Effect of hydrophobicity and surface roughness on two-phase flow in rectangular microchannels

Two-phase flows in microchannels have received significant attention recently, and have become the cornerstone of numerous microfluidic devices. Microscale devices used for bioengineering applications, oil recovery, and chemical and catalytic microreactor applications involve the transport of bubbles in confined fluidic networks in channels of micrometer length scale. These types of two-phase flows result in pressure variations, leading to an overall increase in pressure drop. Among various flow parameters, pressure drop is extensively used in design of microfluidic devices. There are several parameters that affect the pressure drop across two-phase flow in microchannels. In the present study, the goal is to be able to predict the pressure drop of two-phase flow in rectangular microchannels as a function of hydrophobicity, surface roughness, and bubble size. The SU-8 channels are fabricated using photolithography to ensure a perfectly smooth surface, which eliminates the effect of surface roughness. The fabricated channels are treated to alter the contact angle of water on SU-8, isolating the effects of hydrophobicity. Pressure drop data of air-water two-phase flow across the channels was collected, and compared to a previously published model, which predicts the pressure drop across a smooth hydrophilic rectangular microchannel with an air bubble flowing through it. Deviations of the experimental pressure drop from the predicted values were observed as a function of hydrophobicity and bubble size; this information was used to introduce a term, accounting for the effects of hydrophobicity and bubble size, into the existing model. A method of fabricating rough SU-8 channels was proposed to isolate the effects of surface roughness. The model was validated using channels of varying aspect ratios. It was found that the proposed model was independent of the aspect ratio --Abstract, page iii

Maternal allergen immunisation to prevent sensitisation in offspring: Th2-polarising adjuvants are more efficient than a Th1-polarising adjuvant in mice

<p>Abstract</p> <p>Background</p> <p>Allergy has been an increasing problem in several parts of the world. Prenatal exposure to allergen and microbial components may affect the development of allergies in childhood, as indicated by epidemiological and experimental studies. We investigated the capacity for allergic sensitisation in offspring after induction of a Th1- or a Th2-polarised immune response to the same allergen in mothers during pregnancy.</p> <p>Results</p> <p>During pregnancy, mice were immunised with ovalbumin (OVA) given with either one of the Th2-adjuvants pertussis toxin (PT) or Al(OH)₃(aluminium hydroxide), or with the Th1 adjuvant CpG. Offspring were immunised with OVA in Al(OH)₃as young adults. Serum and supernatants from <it>ex vivo </it>stimulated or non-stimulated spleen cells from mothers and offspring were analysed for OVA-specific antibodies and cytokines, respectively. Mothers immunised with OVA together with either Al(OH)₃or PT had increased levels of OVA-specific IgE and IgG1 compared to naive mothers, whereas mothers immunised with OVA together with CpG had increased levels of OVA-specific IgG2a compared to naive mothers. In general the highest levels of IL-5, IL-10, and IFNγ were observed in spleen cells from mothers immunised with PT and OVA. Upon immunisation, offspring from mothers immunised with OVA and either PT or Al(OH)₃showed reduced levels of OVA-specific IgE and IgG1 and increased levels of OVA-specific IgG2a antibodies compared to offspring from naive mothers. Maternal immunisation with CpG and OVA did not affect antibody responses in offspring.</p> <p>Conclusion</p> <p>Allergic sensitisation in the offspring was affected by the type of adjuvant used for immunisation of the mothers with the same allergen. Th2 polarisation of the immune response in the mothers was found to give reduced IgE levels upon sensitisation of the offspring, whereas no reduction was achieved with Th1 polarisation in the mothers.</p

Clinical comparison of different cardiovascular risk scores for cardiovascular risk prediction in Indian patients

Background: Cardiovascular diseases (CVD) are the main cause of mortality and disability in India. Early and sustained exposure to behavioral risk factors leads to development of CVD. The present study was conducted to compare different cardiovascular calculators for CVD risk assessment models in young Indian patients presenting with myocardial infarction.Methods: This study included 85 patients with myocardial infarction (MI). Their predicted 10-year risk of CVD was calculated using three clinically most relevant risk assessment models viz. Framingham Risk score (RiskFRS), American College of Cardiology/American Heart Association (RiskACC/AHA) and the 3rd Joint British Societies risk calculator (RiskJBS).Results: RiskFRS recognized the highest number of patients (15.4%) at high CVD risk while RiskACC/AHA and RiskJBS calculators provided inferior risk assessment but statistically significant relationship. RiskFRS and RiskACC/AHA (Pearson's r 0.870, p<0.001).Conclusions: RiskFRS seems to be as most useful CVD risk assessment model in young Indian patients. RiskFRS is likely to identify the number of patients at ‘high-risk’ as compared to RiskJBS and RiskACC/AHA

Age distribution of exoplanet host stars: Chemical and Kinematics age proxies from GAIA DR3

The GAIA space mission is impacting astronomy in many significant ways by providing a uniform, homogeneous and precise data set for over 1 billion stars and other celestial objects in the Milky Way and beyond. Exoplanet science has greatly benefited from the unprecedented accuracy of stellar parameters obtained from GAIA. In this study, we combine photometric, astrometric, and spectroscopic data from the most recent Gaia DR3 to examine the kinematic and chemical age proxies for a large sample of 2611 exoplanets hosting stars whose parameters have been determined uniformly. Using spectroscopic data from the Radial Velocity Spectrometer (RVS) onboard GAIA, we show that stars hosting massive planets are metal-rich and $\alpha$-poor in comparison to stars hosting small planets. The kinematic analysis of the sample reveals that the stellar systems with small planets and those with giant planets differ in key aspects of galactic space velocity and orbital parameters, which are indicative of age. We find that the galactic orbital parameters have a statistically significant difference of 0.06 kpc for $Z_{max}$ and 0.03 for eccentricity respectively. Furthermore, we estimated the stellar ages of the sample using the MIST-MESA isochrone models. The ages and its proxies for the planet-hosting stars indicate that the hosts of giant planetary systems are younger compared to the population of stars harboring small planets. These age trends are also consistent with the chemical evolution of the galaxy and the formation of giant planets from the core-accretion process.Comment: Accepted for Publication in The Astronomical Journa

Genetic dissection of MHC-associated susceptibility to Lepeophtheirus salmonis in Atlantic salmon

Background: Genetic variation has been shown to play a significant role in determining susceptibility to the salmon louse, Lepeophtheirus salmonis. However, the mechanisms involved in differential response to infection remain poorly understood. Recent findings in Atlantic salmon (Salmo salar) have provided evidence for a potential link between marker variation at the major histocompatibility complex (MHC) and differences in lice abundance among infected siblings, suggesting that MHC genes can modulate susceptibility to the parasite. In this study, we used quantitative trait locus (QTL) analysis to test the effect of genomic regions linked to MHC class I and II on linkage groups (LG) 15 and 6, respectively. Results: Significant QTL effects were detected on both LG 6 and LG 15 in sire-based analysis but the QTL regions remained unresolved due to a lack of recombination between markers. In dam-based analysis, a significant QTL was identified on LG 6, which accounted for 12.9% of within-family variance in lice abundance. However, the QTL was located at the opposite end of DAA, with no significant overlap with the MHC class II region. Interestingly, QTL modelling also revealed evidence of sex-linked differences in lice abundance, indicating that males and females may have different susceptibility to infection. Conclusion: Overall, QTL analysis provided relatively weak support for a proximal effect of classical MHC regions on lice abundance, which can partly be explained by linkage to other genes controlling susceptibility to L. salmonis on the same chromosom

Universality in spectral condensation

Self-organization is the spontaneous formation of spatial, temporal, or spatiotemporal patterns in complex systems far from equilibrium. During such self-organization, energy distributed in a broadband of frequencies gets condensed into a dominant mode, analogous to a condensation phenomena. We call this phenomenon spectral condensation and study its occurrence in fluid mechanical, optical and electronic systems. We define a set of spectral measures to quantify this condensation spanning several dynamical systems. Further, we uncover an inverse power law behaviour of spectral measures with the power corresponding to the dominant peak in the power spectrum in all the aforementioned systems.Comment: 5 pages, 3 figure

Universality in spectral condensation

Self-organization is the spontaneous formation of spatial, temporal, or spatiotemporal patterns in complex systems far from equilibrium. During such self-organization, energy distributed in a broadband of frequencies gets condensed into a dominant mode, analogous to a condensation phenomenon. We call this phenomenon spectral condensation and study its occurrence in fluid mechanical, optical and electronic systems. We define a set of spectral measures to quantify this condensation spanning several dynamical systems. Further, we uncover an inverse power law behaviour of spectral measures with the power corresponding to the dominant peak in the power spectrum in all the aforementioned systems