bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nesting ecology and offspring recruitment in a long‐lived turtle
Authors: Schwanz Lisa E. , Bowden Rachel M. , Spencer Ricky-John , Janzen Fredric J. 
Published: June 2009

The role of early life stages (eggs, neonates, and juveniles) for population persistence in long‐lived organisms is thought to be minor. However, few long‐term data sets are available to test this assumption. Variation in vital rates over space and time and the potential for the success of early life stages to shape adult reproductive behavior evolutionarily suggest that more thorough consideration of these life stages is necessary. In particular, the impact of climatic variation on early life‐stage recruitment is not well understood. Furthermore, predation occupies a significant role in theoretical models of population dynamics, but its impact on populations through variable vital rates of early life stages is unknown. Maternal nest‐site choice, an important component of nesting ecology, may influence many offspring traits and respond to selection to optimize offspring success. Overall, we have limited information regarding the long‐term patterns of natural fluctuations in the nesting ecology and hatchling recruitment of populations of long‐lived organisms.The research site for this ongoing long‐term project is on an island in the Mississippi River near Thomson, Illinois, USA. Painted turtles (Chrysemys picta) have been studied extensively at this location since 1989 to examine the ecology and potential demographic consequences of nest‐site choice and depredation, with the aim of understanding the evolution of maternal nesting behavior and its effects on offspring phenotype. We monitored the site every day of the nesting season each year to record nesting and depredation events. The data presented here include nesting phenology, nest vegetation cover, total number of nesting events, clutch size, depredation, and hatchling survival.Portions of this data set have been used to address related questions in ecology and evolutionary biology. In particular, climatic variation influences the probability of nest depredation events. Such events are typically nonrandom, primarily occurring adjacent to habitat edges. Because habitat edges may have atypical vegetation composition and vegetation influences nest temperature, such nonrandom depredation could influence offspring recruitment and, hence, population structure. Given the unique scope and accessibility of this data set, researchers and teachers should find it to be a valuable empirical resource for exploring important facets of nesting ecology and hatchling recruitment in a wild population of a long‐lived species.The complete data sets corresponding to abstracts published in the Data Papers section of the journal are published electronically in Ecological Archives at 〈http://esapubs.org/archive〉. (The accession number for each Data Paper is given directly beneath the title.)
Does size predict demographic fate? Modular demography and constraints on growth determine response to decreases in size
Authors: Hart Simon P. , Keough Michael J. 
Published: June 2009

The modular construction of many plants and animals defies conventional approaches to the study of life histories and population dynamics. An important complication of modular construction is that individuals can rapidly decrease in size when some modules are removed or die or when an individual fragments. Most attempts to describe life histories and population dynamics of modular organisms classify individuals according to their size. This approach relies on the fundamental assumption that fragmentation and module loss have no consequences for an individual apart from a simple decrease in size. Here we experimentally test this assumption.Using a modular marine invertebrate, the encrusting bryozoan Watersipora subtorquata, as a model species, we manipulated colony size and then assessed performance against three potential explanatory models based on size, age, and damage. In a second experiment we disrupted the internal modular demography of colonies to determine whether the performance of a fragment is influenced by the type of modules that remain. Finally, we investigated how constraints on growth in modular organisms uniquely influence growth after module loss. We found that single‐state variables such as size or age do not describe performance in our species. Internal constraints substantially reduce growth after a decrease in size, and the age of modules that remain determines the timing of reproductive onset and fecundity. A knowledge of the size history of individuals, including any decreases in size, is necessary to accurately describe life histories and population dynamics in this modular organism. Our results have major consequences for established methods for modeling the demography of modular organisms.
A Study of Polyacrylamide-Based Gels Crosslinked With Polyethyleneimine
Authors: Al-Muntasheri Ghaithan A. , Nasr-El-Din Hisham A. , Al-Noaimi Khalid R. , Zitha Pacelli L. J. 
Published: June 2009

Summary
Organically crosslinked gels have been used to control water production in high-temperature reservoirs. Most of these gels consist of a polyacrylamide-based polymer and an organic crosslinker. Polyethyleneimine (PEI) has been used as an organic crosslinker for polyacrylamide tertiary butyl acrylate (PAtBA) copolymer. Literature reported that PEI can also form ringing gels with polyacrylamide (PAM) copolymers in addition to simple PAM homopolymers.
We report a comparative study of two water-control gel systems (i.e., PAtBA copolymer and PAM crosslinked with PEI). Several techniques were used in the present study, including gas chromatography (GC), carbon 13 nuclear-magnetic-resonance (C13 NMR) spectroscopy, and steady-shear viscometry. The gases produced during the reaction, structural changes, and gelationtime data were all integrated to provide further insights into differences between the two gelling systems.
The evolution of isobutene gas was identified at temperatures as low as 60°C during the formation of PAtBA/PEI gels. In addition, GC studies revealed the release of carbon dioxide (CO2) as a product of thermal decomposition of the tBA groups on PAtBA during PAtBA/PEI gelation.
Lower initial pH values were found to delay the gelation time of the two systems. Salts were found to increase the gelation time. This paper summarizes these results and investigates the main reaction mechanisms involved. It also discusses how these new findings will affect the application of these gels in the field.
Quantitative Mechanism for Permeability Reduction by Small Water Saturation in Tight-Gas Sandstones
Authors: Motealleh Siyavash , Bryant Steven L. 
Published: June 2009

Summary
In tight-gas sandstone, the productivity of a well is sometimes quite different from that of a nearby well. Several mechanisms for this observation have been advanced. Of interest in this paper is the possibility that a small change in water saturation can change the gas-phase permeability significantly in rocks with small porosity and very small permeability.
We quantify the effect of small saturations of the wetting phase on nonwetting-phase relative permeability by modeling the geometry of the wetting phase. We also show how a porosity-reducing process relevant in tight-gas sandstones magnifies this effect. The basis for these observations is a model of the grain-scale geometry of low-porosity sandstones. The model is built from a dense random packing of spheres modified geometrically to simulate quartz-overgrowth cementation. To compute phase geometry and permeability, we use a physically representative network model extracted from the model rock. At small saturations (at or near the drainage endpoint), the wetting phase exists largely in the form of pendular rings held at grain contacts. Pore throats correspond to the constriction between groups of three grains, each pair of which can be in contact. Thus, the existence of these pendular rings decreases the void area available for flowing nonwetting phase. Because the hydraulic conductance of the throat varies with the square of the void area, the effect on permeability is disproportionate to the volume occupied by the rings.
Convention holds that connate water has little effect on oil or gas permeability because it occupies the smaller pores. Comparing predictions for unconsolidated model rocks with those for cemented model rocks allows one to reconcile this view with the sensitivity reported in the field and the laboratory.
Estimating Channelized-Reservoir Permeabilities With the Ensemble Kalman Filter: The Importance of Ensemble Design
Authors: Jafarpour Behnam , McLaughlin Dennis B. 
Published: June 2009

Summary
Efficient management of smart oil fields requires a reservoir model that can provide reliable forecasts of future production and realistic measures of prediction uncertainty. Reliable forecasts depend on an accurate representation of reservoir geology, which is conveyed largely by the permeabilities used in the reservoir simulator. Because these permeabilities cannot be measured directly, they must be inferred from measurements of related variables, using procedures such as history matching or Bayesian estimation. The ensemble Kalman filter (EnKF) is an attractive option for permeability estimation in real-time reservoir-control applications. It is easy to implement, provides considerable flexibility for describing geological heterogeneity, and supplies valuable information about prediction uncertainty. However, it is more suited for geological heterogeneities that are amenable to second-order (covariance-based) descriptions. In this paper, we investigate the performance of the EnKF for estimation of channel permeabilities that usually follow a bimodal distribution. We consider two synthetic water-flooding problems based on true permeability distributions characterized by conductive channels. The permeability ensembles are obtained from a multipoint geostatistical simulation method. If the ensemble replicates are derived from training images that do not describe the channel geometry properly, the Kalman filter has difficulty identifying the correct permeability field. In fact, the permeability estimates tend to diverge from the true values as more measurements are included. However, if the filter-ensemble replicates are generated by a training image that contains features that are consistent with those in the true permeability field, the filter's estimates are much better. These results emphasize the importance of generating realistic permeability replicates when using ensemble methods to estimate reservoir properties. In fact, a realistic permeability ensemble appears to be essential for successful estimation performance. With a proper ensemble design, despite the bimodality in the initial permeability distribution, the filter exhibits good performance in identifying the patterns in the true permeability field. In practical applications where the true permeability distribution is highly uncertain, the prior information used for ensemble generation should properly reflect the full range of possible geological conditions.
A Method for Determining Optimum Drilling Techniques
Authors: Speer John W. 
Published: June 2009

Abstract
This report develops a simple method for determining the combination of weight-on-bit, rotary speed and hydraulic horsepower which produces minimum drilling cost. Empirical relationships are developed to show the influence on penetration rate of weight-on-bit, rotary speed and hydraulic horsepower. Optimum weight-on-bit is shown in relation to formation drill ability, and optimum rotary speed is related to weight-on-bit. These five relationships are then combined into a chart for determining optimum drilling techniques from a minimum of field test data.
Secondary issues discussed are: Advantages of the jet bit over the regular bit and minimum nozzle fluid velocity requirements for jet bit use relative to formation drill ability; and distribution of pump horsepower into nozzle fluid velocity and circulating volume.

Introduction
The wide variations in drilling conditions encountered in oilfield work make it difficult to develop general rules of operation for obtaining maximum drilling efficiency. Field experience and test data usually provide the basis for operations in a particular locale, but testing often is too costly and experience too late. Consequently, a method for determining optimum drilling techniques for any particular drilling condition, with a minimum of engineering effort and drilling experience, is greatly needed.
To assist in developing such a method is the purpose of this report. It is recognized that sufficient drilling information has not been accumulated to accomplish this ambitious job without some shortcomings along the way. It is believed, however, that the method proposed is flexible to improvements which are sure to be made, and that ultimately the purpose of the report will be accomplished more comprehensively through a combined effort of interested parties.

Controllable Factors That Affect Bit Performance
Drill bit performance depends primarily on five controllable factors:Weight-on-bit,rate of rotation,hydraulic horsepower,type of bit, andproperties of the circulating medium.
Although each parameter contributes individually to bit performance, they are closely interrelated and their combined influence governs the degree of drilling efficiency obtained. The influences of circulating media have been covered in literature and will not be discussed herein.
Numerical Studies on the Geomechanical Stability of Hydrate-Bearing Sediments
Authors: Rutqvist Jonny , Moridis George J. 
Published: June 2009

Summary
The thermal and mechanical loading of oceanic hydrate-bearing sediments (HBS) can result in hydrate dissociation and a significant pressure increase with potentially adverse consequences on the integrity and stability of the wellbore assembly, the HBS, and the bounding formations. The perception of HBS instability, coupled with insufficient knowledge of their geomechanical behavior and the absence of predictive capabilities, has resulted in a strategy of avoidance of HBS when locating offshore production platforms and can impede the development of hydrate deposits as gas resources.
In this study, we investigate coupled (interacting) hydraulic, thermodynamic, and geomechanical behavior of oceanic HBS in three cases. The first involves hydrate heating as warm fluids from deeper conventional reservoirs ascend to the ocean floor through uninsulated pipes intersecting the HBS. The second case describes system response during gas production from a hydrate deposit, and the third involves mechanical loading caused by the weight of structures placed on the ocean floor overlying the HBS.
For the analysis of the geomechanical stability of HBS, we developed and used a numerical simulator that integrates a commercial geomechanical simulator and a simulator describing the coupled processes of fluid flow, heat transport, and thermodynam-ic behavior in the HBS. Our simulation results indicate that the stability of HBS in the vicinity of warm pipes may be affected significantly. Gas production from oceanic deposits may also affect the geomechanical stability of HBS under the conditions that are deemed desirable for production. Conversely, the increased pressure caused by the weight of structures on the ocean floor increases the stability of underlying hydrates.
Recent Development in the Use of Calcium Q-Broxin Muds
Authors: McLennan I.C. , Edwards C.A. , Reiman K. 
Published: June 2009

Summary
These notes have been written to bring up to date information contained in the report "Evaluation and Application of Gypsum Q-Broxin Muds"published in December, 1958.
During the past year calcium Q-Broxin muds have been used in eight wells which had total depths varying from 13,200 feet to 15,500 feet. In seven of the eight wells no drilling trouble of any kind was experienced, and in the eighth where stuck pipe resulted, this has been ascribed to differential pressure effects due to the use of excessively heavy mud. In all wells maintenance of excellent rheological and filtration properties of the muds has been easily attained at relatively low cost.
Flattening of the profile of the self potential curve when using this type of mud led to difficulties in quantitative evaluation of the fluid content of formations and in subsurface correlation studies. Investigation revealed that this was due to the low resistivity of the muds and modifications in mud treatment have resolved this problem
Since this type of mud has been used in wells with very high bottom hole temperatures, an examination of the filtration characteristics at a series of temperatures and pressures has been commenced.
A very simple relationship has been established between the rheological properties of a mud at any two given temperatures. This has permitted the comparison of results obtained in the laboratory with those measured at flowline temperatures at the well site.
A Functional Melanocortin System May Be Required for Chronic CNS-Mediated Antidiabetic and Cardiovascular Actions of Leptin
Authors: da Silva Alexandre A. , do Carmo Jussara M. , Freeman J. Nathan , Tallam Lakshmi S. , Hall John E. 
Published: June 2009

OBJECTIVE
We recently showed that leptin has powerful central nervous system (CNS)-mediated antidiabetic and cardiovascular actions. This study tested whether the CNS melanocortin system mediates these actions of leptin in diabetic rats.

RESEARCH DESIGN AND METHODS
A cannula was placed in the lateral ventricle of Sprague-Dawley rats for intracerebroventricular infusions, and arterial and venous catheters were implanted to measure mean arterial pressure (MAP) and heart rate 24 h/day and for intravenous infusions. After recovery from surgery for 8 days, rats were injected with streptozotocin (STZ), and 5 days later, either saline or the melanocortin 3 and 4 receptor (MC3/4R) antagonist SHU-9119 (1 nmol/h) was infused intracerebroventricularly for 17 days. Seven days after starting the antagonist, leptin (0.62 μg/h) was added to the intracerebroventricular infusion for 10 days. Another group of diabetic rats was infused with the MC3/4R agonist MTII (10 ng/h i.c.v.) for 12 days, followed by 7 days at 50 ng/h.

RESULTS
Induction of diabetes caused hyperphagia, hyperglycemia, and decreases in heart rate (−76 bpm) and MAP (−7 mmHg). Leptin restored appetite, blood glucose, heart rate, and MAP back to pre-diabetic values in vehicle-treated rats, whereas it had no effect in SHU-9119–treated rats. MTII infusions transiently reduced blood glucose and raised heart rate and MAP, which returned to diabetic values 5–7 days after starting the infusion.

CONCLUSIONS
Although a functional melanocortin system is necessary for the CNS-mediated antidiabetic and cardiovascular actions of leptin, chronic MC3/4R activation is apparently not sufficient to mimic these actions of leptin that may involve interactions of multiple pathways.
Experimental Validation of the Brush Tire Model
Authors: Svendenius J. , Gäfvert M. , Bruzelius F. , Hultén J. 
Published: June 2009

Abstract
The paper contains an experimental validation of the physically based brush-tire model toward the tire behavior in a number of different realistic conditions. Results of measurements performed with summer, winter, and studded tires on different road foundations such as wet and dry asphalt, basalt, snow, and ice are presented. The purpose behind the validation is to study the possibilities of using the brush model to estimate the friction coefficient from measurements or estimates of the longitudinal tire forces and tire slip. The sensitivity of the included tire parameters toward various factors that may change during normal run of the vehicle is also investigated.
Effect of remifentanil on requirements for propofol administered by use of a target-controlled infusion system for maintaining anesthesia in dogs
Authors: Beier Suzane L. , de Araujo Aguiar Antonio J. , Vianna Pedro T. G. , Mattoso Cláudio R. S. , Massone Flavio 
Published: June 2009

Abstract
Objective—To evaluate the effect of remifentanil administered by use of a constant rate infusion on the predicted plasma concentration (Cppredicted) of propofol required to prevent awareness in 50% of anesthetized dogs (Cp50predicted).
Animals—6 healthy dogs.
Procedures—Each dog received 2 treatments (1-week interval): induction and maintenance of anesthesia with propofol alone and induction of anesthesia with propofol and maintenance of anesthesia by use of propofol and a constant rate infusion of remifentanil (0.3 μg/kg/min). To induce anesthesia, propofol was administered by use of a target-controlled infusion system to achieve Cppredicted of 6.0 μg/mL. Propofol Cppredicted was adjusted in 0.5 μg/mL increments or decrements; the motor response to a supramaximal electrical nociceptive stimulus was assessed after each change to determine Cp50predicted (mean of the highest Cppredicted at which gross purposeful movement was detected in response to stimulation and the lowest Cppredicted at which such movement was not detected).
Results—Mean ± SD duration of anesthesia for dogs receiving propofol (148 ± 35 minutes) and dogs receiving propofol-remifentanil treatment (141 ± 28 minutes) did not differ. Overall mean propofol Cppredicted for induction of anesthesia was 6.0 ± 0.5 μg/mL. For maintenance of anesthesia, propofol Cp50predicted was significantly reduced following addition of remifentanil to the protocol (2.0 ± 0.5 μg/mL vs 0.9 ± 0.4 μg/mL; 55% decrease).
Conclusions and Clinical Relevance—In nonpremedicated dogs, propofol Cp50predicted of 6.0 μg/mL may be recommended for induction of anesthesia. Propofol requirements for maintaining target-controlled infusion system–based anesthesia were reduced via infusion of remifentanil at a rate of 0.3 μg/kg/min.
In vitro biomechanical evaluations of screw-bar–polymethylmethacrylate and pin-polymethylmethacrylate internal fixation implants used to stabilize the vertebral motion unit of the fourth and fifth cervical vertebrae in vertebral column specimens from dogs
Authors: Hicks Daniel G. , Pitts Marvin J. , Bagley Rodney S. , Vasavada Anita , Chen Annie V. , Wininger Fred A. , Simon Julianna C. 
Published: June 2009

Abstract
Objective—To determine the change in stiffness as evaluated by the dorsal bending moment of cervical vertebral specimens obtained from canine cadavers after internally stabilizing the vertebral motion unit (VMU) of C4 and C5 with a traditional pin-polymethylmethacrylate (PMMA) fixation implant or a novel screw-bar–PMMA fixation implant.
Sample Population—12 vertebral column specimens (C3 through C6) obtained from canine cadavers.
Procedures—A dorsal bending moment was applied to the vertebral specimens before and after fixation of the VMU of C4 and C5 by use of a traditional pin-PMMA implant or a novel screw-bar–PMMA implant. Biomechanical data were collected and compared within a specimen (unaltered vs treated) and between treatment groups. Additionally, implant placement was evaluated after biomechanical testing to screen for penetration of the transverse foramen or vertebral canal by the pins or screws.
Results—Treated vertebral specimens were significantly stiffer than unaltered specimens. There was no significant difference in stiffness between vertebral specimen groups after treatment. None of the screws in the novel screw-bar–PMMA implant group penetrated the transverse foramen or vertebral canal, whereas there was mild to severe penetration for 22 of 24 (92%) pins in the traditional pin-PMMA implant group.
Conclusions and Clinical Relevance—Both fixation treatments altered the biomechanical properties of the cervical vertebral specimens as evaluated by the dorsal bending moment. There was reduced incidence of penetration of the transverse foramen or vertebral canal with the novel screw-bar–PMMA implant, compared with the incidence for the traditional pin-PMMA implant.