Reconstruction of Surface Electron Spectrum and Cyclotron Motion in the Charge Density Wave Phase of Weyl Semimetals.

Charge density wave (CDW) instability drastically affects the surface electron spectrum of a Weyl semimetal. We show that in the CDW phase, the Fermi arcs reconnect into either closed Fermi loops or Frieze patterns traversing the reconstructed surface mini Brillouin zone. For the closed reconnection topology, application of an out of plane magnetic field leads to a cyclotron motion of the surface electrons. We determine the cyclotron frequency as a function of the electron energy and the magnitude of the CDW gap Δ for various orientations of the Fermi arcs. For weak coupling, the period of cyclotron motion is dominated by the time of traversal of the arc reconnection regions and is inversely proportional to Δ.

[Experimental evaluation of the efficacy of tissue-engineered constructs in the treatment of limbal stem cell deficiency]. / Eksperimental'naya otsenka effektivnosti primeneniya tkaneinzhenernoi konstruktsii v lechenii limbal'noi nedostatochnosti.

Limbal stem cell deficiency (LSCD) is one of the leading factors negatively affecting the success of keratoplasty, and its treatment remains an urgent problem in ophthalmology. With the development of regenerative medicine, one of the promising approaches is the transplantation of tissue-engineered constructs from cultured limbal stem cells (LSCs) in biopolymer carriers. PURPOSE: This study was conducted to develop an experimental model of LSCD and evaluate the effectiveness of transplantation of a tissue-engineered construct consisting of cultured cells containing a population of LSCs and a collagen carrier. MATERIAL AND METHODS: The study was performed on 12 rabbits and included several stages. At the first stage, the physiological effects of collagen matrix implantation into the limbal zone were studied. At the second stage, tissue-engineered constructs consisting of LSCs on a collagen matrix were formed and their effect on the regeneration processes in the experimental LSCD model was analyzed. The animals were divided into 2 groups: surgical treatment (transplantation of the tissue-engineered construct) was used in the experimental group, and conservative treatment was used in the control group. Slit-lamp biomicroscopy with photo-registration, fluorescein corneal staining, optical coherence tomography of the anterior segment of the eye, and impression cytology were used to assess the results. RESULTS: No side reactions were observed after implantation of the collagen matrix into the limbal zone. One month after surgical treatment of the LSCD model in the experimental group, complete epithelization with minor manifestations of epitheliopathy was observed. In the control group, erosion of the corneal epithelium was noted. The time of corneal epithelization in the experimental and control groups was 9.2±2.95 and 46.20±12.07 days, respectively (p=0.139). According to the data of impression cytology, in the experimental group there were no goblet cells in the central part of the cornea, which indicates the restoration of corneal type epithelial cells, in contrast to the control group. CONCLUSION: Transplantation of a tissue-engineered construct from cultured limbal cells on a collagen membrane should be considered as a promising method for the treatment of limbal stem cell deficiency.

[Direct transfistulous ultrasound in minimally invasive surgical treatment of infected pancreatic necrosis]. / Pryamoe chresfistul'noe ul'trazvukovoe issledovanie pri minimal'no invazivnom khirurgicheskom lechenii patsientov s infitsirovannym pankreonekrozom.

OBJECTIVE: To develop a method for direct transfistulous ultrasound in minimally invasive treatment of infected pancreatic necrosis. MATERIAL AND METHODS: There were 148 patients with infected pancreatic necrosis between 2015 and 2019 at the Krasnodar City Clinical Hospital No. 2. Drainage with 28-32 Fr tubes was carried out at the first stage, endoscopic transfistulous sequestrectomy - at the second stage (19 (12.8%) patients). In 84 (56.8%) patients, we applied original diagnostic method (transfistulous ultrasonic assessment of inflammatory focus). RESULTS: There were 3 accesses to omental bursa in 93 (62.8%) patients and 2 in 43 (29.1%) patients. We also performed 2 access to retroperitoneal space in 63 (42.6%) patients and 1 access in 38 (25.8%) cases. Transfistulous ultrasound was used once in 19 (22.6%) patients, twice in 28 (33.3%) and 3 times in 37 (44.1%) patients. Examination was not performed in 18 (12.2%) patients due to the following reasons: migration of drainage catheters - 5, non-rectilinear fistulous tract - 13. No complications were observed. CONCLUSION: Transfistulous ultrasound makes it possible to diagnose pathological changes in the pancreas and parapancreatic tissue at various stages of surgical treatment.

[A modified method for percutaneous drainage of acute necrotic collections in patients with infected pancreatic necrosis]. / Modifitsirovannyi metod chreskozhnogo drenirovaniya ostrykh nekroticheskikh skoplenii u patsientov s infitsirovannym pankreonekrozom.

OBJECTIVE: To develop a modified method for percutaneous drainage of acute necrotic collections in patients with infected pancreatic necrosis. MATERIALS AND METHODS: Minimally invasive surgical technologies were used in 74 patients with infected acute necrotic collections at the Krasnodar Regional Clinical Hospital No. 2 between 2017 and 2019. Of these, 59 (79.7%) people underwent percutaneous drainage as a final treatment. In 11 (14.9%) patients, video sequestrectomy through the fistula was additionally used to increase efficiency of percutaneous drainage. RESULTS: PCD in our modification implies delivery of double-lumen drains 26-32 Fr in the same plane to zones of necrosis, their programmed replacement for prevention of obstruction and flexible endoscopy for control of pathological process. Local purulent-necrotic parapancreatitis occurred in 31 (41.9%) patients, widespread parapancreatitis - in 43 (58.1%) patients. There were 339 minimally invasive interventions. Laparotomy was required in 4 (5.4%) patients. Incidence of perioperative complications was 10.6%, mortality - 16.2%. CONCLUSION: A modified percutaneous drainage method may be used as final surgical treatment in 79.7% of patients with infected pancreatic necrosis.

A Model of Acute Peritonitis.

The biological models used in the study of generalized peritonitis can be subdivided into 5 groups (introduction of foreign bodies, cultures of microorganisms, suspensions of feces, chemicals, and mechanical damage to the gastrointestinal tract) or into 4 groups (introduction of foreign bodies, chemicals, bacterial contamination of the abdominal cavity, and combined methods). After analysis of published reports, the most justified classification of methods of peritonitis modelling is based on the type of peritonitis-inducing agent and the administration route and on the nature of peritonitis developing in the abdominal cavity. The choice of the model maximally close reproducing clinical conditions of peritonitis should be based on the specific objectives of the study, focusing on the etiology, pathogenesis, and severity of the disease course, planned measures aimed at eliminating the process, and other factors.

[Technological features of open and minimally invasive surgical treatment of local complications of purulent-necrotic pancreatitis]. / Sravnenie tekhnologicheskikh osobennostei primeneniya otkrytykh i minimal'no invazivnykh sposobov khirurgicheskogo lecheniya mestnykh oslozhnenii gnoino-nekroticheskogo pankreatita.

There are various options for surgical treatment of purulent-necrotic pancreatitis with significant technological differences. Combining surgical methods other than traditional ones into a group of minimally invasive ones based on the principle of the absence of standard laparotomy is not entirely correct. The review presents modern methods of surgical treatment of acute pancreatitis, comparison of their technology regarding classical stages of surgical intervention and their classification.

COMPARISON OF THE CLINICAL RESULTS FROM THE RECONSTRUCTION OF АCL WITH AUTOGRAFT AND ALLOGRAFT TISSUE.

The ACL is the primary stabilizer of the knee joint. The injury leads to instability of the knee joint, which is a trigger for the subsequent destructive changes of the intra-articular structures such as menisci and cartilage of the joint surfaces. The most affected group is people of an active age, engaged in amateur sports. Also, this pathology is an occupational hazard in the military. In this community, ACL injuries have reached 3.24% in men and 3.51% in women, with increasing trends, especially among women. This data is derived from a study by Keller Army Hospital, West Point, New York. In this study we selected 2 groups of patients - operated with autograft and operated with allograft. The groups included 25 patients followed for a period of 18 months. The tissues used for ACL reconstruction were: 1) for allograft - BTB donor tissue / allograft / 2) for autologous transplantation - mm. Semitendinosus et Gracillis / autograft /. After the operation, the patients are placed in a rehabilitation program in five interconnected phases. The way they are performed allows the principle of gradual loading and constant feedback between the patient and the physiotherapist to be observed. Each of the phases has specific goals in the rehabilitation cycle, which has a certain approximate duration. After completion of the rehabilitation process, the clinical outcomes of both groups were compared using the International Documentation Committee (IKDC), Lysholm, and three in-house diagnostic methods. Our own diagnostic methods are Power test (a strength simulator is used, which directly examines the strength of the limb in flexion and extension in real life test. The results from IKDC were in favor of the autograft group (92.82) and from Lischolm of the allograft group (92.24). In terms of the power test the results were in favor of the allograft group. The result from the Power 1 test clearly shows statistically significant difference in symmetry of power in flexion and extension which is better in the allograft group compared to the autograft group. In our research we did not come across such a test in other studies. In conclusion we proved that the development of a single strict rehabilitation protocol focusing on the principle of gradual increase in workloads achieves comparable results in the frequency of re-rupture in both the allograft and auto-graft groups.

[Methods of surgical reconstruction of the conjunctiva]. / Metody khirurgicheskoi rekonstruktsii kon"yunktivy.

Reconstruction of the conjunctiva is required for restoration of damaged ocular surface and is an essential part of that process. Traumas, chemical and thermal burns, multiple surgical intervention can seriously damage the integrity of conjunctival tissue and promote the growth of fibrous tissue, scarring of contractures and their shortening, as well as other complications such as trichiasis, erosion and ulcers on the cornea. When a larger area is affected, there may not be enough donor tissue to replace the defect, in which case the tissue grafts are required to be large enough. Modern modifications of surgical techniques and the continued development of tissue engineering, as well as advancements in stem cell research offer promising novel alternatives for solution of those problems. This article reviews the existing surgical methods of conjunctival reconstruction.

[Transfistulous endoscopic sequestrectomy in the treatment of infected pancreatic necrosis]. / Sposob chresfistul'noi videoskopicheskoi nekrsekvestrektomii v lechenii infitsirovannogo pankreonekroza.

OBJECTIVE: To develop an effective minimally invasive method for the treatment of infected pancreatic necrosis. MATERIAL AND METHODS: There were 168 patients with infected pancreatic necrosis who were treated at the Regional Clinical Hospital No. 2 between 2011 and 2018. Eighty-seven (51.8%) patients underwent primary drainage with large-diameter double-lumen drains 28-32 Fr, and original technique of transfistulous endoscopic sequestrectomy was used. Puncture-drainage interventions with transfistulous endoscopic sequestrectomy were used in 23 (26.4%) patients with local and 64 (73.6%) patients with widespread purulent-necrotic parapancreatitis. RESULTS: Percutaneous channels are accesses to purulent-necrotic cavity and used for transfistulous endoscopic sequestrectomy. This procedure was performed 98 times. Time of primary sanitation in patients with 3 accesses in omental bursa was significantly less compared to 2 accesses (62±4.3 vs. 89±8.2 min, p<0.05). In case of repeated sanitation, time of intervention did not depend on the number of accesses. Incidence of local complications was 9.1%, extra-abdominal complications - 19.4%. Mortality rate was 12.6%. CONCLUSION: Original technique of transfistulous endoscopic sequestrectomy increases efficiency of sanitation of infected parapancreatitis, improves treatment outcomes and reduces mortality to 12.3%.

[Modern prerequisites for creating a collagen-based artificial analogue of the corneal stroma]. / Sovremennye predposylki sozdaniya iskusstvennogo analoga stromy rogovitsy na osnove kollagenovogo materiala.

Despite the fact that various collagen biomaterials have been actively used in ophthalmology for more than 30 years, the problem of creating a material that could replace the donor cornea have not been solved. Recent advances in the field of tissue engineering and regenerative medicine have shifted the focus of approaches to solving the problem of creating an artificial cornea towards laying conditions for the restoration of its specific layers through mechanisms of its own cellular regeneration. In this regard, extracellular matrices based on collagen are gaining popularity. This review discusses general limitations and advantages of collagen for creating an artificial cornea.

[Nerve fiber structure after different types of corneal transplantation]. / Struktura nervnykh volokon posle razlichnykh variantov peresadki rogovitsy.

This review presents basic information about the state of corneal nerve fibers and Langerhans cells before and after keratoplasty. Keratoplasty is a common corneal surgery that carries a risk of graft rejection. The state of corneal nerve fibers can vary after different types of keratoplasty. Corneal confocal microscopy allows in vivo evaluation of the cornea, which can help assess the condition of corneal nerve fibers, as well as reveal the presence of Langerhans cells. Further research in this direction would contribute to identifying the relationship between the state of corneal nerve fibers, the presence of Langerhans cells, and graft rejection.

[Capabilities of optical coherence tomography in examination of senile scleral plaques]. / Vozmozhnosti opticheskoi kogerentnoi tomografii v otsenke senil'noi skleral'noi blyashki.

Senile scleral plaque (SSP) is a degenerative disease of the sclera manifested by the appearance of gray spots with clearly defined borders anteriorly from the insertion site of horizontal rectus muscles. Even with minimal changes over time changes over time are minor, SSP weakens the structural function of the sclera and creates a risk of a complicated course associated with scleromalacia. Interest in the study of SSP is increasing due to the growing number of transscleral intravitreal injections. PURPOSE: To assess the morphological characteristics of SSP using spectral optical coherence tomography (OCT). MATERIAL AND METHODS: The study examined 13 patients (21 eyes) with average age of 77.1±6.3 years. OCT scanning was performed to determine OCT signs of SSP, the length (parallel to the limb), the width and height of the SSP, as well as the depth and thickness of the overlying sclera. RESULTS: A combination of nasal and temporal SSP was observed in 14 eyes, and nasal only SSP was detected in 6 eyes. In all cases, OCT presented a characteristic picture of SSP observed as an intrascleral cavity with hyperreflective content with lower reflectivity than the surrounding tissues, and clear borders represented by unchanged scleral fibers. The length of the SSP parallel to the limb was 3296±820 µm, the width - 2312±436 µm, the height of the SSP cavity - 482±89 µm. The depth of SSP site was 213±36 µm, the thickness of the overlying sclera - 125±29 µm. CONCLUSION: Updated information about SSP structure can be used in the development of standard surgical algorithms contributing to prevention of postoperative complications.

Simulation of Mechanical and Thermal Wounds of Soft Tissues.

Millions of accidental and surgical injuries of soft tissues are registered annually around the world [5]. Untimely and insufficiently effective treatment of wounds in 50-70% leads to the development of purulent-septic infection and the development of septic conditions and fatal outcomes [1-4], which necessitates thorough study of inflammatory and regenerative processes occurring in the injured soft tissues. Various models of mechanical and thermal damage to soft tissues are proposed for studying the inflammatory and reparative processes, for assessing the therapeutic effects and developing new approaches to wound treatment. However, the developed models do not fully meet the requirements of researchers and are not always simple and uniformly reproducible, close to the course of the pathology in humans, and highly reliable. When choosing the model of mechanical and thermal wounds, the experience of other researchers should be taken into consideration due to the need of actualization and improvement of existing models.

[Dynamics of mortality according to the materials of the forensic medical examination bureau of a particular region]. / Dinamika smertnosti po materialam byuro sudebno-meditsinskoi ekspertizy otdel'no vzyatogo regiona.

OBJECTIVE: To show the dynamics of the structure of deaths of the main types of violent and non-violent death on the material of the thanatological department of a separate regional bureau of forensic medical examination. Among the violent causes are considered: mechanical injury, mechanical asphyxia, transport injury, poisoning. Among the nonviolent causes of death the diseases of circulatory system, pneumonia, infectious and oncological pathology have been studied. The period from 2001 to 2020 was investigated. Dynamic changes over a selected period are most clearly demonstrated by the ratio of numerical data to the original 2001 indicators taken as 100%. The data presented objectively reflecting the dynamics of the number and proportion of certain types of death are only the initial stage of the analysis undertaken. The second step should be the determination of the causes of the identified changes that require an integrated approach including medical, demographic and socio-economic data.

Generation and collective interaction of giant magnetic dipoles in laser cluster plasma.

Interaction of circularly polarized laser pulses with spherical nano-droplets generates nanometer-size magnets with lifetime on the order of hundreds of femtoseconds. Such magnetic dipoles are close enough in a cluster target and magnetic interaction takes place. We investigate such system of several magnetic dipoles and describe their rotation in the framework of Lagrangian formalism. The semi-analytical results are compared to particle-in-cell simulations, which confirm the theoretically obtained terrahertz frequency of the dipole oscillation.

The Historical Consciousness of Modern Russian Society.

What is the current assessment of the comparative significance of historical events in the mass consciousness of Russians? From what sources do our compatriots draw their knowledge about the past of the country? Can one talk about "good" and "bad" eras in the development of Russia? Based on the materials of empirical research, the author of this article undertakes an attempt to analyze the dynamics of features characteristic of the historical consciousness of Russian society. In his opinion, the transformation of people's ideas about the historical path of the country can be considered as one of the analytical tools for early diagnostics of the changes simmering in society. In addition, a conclusion is formulated that Russian society demonstrates an expressed demand for the elaboration of stable historical reference points and interpretations, a certain unified historical narrative.

[Possibilities of an experimental damaging effect on the retinal pigment epithelium]. / Vozmozhnosti eksperimental'nogo modelirovaniya povrezhdayushchego vozdeistviya na pigmentnyi epitelii setchatki.

PURPOSE: To simulate the damaging effect on retinal pigment epithelium (RPE) in an experiment studying the effect of human neuronal precursors (NPs). MATERIAL AND METHODS: The study was carried out on 31 rabbits (31 eyes) of the Chinchilla breed, which were divided into 3 groups: the 1st group received a subretinal injection of balanced saline solution (BSS); the 2nd group - subretinal injection of BSS with vitrectomy, displacement of the injection bladder away from the injection site using a perfluororganic compound (PFOC) and laser coagulation; the 3rd group - subretinal injection of a culture of NPs using the same method as in the group 2. All rabbits were observed for 21 days using ophthalmoscopy, optical coherence tomography (OCT) and autofluorescence (AF). RESULTS: In the 1st group, 4 out of 5 rabbits were observed to have total retinal detachment and vitreoretinal proliferative processes in the early postoperative period after subretinal injection of the BSS. In the 2nd group, OCT and AF revealed atrophy of the outer and inner layers of the retina as well as disorganization of the photoreceptors-RPE-Bruch's membrane complex in the area of injection on the 21 day after the operation. In the 3rd group, the OCT data obtained during the 21 days of observation showed that a hyperreflective zone at the level of the RPE-Bruch's membrane complex corresponding to the NPs injection site was preserved, while there was a partial loss of the outer retinal layers - but of a smaller volume compared to the BSS injection. The suggested method of subretinal injection led to a reduced number of complications: in the 1st group, postoperative complications amounted to 80%, while in the 2nd and 3rd groups - 45%. CONCLUSION: The study proposes a new method for retinal injection of BSS, which can help reduce RPE degeneration patterns and possible postoperative complications, thus increasing research efficiency. Subretinal injection of a culture of neuronal precursors derived from human induced pluripotent stem cells (iPSCs) in an experiment can serve as a universal model for studying the survival and integration of stem cells.

[Anterior stromal micropuncture for the treatment of persistent corneal epithelial graft defects after penetrating keratoplasty]. / Perednyaya stromal'naya mikropunktsiya v lechenii persistiruyushchei erozii transplantata rogovitsy posle skvoznoi keratoplastiki.

Persistent corneal graft erosion or persistent epithelial corneal defect is a frequent complication of penetrating keratoplasty. Its development can be contributed by the dry eye syndrome, rare blinking, lagophthalmos, symblepharon, viral infection, autoimmune aggression, and the use of epithelial-toxic eye drops. The article presents three clinical observations of patients who developed persistent corneal graft erosion after penetrating keratoplasty. Due to the ineffectiveness of local conservative therapy for more than 3 weeks, anterior stromal corneal micropuncture was performed. After the procedure, there was a gradual epithelial proliferation, complete healing of the corneal surface was observed 10-16 days after the manipulation, the follow-up period was at least 1 year. The mechanism of action of stromal micropuncture is associated with the creation of a porous surface with better adhesion properties, as well as with the activation of the production of extracellular matrix glycoproteins such as fibronectin, type IV collagen and laminin, which are necessary for stable adhesion of the epithelium. The use of stromal micropuncture of the donor flap in the treatment of post-keratoplasty persistent corneal epithelial defect was proposed for the first time.

[Cutaneous and visceral leishmaniasis in patients with HIV infection in Russia. Case report].

The article contains information on the problem of the combined course of HIV infection and leishmaniasis: a number of statistical and overview data in the world. It also presents a brief description of known cases of HIV patients with leishmaniasis in the Russian Federation. In all cases the diagnostics of leishmaniasis was difficult due to the lack of alertness of physicians to this illness, as well as poor knowledge of epidemiological situation of leishmaniasis. All patients with visceral leishmaniasis but one caught it during their stay in Crimea. Cutaneous leishmaniasis was described in HIV infection in the Russian Federation for the second time and is associated with the patient's residence in the Chechen Republic.

Substantial enhancement of betatron radiation in cluster targets.

Betatron radiation generated by relativistic electrons during their wiggling motion in an ion channel is a well-studied source of x-ray photons. Due to the highly collimated emission such compact laser-driven sources have attracted significant attention in various laser or plasma-based applications, but the spectral intensity is still too low. The high repetition rate is also demanded, thus the pulse energy is strongly limited. Here, based on theory and computer simulations, we present a different method to enhance the radiation power by increasing the number of betatron oscillations along the acceleration path of electrons. A stronger wiggling of electrons is achieved by using clusterized gas targets, which allows one to achieve three orders of magnitude higher x-ray yield than in optimized uniform gas target with similar average electron density.