Characterization of Power-to-Phase Conversion in High-Speed P-I-N Photodiodes

Fluctuations of the optical power incident on a photodiode can be converted into phase fluctuations of the resulting electronic signal due to nonlinear saturation in the semiconductor. This impacts overall timing stability (phase noise) of microwave signals generated from a photodetected optical pulse train. In this paper, we describe and utilize techniques to characterize this conversion of amplitude noise to phase noise for several high-speed (>10 GHz) InGaAs P-I-N photodiodes operated at 900 nm. We focus on the impact of this effect on the photonic generation of low phase noise 10 GHz microwave signals and show that a combination of low laser amplitude noise, appropriate photodiode design, and optimum average photocurrent is required to achieve phase noise at or below -100 dBc/Hz at 1 Hz offset a 10 GHz carrier. In some photodiodes we find specific photocurrents where the power-to-phase conversion factor is observed to go to zero

The Merging History of Massive Black Holes

We investigate a hierarchical structure formation scenario describing the evolution of a Super Massive Black Holes (SMBHs) population. The seeds of the local SMBHs are assumed to be 'pregalactic' black holes, remnants of the first POPIII stars. As these pregalactic holes become incorporated through a series of mergers into larger and larger halos, they sink to the center owing to dynamical friction, accrete a fraction of the gas in the merger remnant to become supermassive, form a binary system, and eventually coalesce. A simple model in which the damage done to a stellar cusps by decaying BH pairs is cumulative is able to reproduce the observed scaling relation between galaxy luminosity and core size. An accretion model connecting quasar activity with major mergers and the observed BH mass-velocity dispersion correlation reproduces remarkably well the observed luminosity function of optically-selected quasars in the redshift range 1<z<5. We finally asses the potential observability of the gravitational wave background generated by the cosmic evolution of SMBH binaries by the planned space-born interferometer LISA.Comment: 4 pages, 2 figures, Contribute to "Multiwavelength Cosmology", Mykonos, Greece, June 17-20, 200

Where are we short and who are we short of? A review of the human resources for health in South Africa

This review showed that thinking about the shortage of health care personnel merely in terms of insufficient numbers prevents sound strategic interventions to solve the country’s human resources for health (HRH) problem. It revealed that the numbers shortage was one facet of a broader problem that included the mal distribution of HRH, production of the wrong skills in the nursing care, the attrition of staff from the public health services and, contextually, the ever-changing demands on the health services. The challenge in South Africa was furthermore to train and retain health care personnel with skills and expertise that are commensurate with the changing demands on the public health services.Uit hierdie oorsig het dit duidelik geblyk dat die tekort van gesondheidsorgpersoneel slegs in terme van ontoereikende getalle val en ’n omvattende strategiese ingryping om die land se menslike gesondheidshulpbron krisis op te los, belemmer. Dit het aangedui dat die getalletekort maar slegs een fasset van ’n groter probleem uitmaak, wat onder andere die volgende insluit: die oneweredige verspeiding van menslike gesondheidshulpbronne, ’n fokus op ontoepaslike vaardighede in die opleiding van verpleegpersoneel, die behoud van personeel in die openbare gesondheidsektor, asook die konstant-veranderlike eise van die gesondheidsdienste. Verder was die uitdaging in Suid Afrika die opleiding en behoud van gesondheidsorgpersoneel met kennis en vaardighede wat tred hou met die veranderlike eise van die openbare gesondheidsdienste

A Non-Sequential Representation of Sequential Data for Churn Prediction

We investigate the length of event sequence giving best predictions when using a continuous HMM approach to churn prediction from sequential data. Motivated by observations that predictions based on only the few most recent events seem to be the most accurate, a non-sequential dataset is constructed from customer event histories by averaging features of the last few events. A simple K-nearest neighbor algorithm on this dataset is found to give significantly improved performance. It is quite intuitive to think that most people will react only to events in the fairly recent past. Events related to telecommunications occurring months or years ago are unlikely to have a large impact on a customer’s future behaviour, and these results bear this out. Methods that deal with sequential data also tend to be much more complex than those dealing with simple nontemporal data, giving an added benefit to expressing the recent information in a non-sequential manner

“Practitioner Wellness, Person Centered Healthcare, Reflective Practice and the Mission of Mindfulness Training. ” Commentary on Garneau, K., Hutchinson, T., Zhan, Q. & Dobkin, P.L. (2013). Cultivating Person-Centered Medicine in Future Physicians. European Journal of Person Centered Medicine 1 (2) 468-477

A primary purpose of healthcare is the enhancement of health, wellbeing and in understanding and responding to the illness experience in individual patients

Sub-femtosecond absolute timing precision with a 10 GHz hybrid photonic-microwave oscillator

We present an optical-electronic approach to generating microwave signals with high spectral purity. By circumventing shot noise and operating near fundamental thermal limits, we demonstrate 10 GHz signals with an absolute timing jitter for a single hybrid oscillator of 420 attoseconds (1Hz - 5 GHz)

A Hybrid N-body--Coagulation Code for Planet Formation

We describe a hybrid algorithm to calculate the formation of planets from an initial ensemble of planetesimals. The algorithm uses a coagulation code to treat the growth of planetesimals into oligarchs and explicit N-body calculations to follow the evolution of oligarchs into planets. To validate the N-body portion of the algorithm, we use a battery of tests in planetary dynamics. Several complete calculations of terrestrial planet formation with the hybrid code yield good agreement with previously published calculations. These results demonstrate that the hybrid code provides an accurate treatment of the evolution of planetesimals into planets.Comment: Astronomical Journal, accepted; 33 pages + 11 figure

Understanding change resistance through the lens of the psychological contract : implications for change agents

1 online resource (25, [2] p.) : col. ill.Includes abstract.Includes bibliographical references (p. [26-27]).The change agent, if attentive to the implication of the employee’s psychological contract, can take action to help the employee transform the psychological contract by perceiving resistance to change as a form of positive feedback. Approaching change with help from the lens provided by a psychological contract will enable change agents to consider the desired change from the perspective of the employee, and also to understand better a wide spectrum of reasons for resistance. The psychological contract is an important tool for the change agent, and the key to everyone’s benefiting from the positive, and sometimes more practical, elements in resistance to change. This research will explore the change agent’s role in activating the change recipient’s psychological contract transformation by determining why change agents perceive resistance and how they can use resistance confidently. It will present a model of the factors that influence individual perception. It is beneficial to everyone, the employer as well as the employees, for the change agent to understand the implications of psychological contract breach and violation, to regard resistance as a normal reaction to change, and to know how the actions of the change agent will have an impact on the outcome

Intersecting Race, Health, and Law: Consequences of the Public Charge Rule for the U.S. Hispanic Population

On February 24, 2020, United States Citizenship and Immigration Services (USCIS) effected the Inadmissibility on Public Charge Grounds Final Rule (Public Charge Rule). The Public Charge Rule denies admission or denial of application or petition for an extension of stay or a change of status to any noncitizen who is deemed likely at any time to become a “public charge.” A public charge determination is based on a noncitizen’s use of specified public benefits, including Medicaid. I argue that a mass disenrollment by immigrants from Medicaid will cause severe poor health outcomes and economic burden on their local communities. The Public Charge Rule will lead to a decrease in Medicaid and CHIP enrollment by millions of otherwise eligible, noncitizen immigrants and their U.S. citizen children and family members. In effect, a loss of insurance coverage will lead to the public health implication of widespread poor health outcomes. Lastly, the Public Charge Rule will cause downstream tax burdens on local economies due to a consequential rise in uncompensated care provided in hospitals. The Public Charge Rule’s alleged purposes purported by the former Trump administration are unfulfilled. Instead, the Public Charge Rule discriminates against immigrants based on their class and follows the U.S. government’s longstanding tradition of racism toward immigrants