bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantifying dilution and amplification in a community of hosts for tick‐borne pathogens
Authors: Levi Taal , Keesing Felicia , Holt Robert D. , Barfield Michael , Ostfeld Richard S.
Published: May 2016

Recent controversy over whether biodiversity reduces disease risk (dilution effect) has focused on the ecology of Lyme disease, a tick‐borne zoonosis. A criticism of the dilution effect is that increasing host species richness might amplify disease risk, assuming that total host abundance, and therefore feeding opportunities for ticks, increase with species richness. In contrast, a dilution effect is expected when poor quality hosts for ticks and pathogens (dilution hosts) divert tick blood meals away from competent hosts. Even if host densities are additive, the relationship between host density and tick encounters can be nonlinear if the number of ticks that encounter a host is a saturating function of host density, which occurs if ticks aggregate on the remaining hosts rather than failing to find a host before death. Both dilution and amplification are theoretical possibilities, and assessing which is more prevalent required detailed analyses of empirical systems. We used field data to explore the degree of tick redistribution onto fewer individuals with variation in intraspecific host density and novel data‐driven models for tick dynamics to determine how changes in vertebrate community composition influence the density of nymphs infected with the Lyme bacterium. To be conservative, we allowed total host density to increase additively with species richness. Our long‐term field studies found that larval and nymphal ticks redistribute onto fewer individuals as host densities decline, that a large proportion of nymphs and adults find hosts, and that mice and chipmunks feed a large proportion of nymphs. White‐footed mice, eastern chipmunks, short‐tailed shrews, and masked shrews were important amplification hosts that greatly increased the density of infected nymphs. Gray squirrels and Virginia opossums were important dilution hosts. Removing these two species increased the maximum number of larvae attached to amplification hosts by 57%. Raccoons and birds were minor dilution hosts under some conditions. Even under the assumption of additive community assembly, some species are likely to reduce the density of infected nymphs as diversity increases. If the assumption of additivity is relaxed, then species that reduce the density of small mammals through predation or competition might substantially reduce disease risk.
Tree mortality from an exceptional drought spanning mesic to semiarid ecoregions
Authors: Moore Georgianne W. , Edgar Christopher B. , Vogel Jason G. , Washington‐Allen Robert A. , March Rosaleen G. , Zehnder Rebekah
Published: May 2016

Significant areas of the southern USA periodically experience intense drought that can lead to episodic tree mortality events. Because drought tolerance varies among species and size of trees, such events can alter the structure and function of terrestrial ecosystem in ways that are difficult to detect with local data sets or solely with remote‐sensing platforms. We investigated a widespread tree mortality event that resulted from the worst 1‐year drought on record for the state of Texas, USA. The drought affected ecoregions spanning mesic to semiarid climate zones and provided a unique opportunity to test hypotheses related to how trees of varying genus and size were affected. The study was based on an extensive set of 599 distributed plots, each 0.16 ha, surveyed in the summer following the drought. In each plot, dead trees larger than 12.7 cm in diameter were counted, sized, and identified to the genus level. Estimates of total mortality were obtained for each of 10 regions using a combination of design‐based estimators and calibrated remote sensing using MODIS 1‐yr change in normalized difference vegetation index products developed by the U.S. Forest Service. As compared with most of the publicized extreme die‐off events, this study documents relatively low rates of mortality occurring over a very large area. However, statewide, regional tree mortality was massive, with an estimated 6.2% of the live trees perishing, nearly nine times greater than normal annual mortality. Dead tree diameters averaged larger than the live trees for most ecoregions, and this trend was most pronounced in the wetter climate zones, suggesting a potential re‐ordering of species dominance and downward trend in tree size that was specific to climatic regions. The net effect on carbon storage was estimated to be a redistribution of 24–30 Tg C from the live tree to dead tree carbon pool. The dead tree survey documented drought mortality in more than 29 genera across all regions, and surprisingly, drought resistant and sensitive species fared similarly in some regions. Both angiosperms and gymnosperms were affected. These results highlight that drought‐driven mortality alters forest structure differently across climatic regions and genera.
Restoring forest structure and process stabilizes forest carbon in wildfire‐prone southwestern ponderosa pine forests
Authors: Hurteau Matthew D. , Liang Shuang , Martin Katherine L. , North Malcolm P. , Koch George W. , Hungate Bruce A.
Published: May 2016

Changing climate and a legacy of fire‐exclusion have increased the probability of high‐severity wildfire, leading to an increased risk of forest carbon loss in ponderosa pine forests in the southwesternUSA. Efforts to reduce high‐severity fire risk through forest thinning and prescribed burning require both the removal and emission of carbon from these forests, and any potential carbon benefits from treatment may depend on the occurrence of wildfire. We sought to determine how forest treatments alter the effects of stochastic wildfire events on the forest carbon balance. We modeled three treatments (control, thin‐only, and thin and burn) with and without the occurrence of wildfire. We evaluated how two different probabilities of wildfire occurrence, 1% and 2% per year, might alter the carbon balance of treatments. In the absence of wildfire, we found that thinning and burning treatments initially reduced total ecosystem carbon (TEC) and increased net ecosystem carbon balance (NECB). In the presence of wildfire, the thin and burn treatmentTECsurpassed that of the control in year 40 at 2%/yr wildfire probability, and in year 51 at 1%/yr wildfire probability.NECBin the presence of wildfire showed a similar response to the no‐wildfire scenarios: both thin‐only and thin and burn treatments increased the C sink. Treatments increasedTECby reducing both mean wildfire severity and its variability. While the carbon balance of treatments may differ in more productive forest types, the carbon balance benefits from restoring forest structure and fire in southwestern ponderosa pine forests are clear.
Landscape patterns of bioenergy in a changing climate: implications for crop allocation and land‐use competition
Authors: Graves Rose A. , Pearson Scott M. , Turner Monica G.
Published: May 2016

Rural landscapes face changing climate, shifting development pressure, and loss of agricultural land. Perennial bioenergy crops grown on existing agricultural land may provide an opportunity to conserve rural landscapes while addressing increased demand for biofuels. However, increased bioenergy production and changing land use raise concerns for tradeoffs within the food–energy–environment trilemma. Heterogeneity of climate, soils, and land use complicate assessment of bioenergy potential in complex landscapes, creating challenges to evaluating future tradeoffs. The hypothesis addressed herein is that perennial bioenergy production can provide an opportunity to avoid agricultural land conversion to development. Using a process‐based crop model, we assessed potential bioenergy crop growth through 2100 in a southern Appalachian Mountain region and asked: (1) how mean annual yield differed among three crops (switchgrassPanicum virgatum, giant miscanthusMiscanthus × giganteus, and hybrid poplarPopulus ×sp.) under current climate and climate change scenarios resulting from moderate and very high greenhouse gas emissions; (2) how maximum landscape yield, spatial allocation of crops, and bioenergy hotspots (areas with highest potential yield) varied among climate scenarios; and (3) how bioenergy hotspots overlapped with current crop production or lands with high development pressure. Under both climate change scenarios, mean annual yield of perennial grasses decreased (−4% to −39%), but yield of hybrid poplar increased (+8% to +20%) which suggests that a switch to woody crops would maximize bioenergy crop production. In total, maximum landscape yield increased by up to 90 000 Mg/yr (6%) in the 21st century due to increased poplar production. Bioenergy hotspots (>18 Mg·ha−1·yr−1) consistently overlapped with high suburban/exurban development likelihood and existing row crop production. If bioenergy production is constrained to marginal (non‐crop) lands, landscape yield decreased by 27%. The removal of lands with high development probability from crop production resulted in losses of up to 670 000 Mg/yr (40%). This study demonstrated that tradeoffs among bioenergy production, crop production, and exurban expansion in a mountainous changing rural landscape vary spatially with climate change over time. If markets develop, bioenergy crops could potentially counter losses of agricultural land to development.
Habitat use of migratory bats killed during autumn at wind turbines
Authors: Voigt Christian C. , Lindecke Oliver , Schönborn Sophia , Kramer‐Schadt Stephanie , Lehmann David
Published: May 2016

The killing of large numbers of migratory bats at wind turbines is a pressing conservation problem. Even though avoidance and mitigation measures could benefit from a better knowledge of the species’ migratory habits, we lack basic information about what habitats and corridors bats use during migration. We studied the isotopic niche dimensions of three bat species that are frequently killed at wind turbines in Germany: non‐migratory Pipistrellus pipistrellus, mid‐distance migratory Nyctalus noctula, and long‐distance migratory Pipistrellus nathusii. We measured stable carbon and nitrogen isotope ratios (δ13C, δ15N) in five tissues that differed in isotopic retention time (fur, wing membrane tissue, muscle, liver, blood) to shed light on the species‐specific habitat use during the autumn migration period using standard ellipse areas (SEAc). Further, we used stable isotope ratios of non‐exchangeable hydrogen (δ2HK) in fur keratin to assess the breeding origin of bats. We inferred from isotopic composition (δ13C, δ15N) of fur keratin that isotopic niche dimensions of P. nathusii was distinct from that of N. noctula and P. pipistrellus, probably because P. nathusii was using more aquatic habitats than the other two species. Isoscape origin models supported that traveled distances before dying at wind turbines was largest for P. nathusii, intermediate for N. noctula, and shortest for P. pipistrellus. Isotopic niche dimensions calculated for each sample type separately reflected the species’ migratory behavior. Pipistrellus pipistrellus and N. noctula showed similar isotopic niche breadth across all tissue types, whereas SEAc values of P. nathusii increased in tissues with slow turnaround time. Isotopic data suggested that P. nathusii consistently used aquatic habitats throughout the autumn period, whereas N. noctula showed a stronger association with terrestrial habitats during autumn compared to the pre‐migration period.
Impacts of harvesting on brine shrimp (Artemia franciscana) in Great Salt Lake, Utah, USA
Authors: Sura Shayna A. , Belovsky Gary E.
Published: May 2016

Selective harvesting can cause evolutionary responses in populations via shifts in phenotypic characteristics, especially those affecting life history. Brine shrimp (Artemia franciscana) cysts in Great Salt Lake (GSL), Utah, USA are commercially harvested with techniques that select against floating cysts. This selective pressure could cause evolutionary changes over time. Our objectives are to (1) determine if there is a genetic basis to cyst buoyancy, (2) determine if cyst buoyancy and nauplii mortality have changed over time, and (3) to examine GSL environmental conditions over time to distinguish whether selective harvesting pressure or a trend in environmental conditions caused changes in cyst buoyancy and nauplii mortality. Mating crosses between floating and sinking parental phenotypes with two food concentrations (low and high) indicated there is a genetic basis to cyst buoyancy. Using cysts harvested from 1991–2011, we found cyst buoyancy decreased and nauplii mortality increased over time. Data on water temperature, salinity, and chlorophyll a concentration in GSL from 1994 to 2011 indicated that although water temperature has increased over time and chlorophyll a concentration has decreased over time, the selective harvesting pressure against floating cysts is a better predictor of changes in cyst buoyancy and nauplii mortality over time than trends in environmental conditions. Harvesting of GSL A. franciscana cysts is causing evolutionary changes, which has implications for the sustainable management and harvesting of these cysts. Monitoring phenotypic characteristics and life‐history traits of the population should be implemented and appropriate responses taken to reduce the impacts of the selective harvesting.
Nitrogen Fertilizer and Seeding Rate Influence on Grain and Forage Yield of Dual‐Purpose Barley
Authors: Hajighasemi S. , Keshavarz‐Afshar R. , Chaichi M. R.
Published: May 2016

Clipping fall‐sown cereals provides a good source of high‐quality forage during late winter. Farmers usually use more inputs, including fertilizers and seed, in dual‐purpose systems compared with grain‐only systems. A 2‐yr field study was conducted in Karaj, Iran, to evaluate the effects of nitrogen (N) rates (0, 50, 100, 150 kg N ha−1) and seeding rates (400, 600, 800 seed m−2) on forage and grain yields of two barley (Hordeum vulgare L.) cultivars (Fasih and CB 744) in grain‐only and dual‐purpose systems. Fasih and CB 744 grain yields in the grain‐only system were 2996 and 3250 kg ha−1, respectively (averaged over experimental treatments). Forage removal in the dual‐purpose system resulted in 25% grain yield penalty. Despite the lower grain yield, the economic return of the dual‐purpose system was considerably greater due to the high price of forage during late winter in the region. Grain yield response to N was linear in the grain‐only system, but the trend was not significant in the dual‐purpose system. In both production systems, grain yield response to seeding rate was quadratic, and the highest yields of both cultivars (2534 and 3192 kg ha−1 for Fasih and CB 744, respectively) were obtained from 600 seed m−2. In both production systems, 600 seed m−2 and 100 kg N ha−1 were optimum for grain and forage production. Our results showed considerably higher revenue in the dual‐purpose system compared with the grain‐only system in this region. Moreover, no additional inputs of N and seed are required for dual‐purpose barley than those usually used in a grain‐only system.

Core Ideas

Dual‐purpose barley yielded 25% less grain than that in grain‐only system.

Despite a lower grain yield, economic return of dual‐purpose barley was considerably greater.

In both production systems, 600 seed m−2 and 100 kg N ha−1 were optimum for grain and forage production.

No additional N and seed are required for dual‐purpose barley than those usually used in grain‐only system.
Assessing the Success of Regional Measures for Lowering Agricultural Nutrient Pollution in Headwater Streams
Authors: Barry C. D. , Foy R. H.
Published: May 2016

Lowland waters in Northern Ireland experience elevated agricultural phosphorus (P) inputs, and in response a variety of control measures targeting farm nutrient management have been implemented. Their efficacy in lowering nitrogen (N) and P exports and improving water quality is examined in 40 headwater streams from 1990 to 2009, and to 2014 for 24 of these. Over this period manure production in the study catchments declined by 7%, but regional chemical fertilizer inputs declined by 37% for N and 79% for P, and the regional nutrient surplus was lowered by 18% for N and 49% for P. Diminished pollution by organic wastes meant that 85% of streams exhibited chemistry suitable for salmonids in 2009 compared to 40% in 1990. Flow‐weighted mean concentrations (FWMCs) of nutrients declined between 1990 and 2009, and their correlations with catchment stocking rates became stronger over time. For catchments with manure inputs <16.6 kg P ha−1, total P and nitrate FWMCs declined from 123 ± 19 μg P L−1and 1.92 ± 0.5 mg N L−1in 1990 at rates of 2.2 ± 0.5 and 30 ± 10 μg L−1yr−1, respectively. For catchments with higher manure inputs the respective rates of decline were greater at 5.8 ± 1.0 μg P L−1yr−1and 160 ± 20 μg N L−1yr−1from 1990 concentrations of 270 ± 25 μg P L−1and 5.99 ± 0.4 mg N L−1. Although now lower, P concentrations in the more highly stocked catchments still exceed regional nutrient standards so that the identification of further factors impinging on nutrient losses is critical if such standards are to be achieved.

Core Ideas

Amelioration of point source and diffuse agricultural pollution over 20 years.

Reductions to diffuse N export more rapid and pronounced than for P.

Nutrient versus land use intensity correlations stronger after pollution amelioration.
Effect of Harsh or Mild Extraction of Soil on Pesticide Leaching to Groundwater
Authors: Boesten Jos J. T. I.
Published: May 2016

Assessment of leaching to groundwater is an important aspect of pesticide risk assessment. The first leaching tier usually consists of simulations with leaching scenarios based on pesticide–soil properties derived from laboratory studies. Because the extractability of pesticide residues in such studies decreases with time, the harshness of the extraction method influences these pesticide–soil properties. This study investigates the effect of using a mild or harsh extraction method on simulated leaching to groundwater with consideration of substances with a range of half‐lives and organic matter sorption coefficient values for selected leaching scenarios. The model for linking the concentrations of the mild and the harsh systems was based on laboratory studies with two pesticides and a Dutch sandy soil and was tested against Canadian field studies with atrazine (6‐chloro‐N2‐ethyl‐N4‐isopropyl‐1,3,5‐triazine‐2,4‐diamine). The degradation rate and the aged‐sorption parameters of each “mild” soil–substance system were derived from a hypothetical laboratory incubation study using prescribed parameter values for the corresponding “harsh” soil–substance system. Simulations were performed for three European leaching scenarios (United Kingdom, France, Portugal). For the best‐guess parameter set, the leaching concentrations of the harsh system were approximately equal to those of the mild system at leaching concentrations greater than 1 μg L−1 and were at most approximately a factor of two higher than those of the mild systems at mild leaching concentrations between 0.01 and 0.1 μg L−1. However, an extreme parameter set led to harsh leaching concentrations that were at most approximately 10 times higher than the mild leaching concentrations at levels between 0.01 and 0.1 μg L−1.

Core Ideas

First model for the effect of harsh or mild extraction on pesticide behavior in soil.

A model based on a Dutch study produced acceptable simulation of Canadian field data.

The effect of harsh or mild extraction on pesticide leaching is comparatively small.

Mild extraction generates faster apparent degradation but less aged sorption.
Models for Genome × Environment Interaction: Examples in Livestock
Authors: Hayes Ben J. , Daetwyler Hans D. , Goddard Mike E.
Published: May 2016

In livestock, genotype × environment interaction (G × E) has been widely investigated, with genotype defined at the level of subspecies, breeds, individual animals within a breed (for example performance of offspring of elite sires across environments), and genotypes at single‐nucleotide polymorphisms (SNPs). Environments can be described by category (e.g., tropical vs. temperate, high vs. low farm input levels, countries) and by continuous variables such as temperature. To predict breeding values of genotypes in environments described by categories, multitrait models with each category a different trait are used. The models are now being used to predict genomic estimated breeding values (GEBV) for different environments such as the value of a bull's genetics for his daughter's milk production in different countries. The multitrait genomic model has also been used to enable reference populations to be merged across environments and across countries, leading to more accurate GEBV. When the environment can be described by a continuous variable, random regression models have been used to predict response of genotypes to the environment. For example, these models have been used to determine if there are SNP genotypes associated with less sensitivity of milk production to increasing temperature. In both livestock and plant breeding, methods that use genomic information can better cope with a reduced degree of replication of individuals across environments, as it is actually the alleles that must be replicated across environments. More accurate estimates of G × E with the genomic approach may therefore be achievable than was possible in the past.
Increasing Seed Viability of Maize Haploid Inducing Lines by Genetic and Non‐Genetic Approaches
Authors: Irani Sayareh , Knapp Allen D. , Lubberstedt Thomas , Frei Ursula , Askari Ehsan
Published: May 2016

Some haploid inducing lines used in the production of maize doubled haploids (DHs) express germination problems and reduced vigor. In this study, two reciprocal F1 populations of the haploid inducing lines RWS and RWK‐76 were examined for viability by Tetrazolium (TZ) and germination ability by standard germination tests. Evaluation based on TZ tests showed that 59% of the seed of RWK‐76/RWS were not viable, compared with only 12% dead seed in RWS/RWK‐76. Similarly, the total germination and speed of germination in RWK‐76/RWS (25%, 1.53) was lower than for RWS/RWK‐76 (74%, 4.30). In an effort to develop a quick method for assessing seed viability in these lines, the TZ test was repeated in a different way. Seed from each genotype was placed in beakers containing distilled water. Seed would either float or sink. Subsequent TZ testing confirmed that seed that floated was dead, and seed that sank was alive, although some of them had defective embryos. The dead seed in both genotypes failed to develop an embryo, leaving an empty cavity that would fill with air and cause seed to float on water. This feature can be exploited for a simple and practical method to separate living from dead seed. In addition, we surveyed the ig1 (indeterminate gametophyte) gene as a candidate for germination problems in inducer lines. Sequencing data from the ig1 region showed that RWS and RWK‐76 differed in one nucleotide and amino acid in the first exon of ig1. Segregation of ig1 alleles from RWS and RWK‐76 was significantly (P ≤ 0.01) distorted in the respective F2 population relative to the expected Mendelian segregation ratio (1:2:1). Thus, either ig1 or a linked gene in the ig1 region affected seed viability.
Resistance to Rhizoctonia solani and Pythium ultimum in Upland Cotton (Gossypium hirsutum L.)
Authors: Jones Whitney M. , Smith C. Wayne , Starr James L.
Published: May 2016

Upland cotton, Gossypium hirsutum L., is grown extensively in the southern United States with an annual farmgate value of $5 billion and an annual national economic impact of over $28 billion. Two seed and seedling disease pathogens, Rhizoctonia solani and Pythium ultimum, are the most significant soilborne pathogens of cotton in the United States. Three germplasm families selected for elevated levels of condensed tannins (HT) along with ‘Tamcot Luxor’, as a resistant control, were evaluated for resistance to R. solani and two HT families were evaluated for resistance to P. ultimum. Two generations of single plant selections resulted in three generations, C0 (original families or cycle 0), C1 selected from the C0 family, and C2 selected from the C1 generation. Individual plants were challenged with either R. solani or P. ultimum and resistance measured as percent survival or by a disease index rating (DIR). One cycle of single plant selection improved resistance to R. solani from 9.3% survival on average to 31% survival across six HT families while resistance to P. ultimum was improved from 31% survival to an average of 59% survival. Challenging individual plants with appropriate levels of R. solani and P. ultimum appears to be an effective tool for selection of germplasm resistant to these seedling disease causing pathogens.
Determining Soil Stress beneath a Tire: Measurements and Simulations
Authors: Keller Thomas , Ruiz Siul , Stettler Matthias , Berli Markus
Published: May 2016

Core Ideas

Bolling probe pressure is a function of soil mean normal stress and the soil's Poisson ratio.

Vertical soil stress could be well described by the Boussinesq solution.

Simulations reveal a significant impact of soil properties on mean normal stress.

This study measured soil stress underneath a rolling wheel by using two different types of sensors: a load cell type probe referred to as an Arvidsson probe to read vertical soil stress and a fluid inclusion type sensor referred to as a Bolling probe to read soil mean normal stress. Measurements were compared with simulations using a semi‐empirical as well as a finite element model. The latter allowed us to consider a layered soil profile as well as an elastoplastic constitutive relationship in the simulations. In addition, the finite element model was used to quantify the ratio between the Bolling probe pressure and the soil mean normal stress. The Bolling probe pressure was found to be primarily a function of the soil's Poisson ratio, which supports findings from earlier studies. Our results showed better agreement between measurements and simulations for vertical stress (obtained from the Arvidsson probe readings) than for mean normal stress (calculated from the Bolling probe measurements). The finite element simulations revealed that soil properties had little influence on vertical stress, and the distribution with depth of the vertical stress could be well described by the classical Boussinesq solution. However, soil properties had a significant impact on the mean normal stress. The widely used semi‐empirical Fröhlich model performed poorly, which may have been because of an inconsistency in the model assumptions.
An alternative method to improve the settleability of gas-vacuolated cyanobacteria by collapsing gas vesicles
Authors: Abeynayaka Helayaye Damitha Lakmali , Asaeda Takashi , Tanaka Kyoko , Atsuzawa Kimie , Kaneko Yasuko , Nishda Hidenori , Inada Seiichi
Published: May 2016

This study estimated the ability of pressurization to collapse gas vesicles and thereby enhance the settleability of fresh water cyanobacteria. Settling velocities of Pseudanabaena galeata and Microcystis aeruginosa were measured at 11 different pressure values from 0 to 0.5 MPa. The morphological variations that occurred in the gas vacuoles according to the applied pressure were investigated using transmission electron microscopy images. The settleability of both cyanobacteria species increased statistically significantly (P = 0.000) with increasing pressure, whereas the gas-vacuolated area of both species decreased significantly (P = 0.000) with the magnitude of the applied pressure. The removal ability of cyanobacterial cells from the water layer increased with high pressure treatment. The maximum removal efficiency observed of P. galeata and M. aeruginosa cells relative to the control culture were 82% and 95%, respectively, at the maximum tested pressure value of 0.5 MPa.
Predictors of 30-Day Hospital Readmission among Maintenance Hemodialysis Patients: A Hospital’s Perspective
Authors: Flythe Jennifer E. , Katsanos Suzanne L. , Hu Yichun , Kshirsagar Abhijit V. , Falk Ronald J. , Moore Carlton R.
Published: May 2016

Background and objectives

Over 35% of patients on maintenance dialysis are readmitted to the hospital within 30 days of hospital discharge. Outpatient dialysis facilities often assume responsibility for readmission prevention. Hospital care and discharge practices may increase readmission risk. We undertook this study to elucidate risk factors identifiable from hospital-derived data for 30-day readmission among patients on hemodialysis.

Design, setting, participants, & measurements

Data were taken from patients on maintenance hemodialysis discharged from University of North Carolina Hospitals between May of 2008 and June of 2013 who received in-patient hemodialysis during their index hospitalizations. Multivariable logistic regression models with 30-day readmission as the dependent outcome were used to identify readmission risk factors. Models considered variables available at hospital admission and discharge separately.

Results

Among 349 patients, 112 (32.1%) had a 30-day hospital readmission. The discharge (versus admission) model was more predictive of 30-day readmission. In the discharge model, malignancy comorbid condition (odds ratio [OR], 2.08; 95% confidence interval [95% CI], 1.04 to 3.11), three or more hospitalizations in the prior year (OR, 1.97; 95% CI, 1.06 to 3.64), ≥10 outpatient medications at hospital admission (OR, 1.69; 95% CI, 1.00 to 2.88), catheter vascular access (OR, 1.82; 95% CI, 1.01 to 3.65), outpatient dialysis at a nonuniversity–affiliated dialysis facility (OR, 3.59; 95% CI, 2.03 to 6.36), intradialytic hypotension (OR, 3.10; 95% CI, 1.45 to 6.61), weekend discharge day (OR, 1.82; 95% CI, 1.01 to 3.31), and serum albumin <3.3 g/dl (OR, 4.28; 95% CI, 2.37 to 7.73) were associated with higher readmission odds. A decrease in prescribed medications from admission to discharge (OR, 0.20; 95% CI, 0.08 to 0.51) was associated with lower readmission odds. Findings were robust across different model–building approaches.

Conclusions

Models containing discharge day data had greater predictive capacity of 30-day readmission than admission models. Identified modifiable readmission risk factors suggest that improved medication education and improved transitions from hospital to community may potentially reduce readmissions. Studies evaluating targeted transition programs among patients on dialysis are needed.
Objective Gait and Balance Impairments Relate to Balance Confidence and Perceived Mobility in People With Parkinson Disease
Authors: Curtze Carolin , Nutt John G. , Carlson-Kuhta Patricia , Mancini Martina , Horak Fay B.
Published: May 2016

Background

Body-worn, inertial sensors can provide many objective measures of balance and gait. However, the objective measures that best reflect patient perception of mobility disability and clinician assessment of Parkinson disease (PD) are unknown.

Objective

The purposes of this study were: (1) to determine which objective measures of balance and gait are most related to patient perception of mobility disability and disease severity in people with PD and (2) to examine the effect of levodopa therapy on these correlates.

Design

This was an experimental correlation study.

Methods

One hundred four people with idiopathic PD performed 3 trials of the Instrumented Stand and Walk Test (ISAW) in the “on” and “off” medication states. The ISAW consists of quiet standing (30 seconds), gait initiation, straight walking (7 m), and turning (180°), yielding 34 objective measures of mobility from body-worn inertial sensors. Patient perception of mobility disability was assessed with the Activities-specific Balance Confidence (ABC) scale and the mobility subscale of the Parkinson's Disease Questionnaire (PDQ-39). Disease severity was assessed with the Unified Parkinson's Disease Rating Scale, part III (motor UPDRS). Spearman correlations were used to relate objective measures of mobility to patient perception and disease severity.

Results

Turning speed, gait speed, and stride length were most highly correlated to severity of disease and patient perception of mobility disability. The objective measures of mobility in the off-medication state were more indicative of patient perception of mobility disability and balance confidence compared with on-medication state measures.

Limitations

Causation is an inherent problem of correlation studies.

Conclusion

Physical therapists should evaluate mobility in people with PD in the off-medication state because the off-medication state is more related to disease severity and patient perception of mobility disability than the on-medication state mobility. Assessment and treatment of mobility in people with PD should target specific measures (ie, turning, gait speed, and stride length) because these measures best reflect patients' quality of life and balance confidence.
Student Preparation and the Power of Visual Input in Veterinary Surgical Education: An Empirical Study
Authors: Langebæk Rikke , Nielsen Søren Saxmose , Koch Bodil Cathrine , Berendt Mette
Published: May 2016

In recent years, veterinary educational institutions have implemented alternative teaching methods, including video demonstrations of surgical procedures. However, the power of the dynamic visual input from videos in relation to recollection of a surgical procedure has never been evaluated. The aim of this study was to investigate how veterinary surgical students perceived the influence of different educational materials on recollection of a surgical procedure. Furthermore, we investigated if surgical technique was associated with a certain method of recollection or use of educational material. During a basic surgical skills course, 112 fourth-year veterinary students participated in the study by completing a questionnaire regarding method of recollection, influence of individual types of educational input, and homework preparation. Furthermore, we observed students performing an orchiectomy in a terminal pig lab. Preparation for the pig lab consisted of homework (textbook, online material, including videos), lecture, cadaver lab, and toy animal models in a skills lab. In the instructional video, a detail was used that was not described elsewhere. Results show that 60% of the students used a visual dynamic method as their main method of recollection and that video was considered the most influential educational input with respect to recollection of a specific procedure. Observation of students' performance during the orchiectomy showed no clear association with students' method of recollection but a significant association (p=.002) with educational input. Our results illustrate the power of a visual input and support prior findings that knowledge is constructed from multiple sources of information.
Learning from failure: persistence of aneurysms following pipeline embolization
Authors: Shapiro Maksim , Becske Tibor , Nelson Peter K.
Published: May 2016

OBJECTIVE

A detailed analysis was performed of anterior circulation aneurysms treated with a Pipeline Embolization Device (PED) that did not progress to complete occlusion by 1-year follow-up. Angiography was performed with the purpose of identifying specific factors potentially responsible for these failed outcomes.

METHODS

From among the first 100 patients with anterior circulation aneurysms, 92 underwent 1-year follow-up angiography and were individually studied through review of their pre- and postembolization studies.

RESULTS

Nineteen aneurysms (21%) remained unoccluded at 12 months. Independent predictors of treatment failure, identified by logistic regression analysis, were found to be fusiform aneurysm morphology, decreasing dome-to-neck ratio, and the presence of a preexisting laser-cut stent. Further examination of individual cases identified several common mechanisms—device malapposition, inadequate coverage of the aneurysm neck with persistent exchange across the device, and the incorporation of a branch vessel into the aneurysm fundus—potentially contributing to failed treatment in these settings.

CONCLUSIONS

Attention to specific features of the aneurysm and device construct can frequently identify cases predisposed to treatment failure and suggest strategies to maximize favorable outcomes.
Operating room waste: disposable supply utilization in neurosurgical procedures
Authors: Zygourakis Corinna C. , Yoon Seungwon , Valencia Victoria , Boscardin Christy , Moriates Christopher , Gonzales Ralph , Lawton Michael T.
Published: May 2016

OBJECTIVE

Disposable supplies constitute a large portion of operating room (OR) costs and are often left over at the end of a surgical case. Despite financial and environmental implications of such waste, there has been little evaluation of OR supply utilization. The goal of this study was to quantify the utilization of disposable supplies and the costs associated with opened but unused items (i.e., “waste”) in neurosurgical procedures.

METHODS

Every disposable supply that was unused at the end of surgery was quantified through direct observation of 58 neurosurgical cases at the University of California, San Francisco, in August 2015. Item costs (in US dollars) were determined from the authors' supply catalog, and statistical analyses were performed.

RESULTS

Across 58 procedures (36 cranial, 22 spinal), the average cost of unused supplies was $653 (range $89-$3640, median $448, interquartile range $230–$810), or 13.1% of total surgical supply cost. Univariate analyses revealed that case type (cranial versus spinal), case category (vascular, tumor, functional, instrumented, and noninstrumented spine), and surgeon were important predictors of the percentage of unused surgical supply cost. Case length and years of surgical training did not affect the percentage of unused supply cost. Accounting for the different case distribution in the 58 selected cases, the authors estimate approximately $968 of OR waste per case, $242,968 per month, and $2.9 million per year, for their neurosurgical department.

CONCLUSIONS

This study shows a large variation and significant magnitude of OR waste in neurosurgical procedures. At the authors' institution, they recommend price transparency, education about OR waste to surgeons and nurses, preference card reviews, and clarification of supplies that should be opened versus available as needed to reduce waste.
Can the anxiety domain of EQ-5D and mental health items from SF-36 help predict outcomes after surgery for lumbar degenerative disorders?
Authors: Carreon Leah Y. , Djurasovic Mladen , Dimar John R. , Owens R. Kirk , Crawford Charles H. , Puno Rolando M. , Bratcher Kelly R. , McGraw Katlyn E. , Glassman Steven D.
Published: May 2016

OBJECTIVE

Studies have shown that anxious or depressed patients may have poorer outcomes after lumbar fusion. These conclusions were drawn from questionnaires specifically designed to measure anxiety and depression. The objective of this study is to determine if responses to the EQ-5D anxiety/depression domain or the items used to calculate the 36-Item Short-Form Health Survey (SF-36) Mental Component Summary (MCS) can predict outcomes after lumbar fusion surgery.

METHODS

Patients enrolled in the National Neurosurgery Quality and Outcomes Database from a single center with 1-year follow-up were identified. The outcomes collected include the Oswestry Disability Index (ODI), EQ-5D, SF-36, and the back- and leg-pain numeric rating scales (range 0–10). Linear regression modeling was performed to predict the 1-year ODI scores using the EQ-5D anxiety/depression domain and the 14 items used to calculate SF-36 MCS.

RESULTS

Complete data were available for 312 (88%) of 353 eligible patients. The mean patient age was 58.5 years, 175 (56%) patients were women, and 52 patients were smokers. After controlling for other factors, the item in the SF-36 that asks “Have you felt downhearted and depressed?” is the strongest predictor of the 1-year ODI score (r2 = 0.191; p = 0.000) and 1-year EQ-5D score (r2 = 0.205; p = 0.000). Neither the EQ-5D anxiety/depression domain nor the diagnoses of anxiety or depression were predictors of 1-year outcomes.

CONCLUSIONS

Patient responses to SF-36 item “Have you felt downhearted and depressed?” account for 20% of the variability of the 1-year ODI and EQ-5D scores and can be used by clinicians to screen for anxiety or depression in patients prior to lumbar fusion surgery. Clinicians may offer psychological support to these patients preoperatively in order to improve treatment outcomes.
Prophylactic adjacent-segment vertebroplasty following kyphoplasty for a single osteoporotic vertebral fracture and the risk of adjacent fractures: a retrospective study and clinical experience
Authors: Eichler Martin C. , Spross Christian , Ewers Alexander , Mayer Ryan , Külling Fabrice A.
Published: May 2016

OBJECTIVE

This study investigated the benefit of prophylactic vertebroplasty of the adjacent vertebrae in single-segment osteoporotic vertebral body fractures treated with kyphoplasty.

METHODS

All patients treated with kyphoplasty for osteoporotic single-segment fractures between January 2007 and August 2012 were included in this retrospective study. The patients received either kyphoplasty alone (kyphoplasty group) or kyphoplasty with additional vertebroplasty of the adjacent segment (vertebroplasty group). The segmental kyphosis with the rate of adjacent-segment fractures (ASFs) and remote fractures were studied on plain lateral radiographs preoperatively, postoperatively, at 3 months, and at final follow-up.

RESULTS

Thirty-seven (82%) of a possible 45 patients were included for the analysis, with a mean follow-up of 16 months (range 3–54 months). The study population included 31 women, and the mean age of the total patient population was 72 years old (range 53–86 years). In 21 patients (57%), the fracture was in the thoracolumbar junction. Eighteen patients were treated with additional vertebroplasty and 19 with kyphoplasty only. The segmental kyphosis increased in both groups at final follow-up. A fracture through the primary treated vertebra (kyphoplasty) was found in 4 (22%) of the vertebroplasty group and in 3 (16%) of the kyphoplasty group (p = 0.6). An ASF was found in 50% (n = 9) of the vertebroplasty group and in 16% (n = 3) of the kyphoplasty group (p = 0.03). Remote fractures occurred in 1 patient in each group (p = 1.0).

CONCLUSIONS

Prophylactic vertebroplasty of the adjacent vertebra in patients with single-segment osteoporotic fractures as performed in this study did not decrease the rate of adjacent fractures. Based on these retrospective data, the possible benefits of prophylactic vertebroplasty do not compensate for the possible risks of an additional cement augmentation.
Bowel perforation presenting with acute abdominal pain and subcutaneous emphysema in a 14-year-old girl with an abandoned distal peritoneal shunt catheter: case report
Authors: Riccardello Gerald J. , Barr Luke K. , Bassani Luigi
Published: May 2016

The authors report the case of 14-year-old girl with a history of myelomeningocele and previously shunt-treated hydrocephalus who presented with right-sided abdominal pain and subcutaneous emphysema that developed over a 1-week period. A CT scan of the patient's abdomen revealed a retained distal ventriculoperitoneal (VP) catheter with air tracking from the catheter to the upper chest wall. Given the high suspicion of the catheter being intraluminal, an exploratory laparotomy was performed and revealed multiple jejunal perforations. The patient required a partial small-bowel resection and reanastomosis for complete removal of the retained catheter. Six other similar cases of bowel perforation occurring in patients with abandoned VP and subdural-peritoneal shunts have been reported. The authors analyzed these cases with regard to age of presentation, symptomatic presentation, management, morbidity, and mortality. While there was 0% mortality associated with bowel perforation secondary to a retained distal VP catheter, the morbidity was significantly high and included peritonitis and small bowel resection.
Dural sinus obstruction following head injury: a diagnostic and clinical study
Authors: Benifla Mony , Yoel Uri , Melamed Israel , Merkin Vladimir , Cohen Avi , Shelef Ilan
Published: May 2016

OBJECTIVE

The aim of this study is to describe the clinical characteristics of patients with skull fracture adjacent to a dural venous sinus (DVS) and evaluate the role of CT venography (CTV) in the diagnosis of the effect of this fracture on the involved DVS.

METHODS

The study comprised patients with vault or skull base fracture adjacent to a DVS who were admitted to 1 medical center during a 2-year period. The medical records were reviewed for the clinical and radiographic characteristics. All patients had undergone CTV to evaluate potential DVS pathology. The clinical and radiological findings of the patients with DVS pathology were compared with those of the patients with normal DVS. The groups were compared using the chi-square and t-tests for categorical and continuous data, respectively. The potential risk for poor outcome among the patients with DVS pathology was also investigated.

RESULTS

Of 434 patients with skull fractures, 41 (9.4%) had fractures adjacent to a DVS. DVS pathology was detected in 51% of patients (21 of 41 patients). For 9 (43%) patients, obstruction was extraluminal without thrombosis, and 12 (57%) patients had dural sinus thrombosis (DST). In patients with a positive-CTV scan, the severity of injury according to the Glasgow Coma Scale score at presentation was correlated with the presence of DST (p = 0.007). The sensitivity of noncontrast CT (NCCT) for DVS involvement was 38% among the patients with positive-CTV scans. For patients with DVS pathology, poor outcome was correlated with DST (intraluminal), rather than extraluminal obstruction without thrombosis (p = 0.02), and superior sagittal sinus (SSS) involvement (p = 0.05).

CONCLUSIONS

NCCT is not sensitive enough to detect DVS obstruction in patients with skull fracture adjacent to a DVS, and CTV should be performed in order to rule it out. A correlation was found between the severity of injury and the presence of DST, rather than extraluminal obstruction. The authors' findings suggest that DST and SSS involvement may be indicators of poor outcome in patients with skull fracture adjacent to DVS.
Ethical Justification of Conducting Research Trials in Lower and Middle Income Countries Including Pakistan: The Responsibilities of Research Enterprises
Authors: Rafique Zoheb
Published: May 2016

Asia is the most diverse continent in the world in terms of culture, religion, population size, finance, education, health care, academic research, general population skills, and governmental drug regulations. Each Asian country has its own unique qualities when it comes to attracting industry sponsored clinical trials. Factors that influence selecting location of a study site for a sponsored trial are mainly population size, infrastructure, education levels, and quality of health care, cost and drug regulatory platform.   Conducting research in traditional countries like Pakistan adds another dimension to the problems in assuring that research conducted in an ethical manner. The indigenous layer of the cultural values makes it even more difficult task, but this is the task that we are morally and ethically bound to shoulder.