Modelling of coalescence in turbulent liquid/liquid dispersions considering droplet charge

Drop size distributions in liquid/liquid systems within a turbulent flow, being an integral part of many technical applications, can be simulated solving population balance equations. Experimental investigations in stirred toluene/water systems at constant ionic strength of 0.1 mol/L showed that with pH values higher than 11, coalescence is hindered considerably due to electrostatic effects. Within this work, two designated models are used to simulate the transient drop size distributions in a stirred tank, showing that the influence of droplet charge due to a change in pH value or ion concentration cannot be predicted satisfactorily by existing models. This finding motivates a new modelling approach implementing the DLVO theory into the population balance framework

Sonar-induced temporary hearing loss in dolphins

Author Posting. © Royal Society, 2009. This is the author's version of the work. It is posted here by permission of Royal Society for personal use, not for redistribution. The definitive version was published in Biology Letters 5 (2009): 565-567, doi:10.1098/rsbl.2009.0099.There is increasing concern that human-produced ocean noise is adversely affecting marine mammals, as several recent cetacean mass strandings may have been caused by animals’ interactions with naval “mid-frequency” sonar. However, it has yet to be empirically demonstrated how sonar could induce these strandings or cause physiological effects. In controlled experimental studies, we show that mid-frequency sonar can induce temporary hearing loss in a bottlenose dolphin (Tursiops truncatus). Mild behavioural alterations were also associated with the exposures. The auditory effects were only induced by repeated exposures to intense sonar pings with total sound exposure levels of 214 dB re: 1 μPa2∙s. Data support an increasing energy model to predict temporary noise-induced hearing loss and indicate that odontocete noise exposure effects bear trends similar to terrestrial mammals. Thus, sonar can induce physiological and behavioural effects in at least one species of odontocete; however, exposures must be of prolonged, high sound exposures levels to generate these effects.Work was funded by the Office of Naval Research (Robert Gisiner and Mardi Hastings) to P.E.N. and SEAPACE (T.A.M.)

Predicting temporary threshold shifts in a bottlenose dolphin (Tursiops truncatus) : the effects of noise level and duration

Author Posting. © Acoustical Society of America, 2009. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 125 (2009): 1816-1826, doi:10.1121/1.3068456.Noise levels in the ocean are increasing and are expected to affect marine mammals. To examine the auditory effects of noise on odontocetes, a bottlenose dolphin (Tursiops truncatus) was exposed to octave-band noise (4–8 kHz) of varying durations (<2–30 min) and sound pressures (130–178 dB re 1 µPa). Temporary threshold shift (TTS) occurrence was quantified in an effort to (i) determine the sound exposure levels (SELs) (dB re 1 µPa2 s) that induce TTS and (ii) develop a model to predict TTS onset. Hearing thresholds were measured using auditory evoked potentials. If SEL was kept constant, significant shifts were induced by longer duration exposures but not for shorter exposures. Higher SELs were required to induce shifts in shorter duration exposures. The results did not support an equal-energy model to predict TTS onset. Rather, a logarithmic algorithm, which increased in sound energy as exposure duration decreased, was a better predictor of TTS. Recovery to baseline hearing thresholds was also logarithmic (approximately −1.8 dB/doubling of time) but indicated variability including faster recovery rates after greater shifts and longer recoveries necessary after longer duration exposures. The data reflected the complexity of TTS in mammals that should be taken into account when predicting odontocete TTS.This work was funded by the Office of Naval Research Grant No. 00014-098-1-687 to P.E.N. and the support of Bob Gisiner and Mardi Hasting is noted. Additional support came from SeaSpace to T.A.M

Significant benefits of AIP testing and clinical screening in familial isolated and young-onset pituitary tumors

Context Germline mutations in the aryl hydrocarbon receptor-interacting protein (AIP) gene are responsible for a subset of familial isolated pituitary adenoma (FIPA) cases and sporadic pituitary neuroendocrine tumors (PitNETs). Objective To compare prospectively diagnosed AIP mutation-positive (AIPmut) PitNET patients with clinically presenting patients and to compare the clinical characteristics of AIPmut and AIPneg PitNET patients. Design 12-year prospective, observational study. Participants & Setting We studied probands and family members of FIPA kindreds and sporadic patients with disease onset ≤18 years or macroadenomas with onset ≤30 years (n = 1477). This was a collaborative study conducted at referral centers for pituitary diseases. Interventions & Outcome AIP testing and clinical screening for pituitary disease. Comparison of characteristics of prospectively diagnosed (n = 22) vs clinically presenting AIPmut PitNET patients (n = 145), and AIPmut (n = 167) vs AIPneg PitNET patients (n = 1310). Results Prospectively diagnosed AIPmut PitNET patients had smaller lesions with less suprasellar extension or cavernous sinus invasion and required fewer treatments with fewer operations and no radiotherapy compared with clinically presenting cases; there were fewer cases with active disease and hypopituitarism at last follow-up. When comparing AIPmut and AIPneg cases, AIPmut patients were more often males, younger, more often had GH excess, pituitary apoplexy, suprasellar extension, and more patients required multimodal therapy, including radiotherapy. AIPmut patients (n = 136) with GH excess were taller than AIPneg counterparts (n = 650). Conclusions Prospectively diagnosed AIPmut patients show better outcomes than clinically presenting cases, demonstrating the benefits of genetic and clinical screening. AIP-related pituitary disease has a wide spectrum ranging from aggressively growing lesions to stable or indolent disease course

Analysis of drop deformation and drop breakage in turbulent flow

Das Dispergieren zweier nicht mischbarer Flüssigkeiten ist Bestandteil zahlreicher Prozesse der chemischen, pharmazeutischen oder lebensmittelverarbeitenden Industrie. Die Größenverteilung der dispersen in der kontinuierlichen Phase beeinflusst dabei nicht nur die Effizienz einiger Prozesse, sondern auch resultierende Eigenschaften wie die Stabilität und Rheologie emulgierter Produkte. Trotz vorliegender industrieller Bedeutung fehlen immer noch zuverlässige Modelle zur Beschreibung und Vorhersage der Tropfengrößenverteilungen. In diesem Zusammenhang müssen die beiden in Konkurrenz stehenden Phänomene des Tropfenbruchs (Zerteilung von Tropfen) und der Tropfenkoaleszenz (Zusammenfließen von Tropfen), welche letztlich die Tropfenbildung bestimmen, betrachtet werden. Der Fokus der vorliegenden Arbeit liegt auf dem Tropfenbruch. Übergeordnetes Ziel ist es, zu einem besseren physikalischen Verständnis des Bruchvorgangs einzelner fluider Partikel in turbulenter Strömung beizutragen. Durch ein umfassendes Versuchsprogramm wurde dazu eine umfangreiche experimentelle Datenbasis erarbeitet. Mittels Hochgeschwindigkeitskamera erfolgte eine detaillierte Analyse des Verhaltens einzelner Tropfen in turbulenter Strömung im Nachlauf eines einzelnen Rührerblatts eines 6-Blatt-Scheibenrührers. Durch eine eigens dafür ausgearbeitete Auswertungsroutine wurde eine objektive Bewertung von mindestens 1000 Tropfen für jeden untersuchten Parametersatz realisiert. Neben der Bestimmung der Bruchwahrscheinlichkeit und des zugehörigen Bruchorts wurden auch die entstehenden Tochtertropfen hinsichtlich Größe und Anzahl analysiert. Zusätzlich wurde im Rahmen dieser Arbeit eine Methode entwickelt, um die Deformationsdynamik in detaillierter Form bewerten zu können. Inwieweit die Ergebnisse zur Vorhersage von Größenverteilungen bruchdominierter gerührter Flüssig/flüssig-Systeme herangezogen werden können, wurde durch experimentelle Vergleichsuntersuchungen abschließend bewertet. Die Ergebnisse der vorliegenden Arbeit zeigen, dass unterschiedliche Beanspruchungsmechanismen eine Rolle spielen können. Insbesondere für höherviskose Tropfen, aber auch mit abnehmendem Tropfendurchmesser oder aber allgemein beim Vorliegen eines sehr großen Bruchwiderstands, also bei sehr großen Verhältnissen zwischen formerhaltenden und deformierenden Spannungen, treten komplexere Bruchmechanismen auf. Synergetische Effekte unterschiedlicher Beanspruchungsarten sind wahrscheinlich und es ist möglich, dass mehrere turbulente Wirbelstrukturen unterschiedlicher Größe in den Zerfallsvorgang involviert sind. Die experimentelle Bruchrate aller untersuchten Einzeltropfen wird nur durch den Bruchwiderstand bestimmt. Das Vorliegen einer kritischen makroskopischen Tropfendeformation, die erreicht werden muss, damit ein Tropfen bricht, kann durch die erarbeiteten experimentellen Daten nicht bestätigt werden. Lediglich bei höherviskosen Tropfen ist ein solcher kritischer Wert nicht auszuschließen. Diese Tropfen werden nicht nur insgesamt stärker deformiert, die Deformationen dauern zudem deutlich länger und es treten verglichen mit niedrigviskosen Tropfen verstärkt Tropfenoszillationen auf. Insgesamt kann die Bruchrate qualitativ als Kriterium zur Übertragung der Einzeltropfenergebnisse auf eine gerührte bruchdominierte Dispersion herangezogen werden. Auch das Verhalten der Größenverteilungen ist in beiden Versuchsanlagen qualitativ gleich.The dispersion of two immiscible fluids is part of many processes in chemical, pharmaceutical or food industry. Resulting drop size distributions thereby determine the efficiency of several processes, but also the stability and rheology of the resulting emulsions. Nevertheless no reliable model for the description of drop size distributions is available in literature. Consequently, drop breakage and drop coalescence, which determine the drop formation, still need to be investigated in more detail. This work focuses on drop breakage; aim is the improvement of the physical understanding of drop breakage mechanism in turbulent flow. Comprehensive experiments were conducted and the behavior of single drops in the turbulent vicinity of a single stirrer blade of a Rushton turbine was analyzed by high-speed imaging. At least 1000 drops were examined for each parameter set. Image data was evaluated fully automatically and the breakage probability and location, as well as the resulting daughter drops were determined. Furthermore, a method was developed in order to describe the dynamics of the drop breakage process properly. Finally the comparability of single drop breakages with the behavior of drop size distributions in breakage dominated stirred systems was discussed. This work shows different breakage mechanisms occurring in the turbulent flow field. Especially breakage of fluids with higher viscosity or breakage of smaller drops is more complex. In that case synergetic effects of different breakage mechanisms are most probable. More than one eddy can be involved in the breakage process and an influence of eddies with different sizes is also possible. In general such behavior was found with increasing breakage resistance, which is defined through the relation between stabilizing and deforming stresses. The experimentally determined breakage rate is only influenced by the breakage resistance. No critical value for the macroscopic drop deformation, which must be exceeded for fragmentation, can be derived from experimental results. Only for higher viscosity drops such a critical value cannot be excluded. These drops generally show more pronounced deformations than drops with low viscosity. Furthermore, the deformations take more time and more oscillations prior the fragmentation occur. The behavior of the breakage rate is at least qualitatively comparable to those of the Sauter mean diameter in breakage dominated stirred dispersions. Also the drop size distributions behave comparable in both set ups.DFG, KR1639/15-1, Modelling, Simulation and Control of Drop Size Distributions in Stirred Liquid/liquid System

Turbulent droplet breakage in a von Kármán flow cell

Droplet dispersion in liquid–liquid systems is a crucial step in many unit operations throughout the chemical, food, and pharmaceutic industries, where improper operation causes billions of dollars of loss annually. A theoretical background for the description of droplet breakup has been established, but many assumptions are still unconfirmed by experimental observations. In this investigation, a von Kármán swirling flow device was used to produce homogeneous, low-intensity turbulence suitable for carrying out droplet breakage experiments using optical image analysis. Individual droplets of known, adjustable, and repeatable sizes were introduced into an isotropic turbulent flow field providing novel control over two of the most important factors impacting droplet breakage: turbulence dissipation rate and parent droplet size. Introducing droplets one at a time, large data sets were gathered using canola, safflower, and sesame oils for the droplet phase and water as the continuous phase. Automated image analysis was used to determine breakage time, breakage probability, and child droplet size distribution for various turbulence intensities. Breakage time and breakage probability were observed to increase with increasing parent droplet size, consistent with the classic and widely used Coulaloglou–Tavlarides breakage model (C–T model). The shape of the child drop size distribution function was found to depend upon the size of the parent droplet.This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in Ravichandar, Krishnamurthy, R. Dennis Vigil, Rodney O. Fox, Stephanie Nachtigall, Andreas Daiss, Michal Vonka, and Michael G. Olsen. "Turbulent droplet breakage in a von Kármán flow cell." Physics of Fluids 34, no. 7 (2022): 073319, and may be found at DOI: 10.1063/5.0096395. Copyright 2022 Author(s). Posted with permission

When genetic load does not correlate with phenotypic spectrum: lessons from the GnRH receptor (GNRHR)

CONTEXT: A broad spectrum of GnRH-deficient phenotypes has been identified in individuals with both mono- and biallelic GNRHR mutations. OBJECTIVE: The objective of the study was to determine the correlation between the severity of the reproductive phenotype(s) and the number and functional severity of rare sequence variants in GNRHR. SUBJECTS: Eight hundred sixty-three probands with different forms of GnRH deficiency, 46 family members and 422 controls were screened for GNRHR mutations. The 70 subjects (32 patients and 38 family members) harboring mutations were divided into four groups (G1-G4) based on the functional severity of the mutations (complete or partial loss of function) and the number of affected alleles (monoallelic or biallelic) with mutations, and these classes were mapped on their clinical phenotypes. RESULTS: The prevalence of heterozygous rare sequence variants in GNRHR was significantly higher in probands vs. controls (P < 0.01). Among the G1-G3 groups (homozygous subjects with successively decreasing severity and number of mutations), the hypogonadotropic phenotype related to their genetic load. In contrast, subjects in G4, with only monoallelic mutations, demonstrated a greater diversity of clinical phenotypes. CONCLUSIONS: In patients with GnRH deficiency and biallelic mutations in GNRHR, genetic burden defined by severity and dose is associated with clinical phenotype. In contrast, for patients with monoallelic GNRHR mutations this correlation does not hold. Taken together, these data indicate that as-yet-unidentified genetic and/or environmental factors may combine with singly mutated GNRHR alleles to produce reproductive phenotypes