Summer stream habitat preferences of Nunavik anadromous Arctic char (Salvelinus alpinus) fry and parr

Arctic char is a fish species known to occupy diverse habitats within the Arctic region. However, summer habitat use during the juvenile stage of the anadromous form is largely unknown. The present study aims to characterize fry and parr summer habitat preferences. Surveys were conducted by electrofishing, associated with physical habitat characterization on several rivers of the Ungava Bay, Nunavik, Canada. At the microhabitat and station scales, fry showed significant habitat preferences for shallow water and slow velocity. At the mesohabitat scale, fry showed a significant habitat selectivity for riffles. This habitat selectivity implies that habitat models can be built to evaluate the potential of habitat suitability for Arctic char fry. However, no significant habitat selectivity was found for parr. Parr size was nonetheless positively correlated with velocity, which was found to be a limitative factor for juvenile habitat use. This first attempt at modeling juvenile anadromous Arctic char habitat in rivers emphasizes the importance of selecting an appropriate spatial scale and reiterates the fact that parr showed relatively high plasticity in stream habitat selection.

Craniocerebral gunshot injury bullet migration to the cardiac right ventricle

Background: Missile embolism is the process of slow velocity projectiles penetrating into vascular spaces followed by arterial, venous, or paradoxical embolism of the fragments. This is a rare complication in craniocerebral gunshot injuries (CGI), with only five other cases previously published demonstrating pulmonary or arterial emboli from these injuries. There is a high rate of mortality from these injuries. Case Description: A patient presented with a CGI from an occipital trajectory, causing penetrating fragments into the venous sinus system. The weapon was a Glock Model 17M 9 mm with a hollow-point bullet, fired close range. Initial chest X-ray demonstrated only atelectasis. After stabilization, 18 min from the initial chest X-ray, subsequent computed tomography (CT) imaging demonstrated extensive intracranial injuries and fragmentation of the bullet with the expected devastating intracranial injuries. Unexpectedly, chest CT revealed metallic fragments in the right cardiac ventricle which was redemonstrated on follow-up chest X-ray. Unfortunately, his extensive intracranial injuries and poor clinical status were nonsurvivable, and thus the family elected to discontinue supportive measures. Conclusion: This case demonstrates radiographic imaging of a metallic intravascular fragment from CGI through presumed transvenous mechanisms. The imaging provides a consistent timeline demonstrating migration can occur in the acute phase. This study additionally supports the presumed mechanism for pulmonary of migration through the right heart. Fragment embolization should be considered in cases of acute deterioration in this patient population.

The Seismic Structure of the Antarctic Upper Mantle

The deployment of seismic stations and the development of ambient noise tomography and new analysis methods provide an opportunity for higher resolution imaging of Antarctica. Here we review recent seismic structure models and describe their implications for the dynamics and history of the Antarctic upper mantle. Results show that most of East Antarctica is underlain by continental lithosphere to depths of ∼ 200 km. The thickest lithosphere is found in a band 500-1000 km west of the Transantarctic Mountains, representing the continuation of cratonic lithosphere with Australian affinity beneath the ice. Dronning Maud Land and the Lambert Graben show much thinner lithosphere, consistent with Phanerozoic lithospheric disruption. The Transantarctic Mountains mark a sharp boundary between cratonic lithosphere and the warmer upper mantle of West Antarctica. In the Southern Transantarctic Mountains, cratonic lithosphere has been replaced by warm asthenosphere, giving rise to Cenozoic volcanism and an elevated mountainous region. The Marie Byrd Land volcanic dome is underlain by slow seismic velocities extending through the transition zone, consistent with a mantle plume. Slow velocity anomalies beneath the coast from the Amundsen Sea Embayment to the Antarctic Peninsula likely result from upwelling of warm asthenosphere during subduction of the Antarctic-Phoenix spreading center.

Stroke Prediction Based on the Spontaneous Nystagmus Suppression Test in Dizzy Patients: A Diagnostic Accuracy Study

ObjectiveFailure of fixation suppression of spontaneous nystagmus is sometimes seen in patients with vestibular strokes involving the cerebellum or brainstem, however, the accuracy of this test for the discrimination between peripheral and central causes in patients with an acute vestibular syndrome (AVS) is unknown.MethodsPatients with AVS were screened and recruited (convenience sample) as part of a prospective cross-sectional study in the Emergency Department between 2015-2020. All patients received neuroimaging which served as a reference standard. We recorded fixation suppression with video-oculography (VOG) for straight, right and left gaze. The ocular fixation index (OFI) and the spontaneous nystagmus slow velocity reduction was calculated.ResultsWe screened 1646 dizzy patients in the emergency department and tested for spontaneous nystagmus in 148 included AVS patients. We analyzed 56 patients with a diagnosed acute unilateral vestibulopathy (vestibular neuritis) and 28 patients with a confirmed stroke. There was a complete nystagmus fixation suppression in 49.5% of AVS patients, in 40% of patients with vestibular neuritis and in 62.5% of vestibular strokes. OFI scores had no predictive value for detecting strokes, however, a nystagmus reduction of less than 2deg/s showed a high accuracy of 76.9% (CI 0.59-0.89) with a sensitivity of 62.2% and specificity of 84.8% in detecting strokes..ConclusionsThe presence of fixation suppression does not rule out a central lesion. The magnitude of suppression was lower compared to patients with vestibular neuritis. The nystagmus suppression test still predicts accurately vestibular strokes provided that eye movements are recorded with VOG.Classification of EvidenceThis study provides Class II evidence that in patients with an acute vestibular syndrome, decreased fixation suppression recorded with VOG occurred more often in stroke (76.9%) than in vestibular neuritis (37.8%).

Velocity dependent measure of spasticity: Reliability in children and juveniles with neuromotor disorders

PURPOSE: The purpose of this study was to create a clear, standardized test description to rate spasticity severity into four categories according to the definition given by Lance [1], referred to as the Velocity Dependent Measure of Spasticity (VDMS). METHOD: Muscle groups of the upper and lower limbs of children with neuromotor disorders were evaluated on their response to passive movement in a fast-versus slow-velocity test condition. The interrater and test-retest reliability were assessed using Gwet’s alpha one (95%-CI) and the percentage agreement. RESULTS: Two physiotherapists independently assessed 45 children and youths (age 4–19 years). The interrater reliability of the VDMS was substantial to almost perfect (Gwet’s alpha one: 0.66–0.99, n= 45) while the test-retest reliability was almost perfect as well (Gwet’s alpha one: 0.83–1.00, n= 42). CONCLUSION: The VDMS can be recommended as a reliable assessment with a standardized procedure to assess spasticity of the extremities in children with neuromotor disorders.

Dynamic Causal Modeling of Neural Responses to an Orofacial Pneumotactile Velocity Array

The effective connectivity of neuronal networks during orofacial pneumotactile stimulation with different velocities is still unknown. The present study aims to characterize the effectivity connectivity elicited by three different saltatory velocities (5, 25, and 65 cm/s) over the lower face using dynamic causal modeling on functional magnetic resonance imaging data of twenty neurotypical adults. Our results revealed the contralateral SI and SII as the most likely sources of the driving inputs within the sensorimotor network for the pneumotactile stimuli, suggesting parallel processing of the orofacial pneumotactile stimuli. The 25 cm/s pneumotactile stimuli modulated forward interhemispheric connection from the contralateral SII to the ipsilateral SII, suggesting a serial interhemispheric connection between the bilateral SII. Moreover, the velocity pneumotactile stimuli influenced the contralateral M1 through both contralateral SI and SII, indicating that passive pneumotactile stimulation may positively impact motor function rehabilitation. Furthermore, the slow velocity 5 cm/s pneumotactile stimuli modulated both forward and backward connections between the right cerebellar lobule VI and the contralateral left SI, SII, and M1, while the medium velocity 25 cm/s pneumotactile stimuli modulated both forward and backward connections between the right cerebellar lobule VI and the contralateral left SI and M1. Our findings suggest that the right cerebellar lobule VI plays a role in the sensorimotor network through feedforward and feedback neuronal pathways.

Fast-Velocity Eccentric Cycling Exercise Causes Greater Muscle Damage Than Slow Eccentric Cycling

This study aims to investigate muscle damage occurring in the early and recovery phases after fast-velocity and slow-velocity eccentric cycling. Eleven untrained men (age, 20.0 ± 1.7 years; height, 171.3 ± 6.8 cm; weight, 61.8 ± 7.7 kg; and %body fat, 13.2 ± 2.9%) performed slow-velocity maximal isokinetic eccentric cycling (slow-velocity; 30°/s) with one leg and fast-velocity (fast-velocity; 210°/s) isokinetic eccentric cycling with the other leg. Changes in maximal voluntary isokinetic concentric contraction (MVCC) torque at velocities of 30 and 210°/s, range of motion (ROM), and muscle soreness were assessed by pressure using a digital muscle stiffness instrument; thigh circumference, muscle echo intensity, and muscle stiffness were assessed before exercise, and immediately after exercise, 1 day, and 4 days after exercise. Comparing with the results obtained for slow-velocity cycling (post: 215.9 ± 32.3 Nm, day 1: 192.9 ± 47.4 Nm, day 4: 184.3 ± 47.2 Nm) and before exercise, MVCC after fast-velocity cycling significantly decreased at immediately (160.4 ± 43.5 Nm), 1 day (143.6 ± 54.1 Nm), and 4 days (150.1 ± 44.5 Nm) after exercise (p < 0.05). Significant increase in muscle soreness for vastus lateralis was observed after fast-velocity cycling (41.2 ± 16.9 mm) compared with slow-velocity cycling (23.7 ± 12.2 mm) 4 days after exercise (p < 0.05). However, no significant difference in muscle soreness was observed for rectus femoris and vastus medialis at any time points after exercise. In addition, no significant differences were observed in the ROM, thigh circumference, muscle echo intensity, and muscle stiffness. In conclusion, fast-velocity eccentric cycling causes a decrease in muscle strength and an increase in soreness as compared to slow-velocity eccentric cycling.

Difference of ecological half-life and transfer coefficient in aquatic invertebrates between high and low radiocesium contaminated streams

The Fukushima accident emitted radioactive substances into the environment, contaminating litter, algae, sand substrate, aquatic invertebrates, and fish in freshwater streams. Because these substances have substantial effects on stream ecology over many years, it is necessary to clarify the diffusion and decay mechanisms of radiocesium. The transfer coefficient differed among aquatic invertebrate groups, likely due to the differences in habitat. The ecological half-life of cesium was longer where the air dose rate was lower. The transfer coefficient was also higher in areas with lower air dose rate. The radiocesium concentration in algae was inversely related to stream current velocity in the radiocesium-contaminated area. However, this relationship was not observed in the lower air dose rate area: the radiocesium concentration in algae in the rapid-velocity areas tended to be higher than that in the slow-velocity areas. This reverse trend would lead to a longer period of freshwater contamination. The radiocesium concentration would continue to decrease in highly contaminated areas, but it would be difficult to reduce the radiocesium concentration in less-contaminated areas because different contamination mechanisms are at work. Controlling the water flow is key to regulating radiocesium concentration in freshwater ecosystems.

Virtual groups: An analysis of new forms of connection

In this probe, I seek to analyse the characteristics and tendencies of virtual groups, which I define as any group of people that are connected in a decentralized and persistent manner, via the internet or cellular networks. By analysing two dimensions that shape virtual groups – their size and their velocity of communication – we can understand some intrinsic environments that are formed, by nature of the medium itself. The velocity of a platform can be understood as how quickly ideas are transferred and a response is expected – consider reading a forum post versus participating in a video chat. Slow-velocity mediums, by nature of the eye, tend to promote an individualistic view and refined thoughts. High-velocity mediums, corresponding to the ear and occurring in real time, promote more unity and collective views. The second dimension (the size or openness of a platform) is determined both by how many members are in the group, but also by how access is controlled. Small and private groups, like a close-knit tribe, function as a whole and promote familial harmony. Large or public groups struggle to maintain a collective vision but benefit from a wide variety of view points. By analysing these dimensions together and looking at specific examples, we can strive to understand deep-seated issues within virtual groups and make predictions for what the future of decentralized gatherings will look like.

A simple tool to automate the insertion process in cochlear implant surgery

Purpose Automated insertion of electrode arrays (EA) in cochlear implant surgery is presumed to be less traumatic than manual insertions, but no tool is widely available in the operating room. We sought (1) to design and create a simple tool able to automate the EA insertion process; and (2) to perform preliminary evaluations of the designed prototype. Methods A first prototype of a tool with maximum simplicity was designed and fabricated to take advantage of hydraulic actuation. The prototype facilitates automated forward motion using a syringe connected to an infusion pump. Initial prototype evaluation included: (1) testing of forward motion at different velocities (2) EA insertion trials into an artificial cochlear model with force recordings, and (3) evaluation of device handling, fixation and positioning using cadaver head specimens and a surgical retractor. Alignment of the tool was explored with CT imaging. Results In this initial phase, the prototype demonstrated easy assembly and ability to respond to hydraulic actuation driven by an infusion pump at different velocities. EA insertions at an ultra-slow velocity of 0.03 mm/s revealed smooth force profiles with mean maximum force of 0.060 N ± 0.007 N. Device positioning with an appropriate insertion axis into the cochlea was deemed feasible and easy to achieve. Conclusions Initial testing of our hydraulic insertion tool did not reveal any serious complications that contradict the initially defined design specifications. Further meticulous testing is needed to determine the safety of the device, its reliability and clinical applicability.