Inflation with an antisymmetric tensor field

We investigate the possibility of inflation with models of antisymmetric tensor field having minimal and nonminimal couplings to gravity. Although the minimal model does not support inflation, the nonminimal models, through the introduction of a nonminimal coupling to gravity, can give rise to stable de-Sitter solutions with a bound on the coupling parameters. The values of field and coupling parameters are sub-planckian. Slow roll analysis is performed and slow-roll parameters are defined which can give the required number of e-folds for sufficient inflation. Stability analysis has been performed for perturbations to antisymmetric field while keeping the metric unperturbed, and it is found that only the sub-horizon modes are free of ghost instability for de-Sitter space.     

Cell Penetrating Synthetic Antimicrobial Peptides (SAMPs) Exhibiting Potent and Selective Killing of Mycobacterium by Targeting Its DNA

Naturally occurring antimicrobial peptides (AMPs) are powerful defence tools to tackle pathogenic microbes. However, limited natural production and high synthetic costs in addition to poor selectivity limit large‐scale use of AMPs in clinical settings. Here, we present a series of synthetic AMPs (SAMPs) that exhibit highly selective and potent killing of Mycobacterium (minimum inhibitory concentration <20 μg mL^?1) over E. coli or mammalian cells. These SAMPs are active against rapidly multiplying as well as growth saturated Mycobacterium cultures. These SAMPs are not membrane‐lytic in nature, and are readily internalized by Mycobacterium and mammalian cells; whereas in E. coli, the lipopolysaccharide layer inhibits their cellular uptake, and hence, their antibacterial action. Upon internalization, these SAMPs interact with the unprotected genomic DNA of mycobacteria, and impede DNA‐dependent processes, leading to bacterial cell death.     

Heat transfer enhancement and pressure drop in viscous liquid flows in isothermal tubes with twisted-tape inserts

Heat transfer enhancement in viscous liquid flows by means of twisted-tape inserts has been investigated in this study. Internal flows in horizontal tubes with uniform wall temperature have been considered. This is representative of typical conditions encountered in practical applications in the chemical and process industry. Experimental data were obtained for water and ehtylene glycol with snug-fit tape inserts of three different twist ratios,y=3.0, 4.5, and 6.0; the tape thickness in each case was 0.483 mm. The data cover a wide range of flow parameters: 3.5Pr<100, and=">Re<35,000, for=" both=" heating=" and=" cooling=" conditions.=" the=" results=">Nu _m andf are strongly influenced by the tape geometry and fluid flow conditions, and can be functionally represented byNu _m=(Re, Pr, _b/_w,L/d, H/d, /d) andf=(Re, H/d, /d).In dieser Untersuchung wurde die Verbesserung des Wärmeübergangs in viskosen Flüssigkeitsströmungen mittels eines Spiralband-Einsatzes erforscht. Es wurden Strömungen in horizontalen Rohren mit einheitlicher Wandtemperatur betrachtet. Diese sind repräsentativ für typische Bedingungen, die in praktischen Anwendungen in der chemischen und weiterverarbeitenden Industrie anzutreffen sind. Für Wasser und Äthylen-Glykol wurden experimentelle Daten für eingepaßte Band-Einsätze mit drei unterschiedlichen Verdrehungsverhältnisseny=3.0, 4.5 und 6.0 erhalten; die Breite des Bandes betrug jeweils 0.483 mm. Die Daten decken einen weiten Bereich von Strömungsparametern ab: 3.5Pr<100 und=">Re<35,000 für=" die=" beiden=" betriebsbedingungen=" heizen=" und=" kühlen.=" die=" ergebnisse=">Nu _m undf sind stark abhängig von der Bandgeometrie und den Strömungsbedingungen und können zweckmäßig durchNu _m=(Re, Pr, _b/_w,L/d, H/d, /d) undf=(Re, H/d, /d) dargestellt werden.Dedicated to Prof. Dr.-Ing. U. Grigull's 80th birthday     

Optically transparent hydrogels from an auxin-amino-acid conjugate super hydrogelator and its interactions with an entrapped dye

Low-molecular-weight organic hydrogelators (LMHGs) that can rigidify water into soft materials are desirable in various applications. Herein, we report the excellent hydrogelating properties of a simple synthetic auxin-amino-acid conjugate, naphthalene-1-acetamide of L-phenylalanine (1-NapF, M(w)=333.38?Da), which gelated water even at 0.025?wt?%, thereby making it the most-efficient LMHG known. Optically transparent gels that exhibited negligible scattering in the range 350-900?nm were obtained. A large shift from the theoretical pK(a) value of the gelator was observed. The dependence of the minimum gelator concentration (MGC) and the gel-melting temperatures on the pH value indicated the importance of H-bonding between the carboxylate groups on adjacent phenylalanine molecules in the gelator assembly. FTIR spectroscopy of the xerogels showed a β-sheet-like assembly of the gelator. Variable-temperature (1)H?NMR spectroscopy demonstrated that π stacking of the aromatic residues was also partly involved in the gelator assembly. TEM of the xerogel showed the presence of a dense network of thin, high-aspect-ratio fibrillar assemblies with diameters of about 5?nm and lengths that exceeded a few microns. Rheology studies showed the formation of stable gels. The entrapment of water-soluble dyes afforded extremely fluorescent gels that involved the formation of J-aggregates by the dye within gel. A strong induced-CD band established that the RhoB molecules were interacting closely with the chiral gelator aggregates. H-bonding and electrostatic interactions, rather than intercalation, seemed to be involved in RhoB binding. The addition of chaotropic reagents, as well as increasing the pH value, disassembled the gel and promoted the release of the entrapped dye with zero-order kinetics.     

Organothiol Monolayer Formation Directly on Muscovite Mica

Organothiol monolayers on metal substrates (Au, Ag, Cu) and their use in a wide variety of applications have been extensively studied. Here, the growth of layers of organothiols directly onto muscovite mica is demonstrated using a simple procedure. Atomic force microscopy, surface X‐ray diffraction, and vibrational sum‐frequency generation IR spectroscopy studies revealed that organothiols with various functional endgroups could be self‐assembled into (water) stable and adaptable ultra‐flat organothiol monolayers over homogenous areas as large as 1 cm². The strength of the mica–organothiol interactions could be tuned by exchanging the potassium surface ions for copper ions. Several of these organothiol monolayers were subsequently used as a template for calcite growth.     

Dynamical Instability Causes the Demise of a Supercooled Tetrahedral Liquid

We investigate the relaxation mechanism of a supercooled tetrahedral liquid at its limit of stability using isothermal isobaric (NPT) Monte Carlo simulations. In similarity with systems which are far from equilibrium but near the onset of jamming (O’Hern et al. in Phys Rev Lett 93:165702, 2004), we find that the relaxation is characterized by two time-scales: the decay of long-wavelength (slow) fluctuations of potential energy is controlled by the slope \([\partial (G/N)/\partial \phi ]\) of the Gibbs free energy (G) at a unique value of per particle potential energy \(\phi = \phi _{{\tiny mid}}\). The short-wavelength (fast) fluctuations are controlled by the bath temperature T. The relaxation of the supercooled liquid is initiated with a dynamical crossover after which the potential energy fluctuations are biased towards values progressively lesser than \(\phi _{{\tiny mid}}\). The dynamical crossover leads to the change of time-scale, i.e., the decay of long-wavelength potential energy fluctuations (intermediate stage of relaxation). Because of the condition [\(\partial ^2 (G/N)/\partial \phi ^2 = 0\)] at \(\phi = \phi _{{\tiny mid}}\), the slope \([\partial (G/N)/\partial \phi ]\) has a unique value and governs the intermediate stage of relaxation, which ends just after the crossover. In the subsequent stage, there is a relatively rapid crystallization due to lack of long-wavelength fluctuations and the instability at \(\phi _{{\tiny mid}}\), i.e., the condition that G decreases as configurations with potential energies lower than \(\phi _{{\tiny mid}}\) are accessed. The dynamical crossover point and the associated change in the time-scale of fluctuations is found to be consistent with the previous studies.