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1.
Psychiatr Serv ; 74(2): 173-181, 2023 02 01.
Article in English | MEDLINE | ID: mdl-35855620

ABSTRACT

The Pennsylvania State Hospital System's use of containment procedures has been studied for >30 years. This prospective study assessed the effects of ending the use of seclusion and mechanical restraint in the system's six civil hospitals and two forensic centers from 2011 to 2020. The study examined the effect of this change on key safety measures: physical restraint, assaults, aggression, and self-injurious behavior. In total, 68,153 incidents, including 9,518 episodes of physical restraint involving 1,811 individuals, were entered into a database along with patients' demographic and diagnostic information. All data were calculated per 1,000 days to control for census changes. During the study, mechanical restraint was used 128 times and seclusion four times. Physical restraint use decreased from a high of 2.62 uses per 1,000 days in 2013 to 2.02 in 2020. The average length of time a person was held in physical restraint was reduced by 64%, from 6.6 minutes in 2011 to 2.4 minutes in 2020 (p<0.001). All safety measures improved or were unchanged. Use of unscheduled medication did not change. The hospital system safely ended the use of mechanical restraint and seclusion by using a recovery approach and by following the six core strategies for seclusion and restraint reduction.


Subject(s)
Hospitals, State , Mental Disorders , Humans , Restraint, Physical , Pennsylvania , Hospitals, Psychiatric , Prospective Studies , Patient Isolation , Mental Disorders/epidemiology , Mental Disorders/therapy
2.
Phys Rev E ; 103(4-1): 043106, 2021 Apr.
Article in English | MEDLINE | ID: mdl-34005982

ABSTRACT

The internal flow and mixing properties inside deformable droplets, after reaching the steady state within two types of passive droplet traps, are visualized and analyzed as dynamical systems. The first droplet trap (constriction) is formed by three spheres arranged in an equilateral triangle, while the second consists of two parallel spherocylinders (capsules). The systems are assumed to be embedded in a uniform far-field flow at low Reynolds number, and the steady shapes and interfacial velocities on the drops are generated using the boundary-integral method. The internal velocity field is recovered by solving the internal Dirichlet problem, also via a desingularized boundary-integral method. Calculation of 2D streamlines within planes of symmetry reveals the internal equilibria of the flow. The type of each equilibrium is classified in 3D and their interactions probed using passive tracers and their Poincaré maps. For the two-capsule droplet, saddle points located on orthogonal symmetry planes influence the regular flow within the drop. For the three-sphere droplet, large regions of chaos are observed, embedded with simple periodic orbits. Flow is visualized via passive dyes, using material lines and surfaces. In 2D, solely the interface between two passive interior fluids is advected using an adaptive number of linked tracer particles. The reduction in dimension decreases the number of required tracer points, and also resolves arbitrarily thin filaments, in contrast to backward cell-mapping methods. In 3D, the advection of a material surface, bounded by the droplet interface, is enabled using an adaptive mesh scheme. Off-lattice 3D contour advection allows for highly resolved visualizations of the internal flow and quantification of the associated degree of mixing. Analysis of the time-dependent growth of material surfaces and 3D mixing numbers suggests the three-sphere droplet exhibits superior mixing properties compared to the two-capsule droplet.

3.
Brain Behav ; 9(11): e01420, 2019 11.
Article in English | MEDLINE | ID: mdl-31625691

ABSTRACT

INTRODUCTION: Pyrovalerone (4-methyl-ß-keto-prolintane) is a synthetic cathinone (beta-keto-amphetamine) derivative. Cathinones are a concern as drugs of abuse, as related street drugs such as methylenedioxypyrovalerone have garnered significant attention. The primary mechanism of action of cathinones is to inhibit reuptake transporters (dopamine and norepinephrine) in reward centers of the central nervous system. METHODS: We measured bioenergetic, behavioral, and molecular responses to pyrovalerone (nM-µM) in zebrafish to evaluate its potential for neurotoxicity and neurological impairment. RESULTS: Pyrovalerone did not induce any mortality in zebrafish larvae over a 3- and 24-hr period; however, seizures were prevalent at the highest dose tested (100 µM). Oxidative phosphorylation was not affected in the embryos, and there was no change in superoxide dismutase 1 expression. Following a 3-hr treatment to pyrovalerone (1-100 µM), larval zebrafish (6d) showed a dose-dependent decrease (70%-90%) in total distance moved in a visual motor response (VMR) test. We interrogated potential mechanisms related to the hypoactivity, focusing on the expression of dopamine-related transcripts as cathinones can modulate the dopamine system. Pyrovalerone decreased the expression levels of dopamine receptor D1 (~60%) in larval zebrafish but did not affect the expression of tyrosine hydroxylase, dopamine active transporter, or any other dopamine receptor subunit examined, suggesting that pyrovalerone may regulate the expression of dopamine receptors in a specific manner. DISCUSSION: Further studies using zebrafish are expected to reveal new insight into molecular mechanisms and behavioral responses to cathinone derivates, and zebrafish may be a useful model for understanding the relationship between the dopamine system and bath salts.


Subject(s)
Central Nervous System Stimulants/pharmacology , Locomotion/drug effects , Pyrrolidines/pharmacology , Receptors, Dopamine D1/drug effects , Animals , Dopamine/metabolism , Dopamine Plasma Membrane Transport Proteins/drug effects , Dopamine Plasma Membrane Transport Proteins/genetics , Larva/drug effects , Larva/metabolism , Oxidative Phosphorylation/drug effects , Receptors, Dopamine/drug effects , Receptors, Dopamine/genetics , Receptors, Dopamine D1/genetics , Seizures/chemically induced , Superoxide Dismutase-1/drug effects , Superoxide Dismutase-1/metabolism , Tyrosine 3-Monooxygenase/drug effects , Tyrosine 3-Monooxygenase/genetics , Zebrafish
4.
Psychiatr Serv ; 66(12): 1326-32, 2015 Dec 01.
Article in English | MEDLINE | ID: mdl-26234329

ABSTRACT

OBJECTIVE: This prospective study assessed the use of seclusion and restraint in Pennsylvania forensic centers from 2001 through 2010. It also examined the correlation between declining use of containment procedures and patient-to-patient and patient-to-staff assaults. METHODS: The 2,741 episodes of restraint or seclusion involving 801 unique individuals served in state forensic centers during the study period were entered into a uniform database. Included in this data set were demographic and diagnostic data as well as the causes and injuries associated with each use of these procedures. These data were correlated with rates of patient-to-patient and patient-to-staff assaults with any injury for each month of this study. RESULTS: From 2001 to 2010, the rate of use of mechanical restraint significantly declined from 1.63 to .04 episodes per 1,000 days (p<.001), and the rate of use of seclusion significantly declined from .89 to .04 episodes per 1,000 days (p<.001). There was a nonsignificant decline in the use of physical restraint during this span. During this decade, the rate of patient-to-staff assaults declined, and the rate of patient-to-patient assaults was unaffected. CONCLUSIONS: Decreasing the use of containment procedures had a positive effect on reducing assaults. Leadership, data transparency, use of clinical alerts, workforce development, policy changes, and discontinuation of psychiatric use of PRN orders were all contributing factors. A philosophical change toward a recovery model of psychiatric care and services was the driving force behind this transformation.


Subject(s)
Hospitals, Psychiatric/statistics & numerical data , Hospitals, State/statistics & numerical data , Patient Isolation/statistics & numerical data , Restraint, Physical/statistics & numerical data , Violence/statistics & numerical data , Adolescent , Adult , Female , Humans , Male , Patient Isolation/psychology , Pennsylvania , Prospective Studies , Restraint, Physical/psychology , Violence/psychology , Young Adult
5.
Psychiatr Serv ; 66(3): 303-9, 2015 Mar 01.
Article in English | MEDLINE | ID: mdl-25727119

ABSTRACT

OBJECTIVE: This prospective study assessed the use of seclusion and restraint in the Pennsylvania state hospital system from 2001 through 2010. It also examined the correlation between declining use of containment procedures and assaults by patients on other patients and staff. METHODS: The 12,900 anonymized records involving the 1,801 unique, civilly committed individuals who were physically or mechanically restrained and secluded in the nine civil hospitals during this study period were entered into a database. The data set included demographic and diagnostic information about the patients and the cause and effect of the procedures. These data were compared with rates of patient-to-patient and patient-to-staff assaults to determine any correlation between changes in use of containment and assaults. RESULTS: From 2001 to 2010, the use of mechanical restraint significantly declined from .37 to .08 episodes per 1,000 days (p<.018), and the use of seclusion significantly declined from .21 to .01 episodes per 1,000 days (p<.001). Persons with an axis I diagnosis of psychotic disorder accounted for 44% of containment procedures used during this study. Patient-to-patient assaults declined slightly, and patient-to-staff assaults were unaffected. CONCLUSIONS: Decreasing the use of containment procedures did not increase assaults. Better leadership, data transparency, use of clinical alerts, workforce development, policy changes, enhanced use of response teams, implementation of dialectical behavior therapy, and discontinuation of the psychiatric use of PRN orders contributed to the change in use of containment procedures. A philosophical change to a recovery model of psychiatric care and services was the driving force behind this transformation.


Subject(s)
Hospitals, Psychiatric/statistics & numerical data , Hospitals, State/statistics & numerical data , Inpatients/statistics & numerical data , Patient Isolation/statistics & numerical data , Restraint, Physical/statistics & numerical data , Violence/statistics & numerical data , Adolescent , Adult , Female , Humans , Inpatients/psychology , Male , Patient Isolation/psychology , Pennsylvania , Prospective Studies , Restraint, Physical/psychology , Violence/psychology , Young Adult
6.
Phys Rev E Stat Nonlin Soft Matter Phys ; 86(2 Pt 1): 021303, 2012 Aug.
Article in English | MEDLINE | ID: mdl-23005756

ABSTRACT

Previous studies on wetted, particle-particle collisions have been limited to head-on collisions, but in many-particle flows, collisions are inherently oblique. In this work, we explore such oblique collisions experimentally and theoretically. Whereas in normal collisions particles rebound only due to solid deformation, we observe in oblique collisions a new outcome where the particles initially form a rotating doublet and then deagglomerate at a later time due to so-called centrifugal forces. Surprisingly, we discover the essential role of capillary forces in oblique collisions even when the capillary number (viscous over capillary forces) is high. This recognition leads to the introduction of a dimensionless number, the centrifugal number (centrifugal over capillary forces), which together with the previously established Stokes number characterizes the regime map of outcomes. Unexpectedly, we observe a normal restitution coefficient greater than unity at large impact angles, the mechanism for which may also be observed in other agglomerating systems.


Subject(s)
Mechanical Phenomena , Models, Theoretical , Wettability
7.
J Colloid Interface Sci ; 383(1): 167-76, 2012 Oct 01.
Article in English | MEDLINE | ID: mdl-22795042

ABSTRACT

An efficient algorithm is developed to determine the three-dimensional shape of a deformable drop trapped under gravity in a constriction, employing an artificial evolution to a steady state. During the simulation, the drop surface is advanced using a rationally-devised normal "velocity", based on local deviation from the Young-Laplace equation and the adjacent solid shape, to approach the trapped drop shape. The artificial "time-dependent" evolution of the drop to the static, trapped shape requires that the free portions of the drop interface eventually satisfy the Young-Laplace equation, and the drop-solid contact portions of the drop interface conform to the solid surface. The significant advantage of this solution method is that a simple, numerically-efficient "velocity" is used to construct the evolution to the steady state; the coated areas where the drop is in near contact with solid boundaries of the constriction do not have to be specified a priori, but are found in the course of the solution. Alternative methods (e.g., boundary integral) based on realistic time-marching would be much more costly for determining the trapped state. Trapping conditions and drop shapes are studied for gravity-induced settling of a deformable drop into a three-dimensional constriction. For conditions near critical, where the trapped-drop steady state ceases to exist, severe surface-mesh distortions are treated by a combination of 'passive mesh stabilization', mesh relaxation and topological mesh transformations through node reconnections. For Bond numbers above a critical value, the drop is deformable enough to pass through the hole of the constriction, with no trapping. Critical Bond numbers are determined by linearly fitting minima of the root-mean-squared (rms) surface velocities versus corresponding Bond numbers greater than critical, and then extrapolating the Bond number to where the minimum rms velocity is zero (i.e., the drop becomes trapped). For ring and hyperbolic-tube constrictions, with axes parallel to the gravity vector, the results for trapped drops and critical Bond numbers are in close agreement with those obtained by the previous, highly-accurate axisymmetric method [1]. Also, the three-dimensional Young-Laplace and boundary-integral methods show good agreement for the static shape of a drop trapped in a tilted three-sphere constriction. For all constriction types studied, including circular rings, hyperbolic tubes and agglomerates of three and four spheres, the critical Bond number increases nearly linearly with an increase in the drop-to-hole size ratio. In contrast, the constriction type and tilt angle, which is the angle between the gravity vector and the normal to the plane of the constriction hole, have generally a weaker effect on the critical Bond number.

8.
Lab Chip ; 11(16): 2772-8, 2011 Aug 21.
Article in English | MEDLINE | ID: mdl-21691663

ABSTRACT

In this work, a novel thiol-ene based photopolymerizable resin formulation was shown to exhibit highly desirable characteristics, such as low cure time and the ability to overcome oxygen inhibition, for the photolithographic fabrication of microfluidic devices. The feature fidelity, as well as various aspects of the feature shape and quality, were assessed as functions of various resin attributes, particularly the exposure conditions, initiator concentration and inhibitor to initiator ratio. An optical technique was utilized to evaluate the feature fidelity as well as the feature shape and quality. These results were used to optimize the thiol-ene resin formulation to produce high fidelity, high aspect ratio features without significant reductions in feature quality. For structures with aspect ratios below 2, little difference (<3%) in feature quality was observed between thiol-ene and acrylate based formulations. However, at higher aspect ratios, the thiol-ene resin exhibited significantly improved feature quality. At an aspect ratio of 8, raised feature quality for the thiol-ene resin was dramatically better than that achieved by using the acrylate resin. The use of the thiol-ene based resin enabled fabrication of a pinched-flow microfluidic device that has complex channel geometry, small (50 µm) channel dimensions, and high aspect ratio (14) features.


Subject(s)
Microfluidic Analytical Techniques/instrumentation , Resins, Synthetic/chemistry , Sulfhydryl Compounds/chemistry , Particle Size , Surface Properties
9.
Appl Biochem Biotechnol ; 161(1-8): 468-82, 2010 May.
Article in English | MEDLINE | ID: mdl-20177821

ABSTRACT

The cellulose hydrolysis kinetics during batch enzymatic saccharification are typified by a rapid initial rate that subsequently decays, resulting in incomplete conversion. Previous studies suggest that changes associated with the solution, substrate, or enzymes may be responsible. In this work, kinetic experiments were conducted to determine the relative magnitude of these effects. Pretreated corn stover (PCS) was used as a lignocellulosic substrate likely to be found in a commercial saccharification process, while Avicel and Kraft lignin were used to create model substrates. Glucose inhibition was observed by spiking the reaction slurry with glucose during initial-rate experiments. Increasing the glucose concentration from 7 to 48 g/L reduced the cellulose conversion rate by 94%. When product sugars were removed using ultrafiltration with a 10 kDa membrane, the glucose-based conversion increased by 9.5%. Reductions in substrate reactivity with conversion were compared directly by saccharifying PCS and Avicel substrates that had been pre-reacted to different conversions. Reaction of substrate with a pre-conversion of 40% resulted in about 40% reduction in the initial rate of saccharification, relative to fresh substrate with identical cellulose concentration. Overall, glucose inhibition and reduced substrate reactivity appear to be dominant factors, whereas minimal reductions of enzyme activity were observed.


Subject(s)
Cellulase , Cellulose/metabolism , Lignin/metabolism , Biomass , Bioreactors , Cellulase/antagonists & inhibitors , Cellulase/metabolism , Glucose/metabolism , Hydrolysis , Substrate Specificity , Zea mays/chemistry , Zea mays/metabolism
10.
J Colloid Interface Sci ; 334(2): 113-23, 2009 Jun 15.
Article in English | MEDLINE | ID: mdl-19406427

ABSTRACT

This article features recent simulation studies of the flow of emulsions containing deformable drops through pores, constrictions, and granular media. The flow is assumed to be at low Reynolds number, so that viscous forces dominate, and boundary-integral methods are used to determine interfacial velocities and, hence, track the drop motion and shapes. A single drop in a flat channel migrates to the channel centerplane due to deformation-induced drift, which increases its steady-state velocity along the channel. A drop moving towards a smaller interparticle constriction squeezes through the constriction if the capillary number (ratio of viscous deforming forces and interfacial tension forces) is large enough, but it becomes trapped when the capillary number is below a critical value. These concepts then influence the flow of an emulsion through a granular medium, for which the drop phase moves faster than the suspending liquid at large capillary numbers but slower than the suspending liquid at smaller capillary numbers. The permeabilities of the granular medium to both phases increase with increasing capillary number, due to the reduced resistance to squeezing of easily deformed drops, though drop breakup must also be considered at large capillary numbers.


Subject(s)
Emulsions/chemistry , Motion , Computer Simulation , Elasticity , Models, Chemical , Rheology , Viscosity
12.
Phys Rev Lett ; 101(4): 044501, 2008 Jul 25.
Article in English | MEDLINE | ID: mdl-18764332

ABSTRACT

At moderate values of the surface Peclet number and the dimensionless gas constant, a surfactant-covered, isolated drop that is initially spherical can undergo large deformations and eventually break in inertialess gravitational motion. A long, thin filament forms, extending from the trailing edge of the drop, with a breakup mechanism that is similar to tip streaming. In the range of parameters studied, the emitted drop has an equivalent spherical radius between 0.01 to 0.03 of the original drop radius and an interfacial tension from 0.2 to 0.6 of the clean-interface value.


Subject(s)
Glycerol/chemistry , Models, Chemical , Surface-Active Agents/chemistry , Water/chemistry , Microfluidics/methods
13.
Community Ment Health J ; 44(4): 261-70, 2008 Aug.
Article in English | MEDLINE | ID: mdl-18297399

ABSTRACT

The objective of this prospective study was to assess patient exposure to the psychiatric use of unscheduled medications at all nine Pennsylvania state hospitals and to unify practice guidelines in this regard. In August 2004, a decision was made to discontinue the use of p.r.n. orders for psychiatric indications. All unscheduled medications, (p.r.n. and STAT physician's order) administered for psychiatric indications were entered into a uniform database. A total of 46,913 unscheduled medications were administered to people served in the hospital system throughout this 15 month study. During March 2004, 87.7 unscheduled medications per 1,000 days-of-care were administered in the hospital system. During the last month of this study, May 2005, this rate had decreased to 17 per 1,000 days-of-care. Many hospital safety measures significantly improved as a result of this change. Cessation of p.r.n. medication use for psychiatric indications has significantly decreased patient exposure to unnecessary psychotropic medications and has resulted in a safer hospital system.


Subject(s)
Drug Prescriptions , Hospitals, State , Psychotropic Drugs/administration & dosage , Adult , Drug Utilization , Female , Humans , Male , Middle Aged , Pennsylvania , Prospective Studies , Psychotic Disorders/drug therapy , Psychotropic Drugs/therapeutic use
14.
J Colloid Interface Sci ; 305(2): 239-49, 2007 Jan 15.
Article in English | MEDLINE | ID: mdl-17081553

ABSTRACT

An on-chip micropump for portable microfluidic applications was investigated using mathematical modeling and experimental testing. This micropump is activated by the addition of water, via a dropper, to ionic polymer particles that swell due to osmotic effects when wetted. The resulting particle volume increase deflects a membrane, forcing a separate fluid from an adjacent reservoir. The micropump components, along with the microfluidic components, are fabricated using the contact liquid photolithographic polymerization (CLiPP) method. The maximum flow rate achieved with this pump is 17 microL per minute per mg of dry polymer particles of 355-425 microm in diameter. The pump flow rate may be controlled by adjusting the particle size and amount, the membrane properties, and the channel dimensions. The experimental results demonstrate good agreement with an analytical model describing the particle swelling and its coupling with resistive forces from the bending membrane, viscous flow in the microchannel, and interfacial effects. Key features of this micropump are that it can be placed directly on a microdevice, and that it requires only a small amount of water and no external power supply to function. Therefore, this pumping system is useful for applications in which a highly portable device is required.


Subject(s)
Microfluidic Analytical Techniques/methods , Nanotechnology , Polymers/chemistry , Water/chemistry , Microfluidic Analytical Techniques/instrumentation , Models, Theoretical , Osmosis , Particle Size , Surface Properties , Time Factors
15.
Lab Chip ; 6(5): 659-66, 2006 May.
Article in English | MEDLINE | ID: mdl-16652182

ABSTRACT

A water-activated, effervescent reaction was used to transport fluid in a controllable manner on a portable microfluidic device. The reaction between sodium bicarbonate and an organic acid, tartaric acid and/or benzoic acid, was modeled to analyze methods of controlling the generation of carbon-dioxide gas for the purposes of pumping fluids. Integration and testing of the effervescent reaction pump in a microfluidic device was made possible by using elastomeric polymers as both photopolymerizable septa and removable lids. These materials combined to enable facile access to otherwise gas-tight devices. Based on theoretical predictions for 0.33 mg of sodium bicarbonate and a stoichiometric amount of organic acid, the pumping flow rate could be varied from 0.01 microL s(-1) to 70 microL s(-1). The flow rate is controlled by adjusting any or all of the particle size of the least soluble reactant, the amount of reactants used, and the type of organic acid selected. The tartaric acid systems rapidly produce carbon dioxide; however, the gas generation rates dramatically decrease over the course of the reaction. In contrast, carbon dioxide production rate in the benzoic acid systems is lower and nearly constant for several minutes. Water activation and direct placement on a microfluidic device are key features of this micropump, which is therefore useful for portable microfluidic applications.


Subject(s)
Microfluidics/instrumentation , Microfluidics/methods
16.
Psychiatr Serv ; 56(9): 1115-22, 2005 Sep.
Article in English | MEDLINE | ID: mdl-16148327

ABSTRACT

OBJECTIVES: This study examined the use of seclusion and mechanical restraint from 1990 to 2000 and the rate of staff injuries from patient assaults from 1998 to 2000 in a state hospital system. METHODS: Records of patients older than 18 years who were civilly committed to one of the nine state hospitals in Pennsylvania were included in the analyses. Two databases were used in each of the nine hospitals: one identified date, time, duration, and justification for each episode of seclusion or restraint and the other identified when a patient was hospitalized and the demographic characteristics and the diagnosis of the patient. Rate and duration of seclusion and restraint were calculated. Reports from compensation claims were used to determine staff injuries from patient assaults. RESULTS: The rate and duration of seclusion and mechanical restraint decreased dramatically during this period. From 1990 to 2000, the rate of seclusion decreased from 4.2 to .3 episodes per 1,000 patient-days. The average duration of seclusion decreased from 10.8 to 1.3 hours. The rate of restraint decreased from 3.5 to 1.2 episodes per 1,000 patient-days. The average duration of restraint decreased from 11.9 to 1.9 hours. Patients from racial or ethnic minority groups had a higher rate and longer duration of seclusion than whites. Seclusion tended to be less likely, but longer, during the night shift. Patients were restrained less often during the night shift, but for a longer duration. The rate of restraint was higher during the week than during weekends and holidays. Younger patients were more likely to be secluded and restrained, but older patients remained secluded and restrained longer. No significant changes were seen in rates of staff injuries from 1998 to 2000. CONCLUSIONS: Many factors contributed to the success of this effort, including advocacy efforts, state policy change, improved patient-staff ratios, response teams, and second-generation antipsychotics.


Subject(s)
Hospitals, Psychiatric/statistics & numerical data , Hospitals, State/statistics & numerical data , Patient Isolation/statistics & numerical data , Restraint, Physical/statistics & numerical data , Adult , Age Factors , Aged , Crisis Intervention , Female , Health Services Needs and Demand/standards , Humans , Male , Middle Aged , Organizational Policy , Outcome Assessment, Health Care , Pennsylvania , Sex Factors , Utilization Review
17.
Lab Chip ; 5(2): 151-7, 2005 Feb.
Article in English | MEDLINE | ID: mdl-15672128

ABSTRACT

Novel fabrication techniques and polymer systems are being explored to enable mass production of low cost microfluidic devices. In this contribution we discuss a new fabrication scheme for making microfluidic devices containing porous polymer components in situ. Contact lithography, a living radical photopolymer (LRPP) system and salt leaching were used to fabricate multilayer microfluidic devices rapidly with various channel geometries and covalently attached porous polymer plugs made of various photopolymerizable substrates. LRPP systems offer the advantages of covalent attachment of microfluidic device layers and facile surface modification via grafting. Several applications of the porous plugs are also explored, including a static mixer, a high surface area-to-volume reactor and a rapidly responding hydrogel valve. Quantitative and qualitative data show an increase in mixing of a fluorescein and a water stream for channels containing porous plugs relative to channels with no porous plugs. Confocal laser scanning microscopy images demonstrate the ability to graft a functional material onto porous plug surfaces. A reaction was carried out on the grafted pore surfaces, which resulted in fluorescent labelling of the grafted material throughout the pores of the plug. Homogenous fluorescence throughout the depth of the porous plug and along pore surfaces indicated that the porous plugs were surface modified by grafting and that reactions can be carried out on the pore surfaces. Finally, porous hydrogel valves were fabricated which swelled in response to contact with various pH solutions. Results indicate that a porous hydrogel valve will swell and close more rapidly than other valve geometries made with the same polymer formulation. The LRPP-salt leaching method provides a means for rapidly incorporating porous polymer components into microfluidic devices, which can be utilized for a variety of pertinent applications upon appropriate selection of porous plug materials and surface treatments.

19.
Appl Biochem Biotechnol ; 113-116: 417-32, 2004.
Article in English | MEDLINE | ID: mdl-15054268

ABSTRACT

We employ in situ deposited secondary membranes of yeast (SMYs) to optimize permeate flux during microfiltration and ultrafiltration of protein solutions. The deposited secondary membrane was periodically removed by backflushing, and a new cake layer was deposited at the start of the next cycle. The effects of backflushing time, backflushing strength, wall shear rate, and amount of secondary membrane deposited on the permeate flux were examined. Secondary membranes were found to increase the permeate flux in microfiltration by severalfold. Protein transmission was also enhanced owing to the presence of the secondary membrane, and the amount of protein recovered was more than twice that obtained during filtration of protein-only solutions under otherwise identical conditions. In ultrafiltration, the flux enhancement owing to the secondary membrane was only 50% or less. In addition, the flux for ultrafiltration was relatively insensitive to changes in the concentration of yeast used during deposition of SMY and to the backflushing strength used to periodically remove the secondary membrane.


Subject(s)
Biotechnology/methods , Proteins/isolation & purification , Ultrafiltration , Dose-Response Relationship, Drug , Filtration , Membranes , Membranes, Artificial , Microscopy, Electron, Scanning , Proteins/chemistry , Suspensions , Time Factors
20.
Appl Biochem Biotechnol ; 113-116: 585-99, 2004.
Article in English | MEDLINE | ID: mdl-15054279

ABSTRACT

Technologies suitable for the separation and reuse of cellulase enzymes during the enzymatic saccharification of pretreated corn stover are investigated to examine the economic and technical viability of processes that promote cellulase reuse while removing inhibitory reaction products such as glucose and cellobiose. The simplest and most suitable separation is a filter with relatively large pores on the order of 20-25 mm that retains residual corn stover solids while passing reaction products such as glucose and cellobiose to form a sugar stream for a variety of end uses. Such a simple separation is effective because cellulase remains bound to the residual solids. Ultrafiltration using 50-kDa polyethersulfone membranes to recover cellulase enzymes in solution was shown not to enhance further the saccharification rate or overall conversion. Instead, it appears that the necessary cellulase enzymes, including beta-glucosidase, are tightly bound to the substrate; when fresh corn stover is contacted with highly washed residual solids, without the addition of fresh enzymes, glucose is generated at a high rate. When filtration was applied multiple times, the concentration of inhibitory reaction products such as glucose and cellobiose was reduced from 70 to 10 g/L. However, an enhanced saccharification performance was not observed, most likely because the concentration of the inhibitory products remained too high. Further reduction in the product concentration was not investigated, because it would make the reaction unnecessarily complex and result in a product stream that is much too dilute to be useful. Finally, an economic analysis shows that reuse of cellulase can reduce glucose production costs, especially when the enzyme price is high. The most economic performance is shown to occur when the cellulase enzyme is reused and a small amount of fresh enzyme is added after each separation step to replace lost or deactivated enzyme.


Subject(s)
Biomass , Biotechnology/methods , Carbohydrates/isolation & purification , Cellulase/chemistry , Cellulose/chemistry , Lignin/chemistry , Membranes, Artificial , Ultrafiltration/methods , Biotechnology/economics , Cellobiose/chemistry , Glucose/chemistry , Hydrolysis , Models, Chemical , Time Factors , Zea mays
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