A Study of the Effect of Bulges on Bar Formation in Disk galaxies

We use N-body simulations of bar formation in isolated galaxies to study the effect of bulge mass and bulge concentration on bar formation. Bars are global disk instabilities that evolve by transferring angular momentum from the inner to outer disks and to the dark matter halo. It is well known that a massive spherical component such as halo in a disk galaxy can make it bar stable. In this study we explore the effect of another spherical component, the bulge, on bar formation in disk galaxies. In our models we vary both the bulge mass and concentration. We have used two sets of models, one that has a dense bulge and high surface density disk. The second model has a less concentrated bulge and a lighter disk. In both models we vary the bulge to disk mass fraction from 0 to 0.7. Simulations of both the models show that there is an upper cutoff in bulge to disk mass ratio M b /M d above which bars cannot form; the cutoff is smaller for denser bulges( M b /M d = 0.2) compared to less denser ones (M b /M d = 0.5). We define a new criteria for bar formation in terms of bulge to disk radial force ratio (F b /F d ) at the disk scale lengths above which bars cannot form. We find that if F b /F d > 0.35, a disk is stable and a bar cannot form. Our results indicate that early type disk galaxies can still form strong bars in spite of having massive bulges.Comment: Accepted at MNRAS,12 pages, 19 figure

Effects of Inner Halo Angular Momentum on the Peanut/X-shapes of Bars

Cosmological simulations show that dark matter halos surrounding baryonic disks have a wide range of angular momenta, measured by the spin parameter ($\lambda$). In this study, we bring out the importance of inner angular momentum($<$30 kpc), measured in terms of the halo spin parameter, on the secular evolution of the bar using N-body simulations. We have varied the halo spin parameter $\lambda$ from 0 to 0.1 for co-rotating (prograde) spinning halos and one counter-rotating (retrograde) halo spin ($\lambda$=-0.1) with respect to the disk. We report that as the halo spin increases, the buckling is also triggered earlier and is followed by a second buckling phase in high-spin halo models. The timescale for the second buckling is significantly longer than the first buckling. We find that bar strength does not reduce significantly after the buckling in all of our models, which provides new insights about the role of inner halo angular momentum, unlike previous studies. Also, the buckled bar can still transfer significant angular momentum to the halo in the secular evolution phase, but it reduces with increasing halo spin. In the secular evolution phase, the bar strength increases and saturates to nearly equal values for all the models irrespective of halo spin and the sense of rotation with respect to the disk. The final boxy/peanut shape is more pronounced ($\sim$20 $\%$) in high spin halos having higher angular momentum in the inner region compared to non-rotating halos. We explain our results with angular momentum exchanges between the disk and halo.Comment: 14 pages,13 figures, 2 tables; Accepted for publication in Ap

Modelling Dark Matter Halo Spin using Observations and Simulations: application to UGC 5288

Dark matter (DM) halo properties are extensively studied in cosmological simulations but are very challenging to estimate from observations. The DM halo density profile of observed galaxies is modelled using multiple probes that trace the dark matter potential. However, the angular momentum distribution of DM halos is still a subject of debate. In this study we investigate a method for estimating the halo spin and halo concentration of low surface brightness (LSB), gas-rich dwarf barred galaxy UGC 5288, by forward modelling disk properties derived from observations - stellar and gas surface densities, disk scale length, HI rotation curve, bar length and bar ellipticity. We combine semi-analytical techniques, N-body/SPH and cosmological simulations to model the DM halo of UGC 5288 with both a cuspy Hernquist profile and a flat-core pseudo-isothermal profile. We find that the best match with observations is a pseudo-isothermal halo model with a core radius of $r_{c} = 0.23$ kpc, and halo spin of $\lambda$= 0.08 at the virial radius. Although our findings are consistent with previous core radius estimates of the halo density profile of UGC 5288, as well as with the halo spin profiles of similar mass analogues of UGC5288 in the high-resolution cosmological-magneto-hydrodynamical simulation TNG50, there still remain some uncertainties as we are limited in our knowledge of the formation history of the galaxy. Additionally, we find that the inner halo spin ($r< 10$ kpc) in barred galaxies is different from the unbarred ones, and the halo spin shows weak correlations with bar properties.Comment: 29 pages including Appendix, 28 figures, accepted in MNRAS, comments are welcome from the communit

Decision-Making in Real-Life Industrial Environment through Graph Theory Approach

The approach called as “graph theory and matrix approach” has been well employed in numerous research studies with a view to perform the decision-making while the situation is becoming perplexed type or where there is a very strong relative importance of one parameter over another. In such cases, the said graph theory and matrix method provides very suitable and fruitful solutions to make the decision to its final effective extent. The further improvements and the outcome enhancement can also be revealed through the use of combined practice of graph theory results along with some artificial intelligence-inspired logics and practices such as fuzzy logic, artificial neural network, etc. The significance and applicability of said method in vast fields of science, engineering, and research are also proved. Nowadays, our manufacturing sectors are getting up to date through the applications of artificial intelligence and several software-based directions. This is all to enhance the overall machine system performance with a view to improve desired performance characteristics of the process under the study. Few sections of this chapter has also elaborated the utility of the artificial intelligence-inspired fuzzy logic-based decision system which has already been a part of previous researches

Testing a theoretical prediction for bar formation in galaxies with bulges

Earlier studies have shown that massive bulges impede bar formation in disk galaxies. Recent N-body simulations have derived a bar formation criterion that depends on the radial bulge force in a galaxy disk. We use those simulations to show that bars can form only when the force constant FB < 0.13, where FB depends on the ratio of the bulge force to the total force of the galaxy at twice the disk scale length 2R d . In this article, we test this theoretical prediction using observational data obtained from the literature. Our sample consists of 63 barred galaxies with a wide range of Hubble classes from the S 4 G catalogue for which bulge, disk and bar decomposition has been done. We find that 92 % of our sample galaxies satisfy the condition FB < 0.13 for bar formation in galaxies and hence agree with the bar formation criterion given by the simulations.Comment: 7 pages, 5 figures, accepted for publication in A&

Otkrivanje i analiza varijacija u otpornosti na antibiotike među izolatima bakterije Staphylococcus aureus životinja i ljudi

In consideration of the importance of Staphylococcus aureus regarding its contribution to antibiotic resistance, the present study was designed to find variability among S. aureus isolates in relation to their multidrug resistance patterns. A total of 157 species-specific 23S rRNA based confirmed S. aureus isolates from various clinical and non- clinical animal sources (cattle, buffalo, goat, sheep, dog, camel, pig and horse), human and pieces of meat from butcher shops were included in the present study. Overall more than 95% isolates were recorded resistant to ampicillin and penicillin-G, while approximately 100% isolates were sensitive to chloramphenicol, meropenem and nitrofurantoin. The isolates from different sources showed highly significant (P≤0.01) variation in their resistance patterns for 39 antibiotics, significant variation (P≤0.05) for levofloxacin and nitrofurantoin, and no significant variation (P>0.05) for clindamycin. In Bonferroni correction, human isolates were significantly variable with a P˂0.0001 probability level of variance in relation to other pieces of meat and animal origin sources for most of the antibiotics. Human isolates had the highest (0.40) MAR index. A highly significant difference was observed in the antibiogram pattern between different sources of S. aureus, which may indicate the pattern and frequency of use of various antibiotics in humans and animals.S obzirom na važnost bakterije Staphylococcus aureus u smislu otpornosti na antibiotike, cilj je ovog istraživanja bio otkriti varijacije među njezinim izolatima s obzirom na rezistenciju prema brojnim lijekovima. Istraživanje je obuhvatilo ukupno 157 vrsno specifičnih 23S rRNA S. aureus izolata iz različitih kliničkih i nekliničkih izvora životinja (goveda, bivoli, koze, ovce, psi, deve, svinje i konji), ljudi i mesa iz mesnica. Zabilježeno je više od 95 % izolata otpornih na ampicilin i penicilin-G dok je gotovo 100 % izolata bilo osjetljivo na kloramfenikol, meropenem i nitrofurantoin. Izolati iz različitih izvora pokazali su znakovite varijacije (P ≤ 0,01) u rezistenciji na 39 antibiotika, znakovite varijacije (P ≤ 0,05) za levofloksacin i nitrofurantoin, no nije bilo znakoviith varijacija (P > 0,05) za klindamicin. Primjenom Bonferronijeve korekcije izolati iz ljudi bili su znakovito različiti (P ˂ 0,0001) u odnosu na uzorke iz mesa i drugih izvora animalnog podrijetla za većinu antibiotika. Izolati podrijetlom od ljudi imali su najviši MAR indeks (0,40). Uočena je vrlo znakovita razlika u antibiogramima među različitim izvorima bakterije S. aureus što može uputiti na način i učestalost primjene različitih antibiotika u ljudi i životinja

FORMULATION AND EVALUATION OF MATRIX DIFFUSION CONTROLLED TRANSDERMAL DRUG DELIVERY SYSTEM OF GLIPIZIDE

Abstract: Context: There has been a tremendous increase in interest for transdermal drug delivery system for sustain release dosage form in chronic manageable diseased conditions like diabetes, hypertension etc to reduce the frequency of dosing. It reduces the risk of exposing the body to drug above maximum safe concentration in case of dosage form failure in comparison to oral sustained release drug delivery system. Aims: Transdermal patches of Glipizide were formulated to achieve sustain release pattern within the therapeutic range. Methods and Material: HPMC 5cps, HPMC 15cps, HPMC K-100M, Ethyl cellulose (EC), Eudragit RS 100 (ERS-100) and Polyvinylpyrrolidone (PVP) K30 were used as matrix forming polymer. Propylene glycol was used as penetration enhancer. Polyethylene glycol (PEG) 400 and n-dibultyl phthalate (n-DB) were used as plasticizer. Methanol and chloroform were used as solvents. Patches were prepared by solvent casting method. Results: Patches prepared, from each batch, gave release profile for over 10 hours. Conclusions: Prepared patches from HPMC 5 cps and ethyl cellulose exhibited good characteristics for sustained release action and other parameters evaluated

Excitation of vertical breathing motion in disc galaxies by tidally-induced spirals in fly-by interactions

It is now clear that the stars in the Solar neighbourhood display large-scale coherent vertical breathing motions. At the same time, Milky Way-like galaxies experience tidal interactions with satellites/companions during their evolution. While these tidal interactions can excite vertical oscillations, it is still not clear whether vertical breathing motions are excited directly by the tidal encounters or are driven by the tidally-induced spirals. We test whether excitation of breathing motions are directly linked to tidal interactions by constructing a set of N-body models (with mass ratio 5:1) of unbound single fly-by interactions with varying orbital configurations. We first reproduce the well-known result that such fly-by interactions can excite strong transient spirals (lasting for ∼2.9−4.2Gyr⁠) in the outer disc of the host galaxy. The generation and strength of the spirals are shown to vary with the orbital parameters (the angle of interaction, and the orbital spin vector). Furthermore, we demonstrate that our fly-by models exhibit coherent breathing motions whose amplitude increases with height. The amplitudes of breathing motions show characteristic modulation along the azimuthal direction with compressing breathing motions coinciding with the peaks of the spirals and expanding breathing motions falling in the inter-arm regions – a signature of a spiral-driven breathing motion. These breathing motions in our models end when the strong tidally-induced spiral arms fade away. Thus, it is the tidally-induced spirals which drive the large-scale breathing motions in our fly-by models, and the dynamical role of the tidal interaction in this context is indirect