Spindle Rate Research Articles

0449 Characterizing Spindle Activity as a Time-Frequency Phenomenon

Abstract Introduction Spindles are currently defined clinically based on observed patterns in the EEG waveform trace, with automated methods seeking to replicate visual scoring by experts. Recent work suggests that sleep spindles may be more readily observed as time-frequency peaks in the EEG spectrogram. This study compares spectral peaks in the multitaper spectrogram to expert and automatic detection scoring, characterizes the variability of spindles across a night, and investigates topographical and temporal clustering of spindles within individual EEG records. Methods We compared spectral peaks, expert scoring, and automatic detection in two datasets (DREAMS, and a high-density control study). Peaks were identified using multitaper spectral estimation and the peak prominence of the normalized power spectrum for each channel. Spatiotemporal variability analysis was performed using cluster and pattern recognition algorithms including penalized sorting of channel activation order, 2D-cross correlation, PCA and UMAP cluster analysis, and the seqNMF method. Results Spectral peaks were shown to be highly robust to and easily differentiated from broadband noise, occuring at rates (10-16 per min) far exceeding spindle rates reported in literature (~2.5 per min). Expert scoring and automated scoring failed to capture clear spectral peaks in the time-frequency domain, indicating an underreporting of the phenomenology. No apparent clustering or patterns of sleep spindle-like activity was observed using the proposed methods, suggesting high variability of spatiotemporal evolution of spindles. Conclusion These results suggest that the difficulty of time-domain visual scoring of spindles causes an artificially low estimate of the underlying phenomenology, which is mirrored in the assumptions implicit in the thresholds of automated scorers. This work shows that spindles are highly variable in their spatiotemporal evolution, suggesting that there is no optimal single electrode for analysis and casting doubt on the presence of a single cortical generation mechanism. We must therefore revisit the concept of the spindle using the time-frequency domain to more robustly characterize underlying phenomenology. Support National Institute Of Neurological Disorders And Stroke Grant R01 NS-096177

The new biocompatible material for mouse ovarian follicle development in three-dimensional in vitro culture systems

To establish a protocol of optimized three-dimensional (3D) culture of ovarian follicles, various biomaterials have been investigated with regard to their properties and functions on in vitro follicle growth. The present study aims to compare the new biomaterial, extracellular matrix-derived soft hydrogel (ES-hydrogel) and alginate, and evaluate the effects of biomaterials on further in vitro 3D culture growth of ovarian follicle and oocyte maturation. The isolated follicles from mouse ovaries were randomly divided into two-dimensional (2D) culture, alginate and ES-hydrogel, and just seeded on culture wells (2D culture) or encapsulated with alginate or ES-hydrogel (3D culture). Culture media from each group were collected on days 4, 8 and 10 or 11 for 17ß-oestradiol (E2) and progesterone (P4) measurement. On day 10 of in vitro culture, follicular survival and pseudo-antrum formation rate were examined, and oocyte maturation was induced by adding human chorionic gonadotropin and epidermal growth factor. After 17 h, ovulated mature oocytes collected and analyzed for oocyte diameter, normal spindle and chromosome alignment configuration, reactive oxygen species (ROS) level, and mitochondrial membrane potential level. To compare mechanical properties of two biomaterials, storage modulus was measured with the advanced rheometric expansion system. Our results showed that follicles cultured in ES-hydrogel, were significantly superior to those cultured 2D or alginate in the pseudo-antrum formation rate, cumulus-oocyte complexes (COCs) rate, MII oocyte rate, normal spindle rate, and E2 production. The ES-hydrogel and alginate groups were not significantly different in follicle survival rate, oocyte diameter, P4 production, ROS, and mitochondrial membrane potential levels. The storage modulus of ES-hydrogel was lower than that of alginate, suggesting that the improved follicular physiology and oocyte maturation in the ES-hydrogel group was due to better hormone exchange through a less stiff encapsulating material. This study shows that 3D culture system using ES-hydrogel effectively improve the outcome of in vitro ovarian follicle culture, supporting follicle morphology and growth and enhancing oocyte maturation. It means one of the most important factors for 3D culture of ovarian follicle was the selection of appropriate and effective biomaterial that can preserve the structure and morphology of ovarian follicle and facilitate nutrition and hormone exchange.

Influence of Rutile Nano TiO2 on Thrust Force, Mechanical, Wear and Microstructural Behavior of Al–SiC Composites

We studied microstructure, mechanical and wear properties of Al6061 SiC reinforced with Rutile Nano TiO2 (1, 2 and 3 wt%) composites. Al MMCs were fabricated by stir casting process and strength of the composite was measured by thrust force using drilling process. Drilling parameter, such as drill diameter, speed of spindle and feed rate produced thrust force on Rutile Nano TiO2 reinforced Al–SiC Composite. Results indicated that thrust force increased due to increased feed rate and drill diameter and was reduced by increasing the spindle speed. Surface of drilled area of given composite was investigated by using Scanning Electron Microscope (SEM) and Atomic Force Microscope (AFM). Tensile, Compressive and Micro hardness were found to increase (16.2%, 33.2% and 22%) by increasing the Nano TiO2 in Al–SiC composites. Moreover, it was also observed that density (2.66%) and impact strength (22.4%) also decreased. Wear test was conducted using pin on disc method and the result showed that the wear rate (14%) was decreased by adding Nano TiO2. Wear tested composite was examined by SEM and indicated that abrasive, cavity, fragmentation and oxidation were the predominant wear mechanisms.

Evaluation of Tensile Toughness and Also Turnout Toughness of Abrasion Uproar Soldered Dissimilar Aluminium Lightweight Metal

Aluminium alloys reveals good mechanical properties when soldered with Friction Stir welding. Thus to get these preferred mechanical properties, particular welding procedure parameters are to become examined. Nowadays aluminium alloys have actually been actually extensively used in industrial uses like aerospace and automobile as a result of their light weight, really good mechanical properties as well as high corrosion resistance. In this work, 3 process parameters including spindle rate, assembly rate and also jump intensity were actually looked at for abrasion rouse assembly. The paper pays attention to technique guidelines that sought after producing effective friction stir welding function.

A novel PU/PVA-co-PE composite nanofiber membrane for water filtration

Filter membranes with high efficiency and low energy consumption are gaining more attention owing to the increase in water pollution. To enhance the filtration performance, a novel spindle polyurethane (PU) / poly(vinyl alcoholco-ethylene) (PVA-co-PE) composite nanofiber membrane was prepared. It is the first time that the spindle composite nanofibers and nanofiber membranes are prepared based on the PU/PVA-co-PE/CAB (cellulose acetate butyrate) immiscible polymer blends. The effects of PU concentration on the morphology, size distribution, and hydrophilicity of PU/PVA-co-PE nanofiber membranes were analyzed. The pure PVA-co-PE nanofiber membrane and PU/PVA-co-PE composite nanofiber membranes were used to filtrate the nanoparticle suspension with scarlet pigments (50–300 nm). Due to the smaller pore size, looser structure, and larger porosity, the rejection rate and flux of spindle PU/PVA-co-PE composite nanofiber membranes are both higher than that of pure PVA-co-PE nanofiber membrane. When the basic weight of nanofiber layer is 6 g/m2, the rejection rate of all the PU/PVA-co-PE membranes are above 99%. This study provided a novel, facile, and high-throughput method to prepare spindle nanofiber membranes and indicated the advantage of spindle PU/PVA-co-PE composite nanofiber membranes in the application of water filtration.

Antioxidants retard the ageing of mouse oocytes.

The aim of the present study was to verify the effects of heavy metal coupling agents (sodium citrate and EDTA) and antioxidants (acetyl carnitine and lipoic acid) on the number of oocytes, as well as the ageing of mitochondria, chromosomes and spindles in mice. C57BL/6 female mice were randomly classified into four groups (n=12 per group): i) Heavy metal coupling agent; ii) antioxidant; iii) mixed group; and iv) the normal control group. For the treatments, heavy metal coupling agents and antioxidants were added to the drinking water provided to the mice. Following 3, 6, 9 and 12 months of treatment, the number of oocytes and mitochondrial membrane potential were determined, and chromosome and spindle structures were observed. With increasing age, the experimental mice in the four groups showed significantly decreased numbers of oocytes, reduced mitochondrial activity, and increased rates of spindle and chromosome abnormalities, which indicated age-induced ageing of mouse oocytes; thus, a mouse ageing oocyte model had been successfully established. For mice of the same age, more oocytes, higher mitochondrial activity, and lower spindle and chromosome malformation rates were detected in the antioxidant and mixed groups when compared with the normal control groups. Furthermore, no significant difference in the number of oocytes, mitochondrial activity or chromosome malformation rates was observed between the heavy metal coupling agent group and normal control group, which was possibly due to less metal being absorbed during the breeding process. Therefore, the results demonstrated that the antioxidants acetyl carnitine and lipoic acid may serve a role in delaying oocyte ageing.

Sleep spindle characteristics and arousability from nighttime transportation noise exposure in healthy young and older individuals.

Nighttime transportation noise elicits awakenings, sleep-stage changes, and electroencephalographic (EEG) arousals. Here, we investigated the potential sleep-protective role of sleep spindles on noise-induced sleep alterations. Twenty-six young (19-33 years, 12 women) and 18 older (52-70 years, 9 women) healthy volunteers underwent a repeated measures polysomnographic 6-day laboratory study. Participants spent one noise-free baseline night, followed by four transportation noise-exposure nights (road traffic or railway noise; continuous or intermittent: average sound levels of 45 dB, maximum sound levels of 50-62 dB), and one noise-free recovery night. Sleep stages were scored manually and fast sleep spindle characteristics were quantified automatically using an individual band-pass filtering approach. Nighttime exposure to transportation noise significantly increased sleep EEG arousal indices. Sleep structure and continuity were not differentially affected by noise exposure in individuals with a low versus a high spindle rate. Spindle rates showed an age-related decline along with more noise-induced sleep alterations. All-night spindle rates did not predict EEG arousal or awakening probability from single railway noise events. Spindle characteristics were affected in noise-exposure nights compared to noise-free nights: we observed a reduction of the spindle amplitude in both age groups and of the spindle rate in the older group. We have evidence that spindle rate is more likely to represent a trait phenomenon, which does not seem to play a sleep-protective role in nighttime transportation noise-induced sleep disruptions. However, the marked reduction in spindle amplitude is most likely a sensitive index for noise-induced sleep alterations.

Patients with a high proportion of immature and meiotically resistant oocytes experience defective nuclear oocyte maturation patterns and impaired pregnancy outcomes.

Patients presenting with abnormally high numbers of immature oocytes at retrieval are more likely to exhibit maturation resistant oocytes. However, the clinical relevance of such events remains unknown. We investigated nuclear maturation competence of immature oocytes from patients showing >40% of collected immature oocytes (Study group) and Controls, in which a normal number of mature oocytes (≥60%) was retrieved. Following in-vitro culture, oocytes were classified as maturation resistant or in-vitro matured (IVM). Treatment outcomes were evaluated in Study and Control groups based on presence of maturation resistant oocytes. Overall, similarly high spindle and chromosome abnormality rates were observed in maturation resistant oocytes from both Study and Control groups. IVM oocytes from the Study group revealed significantly higher percentages of misaligned chromosomes compared with Controls (P < 0.05). Remarkably, Study group patients with at least one maturation resistant oocyte showed significantly reduced cumulative pregnancy and live birth rates compared with Control group maturation resistant patients (P < 0.05). When further investigating the aetiology, a maturation resistant mouse model revealed defective Ca2+ signalling of maturation resistant oocytes at germinal vesicular breakdown and parthenogenetic activation. In conclusion, appropriate treatment strategies, including clinical utilization of IVM oocytes from Study group patients, warrant further investigation.

Comparison of Follicle Isolation Methods for Mouse Ovarian Follicle Culture In Vitro

Ovarian follicle in vitro culture is a promising fertility preservation option to avoid risk of reintroduction of malignant cells. The objective of this study is to compare 4 different follicle isolation methods from ovarian tissue and evaluate the effect of follicle isolation on further in vitro follicle culture and oocyte competency. Mouse ovaries were dissected and randomly divided into 4 groups according to follicle isolation method: mechanical (MCH) isolation, mincing (MNC) isolation, enzymatically digestion using collagenase (COL), and enzymatically digestion using liberase (LIB). The isolated early secondary follicles were cultured for day 10, and ovulation induction was conducted. Follicular diameter and concentrations of steroid hormone in spent media were measured. Also, follicular survival rate and pseudo-antrum formation rate were examined. After ovulation induction, the cumulus oocyte complexes rate and the number of mature oocyte, normal spindle rate, and mitochondrial activity in ovulated oocyte were counted. After in vitro culture, follicular diameter was significantly greater in MNC and MCH group than other groups. Also, follicle survival rate was significantly higher in MNC and MCH groups than other groups. The MNC group had made a result that significantly improved the mature oocyte rate than other groups. The normal meiotic spindle and chromosome rate is significantly higher in MNC and MCH groups than other groups. The MNC method showed significantly improved rate of follicle diameter, survival, pseudo-antrum formation, a mature oocyte, and normal spindle in ovulated oocyte after in vitro culture. Based on the results, MNC method can be an alternative for MCH method that is laborious and time-consuming.

Effects of methotrexate on the quality of oocyte maturation in vitro.

Methotrexate (MTX), an antifolate drug, is widely used for clinical treatment of malignancies and ectopic pregnancy. Many studies have documented that MTX has strong side-effects on rapidly dividing somaticcells. However, its side-effects on female reproductive cells have not been widely reported. Combined with in vitro culture, two-photon fluorescence imaging and three-dimensional reconstruction, this study analyzed the effects of MTX on oocyte maturation time, chromosome arrangement, karyotype, spindle morphology, and the localization of microtubule organizing centers (MTOCs). Compared with a control group (84%), the rate of germinal vesical breakdown in the MTX group dropped to 73% (P<0.05). The rate of the first polar body extrusion in the MTX group (53%) was also below the control group (63%; P<0.05). The rate of abnormal chromosomal arrangement in the MTX group was 60%, but 24% in the control group (P<0.05). The matured oocyte karyotypes showed 20 univalents in both control and MTX groups, while point-shaped DAPI signals were detected in the MTX group. The rate of abnormal spindle in the MTX group was 49%, but 17% in the control group (P<0.05). MTOCs in oocytes with normal spindles concentrated at the poles, while MTOCs in oocytes with abnormal spindles were scattered around the poles or in the ooplasm. MTX changes the structures of chromosomes and spindles, potentially by interfering with DNA methylation. The above results indicate a basis for understanding negative effects of MTX on oocyte maturation quality, and provide information for the clinical application of MTX in female patients.

Neural and non-neural related properties in the spastic wrist flexors: An optimization study

Quantifying neural and non-neural contributions to increased joint resistance in spasticity is essential for a better understanding of its pathophysiological mechanisms and evaluating different intervention strategies. However, direct measurement of spasticity-related manifestations, e.g., motoneuron and biophysical properties in humans, is extremely challenging. In this vein, we developed a forward neuromusculoskeletal model that accounts for dynamics of muscle spindles, motoneuron pools, muscle activation and musculotendon of wrist flexors and relies on the joint angle and resistant torque as the only input measurement variables. By modeling the stretch reflex pathway, neural and non-neural related properties of the spastic wrist flexors were estimated during the wrist extension test. Joint angle and resistant torque were collected from 17 persons with chronic stroke and healthy controls using NeuroFlexor, a motorized force measurement device during the passive wrist extension test. The model was optimized by tuning the passive and stretch reflex-related parameters to fit the measured torque in each participant. We found that persons with moderate and severe spasticity had significantly higher stiffness than controls. Among subgroups of stroke survivors, the increased neural component was mainly due to a lower muscle spindle rate at 50% of the motoneuron recruitment. The motoneuron pool threshold was highly correlated to the motoneuron pool gain in all subgroups. The model can describe the overall resistant behavior of the wrist joint during the test. Compared to controls, increased resistance was predominantly due to higher elasticity and neural components. We concluded that in combination with the NeuroFlexor measurement, the proposed neuromusculoskeletal model and optimization scheme served as suitable tools for investigating potential parameter changes along the stretch-reflex pathway in persons with spasticity.

Effects of lipopolysaccharide on maturation of bovine oocyte in vitro and its possible mechanisms.

Lipopolysaccharide disturbs the secretion of gonadotropin, endometrial function and implantation efficiency. However, there is little information regarding the effects of lipopolysaccharide on cyclic ovary activity, especially oocyte maturation. Therefore, we aimed to investigate the effects of lipopolysaccharide on the maturation potential of bovine oocytes. We found that lipopolysaccharide exposure significantly decreased the first polar body extrusion rate and delayed the cell cycle progression. The abnormal spindle rate was significantly increased in lipopolysaccharide treatment group, accompanied by disrupted localization and level of phosphorylated mitogen-activated protein kinase (p-MAPK). Moreover, lipopolysaccharide treatment significantly increased intracellular reactive oxygen species (ROS) levels and the early apoptotic rate in oocytes. The pro-apoptotic caspase-3 and Bax mRNA levels and caspase-3 protein level were significantly increased, whereas the anti-apoptotic Bcl-2 and XIAP transcript abundance were significantly decreased in lipopolysaccharide exposure group. Furthermore, the dimethyl-histone H3 lysine 4 (H3K4me2) level was significantly increased, while the DNA methylation (5-mC) and dimethyl-histone H3 lysine 9 (H3K9me2) levels were markedly decreased in oocytes treated with lipopolysaccharide. In conclusion, lipopolysaccharide exposure inhibits the maturation potential of bovine oocytes by affecting cell cycle, cytoskeletal dynamics, oxidative stress, and epigenetic modifications.

How Often Does Spindle Failure Occur in Compressive Osseointegration Endoprostheses for Oncologic Reconstruction?

Compressive osseointegration is a promising modality for limb salvage in distal femoral oncologic tumors. However, few studies have explored short-term survival rates in a large patient cohort of distal femur compressive endoprostheses or highlighted the risk factors for spindle failures. We asked: (1) What is the frequency of compressive osseointegration spindle failure in distal femoral reconstructions? (2) What are the characteristics of rotational failure cases with distal femur compressive osseointegration endoprostheses? (3) What are the risk factors for mechanical and rotational failure of distal femur compressive osseointegration implantation? (4) What are other modalities of failure or causes of revision surgery, which affect patients undergoing distal femur compressive osseointegration implantation for oncologic reconstruction? Between 1996 and 2013, 127 distal femoral reconstructions with the Compress(®) prosthesis were performed in 121 patients. During that time, 116 Compress(®) prostheses were implanted for aggressive primary tumors of the distal femur and/or failure of previous oncologic reconstruction. This approach represented approximately 91% of the distal femoral reconstructions performed during that time. Of the patients with prostheses implanted, four patients (four of 116, 3%) had died, and 37 (37 of 116, 32%) were lost to followup before 24 months. The median followup was 84 months (range, 24-198 months), and 71 patients (66% of all patients) were seen within the last 3 years. A retrospective chart review was performed to determine failure modality as defined by radiographs, clinical history, and intraoperative findings. Risk factors including age, sex, BMI, resection length, and perioperative chemotherapy were analyzed to determine effect on spindle and rotational failure rates. Survival analysis was determined using the Kaplan-Meier estimator. Differences in survival between groups were analyzed using the log rank test. Risk factors were determined using Cox proportional hazard modeling. Spindle survival at 5 and 10 years was 91% (95% CI, 82%-95%). Survival rates from rotational failure at 5 and 10 years were 92% (95% CI, 83%-96%); the majority of failures occurred within the first 2 years postoperatively and were the result of a twisting mechanism of injury. With the numbers available, none of the potential risk factors examined were associated with mechanical failure. The 5-year and 10-year all-cause revision-free survival rates were 57% (95% CI, 44%-67%) and 50% (95% CI, 36%-61%), respectively. Distal femur compressive osseointegration is a viable method for endoprosthetic reconstruction. Rotational failure is rare with the majority occurring early. No variables were found to correlate with increased risk of mechanical failure. More research is needed to evaluate methods of preventing mechanical and rotational failures in addition to other common causes of revision such as infection in these massive endoprosthetic reconstructions. Level IV, therapeutic study.

Interictal Hippocampal Spiking Influences the Occurrence of Hippocampal Sleep Spindles.

The significance of hippocampal sleep spindles and their relation to epileptic activity is still a matter of controversy. Hippocampal spindles have been considered a physiological phenomenon, an evoked response to afferent epileptic discharges, or even the expression of an epileptic manifestation. To address this question, we investigated the presence and rate of hippocampal spindles in focal pharmacoresistant epilepsy patients undergoing scalp-intracerebral electroencephalography (EEG). Sleep recording with scalp-intracerebral EEG. Tertiary referral epilepsy center. Twenty-five epilepsy patients (extratemporal: n = 6, temporal: n = 15, and multifocal including the temporal lobe: n = 4). N/A. We analyzed associations between hippocampal spindles and hippocampal electrophysiological findings (interictal spiking, seizure onset zone) and magnetic resonance imaging volumetry. Sixteen of 25 patients (64%) had hippocampal spindles (extratemporal epilepsy: 6/6; temporal epilepsy: 10/15; and multifocal epilepsy: 0/4; P = 0.005). Median spindle rate was 0.6 (range, 0.1-8.6)/min in nonrapid eye movement sleep. Highest spindle rates were found in hippocampi of patients with extratemporal epilepsy (P < 0.001). A negative association was found between hippocampal spiking activity and spindle rate (P = 0.003). We found no association between the presence (n = 21) or absence (n = 17) of hippocampal seizure onset zone and hippocampal spindle rate (P = 0.114), and between a normal (n = 30) or atrophic (n = 8) hippocampus and hippocampal spindle rate (P = 0.195). Hippocampal spindles represent a physiological phenomenon, with an expression that is diminished in epilepsy affecting the temporal lobe. Hippocampal spiking lowered the rate of hippocampal spindles, suggesting that epileptic discharges may at least in part be a transformation of these physiological events, similar to the hypothesis considering generalized spike-and-waves a transformation of frontal spindles.

Influence of Functional and Construction Parameters Over Sieving Process – Rotary Cylindrical Sieve

This paper studied functional parameters: the angle of the shaft section (feed flow rotor) and rotor speed which directly influences the yield of screening with three types of sand (NR1, NC2 and NT3). Experiments was determined following an increase of the values of the shaft angle makes sifting efficiency decrease; the greater the passage section of the material, so the feed rate of the rotor, the efficiency decreases; and a higher rotor speed makes sifting flow to increase with increasing speed. Based on experimental data it was obtained a program that is subject to problem solving regression analysis in which the efficiency is represented as a function of two dependent random variables (speed and angle tilt rotor shaft/rotor speed and power flow rotor/angle tilting spindle and feed rate). The test is a prediction of the values output in certain circumstances depending the two variables. With these predictions decisions can be made for the construction/purchase or for screening.

Acrylamide toxic effects on mouse oocyte quality and fertility in vivo.

Acrylamide is an industrial chemical that has attracted considerable attention due to its presumed carcinogenic, neurotoxic, and cytotoxic effects. In this study we investigated possible acrylamide reproductive toxic effects in female mice. Mice were fed an acrylamide-containing diet for 6 weeks. Our results showed the following effects of an acrylamide-containing diet. (1) Ovary weights were reduced in acrylamide-treated mice and oocyte developmental competence was also reduced, as shown by reduced GVBD and polar body extrusion rates. (2) Acrylamide feeding resulted in aberrant oocyte cytoskeletons, as shown by an increased abnormal spindle rate and confirmed by disrupted γ-tubulin and p-MAPK localization. (3) Acrylamide feeding resulted in oxidative stress and oocyte early stage apoptosis, as shown by increased ROS levels and p-MAPK expression. (4) Fluorescence intensity analysis showed that DNA methylation levels were reduced in acrylamide-treated oocytes and histone methylation levels were also altered, as H3K9me2, H3K9me3, H3K4me2, and H3K27me3 levels were reduced after acrylamide treatment. (5) After acrylamide feeding, the litter sizes of acrylamide-treated mice were significantly smaller compared to thus of control mice. Thus, our results indicated that acrylamide might affect oocyte quality through its effects on cytoskeletal integrity, ROS generation, apoptosis induction, and epigenetic modifications.

Cutting Characteristics of Zr-Based Bulk Metallic Glass

Cutting behavior exerts a considerable influence on the fabrication of bulk metallic glass (BMG) components. In this study, the influences of machining parameters (i.e., depth of cutting, feed rate, and spindle rate) on the turned surface of a Zr-based BMG after observing the 3D morphologies of this surface were characterized. The results showed that the influence of the spindle rate on the surface morphologies is more substantial as compared to the depth of cutting and the feed rate. Nanoscratch tests were conducted to further characterize the separation mechanism of the chips, which revealed that the chips are torn off the surface of a BMG because of inhomogeneous localized maximum shear stress.

Simulation and Evaluation of a Bone Sawing Procedure for Orthognathic Surgery Based on an Experimental Force Model

Bone sawing is widely used in orthognathic surgery to correct maxillary deformities. Successful execution of bone sawing requires a high level of dexterity and experience. A virtual reality (VR) surgical simulator can provide a safe, cost-effective, and repeatable training method. In this study, we developed a VR training simulator with haptic functions to simulate bone-sawing force, which was generated by the experimental force model. Ten human skulls were obtained in this study for the determination of surgical bone-sawing force. Using a 5-DOF machining center and a micro-reciprocating saw, bone specimens with different bone density were sawed at different feed rates (20, 40, and 60 mm/min) and spindle speeds (9800, 11,200 and 12,600 cycles per minute). The sawing forces were recorded with a piezoelectric dynamometer and a signal acquisition system. Linear correlation analysis of all experimental data indicates that there were significant positive linear correlations between bone-sawing force and bone density and tool feed rate and a moderate negative linear correlation with tool spindle rate. By performing multiple regression analysis, the prediction models for the bone-sawing procedure were determined. By employing Omega.6 as a haptic device, a medical simulator for the Lefort I osteotomy was developed based on an experimental force model. Comparison of the force-time curve acquired through experiments and the curve computed from the simulator indicate that the obtained forces based on the experimental force model and the acquired data had the same trend for the bone-sawing procedure of orthognathic surgery.

EEG alpha spindles and prolonged brake reaction times during auditory distraction in an on-road driving study

Driver distraction is responsible for a substantial number of traffic accidents. This paper describes the impact of an auditory secondary task on drivers’ mental states during a primary driving task. N=20 participants performed the test procedure in a car following task with repeated forced braking on a non-public test track. Performance measures (provoked reaction time to brake lights) and brain activity (EEG alpha spindles) were analyzed to describe distracted drivers. Further, a classification approach was used to investigate whether alpha spindles can predict drivers’ mental states.Results show that reaction times and alpha spindle rate increased with time-on-task. Moreover, brake reaction times and alpha spindle rate were significantly higher while driving with auditory secondary task opposed to driving only. In single-trial classification, a combination of spindle parameters yielded a median classification error of about 8% in discriminating the distracted from the alert driving. Reduced driving performance (i.e., prolonged brake reaction times) during increased cognitive load is assumed to be indicated by EEG alpha spindles, enabling the quantification of driver distraction in experiments on public roads without verbally assessing the drivers’ mental states.

The Friction Welding Characteristic Analysis of the Al 7075-T6 According to the Spindle Speed and Upset Pressure

The propeller shaft of rear-wheel drive vehicle is an axis which transfers power from an engine to rear-wheel through differential gear box. In this study, we studied the properties of friction welding required to produce the aluminum propeller shaft of lightweight rear-wheel-drive vehicle. We studied welding property to apply Al 7075-T6 aluminum yoke to automobile connects driving shaft and differential gear box. Here, solid phase friction welding method was used. In friction welding process, the principal parameter is spindle speed, up-set pressure and up-set time. We analyzed variable characteristics of friction welding strength according to the change of the spindle rate and up-set pressure. Friction welding strength was analyzed with ultimate tensile strength test with universal testing machine (UTM). The Al 7075-T6 was used as the round bar of the diameter of 25mm. The ultimate tensile strength was 552.3 MPa. It is 94% of ultimate tensile strength of pure Al 7075-T6 material. The main parameters of characteristics are discussed in detail based on analysis of the main effects plot and multi-vari chart. Finally, the core factors to get the maximum effect of friction welding investigated.