bluuebunny/crossref_metadata_2025 huggingface dataset:
Estimating Wind Turbine‐Caused Bird Mortality
Authors: SMALLWOOD K. SHAWN
Published: November 2007

ABSTRACT  Mortality estimates are needed of birds and bats killed by wind turbines because wind power generation is rapidly expanding worldwide. A mortality estimate is based on the number of fatalities assumed caused by wind turbines and found during periodic searches, plus the estimated number not found. The 2 most commonly used estimators adjust mortality estimates by rates of searcher detection and scavenger removal of carcasses. However, searcher detection trials can be biased by the species used in the trial, the number volitionally placed for a given fatality search, and the disposition of the carcass on the ground. Scavenger removal trials can be biased by the metric representing removal rate, the number of carcasses placed at once, the duration of the trial, species used, whether carcasses were frozen, whether carcasses included injuries consistent with wind turbine collisions, season, distance from the wind turbines, and general location. I summarized searcher detection rates among reported trials, and I developed models to predict the proportion of carcasses remaining since the last fatality search. The summaries I present can be used to adjust previous and future estimates of mortality to improve comparability. I also identify research directions to better understand these and other adjustments needed to compare mortality estimates among wind farms.
Estimating the Breeding Population of Long‐Billed Curlew in the United States
Authors: STANLEY THOMAS R. , SKAGEN SUSAN K.
Published: November 2007

ABSTRACT  Determining population size and long‐term trends in population size for species of high concern is a priority of international, national, and regional conservation plans. Long‐billed curlews (Numenius americanus) are a species of special concern in North America due to apparent declines in their population. Because long‐billed curlews are not adequately monitored by existing programs, we undertook a 2‐year study with the goals of 1) determining present long‐billed curlew distribution and breeding population size in the United States and 2) providing recommendations for a long‐term long‐billed curlew monitoring protocol. We selected a stratified random sample of survey routes in 16 western states for sampling in 2004 and 2005, and we analyzed count data from these routes to estimate detection probabilities and abundance. In addition, we evaluated habitat along roadsides to determine how well roadsides represented habitat throughout the sampling units. We estimated there were 164,515 (SE=42,047) breeding long‐billed curlews in 2004, and 109,533 (SE=31,060) breeding individuals in 2005. These estimates far exceed currently accepted estimates based on expert opinion. We found that habitat along roadsides was representative of long‐billed curlew habitat in general. We make recommendations for improving sampling methodology, and we present power curves to provide guidance on minimum sample sizes required to detect trends in abundance.
Habitat‐Suitability Models for Cavity‐Nesting Birds in a Postfire Landscape
Authors: RUSSELL ROBIN E. , SAAB VICTORIA A. , DUDLEY JONATHAN G.
Published: November 2007

ABSTRACT  Models of habitat suitability in postfire landscapes are needed by land managers to make timely decisions regarding postfire timber harvest and other management activities. Many species of cavity‐nesting birds are dependent on postfire landscapes for breeding and other aspects of their life history and are responsive to postfire management activities (e.g., timber harvest). In addition, several cavity nesters are designated as species at risk. We compare the ability of 2 types of models to distinguish between nest and non‐nest locations of 6 cavity‐nesting bird species (Lewis's woodpecker [Melanerpes lewis], black‐backed woodpecker [Picoides arcticus], hairy woodpecker [P. villosus], northern flicker [Colaptes auratus], western bluebird [Sialia mexicana], and mountain bluebird [S. currucoides]) in the early postfire years for a ponderosa pine (Pinus ponderosa) forest in Idaho, USA. The 2 model sets consisted of 1) models based on readily available remotely sensed data and 2) models containing field‐collected data in addition to remotely sensed data (combination models). We evaluated models of nesting habitat by quantifying the model's ability to correctly identify nest and non‐nest locations and by determining the percentage of correctly identified nest locations. Additionally, we developed relative habitat‐suitability maps for nesting habitat of black‐backed and Lewis's woodpeckers from the best models. For all species except Lewis's woodpeckers, model performance improved with the addition of field‐collected data. Models containing remotely sensed data adequately distinguished between nest and non‐nest locations for black‐backed woodpecker and Lewis's woodpecker only, whereas models containing both field‐collected and remotely sensed data were adequate for all 6 species. Improvements in the availability of more accurate remote sensing technology would likely lead to improvements in the ability of the models to predict nesting locations. External validation with data from other wildfires is necessary to confirm the general applicability of our habitat‐suitability models to other forests. Land managers responsible for maintaining habitat for cavity‐nesting birds in postfire landscapes can use these models to identify potential nesting areas for these species and select areas in burned forests where postfire salvage logging is most likely to have minimal impacts on cavity‐nesting bird habitats.
Prairie Dogs: An Ecological Review and Current Biopolitics
Authors: MILLER BRIAN J. , READING RICHARD P. , BIGGINS DEAN E. , DETLING JAMES K. , FORREST STEVE C. , HOOGLAND JOHN L. , JAVERSAK JODY , MILLER STERLING D. , PROCTOR JONATHAN , TRUETT JOE , URESK DANIEL W.
Published: November 2007

ABSTRACT  In recent years, people have interpreted scientific information about the black‐tailed prairie dog (Cynomys ludovicianus) in various, and sometimes conflicting, ways. Political complexity around the relationship among black‐tailed prairie dogs, agricultural interests, and wildlife has increased in recent years, particularly when prairie dogs occur on publicly owned lands leased to private entities for livestock grazing. Some have proposed that estimates of prairie dog (Cynomys spp.) numbers from 1900 are inflated, that prairie dog grazing is not unique (other grazers have similar affects on vegetation), and that prairie dogs significantly reduce carrying capacity for livestock and wildlife. We address all these issues but concentrate on the degree of competition between prairie dogs and ungulates because this motivates most prairie dog control actions. We conclude that the available information does not justify holding distribution and numbers of prairie dogs at a level that is too low to perform their keystone ecological function. We further conclude that it is especially important that prairie dogs be sufficiently abundant on public lands to perform this function.
Economic Benefit of Fertility Control in Wild Horse Populations
Authors: BARTHOLOW JOHN
Published: November 2007

ABSTRACT  I projected costs for several contraceptive treatments that could be used by the Bureau of Land Management (BLM) to manage 4 wild horse (Equus caballus) populations. Potential management alternatives included existing roundup and selective removal methods combined with contraceptives of different duration and effectiveness. I projected costs for a 20‐year economic life using the WinEquus© wild horse population model and state‐by‐state cost estimates reflecting BLM's operational expenses. Findings revealed that 1) currently available 2‐year contraceptives in most situations are capable of reducing variable operating costs by 15%, 2) experimental 3‐year contraceptives may be capable of reducing costs by 18%, and 3) combining contraceptives with modest changes to herd sex ratio (e.g., 55–60% M) could trim costs by 30%. Predicted savings can increase when contraception is applied in conjunction with a removal policy that targets horses aged 0–4 years instead of 0–5 years. However, reductions in herd size result in greater variation in annual operating expenses. Because the horse program's variable operating costs make up about half of the total program costs (which include other fixed costs), contraceptive application and management can only reduce total costs by 14%, saving about $6.1 million per year. None of the contraceptive options I examined eliminated the need for long‐term holding facilities over the 20‐year period simulated, but the number of horses held may be reduced by about 17% with contraceptive treatment. Cost estimates were most sensitive to the oldest age adoptable and per‐day holding costs. The BLM will experience significant cost savings as carefully designed contraceptive programs become widespread in the wild horse herds it manages.
Using Video Surveillance to Estimate Wildlife Use of a Highway Underpass
Authors: KLEIST ANDREA M. , LANCIA RICHARD A. , DOERR PHILLIP D.
Published: November 2007

ABSTRACT  Roads pose many threats to wildlife including wildlife‐vehicle collisions, which are a danger to humans as well as wildlife. Bridges built with provisions for wildlife can function as important corridors for wildlife passage. We used video surveillance to record wildlife passage under a bridge near Durham, North Carolina, USA, to determine whether it functioned as a wildlife underpass. This is particularly important for white‐tailed deer (Odocoileus virginianus) because forests associated with the bridge created a corridor between 2 natural areas. We calculated detection probabilities and estimated the number of crossings as observed crossings divided by detection probability. We observed 126 crossings by >10 species of mammals. Detection probability was 42%; therefore, an estimated 299 wildlife crossings occurred. We observed 75 deer: 17 deer approached the underpass and retreated. We estimated sighting 40% of deer crossings and 92% of deer approaches. Thus, an estimated 185 deer crossings and 18 approaches occurred. As an index of road mortality, we conducted weekly surveys of vehicle‐killed animals on a 1.8‐km section containing the underpass. We discovered only 5 incidences of animals killed by vehicles. The size and design of the bridge promoted wildlife use of the underpass, providing landscape connectivity between habitats on opposite sides of the highway and likely increasing motorist safety. Thus, bridges in the appropriate landscape context and with a design conducive to wildlife use, can function as a corridor to reduce the effects of fragmentation.
Bait Stations for Detection and Control of Alien Rats in Galapagos
Authors: PHILLIPS R. BRAND , HARRIS DONNA B. , SNELL HOWARD L.
Published: November 2007

ABSTRACT  Alien rats have impacted native systems worldwide, yet wildlife managers lack techniques to efficiently monitor for rodent invasions where native rodents are present and to control alien rodents sympatric with native rodents. We tested the ability of vertical bait stations to exclude native rodents in the Galapagos Islands, Ecuador. Norway rats (Rattus norvegicus) appeared able to enter all station sizes, whereas black rats (R. rattus) were excluded from larger stations. The endemic rodents Oryzomys bauri and Nesoryzomys narboroughi were unable to enter bait stations of any size, but N. swarthi entered the smallest station. Differences in climbing technique contributed to the advantage of alien rodents over endemic species. Our technique provides wildlife managers in the Galapagos, and potentially other islands with native rodents, a means for early detection and control of alien rats.
Monitoring Texas Wood Ducks With a Cooperative Nest‐Box Program
Authors: RANSOM DEAN , FRENTRESS CARL D.
Published: November 2007

ABSTRACT  We analyzed 8 years of data from the Texas Cooperative Nest Box Program initiated in 1988 by Texas Parks and Wildlife, USA, as a means of involving private cooperators in statewide wood duck (Aix sponsa) management. Cooperators operated ≤9 boxes and most reported nest‐box data for only 1 year (56.5%) and 2 years (20.6%) over the 8‐year life of the project. Mean nest‐box use differed among ecological regions of the state (F=4.23, df=6, P= 0.001) but did not exceed 30% in any region. Mean nest‐box success ranged between 74–91% across ecological regions during 1988–1995, but annual estimates of nest‐box success lacked precision (CVs >30%) in most years for all regions. Our project was unsuccessful as a management tool for monitoring wood duck demographics. Future efforts should focus on improving the amount and quality of data collected from box‐nesting wood ducks.
Bombing and Sonoran Pronghorn: A Clear and Present Danger?
Authors: KRAUSMAN PAUL R. , HARRIS LISA K. , WILSON RYAN R. , CAIN JAMES W. , KOENEN KIANA K. G.
Published: November 2007

ABSTRACT  The United States Air Force (USAF) uses part of Sonoran pronghorn (Antilocapra americana sonoriensis) habitat for bombing exercises (i.e., Barry M. Goldwater Air Force Range [BMGR], southwest AZ, USA) that could be detrimental to the endangered subspecies. To minimize injury or death to Sonoran pronghorn, the USAF and United States Fish and Wildlife Service developed a monitoring protocol that would eliminate live ordnance delivery in the vicinity of pronghorn. From 1998 to 2003, we searched for pronghorn on or near military targets prior to ordnance delivery. If we observed pronghorn within 5 km of a target, the target was closed for ≥24 hours. We monitored bombing ranges on BMGR and closed >5,000 targets for >1,000 days due to military activity. To our knowledge, no pronghorn were killed or injured. We recommend that the monitoring program continue as long as military activity occurs in pronghorn habitat.
Wind Energy Development and Wildlife Conservation: Challenges and Opportunities
Authors: KUVLESKY WILLIAM P. , BRENNAN LEONARD A. , MORRISON MICHAEL L. , BOYDSTON KATHY K. , BALLARD BART M. , BRYANT FRED C.
Published: November 2007

ABSTRACT  Wind energy development represents significant challenges and opportunities in contemporary wildlife management. Such challenges include the large size and extensive placement of turbines that may represent potential hazards to birds and bats. However, the associated infrastructure required to support an array of turbines—such as roads and transmission lines—represents an even larger potential threat to wildlife than the turbines themselves because such infrastructure can result in extensive habitat fragmentation and can provide avenues for invasion by exotic species. There are numerous conceptual research opportunities that pertain to issues such as identifying the best and worst placement of sites for turbines that will minimize impacts on birds and bats. Unfortunately, to date very little research of this type has appeared in the peer‐reviewed scientific literature; much of it exists in the form of unpublished reports and other forms of gray literature. In this paper, we summarize what is known about the potential impacts of wind farms on wildlife and identify a 3‐part hierarchical approach to use the scientific method to assess these impacts. The Lower Gulf Coast (LGC) of Texas, USA, is a region currently identified as having a potentially negative impact on migratory birds and bats, with respect to wind farm development. This area is also a region of vast importance to wildlife from the standpoint of native diversity, nature tourism, and opportunities for recreational hunting. We thus use some of the emergent issues related to wind farm development in the LGC—such as siting turbines on cropland sites as opposed to on native rangelands—to illustrate the kinds of challenges and opportunities that wildlife managers must face as we balance our demand for sustainable energy with the need to conserve and sustain bird migration routes and corridors, native vertebrates, and the habitats that support them.
Assessing Impacts of Wind‐Energy Development on Nocturnally Active Birds and Bats: A Guidance Document
Authors: KUNZ THOMAS H. , ARNETT EDWARD B. , COOPER BRIAN M. , ERICKSON WALLACE P. , LARKIN RONALD P. , MABEE TODD , MORRISON MICHAEL L. , STRICKLAND M. DALE , SZEWCZAK JOSEPH M.
Published: November 2007

ABSTRACT Our purpose is to provide researchers, consultants, decision‐makers, and other stakeholders with guidance to methods and metrics for investigating nocturnally active birds and bats in relation to utility‐scale wind‐energy development. The primary objectives of such studies are to 1) assess potential impacts on resident and migratory species, 2) quantify fatality rates on resident and migratory populations, 3) determine the causes of bird and bat fatalities, and 4) develop, assess, and implement methods for reducing risks to bird and bat populations and their habitats. We describe methods and tools and their uses, discuss limitations, assumptions, and data interpretation, present case studies and examples, and offer suggestions for improving studies on nocturnally active birds and bats in relation to wind‐energy development. We suggest best practices for research and monitoring studies using selected methods and metrics, but this is not intended as cookbook. We caution that each proposed and executed study will be different, and that decisions about which methods and metrics to use will depend upon several considerations, including study objectives, expected and realized risks to bird and bat populations, as well as budgetary and logistical considerations. Developed to complement and extend the existing National Wind Coordinating Committee document “Methods and Metrics for Assessing Impacts of Wind Energy Facilities on Wildlife” (Anderson et al. 1999), we provide information that stakeholders can use to aid in evaluating potential and actual impacts of wind power development on nocturnally active birds and bats. We hope that decision‐makers will find these guidelines helpful as they assemble information needed to support the permitting process, and that the public will use this guidance document as they participate in the permitting processes. We further hope that the wind industry will find valuable guidance from this document when 1) complying with data requirements as a part of the permitting process, 2) evaluating sites for potential development, 3) assessing impacts of operational wind‐energy facilities, and 4) mitigating local and cumulative impacts on nocturnally active birds and bats.
Modeling short-range ordering in solutions
Authors: Pelton Arthur D. , Kang Youn-Bae
Published: November 2007

Various aspects of the modeling of short-range order in binary and ternary solutions using the Bragg – Williams (random mixing), associate, and quasichemical models are examined. The models are compared with respect to their ability to predict properties of ternary solutions from optimized binary model parameters in the presence of short-range order. It is shown how introducing short-range order through the quasichemical model can explain the observed flattened shape of most miscibility gaps. The combination of the quasichemical model for nearest-neighbor short-range order with the Bragg – Williams model for the remaining lattice interactions is described.
Preparation and Properties of Metallocene-catalyzed PE/Starch Nanocomposites: Role of Nanocompatibilizer
Authors: Lai S.-M. , Ti K.-T.
Published: November 2007

The properties of metallocene catalyzed polyethylene (mPE)/starch blends and nanocomposites containing mPE-g-maleic anhydride (mPE-g-MA) compatibilizer, reinforced with 1 phr commercial organoclay (20A) at various amounts of pristine starch are discussed. The results from X-ray diffraction (XRD) and transmission electron microscope (TEM) experiments revealed that nanocomposites were achieved in all cases. No observable diffraction peaks in the low angle region were detected. Clay was preferentially located within the mPE and starch interface and the mPE matrix. The crystallization temperatures of nanocomposites increased with the addition of clay acting as a nucleating agent. However, the melting temperatures and the glass transition temperatures remained largely unchanged. Clay incorporation provided a heat barrier that profoundly increased the blend thermal stability. A maximum increase in tensile strength and Young's modulus was obtained, up to 60% and 105%, respectively, using nanoclay reinforced compatibilizer (termed nanocompatibilizer) in comparison with neat compatibilizer for pristine starch filled cases. Slightly lower water absorption capability was observed for nanocompatibilizer reinforced cases through the sheet-like structure of clay compared with neat compatibilizer cases.
Effects of Starch Types on Mechanical Properties of Poly(lactic acid)/Starch Composites
Authors: Sun X. S. , Acioli-Moura R. , Li W.
Published: November 2007

Poly(lactic acid) (PLA) and its blends with starch and methylenediphenyl diisocyanate (MDI) were extruded in a twin-screw extruder and compress-molded in a dog-bone shaped tensile bars to form test specimens. The effects of starch types (rice, corn, wheat, and potato) on mechanical properties of the PLA/starch/MDI composites were evaluated. Starch type and granule size had no significant effects on mechanical properties of the composite. But crystallinity of the composite decreased as the starch granule size increased. Potato starch was used to study effects of granule size (19 to 63 μm) on mechanical properties of the PLA/starch composites. Both tensile strength and elongation of the PLA/starch/MDI (55/45/0.5) composites reduced slightly as starch granule size increased from 19 to 63 μm. While crystallinity of the composites was significantly decreased as granule size increased. Modulus of the composites remained the same regardless starch types and granule size.
Rheological Evaluation and Observations of Extrusion Instabilities of Biodegradable Polyesters
Authors: Kanev D. , Takacs E. , Vlachopoulos J.
Published: November 2007

The rheological properties of two commercially available biodegradable polyesters – poly(lactic acid) (PLA) and aliphatic-aromatic co-polyester Ecoflex™ – have been investigated. The rheological study was focused on measuring the viscosity and examining sharkskin, melt fracture, and extrudate swell phenomena, which are crucial in industrial applications. The experiments show that the two biodegradable polyesters exhibit shear-thinning behavior similar to other polymers and the Cox-Merz rule is obeyed. It was observed that with increasing shear rate PLA exhibits sharkskin and gross melt fracture while Ecoflex™ exhibits only gross melt fracture. Experimental results indicate that both biodegradable polyesters exhibit small extrudate swell, up to 28% for PLA and up to 34% for Ecoflex™.
Tapioca Starch-poly (lactic acid)-based Nanocomposite Foams as Affected by Type of Nanoclay
Authors: Lee S.-Y. , Xu Y. X. , Hanna M. A.
Published: November 2007

Tapioca starch (TS), poly (lactic acid) (PLA), and clay nanocomposite foams, with three clays (Cloisite 30B, Na+, and 20A), were prepared by melt-intercalation method. The structural, thermal, physical and mechanical properties were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and Instron universal testing machine, respectively. XRD results indicated that the intercalation of TS/PLA into the nanoclay layers occurred for all three clays. The extents of intercalation depended on the types of clay and were exhibited in the sequence of Cloisite 30B>Na+ > 20A. At the same time, a mixture of intercalation and tactoid phenomena was observed for the TS/PLA/Cloisite Na+ nanocomposite. SEM results indicated a decrease in cell size of the TS/PLA foam matrix with the addition of nanoclay and cells had hexagonal and pentagonal shapes. Melting temperature (Tm) decreased with the addition of clays into TS/PLA matrix. Expansion ratios of the nanocomposites were significantly different (p<0.05) from each other. TS/PLA/Cloisite Na+ nanocomposite had the highest expansion ratio of 20.9 compared to its TS/PLA/Cloisite 20A (9.65) and TS/PLA/Cloisite 30B counterparts (8.23). Addition of Cloisite Na+ resulted in the lowest unit density of 0.046 kg/m3, while no significant differences in unit density were observed for the foams with addition of Cloisite 30B and Cloisite 20A. Bulk spring index (BSI) was influenced significantly (p<0.05) with the addition of nanoclays into the TS/PLA matrix. TS/PLA/Cloisite Na+ nanocomposite had the lowest BSI of 0.936. The bulk compressibility was decreased from 14.1MPa for pure tapioca starch foam to 4.45MPa with the addition of PLA. The nanocomposite with Cloisite 30B showed the highest value of 17.4MPa, followed by those with Cloisite 20A (10.4MPa), and Cloisite Na+ (6.47MPa).
Viscous Properties of Thermoplastic Starches from Different Botanical Origin
Authors: Valle G. Della , Vergnes B. , Lourdin D.
Published: November 2007

Starches from various botanical origins were plasticized in a twin screw extruder with different glycerol contents (from 23 to 32%, total wet basis) in order to prepare pellets of amorphous thermoplastic starches (TPS) that can further be processed for manufacturing purposes. The viscous behaviour of these starches was studied with a capillary pre-shearing rheometer, which achieved an homogeneous molten phase under controlled thermomechanical conditions. After performing Bagley corrections and Rabinowitsch analysis, it was found that all samples exhibited a non-Newtonian shear-thinning behaviour, which could be modeled in the range 1 to 103 s−1 either by a simple power law or by a Herschel-Bulkley relationship. For the consistency index, the influence of temperature and plasticizer content was accounted for by Arrhenius-like laws, applying time-temperature and time-plasticizer superposition. For the same plasticizer content and temperature, comparison of starches from different botanical origins showed that shear viscosity values usually increased with the starch amylose content. This trend was partly confirmed for the elongational behaviour, estimated by the Cogswell's analysis of entrance effects. These results can be interpreted by the greater ability of linear molecules of amylose to entangle, compared to the more compact amylopectin molecules.
Biocomposites Based on Bacterial Cellulose and Apple and Radish Pulp
Authors: Gea S. , Torres F. G. , Troncoso O. P. , Reynolds C. T. , Vilasecca F. , Iguchi M. , Peijs T.
Published: November 2007

Bacterial cellulose (BC) pellicles obtained from an Acetobacter xylinum culture were disintegrated using mechanical methods to be used as reinforcement to produce biocomposite sheets with Apple and Radish Pulp. The nanosize disintegrated BC pellicles were blended with microsize apple and radish pulp in the wet state and then hot pressed to produce paper-like sheets.

Thermal analysis was carried out by Thermogravimetry Analysis (TGA). Mechanical properties were assessed by Quasistatic Tensile Tests and Dynamic Mechanical Analysis (DMA). High tensile moduli were obtained (up to 8 GPa) and a nearly linear dependence of Young's modulus on the BC volume fraction was observed. Morphological characterisation of biocomposite sheets and fracture surfaces performed by Scanning Electron Microscopy (SEM) revealed the structure of the disintegrated cellulose network and the failure mechanisms of the biocomposites.
Evaluation of Properties and Biodeterioration Potential of Polyethylene and Aliphatic Polyester Blends
Authors: Machado A. V. , Moura I. , Duarte F. M. , Botelho G. , Nogueira R. , Brito A. G.
Published: November 2007

Blends of high density polyethylene (HDPE) and biodegradable polymers – polylactic acid, PLA, poly(∊-caprolactone), PCL and Mater-Bi® (thermoplastic starch (TPS) with PLA or PCL) – were prepared in a co-rotating twin-screw extruder, together with polyethylene modified with maleic anhydride (PE-g-MA) used as compatibiliser. The mechanical and rheological properties, morphology and potential for biodeterioration of polymeric materials were evaluated. Blends with PLA showed a reduced elongation at break but an increased Young's modulus while the addition of PCL led to materials with a greater elongation at break and a lower Young modulus. The rheological results evidenced that HPDE and the blend with the highest TPS level exhibited the highest viscosity. The microbial growth test carried out to evaluate the potential for biodeterioration of the blends, using a pure culture of Pseudomonas fluorescens, indicated that HDPE/PCL had a lower resistance to bacterial attack than the blend of HDPE/PLA. This was verified by a higher cell number on its surface after 10 weeks of incubation. The addition of 30% starch to the HDPE/PLA blend enhanced its biodeterioration potential, the same was not observed in the case of the HDPE/PCL blend containing just 18% starch.
The Linear Viscoelastic Behavior of a Series of 3-Hydroxybutyrate-based Copolymers
Authors: Melik D. H. , Harrison G. M.
Published: November 2007

The thermal and linear viscoelastic behavior of a series of synthetically produced 3-hydroxybutyrate-based copolymers is reported. The comonomers employed include 4-hydroxybutyrate (4HB), 5-hydroxyvalerate (5HV), and 6-hydroxyhexanoate (6HH). The polymers investigated differed in the concentration of comonomer randomly distributed within the material and in the length of the carbon backbone of the comonomer. The glass transition temperature follows the Fox equation and decreases with increasing comonomer concentration. The molecular weight between entanglements Me was determined from the linear viscoelastic data for each copolymer, and a mixing rule was used to determine Me for homopolymers made from the comonomers studied. Depending on comonomer type and concentration, Me can be varied systematically, resulting in a wide range of potential applications depending on the chemistry employed. Using the complex viscosity data, master curves were constructed for both the zero-shear viscosity and the shear-thinning behavior depending upon the temperature and the molecular weight between entanglements. The analysis of rheological results and polymer properties based upon copolymer content provides an opportunity to process bio-based materials for a wide range of applications.
Thermoplastic Foams from Zein and Gelatin
Authors: Salerno A. , Oliviero M. , Di Maio E. , Iannace S.
Published: November 2007

The aim of this study was to characterize the foaming of natural proteins as thermoplastic polymers. In particular, two proteins, one of vegetal origin, zein, and one of animal origin, gelatin, were processed to achieve thermoplastic polymers, and subsequently foamed by a gas foaming batch process. The effects of suitable plasticizing additives and melt-mixing process on the thermal and mechanical properties of the thermoplasticized proteins were evaluated to assess the thermoplastic characteristics of these materials. Furthermore, selected protein/plasticizers systems were foamed with mixtures of CO2 and N2 as blowing agents, in a batch foaming apparatus, at different temperatures, pressures and pressure drop rates, to evaluate the processing window and the final properties of the foams. Foams with densities of 0.1 g/cm3 and morphologies characterized by uniform distributions of cells with 10 μm diameters were obtained. Results indicated the suitability of zein and gelatin for being processed with classical thermoplastic processing technologies including melt mixing and foaming and their potentials as biodegradable polymers.
Crystallization and Mechanical Propertiesof Poly (D, L) Lactide-based Blown Films
Authors: Stoclet G. , Elkoun S. , Miri V. , Séguéla R. , Lefebvre J.-M.
Published: November 2007

The crystallization, uniaxial and biaxial mechanical behavior of poly(D-, L-lactide)-based-blown films was investigated. It was shown that the selected grade of polylactic acid exhibits low isothermal and non-isothermal crystallization kinetics. In addition, the uniaxial stretching evidenced a ductile/fragile transition temperature located between 35 and 45°C. Eventually stress-induced crystallization was revealed upon uniaxial and simultaneous and sequential biaxial drawing.
Rheological Behavior and Modeling of Thermal Degradation of Poly(∊-Caprolactone) and Poly(L-Lactide)
Authors: Arraiza A. López , Sarasua J. R. , Verdu J. , Colin X.
Published: November 2007

Growing environmental concerns have led to the development of alternative biodegradable polymers with properties comparable to the conventional poly(ethylene), poly(propylene) or poly(ethylene terephthalate). In this paper the thermal degradation of poly(∊-caprolactone) (PCL) and poly(L-lactide) (PLLA) melts was investigated by rheometry and thermogravimetry under different temperatures and inert atmosphere. The chain scission process was modeled to explain the phenomenon. The analysis suggests that PLLA is degraded by an unzipping depolymerization process from the hydroxyl end of the polymer chains. In contrast, the thermal degradation behavior of PCL was very complex because various reactions occurred concurrently: post-polymerization, loss of structural regularities and random chain scissions.
Biaxial Orientation of Polylactide/Thermoplastic Starch Blends
Authors: Chapleau N. , Huneault M. A. , Li H.
Published: November 2007

The biaxial stretchability and film properties of polylactide/thermoplastic starch blends were investigated. Polylactide (PLA) and thermoplastic starch (TPS) were blended in various proportions. Blends containing 27, 42 and 60 wt.% TPS were prepared via a twin-screw extrusion process. Interfacial modification was performed by grafting the PLA with maleic anhydride. These blends were subsequently cast into sheets and biaxially drawn using a laboratory biaxial stretcher. The morphology of extruded strands and cast sheets was investigated using scanning electron microscopy. The compatibilized blends exhibited a much finer morphology as well as preferential minor phase size orientation along the machine direction. The addition of starch did not affect significantly the biaxial stretchability of the pure PLA. Even at high starch content (60 wt.%), the biaxial draw ratio at which the sample breaks is very similar to that of the pure PLA. At higher temperatures, all blends could be stretched at significantly much higher biaxial draw ratio and very thin films could be obtained. The starch content and processing variables affected the tensile properties.
Fabrication of Porous 3-D Structure from Poly(L-lactide)-based Nanocomposite Foam via Enzymatic Degradation
Authors: Bitou M. , Okamoto M.
Published: November 2007

In order to prepare a porous three-dimensional (3-D) structure in biodegradable polyester materials we have conducted the enzymatic degradation of a poly(L-lactide) (PLLA)-based nano-composite foam, having a nanocellular structure, using proteinase-K as a degrading agent at 37°C. The surface and cross sectional morphologies of the foam recovered after enzymatic hydrolysis for different intervals were investigated by using a scanning electron microscope. The nanocellular material took up a large amount of water, which led to the swelling of the foam due to the large surface area inside the nanocelluar structure, and facilitated the enzymatic degradation of the PLLA matrix as compared with the bulk (pre-foamed) sample. Consequently, we have successfully prepared a porous 3-D structure as a remaining scaffold in the core part of the nano-composite foam, reflecting the spherulites of the crystallized PLLA.
Improvement of the Mechanical Properties of Soy Protein Isolate Based Plastics through Formulation and Processing
Authors: Baboi M. , Srinivasan G. , Jane J.-L. , Grewell D.
Published: November 2007

This paper reviews the characterization of the base strength and impact of water absorption on biodegradable, namely, soy protein-based plastics prepared by different methods. The initial approach included using different quantities of soy hydrolysate plasticized with glycerol, which is widely known for its plasticizing effect. With the second approach, the raw polymer was which plasticized with glycerol compounded with different additives such as polycaprolactone or zinc sterate, and was also heat-treated at various temperatures after injection molding. The results indicated the polycaprolactone and, respectively, a medium to high heat treatment significantly enhanced tensile strength and greatly decreased water absorption. The soy hydrolysate formulations that were studied enhanced tensile strength but didn not significantly improve elongation or water absorption.
New Developments in Biodegradable Starch-based Nanocomposites
Authors: Raquez J.-M. , Nabar Y. , Narayan R. , Dubois P.
Published: November 2007

This contribution outlines the new developments in thermoplastic starch-based (nano)composites useful for more specific applications compatible with our environment, partially based on our ongoing research over the past few years. Accordingly, melt-intercalating starch macromomolecules into layered silicates (e.g., natural clays) has proved to be an efficient way for preparation of thermoplastic starch-layered silicate nanocomposites with interesting thermo-mechanical properties, as well as improved solvent-resistance. Cellulosic (nano)whiskers were also added as another environmentally benign (nano)filler in starch-based compositions. The design of such thermoplastic starch-based (nano)composites with enhanced properties relies upon the control over the phase behavior and morphology of the nanofiller within the matrix by more defined interfacial compatibility as well as by fine tuning of processing parameters. A special emphasis was also given to the introduction of layered silicates (nano)filler in biodegradable melt-blends made of hydrophilic thermoplastic starch and hydrophobic biodegradable polyesters as a valuable way to increase the compatibility between the two polymeric partners.
Semantic inheritance in unifying theories of programming
Authors: Chen Yifeng
Published: November 2007

This paper introduces a number of new techniques that support systematic manipulation of predicates, operators, healthiness conditions, laws and fixpoints of recursive programs. Necessary restrictions are imposed on the definition of each model so that the inheritance relation can be established by checking a few conditions on the healthiness conditions and the commands. In particular, we intend to identify the conditions that simplify the closure proof of the program operators and enable laws and fixpoints of a model to be inherited by its submodel without re-proof. A recursive program may correspond to different recursive functions in a model and its submodels, because the primitives such as abort and assignment statements are normally represented as different predicates in different models (although the original definition of each operator is unchanged). This paper studies meta-theory in this more general setting. A fixpoint theorem is discovered and applied to clarify the relationship between the partially correct relational model and the totally correct sequential model in UTP. It is shown that, although assignment statements are modified by the new healthiness conditions in the latter model, most laws (including many that are re-proved in UTP) and fixpoints can be inherited directly without re-proof, if the first argument of every sequential composition in each command tree corresponds to a terminating computation. This result also singles out a small number of laws and fixpoints that may no longer hold in the totally correct model.
Voting for an ethnic identity: procedural and institutional responses to ethnic conflict in Ethiopia
Authors: Smith Lahra
Published: November 2007

The literature on democratisation in diverse and divided societies suggests that procedural and institutional innovations can help create the conditions for democracy by adjudicating among groups with competing claims for recognition and inclusion. Some of the most critical assumptions about the relationship between ethnic identity and formal political institutions have been tested in Ethiopia since the early 1990s. Ethnic federalism is a unique and controversial attempt to account for the contested nature of ethnic identities in contemporary Ethiopian politics through a variety of mechanisms, including the use of a referendum to determine ethnic identity. In 2001 the Siltie people voted to separate from the Gurage ethnic group. With this political manoeuvre, the Siltie accessed greater levels of political power and greater resources, but also recognition under the constitutional arrangement as a distinct ethnic group. The Siltie case suggests that formal political institutions have a limited, though important, role in resolving contested citizenship claims. At the same time, it raises vital questions about the challenges of procedural solutions in the context of contested citizenship and democratic transition in sub-Saharan Africa.
What can X-rays tell us about accretion, mass loss and magnetic fields in young stars?
Authors: Montmerle Thierry
Published: November 2007

Until recently, X-rays from low-mass young stars (105–106 yr) were thought to be a universal proxy for magnetic activity, enhanced by 3-4 orders of magnitude with respect to the Sun, but otherwise similar in nature to all low-mass, late-type convective stars (including the Sun itself). However, there is now evidence that other X-ray emission mechanisms are at work in young stars. The most frequently invoked mechanism is accretion shocks along magnetic field lines (“magnetic accretion”). In the case of the more massive A- and B-type stars, and their progenitors the Herbig AeBe stars, other, possibly more exotic mechanisms can operate: star-disk magnetic reconnection, magnetically channeled shocked winds, etc. In any case, magnetic fields, both on small scale (surface activity) and on large scale (dipolar magnetospheres), play a distinctive role in the emission of X-rays by young stars, probably throughout the IMF.
Measurements of Label Free Protein Concentration and Conformational Changes Using a Microfluidic UV‐LED Method
Authors: Lee Jinkee , Tripathi Anubhav
Published: November 2007

This paper presents a microchip‐based system for measuring concentrations and dynamic conformational changes in proteins without any use of extrinsic fluorescent labeling. The microchannel flow of protein molecules was integrated with an ultraviolet light‐emitting diode (UV‐LED, λex = 295 nm) and a photodetector (λem = 330 nm). The intrinsic fluorescence shift, arising from selectively exciting aromatic amino acid tryptophan (Trp), was monitored to quantify refolding pathways by dynamically varying the concentration of the chemical denaturant, urea. Short diffusion distances in the microchannel result in rapid equilibrium between protein and titrating solutions. Dilutions on the chip were tightly regulated using pressure controls, rather than syringe‐based flow, as verified with extensive on‐chip tracer dye controls. The concentrations of proteins were first measured using the UV‐LED microfluidic platform, and the data showed detection limits down to 72, 128, and 250 nM for tryptophan, bovine serum albumin (BSA), and bovine carbonic anhydrase (BCA), respectively. To validate the protein assay method, folding transition experiments were performed using a well‐characterized protein, BSA. The microchip protein refolding transitions using intrinsic fluorescence were well‐correlated with conventional fluorometer experiments. The microfluidic platform facilitates refolding studies to identify rapidly the optimal folding strategy for a protein using small quantities of material. The technique offers a real alternative to bulky microfluidic systems consisting of large and expensive laser‐based designs.
High‐Level Transient Production of a Heterologous Protein in Plants by Optimizing Induction of a Chemically Inducible Viral Amplicon Expression System
Authors: Plesha Michael A. , Huang Ting‐Kuo , Dandekar Abhaya M. , Falk Bryce W. , McDonald Karen A.
Published: November 2007

We have demonstrated that the method of chemical induction using a chemically inducible viral amplicon expression system can be optimized to increase expression of a heterologous protein in plants. A cucumber mosaic virus inducible viral amplicon (CMViva) expression system was used to transiently produce a recombinant human blood protein, α‐1‐antitrypsin (AAT), by co‐infiltrating intact and detached Nicotiana benthamiana leaves with two Agrobacterium tumefaciens strains, one containing the CMViva expression cassette carrying the AAT gene and the other containing a binary vector carrying the gene silencing suppressor p19. Infiltrated plants were induced by either topical applications or pressure injections and inducer was applied at either a single or multiple time points. Applying induction solution every 2 days via topical application resulted in increasing maximum levels of biologically functional rAAT from 0.71% to 1.3% of the total soluble protein (TSP) in detached plant leaves, a 1.8‐fold improvement. Multiple applications of induction solution via pressure injection into intact leaves resulted in maximum levels of biologically functional rAAT being elevated 3‐fold up to 2.4% of TSP compared to 0.8% of TSP when using the conventional method of a single topical application, and expression levels remained high 6 days post‐induction. Overall production of rAAT in intact leaves was found to have a maximum level of 5.8% of TSP or 390 mg rAAT per kg leaf tissue when applying multiple injections of chemical induction solution.
Dynamics of a horizontal thin liquid film in the presence of reactive surfactants
Authors: Pereira A. , Trevelyan P. M. J. , Thiele U. , Kalliadasis S.
Published: November 2007

We investigate the interplay between a stable horizontal thin liquid film on a solid substrate and an excitable or bistable reactive mixture on its free surface. Their coupling is twofold. On the one hand, flow in the film transports the reacting surfactants convectively. On the other hand, gradients in the surfactant concentration exert Marangoni stresses on the free surface of the film. A reduced model is derived based on the long-wave approximation. We analyze the linear stability of the coupled system as well as the nonlinear behavior, including the propagation of solitary waves, fronts, and pulses. We show, for instance, that the coupling of thin film hydrodynamics and surfactant chemistry can either stabilize instabilities occurring in the pure chemical system, or in a regime where the pure hydrodynamic and chemical subsystems are both stable, the coupling can induce instabilities.