Serological responses (Seroresponse) and durability of hepatitis A virus (HAV) vaccination are reduced among human immunodeficiency virus (HIV)‐positive patients. Incidence of and associated factors with early seroreversion (loss of seroresponse) among HIV‐positive patients who have achieved seroresponses after two doses of HAV vaccination remain unclear. In this multicenter study, we followed HIV‐positive adults who had mounted seroresponses after completing two doses of HAV vaccination during a recent outbreak of acute hepatitis A between 2015 and 2017, a 1:4 case‐control study was conducted to identify factors associated with seroreversion. Case patients were those with seroreversion, and controls were those with similar follow‐up durations who were able to maintain seroresponses. During the study period, 49 of the 1,256 patients (3.9%) seroreverted after a median follow‐up of 611 days. In a case‐control study, seroreversion was more likely to occur in patients with a higher weight (adjusted odds ratio [aOR], 1.703; 95% confidence interval [CI], 1.292‐2.323, per 10‐kg increment) and HIV viremia at the time of vaccination (aOR, 2.922; 95% CI, 1.067‐7.924), whereas positive seroresponse at 6 months of HAV vaccination and higher CD4 lymphocyte counts at vaccination were inversely associated with early seroreversion with an aOR of 0.059 (95% CI, 0.020‐0.154) and 0.837 (95% CI, 0.704‐0.979, per 100‐cell/mm3 increment), respectively, in multivariable analyses. Conclusion: During an outbreak setting, early seroreversion following two‐dose HAV vaccination occurred in 3.9% of HIV‐positive patients. Lower and delayed seroresponses to HAV vaccination, a higher weight, and HIV viremia and lower CD4 lymphocyte counts at the time of HAV vaccination were associated with early seroreversion. Regular monitoring of seroresponse and booster vaccination might be warranted, especially in HIV‐positive adults with predictors of early seroreversion.

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A narrowband radio interferometer has been developed and used to locate the entire sources of VHF radiations from a negative cloud-to-ground (CG) lightning discharge which contains 19 strokes. This system uses five antennas to form an array consisting of short-and long-baselines along two orthogonal directions. The system error which comes from frequency conversion is reduced by phase detection through direct high frequency amplifying. An interactive graphic analysis procedure is used to remove the fringe ambiguities which exist inherently in interferometry and to determine the direction of lightning radiation sources in two dimensions (azimuth and elevation) as a function of time at a time resolution of microsecond orders. With the developed system, the whole progression process in time and space of a lightning flash can be reconstructed. In this paper, combining the synchronous data of electric filed change and VHF radiation, the whole processes of an example negative CG flash have been studied in detail. It is found that the preliminary breakdown event of the CG flash started from negative charge region and exhibited firstly a downward pregression and then an upward propagation. There were very intense and continuous radiations during stepped leaders which became much stronger when the first return stroke began. In contrast, there were less and only discrete radiations during dart leaders. Stepped leader and dart leader may transform to each other depending on the state of the ionization of the path. The progression speed of initial stepped leaders was about 10 5 ms 1 , while that was about 4.1×10 6 and 6.0×10 6 ms 1 for dart leaders and dart-stepped leaders, respectively. M events produced hook-shaped field changes accompanied by active burst of radiations at their beginnings. Followed these active radiation processes, M events appeared to contact finally into conducting main discharge channels. The mean progression speed of M events was about 7×10 7 ms 1 , greater than that of the dart leaders and dart-step leaders. K events and attempted leaders were essentially the same as dart leaders except that they could not reach the ground and initiate return strokes.lightning, narrowband interferometer, dart leader, K events, M events, the whole process of cloud-to-ground lightning Most parts of the lightning discharges, including intracloud (IC) flash and initial part of cloud-to-ground (CG) flash, occur inside the cloud where they are obscured from viewing at optical frequencies. Therefore, the study on incloud discharges is very important not only for the understanding of lightning mechanism, but for the detection and early warning of lightning hazard as well.

The data of electric field and electric field changes produced by lightning on the ground in Nagqu area of Qinghai-Xizang plateau in the summer of 2002 were analyzed. The results showed that the charge structure in thunderstorms was varied and complex. Few cloud-to-ground (CG) lightning flashes occurred in the thunderstorm. A long time discharge process in cloud occurred just before step leader of positive and negative CG lightning. Most of CG lightning discharges only involved one return stroke. The proportion of positive CG lightning discharges was 33%, which was obviously higher than that in lower and middle latitude area, and negative 67% in thunderstorms. A continuing current process with short lasting time occurred just after the return-stroke.

By means of a fast Fourier transform (FFT), average energy spectra in the interval from 25 to 100 MHz are presented for most of the components that produce large radiation field pulses from lightning: first and subsequent return strokes; stepped and dart leaders; preliminary breakdown and Intracloud K changes.