19 research outputs found
The simplified perturbed hard chain theory: Development, performance and modifications
No full textThe Simplified Perturbed Hard Chain Theory (SPHCT) developed by Kim et al. (1986) is an equation of state based on the Generalized van der Waals Theory (Vera and Prausnitz, 1972, Sandler, 1985). The SPHCT is accurate in describing thermodynamic properties of chain molecules. This in contrast with the common used Peng-Robinson or Redlich-Kwong equations of state. The SPHCT is a simplification of the Perturbed Hard Chain Theory (PHCT). The PHCT is described in chapter 2. Donohue and Prausnitz (1978) treated all density dependent (external) rotations and vibrations equivalent to translations. Prigogine (1957) postulated that a molecule has 3c degrees of freedom that are density dependent (3 translational and 3c-3 external rotational/vibrational degrees of freedom). These two assumptions form the basis for the PHCT. The SPHCT developed by Kim et al. (1986) uses the same assumptions. Point of difference is the replacement of the potential energy term. While Donohue and Prausnitz used a term that was based on computer simulation data by Alder et al. (1972), Kim et al. developed an expression for the potential energy based on the local composition model, following Lee et al. (1985). This derivation is given in chapter 3. The SPHCT is in the first place derived for chain molecules like n-alkanes. The performance of the SPHCT is given in chapter 4 (pure components) and chapter 5 (mixtures). It appears that also polar molecules can be described reasonably well with the SPHCT equation of state. The SPHCT has been modified (chapter 6) to give better predictions of thermodynamic properties. The modifications make the SPHCT more complex, by implementing theoretical or empirical relations.Applied SciencesChemical Engineering and Materials ScienceApplied Thermodynamics and Phase Equilibri
Modifications in multi-phase flash calculation program OAA500, to include solid-solid transitions, followed by modelisation of three synthetic gas condensates
No full textPresently most high temperature-high pressure oil and gas accumulations in deep reservoirs of oil producing regions, are not equipped for production, due to economic as well as technical difficulties. These difficulties arise from the scarcity of operational equipment suited to this pressure range, but also from the original phase behaviour of these reservoir fluids. A solid phase may be detected at temperatures below 30 ° c, due to crystallization of the heavy hydrocarbons, such as normal alkanes heavier than c20. This may lead to high corrosion rates in the pipelines, when the precipitated solids are transported with the same speed as the fluid, or even to plugging in the pipes. Modelisation of such complex mixtures becomes increasingly important. During this project, modifications were made in the solid-liquid phase equilibrium theory proposed by Prausnitz (Prausnitz et al., 1986). This model is included in a multi-phase flash calculation program, which was used to predict phase behaviour of three different synthetic gas condensate mixtures... - Jaartal geschatApplied Science
Thermodynamic methods to describe phase equilibria involving a solid phase: Literature survey
No full textFour different methods (Prausnitz, Won, Hansen and Salim) that can be used to calculate phase equilibria involving a solid phase, are described. Improved versions of these methods (Ungerer, Chung, Erickson and Brown) are discussed as well. The model proposed by Prausnitz (Prausnitz et al., 1986), can be applied to calculate solid-liquid phase equilibria assuming that different solid forming components do not form a solid solution. The models proposed by Won (1986), Hansen (Hansen et al., 1988) and Salim (Salim et al., 1994) can be used to calculate vapour-liquid-solid wax phase equilibria for paraffinic hydrocarbon mixtures. The model proposed by Salim has the advantage that only one equation of state is used to calculate the entire phase diagram, whereas the other models have to be used in combination with an equation of state to calculate the liquid-vapour equilibrium. Modifications for the model, originally given by Prausnitz, were proposed to describe the influence of the pressure and to include the possibility of solid-solid transitions (Ungerer et al., 1994). Ungerer used a simplification of this model, to reproduce crystallisation in four synthetic gas condensate mixtures, achieving good agreement with experimental data. Gas-solid equilibria, are adequately described with a negative slope of the gas/gas-solid transition curve in the P, T diagram, which seems to be characteristic of solid forming gas condensates at high pressure, above the dew point curve. Chung (1992) proposed a method based on Won's model, with improved predictions for the wax appearance points (W APs). This model was used to calculate W APs for three North Sea crudes, showing good agreement with measured temperatures. The quantity and composition of the precipitated wax can also be calculated but accurate experimental data are scarce, since waxy crystals entrap significant amounts of liquid hydrocarbons. Alphaltene solubilities in organic solvents and oils can be accurately predicted. For highly polar or associating solvents, however, the model is inadequate and the activity coefficient of the solid in the liquid phase has to be predicted by other methods such as group contribution methods. Erickson (Erickson et al., 1993) proposed modifications for the model described by Won, to obtain a better fit with experimental data. The model does not take into account the influence of the pressure, the difference in molar heat capacity between the solid and the liquid phase and assumes unity for the ratio of activity coefficients between the liquid and the solid phase. The model was used to predict WAPs and the amount of wax formed as function of the temperature, for 16 real crudes and condensates, using only a compositional analysis and no tuning parameters. It provided excellent predictions of the W APs, as well as a good qualitative agreement for the solid wax content. Since the model does not need to be tuned to individual crudes, the mixing of crudes, solvents and condensates can easily be included in the model. This model also provides an excellent method for predicting solid-liquidvapour phase behaviour for hydrocarbon systems, based solely upon detailed compositional analysis... - Jaartal geschatApplied SciencesChemical Technology and Materials Scienc
Mengregels
No full textIn de loop van de jaren zijn er door verschillende onderzoekers vele methoden ontwikkeld om tot een zo goed als mogelijke fasenbeschrijving te komen. In deze scriptie wordt geprobeerd een zo compleet raogelijk overzicht te geven van de verschillende bestaande mengregels. Allereerst worden enkele toestandsvergelijkingen behandeld, waar in deze scriptie veelvuldig naar terug verwezen wordt. Vervolgens wordt er gestart met de klassieke mengregels van Van der Waals welke onderbouwd worden met de zogenaamde 1-fluid theory. Deze klassieke mengregels zijn in principe alleen geschikt voor apolaire systemen bij niet te hoge druk. Een eerste verbetering van deze klassieke mengregels komt tot uiting in een uitgebreidere uitdrukking van de stofparameter b, wat een grotere flexibiliteit van de vergelijking met zich meebrengt. Wat als gevolg heeft dat een betere fasenbeschrijving mogelijk wordt. Een verbetering voor de beschrijving van polaire systemen wordt bereikt door de voorstellen van Stryjek en Vera welke twee nieuwe samenstellings afhankelijke mengregels ontwikkelden. Een ander voorstel tot modificatie van de mengregels is gedaan door Adachi en Sugie welke uitgaande van de Redlich-Kister vergelijking een nieuwe mengregel ontwikkelden. Vervolgens worden een aantal locale compositie afhankelijke mengregels besproken (Wilson, Renon, Prausnitz, Mansoor! en Ely, Mathias en Copeman, Whiting, Sandler en Lee, Mollerup). Deze locale compositie concepten geven een duidelijk inzicht op de problematiek en zijn hoopvol voor de ontwikkelingen in de toekomst. In hoofdstuk 3 worden enkele aan de Excess Gibbs energie gerelateerde mengregels besproken, waarin vooral Huron en Vidal een groot aandeel hebben. Deze Huron-Vidal mengregel is veelvuldig onderzocht en uitgebreid door verschillende onderzoekers (Gupte en Daubert, Pandit en Singh, Adachi en Sugie, Stryjek en Vera, Lerraitte en Mollerup). Vervolgens worden enkele dichtheidsafhankelijke mengregels besproken, startende met de mengregel van Whiting en Prausnitz. Gevolgd door een methode van Shatynski en Knox, en Luedecke en Prausnitz. Deiters heeft een methode ontwikkeld voor cryogene mengsels met behulp van een variabele exponent in de Van der Waals mengregels. Dit hoofdstuk eindigt met een methode van Won welke geldig is voor CO2 bevattende mengsels. Het volgende hoofdstuk handelt over de combinatie van mengregels met groeps bijdrage methoden. Herin worden een aantal methodes beschreven waarin gebruik gemaakt wordt van de ASOG en UNIFAC methoden (Pandit en Sigh, Tochigi en Kohima, Gupte en Daubert). Vervolgens worden een aantal effecten van mengregels op fasenevenwichten bekeken. Hieruit volgt dat bij het toepassen van een bepaalde mengregel de verschillende toestandsvergelijkingen eenzelfde resultaat geven. Verder dat dichtheidsafhankelijke mengregels het fasengedrag niet per definitie beter beschrijven en dat de functionele vorm van de mengregels niet zo'n grote invloed heeft op de resultaten. Uiteindelijk blijkt dat er op dit moment nog geen mengregels is, die in staat is alle fasenevenwichten van verschillende systemen te beschrijven. De grootste toekomst lijkt weggelegd voor Excess Gibbs energie gerelateerde mengregels in combinatie met het locale compositie concept.Applied SciencesChemische Technologi
Impact of 2012 USPSTF prostate cancer screening recommendations on prostate cancer detection and presentation at Kaiser Permanente Northern California (KPNC).
No full text 37 Background: In 2012, the USPSTF gave a “D” grade to PSA-based prostate cancer screening stating “the benefits of PSA-based screening for prostate cancer do not outweigh the harms”. The impact on prostate cancer screening, detection and presentation are unknown. Methods: A retrospective cohort design encompassing the years 2010 to 2015. In screen-eligible, KPNC members (African American men ages 45-69 and all other men ages 50-69), the annual rates of PSA testing, prostate biopsy and the grade and stage of all prostate cancers at presentation were compared between the pre-guideline period, 2010/2011; and the post-guideline period , 2014/2015. Results: The rate of screening declined substantially from the pre-guideline period to the post-guideline period, from a rate of 42.7% of eligible men screened per year during 2010/2011 to a rate of 32.5% of eligible men screened per year during 2014/2015; the relative rate and 95% confidence interval (CI) was 0.762 (0.759-0.765). Comparing the same time periods, the rates of prostate biopsy and overall prostate cancer detection declined even more sharply, with relative rates of 0.391 (95%CI 0.375-0.407) and 0.455 (95%CI 0.436-0.475) respectively. There was a modest increase in the rate of metastatic disease between these two time periods, with a relative rate of 1.29 (95%CI 1.11-1.48). Conclusions: Following the 2012 USPSTF statement, significant declines in PSA testing, prostate biopsy and overall cancer detection rates were seen along with a significant increase in the rate of patients presenting with metastatic disease. [Table: see text] </jats:p
The implementation checklist: A pragmatic instrument for accelerating research‐to‐implementation cycles
No full textAbstract Introduction Learning health systems require rapid‐cycle research and nimble implementation processes to maximize innovation across disparate specialties and operations. Existing detailed research‐to‐implementation frameworks require extensive time commitments and can be overwhelming for physician‐researchers with clinical and operational responsibilities, inhibiting their widespread adoption. The creation of a short, pragmatic checklist to inform implementation processes may substantially improve uptake and implementation efficiency across a variety of health systems. Methods We conducted a systematic review of existing implementation frameworks to identify core concepts. Utilizing comprehensive stakeholder engagement with 25 operational leaders, embedded physician‐researchers, and delivery scientists, concepts were iteratively integrated to create and implement a final concise instrument. Results A systematic review identified 894 publications describing implementation frameworks, which included 15 systematic reviews. Among these, domains were extracted from three commonly utilized instruments: the Quality Implementation Framework (QIF), the Consolidated Framework for Implementation Research (CFIR), and the Reach, Effectiveness, Adoption, Implementation, and Maintenance (RE‐AIM) framework. Iterative testing and stakeholder engagement revision of a four‐page draft implementation document with five domains resulted in a concise, one‐page implementation planning instrument to be used at project outset and periodically throughout project implementation planning. The instrument addresses end‐user feasibility concerns while retaining the main goals of more complex tools. This instrument was then systematically integrated into projects within the Kaiser Permanente Northern California Delivery Science and Applied Research program to address stakeholder engagement, efficiency, project planning, and operational implementation of study results. Conclusion A streamlined one‐page implementation planning instrument, incorporating core concepts of existing frameworks, provides a pragmatic, robust framework for evidence‐based healthcare innovation cycles that is being broadly implemented within a learning health system. These streamlined processes could inform other settings needing a best practice rapid‐cycle research‐to‐implementation tool for large numbers of diverse projects
Partnering With Patient Advisors in the PORTAL Clinical Data Research Network
No full textBackground/Aims: PORTAL, composed of Kaiser Permanente, Group Health Cooperative, Health Partners and Denver Health, is a PCORnet network focusing start-up efforts on identifying what matters most for patients with obesity, colorectal cancer and congenital heart disease (three cohorts) and building capacity to conduct patient-centered research to address those priorities. This presentation will describe the Patient Engagement Council (PEC) and an associated Online Advisor group guiding PORTAL’s development.
Methods: The PEC is composed of 10 patients representing each of the cohorts as well as three representatives from cohort-specific advocacy organizations. PEC members attend an in-person meeting for orientation/team-building and subsequently offer guidance through 10 webinars, emails and conference calls. PORTAL seeks PEC members’ input about how to engage patients in research, identify research questions and methods that matter to patients, and facilitate communication between PORTAL and broader audiences. Eighteen online advisors are being recruited to help PORTAL establish three cohort-specific online Smart Patients communities –– where patients and caregivers learn from each other about the latest science, treatments and patient concerns. Online advisors work with Smart Patients to identify key topics and develop early content for the online communities’ discussion boards.
Results: Eligible members were identified within each health system through clinical and operational liaisons and were then interviewed by PORTAL staff. Selected candidates were invited to join as PEC members or online advisors. All of the PEC members have been recruited, completed the orientation, and participated in the first webinar focused on cohort-specific survey questions/modes of survey administration. The successes and challenges of recruitment, hosting in-person and online meetings, and PEC contributions to PORTAL’s start-up phase will be presented. Prior to the conference, all 18 online advisors will have been recruited and completed their work setting up online communities. The benefits and challenges of engaging online advisors will be presented and the online communities will be described.
Discussion: This presentation of the process and initial outcomes of engaging patients in the development of a large multisite network will have broad significance as a model for engaging patients in research network development
Author's personal copy Bacillus Calmette-Guérin vaccination using a microneedle patch
No full texta b s t r a c t Tuberculosis (TB) caused by Mycobacterium tuberculosis continues to be a leading cause of mortality among bacterial diseases, and the bacillus Calmette-Guérin (BCG) is the only licensed vaccine for human use against this disease. TB prevention and control would benefit from an improved method of BCG vaccination that simplifies logistics and eliminates dangers posed by hypodermic needles without compromising immunogenicity. Here, we report the design and engineering of a BCG-coated microneedle vaccine patch for a simple and improved intradermal delivery of the vaccine. The microneedle vaccine patch induced a robust cell-mediated immune response in both the lungs and the spleen of guinea pigs. The response was comparable to the traditional hypodermic needle based intradermal BCG vaccination and was characterized by a strong antigen specific lymphocyte proliferation and IFN-␥ levels with high frequencies of CD4 + IFN-␥ + , CD4 + TNF-␣ + and CD4 + IFN-␥ + TNF-␣ + T cells. The BCG-coated microneedle vaccine patch was highly immunogenic in guinea pigs and supports further exploration of this new technology as a simpler, safer, and compliant vaccination that could facilitate increased coverage, especially in developing countries that lack adequate healthcare infrastructure
Author Correction: Intradermal immunization by Ebola virus GP subunit vaccines using microneedle patches protects mice against lethal EBOV challenge
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Pharmacist vs physician management of e-visit requests for COVID-19 medication: A randomized clinical trial.
No full textBackgroundElectronic visits (e-visits), defined as structured asynchronous electronic messages between patients and clinicians requiring clinical decision-making, are being increasingly used to enhance access to outpatient health care services, but the primary care physicians who typically manage them face work overflow. Pharmacists have been proposed to manage e-visits that lead to prescription requests, but scant evidence exists about the effectiveness of this approach.ObjectiveTo compare pharmacist management of structured asynchronous e-visit requests for COVID-19 medication with physician management regarding quality of care, timeliness, and patient care experience.MethodsThis cluster-randomized clinical trial included adults from 17 medical facilities of Kaiser Permanente Northern California who made e-visits requesting COVID-19 medication (nirmatrelvir-ritonavir) from October 9 to December 11, 2023. In the Pharmacist Care group, a regional team of pharmacists managed e-visits for COVID-19 medication; in the Physician Care group, pools of adult and family medicine physicians managed these visits. The primary outcome was whether a patient with 1 or more potential serious drug-drug interactions received counseling via an electronic secure message. Secondary outcomes included prescribing rates, time to the prescription, and patient perceptions of care quality.ResultsAmong the 1,753 eligible patients (mean age = 52.2 [SD = 15.9] years; 57.7% female), 642 received Pharmacist Care and 1,111 received Physician Care. The percentage of patients with a potential drug-drug interaction who were sent counseling messages by the clinician did not differ between the Pharmacist Care (76 of 79 [96.2%]) and Physician Care groups (193 of 201 [96.0%]) (risk difference [RD] = 0.18%; 95% CI = -4.8% to 5.2%). The pharmacist and physician groups had similar rates of prescribing (87.4% vs 84.4%; RD = 2.9; 95% CI = -0.4 to 6.3). Pharmacist Care compared with Physician Care had faster mean time from the initial e-visit submission to the resulting prescription (1.0 vs 2.5 hours; RD = -1.5; 95% CI = -1.9 to -1.2). Pharmacist Care took more clinician time per visit than Physician Care (10.7 vs 4.2 minutes), resulting in higher estimated cost (6.70). After the study period, the pharmacist team made protocol changes to improve workflow efficiency, and a follow-up analysis 12 months later found significant reductions in per-visit time (to 5.7 minutes) and estimated cost (to $6.03) under Pharmacist Care. Patient perceptions of care did not differ significantly between groups.ConclusionsPharmacist care and physician care for patient e-visits for COVID-19 medication both yielded high quality of care, with no significant group differences. Evaluation of pharmacist care may be warranted for other e-visits designed to facilitate medication prescribing.Clinical trialClinicalTrials.gov NCT06096863
