pinecone/core-2020-05-10-deduplication huggingface dataset:
Smooth particle hydrodynamics simulations of low Reynolds number flows through porous media

In this paper, a three-dimensional smooth particle hydrodynamics (SPH) simulator for modeling grain scale fluid flow in porous media is presented. The versatility of the SPH method has driven its use in increasingly complex areas of flow analysis, including the characterization of flow through permeable rock for both groundwater and petroleum reservoir research. SPH provides the means to model complex multi-phase flows through such media; however, acceptance of the methodology has been hampered by the apparent lack of actual verification within the literature, particulary in the three-dimensional case. In this paper, the accuracy of SPH is addressed via a comparison to the previously recognized benchmarks of authors such as Sangani and Acrivos (<i>Int. J. Multiphase Flow</i> 1982; <b>8</b>(4): 343–360), Zick and Homsy (<i>J. Fluid Mech</i>. 1982; <b>115</b>:13–26) and Larson and Higdon (<i>Phys. Fluids A</i> 1989; <b>1</b>(1):38–46) for the well-defined classical problems of flow through idealized two- and three-dimensional porous media. The accuracy of results for such low Reynolds number flows is highly dependent on the implementation of no-slip boundary conditions. A new, robust and numerically efficient, method for implementing such boundaries in SPH is presented. Simulation results for friction coefficient and permeability are shown to agree well with the available benchmarks
Dilatancy of granular materials in a strain space multiple mechanism model

A granular material consists of an assemblage of particles with contacts newly formed or disappeared, changing the micromechanical structures during macroscopic deformation. These structures are idealized through a strain space multiple mechanism model as a twofold structure consisting of a multitude of virtual two-dimensional mechanisms, each of which consists of a multitude of virtual simple shear mechanisms of one-dimensional nature. In particular, a second-order fabric tensor describes direct macroscopic stress–strain relationship, and a fourth-order fabric tensor describes incremental relationship. In this framework of modeling, the mechanism of interlocking defined as the energy less component of macroscopic strain provides an appropriate bridge between micromechanical and macroscopic dilative component of dilatancy. Another bridge for contractive component of dilatancy is provided through an obvious hypothesis on micromechanical counterparts being associated with virtual simple shear strain. It is also postulated that the dilatancy along the stress path beyond a line slightly above the phase transformation line is only due to the mechanism of interlocking and increment in dilatancy due to this interlocking eventually vanishing for a large shear strain. These classic postulates form the basis for formulating the dilatancy in the strain space multiple mechanism model. The performance of the proposed model is demonstrated through simulation of undrained behavior of sand under monotonic and cyclic loading
Two-scale modeling of solute dispersion in unsaturated double-porosity media: Homogenization and experimental validation

International audienceA two-scale modeling of solute transport in double-porosity (DP) media under unsaturated water flow conditions is presented. The macroscopic model was developed by applying the asymptotic homogenization method. It is based on theoretical and empirical considerations dealing with the orders of magnitude of characteristic quantities involved in the process. For this purpose a physical model that mimics the behavior of DP medium was built. The resulting two-equation model relies on a coupling exchange term between micro- and macro-porosity subdomains associated with local non-equilibrium solute concentrations. The model was numerically implemented (Comsol Multiphysics®) to simulate the macroscopic one-dimensional physical process taking place into the porous medium of 3D periodic microstructure. A series of dispersion experiments of NaCl solution under unsaturated steady-state flow conditions were performed. The experimental results were used first to calibrate the dispersion coefficient of the model, and second to validate it through two other independent experiments. The excellent agreement between the numerical simulations and the measurements of the time evolution of the non-symmetrical breakthrough curves provides a proof of predictive capacity of the developed model. Copyright © 2010 John Wiley & Sons, Ltd
New concepts in relation to urge and detrusor activity

Investigations of micromotion characteristics of bladder wall strips and pressure wave phenomena in total bladders in vitro and in vivo indicate that micromotion phenomena occur in the bladder wall. Local contractions can occur without an increase in tension or pressure, because other parts are in antiphase. Local contractions stretch surrounding tissues, which can stimulate fast stretch receptors. Synchronisation of these micromotion phenomena appears to be possible. Hence, above threshold levels urge can theoretically occur, even in the absence of a pressure increase. This hypothesis could explain the weak relation between urge and pressure. The distinction between motor and sensory urge could be artifactual based on a misunderstanding of fundamental bladder wall processes
Effect of partial urethral obstruction on force development of the guinea pig bladder

We created gradual partial urethral obstruction in 20 guinea pigs using silver jeweler's jump rings. After 4 or 8 weeks obstruction all animals underwent cystometry and were assigned to one of five urodynamic categories: normal, high pressure voiding, unstable, low compliance, or decompensated. After sacrifice, the contractile responses of bladder strips to electrical field stimulation of intramural nerves, direct electrical muscle stimulation, 0.1 mM carbachol, and high K + solution were sampled by computer for phase plot analysis. Following 8 weeks obstruction, the value of the phase plot parameter Fiso, indicative of the number of contractile muscle units, was reduced to 60% of the control response to nerve stimulation (P < 0.05) and to 77% of the control response to carbachol stimulation (P < 0.05). Parameter C, the slope of the phase plot (indicative of unit recruitment during force development), was unchanged for all forms of stimulation. Although in the latter case not statistically significant, obstruction affected responses to nerve and muscle stimulation similarly suggesting that muscle change may possibly be a common denominator of dysfunction. In view of the reduction in Fiso and the increase in bladder weight, instability may represent a more advanced form of dysfunction due to obstruction than high pressure voiding
Statistical evaluation of the function of the 1992 International Continence Society scientific committee

Papers submitted to the International Confidence Society arc read by the six members of the scientific committee, who assign three scores to each paper, one for its originality, one for its scientific value, and one for its academic or clinical interest. Following discussion at the scientific committee meeting, a program is made from the abstracts with the highest scores. In this study statistical properties of the assigned score values for the 1992 ICS meeting are discussed It is concluded that the three scores do not measure independent properties of the abstracts, that different abstract types (for instance “clinical” and “basic” papers) are scored differently by the different committee members, that there is a significant consensus among the committee members, that the scientific committee meeting has a relatively small effect on the scores, and that different abstract types are not equally represented in the final program
Contractility of the guinea pig bladder measured in situ and in vitro

To study the relative importance of neurogenic factors in detrusor contractility and to relate a total bladder in vitro contractility model to a previously described bladder wall strip model, active intravesical pressure values were compared in situ and in vitro in eight male guinea pigs. In situ, the active pressure was measured in spontaneous isometric and nonisometric micturition contractions. In vitro, the active pressure was measured in isometric contractions of the same bladders, developed in response to optimal electrical stimulation. The volume dependence of the active pressure generated by the bladder was measured in vitro in order to relate bladder capacity to the volume where the generated force is maximal and to determine the optimal volume at which to study detrusor contractility. The results indicated that in normal micturition the detrusor muscle was not fully stimulated: active pressure in isometric contractions in vivo was about 60% of the pressure values attained in vitro at the same bladder volume. Most micturitions occurred at a volume where the active pressure generated in vitro was about 80% of the maximal pressure. The active pressure-bladder volume relationship complied with the sliding filament-cross bridge theory. In whole bladder preparations active stress was about twice as high as in strips
Estimation of the lag time between detrusor pressure- and flow rate- signals

In a urodynamic measurement setup there is a considerable spatial separation between the uroflowmeter and the location where the detrusor pressure is measured. Therefore, a “time shift” (or lag time correction) has to be applied to one of these signals in order to align related samples in studies where pressure and flow rate are considered simultaneously (e.g., assessment of bladder contractility or bladder outlet resistance).\ud
\ud
Currently, a heuristic value for this time shift of 0.8 s is applied. In this article, we present a method to estimate the lag time directly from the measurements.\ud
\ud
Using this method we have found, amongst others, that the mean lag time in our clinic is 0.6 s for males, 0.4 s for females voiding in sitting position, and 1.1 s for females voiding in standing position using a special receptacle in video urodynamics. Furthermore, we found that sphincter/urethral activity during voiding (which causes a drop in flow rate and an accompanying increase in detrusor pressure) is associated (on average) with shorter lag times than straining (when a positive pressure rise accompanies an increase in flow rate). Additionally strong evidence is provided that lag time correction is not a major source of error in urodynamics
Direct inhibition of rat detrusor muscle contraction by erythromycin

This is the authors' final draft of the paper published as Neurourology and Urodynamics, 2004, 23(3), pp. 273-9.Purpose\ud
Detrusor instability is a common problem in the elderly, which is usually treated with anti-cholinergic medication. This study investigates the effect of erythromycin on rat detrusor muscle contractile response to characterise its potential as an alternative inhibitor of bladder muscle contraction.\ud
Materials and Methods\ud
\ud
Strips of rat detrusor muscle were suspended in a perfusion organ bath. The contractile response to direct muscle stimulation, electrical field stimulation (EFS, 0.5–60 Hz), carbachol (10−5 M), and potassium (10–80 × 10−3 M) were determined before and after the addition of erythromycin (10−4–10−3 M). The contractile response to carbachol (10−5 M) in the presence of nifedipine (10−8 or 10−6 M) or in calcium-free Kreb's solution was also determined in the absence and presence of erythromycin.\ud
Results\ud
\ud
Erythromycin 5 × 10−4 M inhibited the maximum contractile response to EFS, carbachol, and potassium by 38% (P < 0.01), 62% (P < 0.001), and 17% (P < 0.05), respectively, but did not significantly reduce the response to direct muscle stimulation. The atropine-resistant component of EFS-evoked contraction was inhibited by 19.5% (P < 0.01) in the presence of erythromycin. In calcium-free Krebs solution, the maximum contractile response to carbachol was reduced by 42% of control (P < 0.0001) and nifedipine 10−8 M had no additional effect. When erythromycin 5 × 10−4 M was added together with nifedipine 10−8 M, the response to carbachol was inhibited by a further 25% (P < 0.005).\ud
Conclusions\ud
\ud
Erythromycin inhibits rat detrusor muscle contraction through the inhibition of calcium influx and the modulation of intracellular calcium movement
On the origin of bladder sensing: Tr(i)ps in urology

The mammalian TRP family consists of 28 channels that can be subdivided into 6 different classes: TRPV (vanilloid), TRPC (canonical), TRPM (Melastatin), TRPP (Polycystin), TRPML (Mucolipin), and TRPA (Ankyrin). TRP channels are activated by a diversity of physical (voltage, heat, cold, mechanical stress) or chemical (pH, osmolality) stimuli and by binding of specific ligands, enabling them to act as multifunctional sensors at the cellular level. Currently, a lot of scientific research is devoted to these channels and their role in sensing mechanisms throughout the body. In urology, there's a growing conviction that disturbances in afferent (sensory) mechanisms are highly important in the pathogenesis of functional problems. Therefore, the TRP family forms an interesting new target to focus on. In this review we attempt to summarize the existing knowledge about TRP channels in the urogenital tract. So far, TRPV1, TRPV2, TRPV4, TRPM8, and TRPA1 have been described in different parts of the urogenital tract. Although only TRPV1 (the vanilloid receptor) has been extensively studied so far, more evidence is slowly accumulating about the role of other TRP channels in the (patho)physiology of the urogenital tract.status: publishe
Proof of principle: The effect of antimuscarinics on bladder filling sensations in healthy subjects-A placebo controlled double blind investigation using 4 and 8 mg tolterodine extended release

AIMS: There is evidence that antimuscarinic drugs have depressant influence not only on bladder muscle activity, but also on bladder sensations. The aim of this study was to evaluate the effect of a single dose tolterodine extended release (ER) 4 and 8 mg on bladder sensations during filling cystometry. METHODS: After approval of the local ethics committee, 30 healthy female subjects (23.7 +/- 2.3 years) were included and randomly assigned to three groups: (A) placebo, (B) tolterodine ER 4 mg, and (C) tolterodine ER 8 mg in a double blind manner. Measurements were performed at baseline and 4 hr postmedication in each group, consisting of: (1) Filling cystometry with 25 ml/min at which subjects had to indicate first sensation of filling (FSF), first desire to void (FDV), and strong desire to void (SDV). (2) Uroflowmetry and ultrasound control for residual urine. RESULTS: In the placebo group, filling volumes at FDV and SDV decreased significantly posttreatment. This effect could not be observed for the tolterodine 8 mg group and only at SDV in the 4 mg group. No significant difference between groups was found regarding uroflowmetry parameters and postvoid residual volume. CONCLUSIONS: No increase of filling volumes in healthy subjects could be observed with tolterodine. However, the results suggest that tolterodine is able to alleviate irritation caused by repeated catheterization and cystometry. There was no significant influence of tolterodine ER 4 or 8 mg on voiding function
Researching Bladder Afferents-Determining the Effects of beta(3)-Adrenergic Receptor Agonists and Botulinum Toxin Type-A

A substantial portion of the current research on lower urinary tract dysfunction is focused on afferent mechanisms. The main goals are to define and modulate the signaling pathways by which afferent information is generated, enhanced and conveyed to the central nervous system. Alterations in bladder afferent mechanisms are a potential source of voiding dysfunction and an emerging source for drug targets. Established drug therapies such as muscarinic receptor antagonists, and two emerging therapies, β3-adrenergic receptor agonists and botulinum toxin type-A, may act partly through afferent mechanisms. This review focuses on these two new principles and new and established methods for determining their sites of action. It also provides brief information on the innervation of the bladder, afferent receptors and transmitters and how these may communicate with the urothelium, interstitial cells and detrusor smooth muscle to regulate micturition. Peripheral and central mechanisms of afferent sensitization and myogenic mechanisms that lead to detrusor overactivity, overactive bladder symptoms and urgency sensations are also covered. This work is the result from ‘Think Tank’ presentations, and the lengthy discussions that followed, at the 2010 International Consultation on Incontinence Research Society meeting in Bristol, UK. Neurourol. Urodynam. Neurourol. Urodynam. 30:684–691, 2011. © 2011 Wiley-Liss, In
Bladder compliance what does it represent: Can we measure it, and is it clinically relevant?

Aims To report the conclusion of the Think Thank 8 on Compliance Discussions during the second ICI-RS meeting in 2010. Methods During a 3-day meeting a group of specialists discussed bladder compliance, what it represents, how it can be measured and if it is clinically relevant. Results Bladder compliance is the result of a mathematical calculation of the volume required for a unit rise of pressure measured during a cystometric filling. It gives an indication on how the different mechanisms in the bladder wall react on stretching. There is a need of standardization of measurement and suggestions for this are given in the text. Pitfalls are described and how to avoid them. There is a wide range of compliance values in healthy volunteers and groups of patients. Poor compliance needs to be defined better as it can have significant clinical consequences. Prevention and treatment are discussed. Conclusion If compliance is correctly measured and interpreted, it has importance in urodynamic testing and gives information relevant for clinical management. Neurourol. Urodynam. Neurourol. Urodynam. 30:714–722, 201
Activation of the striated urethral sphincter to maintain continence during dynamic tasks in healthy men

Aims  Function of the striated urethral sphincter (SUS) in men is debated. Current evidence is limited to electromyographic (EMG) recordings made with concentric needle electrodes in supine. Understanding of SUS function requires investigation of SUS EMG activity using new recording techniques in dynamic tasks. The aim of this study was to evaluate timing and amplitude of SUS EMG at rest and during dynamic tasks that challenge continence by increasing intra‐abdominal pressure (IAP).    Methods  Investigative study of five healthy men aged 25–39 years. Measurements included SUS, anal sphincter (AS), and transversus abdominus (TrA) EMG, and IAP (recorded with a nasogastric pressure catheter). Participants performed four tasks that challenged postural control in standing (single and repetitive arm movement, stepping and load catching).    Results  IAP amplitude and SUS activity were linearly correlated during repetitive arm movement (R 2 : 0.67–0.88). During stepping SUS EMG onset preceded the IAP increase, but followed it with rapid arm movements. When the trunk was loaded unpredictably onset of SUS generally followed the increase in IAP. The modest sample size meant only younger men were tested. Future studies might investigate healthy older men or those with certain pathologies.    Conclusions  Data show that SUS activity increases proportionally with IAP. This provided evidence that SUS contributes to continence when IAP is increased, and that postural control of the trunk involves activation of this muscle. Neurourol. Urodynam. 31:36–43, 2012. © 2011 Wiley Periodicals, Inc
A comparison of the effect of age on levator ani and obturator internus muscle cross‐sectional areas and volumes in nulliparous women

Aims  Functional tests have demonstrated minimal loss of vaginal closure force with age. So we tested the null hypotheses that age neither affects the maximum cross‐sectional area (CSA) nor the volume of the levator muscle. Corresponding hypotheses were also tested in the adjacent obturator internus muscle, which served as a control for the effect of age on appendicular muscle in these women.    Methods  Magnetic resonance images of 15 healthy younger (aged 21–25 years) and 12 healthy older nulliparous women (aged >63 years) were selected to avoid the confounding effect of childbirth. Models were created from tracing outlines of the levator ani muscle in the coronal plane, and obturator internus in the axial plane using 3D Slicer v. 3.4. Muscle volumes were calculated using Slicer, while CSA was measured using Imageware™ at nine locations. The hypotheses were tested using repeated measures analysis of variance with  P  < 0.05 being considered significant.    Results  The effect of age did not reach statistical significance for the decrease in levator ani muscle maximum CSA or the decrease in volume (4.3%,  P  = 0.62 and 10.9%, 0.12, respectively). However, age did significantly adversely decrease obturator internus muscle maximum CSA and volume (24.5% and 28.2%,  P  < 0.001, respectively). Significant local age‐related changes were observed dorsally in both muscles.    Conclusions  Unlike the adjacent appendicular muscle, obturator internus, the levator ani muscle in healthy nullipara does not show evidence of significant age‐related atrophy. Neurourol. Urodynam. 31:481–486, 2012. © 2012 Wiley Periodicals, Inc
Neuronal-derived nitric oxide modulates the activity of mouse detrusor smooth muscle

Aims We investigated the roles of neuronal-derived nitric oxide (NO) in the modulation of spontaneous activity of mouse detrusor smooth muscle. Methods Detrusor smooth muscle strips were isolated from nNOS gene knock-out (nNOS ) mice and their wild type siblings (nNOS ). The properties of smooth muscle cells were assessed using intracellular electrophysiology and Ca imaging by laser-scanning confocal microscopy. The effects of an nNOS inhibitor, 7-nitro indazole (7-NI) on electrically evoked contractility were assessed using nNOS mouse detrusor strips. Results In spontaneously active cells, the frequency of spontaneous action potentials (sAPs) and whole cell Ca flashes in nNOS preparations was lower than that in the nNOS preparations. The frequency of sAPs was enhanced by a nitric oxide donor, diethylamine NONOate sodium salt (NONOate; 100μM), both when used alone and when the cGMP pathway was blocked by 1H-[1,2,4] oxadiazolo [4,3-a] quinoxalin-1-one (ODQ, 10μM). 7-NI (100μM) significantly suppressed the electrically evoked contraction of mouse detrusor strips. Conclusions We suggest that neuronal-derived NO facilitates the generation of spontaneous activity via a cGMP-independent pathway, and consequently enhances the evoked contraction of detrusor. Dysregulation of nNOS containing nerves may underlie bladder pathologies. Copyright © 2012 Wiley Periodicals, Inc