bluuebunny/crossref_metadata_2025 huggingface dataset:
Use of HRP-2-based rapid diagnostic test for Plasmodium falciparum malaria: assessing accuracy and cost-effectiveness in the villages of Dielmo and Ndiop, Senegal
Authors: Ly Alioune Badara , Tall Adama , Perry Robert , Baril Laurence , Badiane Abdoulaye , Faye Joseph , Rogier Christophe , Touré Aissatou , Sokhna Cheikh , Trape Jean-François , Michel Rémy
Published: June 2010

Background

In 2006, the Senegalese National Malaria Control Programme (NMCP) has recommended artemisinin-based combination therapy (ACT) as the first-line treatment for uncomplicated malaria and, in 2007, mandated testing for all suspected cases of malaria with a Plasmodium falciparum HRP-2-based rapid diagnostic test for malaria (RDT(Paracheck®). Given the higher cost of ACT compared to earlier anti-malarials, the objectives of the present study were i) to study the accuracy of Paracheck® compared to the thick blood smear (TBS) in two areas with different levels of malaria endemicity and ii) analyse the cost-effectiveness of the strategy of the parasitological confirmation of clinically suspected malaria cases management recommended by the NMCP.

Methods

A cross-sectional study was undertaken in the villages of Dielmo and Ndiop (Senegal) nested in a cohort study of about 800 inhabitants. For all the individuals consulting between October 2008 and January 2009 with a clinical diagnosis of malaria, a questionnaire was filled and finger-prick blood samples were taken both for microscopic examination and RDT. The estimated costs and cost-effectiveness analysis were made considering five scenarios, the recommendations of the NMCP being the reference scenario. In addition, a sensitivity analysis was performed assuming that all the RDT-positive patients and 50% of RDT-negative patients were treated with ACT.

Results

A total of 189 consultations for clinically suspected malaria occurred during the study period. The sensitivity, specificity, positive and negative predictive values were respectively 100%, 98.3%, 80.0% and 100%. The estimated cost of the reference scenario was close to 700€ per 1000 episodes of illness, approximately twice as expensive as most of the other scenarios. Nevertheless, it appeared to us cost-effective while ensuring the diagnosis and the treatment of 100% of malaria attacks and an adequate management of 98.4% of episodes of illness. The present study also demonstrated that full compliance of health care providers with RDT results was required in order to avoid severe incremental costs.

Conclusions

A rational use of ACT requires laboratory testing of all patients presenting with presumed malaria. Use of RDTs inevitably has incremental costs, but the strategy associating RDT use for all clinically suspected malaria and prescribing ACT only to patients tested positive is cost-effective in areas where microscopy is unavailable.
MicroRNA-101 negatively regulates Ezh2 and its expression is modulated by androgen receptor and HIF-1α/HIF-1β
Authors: Cao Paul , Deng Zhiyong , Wan Meimei , Huang Weiwei , Cramer Scott D , Xu Jianfeng , Lei Ming , Sui Guangchao
Published: June 2010

Background

In prostate cancer (PCa), the common treatment involving androgen ablation alleviates the disease temporarily, but results in the recurrence of highly aggressive and androgen-independent metastatic cancer. Therefore, more effective therapeutic approaches are needed. It is known that aberrant epigenetics contributes to prostate malignancy. Unlike genetic changes, these epigenetic alterations are reversible, which makes them attractive targets in PCa therapy to impede cancer progression. As a histone methyltransferease, Ezh2 plays an essential role in epigenetic regulation. Since Ezh2 is overexpressed and acts as an oncogene in PCa, it has been proposed as a bona fide target of PCa therapy. MicroRNAs (miRNAs) regulate gene expression through modulating protein translation. Recently, the contribution of miRNAs in cancer development is increasingly appreciated. In this report, we present our study showing that microRNA-101 (miR-101) inhibits Ezh2 expression and differentially regulates prostate cancer cells. In addition, the expression of miR-101 alters upon androgen treatment and HIF-1α/HIF-1β induction.

Result

In our reporter assays, both miR-101 and miR-26a inhibit the expression of a reporter construct containing the 3'-UTR of Ezh2. When ectopically expressed in PC-3, DU145 and LNCaP cells, miR-101 inhibits endogenous Ezh2 expression in all three cell lines, while miR-26a only decreases Ezh2 in DU145. Ectopic miR-101 reduces the invasion ability of PC-3 cells, while restored Ezh2 expression rescues the invasiveness of PC-3 cells. Similarly, miR-101 also inhibits cell invasion and migration of DU145 and LNCaP cells, respectively. Interestingly, ectopic miR-101 exhibits differential effects on the proliferation of PC-3, DU-145 and LNCaP cells and also causes morphological changes of LNCaP cells. In addition, the expression of miR-101 is regulated by androgen receptor and HIF-1α/HIF-1β. While HIF-1α/HIF-1β induced by deferoxamine mesylate (DFO) decreases miR-101 levels, the overall effects of R-1881 on miR-101 expression are stimulatory.

Conclusions

This study indicates that miR-101 targets Ezh2 and decreases the invasiveness of PCa cells, suggesting that miR-101 introduction is a potential therapeutic strategy to combat PCa. MiR-101 differentially regulates prostate cell proliferation. Meanwhile, the expression of miR-101 is also modulated at different physiological conditions, such as androgen stimulation and HIF-1α/HIF-1β induction.
Suppressive actions of eicosapentaenoic acid on lipid droplet formation in 3T3-L1 adipocytes
Authors: Manickam Elizabeth , Sinclair Andrew J , Cameron-Smith David
Published: June 2010

Background

Lipid droplet (LD) formation and size regulation reflects both lipid influx and efflux, and is central in the regulation of adipocyte metabolism, including adipokine secretion. The length and degree of dietary fatty acid (FA) unsaturation is implicated in LD formation and regulation in adipocytes. The aims of this study were to establish the impact of eicosapentaenoic acid (EPA; C20:5n-3) in comparison to SFA (STA; stearic acid, C18:0) and MUFA (OLA; oleic acid, C18:1n-9) on 3T3-L1 adipocyte LD formation, regulation of genes central to LD function and adipokine responsiveness. Cells were supplemented with 100 μM FA during 7-day differentiation.

Results

EPA markedly reduced LD size and total lipid accumulation, suppressing PPARγ, Cidea and D9D/SCD1 genes, distinct from other treatments. These changes were independent of alterations of lipolytic genes, as both EPA and STA similarly elevated LPL and HSL gene expressions. In response to acute lipopolysaccharide exposure, EPA-differentiated adipocytes had distinct improvement in inflammatory response shown by reduction in monocyte chemoattractant protein-1 and interleukin-6 and elevation in adiponectin and leptin gene expressions.

Conclusions

This study demonstrates that EPA differentially modulates adipogenesis and lipid accumulation to suppress LD formation and size. This may be due to suppressed gene expression of key proteins closely associated with LD function. Further analysis is required to determine if EPA exerts a similar influence on LD formation and regulation in-vivo.
A rapid and scalable method for selecting recombinant mouse monoclonal antibodies
Authors: Crosnier Cécile , Staudt Nicole , Wright Gavin J
Published: June 2010

Background

Monoclonal antibodies with high affinity and selectivity that work on wholemount fixed tissues are valuable reagents to the cell and developmental biologist, and yet isolating them remains a long and unpredictable process. Here we report a rapid and scalable method to select and express recombinant mouse monoclonal antibodies that are essentially equivalent to those secreted by parental IgG-isotype hybridomas.

Results

Increased throughput was achieved by immunizing mice with pools of antigens and cloning - from small numbers of hybridoma cells - the functionally rearranged light and heavy chains into a single expression plasmid. By immunizing with the ectodomains of zebrafish cell surface receptor proteins expressed in mammalian cells and screening for formalin-resistant epitopes, we selected antibodies that gave expected staining patterns on wholemount fixed zebrafish embryos.

Conclusions

This method can be used to quickly select several high quality monoclonal antibodies from a single immunized mouse and facilitates their distribution using plasmids.
Multifocal Stevens-Johnson syndrome after concurrent phenytoin and cranial and thoracic radiation treatment, a case report
Authors: Kandil Abdullah O , Dvorak Tomas , Mignano John , Wu Julian K , Zhu Jay-Jiguang
Published: June 2010

A 46 year old male patient with metastatic prostate cancer developed Stevens-Johnson syndrome (SJS), initially in three well-demarcated areas on his scalp, chest and back, corresponding to ports of radiation therapy while on phenytoin. The rash spread from these locations and became more generalized and associated with pain and sloughing in the mucous lining of the mouth. There is a documented association between phenytoin administration with concurrent cranial radiation therapy and development of SJS. Erythema multiforme (EM) associated with phenytoin and cranial radiation therapy (EMPACT) is the term that describes this reaction. However, this term may not cover the full spectrum of the disease since it describes EM associated with phenytoin and only cranial radiation therapy. This case report presents evidence that SJS may be induced by radiation to other parts of the body in addition to the cranium while phenytoin is administered concomitantly. With increasing evidence that phenytoin and levetiracetam are equally efficacious for seizure treatment and prophylaxis, and since there is no link identified so far of an association between levetiracetam and SJS, we believe that levetiracetam is a better option for patients who need anticonvulsant medication(s) while undergoing radiation therapy, especially cranial irradiation.
Visualization and characterization of structural deformation fabric and velocity anisotropy
Authors: Guo Hao , Marfurt Kurt J. , Nissen Susan E. , Sullivan Charlotte E.
Published: June 2010

Fractures develop with different intensity and preferred orientations in response to changing stress regimes throughout geologic time. Fractures with preferred orientations are often interpreted as the cause of seismic P-wave velocity ([Formula: see text]) anisotropy as well as linear features seen in seismic attribute volumes. Field experiments show that stress orientation can often be directly measured by P-wave anisotropy while the lineaments seen in the volumetric curvature attributes are related to deformation.
3D VSP technology now a standard high-resolution reservoir-imaging technique: Part 1, acquisition and processing
Authors: Müller Klaus W. , Soroka William L. , Paulsson Björn N. P. , Marmash Samer , Al Baloushi Mariam , Al Jeelani Omar
Published: June 2010

Abu Dhabi Company for Onshore Oil Operations (ADCO) undertook a two-well 3D VSP pilot project in 2007. Because it was acquired concurrently with a high-resolution wide-azimuth surface seismic survey, it was at the time the largest 3D VSP ever recorded. The project consisted of four main parts: acquisition, processing, interpretation, and quantifying value. In part 1 of this paper the acquisition and processing of the 3D VSP is described with an emphasis on the lessons learned. Significant advances in processing are described that demonstrate how larger 3D VSP images with better amplitudes and structural preservation can be produced. In part 2, the results of the 3D VSP interpretation and economic evaluation effort are described and illustrate different ways that a VSP image can help characterize a hydrocarbon reservoir.
Crosswell seismic imaging of acoustic and shear impedance in a Michigan reef
Authors: Ibrahim Mohamed S. , Pennington Wayne D. , Turpening Roger M.
Published: June 2010

Acoustic and shear impedance images, obtained from deterministic simultaneous inversion of a high-resolution crosswell seismic survey, were used to obtain the internal structure of Niagaran reef in Michigan. The crosswell seismic survey was conducted using two monitor wells external to the reef. These wells had depths that extended beyond the depth of the reef, and imaging used reflections from above and beneath the reef, resulting in the best seismic images of any Niagaran pinnacle reef obtained to date. The top of the reservoir can be clearly distinguished, as well as its lateral extent or dipping edges. Reflection events internal to the reef are evident; some are fairly continuous across the reef and others are discontinuous.
Borehole electrokinetics
Authors: Glover Paul W.J. , Jackson Matthew D.
Published: June 2010

We now understand the electrical double layer that exists between the minerals that form the rock matrix and the bulk electrolyte which saturates the pores of the rock, at least in the steady state. It is the presence of this double layer that allows the link between the electrical properties and the fluid-flow properties of the rock to exist. In addition, because pore fluid pressure perturbations can be caused by the passage of poroelastic waves, there is also a link between the seismic properties of rocks and their electrical properties. Although postulated more than 70 years ago, there has been an acceleration in the application of electrokinetic and seismoelectric principles to reservoir problems in general and to borehole measurements in particular. In this paper we review briefly the origin of electrokinetic and seismoelectric phenomena before looking at some of the new borehole applications that are being developed.
Geomechanics field characterization of Woodford Shale and Barnett Shale with advanced logging tools and nano-indentation on drill cuttings
Authors: Abousleiman Younane , Tran Minh , Hoang Son , Ortega J. Alberto , Ulm Franz-J.
Published: June 2010

The Woodford Shale and Barnett Shale have emerged as prolific gas plays in the US midcontinent. However, the intrinsically low permeability of these gas shales hinders profitable pro-duction unless horizontal well drilling and multistage hydraulic fracturing are employed. The success of these operations depends on accurate de-terminations of the anisotropic elastic and poroelastic properties of these shale formations.
THE ROLE OF SOCIAL FACTORS IN THE CANADIAN VOWEL SHIFT: EVIDENCE FROM TORONTO
Authors: HOFFMAN MICHOL F.
Published: June 2010

The Canadian Vowel Shift (CVS) has been the focus of a number of recent impressionistic and acoustic studies. This study provides further information about the social profile of the CVS in Toronto, with a focus on the roles of gender, age, and ethnicity. It offers an acoustic analysis of bit, bet, and bat vowels using tokens from sociolinguistic interviews with Torontonians of British, italian, and Chinese ancestry. While age and sex contribute to variation, there are no significant differences according to ethnicity for vowel height or backness of any vowel. These results suggest that Torontonians participate in this change in progress, regardless of ethnic group.
NORTHERN CITIES MEXICAN AMERICAN ENGLISH: VOWEL PRODUCTION AND PERCEPTION
Authors: ROEDER REBECCA V.
Published: June 2010

This article investigates the influence of the Northern Cities Shift (NCS) on the production and perception of English vowels by Mexican Americans in Lansing, Michigan. Findings indicate full accommodation to local mainstream norms with respect to all NCS vowels except /æ/, which displays unique patterning both prenasally and in other environments. The evidence also reveals that young women in Lansing, both Anglo and Mexican American, have adopted more advanced stages of the NCS than men in their pronunciations of the vowels /I/, /ϵ/, and prenasal /æ/. Perception results match production results such that, among the six vowels examined, only /æ/ differs significantly between groups. These findings suggest that, although constant exposure to and interaction with the local matrix group appear to have led to nearly total accommodation to local NCS features in the English of Mexican Americans in Lansing, pronunciation of the vowel /æ/, in particular, reflects unique patterns of history and identity.
Effectiveness of an e-learning course in evidence-based medicine for foundation (internship) training
Authors: Hadley Julie , Kulier Regina , Zamora Javier , Coppus Sjors FPJ , Weinbrenner Susanne , Meyerrose Berrit , Decsi Tamas , Horvath Andrea R , Nagy Eva , Emparanza Jose I , Arvanitis Theodoros N , Burls Amanda , Cabello Juan B , Kaczor Marcin , Zanrei Gianni , Pierer Karen , Kunz Regina , Wilkie Veronica , Wall David , Mol Ben WJ , Khan Khalid S
Published: June 2010

Summary

Aim

To evaluate the educational effectiveness of a clinically integrated e-learning course for teaching basic evidence-based medicine (EBM) among postgraduate medical trainees compared to a traditional lecture-based course of equivalent content.

Methods

We conducted a cluster randomized controlled trial to compare a clinically integrated e-learning EBM course (intervention) to a lecture-based course (control) among postgraduate trainees at foundation or internship level in seven teaching hospitals in the UK West Midlands region. Knowledge gain among participants was measured with a validated instrument using multiple choice questions. Change in knowledge was compared between groups taking into account the cluster design and adjusted for covariates at baseline using generalized estimating equations (GEE) model.

Results

There were seven clusters involving teaching of 237 trainees (122 in the intervention and 115 in the control group). The total number of postgraduate trainees who completed the course was 88 in the intervention group and 72 in the control group. After adjusting for baseline knowledge, there was no difference in the amount of improvement in knowledge of EBM between the two groups. The adjusted post course difference between the intervention group and the control group was only 0.1 scoring points (95% CI −1.2–1.4).

Conclusion

An e-learning course in EBM was as effective in improving knowledge as a standard lecture-based course. The benefits of an e-learning approach need to be considered when planning EBM curricula as it allows standardization of teaching materials and is a potential cost-effective alternative to standard lecture-based teaching.
Competition and Cooperation in a Two-Stage Supply Chain with Demand Forecasts
Authors: Iida Tetsuo , Zipkin Paul
Published: June 2010

We consider a serial supply chain with one supplier and one retailer. Each obtains some demand forecast information, which may be shared or not. We investigate the members' benefits from sharing information. The forecasts follow a variant of the Martingale model of forecast evolution (MMFE). We construct a simple transfer-payment scheme to align the players' incentives with that of the overall system. The main finding is that, unless the players' incentives are aligned in this way, sharing information makes little sense. It might hurt one or the other player and the system as a whole.
Correction to the Paper “Optimal Product Launch Times in a Duopoly: Balancing Life-Cycle Revenues with Product Cost”
Authors: Guseo Renato , Mortarino Cinzia
Published: June 2010

The aim of this note is to correct an error in the formulation of Theorem 1 by Savin and Terwiesch [Savin, S., C. Terwiesch. 2005. Optimal product launch times in a duopoly: Balancing life-cycle revenues with product cost. Oper. Res. 53(1) 26–47].
Monotone Approximation of Decision Problems
Authors: Chehrazi Naveed , Weber Thomas A.
Published: June 2010

Many decision problems exhibit structural properties in the sense that the objective function is a composition of different component functions that can be identified using empirical data. We consider the approximation of such objective functions, subject to general monotonicity constraints on the component functions. Using a constrained B-spline approximation, we provide a data-driven robust optimization method for environments that can be sample-sparse. The method, which simultaneously identifies and solves the decision problem, is illustrated for the problem of optimal debt settlement in the credit-card industry.
Terror Queues
Authors: Kaplan Edward H.
Published: June 2010

This article presents the first models developed specifically for understanding the infiltration and interdiction of ongoing terror plots by undercover intelligence agents, and does so via novel application of ideas from queueing theory and Markov population processes. The resulting “terror queue” models predict the number of undetected terror threats in an area from agent activity/utilization data, and also estimate the rate with which such threats can be detected and interdicted. The models treat terror plots as customers and intelligence agents as servers. Agents spend all of their time either detecting and infiltrating new terror plots (in which case they are “available”), or interdicting already detected terror plots (in which case they are “busy”). Initially we examine a Markov model assuming that intelligence agents, while unable to detect all plots, never err by falsely detecting fake plots. While this model can be solved numerically, a simpler Ornstein-Uhlenbeck diffusion approximation yields some results in closed form while providing nearly identical numerical performance. The transient behavior of the terror queue model is discussed briefly along with a sample sensitivity analysis to study how model predictions compare to simulated results when using estimated versus known terror plot arrival rates. The diffusion model is then extended to allow for the false detection of fake plots. Such false detection is a real feature of counterterror intelligence given that intelligence agents or informants can make mistakes, as well as the proclivity of terrorists to deliberately broadcast false information. The false detection model is illustrated using suicide bombing data from Israel.
Positively versus negatively charged moral emotion expectancies in adolescence: The role of situational context and the developing moral self
Authors: Krettenauer Tobias , Johnston Megan
Published: June 2010

The study analyses adolescents' positively charged versus negatively charged moral emotion expectancies. Two hundred and five students (M= 14.83 years, SD= 2.21) participated in an interview depicting various situations in which a moral norm was either regarded or transgressed. Emotion expectancies were assessed for specific emotions (pride, guilt) as well as for overall strength and valence. In addition, self‐importance of moral values was measured by a questionnaire. Results revealed that positively charged emotion expectancies were more pronounced in contexts of prosocial action than in the context of moral transgressions, whereas the opposite was true for negatively charged emotions. At the same time, expectations of guilt and pride were substantially related to the self‐importance of moral values.
The role of G-quadruplex/i-motif secondary structures as cis-acting regulatory elements
Authors: Kendrick Samantha , Hurley Laurence H.
Published: June 2010

The nature of DNA has captivated scientists for more than 50 years. The discovery of the double-helix model of DNA by Watson and Crick in 1953 not only established the primary structure of DNA, but also provided the mechanism behind DNA function. Since then, researchers have continued to further the understanding of DNA structure and its pivotal role in transcription. The demonstration of DNA secondary structure formation has allowed for the proposal that the dynamics of DNA itself can function to modulate transcription. This review presents evidence that DNA can exist in a dynamic equilibrium between duplex and secondary conformations. In addition, data demonstrating that intracellular proteins as well as small molecules can shift this equilibrium in either direction to alter gene transcription will be discussed, with a focus on the modulation of proto-oncogene expression.
Linking precipitation and C3–C4 plant production to resource dynamics in higher‐trophic‐level consumers
Authors: Warne Robin W. , Pershall Alaina D. , Wolf Blair O.
Published: June 2010

In many ecosystems, seasonal shifts in temperature and precipitation induce pulses of primary productivity that vary in phenology, abundance, and nutritional quality. Variation in these resource pulses could strongly influence community composition and ecosystem function, because these pervasive bottom‐up forces play a primary role in determining the biomass, life cycles, and interactions of organisms across trophic levels. The focus of this research is to understand how consumers across trophic levels alter resource use and assimilation over seasonal and interannual timescales in response to climatically driven changes in pulses of primary productivity. We measured the carbon isotope ratios (δ13C) of plant, arthropod, and lizard tissues in the northern Chihuahuan Desert to quantify the relative importance of primary production from plants using C3 and C4 photosynthesis for consumers. Summer monsoonal rains on the Sevilleta Long Term Ecological Research (LTER) site in New Mexico support a pulse of C4 plant production that has tissue δ13C values distinct from C3 plants. During a year when precipitation patterns were relatively normal, δ13C measurements showed that consumers used and assimilated significantly more C4‐derived carbon over the course of a summer, tracking the seasonal increase in abundance of C4 plants. In the following spring, after a failure in winter precipitation and the associated failure of spring C3 plant growth, consumers showed elevated assimilation of C4‐derived carbon relative to a normal rainfall regime. These findings provide insight into how climate, pulsed resources, and temporal trophic dynamics may interact to shape semiarid grasslands such as the Chihuahuan Desert in the present and future.
Variable direct and indirect effects of a habitat‐modifying invasive species on mortality of native fauna
Authors: Byers James E. , Wright Jeffrey T. , Gribben Paul E.
Published: June 2010

Habitat‐modifying invasive species can influence rates of predation on native prey either directly by providing protective structure or indirectly by modifying traits of prey species responding to the habitat. The alga Caulerpa taxifolia is one of the most successful invasive species of shallow‐water marine systems globally, often provisioning habitat in areas previously lacking in vegetated structure. We experimentally evaluated the direct effect of Caulerpa to provide refuge for the native clam Anadara trapezia and how this balances with its influence on two trait‐mediated indirect interactions that may increase Anadara's susceptibility to predators. Specifically, Caulerpa's alteration of physical and chemical properties of the surrounding water and sediment deteriorate Anadara's condition and predator resistance properties and also cause Anadara, though normally buried, to project from beneath the sediment, exposing it to predators. Our results show that Anadara are somewhat (but not consistently) protected from predators by living among Caulerpa. Shallow burial depth did not counteract this protective effect. However at times of year when predator activity diminishes and conducive environmental conditions develop, negative effects of Caulerpa habitat such as hypoxia and lowered flow may dominate. Under such situations, poor clam condition accentuates Anadara's susceptibility to mortality. Ultimately, a slight and inconsistent positive effect of Caulerpa to protect Anadara from predators is exceeded by the strong negative effect of Caulerpa on clam mortality, which is heightened by clams' weakened condition produced by chronic exposure to Caulerpa. Our results show that invasive habitat‐modifying species can affect mortality of native species not simply through obvious positive direct effects of their protective structure, but indirectly through contrasting negative modification of the traits of prey species responding to the habitat.
When does local spatial structure hinder competitive coexistence and reverse competitive hierarchies?
Authors: Murrell David J.
Published: June 2010

Classical theory states that if conspecifics have a greater competitive effect on individuals than heterospecifics then coexistence should occur, and ecologists have spent much effort exploring ways to generate coexistence when this condition is not met. One process that has received particular attention in the last two decades is the effect of within‐species aggregation and between‐species segregation caused by limited dispersal. A number of theories have emerged as to how this common spatial pattern may help maintain biodiversity, and the general conclusion that has emerged is that spatial structure should almost always help competitors to coexist. But does spatial structure really always aid biodiversity? An individual‐based model based on a spatial extension to the Lotka‐Volterra competition equations and its mathematical approximation are presented to determine how local spatial structure may affect communities in which there is strong niche differentiation. Two main results emerge from analyses of the models. First, intraspecific competition being greater than interspecific competition coexistence may no longer be sufficient to generate coexistence when spatial structure is strong; and the species with the highest intraspecific competition coefficient is likely to be excluded. Second, dominance hierarchies may be reversed so that a competitor may become the subordinate species when dispersal and competitive interactions occur over short spatial scales. Both results emerge because, even though a species may be globally rare, intense clumping means most interactions occur between conspecifics, and if this is very intense it may be sufficient to stop a species from invading. However, long‐range dispersal may ameliorate these effects by reducing the frequency of conspecific interactions, and this is especially important when a species is rare since it is very likely to land in an area dominated by heterospecifics. These results are most relevant to sessile organisms that produce relatively few viable offspring that survive to adulthood and that have relatively weak dispersal. The conclusion is that within‐species aggregation may hinder coexistence when the toughest competitor an individual is likely to face is a member of its own species.
El Niño–Southern Oscillation effect on a fire regime in northeastern Mexico has changed over time
Authors: Yocom Larissa L. , Fulé Peter Z. , Brown Peter M. , Cerano Julián , Villanueva-Díaz José , Falk Donald A. , Cornejo-Oviedo Eladio
Published: June 2010

The El Niño Southern Oscillation (ENSO) is a climate‐forcing mechanism that has been shown to affect precipitation and the occurrence of wildfires in many parts of the world. In the southern United States and northern Mexico, warm events (El Niño) are associated with moist winter conditions and fewer fires, while cool events (La Niña) tend to favor dry winters and more fires. We tested this relationship in a region of northeastern Mexico by characterizing the historical fire regime and climatic influences. Fire regimes were reconstructed from fire‐scar samples collected from 100 trees in three high‐elevation sites on Peña Nevada in southern Nuevo León. The sites were∼25 ha each, and the site centers were∼1 km apart. The earliest recorded fire occurred in 1521 and the time period we used for analysis was 1645–1929. The sites were characterized by frequent surface fires before the 1920s. In the three sites, mean fire intervals ranged from 8.6 to 9.6 years (all fires) and 11.9 to 18.6 years (fires that scarred ≥25% of recording trees). The per‐tree mean fire return interval was 17 years, and all three sites burned in the same year seven times between 1774 and 1929. After 1929, fires were nearly eliminated in all sites, likely due to human causes. We found a temporal change in the association between ENSO events and fires; before the 1830s La Niña events were significantly associated with fire years, while after the 1830s this association was not significant. In 1998, when the most severe El Niño event of the past century occurred, the three sites experienced severe, stand‐replacing fires that killed many trees that had survived multiple surface fires in the past. Prior to the 1830s, fires tended to occur during dry La Niña years, but since then both La Niña and El Niño have been associated with dry years in this region, especially during the last three decades. This result suggests that ENSO effects have changed over time in this location and that phases of ENSO are not consistent indicators of precipitation, fire occurrence, or fire behavior in this area of northeastern Mexico.
Foraging decisions of bison for rapid energy gains can explain the relative risk to neighboring plants in complex swards
Authors: Courant Sabrina , Fortin Daniel
Published: June 2010

Herbivores commonly base their foraging decisions not only on the intrinsic characteristics of plants, but also on the attributes of neighboring species. Although herbivores commonly orient their food choices toward the maximization of energy intake, the impact of such choices on neighboring plants remains largely unexplored. We evaluated whether foraging decisions by herbivores aiming at a rapid intake of digestible energy could explain multiple neighboring effects in complex swards. Specifically, we assessed how spatial patterns of occurrence of Carex atherodes, a highly profitable sedge species, could control the risk of bison (Bison bison) herbivory for seven other plant species. The foraging behavior of 70 free‐ranging bison was evaluated in their natural environment during summer, and then related to plant characteristics. We used this information to estimate the instantaneous intake rate of digestible energy at individual feeding stations. We found that neighbor contrast defense and associational susceptibility can both be explained by simple foraging rules of energy maximization. Energy gains were higher when C. atherodes was consumed while avoiding the species for which we detected neighbor contrast defense. The lower intake rate associated with their consumption was due to an increase in handling time caused by their small size relative to C. atherodes. Bison also had higher energy gains by consuming instead of avoiding the plant species that experienced associational susceptibility. Because most of these plants were at least as tall as C. atherodes, their presence increased the heterogeneity of the grazed stratum. Avoiding their consumption increased handling time thereby reducing the instantaneous rate of energy intake. Overall, we found that bison adjust their fine‐scale foraging decisions to vertical and horizontal sward structures in a way that maximizes their energy intake rate. Energy maximization principles thus provide a valuable framework to evaluate a broad‐range of neighboring effects for prey faced with generalist consumers.
Height is more important than light in determining leaf morphology in a tropical forest
Authors: Cavaleri Molly A. , Oberbauer Steven F. , Clark David B. , Clark Deborah A. , Ryan Michael G.
Published: June 2010

Both within and between species, leaf physiological parameters are strongly related to leaf dry mass per area (LMA, g/m2), which has been found to increase from forest floor to canopy top in every forest where it has been measured. Although vertical LMA gradients in forests have historically been attributed to a direct phenotypic response to light, an increasing number of recent studies have provided evidence that water limitation in the upper canopy can constrain foliar morphological adaptations to higher light levels. We measured height, light, and LMA of all species encountered along 45 vertical canopy transects across a Costa Rican tropical rain forest. LMA was correlated with light levels in the lower canopy until approximately 18 m sample height and 22% diffuse transmittance. Height showed a remarkably linear relationship with LMA throughout the entire vertical canopy profile for all species pooled and for each functional group individually (except epiphytes), possibly through the influence of gravity on leaf water potential and turgor pressure. Models of forest function may be greatly simplified by estimating LMA‐correlated leaf physiological parameters solely from foliage height profiles, which in turn can be assessed with satellite‐ and aircraft‐based remote sensing.
Deforestation homogenizes tropical parasitoid–host networks
Authors: Laliberté Etienne , Tylianakis Jason M.
Published: June 2010

Human activities drive biotic homogenization (loss of regional diversity) of many taxa. However, whether species interaction networks (e.g., food webs) can also become homogenized remains largely unexplored. Using 48 quantitative parasitoid–host networks replicated through space and time across five tropical habitats, we show that deforestation greatly homogenized network structure at a regional level, such that interaction composition became more similar across rice and pasture sites compared with forested habitats. This was not simply caused by altered consumer and resource community composition, but was associated with altered consumer foraging success, such that parasitoids were more likely to locate their hosts in deforested habitats. Furthermore, deforestation indirectly homogenized networks in time through altered mean consumer and prey body size, which decreased in deforested habitats. Similar patterns were obtained with binary networks, suggesting that interaction (link) presence–absence data may be sufficient to detect network homogenization effects. Our results show that tropical agroforestry systems can support regionally diverse parasitoid–host networks, but that removal of canopy cover greatly homogenizes the structure of these networks in space, and to a lesser degree in time. Spatiotemporal homogenization of interaction networks may alter coevolutionary outcomes and reduce ecological resilience at regional scales, but may not necessarily be predictable from community changes observed within individual trophic levels.
Bias, precision, and parameter redundancy in complex multistate models with unobservable states
Authors: Bailey Larissa L. , Converse Sarah J. , Kendall William L.
Published: June 2010

Multistate mark–recapture models with unobservable states can yield unbiased estimators of survival probabilities in the presence of temporary emigration (i.e., in cases where some individuals are temporarily unavailable for capture). In addition, these models permit the estimation of transition probabilities between states, which may themselves be of interest; for example, when only breeding animals are available for capture. However, parameter redundancy is frequently a problem in these models, yielding biased parameter estimates and influencing model selection. Using numerical methods, we examine complex multistate mark–recapture models involving two observable and two unobservable states. This model structure was motivated by two different biological systems: one involving island‐nesting albatross, and another involving pond‐breeding amphibians. We found that, while many models are theoretically identifiable given appropriate constraints, obtaining accurate and precise parameter estimates in practice can be difficult. Practitioners should consider ways to increase detection probabilities or adopt robust design sampling in order to improve the properties of estimates obtained from these models. We suggest that investigators interested in using these models explore both theoretical identifiability and possible near‐singularity for likely parameter values using a combination of available methods.
Lidar remote sensing variables predict breeding habitat of a Neotropical migrant bird
Authors: Goetz Scott J. , Steinberg Daniel , Betts Matthew G. , Holmes Richard T. , Doran Patrick J. , Dubayah Ralph , Hofton Michelle
Published: June 2010

A topic of recurring interest in ecological research is the degree to which vegetation structure influences the distribution and abundance of species. Here we test the applicability of remote sensing, particularly novel use of waveform lidar measurements, for quantifying the habitat heterogeneity of a contiguous northern hardwoods forest in the northeastern United States. We apply these results to predict the breeding habitat quality, an indicator of reproductive output of a well‐studied Neotropical migrant songbird, the Black‐throated Blue Warbler (Dendroica caerulescens). We found that using canopy vertical structure metrics provided unique information for models of habitat quality and spatial patterns of prevalence. An ensemble decision tree modeling approach (random forests) consistently identified lidar metrics describing the vertical distribution and complexity of canopy elements as important predictors of habitat use over multiple years. Although other aspects of habitat were important, including the seasonality of vegetation cover, the canopy structure variables provided unique and complementary information that systematically improved model predictions. We conclude that canopy structure metrics derived from waveform lidar, which will be available on future satellite missions, can advance multiple aspects of biodiversity research, and additional studies should be extended to other organisms and regions.
The role of environmental variables in structuring landscape‐scale species distributions in seafloor habitats
Authors: Kraan Casper , Aarts Geert , van der Meer Jaap , Piersma Theunis
Published: June 2010

Ongoing statistical sophistication allows a shift from describing species' spatial distributions toward statistically disentangling the possible roles of environmental variables in shaping species distributions. Based on a landscape‐scale benthic survey in the Dutch Wadden Sea, we show the merits of spatially explicit generalized estimating equations (GEE). The intertidal macrozoobenthic species, Macoma balthica, Cerastoderma edule, Marenzelleria viridis, Scoloplos armiger, Corophium volutator, and Urothoe poseidonis served as test cases, with median grain‐size and inundation time as typical environmental explanatory variables. GEEs outperformed spatially naïve generalized linear models (GLMs), and removed much residual spatial structure, indicating the importance of median grain‐size and inundation time in shaping landscape‐scale species distributions in the intertidal. GEE regression coefficients were smaller than those attained with GLM, and GEE standard errors were larger. The best fitting GEE for each species was used to predict species' density in relation to median grain‐size and inundation time. Although no drastic changes were noted compared to previous work that described habitat suitability for benthic fauna in the Wadden Sea, our predictions provided more detailed and unbiased estimates of the determinants of species–environment relationships. We conclude that spatial GEEs offer the necessary methodological advances to further steps toward linking pattern to process.
Morphological response of songbirds to 100 years of landscape change in North America
Authors: Desrochers A.
Published: June 2010

Major landscape changes caused by humans may create strong selection pressures and induce rapid evolution in natural populations. In the last 100 years, eastern North America has experienced extensive clear‐cutting in boreal areas, while afforestation has occurred in most temperate areas. Based on museum specimens, I show that wings of several boreal forest songbirds and temperate songbirds of non‐forest habitats have become more pointed over the last 100 years. In contrast, wings of most temperate forest and early‐successional boreal forests species have become less pointed over the same period. In contrast to wing shape, the bill length of most species did not change significantly through time. These results are consistent with the “habitat isolation hypothesis,” i.e., songbirds evolved in response to recent changes in the amount of available habitat and associated implications for mobility. Rapid morphological evolution may mitigate, without necessarily preventing, negative consequences of habitat loss caused by humans through direct exploitation or climate change.
Some Remarks on Delayed Renewal Risk Models
Authors: Woo Jae-Kyung
Published: June 2010

Some extensions to the delayed renewal risk models are considered. In particular, the independence assumption between the interclaim time and the subsequent claim size is relaxed, and the classical Gerber-Shiu penalty function is generalized by incorporating more variables. As a result, general structures regarding various joint densities of ruin related quantities as well as their probabilistic interpretations are provided. The numerical example in case of time-dependent claim sizes is provided, and also the usual delayed model with time-independent claim sizes is discussed including a special case with exponential claim sizes. Furthermore, asymptotic formulas for the associated compound geometric tail for the present model are derived using two alternative methods.
Applications of Metric Coinduction
Authors: Kozen Dexter , Ruozzi Nicholas
Published: June 2010

Metric coinduction is a form of coinduction that can be used to establish
properties of objects constructed as a limit of finite approximations. One can
prove a coinduction step showing that some property is preserved by one step of
the approximation process, then automatically infer by the coinduction
principle that the property holds of the limit object. This can often be used
to avoid complicated analytic arguments involving limits and convergence,
replacing them with simpler algebraic arguments. This paper examines the
application of this principle in a variety of areas, including infinite
streams, Markov chains, Markov decision processes, and non-well-founded sets.
These results point to the usefulness of coinduction as a general proof
technique.
A rich hierarchy of functionals of finite types
Authors: Normann Dag
Published: June 2010

We are considering typed hierarchies of total, continuous functionals using complete, separable metric spaces at the base types. We pay special attention to the so called Urysohn space constructed by P. Urysohn. One of the properties of the Urysohn space is that every other separable metric space can be isometrically embedded into it. We discuss why the Urysohn space may be considered as the universal model of possibly infinitary outputs of algorithms. The main result is that all our typed hierarchies may be topologically embedded, type by type, into the corresponding hierarchy over the Urysohn space. As a preparation for this, we prove an effective density theorem that is also of independent interest.
A Step-indexed Semantics of Imperative Objects
Authors: Hritcu Catalin , Schwinghammer Jan
Published: June 2010

Step-indexed semantic interpretations of types were proposed as an alternative to purely syntactic proofs of type safety using subject reduction. The types are interpreted as sets of values indexed by the number of computation steps for which these values are guaranteed to behave like proper elements of the type. Building on work by Ahmed, Appel and others, we introduce a step-indexed semantics for the imperative object calculus of Abadi and Cardelli. Providing a semantic account of this calculus using more `traditional', domain-theoretic approaches has proved challenging due to the combination of dynamically allocated objects, higher-order store, and an expressive type system. Here we show that, using step-indexing, one can interpret a rich type discipline with object types, subtyping, recursive and bounded quantified types in the presence of state.