Lasing Effect in Symmetrical van der Waals Heterostructured Metasurfaces Due to Lattice-Induced Multipole Coupling

New practical ways to reach the lasing effect in symmetrical metasurfaces have been developed and theoretically demonstrated. Our approach is based on excitation of the resonance of an octupole quasi-trapped mode (OQTM) in heterostructured symmetrical metasurfaces composed of monolithic disk-shaped van der Waals meta-atoms featured by thin photoluminescent layers and placed on a substrate. We revealed that the coincidence of the photoluminescence spectrum maximum of these layers with the wavelength of high-quality OQTM resonance leads to the lasing effect. Based on the solution of laser rate equations and direct full-wave simulation, it was shown that lasing is normally oriented to the metasurface plane and occurs from the entire area of metasurface consisting of MoS2/hBN/MoTe2 disks with line width of generated emission of only about 1.4 nm near the wavelength 1140 nm. This opens up new practical possibilities for creating surface emitting laser devices in subwavelength material systems

Easy method to simplify “freehand” subaxial cervical pedicle screw insertion

Study Design: Technical note. Objectives: The objective of this study is to check out safety and rationality of standardized and fast tricks to select trajectory of subaxial cervical pedicle screw (SCPS) insertion, based on simple angles to bony landmarks. Materials and Methods: Stage 1 – Computed tomography (CT)-morphometric analysis of C3–C7 vertebrae of ten patients with cervical degenerative diseases. Stage 2 – SCPS insertion in 6 cadavers, according to the developed technique (59 pedicle screws). Stage 3 – SCPS insertion in 6 patients, according to the developed technique (32 pedicle screws). Results: CT-morphometric analysis showed that the average length of C3–C7 pedicle channels was 32 mm, the average angle between a pedicle axis and an axis of contralateral lamina - 180°, the average angle between a pedicle axis and plane of a posterior surface of a lateral mass amounted to 90° and the coordinates of an optimal entry point – 2 mm from a lateral edge and 2 mm from an upper edge of the lateral mass posterior surface. During the cadaveric study, 39 screws had a satisfactory position (66.1%), 7 screws permissible (11.9%), and 13 screws unacceptable (22%). During the clinical study, 26 screws (81.25%) had satisfactory position, 4 (12.5%) had permissible position, and 2 (6.25%) unacceptable position. Conclusion: Developed and clinically approved a method for simplicity SCPS insertion is relatively safe and cheap. No doubt, it requires further investigation, but the results of primary analysis allow us to recommend it to wide practical application

Multiresonances of Quasi-Trapped Modes in Metasurfaces Based on Nanoparticles of Transition Metal Dichalcogenides

The features of polarization control of multiple multiresonances for quasi-trapped modes excited by synchronization of bianisotropic dipole responses in MoS2 disks with a hole are considered. Using numerical calculations with analytical multipole analysis, we showed that the presence of a strong optical anisotropy of MoS2 nanoparticles provides an additional degree of freedom and makes it possible to observe several resonances of electric and magnetic dipoles at once in a narrow spectral range. Based on the simulation results, we obtained the frequency dependences for the dipole polarizabilities of the MoS2 disk with a hole, which can be used to distinguish the contributions of the nonlocal and bianisotropic dipole responses and possessing several features in the near-infrared range. Using the polarizability spectra of single nanoparticles and applying the tuning strategy, the design of the MoS2 metasurface placed in air and supporting three resonances of quasi-trapped modes at once in a narrow spectral range was developed. One of these resonances corresponds to the telecom wavelength of about 1550 nm. The spectrum of light reflection for the MoS2 metasurface is characterized by three narrowband dips corresponding to the wavelengths of the quasi-trapped modes. It was shown that a change in the polarization of a wave normally incident on the metasurface to orthogonal one leads to a change in the type of bianisotropic response excited in each MoS2 disk and to the excitation of three other features in the reflection spectrum of the metasurface at wavelengths close to the initial values

All-Plasmonic Switching Effect in the Graphene Nanostructures Containing Quantum Emitters

Nonlinear plasmonic effects in perspective 2D materials containing low-dimensional quantum emitters can be a basis of a novel technological platform for the fabrication of fast all-plasmonic triggers, transistors, and sensors. This article considers the conditions for achieving a strong coupling between the surface plasmon–polariton (SPP) and quantum emitter taking into account the modification of local density of optical states in graphene waveguide. In the condition of strong coupling, nonlinear interaction between two SPP modes propagating along the graphene waveguide integrated with a stub nanoresonator loaded with core–shell semiconductor nanowires (NWs) was investigated. Using the 2D full-wave electromagnetic simulation, we studied the different transmittance regimes of the stub with NW for both the strong pump SPP and weak signal SPP tuned to interband and intraband transition in NW, respectively. We solved the practical problem of parameters optimization of graphene waveguide and semiconductor nanostructures and found such a regime of NW–SPP interaction that corresponds to the destructive interference with the signal SPP transmittance through the stub less than 7 % in the case for pump SPP to be turned off. In contrast, the turning on the pump SPP leads to a transition to constructive interference in the stub and enhancement of signal SPP transmittance to 93 % . In our model, the effect of plasmonic switching occurs with a rate of 50 GHz at wavelength 8 µ m for signal SPP localized inside 20 nm graphene stub loaded with core–shell InAs/ZnS NW.</jats:p

NEW ALGORITHMS OF DIAGNOSTICS OF HEAVY COMPLICATIONS OF ACUTE ODONTOGENIC INFECTION

Introduction. At present, objective difficulties remain in the timely diagnosis and treatment of severe complications of acute odontogenic infection, including progressive odontogenic phlegmon, contact odontogenic mediastinitis, odontogenic sepsis. Goal. Develop an algorithm for diagnosis and treatment of severe inflammatory complications of acute odontogenic infection, taking into account the criteria of “Sepsis-3” and evaluate its effectiveness. Material and methods. To conduct a comparative evaluation of the results of the study, patients (311 people) were divided into 2 groups: a control group (247 people), in which diagnosis and treatment were performed using the criteria “Sepsis-1”, and the main group (64 people), diagnosis and treatment were performed with using the developed algorithm for diagnosis and treatment, which includes a number of additions to the criteria of “Sepsis-3” of the European Society of Critical States Medicine and the Society of Critical States Medicine (SCCM / ESICM). Results. Using the developed algorithm for diagnosis and treatment of patients with odontogenic inflammatory diseases of the maxillofacial area allows to significantly increase the efficiency of early diagnosis of purulent-inflammatory processes in the maxillofacial region (by 5.7%), to reduce the number of severe septic complications (by 6.6%). Discussion. The application of the criteria “Sepsis-3” is not an effective method of early diagnosis of odontogenic sepsis. The conclusion. The conducted study confirmed the effectiveness of the developed algorithm for diagnosis and treatment of severe inflammatory complications of acute odontogenic infection, taking into account the criteria of “Sepsis-3”.</jats:p

EFFECT OF TRAHEOSTOMY ON THE INPATIENT TREATMENT OF PATIENTS WITH CONTACT MEDIASTINITES

The aimwas to assess the impact of emergency and planned tracheostomy on the main indicators of inpatient treatment in patients with contact mediastinitis.Materials and methods.This work was performed on the basis of the Department of Maxillofacial Surgery of the Kursk Regional Clinical Hospital. In order to conduct a comparative assessment of the treatment results, the patients with contact mediastinitis (46 people, surveyed period 2008–2017) were divided into 2 subgroups: control (25 people, 7 women, 18 men), who were treated without a tracheostomy; and the main group (21 people: 9 women, 12 men), with tracheostomy performed. The etiological and microbiological characteristics of the disease, the total duration of inpatient treatment, the length of stay in the resuscitation and intensive care units (bed-days), the dependence of the disease outcome (death, recovery) on the form of surgical intervention (tracheostomy) were evaluated.Results.A statistically significant effect of tracheostomy on the total duration of hospitalization and mortality rate was established (p0.05). Consequently, at present this issue cannot be resolved unambiguously and requires further research and mathematical analysis.Conclusion.The implementation of tracheostomy significantly increases the duration of inpatient treatment of patients with contact odontogenic mediastinites (p0.05).Conflict of interest: the authors declare no conflict of interest.</jats:p