to suicidal ideation or behavior in older adult populations. Our aim was to test associations between passive and active suicidal ideation and polygenic risk scores (PRSs) for suicidality and other traits of relevance for suicidality in old age (i.e. depression, neuroticism, loneliness, Alzheimer’s disease, cognitive performance, educational attainment, and several specified vascular diseases) in a population-based sample aged 70 years and older. / Methods: Participants in the prospective H70 study in Gothenburg, Sweden, took part in a psychiatric examination that included the Paykel questions on active and passive suicidal ideation. Genotyping was performed with the Neurochip (Illumina). After quality control of the genetic data the sample included 3467 participants. PRSs for suicidality and other related traits were calculated based on summary statistics from recent GWASs of relevance. Exclusion of persons with dementia or incomplete data on suicidal ideation yielded 3019 participants, age range 70–101 years. Associations between past year suicidal ideation (any level) and selected PRSs were analysed using general estimation equation (GEE) models, adjusted for sex and age. / Results: We observed associations between passive/active suicidal ideation and PRSs for depression (three versions), neuroticism, and general cognitive performance. After excluding individuals with current major depressive disorder (MDD), similar associations were seen with PRS for neuroticism, general cognitive performance and two PRSs for depression. No associations were found between suicidal ideation and PRSs for suicidality, loneliness, Alzheimer’s disease, educational attainment, or vascular disease. / Discussion: Our results could indicate which types of genetic susceptibility that are of importance for suicidality in old age, and these findings can help to shed light on potential mechanisms that may be involved in passive and active suicidal ideation in late-life, also in those with no current MDD. However, due to the limited sample size, the results need to be interpreted with caution until replicated in larger samples

Convergence of detrital stoichiometry predicts thresholds of nutrient-stimulated breakdown in streams

Nutrient enrichment of detritus‐based streams increases detrital resource quality for consumers and stimulates breakdown rates of particulate organic carbon (C). The relative importance of dissolved inorganic nitrogen (N) vs. phosphorus (P) for detrital quality and their effects on microbial‐ vs. detritivore‐mediated detrital breakdown are poorly understood. We tested effects of experimental N and P additions on detrital stoichiometry (C:N, C:P) and total and microbial breakdown (i.e., with and without detritivorous shredders, respectively) of five detritus types (four leaf litter species and wood) with different initial C : nutrient content. We enriched five headwater streams continuously for two years at different relative availabilities of N and P and compared breakdown rates and detrital stoichiometry to pretreatment conditions. Total breakdown rates increased with nutrient enrichment and were predicted by altered detrital stoichiometry. Streamwater N and P, fungal biomass, and their interactions affected stoichiometry of detritus. Streamwater N and P decreased detrital C:N, whereas streamwater P had stronger negative effects on detrital C:P. Nutrient addition and fungal biomass reduced C:N by 70% and C:P by 83% on average after conditioning, compared to only 26% for C:N and 10% for C:P under pretreatment conditions. Detritus with lowest initial nutrient content changed the most and had greatest increases in total breakdown rates. Detrital stoichiometry was reduced and differences among detritus types were homogenized by nutrient enrichment. With enrichment, detrital nutrient content approached detritivore nutritional requirements and stimulated greater detritivore vs. microbial litter breakdown. We used breakpoint regression to estimate values of detrital stoichiometry that can potentially be used to indicate elevated breakdown rates. Breakpoint ratios for total breakdown were 41 (C:N) and 1518 (C:P), coinciding with total breakdown rates that were ~1.9 times higher when C:N or C:P fell below these breakpoints. Microbial and shredder‐mediated breakdown rates both increased when C:N and C:P were reduced, suggesting that detrital stoichiometry is useful for predicting litter breakdown dominated by either microbial or shredder activity. Our results show strong effects of nutrient enrichment on detrital stoichiometry and offer a robust link between a potential holistic nutrient loading metric (decreased and homogenized detrital stoichiometry) and increased C loss from stream ecosystems

Carbon flux from decomposing wood and its dependency on temperature, wood N2 fixation rate, moisture and fungal composition in a Norway spruce forest

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Triptycene-Roofed Quinoxaline Cavitands for the Supramolecular Detection of BTEX in Air

Two novel triptycene quinoxaline cavitands (DiTriptyQxCav and MonoTriptyQxCav) have been designed, synthesized, and applied in the supramolecular detection of benzene, toluene, ethylbenzene, and xylenes (BTEX) in air. The complexation properties of the two cavitands towards aromatics in the solid state are strengthened by the presence of the triptycene moieties at the upper rim of the tetraquinoxaline walls, promoting the confinement of the aromatic hydrocarbons within the cavity. The two cavitands were used as fiber coatings for solid-phase microextraction (SPME) BTEX monitoring in air. The best performances in terms of enrichment factors, selectivity, and LOD (limit of detection) values were obtained by using the DiTriptyQxCav coating. The corresponding SPME fiber was successfully tested under real urban monitoring conditions, outperforming the commercial divinylbenzene\u2013Carboxen\u2013polydimethylsiloxane (DVB\u2013CAR\u2013PDMS) fiber in BTEX adsorption

Subtle Differences in Cognition in 70-Year-Olds with Elevated Cerebrospinal Fluid Neurofilament Light and Neurogranin: A H70 Cross-Sectional Study

BACKGROUND: Most research on cerebrospinal fluid (CSF) neurofilament light protein (NfL) as a marker for neurodegeneration and neurogranin (Ng) for synaptic dysfunction has largely focused on clinical cohorts rather than population-based samples. OBJECTIVE: We hypothesized that increased CSF levels of NfL and Ng are associated with subtle cognitive deficits in cognitively unimpaired (CU) older adults. METHODS: The sample was derived from the Gothenburg H70 Birth Cohort Studies and comprised 258 CU 70-year-olds, with a Clinical Dementia Rating score of zero. All participants underwent extensive cognitive testing. CSF levels of NfL and Ng, as well as amyloid β1 - 42, total tau, and phosphorylated tau, were measured. RESULTS: Participants with high CSF NfL performed worse in one memory-based test (Immediate recall, p = 0.013) and a language test (FAS, p = 0.016). Individuals with high CSF Ng performed worse on the memory-based test Supra Span (p = 0.035). When stratified according to CSF tau and Aβ42 concentrations, participants with high NfL and increased tau performed worse on a memory test than participants normal tau concentrations (Delayed recall, p = 0.003). In participants with high NfL, those with pathologic Aβ42 concentrations performed worse on the Delayed recall memory (p = 0.044). In the high Ng group, participants with pathological Aβ42 concentrations had lower MMSE scores (p = 0.027). However, in regression analysis we found no linear correlations between CSF NfL or CSF Ng in relation to cognitive tests when controlled for important co-variates. CONCLUSION: Markers of neurodegeneration and synaptic pathology might be associated with subtle signs of cognitive decline in a population-based sample of 70-year-olds

The adaptive evolution of herbivory in freshwater systems

Herbivory is thought to be nutritionally inefficient relative to carnivory and omnivory, but herbivory evolved from carnivory in many terrestrial and aquatic lineages, suggesting that there are advantages of eating plants. Herbivory has been well-studied in both terrestrial and aquatic systems, and there is abundant information on feedbacks between herbivores and plants, coevolution of plant and herbivore defenses, mechanisms for mediating nutrient limitation, effects of nutrient limitation on herbivore life history, and, more recently, the origins of the herbivorous diet. Researchers have sufficiently defined the ecological context and evolutionary origins of the herbivorous diet, and these main areas of research have laid the groundwork for studying herbivory as an adaptation. However, we have yet to synthesize this information in a way that allows us to establish a framework of testable adaptive hypotheses. To understand the adaptive significance of this diet transition, we review the current literature and use evidence from these works as support for five hypotheses on the evolution of herbivory from carnivory: (1) intake efficiency—herbivores use part of their food source as habitat, thus minimizing the energy/time spent searching for food and avoiding predators; (2) suboptimal habitat—herbivory allows organisms to invade and establish populations in habitats that have high primary production but low abundance of animal prey; (3) heterotroph facilitation—herbivory is adaptive because herbivores consume microbes associated with producers; (4) lipid allocation—herbivory is adaptive because producers are rich in fatty acids, which fuel reproduction and storage; and (5) disease avoidance—herbivory minimizes animal-facilitated disease transmission. Due to the extensive literature, we have limited this review to discussing herbivory in freshwater systems. To our knowledge, no prior work has compiled a comprehensive list of conditions that favor an herbivorous diet in nature. With backgrounds in both theoretical and experimental ecology, the incorporation of these hypotheses to the current literature will provide information about diet evolution, where it is currently lacking

Rewiring coral: Anthropogenic nutrients shift diverse coral–symbiont nutrient and carbon interactions toward symbiotic algal dominance

Improving coral reef conservation requires heightened understanding of the mechanisms by which coral cope with changing environmental conditions to maintain optimal health. We used a long‐term (10 month) in situ experiment with two phylogenetically diverse scleractinians (Acropora palmata and Porites porites) to test how coral–symbiotic algal interactions changed under real‐world conditions that were a priori expected to be beneficial (fish‐mediated nutrients) and to be harmful, but non‐lethal, for coral (fish + anthropogenic nutrients). Analyzing nine response variables of nutrient stoichiometry and stable isotopes per coral fragment, we found that nutrients from fish positively affected coral growth, and moderate doses of anthropogenic nutrients had no additional effects. While growing, coral maintained homeostasis in their nutrient pools, showing tolerance to the different nutrient regimes. Nonetheless, structural equation models revealed more nuanced relationships, showing that anthropogenic nutrients reduced the diversity of coral–symbiotic algal interactions and caused nutrient and carbon flow to be dominated by the symbiont. Our findings show that nutrient and carbon pathways are fundamentally “rewired” under anthropogenic nutrient regimes in ways that could increase corals’ susceptibility to further stressors. We hypothesize that our experiment captured coral in a previously unrecognized transition state between mutualism and antagonism. These findings highlight a notable parallel between how anthropogenic nutrients promote symbiont dominance with the holobiont, and how they promote macroalgal dominance at the coral reef scale. Our findings suggest more realistic experimental conditions, including studies across gradients of anthropogenic nutrient enrichment as well as the incorporation of varied nutrient and energy pathways, may facilitate conservation efforts to mitigate coral loss.We provide a long‐term field experiment to test the implications of different nutrient sources, fish excretion and moderate levels of anthropogenic nutrients, for coral health and coral–symbiont interactions. Our study identifies a potentially novel "transition state" whereby despite maintaining high growth rates and creating no apparent negative external effects, anthropogenic nutrient enrichment drives coral–algal interactions to be dominated by the algal symbiont—that is, increased prominence of energy and nutrient flow from the algal symbiont under conditions of Fish + anthropogenic nutrients (NPK) in the figure. We hypothesize that this “rewiring” of the coral–symbiont interactions may render the coral more vulnerable to additional stressors.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/162733/2/gcb15230_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/162733/1/gcb15230.pd

Overcoming Public Resistance to Carbon Taxes

Carbon taxes represent a cost-effective way to steer the economy toward a greener future. In the real world, their application has however been limited. In this paper, we address one of the main obstacles to carbon taxes: public opposition. We identify drivers of and barriers to public support, and, under the form of stylized facts, provide general lessons on the acceptability of carbon taxes. We derive our lessons from a growing literature, as well as from a combination of policy “failures” and “successes.” Based on our stylized facts, we formulate a set of suggestions concerning the design of carbon taxes. We consider the use of trial periods, tax escalators, environmental earmarking, lump-sum transfers, tax rebates, and advanced communication strategies, among others. This paper contributes to the policy debate about carbon taxes, hopefully leading to more success stories and fewer policy failures