Computing resonance energies, widths, and wave functions using a Lanczos method in real arithmetic

We introduce new ideas for calculating resonance energies and widths. It is shown that a non-Hermitian-Lanczos approach can be used to compute eigenvalues of H+W, where H is the Hamiltonian and W is a complex absorbing potential (CAP), without evaluating complex matrix-vector products. This is done by exploiting the link between a CAP-modified Hamiltonian matrix and a real but nonsymmetric matrix U suggested by Mandelshtam and Neumaier [J. Theor. Comput. Chem. 1, 1 (2002)] and using a coupled-two-term Lanczos procedure. We use approximate resonance eigenvectors obtained from the non-Hermitian-Lanczos algorithm and a very good CAP to obtain very accurate energies and widths without solving eigenvalue problems for many values of the CAP strength parameter and searching for cusps. The method is applied to the resonances of HCO. We compare properties of the method with those of established approaches.     

Investigation of a new thermosensitive block copolymer micelle: hydrolysis, disruption, and release

Thermosensitive polymer micelles are generally obtained with block copolymers in which one block exhibits a lower critical solution temperature in aqueous solution. We investigate a different design that is based on the use of one block bearing a thermally labile side group, whose hydrolysis upon heating shifts the hydrophilic-hydrophobic balance toward the destabilization of block copolymer micelles. Atom transfer radical polymerization was utilized to synthesize a series of diblock copolymers composed of hydrophilic poly(ethylene oxide) (PEO) and hydrophobic poly(2-tetrahydropyranyl methacrylate) (PTHPMA). We show that micelles of PEO-b-PTHPMA in aqueous solution can be destabilized as a result of the thermosensitive hydrolytic cleavage of tetrahydropyranyl (THP) groups that transforms PTHPMA into hydrophilic poly(methacrylic acid). The three related processes occurring in aqueous solution, namely, hydrolytic cleavage of THP, destabilization of micelles, and release of loaded Nile Red (NR), were investigated simultaneously using 1H NMR, dynamic light scattering, and fluorescence spectroscopy, respectively. At 80 degrees C, the results suggest that the three events proceed with a similar kinetics. Although slower than at elevated temperatures, the disruption of PEO-b-PTHPMA micelles can take place at the body temperature (approximately 37 degrees C), and the release kinetics of NR can be adjusted by changing the relative lengths of the two blocks or the pH of the solution.     

Low frequency vocalizations attributed to sei whales (Balaenoptera borealis)

Low frequency (<100 Hz) downsweep vocalizations were repeatedly recorded from ocean gliders east of Cape Cod, MA in May 2005. To identify the species responsible for this call, arrays of acoustic recorders were deployed in this same area during 2006 and 2007. 70 h of collocated visual observations at the center of each array were used to compare the localized occurrence of this call to the occurrence of three baleen whale species: right, humpback, and sei whales. The low frequency call was significantly associated only with the occurrence of sei whales. On average, the call swept from 82 to 34 Hz over 1.4 s and was most often produced as a single call, although pairs and (more rarely) triplets were occasionally detected. Individual calls comprising the pairs were localized to within tens of meters of one another and were more similar to one another than to contemporaneous calls by other whales, suggesting that paired calls may be produced by the same animal. A synthetic kernel was developed to facilitate automatic detection of this call using spectrogram-correlation methods. The optimal kernel missed 14% of calls, and of all the calls that were automatically detected, 15% were false positives.     

Differential modulation of corticospinal excitability during haptic sensing of 2-D patterns vs. textures

Background  

Recently, we showed a selective enhancement in corticospinal excitability when participants actively discriminated raised 2-D symbols with the index finger. This extra-facilitation likely reflected activation in the premotor and dorsal prefrontal cortices modulating motor cortical activity during attention to haptic sensing. However, this parieto-frontal network appears to be finely modulated depending upon whether haptic sensing is directed towards material or geometric properties. To examine this issue, we contrasted changes in corticospinal excitability when young adults (n = 18) were engaged in either a roughness discrimination on two gratings with different spatial periods, or a 2-D pattern discrimination of the relative offset in the alignment of a row of small circles in the upward or downward direction.     

Remote sensing with intense filaments enhanced by adaptive optics

A method involving a closed loop adaptive optic system is investigated as a tool to significantly enhance the collected optical emissions, for remote sensing applications involving ultrafast laser filamentation. The technique combines beam expansion and geometrical focusing, assisted by an adaptive optics system to correct the wavefront aberrations. Targets, such as a gaseous mixture of air and hydrocarbons, solid lead and airborne clouds of contaminated aqueous aerosols, were remotely probed with filaments generated at distances up to 118 m after the focusing beam expander. The integrated backscattered signals collected by the detection system (15–28 m from the filaments) were increased up to a factor of 7, for atmospheric N₂ and solid lead, when the wavefronts were corrected by the adaptive optic system. Moreover, an extrapolation based on a simplified version of the LIDAR equation showed that the adaptive optic system improved the detection distance for N₂ molecular fluorescence, from 45 m for uncorrected wavefronts to 125 m for corrected.     

Solid‐Phase Parallel Synthesis of Functionalised Medium‐to‐Large Cyclic Peptidomimetics through Three‐Component Coupling Driven by Aziridine Aldehyde Dimers

The first solid‐phase parallel synthesis of macrocyclic peptides using three‐component coupling driven by aziridine aldehyde dimers is described. The method supports the synthesis of 9‐ to 18‐membered aziridine‐containing macrocycles, which are then functionalized by nucleophilic opening of the aziridine ring. This constitutes a robust approach for the rapid parallel synthesis of macrocyclic peptides.     

ORBKIT: A modular python toolbox for cross‐platform postprocessing of quantum chemical wavefunction data

ORBKIT is a toolbox for postprocessing electronic structure calculations based on a highly modular and portable Python architecture. The program allows computing a multitude of electronic properties of molecular systems on arbitrary spatial grids from the basis set representation of its electronic wavefunction, as well as several grid‐independent properties. The required data can be extracted directly from the standard output of a large number of quantum chemistry programs. ORBKIT can be used as a standalone program to determine standard quantities, for example, the electron density, molecular orbitals, and derivatives thereof. The cornerstone of ORBKIT is its modular structure. The existing basic functions can be arranged in an individual way and can be easily extended by user‐written modules to determine any other derived quantity. ORBKIT offers multiple output formats that can be processed by common visualization tools (VMD, Molden, etc.). Additionally, ORBKIT possesses routines to order molecular orbitals computed at different nuclear configurations according to their electronic character and to interpolate the wavefunction between these configurations. The program is open‐source under GNU‐LGPLv3 license and freely available at https://github.com/orbkit/orbkit/ . This article provides an overview of ORBKIT with particular focus on its capabilities and applicability, and includes several example calculations. © 2016 Wiley Periodicals, Inc.     

A magnetic and Mössbauer study of magnetic ordering and vacancy clustering in Cu5FeS4

Magnetic susceptibilities and Mössbauer spectra recorded at temperatures between 4° and 300°K show that the low temperature form of Cu₅FeS₄, bornite, orders magnetically at 76±2°K. At a lower temperature 8°K a second magnetic phase transition occurs. The Mössbauer spectra suggest that there is significant partial disordering of cations and vacancies in tetrahedral holes of the face-centred cubic sulphur lattice. Thermoelectric power measurements indicate that bornite is a p-type semiconductor.For a three dimensional magnetic superexchange interaction between Fe(III) atoms a small super-transferred spin density would be required on intermediate Cu(I) atoms.     

High-pressure amplified stimulated emission effect in a N2 laser produced plasma with axicon lenses

An axicon is used to focus a CO₂-TEA laser pulse in a high pressure preionized mixture of He-N₂. An amplified stimulated emission (ASE) effect at 337.1 nm (N₂) is obtained. The dependence of inversion population on the electron density is shown. Also presented is the electron temperature as a function of the CO₂ pulse intensity for different mixtures of He-N₂.