Luminescence properties of the structure built from 3‐cyano‐4‐dicyanomethylene‐5‐oxo‐4,5‐dihydro‐1H‐pyrrol‐2‐olate and caesium(I)

The structure of caesium(I) 3‐cyano‐4‐dicyanomethylene‐5‐oxo‐4,5‐dihydro‐1H‐pyrrol‐2‐olate (CsA), Cs⁺·C₈HN₄O₂⁻, is related to its luminescence properties. The structure of CsA (triclinic, P) is not isomorphous with previously reported structures (monoclinic, P2₁/c) of the KA and RbA salts. Nevertheless, the coordination numbers of the metals are equal for all salts (nine). Each anion in the CsA salt is connected by pairs of inversion‐related N—H...O hydrogen bonds to another anion, forming a centrosymmetric dimer. The dimers are linked into infinite ribbons, stacked by means of π–π interactions, thus building up an anionic wall. Time‐dependent density functional theory calculations show that the formation of the dimer shifts the wavelength of the luminescence maximum to the blue region. Shortening the distance between stacked anions in the row [from 3.431 (5) Å for RbA to 3.388 (2) Å for KA to 3.244 (10) Å for CsA] correlates with a redshift of the luminescence maximum from 574 and 580 nm to 596 nm, respectively.     

Correlation of acoustic and optical emission signals produced at 1064 and 532 nm laser-induced breakdown spectroscopy (LIBS) of glazed wall tiles

An acoustic signal was used for the internal standardization of laser-induced breakdown spectroscopy (LIBS) of a glazed wall tile. For the LIBS analyses, 1064 nm and 532 nm wavelengths of the Nd:YAG laser were utilized. The tile was depth profiled by a single-spot ablation from the glaze into the substrate. Some lines of major elements Si(I) 252.418, Si(I) 252.851, Al(I) 257.509, Cr(I) 295.368, Al(I) 309.271 nm and Ti(II) 334.904 nm were monitored. The decrease in the optical emissions during the ablation was successfully compensated for by normalization to the square power of the acoustic signal in the interval of 290–340 nm. This approach failed for the lines between 250–270 nm. The results were the same for both lasing wavelengths despite different irradiances. The acquired profiles are in good agreement with the reference X-ray fluorescence measurement.     

Factors Affecting DNA–DNA Interstrand Cross‐Links in the Antiparallel 3′–3′ Sense: A Comparison with the 5′–5′ Directional Isomer

Reported herein is a study of the unusual 3′–3′ 1,4‐GG interstrand cross‐link (IXL) formation in duplex DNA by a series of polynuclear platinum anticancer complexes. To examine the effect of possible preassociation through charge and hydrogen‐bonding effects the closely related compounds [{trans‐PtCl(NH₃)₂}₂(μ‐trans‐Pt(NH₃)₂{NH₂(CH₂)₆NH₂}₂)]⁴⁺ (BBR3464, 1 ), [{trans‐PtCl(NH₃)₂}₂(μ‐NH₂(CH₂)₆NH₂)]²⁺ (BBR3005, 2 ), [{trans‐PtCl(NH₃)₂}₂(μ‐H₂N(CH₂)₃NH₂(CH₂)₄)]³⁺ (BBR3571, 3 ) and [{trans‐PtCl(NH₃)₂}₂{μ‐H₂N(CH₂)₃‐N(COCF₃)(CH₂)₄}]²⁺ (BBR3571‐COCF₃, 4 ) were studied. Two different molecular biology approaches were used to investigate the effect of DNA template upon IXL formation in synthetic 20‐base‐pair duplexes. In the “hybridisation directed” method the monofunctionally adducted top strands were hybridised with their complementary 5′‐end labelled strands; after 24 h the efficiency of interstrand cross‐linking in the 5′–5′ direction was slightly higher than in the 3′–3′ direction. The second method involved “postsynthetic modification” of the intact duplex; significantly less cross‐linking was observed, but again a slight preference for the 5′–5′ duplex was present. 2D [¹H, ¹⁵N] HSQC NMR spectroscopy studies of the reaction of [¹⁵N]‐ 1 with the sequence 5′‐d{TATACATGTATA}₂ allowed direct comparison of the stepwise formation of the 3′–3′ IXL with the previously studied 5′–5′ IXL on the analogous sequence 5′‐d(ATATGTACATAT)₂. Whereas the preassociation and aquation steps were similar, differences were evident at the monofunctional binding step. The reaction did not yield a single distinct 3′–3′ 1,4‐GG IXL, but numerous cross‐linked adducts formed. Similar results were found for the reaction with the dinuclear [¹⁵N]‐ 2 . Molecular dynamics simulations for the 3′–3′ IXLs formed by both 1 and 2 showed a highly distorted structure with evident fraying of the end base pairs and considerable widening of the minor groove.     

Electron Density Shift in Imidazolium Derivatives upon Complexation with Cucurbit[6]uril

In this study, we have investigated the supramolecular interaction between series of 1‐alkyl‐3‐methylimidazolium guests with variable alkyl substituent lengths and cucurbit[6]uril (CB6) in the solution and the solid state. Correct interpretation of ¹H NMR spectra was a key issue for determining the binding modes of the complexes in solution. Unusual chemical shifts of some protons in the ¹H NMR spectra were explained by the polarization of the imidazolium aromatic ring upon the complexation with the host. The formation of 1:1 complex between 1‐ethyl‐3‐methylimidazolium and CB6 is in disagreement with previously reported findings describing an inclusion of two guest molecules in the CB6 cavity.     

Spectral imaging of individual split-ring resonators

We report on spectral imaging within individual silver split-ring resonators (SRRs) operating in the near infrared-visible range. We classified the optical eigenmodes from the measurement of their energies and nanometer scale spatial distributions. They are plasmonic standing waves that show great similarities with that of nanoantennas. We, however, evidenced marked differences in the near-field electric field lines' spatial distribution and the energies' dispersion. We also showed that the subwavelength defect's influence on the SRRs' eigenmodes spatial distribution is small.     

Dynamics in mesoscopic superconducting rings: Multiple phase-slips and vortex–antivortex pairs

We investigate the situation where a mesoscopic 1D ring or 2D cylinder is subject to a magnetic field by simulating the time dependant Ginzburg–Landau equations with periodic boundary conditions. We investigate the different possible evolutions for the 1D phase slip phenomenon. The case of the multiple phase slips is analyzed in details and we study the competition between simultaneous and consecutive multiple phase slips analytically and numerically. In 2D we study the creation of vortex–antivortex pairs. Following the theory of the Kibble–Zurek mechanism, we quenched the sample by applying a strong current and observe vortex–antivortex pairs dynamics.     

Higher borides and oxygen-enriched Mg–B–O inclusions as possible pinning centers in nanostructural magnesium diboride and the influence of additives on their formation

The study of high pressure (2 GPa) synthesized MgB₂-based materials allows us to conclude that higher borides (with near MgB₁₂ stoichiometry) and oxygen-enriched Mg–B–O inclusions can be pinning centers in nanostructural magnesium diboride matrix (with average grain sizes of 15–37 nm). It has been established that additions of Ti or SiC as well as manufacturing temperature can affect the size, amount and distribution of these inclusions in the material structure and thus, influence critical current density. The superconducting behavior of materials with near MgB₁₂ stoichiometry of matrix is discussed.     

Nonlinear electromechanical response of the ferroelectret ultrasonic transducers

The ultrasonic transmission between two air-coupled polypropylene (PP) ferroelectret (FE) transducers in dependence on the amplitude of the high-voltage exciting pulse revealed a strongly nonlinear electromechanical response of the FE transmitter. This phenomenon is described by a linear increase of the inverse electromechanical transducer constant t₃₃⁽¹⁾t_{33}^{(1)} of the PP FE film with an increase of the exciting electrical pulse amplitude. Enlargement of t₃₃⁽¹⁾t_{33}^{(1)} by a factor of 4 was achieved by application of 3500 V exciting pulses. The electrostriction contribution to t₃₃⁽¹⁾t_{33}^{(1)} can be attributed to the electrostatic force between electrodes and the Maxwell stress effect. The nonlinear electromechanical properties of the PP FE result in a strong increase of its air-coupled ultrasonic (ACUS) figure of merit (FOM) under the high-voltage excitation, which exceeds results of the PP FE technological optimization. The FOM increase can be related to the increase of PP FE coupling factor and/or to the decrease of its acoustic impedance. A significant enhancement of the ACUS system transmission (12 dB) and signal-to-noise ratio (32 dB) was demonstrated by the increase of excitation voltage up to 3500 V. The nonlinear electromechanical properties of the PP FEs seem to be very important for their future applications.     

Study of RPC gas composition using Daya Bay RPCs

This study uses Daya Bay RPCs operating in streamer mode to investigate gas mixtures of at least 50% argon,at most 6% isobutane,and with small amounts of SF6.Isobutane is reduced to 2% without degradation of performance,and SF6 reduces the noise rate and current,as well as the signal size.This study provides quantitative relationships between basic RPC operating parameters and various gas compositions.     

Laser heating in diamond anvil cells: developments in pulsed and continuous techniques

Developments in continuous and pulsed laser‐heating techniques, and finite‐element calculations for diamond anvil cell experiments are reported. The methods involve the use of time‐resolved (5 ns gated) incandescent light temperature measurements to determine the time dependence of heat fluxes, while near‐IR incandescent light temperature measurements allow temperature measurements to as low as 500 K. Further optimization of timing in pulsed laser heating together with sample engineering will provide additional improvements in data collection in very high P–T experiments.