Voiding Efficiency Research Articles

Analysis of the Relationship between Void Direction and Closure Efficiency in Forging Process

In this paper, both the numerical simulation and the experimental test are carried out to analyze the relationship between the direction and closure efficiency of voids during the forging process. The closing behaviors of through holes which are parallel and perpendicular to the pressure direction respectively are studied in comparison. Furthermore, the stress status and crash degree of internal voids with different axial ratio are examined to analysis the relationship between the closure efficiency and the axis direction. Finally, a method to determine the closure of voids by using stress curves is proposed.

Numerical study of fracture arrest on snow cover

Under the hypothesis of a perfectly brittle phenomenon, avalanche triggering can be investigated numerically by means of Linear Elastic Fracture Mechanics (LEFM). Since, however, the real phenomenon is intrinsically dynamical, another aspect to investigate is represented by dynamic fracture propagation. In this paper, we model dynamic crack propagation into a dry snow slab and we investigate the possibility to arrest the crack propagation through the presence of weak zones distributed along the extension of the snow slope. Assuming that the weak layer is almost collapsed, we simulate the efficiency of artificial voids in the slab to arrest fracture propagation, into the framework of Dynamical Fracture Mechanics. We put forward here a new philosophy for the use of artificial discontinuities (void) into the snowpack able to perform as crack arresters distributed along the snow slope area: the target is to split a large avalanche slab into smaller slabs, causing small avalanches to propagate with less catastrophic effects.

Comparison of 2 Techniques to Predict Voiding Efficiency After Inpatient Urogynecologic Surgery

We compared 2 techniques used to assess adequate postoperative bladder emptying. We performed a prospective, randomized, crossover study of 2 voiding trial techniques. 1) For back fill the bladder is filled with 300 cc saline before the Foley catheter is removed. 2) For auto fill the catheter is removed and the bladder is allowed to fill spontaneously. Patients were randomized into 2 groups for voiding trials, including group 1-auto fill followed by back fill or group 2-back fill followed by auto fill. Within 15 minutes of each void we measured post-void residual urine by straight catheterization. A void of two-thirds or greater of total bladder volume (voided volume plus post-void residual urine) at void 2 of the 2 voids was considered successful voiding. Patients who voided successfully were discharged home without a urethral catheter. We used the chi-square test with κ to determine successful bladder emptying. We recruited 79 patients, of whom 65 with a mean age of 59.7 years (range 33 to 81) had complete data sets available for analysis. Of the patients 38 (58%) underwent prolapse repair only, 1 (2%) underwent a continence procedure only and 26 (40%) underwent each procedure. The back fill void trial correlated better with a successful voiding trial than the auto fill trial (κ = 0.91, 95% CI 0.81-1.00 vs κ = 0.56, 95% CI 0.39-0.74). Overall 40.5% of patients had an unsuccessful void trial on day 1 postoperatively and were discharged home with a catheter. None subsequently experienced urinary retention. The back fill technique appears to be a better predictor of adequate postoperative bladder emptying than the auto fill technique for inpatient void trials.

Effects of cholinesterase inhibition in supraspinal and spinal neural pathways on the micturition reflex in rats

To investigate whether activation of brain and spinal cholinergic pathways affects the micturition reflex in rats. The effects of intracerebroventricular (i.c.v.) or intrathecal (i.t.) administration of neostigmine as a cholinesterase inhibitor and oxotremorine-M (OXO-M) as a muscarinic acetylcholine receptor (mAChRs) agonist, on the micturition reflex were evaluated by infusion cystometrography (CMG) in urethane-anaesthetized untreated rats or rats pretreated with capsaicin. Neostigmine injected i.c.v. increased bladder capacity (BC) and pressure threshold (PT) dose-dependently, with an increase in maximum voiding pressure (MVP) and a decrease in voiding efficiency (VE) at higher doses. Also, neostigmine injected i.t. increased the BC and PT dose-dependently without changing MVP or VE, and these effects were not apparent in capsaicin-pretreated rats. In both routes, atropine as an antagonist of mAChRs, but not mecamylamine as a nicotinic-AChR antagonist, almost completely antagonized the effects of neostigmine. The rank order of potencies of the antagonists for increasing effects of BC induced by 1 nmol of neostigmine was: pirenzepine (an M(1) mAChR antagonist) = atropine > 4-DAMP (an M(3) mAChR antagonist) " methoctramine (an M(2) mAChR antagonist) and tropicamide (an M(4) mAChR antagonist) via the i.c.v. route; and atropine > methoctramine > pirenzepine > tropicamide and 4-DAMP via the i.t. route, respectively. OXO-M injected via i.c.v. and i.t. had the same effects on BC, PT, MVP and VE as neostigmine by i.c.v. and i.t., respectively. These results indicate that activation of muscarinic cholinergic mechanisms by the cholinesterase inhibitor in the brain and spinal cord can inhibit the micturition reflex, mainly by affecting afferent pathways. These mAChR-induced inhibitory effects seem to be mediated through M(1)/M(3) receptor subtypes in the brain, while in the spinal cord, the M(1)/M(2) receptor subtypes might be involved in inhibitory effects, which are mediated via inhibition of mechanoceptive C-fibre afferent pathways.

Re-established micturition reflexes show differential activation patterns after lumbosacral ventral root avulsion injury and repair in rats

Previous studies have demonstrated that an acute implantation of lesioned lumbosacral ventral roots into the rat conus medullaris (CM) results in functional reinnervation of the lower urinary tract (LUT). Although the root implantation procedure results in a return of reflexive micturition, voiding efficiency (VE) remains incompletely recovered. Here, we performed a detailed urodynamic analysis of cystometry and external urethral sphincter (EUS) electromyography (EMG) recordings to determine underlying mechanisms for the incompletely recovered VE. For this purpose, adult female rats were studied at 12 weeks after a bilateral L5–S2 ventral root avulsion injury followed by an acute surgical implantation of the avulsed L6 and S1 ventral roots into the CM ( n = 6). Age-matched sham-operated rats ( n = 6) were included for control purposes. Compared to sham-operated controls, rats of the implanted series showed 1) reflex bladder contractions with a significantly shortened urine expulsion phase, 2) markedly decreased phasic EUS EMG activity during micturition, and 3) a pronounced bladder–sphincter dys-coordination, as demonstrated by a significantly delayed onset of the switch from low-amplitude tonic EUS EMG activity to either phasic EUS EMG activity or a large-amplitude tonic EUS EMG activity during the urine expulsion phase. Our findings provide a mechanistic explanation for the incomplete recovery of the VE following implantation of avulsed ventral roots into the spinal cord. Our future studies will aim to increase successful axonal regeneration in attempts to augment the recovery of the LUT after cauda equina injury and repair.

Effect of Menthol on Detrusor Smooth-Muscle Contraction and the Micturition Reflex in Rats

To investigate the effects of menthol, an activator of the temperature-sensitive transient receptor potential family member TRPM8, on detrusor smooth-muscle contraction and the micturition reflex in rats. We evaluated the effect of intravesical infusion of 1 or 3 mM menthol by cystometry in conscious female Sprague-Dawley rats. Some of the animals were pretreated with 125 mg/kg capsaicin subcutaneously 4 days earlier. The parameters measured were voided volume (VV), residual volume (RV), volume threshold for inducing micturition (VT), voiding efficiency (VE), micturition pressure (MP), and pressure threshold for inducing micturition (PT). Strips of detrusor muscle were mounted in organ baths to study the effect of menthol on the contractile response to 0.01 mM carbachol. Intravesical infusion of 3 mM menthol reduced VV by 20%, VT by 19%, and PT by 31%. RV, VE, and MP were unaltered. Capsaicin pretreatment had no effect on baseline cystometric parameters, and 3 mM menthol caused similar reductions in VV (24%), VT (22%), and PT (30%), while having no effect on RV, VE, and MP. Menthol at 0.1, 0.3, and 1 mM inhibited carbachol-induced contractions by 10.7%, 36.7%, and 97.3%, respectively. Our results demonstrated that intravesical infusion of menthol facilitated the micturition reflex, and capsaicin pretreatment had no effect on this response. Menthol inhibited carbachol-induced contraction of the detrusor smooth muscle. This suggests that intravesically infused menthol cannot relax detrusor muscle, and acts on capsaicin-resistant afferents (probably through TRPM8 in urothelium or sensory nerve endings) to facilitate the micturition reflex.

Effect of Bilateral Hypogastric Nerve Transection on Voiding Dysfunction in Rats with Spinal Cord Injury

We determined if bilateral section of the hypogastric nerves (HGN), which provide the major sympathetic input to the urinary bladder neck/proximal urethra, could improve voiding by reducing urethral resistance in conscious, female spinal-cord-injured (SCI) rats 2–3 weeks after T7–9 transection of the spinal cord. Cystometry was performed in animals with HGN intact and with HGN sectioned bilaterally 1–2 h before the experiment. Residual volume (RV), volume threshold for inducing micturition (VT), maximal voiding pressure, and bladder compliance were significantly lower (71, 35, 33, and 31%, respectively) in SCI rats with sectioned HGN than in rats with intact HGN, whereas voided volume (VV), pressure threshold for micturition, and bladder contraction duration (BCD) in the two groups were similar. Voiding efficiency (VE) in the HGN-sectioned group was 36% greater than that in the HGN-intact group. Antagonists for AMPA and NMDA glutamatergic receptors (LY215490 and MK-801, respectively) were administered to rats with sectioned HGN, to determine if activity in the HGN contributes to the previously reported inhibitory effects of these drugs, on voiding function after SCI. MK-801 (3 mg/kg iv) significantly reduced VV (75%) and VE (85%) and increased RV (8-fold), VT (87%), and bladder compliance (60%), whereas LY215490 (10 mg/kg iv) significantly increased VT and BCD by 15 and 19%, respectively. It is concluded that bilateral section of HGN reduces voiding dysfunction in the SCI rat but does not alter the effects of AMPA and/or NMDA glutamatergic receptor antagonists on the micturition reflex in the SCI rat. Thus the effects of these drugs are not dependent on changes in activity of sympathetic axons in the HGN.

Ni reactions with surfaces: dependence of gettering efficiencies for Ni on crystal-growth conditions, back-side-gettering techniques, oxygen precipitates and thermal treatments

We have performed measurements on the gettering efficiencies for Ni in different silicon wafers. Gettering efficiencies were measured of wafers grown by different crystal-growth techniques, such as Czochralski-grown (CZ) and floating zone (FZ), as well as wafers containing crystal-originated particles (COPs) of different size and density. Lightly boron doped CZ wafers covered with an epitaxial layer were also evaluated. In another set of experiments, we compared different back-side-gettering techniques, like poly-silicon, stacking faults and He-implanted back sides and the dependence of back-side gettering on cooling rate and contamination level. Internal surfaces of oxygen precipitates were also investigated. The gettering test started with a reproducible spin-on contamination in the range around 1012 atoms/cm2 and was followed by a thermal treatment to redistribute the Ni impurity in the wafer. Subsequently, wafers were analyzed for their surface and bulk contamination by a novel layer-by-layer etching, stratigraphical technique in combination with inductively coupled plasma mass spectrometry. No detectable gettering effect of COPs was found. FZ wafers differed remarkably in their gettering behavior from CZ wafers, obviously due to differences in aggregated self-point defects. Most remarkably, the deposition process of an epitaxial layer changed the gettering behavior of p/p- wafers. Comparing the gettering efficiencies of different back sides, an extraordinarily high gettering efficiency of He-implanted voids can be anticipated, which was higher than the gettering efficiency of poly-silicon and stacking faults. High cooling rates at the end of the drive-in cycle and low contamination levels lowered the gettering efficiencies of back-side-gettering techniques, suggesting a diffusion-limited gettering process. Based on the dependence of the gettering efficiencies on different drive-in cycles, a surface reaction as a mechanistic initiation of the drive-in must be assumed. Oxygen precipitates exhibited a high gettering effect for Ni contamination. All experimental results are interpreted by available active surfaces in the gettering phases.

Influences of external urethral sphincter relaxation induced by alpha-bungarotoxin, a neuromuscular junction blocking agent, on voiding dysfunction in the rat with spinal cord injury

Objectives. To determine whether external urethral sphincter (EUS) relaxation induced by alpha-bungarotoxin, a highly selective neuromuscular junction blocking agent, could ameliorate voiding dysfunction after spinal cord injury (SCI) in rats. Methods. The effects of intravenous alpha-bungarotoxin (333 μg/kg) were evaluated during cystometry in decerebrate, unanesthetized female Sprague-Dawley rats (250 to 300 g) with spinal cords chronically transected at T7-9 (n = 7) or with normal spinal cords (NSC) (n = 7). Parameters measured included voided volume (VV), residual volume (RV), volume threshold for inducing micturition (VT), voiding efficiency (VE), micturition pressure (MP), pressure threshold for inducing micturition (PT), bladder contraction duration (BCD), and compliance (CP). Results. In SCI rats, treatment with alpha-bungarotoxin improved voiding. The toxin increased VE (31%) and reduced RV (42%), MP (52%), BCD (14%), and VT (31%). VV, PT, and CP were not altered. In NSC rats, alpha-bungarotoxin decreased VE (23%), increased RV (63%), and decreased MP (36%), VV (38%), and VT (20%) but did not change BCD and CP. Conclusions. The results of our study demonstrated that alpha-bungarotoxin improved voiding in SCI rats by reducing urethral outlet resistance. However, in NSC rats, the toxin reduced voiding, probably by suppressing high-frequency phasic sphincter activity, necessary for efficient urine elimination in normal animals. The present results provide further support for the view that drugs that depress striated muscle activity can be useful in the treatment of voiding dysfunction after SCI.

Influence of Glutamate Receptor Antagonists on Micturition in Rats with Spinal Cord Injury

This study was undertaken to determine if an AMPA (LY215490) or an NMDA (MK-801) glutamatergic receptor antagonist can reduce urinary tract dysfunctions related to detrusor hyperreflexia and detrusor–sphincter dyssynergia in awake, spinal cord-injured (SCI) rats. Experiments were performed on female Sprague–Dawley rats in which the spinal cord was completely transected at T8–10 level, 2–3 weeks prior to performing an intravesical continuous infusion cystometrogram (CMG). Bladder volume threshold (VT) for inducing voiding and voiding efficiency (VE) were determined by measuring voided volumes and residual volumes (RV). After control CMGs were performed, cumulative intravenous doses of LY215490 (0.1, 1, and 10 mg/kg) or MK-801 (0.03, 0.3, and 3 mg/kg) were administered at 120-min intervals. Small doses of LY215490 (0.1 mg/kg) or MK-801 (0.03 and 0.3 mg/kg) did not affect any parameters. A large dose (10 mg/kg) of LY215490 decreased maximal voiding pressure (MVP) by 27% and increased RV by 119% and VT by 58% but did not decrease VE. The highest cumulative dose (3 mg/kg) of MK-801 significantly increased RV by 134% and VT by 44% and markedly decreased VE by 60% and MVP by 18%. The effects of LY215490 to reduce MVP and increase VT without changing VE suggest that an AMPA receptor antagonist might be useful in treating detrusor–sphincter dyssynergia and bladder hypertrophy after SCI. The effect of MK-801 to markedly reduce VE indicates that NMDA receptor antagonists may exacerbate neurogenic bladder dysfunction in SCI patients.

Voids in silicon as sink for interstitials

Transmission electron microscopy has been extensively used to quantify the reduction of extended defects formation in B- (up to 2 × 10 15/cm 2 at 80 keV) implanted regions of silicon crystals annealed at high temperatures. The suppression of dislocation formation does not depend on the depth at which voids are located, on their density and on the purity of the adopted silicon wafer. The carrier mobility measured in samples containing void layers is ideal, confirming that the presence of voids inhibits defect formation while they do not influence carrier mobility. Also B diffusivity, which is proportional to the interstitials concentration, is decreased when a void layer is present. The effects were observed for thermal treatments at temperatures higher than 1000°C. The results are interpreted on the basis of the measured efficiency of voids for the capture of interstitial silicon atoms.

Secondary defect dissolution by voids in silicon

Clustering of point defects into dislocations as a consequence of ion implantation and annealing in silicon has been inhibited through the presence of cavities produced by helium ion implantation and located at depths up to 1 μm. We will show that annealing at 1200 °C will result in the complete absence of extended defects for the case of either partial damage produced by boron ion implantation or continuous amorphous layers produced by germanium implantation. The suppression of dislocation formation does not depend on the depth at which cavities are located, on their density and on the purity of the adopted silicon wafer. The results are interpreted on the basis of the measured efficiency of voids in the capture of interstitial silicon atoms.

Ａｌ‐８％Ｍｇ合金における中間相の析出

The precipitate structure of the intermediate phase β', as well as the secondary defect structure, in an Al-8%Mg alloy was observed to clarify the nucleation process. Peculiar cares were allocated to reveal the effect of gas impurities by changing the casting procedure and the solution treatment atmosphere and by using the TEM tritium autoradiography technique. When the cooling rate during solidification was high enough, i. e. absence of porosity, regular-tetrahedronshaped voids were newly observed as secondary defects. Some of these voids happened to be nucleation sites for β' and thus the precipitate density was relatively high. On the contrary when the cooling rate was slow, voids were replaced by dislocation loops which played no role with respect to the nucleation process. Furthermore, a solution treatment under water vapor stream resulted in a substantial increase in precipitate density owing to the enhancement of the efficiency of voids as nucleation sites. Consequently, void formation was thought to be promoted by hydrogen which was dissolved into the matrix during solidification and then retained inside voids. The relationship between β' precipitation and hydrogen through void formation was confirmed by tritium autoradiography.

Neuroeffector mechanisms in the voiding cycle of the guinea-pig urinary bladder.

1. The effect of drugs expected to modify cholinergic (atropine, physostigmine) or GABA-ergic (GABA, picrotoxin, bicuculline methiodide, BMI) neurotransmission were investigated on the voiding cycle of the urinary bladder in urethane-anaesthetized guinea-pigs. 2. Transvesical saline infusion elicited a series of regular voiding cycles which were abolished by topical tetrodotoxin as well as by topical or intravenous (i.v.) hexamethonium, thus indicating their reflex neurogenic origin. 3. Either i.v. or topical atropine decreased amplitude and duration of micturition contraction, reduced efficiency of bladder voiding and, in about 30% of preparations, suppressed micturition (overflow incontinence). Either topical or i.v. physostigmine potentiated, in an atropine-sensitive manner, voiding efficiency. 4. GABA was administered during the ascending limb of the voiding cycle: i.v. GABA inhibited while topical GABA increased efficiency of the first voiding cycle. Both direction and intensity of the effect of GABA were dependent upon initial pressures. The second and following voiding cycles after GABA administration were inhibited transiently. 5. Either topical or i.v. picrotoxin or BMI potentiated the efficiency of the voiding cycle of the guinea-pig bladder. In these preparations either i.v. or topical GABA (administered during the ascending limb of the voiding cycle) produced only inhibitory effects on voiding efficiency. 6. These findings indicate that, in guinea-pigs, bladder voiding is largely dependent upon an intact cholinergic neurotransmission. Although amplitude of the initial voiding contraction is largely atropine-resistant, its duration and, consequently, degree of bladder voiding, are strongly influenced by blockade (atropine) or potentiation (physostigmine) of cholinergic neurotransmission. Endogenous GABA-ergic mechanism modulate, possibly at peripheral level, the voiding efficiency of the guinea-pig bladder. GABA exerts a complex neuromodulatory influence on voiding function, its overall effect being mainly influenced by resting parameters.