An improved method for determining the DC magnetization curve using a ring specimen

When the DC magnetization curve (B-H) of nonoriented material is measured in a ring specimen, there is an intrinsic error due to the assumption that the mean magnetic path length is equal to the mean geometric path length. A novel method for determining the B-H curve accurately is proposed. The validity of the method is verified by experiments</p

Young stellar population and ongoing star formation in the HII complex Sh2-252

In this paper an extensive survey of the star forming complex Sh2-252 has been undertaken with an aim to explore its hidden young stellar population as well as to understand the structure and star formation history. This complex is composed of five embedded clusters associated with the sub-regions A, C, E, NGC 2175s and Teu 136. Using 2MASS-NIR and Spitzer-IRAC, MIPS photometry we identified 577 young stellar objects (YSOs), of which, 163 are Class I, 400 are Class II and 14 are transition disk YSOs. Spatial distribution of the candidate YSOs shows that they are mostly clustered around the sub-regions in the western half of the complex, suggesting enhanced star formation activity towards its west. Using the spectral energy distribution and optical colour-magnitude diagram based age analyses, we derived probable evolutionary status of the sub-regions of Sh2-252. Our analysis shows that the region A is the youngest (~ 0.5 Myr), the regions B, C and E are of similar evolutionary stage (~ 1-2 Myr) and the clusters NGC 2175s and Teu 136 are slightly evolved (~ 2-3 Myr). Morphology of the region in the 1.1 mm map shows a semi-circular shaped molecular shell composed of several clumps and YSOs bordering the western ionization front of Sh2-252. Our analyses suggest that next generation star formation is currently under way along this border and that possibly fragmentation of the matter collected during the expansion of the HII region as one of the major processes responsible for such stars. We observed the densest concentration of YSOs (mostly Class I, ~ 0.5 Myr) at the western outskirts of the complex, within a molecular clump associated with water and methanol masers and we suggest that it is indeed a site of cluster formation at a very early evolutionary stage, sandwiched between the two relatively evolved CHII regions A and B.Comment: 19 pages, 13 figures, Accepted for publication in MNRA

Optical and Near-infrared survey of the stellar contents associated with the star-forming Complex Sh2-252

We present the analyses of the stellar contents associated with the HII region Sh2-252 using UBVRI photometry, slit and slitless spectroscopy along with the NIR data from 2MASS for an area ~1 degree x 1 degree. We studied the sub-regions of Sh2-252 which includes four compact-HII (CHII) regions, namely A, B, C and E and two clusters NGC 2175s and Teutsch 136 (Teu 136). Of the fifteen spectroscopically observed bright stars, eight have been identified as massive members of spectral class earlier than B3. From the spectro-photometric analyses, we derived the average distance of the region as 2.4+/-0.2 kpc and the reddening of the massive members is found to vary between 0.35 to 2.1 mag. We found that NGC 2175s and Teu 136, located towards the eastern edge of the complex are the sub-clusters of Sh2-252. The stellar surface density distribution in K-band shows clustering associated with the regions A, C, E, NGC 2175s and Teu 136. We have also identified the candidate ionizing sources of the CHII regions. 61 H_alpha emission sources are identified using slitless spectroscopy. The distribution of the H_alpha emission sources and candidate YSOs with IR excess on the V/(V-I) CMD shows that a majority of them have approximate ages between 0.1 - 5 Myr and masses in the range of 0.3 - 2.5 M_sun. The CMDs of the candidate YSOs in the individual regions also show an age spread of 0.1 - 5 Myr for each of them. We calculated the KLFs for the sub-regions A, C, E, NGC 2175s and Teu 136. Within errors, the KLFs for all the sub-regions are found to be similar and comparable to that of young clusters of age < 5 Myr. We also estimated the mass functions (MFs) of the PMS sample of the individual regions in the mass range of 0.3 - 2.5 M_sun. In general, the slopes of the MFs of all the sub-regions are found comparable to the Salpeter value.Comment: published in MNRA

Deep optical survey of the stellar content of Sh2-311 region

The stellar content in and around Sh2-311 region have been studied using the deep optical observations as well as near-infrared (NIR) data from 2MASS. The region contains three clusters, viz. NGC 2467, Haffner 18 and Haffner 19. We have made an attempt to distinguish the stellar content of these individual regions as well as to re-determine their fundamental parameters such as distance, reddening, age, onto the basis of a new and more extended optical and infrared photometric data set. NGC 2467 and Haffner 19 are found to be located in the Perseus arm at the distances of 5.0 $\pm$ 0.4 kpc and 5.7 $\pm$ 0.4 kpc, respectively, whereas Haffner 18 is located at the distance of 11.2 $\pm$ 1.0 kpc. The clusters NGC 2467 and Haffner 19 might have formed from the same molecular cloud, whereas the cluster Haffner 18 is located in the outer galactic arm, i.e. the Norma-Cygnus arm. We identify 8 class II young stellar objects (YSOs) using the NIR $(J - H)/(H - K)$ two colour diagram. We have estimated the age and mass of the YSOs identified in the present work and those by Snider et al. (2009) using the $V/(V - I)$ colour-magnitude diagram. The estimated ages and mass range of the majority of the YSOs are $\lesssim$1 Myr and $\sim$0.4 - 3.5 \msun, respectively, indicating that these sources could be T-Tauri stars or their siblings. Spatial distribution of the YSOs shows that some of the YSOs are distributed around the H II region Sh2-311, suggesting a triggered star formation at its periphery.Comment: 19 pages, 13 figures, 9 table; Accepted for publication in New Astronom

Investigation of the transport properties for saline water in porous materials -- Modeling of the permeability coefficient for saline water--

8th International Building Physics Conference (IBPC 2021) 25-27 August 2021, Copenhagen, DenmarkSalt weathering is a major concern for cultural heritages such as ruins and tombs, and desalination by poulticing is an interesting potential method to efficiently remove contaminating salt. Predicting the degree of achievable desalination is very important. However, many existing models used to consider saline water transport in porous materials have been developed based on the theory of pure water. To understand saline water flow in porous materials, we determined the saline water permeability of a tuff stone by the falling-head method. We found that the permeability of the tuff stone was affected by factors other than the density and dynamic viscosity of the saline water

Multiwavelength Study of NGC 281 Region

We present a multiwavelength study of the NGC 281 complex which contains the young cluster IC 1590 at the center, using deep wide-field optical UBVI_c photometry, slitless spectroscopy along with archival data sets in the near-infrared (NIR) and X-ray. The extent of IC 1590 is estimated to be ~6.5 pc. The cluster region shows a relatively small amount of differential reddening. The majority of the identified young stellar objects (YSOs) are low mass PMS stars having age <1-2 Myr and mass 0.5-3.5 M_\odot. The slope (\Gamma) of the mass function for IC 1590, in the mass range 2 < M/M_\odot \le 54, is found to be -1.11+-0.15. The slope of the K-band luminosity function (0.37+-0.07) is similar to the average value (~0.4) reported for young clusters. The distribution of gas and dust obtained from the IRAS, CO and radio maps indicates clumpy structures around the central cluster. The radial distribution of the young stellar objects, their ages, \Delta(H-K) NIR-excess, and the fraction of classical T Tauri stars suggest triggered star formation at the periphery of the cluster region. However, deeper optical, NIR and MIR observations are needed to have a conclusive view of star formation scenario in the region. The properties of the Class 0/I and Class II sources detected by using the Spitzer mid-infrared observations indicate that a majority of the Class II sources are X-ray emitting stars, whereas X-ray emission is absent from the Class 0/I sources. The spatial distribution of Class 0/I and Class II sources reveals the presence of three sub-clusters in the NGC 281 West region.Comment: 29 pages, 21 figures and 11 tables, Accepted for the publication in PAS

Synthesis and properties of 2-(2-pyridyl)-1-azaazulene

ArticleTETRAHEDRON LETTERS. 48(26): 4471-4475 (2007)journal articl

Wide-Field Survey of Emission-line Stars in IC 1396

We have made an extensive survey of emission-line stars in the IC 1396 HII region to investigate the low-mass population of pre-main sequence (PMS) stars. A total of 639 H-alpha emission-line stars were detected in an area of 4.2 deg^2 and their i'-photometry was measured. Their spatial distribution exhibits several aggregates near the elephant trunk globule (Rim A) and bright-rimmed clouds at the edge of the HII region (Rim B and SFO 37, 38, 39, 41), and near HD 206267, which is the main exciting star of the HII region. Based on the extinction estimated from the near-infrared (NIR) color-color diagram, we have selected pre-main sequence star candidates associated with IC 1396. The age and mass were derived from the extinction corrected color-magnitude diagram and theoretical pre-main sequence tracks. Most of our PMS candidates have ages of < 3 Myr and masses of 0.2-0.6 Mo. Although it appears that only a few stars were formed in the last 1 Myr in the east region of the exciting star, the age difference among subregions in our surveyed area is not clear from the statistical test. Our results may suggest that massive stars were born after the continuous formation of low-mass stars for 10 Myr. The birth of the exciting star could be the late stage of slow but contiguous star formation in the natal molecular cloud. It may have triggered to form many low-mass stars at the dense inhomogeneity in and around the HII region by a radiation-driven implosion.Comment: 48 pages, 12 figures, 5 tables, accepted for publication in A

New Herbig-Haro Objects and Giant Outflows in Orion

We present the results of a photographic and CCD imaging survey for Herbig-Haro (HH) objects in the L1630 and L1641 giant molecular clouds in Orion. The new HH flows were initially identified from a deep H-alpha film from the recently commissioned AAO/UKST H-alpha Survey of the southern sky. Our scanned H-alpha and broad band R images highlight both the improved resolution of the H-alpha survey and the excellent contrast of the H-alpha flux with respect to the broad band R. Comparative IVN survey images allow us to distinguish between emission and reflection nebulosity. Our CCD H-alpha, [SII], continuum and I band images confirm the presence of a parsec-scale HH flow associated with the Ori I-2 cometary globule and several parsec-scale strings of HH emission centred on the L1641-N infrared cluster. Several smaller outflows display one-sided jets. Our results indicate that for declinations south of -6 degrees in L1641, parsec-scale flows appear to be the major force in the large-scale movement of optical dust and molecular gas.Comment: 14 pages, Latex using MN style, 21 figures in JPEG format. Higher resolution figures available from S.L. Mader. Accepted by MNRAS. Email contact for higher resolution images: [email protected]