ABSTRACT
In seasonal environments, many animals, including insects, enter dormancy, where they are limited to a fixed energy budget. The inability to replenish energetic stores during these periods ...suggests insects should be constrained by pre-dormancy energy stores. Over the last century, the community of researchers working on survival during dormancy has operated under the strong assumption that energy limitation is a key fitness trait driving the evolution of seasonal strategies. That is, energy use has to be minimized during dormancy because insects otherwise run out of energy and die during dormancy, or are left with too little energy to complete development, reproductive maturation or other costly post-dormancy processes such as dispersal or nest building. But if energy is so strongly constrained during dormancy, how can some insects – even within the same species and population – be dormant in very warm environments or show prolonged dormancy for many successive years? In this Commentary, we discuss major assumptions regarding dormancy energetics and outline cases where insects appear to align with our assumptions and where they do not. We then highlight several research directions that could help link organismal energy use with landscape-level changes. Overall, the optimal energetic strategy during dormancy might not be to simply minimize metabolic rate, but instead to maintain a level that matches the demands of the specific life-history strategy. Given the influence of temperature on energy use rates of insects in winter, understanding dormancy energetic strategies is critical in order to determine the potential impacts of climate change on insects in seasonal environments.
Binary single-phase concentrated solid solution alloys (SPCSAs), including Ni80Co20, Ni80Fe20, Ni80Cr20, Ni80Pd20, and Ni80Mn20 (in atomic percentage), were irradiated with 200 keV He+ ions at ...500 °C. He cavity size and density distribution were systematically investigated using transmission electron microscope. Here we show that alloying elements have a clear impact on He cavity formation. Cavity size is the smallest in Ni80Mn20 but the largest in Ni80Co20. Alloying elements could also substantially affect cavity density profile. In-depth examination of cavities at peak damage region (∼500 nm) and at low damage region (∼300 nm) demonstrates that cavity size is depth (damage) dependent. Competition between consumption and production of vacancies and He atoms could lead to varied cavity size. Density functional theory (DFT) calculations were performed to obtain the formation and migration energies of interstitials and vacancies. Combined experimental and simulation results show that smaller energy gap between interstitial and vacancy migration energies may lead to smaller cavity size and narrower size distribution observed in Ni80Mn20, comparing with Ni80Co20. The results of this study call attention to alloying effects of specific element on cavity formation and defect energetics in SPCSAs, and could provide fundamental understanding to predict radiation effects in more complexed SPCSAs, such as high entropy alloys.
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Objective
The northern stock of Black Sea Bass Centropristis striata has spatially expanded over the past decade, potentially due to warming northwest Atlantic Shelf waters affecting overwintering.
...Methods
To gather empirical data on temperature‐dependent energetics, we quantified winter growth and lipid accumulation in juveniles from Long Island Sound using two experiments.
Result
Experiment 1 measured individual length growth (GR), weight‐specific growth (SGR), growth efficiency, and lipid content at constant food levels and three static temperatures (6, 12, 19°C), resulting in decreasing GR from 0.24 mm/day at 19°C (SGR = 0.89%/day) to 0.15 mm/day at 12°C (0.54%/day) to 0.04 mm/day at 6°C (0.17%/day). Even at the coldest temperature, most juveniles sustained positive GRs and SGRs; hence, the species' true thermal growth minimum may be below 6°C. Lipid accumulation was greatest at 12°C, which is close to what overwintering juveniles likely encounter offshore. Experiment 2 measured the same traits but combined a representative thermal overwinter profile (20°C → 13°C, October–March) with seasonally varying rations designed to mimic low and high levels of food availability offshore. Monthly GR and SGR responded in the direction of seasonal food level changes. The “winter pulse” consumption average of 1.7%/feeding elicited a mean GR of 0.15 mm/day and SGR of 0.55%/day, whereas the “winter dip” consumption average of 3.8%/feeding yielded faster GR (0.20 mm/day) and SGR (0.71%/day). Growth efficiency ranged between 15% and 30% and was inversely related to food consumption. In both experiments, juveniles disproportionally accumulated lipid over lean mass, with lipid proportions tripling in experiment 2 from 4% at 65 mm to 12% at 120 mm.
Conclusion
As inshore winter waters continue to warm, the energetic trade‐offs of overwinter offshore migration are likely to shift, potentially leading to a year‐round inshore Black Sea Bass presence.
Impact statement
Black Sea Bass juveniles from Long Island Sound showed positive overwinter growth even at temperatures as low as 6°C. However, the best temperature for growth, survival, and lipid accumulation was 12°C, which is close to the presumed conditions at offshore overwintering habitats of this species. In addition, high food levels during winter months elicited compensatory growth.
BACKGROUND:Takotsubo cardiomyopathy is an increasingly recognized acute heart failure syndrome precipitated by intense emotional stress. Although there is an apparent rapid and spontaneous recovery ...of left ventricular ejection fraction, the long-term clinical and functional consequences of takotsubo cardiomyopathy are ill-defined.
METHODS:In an observational case-control study, we recruited 37 patients with prior (>12-month) takotsubo cardiomyopathy, and 37 age-, sex-, and comorbidity-matched control subjects. Patients completed the Minnesota Living with Heart Failure Questionnaire. All participants underwent detailed clinical phenotypic characterization, including serum biomarker analysis, cardiopulmonary exercise testing, echocardiography, and cardiac magnetic resonance including cardiac P-spectroscopy.
RESULTS:Participants were predominantly middle-age (64±11 years) women (97%). Although takotsubo cardiomyopathy occurred 20 (range 13–39) months before the study, the majority (88%) of patients had persisting symptoms compatible with heart failure (median of 13 range 0–76 in the Minnesota Living with Heart Failure Questionnaire) and cardiac limitation on exercise testing (reduced peak oxygen consumption, 24±1.3 versus 31±1.3 mL/kg/min, P<0.001; increased VE/VCO2 slope, 31±1 versus 26±1, P=0.002). Despite normal left ventricular ejection fraction and serum biomarkers, patients with prior takotsubo cardiomyopathy had impaired cardiac deformation indices (reduced apical circumferential strain, −16±1.0 versus −23±1.5%, P<0.001; global longitudinal strain, −17±1 versus −20±1%, P=0.006), increased native T1 mapping values (1264±10 versus 1184±10 ms, P<0.001), and impaired cardiac energetic status (phosphocreatine/γ-adenosine triphosphate ratio, 1.3±0.1 versus 1.9±0.1, P<0.001).
CONCLUSIONS:In contrast to previous perceptions, takotsubo cardiomyopathy has long-lasting clinical consequences, including demonstrable symptomatic and functional impairment associated with persistent subclinical cardiac dysfunction. Taken together our findings demonstrate that after takotsubo cardiomyopathy, patients develop a persistent, long-term heart failure phenotype.
CLINICAL TRIAL REGISTRATION:URLhttps://clinicaltrials.gov. Unique identifierNCT02989454.
Interfacial chemistry and energetics significantly impact the performance of photovoltaic devices. In the case of Pb-containing organic metal halide perovskites, photoelectron spectroscopy has been ...used to determine the energetic alignment of frontier electronic energy levels at various interfaces present in the photovoltaic device. For the Sn-containing analogues, which are less toxic, no such measurements have been made. Through a combination of ultraviolet, inverse, and X-ray photoelectron spectroscopy (UPS, IPES, and XPS, respectively) measurements taken at varying thickness increments during stepwise deposition of C60 on FASnI3, we present the first direct measurements of the frontier electronic energy levels across the FASnI3/C60 interface. The results show band bending in both materials and transport gap widening in FASnI3 at the interface with C60. The XPS results show that iodide diffuses into C60 and results in n-doping of C60. This iodide diffusion out of FASnI3 impacts the valence and conduction band energies of FASnI3 more than the core levels, with the core level shifts displaying a different trend than the valence and conduction bands. Surface treatment of FASnI3 with carboxylic acids and bulky ammonium substituted surface ligands results in slight alterations in the interfacial energetics, and all surface ligands result in similar or improved PV performance relative to the untreated devices. The greatest PV stability results from treatment with a fluorinated carboxylic acid derivative; however, iodide diffusion is still observed to occur with this surface ligand.
We report results of density functional theory calculations of structure and properties of 1‒5 monolayer (ML) thin FeO(001) films and their interactions with the Fe(001) surface. It is found that ...deposition of an iron-oxide film affects weakly geometry of the Fe(001) support, causing small < 2% expansion of the first interplanar distance compared to clean iron surface. Analysis of the electronic structure of the FeO/Fe system shows that after interface formation, the oxide layer remains semiconducting and the substrate metallic. Electronic structure of the FeO(001) layer in direct contact with the Fe(001) surface exhibits metallic character. Magnetism of the metal/semiconductor interface is only slightly disturbed compared to that of isolated components. The FeO adlayers preserve antiferromagnetic (AFM) nature of the oxide and the sharp boundary between higher AFM phase of FeO and lower ferromagnetic (FM) phase of Fe is observed at the interface.
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During downhill running, manoeuvring, negotiation of obstacles and landings from a jump, mechanical energy is dissipated via active lengthening of limb muscles. Tendon compliance provides a ...‘shock-absorber’ mechanism that rapidly absorbs mechanical energy and releases it more slowly as the recoil of the tendon does work to stretch muscle fascicles. By lowering the rate of muscular energy dissipation, tendon compliance likely reduces the risk of muscle injury that can result from rapid and forceful muscle lengthening. Here, we examine how muscle–tendon mechanics are modulated in response to changes in demand for energy dissipation. We measured lateral gastrocnemius (LG) muscle activity, force and fascicle length, as well as leg joint kinematics and ground-reaction force, as turkeys performed drop-landings from three heights (0.5–1.5 m centre-of-mass elevation). Negative work by the LG muscle–tendon unit during landing increased with drop height, mainly owing to greater muscle recruitment and force as drop height increased. Although muscle strain did not increase with landing height, ankle flexion increased owing to increased tendon strain at higher muscle forces. Measurements of the length–tension relationship of the muscle indicated that the muscle reached peak force at shorter and likely safer operating lengths as drop height increased. Our results indicate that tendon compliance is important to the modulation of energy dissipation by active muscle with changes in demand and may provide a mechanism for rapid adjustment of function during deceleration tasks of unpredictable intensity.
•Visual systems in vertebrates are energetically costly, especially in the dark.•Fish, birds, reptiles, and mammals each supply metabolites to retinas differently.•Mammals have avascular or ...vascularized retinas, with accordant metabolic changes.•Photoreceptors have unique metabolisms including phosphocreatine and lactate shuttles.•Ischemia and hypoxia underlie several Western diseases which lead to blindness.
The retina is part of the central nervous system, and shares the characteristically high metabolism of the brain. The high energy demand of the retina is normally matched with a large supply of metabolites. When supply does not equal demand (e.g. if retinal blood flow is impaired), retinal neurons are at risk of excitotoxic cell death and vision is impaired or lost. Understanding the energetic budget of the retina is therefore crucial for understanding the pathology and treatment of retinal disease. In this minireview I give an overview of the energetics of the retina, with a focus on lessons learnt from comparative physiology. Retinas of all species studied thus far receive blood flow from choroidal capillaries. Additionally, fish, reptiles, and birds each have unique structures to increase metabolite supply. Primates and some mammals also have intra- and supraretinal vasculature to supply the retina, while other mammals rely solely on the choroid at the cost of retinal thickness. Neuroglobin, an oxygen-binding protein, may assist in oxygen delivery to counteract large diffusion distances from capillaries to mitochondria. Energy demand differs among models, as does mitochondrial location. More ATP is consumed in the dark due to Na+/K+ ATPase activity to counteract the dark current, whereas phototransduction dominates ATP demand in the light. Photoreceptor metabolism is therefore especially high, and may be sustained with phosphocreatine and lactate shuttles. This comparative physiology approach raises new research questions, and suggests caution in comparing animal models of retinal disease, as they differ greatly in vasculature and energetics.
Molecular Mechanisms of Winter Survival Teets, Nicholas M; Marshall, Katie E; Reynolds, Julie A
Annual review of entomology,
2023-Jan-23, Letnik:
68, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Winter provides many challenges for insects, including direct injury to tissues and energy drain due to low food availability. As a result, the geographic distribution of many species is tightly ...coupled to their ability to survive winter. In this review, we summarize molecular processes associated with winter survival, with a particular focus on coping with cold injury and energetic challenges. Anticipatory processes such as cold acclimation and diapause cause wholesale transcriptional reorganization that increases cold resistance and promotes cryoprotectant production and energy storage. Molecular responses to low temperature are also dynamic and include signaling events during and after a cold stressor to prevent and repair cold injury. In addition, we highlight mechanisms that are subject to selection as insects evolve to variable winter conditions. Based on current knowledge, despite common threads, molecular mechanisms of winter survival vary considerably across species, and taxonomic biases must be addressed to fully appreciate the mechanistic basis of winter survival across the insect phylogeny.
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