Pyrene, a Test Case for Deep-Ultraviolet Molecular Photophysics

We determined the complete relaxation dynamics of pyrene in ethanol from the second bright state, employing experimental and theoretical broadband heterodyne detected transient grating and two-dimensional photon echo (2DPE) spectroscopy, using pulses with duration of 6 fs and covering a spectral range spanning from 250 to 300 nm. Multiple lifetimes are assigned to conical intersections through a cascade of electronic states, eventually leading to a rapid population of the lowest long-living excited state and subsequent slow vibrational cooling. The lineshapes in the 2DPE spectra indicate that the efficiency of the population transfer depends on the kinetic energy deposited into modes required to reach a sloped conical intersection, which mediates the decay to the lowest electronic state. The presented experimental–theoretical protocol paves the way for studies on deep-ultraviolet-absorbing biochromophores ubiquitous in genomic and proteic systems

Reduction of longitudinal axial residual stresses in near-root region of circumferential joint of steam pipeline in technological way

The paper proposes a variant for solving the problem of reduction of longitudinal residual stresses in near-root region of a circumferential welded joint of section of steam pipeline by FEM simulation of the stress-strain state of repaired section of a circumferential weld in the zone of lack of root penetration on a thin-wall shell of 89 mm diameter and 6 mm wall thickness from steel 20. The result of solving the problem is total distribution of stresses and residual plastic deformations in the repaired zone

New Insights into the Photophysics of DNA Nucleobases

We report the results of an extended time-resolved study of DNA nucleobases in aqueous solutions conducted in the deep UV using broad-band femtosecond transient absorption and electronic two-dimensional spectroscopies. We found that the photodeactivation in all DNA nucleobases occurs in two steps: fast relaxation (500-700 fs) from the excited state ππ* to a "dark" state and its depopulation to the ground state within 1-2 ps. Our experimental observations and performed theoretical modeling allow us to conclude that this dark state can be associated with the nπ* electronic state, which is connected to the excited and ground states via conical intersections

Quantum criticality at cryogenic melting of polar bubble lattices

Quantum fluctuations (QFs) caused by zero-point phonon vibrations (ZPPVs) are known to prevent the occurrence of polar phases in bulk incipient ferroelectrics down to 0K1-3. On the other hand, little is known about the effects of QFs on the recently discovered topological patterns in ferroelectric nanostructures4-9. Here, by using an atomistic effective Hamiltonian within classical Monte Carlo (CMC) and path integral quantum Monte Carlo (PI-QMC)1,3,10,11, we unveil how QFs affect the topology of several dipolar phases in ultrathin Pb(Zr0.4Ti0.6)O3 (PZT) films. In particular, our PI-QMC simulations show that the ZPPVs do not suppress polar patterns but rather stabilize the labyrinth4, bimeron5 and bubble phases12,13 within a wider range of bias field magnitudes. Moreover, we reveal that quantum fluctuations induce a quantum critical point (QCP) separating a hexagonal bubble lattice from a liquid-like state characterized by spontaneous motion, creation and annihilation of polar bubbles at cryogenic temperatures. Finally, we show that the discovered quantum melting is associated with anomalous physical response, as, e.g., demonstrated by a negative longitudinal piezoelectric coefficient.Comment: Nature communication, accepted, 21 pages, 4 Fig

Surgical treatment of intra-articular fractures of the proximal humerus

Background. The most severe category of fractures of the proximal humerus are  intra-articular injuries which are accompanied with humeral head ischemia caused by an injury and aggravated by surgical intervention. Due to frequent disruption of vascularization with subsequent necrosis of the humeral head, there is a need to stimulate reparative osteogenesis in intra-articular injuries to prevent ischemic changes in the humeral head. The aim of the study. To improve the results of surgical treatment of intra-articular fractures ofthe proximal humerus based on the development of a new osteosynthesis technique using non-free osteomuscular graft. Material and methods. We analyzed the results of treatment of 48patients with 11- C1 and 11-C2 intra-articular fractures of the proximal humerus, who had hospital treatment at the emergency department of traumatology of the Novosibirsk City Clinical Hospital No.  1 and were subsequently observed on an outpatient basis. An  analysis of literature data using search words was carried out in the PubMed and eLibrary databases. Results. According to the data obtained during the study, the functional and radiological results of the patients who were treated using the method of reparative stimulation with a non-free osteomuscular graft from the coracoid process are statistically significantly higher than the results of the control group. Conclusion. Using autoplasty with a non-free osteomuscular graft from the coracoid process improves the results and reduces the risk of developing post-traumatic aseptic necrosis of the humeral head

Reactive trityl derivatives: stabilised carbocation mass-tags for life sciences applications

The rational design of novel triarylmethyl (trityl)-based mass tags (MT) for mass-spectrometric (MS) applications is described. We propose a "pKR+ rule" to correlate the stability of trityl carbocations with their MS performance: trityls with higher pKR+ values ionise and desorb better. Trityl blocks were synthesised that have high pKR+ values and are stable in conditions of MS analysis; these MTs can be ionised by matrix as well as irradiation with a 337 nm nitrogen laser. 13C-Labelled tags were prepared for MS quantitation applications. Moreover, the tags were equipped with a variety of functional groups allowing conjugation with different functionalities within (bio)molecules to enhance the MS characteristics of the latter. The MS behaviour of model polycationic trityl compounds with and without the matrix was studied to reveal that poly-trityl clusters are always singly charged under the (MA)LDI-TOF conditions. Several peptide-trityl conjugates were prepared and comparisons revealed a beneficial effect of trityl tags on the conjugate detection in MS. Trityl compounds containing para-methoxy- and dimethylamine groups, as well as a xanthene fragment, showed considerable enhancement in MS detection of model peptides; thus they are promising tools for proteomic applications. Dimethoxytrityl derivatives allow one to distinguish between Arg- and Lys-containing peptides. Maleimido trityl derivatives are suitable for the efficient derivatisation of thiol-containing peptides in pyridine

Resolving vibrational from electronic coherences in two-dimensional electronic spectroscopy: The role of the laser spectrum

The observation of coherent quantum effects in photosynthetic light-harvesting complexes prompted the question whether quantum coherence could be exploited to improve the efficiency in new energy materials. The detailed characterization of coherent effects relies on sensitive methods such as two-dimensional electronic spectroscopy (2D-ES). However, the interpretation of the results produced by 2D-ES is challenging due to the many possible couplings present in complex molecular structures. In this work, we demonstrate how the laser spectral profile can induce electronic coherence-like signals in monomeric chromophores, potentially leading to data misinterpretation. We argue that the laser spectrum acts as a filter for certain coherence pathways and thus propose a general method to differentiate vibrational from electronic coherences

Optically induced forces and torques:Interactions between nanoparticles in a laser beam

Distinctive optical forces and torques arise between nanoparticles irradiated by intense laser radiation. These forces, associated with a pairwise process of stimulated scattering, prove to enable the possibility of producing significant modifications to both the form and magnitude of interparticle forces, with additional contributions arising in the case of dipolar materials. Moreover, such forces have the capacity to generate unusual patterns of nanoscale response, entirely controlled by the input beam characteristics- principally the optical frequency, intensity, and polarization. Based on quantum electrodynamical theory, a general result is secured for the laser-induced force under arbitrary conditions, incorporating both static and dynamic coupling mechanisms. Specific features of the results are identified for pairs of particles with prolate cylindrical symmetry, e.g., carbon nanotubes, where it is shown that the laser-induced forces and torques are sensitive functions of the pair spacing and orientation, and the laser beam geometry; significantly, they can be either repulsive or attractive according to conditions. For nanoparticles trapped in a Laguerre-Gaussian laser beam the results also reveal additional and highly distinctive torques that suggest further possibilities for nanomanipulation with light. The paper concludes with a discussion on several potential applications of such forces. © 2005 The American Physical Society

Quantum coherent energy transport in the Fenna–Matthews–Olson complex at low temperature

In the primary step of natural light harvesting, the solar photon energy is captured in a photoexcited electron–hole pair, or an exciton, in chlorophyll. Its conversion to chemical potential occurs in the special pair reaction center, which is reached by downhill ultrafast excited-state energy transport through a network of chromophores. Being inherently quantum, transport could in principle occur via a matter wave, with vast implications for efficiency. How long a matter wave remains coherent is determined by the intensity by which the exciton is disturbed by the noisy biological environment. The stronger this is, the stronger the electronic coupling between chromophores must be to overcome the fluctuations and phase shifts. The current consensus is that under physiological conditions, quantum coherence vanishes on the 10-fs time scale, rendering it irrelevant for the observed picosecond transfer. Yet, at low-enough temperature, quantum coherence should in principle be present. Here, we reveal the onset of longer-lived electronic coherence at extremely low temperatures of ∼20 K. Using two-dimensional electronic spectroscopy, we determine the exciton coherence times in the Fenna–Matthew–Olson complex over an extensive temperature range. At 20 K, coherence persists out to 200 fs (close to the antenna) and marginally up to 500 fs at the reaction center. It decays markedly faster with modest increases in temperature to become irrelevant above 150 K. At low temperature, the fragile electronic coherence can be separated from the robust vibrational coherence, using a rigorous theoretical analysis. We believe that by this generic principle, light harvesting becomes robust against otherwise fragile quantum effects

Clinical case of the surgical treatment of complete rupture of distal biceps tendon using two cortical buttons

Distal biceps tendon injuries mainly occur in men from the active groups of population. Among the athletes and military personnel, the incidence rate is 2–10  % of  the  upper limb tendon injuries. Comparative studies have shown the achievement of better functional results in surgical treatment, while maintaining overall complication rate of 4.6–25 %. The aim. To demonstrate a new reinsertion technique with two cortical buttons in case of complete rupture of distal biceps tendon as part of a clinical case. Materials and methods. The article presents a clinical case of surgical treatment of a patient with complete rupture of dominant limb distal biceps tendon which was more than 2 weeks old and was accompanied by lacertus fibrosus provocation and persistent muscle retraction. Results. We obtained the following clinical results by the week 24 after the surgery: VAS (Visual Analogue Scale) score – 1  cm, ASES (American Shoulder and Elbow Surgeons) score – 99  points, DASH (Disabilities of the Arm, Shoulder and Hand) score – 15 points. Dynamometry results: Dex. 85; sin. 90 (2daN); range of motion corresponds to the same of a healthy joint. MRI at 1.5 T shows no signs of synostosis or heterotopic ossification; MSCT shows no signs of migration of cortical buttons in comparison with intraoperative X-ray control. Discussion. Extracortical methods of distal biceps tendon positioning in anatomical reinsertion have lower strength indicators, comparable with the use of transosseous sutures and anchor fixators. A larger area of contact of the studied zone in case of minimal tendon compression in the area of proximal radioulnar space or inside the formed radial bone canal provides high strength indicators and reduces the risk of repeated injury. Conclusion. The scores of the scales (VAS, DASH, ASES) turned out to be better than when using other common methods. The technique of dipping distal biceps tendon stump into the formed oval canal of the “anatomical impression” using the proposed method meets the objectives of careful attitude to the tendon and provides the largest area of its contact with the bone