Effects of parameters of Helmholtz resonator on transmission loss of hybrid muffler

Expansion chamber and Helmholtz resonators are widely used in noise control. In this paper, they are combined to use as a hybrid muffler. The analysis is done to investigate the influence of the parameters of Helmholtz resonator on transmission loss. The transfer matrix method is used in the analysis. The result of transmission loss from the transfer matrix method is validated with the result from experimental two-load method using four microphones impedance tube. After had the transmission loss of the hybrid muffler been validated, the study was proceeded to investigate the effects of parameters of Helmholtz resonator on the transmission loss. The root mean square value of transmission loss were also calculated to compare the transmission losses clearly. In this paper, we investigated the effect of length of the neck of Helmholtz resonator, the effect of diameter of the neck of Helmholtz resonator, the effect of the length of the Helmholtz resonator cavity and the effect of the diameter of the Helmholtz resonator cavity for stationary medium. It is found that the transmission loss is increased when the diameter of the neck of Helmholtz resonator is increased. When the length of the neck is reduced, the transmission loss is increased. The transmission loss can also be increased by reducing the diameter of resonator cavity. It is better to increase the transmission loss at low frequencies by increasing the length of the resonator cavity

The Megamaser Cosmology Project. III. Accurate Masses of Seven Supermassive Black Holes in Active Galaxies with Circumnuclear Megamaser Disks

Observations of H$_2$O masers from circumnuclear disks in active galaxies for the Megamaser Cosmology Project allow accurate measurement of the mass of supermassive black holes (BH) in these galaxies. We present the Very Long Baseline Interferometry (VLBI) images and kinematics of water maser emission in six active galaxies: NGC~1194, NGC~2273, NGC~2960 (Mrk~1419), NGC~4388, NGC~6264 and NGC~6323. We use the Keplerian rotation curves of these six megamaser galaxies, plus a seventh previously published, to determine accurate enclosed masses within the central $\sim0.3$ pc of these galaxies, smaller than the radius of the sphere of influence of the central mass in all cases. We also set lower limits to the central mass densities of between 0.12 and 60 $\times 10^{10} M_{\odot}$~pc$^{-3}$. For six of the seven disks, the high central densities rule out clusters of stars or stellar remnants as the central objects, and this result further supports our assumption that the enclosed mass can be attributed predominantly to a supermassive black hole. The seven BHs have masses ranging between 0.76 and 6.5$\times$10$^7 M_{\odot}$. The BH mass errors are $\approx11$\%, dominated by the uncertainty of the Hubble constant. We compare the megamaser BH mass determination with other BH mass measurement techniques. The BH mass based on virial estimation in four galaxies is consistent with the megamaser BH mass given the latest empirical value of $\langle f \rangle$, but the virial mass uncertainty is much greater. MCP observations continue and we expect to obtain more maser BH masses in the future.Comment: 18 pages, 4 figures. This paper has been submitted to ApJ. An updated version of this paper will be posted when it gets accepte

Bacteria isolated from Bengal cat (Felis catus × Prionailurus bengalensis) anal sac secretions produce volatile compounds potentially associated with animal signaling.

In social animals, scent secretions and marking behaviors play critical roles in communication, including intraspecific signals, such as identifying individuals and group membership, as well as interspecific signaling. Anal sacs are an important odor producing organ found across the carnivorans (species in the mammalian Order Carnivora). Secretions from the anal sac may be used as chemical signals by animals for behaviors ranging from defense to species recognition to signaling reproductive status. In addition, a recent study suggests that domestic cats utilize short-chain free fatty acids in anal sac secretions for individual recognition. The fermentation hypothesis is the idea that symbiotic microorganisms living in association with animals contribute to odor profiles used in chemical communication and that variation in these chemical signals reflects variation in the microbial community. Here we examine the fermentation hypothesis by characterizing volatile organic compounds (VOC) and bacteria isolated from anal sac secretions collected from a male Bengal cat (Felis catus × Prionailurus bengalensis), a cross between the domestic cat and the leopard cat. Both left and right anal sacs of a male Bengal cat were manually expressed (emptied) and collected. Half of the material was used to culture bacteria or to extract bacterial DNA and the other half was used for VOC analysis. DNA was extracted from the anal sac secretions and used for a 16S rRNA gene PCR amplification and sequencing based characterization of the microbial community. Additionally, some of the material was plated out in order to isolate bacterial colonies. Three taxa (Bacteroides fragilis, Tessaracoccus, and Finegoldia magna) were relatively abundant in the 16S rRNA gene sequence data and also isolated by culturing. Using Solid Phase Microextraction (SPME) gas chromatography-mass spectrometry (GC-MS), we tentatively identified 52 compounds from the Bengal cat anal sac secretions and 67 compounds from cultures of the three bacterial isolates chosen for further analysis. Among 67 compounds tentatively identified from bacterial isolates, 51 were also found in the anal sac secretion. We show that the bacterial community in the anal sac consists primarily of only a few abundant taxa and that isolates of these taxa produce numerous volatiles that are found in the combined anal sac volatile profile. Several of these volatiles are found in anal sac secretions from other carnivorans, and are also associated with known bacterial biosynthesis pathways. This is consistent with the fermentation hypothesis and the possibility that the anal sac is maintained at least in part to house bacteria that produce volatiles for the host

N-(Biphenyl-4-ylcarbon­yl)-N′-(2-pyridylmeth­yl)thio­urea

In the title compound, C20H17N3OS, the dihedral angle between the benzene rings of the biphenyl fragment is 36.84 (9)°. The trans–cis geometry of the thio­urea unit is stabilized by intra­molecular N—H⋯O and N—H⋯N hydrogen bonds between the H atom of the cis thio­amide and the carbonyl O and pyridine N atoms, respectively. In the crystal structure, inter­molecular N—H⋯S hydrogen bonds form centrosymmetric dimers extending along the b axis

The Association of NOV/CCN3 With Obstructive Sleep Apnea (OSA): Preliminary Evidence of a Novel Biomarker in OSA

Obstructive sleep apnea (OSA) has a strong association with cardiovascular and metabolic abnormalities, although the mechanism driving this association is not well established. NOV/CCN3, a multifunctional extracellular matrix protein, may play a mechanistic and/or prognostic role in these associations. We hypothesized that patients with OSA, which primarily affects obese individuals, will have increased levels of NOV, and that NOV can serve as a biomarker in patients to predict OSA as well as metabolic and cardiac risk. Ten morbidly obese and 10 healthy lean subjects underwent overnight polysomnography (PSG) and clinical evaluation. Blood samples were analyzed for NOV levels, adiponectin and IL-6. OSA was found in nine obese subjects and three lean subjects. NOV levels were significantly higher in the OSA vs. no OSA group (2.1 +/- 0.9 vs. 1.3 +/- 0.8, p \u3c 0.03). NOV levels were significantly higher in the obese vs. lean group (2.2 +/- 0.3 vs. 1.4 +/- 0.2-fold change, p \u3c 0.03). Among lean subjects, NOV levels were significantly higher in the OSA vs. no OSA group (2.1 +/- 0.9 vs. 1.0 +/- 0.4, p \u3c 0.05). NOV and AHI were positively correlated (rho = 0.49, p = 0.033). IL-6 and adiponectin differences in obese vs. lean and OSA vs. no OSA were consistent with an inflammatory phenotype in obese subjects and OSA subjects. NOV is a novel biomarker of the presence and severity of OSA and a potential marker of future cardiovascular and metabolic disease in OSA patients

The WiFeS S7 AGN survey: Current status and recent results on NGC 6300

The Siding Spring Southern Seyfert Spectroscopic Snapshot Survey (S7) is a targeted survey probing the narrow-line regions (NLRs) of a representative sample of ~140 nearby (z<0.02) Seyfert galaxies by means of optical integral field spectroscopy. The survey is based on a homogeneous data set observed using the Wide Field Spectrograph WiFeS. The data provide a 25x38 arcsec$^2$ field-of-view around the galaxy centre at typically ~1.5 arcsec spatial resolution and cover a wavelength range between ~3400 - 7100 $\AA$ at spectral resolutions of ~100 km s$^{-1}$ and ~50 km s$^{-1}$ in the blue and red parts, respectively. The survey is primarily designed to study gas excitation and star formation around AGN, with a special focus on the shape of the AGN ionising continuum, the interaction between radio jets and the NLR gas, and the nature of nuclear LINER emission. We provide an overview of the current status of S7-based results and present new results for NGC 6300.Comment: 5 pages, 1 figure, Refereed Proceeding of the "The Universe of Digital Sky Surveys" conference held at the INAF - Observatory of Capodimonte, Naples, on 25th-28th november 2014, to be published on Astrophysics and Space Science Proceedings, edited by Longo, Napolitano, Marconi, Paolillo, Iodic

Development of 68Ga Generator at ANSTO

A 68 Ge/ 68 Ga generator combined with automated 68 Ga eluate purification unit was developed to produce 68 Ga solution suitable for labelling peptide ligands for PET radiopharmaceutical applications. The sorbent of a Ti-Zr ceramic structure [1] was used as a generator column packing material. 68 Ga eluate of around 5 mL volume in 0.1 M HCl solution was purified on a small cation exchanger column with an aqueous alcohol solution mixture of hydrochloric acid, ascorbic acids and halide salts. An alkali solution was used for elution of 68 Ga from the ion exchange resin column to obtain a purified 68 Ga solution which is conditioned with acidic solutions to obtain a final 68 Ga product of pH=3-4 in 0.75 mL 0.5 M NaCl or 0.5 M sodium acetate solution. The organic solvent free 68 Ga solution product of acidity suitable for coordination chemistry based labelling of the peptide ligands was successfully used for preparation of DOTATATE and DOTATOC PET radiopharmaceuticals. The process of 68 Ga elution from the generator followed by 68 Ga eluate purification was performed using a low-cost automation bench-top system. [2] This system is designed based on the timing sequence of seven processing steps without feedback control. The variable flow rate of eluents used for elution/purification in this system also ensure the optimisation of operating times with respect to different adsorption/ desorption kinetics of 68 Ga ion species, which is controlled by the sorbent and ion exchange resin used in the generator and purification columns. © 2011, Medknow publicatio