Research of Wood Waste as a Potential Filler for Loose-Fill Building Insulation: Appropriate Selection and Incorporation into Polyurethane Biocomposite Foams

Currently, the recycling potential of wood waste (WW) is still limited, and in a resource efficiency approach, recycling WW in insulation materials, such as polyurethane (PUR), appears as an appropriate solution. It is known that the quality of WW is the main aspect which influences the stability of the final products. Therefore, the current study analyses different WW-based fillers as possible modifiers for polyurethane biocomposite foams for the application as loose-fill materials in building envelopes. During the study of WW-based fillers, it was determined that the most promising filler is wood scobs (WS) with a thermal conductivity of 0.0496 W/m·K, short-term water absorption by partial immersion—12.5 kg/m², water vapour resistance—0.34 m²·h·Pa/mg and water vapour diffusion resistance factor—2.4. In order to evaluate the WS performance as a filler in PUR biocomposite foams, different ratios of PUR binder and WS filler (PURb/WS) were selected. It was found that a 0.40 PURb/WS ratio is insufficient for the appropriate wetting of WS filler while a 0.70 PURb/WS ratio produced PUR biocomposite foams with the most suitable performance: thermal conductivity reduced from 0.0523 to 0.0476 W/m·K, water absorption—from 5.6 to 1.3 kg/m², while the compressive strength increased from 142 to 272 kPa and the tensile strength increased from 44 to 272 kPa.     

The Time-Course of Voluntary and Electrically Evoked Muscle Performance During and After Stretch-Shortening Exercise is Different

The aim of the study was to establish the dynamics of maximal voluntary contraction force (MVCF), height of drop jump (DJ) and electrically evoked quadriceps muscle force at different stimulation frequencies during and after 100 DJs (stretch-shortening exercise, SSE). Healthy untrained men (n = 11; age = 21.8 ± 1.7 years) participated in the study. DJs were performed with 30 s intervals between jumps from the height of 0.5 m with counter-movement to 90 degrees angle in the knee and immediate maximal rebound. The force of the quadriceps muscle, evoked by electrical stimulation at 1 Hz (Pt), 20 Hz (P20) and 100 Hz (P100) frequencies (electrically evoked performance, EEP), MVCF and height of DJ (voluntary evoked performance, VEP) were established during SSE (after 10, 50, 100 DJ) as well as at 1, 4, 8, 24, 48 and 72 h after SSE. Time-course of P20 and P100 during and after SSE was time (ANOVA: p < 0.001) and frequency dependent (ANOVA: p < 0.001) The Pt, P20 and P100 decreased significantly (p < 0.01) more than MVCF and H of DJ during SSE. At the beginning of SSE (during 1-10 DJs) P20 and P100 decreased significantly (p < 0.001) more than during 11-50 and 51-100 DJs. There was a significant (p < 0.05) increase in Pt, P20 and P100 from 8 h to 48 h, whereas height of DJ and MVCF significantly decreased at that time. In conclusion, the differences in time course of VEP and EEP are most evident at beginning of SSE, where VEP does not change as EEP decreases, and within 8-48 hours after SSE, where VEP decreases as EEP increases.

Key points

• There was no change in voluntary muscle performance while electrically evoked performance decreased significantly during first 10 drop jumps.
• There was a significant increase in electrically evoked muscle performance from 8 h to 48 h after 100 drop jumps, whereas voluntary contraction force, decreased significantly.
• The secondary decrease in the height of drop jump as well as in maximal voluntary contraction force correlated significantly with muscle soreness within 24-48 h after exercise.

Key words: Drop jump, muscle damage, electrical stimulation, low frequency fatigue     

Biological assessment of contaminated shooting range soil using earthworm biomarkers

Ecotoxicology - Environmental contamination at shooting ranges is a widely known ecological problem. The aim of the study was to evaluate the extent of contamination and the ecotoxicity of a...     

Spawning site selection and redd gravel characteristics of sea trout Salmo trutta in the lowland streams of Lithuania

To date, no characterization of spawning habitats on scientific basis was made for the eastern Baltic salmonid populations. The aim of the present study was to characterize spawning habitat preferences and redd gravel structure of sea trout in lowland streams of western Lithuania. The redd position at the habitat-unit scale, microhabitat hydrological characteristics and the redd gravel structure have been analyzed. The spawning site selection by sea trout was related to the in-stream characteristics, but not to the riparian features. Redds were positioned mainly in the transitional pool-riffle zones, associated with close proximity to potential cover for spawners. At the microhabitat scale, sites with relatively consistent hydrological parameters (mode of water depth 0.25–0.40 m, flow velocity 0.4–0.7 m s^?1 and Froude number 0.2–0.4) were selected from a wide range of available sites. Egg incubation conditions, in terms of the redd gravel structure in the spring, were of intermediate quality, while varied widely within particular reaches. According to the results of the present study, it is apparent that sea trout have particular preferences for spawning sites, which should be considered in emerging river-restoration projects.     

Riluzole blocks persistent Na+ and Ca2+ currents and modulates release of glutamate via presynaptic NMDA receptors on neonatal rat hypoglossal motoneurons in vitro

The neuroprotective agent riluzole is used for the symptomatic treatment of motoneuron disease, which strongly affects the brainstem nucleus hypoglossus. The mechanism of action of riluzole was investigated using, as a model, patch-clamp recording from hypoglossal motoneurons of the neonatal rat brainstem slice preparation. In the presence of riluzole (10 µ m ), theta-rhythm oscillations evoked by nicotine continued even though the persistent inward current (comprising sodium and calcium components) was halved, but they disappeared when the high frequency of spontaneous glutamatergic currents waned. Riluzole fully inhibited the persistent sodium current and partly depressed a tetrodotoxin (TTX)-insensitive slow current antagonized by Mn²⁺ or Cd²⁺. Repetitive firing was inhibited by riluzole without changing single action potentials. In the presence of TTX, riluzole depressed miniature glutamatergic currents occurring at high rate. Synaptic transmission with low release probability became sensitive to riluzole if release was stimulated by high potassium solution. Miniature current frequency was depressed by the N-methyl- d -aspartic acid (NMDA) receptor antagonist d -amino-phosphonovaleriate (50 µ m ), which fully occluded the action of riluzole. As riluzole is a protein kinase C (PKC) inhibitor, the PKC antagonist chelerythrine (2.5 µ m ) mimicked the effect of riluzole and prevented it. In summary, riluzole blocked the persistent sodium current fully, and the calcium one partly, plus it decreased glutamatergic transmission probably via inhibition of PKC that regulated presynaptic NMDA receptors having a facilitatory effect on glutamate release. Controlling NMDA receptor function and, thus, excitatory transmitter release via modulation of PKC suggests a novel potential target to contrast glutamate excitotoxicity in this motor nucleus.     

Single retinal changing contrast (third) detector elicits NMDA receptor response and higher activity level of frog tectum neuron network

The present study was designed to explore whether a discharge of a certain type of frog retinal ganglion cell [likely changing contrast (third) detector] can evoke NMDA response in frog tectum neurons and higher level of activity of tectal neuron network. Discharge of a single retinal ganglion cell was elicited by electrical stimulation of the retina. Evoked electrical activity of the tectum was recorded by the carbon-fiber microelectrode brought into the optic fiber layer F. We show that: (1) strong discharge of a frog individual retinal ganglion cell (third detector) has evoked NMDA response of tectal neurons and higher level of tectal neuron network activity characterized by prominent suprathreshold excitation of efferent neurons. Consequently, the firing of only one retinal ganglion cell (third detector) could lead to the activation of the tectobulbospinal tract and motor reaction. (2) The excitation of a retinotectal fiber of the first kind (axon of third detector) gave rise to the same effects as activation of a retinotectal fiber of the second kind (axon of fifth detector): the suprathreshold excitation of recurrent and efferent tectal neurons, the slow depolarizing potential (seen as the sNW), and the NMDA receptor activation were observed. However, stronger excitation (longer bursts of action potentials) was needed to evoke those effects in the considered case of the retinotectal input of the first kind. This difference could be attributed to the lower quantal size of neurotransmitter release in synapses of the retinotectal input of the first than second kind.     

Extension and flexion torque variability in ACL deficiency

Purpose  

To evaluate possible differences in knee extension and flexion torque variability in the anterior cruciate ligament—deficient (ACLD) leg and their dependence on muscle length and visual feedback (VF). Although a knee extension torque deficit is found in the ACLD leg, there is no evidence that variability in submaximal isometric knee extension and flexion torque is affected in the ACLD leg or that it depends on VF.     

Activation and desensitization of neuronal nicotinic receptors modulate glutamatergic transmission on neonatal rat hypoglossal motoneurons

In the neonate the muscles of the tongue, which are exclusively innervated by the XII cranial nerves originating from the brainstem nucleus hypoglossus, must contract rhythmically in coincidence with breathing, suckling and swallowing. These motor commands are generated by hypoglossal motoneurons excited by glutamatergic inputs. Because in forebrain areas the efficiency of glutamatergic transmission is modulated by neuronal nicotinic receptors (nAChRs), the role and identity of nAChRs within the nucleus hypoglossus of the neonatal rat were explored using an in vitro brainstem slice preparation. This area expressed immunoreactivity for alpha4, alpha7 and beta2 nAChR subunits. Whole-cell patch-clamp recording from hypoglossal motoneurons showed lack of spontaneous cholinergic events mediated by nAChRs even in the presence of a cholinesterase inhibitor. However, pharmacological antagonism of alpha7- or beta2-containing receptors depressed glutamatergic currents arising either spontaneously or by electrical stimulation of the reticular formation. Hypoglossal motoneurons expressed functional nAChRs with characteristics of alpha4beta2 and alpha7 receptor subunits. Such receptors underwent fast desensitization (time constant of 200 ms) with full recovery within 1 min. Low (0.5 microm) concentration of nicotine first facilitated glutamatergic transmission on motoneurons and later depressed it through receptor desensitization. When 0.1 microm nicotine was used, only depression of synaptic transmission occurred, in keeping with the suggestion that nAChRs can be desensitized without prior activation. These results highlight the role of tonic nAChR activity in shaping excitatory inputs to hypoglossal motoneurons, and suggest that nAChR desensitization by ambient nicotine could contribute to disorders of tongue muscle movements.