Nonmodal Growth of TravelingWaves on Blunt Cones at Hypersonic Speeds

The existing database of transition measurements in hypersonic ground facilities has established that, as the nosetip bluntness is increased, the onset of boundary layer transition over a circular cone at zero angle of attack shifts downstream. However, this trend is reversed at sufficiently large values of the nose Reynolds number, so that the transition onset location eventually moves upstream with a further increase in nose-tip bluntness. Because modal amplification is too weak to initiate transition at moderate-to-large bluntness values, nonmodal growth has been investigated as the potential basis for a physics-based model for the frustum transition. The present analysis investigates the nonmodal growth of traveling disturbances initiated within the nose-tip vicinity that peak within the entropy layer. Results show that, with increasing nose bluntness, both planar and oblique traveling disturbances experience appreciable energy amplification up to successively higher frequencies. For moderately blunt cones, the initial nonmmodal growth is followed by a partial decay that is more than overcome by an eventual, modal growth as Mack-mode waves. For larger bluntness values, the Mack-mode waves are not amplified anywhere upstream of the experimentally measured transition location, but the traveling modes still undergo a significant amount of nonmodal growth. This finding does not provide a definitive link between optimal growth and the onset of transition, but it is qualitatively consistent with the experimental observations that frustum transition in the absence of sufficient Mack-mode amplification implies a double peak in disturbance amplification and the appearance of transitional events above the boundary-layer edge

Simulation of Supersonic Injection of Underexpanded Aerated Liquid Jet

The present computational study for underexpanded 2D and axisymmetric nozzle configuration is carried out for both gas-only and aerated liquid jet. The study is motivated by the application of fuel injection in air-breathing propulsion systems, e.g. scramjet engines, ramjet engines and afterburners. The simulation of gas-only jet carried out using Ansys-Fluent student version. The results show that air reaches sonic condition at the injector exit due to the Fanno flow effect in the injector passage. The aerated liquid jet flow from the injector is alternately expanded by Prandtl-Meyer expansion fan and compressed by oblique shock waves due to the difference between the back (chamber) pressure and the flow pressure. The process then repeats itself and shock (Mach) diamonds are formed downstream of the injector exit similar to those typical of exhaust plumes of propulsion system. The numerical results of gas-only jet for 2D and axisymmetric configuration are validated with theory of gas dynamics and experimental results. The numerical results of gas-only jet are in good agreement with theory and experiment. Similar to gas-only jet, simulation of aerated liquid jet is carried out for both 2D and axisymmetric nozzle configuration. The simulation of aerated liquid jet is conducted using VOF model and SST k-? turbulence model. The test conditions included: jet exit diameter of 1 mm and Gas to Liquid Ratio as 4%. The simulated result of 2D aerated liquid jet is compared with 2D gas-only jet using the contours of Mach number and static pressure. The flow field of axisymmetric aerated liquid jet differs from the 2D aerated liquid jet field; this can be explained based on the nozzle configuration. The present results also compare the cone angle expansion of aerated liquid jet. The cone angle expansion of aerated liquid jet is agreed with Prandtl-Meyer expansion analysis for 2D configuration and method of characteristics for axisymmetric configuration. The computed cone angle is always smaller than the theory, and this is probably due to inertia of the liquid jet. Present investigation shows that, the experimental results for aerated liquid jet expansion angle can be explained with the method of characteristics rather than the 2D Prandtl-Meyer expansion analysis.Mechanical & Aerospace Engineerin

Evaluation of used eye drop containers for microbial contamination in outpatient department of tertiary care teaching hospital

Background: Contaminated eyedrops are considered as serious risk factor for many iatrogenic ocular infections. Apart from the risk of infection, microbial contamination may alter the pH of the solution thereby reducing the efficacy of drugs. Presently many preservatives are added to these eye drops preparations to extend the duration of use. Hence authors aimed this study to find the contamination rates in such eye drop preparations.Methods: This was a prospective observational research conducted at Ophthalmology OPD, of tertiary care teaching hospital for the period of 2 months. Total fifty five used eyedrops were collected.Results: Authors found that 25.45% of the collected eye drops were contaminated with various organisms, viz. E. coli (10.90%), Staphylococcus aureus (9.09%), Pseudomonas aerugenosa (1.81%), Bacillus subtilis (1.81%) and Candida albicans (1.81%). Among various eyedrops, mydriatic (60%) eyedrops had the highest rate of contamination. We also found that, different preservatives in the eye drops were presents with different level of microbial contamination.Conclusions: The present study showed that there is a definite co-occurrence between eyedrop contamination and ocular infections irrespective of preservatives. This research raises a concern about questionable efficacy of preservatives.

DEVELOPMENT AND VALIDATION OF SPECTROPHOTOMETRIC AND ION PAIR CHROMATOGRAPHIC TECHNIQUE FOR ESTIMATION OF VALSARTAN AND HYDROCHLOROTHIAZIDE

Two new simple, sensitive, rapid, accurate and reproducible methods (UV-spectrophotometric and ion pair chromatography) have been developed for simultaneous estimation of valsartan (VAL) and hydrochlrothiazide (HCTZ) from their tablet dosage form. The first method involves multiwavelength spectrophotometric method (Method 1) in which interference of HCTZ at 245nm (wavelength for estimation of VAL) was removed by recording absorbance difference at 245nm and 301 nm whereas HCTZ was estimated directly from its absorbance at 316 nm at which VAL shows no absorbance. Linearity of the response was demonstrated by VAL in the concentration range of 5-45 g/ml with a square correlation coefficient (r2) of 0.9998. Linearity of the response was demonstrated by HCTZ in the concentration range of 2-18 g/ml with a square correlation coefficient (r2) of 0.9994. The second method utilizes ion pair chromatography (Method 2) on a HIQ sil ODS column (250 mm* 4.6 mm i.d.) using methanol: 0.0025 M orthophosphoric acid: (70:30 by volume) having pH 4.6: 0.1% hexane sulphonic acid as mobile phase with UV detection at 259nm over concentration range for VAL is 240-0 μg/ml, and for HCTZ is 75-0μg/ml. Losartan potassium was used as the internal standard. The suggested procedures were checked using laboratory prepared mixtures and were applied successfully for the analysis of their tablet dosage form. The results of analysis were statistically analysed. Both the methods were validated as per ICH Q2B guideline

Detailed Comparison of DNS to PSE for Oblique Breakdown at Mach 3

A pair of oblique waves at low amplitudes is introduced in a supersonic flat-plate boundary layer. Their downstream development and the concomitant process of laminar to turbulent transition is then investigated numerically using Direct Numerical Simulations (DNS) and Parabolized Stability Equations (PSE). This abstract is the last part of an extensive study of the complete transition process initiated by oblique breakdown at Mach 3. In contrast to the previous simulations, the symmetry condition in the spanwise direction is removed for the simulation presented in this abstract. By removing the symmetry condition, we are able to confirm that the flow is indeed symmetric over the entire computational domain. Asymmetric modes grow in the streamwise direction but reach only small amplitude values at the outflow. Furthermore, this abstract discusses new time-averaged data from our previous simulation CASE 3 and compares PSE data obtained from NASA's LASTRAC code to DNS results

Dynamics of silver elution from functionalised antimicrobial nanofiltration membranes

In an effort to mitigate biofouling on thin film composite membranes such as nanofiltration and reverse osmosis, a myriad of different surface modification strategies has been published. The use of silver nanoparticles (Ag-NPs) has emerged as being particularly promising. Nevertheless, the stability of these surface modifications is still poorly understood, particularly under permeate flux conditions. Leaching or elution of Ag-NPs from the membrane surface can not only affect the antimicrobial characteristics of the membrane, but could also potentially present an environmental liability when applied in industrial-scale systems. This study sought to investigate the dynamics of silver elution and the bactericidal effect of an Ag-NP functionalised NF270 membrane. Inductively coupled plasma-atomic emission spectroscopy was used to show that the bulk of leached silver occurred at the start of experimental runs, and was found to be independent of salt or permeate conditions used. Cumulative amounts of leached silver did, however, stabilise following the initial release, and were shown to have maintained the biocidal characteristics of the modified membrane, as observed by a higher fraction of structurally damaged Pseudomonas fluorescens cells. These results highlight the need to comprehensively assess the time-dependent nature of bactericidal membranes

STABILITY INDICATING RP-HPLC-PDA METHOD FOR DETERMINATION OF ABIRATERONE ACETATE AND CHARACTERIZATION OF ITS BASE CATALYZED DEGRADATION PRODUCT BY LC-MS

Objective: The present work describes stability indicating (SI) RP-HPLC-PDA method for determination of abiraterone acetate (ABA) and characterization of its base catalyzed degradation product by LC-MS.Methods: The separation was achieved by using column Kromasil C18 (250 mm × 4.6 mm, 4.0 µ) using acetonitrile (ACN): ammonium acetate buffer 10 mM, pH adjusted to 3.5 with acetic acid (AA) in the ratio of 10:90 % v/v as eluent. The Mobile phase flow rate was 0.6 ml/min and data integration was achieved at 235 nm.Results: The retention time of ABA was 5.4±0.01 min. Linearity was found to be in the range of 5–30 μg/ml. The limit of detection and quantitation were 0.25 μg/ml and 0.75 μg/ml respectively, and percentage recovery of ABA was found to be 99.52 to 100.13 %. Mass spectral data of base degraded product of ABA shows a prominent molecular ion peak at m/z-391.5. Major fragmentation leads to formation of 10–Methyl 2,3,4,7,8,9,10,11,12,13,14,15-dodecanhydro-1H cyclopenta (α)phenanthren-3-ol as a degradant (D2) at m/z-257.81, due to corresponding loss of C8H12ON. All the analytical validation parameters were determined and found in the limit as per ICH guidelines.Conclusion: The results of the various validation studies showed that the LC method is fast, specific, accurate, reproducible, possessed significant linearity and precision. The drug was found to be stable under all the stress conditions except basic stress. Thus developed method reported first time is novel with a very short run time of 6 min.Â

Study of OwnCloud Replication of Mobile Information on ownCloud

Main aim of this paper is to produce info on ownCloud. Several staff use cloud primarily based services to share sensitive company knowledge with one another, vendors, customers and partners. They synchronize knowledge to their personal devices and residential computers in a trial to try to to their jobs quickly and with efficiency. Replication is that the method of making and managing duplicate version of info. It not solely copies the info; however, additionally synchronize the set of duplicates in order that changes created in one replica area unit created in different info

Transition Analysis for the HIFiRE-1 Flight Experiment

The HIFiRE-1 flight experiment provided a valuable database pertaining to boundary layer transition over a 7-degree half-angle, circular cone model from supersonic to hypersonic Mach numbers, and a range of Reynolds numbers and angles of incidence. This paper reports the initial findings from the ongoing computational analysis pertaining to the measured in-flight transition behavior. Transition during the ascent phase at nearly zero degree angle of attack is dominated by second mode instabilities except in the vicinity of the cone meridian where a roughness element was placed midway along the length of the cone. The first mode instabilities were found to be weak at all trajectory points analyzed from the ascent phase. For times less than approximately 18.5 seconds into the flight, the peak amplification ratio for second mode disturbances is sufficiently small because of the lower Mach numbers at earlier times, so that the transition behavior inferred from the measurements is attributed to an unknown physical mechanism, potentially related to step discontinuities in surface height near the locations of a change in the surface material. Based on the time histories of temperature and/or heat flux at transducer locations within the aft portion of the cone, the onset of transition correlated with a linear PSE N-factor of approximately 14