Characterization and Analysis of Integrated Silicon Photonic Detectors for High-Speed Communications

As the digital age of rapidly expanding information systems and technology continue to grow and develop at an ever increasing rate, new fabrication media must be investigated in order to keep up with these trends. The modern age has been defined by the innovation and advancement of the semiconductor transistor specifically Silicon, however these days of exponential performance gain through gate minimization are coming to a close. One such field which shows great promise for meeting the challenges of the future is the integration of photonic and complementary metal oxide semiconductor components; leveraging the long standing fabrication history of Silicon devices. This document describes the characterization and analysis of integrated photodiodes for digital and analog applications. The photodiode is one small but necessary component for the integration of system-level photonic devices. A number of standard measurements were taken on the photodiodes to analyze their performance and potential application. Additionally, an anomalous detector behavior was investigated through both transient measurements to identify the driving mechanism of the abnormality. Through this testing the devices were found to perform with up to 30-GHz of bandwidth while maintaining dark currents below 5 nA. The non-linear behavior was observed under CW conditions and analyzed using the transient response of the photodiode. The transient response of the photodiode supported that the non-linear mechanism was photon-induced avalanche-like effect, however, further investigation is required. Additional work is described to further investigate this behavior, as well to identify potential effects on future application in system level communication designs

Can angular momentum loss cause the period change of NN Ser?

NN Ser is a non mass-transferring pre-cataclysmic variable containing a white dwarf with a mass of $\sim 0.5 M_{\odot}$ and an M dwarf secondary star with a mass of $\sim 0.2 M_{\odot}$. Based on the data detected by the high-speed CCD camera ULTRACAM, it was observed that the orbital period of NN Ser is decreasing, which may be caused by a genuine angular momentum loss or the presence of a third body. However, neither gravitational radiation and magnetic braking can ideally account for the period change of NN Ser. In this Letter, we attempt to examine a feasible mechanism which can drain the angular momentum from NN Ser. We propose that a fossil circumbinary disk (CB disk) around the binary may have been established at the end of the common envelope phase, and the tidal torques caused by the gravitational interaction between the disk and the binary can efficiently extract the orbital angular momentum from the system. We find that only if M dwarf has an ultra-high wind loss rates of $\sim 10^{-10} M_{\odot} \rm yr^{-1}$, and a large fraction ($\delta\sim 10$) of wind loss is fed into the CB disk, the loss rates of angular momentum via the CB disk can interpret the period change observed in NN Ser. Such a wind loss rate and $\delta$-value seem to be incredible. Hence it seems that the presence of a third body in a long orbit around the binary might account for the changing period of NN Ser.Comment: 4 pages, accepted for publication in A&A Letter

Astroclimatic Characterization of Vallecitos: A candidate site for the Cherenkov Telescope Array at San Pedro Martir

We conducted an 18 month long study of the weather conditions of the Vallecitos, a proposed site in Mexico to harbor the northern array of the Cherenkov Telescope Array (CTA). It is located in Sierra de San Pedro Martir (SPM) a few kilometers away from Observatorio Astron\'omico Nacional. The study is based on data collected by the ATMOSCOPE, a multi-sensor instrument measuring the weather and sky conditions, which was commissioned and built by the CTA Consortium. Additionally, we compare the weather conditions of the optical observatory at SPM to the Vallecitos regarding temperature, humidity, and wind distributions. It appears that the excellent conditions at the optical observatory benefit from the presence of microclimate established in the Vallecitos.Comment: 16 pages, 16 figures, Publication of the Astronomical Society of the Pacific, accepte

Low-lying GT(+) strength in Co-64 studied via the Ni-64(d,He-2)Co-64 reaction

The Ni-64(d,He-2)Co-64 reaction was studied at the AGOR cyclotron of KVI, Groningen, with the Big-Bite Spectrometer and the EuroSuperNova detector using a 171-MeV deuteron beam. An energy resolution of about 110 keV was achieved. In addition to the J(pi) = 1(+) ground state, several other 1(+) states could be identified in Co-64 and the strengths of the corresponding Gamow-Teller transitions were determined. The obtained strength distribution was compared with theoretical predictions and former (n,p) experimental results and displayed a good agreement. Due to the good energy resolution, detailed spectroscopic information was obtained, which supplements the data base needed for network calculations for supernova scenarios

Squamous cell carcinoma of the vulva in a patient with androgen insensitivity syndrome

The first case of squamous cell carcinoma of the vulva in a patient with androgen insensitivity syndrome is described.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/28491/1/0000287.pd

Distance to the RR Lyrae Star V716 Monocerotis

We present high quality BVRI CCD photometry of the variable star V716 Monocerotis (= NSV 03775). We confirm it to be an RR Lyrae star of variability type ab (i.e. a fundamental mode pulsator), and determine its metallicity ([Fe/H] = -1.33 +/- 0.25), luminosity (Mv = 0.80 +/- 0.06), and foreground reddening (E(B-V) = 0.05-0.17) from the Fourier components of its light curve. These parameters indicate a distance of 4.1 +/- 0.3 kpc, placing V716 Mon near the plane of the Galaxy well outside the solar circle. This research was conducted as part of the 1999 Research Experiences for Undergraduates (REU) and Practicas de Investigacion en Astronomia (PIA) Programs at Cerro Tololo Inter-American Observatory (CTIO).Comment: 9 pages including 2 figures and 2 tables; accepted by PAS

DE Canum Venaticorum : a bright, eclipsing red dwarf–white dwarf binary

Context. Close white dwarf–red dwarf binaries must have gone through a common-envelope phase during their evolution. DE CVn is a detached white dwarf–red dwarf binary with a relatively short (∼8.7 h) orbital period. Its brightness and the presence of eclipses makes this system ideal for a more detailed study. Aims. From a study of photometric and spectroscopic observations of DE CVn we derive the system parameters that we discuss in the framework of common-envelope evolution. Methods. Photometric observations of the eclipses are used to determine an accurate ephemeris. From a model fit to an average lowresolution spectrum of DE CVn, we constrain the temperature of the white dwarf and the spectral type of the red dwarf. The eclipse light curve is analysed and combined with the radial velocity curve of the red dwarf determined from time-resolved spectroscopy to derive constraints on the inclination and the masses of the components in the system. Results. The derived ephemeris is HJDmin = 2 452 784.5533(1) + 0.3641394(2) × E. The red dwarf in DE CVn has a spectral type of M3V and the white dwarf has an effective temperature of 8 000 K. The inclination of the system is 86+3◦ −2 and the mass and radius of the red dwarf are 0.41 ± 0.06 M and 0.37+0.06 −0.007 R, respectively, and the mass and radius of the white dwarf are 0.51+0.06 −0.02 M and 0.0136+0.0008 −0.0002 R, respectively. Conclusions. We found that the white dwarf has a hydrogen-rich atmosphere (DA-type). Given that DE CVn has experienced a common-envelope phase, we can reconstruct its evolution and we find that the progenitor of the white dwarf was a relatively lowmass star (M ≤ 1.6 M). The current age of this system is 3.3−7.3 × 109 years, while it will take longer than the Hubble time for DE CVn to evolve into a semi-detached system