[Transcranial direct current stimulation in substance use disorders: an update]. / Transcraniële gelijkstroomstimulatie bij stoornissen in het gebruik van middelen: een update.

BACKGROUND: Existing treatments for substance use disorders are often subject to drop-out or relapse. Transcranial direct current stimulation (tDCS) possibly has a positive effect on this problem. AIM: To give an updated qualitative review of existing studies investigating the clinical effects of transcranial direct current stimulation for people with a substance use disorder, considering the many recently published studies. METHOD: Extensive literature search in the electronic database PubMed. We included 43 studies on top of the 7 studies already included in the previous review of Herremans and Baeken (2017) in this journal. RESULTS: The majority of the studies showed a positive effect of transcranial direct current stimulation on clinical measures as craving and abstinence. However, there was little uniformity in used protocols. CONCLUSION: Transcranial direct current stimulation can be an effective treatment for people with a substance use disorder. Optimal parameters need to be established to make the treatment maximally effective and adapted to the individual patient.

Direct and indirect drift assessment means. Part 1: PDPA laser based droplet characterisation.

The spray quality generated by agricultural nozzles is important considering the efficiency of the pesticide application process because it affects spray deposits, biological efficacy and driftability. That is why a measuring set-up for the characterisation of spray nozzles was developed. This set-up is composed of a controlled climate room, a spray unit, a three-dimensional automated positioning system and an Aerometrics PDPA laser system which measures droplet size and velocity characteristics based on light scattering principles. Using this set-up and a well defined measuring protocol, droplet size and velocity characteristics of 15 different nozzle-pressure combinations were measured. It was found that at a nozzle distance of 0.50 m, droplet sizes vary from a few up to some hundreds of micrometres and droplet velocities from about 0 m.s(-1) up to 16 m.s(-1). From the results, the importance of the nozzle type and size on the droplet size and velocity spectra is clear. Standard flat fan nozzles produced the finest droplet size spectrum followed by low-drift and the air injection nozzles which results in significant differences in the proportion of small droplets. The larger the ISO nozzle size, the coarser is the droplet size spectrum and the lower is the proportion of small droplets. This effect is most pronounced for the standard flat fan followed by the low-drift nozzles and is less important for the air inclusion nozzles. Comparing the PDPA measuring results with other studies confirmed the need for reference nozzles to classify sprays because of the considerable variation of absolute results depending on variations in reference sprays, measuring protocol, measuring equipment and settings. As described in part 4, these results will be linked with the drift potential of different nozzle-pressure combinations.

Direct and indirect drift assessment means. Part 2: wind tunnel experiments.

Wind tunnel measurements, performed in Silsoe Research Institute (SRI), were used to measure airborne and fallout spray volumes under directly comparable and repeatable conditions for single and static nozzles. Based on these measurements, drift potential reduction percentages (DPRP), expressing the percentage reduction of the drift potential compared with the reference spraying, were calculated following three approaches. The first approach was based on the calculation of the first moment of the airborne spray profile (DPRPv1). In the second and third approach, the surface under the measured airborne (DPRPv2) and fallout (DPRP(H)) deposit curve were used. These DPRP values express the percentage reduction of the drift potential compared with the reference spraying. Ten different spray nozzles were tested. The results showed the expected fallout profiles with the highest deposits closest to the nozzle and a systematic decrease with distance from the nozzle. For the airborne deposit profiles, the highest deposits were found at the Lowest collectors with an important systematic decrease with increasing heights. For the same nozzle size and spray pressure, DPRP values are generally higher for the air inclusion nozzles followed by the low-drift nozzles and the standard flat fan nozzles and the effect of nozzle type is most important for smaller nozzle sizes. In general, the bigger the ISO nozzle size, the higher the DPRP values. Comparing results from the three different approaches namely, DPRPv1, DPRPv2 and DPRP(H), some interesting conclusions can be drawn. For the standard flat fan nozzles, DPRPv1, values were the highest followed by DPRPv2 and DPRP(H) while for the low-drift nozzles opposite results were found. For the air inclusion nozzles, there was a relatively good agreement between DPRPv1, DPRPv1 and DPRP(H) values. All of this is important in the interpretation of wind tunnel data for different nozzle types and sampling methodologies.

Direct and indirect drift assessment means. Part 4: a comparative study.

Three contrasting drift risk assessment means were evaluated when predicting absolute losses of sedimenting pesticide drift from field crop sprayers namely PDPA laser measurements, wind tunnel measurements (both indirect drift risk assessment means) and field drift experiments (direct drift risk assessment means). In total, 90 PDPA laser measurements, 45 wind tunnel experiments and 61 field drift experiments were performed with 10 different spray nozzles at a pressure of 3.0 bar. The effect of nozzle size (ISO 02, 03 04 and 06) and nozzle type (standard flat fan, low-drift flat fan, air inclusion) on the amount of near-field sedimenting spray drift was studied. The reference spray application was defined as a Hardi ISO F 110 03 standard flat fan nozzle at a pressure of 3.0 bar with a nozzle or boom height of 0.50 m and a driving speed of 8 km.h(-1) for the field measurements; conditions that were always used for the comparative assessment of the different investigated nozzle-pressure combinations. A comparison is made between the results obtained with the indirect drift assessment means and the direct drift assessment method to evaluate the potential of these three different drift assessment means. Droplet size as well as droplet velocity characteristics are related with DRPt (field experiments) and DPRP (wind tunnel experiments). Because of the strong intercorrelation between droplet size and velocity characteristics for the nozzle-pressure combinations investigated in this study, simple first-order linear regressions with one of the droplet characteristics as a predictor variable, were the best choice to predict DRPt and DPRP. Results showed that with the indirect risk assessment means (wind tunnel and PDPA laser measurement), driftability experiments can be made with different spraying systems under directly comparable and repeatable conditions and both methods are suited to permit relative studies of drift risk. Moreover, based on these indirect drift measurements and a statistical drift prediction equation for the reference spraying, it is possible to come to a realistic estimate of field drift data at a driving speed of 8 km.h(-1) and a boom height of 0.50 m.

Direct and indirect drift assessment means. Part 3: field drift experiments.

A whole series of field drift experiments were performed to investigate the effect of nozzle type (flat fan, low-drift, air inclusion) and size (ISO 02, 03, 04 and 06) on sedimenting spray drift. Sedimenting spray drift was determined by sampling in a downwind area at 24 different positions using horizontal drift collectors in combination with a fluorescent tracer with measurements up to 20 m from the directly sprayed zone. Meteorological conditions were continuously monitored. Based on 27 drift experiments with the reference spraying at various environmental conditions, the important effect of atmospheric conditions on the amount of near-field sedimenting spray drift was demonstrated and quantified. A non-linear drift prediction equation was set up and validated. This equation was used to compare the drift results of the different spraying techniques under various weather conditions with the reference spraying by calculating their total drift reduction potential (DRPt). Air inclusion nozzles have the highest drift reduction potential followed by the low-drift nozzles and the standard flat fan nozzles and the effect on drift deposits is high with DRPt values varying from -136.5 up to 89.8%. The effect of nozzle type is most important for smaller nozzle sizes A large database with (absolute) near-field drift results is made available to enlarge the international drift database with information about the effect of climatological conditions and spray application technology. The results are generally in good agreement with the results from different other studies although drift studies are difficult to compare due to differences in weather conditions, spray application techniques, methodologies and crop conditions.

The effect of air support on droplet characteristics and spray drift.

Air assistance on field sprayers creates a forced airstream under the spray boom which blows the spray droplets into the crop. The advantages of this relative new technique are less drift of spray droplets and the possibility to reduce the amount of pesticides and spray Liquid. The purpose of this work was to investigate the effect of air assistance on the characteristics of spray droplets and their driftability. Based on air velocity measurements on an air assisted field sprayer, a system of air assistance was developed in addition to a laser-based measuring set-up for the characterisation of spray droplets. With this set-up, the effect of air support on the droplet characteristics was investigated for different settings of the air assistance. The effect on spray drift was quantified based on field drift measurements. A reducing effect on the total amount of spray drift was demonstrated for the Hardi ISO F 110 02, F 110 03 and LD 110 02 nozzles with drift reduction factors a(d) of, respectively, 2.08, 1.77 and 1.53. The use of air support had no significant effect for the LD 110 03 nozzles on the total amount of spray drift. Comparing droplet size and drift results, it was found that air support has the highest impact on the amount of spray drift for the finer sprays by increasing droplet velocities. The effect of air support on droplet sizes is rather limited.

Classification of spray nozzles based on droplet size distributions and wind tunnel tests.

Droplet size distribution of a pesticide spray is recognised as a main factor affecting spray drift. As a first approximation, nozzles can be classified based on their droplet size spectrum. However, the risk of drift for a given droplet size distribution is also a function of spray structure, droplet velocities and entrained air conditions. Wind tunnel tests to determine actual drift potentials of the different nozzles have been proposed as a method of adding an indication of the risk of spray drift to the existing classification based on droplet size distributions (Miller et al, 1995). In this research wind tunnel tests were performed in the wind tunnel of the International Centre for Eremology (I.C.E.), Ghent University, to determine the drift potential of different types and sizes of nozzles at various spray pressures. Flat Fan (F) nozzles Hardi ISO 110 02, 110 03, 110 04, 110 06; Low-Drift (LD) nozzles Hardi ISO 110 02, 110 03, 110 04 and Injet Air Inclusion (AI) nozzles Hardi ISO 110 02, 110 03, 110 04 were tested at a spray pressures of 2, 3 and 4 bar. The droplet size spectra of the F and the LD nozzles were measured with a Malvern Mastersizer at spray pressures 2 bar, 3 bar and 4 bar. The Malvern spectra were used to calculate the Volume Median Diameters (VMD) of the sprays.

Spray drift as affected by meteorological conditions.

Spray drift can be defined as the quantity of plant protection product that is carried out of the sprayed (treated) area by the action of air currents during the application process. This continues to be a major problem in applying agricultural pesticides. The purpose of this research is to measure and compare the amount of drift for different climatological conditions under field conditions. Spray drift was determined by sampling in a defined downwind area at different positions in a flat meadow using horizontal drift collectors (sedimenting spray drift) and pipe cleaners (airborne spray drift) for a reference spraying. Meteorological conditions were monitored during each experiment. A drift prediction equation for the reference spraying was set up to predict the expected magnitude of sedimenting drift at various drift distances and atmospheric conditions (wind speed and temperature). This equation can be used to compare measurements using other spraying techniques under different weather conditions to the reference spraying. In 2005, more measurements will be performed to validate the statements and the model reflected in this paper.

A pdpa laser-based measuring set-up for the characterisation of spray nozzles.

The characteristics of agricultural sprays belong to the most critical factors affecting spray drift, deposition on plants, spray coverage and biological efficacy. Hence, within the framework of a research project about agricultural spray drift, a measuring set-up for the characterisation of spray nozzles using a Phase Doppler Particle Analyser (PDPA) was developed. This set-up is able to measure droplet sizes and velocities based on light-scattering principles. It is composed of different parts i.e.: a climate room, a spray unit, a three-dimensional automated positioning system and an Aerometrics PDPA 1D system. This paper presents a detailed description of this measuring set-up along with some first measuring results. These measurements will be used as an input for a Computational Fluid Dynamics drift-prediction model and to classify nozzles based on their driftability.

Wind tunnel evaluation of several tracer and collection techniques for the measurement of spray drift.

In the history of pesticide drift measuring techniques, different tracers and a lot of different collection techniques have been used. At the start of a new Flemish project 'Protecting the Flemish environment against drift - The importance of drift-reducing techniques', wind tunnel tests have been executed to select the most efficient tracer and collection technique. As tracer types a fluorescent tracer Renaissance W15, 2 different chelates, a NaCl-solution and a fungicide Tolylfluanide were used. 2 different collection techniques were tested: drains incorporated in the wind tunnel floor filled with filter paper and filled with cloths. The recovery of the different tracers combined with the 2 collection materials was calculated. The advantages and disadvantages of the tracers and collection materials are enumerated in this article.