Environmental drivers of increased ecosystem respiration in a warming tundra.

Arctic and alpine tundra ecosystems are large reservoirs of organic carbon1,2. Climate warming may stimulate ecosystem respiration and release carbon into the atmosphere3,4. The magnitude and persistency of this stimulation and the environmental mechanisms that drive its variation remain uncertain5-7. This hampers the accuracy of global land carbon-climate feedback projections7,8. Here we synthesize 136 datasets from 56 open-top chamber in situ warming experiments located at 28 arctic and alpine tundra sites which have been running for less than 1 year up to 25 years. We show that a mean rise of 1.4 °C [confidence interval (CI) 0.9-2.0 °C] in air and 0.4 °C [CI 0.2-0.7 °C] in soil temperature results in an increase in growing season ecosystem respiration by 30% [CI 22-38%] (n = 136). Our findings indicate that the stimulation of ecosystem respiration was due to increases in both plant-related and microbial respiration (n = 9) and continued for at least 25 years (n = 136). The magnitude of the warming effects on respiration was driven by variation in warming-induced changes in local soil conditions, that is, changes in total nitrogen concentration and pH and by context-dependent spatial variation in these conditions, in particular total nitrogen concentration and the carbon:nitrogen ratio. Tundra sites with stronger nitrogen limitations and sites in which warming had stimulated plant and microbial nutrient turnover seemed particularly sensitive in their respiration response to warming. The results highlight the importance of local soil conditions and warming-induced changes therein for future climatic impacts on respiration.

A conical passive magnetic bearing with constant stiffness.

A nested conical passive magnetic bearing is presented. The bearing consists of a nested conical rotor inside a conical stator, i.e. two coaxial tilted rings of permanent magnets, both with a rectangular cross section. Varying the cone or tilt angle of the rotor and stator we determine the rotor radius that provides the highest force for three different magnetization cases. For this optimal rotor radius, we show that the bearing with the highest volume normalized force also has the highest stiffness, and furthermore often also the highest varying stiffness with axial displacement. Finally, we show that a conical bearings with a tilt angle of [Formula: see text] has an almost constant stiffness and a linearly varying force with axial displacement, making it ideal as a bearing.

Global plant trait relationships extend to the climatic extremes of the tundra biome.

The majority of variation in six traits critical to the growth, survival and reproduction of plant species is thought to be organised along just two dimensions, corresponding to strategies of plant size and resource acquisition. However, it is unknown whether global plant trait relationships extend to climatic extremes, and if these interspecific relationships are confounded by trait variation within species. We test whether trait relationships extend to the cold extremes of life on Earth using the largest database of tundra plant traits yet compiled. We show that tundra plants demonstrate remarkably similar resource economic traits, but not size traits, compared to global distributions, and exhibit the same two dimensions of trait variation. Three quarters of trait variation occurs among species, mirroring global estimates of interspecific trait variation. Plant trait relationships are thus generalizable to the edge of global trait-space, informing prediction of plant community change in a warming world.

Traditional plant functional groups explain variation in economic but not size-related traits across the tundra biome.

AIM: Plant functional groups are widely used in community ecology and earth system modelling to describe trait variation within and across plant communities. However, this approach rests on the assumption that functional groups explain a large proportion of trait variation among species. We test whether four commonly used plant functional groups represent variation in six ecologically important plant traits. LOCATION: Tundra biome. TIME PERIOD: Data collected between 1964 and 2016. MAJOR TAXA STUDIED: 295 tundra vascular plant species. METHODS: We compiled a database of six plant traits (plant height, leaf area, specific leaf area, leaf dry matter content, leaf nitrogen, seed mass) for tundra species. We examined the variation in species-level trait expression explained by four traditional functional groups (evergreen shrubs, deciduous shrubs, graminoids, forbs), and whether variation explained was dependent upon the traits included in analysis. We further compared the explanatory power and species composition of functional groups to alternative classifications generated using post hoc clustering of species-level traits. RESULTS: Traditional functional groups explained significant differences in trait expression, particularly amongst traits associated with resource economics, which were consistent across sites and at the biome scale. However, functional groups explained 19% of overall trait variation and poorly represented differences in traits associated with plant size. Post hoc classification of species did not correspond well with traditional functional groups, and explained twice as much variation in species-level trait expression. MAIN CONCLUSIONS: Traditional functional groups only coarsely represent variation in well-measured traits within tundra plant communities, and better explain resource economic traits than size-related traits. We recommend caution when using functional group approaches to predict tundra vegetation change, or ecosystem functions relating to plant size, such as albedo or carbon storage. We argue that alternative classifications or direct use of specific plant traits could provide new insights for ecological prediction and modelling.

Meta-analysis of negative pressure wound therapy of closed groin incisions in arterial surgery.

BACKGROUND: Surgical-site infection (SSI) after groin incisions for arterial surgery is common and may lead to amputation or death. Incisional negative pressure wound therapy (NPWT) dressings have been suggested to reduce SSIs. The aim of this systematic review with meta-analysis was to assess the effects of incisional NPWT on the incidence of SSI in closed groin incisions after arterial surgery. METHODS: A study protocol for this systematic review of RCTs was published in Prospero (CRD42018090298) a priori, with predefined search, inclusion and exclusion criteria. The records generated by the systematic research were screened for relevance by title and abstract and in full text by two of the authors independently. The selected articles were rated for bias according to the Cochrane risk-of-bias tool. RESULTS: Among 1567 records generated by the search, seven RCTs were identified, including 1049 incisions. Meta-analysis showed a reduction in SSI with incisional NPWT (odds ratio (OR) 0·35, 95 per cent c.i. 0·24 to 0·50; P < 0·001). The heterogeneity between the included studies was low (I2 = 0 per cent). The quality of evidence was graded as moderate. Two studies had multiple domains in the Cochrane risk-of-bias tool rated as high risk of bias. A subgroup meta-analysis of three studies of lower limb revascularization procedures only (363 incisions) demonstrated a similar reduction in SSI (OR 0·37, 0·22 to 0·63; P < 0·001; I2 = 0 per cent). CONCLUSION: Incisional NPWT after groin incisions for arterial surgery reduced the incidence of SSI compared with standard wound dressings. The risk of bias highlighted the need for a high-quality RCT with cost-effectiveness analysis.

Direct measurements of the magnetic entropy change.

An experimental device that can accurately measure the magnetic entropy change, Δs, as a function of temperature, T, and magnetic field, H, is presented. The magnetic field source is in this case a set of counter-rotating concentric Halbach-type magnets, which produce a highly homogeneous applied field with constant orientation. The field may be varied from 0 to 1.5 T in a continuous way. The temperature stability of the system is controlled to within ±10 mK and the standard range for the current setup is from 230 K to 330 K. The device is under high vacuum and we show that thermal losses to the ambient are negligible in terms of the calorimetric determination of the magnetic entropy change, while the losses cannot be ignored when correcting for the actual sample temperature. We apply the device to two different types of samples; one is commercial grade Gd, i.e., a pure second-order phase transition material, while the other is Gd5Si2Ge2, a first order magnetic phase transition material. We demonstrate the device's ability to fully capture the thermal hysteresis of the latter sample by following appropriate thermal resetting scheme and magnetic resetting scheme.

Alpine cushion plants inhibit the loss of phylogenetic diversity in severe environments.

Biotic interactions can shape phylogenetic community structure (PCS). However, we do not know how the asymmetric effects of foundation species on communities extend to effects on PCS. We assessed PCS of alpine plant communities around the world, both within cushion plant foundation species and adjacent open ground, and compared the effects of foundation species and climate on alpha (within-microsite), beta (between open and cushion) and gamma (open and cushion combined) PCS. In the open, alpha PCS shifted from highly related to distantly related with increasing potential productivity. However, we found no relationship between gamma PCS and climate, due to divergence in phylogenetic composition between cushion and open sub-communities in severe environments, as demonstrated by increasing phylo-beta diversity. Thus, foundation species functioned as micro-refugia by facilitating less stress-tolerant lineages in severe environments, erasing a global productivity - phylogenetic diversity relationship that would go undetected without accounting for this important biotic interaction.

Prefrontal contributions to executive control: fMRI evidence for functional distinctions within lateral Prefrontal cortex.

The prefrontal cortex (PFC) plays a fundamental role in internally guided behavior. Although it is generally accepted that PFC subserves working memory and executive control operations, it remains unclear whether the subregions within lateral PFC support distinct executive control processes. An event-related fMRI study was implemented to test the hypothesis that ventrolateral and dorsolateral PFC are functionally distinct, as well as to assess whether functional specialization exists within ventrolateral PFC. Participants performed two executive control tasks that differed in the types of control processes required. During rote rehearsal, participants covertly rehearsed three words in the order presented, thus requiring phonological access and maintenance. During elaborative rehearsal, participants made semantic comparisons between three words held in working memory, reordering them from least to most desirable. Thus, in addition to maintenance, elaborative rehearsal required goal-relevant coding of items in working memory ("monitoring") and selection from among the items to implement their reordering. Results revealed that left posterior ventrolateral PFC was active during performance of both tasks, whereas right dorsolateral PFC was differentially engaged during elaborative rehearsal. The temporal characteristics of the hemodynamic responses further suggested that dorsolateral activation lagged ventrolateral activation. Finally, differential activation patterns were observed within left ventrolateral PFC, distinguishing between posterior and anterior regions. These data suggest that anatomically separable subregions within lateral PFC may be functionally distinct and are consistent with models that posit a hierarchical relationship between dorsolateral and ventrolateral regions such that the former monitors and selects goal-relevant representations being maintained by the latter.

Metacognition in motor learning.

Research on judgments of verbal learning has demonstrated that participants' judgments are unreliable and often overconfident. The authors studied judgments of perceptual-motor learning. Participants learned 3 keystroke patterns on the number pad of a computer, each requiring that a different sequence of keys be struck in a different total movement time. Practice trials on each pattern were either blocked or randomly interleaved with trials on the other patterns, and each participant was asked, periodically, to predict his or her performance on a 24-hr test. Consistent with earlier findings, blocked practice enhanced acquisition but harmed retention. Participants, though, predicted better performance given blocked practice. These results augment research on judgments of verbal learning and suggest that humans, at their peril, interpret current ease of access to a perceptual-motor skill as a valid index of learning.

When further learning fails: stability and change following repeated presentation of text.

Kay (1955) presented a text passage to participants on a weekly basis and found that most errors and omissions in recall persisted despite repeated re-presentation of the text. Experiment I replicated and extended Kay's original research, demonstrating that after a first recall attempt there was very little evidence of further learning, whether measured in terms of further acquisition or error correction, over three more presentations of the text passages. Varying the schedule of presentations and tests had little effect, although performance was better when intermediate trials included both presentation and test than when only presentations or tests occurred. Experiment 2 explored whether this 'failure of further learning' effect could be overcome by (a) warning participants against basing their recall on their previous recall efforts and specifically directing them to base their recall upon the passages, (b) making each presentation more distinctive, or (c) drawing participants' attention to areas that would benefit from further learning by requiring them to tally their omissions and errors. The effect persisted in all cases. The findings have serious implications for the learning of text material.

Retrieval-induced forgetting: evidence for a recall-specific mechanism.

Previous work has shown that recalling information from long-term memory can impair the long-term retention of related representations--a phenomenon known as retrieval-induced forgetting (Anderson, Bjork, & Bjork, 1994). We report an experiment in which the question of whether retrieval is necessary to induce this form of impairment was examined. All the subjects studied six members from each of eight taxonomic categories (e.g., fruit orange). In the competitive practice condition, the subjects practiced recalling three of the six members, using category-stem cues (e.g., fruit or__). In the noncompetitive practice condition, the subjects were reexposed to these same members for the same number of repetitions but were asked to recall the category name by using the exemplar and a stem as cues (e.g., fr__orange). Despite significant and comparable facilitation of practiced items in both conditions, only the competitive practice subjects were impaired in their ability to recall the nonpracticed members on a delayed cued-recall test. These findings argue that retrieval-induced forgetting is not caused by increased competition arising from the strengthening of practiced items, but by inhibitory processes specific to the situation of recall.

Independence of scientific publishing. Reaffirming the principle.

Historically, the American Psychological Association (APA), as part of its contract with the editors of APA journals, has granted to the editors sole responsibility to accept or reject manuscripts for publication, without such actions being open for review by APA. Such a policy fosters the freedom of inquiry and expression so necessary for a healthy science. It also serves to protect the Association because publication of an article in an APA journal does not represent endorsement by APA itself. The lessons of history are clear: When political or other pressures interfere with the autonomy of science, the societal and scientific consequences are grim. APA should reaffirm the principle that a healthy science of psychology requires an open exchange of ideas and findings.

On the relationship between recognition speed and accuracy for words rehearsed via rote versus elaborative rehearsal.

Tacit within both lay and cognitive conceptualizations of learning is the notion that those conditions of learning that foster "good" retention do so by increasing both the probability and the speed of access to the relevant information. In 3 experiments, time pressure during recognition is shown to decrease accessibility more for words learned via elaborative rehearsal than for words learned via rote rehearsal, despite the fact that elaborative rehearsal is a more efficacious learning strategy as measured by the probability of access. In Experiment 1, participants learned each word using both types of rehearsal, and the results show that access to the products of elaborative rehearsal is more compromised by time pressure than is access to the products of rote rehearsal. The results of Experiment 2, in which each word was learned via either pure rote or pure elaborative rehearsal, exhibit the same pattern. Experiment 3, in which the authors used the response-signal procedure, provides evidence that this difference in accessibility owes not to differences in the rate of access to the 2 types of traces, but rather to the higher asymptotic level of stored information for words learned via elaborative rehearsal.

Psychological Science in the Public Interest: the case for juried analyses.

The inaugural issue of Psychological Science in the Public Interest (PSPI), a new publishing initiative by the American Psychological Society, accompanies this issue of Psychological Science. The report it contains, "Psychological Science Can Improve Diagnostic Decisions," by John Swets, Robyn Dawes, and John Monahan, represents a careful effort by those authors to summarize the potential of modern psychological science to enhance real-world diagnostic decisions. Such decisions (Is a cancer present? Will this individual commit violence? Will an impending storm strike? Will this applicant succeed?) are prevalent and crucial to the lives of individuals and to the well-being of our society. Subsequent issues of PSPI will address other important topics of public interest in areas where psychological science may have the potential to inform and improve public policy. Each of those reports will also represent the efforts of a distinguished team of scientists to report the available evidence, and the implications of that evidence, fairly and comprehensively. In this article, we describe the goals, procedures, and potential of PSPI.

Specialty care for patients with epilepsy must become standard of care. Promotion of Specialty Care for Epilepsy Group.

Epilepsy is a complex, common disorder with severe consequences for patients. The authors believe that a significant percentage of patients are receiving suboptimal care. The national standard of care needs to be upgraded to include the notion that patients with less than total seizure control or those suffering from any medication side-effects should be given the opportunity to receive specialty care by physicians with specific expertise in the field of epilepsy.

Predicting the future and reconstructing the past: a Bayesian characterization of the utility of subjective fluency.

The subjective sense of fluency with which an item can be perceived or remembered is proposed to be a vital cue in making decisions about the future memorability and the nature of our past experience with that stimulus. We first outline a number of cases in which such perceptual or retrieval fluency influences judgments both about our own future performance and our likely past experience, and then present a Bayesian analysis of how judgments of recognition--deciding whether or not a currently viewed item was studied at a particular point in the past--may incorporate information about the perceptual fluency of that item. Using a simple mathematical model, we then provide an interpretation of certain enigmatic phenomena in recognition memory.

The mismeasure of memory: when retrieval fluency is misleading as a metamnemonic index.

The experiments address the degree to which retrieval fluency--the case with which information is accessed from long-term memory--guides and occasionally misleads metamnemonic judgments. In each of 3 experiments, participants' predictions of their own future recall performance were examined under conditions in which probability or speed of retrieval at one time or on one task is known to be negatively related to retrieval probability on a later task. Participants' predictions reflected retrieval fluency on the initial task in each case, which led to striking mismatches between their predicted and actual performance on the later tasks. The results suggest that retrieval fluency is a potent but not necessarily reliable source of information for metacognitive judgments. Aspects of the results suggest that a basis on which better and poorer rememberers differ is the degree to which certain memory dynamics are understood, such as the fleeting nature of recency effects and the consequences of an initial retrieval. The results have pedagogical as well as theoretical implications, particularly with respect to the education of subjective assessments of ongoing learning.

Continuing influences of to-be-forgotten information.

In the present paper, we first argue that it is critical for humans to forget; that is, to have some means of preventing out-of-date information from interfering with the recall of current information. We then argue that the primary means of accomplishing such adaptive updating of human memory is retrieval inhibition: Information that is rendered out of date by new learning becomes less retrievable, but remains at essentially full strength in memory as indexed by other measures, such as recognition and word-fragment completion. We conclude with a speculation that certain unconscious influences of prior events may, in fact, be stronger if those events were to be forgotten rather than to be remembered.