On one loop corrections in higher spin gravity

We propose an approach to compute one-loop corrections to the four-point amplitude in the higher spin gravities that are holographically dual to free $O(N)$, $U(N)$ and $USp(N)$ vector models. We compute the double-particle cut of one-loop diagrams by expressing them in terms of tree level four-point amplitudes. We then discuss how the remaining contributions to the complete one-loop diagram can be computed. With certain assumptions we find nontrivial evidence for the shift in the identification of the bulk coupling constant and $1/N$ in accordance with the previously established result for the vacuum energy.Comment: 25 pages, several figures; few comments added, the discussion of the incompleteness of Vasiliev equations reduced; replaced with the published versio

Non-abelian cubic vertices for higher-spin fields in anti-de Sitter space

We use the Fradkin-Vasiliev procedure to construct the full set of non-abelian cubic vertices for totally symmetric higher spin gauge fields in anti-de Sitter space. The number of such vertices is given by a certain tensor-product multiplicity. We discuss the one-to-one relation between our result and the list of non-abelian gauge deformations in flat space obtained elsewhere via the cohomological approach. We comment about the uniqueness of Vasiliev's simplest higher-spin algebra in relation with the (non)associativity properties of the gauge algebras that we classified. The gravitational interactions for (partially)-massless (mixed)-symmetry fields are also discussed. We also argue that those mixed-symmetry and/or partially-massless fields that are described by one-form connections within the frame-like approach can have nonabelian interactions among themselves and again the number of nonabelian vertices should be given by tensor product multiplicities.Comment: 30 pages, v2: minor corrections, reference adde

On the uniqueness of higher-spin symmetries in AdS and CFT

We study the uniqueness of higher-spin algebras which are at the core of higher-spin theories in AdS and of CFTs with exact higher-spin symmetry, i.e. conserved tensors of rank greater than two. The Jacobi identity for the gauge algebra is the simplest consistency test that appears at the quartic order for a gauge theory. Similarly, the algebra of charges in a CFT must also obey the Jacobi identity. These algebras are essentially the same. Solving the Jacobi identity under some simplifying assumptions spelled out, we obtain that the Eastwood-Vasiliev algebra is the unique solution for d=4 and d>6. In 5d there is a one-parameter family of algebras that was known before. In particular, we show that the introduction of a single higher-spin gauge field/current automatically requires the infinite tower of higher-spin gauge fields/currents. The result implies that from all the admissible non-Abelian cubic vertices in AdS(d), that have been recently classified for totally symmetric higher-spin gauge fields, only one vertex can pass the Jacobi consistency test. This cubic vertex is associated with a gauge deformation that is the germ of the Eastwood-Vasiliev's higher-spin algebra.Comment: 37 pages; refs added, proof of uniquiness was improve

Gapful electrons in a vortex core in granular superconductors

We calculate the quasiparticle density of states (DoS) inside the vortex core in a granular superconductor, generalizing the classical solution applicable for dirty superconductors. A discrete version of the Usadel equation for a vortex is derived and solved numerically for a broad range of parameters. Electron DoS is found to be gapful when the vortex size $\xi$ becomes comparable to the distance between neighboring grains $l$. Minigap magnitude $E_g$ grows from zero at $\xi \approx 1.4 l$ to third of superconducting gap $\Delta_0$ at $\xi \approx 0.5 l$. The absence of low-energy excitations is the main ingredient needed to understand strong suppression of microwave dissipation recently observed in a mixed state of granular Al

Instability of the Knee Joint Before and After Reconstruction of the Anterior Cruciate Ligament According to the Questionnaire

Background: The instability of the knee joint after a rupture of the anterior cruciate ligament in recent decades has acquired the character of a meme among Russian orthopedists with a very wide use and meaning. Aim: In this study, we tried to find out how often the phenomenon of instability occurs and how it can be associated with joint injury. Methods: The method of questioning, collecting anamnesis in patients at the primary orthopedic appointment and in patients after surgical reconstruction by the method of questioning was used. Results: The data collected in 433 patients with a verified rupture of the anterior cruciate ligament showed that 77% experienced a feeling of instability in the knee joint, and 19% did not experience them at all. Arthroscopic reconstruction was performed in 297 patients, 71 of them were surveyed. The period of time from surgery to questioning was 6.5 years on average. Not all patients can note the moment of injury. Even if there was an injury to the knee joint, 10% of patients do not note the development of instability immediately after injury. The duration of the sensation of instability in the knee joint after injury varies from one week to a year or more. The very moment of joint instability is accompanied by pain in more than half of the cases. At the same time, 12% of the respondents had no pain. A third of the respondents had never noted episodes of instability in the knee joint before surgical reconstruction. But 11% had such episodes daily. In the postoperative period, 27% note the recurrence of joint instability at different times. Conclusions: Thus, an ACL tear does not equal knee instability. Instability is not a condition, but a short-term episode that occurs during the period of support and leads to buckling of the limb

The functional instrumental test of flexion-extension motion in the radiocarpal joint: reference parameters

BACKGROUND: The stroke represents a significant medical-social problem due to its high morbidity and mortality with a tendency towards increasing the overall occurrence rates. A total 80% of the patients show persisting impaired functions of the upper limb. The current approaches, such as Clinical scales and Questionnaires, are being criticized for subjectivity and insufficient precision. It is necessary to develop an instrumental method for evaluating the functions of the upper limb, the method that is applicable in the clinical settings. AIM: To develop a functional test for the objective diagnostics of the wrist joint functions, applicable in the clinical settings. METHODS: A functional test was proposed for evaluating the biomechanics of the radiocarpal joint by means of using the inertial sensors. The research sample was a group of 15 healthy volunteers (5 males and 10 females aged from 23 to 33 years), not having any joint diseases or neurological disorders. The research was carried out within a period of one year (2022–2023). The primary endpoint was the determination of the amplitude, the time and the motion trajectory in the wrist joint when performing two tests - the “Wrist-0” and “Wrist-flex”. An assessment was done of the duration of the motion cycle, of the motion maximal amplitude and phase. RESULTS: The evaluation of the upper limb functions using the clinical scales (ARAT, FMA-UE, MRC) has demonstrated, that the parameters correspond to the ones in healthy individuals. When using the “Wrist-0” test, the motion amplitude was significantly lower than in the «Wrist-flex» test (p 0.05). No statistically significant differences were found in the motion amplitude between the right and left limbs determined using both tests (p 0.05). The maximal flexion phase for the “Wrist-0” tests occurs significantly earlier than for the “Wrist-flex” test for the right hand (p 0.05). The duration of the motion cycle did not significantly differ between the tests for the right hand (p 0.05) and was significantly higher for the “Wrist-flex” test in the left hand (p 0.05). CONCLUSION: A set of reference values was established for the functional tests. Insignificant differences were reported for the functions of the right and left radiocarpal joints. The test proposed requires insignificant time for its implementation and it can be used for objective diagnostics of the radiocarpal joint functions in patients

Targeted training of the function of walking according to the stance and single support phase in patients in the early recovery period of cerebral stroke

Background: The phases of support and single support on a limb are significant basic parameters of walking (phase of support means the whole limb support time, while the phase of single support is when only one limb is on the ground). Both can be used as targets for biofeedback training. Aim: to investigate the effectiveness of both target parameters for training the function of walking with biofeedback in patients in the early recovery period of cerebral stroke. Methods: The study involved 40 patients, 20 in each group, who underwent a training course to harmonize walking: the first group for the period of support, and the second group for the period of single support. The control group of healthy people also consisted of 20 people. We studied the spatiotemporal parameters of walking at an arbitrary pace at the beginning and after the end of the training course, as well as classical clinical scales. The treadmill training consisted of 10 sessions. Results: The clinical and biomechanical parameters of walking changed their values in the direction of a significant improvement in the performance. At the same time, the biomechanical parameters of the second group indicated a more severe functional state before the start of the treatment, with the same clinical parameters according to the Barthel scale, Rivermead Mobility Index, modified Rankin scale, rehabilitation routing scale, and manual muscle testing. In the first group, indirect data were obtained on the possible effect of the target indicator on the training and direct data on its effect on the function of a healthy limb, which also allows increasing the load on the paretic one. In the second group, there were no reliable data on the effect of biofeedback training on the functional outcome. Conclusion: The conducted study showed that the classical clinical assessment of the patient's condition may not correspond to the instrumental functional study of walking. When using the support period as the training target parameter, indirect evidence was obtained that such a training is effective

Multi-channel functional electrostimulation: the method of restoring the walking function in patients with a past history of acute cerebrovascular event

Multi-channel functional electrostimulation (MFES) represents a promising method for the rehabilitation of post-stroke patients, aimed at restoring the walking function in various periods after an acute cerebrovascular event. The review systematizes the modern concepts of using the MFES in patients with the consequences of cerebral stroke, analyzing the technical parameters of stimulation, the methodical approaches to conducting the procedures and the clinical efficiency of the method. The analysis of literature data demonstrates significant variability of MFES protocols: the stimulation frequency varies from 20 to 100 Hz, the duration of the procedure ranges from 15 to 60 minutes, the treatment course can last from 3 to 30 weeks. The main targets of stimulation are the four groups of muscles in the lower limbs — the anterior tibial muscle, the plantar flexors, the quadriceps muscle of thigh and the group of muscles on the posterior surface of thigh. The synchronization of stimulation with the walking cycle is conducted predominantly by means of contact sensors, accelerometers and electromyographic signals; modern developments include the inertial systems and the machine learning algorithms. The review presents a combined analysis of the technical aspects of MFES from the point of view of staging of motor learning and individualization of the stimulation parameters. Special attention was paid to the integration of MFES with the robotic devices, including the exoskeletons, which represents a new trend in rehabilitation. Along with the absence of the unified criteria for choosing the stimulation parameters, it is worth noting that there is a necessity of differentiated approach depending on the type of motor disorders, on the duration of the disease and on the cognitive capabilities of the patient. The analysis presented justifies the necessity of developing personalized MFES protocols and arranging a large-scale research for optimizing the stimulation parameters in the rehabilitation of post-stroke patients

The use of the long peroneal muscle tendon as an autograft during the primary plastics of the anterior cruciate ligament: a systematic review

The anterior cruciate ligament injuries take the leading place among all the injuries of the knee joint. The rupture of the anterior cruciate ligament most frequently occurs during sports-related and high-energy traumas. The aim of the present systematic review is to compare the results obtained after the anterior cruciate ligament plastics with using the long peroneal muscle tendon and the autograft made from the common tendon of the semitendinous and gracilis muscles. The analysis includes the original articles from the PubMed, Google Scholar, eLibrary, Scopus and Web of Science search systems. The key words for the search included (“peroneus longus tendon” or “fibularis longus tendon”) and (“anterior cruciate ligament reconstruction” or “ACL reconstruction”). In the Russian data bases, the same terms were used. From the articles found, the following parameters were extracted: the evaluation of the functional results using the Tegner–Lysholm scale and the questionnaire for subjective assessment of the status among the patients with various knee joint injuries — IKDC (International Knee Documentation Committee); the evaluation of the mean diameter of the autotransplant; the instability of the knee joint; as well as the possible complications; the evaluation of the functions in the ankle joint and the foot using the AOFAS (American Orthopaedic Foot and Ankle Society) and FADI (Foot and Ankle Disability Index) scales. These parameters were used for evaluating the clinical research works on using the autograft made from the long peroneal muscle tendon for the reconstruction of the anterior cruciate ligament. The authors have analyzed the treatment results in 2322 patients which underwent anterior cruciate ligament plastics using the long peroneal muscle tendon (n=1660) and the semitendinous muscle tendon (n=662) autotransplants. The parameters of the postoperative status according to the AOFAS and FADI scales for the long peroneal muscle tendon were 96.47±2.71 and 97.72±2.58, respectively, which does not differ from the uninjured side (p 0.05). The best IKDC scale scores were 94.13±4.66 for the long peroneal muscle tendon and 95.12±0.73 for the semitendinous muscle tendon, while the scores of the Tegner–Lysholm scale were 99.15±2.89 and 99.85±0.37, respectively. Thus, the autograft made using the long peroneal muscle tendon is a proper alternative for the reconstruction of the anterior cruciate ligament, for it is located outside the area of the knee joint