Over the past half century, the Arctic has warmed at about twice the global rate. The reduction of sea ice and snow cover has contributed to the high-latitude warming, as the maximum of the ...amplification during autumn is a fingerprint of the ice-albedo feedback. There is evidence that atmospheric water vapor, a greenhouse gas, has increased in the Arctic over the past several decades. Ocean heat fluxes into the Arctic from the North Atlantic and North Pacific have also contributed to the Arctic warming through a reduction of sea ice. Observational and modeling studies suggest that reduced sea ice cover and a warmer Arctic in autumn may affect the middle latitudes by weakening the west-to-east wind speeds in the upper atmosphere, by increasing the frequency of wintertime blocking events that in turn lead to persistence or slower propagation of anomalous temperatures in middle latitudes, and by increasing continental snow cover that can in turn influence the atmospheric circulation. While these effects on middle latitudes have been suggested by some analyses, natural variability has thus far precluded a conclusive demonstration of an impact of the Arctic on mid-latitude weather and climate.
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High-fat diet (HFD)-induced obesity is associated with insulin resistance, which may affect brain synaptic plasticity through impairment of insulin-sensitive processes underlying neuronal survival, ...learning, and memory. The experimental model consisted of 3 month-old C57BL/6J mice fed either a normal chow diet (control group) or a HFD (60% of calorie from fat; HFD group) for 12 weeks. This model was characterized as a function of time in terms of body weight, fasting blood glucose and insulin levels, HOMA-IR values, and plasma triglycerides. IRS-1/Akt pathway was assessed in primary hepatocytes and brain homogenates. The effect of HFD in brain was assessed by electrophysiology, input/output responses and long-term potentiation. HFD-fed mice exhibited a significant increase in body weight, higher fasting glucose- and insulin levels in plasma, lower glucose tolerance, and higher HOMA-IR values. In liver, HFD elicited (a) a significant decrease of insulin receptor substrate (IRS-1) phosphorylation on Tyr608 and increase of Ser307 phosphorylation, indicative of IRS-1 inactivation; (b) these changes were accompanied by inflammatory responses in terms of increases in the expression of NFκB and iNOS and activation of the MAP kinases p38 and JNK; (c) primary hepatocytes from mice fed a HFD showed decreased cellular oxygen consumption rates (indicative of mitochondrial functional impairment); this can be ascribed partly to a decreased expression of PGC1α and mitochondrial biogenesis. In brain, HFD feeding elicited (a) an inactivation of the IRS-1 and, consequentially, (b) a decreased expression and plasma membrane localization of the insulin-sensitive neuronal glucose transporters GLUT3/GLUT4; (c) a suppression of the ERK/CREB pathway, and (d) a substantial decrease in long-term potentiation in the CA1 region of hippocampus (indicative of impaired synaptic plasticity). It may be surmised that 12 weeks fed with HFD induce a systemic insulin resistance that impacts profoundly on brain activity, i.e., synaptic plasticity.
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Inflammasomes in the CNS Walsh, John G; Muruve, Daniel A; Power, Christopher
Nature reviews. Neuroscience,
02/2014, Volume:
15, Issue:
2
Journal Article
Peer reviewed
Microglia and macrophages in the CNS contain multimolecular complexes termed inflammasomes. Inflammasomes function as intracellular sensors for infectious agents as well as for host-derived danger ...signals that are associated with neurological diseases, including meningitis, stroke and Alzheimer's disease. Assembly of an inflammasome activates caspase 1 and, subsequently, the proteolysis and release of the cytokines interleukin-1β and interleukin-18, as well as pyroptotic cell death. Since the discovery of inflammasomes in 2002, there has been burgeoning recognition of their complexities and functions. Here, we review the current understanding of the functions of different inflammasomes in the CNS and their roles in neurological diseases.
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Summary Exercise interventions in individuals with Parkinson's disease incorporate goal-based motor skill training to engage cognitive circuitry important in motor learning. With this exercise ...approach, physical therapy helps with learning through instruction and feedback (reinforcement) and encouragement to perform beyond self-perceived capability. Individuals with Parkinson's disease become more cognitively engaged with the practice and learning of movements and skills that were previously automatic and unconscious. Aerobic exercise, regarded as important for improvement of blood flow and facilitation of neuroplasticity in elderly people, might also have a role in improvement of behavioural function in individuals with Parkinson's disease. Exercises that incorporate goal-based training and aerobic activity have the potential to improve both cognitive and automatic components of motor control in individuals with mild to moderate disease through experience-dependent neuroplasticity. Basic research in animal models of Parkinson's disease is beginning to show exercise-induced neuroplastic effects at the level of synaptic connections and circuits.
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Summary
Serum thyroid‐stimulating hormone (TSH) testing is the best screening tool for thyroid dysfunction. When TSH levels are in the reference range, additional tests such as free thyroxine, free ...triiodothyronine or thyroid antibodies rarely add value, except in patients with pituitary disease, when TSH is unreliable.
Overt hypothyroidism and subclinical hypothyroidism with TSH levels > 10 mU/L can be treated without further investigation. The health impact of subclinical hypothyroidism with mildly elevated levels of TSH (4–10 mU/L) remains uncertain, particularly in older people; treatment or observation are reasonable options.
Thyroxine remains standard treatment for hypothyroidism, with optimal dosage determined by clinical response and serum TSH.
Hyperthyroidism is commonly caused by Graves' disease, thyroiditis or toxic nodular goitre. The cause should be established before offering treatment. Radionuclide scanning is the imaging modality of choice. Positive TSH‐receptor antibodies indicate Graves' disease.
Thyroid ultrasound is indicated for assessment of palpable goitre and thyroid nodules. It is not part of routine assessment of hyperthyroidism or hypothyroidism. Overzealous use of ultrasound identifies clinically unimportant thyroid nodules and can lead to overdiagnosis of thyroid cancer.
For thyroid nodules, the key investigation is ultrasound‐guided fine needle aspiration biopsy, depending on size and sonographic appearance. Biopsy should not be performed routinely on small nodules < 1 cm.
It remains controversial whether pregnant women should be screened for thyroid disease. Reference intervals for thyroid function tests during pregnancy are not well established, and it is uncertain whether thyroxine treatment for pregnant women with serum TSH levels between 2.5 and 4.0 mU/L is beneficial. Iodine supplementation is recommended during pregnancy.
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•Use bibliometric and survey data to analyze the dynamics of size, knowledge variety, and creativity in scientific teams.•Team size has inverted-U relation with novelty and continually increasing ...relation with impact.•Size–novelty relationship is driven by effect of knowledge variety.•Knowledge variety does not have a direct effect on impact, net of novelty and size.•Suggests the need for a governance approach to scientific work and S&T policies unpacking novelty and impact.
The increasing dominance of team science highlights the importance of understanding the effects of team composition on the creativity of research results. In this paper, we analyze the effect of team size, and field and task variety on creativity. Furthermore, we unpack two facets of creativity in science: novelty and impact. We find that increasing team size has an inverted-U shaped relation with novelty. We also find that the size–novelty relationship is largely due to the relation between size and team field or task variety, consistent with the information processing perspective. On the other hand, team size has a continually increasing relation with the likelihood of a high-impact paper. Furthermore, variety does not have a direct effect on impact, net of novelty. This study develops our understanding of team science and highlights the need for a governance approach to scientific work. We also advance the creativity literature by providing an ex ante objective bibliometric measure that distinguishes novelty from impact, and illustrate the distinct team-level drivers of each. We conclude with a discussion of the policy implications of our findings.
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Changing demographics of scientific careers Milojević, Staša; Radicchi, Filippo; Walsh, John P.
Proceedings of the National Academy of Sciences - PNAS,
12/2018, Volume:
115, Issue:
50
Journal Article
Peer reviewed
Open access
Contemporary science has been characterized by an exponential growth in publications and a rise of team science. At the same time, there has been an increase in the number of awarded PhD degrees, ...which has not been accompanied by a similar expansion in the number of academic positions. In such a competitive environment, an important measure of academic success is the ability to maintain a long active career in science. In this paper, we study workforce trends in three scientific disciplines over half a century. We find dramatic shortening of careers of scientists across all three disciplines. The time over which half of the cohort has left the field has shortened from 35 y in the 1960s to only 5 y in the 2010s. In addition, we find a rapid rise (from 25 to 60% since the 1960s) of a group of scientists who spend their entire career only as supporting authors without having led a publication. Altogether, the fraction of entering researchers who achieve full careers has diminished, while the class of temporary scientists has escalated. We provide an interpretation of our empirical results in terms of a survival model from which we infer potential factors of success in scientific career survivability. Cohort attrition can be successfully modeled by a relatively simple hazard probability function. Although we find statistically significant trends between survivability and an author’s early productivity, neither productivity nor the citation impact of early work or the level of initial collaboration can serve as a reliable predictor of ultimate survivability.
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Arctic sea ice data from a variety of historical sources have been synthesized into a database extending back to 1850 with monthly time-resolution. The synthesis procedure includes interpolation to a ...uniform grid and an analog-based estimation of ice concentrations in areas of no data. The consolidated database shows that there is no precedent as far back as 1850 for the 21
st
century's minimum ice extent of sea ice on the pan-Arctic scale. A regional-scale exception to this statement is the Bering Sea. The rate of retreat since the 1990s is also unprecedented and especially large in the Beaufort and Chukchi Seas. Decadal and multidecadal variations have occurred in some regions, but their magnitudes are smaller than that of the recent ice loss. Interannual variability is prominent in all regions and will pose a challenge to sea ice prediction efforts.
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BFBNIB, DOBA, FZAB, GIS, IJS, INZLJ, IZUM, KILJ, NLZOH, NMLJ, NUK, ODKLJ, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, SIK, UILJ, UKNU, UL, UM, UPUK, ZRSKP
In the 1770s’ lectures on ethics, Kant distinguishes between two principles of obligation: the principle of adjudication and the principle of execution. The former is the normative standard of moral ...evaluation, while the latter denotes the incentive for performing an obligatory action. This distinction is significant in that it anticipates Kant’s mature position of combining these two principles, i.e. the moral law later becomes the supreme principle of moral judgment and (via respect) is itself the incentive to moral action. I explicate Kant’s distinction in view of the moral thought of Francis Hutcheson, Adam Smith and Christian Wolff. I challenge the dominant views which interpret Kant’s distinction in connection with Hutcheson and Smith, and argue that it is best understood in relation to Wolff’s conception of obligation. While Hutcheson’s distinction between exciting and justifying reasons is broadly similar to Kant’s distinction, Hutcheson’s account does not centre on the concept of obligation. Furthermore, I argue that Smith’s distinction between the character of virtue and the faculty of the mind by which it is recommended to us does not concern the normative and motivational moments of moral agency, but rather the meta-ethical question of the nature of virtue and the faculty that conditions its appraisal. Finally, I show that Wolff’s conception of obligation involves normative and motivational aspects conceptually similar to Kant’s distinction between the two principles of obligation.
Abstract
Polar lows (PLs) are intense maritime mesocyclones that typically develop during marine cold-air outbreak events over the high latitudes. The impacts posed by these systems to humans and the ...broader environment demand a robust understanding of the environmental factors that promote PL formation and, in turn, skillful prediction of PL activity. We hypothesize that the variability of PL activity is associated with some key large-scale climate variables skewed toward “extreme” values, which can provide predictable information on PL activity beyond the synoptic time scale. A PL genesis potential index (PGI) is developed that relates the climatological spatial distribution of PL genesis frequency and key climate variables in a Poisson regression framework. The optimal set of predictors consists of a static stability parameter and an environmental baroclinicity parameter. The optimal predictor categories are shown to be robust across different reanalyses and PL track datasets. The observed spatial distribution and seasonal cycle of PL genesis frequency are represented well by the PGI, and the interannual variability of PL activity is captured skillfully. The effects of the Arctic Oscillation (AO), El Niño–Southern Oscillation (ENSO), and a few other climate modes on the interannual variability of PL activity are explored. Overall, our results suggest that the PGI may be used to inform skillful subseasonal to seasonal prediction of PL activity.
Significance Statement
Polar lows are intense mesocyclones over high-latitude oceans, and they have destructive impacts on coastal and island communities, and maritime and air operations. However, skillful prediction of polar lows on the subseasonal and longer time scales remains challenging. This study links polar low activity to large-scale environmental conditions in the Arctic through a statistical modeling approach. This work is based on the hypothesis that a shared statistical relationship exists between the large-scale climate variables and polar low activity across the Arctic, which enables a geographical unification of the controlling factors on polar low activity. Our results reveal two dominant factors, one related to the lower-tropospheric stratification and the other to the hydrodynamic instability of the lower-tropospheric flow. This statistical framework has potential applications to climate prediction and projection of polar low activity.
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