1,432 research outputs found
Cumulants of Hawkes point processes
We derive explicit, closed-form expressions for the cumulant densities of a
multivariate, self-exciting Hawkes point process, generalizing a result of
Hawkes in his earlier work on the covariance density and Bartlett spectrum of
such processes. To do this, we represent the Hawkes process in terms of a
Poisson cluster process and show how the cumulant density formulas can be
derived by enumerating all possible "family trees", representing complex
interactions between point events. We also consider the problem of computing
the integrated cumulants, characterizing the average measure of correlated
activity between events of different types, and derive the relevant equations.Comment: 11 pages, 4 figure
An Analysis of Multiple Configurations of Next-Generation Cathodes in a Low Power Hall Thruster
The research presented here is an effort to integrate an existing hollow cathode design with a low power production Hall thruster in multiple geometries. Both externally- and internally-mounted cathodes were fabricated and operated in conjunction with a Busek BHT-1500 Hall thruster. Three insert materials were evaluated; Cerium Hexaboride (CeB6), Lanthanum Hexaboride (LaB6), and impregnated tungsten. The thruster was operated at a single operating condition for all testing. The operating specifications for the discharge were 300 V and 2.25 A, giving a total power of 675 W. The boride-based cathodes were tested in both geometries while the tungsten-based cathode was only tested in an external configuration. A Faraday probe was used to measure current density in the plume and a single Langmuir probe was used to characterize the plasma. The charge state of the ions was measured with an ExB probe. All assembly and testing occurred at the Air Force Institute of Technology\u27s (AFIT) Space Propulsion Analysis and System Simulation (SPASS) lab facility. The thruster\u27s performance with the externally-mounted boride-based cathodes installed demonstrated the highest levels of efficiency and performance. The thruster\u27s performance with the tungsten-based cathode installed was slightly less than with the externally-mounted boride-based cathodes. The lowest thruster performance occurred with the internally-mounted cathodes installed. The primary loss mechanism observed was an increase in multiply-ionized propellant with the internally-mounted cathodes
Baseline characteristics and enrichment results from the SONAR trial
Aim:
The SONAR trial uses an enrichment design based on the individual response to the selective endothelin receptor antagonist atrasentan on efficacy (the degree of the individual response in the urinary albuminâtoâcreatinine ratio [UACR]) and safety/tolerability (signs of sodium retention and acute increases in serum creatinine) to assess the effects of this agent on major renal outcomes. The patient population and enrichment results are described here.
Methods:
Patients with type 2 diabetes with an estimated glomerular filtration rate (eGFR) within 25 to 75âmL/min/1.73âm2 and UACR between 300 and 5000âmg/g were enrolled. After a runâin period, eligible patients received 0.75âmg/d of atrasentan for 6âweeks. A total of 2648 responder patients in whom UACR decreased by â„30% compared to baseline were enrolled, as were 1020 nonâresponders with a UACR decrease of <30%. Patients who experienced a weight gain of >3âkg and in whom brain natriuretic peptide exceeded â„300âpg/mL, or who experienced an increase in serum creatinine >20% (0.5âmg/dL), were not randomized.
Results:
Baseline characteristics were similar for atrasentan responders and nonâresponders. Upon entry to the study, median UACR was 802âmg/g in responders and 920âmg/g in nonâresponders. After 6âweeks of treatment with atrasentan, the UACR change in responders was â48.8% (95% CI, â49.8% to â47.9%) and in nonâresponders was â1.2% (95% CI, â6.4% to 3.9%). Changes in other renal risk markers were similar between responders and nonâresponders except for a marginally greater reduction in systolic blood pressure and eGFR in responders.
Conclusions:
The enrichment period has successfully identified a population with a profound UACR reduction without clinical signs of sodium retention in whom a large atrasentan effect on clinically important renal outcomes is possible. The SONAR trial aims to establish whether atrasentan confers renal protection
Beliefs around luck : confirming the empirical conceptualization of beliefs around luck and the development of the Darke and Freedman beliefs around luck scale
The current study developed a multi-dimensional measure of beliefs around luck. Two studies introduced the Darke and Freedman beliefs around luck scale where the scale showed a consistent 4 component model (beliefs in luck, rejection of luck, being lucky, and being unlucky) across two samples (n = 250; n = 145). The scales also show adequate reliability statistics and validity by ways of comparison with other measures of beliefs around luck, peer and family ratings and expected associations with measures of personality, individual difference and well-being variables
Effect of flange and stiffener rigidity on the boundary conditions and shear buckling stress of plate girders
FRP Strengthening of Web Panels of Steel Plate Girders against Shear Buckling under Static and Cyclic Loading
Coupling between diffusion and orientation of pentacene molecules on an organic surface.
The realization of efficient organic electronic devices requires the controlled preparation of molecular thin films and heterostructures. As top-down structuring methods such as lithography cannot be applied to van der Waals bound materials, surface diffusion becomes a structure-determining factor that requires microscopic understanding. Scanning probe techniques provide atomic resolution, but are limited to observations of slow movements, and therefore constrained to low temperatures. In contrast, the helium-3 spin-echo (HeSE) technique achieves spatial and time resolution on the nm and ps scale, respectively, thus enabling measurements at elevated temperatures. Here we use HeSE to unveil the intricate motion of pentacene admolecules diffusing on a chemisorbed monolayer of pentacene on Cu(110) that serves as a stable, well-ordered organic model surface. We find that pentacene moves along rails parallel and perpendicular to the surface molecules. The experimental data are explained by admolecule rotation that enables a switching between diffusion directions, which extends our molecular level understanding of diffusion in complex organic systems.The authors acknowledge financial support from the EPSRC (EP/E0049621, B.A.J.L., D.J.W., D.M.C., A.P.J., J.E., W.A.), the Austrian Academy of Sciences (B.A.J.L.), the Royal Society (A.P.J.), the E.U. ERASMUS programme (A.M.) and the Deutsche Forschungsgemeinschaft (GRK 1782, P.R.). Underlying data are available at the University of Cambridge Research data repository (https://www.repository.cam.ac.uk).This is the author accepted manuscript. The final version is available from Nature Publishing Group via http://dx.doi.org/10.1038/nmat457
Self-Pity: Exploring the Links to Personality, Control Beliefs, and Anger
Self-pity is a frequent response to stressful events. So far, however, empirical research has paid only scant attention to this subject. The present article aims at exploring personality characteristics associated with individual differences in feeling sorry for oneself. Two studies with N = 141 and N = 161 university students were conducted, employing multidimensional measures of personality, control beliefs, anger, loneliness, and adult attachment. With respect to personality, results showed strong associations of self-pity with neuroticism, particularly with the depression facet. With respect to control beliefs, individuals high in self-pity showed generalized externality beliefs, seeing themselves as controlled by both chance and powerful others. With respect to anger expression, self-pity was primarily related to anger-in. Strong connections with anger rumination were also found. Furthermore, individuals high in self-pity reported emotional loneliness and ambivalent-worrisome attachments. Finally, in both studies, a strong correlation with gender was found, with women reporting more self-pity reactions to stress than men. Findings are discussed with respect to how they support, extend, and qualify the previous literature on self-pity, and directions for future empirical research are pointed out
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