How Saharan dust and elevated convection can produce negative dipole charge structure ?

The 10–12 April 2019 thundersnow (i.e., lightning within snowfall) outbreak was examined via ground‐ and space‐based lightning observations and was simulated using a numerical weather prediction model with an explicit electrification parameterization. When compared to observations, the simulation propagated the synoptic snowband two to six hours faster while also exaggerating the 3‐D reflectivity structure. Throughout the event, the simulation produced 1,733 thundersnow flashes which was less than what was observed by ground‐ and space‐based lightning sensors. In general, simulated thundersnow flashes were spatially offset from the largest reflectivities within the synoptic snowband and tended to occur within elevated convection that traversed isentropically along the top of mid‐level frontogenesis. These simulated thundersnow flashes were associated with a tripole charge structure with ice/snow hydrometeors contributing most to the main negative charge region. Both simulated and observed thundersnow flashes initiated in conditionally unstable environments. Lastly, a conceptual model was developed to explain the spatial separation between the largest reflectivities in the snowband and the occurrence of thundersnow. It is hypothesized that the spatial offset of thundersnow initiation from the reflectivity cores within the synoptic snowband arose from a thermal circulation—induced by mid‐level frontogenesis—that advects positively charged ice/snow hydrometeors toward the surface and creates a nearly homogeneous vertical charge structure.

A plume of Saharan dust and Iberian smoke was carried across the southern UK on 16th October 2017, entrained into an Atlantic cyclone which had originated as Hurricane Ophelia. The dust plume aloft was widely noticed as it was sufficiently dense to redden the visual appearance of the sun. Time series of backscatter from ceilometers at Reading and Chilbolton show two plumes: one carried upwards to 2.5 km, and another below 800 m into the boundary layer, with a clear slot between. Steady descent of particles at about 50 cm s−1 continued throughout the morning, and coarse mode particles reached the surface. Plumes containing dust are frequently observed to be strongly charged, often through frictional effects. This plume passed over atmospheric electric field sensors at Bristol, Chilbolton and Reading. Consistent measurements at these three sites indicated negative plume charge. The lower edge plume charge density was (−8.0 ± 3.3) nC m−2, which is several times greater than that typical for stratiform water clouds, implying an active in situ charge generation mechanism such as turbulent triboelectrification. A meteorological radiosonde measuring temperature and humidity was launched into the plume at 1412 UTC, specially instrumented with charge and turbulence sensors. This detected charge in the boundary layer and in the upper plume region, and strong turbulent mixing was observed throughout the atmosphere’s lowest 4 km. The clear slot region, through which particles sedimented, was anomalously dry compared with modelled values, with water clouds forming intermittently in the air beneath. Electrical aspects of dust should be included in numerical models, particularly the charge-related effects on cloud microphysical properties, to accurately represent particle behaviour and transport.

Five soundings of the electric field and thermodynamic properties were made in a mesoscale convective system (MCS) that occurred in Oklahoma and Texas on 2–3 June 1991. Airborne Doppler radar data were obtained from three passes through the stratiform echo. From these electrical, kinematical, and reflectivity measurements, a conceptual model of the electrical structure of an MCS is developed. Low-level reflectivity data from the storm's mature and dissipating stages show typical MCS characteristics. The leading convective region is convex forward, and the back edge of the stratiform echo is notched inward. The maximum areal extent of the low-level echo is about 250 km × 550 km, and the radar bright band is intense (reflectivity 45–50 dBZ) through an area of at least 50 km × 100 km. The reflectivity above the bright band is horizontally stratified with decreasing intensity and echo-top height toward the rear of the system. Analyses of the velocity data reveal a convective-line-relative flow structure of front-to-rear flow and mesoscale ascent aloft, and weak rear inflow and descent below about 5 km. The electric field soundings are similar over a period of 3 h and a horizontal scale of 100 km across the stratiform region, suggesting that the charge structure is nearly steady state and the charge regions are horizontally extensive and layered. The basic charge structure consists of four layers: a 1–3-km-deep region of positive charge (density ρ ≈ +0.2 nC m−3) between 6 and 10 km, negative charge (ρ ≈ −1.0–2.5 nC m−3) between 5 and 6 km, positive charge (ρ ≈ +1.0–3.0 nC m−3) near 0°C, and negative charge (ρ ≈ −0.5 nC m−3) near cloud base. The upper positive and densest negative charge layers could result from advection of charge from the convective region. The negative charge layer may be augmented by noninductive collisional charging in the stratiform region. The positive charge near 0°C is probably caused by one or more in situ charging mechanisms. The negative charge near cloud base is likely the result of screening layer formation. In addition to the basic four charge layers, positive charge is found below the cloud in each sounding, and in the two soundings closest to the convection (70–100 km distant) there is a low-density negative charge region near echo top.

The spatial and temporal variations of charge structure and the relationship with intensity of radar echo of a thunderstorm over low elevation, Shandong of China, have been analyzed with the radiation sources of lightning discharge three‐dimensional mapping system. The results indicate the charge structure was typical dipolar in the convective areas. The intensity of the positive charge region increased and the height of location rose with the development of thunderstorm. The negative charge region was in the area where the intensity of radar echo was more than 40 dBz and the positive charge region was in the 40 dBz radar echo area approximately. The charge structure was also inferred to be dipolar with low charge height and weak charge intensity in stratiform areas. In the dissipation stage of thunderstorm, the charge structure was ruptured for the different dissipation levels of different parts in cloud. The positive and negative charge regions sank in front of the cloud, and the height of the positive and negative charge regions had a little change in the middle part of the cloud, whereas the negative charge region attenuated. So the charge region was four layers in convective areas during dissipation stage. The above results show that the advantage charge generation mechanism often generates dipole or tripole charge structure and does not generate multipole charge structure. This paper also analyzes a negative cloud‐ to‐ground flash discharge process. Its charge structure is the same as the thunderstorm charge structure. So the thunderstorm charge structure can be illustrated by the observations of the three‐dimensional lightning mapping system.

Observation and analysis of electrical structure change and diversity in thunderstorms on the Qinghai-Tibet Plateau

Highly negatively charged nanofiltration membrane prepared with a novel diamino-sulfonamide aqueous monomer for efficient removal of anionic dyes

In our works we theoretically prove that the cumulation (self-focusing) of charged particles in a inhomogeneous plasma (with current) is a universal property of cumulative-dissipative structures with characteristic sizes from 10-15 to 1026 m. Electrical phenomena are observed in non-uniform atmospheres and ionospheres of all planets of the Solar System. In this paper, the most complete theory of perturbations to describe phenomena in gas discharge plasma is formulated and, based on this theory, the most complete classification of ambipolar transfer processes in plasma with current and the classification of non-uniform plasma parameter profiles are given. We compare our theoretical results with existing experiments and results obtained in other areas of the natural sciences. In this work, we theoretically (Part 6.1) and experimentally (Part 6.2) we prove that shock waves of electric fields are focusing shells for inhomogeneous plasma cumulative-dissipative positively charged 3D structures. In the Part 6.1 of this work, we provide detailed theoretical justifications for the possibility of the existence of (locally self-focusing by ambipolar drift) Vysikaylo’s electric field shock waves caused by ambipolar diffusion due to a violation of the electrical neutrality of the plasma (in the presence of an electric current). Due to the greater mobility of electrons (ions are more massive), a structure with a positive space charge is formed in the electric field shock waves that self-form in the plasma (with current). Unlike Mach’s shock waves, in closed Vysikaylo’s shock waves transverse electric fields are generated due to the space charge. This makes the problem (in the electric field shock wave region) three-dimensional (in particular, spherically or cylindrical symmetric in this region). In Part 6.1, we will limit ourselves to the study of stationary one-dimensional profiles: 1) parameters in shock waves of the electric field and 2) processes of ambipolar drift, leading to local cumulation of positive charge in the shock wave of the electric field. In Part 6.1, the author will limit himself to obvious remarks arising from the properties of three-dimensional structures with a positive space charge. Based on laboratory 3D experiments (Part 6.2) and theoretical studies of gas-discharge plasma, we prove that ambipolar drift caused by different dependences of the mobility of electrons and positive ions in a simple plasma (with one type of ions) determines the dynamic processes of cumulation of plasma structures – 4D plasmoids in plasma (with current). 4D plasma structures are non-stationary three-dimensional structures. The author draws attention to self-formation in plasma structures (plasmoids) of stationary Vysikaylo’s plasma nozzles - analogues of Laval’s nozzles. A comparison of theoretical 1D and experimental 3D observations of discharge glow (this corresponds to changes in the main parameters) in gas discharge tubes will be presented in Part 6.2. In these experiments, a homogeneous plasma in a gas discharge tube is locally disturbed by a beam of fast electrons. This leads to the self-formation: 1) of electric field shock waves (a layer of positive volume charge) stopped by gas pumping and 2) of transition 3D profiles and Vysikaylo’s plasma 3D nozzles already in a quasi-neutral inhomogeneous plasma. In this work, we were the first to theoretically and experimentally study the processes of nonlinear ambipolar transport caused by the violation of electrical neutrality and 3D interaction of electric fields with matter (charged particles) in an inhomogeneous plasma with current. For the first time it has been proven that the coefficients of ambipolar diffusion due to the violation of electroneutrality are vectors determined by the electric field vector.

This second part of a two-part study examines the lightning and charge structure evolution of the 29 June 2000 tornadic supercell observed during the Severe Thunderstorm Electrification and Precipitation Study (STEPS). Data from the National Lightning Detection Network and the New Mexico Tech Lightning Mapping Array (LMA) are used to quantify the total and cloud-to-ground (CG) flash rates. Additionally, the LMA data are used to infer gross charge structure and to determine the origin locations and charge regions involved in the CG flashes. The total flash rate reached nearly 300 min−1 and was well correlated with radar-inferred updraft and graupel echo volumes. Intracloud flashes accounted for 95%–100% of the total lightning activity during any given minute. Nearly 90% of the CG flashes delivered a positive charge to ground (+CGs). The charge structure during the first 20 min of this storm consisted of a midlevel negative charge overlying lower positive charge with no evidence of an upper positive charge. The charge structure in the later (severe) phase was more complex but maintained what could be roughly described as an inverted tripole, dominated by a deep midlevel (5–9 km MSL) region of positive charge. The storm produced only two CG flashes (both positive) in the first 2 h of lightning activity, both of which occurred during a brief surge in updraft and hail production. Frequent +CG flashes began nearly coincident with dramatic increases in storm updraft, hail production, total flash rate, and the formation of an F1 tornado. The +CG flashes tended to cluster in or just downwind of the heaviest precipitation, which usually contained hail. The +CG flashes all originated between 5 and 9 km MSL, centered at 6.8 km (−10°C), and tapped LMA-inferred positive charge both in the precipitation core and (more often) in weaker reflectivity extending downwind. All but one of the −CG flashes originated from >9 km MSL and tended to strike near the precipitation core.

Based on thermally-stimulated current (TSC), laser-induced pressure pulse (LIPP), and isothermal charge decay (ICD) measurements of PET films in various stages of production, we discuss charge accumulation and dipole orientation introduced by the production process and subsequent positive or negative corona charging of such PET films. In the prefilms and in the final films, negative charge is more stable than positive charge. Negative charge is generally injected into both sample surfaces by a pinning process and by contact electrification during the production process, where the film is running over metal and other rollers. The TSC depolarization temperatures are about 80/spl deg/C for the polarization, 90 to 130/spl deg/C for positive charges and 110 to 140/spl deg/C for negative charges.

Electrical structure of a Qinghai–Tibet Plateau thunderstorm based on three-dimensional lightning mapping

Inverted-polarity electrical structures in thunderstorms in the Severe Thunderstorm Electrification and Precipitation Study (STEPS)

The main charge region in thunderstorms over Lhasa city with an elevation of 3700 m is investigated by using a VHF interferometer, incorporating with fast antenna, weather radar and cloud-to-ground lightning location. The evolution of charge structure and its effects on lightning discharges were discussed in a bottom-heavy thunderstorm. During the early developing stage, the thunderstorm exhibited an inverted dipolar charge structure with negative charge center over the positive, and lower negative intracloud (IC) lightning occurred in between. Then an upper positive charge region appeared as the convection intensifying, and the charge structure exhibited obvious tripolar pattern and with large lower positive charge center (LPCC), and fewer positive IC discharges occurred in the upper dipole but lower negative IC lightning still dominated. As the thunderstorm entered the later mature stage, both negative IC between the lower dipole and positive IC between the upper dipole observed simultaneously. With gradually depleting of the positive charge carriers by precipitation, the LPCC weakened, the positive IC lightning between the upper dipole dominated, and two negative CG flashes were able to occur. In the later stage, positive IC dominated, although not much.  The study further confirms the previous conclusion (Qie et al., GRL, 2005) that weak thunderstorms are characterized by a bottom-heavy charge structure, and in the vigorous stage of thunderstorm, it may exhibit tripolar charge structure with a large LPCC, which has a significant impact on lightning types.

Microphysical and kinematic characteristics of two storm populations, based on their macroscale charge structures, are investigated in an effort to increase our understanding of the processes that lead to anomalous (or inverted charge) structures. Nine normal polarity cases (mid-level negative charge) with dual-Doppler and polarimetric coverage that occurred in northern Alabama, and six anomalous polarity cases (mid-level positive charge) that occurred in northeastern Colorado are included in this study. The results show that even though anomalous polarity storms formed in environments with similar instability, they had significantly larger and stronger updrafts. Moreover, the anomalous polarity storms evidently have more robust mixed-phase microphysics, based on a variety of metrics. Anomalous polarity storms in Colorado have much higher cloud base heights and shallower warm cloud depths in this study, leading us to hypothesize that anomalous polarity storms have lower amounts of dilution and entrainment. We infer positively charged graupel, and therefore high supercooled water contents, in the mid-levels of the anomalous storms based on the relationship between colocations of graupel and inferred positive charge from Lightning Mapping Array data. Using representative updraft speeds and warm cloud depths, the time required for a parcel to traverse from cloud base to the freezing level was estimated for each storm observation. We suggest this metric is the key discriminator between the two storm populations and leads us to hypothesize that it strongly influences the amount of supercooled water and the probability of positive charge in the midlevels, leading to an anomalous charge structure.

Mucosal delivery of vaccine-loaded nanoparticles (NP) is an attractive proposition from an immunologic perspective. Although numerous NP preparation methods are known, sufficient antigen loading of NP remains a challenge. The aim of this study was to evaluate adsorptive loading of NP with a negatively charged surface structure using tetanus toxoid (TT) as a model vaccine. Blank NP, consisting of poly(sulfobutyl-polyvinyl alcohol)-g-(lactide-co-glycolide), as well as poly(lactide-co-glycolide) NP were prepared by a solvent displacement technique. The use of polymers with different degrees of substitution resulted in NP with different negative surfaces charges. Adsorption of TT to NP was performed varying to NP surface properties, protein equilibrium concentration, and loading conditions. The protein adsorption was controlled by NP surface properties, and maximum TT adsorption occurred at highly negatively charged NP surfaces. Results from isothermal titration calorimetry and zeta-potential measurement suggest an adsorption process governed by electrostatic interactions. The adsorption followed the Langmuir isotherm in the concentration ranges studied. TT withstood this gentle loading procedure in a nonaggregated, enzyme-linked immunoabsorbant assay-active form. The results demonstrate that negatively charged NP consisting of poly(sulfobutyl-polyvinyl alcohol)-g-(lactide-co-glycolide) are suitable for adsorptive loading with TT and may have potential for mucosal vaccination.

Event Abstract Back to Event pH-sensitive surface charge-conversion nanomicelle for anti-tumor drug delivery Wei Wu1, 2*, Guixue Wang1* and Jianshu Li2* 1 Chongqing University, Bioengineering College, China 2 Sichuan University, College of Polymer Science and Engineering, China Introduction: During the last decade, tremendous efforts have been attained in the development of stimuli-responsive polymeric nanocarriers for the controlled delivery of various anti-cancerous drugs[1]. Physiological stimuli-responsive nanocarriers provide the feasible platforms for cancer therapy due to their improved anticancer efficiency as well as reduced systematic cytotoxicity via the tumor specific enhanced permeability and retention (EPR) effect[2]. It is interesting to note the pH-sensitive surface charge-conversion strategy, which is potential for enhancing tumor cell internalization efficiency. In this study, we attempt to engineer this smart tumor-acidity activated surface charge-conversion function into a biodegradable amphiphilic block copolymers for anticancer application. Materials and Methods: Poly(D, L-lactide)-block-poly(2-aminoethyl methacrylate) (PLA-b-PAEMA, MW 8900, PDI 1,24) was firstly synthesized through ring-opening polymerization (ROP) and subsequently atom transition radical polymerization method. PLA-b-PAEMA/DMMA was obtained by using 2,3-dimethykmaleic anhydride (DMMA) modified PLA-b-PAEMA. Results and Discussion: The well-defined PLA-b-PAEMA is further modified by DMMA and succinic anhydride (SA) to yield the tumor-acidity activated surface charge-conversional block copolymer (PLA-b-PAEMA/DMMA) and the control sample (PLA-b-PAEMA/SA). In this design, the biodegradable PLA block and the functional PAEMA/DMMA (or PAEMA/SA) block provide the amphiphilic driving force to self-assemble into nanocarriers, which have PLA aggregated hydrophobic inner core and PAEMA/DMMA (or PAEMA/SA) outer corona, in aqueous solution. As compared with the invariable negative surface charge of PAEMA/SA block, PAEMA/DMMA block shows the tumor-acidity activated surface charge-conversion feature, i.e., exhibiting negatively charged surface during the blood circulation time and positively charged surface in response to slight tumor acidic environment through the hydrolysis of DMMA functional agents. Thus, after the loading of positively charged doxorubicin hydrochloride (DOX·HCl) into the negatively charged corona structure through electrostatic attraction, the DOX·HCl-loaded PLA-b-PAEMA/DMMA carrier (PLA-b-PAEMA/DMMA@DOX·HCl) is expected to prolong blood circulation time because its “stealthy” negatively charged surface could effectively decrease the undesired consumption by the reticuloendothelial system (RES) and the protein adsorption in vivo, and promote the anti-cancer therapeutic efficiency though the tumor activated positively charged surface for enhanced tumor cell adhesion and targeted drug release (Scheme 1). Scheme1. Illustration of tumor-acidity activated carriers for enhanced cell uptake and targeted drug release. Conclusions: In summary, we construct a smart nanocarrier based on biodegradable PLA-b-PAEMA/DMMA copolymer, which could convert surface charge from negative to positive in response to the tumor-acidity. It exhibits various superiorities for tumor-specific drug delivery, including long blood circulation time, enhanced tumor-cell adhesion, tumor targeted drug release and additional cytotoxicity for tumor cells after the charge-conversion. Thus, this biodegradable smart carrier integrated high drug delivery efficiency and well-improved biocompatibility provides a feasible platform for the ideal anti-tumor therapy. Financial support from the National Natural Science Foundation of China (51322303); Financial support from the Foundations of Sichuan Province (2012JQ0009)