Passage Criteria Research Articles

Effect of thermo-velocity barriers on fish: influence of water temperature, flow velocity and body size on the volitional swimming capacity of northern straight-mouth nase (Pseudochondrostoma duriense).

Water temperature and flow velocity directly affect the fish swimming capacity, and thus, both variables influence the fish passage through river barriers. Nonetheless, their effects are usually disregarded in fishway engineering and management. This study aims to evaluate the volitional swimming capacity of the northern straight-mouth nase (Pseudochondrostoma duriense), considering the possible effects of water temperature, flow velocity and body size. For this, the maximum distance, swim speed and fatigue time (FT) were studied in an outdoor open-channel flume in the Duero River (Burgos, Spain) against three nominal velocities (1.5, 2.5 and 3m s-1 ) and temperatures (5.5, 13.5 and 18.5°C), also including the changes between swimming modes (prolonged and sprint). Results showed that a nase of 20.8cm mean fork length can develop a median swim speed that exceeds 20.7BL s-1 (4.31 m s-1 ) during a median time of 3.4s in sprint mode, or 12.2BL s-1 (2.55 m s-1 ) for 23.7s in prolonged mode under the warmest scenario. During prolonged swimming mode, fish were able to reach further distances in warmer water conditions for all situations, due to a greater swimming speed and FT, whereas during sprint mode, warmer conditions increased the swim speed maintaining the FT. In conclusion, the studied temperature range and flow velocity range influence fish swimming performance, endurance and distance travelled, although with some differences depending on the swimming mode. The provided information goes a step forward in the definition of real fish swimming capacities, and in turn, will contribute to establish clear passage criteria for thermo-velocity barriers, allowing the calculation of the proportion of fish able to pass a barrier under different working scenarios, as well designing of the optimized solutions to improve the fish passage through river barriers.

Modified method of patency judgement using patency capsule prior to capsule endoscopy in clinical practice

In 2012, Japan approved the use of a tag-less patency capsule (PC), which evaluates gastrointestinal patency before small-bowel capsule endoscopy (SBCE). This study aimed to evaluate the validity of our modification on the passage criteria for this PC in clinical practice. We retrospectively enrolled 326 consecutive patients who underwent PC examination before SBCE. If X-ray could not reveal the PC in the body during the judgement time (30–33 h after ingestion), we defined it as ‘estimated patency’ and performed SBCE. We employed plain computed tomography (CT) for the second judgement, as needed. The overall patency rate was 95.1%. By X-ray, 41 (12.6%) patients were judged to have ‘estimated patency’, and SBCE could be safely performed. Plain CT judgement was necessary in 106 patients (32.5%). One PC case had a residual coating film associated with stenosis in a patient with Crohn’s disease (CD), and one (0.3%) SBCE case had capsule retention resulting from false CT judgement. Multivariate analysis revealed that established CD and inpatient were factors related to no-patency. In conclusion, PC is useful for examining gastrointestinal patency, keeping in mind CT misjudgement. If PC was not found in the body via X-ray, performing SBCE as ‘estimated patency’ seemed appropriate.

AVOIDING POPLITEAL NEURO-VASCULAR INJURY DURING ILIOTIBIAL BAND ACL RECONSTRUCTION

Background:For patients with significant growth remaining, the Iliotibial Band ACL reconstruction technique has proven to be reliable procedure with minimal risk for growth disturbance. Recent dissection studies confirm the neuro-vascular bundle is within 1 cm of the ACL graft over the top position, confirming the importance of careful graft passage technique to avoid neurovascular injury.Purpose:The purpose of this study was to evaluate the over the top graft passage technique using pediatric 3-D knee models. Instrument placement for graft passage was assessed for its proximity to the posterior aspect of the femur, maintaining a safe distance from the neurovascular bundle.Materials and Methods:3D knee models (ages 7, 9, 11 years) were printed from high resolution knee CT scans, including a hinge/pivot mechanism to allow for simulation of knee position during flexion and extension. Various curved tip instruments were used to evaluate the path of the graft passage, with several goals: 1. Allow the instrument to create a graft path through the posterior capsule in the most anatomic femoral position. 2. Keep the tip of the instrument close to posterior and lateral cortex of the femur, to avoid neurovascular injury. The instruments varied in design, arc of curvature, overall length, diameters.Results:Clamp passage was performed using a retrograde approach, i.e. through the notch, passing outside the periosteum of the postero-lateral femur (Figure 1). For some clamps, the arc of the curvature allowed for passage of the instrument with minimal risk of neurovascular injury. For some clamp configurations, the clamps deviated significant from the posterior aspect of the femur during graft passage, which may increase the risk of neurovascular bundle injury. In each case, an instrument was identified that met the criteria for safe passage, but different instruments were required based upon the size of the knee joint.Conclusions:The ITB ACL reconstruction is one of the best options for ACL reconstruction in the skeletally immature. The neurovascular structures are very close to the path for over the top graft placement. Due to the wide range of knee dimensions in this group, different clamp designs may be necessary for optimal over the top graft passage. 3D knee models may guide surgeons for procedure technique and optimal instrument selection for safe graft passage.Figure 1.

Considerations for Multi-Species Fish Passage in California: A Literature Review

This review serves as a guide to improve multi-species fish passage. Human development along waterways in California during the last 160 years has adversely affected fish populations in many watersheds. Conflicts in water usage will only intensify with modern developments and population growth. Since most past fish-passage improvement efforts in California have focused on salmonids, I summarize the published studies and considerations that affect multi-species fish passage. To be effective, conditions in fishways need to meet the specific hydraulic requirements, as well as abilities, behavior, and size consideration for all fish species being considered. Turbulence, water depth, velocity, passage location, and design of a passage facility are essential elements to successful fish passage. Because of a lack of research on most of the native species, species-specific passage criteria are not fully defined, and it may be helpful to use data for physically similar, surrogate species found in similar habitats.

The Accutension Stetho, an automated auscultatory device to validate automated sphygmomanometer readings in individual patients

The aim of this report is to describe a new device that can validate, by automated auscultation, individual blood pressure (BP) readings taken by automated sphygmomanometers.The Accutension Stetho utilizes a smartphone application in conjunction with a specially designed stethoscope that interfaces directly into the smartphone via the earphone jack. The Korotkoff sounds are recorded by the application and are analyzed by the operator on the screen of the smartphone simultaneously with the images from the sphygmomanometer screen during BP estimation. Current auscultatory validation standards require at least 85 subjects and strict statistical criteria for passage. A device that passes can make no guarantee of accuracy on individual patients. The Accutension Stetho is an inexpensive smartphone/stethoscope kit combination that estimates precise BP values by auscultation to confirm the accuracy of an automated sphygmomanometer’s readings on individual patients. This should be of great value for both professional and, in certain circumstances, self-measurement BP. Patients will avoid both unnecessary treatment and errors of underestimation of BP, in which the patient requires therapy. The Stetho’s software has been validated in an independent ANSI/AAMI/ISO standard study. The Stetho has been shown to perform without difficulty in multiple deflation-based devices by many manufacturers.

51. Comparison of ORL and prostate VMAT treatment plans verifications by ArcCheck® Sun Nuclear™ 3D detector and Varian™ PDIP® module: assessment of the errors detection sensitivity and the capability of each process

Introduction The complexity of intensity modulation radiation requires a planned dose distribution verification prior treatment. Delivery a patient treatment plan quality assurance can be carried out by EPID, 2D/3D detector or by ionization chamber. In our department, VMAT treatment plans are checked by ArcCheck® Sun Nuclear™ 3D detector and Varian™ PDIP® module. In order to assess the feasibility of reducing the number of verification processes, we studied the detection sensitivity of different errors [1] and the capability of each process. Methods Treatment plans are checked by ArcCheck® Sun Nuclear™ 3D detector + SNC patient™ v6.7.1 software (AC) and Varian™ As 1000 EPID + Varian™ PDIP® v13.0 module (PDIP). For 5 ORL and prostate treatment plans, errors of collimator angulation (1–5°), dose rate (2–3%) and multi-leaf collimator (opening leaves banks from 0.5–1–2 mm) are simulated. Treatment plans are assessed by γ index (3%/3 mm, 2%/2 mm) with a respective passage criteria of 95% and 90% of the total pixels in global and local mode. A database of 80 ORL treatment plans and 30 prostate treatment plans is analyzed in order to check the capability of each process according to the different γ index analysis criterias used. Results As regards the detection sensitivity of errors, according to the analysis criterias of the γ index, the AC and the PDIP respectively make it possible to detect on average: collimator errors from 2° and 3° for the ORL plans and 4° and above 5° for prostate plans; Dose rate errors of 2% for ORL plans and 3% for prostate plans; MLC banks opening errors of 0.5 mm for ORL plans and 0.5 mm and 1 mm for prostate plans. With a fixed analysis criteria, the error detection sensitivity of the AC appears higher than the PDIP. Concerning the database analysis, for the AC, the mean γ indexes with 3%/3 mm global/local mode, and 2%/2 mm global mode are respectively 99,7 [96,3–100]; 95.8 [83.0–100]; 96.8 [81.0–100] for ORL treatment plans and 99.8 [98.8–100]; 98.2 [93.9–100]; 97.6 [90.0–99.8] for prostate treatment plans. The respective CPM capability indices are 5.2; 0.1; 0.9 for ORL treatment plans and 9.2; 1.0; 1.5 for prostate treatment plans. For the PDIP, the mean γ indexes with 3%/3 mm global/local mode and 2%/2 mm global mode are respectively 99.9 [98.8–100]; 97.6 [92.1–100]; 99.0 [93.6–100] for ORL treatment plans and 99.8 [99.0–100]; 99.0 [93.6–99.9]; 98.6 [95.8–100] for prostate treatment plans. The respective CPM capability indices are 17.4; 0.6; 1.5 for ORL treatment plans and 9.8; 1.6; 3.1 for prostate treatment plans. Conclusions The detection sensitivity of the errors appears equivalent between the two processes AC and PDIP by selecting a suited γ index analysis criteria. Analysis with 3%/3 mm local mode appears the most efficient in the detection of error but also leads to a risk of false positive. On a case by case basis, none of the processes can systematically detect the simulated errors.

Fish passage design for sustainable hydropower in the temperate Southern Hemisphere: an evidence review

The development of hydropower and other infrastructure that disrupts river connectivity poses a serious threat to highly endemic and genetically distinct freshwater fish species in temperate parts of the Southern Hemisphere. Such locations have been neglected in previous reviews on fish passage. Fishways have long been constructed to mitigate the impacts of riverine barriers on fish, yet they have often failed for all but the largest, strongest swimming taxa. This is a particular problem in the temperate south, which is home to native species that are non-recreational and generally small-bodied with weak swimming abilities (e.g. Galaxiidae) relative to typical target species for fishway design (e.g. Salmonidae). Using the Eco Evidence method for rapid evidence synthesis, we undertook an assessment of evidence for effective fishway design focusing on species representative of the temperate south, including eel and lamprey. Systematic literature searches resulted in 630 publications. Through a rigorous screening process these were reduced to 46 publications containing 76 evidence items across 19 hypotheses relating to design criteria for upstream and downstream passage. We found an overwhelming lack of evidence for effective fishway design in the temperate south. Particular deficiencies were found with regard to the design of effective facilities for downstream passage. The attraction and entrance of upstream migrating fish into fishways is also relatively under-researched. Given the urgent need for effective fishways in the temperate south, these results justify an approach to fishway design based on a combination of empirical data and expert knowledge. In the meantime, significant resources should be assigned to improve the evidence base through high quality research. The particular deficiencies identified here could guide that research agenda.

Mean-variance optimality for semi-Markov decision processes under first passage criteria

This paper deals with a first passage mean-variance problem for semi-Markov decision processes in Borel spaces. The goal is to minimize the variance of a total discounted reward up to the system's first entry to some target set, where the optimization is over a class of policies with a prescribed expected first passage reward. The reward rates are assumed to be possibly unbounded, while the discount factor may vary with states of the system and controls. We first develop some suitable conditions for the existence of first passage mean-variance optimal policies and provide a policy improvement algorithm for computing an optimal policy. Then, two examples are included to illustrate our results. At last, we show how the results here are reduced to the cases of discrete-time Markov decision processes and continuous-time Markov decision processes.

Discrete-time zero-sum Markov games with first passage criteria

In this paper, we deal with two-person zero-sum stochastic games for discrete-time Markov processes. The optimality criterion to be studied is the discounted payoff criterion during a first passage time to some target set, where the discount factor is state-dependent. The state and action spaces are all Borel spaces, and the payoff functions are allowed to be unbounded. Under the suitable conditions, we first establish the optimality equation. Then, using dynamic programming techniques, we obtain the existence of the value of the game and a pair of optimal stationary policies. Moreover, we present the exponential convergence of the value iteration and a ‘martingale characterization’ of a pair of optimal policies. Finally, we illustrate the applications of our main results with an inventory system.

Barriers to upstream passage by two migratory sculpins, prickly sculpin (Cottus asper) and coastrange sculpin (Cottus aleuticus), in northern Puget Sound lowland streams

We identified and characterized barriers to the upstream distribution by prickly sculpin (Cottus asper) and coastrange sculpin (Cottus aleuticus), based on their longitudinal distribution in 11 streams in the Puget Sound lowlands of Washington State. Eight streams had upstream limits associated with particular instream structures, and these were compared to distinguish features of barriers and non-barriers. In seven streams perch height greater than 15 cm resulted in a complete barrier. In one stream water velocity >4 m·s−1 created a partial barrier. Five of the eight barriers were one- or two-step fish ladders installed to facilitate upstream passage of Pacific salmon and trout. Water quality, physical habitat, and the presence of other fishes were not related to the presence or absence of sculpin species. Fish passage criteria in western North American streams are based on the swimming abilities of Pacific salmon and trout, without consideration for other, less motile native fishes. Structures installed to surmount previously identified impediments to upstream migration continue to inhibit sculpin movement, resulting in loss of upstream habitats for adults, with potential consequences to population size and trophic dynamics.

Can avatars pass the Turing test? Intelligent agent perception in a 3D virtual environment

The current study involved the first natural language, modified Turing Test in a 3D virtual environment. One hundred participants were given an avatar-guided tour of a virtual clothing store housed in the 3D world of Second Life. In half of the cases, a human research assistant controlled the avatar-guide; in the other half, the avatar-guide was a visually indistinguishable virtual agent or “bot” that employed a chat engine called Discourse, a more robust variant of Artificial Intelligence Markup Language (AIML). Both participants and the human research assistant were blind to variations in the controlling agency of the guide. The results indicated that 78% of participants in the artificial intelligence condition incorrectly judged the bot to be human, significantly exceeding the 50% rate that one would expect by chance alone that is used as the criterion for passage of a modified Turing Test. An analysis of participants׳ decision-making criteria revealed that agency judgments were impacted by both the quality of the AI engine and a number of psychological and contextual factors, including the naivety of participants regarding the possible presence of an intelligent agent, the duration of the trial period, the specificity and structure of the test situation, and the anthropomorphic form and movements of the agent. Thus, passage of the Turing Test is best viewed not as the sole product of advances in artificial intelligence or the operation of psychological and contextual variables, but as a complex process of human–computer interaction.

Role of Molecular Charge in Nucleocytoplasmic Transport

Transport of genetic materials and proteins between the nucleus and cytoplasm of eukaryotic cells is mediated by nuclear pore complexes (NPCs). A selective barrier formed by phenylalanine-glycine (FG) nucleoporins (Nups) with net positive charges in the NPC allows for passive diffusion of signal-independent small molecules and transport-receptor facilitated translocation of signal-dependent cargo molecules. Recently, negative surface charge was postulated to be another essential criterion for selective passage through the NPC. However, the charge-driven mechanism in determining the transport kinetics and spatial transport route for either passive diffusion or facilitated translocation remains obscure. Here we employed high-speed single-molecule fluorescence microscopy with an unprecedented spatiotemporal resolution of 9 nm and 400 µs to uncover these mechanistic fundamentals for nuclear transport of charged substrates through native NPCs. We found that electrostatic interaction between negative surface charges on transiting molecules and the positively charged FG Nups, although enhancing their probability of binding to the NPC, never plays a dominant role in determining their nuclear transport mode or spatial transport route. A 3D reconstruction of transport routes revealed that small signal-dependent endogenous cargo protein constructs with high positive surface charges that are destined to the nucleus, rather than repelled from the NPC as suggested in previous models, passively diffused through an axial central channel of the NPC in the absence of transport receptors. Finally, we postulated a comprehensive map of interactions between transiting molecules and FG Nups during nucleocytoplasmic transport by combining the effects of molecular size, signal and surface charge.

Constrained Markov decision processes with first passage criteria

This paper deals with constrained Markov decision processes (MDPs) with first passage criteria. The objective is to maximize the expected reward obtained during a first passage time to some target set, and a constraint is imposed on the associated expected cost over this first passage time. The state space is denumerable, and the rewards/costs are possibly unbounded. In addition, the discount factor is state-action dependent and is allowed to be equal to one. We develop suitable conditions for the existence of a constrained optimal policy, which are generalizations of those for constrained MDPs with the standard discount criteria. Moreover, it is revealed that the constrained optimal policy randomizes between two stationary policies differing in at most one state. Finally, we use a controlled queueing system to illustrate our results, which exhibits some advantage of our optimality conditions.

EFFECTS OF GRADE CONTROL STRUCTURES ON FISH PASSAGE, BIOLOGICAL ASSEMBLAGES AND HYDRAULIC ENVIRONMENTS IN WESTERN IOWA STREAMS: A MULTIDISCIPLINARY REVIEW

ABSTRACTLand use changes and channelization of streams in the deep loess region of western Iowa have led to stream channel incision, altered flow regimes, increased sediment inputs, decreased habitat diversity and reduced lateral connectivity of streams and floodplains. Grade control structures (GCSs) are built in streams to prevent further erosion, protect infrastructure and reduce sediment loads. However, GCS can have a detrimental impact on fisheries and biological communities. We review three complementary biological and hydraulic studies on the effects of GCS in these streams. GCS with steep (≥1:4 rise : run) downstream slopes severely limited fish passage, but GCS with gentle slopes (≤1:15) allowed greater passage. Fish assemblages were dominated by species tolerant of degradation, and Index of Biotic Integrity (IBI) scores were indicative of fair or poor biotic integrity. More than 50% of fish species had truncated distributions. After modification of GCS to reduce slopes and permit increased passage, IBI scores increased and several species were detected further upstream than before modification. Total macroinvertebrate density, biomass and taxonomic diversity and abundance of ecologically sensitive taxa were greater at GCS than in reaches immediately upstream, downstream or ≥1 km from GCS. A hydraulic study confirmed results from fish passage studies; minimum depths and maximum current velocities at GCS with gentle slopes (≤1:15) were more likely to meet minimum criteria for catfish passage than GCS with steeper slopes. Multidisciplinary approaches such as ours will increase understanding of GCS‐associated factors influencing fish passage, biological assemblage structure and other ecological relationships in streams. Copyright © 2011 John Wiley & Sons, Ltd.

The influence of discharge and temperature on the ability of upstream migrant adult river lamprey (Lampetra fluviatilis) to pass experimental overshot and undershot weirs

AbstractThe efficiencies of fish passes specifically designed and constructed to facilitate the movement of a limited number of species and life‐stages past structural barriers are likely to decline as site‐specific conditions shift with a changing climate. There is a need to develop realistic fish passage criteria based on understanding swimming capability and behaviour of multiple species in relation to temperature and flow. The influence of temperature and discharge on behaviour and ability of groups of migrating adult river lamprey (Lampetra fluviatilis), a threatened species, to pass a small overshot or undershot weir at night was investigated using a large experimental flume. Lamprey approached the weirs less, and more often maintained station by using the oral disk to attach to structure, under high flows. Oral disk attachment was more commonly observed during tests employing the undershot weir. Upstream movement tended to be in close proximity to the channel walls and floor where, compared to the mid‐channel, velocities were generally lower and velocity vectors more likely to be in a direction other than the bulk flow. Upstream movement was positively related to temperature, and was higher for the overshot weir. Weir passage rate was higher for undershot than overshot weirs, and negatively related to the maximum velocity at the weir. Passage rate was low when maximum velocities at the weir exceeded 1.5 m s−1, although some fish passed at c. 1.7 m s−1. Passage efficiency, the number of weir passes as a percentage of the number of approaches, was also higher for the undershot weir, but was not affected by discharge because lamprey approached less frequently at high flows. This study provides fish passage criteria under realistic conditions for an infrequently studied anguilliform species of conservation concern and provides a methodological perspective by which to improve fishway suitability for a wider range of species subject to changing climate. Copyright © 2010 John Wiley & Sons, Ltd.This article was published online on March 3, 2010. An error was subsequently identified in the Article title. This notice is included in the online and print versions to indicate that both have been corrected [April 12, 2010].

Experimental quantification of the swimming performance and behaviour of spawning run river lamprey Lampetra fluviatilis and European eel Anguilla anguilla

Using a large-scale open-channel flume, the swimming ability and behaviour of individual adult European eel Anguilla anguilla and river lamprey Lampetra fluviatilis, species that exhibit anguilliform locomotion, were quantified under complex hydraulic conditions created by a 0·2-0·3 m high under- or overshot weir during four discharge regimes. Fishes were allowed to approach the weirs from both up- and downstream. All fishes passed the undershot weir, independent of discharge and direction of movement, and under high flow (mean ±S.E. 194·63 ± 6·48 l s(-1)) moved upstream against velocities that ranged between 1·75 and 2·12 m s(-1), suggesting greater maximum swimming capability than previously reported. In comparison, passage efficiency during upstream movement was lower for the overshot weir for both L. fluviatilis and A. anguilla. Downstream moving A. anguilla took longer to pass the over- than undershot weir. This study describes a methodology to attain realistic measures of swimming ability and behavioural performance required to develop multispecies fish passage criteria.

Response of downstream migrating adult European eels (Anguilla anguilla) to bar racks under experimental conditions

Russon IJ, Kemp PS, Calles O. Response of downstream migrating adult European eels (Anguilla anguilla) to bar racks under experimental conditions. Ecology of Freshwater Fish 2010: 19: 197–205. © 2010 John Wiley & Sons A/SAbstract – The behavioural response of downstream migrating nonsalmonid fish to hydraulic conditions associated with river infrastructure is poorly understood. The response of downstream migrating adult European eels (Anguilla anguilla) to bar racks (12 mm bar spacing) angled on the vertical and horizontal planes under different flow regimes and during periods of darkness was assessed. Eels predominantly moved along the channel floor and wall, tending to follow routes where turbulence intensity was high. Time taken to approach the racks was greater than expected if fish had moved passively with the flow. Eels did not exhibit clear avoidance behaviour prior to encountering the racks, instead marked changes in behaviour occurred only after physical contact was made with the structure. No impingement or passage through the racks occurred, and passes per approach were high (98.3%), when vertical racks were angled 15°, 30° or 45° relative to the flow. Impingement and passage through the racks only occurred when horizontally inclined racks were placed perpendicular to the flow. The time eels were impinged on the racks was negatively related to discharge when angled at 30° relative to the channel floor, and positively related when upright. Frequency of impingement was higher under low discharge (132.9 ± 16.6 l·s−1). Impinged eels escaped from racks at approach velocities of 0.90 ± 0.05 m·s−1. Passage through the upright rack was common under high discharge (278.9 ± 36.2 l·s−1). The information presented will improve current fish passage criteria for European eels that are required to develop more effective fish passage facilities.

Charge as a Selection Criterion for Translocation through the Nuclear Pore Complex

Nuclear pore complexes (NPCs) are highly selective filters that control the exchange of material between nucleus and cytoplasm. The principles that govern selective filtering by NPCs are not fully understood. Previous studies find that cellular proteins capable of fast translocation through NPCs (transport receptors) are characterized by a high proportion of hydrophobic surface regions. Our analysis finds that transport receptors and their complexes are also highly negatively charged. Moreover, NPC components that constitute the permeability barrier are positively charged. We estimate that electrostatic interactions between a transport receptor and the NPC result in an energy gain of several k B T, which would enable significantly increased translocation rates of transport receptors relative to other cellular proteins. We suggest that negative charge is an essential criterion for selective passage through the NPC.

Comparing Fish Screen Performance to Physical Design Criteria

Fish screens associated with irrigation diversion structures perform a vital function by protecting rearing and migrating fishes. Irrigation diversions in the western United States were developed in the late 1800s and early 1900s with little regard to how they might affect fish populations. Fish screens were installed on some diversions beginning in the 1930s but were often ineffective. Beginning in the 1980s a “modern-era” fish screening program was initiated in the Yakima River basin in Washington State. A systematic phased approach was employed, with federal funding, to replace antiquated screens and to install screens where there had not previously been fish protection devices. Also during this time, the federal and state agencies responsible for protecting the fish resources developed regional criteria to guide design of these facilities. These criteria, developed by the National Marine Fisheries Service and used by the Washington Department of Fish and Wildlife, dictated physical metrics such as approach velocity (and mesh size) for fish screen facilities. Scientists at the Pacific Northwest National Laboratory (PNNL) developed methods for evaluating new fish screen facilities as they came “on line” to document whether the facilities were designed, constructed, operated, and maintained to be within the fish passage criteria. PNNL uses a combination of water velocity measurements, visual inspection, and underwater videography to determine whether fish screen sites are within the fish protection criteria. This annual evaluation schedule (most sites are evaluated three times/year) is a vital tool to ensure that the large initial capital investment (over $75 million USD) is being operated and maintained to protect fish.

A mechanistic model of plasma filtration

A model describing the sieving and transmembrane pressure behavior of plasma filtration is developed and numerically simulated. The model assumes a mechanistic criteria for particle passage through a membrane with cylindrical pores. The initial pore diameter distribution and porosity are assumed to be known. Model inputs include the particle diameter distribution, concentration and total flow rate of the permeate plasma solution. Outputs of the model include transmembrane pressure, the time-averaged sieving coefficients, and size distributions of the deposited particles and accumulated filtrate particles. Optimal filtration is characterized by high, stable sieving coefficients for desired particles, high retention of larger particles and relatively small increases in transmembrane pressure. These characteristics are realized for membranes with mean pore diameters equal to or slightly larger than mean permeate particle diameters. Simulations demonstrate that the incorporation of membrane properties into models of plasma filtration is both significant and readily possible.