Design and Synthesis of a New Amphipathic Cyclic Decapeptide with Rapid, Stable, and Continuous Antibacterial Effects

Pathogens can acquire high resistance against even the most powerful antibiotics because of the long periods of treatment and high usage of antimicrobial agents. In addition, the severe side effects of commonly used antibiotics can initiate secondary diseases or may lead to death. Antimicrobial peptides (AMPs) have been reported to exhibit prokaryotic selectivity and low microbial resistance. Furthermore, AMPs show a good ability to penetrate the cell walls of microorganisms. In this study, a cyclic decapeptide and its linear counterpart were synthesized by a standard solid phase peptide synthesis method (SPPS) in a quantitative yield of the linear decapeptide (97%) and a good yield of the cyclic form (45%). Antibacterial studies were performed using Escherichia coli (a widespread Gram-negative pathogen) and Bacillus thuringiensis as a representative Gram-positive pathogen. The minimal inhibitory concentration (MIC) values were evaluated by the broth microdilution method. The cyclic peptide and its linear counterpart exhibited MIC values of 0.16 and 0.3 mg/mL, respectively, against Escherichia coli. Against Bacillus thuringiensis, the peptides had the same MIC value of 0.24 mg/mL. Time-kill studies were performed using E. coli, which indicated a fast killing effect of both peptides (≥ 99% of the bacterial cells) after 1 h of incubation using a concentration of two times the MIC value for each peptide. Moreover, bacterial cell viability studies against E. coli carried out using a high bacterial concentration showed that both peptides have a maximum killing effect of more than 80% of the tested bacterial cells.

Asymmetric Perfect Absorption and Lasing of Nonlinear Waves by a Complex δ-Potential

Spectral singularities and coherent perfect absorption are two interrelated concepts that have originally been introduced and studied for linear waves interacting with complex potentials. In the meantime, the distinctive asymptotic behavior of perfectly absorbed waves suggests considering possible generalizations of these phenomena for nonlinear waves. Here, we address the perfect absorption of nonlinear waves by an idealized infinitely narrow dissipative potential modeled by a Dirac δ-function with an imaginary amplitude. Our main result is the existence of perfectly absorbed flows whose spatial amplitude distributions are asymmetric with respect to the position of the absorber. These asymmetric states do not have a linear counterpart. Their linear stability is verified numerically. The nonlinear waveguide also supports symmetric and constant-amplitude perfectly absorbed flows. The stability of solutions of the latter type can be confirmed analytically.

Design and Analysis of a Geometrically Nonlinear Dynamic Vibration Absorber

The design and optimization of a nonlinear dynamic vibration absorber based on a snap-through truss geometry is investigated. The effect of absorber's parameters on primary system (PS) vibration amplitude reduction and frequency range of operation is analyzed. Within parametric analyses of the absorber, a methodology was proposed to tune the absorber's stiffness. Results show that the nonlinear vibration absorber may be substantially more effective than its linear counterpart both in terms of vibration amplitude reduction and absorption frequency range. Possible difficulties and/or limitations caused by the nonlinearity induced by the absorber are analyzed and, for the studied case, do not diminish the advantages of the nonlinear absorber (NLAbs). The effect of absorber's damping on the vibration reduction performance was also analyzed indicating that the NLAbs outperforms its linear counterpart even for higher damping levels.

An Exact Analytical Solution to the Shallow Water Equations Near Beaches

<p>The nonlinear differential equation governing the dynamics of water waves can be well approximated by a linear counterpart in the case of shallow waters near beaches. The linear equation, which is of second order nature, cannot be exactly solved in many apparently simple cases. In our work, we consider the shape of system as a complete second-order polynomial which contains the constant (step-like), linear and quadratic shapes near the beach. We then apply some novel transformations and transform the problem into a form which can be solved in an exact analytical manner via the powerful Nikiforov-Uvarov technique. The eigenfunctions of the problem are obtained in terms of the Jacobi polynomials and the eigenvalue equation is reported for any arbitrary mode. </p>

Functionalization of single-walled carbon nanotubes with thermo-responsive poly(N-isopropylacrylamide): effect of the polymer architecture

Star-shaped and linear thermo-responsive PNIPAM polymers were compared for the functionalization of SWNTs. The star-shaped polymer gave the SWNTs a higher solubility and more thermo-responsive properties than its linear counterpart.

Sensitivity to Over-Etching of Improved V-Shaped Microcantilever

In this paper we have analyzed the sensitivity to over-etching of our recently proposed improved V-Shaped microcantilever. For V-shaped microcantilever, the final length is very sensitive to over-etching because of the sharp corner at the free end of the cantilever. It has been observed that for different values of over-etching the improved V-shape microcantilever tip is more robust compared to the linear counterpart.

DECAY OF MASSLESS DIRAC FIELD AROUND THE BORN–INFELD BLACK HOLE

In this paper we investigate the perturbations by a massless Dirac spinor of a Born–Infeld black hole. The decay rates of the spinor field which is given by the quasinormal mode frequencies are computed using the sixth-order WKB approximation. The behavior of the quasinormal modes with the nonlinear parameter, temperature and charge of the black hole are analyzed in detail. We also compare the decay rates of the Born–Infeld black hole with its linear counterpart Reissner–Nordstrom black hole.