Numerical investigations of flow and energy fields near a thermoacoustic couple

The flow field and the energy transport near thermoacoustic couples are simulated using a 2D full Navier-Stokes solver. The thermoacoustic couple plate is maintained at a constant temperature; plate lengths, which are short and long compared with the particle displacement lengths of the acoustic standing waves, are tested. Also investigated are the effects of plate spacing and the amplitude of the standing wave. Results are examined in the form of energy vectors, particle paths, and overall entropy generation rates. These show that a net heat-pumping effect appears only near the edges of thermoacoustic couple plates, within about a particle displacement distance from the ends. A heat-pumping effect can be seen even on the shortest plates tested when the plate spacing exceeds the thermal penetration depth. It is observed that energy dissipation near the plate increases quadratically as the plate spacing is reduced. The results also indicate that there may be a larger scale vortical motion outside the plates which disappears as the plate spacing is reduced. (C) 2002 Acoustical Society of America

Role of nicotine in depression through dopaminergic mechanism

Background: There are interesting reports in the literature indicating relationship of smoking /nicotine and depression. Smokers use nicotine to treat depression. The objectives of present study were to evaluate the role of nicotine in depression through Dopaminergic mechanism by using haloperidol induced catalepsy model in rats and to estimate Dopamine level in brain of depressed rats after nicotine and imipramine.Methods: Dopaminergic activity was evaluated in haloperidol induced catalepsy in rats. Levels of dopamine in normal as well as in depressed rats brain was estimated using fluorimetric method. The study treatment were administered as follows - Vehicle (s.c.), Imipramine (i.p.) - 7days, Nicotine (subcutaneous), Nicotine (inhalation) were administered in a dose of 1ml/kg,10mg/kg,0.4mg/kg,0.2mg/kg respectively.Results: In haloperidol induced catalepsy model, vehicle treated group showed cataleptic effect starting at 1 hour and lasting for 6 hours. Nicotine administered by subcutaneous route significantly reduced cataleptic score as compared to vehicle treated group till 6 hours. Nicotine administered by inhalation route reduced cataleptic score up to 6 hours compared with that of vehicle. Catalepsy score in nicotine (inhalation) group was significantly less as compared to nicotine (subcutaneous) at all time points period except 2 hours. Isolation induced hyperactivity model was used to induce depression in rats. Dopamine levels in rats after isolation were significantly less as compared to normal rats (before isolation). After isolation, dopamine levels in imipramine treated rats were significantly higher as compared to vehicle treated group. After isolation, dopamine levels were significantly high in both groups i.e., nicotine (subcutaneous) and nicotine (inhalation). Imipramine (7 days) and single dose of nicotine (inhalation) showed comparable results with normal dopamine level i.e. before isolation rats.Conclusions: Nicotine has increased dopaminergic activity as evident by reversal of haloperidol induced catalepsy. Dopamine level reduced in depressed rats. Dopamine brain levels were increased, when depressed rats were treated with Imipramine (i.p.), nicotine (s.c.), nicotine(inhaled). Single dose nicotine given by inhalation route has produced significant antidepressant action comparable to that of seven days’ treatment of standard antidepressant drug imipramine in rats. In rats, nicotine by both routes i.e subcutaneous and inhalational increased dopaminergic activity

Evaluation of the effect of lycopene on lipid profile, serum antioxidant enzymes and blood sugar level in New Zealand white rabbits

Background: Dyslipidaemias are the major cause of increased atherogenesis. Lycopene is a pigment that imparts red colour to fruits and vegetables like tomatoes. Risk of cardiovascular diseases has been shown to decrease with dietary intake of tomatoes. Although the antioxidant and hypolipidaemic properties of tomatoes have been studied extensively, beneficial effect of pure lycopene supplement as hypolipidaemic is still debatable So, we aimed to evaluate the effect of pure lycopene powder on lipid profile, serum antioxidant enzymes and blood sugar level in hyperlipidaemic rabbits.Methods: Adult male New Zealand White rabbits (1.5-2.5kg) were divided into three groups of six each. Group I-High Fat Diet (HFD) (5ml/kg). Group II-HFD (5ml/kg) + lycopene (10mg/kg) orally. Group III-HFD (5ml/kg) + lycopene (20mg/kg) orally. Blood samples were taken from all rabbits for baseline estimations of serum lipids, serum superoxide dismutase (SOD) and blood sugar. Same tests were performed after six weeks.Results: There was significant decrease in the levels of serum TC, LDL-C, TG and VLDL and an increase in serum HDL-C and antioxidant SOD with lycopene administration. However, significant increase in HDL was not seen with lycopene 10mg. TG and VLDL levels were significantly less with 20mg lycopene compared to 10mg lycopene. There was however no change in blood sugar level with lycopene.Conclusions: Pure lycopene supplement showed significant hypolipidaemic and antioxidant activity. However, it did not show significant effect on blood glucose levels

Mixing and chemical reaction in an idealized swirl chamber

A vorticity-based, low-Mach-number model for simulating combustion in closed chambers is constructed. Numerical scheme is based on a mixed finite-difference pseudo-spectral discretization of the governing equations. Discrete evolution equations are integrated in time using a predictor-corrector scheme, while discrete elliptic systems are inverted with the help of fast-Poisson solver. Scheme is applied to analyze mixing and combustion in an idealized swirl cavity, which consists of the annular space between a spinning inner cylinder and a stationary reaction. To this end, we assume that the oxidizer and fuel are initially separated by a thin mixed region, and carefully control mixing levels by varying the duration of the swirl-driven mixing period. The mixture is then ignited along the boundary of the inner cylinder. When pre-mixing is complete, an axisymmetric flame front is established, and the reactants are consumed as the front propagates radially outwards. When the charge is partially mixed, combustion in the early stages predominantly occurs within a non-uniform premixed front. As this non-uniform front approaches the outer cylinder, a transition to a distributed combustion regime occurs. Following the transition, the remaining fuel burns at a slow rate within non-premixed flames which wrap around the inner cylinder. Results show that the mixing time has substantial effects on the pressure rise within the cavity and on the evolution of the burnt fraction, and that these effects become more pronounced as the Damkoehler number increases

Effect of nicotine on serotonin (5-HT) levels in brain of depressed rats

Background: Reduction in brain serotonin (5-HT) levels contributes to depression. Nicotine may have antidepressant properties and smokers self-medicate underlying depression. Epidemiological findings suggest that smokers more often demonstrate depressive symptoms than non-smokers and depressed patients are less likely to cease smoking. Therefore, the study was planned to evaluate the effect of nicotine on serotonin levels in brain of depressed rats.Methods: Antidepressant action of study drugs was evaluated using isolation induced hyperactivity model in rats. Rats were divided into five groups with six rats in each group. Study groups: Vehicle in normal rats 1 ml/kg (subcutaneous); vehicle after isolation 1ml/kg (subcutaneous); imipramine 10 mg/kg (intraperitoneal) for 7 consecutive days; single dose of nicotine 0.4 mg/kg (subcutaneous); single dose of nicotine 0.2 mg/kg (inhalational). Brain serotonin assay was carried out. The statistical significance was determined by ANOVA followed by Tukey test (p<0.05).Results: Serotonin levels (55.93ng/g of brain tissue) in rats after isolation were significantly less than in normal rats (335.87ng/g) (p<0.001). In imipramine treated group, serotonin levels (301.4ng/g) after isolation were highly significant as compared to serotonin levels in vehicle treated group after isolation (p<0.001). Nicotine administered by subcutaneous and inhalational route showed significantly higher brain serotonin levels, i.e. 175ng/g and 254.62ng/g respectively as compared to vehicle treated rats after isolation (p<0.001).Conclusions: Single dose nicotine (inhalational) produced significant antidepressant action comparable to that of seven days’ treatment of standard antidepressant drug imipramine in rats. In rats, nicotine by both routes i.e. subcutaneous and inhalational increased serotonergic activity

The Thermal Filter for the Solar Ultraviolet Imaging Telescope (SUIT) on-board Aditya-L1

The Solar Ultraviolet Imaging Telescope (SUIT) is an imaging telescope on-board the Aditya-L1 satellite, which is India’s maiden space mission dedicated solely to solar observations. The spatially resolved, high cadence observations are designed to be taken in eleven science filters with Full Width Half Maxima ranging between 0.1–58 nm and spread over the Near-Ultraviolet (NUV) domain of the solar spectrum (200–400 nm). The huge incoming solar flux, limited by the linearity regime performance of the Charge Coupled Device (CCD) as well as the thermal operational constraints, mandate the use of an entrance aperture filter, the Thermal Filter (TF), for SUIT. The design of this filter is, further, constrained by exposure time and enhanced emission of the Sun during eruptive events. From performance perspective, the TF reflects ∼50% of the incident radiation and allows only 0.1–0.45% of the incoming flux to pass within 200–400 nm. The transmission on either side of the operational range is satisfactorily reduced, so as to ensure minimum unwanted light leaking into the imaging system. Therefore, the TF plays a significant role in increasing the photometric efficiency as well as maintaining the operational temperature of the telescope. To the best of our knowledge, this is the first time any attempt of designing and manufacturing any such rejection filter aiming optimized performance in the NUV range is being done for a space-based imaging solar telescope. The choice of materials for substrate and coating for the filter poses several challenges in terms of contamination, corrosion/ oxidation, durability during manufacturing process, long-term exposure to harsh space environment as well as formation of pinholes. The transmission and reflection profiles of the fabricated TF is satisfactory to meet our design and technical constraints. The TF is also qualified for various environmental and radiation conditions. The transmission of the TF is seen to be well within our allowed margins (±10% of the design value) even after being exposed to these qualification tests. © 2022 SPIE. All rights reserved.Immediate accessThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]