Entrainment and chaos in a pulse-driven Hodgkin-Huxley oscillator

The Hodgkin-Huxley model describes action potential generation in certain types of neurons and is a standard model for conductance-based, excitable cells. Following the early work of Winfree and Best, this paper explores the response of a spontaneously spiking Hodgkin-Huxley neuron model to a periodic pulsatile drive. The response as a function of drive period and amplitude is systematically characterized. A wide range of qualitatively distinct responses are found, including entrainment to the input pulse train and persistent chaos. These observations are consistent with a theory of kicked oscillators developed by Qiudong Wang and Lai-Sang Young. In addition to general features predicted by Wang-Young theory, it is found that most combinations of drive period and amplitude lead to entrainment instead of chaos. This preference for entrainment over chaos is explained by the structure of the Hodgkin-Huxley phase resetting curve.Comment: Minor revisions; modified Fig. 3; added reference

Combustion synthesis of ceramic and metal-matrix composites

Combustion synthesis or self-propagating high temperature synthesis (SHS) is effected by heating a reactant mixture, to above the ignition temperature (Tig) whereupon an exothermic reaction is initiated which produces a maximum or combustion temperature, Tc. These SHS reactions are being used to produce ceramics, intermetallics, and composite materials. One of the major limitations of this process is that relatively high levels of porosity, e.g., 50 percent, remain in the product. Conducting these SHS reactions under adiabatic conditions, the maximum temperature is the adiabatic temperature, Tad, and delta H (Tad) = 0, Tad = Tc. If the reactants or products go through a phase change, the latent heat of transformation needs to be taken into account

Information Technology and the Volatility of Firm Performance

This study investigates the impact of IT investments and several contextual variables on the volatility of future earnings. We find evidence that IT investments strongly increases the volatility of future earnings and that four contextual factors - industry concentration, sales growth, diversification, and leverage - strongly moderate IT's effect on earnings volatility. It is notable that while the main effect of IT spending on earnings volatility is strongly positive, not all of the moderators are. This suggests that there are conditions under which the positive risk-return relation can be either offset or even reversed. Taken together, these results suggest an explanation for what has recently been termed the "new productivity paradox", i.e. the apparent under-investment in information technology despite evidence of highly positive returns for doing so

Effects of Footwear on Deadlift Performance between a Hex Bar and Traditional Bar

The conventional deadlift is mainly performed using a straight (traditional) bar, however variations of the deadlift can use other types of bar such as the hexagonal (hex) bar which shifts the loading to a lateral position on the body. Despite the limited research available, training barefoot has become an uprising training modality that anecdotally suggests improved performance. PURPOSE: To observe the performance differences between a hex bar deadlift (HEX) and the traditional bar deadlift (TRAD) in barefoot and shod conditions. METHODS: On day one, one-repetition maximums (1RM) were assessed for thirteen resistance-trained male and female subjects in only the TRAD condition. At least 72hr later, subjects performed five repetitions in four different conditions (barefoot and shod for both HEX and TRAD) at 70% 1RM. A 2 x 2 (footwear x bar) ANOVA was used to assess differences in barbell vertical displacement (DISP), peak vertical velocity (PV), peak vertical ground reaction force (VGRF), total mechanical work (WORK), and lift time (TIME) during the concentric phase. RESULTS: It was observed that there was no significant interaction between the footwear and bar conditions (p\u3e0.05), however there were significant main effects within the footwear condition (p \u3c 0.001) and the bar condition (p = 0.024). The shod condition was observed to have significantly greater DISP (0.522m vs 0.491m) and WORK (473.5J vs 451.9J) compared to the barefoot condition. The HEX condition was observed to have significantly greater PV (0.847m/s vs 0.784m/s) and WORK (474.0J vs 451.3J) compared to the TRAD condition. CONCLUSION: Despite contrary belief, this study suggests that there is no improvement in deadlift performance when lifting barefoot compared to lifting with shoes. However, the shoe does provide an increase in DISP and WORK performed during the deadlift, which implies an increase in the total mechanical load is applied during the shod condition at a given weight. Deadlifting with a hexagonal bar does elicit greater PV and WORK, which can be taken into consideration when being implemented in training programs as mechanical work is related to the volume of work in a training program

Judicial Work and Traumatic Stress: Vilification, Threats, and Secondary Trauma on the Bench

This article reports the results of a survey of judicial officers’ exposure to potentially traumatic stressors in a single state in Australia. An online survey was fully or partially completed by 205 serving and retired members of state courts between June and August of 2019. Respondents answered questions in a Yes/No and Likert scale format and provided comments on their experience and recommendations for the future. The survey focused on the prevalence and impact of three kinds of traumatic stress: threats to the person, vicarious trauma, and vilification. It sought to measure prevalence and to identify how different events in the workplace impacted psychological wellbeing and traumatic stress. The overall response rate was 55.3%, with 205 out of 371 judicial officers providing a full or partial response. The results indicated that 61% of respondents had experienced threats of violence to themselves or someone close to them. Three quarters (75.1%) of respondents reported being exposed to events associated with vicarious trauma, and 61 (29.7%) reported symptoms consistent with trauma-related effects. Just over half (52.7%) reported instances of harsh public criticism amounting to vilification. On the Kessler 10 scale of psychological distress 25.9% scored in the “moderate” range, 18.9% in the “high” range, and 9.8% in the “very high” range, much higher than the general population’s distress distribution. Respondents also rated the usefulness of current support resources and made recommendation for future resources

A healthier way to meet people: the experiences of LGBT people exercising with a peer group

Background: Lesbian, gay, bisexual and trans (LGBT) individuals have been shown to have poorer health when compared to those who identified as heterosexual. Additionally, they encounter barriers that deter participation in sports. Aim: To understand the experiences of LGBT individuals who participate in physical activity with peers. Method: An exploratory-descriptive qualitative (EDQ) study with data collected via face-to-face interviews from 12 participants. Data were thematically analysed to identify findings. Findings: exercising with peers represents a healthier way to meet people. Participants experienced improved physical, mental and social health. Conclusion: Engaging with a peer group for physical activity can have a transformational effect on members of the LGBT community, impacting on all aspects of their wellbeing. Nurses, and other health professionals, should be aware of the multifaceted benefits that exercising with a peer group can have, using their regular interactions with this patient group to recommend peer-supported exercise

Wearing Knee Sleeves During Back Squats Does Not Improve Mass Lifted or Affect Knee Biomechanics

Purpose:Knee sleeves have become widely popular in the exercise realm, especially for knee support during back squats. Knee sleeves are successful in providing frontal plane knee support during functional tasks, but have not been investigated in back squats. Knee wraps, a somewhat similar elastic material, provide elastic energy that increases weight lifted during back squats. Thus, it is possible the thick neoprene knee sleeves could prove advantageous for back squats. The purpose of this study was to examine the effects of knee sleeves on weight lifted, knee biomechanics, and muscle activations during back squats.Methods:Fifteen resistance trained men and women performed 1-repetition maximum (1-RM) squats to full depth and 80% 1-RM to full and parallel depths during two separate randomized sessions: with/without knee sleeves. Three-dimensional motion capture, force platforms, and electromyography recorded knee biomechanics and activations of the rectus femoris, vastus medialis, biceps femoris long head, and gluteus maximus during all squats.Results:Maximal weight lifted did not improve when using knee sleeves. Frontal plane knee biomechanics did not differ for 1-RM or submaximal squats to either depth between conditions. Knee external rotation moments during descent were larger with sleeves during submaximal squats. Reduced integrated ascent phase gluteus maximus activations occurred during both 1-RM and submaximal squats with knee sleeves.Conclusions:The results of this study show that wearing knee sleeves does not provide additive effects to weight lifted and do not appear to alter frontal plane mechanics during weighted back squats

Walking Biomechanics and Energetics of Individuals with a Visual Impairment: A Preliminary Report

Purpose. Although walking gait in sighted populations is well researched, few studies have investigated persons with visual impairments (VIs). Given the lack of physical activity in people with VIs, it is possible that reduced efficiency in walking could adversely affect activity. The purposes of this preliminary study were to (1) examine the biomechanics and energetics utilized during independent and guided walking in subjects with VIs, and (2) compare gait biomechanics between people with VIs and sighted controls. Methods. Three-dimensional motion capture and force platforms were used during independent and guided walking at self-selected speeds. Joint angles, moments, external work, and recovery were compared. Results. The VI group performed independent walking slower and with reduced stride lengths compared with guided walking and sighted controls. Hip range of motion and peak joint moments were reduced during independent walking in the VI group compared with guided walking and controls. Work was greater by 114%, 32%, and 16% in the VI group during independent than during guided walking. Recovery was 11% greater in guided vs. independent walking. Conclusions. In the presented preliminary study among 3 persons with congenital VIs, independent walking was a less efficient mode of walking compared with guided walking and that of sighted controls

Further pseudo-operational trials with the Lumicyano double and co-fuming process for the detection of latent fingermarks

This study presents a number of pseudo-operational trials on plastic bags investigating the double and co-fuming process of a one-step fluorescent cyanoacrylate (LumicyanoTM) with comparisons to the two-step process with basic yellow 40 (BY40) staining for the detection of latent fingermarks. The results demonstrate that both the Lumicyano solution and dye contribute to the increased detection of latent fingermarks during the double fuming process (trial 1). Co-fuming the Lumicyano solution and dye separately (at a concentration of 8%) but simultaneously was less effective than 8% Lumicyano (trial 2). Co-fuming Lumicyano 8% and an additional 8% Lumicyano dye by weight was more effective than Lumicyano 8% (trial 3), possibly due to increased fluorescent material deposition during co-fuming allowing for better visualisation. The use of BY40 after Lumicyano resulted in a considerable increase of detected fingermarks