Theoretical insights on the excited-state-deactivation mechanisms of protonated thymine and cytosine

Excited-state deactivation mechanism of protonated cytosine and thymine is investigated based on ab initio and NAMD simulation methods. The ring deformation from C6 region is suggested to play the most prominent role in deactivation mechanism.

Spectral Tuning of Chlorophylls in Proteins – Electrostatics vs. Ring Deformation

: In photosynthetic complexes, tuning of chlorophyll light-absorption spectra by the protein environment is crucial to their efficiency and robustness. Water Soluble Chlorophyll-binding Proteins from Brassicaceae (WSCPs) are useful for...

Experimental measurements of the thermo elastic behavior of a dry gas seal operating with logarithmic spiral grooves of 11° and 15°

This work shows the experimental thermo elastic behavior of the stationary ring of a dry gas seal with logarithmic spiral grooves of 15° (common commercial configuration) and 11° spiral (configuration evaluated to confirm analytical predictions developed on previous works), as well as the hydrodynamic pressure of the fluid film. The stationary ring temperature is obtained through an array of sensors embedded in the ring and the ring deformation, resulting from the thermal and mechanical load, is collected by two strain gages. The hydrodynamic pressure produced in the fluid film is measured using dynamic pressure sensors. Two novel instrumentation methods are defined to collect the ring deformation and the dynamic pressure of the seal. The results show that the seal with spiral grooves of 11° at low speed presents a temperature increment induced by the contact between the rings; this contact may induce the premature fault of the rings, so that the 11° spiral seal needs more speed than the spiral of 15° to enter a hydrodynamic lubrication regime. The experiments show that the stationary ring distortion is induced by the temperature gradient and by the hydrostatic and hydrodynamic pressure; however, the thermal distortion of the ring is dominant for the current experimental conditions. The ring’s axial distortion also affects the seal static and dynamic performance due to the modification of the hydrodynamic regime.

Time-Dependent Compressibility of Crude Oil in Gelled State Measured by a New Apparatus

Summary Compressibility is a basic property of gelled crude oil, which was always regarded as a constant in the unsteady-pipe-flow process. In this article, the compressibility of gelled crude oil was accurately measured, and some new characteristics were discovered by a new apparatus that was developed using a special sealing method consisting of an elastic film and the Newtonian fluid. There was no leakage in the special hermetical method, and the unexpected seal-ring deformation of the piston in the traditional compression apparatus was also well-avoided. Using the new apparatus, compressibility of the gelled crude oil was tested and it was found that the compressibility of gelled crude oil is strongly time dependent.

Spectral Tuning of Chlorophylls in Proteins – Electrostatics vs. Ring Deformation

In photosynthetic complexes, tuning of chlorophyll light-absorption spectra by the protein environment is crucial to their efficiency and robustness. Water Soluble Chlorophyll-binding Proteins from <i>Brassicaceae</i> (WSCPs) are useful for studying spectral tuning mechanisms due to their symmetric homotetramer structure, the ability to rigorously modify the chlorophyll’s protein surroundings, and the availability of crystal structures. Here, we present a rigorous analysis based on hybrid Quantum Mechanics and Molecular Mechanics simulations with conformational sampling to quantify the relative contributions of steric and electrostatic factors to the absorption spectra of WSCP-chlorophyll complexes. We show that when considering conformational dynamics, chlorophyll ring deformation accounts for about one-third of the spectral shift, whereas protein electrostatics accounts for the remaining two-thirds. From a practical perspective, protein electrostatics is easier to manipulate than chlorophyll conformations, thus, it may be more readily implemented in designing artificial protein-chlorophyll complexes with desired spectral shift.

Spectral Tuning of Chlorophylls in Proteins – Electrostatics vs. Ring Deformation

In photosynthetic complexes, tuning of chlorophyll light-absorption spectra by the protein environment is crucial to their efficiency and robustness. Water Soluble Chlorophyll-binding Proteins from <i>Brassicaceae</i> (WSCPs) are useful for studying spectral tuning mechanisms due to their symmetric homotetramer structure, the ability to rigorously modify the chlorophyll’s protein surroundings, and the availability of crystal structures. Here, we present a rigorous analysis based on hybrid Quantum Mechanics and Molecular Mechanics simulations with conformational sampling to quantify the relative contributions of steric and electrostatic factors to the absorption spectra of WSCP-chlorophyll complexes. We show that when considering conformational dynamics, chlorophyll ring deformation accounts for about one-third of the spectral shift, whereas protein electrostatics accounts for the remaining two-thirds. From a practical perspective, protein electrostatics is easier to manipulate than chlorophyll conformations, thus, it may be more readily implemented in designing artificial protein-chlorophyll complexes with desired spectral shift.

Identification and Visualization of the Full-Ring Deformation Characteristics of a Large Stormwater Sewage and Storage Tunnel Using Terrestrial Laser Scanning Technology

Constructing deeply-buried stormwater sewage and storage tunnels is an effective method to mitigate the waterlogging and sewer overflow problems in modern cities. Prior to construction of such tunnels, a structural loading test is essential for acquiring the mechanical responses under complex loading conditions, such as cyclic inner hydraulic head, during which capturing the full-ring deformation of the tunnel lining is significant for a comprehensive understanding of the tunnel’s mechanical behaviors. This paper introduces the application of terrestrial laser scanning (TLS) technology in the full-scale structural loading tests of a large stormwater sewage and storage tunnel, which gives the full-ring deformation throughout the tests. A data processing methodology was developed to extract the key data points of the lining segments from the original data cloud by removing noise points and mitigating data jump, based on which the deformation of testing the lining segments at arbitrary locations can be calculated. Furthermore, a post-processing software was developed to visualize the full-ring deformation. The full-ring deformation at different loading conditions and its evolution under cyclic loading were captured. It is shown that the lining’s convergence deformation is more sensitive to the inner hydraulic head than to the external soil-water pressure, and the deformation cannot fully recover in a water-inflow-and-drainage cycle due to the presence of joints.