ESTIMATES OF PERSISTENT INWARD CURRENTS INCREASE WITH THE LEVEL OF VOLUNTARY DRIVE IN LOW-THRESHOLD MOTOR UNITS OF PLANTAR FLEXOR MUSCLES

This study tested if estimates of persistent inward currents (PICs) in the plantar flexors would increase with the level of voluntary drive. High-density surface electromyograms were collected from soleus and gastrocnemius medialis of 21 participants during ramp-shaped isometric contractions to 10%, 20%, and 30% (torque rise and decline of 2%/s and 30-s duration) of each participant's maximal torque. Motor units identified in all the contraction intensities were included in the paired-motor unit analysis to calculate delta frequency (ΔF) and estimate the PICs. ΔF is the difference in discharge rate of the control unit at the time of recruitment and de-recruitment of the test unit. Increases in PICs were observed from 10% to 20% (Δ=0.6 pulse-per-second, pps; p<0.001) and 20% to 30% (Δ=0.5pps; p<0.001) in soleus, and from 10% to 20% (Δ=1.2pps; p<0.001) but not 20% to 30% (Δ=0.09pps; p=0.724) in gastrocnemius medialis. Maximal discharge rate increased for soleus and gastrocnemius medialis from 10% to 20% (respectively, Δ=1.75pps, p<0.001; and Δ=2.43pps, p<0.001) and 20% to 30% (respectively, Δ=0.80pps, p<0.017; and Δ=0.92pps, p=002). The repeated-measures correlation identified associations between ΔF and increases in maximal discharge rate for soleus (r=0.64; p<0.001) and gastrocnemius medialis (r=0.77; p<0.001). An increase in voluntary drive tends to increase PIC strength, which has key implications for the control of force but also for comparisons between muscles or studies when relative force levels are different. Increases in voluntary descending drive amplify PICs in humans and provide an important spinal mechanism for motor unit discharging, and thus force output modulation.

Persistent Inward Currents Increase With The Level Of Voluntary Drive In Plantar Flexor Low-Threshold Motor Units

This study tested the hypothesis that estimates of persistent inward currents (PICs) in the human plantar flexors would increase with the level of voluntary drive. Twenty-one participants volunteered for this study (29.2±2.6 years). High-density surface electromyograms were collected from soleus and gastrocnemius medialis during ramp-shaped isometric contractions to 10%, 20%, and 30% (torque rise of 2%/s and 30-s duration) of each participant's maximal torque. Motor units identified in all the contraction intensities were included in the paired-motor unit analysis to calculate delta frequency (ΔF) and estimate the PICs. Increases in PICs were observed from 10% to 20% (Δ=0.6 pps; p<0.001) and 20% to 30% (Δ=0.5 pps; p<0.001) in soleus, and from 10% to 20% (Δ=1.2 pps; p<0.001) but not 20% to 30% (Δ=0.09 pps; p=0.724) in gastrocnemius medialis. Maximal discharge rate increased for soleus and gastrocnemius medialis from 10% to 20% (respectively, Δ=1.75 pps, p<0.001; and Δ=2.43 pps, p<0.001) and 20% to 30% (respectively, Δ=0.80 pps, p<0.017; and Δ=0.92 pps, p=002). The repeated-measures correlation identified associations between ΔF and increases in maximal discharge rate for both soleus (r=0.64; p<0.001) and gastrocnemius medialis (r=0.77; p<0.001). An increase in voluntary drive tends to increase PIC strength, which has key implications for the control of force but also for comparisons between muscles or between studies when relative force levels might be different. These data indicate that increases in voluntary descending drive amplify PICs in humans and provide an important spinal mechanism for motor unit firing, and thus force output modulation.

Changes in the hydrological status of the basin due to the application of erosion control works

Protection of land with vegetation is the primary factor in the fight against water erosion with necessary application of biotechnical, technical, administrative and planning measures. One of the first basins to be treated with works for the protection against erosion and torrent control is the Gradasnica River basin. The basic parameters to display the changes of the hydrological status of the land are the state of erosion, the change of erosion-coefficient, annual sediment yield, specific annual sediment discharge through the hydrographic network, the value of the runoff curve number and value of the maximal discharge. Works on protection from erosion and regulations of torrents have influenced the decrease in erosion coefficient values from strong erosion (Z=0.99) to the value of weak erosion (Z=0.40), as well as the reduction of the maximum discharge value from Qmax(1956)=108,12m3/s to the value of Qmax(2014)=87.2 m3/s.

Effect of Ti Content on Hydrogen Storage Properties of Amorphous MgNi Alloy

Cycle capacities of Amorphous Mg-Ni alloys declined so fast therefore they can’t be used practically. In this paper，the influence of adding Ti on the discharge capacity and cycle stability of the alloys were investigated. Amorphous Mg1-xTixNi (x=0, 0.1, 0.2, 0.3) alloy powder was prepared successfully by mechanical alloying (MA). X-ray diffraction (XRD) results show that MgNi alloy formed completely amorphous phase after ball milling with 15h. But for Mg1-xTixNi (x=0.1, 0.2, 0.3) alloy, it took 23h. It can be concluded that Ti partial substituting Mg would decrease the amorphous phase forming ability of Mg-Ni based alloy. Compared with amorphous MgNi alloy, the maximal discharge capacities of Mg1-xTixNi (x=0.1, 0.2, 0.3) alloy were decreased slightly, but the cycle stabilities were significantly enhanced. Mg0.9Ti0.1Ni alloy showed the largest discharge capacity and the best cycle stability.

Characteristics of maximal discharges on toorential watersheds in Serbia

Torrential floods are the most frequent phenomenon in the arsenal of 'natural risks', in Serbia (droughts, avalanches, landslides, rockslides, hail, forest fires, storm wind and earthquakes). Regime of occurrence of floods was studied on the basis of investigations carried out on 128 control profiles, on all important river systems in Serbia, south from Sava and Danube. Frequency of event of maximal discharge Qmax, over determined threshold, defined as average maximal discharge Qmaxsr, was analyzed. The primary maximum of frequencies was noticed in the period May-June, and the secondary maximum of frequencies in the period February-March. The absolute maximal discharges Qmaxa registered on certain profiles follow the periods with the most expressed frequencies, but there are also significant exceptions. A few equations have been derived, which point out close relations between average maximal discharge Qmaxsr, magnitude of the catchment area A, average annual discharge Qsr and the absolute maximal discharge Qmaxa [Qmaxsr=f(A); Qmaxsr=f(Qsr); Qmaxsr=f(A, Qsr); Qmaxa=f(Qmaxsr)]. Historical cases of maximal discharges, reconstructed on the basis of 'hydraulics flood traces' are presented.

PENNING DISCHARGE PLASMA SOURCE AND ITS APPLICATION TO SYNTHESIS OF NANOSTRUCTURED AlN FILMS

Penning discharge (PD) sputtering deposition technique is developed and first used in synthesis of nanostructured aluminum nitride (AlN) films. The advantage of the present PD is that discharge current is linearly dependent on power supply voltage. Maximal discharge current up to 180 mA is obtained for power supply voltage of 5 kV with a ballast resistor of 25 kΩ. In contrast, the discharge voltage is only 290 V. Installation of smaller value of the ballast resistor will yield larger discharge current, whereas discharge voltage remains nearly unchanged, which is an important factor employed to the synthesis of high quality of AlN films. The preferred orientations of nanoscale AlN particles distributions on the surface of the substrates are observed. The increase of the power voltage (discharge current) for sputtering deposition yields different patterns of the nanoscale particles, but sizes of the particles are unchanged. Typical A 1– TO and A1– LO bands in Raman spectra of the films are identified, respectively.

Time of concentration in torrential catchments in Serbia

Maximal discharge Qmax,p is the basic input data for the design of longitudinal and transversal objects in torrential beds. Calculation of maximal discharge Qmax, on unstudied catchments is performed by the following methods: combined procedure (the theory of synthetic unit hydrograph and SCS methodology for the separation of effective rainfall Pe from total rainfall Pb), rational theory and theory of maximal runoff intensity. Rational theory is a suitable method with representative time of concentration Tc. The time of concentration was determined on the basis of investigation on 93 control profiles, south from the Sava and the Danube. Time of concentration and dominant physical-geography characteristics of the catchments were the basis for deriving the equations with regional significance [Tc=f(A), Tc=f(L), Tc=f(L, Lc, Iu), Tc=f(L, Iu), Tc=f(L, Isr), Tc=f(L, Iu, Isr)]. The relation between time of concentration Tc and lag time tp was determined [Tc=f(tp)].