The quest for cradles of life: using the fundamental metallicity relation to hunt for the most habitable type of galaxy

The field of astrobiology has made huge strides in understanding the habitable zones around stars (stellar habitable zones) where life can begin, sustain its existence and evolve into complex forms. A few studies have extended this idea by modeling galactic-scale habitable zones (galactic habitable zones) for our Milky Way (MW) and specific elliptical galaxies. However, estimating the habitability for galaxies spanning a wide range of physical properties has so far remained an outstanding issue. Here, we present a "cosmobiological" framework that allows us to sift through the entire galaxy population in the local universe and answer the question, "Which type of galaxy is most likely to host complex life in the cosmos?" Interestingly, the three key astrophysical criteria governing habitability (total mass in stars, total metal mass and ongoing star formation rate) are found to be intricately linked through the "fundamental metallicity relation" as shown by Sloan Digital Sky Survey observations of more than a hundred thousand galaxies in the local universe. Using this relation we show that metal-rich, shapeless giant elliptical galaxies at least twice as massive as the MW (with a tenth of its star formation rate) can potentially host ten thousand times as many habitable (Earth-like) planets, making them the most probable "cradles of life" in the universe

Characterizing Shear Wave Contact Transducers by Immersion Scanning

Shear wave ultrasonic transducers for contact mode testing are commercially available. These packaged transducers usually contain a circular piezoelectric element and the mounting is such that the polarization direction of the shear vibration is defined by a line passing through the center of the transducer and the electrical connector. For measure ments in isotropic materials, the polarization direction is not important. For quantitative shear wave measurements in anisotropic materials such as composites1–3, it is important to know the polarization direction of the transducer with a good precision. Unfortunately, commercial shear wave transducers are usually not very accurate in their mounting; it is not uncommon to have +/- 10° of error in their polarization direction and much greater errors have also been encountered

Is strontium isotope record a strict proxy for chemical weathering rates during the late Miocene (Ocean Drilling Program Site 758A)?

The strontium isotope ratios are examined in the shells of planktic foraminifer Orbulina universa in 20 samples from the late Miocene (8.03-6.36 Ma) sequence of Ocean Drilling Program (ODP) Site 758A, northeastern Indian Ocean. The Sr isotope ratios increased between 7.91 and 7.36 Ma and in the latest Miocene (6.48-6.36 Ma) reflecting high riverine flux from increased chemical weathering and high precipitation in the Himalayan region. The 87Sr/86Sr values decreased during 7.36 to 6.48 Ma coincident with the main phase of Chron-6 negative carbon shift. The carbon shift reflects high delivery of nutrients to the oceans. This contradicts the use of Sr isotope record as a strict proxy for global chemical weathering rates. The Sr isotope ratio should be used with great care in understanding the climatic- tectonic connections

Wild Halophyte Plants as Potential Fodder Resource under Extreme Saline Environment of Kachchh, Gujarat, India

Rann of Kachchh in North West India is a unique saline marshy desert. It is described as a desolate area of unrelieved, sun-baked saline clay desert, shimmering with the images of a perpetual mirage (Mountfort et al., 1991) and is regarded as the largest salt desert in the world. In the Indian part it stretches in 7505.22 sq. km known as Great Rann and 4,953 sq. km known as Little Rann. The Ranns turns into marshy land by inundated water from runoff during monsoonal rainfall and water driven by forces of winds and tides from Arabian Sea making the area unapproachable especially during June to September and in reminder of months the area remain as a hyper saline desert. Even at these extreme saline conditions certain halophytic plants come up from the native seed bank/ roots once the water gets evaporated as these plants possess some mechanisms to survive salinity even higher than that of sea water (Goswami et al., 2014). Some of these plants are grazed by livestock of the area. Due to uncontrolled grazing by ever increasing livestock population and increasing demand for fuel wood, in these deserts the natural diversity of these halophytes are at stake (Arndt et al., 2004). Information on the diversity of halophytes in the hyper saline desert in relation to varying degree of salinization is not available. Therefore the present study was undertaken to study the distribution of halophyte grasses and non-grasses in Great Rann of Kachchh and their usefulness as fodder resource

Euclid preparation: XXI. Intermediate-redshift contaminants in the search for z>6 galaxies within the Euclid Deep Survey

The author list was incorrect in the published version. The name of the collaboration has been added here

Effect of dietary supplementation of cassia auriculata leaf powder on growth and immune responses of milkfish, Chanos chanos

A 30 days feeding trial was conducted to evaluate the effects of Cassia auriculata leaf powder on growth and immunomological parameters of the juveniles of Milkfish, Chanos chanos and disease resistance against Vibrio anguillarum. The juvenile fishes with an average weight of 20±3 g were stocked in four treatments each with three replicates. Four practical diets were prepared with graded level of Cassia auriculata leaf powder (CAL) at the rate of 0%, 0.5%, 1% and 1.5% and fed to four treatments respectively named as CAL0, CAL0.5, CAL1 and CAL1.5. At the end of the experiment blood samples were collected for immunological parameters. After sampling, the remaining fishes were challenged with 0.1 mL of virulent V. anguillarum suspension at a concentration of 107 CFU mL-1 and mortality was observed for 7 days. Post challenge sampling was performed for the collection of blood samples. The growth parameters such as Weight gain%, SGR%, PER were positively affected by Cassia auriculata leaf powder incorporated diet. Higher weight gain %, SGR% and PER were noticed in CAL1.5 group followed by CAL1, CAL0.5 and CAL0. The respiratory burst, lysozyme and phagocytic activities were increased with increasing level of CAL in the diet which indicates better immune response of the fishes fed with CAL. The higher respiratory burst (0.522 ± 0.03), lysozyme (70.07 ± 1.57) and phagocytic (52.91 ± 1.76) activitieswere observed in CAL1.5, CAL1 and CAL1.5 groups respectively during pre-challenge and post challenge. There was significant difference in the survival rate of control (CAL0) and CAL incorporated diet fed groups (P<0.05). Maximum survival was witnessed in CAL1 followed by CAL1.5 and least survival was in CAL0 group. The results indicate that diets supplemented with 1% CAL potentially enhance the immune system and effectively protects the host against V. anguillarum infection and thereby improve the survivability of the fish against this dreadful pathogen

Performance Limitations of Flat Histogram Methods and Optimality of Wang-Landau Sampling

We determine the optimal scaling of local-update flat-histogram methods with system size by using a perfect flat-histogram scheme based on the exact density of states of 2D Ising models.The typical tunneling time needed to sample the entire bandwidth does not scale with the number of spins N as the minimal N^2 of an unbiased random walk in energy space. While the scaling is power law for the ferromagnetic and fully frustrated Ising model, for the +/- J nearest-neighbor spin glass the distribution of tunneling times is governed by a fat-tailed Frechet extremal value distribution that obeys exponential scaling. We find that the Wang-Landau algorithm shows the same scaling as the perfect scheme and is thus optimal.Comment: 5 pages, 6 figure

Trace element and isotopic studies of Permo-Carboniferous carbonate nodules from Talchir sediments of peninsular India: environmental and provenance implications

Syngenetic carbonate nodules constitute an interesting feature of the glaciogene sediments of various Talchir basins in peninsular India. Petrographic, cathodoluminescence and sedimentary results suggest that many of these nodules contain primary carbonate precipitates whose geochemical signatures can be used for determining environment of deposition and provenance of the sediments and drainage source. Several nodules were collected from Gondwana basins of east-central India and analyzed for stable carbon and oxygen isotope ratios, REE and trace element composition, and Sr isotope ratio. The mean δ18O and δ13C values of the calcites in the nodules are - 19.5% and-9.7% (w.r.t. PDB) respectively suggesting a freshwater environment (probably lacustrine) for formation of these objects. Trace element ratios (Eu/Eu* and La/Yb) of the nodule samples show that the source of the sediments in the Damodar valley basin was the granites, gneisses and intrusives in the Chotanagpur region. The sediments in the Mahanadi valley were derived from granulites, charnockites and granites of the eastern ghat region. The Sr concentration of the carbonate phase of the nodules is low, ranging from 10-60 ng/g. The87Sr/86Sr ratios of the samples from the west Bokaro basin and Ramgarh basin vary from 0.735 to 0.748 (mean: 0.739) and from 0.726 to 0.733 (mean: 0.730) respectively. These values are consistent with our proposition that water of these basins drained through the granitic rocks of the Chotanagpur region. In contrast, the87Sr/86Sr ratios of the samples from the Talchir basin (Type area) of Mahanadi valley vary from 0.718 to 0.723 (mean: 0.719). These87Sr/86Sr ratios are close to those of the granulites in the adjoining eastern ghat belt suggesting that area as the drainage source