Assessment of a subgrid-scale model for convection-dominated mass transfer for initial transient rise of a bubble

The mass transfer between a rising bubble and the surrounding liquid is mainly determined by an extremely thin layer of dissolved gas forming at the liquid side of the gas-liquid interface. Resolving this concentration boundary layer in numerical simulations is computationally expensive. Subgrid-scale models mitigate the resolution requirements enormously and allow approximating the mass transfer in industrially relevant flow conditions with high accuracy. However, the development and validation of such models is difficult as only integral mass transfer data for steady-state conditions are available. Therefore, it is difficult to assess the validity of the sub-grid models in transient conditions. In this contribution, we compare the local and global mass transfer of an improved subgrid-scale model for rising bubbles (Re = 72-569 and Sc = 10^2-10^4) to a single-phase simulation approach, which maps the two-phase flow field to a highly-resolved mesh comprising only the liquid phase.

Evaluating participant experience in Balint online sessions held during the COVID-19 pandemic – lessons learnt and moving forward

AimsFrom the outset of the COVID-19 global pandemic and the lockdown that subsequently ensued, a challenge was posed to reshape previously face-to-face meetings in all walks of life. One area that rose to this, with quick introduction of online sessions, was the Balint Group. We aimed to take a snapshot of the effect virtual Balint sessions have had and analyse the themes that members of virtual Balint groups have been identifying about their online group experience at this particularly challenging time for healthcare workers. We hope this will inform both leaders and participants of future online groups of the benefits and pitfalls found by these members reflecting on their first experiences of virtual Balint.MethodSeven members of virtual Balint groups across the UK were randomly selected for interview from a pool of volunteers facilitated by the UK Balint Society after the first 6 months of their first virtual Balint experience. Interviews were conducted by two academic foundation doctors who were not members of the Balint groups. Qualitative thematic analysis was then conducted on these interview transcripts. Going forward, as Balint groups continue online, the researchers plan to interview further group members and leaders to look for change and development in the primary themes identified.ResultKey positive themes identified when discussing virtual Balint were ease of access, increased anonymity, attention to facial expressions and interaction with participants from different parts of the country. The most common drawback themes were a lack of socialising and different group dynamic as well as the expected technical and environmental challenges. Interestingly all participants reported that ‘silence’ and ‘sitting/stepping back’ were still used in their online sessions. Core theme analysis indicates the virtual Balint descriptions draw out sentiments of safe, open and structured sessions. In these early sessions a frequent theme was the increased role of the leader.ConclusionAll participants interviewed so far have felt their online experiences have had many positive aspects. They highlight areas they feel virtual Balint could develop to better replicate the original sessions. The fact some interviewees would prefer to maintain online Balint groups even when ‘in person’ options resume makes it likely this will not be a transient rise in virtual Balint and that the style may be here to stay. Based on this, the role for feedback and constant evaluation and improvement will be central to virtual Balint evolution.

Finasteride interferes with prostaglandin-induced CatSper signalling in human sperm

Ca2+ signalling controls human sperm functions necessary for successful fertilization. Multiple endocrine-disrupting chemicals have been found to activate the CatSper Ca2+ channel and thereby interfering with Ca2+ signalling in human sperm. Finasteride is prescribed to men in the fertile age to treat hair loss and its use has been associated with impaired male fertility. Due to the structural relatedness of finasteride to the endogenous CatSper ligand progesterone, this study aimed to investigate whether finasteride affects human sperm in a progestogen-like manner. The effect of finasteride on Ca2+ signalling via CatSper in human sperm was investigated in cell suspensions by single-cell imaging. Additionally, effects on sperm penetration into viscous medium and acrosome reaction were assessed. Finasteride alone caused a minor transient rise in the intracellular, free Ca2+ concentration ([Ca2+]i) at physiologically relevant concentrations. Ca2+ signals induced by PGE1 were inhibited by finasteride displaying mixed type of inhibition consistent with multiple binding sites. Finasteride did not interfere with progesterone-induced Ca2+ signalling and no effect on acrosome reaction or sperm viability was found. Finasteride significantly decreased PGE1-induced penetration into viscous medium but in concentrations above what is measured in blood and seminal fluids during regular finasteride administration. In conclusion, the use of finasteride may affect Ca2+ signalling in human sperm through an interaction with the PGE1-binding site, but to which extend it alters the chances of a successful fertilization needs further investigation. It remains to be investigated whether finasteride administration may give rise to side effects by interfering with prostaglandin signalling elsewhere in the human body.

Passive Thermography Measurement of Damage Depth During Composites Load Testing

Passive thermography is commonly used for composites load testing to detect damage formation as a function of the applied load. The advantages of passive thermography are real time implementation, large area coverage, and noncontact measurement. Passive thermography is able to detect the damage location and size, however, damage depth has been a challenge for quasistatic loading. Recent work has shown that damage formation during loading produces heating that is composed of two heat generation components. The first component is an instantaneous thermal response due to an irreversible thermoelastic strain release due to rapid damage formation. The second component observed is mechanical heating, at the interface of failure, due to fracture damage that produces a transient rise in surface temperature as a function of damage depth. The first component defines the thermal start time for the transient response. A one-dimensional thermal model, that is independent of delamination damage gap spacing, is presented and fitted to the data pixel by pixel, to produce imagery of the damage depth. The percent difference between thermal results, as compared to the ultrasonic measurements of damage length and width, was on average 15%. The percent difference between the thermal results, as compared to the X-ray CT measurements for damage depth was on average 7%. This same processing technique was applied for detection of damage depth during cyclic loading as well.

Postoperative lumbar paraspinal compartment syndrome

Lower lumbar paraspinal muscles constitute a compartment as they are surrounded by distinct fascial and bony boundaries. Lumbar paraspinal compartment syndrome is a rare entity, often caused by intense exercise, but also can be a postoperative complication. We present a 60-year-old man with low back pain, numbness in the left lower back and radicular pain in the left lower extremity, which started after a surgery that involved prolonged positioning on the left side 7 years before, and persisted to the day of evaluation. There was an immediate transient rise in the creatine kinase after surgery. Electromyography showed a left lower lumbar–sacral plexopathy and a lumbar spine MRI revealed fatty infiltration of the lower lumbar–sacral paraspinal muscles. The emergence of radicular lower limb pain was likely due to the compression of the proximal portion of lumbar–sacral plexus during the acute stage of rhabdomyolysis.

Scleral fixation of Carlevale intraocular lens: A new tool in correcting aphakia with no capsular support

Purpose: To report the clinical outcomes of the use of a novel specially designed scleral fixated intraocular lens, the Carlevale intraocular lens (carlevale IOL, Soleko, Italy) for the correction of aphakia in the absence of capsular support of variable etiology. Methods: This retrospective, non-comparative study included 169 eyes of 169 consecutive patients who underwent 3-port pars plana vitrectomy and scleral fixation on Carlevale IOL. Inclusion criteria were at least 6 months’ follow-up period, patients > 18 years old who underwent vitrectomy and Carlevale IOL placement for aphakia and inadequate capsular support Results: The median follow up period of 9 months (range 6–18 months). Mean post-operative BCVA at the last follow-up visit was 20/25 (0.09 ± 0.1 LogMAR), improving from a mean baseline BCVA of 20/80 (0.58 ± 0.49 LogMAR), a statistically significant change ( p = 0.0001). Regarding the post-operative complications, a transient rise in the IOP was observed in 28 patients (16.5%) and mild vitreous hemorrhage was observed in the immediate post-operative period in eight eyes (4.7%) and it spontaneously resolved within 3 weeks. All patients demonstrated good IOL position at the end of the follow-up without IOL capture. None of the patients required re-operation. Conlcusion: The present study represents the largest to date in evaluating the use of carlevale IOL in patients with aphakia and inadequate capsular support. The technique is safe and provides excellent post-operative IOL fixation without IOL capture in any of the patients studied.

Calcium Sensors STIM1 and STIM2 Regulate Different Calcium Functions in Cultured Hippocampal Neurons

There are growing indications for the involvement of calcium stores in the plastic properties of neurons and particularly in dendritic spines of central neurons. The store-operated calcium entry (SOCE) channels are assumed to be activated by the calcium sensor stromal interaction molecule (STIM)which leads to activation of its associated Orai channel. There are two STIM species, and the differential role of the two in SOCE is not entirely clear. In the present study, we were able to distinguish between transfected STIM1, which is more mobile primarily in young neurons, and STIM2 which is less mobile and more prominent in older neurons in culture. STIM1 mobility is associated with spontaneous calcium sparks, local transient rise in cytosolic [Ca2+]i, and in the formation and elongation of dendritic filopodia/spines. In contrast, STIM2 is associated with older neurons, where it is mobile and moves into dendritic spines primarily when cytosolic [Ca2+]i levels are reduced, apparently to activate resident Orai channels. These results highlight a role for STIM1 in the regulation of [Ca2+]i fluctuations associated with the formation of dendritic spines or filopodia in the developing neuron, whereas STIM2 is associated with the maintenance of calcium entry into stores in the adult neuron.

Ucp2-dependent microglia-neuronal coupling controls ventral hippocampal circuit function and anxiety-like behavior

Microglia have been implicated in synapse remodeling by phagocytosis of synaptic elements in the adult brain. However, the underlying mechanism of such process is ill-defined. By examining microglia-neuronal interaction in the ventral hippocampus, we found a significant reduction in spine synapse number during the light phase of the light/dark cycle accompanied by increased microglial phagocytosis. This was followed by a transient rise in microglial production of reactive oxygen species (ROS) and uncoupling protein 2 (Ucp2) expression, which is a regulator of mitochondrial ROS generation. Conditional ablation of microglial Ucp2 hindered phasic elimination of spine synapses, increased accumulations of ROS and lysosome-lipid droplet complexes leading to hippocampal circuitry disruption assessed by electrophysiology, and, altered anxiety-like behavior. These observations unmasked a novel and chronotypical interaction between microglia and neurons involved in control of brain functions.

Consuming sucrose solution promotes leptin resistance and site specifically modifies hypothalamic leptin signaling in rats

Rats consuming 30% sucrose solution and a sucrose-free diet (LiqS) become leptin resistant whereas rats consuming sucrose from a formulated diet (HS) remain leptin responsive. This study tested whether leptin resistance in LiqS rats extended beyond a failure to inhibit food intake and examined leptin responsiveness in the hypothalamus and hindbrain of rats offered HS, LiqS or a sucrose free diet (NS). Female LiqS Sprague Dawley rats initially only partially compensated for the calories consumed as sucrose, but energy intake matched that of HS and NS rats when they were transferred to calorimetry cages. There was no effect of diet on energy expenditure, IBAT temperature or fat pad weight. A peripheral injection of 2 mg leptin/kg on Day 23 or 26 inhibited energy intake of HS and NS, but not LiqS rats. Inhibition occurred earlier in HS than NS rats and was associated with a smaller meal size. Leptin had no effect on energy expenditure, but caused a transient rise in IBAT temperature of HS rats. Leptin increased pSTAT3 in the hindbrain and ventromedial hypothalamus of all rats. There was a minimal effect of leptin in the arcuate nucleus and only the dorsomedial hypothalamus showed a correlation between pSTAT3 and leptin responsiveness. These data suggest that the primary response to leptin is inhibition of food intake and that the pattern of sucrose consumption, rather than calories consumed as sucrose causes leptin resistance associated with site specific differences in hypothalamic leptin signaling.