Liquid film drag out in the presence of molecular forces

From a practical as well as a conceptual point of view, one of the most interesting problems of physicochemical hydrodynamics is the drag out of a liquid film by a moving solid out of a pool of liquid. The basic problem, sometimes denoted the Landau-Levich problem [L. Landau and B. Levich, “Dragging of a liquid by amoving plate,” Acta Physicochim. USSR 17, 42–54 (1942)], involves an interesting blend of capillary and viscous forces plus a matching of the static solution for capillary rise with a numerical solution of the film evolution equation, neglecting gravity, on the downstream region of the flow field. The original solution describes experimental data for a wide range of Capillary numbers but fails to match results for large and very small Capillary numbers. Molecular level forces are introduced to create an augmented version of the film evolution equation to show the effect of van derWaals forces at the lower range of Capillary numbers. A closed form solution for static capillary rise, including molecular forces, was matched with a numerical solution of the augmented film evolution equation in the dynamic meniscus region. Molecular forces do not sensibly modify the static capillary rise region, since film thicknesses are larger than the range of influence of van der Waals forces, but are determinant in shaping the downstream dynamic meniscus of the very thin liquid films. As expected, a quantitatively different level of disjoining pressure for different values of molecular constants remains in the very thin liquid film far downstream. Computational results for a wide range of Capillary numbers and Hamaker constants show a clear transition towards a region where the film thickness becomes independent of the coating speed.Fil: Schmidhalter, Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química (i); ArgentinaFil: Cerro, R. L.. University of Alabama in Huntsville; Estados UnidosFil: Giavedoni, Maria Delia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química (i); ArgentinaFil: Saita, Fernando Adolfo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química (i); Argentin

Protocol for a prospective, randomized study on neurophysiological assessment of lower urinary tract function in a healthy cohort

Background: Lower urinary tract symptoms are highly prevalent and a large proportion of these symptoms are known to be associated with a dysfunction of the afferent pathways. Diagnostic tools for an objective and reproducible assessment of afferent nerve function of the lower urinary tract are missing. Previous studies showed first feasibility results of sensory evoked potential recordings following electrical stimulation of the lower urinary tract in healthy subjects and patients. Nevertheless, a refinement of the methodology is necessary. Methods: This study is a prospective, randomized trial conducted at Balgrist University Hospital, Zürich, Switzerland. Ninety healthy subjects (forty females and fifty males) without lower urinary tract symptoms are planned to be included in the study. All subjects will undergo a screening visit (including standardized questionnaires, 3-day bladder diary, urinalysis, medical history taking, vital signs, physical examination, neuro-urological examination) followed by two measurement visits separated by an interval of 3 to 4 weeks. Electrical stimulations (0.5Hz-5Hz, bipolar, square wave, pulse width 1 ms) will be applied using a custom-made transurethral catheter at different locations of the lower urinary tract including bladder dome, trigone, proximal urethra, membranous urethra and distal urethra. Every subject will be randomly stimulated at one specific site of the lower urinary tract. Sensory evoked potentials (SEP) will be recorded using a 64-channel EEG cap. For an SEP segmental work-up we will place additional electrodes on the scalp (Cpz) and above the spine (C2 and L1). Visit two and three will be conducted identically for reliability assessment. Discussion: The measurement of lower urinary tract SEPs elicited by electrical stimulation at different locations of the lower urinary tract has the potential to serve as a neurophysiological biomarker for lower urinary tract afferent nerve function in patients with lower urinary tract symptoms or disorders. For implementation of such a diagnostic tool into clinical practice, an optimized setup with efficient and reliable measurements and data acquisition is crucial. In addition, normative data from a larger cohort of healthy subjects would provide information on variability, potential confounding factors and cut-off values for investigations in patients with lower urinary tract dysfunction/symptoms. Trial registration: Clinicaltrials.gov; Identifier: NCT02272309

Impact of different leaf velocities and dose rates on the number of monitor units and the dose-volume-histograms using intensity modulated radiotherapy with sliding-window technique

<p>Abstract</p> <p>Background</p> <p>Intensity modulated radiotherapy (IMRT) using sliding window technique utilises a leaf sequencing algorithm, which takes some control system limitations like dose rates (DR) and velocity of the leafs (LV) into account. The effect of altering these limitations on the number of monitor units and radiation dose to the organs at risk (OAR) were analysed.</p> <p>Methods</p> <p>IMRT plans for different LVs from 1.0 cm/sec to 10.0 cm/sec and different DRs from 100 MU/min to 600 MU/min for two patients with prostate cancer and two patients with squamous cell cancer of the scalp (SCCscalp) were calculated using the same "optimal fluence map". For each field the number of monitor units, the dose volume histograms and the differences in the "actual fluence maps" of the fields were analysed.</p> <p>Results</p> <p>With increase of the DR and decrease of the LV the number of monitor units increased and consequentially the radiation dose given to the OAR. In particular the serial OARs of patients with SCCscalp, which are located outside the end position of the leafs and inside the open field, received an additional dose of a higher DR and lower LV is used.</p> <p>Conclusion</p> <p>For best protection of organs at risk, a low DR and high LV should be applied. But the consequence of a low DR is both a long treatment time and also that a LV of higher than 3.0 cm/sec is mechanically not applicable. Our recommendation for an optimisation of the discussed parameters is a leaf velocity of 2.5 cm/sec and a dose rate of 300–400 MU/min (prostate cancer) and 100–200 MU/min (SCCscalp) for best protection of organs at risk, short treatment time and number of monitor units.</p

Lower urinary tract electrical sensory assessment: A systematic review and meta-analysis

OBJECTIVE To summarize the current literature on lower urinary tract electrical sensory assessment (LUTESA), with regard to current perception thresholds (CPTs) and sensory evoked potentials (SEPs). The applied methods will be discussed in terms of technical aspects, confounding factors, and potential for lower urinary tract (LUT) diagnostics. METHODS The review was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. Medline (PubMed), Embase and Scopus were searched upon October 13, 2020. Meta-analyses were performed and methodological qualities of the included studies were defined by assessing risk-of-bias (RoB) as well as confounding. RESULTS After screening 9925 articles, 80 studies (5 randomized controlled trials (RCTs) and 75 non-RCTs) were included, comprising a total of 3732 patients and 692 healthy subjects. 61 studies investigated exclusively CPTs and 19 studies reported on SEPs, with or without corresponding CPTs. The recording of LUTCPTs and -SEPs was shown to represent a safe and reliable assessment of LUT afferent nerve function in healthy subjects and patients. LUTESA demonstrated significant differences in LUT sensitivity between healthy subjects and neurological patients as well as after interventions such as pelvic surgery or drug treatments. Pooled analyses revealed that several stimulation parameters (e.g. stimulation frequency, location) as well as patient characteristics might affect the main outcome measures of LUTESA (CPTs, SEP latencies, peak-to-peak amplitudes, responder rate). RoB and confounding was high in most studies. CONCLUSIONS Preliminary data show that CPT and SEP recordings are valuable tools to more objectively assess LUT afferent nerve function. LUTESA complement already established diagnostics such as urodynamics, allowing for a more comprehensive patient workup. The high RoB and confounding rate was rather related to inconsistency and inaccuracy in reporting than the technique itself. LUTESA standardization and well-designed RCTs are crucial to implement LUTESA as a clinical assessment tool

Adjuvant therapy after resection of brain metastases: Frameless image-guided LINAC-based radiosurgery and stereotactic hypofractionated radiotherapy

Background: Tumor bed stereotactic radiosurgery (SRS) after resection of brain metastases is a new strategy to delay or avoid whole-brain irradiation (WBRT) and its associated toxicities. This retrospective study analyzes results of frameless image-guided linear accelerator (LINAC)-based SRS and stereotactic hypofractionated radiotherapy (SHRT) as adjuvant treatment without WBRT. Materials and methods: Between March 2009 and February 2012, 44resection cavities in 42patients were treated with SRS (23cavities) or SHRT (21cavities). All treatments were delivered using a stereotactic LINAC. All cavities were expanded by ≥ 2mm in all directions to create the clinical target volume (CTV). Results: The median planning target volume (PTV) for SRS was 11.1cm3. The median dose prescribed to the PTV margin for SRS was 17Gy. Median PTV for SHRT was 22.3cm3. The fractionation schemes applied were: 4fractions of 6Gy (5patients), 6fractions of 4Gy (6patients) and 10fractions of 4Gy (10patients). Median follow-up was 9.6months. Local control (LC) rates after 6and 12months were 91and 77 %, respectively. No statistically significant differences in LC rates between SRS and SHRT treatments were observed. Distant brain control (DBC) rates at 6and 12months were 61and 33 %, respectively. Overall survival (OS) at 6and 12months was 87and 63.5 %, respectively, with a median OS of 15.9months. One patient treated by SRS showed symptoms of radionecrosis, which was confirmed histologically. Conclusion: Frameless image-guided LINAC-based adjuvant SRS and SHRT are effective and well tolerated local treatment strategies after resection of brain metastases in patients with oligometastatic diseas

Improving interinstitutional and intertechnology consistency of pulmonary SBRT by dose prescription to the mean internal target volume dose.

Dose, fractionation, normalization and the dose profile inside the target volume vary substantially in pulmonary stereotactic body radiotherapy (SBRT) between different institutions and SBRT technologies. Published planning studies have shown large variations of the mean dose in planning target volume (PTV) and gross tumor volume (GTV) or internal target volume (ITV) when dose prescription is performed to the PTV covering isodose. This planning study investigated whether dose prescription to the mean dose of the ITV improves consistency in pulmonary SBRT dose distributions. This was a multi-institutional planning study by the German Society of Radiation Oncology (DEGRO) working group Radiosurgery and Stereotactic Radiotherapy. CT images and structures of ITV, PTV and all relevant organs at risk (OAR) for two patients with early stage non-small cell lung cancer (NSCLC) were distributed to all participating institutions. Each institute created a treatment plan with the technique commonly used in the institute for lung SBRT. The specified dose fractionation was 3 × 21.5 Gy normalized to the mean ITV dose. Additional dose objectives for target volumes and OAR were provided. In all, 52 plans from 25 institutions were included in this analysis: 8 robotic radiosurgery (RRS), 34 intensity-modulated (MOD), and 10 3D-conformal (3D) radiation therapy plans. The distribution of the mean dose in the PTV did not differ significantly between the two patients (median 56.9 Gy vs 56.6 Gy). There was only a small difference between the techniques, with RRS having the lowest mean PTV dose with a median of 55.9 Gy followed by MOD plans with 56.7 Gy and 3D plans with 57.4 Gy having the highest. For the different organs at risk no significant difference between the techniques could be found. This planning study pointed out that multiparameter dose prescription including normalization on the mean ITV dose in combination with detailed objectives for the PTV and ITV achieve consistent dose distributions for peripheral lung tumors in combination with an ITV concept between different delivery techniques and across institutions

Refining Treatment Planning in STereotactic Arrhythmia Radioablation (STAR): Benchmark Results and Consensus Statement from the STOPSTORM.eu Consortium.

BACKGROUND AND PURPOSE STereotactic Arrhythmia Radioablation (STAR) showed promising results in patients with refractory ventricular tachycardia (VT). However, clinical data is scarce and heterogeneous. The STOPSTORM.eu consortium was established to investigate and harmonize STAR in Europe. The primary goal of this benchmark study was to investigate current treatment planning practice within the STOPSTORM project as a baseline for future harmonization. METHODS Planning target volumes (PTV) overlapping extra-cardiac organs-at-risk and/or cardiac substructures were generated for three STAR cases. Participating centers were asked to create single fraction treatment plans with 25 Gy dose prescription based on in-house clinical practice. All treatment plans were reviewed by an expert panel and quantitative crowd knowledge-based analysis was performed with independent software using descriptive statistics for ICRU report 91 relevant parameters and crowd dose-volume-histograms. Thereafter, treatment planning consensus statements were established using a dual-stage voting process. RESULTS Twenty centers submitted 67 treatment plans for this study. In most plans (75%) Intensity Modulated Arc Therapy (IMAT) with 6 MV flattening-filter-free beams was used. Dose prescription was mainly based on PTV D95% (49%) or D96-100% (19%). Many participants preferred to spare close extra-cardiac organs-at-risk (75%) and cardiac substructures (50%) by PTV coverage reduction. PTV D0.035cm3 ranged 25.5-34.6 Gy, demonstrating a large variety of dose inhomogeneity. Estimated treatment times without motion compensation or setup ranged 2-80 minutes. For the consensus statements, strong agreement was reached for beam technique planning, dose calculation, prescription methods and trade-offs between target and extra-cardiac critical structures. No agreement was reached on cardiac substructure dose limitations and on desired dose inhomogeneity in the target. CONCLUSION This STOPSTORM multi-center treatment planning benchmark study showed strong agreement on several aspects of STAR treatment planning, but also revealed disagreement on others. To standardize and harmonize STAR in the future, consensus statements were established, however clinical data is urgently needed for actionable guidelines for treatment planning

Effect of salt and osmotic stresses on the germination of pepper seeds of different maturation stages

Germination percentage, seedling fresh weight and sensitivity index of the pepper (Capsicum annuum L. cv. Sera Demre) seed lots harvested 50, 60 and 70 days after the anthesis (daa) in 2001 and 2002 were determined under the salt (NaCl) and osmotic (PEG) stresses at the same water potentials of -0.3, -0.6 and -0.9 MPa. The objective was to study whether the germination and seedling growth were inhibited by the salt toxicity or osmotic effect during the development. The higher the salt and osmotic stress concentrations the lower was the germination percentage and seedling fresh weight. The seed germination was higher and sensitivity index were lower in NaCl than in PEG at the same water potential and harvest in both the years. They were able to germinate at all the concentrations of NaCl but at -0.9 MPa of PEG, none of the seeds of any harvest germinated in both the years. The seeds harvested 70 daa showed the highest germination and seedling weight in all the NaCl and PEG concentrations in both the years. Results showed that the inhibition of the germination at the same water potential of NaCl and PEG resulted from the osmotic effect rather than the salt toxicity. Moreover, the seeds harvested 70 daa appeared to be more tolerant to the salt and osmotic water stress conditions than the other two lots