Laser-induced rotation of iodine molecules in He-nanodroplets: revivals and breaking-free

Rotation of molecules embedded in He nanodroplets is explored by a combination of fs laser-induced alignment experiments and angulon quasiparticle theory. We demonstrate that at low fluence of the fs alignment pulse, the molecule and its solvation shell can be set into coherent collective rotation lasting long enough to form revivals. With increasing fluence, however, the revivals disappear -- instead, rotational dynamics as rapid as for an isolated molecule is observed during the first few picoseconds. Classical calculations trace this phenomenon to transient decoupling of the molecule from its He shell. Our results open novel opportunities for studying non-equilibrium solute-solvent dynamics and quantum thermalization.Comment: 6+7 pages; 4+1 figures; 1 tabl

Nucleosome stacking in chromatin fibers probed with single-molecule force- and torque-spectroscopy

In human cells, a meter-long DNA is condensed inside a micrometer-sized cell nucleus. Simultaneously, the genetic code must remain accessible for its replication and transcription to functional proteins. Such plasticity of the genome is maintained by dynamic folding and unfolding of DNA-protein spools called nucleosomes. It is unclear, however, how this process is controlled when multiple nucleosomes stack on top of each other and form compact chromatin fibers. This is particularly important since nucleosomes are rarely present in isolation inside a densely packed cell nucleus. Therefore, the aim of this thesis was to increase the understanding of the chromatin fiber structure and its dynamics. Knowing these details would provide many new insights into the mechanisms of gene expression (epigenetic regulation) which, upon malfunction, may cause severe diseases. The presented work consists of an experimental approach involving the application of single-molecule force spectroscopy, and makes use of theoretical modelling based on statistical mechanics. By using magnetic tweezers, we stretched and twisted individual chromatin fibers reconstituted in vitro in order to unfold its nucleosomes. These studies show that folding of nucleosomes into chromatin fibers opens up a plethora of regulatory pathways for controlling the level of DNA organization in cells.This work was supported by the Netherlands Organisation for Scientific Research (NWO/OCW), as part of the Frontiers of Nanoscience program, and by the NWO-VICI Research Program Project 680-47-616.Biological and Soft Matter Physic

Influence of cryopreservation on the cytosine methlation state of potato genomic DNA

Shoot tips of Solanum tuberosum 'Desiree' were successfully cryopreserved by the DMSO droplet method and stored for almost 7 years, while control material was maintained in vitro for the same period of time. To analyse potential epigenetic changes, the DNA methylation status was assayed by methylation-sensitive amplified polymorphism (MSAP) analysis using restriction endonucleases MspI and HpaII. An amount of 93.6% of the analysed MSAP signals were stable among all cryopreserved and in vitro maintained samples tested, indicating extensive stability of DNA methylation. Only 0.9% of MSAP signals showed results that differed between the two treatments and at the same time matched for all three biological replications within each treatment. These can be seen as indicating directed effects of the two treatments on the DNA methylation. Cryopreserved samples displayed in comparison to in vitro stored samples consistent hypomethylation for 0.6% (3 of 469) of MSAP signals (Table 4, pattern 4) and consistent hypermethylation for 0.2% (1 of 469), respectively. For 5.6% of all MSAP signals, inconsistent results were observed among the three biological replications at least for one of the two treatments. These were interpreted as resulting from stochastic DNA methylation changes in individual samples. As results for two biological replications were identical and different from the result for the third biological replication, the direction of methylation change could be determined in those cases. Cases of stochastic loss of CG methylation in cryopreserved samples were most frequent among them, adding up to 3.4% of MSAP signals. Stochastic loss of CG methylation was also found inmaterial maintained in vitro, only for 0.6% of all MSAP signals. In conclusion, methylation changes occurred in long-term cryopreservation of potato, in a random rather than directed fashion. Hence, cryopreservation and long-term in vitro maintenance both induce limited changes of DNA methylation status. The order of magnitude of methylation changes observed was consistent with other studies, where similar rates of DNA methylation changes have been found

Unconventional superconducting phases in a correlated two-dimensional Fermi gas of nonstandard quasiparticles: a simple model

We discuss a detailed phase diagram and other microscopic characteristics on the applied magnetic field - temperature (H_a-T) plane for a simple model of correlated fluid represented by a two-dimensional (2D) gas of heavy quasiparticles with masses dependent on the spin direction and the effective field generated by the electron correlations. The consecutive transitions between the Bardeen-Cooper-Schrieffer (BCS) and the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phases are either continuous or discontinuous, depending on the values of H_a and T. In the latter case, weak metamagnetic transitions occur at the BCS-FFLO boundary. We single out two different FFLO phases, as well as a reentrant behaviour of one of them at high fields. The results are compared with those for ordinary Landau quasiparticles in order to demonstrate the robustness of the FFLO states against the BCS state for the case with spin-dependent masses (SDM). We believe that the mechanism of FFLO stabilization by SDM is generic: other high-field low-temperature (HFLT) superconducting phases benefit from SDM as well.Comment: 10 pages, 4 figure

Anderson lattice with explicit Kondo coupling: general features and the field-induced suppression of heavy-fermion state in ferromagnetic phase

We apply the extended (statistically-consistent, SGA) Gutzwiller-type approach to the periodic Anderson model (PAM) in an applied magnetic field and in the strong correlation limit. The finite-U corrections are included systematically by transforming PAM into the form with Kondo-type interaction and residual hybridization, appearing both at the same time. This effective Hamiltonian represents the essence of \textit{Anderson-Kondo lattice model}. We show that in ferromagnetic phases the low-energy single-particle states are strongly affected by the presence of the applied magnetic field. We also find that for large values of hybridization strength the system enters the so-called \textit{locked heavy fermion state}. In this state the chemical potential lies in the majority-spin hybridization gap and as a consequence, the system evolution is insensitive to further increase of the applied field. However, for a sufficiently strong magnetic field, the system transforms from the locked state to the fully spin-polarized phase. This is accompanied by a metamagnetic transition, as well as by drastic reduction of the effective mass of quasiparticles. In particular, we observe a reduction of effective mass enhancement in the majority-spin subband by as much as 20% in the fully polarized state. The findings are consistent with experimental results for Ce$_x$La$_{1-x}$B$_6$ compounds. The mass enhancement for the spin-minority electrons may also diminish with the increasing field, unlike for the quasiparticles states in a single narrow band in the same limit of strong correlations

Influence of surgical resection no plasma Endoglin (CD105) level in non-small cell lung cancer patients

Background and Aim: Endoglin is a proliferation-associated antigen on endothelial cells and essential for angiogenesis. Soluble endoglin (s‑endoglin), formed by proteolytic cleavage of ectodomain of membrane receptor could be an indicator of tumor‑activated endothelium. The aim of present study was to analyze changes of s‑endoglin level in plasma of lung cancer patients following surgical resection and to estimate the correlation of s‑endoglin with other soluble receptors, sTie2 and sVEGF R1. Patients and Methods: The study group consisted of 37 patients with stage I of non-small cell lung cancer. Plasma concentrations of s‑endoglin, sTie2 and sVEGF R1 were evaluated by ELISA, three times: before surgical resection and on postoperative day 7 and 30. Results: The median of s‑endoglin concentration decreased significantly on postoperative day 7 when compared with preoperative level and next increased on 30th day and it was comparable with that before surgery. s-Endoglin correlated with another soluble receptors, with sTie2 both before surgery (r=0.44) and on postoperative day 7 (r=0.52) and on 30th day (r=0.58), with sVEGF R1 — only on postoperative day 7 (r=0.75). Conclusion: The increased level of serum endoglin in lung cancer patients compared to controls and its changes after surgical treatment suggest potential application of soluble form of endoglin as potential tumor marker

Multi-scale computational homogenisation to predict the long-term durability of composite structures

A coupled hygro-thermo-mechanical computational model is proposed for fibre reinforced polymers, formulated within the framework of Computational Homogenisation (CH). At each macrostructure Gauss point, constitutive matrices for thermal, moisture transport and mechanical responses are calculated from CH of the underlying representative volume element (RVE). A degradation model, developed from experimental data relating evolution of mechanical properties over time for a given exposure temperature and moisture concentration is also developed and incorporated in the proposed computational model. A unified approach is used to impose the RVE boundary conditions, which allows convenient switching between linear Dirichlet, uniform Neumann and periodic boundary conditions. A plain weave textile composite RVE consisting of yarns embedded in a matrix is considered in this case. Matrix and yarns are considered as isotropic and transversely isotropic materials respectively. Furthermore, the computational framework utilises hierarchic basis functions and designed to take advantage of distributed memory high performance computing

Development of cryopreservation for Loxocarya cinerea - an endemic Australian plant species important for post-mining restoration

We report the development of a cryopreservation protocol for the endemic Western Australian plant species Loxocarya cinerea (Restionaceae). Shoot tips from two genotypes, SXH404 and SXH804, were cryopreserved using the droplet-vitrification technique. Control explants, which were cryoprotected, but not cooled, showed regeneration for both genotypes (SXH404, 22.1 ± 5.9%; SXH804, 67.7 ± 9.6%). Extension of incubation in PVS2 from 30 to 60 min did not lead to survival after cryopreservation. Thermal analysis using differential scanning calorimetry confirmed the beneficial effect of a loading phase but also revealed no or very little ice formation after cryoprotection of shoot tips in other treatments. Regeneration following cryopreservation was obtained for genotype SXH804 (4.3 ± 2.1%) but not for SXH404. Regenerated explants of L. cinerea SXH804 were morphologically identical to tissue-cultured plants. As an alternative to shoot tips, callus tissues of clone SXH404 were successfully cryopreserved (>66.7% post LN survival) using the same protocol

Generation of versatile ss-dsDNA hybrid substrates for single-molecule analysis.

Here, we describe a rapid and versatile protocol to generate gapped DNA substrates for single-molecule (SM) analysis using optical tweezers via site-specific Cas9 nicking and force-induced melting. We provide examples of single-stranded (ss) DNA gaps of different length and position. We outline protocols to visualize these substrates by replication protein A-enhanced Green Fluorescent Protein (RPA-eGFP) and SYTOX Orange staining using commercially available optical tweezers (C-TRAP). Finally, we demonstrate the utility of these substrates for SM analysis of bidirectional growth of RAD-51-ssDNA filaments. For complete details on the use and execution of this protocol, please refer to Belan et al. (2021)