Linear fast shutdown technology based on self-resonant constant voltage clamping

Transient electromagnetic method(TEM)has been widely used in the field of medium and shallow underground detection due to its high detection efficiency and large detection depth.However,due to the long turn-off time of the transmitting current caused by the inductive characteristics of the transmitting coil,the early signals will be overwhelmed by primary field.Since the early signals contain most of shallow geological signals,it is necessary to reduce the long turn-off time to get shallow layer signal.Due to lack of a reliable and effective clamping method for high-power transmission at present,we design a TEM transmitter fast turn-off circuit,combining self-resonant zero-voltage switching technology with the corresponding timing control circuit to solve this problem effectively.A transient electromagnetic transmitter based on self-resonant constant voltage clamping technology was fabricated to charge the clamping capacitor.The rated transmitting current of the transmitter is 20 A,and the turn-off time is continuously adjustable from 550-50μs.Moreover,the current drop process is approximately linear rather than exponential attenuation.Compared with the existing clamping methods,the proposed clamping method solves the problems that transient voltage suppressor(TVS)clamping cannot be used in high-power occasions and has a high failure rate.It also solves the problem of long pre-charge time in traditional capacitor clamping methods due to insufficient inductance of the small size transmitting coil.The proposed method can provide a reference for fast shutdown of large current.

Deglycosylation altered the gating properties of rNav1.3:glycosylation/deglycosylation homeostasis probably complicates the functional regulation of voltage-gated sodium channel

Objective To examine the effect of deglycosylation on gating properties of rNav1.3. Methods rNav1.3 was expressed in Xenopus oocyte, with glycosylation inhibition by using tunicamycin. Two-electrode voltage clamp was employed to record the whole-cell sodium current and data were analyzed by Origin software. Those of glycosylated rNav1.3 were kept as control. Results Compared with glycosylated ones, the steady-state activation curve of deglycosylated rNav1.3 was positively shifted by about 10 mV, while inactivation curve was negatively shifted by about 8 mV. Conclusion Glycosylation altered the gating properties of rNav 1.3 and contributed to the functional diversity.

Effects of 2-[p-(Dimethylamino)Styrl] PyridineMethiodide on Slow Response Action Potentialand Slow lnward Current of Guinea PigPapillary Muscles

The effects of 2-[p-(Dimethylamino)styryl] pyridine methiodide(DSPM)on slow response action potential(SRAP)and slow inward current(Isi) of guinea pig papillary muscles were studied by intracellular microelectrodes and voltage clamp techniques.The APA and V_(max) of SRAP induced by high K￣+were decreased after 50 min of perfusion with DSPM solu- tion. Isi was suppressed from a peak value of8.8± 1.6μA to 5.7± 1.8μA, The results indicated that DSPM has a selective blocking effect on calcium channel.

Identification and functional characterization of ApisOr23 in pea aphid Acyrthosiphon pisum

Pea aphid,Acyrthosiphon pisum,is a serious pest of many different leguminous plants,and it mainly relies on its odorant receptors(Ors)to discriminate among host species.However,less is known about the role that Ors play in the host plant location.In this study,we identified a novel conserved odorant receptor clade by phylogenetic analysis,and conducted the functional analysis of ApisOr23 in A.pisum.The results showed that the homologous Ors from A.pisum,Aphis glycines and Aphis gossypii share 94.28% identity in amino acid sequences.Moreover,conserved motifs were analyzed using the annotated homologous Or23 from eight aphid species,providing further proof of the high conservation level of the Or23 clade.According to the tissue expression pattern analysis,ApisOr23 was mainly expressed in the antennae.Further functional study using a heterologous Xenopus expression system revealed that ApisOr23 was tuned to five plant volatiles,namely trans-2-hexen-1-al,cis-2-hexen-1-ol,1-heptanol,4’-ethylacetophenone,and hexyl acetate.Among them,trans-2-hexen-1-al,which is one of the main volatile organic compounds released from legume plants,activated the highest response of ApisOr23.Our findings suggest that the conserved Or23 clade in most aphid species might play an important role in host plant detection.

Mifepristone modulates serotonin transporter function

Regulating serotonin expression can be used to treat psychotic depression. Mifepristone, a glu- cocorticoid receptor antagonist, is an effective candidate for psychotic depression treatment. However, the underlying mechanism related to serotonin transporter expression is poorly un- derstood. In this study, we cloned the human brain serotonin transporter into Xenopus oocytes, to establish an in vitro expression system. Two-electrode voltage clamp recordings were used to detect serotonin transporter activity. Our results show that mifepristone attenuates serotonin transporter activity by directly inhibiting the serotonin transporter, and suggests that the se- rotonin transporter is a pharmacological target of mifepristone for the treatment of psychotic depression.

Circuit breakers in HVDC systems: state-of-the-art review and future trends

High voltage direct current(HVDC)systems are efficient solutions for the integration of large-scale renewable energy sources with the main power grids.The rapid development of the HVDC grid has resulted in a growing interest in DC circuit breakers(DCCBs).A fast and reliable circuit breaker is a necessary requirement in the development of large scale HVDC grids.This paper provides a comprehensive review and survey of the HVDC CBs and discusses potential research directions.Operational principles and the main features of various DCCBs are described and their merits and shortcomings are also highlighted.

Current Injection Provokes Rapid Expansion of the Guard Cell Cytosolic Volume and Triggers Ca^2＋ Signals

High-resolution microscopy opens the door for detailed single-cell studies with fluorescent reporter dyes and proteins. We used a confocal spinning disc microscope to monitor fluorescent dyes and the fluorescent protein Venus in tobacco and Arabidopsis guard cells. Multi-barreled microelectrodes were used to inject dyes and apply voltage pulses, which provoke transient rises in the cytosolic Ca^2＋ level. Voltage pulses also caused changes in the distribution of Lucifer Yellow and Venus, which pointed to a reversible increase of guard cell cytosolic volume. The dynamic cytosolic volume changes turned out to be provoked by current injection of ions. A reduction of the clamp current, by blocking K^＋ uptake channels with Cs^＋, strongly suppressed the cytosolic volume changes. Cs^＋ not only inhibited the expansion of the cytosol, but also inhibited hyperpolarization-induced elevations of the cytosolic Ca^2＋ concentration. A complete loss of voltage-induced Ca^2＋ signals occurred when Ca^2＋-permeable plasma membrane channels were simultaneously blocked with La^3＋. This shows that two mechanisms cause hyperpolarization-induced elevation of the cytosolic Ca^2＋-concentration： （i） activation of voltage-dependent Ca^2＋-permeable channels, （ii） osmotically induced expansion of the cytosol, which leads to a release of Ca^2＋ from intracellular stores.

Kinetics of low threshold calcium channels of relay cells in cat lateral geniculate nucleus

Kinetics of the low threshold T-type Ca2+ channel is studied with single electrode voltage damp technique on brain slices of the cat lateral geniculate nucleus (LGN). Space damp is dramatically improved by blocking various K+ and Na+ channels, decreasing Ca2+ current and selecting proper holding potentials. Results from this study are similar to those obtained from acutely dissociated LGN neurons of the rat, indicating that the kinetics of T-Ca2+ channels of the cat LGN neurons is the same as that of the rat LGN. The result reported previously on the cat LGN may result from a defect in space damp.