bluuebunny/crossref_metadata_2025 huggingface dataset:
Landscape development in Dutch coastal dunes: the breakdown and restoration of geomorphological and geohydrological processes
Authors: van der Meulen F. , Jungerius P. D.
Published: May 2017

Synopsis

In Dutch coastal dunes, geomorphological and geohydrological processes have been adversely affected by intensive utilisation of the dunes. In the past, wide-scale stabilisation, notably for reasons of coastal defence, stopped nearly all aeolian activity. Rejuvenation did not take place and succession to mature-type ecosystems increased. Artificial infiltration with eutrophic river water and extraction of groundwater for drinking water catchment modified the geohydrology of the wet-dune environment.

Today, actions are being taken to restore geomorphological and geohydrological processes. Managing authorities join forces with universities and policy makers to strike the right balance between conflicting interests. Applied research helps to develop management strategies.

Two types of research are discussed: (a) geomorphological work on the development of blow-outs; (b) geohydrological work on the development of dune slacks. Questions considered are: do blow-outs grow to an unlimited extent or do they have optimum size and shape corresponding to aerodynamic conditions? Are there natural stabilisation mechanisms for blow-outs? What is the ecological impact of drinking water catchment? Which aspects should be considered to restore the dune slack environment in catchment areas?

Our findings are that blow-outs in The Netherlands have an optimum length:width ratio of about 2 with a blow-out length varying between 20 and 30 m. After 10–15 years without artificial stabilisation measures, the areas studied present an average of about one blow-out per hectare. Natural stabilisation mechanisms include algae which colonise deflation sites inside the blow-out and low secondary dunes which develop at the immediate leeward side of the blow-out. Blow-outs situated at or near downhill slopes of 6–12° may easily extend into larger deflation surfaces. Water erosion, probably caused by the water-repellency of humus-rich top soil, often precedes wind erosion on south- and south-east oriented slopes.

Drinking water production caused dessiccation of dune slacks and the disappearance of associated vegetation. In areas where infiltration with river water from outside the dunes is also applied, inudation and eutrophication drastically changed the dune environment. Nitrophilous plants appeared, especialy along banks of infiltration ponds, but also in seepage ponds. The plant cover depends on nutrient concentration of the (infiltrated) groundwater but especially on the flux of the groundwater. A high rate of flux leads to high nutrient loads, encouraging the growth and eventually dominance of nitrophilous plants. Restoration of dune slacks depends on the quality and the flux of the groundwater, on the streamlines of the groundwater flow in the dune body in relation to the orientation of the seepage ponds, on the presence of peaty or clayey adsorptive layers in the subsoil and possibly also on the presence of a rainwater lens occurring on top of the infiltration water.
Management for nature conservation
Authors: Doody J. P.
Published: May 2017

Synopsis

Sand dunes occur extensively around the coastline of Great Britain and in a wide variety of forms. Management for nature conservation is influenced by a long-term historical perspective which has led to a continued policy of protection. It has aimed firstly to prevent damaging developments such as building and orestry, and secondly to control excessive erosion brought about predominantly by man's own activities. However, an assessment of current nature conservation management problems suggests that at many sites in Great Britain over-stabilisation may be as much a problem as erosion. The implications for management in the face of other competing demands is discussed.
An application of science to the management of coastal dunes along the Atlantic coast of the U.S.A.
Authors: Psuty Norbert P.
Published: May 2017

Synopsis

Coastal foredune management begins with an understanding of and appreciation for the dynamics of dune creation, development and decay. Sediment exchange between the dune and beach components of the total dune–beach profile is a necessary element in foredune creation and development. Foredune development is enhanced by a slightly negative total dune–beach budget. Foredune crestlines display alongshore periodicities in displacement that are related to beach processes. Effective management is based on the dimensions of the alongshore foredune variations and the retention of sediment in the migrating foredune system.
Pain Perception and Response: Central Nervous System Mechanisms
Authors: Hudson Arthur J.
Published: May 2017

Although several decades of studies have detailed peripheral and ascending nociceptive pathways to the thalamus and cerebral cortex, pain is a symptom that has remained difficult to characterize anatomically and physiologically. Positron emission tomography (PET) and functional magnetic imaging (fMRI) have recently demonstrated a number of cerebral and brain stem loci responding to cutaneous noxious stimuli. However, intersubject variability, both in the frequency and increased or decreased intensity of the responses, has caused uncertainty as to their significance. Nevertheless, the large number of available imaging studies have shown that many areas with recognized functions are frequently affected by painful stimuli. With this evidence and recent developments in tracing central nervous system connections between areas responding to noxious stimuli, it is possible to identify nociceptive pathways that are within, or contribute to, afferent spinothalamo-cortical sensory and efferent skeletomotor and autonomic motor systems. In this study it is proposed that cortical and nuclear mechanisms for pain perception and response are hierarchically arranged with the prefrontal cortex at its highest level. Nevertheless, all components make particular contributions without which certain nociceptive failures can occur, as in pathological pain arising in some cases of nervous system injury.
Predicting Who Will Develop Dementia in a Cohort of Canadian Seniors
Authors: Hogan David B. , Ebly Erika M.
Published: May 2017

Objectives:

We examined whether easily attainable variables were useful in predicting who became demented over a five year period and determined the rates of incident dementia for different categories of mild cognitive impairment.

Methods:

This was a cohort study of subjects recruited nationally in a population-based survey of Canadians 65 years and older (the Canadian Study of Health and Aging). After standardized clinical assessments, a subset of subjects (n=1782) was categorized as not demented at time one. Identical study methods allowed a reassessment of the cognitive status of surviving subjects (n=892) five years later.

Results:

Three baseline variables (Modified Mini Mental State (3MS) score, subject's age, and an informant's report of the presence of memory problems) were statistically significant predictors of the development of a dementia. An equation incorporating these three variables had a sensitivity of 79% and a specificity of 56% for predicting dementia among survivors at time two. An equation substituting the MMSE for the 3MS showed similar results. The various categories of mild cognitive impairment examined showed significantly different likelihoods for the subsequent development of a dementia. Some categories with a higher dementia risk were characterized by inclusion criteria requiring neuropsychological test scores that were greater than one standard deviation (SD) below the mean of age based normative data.

Conclusion:

In the absence of extensive laboratory, radiologic or neuropsychological tests, simple variables that can be easily determined in the course of a single clinical encounter were useful in predicting subjects with a higher risk of developing dementia. Attempts to use neuropsychological results to predict the development of dementia should look for significant impairments on age-standardized tests.
Post-traumatic Cervical Dystonia: A Distinct Entity?
Authors: Samii A. , Pal P.K. , Schulzer M. , Mak E. , Tsui J.K.C.
Published: May 2017

Background/Objective:

The incidence of head/neck trauma preceding cervical dystonia (CD) has been reported to be 5-21%. There are few reports comparing the clinical characteristics of patients with and without a history of injury. Our aim was to compare the clinical characteristics of idiopathic CD (CD-I) to those with onset precipitated by trauma (CD-T). Methods: We evaluated 114 consecutive patients with CD over a 9-month period. All patients were interviewed using a detailed questionnaire and had a neurological examination. Their clinical charts were also reviewed.

Methods:

We evaluated 114 consecutive patients with CD over a 9-month period. All patients were interviewed using a detailed questionnaire and had a neurological examination. Their clinical charts were also reviewed.

Results:

Fourteen patients (12%) had mild head/neck injury within a year preceding the onset of CD. Between the two groups (CD-I and CD-T), the gender distribution (F:M of 3:2), family history of movement disorders (32% vs. 29%), the prevalence of gestes antagonistes (65% vs. 64%), and response to botulinum toxin were similar. There were non-specific trends, including an earlier age of onset (mean ages 43.3 vs. 37.6), higher prevalence of neck pain (86% vs. 100%), head tremor (67% vs. 79%), and dystonia in other body parts (23% vs. 36%) in CD-T.

Conclusion:

CD-I and CD-T are clinically similar. Trauma may be a triggering factor in CD but this was only supported by non-significant trends in its earlier age of onset.
Clinical and Electromyographic Examinations of Patients with Essential Tremor
Authors: Milanov Ivan
Published: May 2017

Background:

It is believed that no clinical differences exist among essential, familial and senile tremor, or between the tremor with synchronous or alternating electromyographic activity. The aim of this study was to evaluate the clinical and electromyographic findings in a large group of patients with different types of essential tremor.

Methods:

Two hundred and twenty patients with sporadic, familial or senile variants of essential tremor were examined. According to the electromyographic activity recorded from the antagonistic muscles, the patients were subdivided into a group with synchronous (SYN) and a group with alternating (ALT) activity. The historical aspects of the disease were noted, and a detailed neurological examination was performed.

Results:

A widespread tremor involving upper and lower limbs and 3-4 different anatomical regions was typical for familial tremor. It also had higher amplitude than the sporadic and senile tremor. ALT tremor had a higher amplitude and longer burst duration than SYN and more often involved lower limbs. Rest tremor was common in the ALT group. Overall, ALT tremor was more common than previously supposed.

Conclusion:

The familial and ALT tremors are more disabling than other types of essential tremor. Since electromyographic ALT activity is common in essential tremor, its presence does not reliably distinguish essential and Parkinsonian tremor.
Genetic moderation of multiple pathways linking early cumulative socioeconomic adversity and young adults' cardiometabolic disease risk
Authors: Wickrama Kandauda A. S. , Lee Tae Kyoung , O'Neal Catherine Walker
Published: May 2017

Recent research suggests that psychosocial resources and life stressors are mediating pathways explaining socioeconomic variation in young adults' health risks. However, less research has examined both these pathways simultaneously and their genetic moderation. A nationally representative sample of 11,030 respondents with prospective data collected over 13 years from the National Study of Adolescent to Adult Health was examined. First, the association between early cumulative socioeconomic adversity and young adults' (ages 25–34) cardiometabolic disease risk, as measured by 10 biomarkers, through psychosocial resources (educational attainment) and life stressors (accelerated transition to adulthood) was examined. Second, moderation of these pathways by the serotonin transporter linked polymorphic region gene (5-HTTLPR) was examined. There was evidence for the association between early socioeconomic adversity and young adults' cardiometabolic disease risk directly and indirectly through educational attainment and accelerated transitions. These direct and mediating pathways were amplified by the 5-HTTLPR polymorphism. These findings elucidate how early adversity can have an enduring influence on young adults' cardiometabolic disease risk directly and indirectly through psychosocial resources and life stressors and their genetic moderation. This information suggests that effective intervention and prevention programs should focus on early adversity, youth educational attainment, and their transition to young adulthood.
Direct genetic and maternal effects affecting litter size, birth weight and pre-weaning losses in Creole goats of Guadeloupe
Authors: Menéndez-Buxadera A. , Alexandre G. , Mandonnet N. , Navès M. , Aumont G.
Published: May 2017

The litter size (LS), or its equivalent the number of kids born in the litter (NB), of Creole goats in Guadeloupe was studied by two procedures. The first approach considered LS as a single trait and as a characteristic of the mother of the litter, and was studied by an univariate animal model (UAM). The second procedure treated NB, the individual birth weight (BW) and loss of kids (LK) as traits belonging to the animals born in the litter and their dam, in a multitrait animal model (MAM). The heritability for genetic direct effect (h2a) for LS estimated by UAM (0·14) was 40% lower than the corresponding value for NB estimated by MAM. The most appropriate of the 6 MAMs tested estimated heritabilities (h2a) of 0·24, 0·22 and 0·17 for NB, BW and LK, respectively, while maternal effects (h2m) were 0·20, 0·24 and 0·09 for the same characters. The genetic correlations between direct and maternal effects (ram) were negative –0·611 and –0·725 for NB and LK, respectively, and not significantly different from zero for BW. This study explored the possibility of using the information on NB, BW and LK recorded in each animal born in the litter in order to analyse the genetic variability of these traits.
Methods of carcass classification based on subjective assessments of carcass fatness and of carcass conformation: effect of sex on the prediction of tissue composition in carcasses of sucking lambs
Authors: Miguel E. , Ruiz de Huidobro F. , Díaz M. T. , Velasco S. , Lauzurica S. , Pérez C. , Onega E. , Blázquez B. , Cañeque V.
Published: May 2017

Forty-eight sucking lambs (26 males and 22 females) of the Manchega breed were used in this work. Lambs were slaughtered at 10, 12 and 14 kg live weight. Carcass degree of fatness was assessed by three assessors from colour photographs of the carcasses, using the European Union scale for light lambs (EU), the Colomer-Rocher method (CF) and another new scale developed by our group (sucking lambs scale, SL). Carcass conformation was assessed according to the Colomer-Rocher method (CC). Fatness and conformation scales were divided to give 0·25 points in each interval. Left half-carcasses were jointed and dissected into lean, fat and bone. Muscle proportion, bone proportion and whole fat proportion (obtained by addition of every fat depot: subcutaneous fat, intermuscular fat, inguinal fat and kidney knob and channel fat) were determined. Male and female carcasses showed a very different tissue composition: both groups had statistically significant differences (P < 0·05) in 20 out of 25 tissue composition variates. Males showed a higher number of variates that were well correlated with assessors’ scoring than females. Correlation coefficients between most of the tissue composition variates and assessors’ scores were higher in males. Furthermore, the number of variates that were significantly correlated with assessors’ scores was lower in females. Therefore, subjective methods for the estimation of carcass degree of fatness and of carcass conformation are poor predictors of tissue composition in female sucking lamb carcasses.
Deterministic predictions of beef cow herd population dynamics with alternative replacement strategies
Authors: Amer P. R. , Roughsedge T. , Lowman B. , Simm G.
Published: May 2017

A deterministic method of predicting numbers of each animal class present over time in a beef cow herd with multiple calving seasons per year is described. Breeding cow classes are defined according to the number of generations of descent from the cows in the herd prior to the introduction of a specific heifer replacement breeding policy. Cow classes are further divided into subgroups defined according to age of cow, calving interval and whether or not the cow was last mated to a terminal sire. The method is demonstrated by showing the evolution of herd breed make-up with several alternative replacement female breeding policies including grading-up, two-breed rotation and three-breed rotation breeding policies. For an example herd, the first generation of replacements peaked at approximately 0·4 of the herd at 6 years after the first matings for a new breeding system. Later generations of replacements reached equivalent proportions of the herd to the previous generation approximately 3·3 years later, with peak proportions at approximately 0·25 of the herd. Differences in the relative levels of expression of heterosis for grade up versus rotational replacement policies increased steadily from 5 years onwards with 0·17 of the heterosis expected in a herd of F1 cows remaining 20 years after the first matings of the new breeding system. The two-breed grading-up system showed less heterosis than the three-breed grading-up system only after 8 years, with the difference increasing to 0·16 of the heterosis in an F1 herd after 20 years. Results are also presented showing the difference in contributions of breeds to the herd gene pool over time with the different breeding systems. With the rotational systems, breeds lag by approximately 3 years in the timing of their contribution according to the order of their introduction to the rotation. The effects of faster heifer replacement rates on results were also discussed. It is concluded that short-to medium-term impacts of breed and replacement breeding system choices are likely to be more relevant in practical decision making by suckler herd managers than the characteristics of breeding systems once herds have reached genetic equilibrium.
Impacts of alternative replacement breeding systems on biological and economic performance in beef suckler production using a herd level bio-economic model
Authors: Roughsedge T. , Lowman B. , Amer P. R. , Simm G.
Published: May 2017

A deterministic bio-economic model was used to investigate the impact of different heifer replacement breeding systems for beef suckler cow production in different environments. It was shown that measures of cow efficiency were highly correlated with profitability in suckled calf production. However, where significant genotype differences exist in final output value due to issues of carcass quality, then more complete characterization of system profitability is recommended. In systems utilizing a terminal sire mating policy for all matings in excess of replacement heifer requirements the proportion of terminal sire matings made are affected by female fertility. Reduced cow fertility combined with late attainment of puberty in heifers and low heifer fertility has a substantial negative effect on the proportion of terminal sire matings made. This illustrates an aspect of production that can be improved by the use of crossbreeding to exploit heterosis in reproductive traits. The time frame of impacts of the different systems was seen to vary. Grading up to a pure breed allowed exploitation of heterosis in the early years of the transition leading to a boost in profitability but this boost was lost as the herd became purebred. Composite and rotational crossing systems were seen to create a steady rise in financial margin to the point where they became stable in breed proportion and heterosis. The effect of cow size was evaluated in three different environments, representing UK lowland, upland and hill. It was found that small cows became more profitable in relation to large cows as food resources became more limiting. In a non-limiting environment large cows were more profitable than small cows.
Effect of season and dietary fibre on feeding behaviour of lactating sows in a tropical climate
Authors: Renaudeau D. , Weisbecker J.-L. , Noblet J.
Published: May 2017

Twenty-seven multiparous Large White sows were used to determine the effect of season in a tropical climate and dietary fibre on their feeding behaviour during lactation. The experiment was conducted in Guadeloupe (French West Indies, latitude 16°N, longitude 61°W) between October 1999 and January 2001; climatic conditions in the farrowing room were equivalent to outdoor conditions. Two seasons were determined a posteriori from climatic criteria recorded continuously in the farrowing room. During the warm season, ambient temperature and relative humidity averaged 25°C and 0·868, respectively. The corresponding values for the hot season were 27·5°C and 0·835. Experimental diets offered during lactation were a control diet (C; 140 g neutral-detergent fibre (NDF) per kg) and a high fibre diet (HF; 200 g NDF per kg). Sows were offered food ad libitum between the 6th and the 27th day of lactation. Daily food intake between day 6 and day 27 decreased during the hot season (P < 0·001; 3226 v. 5571 g/d during the warm season). This was achieved by a reduction of both meal size (P < 0·05; 460 v. 718 g per meal) and ingestion and consumption time (P < 0·01; -11·1 and -15·3 min/day, respectively) whereas the number of meals remained constant (8·4 meals per day on average). During warm season, hourly food intake peaked twice daily near sunrise and sunset. During the hot season, peaks were attenuated and food intake was reduced during the hotter periods of the day and increased during the fresher period of the day, especially in early morning. As a result the diurnal partition of food intake was significantly affected by season; proportionately 0·62 and 0·47 of total food intake occurred during the day in warm and in hot seasons, respectively. Standing duration averaged 138 min/ day with no significant difference between seasons. Feeding behaviour criteria were not influenced by diet composition. In conclusion, the season in a humid tropical climate significantly affects the feeding behaviour of lactating sows.
The effects of increasing the sodium content of grass or concentrates on the nutrition of sheep
Authors: Phillips C. J. C. , Mohamed M. O. , Omed H.
Published: May 2017

Supplementary salt is often added to the diet of sheep by including it in concentrate food, but an alternative is to soak their forage in a weak salt solution, which could prevent the sudden influx of large doses of sodium(Na) to the rumen. An experiment was conducted to compare low and moderate levels of salt in forage with moderate and high levels added to the concentrate. Twenty sheep were housed in individual chambers equipped for faeces and urine collection and offered fresh grass and concentrate, with the salt being added to the grass by soaking in salt water and to the concentrate by direct mixing. The grass for sheep offered the supplementary Na in concentrates and for a control treatment was soaked in water without salt. Grass was offered in two daily meals and was availablead libitum, and concentrates were offered at a restricted level just before the first feeding of grass. Adding salt at the low and moderate levels to the water in which the grass was soaked increased the Na intake from 1·1 g/day (the control treatment) to 2·1 and 3·8 g/day, respectively, and reduced the Mg and Ca contents in the grass, compared with grass soaked in unsalted water. Adding salt to the concentrate at moderate and high levels increased Na intake to 3·7 and 5·9 g/day, respectively. Grass dry matter (DM) intakes were increased by adding Na to the concentrates, but not to the grass, and DM digestibility was increased in all salt supplement treatments except the high level added to the concentrate. The apparent absorption of Na was increased in proportion to the amount of Na added to the diet and that of K was increased at the moderate and high levels. The apparent absorption and retention of Mg and Ca were decreased at the low level of Na supplementation in herbage. It is concluded that the potential benefits of adding salt to the diet, namely increased food intake and digestibility and increased mineral absorption, are dependent on the level of addition and the method of adding it.
A COMPARISON OF NUMERICAL METHODS FOR THE SOLUTION OF CONTINUOUS-TIME DSGE MODELS
Authors: Parra-Alvarez Juan Carlos
Published: May 2017

This study evaluates the accuracy of a set of techniques that approximate the solution of continuous-time Dynamic Stochastic General Equilibrium models. Using the neoclassical growth model, I compare linear-quadratic, perturbation, and projection methods. All techniques are applied to the Hamilton–Jacobi–Bellman equation and the optimality conditions that define the general equilibrium of the economy. Two cases are studied depending on whether a closed-form solution is available. I also analyze how different degrees of non-linearities affect the approximated solution. The results encourage the use of perturbations for reasonable values of the structural parameters of the model and suggest the use of projection methods when a high degree of accuracy is required.
Effects of folic acid fortification on orofacial clefts prevalence: a meta-analysis
Authors: Millacura Natalia , Pardo Rosa , Cifuentes Lucia , Suazo José
Published: May 2017

Objective

Orofacial clefts (OFC) are the most prevalent craniofacial birth defect. Folic acid (FA) supplementation has been demonstrated as an effective intervention to reduce risk of OFC occurrence. However, the effect of mandatory FA fortification of wheat and/or maize flour on OFC prevalence has shown controversial results among countries adopting this policy. Thus, we performed a meta-analysis to synthesize the available evidence evaluating the global impact of this mandatory policy on OFC occurrence.

Design

Literature search in conventional and grey medical/scientific databases showed fifteen studies considering OFC prevalence in pre- and post-fortification periods with FA. The effect of this policy was evaluated by computing relative risk (RR) and separating samples into total OFC, non-syndromic forms, cleft lip with or without cleft palate (CL/P) and cleft palate only (CPO).

Results

We found a significant effect of FA fortification only on non-syndromic CL/P (RR=0·88; 95 % CI 0·81, 0·96), whereas neutral effects were detected for total OFC (syndromic plus non-syndromic) and CPO.

Conclusions

Our results may reflect the different aetiology of syndromic OFC with respect to non-syndromic forms and the CL/P related to CPO. Although the number of non-syndromic CL/P samples was lower than that for total OFC, the absence of both between-study heterogeneity and publication bias leads us to conclude that FA fortification may have beneficial effects on non-syndromic CL/P.
Injecting Compassion into International Wildlife Law: From Conservation to Protection?
Authors: Scholtz Werner
Published: May 2017

International wildlife law is concerned with the conservation of sentient species, but generally ignores the welfare of individual animals. It therefore does not reflect a recognition of the moral worth of animals and perpetuates the dichotomy between conservation and welfare. It is the primary goal of this article to ascertain how welfare concerns may be incorporated into international wildlife law in order to ensure that it takes cognizance of the moral worth of animals. The article advocates an injection of ethics, via a welfare-centric approach, into wildlife law in order to escape the dichotomy between conservation and welfare in relation to wild animals, and so to advance the progressive development of law that is conducive to wildlife protection rather than merely to its conservation.
Manual Flying and Energy Awareness
Authors: Müller Simon , Schreiter Karolin , Luckner Robert , Manzey Dietrich
Published: May 2017

Abstract. In order to enable pilots to better maintain energy awareness and energy management in manual flight, a new concept has been proposed, which transfers the demand control principle of fly-by-wire control laws also to the control of thrust. It includes a total-energy-related augmented thrust controller combined with a modified cockpit instrumentation enriched by specific energy displays. In order to empirically evaluate the human performance consequences of this new approach, an experimental study was conducted in a flight simulator investigating its effects on pilots’ performance, workload, and situation awareness. A total of 24 commercial aircraft pilots performed a landing and approach on a complex flight trajectory with and without the new system elements. The results confirm the expected beneficial effects of the new system on flight precision and lowered effort involved in thrust control as compared with conventional raw data flying. No negative side effects, for example, impaired situation awareness, were found.
Plastic Waste Knows No Bounds
Authors: Wendel JoAnna
Published: May 2017

Despite the vastness of Earth’s oceans, human plastic pollution overwhelms even remote corners.
Epibionts dominate metabolic functional potential of Trichodesmium colonies from the oligotrophic ocean
Authors: Frischkorn Kyle R , Rouco Mónica , Van Mooy Benjamin A S , Dyhrman Sonya T
Published: May 2017

Trichodesmium is a genus of marine diazotrophic colonial cyanobacteria that exerts a profound influence on global biogeochemistry, by injecting ‘new’ nitrogen into the low nutrient systems where it occurs. Colonies of Trichodesmium ubiquitously contain a diverse assemblage of epibiotic microorganisms, constituting a microbiome on the Trichodesmium host. Metagenome sequences from Trichodesmium colonies were analyzed along a resource gradient in the western North Atlantic to examine microbiome community structure, functional diversity and metabolic contributions to the holobiont. Here we demonstrate the presence of a core Trichodesmium microbiome that is modulated to suit different ocean regions, and contributes over 10 times the metabolic potential of Trichodesmium to the holobiont. Given the ubiquitous nature of epibionts on colonies, the substantial functional diversity within the microbiome is likely an integral facet of Trichodesmium physiological ecology across the oligotrophic oceans where this biogeochemically significant diazotroph thrives.
Successive range expansion promotes diversity and accelerates evolution in spatially structured microbial populations
Authors: Goldschmidt Felix , Regoes Roland R , Johnson David R
Published: May 2017

Successive range expansions occur within all domains of life, where one population expands first (primary expansion) and one or more secondary populations then follow (secondary expansion). In general, genetic drift reduces diversity during range expansion. However, it is not clear whether the same effect applies during successive range expansion, mainly because the secondary population must expand into space occupied by the primary population. Here we used an experimental microbial model system to show that, in contrast to primary range expansion, successive range expansion promotes local population diversity. Because of mechanical constraints imposed by the presence of the primary population, the secondary population forms fractal-like dendritic structures. This divides the advancing secondary population into many small sub-populations and promotes intermixing between the primary and secondary populations. We further developed a mathematical model to simulate the formation of dendritic structures in the secondary population during succession. By introducing mutations in the primary or dendritic secondary populations, we found that mutations are more likely to accumulate in the dendritic secondary populations. Our results thus show that successive range expansion can promote intermixing over the short term and increase genetic diversity over the long term. Our results therefore have potentially important implications for predicting the ecological processes and evolutionary trajectories of microbial communities.
Crystal structure of the receptor binding domain of the spike glycoprotein of human betacoronavirus HKU1
Authors: Ou Xiuyuan , Guan Hongxin , Qin Bo , Mu Zhixia , Wojdyla Justyna A. , Wang Meitian , Dominguez Samuel R. , Qian Zhaohui , Cui Sheng
Published: May 2017

Human coronavirus (CoV) HKU1 is a pathogen causing acute respiratory illnesses and so far little is known about its biology. HKU1 virus uses its S1 subunit C-terminal domain (CTD) and not the N-terminal domain like other lineage A β-CoVs to bind to its yet unknown human receptor. Here we present the crystal structure of HKU1 CTD at 1.9 Å resolution. The structure consists of three subdomains: core, insertion and subdomain-1 (SD-1). While the structure of the core and SD-1 subdomains of HKU1 are highly similar to those of other β-CoVs, the insertion subdomain adopts a novel fold, which is largely invisible in the cryo-EM structure of the HKU1 S trimer. We identify five residues in the insertion subdomain that are critical for binding of neutralizing antibodies and two residues essential for receptor binding. Our study contributes to a better understanding of entry, immunity and evolution of CoV S proteins.
Molecular basis for PrimPol recruitment to replication forks by RPA
Authors: Guilliam Thomas A. , Brissett Nigel C. , Ehlinger Aaron , Keen Benjamin A. , Kolesar Peter , Taylor Elaine M. , Bailey Laura J. , Lindsay Howard D. , Chazin Walter J. , Doherty Aidan J.
Published: May 2017

DNA damage and secondary structures can stall the replication machinery. Cells possess numerous tolerance mechanisms to complete genome duplication in the presence of such impediments. In addition to translesion synthesis (TLS) polymerases, most eukaryotic cells contain a multifunctional replicative enzyme called primase–polymerase (PrimPol) that is capable of directly bypassing DNA damage by TLS, as well as repriming replication downstream of impediments. Here, we report that PrimPol is recruited to reprime through its interaction with RPA. Using biophysical and crystallographic approaches, we identify that PrimPol possesses two RPA-binding motifs and ascertained the key residues required for these interactions. We demonstrate that one of these motifs is critical for PrimPol’s recruitment to stalled replication forks in vivo. In addition, biochemical analysis reveals that RPA serves to stimulate the primase activity of PrimPol. Together, these findings provide significant molecular insights into PrimPol’s mode of recruitment to stalled forks to facilitate repriming and restart.
Rules of engagement between αvβ6 integrin and foot-and-mouth disease virus
Authors: Kotecha Abhay , Wang Quan , Dong Xianchi , Ilca Serban L. , Ondiviela Marina , Zihe Rao , Seago Julian , Charleston Bryan , Fry Elizabeth E. , Abrescia Nicola G. A. , Springer Timothy A. , Huiskonen Juha T. , Stuart David I.
Published: May 2017

Foot-and-mouth disease virus (FMDV) mediates cell entry by attachment to an integrin receptor, generally αvβ6, via a conserved arginine–glycine–aspartic acid (RGD) motif in the exposed, antigenic, GH loop of capsid protein VP1. Infection can also occur in tissue culture adapted virus in the absence of integrin via acquired basic mutations interacting with heparin sulphate (HS); this virus is attenuated in natural infections. HS interaction has been visualized at a conserved site in two serotypes suggesting a propensity for sulfated-sugar binding. Here we determined the interaction between αvβ6 and two tissue culture adapted FMDV strains by cryo-electron microscopy. In the preferred mode of engagement, the fully open form of the integrin, hitherto unseen at high resolution, attaches to an extended GH loop via interactions with the RGD motif plus downstream hydrophobic residues. In addition, an N-linked sugar of the integrin attaches to the previously identified HS binding site, suggesting a functional role.
Covalently linked dengue virus envelope glycoprotein dimers reduce exposure of the immunodominant fusion loop epitope
Authors: Rouvinski Alexander , Dejnirattisai Wanwisa , Guardado-Calvo Pablo , Vaney Marie-Christine , Sharma Arvind , Duquerroy Stéphane , Supasa Piyada , Wongwiwat Wiyada , Haouz Ahmed , Barba-Spaeth Giovanna , Mongkolsapaya Juthathip , Rey Félix A. , Screaton Gavin R.
Published: May 2017

A problem in the search for an efficient vaccine against dengue virus is the immunodominance of the fusion loop epitope (FLE), a segment of the envelope protein E that is buried at the interface of the E dimers coating mature viral particles. Anti-FLE antibodies are broadly cross-reactive but poorly neutralizing, displaying a strong infection enhancing potential. FLE exposure takes place via dynamic ‘breathing’ of E dimers at the virion surface. In contrast, antibodies targeting the E dimer epitope (EDE), readily exposed at the E dimer interface over the region of the conserved fusion loop, are very potent and broadly neutralizing. We here engineer E dimers locked by inter-subunit disulfide bonds, and show by X-ray crystallography and by binding to a panel of human antibodies that these engineered dimers do not expose the FLE, while retaining the EDE exposure. These locked dimers are strong immunogen candidates for a next-generation vaccine.
Engaging and disengaging recurrent inhibition coincides with sensing and unsensing of a sensory stimulus
Authors: Saha Debajit , Sun Wensheng , Li Chao , Nizampatnam Srinath , Padovano William , Chen Zhengdao , Chen Alex , Altan Ege , Lo Ray , Barbour Dennis L. , Raman Baranidharan
Published: May 2017

Even simple sensory stimuli evoke neural responses that are dynamic and complex. Are the temporally patterned neural activities important for controlling the behavioral output? Here, we investigated this issue. Our results reveal that in the insect antennal lobe, due to circuit interactions, distinct neural ensembles are activated during and immediately following the termination of every odorant. Such non-overlapping response patterns are not observed even when the stimulus intensity or identities were changed. In addition, we find that ON and OFF ensemble neural activities differ in their ability to recruit recurrent inhibition, entrain field-potential oscillations and more importantly in their relevance to behaviour (initiate versus reset conditioned responses). Notably, we find that a strikingly similar strategy is also used for encoding sound onsets and offsets in the marmoset auditory cortex. In sum, our results suggest a general approach where recurrent inhibition is associated with stimulus ‘recognition’ and ‘derecognition’.
Pseudoexfoliation syndrome-associated genetic variants affect transcription factor binding and alternative splicing of LOXL1
Authors: Pasutto Francesca , Zenkel Matthias , Hoja Ursula , Berner Daniel , Uebe Steffen , Ferrazzi Fulvia , Schödel Johannes , Liravi Panah , Ozaki Mineo , Paoli Daniela , Frezzotti Paolo , Mizoguchi Takanori , Nakano Satoko , Kubota Toshiaki , Manabe Shinichi , Salvi Erika , Manunta Paolo , Cusi Daniele , Gieger Christian , Wichmann Heinz-Erich , Aung Tin , Khor Chiea Chuen , Kruse Friedrich E. , Reis André , Schlötzer-Schrehardt Ursula
Published: May 2017

Although lysyl oxidase-like 1 (LOXL1) is known as the principal genetic risk factor for pseudoexfoliation (PEX) syndrome, a major cause of glaucoma and cardiovascular complications, no functional variants have been identified to date. Here, we conduct a genome-wide association scan on 771 German PEX patients and 1,350 controls, followed by independent testing of associated variants in Italian and Japanese data sets. We focus on a 3.5-kb four-component polymorphic locus positioned spanning introns 1 and 2 of LOXL1 with enhancer-like chromatin features. We find that the rs11638944:C>G transversion exerts a cis-acting effect on the expression levels of LOXL1, mediated by differential binding of the transcription factor RXRα (retinoid X receptor alpha) and by modulating alternative splicing of LOXL1, eventually leading to reduced levels of LOXL1 mRNA in cells and tissues of risk allele carriers. These findings uncover a functional mechanism by which common noncoding variants influence LOXL1 expression.
Top predators constrain mesopredator distributions
Authors: Newsome Thomas M. , Greenville Aaron C. , Ćirović Duško , Dickman Christopher R. , Johnson Chris N. , Krofel Miha , Letnic Mike , Ripple William J. , Ritchie Euan G. , Stoyanov Stoyan , Wirsing Aaron J.
Published: May 2017

Top predators can suppress mesopredators by killing them, competing for resources and instilling fear, but it is unclear how suppression of mesopredators varies with the distribution and abundance of top predators at large spatial scales and among different ecological contexts. We suggest that suppression of mesopredators will be strongest where top predators occur at high densities over large areas. These conditions are more likely to occur in the core than on the margins of top predator ranges. We propose the Enemy Constraint Hypothesis, which predicts weakened top-down effects on mesopredators towards the edge of top predators’ ranges. Using bounty data from North America, Europe and Australia we show that the effects of top predators on mesopredators increase from the margin towards the core of their ranges, as predicted. Continuing global contraction of top predator ranges could promote further release of mesopredator populations, altering ecosystem structure and contributing to biodiversity loss.
An engineered high affinity Fbs1 carbohydrate binding protein for selective capture of N-glycans and N-glycopeptides
Authors: Chen Minyong , Shi Xiaofeng , Duke Rebecca M. , Ruse Cristian I. , Dai Nan , Taron Christopher H. , Samuelson James C.
Published: May 2017

A method for selective and comprehensive enrichment of N-linked glycopeptides was developed to facilitate detection of micro-heterogeneity of N-glycosylation. The method takes advantage of the inherent properties of Fbs1, which functions within the ubiquitin-mediated degradation system to recognize the common core pentasaccharide motif (Man3GlcNAc2) of N-linked glycoproteins. We show that Fbs1 is able to bind diverse types of N-linked glycomolecules; however, wild-type Fbs1 preferentially binds high-mannose-containing glycans. We identified Fbs1 variants through mutagenesis and plasmid display selection, which possess higher affinity and improved recovery of complex N-glycomolecules. In particular, we demonstrate that the Fbs1 GYR variant may be employed for substantially unbiased enrichment of N-linked glycopeptides from human serum. Most importantly, this highly efficient N-glycopeptide enrichment method enables the simultaneous determination of N-glycan composition and N-glycosites with a deeper coverage (compared to lectin enrichment) and improves large-scale N-glycoproteomics studies due to greatly reduced sample complexity.
Electronic evidence of temperature-induced Lifshitz transition and topological nature in ZrTe5
Authors: Zhang Yan , Wang Chenlu , Yu Li , Liu Guodong , Liang Aiji , Huang Jianwei , Nie Simin , Sun Xuan , Zhang Yuxiao , Shen Bing , Liu Jing , Weng Hongming , Zhao Lingxiao , Chen Genfu , Jia Xiaowen , Hu Cheng , Ding Ying , Zhao Wenjuan , Gao Qiang , Li Cong , He Shaolong , Zhao Lin , Zhang Fengfeng , Zhang Shenjin , Yang Feng , Wang Zhimin , Peng Qinjun , Dai Xi , Fang Zhong , Xu Zuyan , Chen Chuangtian , Zhou X. J.
Published: May 2017

The topological materials have attracted much attention for their unique electronic structure and peculiar physical properties. ZrTe5 has host a long-standing puzzle on its anomalous transport properties manifested by its unusual resistivity peak and the reversal of the charge carrier type. It is also predicted that single-layer ZrTe5 is a two-dimensional topological insulator and there is possibly a topological phase transition in bulk ZrTe5. Here we report high-resolution laser-based angle-resolved photoemission measurements on the electronic structure and its detailed temperature evolution of ZrTe5. Our results provide direct electronic evidence on the temperature-induced Lifshitz transition, which gives a natural understanding on underlying origin of the resistivity anomaly in ZrTe5. In addition, we observe one-dimensional-like electronic features from the edges of the cracked ZrTe5 samples. Our observations indicate that ZrTe5 is a weak topological insulator and it exhibits a tendency to become a strong topological insulator when the layer distance is reduced.
Structural water engaged disordered vanadium oxide nanosheets for high capacity aqueous potassium-ion storage
Authors: Charles Daniel Scott , Feygenson Mikhail , Page Katharine , Neuefeind Joerg , Xu Wenqian , Teng Xiaowei
Published: May 2017

Aqueous electrochemical energy storage devices using potassium-ions as charge carriers are attractive due to their superior safety, lower cost and excellent transport properties compared to other alkali ions. However, the accommodation of potassium-ions with satisfactory capacity and cyclability is difficult because the large ionic radius of potassium-ions causes structural distortion and instabilities even in layered electrodes. Here we report that water induces structural rearrangements of the vanadium-oxygen octahedra and enhances stability of the highly disordered potassium-intercalated vanadium oxide nanosheets. The vanadium oxide nanosheets engaged by structural water achieves high capacity (183 mAh g−1 in half-cells at a scan rate of 5 mV s−1, corresponding to 0.89 charge per vanadium) and excellent cyclability (62.5 mAh g−1 in full cells after 5,000 cycles at 10 C). The promotional effects of structural water on the disordered vanadium oxide nanosheets will contribute to the exploration of disordered structures from earth-abundant elements for electrochemical energy storage.
Long-term mutual phase locking of picosecond pulse pairs generated by a semiconductor nanowire laser
Authors: Mayer B. , Regler A. , Sterzl S. , Stettner T. , Koblmüller G. , Kaniber M. , Lingnau B. , Lüdge K. , Finley J. J.
Published: May 2017

The ability to generate phase-stabilized trains of ultrafast laser pulses by mode-locking underpins photonics research in fields, such as precision metrology and spectroscopy. However, the complexity of conventional mode-locked laser systems has hindered their realization at the nanoscale. Here we demonstrate that GaAs-AlGaAs nanowire lasers are capable of emitting pairs of phase-locked picosecond laser pulses with a repetition frequency up to 200 GHz when subject to incoherent pulsed optical excitation. By probing the two-pulse interference spectra, we show that pulse pairs remain mutually coherent over timescales extending to 30 ps, much longer than the emitted laser pulse duration (≤3 ps). Simulations performed by solving the optical Bloch equations produce good quantitative agreement with experiments, revealing how the phase information is stored in the gain medium close to transparency. Our results open the way to phase locking of nanowires integrated onto photonic circuits, optical injection locking and applications, such as on-chip Ramsey comb spectroscopy.