Optimal design of a dry-type natural-draft cooling tower by geometric programming

In this paper, the optimal design of dry-type natural-draft cooling towers is investigated. Using physical laws and engineering design relations that govern the system, a rather detailed optimization model is developed. This model is then reformulated as a geometric programming problem. A primary consideration in this reformulation is how certain polynomial equations may be effectively replaced by inequalities. A numerical example follows.     

Elastic neutrino proton scattering and the structure of the neutral current

Optimal constraints on the structure of a general V, A hadronic neutral current are derived from neutrino proton scattering and compared with corresponding results from inclusive neutrino scattering and single pion production by neutrinos. For an arbitrary axial component of the neutral current, restrictions for the vector coupling constants are obtained. It is shown that the most general neutral current which can be related to charged weak and electromagnetic currents accounts for all existing data on neutrino hadron scattering. The neutral current coupling constants are determined for the pure isovector model, the Salam-Weinberg model and the bottom-quark model. All three models lead to practically the same isovector couplings but they differ in the strength of the isoscalar current.     

Space-time structure of neutral currents and y-distributions

Assuming scaling of the nucleon structure functions, we derive relations for the y-distributions in deep inelastic neutrino scattering for the most general local interaction of neutrinos with hadrons via neutral currents with V, A, S, P and T pieces. In addition, optimal bounds for the y-distributions are presented which follow from positivity requirements for the structure functions and which may serve to discriminate between pure V, A currents and the presence of S, P, T couplings. The influence of the predictions of the $\text{spin}\text{-}\text{1}\text{2}$ parton model on the bounds is investigated. All relations and bounds depend only on the ratio of total neutrino and antineutrino cross sections.     

Structure based classification for bile salt export pump (BSEP) inhibitors using comparative structural modeling of human BSEP

The bile salt export pump (BSEP) actively transports conjugated monovalent bile acids from the hepatocytes into the bile. This facilitates the formation of micelles and promotes digestion and absorption of dietary fat. Inhibition of BSEP leads to decreased bile flow and accumulation of cytotoxic bile salts in the liver. A number of compounds have been identified to interact with BSEP, which results in drug-induced cholestasis or liver injury. Therefore, in silico approaches for flagging compounds as potential BSEP inhibitors would be of high value in the early stage of the drug discovery pipeline. Up to now, due to the lack of a high-resolution X-ray structure of BSEP, in silico based identification of BSEP inhibitors focused on ligand-based approaches. In this study, we provide a homology model for BSEP, developed using the corrected mouse P-glycoprotein structure (PDB ID: 4M1M). Subsequently, the model was used for docking-based classification of a set of 1212 compounds (405 BSEP inhibitors, 807 non-inhibitors). Using the scoring function ChemScore, a prediction accuracy of 81% on the training set and 73% on two external test sets could be obtained. In addition, the applicability domain of the models was assessed based on Euclidean distance. Further, analysis of the protein–ligand interaction fingerprints revealed certain functional group-amino acid residue interactions that could play a key role for ligand binding. Though ligand-based models, due to their high speed and accuracy, remain the method of choice for classification of BSEP inhibitors, structure-assisted docking models demonstrate reasonably good prediction accuracies while additionally providing information about putative protein–ligand interactions.     

Enhanced damping of a cantilever beam by axial parametric excitation

A uniform cantilever beam under the effect of a time-periodic axial force is investigated. The beam structure is discretized by a finite-element approach. The linearised equations of motion describing the planar bending vibrations of the beam structure lead to a system with time-periodic stiffness coefficients. The stability of the system is investigated by a numerical method based on Floquet’s theorem and an analytical approach resulting from a first-order perturbation. It is demonstrated that the parametrically excited beam structure exhibits enhanced damping properties, when excited near a specific parametric combination resonance frequency. A certain level of the forcing amplitude has to be exceeded to achieve the damping effect. Upon exceeding this value, the additional artificial damping provided to the beam is significant and works best for suppression of vibrations of the first vibrational mode of the cantilever beam.