Acetylene-ammonia-18-crown-6 (1/2/1)

The title compound, C2H2·C12H24O6·2NH3, was formed by co-crystallization of 18-crown-6 and acetylene in liquid ammonia. The 18-crown-6 molecule has threefold rotoinversion symmetry. The acteylene molecule lies on the threefold axis and the whole molecule is generated by an inversion center. The two ammonia molecules are also located on the threefold axis and are related by inversion symmetry. In the crystal, the ammonia molecules are located below and above the crown ether plane and are connected by intermolecular N-H...O hydrogen bonds. The acetylene molecules are additionally linked by weak C-H...N interactions into chains that propagate in the direction of the crystallographic c axis. The 18-crown-6 molecule [occupancy ratio 0.830 (4):0.170 (4)] is disordered and was refined using a split model

High Speed Clock Glitching

In recent times, hardware security has drawn a lot of interest in the research community. With physical proximity to the target devices, various fault injection hardware attack methods have been proposed and tested to alter their functionality and trigger behavior not intended by the design. There are various types of faults that can be injected depending on the parameters being used and the level at which the device is tampered with. The literature describes various fault models to inject faults in clock of the target but there are no publications on overclocking circuits for fault injection. The proposed method bridges this gap by conducting high-speed clock fault injection on latest high-speed micro-controller units where the target device is overclocked for a short duration in the range of 4-1000 ns. This thesis proposes a method of generating a high-speed clock and driving the target device using the same clock. The properties of the target devices for performing experiments in this research are: Externally accessible clock input line and GPIO line. The proposed method is to develop a high-speed clock using custom bit-stream sent to FPGA and subsequently using external analog circuitry to generate a clock-glitch which can inject fault on the target micro-controller. Communication coupled with glitching allows us to check the target\u27s response, which can result in information disclosure.This is a form of non-invasive and effective hardware attack. The required background, methodology and experimental setup required to implement high-speed clock glitching has been discussed in this thesis. The impact of different overclock frequencies used in clock fault injection is explored. The preliminary results have been discussed and we show that even high-speed micro-controller units should consider countermeasures against clock fault injection. Influencing the execution of Tiva C Launchpad and STM32F4 micro-controller units has been shown in this thesis. The thesis details the method used for the testing a

Minimizing the Disruption of Traffic Flow of Automated Vehicles During Lane Changes

In intelligent transportation systems, most of the research work has focused on lane change assistant systems. No existing work considers minimizing the interruption of traffic flow by maximizing the number of lane changes while eliminating the collisions. In this thesis, we develop qualitative and quantitative approaches for minimizing the interruption of traffic flow for three lane scenarios and show that we can extend our approach to any random number of lanes. The algorithm we propose in this thesis is able to achieve the maximum number of lane changes provided that only one vehicle per group (novel concept which is described in this thesis) is allowed to change lanes at a time. Simulation results show that our approach provides much better performance when compared with different lane change algorithms without incurring large overhead, and is hence suitable for online use

A method of calculating the total flow from a given sea surface topography

Using a simple dynamical model of a wind-driven ocean circulation of the Stommel type, and an analytical basis developed to objectively analyze the sea surface height residuals from an altimeter and, in the process, to determine the total flow instead of just the near surface geostrophic component associated with the given sea surface topography. The method is based on first deriving the solution to the forced problem for a given wind stress required to develop a hypothetical true or perfect data field and to establishing the basis for the objective analysis. The stream function and the surface height field for the forced problem are developed in terms of certain characteristic functions with the same expansion coefficients for both fields. These characteristic functions are simply the solutions for a homogeneous elliptic equation for the stream function and the solutions of an inhomogeneous balance equation for the height field. For the objective analysis, using a sample of randomly selected height values from the true data field, the height field characteristic functions are used to fit the given topography in a least squares sense. The resulting expansion coefficients then permit the synthesis of the total flow field via the stream function characteristic modes and the solution is perfectly well behaved even along the equator. The method of solution is easily adaptable to realistic ocean basis by straight forward numerical methods. The analytical basis of the theory and the results for an ideal rectangular basin on a beta plane are described

Chemistry: the middle kingdom

Chemistry occupies a unique middle position between physics and mathematics on the one side and biology, ecology, sociology and economics on the other. It is said that chemistry is reducible into physics and finally mathematics. However, in moving from the covalent to the non-covalent world we obtain a new chemistry, one that is a starting point for the emergence of the soft sciences. This article argues that this new chemistry represents a paradigm shift in the way in which chemists think about their subject today. Biology may be considered as emerging out of this new chemistry, which in itself cannot be reduced into physics and mathematics as was the case for chemistry thus far practiced. This dualistic nature of chemistry, reducible and irreducible, is a new development but one that ensures that the subject will remain alive and well in the foreseeable future

Hydrogen bonds and other intermolecular interactions in organometallic crystals

Organometallic compounds have been studied with X-ray crystallography from their very discovery. Yet structural organometallic chemists were almost exclusively concerned with the molecular structure and stereochemistry of organometallic compounds and clusters rather than with their crystal structures and packing characteristics. The growing importance of crystal engineering and supramolecular chemistry, however, led to interest in the nature of the interactions that bind organometallic molecules into crystals. In part, these interactions are similar to those found in purely organic crystals because the peripheries of these molecules often contain organic residues. Yet molecular features peculiar to organometallic compounds also do lead to distinctive supramolecular characteristics. Most notable among these intermolecular interactions are hydrogen bonds. Organometallic compounds contain a wealth and diversity of hydrogen bonds that are without counterpart in the organic world. These include C-H···O bonds to M-C≡O acceptors, and hydrogen bonds wherein the metal atom itself acts as a donor or as an acceptor. Even more exotic is the dihydrogen bond M1-H ··· H-M2. Despite this variety, all these weak interactions have properties that resemble those of the more familiar hydrogen bonds such as O-H ··· O, N-H ··· O, O-H ··· N and N-H ··· N. Other interactions that are distinctive to organometallic compounds are the agostic interaction to electron deficient metals (C-H) ··· M and the aurophilic interaction Au···Au. The Cambridge Structural Database (CSD) is an essential tool in the analysis of weak intermolecular interactions. Since the number of organometallic crystal structures in the CSD is very large, the weakest of intermolecular interactions may be studied with ever-increasing degrees of reliability. Through such analysis one is able to obtain a more complete idea of organometallic crystal architecture. Crystal engineering must pass through the stage of analysis before crystal synthesis can be attempted and organometallic crystal engineering is still in its infancy. However, the progress made so far in understanding the nature of intermolecular interactions in these crystals indicates that one may expect rapid progress in the engineering of organometallic crystals with desired structures and properties

Designer crystals: intermolecular interactions, network structures and supramolecular synthons

Questions relating to the prediction of the crystal structure or structures of a given organic molecule may be more gainfully reversed so that retrosynthetic analysis of a target crystal network leads to the identification of molecular precursors. Crystal engineering is solid state supramolecular synthesis and supramolecular synthons, units formed by synthetic operations involving intermolecular interactions, may be used to focus efforts in such logic-driven retrosynthesis

C-H … O hydrogen bonding and the deliberate design of organic crystal structures

The C-H…O interaction, though weak, is not van deer Wails in nature but electrostatic and resembles O-H…O and N-H…O hydrogen bonds in its geometrical properties. Spectroscopic evidence hints at some degree of covalent bonding between H and 0 atoms. The long-range, electrostatic character of the C-H…O interaction determines its important role in crystal engineering. Planar aromatic hydrocarbons adopt herringbone structures but if a critical number of O atoms is present, a planar molecule will cross the structural threshold from a C…H stabilised herringbone structure to a C-H…O stabilised layer structure wherein adjacent molecules are parallel and highly overlapped. These ideas have been used to design a family of crystal structures of alkoxyphenylpro-piolic acids that participate in an intermolecular, solid state Diels-Alder reaction. When the number of C-H…O interactions in a structure is unusually large or small, there is a possibility of distortions in the O-H…O network