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Abstract Background In human primary motor cortex (M1), the paired-pulse transcranial magnetic stimulation (TMS) paradigm of short-interval intracortical inhibition (SICI) can be expressed conventionally as a percent change in the relative amplitude of a conditioned motor evoked potential to non-conditioned; or adaptive threshold-hunting a target motor evoked potential amplitude in the absence or presence of a conditioning stimulus, and noting the relative change in stimulation intensity. The suitability of each approach may depend on the induced current direction, which probe separate M1 interneuronal populations. Objective To examine the influence of conditioning stimulus intensity, interstimulus interval (ISI) and current direction for adaptive threshold-hunting and conventional SICI using equivalent TMS intensities. Methods In 16 participants (21–32 years), SICI was examined using adaptive threshold-hunting and conventional paired-pulse TMS with posterior-anterior and anterior-posterior stimulation, ISIs of 2 and 3 ms, and a range of conditioning intensities. Results Inhibition with adaptive threshold-hunting was greater for anterior-posterior stimulation with an ISI of 3 ms (23.6 ± 9.0%) compared with 2 ms (7.5 ± 7.8%, P < 0.001) and posterior-anterior stimulation at both ISIs (2 ms 8.6 ± 8.7%, 3 ms 5.9 ± 4.8%; P < 0.001). There was an association between inhibition obtained with conventional and adaptive threshold-hunting for posterior-anterior but not anterior-posterior stimulation (2 ms only, r = 0.68, P = 0.03). Conclusions More inhibition was evident with anterior-posterior than posterior-anterior current for both adaptive threshold-hunting and conventional paired-pulse TMS. Assessment of SICI with anterior-posterior stimulation was not directly comparable between the two approaches. However, the amount of inhibition was dependent on conditioning stimulus intensity and ISI for both SICI techniques. Highlights • Greater intracortical inhibition can be obtained using anterior-posterior induced current in the brain compared with posterior-anterior for both conventional and adaptive threshold-hunting paired-pulse transcranial magnetic stimulation. • With both techniques, the amount of inhibition assessed with anterior-posterior induced current was dependent on the conditioning stimulus intensity and interstimulus interval. • Assessment of primary motor cortex short-latency inhibition using equivalent stimulation intensities may not be directly comparable between conventional and adaptive threshold-hunting techniques. [ABSTRACT FROM AUTHOR]

Particulate wastes drive benthic organic enrichment from cage fish farming. Differentiation between faeces and uneaten feed estimates at cage level are of great value to both economize the feeding process and reduce waste. This study estimates the particulate waste outflowing cages at different depths and orientations, and the wasted feed component by combining in situ measurements and modelling. Particulate matter flux (PMF) was greater vertically through the cage bottoms (60.89%), but lateral outflow was also substantial (39.11%). PMF occurs all around the cages, and the influence of the mainstream current was low. Wasted feed was greatly variable, reaching high values (about 50% of supplied feed. The self-application of feed wastage monitoring and estimates by fish farmers is recommended to improve sustainability. [ABSTRACT FROM AUTHOR]

Background Previous research suggested that anterior–posterior (AP) directed currents induced by TMS in motor cortex (M1) activate interneuron circuits different from those activated by posterior–anterior currents (PA). The present experiments provide evidence that pulse duration also determines the activation of specific interneuron circuits. Objective To use single motor unit (SMU) recordings to confirm the difference in onset latencies of motor-evoked potentials (MEPs) evoked by different current directions and pulse durations: AP 30 , AP 120 , PA 30 and PA 120 . To test whether the amplitude of the MEPs is differentially influenced by somatosensory inputs from the hand (short-latency afferent inhibition, SAI), and examine the sensitivity of SAI to changes in cerebellar excitability produced by direct current stimulation (tDCS Cb ). Methods Surface electromyograms and SMUs were recorded from the first dorsal interosseous muscle. SAI was tested with an electrical stimulus to median or digital nerves ~20–25 ms prior to TMS delivered over the M1 hand area via a controllable pulse parameter TMS (cTMS) device. SAI was also tested during the application of anodal or sham tDCS Cb . Because TMS pulse specificity is greatest at low stimulus intensities, most experiments were conducted with weak voluntary contraction to reduce stimulus threshold. Results AP 30 currents recruited the longest latency SMU and surface MEP responses. During contraction SAI was greater for AP 30 responses versus all other pulses. Online anodal tDCS Cb reduced SAI for the AP 30 currents only. Conclusions AP 30 currents activate an interneuron circuit with functional properties different from those activated by other pulse types. Pulse duration and current direction determine what is activated in M1 with TMS. [ABSTRACT FROM AUTHOR]

Abstract Background Paired associative stimulation (PAS), with stimulus interval of 21.5 or 25 ms, using transcranial magnetic stimulation in the posterior-anterior (PA) current direction, produces a long-term-potentiation-like effect. Stimulation with PA directed current generates both early and late indirect (I)-waves while that in anterior-posterior (AP) current predominantly elicits late I-waves. Short interval intracortical inhibition (SICI) inhibits late I-waves but not early I-waves. Objective To investigate how cortical inhibition modulates the effects of PAS. Methods PAS at stimulus interval of 21.5 ms conditioned by SICI (SICI-PAS) was compared to PAS alone with both PA and AP directed currents. Results PAS with both current directions increased cortical excitability. SICI-PAS increased cortical excitability in the PA but not the AP current direction. Conclusions Both early and late I-waves circuits can mediate cortical PAS plasticity under different conditions. Plasticity induction with the late but not the early I-wave circuits is blocked by SICI. Highlights • Cortical circuits mediating early and late I-waves can produce associative plasticity. • The circuits involved depend on current direction and stimulus interval. • Plasticity induction can be blocked by cortical inhibition. [ABSTRACT FROM AUTHOR]

Siltation is of primary concern for the construction and maintenance of the waterways worldwide. Lingding Channel (LC) and Hengmen Channel (HC) are two major seagoing waterways in the Lingding (LD) Bay, Pearl River Delta, South China. TELEMAC-2D numerical modeling was performed to elucidate the characteristics and mechanism of siltation in the two seagoing waterways under usual and extreme flood conditions. The deposition thickness during usual flood conditions was 0.22 m in the LC and 0.16 m in the HC; during extreme flood conditions, the thickness reached 0.32 m in the LC and 0.44 m in the HC. In the LC, the main sediment deposition area was in the lower section of the LC, south of Neilingding Island. In the HC, the main deposition areas were in the Lanshan, Ermao, and Qi'ao Shoals. Under extreme flood conditions, the sediment loads into the LD Bay from the Humen, Jiaomen, Hongqili and Hengmen outlets reach 16.65 × 106 t in total, compared with 4.54 × 106 t under usual flood. The certain amount of sediment in the upper and middle parts of the estuary is resuspended by high bottom shear stress and transported downstream, deposited in the lower sections of the HC and LC. High sediment load combined strong resuspension contribute to the sudden and substantial sedimentation in the navigation channels during extreme floods. Siltation intensity varies with the velocity change along the navigation channel, and the main deposition appears in areas with low velocity. The angle between the current direction and channel axis is favorable to the sediment deposition location and intensity, which results in serious deposition in the lower sections of HC and LC. The stagnation point moves around the middle of estuary under usual and extreme flood conditions, so, the middle and lower parts of the LD Bay is heavily silted. The impacts of extreme floods on the navigation channels can not be overlooked and mitigation measures such as bathymetric monitoring, flood control and dredging should be taken. • A coupled model is established to examine the waterway sedimentation in the Lingding Bay under usual and extreme flood events. • High sediment transport rates and strong resuspension contribute to the sudden and substantial sedimentation in the navigation channels during extreme floods. • The current variation, the combined effects of tide and runoff and the jets associated with outlets results in spatial deposition difference along the channel. [ABSTRACT FROM AUTHOR]