HOLOCENE GEOLOGY AND MULTI-PROXY PALEOENVIRONMENTAL RECONSTRUCTION OF THE SUNDA SHELF OFF THE EAST COAST OF PENINSULAR MALAYSIA

In May (2016), six 1.25 to 2.2 m long gravity cores were collected at water depths ranging from 68 m to 77 m along a transect crossing the incised Chao-Phraya paleo-river valley between Peninsular Malaysia and southern Vietnam, on the Sunda Shelf (southern South China Sea). The objective of this research is to use multiple proxies to make paleoenvironmental reconstructions of the cored sediments’ depositional environments. The six cores provided 130 samples selected for analysis of bulk sediment magnetic susceptibility (BMS), 66 for elemental analysis by means of x-ray fluorescence spectrometry (XRF), 52 for analysis of foraminiferal assemblages, and 10 for AMS radiocarbon dating. BMS data show that sediments near the base of the cores typically display higher magnetic susceptibility than sediments closer to the surface, although results vary between and within cores. Other studies show that variations in BMS magnitudes are a result of changes in terrestrial sediment flux during deposition. XRF data will help constrain origins on the cored sediment (e.g. terrestrial or marine). For example, aluminum is typically concentrated in aluminosilicates and can be used as a proxy for variations in grain size. Concentrations of calcium, when inversely correlated with aluminum, are commonly interpreted to derive from a different source (e.g., marine). Foraminiferal assemblages will be used as a proxy for environmental change in conjunction with BMS and XRF.Research and Creative Achievement Wee

uvbyCa H beta CCD Photometry of Clusters. VII. The Intermediate-Age Anticenter Cluster Melotte 71

CCD photometry on the intermediate-band uvbyCa H beta system is presented for the anticenter, intermediate-age open cluster, Melotte 71. Restricting the data to probable single members of the cluster using the color-magnitude diagram and the photometric indices alone generates a sample of 48 F dwarfs on the unevolved main sequence. The average E(b-y) = 0.148 +/- 0.003 (s.e.m.) or E(B-V) = 0.202 +/- 0.004 (s.e.m.), where the errors refer to internal errors alone. With this reddening, [Fe/H] is derived from both m1 and hk, using H beta and b-y as the temperature index, with excellent agreement among the four approaches and a final weighted average of [Fe/H] = -0.17 +/- 0.02 (s.e.m.) for the cluster, on a scale where the Hyades has [Fe/H] = +0.12. When adjusted for the higher reddening estimate, the previous metallicity estimates from Washington photometry and from spectroscopy are now in agreement with the intermediate-band result. From comparisons to isochrones of appropriate metallicity, the cluster age and distance are determined as 0.9 +/- 0.1 Gyr and (m-M) = 12.2 +/- 0.1 or (m-M)_0 = 11.6 +/- 0.1. At this distance from the sun, Mel 71 has a galactocentric distance of 10.0 kpc on a scale where the sun is 8.5 kpc from the galactic center. Based upon its age, distance, and elemental abundances, Mel 71 appears to be a less populous analog to NGC 3960.Comment: Accepted for Astronomical Journal. 38 page latex file includes 11 figures and short version of data table. Full table will appear in online AJ or may be requested from author

Iron abundances from high-resolution spectroscopy of the open clusters NGC 2506, NGC 6134, and IC 4651

This is the first of a series of papers devoted to derive the metallicity of old open clusters in order to study the time evolution of the chemical abundance gradient in the Galactic disk. We present detailed iron abundances from high resolution (R~40000) spectra of several red clump and bright giant stars in the open clusters IC 4651, NGC 2506 and NGC 6134. We observed 4 stars of NGC 2506, 3 stars of NGC 6134, and 5 stars of IC 4651 with the FEROS spectrograph at the ESO 1.5 m telescope; moreover, 3 other stars of NGC 6134 were observed with the UVES spectrograph on Kueyen (VLT UT2). After excluding the cool giants near the red giant branch tip (one in IC 4651 and one in NGC 2506), we found overall [Fe/H] values of -0.20 +/- 0.01, rms = 0.02 dex (2 stars) for NGC 2506, +0.15 +/- 0.03, rms = 0.07 dex (6 stars) for NGC 6134, and +0.11 +/- 0.01, rms = 0.01 dex (4 stars) for IC 4651. The metal abundances derived from line analysis for each star were extensively checked using spectrum synthesis of about 30 to 40 Fe I lines and 6 Fe II lines. Our spectroscopic temperatures provide reddening values in good agreement with literature data for these clusters, strengthening the reliability of the adopted temperature and metallicity scale. Also, gravities from the Fe equilibrium of ionization agree quite well with expectations based on cluster distance moduli and evolutionary masses.Comment: 13 pages, 7 figures, uses aa.cls, accepted for publication on Astronomy & Astrophysic

Holocene Paleoenvironmental Reconstruction of Depositional Environments on the Sunda Shelf, Southwest South China Sea, using a Multidisciplinary Approach

The last glacial maximum, ca. 21,000 years ago, caused a fall in eustatic sea level of ca. 120 m below present. The low-gradient, shallow Sunda Shelf, Southeast Asia was subaerially exposed during this sea-level lowstand and experienced rising sea level thereafter. Sea level rose to a +1.3--5 m highstand ca. 6,500 cal yr BP, and then fell to modern sea level. The objective of this research is to characterize environmental change on the Sunda Shelf in response to the post-glacial rising eustatic sea level. To address this objective, six gravity cores were collected along a transect crossing the paleo-Chao Phraya incised river valley complex between peninsular Malaysia and southern Vietnam. Thirteen AMS radiocarbon samples, 130 bulk sediment magnetic susceptibility samples (BMS), 66 X-ray fluorescence spectrometry (XRF) samples, and 54 samples for the analysis of foraminiferal assemblages were used to characterize change in the depositional environments of the cored sediments. BMS, XRF, and foraminiferal analysis distinguish two main units. Unit 1 is found in the lower part of the cores and typically contains more terrestrial material than sediments further up-core as shown by higher BMS values, higher % Ti, % Al, % Fe, and lower indicators of marine influence, for example, lower % Ca, % planktonic foraminifera, and percentages of deeper water benthic foraminifera such as Heterolepa dutemplei. Unit 2 is characterized by a significant increase in % Ca, % Heterolepa dutemplei and % planktonic foraminifera ca. 6,500 cal yr BP. Unit 1 is consistent with shallower water depths and is part of a transgressive systems tract (TST, ca. 1 m thick) that terminates ca. 6,500 cal yr BP. Unit 2 represents the overlying highstand systems tract (HST, ca. 1 m thick) and is characterized by an increase in % planktonics, % Ca, and shifts in benthic foraminiferal assemblages, indicating deeper water conditions than the sediments below. This shift from a TST to a HST ca. 6500 cal yr BP is consistent with the Sunda Shelf sea-level record

Playing with Puffball: Simple Scale-Invariant Inflation for Use in Vision and Graphics

We describe how inflation, the act of mapping a 2D silhouette to a 3D region, can be applied in two disparate problems to offer insight and improvement: silhouette part segmentation and image-based material transfer. To demonstrate this, we introduce Puffball, a novel inflation technique, which achieves similar results to existing inflation approaches -- including smoothness, robustness, and scale and shift-invariance -- through an exceedingly simple and accessible formulation. The part segmentation algorithm avoids many of the pitfalls of previous approaches by finding part boundaries on a canonical 3-D shape rather than in the contour of the 2-D shape; the algorithm gives reliable and intuitive boundaries, even in cases where traditional approaches based on the 2D Minima Rule are misled. To demonstrate its effectiveness, we present data in which subjects prefer Puffball's segmentations to more traditional Minima Rule-based segmentations across several categories of silhouettes. The texture transfer algorithm utilizes Puffball's estimated shape information to produce visually pleasing and realistically synthesized surface textures with no explicit knowledge of either underlying shape.National Eye Institute (Special Training Grant

Higher-dimensional computational models of perceptual grouping and silhouette analysis and representation

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Brain and Cognitive Sciences, 2012.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (p. 100-105).In the following thesis, I describe the investigation of two problems related to the organization and structural analysis of visual information: perceptual grouping and silhouette analysis and representation. For the problem of perceptual grouping, an intuitive model framework was developed which operates on raw images and locates relevant groupings utilizing a higher dimensional space that contains not only the two spatial dimensions of the image but one or more dimension corresponding to relevant image features such as luminance, hue, or orientation. A psychophysical experiment was run to measure how human visual observers perform perceptual grouping across a variety of spatial scales and luminance differences. These results were compared with the predictions of our grouping model, and the model was able to capture much of the grouping behavior of the human subjects. A second experiment was run in which the perception of groups was disrupted by the presence of noise or shifts in brightness. Though the experiments showed only small effects resulting from these disruptions on the behavior of human subjects, the model was still able to successfully capture much of the image-to-image variability. For the question of silhouette representation and analysis, I suggest that human silhouette representation may be inextricably tied to 3D interpretation of 2D shapes. To support this, I propose a novel algorithm for 2D silhouette inflation called Puffball, which closely matches human intuition for a variety of simple shapes and can be run on almost any input. Using this algorithm, a new model of human part segmentation was derived using 2D-to-3D inflation; this model was evaluated against human-generated part segmentations and two competing part segmentation algorithms. Across a variety of different analyses, Puffball part segmentation performed as well or better than its competitors, suggesting a potential role for 2D-to-3D inflation in the segmentation of silhouette parts. Finally, I suggest several avenues of research which may further illuminate the role of inflation in the human representation and analysis of 2D and 3D shape.by Nathaniel R. Twarog.Ph.D

A Stromgren view of the multiple populations in globular clusters

We discuss a variety of photometric indices assembled from the uvby Stromgren system. Our aim is to examine the pros and cons of the various indices to find the most suitable one(s) to study the properties of multiple populations in globular clusters (GCs) discovered by spectroscopy. We explore in particular the capabilities of indices like m_1 and c_y at different metallicities. We define a new index delta_4=(u-v)-(b-y) to separate first and second stellar generations in GCs of any metal abundance, since it keeps the sensitivity to multiple stellar populations over all the metallicity range and at the same time minimizes the sensitivity to photometric errors. We detecte clear differences in the red giant branches of the GCs examined, like skewness or bi/multi-modality in color distribution. We connect the photometric information with the spectroscopic results on O, Na abundances we obtained in our survey of GCs. Finally, we compute the effects of different chemical composition on the Stromgren filters and indices using synthetic spectra.Comment: Accepted for publication on Astronomy and Astrophysics. Figures 1,3,5 degraded in resolutio

The chemical abundance of the very metal rich old Open Clusters NGC 6253 and NGC 6791

In the framework of a project aiming at deriving in a homogeneous way the properties (age, distance, reddening and detailed chemical abundances) of a large sample of old open clusters, we present here the metal abundance and the abundance ratios of light (C, N, O, Na, Mg, Al, Si, Ca, Ti) and heavier (Cr, Mn, Ni, Ba, Eu) elements in the galactic open clusters NGC 6253 and NGC 6791. We performed spectrum synthesis of selected lines on high resolution spectra of four red clump stars in NGC 6253, taken with the UVES and FEROS spectrographs. We also determined abundances of the same elements for four red clump stars in NGC 6791, observed with SARG, for which we had derived the atmospheric parameters and the iron, carbon and oxygen abundances in a previous paper (Gratton et al. 2006). The average metallicity of NGC 6253 is [Fe/H]=+0.46 (rms = 0.03 dex, systematic error = 0.08 dex), obtained by extensive spectral synthesis of Fe lines. This intermediate age cluster closely resembles the old open cluster NGC 6791, as far as the chemical composition is concerned. C, N, O do not show any significant abundance scatter; they are underabundant with respect to the solar values both in NGC 6253 and NGC 6791. We also find no evident star-to-star scatter in any of the elements measured in both clusters, with the possible exception of Na in NGC 6791. The two clusters show very similar abundances, except for Mg, overabundant in NGC 6791 and not in NGC 6253. Both have solar scaled alpha-elements abundances. We have compared our abundance ratios with literature values for disk giants and dwarfs and bulge giants, finding a general good agreement with the run of elemental ratios with [Fe/H] of disk objects.Comment: Accepted for publication on A&

VLT multi-epoch radial velocity survey toward NGC 6253. Analysis of three transiting planetary candidates

We measured the radial velocity of 139 stars in the region of NGC 6253, discussing cluster's membership and binarity in this sample, complementing our analysis with photometric, proper motion, and radial velocity data available from previous studies of this cluster, and analyzing three planetary transiting candidates we found in the field of NGC 6253. Spectra were obtained with the UVES and GIRAFFE spectrographs at the VLT, during three epochs in August 2008. The mean radial velocity of the cluster is -29.11+/-0.85 km/s. Using both radial velocities and proper motions we found 35 cluster's members, among which 12 are likely cluster's close binary systems. One star may have a sub-stellar companion, requiring a more intensive follow-up. Our results are in good agreement with past radial velocity and photometric measurements. Furthermore, using our photometry, astrometry and spectroscopy we identified a new sub-giant branch eclipsing binary system, member of the cluster. The cluster's close binary frequency at 29% +/- 9% (34% +/-10% once including long period binaries), appears higher than the field binary frequency equal to (22% +/- 5%, though these estimates are still consistent within the uncertainties. Among the three transiting planetary candidates the brightest one (V=15.26) is worth to be more intensively investigated with higher percision spectroscopy. We discussed the possibility to detect sub-stellar companions (brown dwarfs and planets) with the radial velocity technique (both with UVES/GIRAFFE and HARPS) around turn-off stars of old open clusters [abridged].Comment: 25 pages, 18 figures, 8 tables. Accepted for publication in A&

WIYN Open Cluster Study. LXIII. Abundance in the Super-Metal-Rich Open Cluster NGC 6253 from Hydra Sprectroscopy of the 7774 Å Oxygen Triplet Region

We present a spectroscopic abundance analysis of the old, super-metal-rich open cluster NGC 6253, with emphasis on its O abundance. High-dispersion, 7774 Å O i triplet region spectra of 47 stars were obtained using Hydra II on the CTIO Blanco 4 m. Radial velocity analysis confirms 39 stars consistent with single star membership, primarily at the turnoff. Thirty-six of these are included in our abundance analysis. Our differential analysis relative to the Sun yields primarily scaled-solar values, with weighted cluster averages of [O/H] = +0.440 ± 0.020, [Fe/H] = +0.445 ± 0.014, [Al/H] = +0.487 ± 0.020, [Si/H] = +0.504 ± 0.018, and [Ni/H] = +0.702 ± 0.018 (where the errors are ${{\sigma }_{\mu }}$). We discuss possible origins for the three known super-metal-rich clusters based upon their abundance patterns, Galactic locations, and space motions. The abundance patterns of NGC 6253 are very similar to those of NGC 6791 and NGC 6583. With the possible exception of oxygen, the abundances of these clusters are all close to scaled-solar, and they are similar to patterns seen in metal-rich disk dwarfs and giants. However, they also seem to differ from those of metal-rich bulge stars. We demonstrate that NGC 6253 is unusually oxygen rich (in [O/H]) for its 3.3 Gyr age. While we find [O/Fe] to be scaled-solar for NGC 6253, the more recently reported values for NGC 6791 show a large variation, from values close to scaled-solar down to values at least a factor of two below scaled-solar. We discuss the possibility that the scaled-solar [O/Fe] abundances of NGC 6253 and NGC 6791 might reflect a flattening of the Galactic [O/Fe] versus [Fe/H] relationship. This possibility may be consistent with disk star abundance data, which show an apparent "floor" at [O/Fe] $\sim -0.1$ for [Fe/H] $\gt \;0$, and with chemical evolution model results, which may predict such a flattening due to a decrease in supernova Fe yields at super-solar-metallicities. Orbit solutions for NGC 6791 allow that it may have formed in the inner disk and was then kicked out, but the origins of the other two much younger clusters remain mysterious. We re-evaluate the age of NGC 6583 in view of the evidence that the cluster is super-metal-rich, and confirm a probable age less than 1 Gyr (best range: 500–900 Myr). We also argue that it is unlikely the cluster is more than 3 kpc away (best range: 2–3 kpc) if the apparent turnoff, main sequence, and giants are all cluster members