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Growing emphasis on sustainability has increased the demand for information on effects of forest management on species diversity. We investigated the hypothesis that plant diversity is a function of microsite heterogeneity by documenting plant diversity and heterogeneity in canopy cover, light, and soil moisture produced by four silvicultural treatments during the first growing season following treatment: prescribed burning, wildlife retention cut with prescribed burning, wildlife retention cut, and shelterwood cutting. Treatments and controls were randomly assigned within four relatively undisturbed, 70–90-year-old oak-hickory stands. Heterogeneity in canopy cover and photosynthetically active radiation was greatest after shelterwood cutting, whereas the wildlife retention cut resulted in less removal of canopy trees and a smaller increase in heterogeneity of these factors. The addition of prescribed burning enhanced the effects of the wildlife retention cut. Prescribed burning alone had the least impact on heterogeneity of these factors. Soil moisture variability appeared to be independent of treatments. Shelterwood cutting increased first-year herbaceous plant diversity, and this increase was likely due, in part, to increased heterogeneity in canopy cover, light, and seedbed condition. These first-year results partially support the hypothesis that plant diversity is a function of microsite diversity in these forests. Long-term monitoring is underway.

There is an increasing desire by land managers to reestablish hardwood forests on reclaimed coal mine sites in the southern Appalachians. Oaks are particularly important for both timber value and wildlife use, however the establishment of planted oak seedlings may be hindered by the competitive nature of groundcover that is typically planted on these sites. In 2004, nine experimental plots were established. Three plots were located in an area that had been reclaimed approximately 30 years ago and had a dense cover of legumes and grasses. Six plots were located in a newly reclaimed area where mixed sandstone and siltstone were placed with minimal compaction in the upper 4 feet of substrate. These plots were seeded with annual rye and birdsfoot trefoil, with 3 plots having a sparse cover of rye at the time oak seedlings were planted (rye), and 3 plots with bare soil initially, seeded one month after oak planting (bare soil). Eight one-year-old seedlings of chestnut oak (Quercus montana), scarlet oak (Q. coccinea) and white oak (Q. alba) were planted on a 2x2 m spacing within each plot, and bud flushing, growth, seedling condition, and survival were monitored over 2 growing seasons. First-year survival for all treatments and species was greater than 84%. Results suggest that ground cover has an influence on oak establishment through both direct competitive effects and indirect effects on soil properties.

Surfactants are used in oil-based drilling fluids to emulsify water and to ensure that cuttings are wetted by oil. The products used are based on drilling conditions and are essentially the same for traditional oil-based and synthetic oil-based fluids. Although much of these surface active materials adsorb on cuttings and filter cake, it is still likely that core samples are exposed to significant concentrations. Additional contamination can occur in subsequent core tests if the oil samples used are themselves contaminated with the drilling fluid. Commercial surfactant packages from several sources have been selected for examination of their effects on the tests normally used to assess the extent of wetting change in crude oil/brine/mineral systems. These products were characterized with respect to their interfacial properties by measurements of interfacial tension as a function of concentration and brine composition. Wetting tests include measurements of contact angles on smooth mineral surfaces and rates of imbibition into porous media. The results show that even very low concentrations of surfactants, much lower than the amounts recommended for use in drilling fluids, can affect the wetting properties of mica surfaces and Berea sandstone cores.

Characterization of reservoir wettability is an important part of assessment of potential oil recovery. Oil-based drilling fluids include surfactants, which can alter the wettability of mineral surfaces. Cores exposed to these fluids may not reflect the true wettability of the reservoir materials. The focus of this study was to observe wettability changes induced by adsorption and removal of surfactants of known structure on mica surfaces using tools that are applicable to studies of wetting alteration by crude oil components. The surfactants used were polyethoxylated coconut and tallow amines with chain lengths of 12 and 18 carbons and head groups consisting of two to five ethoxy groups. Mica was exposed to decane solutions of the surfactants. The treated mica was characterized macroscopically using contact angle measurements and microscopically using atomic force microscopy (AFM). Upon exposure to the surfactant solutions, the mica became oil-wet (∼ 170° for both advancing and receding conditions). AFM examination of similarly treated surfaces imaged in air revealed surfactant layers that were easily disrupted or surfaces that showed no surfactant at all. Contact angles were in the intermediate to water-wet range if the mica samples were removed from the surfactant solution, rinsed with non-aqueous solvents, and submerged in decane for measurements of water/decane contact angles. These results suggest only weak surfactant adsorption occurred from non-aqueous solutions. Differences among the structures tested were greater for increased levels of ethoxylation; differences due to hydrocarbon chain length were negligible. Stronger adsorption, higher contact angles, and more stable surfactant layers could be demonstrated when mica was exposed to aqueous solutions after surfactant sorption, depending on the pH of the aqueous phase. Low pH conditions that promote protonation of the surfactants' amine head group produced the greatest wetting alteration. Above a pH of 8 or 9, no surfactant remained adsorbed on mica surfaces.

Red pine (Pinus resinosa Ait.) was the most abundant species in the overstory on intermediate-quality sites in north central Lower Michigan prior to the lumbering era of the late 1800s. Northern red oak (Quercus rubra L.) stands that replaced portions of the presettlement pinery are maturing. However, these sites are not returning to the former species composition due to greater abundance of red maple (Acer rubrum L.) and white pine (Pinus strobus L.) and a lack of oak and red pine regeneration. Our primary objective was to compare the effects of pine and oak cover types on natural oak and red maple regeneration. We measured oak and red maple regeneration in 2001, 10 years after initial application of canopy cover and understory treatments in natural oak stands and red pine plantations on comparable sites. Oak shelterwoods harvested to 25% canopy cover contained significantly more oak seedlings (∼60 cm height) than all other treatments, a majority of which were located in understory treatment plots, where red maple regeneration was mechanically removed. In agreement with other research in oak-dominated stands, these results suggest that light shelterwoods with understory control may be the most viable means of recruiting oaks. Lack of oak regeneration that was progressing toward the canopy in the oak stands compared to the pine stands suggested that, even with understory control after shelterwood cutting, oak may not compete as well in the understory of oak as in pine stands. In contrast, red maple dominated the understory of oak stands, but exhibited poor development and was significantly less abundant in the pine stands. Oak regeneration was also less dense in the pine stands, but free to grow. Factors in the red pine plantations studied, such as increased litter depth, few seed sources, and decreased availability of soil moisture and nitrogen are likely to have reduced the germination and competitive ability of understory red maple stems, thereby benefiting the growth of oak seedlings having lesser shade tolerance. The differential success of oak and red maple regeneration observed in the red pine stands on intermediate-quality sites has led us to suggest that restoration of beneficial oak and pine interactions and a shift in focus from regenerating oak beneath oak to regenerating oak beneath pine may be warranted.

Objective To examine the relationship between ultrasound and histological features in the screening for molar changes in missed miscarriage. Methods A prospective cohort study was conducted on all missed miscarriages, with features suspicious of molar pregnancy, on transvaginal ultrasound and/or on histological examination over a 5-year period. All cases of molar pregnancy diagnosed histologically were examined and cross-referenced with cases diagnosed on ultrasound and with the supplementary report from the regional referral center. When available, maternal serum β-human chorionic gonadotropin (hCG) levels were recorded. Results Fifty-one cases of suspected molar pregnancy were referred to the regional center for further histological opinion and follow-up, and five cases were subsequently excluded from the final analysis because of the diagnosis of hydropic abortion (HA). In 33 cases a molar pregnancy was suspected at the initial scan. Of these, 26 (78.8%) were confirmed on histology, resulting in a 56% detection rate using ultrasound alone. In 15 cases hCG results were available, of which nine were greater than two multiples of the median. Conclusions The diagnosis of both complete (CHM) and partial (PHM) hydatidiform moles in first-trimester miscarriages is difficult. hCG is significantly higher in both CHM and PHM and, in conjunction with transvaginal ultrasound, could provide the screening test required to enable clinicians to counsel women more confidently towards non-surgical methods of management of their miscarriage, where histopathological examination is not available. Copyright © 2005 ISUOG. Published by John Wiley & Sons, Ltd.

Tests of imbibition rates in Berea sandstone cores have been used to examine the wettability effects of displacement of crude oils with a number of synthetic base oils. In all cases examined to date, the products that flocculated asphaltenes from crude oils also caused water-wet sandstone cores to become markedly less water-wet or even oil-wet. Relatively minor effects on wetting were observed with base oils that did not destabilize asphaltenes. A simple diagnostic test of asphaltene stability can be used to identify specific crude oil/base oil pairs that precipitate asphaltenes.

Retinoblastoma (RB) tumor suppressor proteins are important regulators of the cell cycle and are implicated in a wide variety of human tumors. Genetic analysis of RB mutations in humans and in model systems indicates that individual RB proteins also have distinct functions in development. Specific target genes or mechanisms of action of individual RB proteins in developmental contexts are not well understood, however. To better understand the developmental activities of the two RB family members in Drosophila, we have characterized endogenous expression patterns of Rbf1 and Rbf2 proteins and transcripts in embryos and imaginal discs. These gene products are coexpressed at several stages of development, however, spatial and temporal differences are evident, including partly complementary patterns of expression in the embryonic central nervous system.

The potential for asphaltene deposition in wellbores and flowlines is a major concern during design of oil production and transportation facilities, especially in deep‐water environments. Understanding the processes that control asphaltene deposition, especially the relationship between precipitation and deposition, can help to reduce the risk and cost. Stainless steel capillary tubes were used to study the influences of factors including temperature, degree of asphaltene instability, and precipitant molar volume on asphaltene deposition from mixtures of stock‐tank oils and n‐alkanes. Temperature varied from 20°C to 60°C. Pressure drop across the capillary tube was used to estimate the amount and distribution of deposit formation. Existing asphaltic particles in stock‐tank oil samples did not create deposits. Below the wax appearance temperature, intermittent pressure spikes indicated deposition of wax. Above the wax appearance temperature, deposition occurred gradually from near‐onset mixtures c...

Both forest harvesting and browsing by white-tailed deer (Odocoileus virginianus Zimmerman) affect the composition and structure of forest vegetation throughout the eastern deciduous forest in the United States. We studied their affect and their interaction by measuring the composition, richness, cover, physical stature, and reproductive potential of vascular plants in the understory of three thinned (uneven-aged, even-aged, managing for old-growth characteristics) and two unthinned (second-growth, old-growth) forests dominated by sugar maple (Acer saccharum Marsh.) in western Upper Michigan. Based on measurements taken five years after deer exclosures were established, we found consistent and strong statistical differences in species richness and percent cover related to forest harvest but not to deer browse. Percent cover of the understory vegetation showed weakly significant interactions between deer browse and forest harvest. Thinned forests had a greater average richness and cover of graminoid species, average cover of wild red raspberry (Rubus strigosus L.) and sugar maple compared to unthinned forests. Measurements of plant morphology and the frequency of flowering and fruiting were more sensitive indicators of deer browse than community measurements such as richness and cover. Based on measures of physical stature and reproductive potential, sugar maple, red-berried elder (Sambucus racemosa L.), bluebead-lily (Clintonia borealis (Aiton) Raf.), small Solomon-seal (Polygonatum pubescens (Willd.) Pursh.), false Solomon-seal (Smilacina racemosa (L.) Desf.), rosy twisted stalk (Streptopus roseus Michaux), and trillium species (Trillium grandiflorum (Michaux) Salisb. and T. cernuum L.) all experienced significant browse damage. A better understanding of the interaction between forest harvest and deer browse and their effect on community composition and structure is critical to maintaining and enhancing biodiversity in managed northern hardwood forests.

Methods of detecting and characterizing asphaltenes abound in the literature, but most can raise significant levels of controversy. Because of real differences between samples, it can be difficult for one lab to validate the results of another. In this work, a suite of seven crude oil samples, including two with recognized asphaltene problems and a sequence of three hydrotreater product fluids, have been selected for comparative testing by relatively simple techniques at ambient conditions. The onset of flocculation in response to addition of heptane was identified in batch mode by microscopic observation with the onset solubility conditions calculated from refractive index measurements. These were compared to continuous heptane titrations of toluene solutions of oil with an optical detection system. At essentially infinite dilution, solubility parameter can be calculated from the known properties of toluene and heptane. Further characterization of some asphaltene fractions was provided by measur...

Oil composition changes during production, transportation, and processing of crude oils. The effects of compositional changes on asphaltene stability have been investigated for different crude oils, fractionated asphaltenes, and resins with hydrocarbons that act either as asphaltene solvents or flocculating agents. The refractive index of onset mixtures is used to quantify solution properties with respect to asphaltene stability, and the results are compared to predictions of an asphaltene solubility model. Asphaltene aggregates in depressurized crude oil samples can be explained in terms of natural flocculants in the oil. The effects on asphaltene stability of adding aromatic solvents to an oil have been investigated. Mixtures of asphaltenes and resins show predictable changes in asphaltene stability. The results of this study have important implications for asphaltene stability testing using dilute oil solutions and can be interpreted without any assumptions about special interactions that are often ass...

Summary Wettability controls the distribution and flow of immiscible fluids in an oil reservoir and thus plays a key role in any oil-recovery process. Once thought to be a fixed property of each individual reservoir, it is now recognized that wettability can vary on both microscopic and macroscopic scales. Polar oil components can adsorb onto the pore-bounding mineral surfaces by several different mechanisms. In this study, we explore a transition in the mechanism of wettability alteration that relates to the asphaltene fraction and its stability in the oil phase. Asphaltene stability was varied by adding n-heptane to samples of five crude oils. Conditions tested ranged from those in which asphaltenes were stable to mixtures in which aggregates formed and separated from the oil. The onset condition—in which the first asphaltene particles become visible—provides a reference point with respect to asphaltene stability in each crude-oil sample. Muscovite mica sheets, treated with brine and with the crude oil/heptane mixtures, were examined using contact angles between decane and water as a measure of altered wettability on the oil-treated surfaces. A significant increase in oil-wet conditions very near the onset of asphaltene precipitation was observed with four of the five oils, indicating the potential for wetting changes during the course of oil production if conditions of asphaltene instability are approached. Implications of changes in the mechanism of wetting alteration during the course of production from an oil reservoir are considered.

We evaluated impacts of disturbance in interior haul roads and skid trails on understory vegetation by documenting the areal extent of these features and plant composition along 10 m ×100 m belt transects. Ten belt transects were sampled in each of three comparable northern hardwood forests under even-aged management. These forests were approximately 80 years old and were last entered for thinning 4–6 years prior to sampling. Soil compaction, canopy cover, and the richness and composition of trees, shrubs, and herbs were quantified within each feature (i.e. haul roads, skid trails, and forest without soil disturbance) encountered along transects. These variables were also quantified in unmanaged northern hardwood stands of comparable age. Differences in photosynthetically active radiation (PAR) and soil moisture between haul roads and adjacent patches of forest were measured along line transects placed across haul roads, perpendicular to their main axis. On average, haul roads and skid trails comprised 1 and 16% of total managed stand area, respectively. Compaction, PAR, and soil moisture were highest in haul roads. Understory plant richness was significantly greater in haul roads than in skid trails and forest, and resulted from significantly greater percentages of introduced species (13%) and wetland species that were native to the area, but not normally abundant in northern hardwood stands (23%). Skid trails had a greater percentage of wetland species (9%) than in forest, but differences in richness between skid trails and forest were not statistically significant. Up to the present time, the impact of haul roads on understory vegetation has received far less attention than impacts on soil properties and water quality. Although haul roads comprise a relatively small proportion of total stand area, they serve as primary conduits for the dispersal of introduced species into the interior of managed stands and contribute to significant shifts in plant richness and composition at the stand level.

Crude oil is typically produced from subsurface rock formations that consist of extensive pore networks filled with oil, water, and gas phases. Such systems exhibit significant heterogeneities in wetting properties due in part to mineralogy, but oil composition, connate water chemistry, and saturation history of the pores can be even more influential. Crude oils contain many polar compounds that can adsorb on mineral surfaces, changing their effective wetting. Most of what is known about crude oil/brine/rock interactions, however, has been inferred from contact angle measurements. There is little direct information about the complex morphology of adsorbed and deposited materials that alter wettability. Atomic force microscopy—optimized for the study of soft material in a variety of fluid environments—is used in this study to observe micron- and nanometer-scale changes in topography on mica surfaces before and after exposure to crude oil. Density of coverage and film structure are related to exposure time and crude oil chemistry. Asphaltene aggregates and other features that form a continuous surface film are resolved with this technique that, coupled with contact angle measurements, provides a powerful method for examining the mechanisms that control wettability in crude oil/brine/rock systems.

We documented patterns in the removal of planted northern red oak (Quercus rubra) acorns by rodents in red pine (Pinus resinosa) stands during a field study of oak regeneration in northern Lower Michigan. Each stand contained four overstory treatments assigned at random: clearcut, 25% cover, 50% cover, and uncut (control). Each level of canopy cover contained four randomly assigned understory treatments: shrub-layer removal, herb-layer removal, litter removal, and a control. Rodents removed acorns from 59% of the seed spots in the uncut control and 12% of the seed spots in the clearcut treatment. This five-fold difference was significant. Acorns were removed from 48% and 40% of the seed spots in the 75% and 50% canopy cover treatments, respectively. Differences in acorn removal between understory treatments were not significant. These results suggest that overstory vegetation treatments can influence the removal of planted acorns by rodents, which has implications for the use of direct seeding for artificially regenerating northern red oak.

Terpolymers of vinylidene fluoride (VDF), trifluoroethylene (TrFE), and chlorotrifluoroethylene (CTFE) were synthesized as potential materials for electromechanical transduction. These terpolymers had relatively high molecular weights (∼30 kg/mol) and CTFE levels in the range of 5−10 mol %. The presence of the bulky CTFE units disrupts the sequence length of the crystal, which lowers both the melting and Curie transitions; however, the degree of crystallinity remains high. The formation of smaller, more mobile polar domains gives rise to good electromechanical response. At low electric fields (7 MV/m), longitudinal strains as high as 0.5% are attained. This is significantly higher than the strains achieved with the same terpolymer obtained by bulk polymerization. The present materials exhibit a low mechanical modulus (ca. 0.2 GPa) relative to other VDF−TrFE copolymers. This might limit their use, depending on the application.

Measures of a crude oil's polar functionality and asphaltene stability are key to predicting its wetting behavior. No publicly available data sources and few proprietary databases include all of the information necessary to characterize a crude oil with respect to its interactions with solid surfaces in the presence of an aqueous phase. At a minimum, this information includes both acid and base numbers, which are related to polar and ionic interactions between oil components and charged mineral surfaces, and refractive indeces (RI) of both the oil and oil mixtures at the onset of asphaltene flocculation, which is related to asphaltene stability. Data accumulated thus far illustrate a linear relationship between API gravity and refractive index that can be used to estimate refractive index from existing data. Acid and base numbers for many different crude oil samples show little evidence of correlation between the two, thus both numbers are needed for prediction of wetting alteration. Measurements of refractive index at the onset of precipitation with n-heptane are used to characterize asphaltene stability. Extensive data for seven crude oils are presented to illustrate how asphaltene stability can be predicted over a wide range of conditions from the n-heptane onsets.

Background Respiratory exposure to crystalline silica in man is associated with autoimmunity that includes a prominent humoral component. We hypothesize that autoimmune B cell recruitment and regulation are altered in silica-exposed lungs in genetically susceptible individuals. Methods Wildtype and autoAb transgenic (Tg+) mice of B6 and lupus-prone NZB, MRL, and BXSB backgrounds were exposed to silica dust or vehicle by oropharyngeal aspiration. After 1–3 months, lung pathology and lymphocytic infiltrates were scored. Lupus and vasculitis autoAb levels were measured in bronchoalveolar lavage fluid (BALF), serum, and supernatants from cultured lung and spleen cells. Results All silica-exposed strains showed extensive lung pathology and focal B and T cell infiltrates consistent with ectopic lymphoid structures (ELS). In wildtype mice, % lung area containing ELS after silica exposure varied by strain (BXSB>MRL>B6>NZB, p=0.03). Significant increases in autoAb production with silica exposure were observed in BALF, lung cell supernatants, and serum, and varied by genetic background. Among Tg+ mice, Tg+ Ig levels in BALF were higher in silica- vs vehicle-exposed mice in B6 and BXSB strains (p Conclusions Respiratory exposure to silica leads to pulmonary B and T cell accumulation with ELS formation and enhanced autoAb production. This occurs in a strain-dependent manner, highlighting the impact of genetic influences on silica-induced autoimmunity. Evidence of local autoAb secretion implicates dysregulated control of autoreactive B cells at the environment/lung interface, possibly through the intermediary of silica-induced ELS.

Appropriate utilization of stress ulcer prophylaxis should be limited to high-risk, intensive care unit (ICU) patients. However, inappropriate stress ulcer prophylaxis use among all hospitalized patients remains a concern. The purpose of this study was to evaluate the clinical and economic impact of a novel pharmacist-managed stress ulcer prophylaxis program in ICU and general ward patients.This retrospective, pre- and poststudy design was conducted in adult ICU and general ward patients at a large academic medical center between January 1, 2011 and January 31, 2012 to compare the rates of inappropriate stress ulcer prophylaxis before and after the implementation of a pharmacist-led stress ulcer prophylaxis management program.A total of 1134 unique patients consisting of 16,415 patient days were evaluated. The relative reduction in the rate of inappropriate stress ulcer prophylaxis days after program implementation in ICU and general ward patients was 58.3% and 83.5%, respectively (P.001). The rates of ICU patients inappropriately continued on stress ulcer prophylaxis upon hospital discharge in the pre- and postimplementation groups were 29.9% and 3.6%, respectively (P.001), whereas general ward patients significantly decreased from 36.2% to 5.4% in the pre- and postimplementation groups, respectively (P .001). Total inpatient costs associated with all stress ulcer prophylaxis administered was $20,052.70 in the pre- and $3280.49 in the postimplementation group (P.001), resulting in an estimated cost savings of$200,000 annually. No differences in clinical outcomes were observed.The implementation of a pharmacist-managed stress ulcer prophylaxis program was associated with a decrease in inappropriate acid suppression rates during hospitalization and upon discharge, as well as significant cost savings.

Pulmonary arterial hypertension (PAH) remains a progressive disease without a cure, despite the development of several treatment options over the past several decades. Its management strategy consists of the endothelin receptor antagonists (ambrisentan, bosentan, macitentan), phosphodiesterase-5 inhibitors (sildenafil, tadalafil, vardenafil), and prostacyclin analogs (epoprostenol, treprostinil, iloprost). Treprostinil, a stable prostacyclin analog, displays vasodilatory effects in the pulmonary vasculature, as well as antiplatelet aggregation properties. Clinical practice guidelines recommend oral endothelin receptor antagonist or phosphodiesterase inhibitor therapy in mild to moderate PAH. Epoprostenol is specifically suggested as first-line therapy in moderate to severe PAH patients (ie, World Health Organization/New York Heart Association functional class III-IV). However, treprostinil may be an alternative option in these severe PAH patients. The longer half-life and stability at room temperature with treprostinil may be associated with lower risk of pulmonary hemodynamic worsening as a result of abrupt infusion discontinuation and less frequent drug preparation. These characteristics make treprostinil an attractive alternative to continuous infusion of epoprostenol, due to convenience and patient safety. The purpose of this review is to evaluate the safety and efficacy of continuous infusion of treprostinil as well as the inhaled and oral routes of administration in PAH.

Metabolic syndrome is an increasingly common condition that can contribute to the development of type 2 diabetes and cardiovascular disease. 35 % of adults living in the United States meet the criteria for having metabolic syndrome, with that number being even higher in populations with health disparities. We describe a ‘healthy lifestyles’ program implemented at a free clinic serving a predominantly Hispanic cohort of low-income, uninsured individuals living in Providence, Rhode Island. The “Vida Sana/Healthy Life” (Vida Sana) program uses low literacy, language-appropriate materials and trained peers to educate participants about healthy lifestyles in a setting that also provided opportunities for social engagement. 192 of 126 (65.6 %) participants in Vida Sana completed 6 out of 8 sessions of the Vida Sana program over a 12-month period. At the completion of the program, nearly 90 % of Vida Sana participants showed an increase in their health literacy, and at least 60 % of participants decreased each of the risk factors (blood sugar, cholesterol, body mass index or waist circumference) associated with metabolic syndrome.

BACKGROUND: The randomised controlled trial (RCT) is widely considered to be the gold standard study for comparing the effectiveness of health interventions. Central to the design and validity of a RCT is a calculation of the number of participants needed (the sample size). The value used to determine the sample size can be considered the 'target difference'. From both a scientific and an ethical standpoint, selecting an appropriate target difference is of crucial importance. Determination of the target difference, as opposed to statistical approaches to calculating the sample size, has been greatly neglected though a variety of approaches have been proposed the current state of the evidence is unclear. OBJECTIVES: The aim was to provide an overview of the current evidence regarding specifying the target difference in a RCT sample size calculation. The specific objectives were to conduct a systematic review of methods for specifying a target difference; to evaluate current practice by surveying triallists; to develop guidance on specifying the target difference in a RCT; and to identify future research needs. DESIGN: The biomedical and social science databases searched were MEDLINE, MEDLINE In-Process and Other Non-Indexed Citations, EMBASE, Cochrane Central Register of Controlled Trials (CENTRAL), Cochrane Methodology Register, PsycINFO, Science Citation Index, EconLit, Education Resources Information Center (ERIC) and Scopus for in-press publications. All were searched from 1966 or the earliest date of the database coverage and searches were undertaken between November 2010 and January 2011. There were three interlinked components: (1) systematic review of methods for specifying a target difference for RCTs - a comprehensive search strategy involving an electronic literature search of biomedical and some non-biomedical databases and clinical trials textbooks was carried out; (2) identification of current trial practice using two surveys of triallists - members of the Society for Clinical Trials (SCT) were invited to complete an online survey and respondents were asked about their awareness and use of, and willingness to recommend, methods; one individual per triallist group [UK Clinical Research Collaboration (UKCRC)-registered Clinical Trials Units (CTUs), Medical Research Council (MRC) UK Hubs for Trials Methodology Research and National Institute for Health Research (NIHR) UK Research Design Services (RDS)] was invited to complete a survey; (3) production of a structured guidance document to aid the design of future trials - the draft guidance was developed utilising the results of the systematic review and surveys by the project steering and advisory groups. SETTING: Methodological review incorporating electronic searches, review of books and guidelines, two surveys of experts (membership of an international society and UK- and Ireland-based triallists) and development of guidance. PARTICIPANTS: The two surveys were sent out to membership of the SCT and UK- and Ireland-based triallists. INTERVENTIONS: The review focused on methods for specifying the target difference in a RCT. It was not restricted to any type of intervention or condition. MAIN OUTCOME MEASURES: Methods for specifying the target difference for a RCT were considered. RESULTS: The search identified 11,485 potentially relevant studies. In total, 1434 were selected for full-text assessment and 777 were included in the review. Seven methods to specify the target difference for a RCT were identified - anchor, distribution, health economic, opinion-seeking, pilot study, review of evidence base (RoEB) and standardised effect size (SES) - each having important variations in implementation. A total of 216 of the included studies used more than one method. A total of 180 (15%) responses to the SCT survey were received, representing 13 countries. Awareness of methods ranged from 38% (n =69) for the health economic method to 90% (n =162) for the pilot study. Of the 61 surveys sent out to UK triallist groups, 34 (56%) responses were received. Awareness ranged from 97% (n =33) for the RoEB and pilot study methods to only 41% (n =14) for the distribution method. Based on the most recent trial, all bar three groups (91%, n =30) used a formal method. Guidance was developed on the use of each method and the reporting of the sample size calculation in a trial protocol and results paper. CONCLUSIONS: There is a clear need for greater use of formal methods to determine the target difference and better reporting of its specification. Raising the standard of RCT sample size calculations and the corresponding reporting of them would aid health professionals, patients, researchers and funders in judging the strength of the evidence and ensuring better use of scarce resources. FUNDING: The Medical Research Council UK and the National Institute for Health Research Joint Methodology Research programme.

This report describes the conceptual design of a proposed free electron laser test facility called CLARA that will be a major upgrade to the existing VELA accelerator test facility at Daresbury Laboratory in the UK. CLARA will be able to test a number of new free electron laser schemes that have been proposed but require a proof of principle experiment to confirm that they perform as predicted. The primary focus of CLARA will be on ultra short photon pulse generation which will take free electron lasers into a whole new regime, enabling a new area of photon science to emerge.

Therapeutic opioid use continues to grow, with greater than a fivefold increase in usage of fentanyl-based products over a 10-year period. Opioids are known for their side-effect profile, including bradycardia and respiratory depression; questions remain, however, regarding lesser known side effects such as opioid-induced hyperalgesia (OIH).A systematic review of published literature addressing remifentanil OIH in the surgical setting was completed. A search was conducted of PubMed, Embase and Ovid from 1946 until June 2013. Inclusion criteria consisted of age ≥ 18 years, humans, full-text articles and English language. A total of 35 unique articles were included. Sixteen articles reported outcomes that supported remifentanil OIH and 6 that refuted and 22 were focused on prevention.There is conflicting evidence regarding the existence of remifentanil OIH. Outcomes evaluating measures of hyperalgesia frequently conclude that remifentanil OIH exists, while those evaluating opioid consumption do not. Therefore, remifentanil does induce a degree of hyperalgesia, but we do not believe that it reaches a level of clinical significance that requires prevention. If a significant concern for the development of remifentanil OIH is suspected, we suggest using the least possible effective dose of remifentanil as the primary prevention strategy.

Fifty-five thousand patients are cared for in the intensive care unit (ICU) daily with sedation utilized to reduce anxiety and agitation while optimizing comfort. The Society of Critical Care Medicine (SCCM) released updated guidelines for management of pain, agitation, and delirium in the ICU and recommended nonbenzodiazepines, such as dexmedetomidine and propofol, as first line sedation agents. Dexmedetomidine, an alpha-2 agonist, offers many benefits yet its use is mired by the inability to consistently achieve sedation goals. Three hypotheses including patient traits/characteristics, pharmacokinetics in critically ill patients, and clinically relevant genetic polymorphisms that could affect dexmedetomidine response are presented. Studies in patient traits have yielded conflicting results regarding the role of race yet suggest that dexmedetomidine may produce more consistent results in less critically ill patients and with home antidepressant use. Pharmacokinetics of critically ill patients are reported as similar to healthy individuals yet wide, unexplained interpatient variability in dexmedetomidine serum levels exist. Genetic polymorphisms in both metabolism and receptor response have been evaluated in few studies, and the results remain inconclusive. To fully understand the role of dexmedetomidine, it is vital to further evaluate what prompts such marked interpatient variability in critically ill patients.

A new, two-component asphaltene solubility model (ASM) has been developed to predict the phase behavior of asphaltenes in crude oils. Previous asphaltene solubility models have relied for solution upon simplifying assumptions (e.g., nucleation of a pure asphaltene or pure solvent phase) and approximation methods for determining crude oil solubility parameters. No such simplifying assumptions or approximations are needed if a simple correlation between the solubility parameter and the refractive index of nonpolar species is used to characterize the oil. Compositional ranges over which asphaltenes are stable, metastable, or unstable to phase separation can be defined from calculations of changes in Gibbs free energy using the Flory−Huggins theory for mixtures of crude oil and known amounts of hydrocarbon solvents and precipitants. Coupled values of the asphaltene solubility parameter and molar volume represent the only adjustable parameters in the model. Predictions have been tested against an extensive set...

This review focuses on the macroscopic phenomena that can be used to assess effective wetting, especially the use of contact angles to quantify wetting conditions in the presence of brine and crude oil or on surfaces that have previously been exposed to brine and crude oil. Reservoir wettability has long been a puzzle. Wetting is almost certainly changed during all but the most careful core recovery processes and there is no guarantee that it can be preserved or recreated in the lab. Thus a great deal of effort has been directed at trying to understand reservoir wetting at a more fundamental level. The most important recent advances have demonstrated that there are multiple ways that crude oil components can adsorb to alter effective wetting, especially when an aqueous phase is also present.

Evaluating a material's suitability for an application includes determination of its expected service lifetime. For alternative fuels, this entails assessing, inter alia, their effect on the durability of polymeric engine components, e.g., seals, gaskets, and O-rings. When this is governed by thermally activated chemical deterioration, the conventional approach to characterizing aging is laboratory measurements of property changes of the polymer subjected to accelerated conditions (usually higher temperatures), with the data analyzed by an Arrhenius analysis. However, this method is inefficient and time-consuming when the number of candidate alternative fuels is large. Herein, we test the hypothesis that the activation energy governing thermal oxidation of elastomeric engine components is independent of the fuel; thus, while the aging rate may vary, the effect of temperature is independent of the contacting liquid. Accelerated testing of the thermal oxidation of nitrile rubber O-rings were carried out in three liquids, including a fossil fuel and a bio-fuel. The activation energy obtained from changes in crosslink density, 582 kJ/mol, was the same for all liquids and consistent with the broad range of literature values for similar compounds aged in air. This result suggests the possibility that estimates of the lifetime of polymeric engine components require only a single accelerated aging test, with the known activation energy used to predict the durability at the service temperature. This would represent at least an order of magnitude reduction in testing requirements. The extension of the approach to the general aging of polymers exposed to different environments is obvious. V C 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40296.

Summary An optical observation cell was added to a mercury-free pressure/volume/temperature apparatus to extend studies of the onset of asphaltene precipitation to elevated temperatures and pressures. Observations for asphaltic, paraffinic, and light-to-medium gravity crude oils are reported as a function of temperature, pressure, and mixing time. Precipitants ranged from heptane to propane. Studies at ambient conditions have shown that the refractive index at the onset of precipitation is an important characteristic of oil/precipitant mixtures. Calculated values of refractive index as a function of temperature, pressure, and composition are being correlated to observations of asphaltene separation at elevated temperature and pressure, as a predictive test.

The urinary bladder is lined by transitional epithelium, the glycocalyx on the luminal surface has interesting properties and is implicated in protective functions. Glycoconjugates are major components of the glycocalyx, but their biochemical nature is not well understood. Previous studies on rabbit bladder indicated the presence of significant levels of sialoglycoproteins compared to glycosaminoglycans in the epithelium. In this study, rabbit explant cultures were radiolabeled by precursor sugars or amino acids and a major lectin-reactive glycoprotein of rabbit bladder mucosa was isolated by affinity chromatography on jacalin-agarose. The radiolabeled glycoprotein was purified to homogeneity by a second cycle on the lectin column, followed by gel filtration and density gradient centrifugation. The average molecular mass of the glycoprotein was estimated to be 245 kDa and 210 kDa by gel filtration and SDS-PAGE, respectively. Its buoyant density was 1.40 g/ml, suggesting a carbohydrate content of approximately 50%. The percent distribution of glucosamine-derived tritium label in sialic acid, galactosamine, and glucosamine was 30, 52, and 18, respectively. The glycoprotein consisted entirely of small sialylated and neutral oligosaccharides O-glycosidically linked to serine and threonine residues. The same glycoprotein could be immunoprecipitated with an antibody against the carboxy terminal 17 amino acid peptide of human MUC1 mucin glycoprotein. This suggests that this mucin glycoprotein is the rabbit homolog of MUC1 glycoprotein, which has been previously established to be a component of human bladder urothelium and has been purified from human urine and biochemically characterized.

Background There is no method of quantifying the severity of mitral regurgitation (MR) from injection of tracer directly into the left ventricular (LV) cavity, a method commonly used in the cardiac catheterization laboratory. Methods and Results We used a previously validated mathematical model that derives regurgitant fraction (RF) from the relative tracer washout from the left atrial (LA) and LV cavities. Thirty-nine patients referred for diagnostic cardiac catheterization with clinical evidence of possible MR were included in the study. Five milliliters of a microbubble mixture was power-injected into the LV during simultaneously performed contrast echocardiography. Relative changes in background-subtracted video intensity were measured from the LV and LA, and the resultant model-derived RF was correlated with the severity of MR on cineangiography. The severity of MR ranged from 0 to 4+ on cineangiography with corresponding model-derived RF of 0 to 0.69 on contrast echocardiography. A close linear relation was noted between angiographic severity of MR and model-derived RF on contrast echocardiography ( y = 0.1 x + 0.03, r = 0.89, P Conclusions We describe a new method of measuring the severity of MR in the cardiac catheterization laboratory. Apart from being quantitative, this method can be safely used during cardiac catheterization in patients in whom iodinated contrast agents may be potentially harmful. (Am Heart J 2000;139:1109-13.)

The glycocalyx of the mucosal surface of urinary bladder acts as an effective barrier against invasion by pathogenic microorganisms and injury from toxic substances in the urine. Defects in these bladder mucosal components could thus be important factors in the development of diseases such as interstitial cystitis and lower urinary tract infections. However, information on the nature of glycoconjugates of mammalian bladder mucosa is very limited. In this study, the glycoconjugates of rabbit bladder were examined histochemically using biotinylated lectins with specificities for a variety of carbohydrate moieties. Three [ Artocarpus integrifolia (Jacalin), Datura stramonium (DSL), and Maackia amurensis II (MAL-II)] of the lectins bound predominantly to the luminal cell layer, with decreased binding to the basal layers of the epithelium. In contrast, Ricinus communis I and Sambucus nigra lectins did not bind to the cells in the epithelium but strongly interacted with the subepithelial layers, especially the lamina propria. The intensity of the staining by Jacalin and MAL-II was significantly reduced by prior treatment of the bladder sections with O -sialoglycoprotein endopeptidase, indicating that the ligands of these lectins are primarily mucin glycoproteins. In parallel biochemical studies, a high-molecular-weight glycoprotein with characteristics typical of epithelial mucins was purified from the mucosa of rabbit bladder explant cultures metabolically labeled with [ 3 H]glucosamine. Quantitative analysis of the sialic acid, uronic acid, and hexosamine contents of delipidated rabbit bladder mucosa revealed a larger proportion of sialoglycoproteins compared with glycosaminoglycans. Taken together, the results of histochemical and biochemical analyses indicate that glycoproteins rather than glycosaminoglycans are the major components of the bladder epithelium, and that the former include a mucin.

The wettability of a crude oil/brine/rock system is of central importance in determining the oil recovery efficiency of water displacement processes in oil reservoirs. Wettability of a rock sample has traditionally been measured using one of two experimental techniques, viz. the United States Bureau of Mines and Amott tests. The former gives the USBM index, IUSBM, and the latter yields the Amott–Harvey index, IAH. As there is no well-established theoretical basis for either test, any relationship between the two indices remains unclear.

Models of the complex interactions among crude oils, brines, and reservoir rocks are needed to facilitate studies of oil reservoir wettability. Sandstone reservoir minerals are usually represented by crystalline quartz or by various glass surfaces, but links between wetting alteration on these mineral surfaces and wetting effects in sandstone cores are difficult to establish. Mica is an alternative that is attractive for several reasons. It is relatively easy to reproduce fresh, molecularly smooth surfaces that are ideal for contact angle measurements. Surface chemistry can be varied by ion exchange. While sandstones may be composed primarily of quartz, pore surfaces may be better represented by high-surface-area clays. Muscovite mica has a similar surface structure to illite, a common clay mineral. Mica itself may be a more common component of reservoir rocks than has generally been recognized. Interactions have been tested with two varieties of mica and compared to previous studies on glass surfaces with the same brines and crude oils. Results are consistent with respect to the water film-stability concepts developed in studies using glass surfaces. The principal difference between mica and glass is the effect of temperature on crude oil/brine/solid interactions.

Square capillaries provide a better model of the pore space in rocks than do capillary tubes of circular cross-section because they have corners where wetting fluid can be retained. We report experimental observations of imbibition of an aqueous phase into square capillary tubes with uniform and mixed wetting. Each capillary had an oil-wet end to ensure that water imbibed in one direction only. Swelling of arc menisci in the corners of the square tubes and formation and movement of main terminal menisci were observed during water imbibition. Clean, strongly water-wet capillaries were studied with water displacing decane or air. Wetting was altered by exposing clean capillaries to crude oil or to decane with polar additives. Uniform changes in wetting were effected by filling the capillary with a single phase. Capillaries exposed first to brine, then drained with crude oil, became mixed-wet. The rates and amounts of oil produced are reported. For crude oil-treated capillaries, a consistent trend of decreased rate and extent of oil production with increased aging time emerged. Wetting alteration by polar and acid/base interactions was consistent with previously proposed interaction mechanisms based on contact angle observations.

With the increased use of variables such as canopy cover, photosynthetically active radiation (PAR) and overstory leaf area index (LAI) in forestry research, relationships between these variables and traditional forestry variables must be defined before recommended levels of these research variables can be achieved by forestry practitioners on the ground. We measured basal area, canopy cover, Ozalid percent full light, PAR, and overstory LAI in thinned and unthinned plots within oak and pine stands with the objectives of: (1) determining the relationships between these variables in two common forest types, (2) investigating the feasibility of using basal area to estimate and achieve recommended levels of canopy cover, PAR, and LAI in the field, and (3) examining the possibility of using direct canopy cover and Ozalid light measurements for estimating PAR and LAI. Very strong relationships (r² > 0.90 and P < 0.0001) were indicated between basal area and canopy cover, PAR, and LAI. Direct canopy cover and Ozalid light measurements were also strongly related to PAR and LAI. It is likely that the even-aged structure of the stands studied contributed to these results. The strength of the relationships between the measures examined suggest that practical variables such as basal area could potentially be used by forestry practitioners to estimate and achieve recommended levels of canopy cover, PAR, and LAI in similar oak and pine stands. The possibility also exists for strong relationships between these variables in other stand types that resemble those studied in terms of overstory structure. North. J. Appl. For. 16(1):25-32.

Despite the complexity of asphaltene chemistry, a simple relationship exists between the onset of precipitation and the refractive index of the mixture in which precipitation is first observed. Separation of asphaltenes from oil is a colloidal phenomenon. Because aggregation and separation of the asphaltenes are primarily dependent on the magnitude of van der Waals forces between nonpolar species, the mixture refractive index can be used to quantify the ability of a crude oil to disperse its asphaltene fraction. In some crude oils, asphaltenes are very close to the onset of precipitation, while in other oils, the asphaltenes are relatively stable. The value of the refractive index of an oil sample and the refractive index at which precipitation is first observed are distinctive properties of each crude oil. The difference between these two values is a measure of the stability of the asphaltenes in their respective crude oils. Mixture refractive index correctly predicts the onset of asphaltene precipitatio...

Summary The wettability of a crude oil/brine/rock system influences both the form of petrophysical parameters (e.g., Pc and krw/kro) and the structure and distribution of remaining oil after secondary recovery. This latter issue is of central importance for improved oil recovery since it represents the "target" oil for any IOR process. In the present study, we have developed a three-dimensional network model to derive capillary pressure curves from nonuniformly wetted (mixed and fractionally wet) systems. The model initially considers primary drainage and the aging process leading to wettability alterations. This is then followed by simulations of spontaneous water imbibition, forced water drive, spontaneous oil imbibition and forced oil drive—i.e., we consider a complete flooding sequence characteristic of wettability experiments. The model takes into account many pore level flow phenomena such as film flow along wetting phase clusters, trapping of wetting and nonwetting phases by snapoff and bypassing. We also consider realistic variations in advancing and receding contact angles. There is a discussion of the effects of additional parameters such as the fraction of oil-wet pores, mean coordination number and pore size distribution upon fractionally and mixed wet capillary pressure curves. Moreover, we calculate Amott oil and water indices using the simulated curves. Results indicate that oil recovery via water imbibition in weakly water-wet cores can often exceed that obtained from strongly water-wet samples. Such an effect has been observed experimentally in the past. The basic physics governing this enhancement in spontaneous water imbibition can be explained using the concept of a capillarity surface. Based on these theoretical calculations, we propose a general "regime based" theory of wettability classification and analysis. We classify a range of experimentally observed and apparently inconsistent waterflood recovery trends into various regimes, depending upon the structure of the underlying oil- and water-wet pore clusters and the distribution of contact angles. Using this approach, numerous published experimental Amott indices and waterflood data from a variety of core/crude oil/brine systems are analyzed.

Change will take place whether an organization plans for it or not. Change can be helpful or harmful to an individual and an organization. One can cause change, accept change, reject or fight change, or try to ignore change. The outcome from all of these actions is likely to be different. Properly managed change can benefit the individual and the organization. Dr. Atchison has provided the theory of intangible and tangible elements of an organization, examples of how two organizations developed strategies for change, and how one can measure influences in the process of motivating individuals. These theories can come alive in an organization and bring forth positive results. Changes will continue to occur at a much more rapid pace in the healthcare industry, and many internal changes will be caused by forthcoming changes in the external environment made by regulatory agencies. The voluntary nature of our healthcare industry affords our leaders the opportunity to use vision and foresight to cause and manage change for the continued improvement and further development in the delivery of healthcare. If we fail to accept this challenge and opportunity, we may only have a chance to react to the change imposed on the healthcare industry.

Mechanisms by which crude oil components may adsorb on high energy mineral surfaces include polar, acid/base, and ion-binding interactions. Surface precipitation of asphaltic material can further alter surface wetting. Design of controlled experiments to investigate the contributions of different mechanisms is hindered by the lack of simple, well-characterized analogs for crude oils that show even qualitatively similar interfacial properties. As an alternative, we observe the wettability altering tendencies of a variety of crude oils with the aim of relating the fluid/solid interactions to crude oil composition. The mixtures of compounds in crude oils, variability of samples, and changes that can occur during storage, all add to the uncertainties of mechanistic studies with crude oils. Nevertheless, consistent trends can be identified.

Crude oils contain a variety of components - including asphaltenes - that can adsorb onto mineral surfaces and alter wetting. What distinguishes the asphaltenes from other constituents of an oil is their tendency to aggregate and even separate from the oil in response to changes in oil solvency. Because they change in size, asphaltenes can be viewed as both macromolecules and colloids. Their influence on wettability can change with this shift from molecular to colloidal regimes. As macromolecules, asphaltenes and other crude oil components with polar functionality can adsorb on mineral surfaces. Many different crude oils have been shown to have similar effects on wetting of dry silicate surfaces. When water is present, however, the results of exposing surfaces to different oils can be quite complex, depending on the distribution of water, the compositions of oil and brine, and mineralogy of rock surfaces. Acid and base numbers and the relationship between them provide a measure of the potential for a particular oil to alter wetting through ionic interactions. As colloids, asphaltenes can alter wetting by an additional mechanism. Near the onset of precipitation, wetting alteration occurs by surface precipitation because of the interfacial aggregation of the colloidal asphaltenes, which can precede flocculation in bulk. The influence of asphaltenes on wetting is thus strongly dependent on the environment in which they are found. Mixture refractive index is a useful measure for quantifying the stability of asphaltenes in a crude oil and thus in differentiating between macromolecular and colloidal contributions of asphaltenes to wetting alteration.

The decreased ability of northern red oak (Quercus rubra) to regenerate throughout its range in the eastern United States has important ecological and economic implications. We studied regeneration of northern red oak in oak and pine stands on moderately productive sites in northern Lower Michigan. Our objectives were (1) to investigate the hypothesis that regeneration of northern red oak is more successful in pine than in oak stands and (2) to test whether removal of potential overstory and understory competitors increases regeneration success on moderately productive sites. Northern red oak acorns and 2-yr-old nursery seedlings were planted in spring 1991 in three natural oak stands and three red pine (Pinus resinosa) plantations on comparable, moderately productive sites. Each stand contained four canopy cover treatments: clearcut, 25% cover (50% the first year), 75% cover, and uncut. Each canopy cover treatment contained four understory treatments: herb-layer removal, shrub-layer removal, litter remov...

Eleven healthy men [mean (SD) for age, height, body mass and maximum oxygen consumption: 25.1 (3.0) years, 1.79 (0.06) m, 78.2 (10.5) kg and 56.9 (7.1) ml x kg(-1) x min(-1), respectively) completed two treadmill walking tests at their self-selected velocity while bilaterally carrying 15-kg and 20-kg loads (in a boxed container) for 4 min in front of the body. Each handle of the boxed container was fitted with a load cell so as to allow quantification of the load supported by each hand during load carriage. During the tests, oxygen uptake (VO2), heart rate (HR), and blood pressure (BP) were monitored using standardized procedures, and cardiac output (Qc) was measured using the carbon dioxide rebreathing method. Stroke volume (SV), arterio-venous oxygen difference (C(a-v)O2), rate pressure product (RPP) and total peripheral resistance (TPR) were calculated from the above measurements. The results showed that the two extremities sustained approximately 60% to 70% of the total load, with the balance being supported by the body. Significant increases (P0.05) in VO2, HR, Qc, and mean BP were observed during both of the load carriage walks compared to unloaded walking. However, SV, C(a-v)O2, RPP and TPR were unchanged (P0.05) during load carriage. Although VO2 was significantly higher during the 20-kg load carriage walk, no significant differences were observed between the two loads for any of the cardiovascular responses monitored. Contrary to our hypothesis, these results suggest that increasing the load from 15 kg to 20 kg during treadmill walking does not significantly increase the cardiovascular stress that occurs in healthy subjects.

It is widely believed that asphaltenes and other high molecular weight, polar components of crude oils are responsible for altering the wetting of reservoir rocks, but the mechanisms by which wetting is affected are still uncertain. The concentration of asphaltenes in an oil is not necessarily a good predictor of rock/oil interactions. The composition of the remainder of the oil phase is equally important, particularly with regard to its properties as a solvent for some of its largest constituents. Solvent quality of the crude oil mixture is a function of composition, temperature, and pressure. Changing solvent quality by addition of an excess volume of low molecular weight paraffins is the basis for definition of the asphaltenes, the material that precipitates from the diluted mixture. The extent to which wetting is altered in oil/brine/rock systems by adsorption of asphaltic material from the crude oil is affected by changes in oil solvent properties, even in mixtures in which the asphaltenes are stable with respect to precipitation. A simple approach, using measurements of mixture refractive index, is applied to quantify oil solvent quality for mixtures of crude oil or asphaltenes with hydrocarbon additives. Wettability alteration with systematic changes in oil composition is evaluated by contact angle measurements. Crude oils generally induce greater alteration as they become poorer asphaltene solvents.

Summary Crude oils are complex mixtures of organic molecules, some of which can adsorb onto high-energy surfaces, altering mineral surface wettability. In cores, the extent of wetting alteration varies with oil and brine compositions and saturations as well as with aging time and temperature. Previous studies on flat surfaces have demonstrated rapid interaction between oil components and solid surfaces that can vary with the composition of the intervening brine phase. This study is designed to investigate interactions that occur after initial oil/solid contact. Wettability alteration is assessed by measurement of contact angles between pure fluids after removal of bulk crude oil. The influences of aging time, temperature, and fluid compositions have been considered. Adsorption appears to proceed in two stages. Initial exposure of wet surfaces to oil produces weakly water-wet conditions. Longer aging may produce oil-wet surfaces or, in some cases, a return to more water-wet conditions. This second stage of the adsorption process may continue for days or even weeks and is influenced by temperature and fluid compositions. Desorption of crude oil components can occur when a treated surface is re-exposed to brine.