Atmospheric electric fields during thunderstorm conditions measured by LOFAR

Sterke atmosferische elektrische velden hebben een aanzienlijk effect op de radio-emissie van cascades van secondaire deeltjes in de atmosfeer (deeltjeslawines) die door kosmische stralen worden geinitieerd, zelfs als deze velden niet sterk genoeg zijn om de bliksemactiviteit te veroorzaken. Metingen van de radio-emissie van de deeltjeslawines bij LOFAR laten zien dat de intensiteit en polarisatie van de radio emissie van de lawine gemeten onder "onweer" omstandigheden zeer verschillend zijn van de waarden tijdens mooi weer. Om deze reden kunnen de "onweers" gebeurtenissen worden gebruikt om de atmosferische elektrische velden te bepalen. Deze techniek is uitgelegd en ontwikkeld in dit proefschrift. Het is aangetoond dat, om deze gebeurtenissen te reconstrueren, de atmosferische elektrische velden in wolken over het algemeen samengesteld is uit drie lagen. De elektrische velden geëxtraheerd uit deze gebeurtenissen hebben grote horizontale componenten van de elektrische velden in de middelste en bovenste lagen. De hoogte van de onderste laag is afhankelijk van het seizoen

Analytic Calculation of Radio Emission from Extensive Air Showers subjected to Atmospheric Electric Fields

We have developed a code that semi-analytically calculates the radio footprint (intensity and polarization) of an extensive air shower subject to atmospheric electric fields. This can be used to reconstruct the height dependence of atmospheric electric field from the measured radio footprint. The various parameterizations of the spatial extent of the induced currents are based on the results of Monte-Carlo shower simulations. The calculated radio footprints agree well with microscopic CoREAS simulations.Comment: Contribution to the proceedings of the ARENA conference, Groningen, The Netherlands, June 7-10, 201

Influence of atmospheric electric fields on radio emission from air showers

We show that atmospheric electric fields as exist in thunderclouds can strongly affect the radio emission from cosmic air showers. We also show, using data from LOFAR, that from the measured radio footprint of cosmic-ray air showers, i.e. intensity, linear and circular polarization at various distances from the shower core, one can determine the direction and strength of the electric field as function of height along the path of the cosmic ray. This method can be regarded as tomography of thundercloud electric fields using cosmic rays as probes. We will present an analysis of selected events measured during thunderstorm conditions in the period from December 2011 till August 2014. The fields we extract are consistent with the generally accepted charge structure in thunderclouds consisting out of three charge layers.</p

Influence of atmospheric electric fields on radio emission from air showers

We show that atmospheric electric fields as exist in thunderclouds can strongly affect the radio emission from cosmic air showers. We also show, using data from LOFAR, that from the measured radio footprint of cosmic-ray air showers, i.e. intensity, linear and circular polarization at various distances from the shower core, one can determine the direction and strength of the electric field as function of height along the path of the cosmic ray. This method can be regarded as tomography of thundercloud electric fields using cosmic rays as probes. We will present an analysis of selected events measured during thunderstorm conditions in the period from December 2011 till August 2014. The fields we extract are consistent with the generally accepted charge structure in thunderclouds consisting out of three charge layers

Determining atmospheric electric fields through radio emmission from air showers

During thunderstorm conditions the radio footprint (intensity as well as polarization) of cosmic ray showers deviates strongly from those measured during fair weather. We have been able to interpret this pattern in terms of atmospheric electric fields. We see that even when there is no thunderstorm activity within 100 km distance within an hour of the event, the radio footprint may be strongly affected

Efek penambahan ekstrak daun mangga arumanis (Mangifera indica l.) pada antibiotik klindamisin dalam menghambat pertumbuhan bakteri Staphylococcus aureus

Staphylococcus aureus termasuk bakteri yang cukup sering dijumpai pada mulut, terutama pada kasus abses periodontal di mana perawatannya memerlukan pemakaian antibiotik. Tingginya angka resisten bakteri Staphylococcus aureus terhadap antibiotik menyebabkan banyaknya dicari pengobatan alternatif menggunakan herbal. Melihat efek penambahan ekstrak daun mangga arumanis (Mangifera indica L.) pada antibiotik klindamisin dalam menghambat pertumbuhan bakteri Staphylococcus aureus. Jenis dari penelitian ini adalah eksperimental laboratorium secara in vitro dengan 25 sampel. Konsentrasi ekstrak daun mangga yang digunakan 25%, 50%, 75%, 100% dan kelompok kontrol. Ekstrak dibuat dengan teknik maserasi dan uji daya hambat dengan metode Kirbi bauer. Hasil dianalisis menggunakan statistik ANOVA, lalu dilanjutkan dengan Post Hoc LSD. Hasil penelitian ini menunjukkan bahwa penambahan ekstrak 50%, 75%, 100% meningkatkan daya hambat terhadap Staphylococcus aureus (p=0,000) dibandingkan kelompok kontrol. Semakin tinggi konsentrasi yang digunakan, maka semakin besar zona hambat yang terbentuk. Sedangkan penambahan ekstrak 25% tidak meningkatkan daya hambat (p=0,618) bila dibandingkan dengan kelompok kontrol. Penambahan ekstrak daun mangga arumanis dengan klindamisin dapat meningkatkan aktivitas antibakteri terhadap Staphylococcus aureus

Calculation of the pressure on the valves of a sluice

This paper is devoted to a numerical method for calculating the pressure on the vertical two-dimensional valve basing on Navier-Stokes equations. Numerical solutions at interior points are established by splitting Navie-Stokes unsteady two-dimensional equations into two unsteady one-dimensional equations. An implicit scheme is obtained and the solution for these equations is established by the double sweep method. The values at the boundary points are calculated by the method of characteristics