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Numerous approaches are used to characterise multiple long-term conditions (MLTC), including counts and indices. Few studies have compared approaches within the same dataset. We aimed to characterise MLTC using simple approaches, and compare their prevalence estimates of MLTC and associations with emergency hospital admission in the UK Biobank.We used baseline data from 495,465 participants (age 38-73 years) to characterise MLTC using four approaches: Charlson index (CI), Byles index (BI), count of 43 conditions (CC) and count of body systems affected (BC). We defined MLTC as more than two conditions using CI, BI and CC, and more than two body systems using BC. We categorised scores (incorporating weightings for the indices) from each approach as 0, 1, 2 and 3+. We used linked hospital episode statistics and performed survival analyses to test associations with an endpoint of emergency hospital admission or death over 5 years.The prevalence of MLTC was 44% (BC), 33% (CC), 6% (BI) and 2% (CI). Higher scores using all approaches were associated with greater outcome rates independent of sex and age group. For example, using CC, compared with score 0, score 2 had 1.95 (95% CI: 1.91, 1.99) and a score of 3+ had 3.12 (95% CI: 3.06, 3.18) times greater outcome rates. The discriminant value of all approaches was modest (C-statistics 0.60-0.63).The counts classified a greater proportion as having MLTC than the indices, highlighting that prevalence estimates of MLTC vary depending on the approach. All approaches had strong statistical associations with emergency hospital admission but a modest ability to identify individuals at risk.

A review of selected on Iran’s nuclear weapons program seized by Israeli intelligence confirms that: senior Iranian officials had decided in the late 1990s to actually manufacture nuclear weapons a...

Obstetric lacerations complicate the majority of deliveries. The application of standardized guidelines for assessing delivery trauma has not been assessed thoroughly in the United States. We recently identified gaps in US midwives' clinical assessment of delivery trauma. We conducted a cross-sectional national survey of practicing obstetricians in the USA to characterize their classification of obstetric lacerations. We hypothesized that attending obstetricians' identification and diagnosis of delivery trauma would be similar to our findings for midwives with frequent inaccuracy.We recruited clinically active obstetricians through the Pregnancy-Related Care Research Network. We asked participants to classify (from written definitions) and diagnose (from standard illustrations) common forms of vaginal delivery trauma using the widely employed perineal laceration degree system. We performed bivariate analysis of high- and low-scoring respondents and logistic regression to model characteristics associated with higher diagnostic accuracy.Of the 162 respondents who started the survey, 76% (123) were included for analysis (22% of solicited emails). Overall, we found wide variation in response accuracy with as few as 62% of respondents correctly classifying certain types of lacerations. Only 49 out of 123 (40%) use the Sultan third-degree subclassification system and 67 out of 123 (52%) continue to use the midline/median approach for episiotomies. Providers reporting fewer deliveries per month and fewer publicly insured patients earned higher scores.Obstetricians in a nationally representative US perinatal provider network inconsistently identify perineal and nonperineal lacerations. We found important clinical knowledge gaps, suggesting that vaginal delivery diagnoses in obstetric quality studies and pelvic floor research might be inaccurate.

Climate-growth relationships in altitudinal treeline forests are particularly informative because they represent the upper limit of a species range where growth is often especially sensitive to climatic variation. Radial growth response to climatic variables typically ranges from energy limited to water limited. In the Pacific Northwest region of North America, treeline forests are typically energy limited. Results from a recent study (Marcinkowski et al. 2015) indicate a change in climate-growth relationships over time in treeline mountain hemlock (Tsuga mertensiana) in northern Washington state. Here, we investigate whether these same relationships hold across 700 km of the range of treeline mountain hemlock in Oregon and Washington. Using cores from trees > 200 years old, we examined temporal and spatial variability of climate-growth relationships since the early 20th century. Results indicate 1) a potential weakening of energy limitation in forest growth at treeline, 2) a nonstationary growth response to climate variables through time, and 3) different patterns of growth response to climate from north to south. Climate-growth relationships were generally similar between different aspects in the same geographic location, with some exceptions. Correlations between climate variables and radial growth differ over time (ranging from significantly positive to significantly negative), indicating the non-stationary nature of climate-growth relationships. These results identify where changes in growth-limiting variables may be occurring at treeline. Additional changes in the effects of climate change on growth at treeline are expected, and may be temporally complex.

As they return to spawn and die in their natal streams, anadromous, semelparous fishes such as Pacific salmon import marine-derived nutrients to otherwise nutrient-poor freshwater and riparian ecosystems. Diverse organisms exploit this resource, and previous studies have indicated that riparian tree growth may be enhanced by such marine-derived nutrients. However, these studies were largely inferential and did not account for all factors affecting tree growth. As an experimental test of the contribution of carcasses to tree growth, for 20 yr, we systematically deposited all sockeye salmon (Oncorhynchus nerka) carcasses (217,055 individual salmon) in the riparian zone on one bank of a 2-km-long stream in southwestern Alaska, reducing carcass accumulation on one bank and enhancing it on the other. After accounting for partial consumption and movement of carcasses by brown bears (Ursus arctos) and variation in salmon abundance and body size, we estimated that 267,620 kg of salmon were deposited on the enhanced bank and 45,200 kg on the depleted bank over the 20 yr, for a 5.9-fold difference in total mass. In 2016, we sampled needles of 84 white spruce trees (Picea glauca) the dominant riparian tree species, for foliar nitrogen (N) content and stable isotope ratios (δ15 N), and took core samples for annual growth increments. Stable isotope analysis indicated that marine-derived N was incorporated into the new growth of the trees on the enhanced bank. Analysis of tree cores indicated that in the two decades prior to our enhancement experiment, trees on the south-facing (subsequently the depleted) bank grew faster than those on the north-facing (later enhanced) bank. This difference was reduced significantly during the two decades of fertilization, indicating an effect of the carcass transfer experiment against the background of other factors affecting tree growth.

The ability to accurately measure interannual variability of the stable isotope of nitrogen, 15N, in tree rings could greatly improve understanding of marine-derived nitrogen delivery to terrestrial ecosystems, soil nitrogen dynamics, and the influences of climate on nitrogen cycles. It could also provide a tool for reconstructing past salmon abundances. However, the mobility of nitrogen throughout the entire tree including between rings has confounded attempts to make full use of 15N in dendrochemistry. We report that despite solvent-based extraction pretreatment to remove nonstructural, mobile nitrogen from increment core samples, an elevated 15N signal is detected in rings formed up to about ten years prior to application of a 15N-enriched tracer in four western redcedar trees. We conclude that the interpretation of the heavy nitrogen signal in tree rings via this pretreatment extraction method is confounded. These findings corroborate work already done in the field.

The study of anatomical irregularities in tree rings has recently gained momentum as a complement to traditional tree-ring measurements as they may provide information on extreme climatic events. Two anomalies, blue rings (BR) and frost rings (FR), were analyzed in bristlecone pine (Pinus longaeva D.K. Bailey) trees located along an elevation gradient in northeastern Nevada. These two subannual ring anomalies were systematically compiled for two periods; one centered on 536 CE (well-known for a volcanically-induced period of climatic cooling) and the other on 1965 CE (useful due to the availability of instrumental climate data). During the period 523–545 CE (n ≥ 10 trees), both BR and latewood FR (LWFR) were recorded abundantly in 532 and 536, as well as a BR cluster from 539 to 542 CE. Years when trees solely recorded a BR (without an accompanying LWFR) were more frequent in the earlier period than in the modern period (1954–2006 CE; n ≥ 10 trees) when both anomalies tended to co-occur. These results suggest a shorter growing season in the 536 period than in the 20th century. Modern BR/LWFR were most abundant in 1965 and 1978 CE. Both anomalies were mainly observed in the highest elevation trees and both were produced in years characterized by cooler than average temperatures throughout the growing season. Anatomically, BR and LWFR did not differ significantly in tracheid dimensions except that LWFR clearly showed damages associated with sub-freezing temperatures. The main feature distinguishing BR and LWFR from “normal” tree rings was a significant reduction in latewood secondary wall thickness. In P. longaeva, BR like pale latewood (light) rings, result from short and cool growing seasons which leads to reduced (or interrupted) lignification of tracheids. In species producing extremely narrow latewood like P. longaeva it may be difficult to macroscopically identify pale latewood years, thus rendering microscopic investigation of BR as a climate proxy useful in paleoclimatic research.

The progress of science is tied to the standardization of measurements, instruments, and data. This is especially true in the Big Data age, where analyzing large data volumes critically hinges on the data being standardized. Accordingly, the lack of community-sanctioned data standards in paleoclimatology has largely precluded the benefits of Big Data advances in the field. Building upon recent efforts to standardize the format and terminology of paleoclimate data, this article describes the Paleoclimate Community reporTing Standard (PaCTS), a crowdsourced reporting standard for such data. PaCTS captures which information should be included when reporting paleoclimate data, with the goal of maximizing the reuse value of paleoclimate data sets, particularly for synthesis work and comparison to climate model simulations. Initiated by the LinkedEarth project, the process to elicit a reporting standard involved an international workshop in 2016, various forms of digital community engagement over the next few years, and grassroots working groups. Participants in this process identified important properties across paleoclimate archives, in addition to the reporting of uncertainties and chronologies; they also identified archive-specific properties and distinguished reporting standards for new versus legacy data sets. This work shows that at least 135 respondents overwhelmingly support a drastic increase in the amount of metadata accompanying paleoclimate data sets. Since such goals are at odds with present practices, we discuss a transparent path toward implementing or revising these recommendations in the near future, using both bottom-up and top-down approaches. ©2019. American Geophysical Union. All Rights Reserved., Code and data to reproduce the figures of this article are available on GitHub and released on Zenodo (doi:10.5281/zenodo.3165019). Definition of properties and recommendations are summarized here: http://wiki.linked.earth/PaCTS_v1.0 . This work was supported by the National Science Foundation through the EarthCube Program with Grant ICER‐1541029. Feedback solicitation on the standard was facilitated by the Past Global Changes (PAGES) organization. The 2016 workshop on Paleoclimate Data Standards was hosted by the World Data Service for Paleoclimatology (WDS/NOAA‐Paleo), and the participation of international attendees was made possible by a PAGES travel grant. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.

Permafrost soils store between 1,330–1,580 Pg carbon (C), which is three times the amount of C in global vegetation, almost twice the amount of C in the atmosphere, and half of the global soil organic C pool. Despite the massive amount of C in permafrost, estimates of soil C storage in the high latitude permafrost region are highly uncertain, primarily due to under sampling at all spatial scales; circumpolar soil C estimates lack sufficient continental spatial diversity, regional intensity, and replication at the field-site level. Siberian forests are particularly under sampled, yet the larch forests that dominate this region may store more than twice as much soil C as all other boreal forest types in the continuous permafrost zone combined. Here we present above and belowground C stocks from twenty sites representing a gradient of stand age and structure in a larch watershed of the Kolyma River near Cherskiy, Sakha Republic, Russia. We found that the majority of C stored in the top 1 m of the watershed was stored belowground (91 %), with 20 % in the top 10 cm of soil and 42 % in the top 30 cm. Carbon was more variable in surface soils (10 cm; coefficient of variation (CV) = 0.35 between stands) than in the top 30 cm (CV = 0.14) or soil profile to 1 m (CV = 0.12). Combined active layer and deep frozen deposits (surface – 15 m) contained 205 kg C m-2 (yedoma, non-ice wedge) and 331 kg C m-2 (alas), which, even when accounting for landscape-level ice content, is an order of magnitude more C than that stored in the top meter of soil and two orders of magnitude more C than in aboveground biomass. Aboveground biomass was composed of primarily larch (53 %) but also included understory vegetation (30 %), woody debris (11 %) and snag (6 %) biomass. While aboveground biomass contained relatively little (9 %) of the C stocks in the watershed, aboveground processes were linked to thaw depth and belowground C storage. Thaw depth was significantly negatively related to stand age, and variability of soil C in the top 10 cm was related to soil moisture and moss and lichen cover. These results suggest that as the climate warms, changes in stand age and structure may be as important as direct climate effects on belowground environmental conditions and permafrost C vulnerability.

This paper presents an experimental program to evaluate the effect of sustained loading and outdoor exposure on the shear strength of precast concrete sandwich panels connected with FRP grid/rigid foam insulation as shear transfer mechanism. CFRP and GFRP grids were considered in this study along with EPS and XPS foam. The experimental program is comprised of three different studies with a total of 26 test panels using different combinations of FRP grid and foam insulation.

We report new data on tree-ring growth in northern European Russia, a region with a hitherto relatively sparse tree-ring network. We explore its associations with climate variability. Areas, sampling locations and trees were selected for representativeness rather than climate sensitivity. Using tree rings from 651 conifers from six widely dispersed areas we show strong intercorrelation between trees within each major conifer species within and between areas. Regional composite tree-ring series for spruce and pine contain a major fraction of decadal and multidecadal variability. The most likely driver of this common variability is interannual to multidecadal climate variability. Gridded monthly instrumental climate data for the period 1902–2008, particularly mean temperature and total precipitation, were tested as predictors of each local species-specific tree-ring site chronology. The most consistent pattern emerged for spruce at all but the southernmost area. Cool and moist summers the year before growth were consistent drivers of spruce ring growth throughout the period, with no change in recent decades. Self-calibrating Palmer Drought Severity Index for prior summer was also a strong and consistent driver of spruce ring growth. For pine, there was a weaker but similarly stable association between larger rings and warm, moist conditions, in this case in the current summer. These associations were also identified at multidecadal time scales, particularly for spruce. On the other hand, the specific role of moisture variability in determining interannual to multidecadal variability in tree growth in this high latitude region raises questions about the relative vulnerability of spruce and pine there under global warming.

The instrumental temperature record is of insufficient length to fully express the natural variability of past temperature. High elevation tree-ring widths from Great Basin bristlecone pine (Pinus longaeva) are a par- ticularly useful proxy to infer temperatures prior to the instrumental record in that the tree-rings are annually dated and extend for millennia. From ring-width measurements integrated with past treeline elevation data we infer dec- adal- to millennial-scale temperature variability over the past 4,500 years for the Great Basin, USA. We find that twentieth century treeline advances are greater than in at least 4,000 years. There is also evidence for substantial volcanic forcing of climate in the preindustrial record and considerable covariation between high elevation tree-ring widths and temperature estimates from an atmosphere- ocean general circulation model over much of the last millennium. A long-term temperature decline of *-1.1 C since the mid-Holocene underlies substantial volcanic forcing of climate in the preindustrial record.

Aim Species distribution models (SDMs) are commonly used to forecast climate change impacts. These models, however, are subject to important assumptions and limitations. By integrating two independent but complementary methods, ensemble SDMs and statistical phylogeography, we addressed key assumptions and created robust assessments of climate change impacts on species distributions while improving the conservation value of these projections. Location North American cordillera. Methods This approach was demonstrated using the arctic-alpine plant Rhodiola integrifolia (Crassulaceae). SDMs were fitted to current and past climates using eight models, two thresholds and one to three climate data sets. These projections were combined to create a map of stable climate (refugia) since the Last Interglacial (124,000 kya). Five biogeographic hypotheses were developed based on the configuration of refugia and tested using statistical phylogeography. Projection of SDMs into the future was contingent on agreement across approaches; future projections (to 2085) used five climate data sets and two greenhouse gas scenarios. Results A multiple-refugia hypothesis was supported by both methods, confirming the assumption of niche conservatism in R. integrifolia and justifying the projection of SDMs onto future climates. Future projections showed substantial loss of climatically suitable habitat. Southern populations had the greatest losses, although the biogeographic scale of modelling may overpredict extinction risks in areas of topographic complexity. Past and future SDMs were assessed for novel values of climate variables; areas of novel climate were flagged as having higher uncertainty. Main conclusions Integrating molecular approaches with spatial analyses of species distributions under global change has great potential to improve conservation decision-making. Molecular tools can support and improve current methods for understanding the vulnerability of species to climate change and provide additional data upon which to base conservation decisions, such as prioritizing the conservation of areas of high genetic diversity to build evolutionary resiliency within populations.

Despite a consistent global relationship between the position of alpine and arctic treeline and temperature, fine-scale variability in treeline response to climate is widespread. In this chapter, we describe two advances in the application of dendroecology to treeline environments. First, we show that obtaining detailed, spatially explicit measurements of the environment can provide a more complete picture of how tree growth responds to climate. Substantial topoclimatic and environmental heterogeneity can occur at a very fine scale, a few tens of meters, at treeline. Unlike traditional approaches that aggregate tree growth across relatively broad areas, applying the approaches of landscape ecology and quantifying this heterogeneity can allow dendroecologists to better understand fine-scale, within-population variation in climate response. Second, the integration of dendroecological approaches with physiological ecology and soil biogeochemical studies can provide a more holistic understanding of tree growth, one that approaches trees as not merely being the sum of their rings, but as complex organisms whose growth integrates the impact of multiple limiting factors filtered through distinct physiological processes. In regions with cold soils, for example, we show that nutrient limitation can strongly mediate the response of tree growth to climate warming. Together, these approaches allow us to understand the causes of fine-scale variation in treeline response to warming, reconcile that variation with global-scale correlations between treeline and temperature, and better predict future responses of treeline ecosystems to warming.

Mean sensitivity (ζ) continues to be used in dendrochronology despite a literature that shows it to be of questionable value in describing the properties of a time series. We simulate first-order autoregressive models with known parameters and show that ζ is a function of variance and autocorrelation of a time series. We then use 500 random tree-ring data sets with unknown parameters and show that ζ is at best equivalent to the standard deviation of a time series in cases without high autocorrelation and is an inefficient estimator of the coefficient of variation. It is hard to justify the use of ζ as a useful, descriptive statistic in dendrochronology on theoretical or empirical grounds. It is better to make a thorough evaluation of the time series properties of a data set and we suggest various avenues for doing so including some that are maybe unfamiliar to most dendrochronologists including generalized autoregressive conditional heteroscedasticity (GARCH) models.

Probabilistic estimates of the cost and performance of future nuclear energy systems under different scenarios of government research, development, and demonstration (RD&D) spending were obtained from 30 U.S. and 30 European nuclear technology experts. We used a novel elicitation approach which combined individual and group elicitation. With no change from current RD&D funding levels, experts on average expected current (Gen. III/III+) designs to be somewhat more expensive in 2030 than they were in 2010, and they expected the next generation of designs (Gen. IV) to be more expensive still as of 2030. Projected costs of proposed small modular reactors (SMRs) were similar to those of Gen. IV systems. The experts almost unanimously recommended large increases in government support for nuclear RD&D (generally 2-3 times current spending). The majority expected that such RD&D would have only a modest effect on cost, but would improve performance in other areas, such as safety, waste management, and uranium resource utilization. The U.S. and E.U. experts were in relative agreement regarding how government RD&D funds should be allocated, placing particular focus on very high temperature reactors, sodium-cooled fast reactors, fuels and materials, and fuel cycle technologies.

At global and regional scales, tree mortality rates are positively correlated with forest net primary productivity (NPP). Yet causes of the correlation are unknown, in spite of potentially profound implications for our understanding of environmental controls of forest structure and dynamics and, more generally, our understanding of broad-scale environmental controls of population dynamics and ecosystem processes. Here we seek to shed light on the causes of geographic patterns in tree mortality rates, and we consider some implications of the positive correlation between mortality rates and NPP. To reach these ends, we present seven hypotheses potentially explaining the correlation, develop an approach to help distinguish among the hypotheses, and apply the approach in a case study comparing a tropical and temperate forest. Based on our case study and literature synthesis, we conclude that no single mechanism controls geographic patterns of tree mortality rates. At least four different mechanisms may be at play, with the dominant mechanisms depending on whether the underlying productivity gradients are caused by climate or soil fertility. Two of the mechanisms are consequences of environmental selection for certain combinations of life-history traits, reflecting trade-offs between growth and defense (along edaphic productivity gradients) and between reproduction and persistence (as manifested in the adult tree stature continuum along climatic and edaphic gradients). The remaining two mechanisms are consequences of environmental influences on the nature and strength of ecological interactions: competition (along edaphic gradients) and pressure from plant enemies (along climatic gradients). For only one of these four mechanisms, competition, can high mortality rates be considered to be a relatively direct consequence of high NPP. The remaining mechanisms force us to adopt a different view of causality, in which tree growth rates and probability of mortality can vary with at least a degree of independence along productivity gradients. In many cases, rather than being a direct cause of high mortality rates, NPP may remain high in spite of high mortality rates. The independent influence of plant enemies and other factors helps explain why forest biomass can show little correlation, or even negative correlation, with forest NPP.

The northern Rocky Mountains (NRMs) are a critical headwaters region with the majority of water resources originating from mountain snowpack. Observations showing declines in western U.S. snowpack have implications for water resources and biophysical processes in high-mountain environments. This study investigates oceanic and atmospheric controls underlying changes in timing, variability, and trends documented across the entire hydroclimatic-monitoring system within critical NRM watersheds. Analyses were conducted using records from 25 snow telemetry (SNOTEL) stations, 148 1 April snow course records, stream gauge records from 14 relatively unimpaired rivers, and 37 valley meteorological stations. Over the past four decades, midelevation SNOTEL records show a tendency toward decreased snowpack with peak snow water equivalent (SWE) arriving and melting out earlier. Temperature records show significant seasonal and annual decreases in the number of frost days (days ≤0°C) and changes in spring minimum temperatures that correspond with atmospheric circulation changes and surface–albedo feedbacks in March and April. Warmer spring temperatures coupled with increases in mean and variance of spring precipitation correspond strongly to earlier snowmeltout, an increased number of snow-free days, and observed changes in streamflow timing and discharge. The majority of the variability in peak and total annual snowpack and streamflow, however, is explained by season-dependent interannual-to-interdecadal changes in atmospheric circulation associated with Pacific Ocean sea surface temperatures. Over recent decades, increased spring precipitation appears to be buffering NRM total annual streamflow from what would otherwise be greater snow-related declines in hydrologic yield. Results have important implications for ecosystems, water resources, and long-lead-forecasting capabilities.

We investigated the climate response of three Siberian taiga species, Larix cajanderi, Picea obovata, and Pinus sylvestris, across a latitudinal gradient in central Siberia. We hypothesized that warming is more frequently associated with increased growth for evergreen conifers (P. obovata and P. sylvestris) than for L. cajanderi, and for northern than for southern sites; we also hypothesized that increased growth is associated with a positive trend in normalized difference vegetation index (NDVI). In mixed stands, growth of L. cajanderi and P. obovata increased over time, but the larger growth increases in P. obovata may presage a shift in competitive balance between these species. Climate response varied among and within populations of all species, and positive responses to temperature prevailed at northern sites, where trees grew faster in years with warm early summers. Negative responses to warming declined along the south to north latitudinal gradient. We observed considerable variability in climate response within populations which even exceeded that among species or sites. Tree response to climate was correlated with NDVI trends, indicating that patterns of tree-growth response to climate were indicative of a coherent landscape-scale response to warming. Our findings suggest that increased productivity with warming is likely only in the northern reaches of the Siberian taiga. An increased prevalence of evergreen conifers in areas currently dominated by deciduous Larix species also seems likely.

I demonstrate new functionality for the Dendrochronology Program Library in R (dplR) that allows for flexible statistical crossdating of tree-ring data. Using a well-dated ring-width file, I give examples of how dplR can be used to examine correlations between each series and a master chronology according to overlapping time periods (segments) specified by the user; examine moving correlations of suspect series; and compute cross-correlation functions to identify specific dating issues. I also show how automatically generated skeleton plots can be used to visually crossdate. Much of the terminology and approach used for crossdating in dplR will be familiar to users of COFECHA.

Defusing Armageddon: Inside NEST, America's Secret Nuclear Bomb Squad, by Jeffrey T. Richelson. W.W. Norton & Company, 2009. 318 pages, $27.95.

the world will need to produce huge quantities of energy in the 21 century to meet the needs of a growing world population, while also working to lift billions of people out of poverty. Providing this energy at a reasonable cost, without causing unmanageable climate disruption, security risks, or other environmental devastation, will be one of the century’s most daunting challenges. This challenge will be even more difficult to meet if nuclear energy does not play a substantial part. But achieving the scale of nuclear energy growth required while managing the risks of that growth will be a major challenge in itself, one that will require both technical and institutional innovations. Consider the scale of growth that is needed for nuclear energy to make a meaningful contribution to mitigating carbon emissions. One oft-cited 2004 analysis broke down the problem of shifting away from a business-as-usual energy path into seven “wedges”—different technologies that would each grow to displace a billion tons of carbon emissions per year by 2050 (see Figure 1). More recent science suggests that 10 to 15 such wedges are likely to be required, as business-asusual emissions are higher than previously projected, the carbon-absorbing properties of the oceans appear to be weaker, and the atmospheric concentration of carbon required to avoid disastrous climate consequences seem to be even lower than once thought. For nuclear power to provide even one such wedge would require a

I present and describe a new software package in the R statistical programming environment for dendrochronology. R is considered the world's pre-eminent open-source statistical computing environment where users can contribute packages, which are freely available on the Internet. The dendrochronology program library in R (dplR) is able to read standard decadal-format files and allows users to perform several standard analyses including interactive detrending, chronology building, and the calculation of standard descriptive statistics. The package can also produce a variety of publication quality plots. The dplR package should make it easier for dendrochronologists to take advantage of R and use it as their primary analytic environment.

Background:Deafness is the hidden disability of childhood, and leads to poor educational and employment prospects. There is little published information on deafness in Pakistan. Profound hearing impairment is more prevalent in countries where consanguineous marriages are common, such as Pakistan. This study aimed to assess causes of childhood deafness and association with parental consanguinity, within deaf and hearing children in the Peshawar district of Pukhtoonkhwa Province, Pakistan.Methods:One hundred and forty deaf children were identified from two schools for deaf children within the Peshawar district. These children were assessed via audiology, otoscopic examination, case note review and parental history, in order to attempt to ascertain the cause of their deafness. Two hundred and twenty-one attendees at a local immunisation clinic (taken as representative of the local childhood population) were also screened for hearing impairment. Parents of both groups of children were assessed by interview and questionnaire in order to ascertain the mother and father's family relationship (i.e. whether cousins or unrelated).Results:Of the 140 deaf school pupils, 92.1 per cent were profoundly hearing impaired and 7.9 per cent were severely hearing impaired. All these children had bilateral sensorineural hearing loss. A possible cause of deafness was identified in only six of these children. Parental consanguinity (i.e. first or second cousins) was established for 86.4 per cent of deaf school pupils and 59.7 per cent of immunisation clinic attendees. None of the control children were identified as having a hearing problem.Conclusion:The prevalence of parental consanguinity was significantly higher in deaf children compared with non-hearing impaired children. However, the study also confirmed a high rate of consanguinity within the general Peshawar community. In this setting, prevention of consanguineous unions is the only means of reducing levels of congenital hearing impairment. The current levels of hearing disability represent both a prominent public health problem and an important, potentially preventable childhood disability.

Aim Tree-line conifers are believed to be limited by temperature worldwide, and thus may serve as important indicators of climate change. The purpose of this study was to examine the potential shifts in spatial distribution of three tree-line conifer species in the Greater Yellowstone Ecosystem under three future climate-change scenarios and to assess their potential sensitivity to changes in both temperature and precipitation. Location This study was performed using data from 275 sites within the boundaries of Yellowstone and Grand Teton national parks, primarily located in Wyoming, USA. Methods We used data on tree-line conifer presence from the US Forest Service Forest Inventory and Analysis Program. Climatic and edaphic variables were derived from spatially interpolated maps and approximated for each of the sites. We used the random-forest prediction method to build a model of predicted current and future distributions of each of the species under various climate-change scenarios. Results We had good success in predicting the distribution of tree-line conifer species currently and under future climate scenarios. Temperature and temperature-related variables appeared to be most influential in the distribution of whitebark pine (Pinus albicaulis), whereas precipitation and soil variables dominated the models for subalpine fir (Abies lasiocarpa) and Engelmann spruce (Picea engelmannii). The model for whitebark pine substantially overpredicted absences (as compared with the other models), which is probably a result of the importance of biological factors in the distribution of this species. Main conclusions These models demonstrate the complex response of conifer distributions to changing climate scenarios. Whitebark pine is considered a ‘keystone’ species in the subalpine forests of western North America; however, it is believed to be nearly extinct throughout a substantial portion of its range owing to the combined effects of an introduced pathogen, outbreaks of the native mountain pine beetle (Dendroctonus ponderosae), and changing fire regimes. Given predicted changes in climate, it is reasonable to predict an overall decrease in pine-dominated subalpine forests in the Greater Yellowstone Ecosystem. In order to manage these forests effectively with respect to future climate, it may be important to focus attention on monitoring dry mid- and high-elevation forests as harbingers of long-term change.

Although the ecological dynamics of the alpine treeline ecotone are influenced by climate, it is an imperfect indicator of climate change. Mechanistic processes that shape the ecotone—seed rain, seed germination, seedling establishment and subsequent tree growth form, or, conversely tree dieback—depend on microsite patterns. Growth forms affect wind and snow, and so develop positive and negative feedback loops that create these microsites. As a result, complex landscape patterns are generated at multiple spatial scales. Although these mechanistic processes are fundamentally the same for all forest-tundra ecotones across western North America, factors such as prior climate, underlying geology and geomorphology, and genetic constraints of dominant tree species lead to geographic differences in the responses of particular ecotones to climate change.

The likelihood of a nuclear terrorist attack depends in part on the ability of terrorist groups to acquire, construct, and detonate a nuclear device. This article attempts to determine the difficulty of such an endeavor by examining the underlying physical facts about nuclear fission, nuclear materials, and nuclear weapons design. The facts bear out a simple conclusion: while the danger should not be exaggerated, a nuclear terrorist attack is potentially within the capabilities of a well-organized and sophisticated terrorist group. A nuclear attack might be one of the most difficult missions a terrorist group could hope to try, but if a highly capable group acquired a stolen nuclear bomb or enough nuclear material to make one, there can be few grounds for confidence that they would be unable to use it.

This article presents a mathematical model for measuring the global risk of nuclear theft and terrorism. One plausible set of parameter values used in a numerical example suggests a 29 percent probability of a nuclear terrorist attack in the next decade. The expected loss over that period would be $1.17 trillion (undiscounted), or more than $100 billion per year. Historical and other evidence is used to explore the likely values of several of the key parameters, and policy options for reducing the risk are briefly assessed. The uncertainties in estimating the risk of nuclear terrorism are very large, but even a risk dramatically smaller than that estimated in the numerical example used in this article would justify a broad range of actions to reduce the threat.

Time series analyses of a 22-yr record of satellite observations across the northern circumpolar high latitudes were conducted, and trends in vegetation photosynthetic activity were assessed using a series of statistical tests. The results indicate that most of the northern circumpolar high latitudes (>85%) showed no significant trend in vegetation activity despite systematic climate warming during the period of analysis. Of the areas that did change, many showed the expected trends in “greening” of vegetation activity. There were, however, significant differences in the magnitude and even in the direction of trends when stratified by vegetation type and density. Tundra areas consistently and predominantly showed greening trends. Forested areas showed declines in activity (“browning”) in many areas, and these were systematically higher in areas with denser tree cover—whether deciduous or evergreen, needle- or broad-leafed. The seasonality of the trends was also distinct between vegetation types, with a divergence in trends between late spring and early summer (positive) versus late summer (negative) portions of the growing seasons in forested areas. In contrast, tundra and other predominantly herbaceous areas showed positive trends in all portions of the growing season. These results confirm recent findings across the high latitudes of North America and are supported by an increasing array of in situ measurements. They indicate that the boreal forest biome might be responding to climate change in previously unexpected ways, and point to a need for an expanded observational network, additional analysis of existing datasets (e.g., tree rings), and improvements in process models of ecosystem responses to climate change.