Fixation Conditions Research Articles

Biomechanical Assessment of the Validity of Sheep as a Preclinical Model for Testing Mandibular Fracture Fixation Devices.

Mandibular fracture fixation and reconstruction are usually performed using titanium plates and screws, however, there is a need to improve current fixation techniques. Animal models represent an important step for the testing of new designs and materials. However, the validity of those preclinical models in terms of implant biomechanics remains largely unknown. In this study, we investigate the biomechanics of the sheep mandible as a preclinical model for testing the mechanical strength of fixation devices and the biomechanical environment induced on mandibular fractures. We aimed to assess the comparability of the biomechanical conditions in the sheep mandible as a preclinical model for human applications of fracture fixation devices and empower analyses of the effect of such defined mechanical conditions on bone healing outcome. We developed 3D finite element models of the human and sheep mandibles simulating physiological muscular loads and three different clenching tasks (intercuspal, incisal, and unilateral). Furthermore, we simulated fractures in the human mandibular body, sheep mandibular body, and sheep mandibular diastema fixated with clinically used titanium miniplates and screws. We compared, at the power stroke of mastication, the biomechanical environment (1) in the healthy mandibular body and (2) at the fracture sites, and (3) the mechanical solicitation of the implants as well as the mechanical conditions for bone healing in such cases. In the healthy mandibles, the sheep mandibular body showed lower mechanical strains compared to the human mandibular body. In the fractured mandibles, strains within a fracture gap in sheep were generally not comparable to humans, while similar or lower mechanical solicitation of the fixation devices was found between the human mandibular body fracture and the sheep mandibular diastema fracture scenarios. We, therefore, conclude that the mechanical environments of mandibular fractures in humans and sheep differ and our analyses suggest that the sheep mandibular bone should be carefully re-considered as a model system to study the effect of fixation devices on the healing outcome. In our analyses, the sheep mandibular diastema showed similar mechanical conditions for fracture fixation devices to those in humans.

A Novel Oscillation-Free Force Measurement for the Determination of Material Properties during High-Speed Tests

Abstract The determination of material properties under high-speed loading has been a challenge for many years. Structural vibrations, or system ringing, in a conventional tensile testing machine deteriorate the quality of the force measurement, which prevents the precise determination of stress-strain curves and the corresponding mechanical properties. In this work, a new sample geometry and a corresponding measurement method are presented and analyzed. This new method allowed for the determination of oscillation-free, true stress-strain curves at high strain rates. Because a new minor plastic deformation area exists in the new Generation III sample, a quasi-movable bearing condition for the sample fixation is created. The forces acting on the sample deformed the cross section and created a displacement in this minor plastic deformation area. In this way, the elastic ringing effect was reduced significantly. This new method could also be applied to the quasi-static test and strain rates ranging from 10−4 to 103/s. Moreover, the filtering or similar manipulation of the results is no longer needed. The validity of the new method was proven by testing two steels with different strain-hardening behaviors.

Movement drift in optic ataxia reveals deficits in hand state estimation in oculocentric coordinates.

When vision is removed, limb position has been shown to progressively drift during repetitive arm movements. The posterior parietal cortex (PPC) is known to be involved in the processing of multisensory information, the formation of internal hand estimate, and online motor control. Here, we compared hand position drift between healthy controls and 2 patients with PPC damage to gain insight into the mechanisms underlying movement drift and investigate the possible role of the PPC in this process. To do so, we asked participants to perform back-and-forth movements between 2 targets, in the dark and under different gaze fixation conditions. Each individual participant consistently drifted to the same end position for a given hand and gaze condition. We found that the final drift distance was related to small systematic errors made on the very first trial in the dark, with an approximate 3.5 fold increase in magnitude. Furthermore, PPC damage resulted in greater movement drift in patients when the unseen hand was in the contralesional oculocentric space and also when the target was located in the lower visual field. We conclude that the PPC is involved in the proprioceptive representation of hand position in oculocentric coordinates used for reach planning and motor control. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Effects of smooth pursuit and second-order stimuli on visual motion prediction.

The purpose of this study was to determine whether smooth pursuit eye movements affect visual motion prediction using a time‐to‐contact task where observers anticipate the exact instant that a partially occluded target would coincide with a stationary object. Moreover, we attempted to clarify the influence of second‐order motion on visual motion prediction during smooth pursuit. One target object moved to another stationary object (6 deg apart) at constant velocity of 3, 4, and 5 deg/s, and then the two objects disappeared 500 ms after the onset of target motion. The observers estimated the moment the moving object would overlap the stationary object and pressed a button. For the pursuit condition, both a Gaussian window and a random dots texture moved in the same direction at the same speed for the first‐order motion, whereas a Gaussian window moved over a static background composed of random dots texture for the second‐order motion. The results showed that the constant error of the time‐to‐contact shifted to a later response for the pursuit condition compared to the fixation condition, regardless of the object velocity. In addition, during smooth pursuit, the constant error for the second‐order motion shifted to an earlier response compared to the first‐order motion when the object velocity was 3 deg/s, whereas no significant difference was found at 4 and 5 deg/s. Therefore, our results suggest that visual motion prediction using a time‐to‐contact task is affected by both eye movements and motion configuration such as second‐order motion.

Evaluation of the reduction, tightening and gripping performance of an innovative set screw technology for instrumented posterior lumbar fusion: A biomechanical study

BackgroundInstrumented posterior lumbar fusion with top-loading pedicle screw systems (PSS) requires fully tightened set screws to achieve a secure fixation and symmetric load condition. This assumes a complete reduction of the rod by 90°, which is not always attainable in situ, especially under constraint. The objective of this work is to compare the mechanical performance of different innovative set screw technologies, which should improve the tightening process. HypothesisThe hypotheses of the study are that modifications to the screw and screwdriver unit can (1) improve the quality of set screw tightening and (2) increase the axial gripping capacity of the construct. Materials and methodsThe four set screw technologies under investigation include a standard set screw with a flat surface (F-S; control group), a set screw with a convex surface (C-S) and a shaft tip method screwdriver used in combination with both flat (F-STM) and convex set screws (C-STM). The quality of set screw tightening is categorized as follows: failed=the rod is not completely reduced; reduced=the rod is successfully reduced but the set screw is not correctly fixed; good=remaining cases. An axial gripping capacity test is performed by a universal testing machine (Instron®) with a force capacity of 5kN. ResultsRegarding the quality of set screw tightening, comparisons between F-S vs. F-STM, F-S vs. C-STM and between C-S vs. C-STM show statistically significant differences (p<0.001). The axial gripping capacity test shows mean gripping forces of 1223N (STD 331) in the F-STM group and of 1724N (STD 168) in the C-STM group with statistically significant differences between both groups (p=0.003). DiscussionSeveral biomechanical and clinical case studies have identified possible effects of misaligned rod-screw interfaces such as screw pull-out during rod reduction, screw loosening, screw or rod breakage, misalignment, adjacent segment degeneration and worsening of the clinical outcome. C-STM-technology thus supports controlled fixation in the sense of applying appropriate forces for correction or fixation during PSS assembly as well as friction-reduced final alignment and tightening with the aim to reduce implant loosening, hardware failure and reoperations, while respecting anatomical and biomechanical balance.

Human DNA decays faster with time than viral dsDNA: an analysis on HPV16 using pathology archive samples spanning 85\xa0years

BackgroundQuality of the nucleic acids extracted from Formalin Fixed Paraffin Embedded (FFPE) samples largely depends on pre-analytic, fixation and storage conditions. We assessed the differential sensitivity of viral and human double stranded DNA (dsDNA) to degradation with storage time.MethodsWe randomly selected forty-four HPV16-positive invasive cervical cancer (ICC) FFPE samples collected between 1930 and 1935 and between 2000 and 2004. We evaluated through qPCR the amplification within the same sample of two targets of the HPV16 L1 gene (69 bp, 134 bp) compared with two targets of the human tubulin-β gene (65 bp, 149 bp).ResultsBoth viral and human, short and long targets were amplified from all samples stored for 15 years. In samples archived for 85 years, we observed a significant decrease in the ability to amplify longer targets and this difference was larger in human than in viral DNA: longer fragments were nine times (CI 95% 2.6–35.2) less likely to be recovered from human DNA compared with 1.6 times (CI 95% 1.1–2.2) for viral DNA.ConclusionsWe conclude that human and viral DNA show a differential decay kinetics in FFPE samples. The faster degradation of human DNA should be considered when assessing viral DNA prevalence in long stored samples, as HPV DNA detection remains a key biomarker of viral-associated transformation.

Divergent Thinking Influences the Perception of Ambiguous Visual Illusions.

This study investigated the relationships between personality and creativity in the perception of two different ambiguous visual illusions. Previous research has suggested that Industriousness and Openness/Intellect (as measured by the Big Five Aspects Scale) are both associated with individual differences in perceptual switching rates for binocular rivalry stimuli. Here, we examined whether these relationships generalise to the Necker Cube and the Spinning Dancer illusions. In the experimental phase of this study, participants viewed these ambiguous figures under both static and dynamic, as well as free-view and fixation, conditions. As predicted, perceptual switching rates were higher: (a) for the static Necker Cube than the Spinning Dancer, and (b) in free-view compared with fixation conditions. In the second phase of the study, personality type and divergent thinking were measured using the Big Five Aspects Scale and the Alternate Uses Task, respectively. Higher creativity/divergent thinking (as measured by the Alternate Uses Task) was found to predict greater switching rates for the static Necker Cube (but not the Spinning Dancer) under both free-view and fixation conditions. These findings suggest that there are differences in the perceptual processing of creative individuals.

Preparing Paraffin Tissue Sections for Staining.

Most histological studies are performed on formalin-fixed, paraffin-embedded (FFPE) tissue samples. Therefore, there is an extensive atlas of most tissues and organs prepared from these sources, and comparing the location of antigens to these data is immediately informative. Fixation and embedding procedures for preparation of paraffin tissue sections are described here. Because of the harsh fixation, embedding, and preparation conditions used in this procedure, many antigens are not well preserved. Thus, cell staining of paraffin-embedded tissue sections usually requires sensitive detection methods and may require amplification using multiple-layer techniques. The protein cross-linking associated with these fixation conditions can mask epitopes. To uncover them and thus improve antibody-antigen binding, the epitopes can be unmasked by reversing the protein cross-linking. One thermal method, heat-induced epitope retrieval, is presented here.

Изучение функциональной подвижности в межберцовом синдесмозе и ее изменений при фиксации разными имплантами (экспериментальное исследование)

For fixing tibiofibular syndesmosis, a full-threaded cortical screw 0 3.5 mm, or a Tight Rope system is often used. Fixing with a screw restricts the amplitude of movements of the foot. A fracture or loosening of the screw before the onset of fusion of the ligaments of tibiofibular syndesmosis is possible. The screw must be removed to avoid the formation of persistent limitations of the function of the ankle joint. The Tight Rope dynamically fixes the syndesmosis, does not limit the amplitude of movements and does not require removal, but its efficiency is insufficiently proven. The purpose — to study the physiological mobility in the tibiofibular syndesmosis for the subsequent more accurate choice of the fixation method. Material and methods. On 5 cadaver samples, 10 studies of fibular mobility were performed with intact ligaments of tibiofibular syndesmosis and after their dissection under conditions of fixation with a full-threaded screw 0 3.5 mm, a partial-threaded screw 0 4.0 mm, and a Tight Rope system. Results. The amplitudes of mobility in the tibiofibular syndesmosis were determined in an intact state and in a state of fixation with different implants; the best fixator and the technique of its installation were determined. Conclusion. During the experiment, the assumption was confirmed that a partial-threaded screw installed without the effect of tightening does not limit the volume of movements in the tibiofibular syndesmosis, which allows starting early functional rehabilitation and excludes the need for a staged removal of the screw.

Динамика частоты альфа-ритма ЭЭГ при слуховом восприятии действий и ее связь с уровнем интеллекта у детей 7–10 лет

A number of studies have shown the possibility of taking the EEG individual alpha peak frequency (IAPF) as an informative neurophysiological indicator of the overall cognitive efficiency of the human brain. The main goal of the present work was to study the IAPF reactivity in primary school age children in the process of auditory perception of sounds accompanying familiar instrumental movements, and to measure its hypothesized correlation to the verbal and non-verbal intelligence development. The effects of gender and age of children on these interrelations have also been estimated. We analyzed the data pertaining to the sample of primary school children aged 7-10 years (62 subjects). To assess possible age-related effects, the sample of children was additionally divided into two groups aged 7-8 years (24 boys and10 girls) and 9-10 years (14 boys and 14 girls). During the experiment, the subject and the experimenter sat at the adjacent places, with a monitor and a computer mouse (CM) placed on the table in front of each of them. A video showing the CM section of the experimenter’s table was displayed on the monitor screen in front of the subject. Experimental tasks comprised a series of stages (30 s each) including the conditions of a passive visual fixation on the video image of a motionless CM, execution of self-paced circular right-hand movements with CM, observation of similar movements produced by the experimenter, real-time imitation of the experimenter’s movements, wakeful rest with eyes closed, and auditory perception of familiar sounds accompanying the CM movements produced by the experimenter (subject’s eyes still closed). In the context of the present study, we analyzed the EEG dynamics in subjects during the two final stages with eyes closed: wakeful rest (WR) and auditory perception (AP) of familiar CM movements produced by the experimenter. The area of interest in the present study was the electrical activity of the laterally located parietal (P3, P4) and occipital (O1, O2) EEG electrodes. IAPF values were calculated for each of them within 7-13 Hz frequency range and averaged for the sum of them for the two corresponding experimental stages. The reactivity of the alpha rhythm frequency was calculated for each subject separately as the difference between the values of the dominant alpha rhythm frequency in two situations: the auditory perception of instrumental movements and the wakeful rest. Positive values of the frequency reactivity indicated its increase under condition of auditory perception of movements, and negative values - its decrease. The intelligence development levels of the participants were assessed with the help of the Wechsler test for children (WISC). In the context of the present study, the verbal and non-verbal intelligence scores were analyzed separately. We can conclude that in the primary school age children, the individual frequency of the parieto-occipital alpha rhythm in boys does not differ significantly between the groups aged 7-8 and 9-10 years. In girls, in the older group this indicator has a significantly higher value (See Table 1). For children aged 7-10 years, a significant positive correlation was identified between IAPF and non-verbal intelligence score. No connection with verbal intelligence has been found (See Fig. 1). The condition of auditory perception of sounds accompanying familiar instrumental actions evokes the decrease in the parieto-occipital alpha rhythm frequency in the majority of primary school age children, which is most characteristic for the groups of girls aged 9-10 years (See Table 2). A relatively small percentage of children (~ 18%) who demonstrated an increase in the frequency of the parieto-occipital alpha rhythm under condition of auditory perception of familiar instrumental actions, are characterized by lower scores of nonverbal intelligence, relative to their peers (See Fig. 2). Thus, nonverbal intelligence development can be related to the individual developmental characteristics of neural network oscillators, which can be reflected in children as multidirectional reactions in alpha rhythm frequency.

Influence of boundary conditions on the strengthening technology of a welded joint with a ball-rod hardener

The article deals with the problem of assessing the influence of the boundary conditions for fixing a plate with a welded seam on the stress-strain state during hardening with a ball-rod hardener. Welded joints are currently a trouble spot of the destruction of heavily loaded structures. Analysis of the microstructure and strength characteristics of the welded joint of 09G2S steel showed that in the fusion and heat-affected zones, the strength decreases due to temperature effects. The problem of modeling the strengthening of a welded joint with a ball-bar hardener under various conditions of plate fixing: with a free and fixed lower face is considered. The FEM model is constructed and the comparison of the conditions of plate fixation is carried out, which makes it possible to assess the degree of hardening and to assess the residual stresses after hardening treatment. It is shown that strengthening of a plate with a free bottom face significantly changes the stress-strain state of the plate and redistributes residual stresses to the weld zone, where strengthening is undesirable.

A Minimally Invasive Method for the Treatment of Post-Traumatic Disorders of the Bone Union of the Tibia

Background . The ability to control regeneration processes is a key link in the development of methods for treating patients with post-traumatic disorders of reparative osteogenesis. Aim of the study. To evaluate the effectiveness of the fusion of the tibia by local application of the interferon-beta preparation with autogenous bone marrow punctate in post-traumatic disorders of reparative regeneration. Material and methods. The analysis of the effectiveness of clinical application of autogenous bone marrow with interferon-beta-1b in 64 patients with delayed consolidation and pseudarthrosis of the tibia was carried out. All patients underwent external bone fixation. In order to optimize reparative osteogenesis during the operation, a mixture containing 3–4 ml of bone marrow with 8 million IU/0.5 ml of interferon beta-1b solution was injected locally into the interfragmental space. Results . With puncture local injection of interferon-beta with punctate of autogenous bone marrow with delayed consolidation, fusion of the tibial fracture was achieved in 100 % of cases. In patients with a diagnosis of a pseudarthrosis of the tibia, a positive result was achieved in 90.3 % of cases. Thus, the local application of autogenous bone marrow together with the interferon-beta preparation made it possible to achieve bone fusion in post-traumatic disorders of bone regeneration in 95.2 % of cases. Conclusion . With delayed consolidation and developing hypertrophic pseudoarthrosis in conditions of stable fixation with anatomical reposition of fragments, puncture autotransplantation of a mixture of bone marrow with a solution of interferon-beta is proposed.

Development of inkjet printing ink based on component solubility parameters and its properties

In textile inkjet printing, it is important to understand the design theory of ink jet printing ink. In this study, according to the solubility parameters of printing ink components (humectant, penetrant, pH regulator, viscosity regulator and deionized water), twelve different complex solvents were designed to prepare disperse ink. By observing the particle size, stratification, rheological property and viscosity of the prepared inks, the ink meeting the requirements was subsequently selected. The low field nuclear magnetic resonance (LF-NMR) and magnetic resonance imaging (MRI) analyses were used to analyze the water distribution and structure information of the ink at the micro level, which provide opportunities to subsequently interpret the macro properties (fluidity) of ink. The ink before and after filtration was tested using an ultraviolet-visible spectrophotometer (UV), and the content of the disperse dye in the ink was observed to be reduced after filtration. The viscosity of the ink before and after filtration were also analyzed. The viscosity of the ink was noted to significantly decrease after filtration, which indicated that the content of the disperse dye in the ink exhibited a vital influence on the ink viscosity. LF-NMR was applied to study the stability of ink (1a, 1c, 3a, 3c, 4a, 4c, 5a, 5c, 6a and 6c) in cold and hot environments. No new peak was found in T2 relaxation time inversion spectra of disperse ink, which indicates that there is no physical or chemical change among the components in disperse ink. The voltage of the driving waveform was adjusted and ejection performance of different inks was characterized. The results indicated linear driving voltage and ligament length of the inks. Different fixation temperatures (160 ℃-190 ℃) were used to optimize the fixation temperature of the printed fabrics, and 180 ℃ was determined to be the optimal fixation condition. Finally, the color fastness of the printed fabric was tested and analyzed. The findings revealed that the color fastness of the printed fabric met the use requirements.

Gaze-Based Vehicle Driving Evaluation of System with an Actual Vehicle at an Intersection with a Traffic Light

Due to the population aging in Japan, more elderly people are retaining their driver’s licenses and the increase in the number of car accidents by elderly drivers is a social problem. To address this problem, an objective data-based method to evaluate whether elderly drivers can continue driving is needed. In this paper, we propose a car driving evaluation system based on gaze as calculated by eye and head angles. We used an eye tracking device (TalkEye Lite) made by the Takei Scientific Instruments Cooperation. For our image processing technique, we propose a gaze fixation condition using deep learning (YOLOv2-tiny). By using an eye tracking device and the proposed gaze fixation condition, we built a system where drivers could be evaluated during actual car operation. We describe our system in this paper. In order to evaluate our proposed method, we conducted experiments from November 2017 to November 2018 where elderly people were evaluated by our system while driving an actual car. The subjects were 22 general drivers (two were 80–89 years old, four were 70–79 years old, six were 60–69 years old, three were 50–59 years old, five were 40–49 years old and two were 30–39 years old). We compared the subjects’ gaze information with the subjective evaluation by a professional driving instructor. As a result, we confirm that the subjects’ gaze information is related to the subjective evaluation by the instructor.

The relationship between measures of foot mobility and subtalar joint stiffness using vibration energy with color Doppler imaging-A clinical proof-of-concept validation study.

IntroductionSubtalar joint (STJ) dysfunction can contribute to movement disturbances. Vibration energy with color Doppler imaging (VECDI) may be useful for detecting STJ stiffness changes.Objectives(1) Support proof-of-concept that VECDI could detect STJ stiffness differences; (2) Establish STJ stiffness range in asymptomatic volunteers; (3) Examine relationships between STJ stiffness and foot mobility; and (4) Assess VECDI precision and reliability for examining STJ stiffness.MethodsAfter establishing cadaveric testing model proof-of-concept, STJ stiffness (threshold units, ΔTU), ankle complex passive range-of-motion (PROM) and midfoot-width-difference (MFWDiff) data were collected in 28 asymptomatic subjects in vivo. Three reliability measurements were collected per variable; Rater-1 collected on all subjects and rater-2 on the first ten subjects. Subjects were classified into three STJ stiffness groups.ResultsCadaveric VECDI measurement intra-rater reliability was 0.80. A significantly lower STJ ΔTU (p = .002) and ankle complex PROM (p < .001) was observed during the screw fixation versus normal condition. A fair correlation (r = 0.660) was observed between cadaveric ΔTU and ankle complex PROM. In vivo VECDI measurements demonstrated good intra-rater (0.76–0.84) versus poor inter-rater (-3.11) reliability. Significant positive correlations were found between STJ stiffness and both dorsum (r = .440) and posterior (r = .390) PROM. MFWDiff exhibited poor relationships with stiffness (r = .103) and either dorsum (r = .256) or posterior (r = .301) PROM. STJ stiffness ranged from 2.33 to 7.50 ΔTUs, categorizing subjects’ STJ stiffness as increased (n = 6), normal (n = 15), or decreased (n = 7). Significant ANOVA main effects for classification were found based on ΔTU (p< .001), dorsum PROM (p = .017), and posterior PROM (p = .036). Post-hoc tests revealed significant: (1) ΔTU differences between all stiffness groups (p < .001); (2) dorsum PROM differences between the increased versus normal (p = .044) and decreased (p = .017) stiffness groups; and (3) posterior PROM differences between the increased versus decreased stiffness groups (p = .044). A good relationship was found between STJ stiffness and dorsum PROM in the increased stiffness group (r = .853) versus poor, nonsignificant relationships in the normal (r = -.042) or decreased stiffness (r = -.014) groups.ConclusionPROM may not clinically explain all aspects of joint mobility. Joint VECDI stiffness assessment should be considered as a complimentary measurement technique.

Abstract 6442: Investigation of custom biomarkers on circulating tumor cells from clinical samples using RarePlex® Developer Kits

Abstract Enumeration and phenotypic profiling of circulating tumor cells (CTCs) can give important information about tumor progression, presence of therapeutic targets, and metastatic potential. New and informative cancer-specific biomarkers are being discovered at a rapid pace, so there is a strong need for tools that enable investigator driven assays to best study and utilize these biomarkers. Through the RareCyte platform, we provide sensitive and specific assays that are optimized and validated for CTC enumeration and biomarker expression. RarePlex Developer Kits enable the addition of user-selected antibodies against biomarkers of interest to a CTC detection assay. Here we demonstrate the application of RarePlex Developer Kits to study the presence of a variety of cancer related biomarkers. Using the Developer strategy, we present results for several biomarkers, including HER2, ER, PR, EGFR, Ki67, AR, ARv7, PDL1, and PSMA. We also characterized clinical samples from prostate (AR and ARv7) and breast (HER2 and ER) cancer patients. The biomarkers demonstrated proper localization on or within model CTC control cells when using default antigen retrieval and fixation conditions. For each biomarker, fluorescence intensity cut-offs that segregated negative and positive cell lines were statistically defined to maximize classification accuracy. For clinical samples, breast and prostate cancer sample staining showed expected localization based on available clinical information. In conclusion, RarePlex Developer Kits provide a flexible tool for custom CTC assay development that enables researchers to develop assays in their own lab for characterization of phenotypic heterogeneity. Citation Format: Edward Lo, Daniel Campton, Arturo Ramirez, Lillian Costandy, Brady Gardner, Ryan Houston, Heather Itamoto, Jeffery L. Werbin, VK Gadi, Tanisha Mojica, Alisa Clein, Celestia Higano, Daniel E. Sabath, Eric P. Kaldjian, Tad George. Investigation of custom biomarkers on circulating tumor cells from clinical samples using RarePlex® Developer Kits [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6442.

Saccadic Eye Movements Attenuate Postural Sway but Less in Sleep-Deprived Young Adults.

Sleep deprivation affects the performance of postural control and several other aspects related to attentional mechanisms that may alter sensory cue acquisition strategies. This study aimed to examine the possible effects of horizontal saccades and ocular fixation on a target in the performance of postural control in young adults with sleep deprivation. Twenty-six adults formed two groups, tested in two evaluations. In the first evaluation, participants slept normally on the night before. In the second evaluation, 13 participants were sleep deprived (SD) and 13 slept normally (control group [CG]) on the night before. In both evaluations, each participant stood upright as still as possible, in two experimental conditions: fixating the eye on a target and performing saccadic movement toward a target presented in two different locations (0.5 Hz). Each participant performed 3 trials in each condition, lasting 62 s each. Body oscillation was obtained in both anterior–posterior and medial–lateral directions. Results showed that SD participants swayed with a larger magnitude and higher velocity after sleep deprivation in the fixation condition. In the saccadic condition, body sway magnitude and velocity were reduced but were still larger/higher in the SD participants. Sleep deprivation deteriorates the performance of postural control. Saccadic eye movements improve postural control performance even in sleep-deprived participants but are still not sufficient to avoid postural control deterioration due to sleep deprivation.

Выпучивание вращающихся стержней при действии осевых сжимающих сил с учетом собственного веса

The article is devoted to the conclusion of resolving equations for solving the tasks of bulging rotating rods subject to the action of compressive co-centric forces taking into account uniformly distributed load along the axis. In this mode, for example, fast-moving shafts operate. The purpose of this article is to provide an engineer with a method for calculating drill pipes, tested diagrams and justification of conditions in rotary drilling. The new mathematical models describing stability of rods taking into account own weight and new software are proposed. Numerical simulation of load intensity distributions in the rod along the axis was carried out, at the same time different types of boundary conditions of rod fixation are used. Mathematical models and software for numerical simulation of stability of rotating rods under action of axial compressive forces have been improved. Note that the effect of torsion moment in the present case may not be considered as insignificant in comparison with the above loads. A new method of calculating stability of rotating rods, allowing to take into account any boundary conditions and taking into account own weight, has been developed and scientifically justified. There are proposed mathematical expressions convenient for practical use, which give very accurate results. Obtained results can be used in evaluation and diagnostics of state of samples of structural materials, in process of experimental investigations and in investigation of fast-flowing rotating processes in rod structures of variable stiffness, made of anisotropic composite materials in machine-building, shipbuilding, aircraft engineering, instrument-making, power engineering, etc.

THE INFLUENCE OF VISUAL FIXATION ON HOP TEST PERFORMANCE

It has been recognized that anterior cruciate ligament (ACL) injuries typically occur when athletes are attending to a secondary task or object, including teammates, opponents, and/or a goal. Commonly applied tests after ACL injury include a series of hop tests to determine functional status, yet do not control for visual fixation. To examine the influence of visual fixation during two functional hop tests in healthy individuals. Repeated measures. Participants performed the crossover triple hop for distance (XHOP) on the left lower limb, and the medial triple hop for distance (MHOP) on the right. For the hop test only conditions, participants were not instructed where to fix their vision while performing the hop test. The visual fixation condition required participants to fix their vision on an alternating plus/minus sign at the center of a display monitor located in front of the participant while performing each hop test, respectively. A retest session occurred 48-72 hours after the initial test session in order to examine reliability. Thirty-four healthy adults (age: 24.0 ± 3.9 years) completed testing procedures, performing the XHOP and MHOP under standard and visual fixation conditions. Of those participants, twelve completed a retest session for reliability analysis. Hop distance was not altered by the addition of visual fixation (p = 0.27), with trivial effect sizes found across conditions (d = 0.02 - 0.07); however, the addition of visual fixation slightly improved within- and between-session intrarater reliability, standard error of measurement, and minimal detectable change of the MHOP. Hop distance during the XHOP and MHOP was not influenced by visual fixation. Measurement of both the XHOP and MHOP was reliable, but lacked precision. Measurement properties for the MHOP including within- and between-session reliability, standard error of measurement, and minimal detectable change improved slightly with the addition of visual fixation compared to normal MHOP procedures. 2b.

Spatiotopic and saccade-specific transsaccadic memory for object detail.

The content and nature of transsaccadic memory are still a matter of debate. Brief postsaccadic target blanking was demonstrated to recover transsaccadic memory and defeat saccadic suppression of displacement. We examined whether blanking would also support transsaccadic transfer of detailed form information. Observers saccaded to a peripheral, checkerboard-like stimulus and reported whether an intrasaccadic change had occurred in its upper or lower half. On half of the trials, the stimulus was blanked for 200 ms with saccade onset. In a fixation condition, observers kept fixation but the stimulus was displaced from periphery to fixation, mimicking the retinal events of the saccade condition. Results show that stimulus blanking improves transsaccadic change detection, with performance being far superior to the retinally equivalent fixation condition. Our findings argue in favor of a remapped memory trace that can be accessed only in the blanking condition, when not being overwritten by the salient postsaccadic stimulus.