38 research outputs found
Akshara- A Global Initiative
No full textabstract: Menstruation - a stigmatized topic and a social taboo- has led to a lack of menstrual hygiene awareness and improper practices impacting women’s health adversely over generations in India. Akshara aims to increase menstrual hygiene education and reduce stigma in India. A creative children’s illustrated book, and interactive workshop curriculum about menstruation were designed and published in Hindi and English. Menstrual hygiene workshops, utilizing the designed tools, were conducted in Delhi and Ghaziabad, India to over 230 students through NGO partnerships in December 2018. The response to the menstrual hygiene and stigma workshops was overwhelmingly positive, and a significant increase in the knowledge and awareness survey scores was observed after the curriculum teachings and classroom discussions. This evaluation highlights and provides a potential solution path to eradicate the root cause of the menstruation stigma in underprivileged women through education and open conversations on the topic starting at a pivotal young age. The main aim of the workshop was to help eradicate the stigma associated with menstruation and menstrual health in India through education
Mapping the ancient Milky Way through metal-poor stars
Full text linkThe Milky Way, our home galaxy, is a cornerstone for understanding galaxy formation. The Galaxy is shaped through mergers and star formation, and its stars preserve invaluable chemical and dynamical clues about its assembly. This thesis uses metal-poor stars--relics of the earliest epochs--to map the Galactic halo and trace the ancient Galaxy.Part I investigates the inner and outer halo: Chapter 2 maps the inner halo using Gaia DR3 proper motion and photometry and identifies density variations in stellar streams like GD-1 and Jhelum. Chapter 3 shows that very metal-poor (VMP) stars ([Fe/H] < -2) are 60 times rarer than metal-poor stars ([Fe/H] < -1) in the inner halo, offering additional insights into its metallicity distribution function (MDF). Chapter 4 maps the outer halo using metal-poor giant stars, inferring its MDF and revealing substructures, including the VMP stellar counterpart to the Magellanic Stream.Part II focuses on the Milky Way’s earliest stages: Chapter 5 reanalyses Gaia RVS spectra, identifying a new sample of 1000 bright VMP stars suitable for high-resolution spectroscopic follow-up. Chapter 6 uses the spectroscopic follow-up of Pristine-Gaia photometric metallicities (with a 77% success rate in finding [Fe/H] < -2.5 stars), mapping new members of the most metal-poor C-19 stream and the excess of VMP stars in disc-like orbits. Chapter 7 models the turbulent proto-Galaxy's rotational coherence using Gaia data, showing a slow, monotonic transition to an ordered, rotating old disc.Overall, this thesis underscores the power of metal-poor stars in studying the ancient Milky Way
Learning to spell in an alphasyllabary: The case of Kannada
No full textWe investigated children's spelling in the alphasyllabic writing system of Kannada, a South Indian language. Kannada represents language at roughly the level of the syllable, but its symbols or 'akshara' can be segmented visually to reveal the consonant and vowel segments within. Having been taught akshara as whole, fourth- and fifth-grade children were poor at constructing complex akshara from their consonant and vowel segments. Analyses of their errors showed confusions between the symbols for phonologically similar consonants, visually based errors, particularly on small diacritic marks, and influences of dialect. Kannada has been considered a transparent writing system, but the challenges that arise in mastering this visuo-spatially complex and extensive orthography suggest that previous studies have missed certain factors that contribute to the ease or difficulty with which a writing system is learned. © The Author 2010. Published by Oxford University Press
A slow spin to win: The gradual kinematic evolution across metallicities of the proto-Galaxy to the high-
No full textContext. Observational studies are identifying stars thought to be remnants from the earliest stages of the Milky Way’s hierarchical mass assembly, referred to as the proto-Galaxy.
Aims. We used red giant stars with kinematics from Gaia DR3 RVS data and [α/M] and [M/H] estimates from low-resolution Gaia XP spectra to investigate the relationship between azimuthal velocity and metallicity. Our aim is to understand the transition from a chaotic proto-Galaxy to a well-ordered rotating (high-α) disc-like population.
Methods. To analyze the structure of the data in [M/H]−vϕ space for both high- and low-α samples with carefully defined α-separation, we developed a model with two Gaussian components in vϕ, one representing a disc-like population and the other a halo-like population. This model is designed to capture the conditional distribution P(vϕ |[M/H]) with a two-component Gaussian mixture model with fixed means and standard deviations in the azimuthal velocities. To quantify the spin-up of the high-α disc population, we extended this two-component model by allowing the mean velocity and velocity dispersion to vary between the spline knots across the metallicity range used. We also compared our findings with existing literature using traditional Gaussian mixture modelling in bins of [M/H] and investigated using orbital circularity instead of azimuthal velocity.
Results. Our findings show that the metal-poor high-α disc gradually spins up across [M/H] ∼−1.7 to −1, while the low-α sample exhibits a sharp transition at [M/H] ≍−1. This latter result is due to the accreted (mostly Gaia-Enceladus-Sausage) debris dominating the metal-poor end, underscoring the critical role of [α/M] selection in studying the Milky Way’s (old, high-α) disc evolution.
Conclusions. These results indicate that the proto-Galaxy underwent a slow, monotonic spin-up phase over increasing metallicities rather than a rapid, dramatic spin-up at [M/H] ∼−1, as previously inferred in the literature
Utilization of Electrochemical Impedance Spectroscopy for the Detection of QSOX1 and CEA
No full textabstract: Improved pancreatic cancer diagnostic technology has the potential to improve patient prognosis by increasing cancer screening rates and encouraging early detection of the cancer. To increase the sensitivity and specificity while decreasing the cost and time investment, the emerging detection method of electrochemical impedance spectroscopy (EIS) was tested to detect two pancreatic cancer specific biomarkers. The antibodies of carcinoembryonic antigen and quiescin sulfhydryl oxidase 1 were immobilized individually to gold disk electrodes and tested for binding to their respective antigens. An AC signal of varying potential and a wide frequency sweep was applied to the electrode system and the resulting imaginary impedance values were analyzed. Based off of the highest slope and R-squared values of the collected impedance values, the optimal binding frequencies of QSOX1 and CEA with their antibodies was determined to be 97.66 Hz and 17.44 Hz, respectively. EIS was also used to test for potential multimarker detection by coimmobilizing anti-CEA and anti-QSOX1 to the surface of gold disk electrodes. Each system's impedance response was correlated to the physiological concentration range of CEA and QSOX1 individually. The resulting impedance and concentration calibration curves had R-squared values of 0.78 and 0.79 for the calculated QSOX1 and CEA, respectively. Both markers showed similar trends between the calculated and actual calibration curves for each marker. The imaginary impedance output lacks two independent peaks for the distinct optimal binding frequencies of both biomarkers after signal subtraction and show a large shift in optimal frequencies. From analyzing the co-immobilization data for the calculated and experimentally determined calibration curves of CEA and QSOX1, both curves had different correlation values between imaginary impedance values and concentration. Add and subtracting the experimental and calculated co-immobilization, QSOX1, and CEA signals suggest an oversaturation of QSOX1 used during the experiments
Typhon: A Polar Stream from the Outer Halo Raining through the Solar Neighborhood
Full text linkInternational audienceWe report on the discovery in the Gaia DR3 astrometric and spectroscopic catalog of a new polar stream that is found as an overdensity in action space. This structure is unique as it has an extremely large apocenter distance, reaching beyond 100 kpc, and yet is detected as a coherent moving structure in the solar neighborhood with a width of ~4 kpc. A subsample of these stars that was fortuitously observed by LAMOST has a mean spectroscopic metallicity of dex and possesses a resolved metallicity dispersion of dex. The physical width of the stream, the metallicity dispersion, and the vertical action spread indicate that the progenitor was a dwarf galaxy. The existence of such a coherent and highly radial structure at their pericenters in the vicinity of the Sun suggests that many other dwarf galaxy fragments may be lurking in the outer halo
Antaeus: A Retrograde Group of Tidal Debris in the Milky Way's Disk Plane
Full text linkInternational audienceWe present the discovery of a wide retrograde moving group in the disk plane of the Milky Way using action-angle coordinates derived from the Gaia DR3 catalog. The structure is identified from a sample of its members that are currently almost at the pericenter of their orbit and are passing through the solar neighborhood. The motions of the stars in this group are highly correlated, indicating that the system is probably not phase mixed. With a width of at least 1.5 kpc and with a probable intrinsic spread in metallicity, this structure is most likely the wide remnant of a tidal stream of a disrupted ancient dwarf galaxy (age ~12 Gyr, ~ -1.74). The structure presents many similarities (e.g., in energy, angular momentum, metallicity, and eccentricity) with the Sequoia merging event. However, it possesses extremely low vertical action J z , which makes it unique even among Sequoia dynamical groups. As the low J z may be attributable to dynamical friction, we speculate that these stars may be the remnants of the dense core of the Sequoia progenitor
Hidden deep in the halo: Selection of a reduced proper motion halo catalogue and mining retrograde streams in the velocity space
Full text linkThe Milky Way halo is one of the few galactic haloes that provides a unique
insight into galaxy formation by resolved stellar populations. Here, we present
a catalogue of 47 million halo stars selected independent of parallax and
line-of-sight velocities, using a combination of Gaia DR3 proper motion and
photometry by means of their reduced proper motion. We select high tangential
velocity (halo) main sequence stars and fit distances to them using their
simple colour-absolute-magnitude relation. This sample reaches out to 21
kpc with a median distance of kpc thereby probing much further out than
would be possible using reliable Gaia parallaxes. The typical uncertainty in
their distances is kpc. Using the colour range
where the main sequence is narrower, gives
an even better accuracy down to kpc in distance. The
median velocity uncertainty for stars within this colour range is 15.5 km/s.
The distribution of these sources in the sky, together with their tangential
component velocities, are very well-suited to study retrograde substructures.
We explore the selection of two complex retrograde streams: GD-1 and Jhelum.
For these streams, we resolve the gaps, wiggles and density breaks reported in
the literature more clearly. We also illustrate the effect of the kinematic
selection bias towards high proper motion stars and incompleteness at larger
distances due to Gaia's scanning law. These examples showcase how the full RPM
catalogue made available here can help us paint a more detailed picture of the
build-up of the Milky Way halo.Comment: 17 pages. Accepted for publication in MNRAS. The catalogue has been
submitted as supplementary material to CDS and MNRAS for use to do more
wonderful science. Comments are welcomed and appreciated
A slow spin to win:The gradual kinematic evolution across metallicities of the proto-Galaxy to the high- α disc
Full text linkContext. Observational studies are identifying stars thought to be remnants from the earliest stages of the Milky Way’s hierarchical mass assembly, referred to as the proto-Galaxy. Aims. We used red giant stars with kinematics from Gaia DR3 RVS data and [α/M] and [M/H] estimates from low-resolution Gaia XP spectra to investigate the relationship between azimuthal velocity and metallicity. Our aim is to understand the transition from a chaotic proto-Galaxy to a well-ordered rotating (high-α) disc-like population. Methods. To analyze the structure of the data in [M/H]−vϕ space for both high- and low-α samples with carefully defined α-separation, we developed a model with two Gaussian components in vϕ , one representing a disc-like population and the other a halo-like population. This model is designed to capture the conditional distribution P(vϕ |[M/H]) with a two-component Gaussian mixture model with fixed means and standard deviations in the azimuthal velocities. To quantify the spin-up of the high-α disc population, we extended this two-component model by allowing the mean velocity and velocity dispersion to vary between the spline knots across the metallicity range used. We also compared our findings with existing literature using traditional Gaussian mixture modelling in bins of [M/H] and investigated using orbital circularity instead of azimuthal velocity. Results. Our findings show that the metal-poor high-α disc gradually spins up across [M/H] ∼−1.7 to −1, while the low-α sample exhibits a sharp transition at [M/H] ≍−1. This latter result is due to the accreted (mostly Gaia-Enceladus-Sausage) debris dominating the metal-poor end, underscoring the critical role of [α/M] selection in studying the Milky Way’s (old, high-α) disc evolution. Conclusions. These results indicate that the proto-Galaxy underwent a slow, monotonic spin-up phase over increasing metallicities rather than a rapid, dramatic spin-up at [M/H] ∼−1, as previously inferred in the literature.</p
Gaia's brightest very metal-poor (VMP) stars: A metallicity catalogue of a thousand VMP stars from Gaia RVS spectra
Full text linkContext. Gaia DR3 has offered the scientific community a remarkable dataset
of approximately one million spectra acquired with the Radial Velocity
Spectrometer (RVS) in the Calcium II triplet region, that is well-suited to
identify very metal-poor (VMP) stars. However, over 40% of these spectra have
no released parameters by Gaia's GSP Spec pipeline in the domain of VMP stars,
whereas VMP stars are key tracers of early Galactic evolution. Aims. We aim to
provide spectroscopic metallicities for VMP stars using Gaia RVS spectra,
thereby producing a catalogue of bright VMP stars distributed over the full sky
that can serve as the basis to study early chemical evolution throughout the
Galaxy. Methods. We select VMP stars using photometric metallicities from the
literature and analyse the Gaia RVS spectra to infer spectroscopic
metallicities for these stars. Results. The inferred metallicities agree very
well with literature high-resolution metallicities with a median systematic
offset of 0.1 dex and standard deviation of 0.15 dex. The purity of this
sample in the VMP regime is 80% with outliers representing a mere
3%. Conclusions. We make available an all-sky catalogue of 1500
stars with reliable spectroscopic metallicities down to [Fe/H]-4.0, of
which 1000 are VMP stars. More than 75% of these stars have either no
metallicity value in the literature to date or are flagged to be unreliable in
their literature metallicity estimates. This catalogue of bright (G<13) VMP
stars is three times larger than the current sample of well-studied VMP stars
in the literature in this magnitude range, making it ideal for high-resolution
spectroscopic follow-up and to study the properties of VMP stars in different
parts of our Galaxy.Comment: Submitted to A&A. 11 pages, 4 pages appendix, 5 figures. Catalogue is
made available public here:
https://astroakshara.github.io/rvs-paper/Gaia-RVS-VMP-catalogue-AV23b-vSep23.csv
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