Short-Lived Large-Amplitude Pulses in the Nonlinear Long-Wave Model Described by the Modified Korteweg–De Vries Equation

The appearance and disappearance of short-lived large-amplitude pulses in a nonlinear long wave model is studied in the framework of the modified Korteweg–de Vries equation. The major mechanism of such wave generation is modulational instability leading to the generation and interaction of the breathers. The properties of breathers are studied both within the modified Korteweg–de Vries equation, and also within the nonlinear Schrödinger equations derived by an asymptotic reduction from the modified Korteweg–de Vries for weakly nonlinear wave packets. The associated spectral problems (AKNS or Zakharov-Shabat) of the inverse-scattering transform technique also are utilized. Wave formation due to this modulational instability is investigated for localized and for periodic disturbances. Nonlinear-dispersive focusing is identified as a possible mechanism for the formation of anomalously large pulses.     

The Lysine48‐Based Polyubiquitin Chain Proteasomal Signal: Not a Single Child Anymore

The conjugation of ubiquitin (Ub) to proteins is involved in the regulation of many processes. The modification serves as a recognition element in trans, in which downstream effectors bind to the modified protein and determine its fate and/or function. A polyUb chain that is linked through internal lysine (Lys)‐48 of Ub and anchored to an internal Lys residue of the substrate has become the accepted “canonical” signal for proteasomal targeting and degradation. However, recent studies show that the signal is far more diverse and that chains based on other internal linkages, as well as linear or heterologous chains made of Ub and Ub‐like proteins and even monoUb, are recognized by the proteasome. In addition, chains linked to residues other than internal Lys were described, all challenging the current paradigm.     

A stealth supersymmetry sampler

Journal of High Energy Physics - In the context of (2+1)-dimensional Chern-Simons SL(N, $ \mathbb{R} $ ) × SL(N, $ \mathbb{R} $ ) gauge fields and spin N black holes we compute the on-shell...     

Synthesis and self-assembly of novel fluorous cationic amphiphiles with a 3,4-dihydro-2(1H)-pyridone spacer

The synthesis of fluorous (highly fluorinated) 3,4-dihydro-2(1H)-pyridone-5-carboxylate cationic amphiphiles have been described, where the dihydropyridone serves as a spacer and either a pyridinium bromide or a triphenylphosphonium bromide form the polar cationic head group. The in water self-assembled aggregates have been observed by atomic force microscopy (AFM) and dynamic light scattering (DLS).     

Wetting properties of the multiscaled nanostructured polymer and metallic superhydrophobic surfaces

A superhydrophobic surface is produced from industrial grade polymer materials. The surface comprises partly disordered triple-scaled arrays of polyvinylidene fluoride (PVDF) globules. An inherently superhydrophobic metallic surface is produced with polymer template. The mathematical model based on the Cassie-Baxter hypothesis of air trapping under a water drop is built, which gives the apparent contact angle on the manifold-scaled interface. The presence of several scales itself is not a sufficient condition of hydrophobicity of inherently wettable surfaces. The geometrical features favoring the increase of the vapor-water interface fraction are necessary for this phenomenon.     

ZnGeP2 optical parametric oscillator with 3.8-12.4-mum tunability

A ZnGeP>(2) (ZGP) optical parametric oscillator (OPO) with wide mid-IR tunability has been demonstrated. The singly resonant angle-tuned ZGP OPO was pumped by 100-ns erbium laser pulses at lambda =2.93mum and yielded output that was continuously tunable from 3.8 to 12.4 mum (type I phase matching) and from 4 to 10 mum (type II phase matching). An OPO pump threshold was less than 1 mJ in the whole 4-12 mum range of the output, and the quantum conversion efficiency reached 35%. An OPO linewidth was typically a few wave numbers; however, with a single intracavity etalon (uncoated Si plate) in a type II OPO it was narrowed to <0.5cm(-1). We demonstrate the sensitive detection of N(2)O gas with the narrow-linewidth OPO.     

Self-assembly in evaporated polymer solutions: influence of the solution concentration

Amorphous polymers were dissolved in chlorinated organic solvents and deposited on thin horizontal substrates. The solutions with various concentrations of polymers were deposited and evaporated under ambient conditions in a slow air current. Self-assembled oriented mesoscopically scaled patterns were observed. The patterns were studied with optical and atomic force microscopy. The concentration of the solution exerts a decisive influence on the mesoscopic cell characteristic dimension. Cell dimensions grow linearly with the polymer solution concentration for all kinds of tested polymers, chlorinated solvents and substrates. The dependence could be explained by a physical mechanism, based on the mass transport instability occurring under the intensive evaporation of the solvent. In situ FTIR study of the process was performed first. It was established with FTIR spectroscopy that film porosity is not due to water droplet condensation under evaporation.     

Benzoylureas as removable cis amide inducers: synthesis of cyclic amides via ring closing metathesis (RCM)

Rapid and high yielding synthesis of medium ring lactams was made possible through the use of a benzoylurea auxiliary that serves to stabilize a cisoid amide conformation, facilitating cyclization. The auxiliary is released after activation under the mild conditions required to deprotect a primary amine, such as acidolysis of a Boc group in the examples given here. This methodology is a promising tool for the synthesis of medium ring lactams, macrocyclic natural products and peptides.