Mobility of Yield Stress Fluids on Lubricant-Impregnated Surfaces

A common problem which we encounter on a daily basis is dispensing of yield stress fluids such as condiments, lotions, toothpaste, etc. from containers. Beyond consumer products, assuring the flow of yield stress fluids such as crude oil, mud, blood, paint, pharmaceutical products, and others, is essential for the respective industries. Elimination of wall-induced friction can lead to significant savings in the energy required for flow of yield stress fluids, as well as associated product loss and cleaning costs. Lubricant-impregnated surfaces (LIS) have been shown to change the dynamic behavior of yield stress fluids and enable them to flow without shearing. Despite the wide applicability of this technology and its general appeal, the fundamental physics governing the flow of yield stress fluids on LIS have not yet been fully explained. In this work, we study the mobility of yield stress fluids on LIS, and explain the relationship between their macroscale flow behavior and the microscale properties of LIS. We show that for yield stress fluids the thermodynamic state of an LIS can be the difference between mobility and immobility. We demonstrate that LIS can induce mobility in yield stress fluids even below their yield stress allowing them to move as a plug without shearing with an infinite slip length. We identify different mobility mechanisms and establish a regime map for drag reduction in terms of the shear stress to yield stress ratio and the microscopic properties of the LIS. We demonstrate these regimes in a practical application of pipe flow thereby providing key insights for the design of LIS to induce mobility of yield stress fluids in a broad range of practical applications.

Monopolar enucleation versus transurethral resection of the prostate for small- and medium-sized (< 80 cc) benign prostate hyperplasia: a prospective analysis

AIM

To assess efficacy and safety of monopolar enucleation of the prostate (MEP) and to compare it with the current treatment standard for medium-sized prostates, < 80 cc, transurethral resection of the prostate (TURP).

METHODS

A prospective analysis patients undergoing a surgical procedure for their diagnosis of BPH (benign prostatic hyperplasia) (IPSS > 20, Q_max < 10; prostate volume < 80 cc) was performed. IPSS, Q_max were assessed preoperatively, at 6 and 12 months postoperatively. The complications were classified according to the modified Clavien-Dindo grading system.

RESULTS

A total of 134 patients were included in the study: 70 underwent MEP and 64 - TURP for BPH (mean prostate volumes were comparable with p = 0.163). The mean surgery time was 44 min in the TURP group and 48.2 min in the MEP group, (p = 0.026). Catheterization time for MEP was 1.7 and 3.2 days for TURP (p < 0.001). Hospital stay for MEP was 3.2 days vs. 4.8 days for TURP (p < 0.001). Both techniques shown comparable efficiency in benign prostatic obstruction relief with IPSS drop in MEP from 23.1 to 5.9 and in TURP group from 22.8 to 7.3, whereas Q_max increased from 8.2 to 20.5 after MEP and from 8.3 and 19.9 after TURP. Urinary incontinence rate after catheter removal in TURP group was 9.0% and 7.8% in MEP group, at 1 year follow-up, it was 1.4% and 3.1% in MEP and TURP, respectively (p = 0.466).

CONCLUSIONS

Our experience demonstrated that MEP is an effective and safe BPH treatment option combining the efficacy of endoscopic enucleation techniques and accessibility of conventional TURP.

Radical prostatectomy performed via robotic, transperitoneal and extraperitoneoscopic approaches: functional and early oncological outcomes

Introduction

Oncological remission along with high postoperative functionality [continence and erectile function (EF)] are the main aspects of prostate cancer (PCa) treatment. The aim of this study was to compare functional and oncological treatment results achieved after a nerve-sparing radical prostatectomy (RP) via transperitoneal (TPRP), extraperitoneal (EPRP) and robot-assisted (RARP) approach.

Material and methods

From March 2015 to March 2016, 507 RP were performed at the Institute for Urology and Reproductive Health (Moscow, Russia). A total of 264 patients with localized (cТ1а–2с) prostate cancer [prostate-specific antigen (PSA) <20 ng/ml, Gleason score ≤7], intact prostate capsule (according to MRI), International Index of Erectile Function (IIEF-5) ≥19 and a life expectancy >10 years were included into the retrospective study. All the surgeries were performed by a single surgeon. The outcomes were evaluated after urethral catheter removal and 3–6–12 months after RP.

Results

Nerve preservation (NP) was performed for 153 patients without significant distinctions in time (р = 0.064) and blood loss (р = 0.073). The International Consultation on Incontinence Questionnaire-Urinary Incontinence Short Form (ICIQ-SF) score was lower for NP: 9.23 ±6.59 and 3.86 ±5.38 after 3 and 12 months respectively compared with continence after RP without nerve preservation (NP): 14.27 ±5.1 vs. 6.15 ±4.76 (р <0.001). Continent was 52.2% vs. 83.3% vs. 81.8% in TPRP, RARP and EPRP groups; р <0.001. IIEF-5 scores were 14.67 ±9.4, 4.2 ±4.26 and 4.0 ±2.07 after RARP, TPRP and EPRP respectively (р = 0.002). After 12 months the PSA: TPRP = 0.11 ±0.19, RARP = 0.03 ±0.05 and EPRP = 0.53 ±1.87 ng/ml (р <0.001). Outcomes depend on surgical approach and was better in the RARP-group (AUC = 0.768 ±0.034 (CI 95% 0,701–0.834; р <0.001).

Conclusions

We suggest RARP with NP as a method of choice for treatment of prostate cancer in patients interested in preservation of EF and quality of life in general.

Impact of endoscopic enucleation of the prostate with thulium fiber laser on the erectile function

Background

The impact of number of endoscopic enucleation of the prostate techniques (holmium laser enucleation - HoLEP for example) on erectile function have already been investigated. However, the thulium-fiber laser, in this setting remains unstudied. In this study, we compared sexual function outcomes in patients with benign prostatic hyperplasia (BPH) treated with transurethral resection of the prostate (TURP) or thulium-fiber laser enucleation (ThuFLEP).

Methods

We performed a retrospective analysis of patients who underwent transurethral resection and endoscopic enucleation of the prostate for BPH; inclusion criteria was the presence of infravesical obstruction (IPSS > 20, Qmax < 10 mL/s). Erectile function (EF) was assessed using the International Index of Erectile Function (IIEF-5) both prior to endoscopic examination, and six months after.

Results

A total of 469 patients with BPH were included in the study; of these, 211 underwent to ThuFLEP, and 258 TURP. Preoperative IIEF-5 in TURP and ThuFLEP groups were 11.7 (±4.5) and 11.1 (±5.0), respectively (p = 0.17). At six month the IIEF-5 score was unchanged (p = 0.26 and p = 0.08) and comparable in both groups (p = 0.49). However, mean IIEF-5 score shown significant increase of 0.72 in ThuFLEP group, comparing to decrease of 0.24 in TURP patients (p < 0.001).

Conclusions

Both TURP and ThuFLEP are effective modalities in the management of infravesical obstruction due to BPH. At six months follow-up after surgery, both techniques lead to comparable IIEF-5 score. However, our results demonstrated that the ThuFLEP is more likely to preserve the erectile function leading to increase of IIEF-5 at six months in contrast to TURP which lead to slight drop in IIEF-5 score.

A Randomized Trial Comparing The Learning Curve of 3 Endoscopic Enucleation Techniques (HoLEP, ThuFLEP, and MEP) for BPH Using Mentoring Approach-Initial Results

OBJECTIVE

To assess the differences in the learning curve associated with different techniques of endoscopic enucleation of the prostate.

MATERIALS AND METHODS

Ninety patients were randomly assigned into 3 groups (30 patients in each): HoLEP, ThuFLEP or MEP. Inclusion criteria for the study included prostate volume <80 cc, IPSS > 20, or Qmax < 10. The EEPs were performed by 3 surgeons experienced in transurethral resection of the prostate. Assignment of surgeons to surgical technique was also randomized. None of the surgeons had prior experience in EEP.

RESULTS

ThuFLEP was slightly superior (with no significant difference [P > .05]) to HoLEP and MEP in terms of overall enucleation rate-1.0 g/min vs 0.8 g/min and 0.7 g/min, respectively. We observed similar enucleation rates at the initial stages of training (first 20 surgeries) with insignificant increase in ThuFLEP efficiency. At next 10 surgeries ThuFLEP and HoLEP efficiency were higher than of MEP (P < .001) without significant difference between techniques of laser EEP (P = .07).

CONCLUSION

Endoscopic enucleation of the prostate can be adopted safely and effectively within 30 surgeries if the technique is learned with a mentoring approach. EEP is shown to be safe and effective even in the initial stages of learning. Laser EEP (HoLEP, ThuFLEP) appears to lend itself to quicker adaptation compared MEP.

Risk factors for urethral stricture and/or bladder neck contracture after monopolar transurethral resection of the prostate for benign prostatic hyperplasia

Objective:

To identify risk factors for urethral stricture and/or bladder neck contracture after transurethral resection of benign prostatic hyperplasia.

Materials and methods:

We performed a retrospective analysis of 402 patients, which underwent a monopolar transurethral resection of the prostate in the urology clinic of Sechenov First Moscow State Medical University for prostatic hyperplasia during the period 2011–2014. Urethral stricture and (or) bladder neck contracture in the postoperative period were diagnosed in 61 (15.27%) patients; 34 patients (8.6%) had urethral stricture, 20 (4.97%) bladder neck contracture, and 7 (1.7%) had a combination of urethral stricture and bladder neck contracture. In 341 of cases (84.73%), no late postoperative complications were observed. A total of 106 of the 341 patients met the inclusion criteria, hence, containing all the information necessary for analysis such as the volume of the prostate, the duration of the surgery, the size of the endoscope, data on concomitant diseases, analysis prostatic secretion, and so on. Thus, two groups were formed. Group 1 (106 patients) is the control group in which urethral strictures and/or bladder neck contractures did not occur in the long-term postoperative period and group 2 (61 patients), in which was observed the formation of these complications. To calculate the statistical significance of the differences for categorical data, Fisher criterion was used. For quantitative variables, in the case of normal data distribution, an unpaired t-test or one-way analysis of variance was used; for data having a distribution different from normal, a Mann–Whitney rank test was used.

Results:

Regression analysis established the significance of the influence of four factors on the development of scar-sclerotic changes of urethra and bladder neck: the tool diameter 27 Fr ( p < 0.0001), presence of prostatitis in past medical history ( p < 0.0001), prostate volume ( p = 0.003), and redraining of the bladder ( p = 0.0162).

Conclusion:

The relationship between the diameter of the instrument, presence of chronic prostatitis in anamnesis, increased volume of the prostate, and repeated drainage of the bladder using the urethral catheter with the risk of developing scar-sclerotic changes in the urethra and/or bladder neck are statistically reliable and confirmed as a result of regression analysis.

Crystallization-Induced Fouling during Boiling: Formation Mechanisms to Mitigation Approaches

Boiling is significantly altered by the presence of dissolved salts. In particular, salts whose solubility decreases with temperature have the tendency to crystallize and adhere to the heat transfer surface and adversely affect the thermal performance. Scaling due to the precipitation of such salts poses serious operational and safety challenges in several practical applications, including heat exchangers, pipelines, and desalination. Here, we study the effect of dissolved salts on the dynamics of pool boiling and its impact on the heat transfer coefficient and critical heat flux (CHF). We find that even undersaturated conditions can lead to crystallization and scale buildup on the boiling surface and dramatically lower heat transfer performance. For example, the CHF for a salt solution that is 75% of the saturation concentration is found to be at least 2 times lower than that for deionized water. Using simultaneous high-speed optical and infrared imaging, we determine the interdependence between crystallization-induced scale formation and bubble evolution dynamics, including bubble nucleation, growth, and departure. We find that salt crystallizes in a "coffee-ring" pattern due to evaporation at the contact line of the bubble. On the basis of the role of the microlayer and triple contact line on scale formation, we propose manipulating surface wettability as a means to avoid scale formation and the associated decrease in the heat transfer coefficient. Surfaces with hybrid wettability are demonstrated as a means to mitigate the reduction in the heat transfer coefficient and CHF in the presence of dissolved salts.

Radially Ejected Bubbles Driven by Thermocapillarity in Equilibrated Vapor-Liquid Mixtures

We report a novel nucleation method that exploits thermocapillary forces in binary fluids to generate a cloud of bubbles ejected radially from a thermally pulsed wire. The bubbles are nucleated within milliseconds of the extinction of the microsecond pulse and are ejected outward from the wire surface due to the thermocapillary force created by the radial temperature gradient. At low temperatures the surface tension of the vapor-liquid mixture, consisting of ethane-n-octane, increases with increasing temperature, ejecting the bubbles away from the heated wire. By proper choice of fluid composition, temperature, or pressure, the sign of the surface tension gradient can be inverted such that nucleated bubbles are attracted to the wire. As opposed to water-alcohol mixtures that have a surface tension minimum, we show that this mixture-which we refer to as an equilibrated vapor-liquid mixture-exhibits a surface tension maximum, creating a unique set of behaviors which have not yet been fully examined in the literature.