Embolização das artérias prostáticas no tratamento da hiperplasia benigna da próstata : estudo anátomo-clínico

Resumo: A hiperplasia benigna da próstata (HBP) tem elevada prevalência nos homens entre os 50 e 79 anos de idade, sendo ubiquitária com o envelhecimento. Devido à significativa morbi-mortalidade associada aos tratamentos médicos e cirúrgicos currentemente disponíveis, são necessárias novas tecnologias para melhorar os resultados e minimizar o desconforto dos doentes. Recentemente, estudos preliminares de experimentação animal e em 3 doentes tratados, sugeriram a embolização arterial prostática selectiva (EAPS) como hipótese terapêutica para a HBP. Decidimos investigar se a EAPS poderia ser um procedimento bem sucedido no tratamento da HBP gravemente sintomática. Para tal realizámos um estudo anátomo-radiológico e clínico em 63 doentes com recurso a uma terapêutica inovadora minimamente invasiva guiada pela imagem. Avaliámos 126 hemipélvis com recurso a Angio-RM, Angio-TC e Angiografia Digital de Subtracção, com o intuito de definir os padrões básicos de bifurcação das artérias ilíacas internas até agora apenas descritos em estudos cadavéricos. Estudámos ainda o suprimento vascular arterial prostático, identificando: 1 as artérias prostáticas; 2 origem e direcção; 3 os ramos intra-prostáticos; 4 anastomoses com outras artérias. Em relação aos resultados anatómicos, identificámos 181 artérias prostáticas, já que em 43.7% das hemipélvis existiam dois pedículos arteriais prostáticos com origens independentes. A origem mais frequente foi a artéria pudenda interna (39.7%), seguida do tronco comum glúteo-pudendo (21%) e da artéria vesical superior (18.2%). Origens menos frequentes foram a artéria obturadora (12.1%), as artérias glúteas inferior (3.9%)ou superior (1.7%), ramos rectais provenientes da artéria mesentérica inferior (1.7%) e a artéria pudenda acessória (1.7%). Identificaram-se anastomoses com as artérias adjacentes em 57.9% dos casos: com a terminação da artéria pudenda interna (41.6%),artérias prostáticas contra-laterais (18.2%) e homo-laterais (11.7%), com ramos rectais (15.6%) e com artérias vesicais (12.9%). Em relação ao estudo clínico tratámos 63 doentes (idades compreendidas entre 52 - 82 anos, média 69.5 anos) com HBP gravemente sintomática refractária à terapêutica médica há mais de 6 meses. Foi possível avaliação após o tratamento em 37 doentes: média de seguimento de 4.7 meses (variando entre 1 e 12 meses). A EAPS unilateral foi possível em todos os doentes, com embolização bilateral em 73% dos casos. A embolização bilateral não foi possível em 27% dos casos devido a tortuosidade, alterações ateroescleróticas e pequeno calibre das artérias ilíacas e/ou prostáticas. Em média houve uma melhoria do International Prostate Symptom Score (IPSS) de 10.8 pontos, da QoL de 1.5 pontos e do Internationl Index of Erectile Function (IIEF) de 2.1 pontos. Houve uma redução média do PSA de 30% (2.4 ng/mL), um aumento do pico de fluxo urinário (Qmax) de 3.1 - 3.85 mL/s e uma redução média do volume prostático de 21% (18.5 mL). Registou-se uma complicação major: pequena área de isquémia da parede vesical tratada cirurgicamente. Em 75% dos doentes tratados obteve-se sucesso clínico com franca melhoria dos sintomas, enquanto 25% dos doentes foram considerados insucesso clínico por se ter registado uma fraca ou ausente melhoria sintomática após a embolização. Os restantes doentes tratados estão sob controlo evolutivo, pararam toda a medicação prostática, sem qualquer caso de disfunção sexual associada com o tratamento. Este trabalho constitui o primeiro estudo anatómico descritivo in vivo das artérias prostáticas, conseguido devido à utilização de técnicas de imagem nunca usadas para este fim. O uso clínico dos dados anatómicos acima referidos permitiu a implementação de técnicas de Radiologia de Intervenção no tratatamento de uma doença de elevada prevalência. ------------------------------- ABSTRACT: Benign prostatic hyperplasia (BPH) has high prevalence in men aged 50–79 years being ubiquitous with aging. Due to significant morbi-mortality associated with currently available medical and surgical treatments, there is the need for innovative technologies to continue to improve outcomes and minimize patient discomfort and morbidity. Recently, prostatic arterial embolization (PAE) was suggested as a treatmentoption for BPH based on preliminary results from animal studies and 3 treated patients. We decided to investigate if PAE might be a successful treatment option for severely symptomatic BPH patients. We performed a clinical and anatomical-radiological study in 63 patients with the use of an inovative image-guided minimally invasive technique. We evaluated 126 pelvic sides using Angio-MR or Angio-CT and Catheter Angiography before embolisation to treat symptomatic BPH. We aimed to define the main branching patterns of the male internal iliac arteries, so far only studied in the cadaver. We also evaluated the prostatic arterial supply, identifying: 1 the prostatic arteries; 2 origin and direction; 3 intra-prostatic branches; 4 anastomoses with surrounding arteries. Regarding the anatomical study we identified 181 prostatic arteries, because in 43.7% of pelvic sides 2 separate prostatic vascular pedicles were found. The most frequent origin was the internal pudendal artery (39.7%) with the common glutealpudendal trunk (21%) and superior vesical arteries (18.2%) the next commonest. Less frequent origins were the obturator artery (12.1%), the inferior (3.9%) or superior (1.7%) gluteal arteries, rectal branches from the inferior mesenteric artery (1.7%) and the accessory pudendal artery (1.7%). There were anastomoses with the surrounding arteries in 57.9% of cases: termination of the internal pudendal artery (41.6%), contralateral prostatic arteries (18.2%), same-side prostatic arteries (11.7%), rectal branches (15.6%), and vesical arteries (12.9%).Regarding the clinical study, we treated 63 patients aged 52–82 years (mean 69.5 years) who presented with symptomatic BPH refractory to medical treatment for at least 6 months. Follow-up evaluation (mean 4.7 months, range 1-12 months) was possible in 37 patients. PAE was achieved in all patients with bilateral embolization in 73%. In 27% PAE was performed unilaterally due to tortuosity, atherosclerotic changes and small size of iliac and prostatic arteries. There was a mean decrease in the IPSS of 10.8 points, a mean improvement in QoL of 1.5 points, and a mean increase in the sexual function score of 2.1 points. There was a mean PSA reduction of 30% (2.4 ng/mL), a Qmax increase of 3.1 to 3.85 mL/sec, and a mean prostate volume decrease of 21% (18.5 mL). There was one major complication: a small area of bladder wall ischemia treated by surgery. Overall, 75% of patients were considered clinical success with major improvement after PAE, while 25% of patients were considered clinical failure with little or no improvement after PAE. All remaining patients are under follow-up, stopped all prostatic medication, and reported no sexual dysfunction. This study is the first one to describe the radiological anatomy of the prostatic arteries, with the use of imaging techniques never used for this purpose before. The clinical use of the anatomical findings allowed the implementation of Interventional Radiology tehniques in the treatment of a disease with a high prevalence.

Comprehensive clinical and molecular analysis of 12 families with type 1 recessive cutis laxa.

Autosomal recessive cutis laxa type I (ARCL type I) is characterized by generalized cutis laxa with pulmonary emphysema and/or vascular complications. Rarely, mutations can be identified in FBLN4 or FBLN5. Recently, LTBP4 mutations have been implicated in a similar phenotype. Studying FBLN4, FBLN5, and LTBP4 in 12 families with ARCL type I, we found bi-allelic FBLN5 mutations in two probands, whereas nine probands harbored biallelic mutations in LTBP4. FBLN5 and LTBP4 mutations cause a very similar phenotype associated with severe pulmonary emphysema, in the absence of vascular tortuosity or aneurysms. Gastrointestinal and genitourinary tract involvement seems to be more severe in patients with LTBP4 mutations. Functional studies showed that most premature termination mutations in LTBP4 result in severely reduced mRNA and protein levels. This correlated with increased transforming growth factor-beta (TGFβ) activity. However, one mutation, c.4127dupC, escaped nonsense-mediated decay. The corresponding mutant protein (p.Arg1377Alafs(*) 27) showed reduced colocalization with fibronectin, leading to an abnormal morphology of microfibrils in fibroblast cultures, while retaining normal TGFβ activity. We conclude that LTBP4 mutations cause disease through both loss of function and gain of function mechanisms.

Effets de l’alcoolisme fœtal sur le développement du corps genouillé latéral du singe

L’exposition du fœtus à l’éthanol est reconnue comme étant la principale cause de maladies évitables lors du développement. Une forte exposition à l’alcool durant la gestation peut occasionner des dysmorphies cranio-faciales et des retards mentaux, ainsi que des troubles d’apprentissages et du comportement. Le développement du système visuel est également perturbé chez une grande majorité d’enfants qui ont été exposés à l’alcool. Lorsque les doses prises sont élevées, le système visuel peut présenter une panoplie de symptômes comme une augmentation de la tortuosité des vaisseaux rétiniens, de la myopie, de l’hypermétropie, du strabisme et une hypoplasie du nerf optique. Cependant, très peu d’études se sont penchées sur les effets de plus faibles doses sur le développement du système visuel du primate. Le singe est un excellent modèle pour étudier le système visuel car il possède plusieurs similitudes avec l’humain tant au niveau développemental qu’au niveau structurel. De plus, le singe utilisé, le Chlrocebus aethiops sabeus, possède l’avantage que des individus de cette espèce ont une consommation naturelle et volontaire à l’alcool. Une étude (Clarren et al., 1990) a suggéré qu’une faible exposition à l’alcool du fœtus du primate non humain occasionnait une diminution du nombre de cellules ganglionnaires de la rétine (CGRs). Étant donné que le corps genouillé latéral dorsal (CGLd) reçoit la plupart de ses intrants de la rétine, il est raisonnable d’assumer que les couches rétino-récipientes du CGLd devraient être aussi affectées. Nous avons alors émis l’hypothèse que le CGLd devrait également subir une diminution du nombre de neurones. Pour la première fois, nous avons utilisé une méthode stéréologique pour quantifier le nombre de cellules dans les couches parvo- (P) et magnocellulaires (M) du CGLd. Contrairement à notre hypothèse de départ, nous n’avons pas observé de diminution dans le nombre global de neurones dans le CGLd des animaux exposés à l’alcool par rapport à des sujets contrôles, ni une diminution de son volume. Nous avons toutefois observé une diminution de la taille du corps cellulaire seulement dans la population M du CGLd. Ces résultats suggèrent que le système visuel est affecté par une faible exposition à l’alcool durant son développement qui devrait se traduire sur le comportement par des déficits dans les fonctions de la voie M.

Animal movement in dynamic landscapes : interaction between behavioural strategies and resource distributions

Most ecological and evolutionary processes are thought to critically depend on dispersal and individual movement but there is little empirical information on the movement strategies used by animals to find resources. In particular, it is unclear whether behavioural variation exists at all scales, or whether behavioural decisions are primarily made at small spatial scales and thus broad-scale patterns of movement simply reflect underlying resource distributions. We evaluated animal movement responses to variable resource distributions using the grey teal (Anas gracilis) in agricultural and desert landscapes in Australia as a model system. Birds in the two landscapes differed in the fractal dimension of their movement paths, with teal in the desert landscape moving less tortuously overall than their counterparts in the agricultural landscape. However, the most striking result was the high levels of individual variability in movement strategies, with different animals exhibiting different responses to the same resources. Teal in the agricultural basin moved with both high and low tortuosity, while teal in the desert basin primarily moved using low levels of tortuosity. These results call into question the idea that broad-scale movement patterns simply reflect underlying resource distributions, and suggest that movement responses in some animals may be behaviourally complex regardless of the spatial scale over which movement occurs.

Carbon Nanotube – Reduced Graphene Oxide Composites for Thermal Energy Harvesting Applications

By controlling the SWNT-rGO electrode composition and thickness to attain the appropriate porosity and tortuosity, the electroactive surface area is maximized while rapid diffusion of the electrolyte through the electrode is maintained. This leads to an increase in exchange current density between the electrode and electrolyte which results in enhanced thermocell performance.

Cocoon of the silkworm Antheraea pernyi as an example of a thermally insulating biological interface.

Biological materials are hierarchically organized complex composites, which embrace multiple practical functionalities. As an example, the wild silkworm cocoon provides multiple protective functions against environmental and physical hazards, promoting the survival chance of moth pupae that resides inside. In the present investigation, the microstructure and thermal property of the Chinese tussah silkworm (Antheraea pernyi) cocoon in both warm and cold environments under windy conditions have been studied by experimental and numerical methods. A new computational fluid dynamics model has been developed according to the original fibrous structure of the Antheraea pernyi cocoon to simulate the unique heat transfer process through the cocoon wall. The structure of the Antheraea pernyi cocoon wall can promote the disorderness of the interior air, which increases the wind resistance by stopping most of the air flowing into the cocoon. The Antheraea pernyi cocoon is wind-proof due to the mineral crystals deposited on the outer layer surface and its hierarchical structure with low porosity and high tortuosity. The research findings have important implications to enhancing the thermal function of biomimetic protective textiles and clothing.

Utilisation of intensive foraging zones by female Australian fur seals

Within a heterogeneous environment, animals must efficiently locate and utilise foraging patches. One way animals can achieve this is by increasing residency times in areas where foraging success is highest (area-restricted search). For air-breathing diving predators, increased patch residency times can be achieved by altering both surface movements and diving patterns. The current study aimed to spatially identify the areas where female Australian fur seals allocated the most foraging effort, while simultaneously determining the behavioural changes that occur when they increase their foraging intensity. To achieve this, foraging behaviour was successfully recorded with a FastLoc GPS logger and dive behaviour recorder from 29 individual females provisioning pups. Females travelled an average of 118 ± 50 km from their colony during foraging trips that lasted 7.3 ± 3.4 days. Comparison of two methods for calculating foraging intensity (first-passage time and first-passage time modified to include diving behaviour) determined that, due to extended surface intervals where individuals did not travel, inclusion of diving behaviour into foraging analyses was important for this species. Foraging intensity 'hot spots' were found to exist in a mosaic of patches within the Bass Basin, primarily to the south-west of the colony. However, the composition of benthic habitat being targeted remains unclear. When increasing their foraging intensity, individuals tended to perform dives around 148 s or greater, with descent/ascent rates of approximately 1.9 m•s-1 or greater and reduced postdive durations. This suggests individuals were maximising their time within the benthic foraging zone. Furthermore, individuals increased tortuosity and decreased travel speeds while at the surface to maximise their time within a foraging location. These results suggest Australian fur seals will modify both surface movements and diving behaviour to maximise their time within a foraging patch.

Nanopore size growth and ultrafiltration performance of SnO2 ceramic membranes prepared by sol-gel route

Supported ceramic membranes have been produced by the sol-casting procedure from aqueous colloidal suspensions prepared by the sol-gel route. Coatings on a tubular alumina support have been successfully performed leading to crack free layers. Samples have been sintered at 400, 500 and 600 degreesC, and the effect of heating treatment on the nanostructure and on the ultrafiltration properties are analyzed. The characterization has been done by high resolution scanning electron microscopy, nitrogen adsorption-desorption isotherms, water permeation and cut-off determination using polyethylene glycol standard solutions. The micrographs have revealed that grains and pore size increase with the temperature, whereas their shape remains invariant. This results is in agreements with N-2 adsorption-desorption analyses, which have revealed that the mean pore size diameter increases from 4 to 10 nm as the sintering temperature increases from 400 to 600 degreesC, while the total porosity remains constant. Furthermore, the tortuosity, calculated from water permeability, is essentially invariant with the sintering temperatures. The membranes cut-off, determined with a retention rate equal to 95%, are 3500, 6500 and 9000 g . mol(-1) for 400, 500 and 600 degreesC, respectively, showing that the permeation properties of SnO2 ultrafiltration membranes can easily be controlled by sintering condition.

Application of impedance spectroscopy to evaluate the effect of different setting accelerators on the developed microstructures of calcium phosphate cements

The main goal of the present study was to evaluate the effect of different setting accelerator agents on the developed microstructures of calcium phosphate cements (CPCs) by employing the impedance spectroscopy (IS) technique. Six compositions of CPCs were prepared from mixtures of commercial dicalcium phosphate anhydrous (DCPA) and synthesized tetracalcium phosphate (TTCP) as the solid phases. Two TTCP/DCPA molar ratios (1/1 and 1/2) and three liquid phases (aqueous solutions of Na(2)HPO(4), tartaric acid (TA) and oxalic acid (OA), 5% volume fraction) were employed. Initial (I) and final (F) setting times of the cement pastes were determined with Gillmore needles (ASTM standard C266-99). The hardened samples were characterized by X-ray powder diffraction (XRD), Fourier transformed infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and apparent density measurements. The IS technique was employed as a non-destructive tool to obtain information related to porosity, tortuosity and homogeneity of the cement microstructures. The formulation prepared from a TTCP/DCPA equimolar mixture and OA as the liquid phase presented the shortest I and F (12 and 20 min, respectively) in comparison to the other studied systems. XRD analyses revealed the formation of low-crystallinity hydroxyapatite (HA) (as the main phase) as well as the presence of little amounts of unreacted DCPA and TTCP after 24 h hardening in 100% relative humidity. This was related to the proposed mechanisms of dissolution of the reactants. The bands observed by FTIR allowed identifying the presence of calcium tartrate and calcium oxalate in the samples prepared from TA and OA, in addition to the characteristic bands of HA. High degree of entanglement of the formed crystals was observed by SEM in samples containing OA. SEM images were also correlated to the apparent densities of the hardened cements. Changes in porosity, tortuosity and microstructural homogeneity were determined in all samples, from IS results, when the TTCP/DCPA ratio was changed from 1/1 to 1/2. The cement formulated from an equimolar mixture of TTCP/DCPA and OA as the liquid phase presented setting times, degree of conversion to low-crystallinity HA and microstructural features suitable to be used as potential bone cement in clinical applications. The IS technique was shown to be a very sensitive and non-destructive tool to relate the paste composition to the developed microstructures. This approach could be very useful to develop calcium phosphate bone cements for specific clinical demands.

Condutividade hidráulica saturada e direcional em xisto: ensaios em laboratório. -

Pós-graduação em Geociências e Meio Ambiente - IGCE

Kawasaki disease and juvenile systemic lupus erythematosus

Kawasaki disease (KD) is a common vasculitis in childhood. To the authors' knowledge, only one case of juvenile systemic lupus erythematosus (JSLE)-like onset mimicking KD and another case of KD and JSLE association have previously been described. However, the prevalence of this association of the two diseases was not reported. Therefore, over 27 consecutive years, 5419 patients were followed at the Pediatric Rheumatology Unit and 271 (5%) of them met the ACR classification criteria for JSLE. Two (0.7%) of them were female. These also had KD according to European League against Rheumatism / Paediatric Rheumatology European Society (EULAR/PReS) consensus criteria and are described in this report. One case was a 13-year-old who presented all six KD criteria. Echocardiogram showed pericardial effusion, dilatation and tortuosity of right and left coronary, and her symptoms promptly improved after treatment with intravenous immunoglobulin (IVIG). Lupus diagnosis was established a few days later. Another case was a 4-year-old who had also met all six KD criteria, with improvement after IVIG, and lupus diagnosis was made 1 year later. In conclusion, the frequency of the association between these two autoimmune diseases was rare. The occurrence of a second autoimmune systemic disease in a patient with a history of KD should also be considered. Furthermore, the initial presentation of lupus may mimic KD. Lupus (2012) 21, 89-92.

Imaging and modeling of pore scale processes in porous media using X-ray computed tomography and lattice Boltzmann solver

In der Erdöl– und Gasindustrie sind bildgebende Verfahren und Simulationen auf der Porenskala im Begriff Routineanwendungen zu werden. Ihr weiteres Potential lässt sich im Umweltbereich anwenden, wie z.B. für den Transport und Verbleib von Schadstoffen im Untergrund, die Speicherung von Kohlendioxid und dem natürlichen Abbau von Schadstoffen in Böden. Mit der Röntgen-Computertomografie (XCT) steht ein zerstörungsfreies 3D bildgebendes Verfahren zur Verfügung, das auch häufig für die Untersuchung der internen Struktur geologischer Proben herangezogen wird. Das erste Ziel dieser Dissertation war die Implementierung einer Bildverarbeitungstechnik, die die Strahlenaufhärtung der Röntgen-Computertomografie beseitigt und den Segmentierungsprozess dessen Daten vereinfacht. Das zweite Ziel dieser Arbeit untersuchte die kombinierten Effekte von Porenraumcharakteristika, Porentortuosität, sowie die Strömungssimulation und Transportmodellierung in Porenräumen mit der Gitter-Boltzmann-Methode. In einer zylindrischen geologischen Probe war die Position jeder Phase auf Grundlage der Beobachtung durch das Vorhandensein der Strahlenaufhärtung in den rekonstruierten Bildern, das eine radiale Funktion vom Probenrand zum Zentrum darstellt, extrahierbar und die unterschiedlichen Phasen ließen sich automatisch segmentieren. Weiterhin wurden Strahlungsaufhärtungeffekte von beliebig geformten Objekten durch einen Oberflächenanpassungsalgorithmus korrigiert. Die Methode der „least square support vector machine” (LSSVM) ist durch einen modularen Aufbau charakterisiert und ist sehr gut für die Erkennung und Klassifizierung von Mustern geeignet. Aus diesem Grund wurde die Methode der LSSVM als pixelbasierte Klassifikationsmethode implementiert. Dieser Algorithmus ist in der Lage komplexe geologische Proben korrekt zu klassifizieren, benötigt für den Fall aber längere Rechenzeiten, so dass mehrdimensionale Trainingsdatensätze verwendet werden müssen. Die Dynamik von den unmischbaren Phasen Luft und Wasser wird durch eine Kombination von Porenmorphologie und Gitter Boltzmann Methode für Drainage und Imbibition Prozessen in 3D Datensätzen von Böden, die durch synchrotron-basierte XCT gewonnen wurden, untersucht. Obwohl die Porenmorphologie eine einfache Methode ist Kugeln in den verfügbaren Porenraum einzupassen, kann sie dennoch die komplexe kapillare Hysterese als eine Funktion der Wassersättigung erklären. Eine Hysterese ist für den Kapillardruck und die hydraulische Leitfähigkeit beobachtet worden, welche durch die hauptsächlich verbundenen Porennetzwerke und der verfügbaren Porenraumgrößenverteilung verursacht sind. Die hydraulische Konduktivität ist eine Funktion des Wassersättigungslevels und wird mit einer makroskopischen Berechnung empirischer Modelle verglichen. Die Daten stimmen vor allem für hohe Wassersättigungen gut überein. Um die Gegenwart von Krankheitserregern im Grundwasser und Abwässern vorhersagen zu können, wurde in einem Bodenaggregat der Einfluss von Korngröße, Porengeometrie und Fluidflussgeschwindigkeit z.B. mit dem Mikroorganismus Escherichia coli studiert. Die asymmetrischen und langschweifigen Durchbruchskurven, besonders bei höheren Wassersättigungen, wurden durch dispersiven Transport aufgrund des verbundenen Porennetzwerks und durch die Heterogenität des Strömungsfeldes verursacht. Es wurde beobachtet, dass die biokolloidale Verweilzeit eine Funktion des Druckgradienten als auch der Kolloidgröße ist. Unsere Modellierungsergebnisse stimmen sehr gut mit den bereits veröffentlichten Daten überein.

Critical review of coupled flux formulations for clay membranes based on nonequilibrium thermodynamics

Extensive research conducted over the past several decades has indicated that semipermeable membrane behavior (i.e., the ability of a porous medium to restrict the passage of solutes) may have a significant influence on solute migration through a wide variety of clay-rich soils, including both natural clay formations (aquitards, aquicludes) and engineered clay barriers (e.g., landfill liners and vertical cutoff walls). Restricted solute migration through clay membranes generally has been described using coupled flux formulations based on nonequilibrium (irreversible) thermodynamics. However, these formulations have differed depending on the assumptions inherent in the theoretical development, resulting in some confusion regarding the applicability of the formulations. Accordingly, a critical review of coupled flux formulations for liquid, current, and solutes through a semipermeable clay membrane under isothermal conditions is undertaken with the goals of explicitly resolving differences among the formulations and illustrating the significance of the differences from theoretical and practical perspectives. Formulations based on single-solute systems (i.e., uncharged solute), single-salt systems, and general systems containing multiple cations or anions are presented. Also, expressions relating the phenomenological coefficients in the coupled flux equations to relevant soil properties (e.g., hydraulic conductivity and effective diffusion coefficient) are summarized for each system. A major difference in the formulations is shown to exist depending on whether counter diffusion or salt diffusion is assumed. This difference between counter and salt diffusion is shown to affect the interpretation of values for the effective diffusion coefficient in a clay membrane based on previously published experimental data. Solute transport theories based on both counter and salt diffusion then are used to re-evaluate previously published column test data for the same clay membrane. The results indicate that, despite the theoretical inconsistency between the counter-diffusion assumption and the salt-diffusion conditions of the experiments, the predictive ability of solute transport theory based on the assumption of counter diffusion is not significantly different from that based on the assumption of salt diffusion, provided that the input parameters used in each theory are derived under the same assumption inherent in the theory. Nonetheless, salt-diffusion theory is fundamentally correct and, therefore, is more appropriate for problems involving salt diffusion in clay membranes. Finally, the fact that solute diffusion cannot occur in an ideal or perfect membrane is not explicitly captured in any of the theoretical expressions for total solute flux in clay membranes, but rather is generally accounted for via inclusion of an effective porosity, n(e), or a restrictive tortuosity factor, tau(r), in the formulation of Fick's first law for diffusion. Both n(e) and tau(r) have been correlated as a linear function of membrane efficiency. This linear correlation is supported theoretically by pore-scale modeling of solid-liquid interactions, but experimental support is limited. Additional data are needed to bolster the validity of the linear correlation for clay membranes. Copyright 2012 Elsevier B.V. All rights reserved.

Critical Review of Coupled Flux Formulations for Clay Membranes Based on Nonequilibrium Thermodynamics

Extensive research conducted over the past several decades has indicated that semipermeable membrane behavior (i.e., the ability of a porous medium to restrict the passage of solutes) may have a significant influence on solute migration through a wide variety of clay-rich soils, including both natural clay formations (aquitards, aquicludes) and engineered clay barriers (e.g., landfill liners and vertical cutoff walls). Restricted solute migration through clay membranes generally has been described using coupled flux formulations based on nonequilibrium (irreversible) thermodynamics. However, these formulations have differed depending on the assumptions inherent in the theoretical development, resulting in some confusion regarding the applicability of the formulations. Accordingly, a critical review of coupled flux formulations for liquid, current, and solutes through a semipermeable clay membrane under isothermal conditions is undertaken with the goals of explicitly resolving differences among the formulations and illustrating the significance of the differences from theoretical and practical perspectives. Formulations based on single-solute systems (i.e., uncharged solute), single-salt systems, and general systems containing multiple cations or anions are presented. Also, expressions relating the phenomenological coefficients in the coupled flux equations to relevant soil properties (e.g., hydraulic conductivity and effective diffusion coefficient) are summarized for each system. A major difference in the formulations is shown to exist depending on whether counter diffusion or salt diffusion is assumed. This difference between counter and salt diffusion is shown to affect the interpretation of values for the effective diffusion coefficient in a clay membrane based on previously published experimental data. Solute transport theories based on both counter and salt diffusion then are used to re-evaluate previously published column test data for the same clay membrane. The results indicate that, despite the theoretical inconsistency between the counter-diffusion assumption and the salt-diffusion conditions of the experiments, the predictive ability of solute transport theory based on the assumption of counter diffusion is not significantly different from that based on the assumption of salt diffusion, provided that the input parameters used in each theory are derived under the same assumption inherent in the theory. Nonetheless, salt-diffusion theory is fundamentally correct and, therefore, is more appropriate for problems involving salt diffusion in clay membranes. Finally, the fact that solute diffusion cannot occur in an ideal or perfect membrane is not explicitly captured in any of the theoretical expressions for total solute flux in clay membranes, but rather is generally accounted for via inclusion of an effective porosity, ne, or a restrictive tortuosity factor, tr, in the formulation of Fick's first law for diffusion. Both ne and tr have been correlated as a linear function of membrane efficiency. This linear correlation is supported theoretically by pore-scale modeling of solid-liquid interactions, but experimental support is limited. Additional data are needed to bolster the validity of the linear correlation for clay membranes.

The role of diameter versus volume as the best prognostic measurement of abdominal aortic aneurysms

Accurate measurement of abdominal aortic aneurysms is necessary to predict rupture risk and, more recently, to follow aneurysm sac behavior following endovascular repair. Up until this point, aneurysm diameter has been the most common measurement utilized for these purposes. Although aneurysm diameter is predictive of rupture, accurate measurement is hindered by such factors as aortic tortuosity and interobserver variability, and it does not account for variations in morphology such as saccular aneurysms. Additionally, decreases in aneurysm diameter do not completely describe the somewhat complex remodeling seen following endovascular repair of aortic aneurysms. Measurement of aneurysm volume has the advantage of describing aneurysm morphology in a multidimensional fashion, but it has not been readily available or easily measured until recently. This has changed with the introduction of commercially available software tools that permit quicker and easier to perform volume measurements. Whether it is time for volume to replace, or compliment, diameter is the subject of the current debate.