We report on a direct search for sub-GeV dark photons (A^{'}), which might be produced in the reaction e^{-}Z→e^{-}ZA^{'} via kinetic mixing with photons by 100 GeV electrons incident on an active ...target in the NA64 experiment at the CERN SPS. The dark photons would decay invisibly into dark matter particles resulting in events with large missing energy. No evidence for such decays was found with 2.75×10^{9} electrons on target. We set new limits on the γ-A^{'} mixing strength and exclude the invisible A^{'} with a mass ≲100 MeV as an explanation of the muon g_{μ}-2 anomaly.
Abstract
In the present study, a method for the synthesis of gelatin-stabilized copper oxide nanoparticles was developed. Synthesis was carried out by direct chemical precipitation. Copper sulfate, ...chloride, and acetate were used as precursors for the copper oxide synthesis. Gelatin was used as a stabilizer. It was found that the formation of monophase copper oxide II only occurred when copper acetate was used as a precursor. Our results showed that particles of the smallest diameter are formed in an aqueous medium (18 ± 6 nm), and those of th largest diameter—in an isobutanol medium (370 ± 131 nm). According to the photon correlation spectroscopy data, copper oxide nanoparticles synthesized in an aqueous medium were highly stable and had a monomodal size distribution with an average hydrodynamic radius of 61 nm. The study of the pH effect on the colloidal stability of copper oxide nanoparticles showed that the sample was stable in the pH range of 6.8 to 11.98. A possible mechanism for the pH influence on the stability of copper oxide nanoparticles is described. The effect of the ionic strength of the solution on the stability of the CuO nanoparticles sol was also studied, and the results showed that Ca
2+
ions had the greatest effect on the sample stability. IR spectroscopy showed that the interaction of CuO nanoparticles with gelatin occurred through the hydroxyl group. It was found that CuO nanoparticles stabilized with gelatin have a fungicidal activity at concentration equivalent 2.5 · 10
−3
mol/L and as a material for food nanopackaging can provide an increase in the shelf life of products on the example of strawberries and tomatoes. We investigated the possibility of using methylcellulose films modified with CuO nanoparticles for packaging and storage of hard cheese “Holland”. The distribution of CuO nanoparticles in the methylcellulose film was uniform. We found that methylcellulose films modified with CuO nanoparticles inhibited the growth and development of QMAFAM, coliforms, yeast and mold in experimental cheese sa mples. Our research has shown that during the cheese storage in thermostat at 35 ± 1 °C for 7 days, CuO nanoparticles migrated to the product from the film. Nevertheless, it is worth noting that the maximum change in the concentration of copper in the experimental samples was only 0.12 µg/mg, which is not a toxic concentration. In general, the small value of migration of CuO nanoparticles confirms the high stability of the developed preparation. Our results indicated that the CuO nanoparticles stabilized with gelatin have a high potential for use in food packaging – both as an independent nanofilm and as part of other packaging materials.
Nanostructured precursors of yttria-alumina garnet powders have been synthesized using the glycine-nitrate technique. It was shown that the main characteristics of the powders are determined by the ...glycine/nitrate (G/N) molar ratio in the initial solution and the temperature of the heat treatment of the precursors. The maximum specific surface area of the powders was obtained for the G/N ratio of 0.4. Subsequently, the powders were subjected to mechanical treatment and sintering. The effects of the treatment conditions and the amount of the sintering additive (Sc
2
O
3
) on the properties of the resulting ceramics were studied using erbium-yttrium garnet (Er
1,5
Y
1,5
Al
5
O
12
) as an example. Ceramics with a transparency of approximately 70% were obtained at 1790°С.
•A new concept is developed for the mathematical modeling of oscillatory processes.•A differential equation of rod oscillations is derived based on the DPL model.•An exact solution is obtained for ...the modified equation of rod oscillations.•The phenomenological resistance and relaxation coefficients are identified.•New physical phenomena are discovered that are confirmed by experimental data.
By introducing relaxation summands in the formula of Hooke’s law, in order to consider the finite propagation velocity of stress and deformations, an equation for damped oscillations of an elastic rod was obtained, including, as opposed to the well-known equation, the third derivative of motion in time as well as the mixed derivative of the spatial variable and time. By using Fourier’s method, its accurate analytical decision was found, the study of which showed that considering relaxation factors results in elimination of step-wise change of stresses and deformations. Comparison of the results of theoretical studies and experimental data applied to longitudinal oscillations of a rod fixed at one end showed that the amplitude and frequency of their oscillation coincided in a satisfactory manner.
Brillouin lasers, with their unique properties, offer an intriguing solution for many applications, yet bringing their performance to integrated platforms has remained questionable. We present a ...theoretical framework to describe Brillouin lasing in integrated ring microcavities. Specifically, a general case of a mismatch between the Brillouin shift and the microresonator inter-mode spacing is considered. We show that although the lasing threshold is increased with the frequency detuning, a significant enhancement of the laser power in comparison with the pure resonant interaction could be achieved. Moreover, there is an optimal pump frequency detuning from the resonant mode frequency, when the effect is most pronounced. An increase of the Brillouin threshold with the pump frequency detuning is accompanied by narrowing the pump frequency range available for lasing. Importantly, at the optimal value of the pump frequency detuning when the Brillouin signal is maximal, Brillouin signal noise level is minimal. Analytical results obtained in the steady-state approach are in quantitative agreement with the results of numerical simulations.
Literature data about qualitative composition of the classes of polar lipids constituting plant cell membranes are discussed. A diversity of classes of phospho-, glyco-, and other lipids and ...hydrophobic compounds lacking acyl groups are given. Fatty acid composition of polar lipids, composition of amino alcohols as components of glycosphingolipids, and oxyacids abundant in cerebrosides are considered. A key role of saturated fatty acids in the creation of an optimal physical state of membranes necessary for their normal operation is emphasized. A necessity and feasibility of construction of 3D models of biomembranes is stressed. A logic approach is proposed to a better understanding of the role of qualitative diversity of lipid composition in membrane organization. Materials showing a possibility of chemical and biological transformation of lipids in plants are cited. Several issues of membrane structure, including microdomains, remodeling of bilayer, and vesicular traffic are addressed.
Literary data on very long-chain fatty acids (VLCFAs) that are present in polar lipids of the plant cell membranes are discussed. Large amounts of VLCFA are found in polar lipids of some cellular ...organelles as well as in nonextractable lipids from diverse plant objects, where the influence of surface lipids on the relative content of these FAs is excluded. In some plants, the VLCFA fraction in membrane lipids increases under several kinds of stress. Amounts and diversity of VLCFAs are lower in flowering plants as compared with the representatives of more ancient taxons—gymnosperms, ferns, and marine algae. Presence of VLCFAs in the composition of annular lipids of the cell membranes is assumed. Biosynthesis of VLCFAs, enzymes involved in the process, and encoding genes are discussed.
For a 5-dimensional 2-step Carnot group
G
3,2
with a codimension 2 horizontal distribution, we prove that any two points
u
,
v
∈
G
3,2
can be joined on it by a horizontal broken line consisting of at ...most three segments. A multi-dimensional generalization of this result is given.
The prototyping/early construction phase of the BAIKAL-GVD project Avrorin, A.D.; Avrorin, A.V.; Aynutdinov, V.M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2014, Letnik:
742
Journal Article
Recenzirano
Odprti dostop
The prototyping phase of the BAIKAL-GVD project has been started in April 2011 with the deployment of a three string engineering array which comprises all basic elements and systems of the Gigaton ...Volume Detector (GVD) in Lake Baikal. In April 2012 the version of engineering array which comprises the first full-scale string of the GVD demonstration cluster had been deployed and operated during 2012. The first stage of the GVD-cluster which consists of three strings was deployed in April 2013. We review the prototyping phase of the BAIKAL-GVD project and describe the configuration and design of the 2013 engineering array.
KNOTTED1-LIKE HOMEOBOX 3 Azarakhsh, M.; Kirienko, A. N.; Zhukov, V. A. ...
Journal of experimental botany,
12/2015, Letnik:
66, Številka:
22
Journal Article
Recenzirano
Odprti dostop
KNOX transcription factors (TFs) regulate different aspects of plant development essentially through their effects on phytohormone metabolism. In particular, KNOX TF SHOOTMERISTEMLESS activates the ...cytokinin biosynthesis ISOPENTENYL TRANSFERASE (IPT) genes in the shoot apical meristem. However, the role of KNOX TFs in symbiotic nodule development and their possible effects on phytohormone metabolism during nodulation have not been studied to date. Cytokinin is a well-known regulator of nodule development, playing the key role in the regulation of cell division during nodule primordium formation. Recently, the activation of IPT genes was shown to take place during nodulation. Therefore, it was hypothesized that KNOX TFs may regulate nodule development and activate cytokinin biosynthesis upon nodulation. This study analysed the expression of different KNOX genes in Medicago truncatula Gaertn. and Pisum sativum L. Among them, the KNOX3 gene was upregulated in response to rhizobial inoculation in both species. pKNOX3::GUS activity was observed in developing nodule primordium. KNOX3 ectopic expression caused the formation of nodule-like structures on transgenic root without bacterial inoculation, a phenotype similar to one described previously for legumes with constitutive activation of the cytokinin receptor. Furthermore, in transgenic roots with MtKNOX3 knockdown, downregulation of A-type cytokinin response genes was found, as well as the MtIPT3 and LONELYGUY2 (MtLOG2) gene being involved in cytokinin activation. Taken together, these findings suggest that KNOX3 gene is involved in symbiotic nodule development and may regulate cytokinin biosynthesis/activation upon nodule development in legume plants.
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