Nest User's Guide

This guide describes building simulations using the simulation library provided with Nest Version 2.5. Nest is available from Columbia University. For information, please contact the authors

Nest User Interface Manual

This manual describes the user interface client provided with Nest Version 2.5. Nest is available from Columbia University. For information, please contact the authors

Nest Library Reference Manual

This manual describes the simulation library provided with Nest Version 2.5. Nest is available from Columbia University. For information, please contact the authors

Nest System Overview

This manual describes the simulation library provided with Nest Version 2.5. Nest is available from Columbia University. For information, please contact the authors

Discovery of a Visual T-Dwarf Triple System and Binarity at the L/T Transition

We present new high contrast imaging of 8 L/T transition brown dwarfs using the NIRC2 camera on the Keck II telescope. One of our targets, the T3.5 dwarf 2MASS J08381155 + 1511155, was resolved into a hierarchal triple with projected separations of 2.5+/-0.5 AU and 27+/-5 AU for the BC and A(BC) components respectively. Resolved OSIRIS spectroscopy of the A(BC) components confirm that all system members are T dwarfs. The system therefore constitutes the first triple T-dwarf system ever reported. Using resolved photometry to model the integrated-light spectrum, we infer spectral types of T3, T3, and T4.5 for the A, B, and C components respectively. The uniformly brighter primary has a bluer J-Ks color than the next faintest component, which may reflect a sensitive dependence of the L/T transition temperature on gravity, or alternatively divergent cloud properties amongst components. Relying on empirical trends and evolutionary models we infer a total system mass of 0.034-0.104 Msun for the BC components at ages of 0.3-3 Gyr, which would imply a period of 12-21 yr assuming the system semi-major axis to be similar to its projection. We also infer differences in effective temperatures and surface gravities between components of no more than ~150 K and ~0.1 dex. Given the similar physical properties of the components, the 2M0838+15 system provides a controlled sample for constraining the relative roles of effective temperature, surface gravity, and dust clouds in the poorly understood L/T transition regime. Combining our imaging survey results with previous work we find an observed binary fraction of 4/18 or 22_{-8}^{+10}% for unresolved spectral types of L9-T4 at separations >~0.1 arcsec. This translates into a volume-corrected frequency of 13^{-6}_{+7}%, which is similar to values of ~9-12% reported outside the transition. (ABRIDGED)Comment: Accepted for publication in the Astrophysical Journal. 23 pages, 12 figure

Mechano-redox control of neutrophil function in thromboinflammation

Mechanical forces and redox reactions are important for regulating protein function. There is an emerging notion combining these two concepts. In vitro force spectroscopy experiments revealed that the redox state of proteins can affect the mechanical properties of proteins and vice-versa. However, the relevance of this in neutrophils is not well studied. The aim of this PhD thesis is to study the mechano-redox interactions in thromboinflammation. Here, I demonstrate that the redox state of two disulphide bonds in the β2 subunit of the Mac-1 integrin in neutrophils, Cys169-Cys176 and Cys224-Cys264, is modified by the redox enzyme Protein Disulphide Isomerase (PDI), affecting adhesion of Mac-1 to Intracellular Adhesion Molecule-1. This changes the directional crawling of neutrophils under shear. PDI belongs to a group of redox enzymes termed thiol oxidoreductases. To further explore the role of thiol oxidoreductases in thromboinflammation, I studied an Endoplasmic Reticulum protein 5 (ERp5) conditional knockout (CKO) model where ERp5 is absent in mouse platelets. Rather than purely affecting integrin-dependent functions of platelets, ERp5 deficiency lead to defective Ca2+ influx, platelet secretion, and promoted ER stress signaling compared to wild type controls. ERp5 CKO were prothrombotic in a laser-induced vessel injury model upon induction of further ER stress by tunicamycin. Finally, I developed an in vitro model to study thromboinflammation. This model involves the stimulation of an endothelial monolayer in a microfluidic device to induce thromboinflammation after whole blood perfusion. I then demonstrate that a small molecule inhibitor of PDI, isoquercetin, is a viable drug for the inhibition of thromboinflammation. Combined, these results demonstrate an important regulatory role in thromboinflammation through mechano-redox control of Mac-1 and potentially through ER stress signaling

An Object-Oriented Model for Network Management

Most networks today lack management tools that support automated identification of faults and bottlenecks and support effective recovery procedures. The NetMATE project, discussed in this paper, addresses the issue related to distributed network management of large, heterogeneous networks. NetMATE employs a modular, object-oriented approach to develop extensible management tools and a model for network information. The first prototype of the system confirms the elegance of the design

Nucleation and growth behavior of multicomponent secondary phases in entropy-stabilized oxides

The rocksalt structured (Co,Cu,Mg,Ni,Zn)O entropy-stabilized oxide (ESO) exhibits a reversible phase transformation that leads to the formation of Cu-rich tenorite and Co-rich spinel secondary phases. Using atom probe tomography, kinetic analysis, and thermodynamic modeling, we uncover the nucleation and growth mechanisms governing the formation of these two secondary phases. We find that these phases do not nucleate directly, but rather they first form Cu-rich and Co-rich precursor phases, which nucleate in regions rich in Cu and cation vacancies, respectively. These precursor phases then grow through cation diffusion and exhibit a rocksalt-like crystal structure. The Cu-rich precursor phase subsequently transforms into the Cu-rich tenorite phase through a structural distortion-based transformation, while the Co-rich precursor phase transforms into the Co-rich spinel phase through a defect-mediated transformation. Further growth of the secondary phases is controlled by cation diffusion within the primary rocksalt phase, whose diffusion behavior resembles other common rocksalt oxides

PHL 5038AB: Is the brown dwarf causing pollution of its white dwarf host star?

We present new results on PHL 5038AB, a widely separated binary system composed of a white dwarf and a brown dwarf, refining the white and brown dwarf parameters and determining the binary separation to be AU. New spectra of the white dwarf show calcium absorption lines suggesting the hydrogen-rich atmosphere is weakly polluted, inferring the presence of planetesimals in the system, which we determine are in an S-type orbit around the white dwarf in orbits closer than 17-32 AU. We do not detect any infrared excess that would indicate the presence of a disc, suggesting all dust present has either been totally accreted or is optically thin. In this system, we suggest the metal pollution in the white dwarf atmosphere can be directly attributed to the presence of the brown dwarf companion disrupting the orbits of planetesimals within the system