Charge and potential distributions for particles approaching substrates with regular structures

The charge and potential distributions for insulating particles approaching a substrate with regular insulating structures are studied by particle-in-cell numerical simulations. An elongated particle and substrate with elongated structures are considered for flowing plasmas. The role of the relative position of the particle and the substrate in their interactions is investigated. It is also demonstrated that the interactions are modified by photoemission due to directed UV light. The simulations are two dimensional with ions and electrons treated as individual particles.Comment: 5 pages, submitted to IEEE Trans Plasma Sc

Numerical simulations of the charging of dust particles by contact with hot plasmas

International audienceCharging of individual dust particles in contact with hot plasmas is studied by numerical methods. The dust particle is treated as a rigid solid body, composed by either perfectly insulating or conducting material. The collisionless plasma, consisting of electrons and singly charged ions, is simulated by Particle-in-Cell methods in two spatial dimensions. It is demonstrated that the surface conditions, i.e. roughness, of the dust particles are significant for the charging. In a streaming plasma, a dust grain develops an electric dipole moment which varies systematically with the relative plasma flow. The strength and direction of this dipole moment depends critically on the material. We observe also Langmuir oscillations excited in the vicinity of the particles, and analyze the spatial variation of their spectral distribution

On the Wake Structure in Streaming Complex Plasmas

The theoretical description of complex (dusty) plasmas requires multiscale concepts that adequately incorporate the correlated interplay of streaming electrons and ions, neutrals, and dust grains. Knowing the effective dust-dust interaction, the multiscale problem can be effectively reduced to a one-component plasma model of the dust subsystem. The goal of the present publication is a systematic evaluation of the electrostatic potential distribution around a dust grain in the presence of a streaming plasma environment by means of two complementary approaches: (i) a high precision computation of the dynamically screened Coulomb potential from the dynamic dielectric function, and (ii) full 3D particle-in-cell simulations, which self-consistently include dynamical grain charging and non-linear effects. The applicability of these two approaches is addressed

More than competition: exploring stakeholder identities at a grassroots cause-related sporting event

The purpose of this paper is to (a) explore stakeholder identities of a grassroots cause-related sporting event; and (b) gain a better understanding of how identities are related to stakeholder development, support of the event, and future intentions. We used a mixed methods research design that consisted of two studies: qualitative followed by quantitative. Study 1 explored stakeholder identities and how they are related to stakeholder development and support of the event, and Study 2 examined how future intentions regarding attendance, donations, and sponsor support differ based on levels of stakeholder identity. Sports marketing and non-profit management literature streams as well as identity theory and social capital theory informed our studies. The National Kidney Foundation Surf Festival was selected because it is a grassroots cause-related sporting event with financial success over the last two decades. In addition, a surf contest, an action sport, is a unique sport setting in the nonprofit sector, which offers insight to marketers seeking to target subcultures. The findings of the qualitative study revealed three identities relevant to participants: sport subculture, community, and cause. A framework emerged from the data that illustrated how these identities unite together to generate social capital, which is linked to effective volunteer and sponsorship management. Quantitative analysis through survey data provided further evidence of the impact of identification with a cause-related sport activity on consumer outcomes. Results indicated attendees with high surf-related identity are more likely to attend future Surf Festivals, have higher intentions to donate to the cause, and have higher sponsor purchase intentions compared to those with low self-identity with the sport subculture. The conclusion discusses implications, framing the findings through the intersection of the sports marketing and non-profit sector industries, and provides suggestions for future research.Ye

The integrated radiotherapeutic line

Zintegrowana linia radioterapeutyczna (ZLR) stanowi złożenie sprzętu i oprogramowania służącego do precyzyjnej radioterapii. W pierwszej kolejności w referacie wyjaśniono różnice pomiędzy teleradioterapią, a brachyterapią, które stanowią podstawowe rodzaje radioterapii. Następnie przedstawiono budowę i funkcje poszczególnych części ZLR: tomografu komputerowego, systemu planowania leczenia, symulatora i akceleratora. W dalszej kolejności przedstawiono typy komputerów sterujących ich pracą. Opis ten zawiera krótką charakterystykę konfiguracji, systemu operacyjnego, sposobu zasilania i komunikacji z pozostałymi komputerami. W referacie przedstawiono także modyfikacje ZLR, które były konieczne do uzyskania zadawalającego poziomu bezpieczeństwa napromienianych pacjentów. Na zakończenie referatu poruszono problematykę rozwoju linii terapeutycznej dla części brachyterapii jak i teleradioterapii.The Integrated Radiotherapeutic Line (IRL) constitutes composition of hardware and software for accurate radiotherapy. First, the paper explains the differences between teleradiotherapy and brachytherapy. Next, a structure of IRL is presented and functions of separate parts are described. The types of control computers are presented as well as a short technical characteristic of hardware, computer network and operating system. Another issue of the paper presents modifications of the Integrated Radiotherapeutic Line, which were necessary to achieve an appropriate level of patient’s safety. Problems arising in the course of the line integration are also presented. Finally, the paper presents issues of development of therapeutic line for brachytherapeutic part and teleradiotherapy part

Electron Wing-Like Structures Formed at a Negatively Charged Spacecraft Moving in a Magnetized Plasma

Spacecraft-plasma interactions are studied with self-consistent numerical simulations of magnetized plasmas, where electrons are strongly magnetized whereas ions are weakly magnetized. It is found that for a spacecraft in such a magnetized plasma corresponding to a low Earth orbit, electrons can be reflected from a negatively charged spacecraft and then guided by geomagnetic field lines. The reflected electrons can leave a sharp trail like wings if the spacecraft size is greater than an average electron gyroradius of the environment. Such an electron wing-like structure is associated with propagating Langmuir waves. This results in nontrivial asymmetric electrostatic potentials close to the spacecraft and even farther than the Debye screening distance. The convective electric field also gives rise to a differential potential of the spacecraft with respect to the plasma, resulting in yet another asymmetry in the plasma dynamics and the potential distribution around the spacecraft. These asymmetries in the plasma dynamics can significantly influence in-situ measurements of space plasma. The results show a good qualitative agreement with actual measurements by a satellite in the polar regions