Generation of low-temperature plasma by low-pressure arcs for synthesis of nitride coatings

Experiments were performed to study gas, metal, and mixed metal-gas plasmas. The plasmas were generated with the use of an arc evaporator and a gas-plasma source with a hot filament and hollow cathode that were operated independently or simultaneously. It has been revealed that the arc current of gas-plasma source affects the parameters of the metal-gas plasma and the element concentrations in the coatings. It has been demonstrated that the characteristics of the nitride coatings produced by plasma-assisted vacuum-arc deposition can be controlled by varying the parameters of the arc in the gas-plasma source

Baxter Q-operators of the XXZ chain and R-matrix factorization

We construct Baxter operators as generalized transfer matrices being traces of products of generic $R$ matrices. The latter are shown to factorize into simpler operators allowing for explicit expressions in terms of functions of a Weyl pair of basic operators. These explicit expressions are the basis for explicit expression for Baxter Q-operators and for investigating their properties.Comment: 19 pages LaTex, references adde

Noncompact SL(2,R) spin chain

We consider the integrable spin chain model - the noncompact SL(2,R) spin magnet. The spin operators are realized as the generators of the unitary principal series representation of the SL(2,R) group. In an explicit form, we construct R-matrix, the Baxter Q-operator and the transition kernel to the representation of the Separated Variables (SoV). The expressions for the energy and quasimomentum of the eigenstates in terms of the Baxter Q-operator are derived. The analytic properties of the eigenvalues of the Baxter operator as a function of the spectral parameter are established. Applying the diagrammatic approach, we calculate Sklyanin's integration measure in the separated variables and obtain the solution to the spectral problem for the model in terms of the eigenvalues of the Q-operator. We show that the transition kernel to the SoV representation is factorized into a product of certain operators each depending on a single separated variable.Comment: 29 pages, 12 figure

Prospective trial of sacroiliac joint fusion using 3D-printed Triangular titanium implants

Background: Prior trials provide strong evidence supporting minimally invasive sacroiliac joint (SIJ) fusion using triangular titanium implants (TTI) for chronic SIJ dysfunction. Objective: To assess the safety and effectiveness of SIJF using a 3D-printed TTI. Methods: Fifty-one subjects with carefully diagnosed SIJ dysfunction underwent SIJF with 3D TTI. Subjects completed pain, disability and quality of life questionnaires at baseline and 3, 6 and 12 months postoperatively. Functional tests were performed in the clinic at each visit. Pelvic CT scans were independently evaluated for radiolucency, bridging bone and other endpoints. Results: Ninety percent had 12-month follow-up. Dysfunction due to pain (Oswestry Disability Index [ODI]) decreased from 52.8 at baseline to 27.9 at 12 months (p\u3c.0001 for change, p=.004 for non-inferiority primary hypothesis). SIJ pain scores improved from 78 preoperatively to 21 at 12-month follow-up (P\u3c.0001). Ninety-six percent experienced an improvement of 20 points or more in VAS SIJ pain by month 12. The percentage of subjects reporting minimal difficulty performing physical activities typically impaired by back/SIJ pain improved significantly for all activities. The proportion of subjects taking opioids for SIJ pain decreased from 57% to 22%. Three physical function tests improved markedly from baseline to 1 year. Positive radiographic findings were observed, including a 70% and 77% rate of bone bridging observed at 6 and 12 months, respectively. There was no evidence of device breakage, migration or subsidence. Conclusion: In this prospective multicenter trial, SIJF with 3D-printed TTI markedly improved pain, disability and quality of life. Results are consistent with 3 prior prospective multicenter trials of a milled implant but suggest accelerated bony fusion with the newer implant. Physical function improved, and high rates of opioid cessation were observed. Level of Evidence: Level II

Gold-plated Mode of CP-Violation in Decays of B_c Meson from QCD Sum Rules

The model-independent method based on the triangle ideology is implemented to extract the CKM-matrix angle gamma in the decays of doubly heavy long-lived meson B_c. We analyze a color structure of diagrams and conditions to reconstruct two reference-triangles by tagging the flavor and CP eigenstates of D^0 meson in the fixed exclusive channels. The characteristic branching ratios are evaluated in the framework of QCD sum rules.Comment: 11 pages, RevTeX4 file, 4 eps-figure

Модернизация скребково-цепного устройства щебнеочистительных машин

Increase in productivity of modern track machines leads to power growth of actuators’ drives. The article offers a way towards modernization of a chain scraper working body of the new generation of ballast cleaners. The developed techniques and the comparative results of the calculations before and after modernization, leading to power gain, show the advantages of the proposed engineering solutions.Повышение производительности современных путевых машин ведет к росту мощности приводов исполнительных устройств. В статье предлагается один из способов модернизации цепного скребкового рабочего органа путевых щебнеочистительных машин нового поколения. Разработана методика и приведены сравнительные результаты расчётов до и после модернизации, исходя из которых явно прослеживается энергетический выигрыш предлагаемого технического решения

The reverse gyrase helicase-like domain is a nucleotide-dependent switch that is attenuated by the topoisomerase domain

Reverse gyrase is a topoisomerase that introduces positive supercoils into DNA in an ATP-dependent manner. It is unique to hyperthermophilic archaea and eubacteria, and has been proposed to protect their DNA from damage at high temperatures. Cooperation between its N-terminal helicase-like and the C-terminal topoisomerase domain is required for positive supercoiling, but the precise role of the helicase-like domain is currently unknown. Here, the characterization of the isolated helicase-like domain from Thermotoga maritima reverse gyrase is presented. We show that the helicase-like domain contains all determinants for nucleotide binding and ATP hydrolysis. Its intrinsic ATP hydrolysis is significantly stimulated by ssDNA, dsDNA and plasmid DNA. During the nucleotide cycle, the helicase-like domain switches between high- and low-affinity states for dsDNA, while its affinity for ssDNA in the ATP and ADP states is similar. In the context of reverse gyrase, the differences in DNA affinities of the nucleotide states are smaller, and the DNA-stimulated ATPase activity is strongly reduced. This inhibitory effect of the topoisomerase domain decelerates the progression of reverse gyrase through the nucleotide cycle, possibly providing optimal coordination of ATP hydrolysis with the complex reaction of DNA supercoiling

Doubly heavy baryons Omega_QQ' vs. Xi_QQ' in sum rules of NRQCD

In the framework of two-point sum rules of NRQCD, the masses and couplings of doubly heavy baryons to the corresponding quark currents are evaluated with account of coulomb-like corrections in the system of doubly heavy diquark as well as the contribution of nonperturbative terms determined by the quark, gluon, mixed condensates and the product of gluon and quark condensates. The introduction of nonzero light quark mass destroys the factorization of baryon and diquark correlators even at the perturbative level and provides the better convergency of sum rules. We estimate the difference M_Omega - M_Xi = 100+/- 10 MeV. The ratio of baryonic constants |Z_Omega|^2/|Z_Xi|^2 is equal to 1.3+/-0.2 indicating the violation of SU(3) flavor symmetry for the doubly heavy baryons.Comment: 18 pages, ReVTeX file, 7 eps-figures, references adde

Ion Channel Density Regulates Switches between Regular and Fast Spiking in Soma but Not in Axons

The threshold firing frequency of a neuron is a characterizing feature of its dynamical behaviour, in turn determining its role in the oscillatory activity of the brain. Two main types of dynamics have been identified in brain neurons. Type 1 dynamics (regular spiking) shows a continuous relationship between frequency and stimulation current (f-Istim) and, thus, an arbitrarily low frequency at threshold current; Type 2 (fast spiking) shows a discontinuous f-Istim relationship and a minimum threshold frequency. In a previous study of a hippocampal neuron model, we demonstrated that its dynamics could be of both Type 1 and Type 2, depending on ion channel density. In the present study we analyse the effect of varying channel density on threshold firing frequency on two well-studied axon membranes, namely the frog myelinated axon and the squid giant axon. Moreover, we analyse the hippocampal neuron model in more detail. The models are all based on voltage-clamp studies, thus comprising experimentally measurable parameters. The choice of analysing effects of channel density modifications is due to their physiological and pharmacological relevance. We show, using bifurcation analysis, that both axon models display exclusively Type 2 dynamics, independently of ion channel density. Nevertheless, both models have a region in the channel-density plane characterized by an N-shaped steady-state current-voltage relationship (a prerequisite for Type 1 dynamics and associated with this type of dynamics in the hippocampal model). In summary, our results suggest that the hippocampal soma and the two axon membranes represent two distinct kinds of membranes; membranes with a channel-density dependent switching between Type 1 and 2 dynamics, and membranes with a channel-density independent dynamics. The difference between the two membrane types suggests functional differences, compatible with a more flexible role of the soma membrane than that of the axon membrane

Identification of Molecular Pathologies Sufficient to Cause Neuropathic Excitability in Primary Somatosensory Afferents Using Dynamical Systems Theory

Pain caused by nerve injury (i.e. neuropathic pain) is associated with development of neuronal hyperexcitability at several points along the pain pathway. Within primary afferents, numerous injury-induced changes have been identified but it remains unclear which molecular changes are necessary and sufficient to explain cellular hyperexcitability. To investigate this, we built computational models that reproduce the switch from a normal spiking pattern characterized by a single spike at the onset of depolarization to a neuropathic one characterized by repetitive spiking throughout depolarization. Parameter changes that were sufficient to switch the spiking pattern also enabled membrane potential oscillations and bursting, suggesting that all three pathological changes are mechanistically linked. Dynamical analysis confirmed this prediction by showing that excitability changes co-develop when the nonlinear mechanism responsible for spike initiation switches from a quasi-separatrix-crossing to a subcritical Hopf bifurcation. This switch stems from biophysical changes that bias competition between oppositely directed fast- and slow-activating conductances operating at subthreshold potentials. Competition between activation and inactivation of a single conductance can be similarly biased with equivalent consequences for excitability. “Bias” can arise from a multitude of molecular changes occurring alone or in combination; in the latter case, changes can add or offset one another. Thus, our results identify pathological change in the nonlinear interaction between processes affecting spike initiation as the critical determinant of how simple injury-induced changes at the molecular level manifest complex excitability changes at the cellular level. We demonstrate that multiple distinct molecular changes are sufficient to produce neuropathic changes in excitability; however, given that nerve injury elicits numerous molecular changes that may be individually sufficient to alter spike initiation, our results argue that no single molecular change is necessary to produce neuropathic excitability. This deeper understanding of degenerate causal relationships has important implications for how we understand and treat neuropathic pain