File Allocation and Join Site Selection Problem in Distributed Database Systems.

There are two important problems associated with the design of distributed database systems. One is the file allocation problem, and the other is the query optimization problem. In this research a methodology that considers both these aspects is developed that determines the optimal location of files and join sites for given queries simultaneously. Using this methodology, three different mixed integer programming models that describe three cases of the file allocation and join site selection problem are developed. Dual-based procedures are developed for each of the three mixed integer programming models. Extensive computational testing is performed which shows that the dual-based algorithms developed are able to generate solutions which are very close to the optimal. Also, these near optimal solutions are found very quickly, even for large scale problems

Analytical Solution for Low-Thrust Minimum Time Control of a Satellite Formation

Satellite formations or distributed satellite systems provide advantages not feasible with single satellites. Efficient operation of this platform requires the use of optimal control of the entire satellite formation. While the optimal control theory is well established, only a very simple dynamical system affords an analytical solution. Any practical optimal control problem solves the resulting two-point boundary value (TPBV) problem numerically. The relative satellite dynamics using Hill\u27s coordinate system and approximations made by Clohessy and Wiltshire, combined with body-fixed thruster control, result in a linearized dynamic system. This dissertation provides the analysis for the minimum time satellite formation control by decoupling the in-plane motion from the out-of-plane motion. While the out-of-plane motion is fully analytic, the in-plane motion is only semi-analytic. The TPBV problem is transformed to solving simultaneous nonlinear equations for the critical control switching times, resulting in an open-loop, bang-bang controller

2-(5-Fluoro-3-isopropyl­sulfanyl-7-methyl-1-benzofuran-2-yl)acetic acid

The title compound, C14H15FO3S, was prepared by alkaline hydrolysis of ethyl 2-(5-fluoro-3-isopropyl­sulfanyl-7-methyl-1-benzofuran-2-yl)acetate. In the crystal, mol­ecules are linked via pairs of O—H⋯O hydrogen bonds, forming inversion dimers. These dimers are connected by weak C—H⋯O hydrogen bonds

The EC-HDA9 complex rhythmically regulates histone acetylation at the TOC1 promoter in Arabidopsis

Circadian clocks are conserved time-keeper mechanisms in some prokaryotes and higher eukaryotes. Chromatin modification is emerging as key regulatory mechanism for refining core clock gene expression. Rhythmic changes in histone marks are closely associated to the TIMING OF CAB EXPRESSION 1 (TOC1) Arabidopsis clock gene. However, the chromatin-related modifiers responsible for these marks remain largely unknown. Here, we uncover that the chromatin modifier HISTONE DEACETYLASE 9 (HDA9) and the Evening complex (EC) component EARLY FLOWERING 3 (ELF3) directly interact to regulate the declining phase of TOC1 after its peak expression. We found that HDA9 specifically binds to the TOC1 promoter through the interaction with ELF3. The EC-HDA9 complex promotes H3 deacetylation at the TOC1 locus, contributing to suppressing TOC1 expression during the night, the time of EC function. Therefore, we have identified the mechanism by which the circadian clock intertwines with chromatin-related components to shape the circadian waveforms of gene expression in Arabidopsis

3-(3-Chloro­phenyl­sulfin­yl)-2,4,6-trimethyl-1-benzofuran

In the title compound, C17H15ClO2S, the 3-chloro­phenyl ring makes a dihedral angle of 71.46 (4)° with the mean plane of the benzofuran fragment. In the crystal, mol­ecules are linked by weak C—H⋯O hydrogen bonds and a slipped π–π inter­action between the 3-chloro­phenyl rings of adjacent mol­ecules [centroid–centroid distance = 3.630 (2) Å, inter­planar distance = 3.375 (2) Å and slippage = 1.337 (2) Å]

2-(3-Fluoro­phen­yl)-5-iodo-7-methyl-3-methyl­sulfinyl-1-benzofuran

In the title compound, C16H12FIO2S, the 3-fluoro­phenyl ring makes a dihedral angle of 34.93 (7)° with the mean plane [r.m.s. deviation = 0.019 (1) Å] of the benzofuran fragment. In the crystal, mol­ecules are linked via pairs of I⋯O contacts [3.088 (2) Å] into inversion dimers. These dimers are connected by weak C—H⋯O hydrogen bonds

3-(3-Chloro­phenyl­sulfon­yl)-2,5,7-trimethyl-1-benzofuran

In the title compound, C17H15ClO3S, the 3-chloro­phenyl ring makes a dihedral angle of 77.76 (6)° with the mean plane [r.m.s. deviation = 0.007 (1) Å] of the benzofuran fragment. In the crystal, mol­ecules are linked by weak inter­molecular C—H⋯O and C—H⋯π inter­actions

2-(5,7-Dimethyl-3-methyl­sulfanyl-1-benzofuran-2-yl)acetic acid

The title compound, C13H14O3S, was prepared by alkaline hydrolysis of ethyl 2-(5,7-dimethyl-3-methyl­sulfanyl-1-benzofuran-2-yl)acetate. In the crystal structure, the carboxyl groups are involved in inter­molecular O—H⋯O hydrogen bonds, which link the mol­ecules into centrosymmetric dimers. These dimers are further packed into stacks along the a axis by weak C—H⋯π inter­actions