Nutrients Export by Rivers to the Coastal Waters of Africa: Past and Future trends

We analyze past and future trends in nitrogen (N), phosphorus (P), and carbon (C) export by rivers to the coastal waters of Africa as calculated by the Global Nutrient Export to WaterShed (NEWS) models for the period 1970–2050. Between 1970 and 2000 the total nutrient export by African rivers increased by 10–80%. For future years (2000–2050) we calculate an increase in the total loads of dissolved forms of N and P, but decreasing trends for dissolved organic C and particulate forms of N and P. There are large regions that deviate from these pan-African trends. We explore the regional patterns and the underlying processes, in particular for the Nile, Zaire, Niger, and Zambezi. In the future, anthropogenic sources may, in large parts of Africa, become larger contributors to riverine nutrient loads than natural source

Electrostatic Structures in Space Plasmas: Stability of Two-dimensional Magnetic Bernstein-Greene-Kruskal Modes

Electrostatic structures have been observed in many regions of space plasmas, including the solar wind, the magnetosphere, the auroral acceleration region, and in association with shocks, turbulence, and magnetic reconnection. Due to potentially large amplitude of electric fields within these structures, their effects on particle heating, scattering, or acceleration can be important. One possible theoretical description of some of these structures is the concept of Bernstein-Greene-Kruskal (BGK) modes, which are exact nonlinear solutions of the Vlasov-Poisson system of equations in collisionless kinetic theory. BGK modes have been studied extensively for many decades, predominately in one dimension (1D), although there have been observations showing that some of these structures have clear 3D features. While there have been approximate solutions of higher dimensional BGK modes, an exact 3D BGK mode solution in a finite magnetic field has not been found yet. Recently we have constructed exact solutions of 2D BGK modes in a magnetized plasma with finite magnetic field strength in order to gain insights of the ultimate 3D theory [Ng, Bhattacharjee, and Skiff, Phys. Plasmas 13, 055903 (2006)]. Based on the analytic form of these solutions, as well as Particle-in-Cell (PIC) simulations, we will present numerical studies of their stability for different levels of background magnetic field strength.Comment: Submitted to AIP Journal Proceedings for "Tenth Annual International Astrophysics Conference

Mobility-Dependence of the Critical Density in Two-Dimensional Systems: An Empirical Relation

For five different electron and hole systems in two dimensions (Si MOSFET's, p-GaAs, p-SiGe, n-GaAs and n-AlAs), the critical density, $n_c$ that marks the onset of strong localization is shown to be a single power-law function of the scattering rate $1/\tau$ deduced from the maximum mobility. The resulting curve defines the boundary separating a localized phase from a phase that exhibits metallic behavior. The critical density $n_c \to 0$ in the limit of infinite mobility.Comment: 2 pages, 1 figur

Asynchronous Corner Tracking Algorithm based on Lifetime of Events for DAVIS Cameras

Event cameras, i.e., the Dynamic and Active-pixel Vision Sensor (DAVIS) ones, capture the intensity changes in the scene and generates a stream of events in an asynchronous fashion. The output rate of such cameras can reach up to 10 million events per second in high dynamic environments. DAVIS cameras use novel vision sensors that mimic human eyes. Their attractive attributes, such as high output rate, High Dynamic Range (HDR), and high pixel bandwidth, make them an ideal solution for applications that require high-frequency tracking. Moreover, applications that operate in challenging lighting scenarios can exploit the high HDR of event cameras, i.e., 140 dB compared to 60 dB of traditional cameras. In this paper, a novel asynchronous corner tracking method is proposed that uses both events and intensity images captured by a DAVIS camera. The Harris algorithm is used to extract features, i.e., frame-corners from keyframes, i.e., intensity images. Afterward, a matching algorithm is used to extract event-corners from the stream of events. Events are solely used to perform asynchronous tracking until the next keyframe is captured. Neighboring events, within a window size of 5x5 pixels around the event-corner, are used to calculate the velocity and direction of extracted event-corners by fitting the 2D planar using a randomized Hough transform algorithm. Experimental evaluation showed that our approach is able to update the location of the extracted corners up to 100 times during the blind time of traditional cameras, i.e., between two consecutive intensity images.Comment: Accepted to 15th International Symposium on Visual Computing (ISVC2020

Analysis of Environmental Carrying Capacity for the Development of Sustainable Settlement in Yogyakarta Urban Area

AbstractThe growth of urbanization in Yogyakarta area has a significant impact on environmental degradation. One of the indications is the environmental carrying capacity and environmental settlement quality that tend to decrease. The research was aimed to analyze the environmental carrying capacity of the settlement land resources and water resources as the development base of sustainable settlement in Yogyakarta Urban Area (YUA). The research method used a studio analysis based on primary and secondary data and available mathematical formulas. The results showed that the carrying capacity of settlement land resources in YUA reached 2.89 or conditionally-save. In addition, the analysis of water resources carrying capacity in YUA indicated a conditionally-save result with the value of 2.44. Land resources carrying capacity is considered as save when reaching 22.73%, conditionally save when the value is 60.60%, and overshoot when it reaches 16.67%. Meanwhile, water resources carrying capacity is entitled save if the value is 15.15%, conditionally-save if it reaches 74.24%, and overshoot if reaching 10.61%

Seeking an "i-deal" balance: Schedule-flexibility i-deals as mediating mechanisms between supervisor emotional support and employee work and home performance

Requests for flexible work practices have become commonplace, with the aim of helping employees perform more effectively in both their private and work lives. One path for employees to secure flexible work is through the negotiation of individualized work arrangements, also known as “i-deals”. This study provides valuable insights into the nomological network of scheduleflexibility i-deals by drawing on the Conservation of Resources (COR) theory. We propose that, via resource accumulation, schedule-flexibility i-deals are a mechanism through which the emotional support of supervisors promotes employees' family performance and reduces deviant work behaviors. Drawing further on the COR framework, we examine two boundary conditions that guide employees' resource investment: perception of family-friendly environment and prosocial motivation. We collected multi-source data from employees working in South America and tested our hypotheses using structural equation modeling. Our results provide support for the key mediating role of schedule-flexibility i-deals. Moreover, the indirect relationship between supervisors' emotional support and family performance through schedule-flexibility i-deals is stronger in family-friendly organizational contexts, as well as when employees are prosocially motivated. Our results also show that, contrary to the expected effect, when prosocial motivation is high, employee supervisors' emotional support is positively linked to deviant behaviors. We contribute to the literature by emphasizing the roles of perceived resources at the levels of leaders (i.e., supervisors' emotional support), context (supervisors' perceptions of a family-friendly environment), and individuals (employees' prosocial motivation). We demonstrate the importance of these resources in establishing and sustaining schedule-flexibility i-deal

Evidence for the η_b(1S) Meson in Radiative Υ(2S) Decay

We have performed a search for the η_b(1S) meson in the radiative decay of the Υ(2S) resonance using a sample of 91.6 × 10^6 Υ(2S) events recorded with the BABAR detector at the PEP-II B factory at the SLAC National Accelerator Laboratory. We observe a peak in the photon energy spectrum at E_γ = 609.3^(+4.6)_(-4.5)(stat)±1.9(syst) MeV, corresponding to an η_b(1S) mass of 9394.2^(+4.8)_(-4.9)(stat) ± 2.0(syst) MeV/c^2. The branching fraction for the decay Υ(2S) → γη_b(1S) is determined to be [3.9 ± 1.1(stat)^(+1.1)_(-0.9)(syst)] × 10^(-4). We find the ratio of branching fractions B[Υ(2S) → γη_b(1S)]/B[Υ(3S) → γη_b(1S)]= 0.82 ± 0.24(stat)^(+0.20)_(-0.19)(syst)

Medium modification of jet fragmentation in Au+Au collisions at sqrt(s_NN)=200 GeV measured in direct photon-hadron correlations

The jet fragmentation function is measured with direct photon-hadron correlations in p+p and Au+Au collisions at sqrt(s_NN)=200 GeV. The p_T of the photon is an excellent approximation to the initial p_T of the jet and the ratio z_T=p_T^h/p_T^\gamma is used as a proxy for the jet fragmentation function. A statistical subtraction is used to extract the direct photon-hadron yields in Au+Au collisions while a photon isolation cut is applied in p+p. I_ AA, the ratio of jet fragment yield in Au+Au to that in p+p, indicates modification of the jet fragmentation function. Suppression, most likely due to energy loss in the medium, is seen at high z_T. The fragment yield at low z_T is enhanced at large angles. Such a trend is expected from redistribution of the lost energy into increased production of low-momentum particles.Comment: 562 authors, 70 insitutions, 8 pages, and 3 figures. Submitted to Phys. Rev. Lett. v2 has minor changes to improve clarity. Plain text data tables for the points plotted in figures for this and previous PHENIX publications are (or will be) publicly available at http://www.phenix.bnl.gov/papers.htm