3,797 research outputs found

    Approximating electronically excited states with equation-of-motion linear coupled-cluster theory

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    A new perturbative approach to canonical equation-of-motion coupled-cluster theory is presented using coupled-cluster perturbation theory. A second-order M{\o}ller-Plesset partitioning of the Hamiltonian is used to obtain the well known equation-of-motion many-body perturbation theory (EOM-MBPT(2)) equations and two new equation-of-motion methods based on the linear coupled-cluster doubles (EOM-LCCD) and linear coupled-cluster singles and doubles (EOM-LCCSD) wavefunctions. This is achieved by performing a short-circuiting procedure on the MBPT(2) similarity transformed Hamiltonian. These new methods are benchmarked against very accurate theoretical and experimental spectra from 25 small organic molecules. It is found that the proposed methods have excellent agreement with canonical EOM-CCSD state for state orderings and relative excited state energies as well as acceptable quantitative agreement for absolute excitation energies compared with the best estimate theory and experimental spectra.Comment: 9 pages 3 figure

    Fabricating New Miniaturized Biosensors for the Detection of Dna Damage and Dna Mismatches

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    A large number of genetic diseases and genetic disorders are simply caused by base alterations in the genome. Therefore, developing efficient and cost effective techniques for routine detection of these alterations is of great importance. Different methods involving gel electrophoresis and Polymerase Chain Reaction have been widely employed, but majority of these methods are costly, time consuming, and lack throughput, creating a fundamental gap between the current state-of-the-art and desired characteristics of low-cost, high-speed, simplicity, versatility, and potential for miniaturization. In this study, we attempt to bridge this gap by developing new sensing platforms to detect DNA base mismatches and DNA damage with higher throughput, better ease-of-use, and with the potential to be miniaturized for greater portability. Two electrochemical mismatch detection sensing platforms were developed. One uses the electrochemical reduction of trans-4-cinnamic acid diazonium tetrafluoroborate. The other takes advantage of the natural ability of MutS protein for single base mismatch recognition. Also, two DNA damage detection assays were developed and the first approach uses Atomic Force Microscopy to monitor minor DNA damage by labeling damaged sites with a biomarker. This site-specific biolabeling was achieved through well-established biotin-streptavidin chemistry. In the second approach, a new layer-by-layer biomolecular immobilization method was introduced and used to detect DNA chemical damage using electrochemical technique

    Single side damage simulations and detection in beam-like structures

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    Beam-like structures are the most common components in real engineering, while single side damage is often encountered. In this study, a numerical analysis of single side damage in a free-free beam is analysed with three different finite element models; namely solid, shell and beam models for demonstrating their performance in simulating real structures. Similar to experiment, damage is introduced into one side of the beam, and natural frequencies are extracted from the simulations and compared with experimental and analytical results. Mode shapes are also analysed with modal assurance criterion. The results from simulations reveal a good performance of the three models in extracting natural frequencies, and solid model performs better than shell while shell model performs better than beam model under intact state. For damaged states, the natural frequencies captured from solid model show more sensitivity to damage severity than shell model and shell model performs similar to the beam model in distinguishing damage. The main contribution of this paper is to perform a comparison between three finite element models and experimental data as well as analytical solutions. The finite element results show a relatively well performanc