Near-Infrared InGaAs Detectors for Background-limited Imaging and Photometry

Originally designed for night-vision equipment, InGaAs detectors are beginning to achieve background-limited performance in broadband imaging from the ground. The lower cost of these detectors can enable multi-band instruments, arrays of small telescopes, and large focal planes that would be uneconomical with high-performance HgCdTe detectors. We developed a camera to operate the FLIR AP1121 sensor using deep thermoelectric cooling and up-the-ramp sampling to minimize noise. We measured a dark current of 163$~e$- s$^{-1}$ pix$^{-1}$, a read noise of 87$~e$- up-the-ramp, and a well depth of 80k$~e$-. Laboratory photometric testing achieved a stability of 230 ppm hr$^{-1/2}$, which would be required for detecting exoplanet transits. InGaAs detectors are also applicable to other branches of near-infrared time-domain astronomy, ranging from brown dwarf weather to gravitational wave follow-up.Comment: Submitted to Proc. SPIE, Astronomical Telescopes + Instrumentation (2014

Precision of a Low-Cost InGaAs Detector for Near Infrared Photometry

We have designed, constructed, and tested an InGaAs near-infrared camera to explore whether low-cost detectors can make small (<1 m) telescopes capable of precise (<1 mmag) infrared photometry of relatively bright targets. The camera is constructed around the 640x512 pixel APS640C sensor built by FLIR Electro-Optical Components. We designed custom analog-to-digital electronics for maximum stability and minimum noise. The InGaAs dark current halves with every 7 deg C of cooling, and we reduce it to 840 e-/s/pixel (with a pixel-to-pixel variation of +/-200 e-/s/pixel) by cooling the array to -20 deg C. Beyond this point, glow from the readout dominates. The single-sample read noise of 149 e- is reduced to 54 e- through up-the-ramp sampling. Laboratory testing with a star field generated by a lenslet array shows that 2-star differential photometry is possible to a precision of 631 +/-205 ppm (0.68 mmag) hr^-0.5 at a flux of 2.4E4 e-/s. Employing three comparison stars and de-correlating reference signals further improves the precision to 483 +/-161 ppm (0.52 mmag) hr^-0.5. Photometric observations of HD80606 and HD80607 (J=7.7 and 7.8) in the Y band shows that differential photometry to a precision of 415 ppm (0.45 mmag) hr^-0.5 is achieved with an effective telescope aperture of 0.25 m. Next-generation InGaAs detectors should indeed enable Poisson-limited photometry of brighter dwarfs with particular advantage for late-M and L types. In addition, one might acquire near-infrared photometry simultaneously with optical photometry or radial velocity measurements to maximize the return of exoplanet searches with small telescopes.Comment: Accepted to PAS

Second Thoughts on Second Punishments: Redefining the Multiple Punishments Prohibition

The Fifth Amendment provides that no person shall be subject for the same offence to be twice put in jeopardy of life or limb. To the layperson twice put in jeopardy means twice tried. The Supreme Court has firmly established, however, that the Double Jeopardy Clause targets two kinds of multiplicity: multiple prosecutions and multiple punishments. The right against multiple punishments is less commonly understood than the right against multiple prosecutions. What does it mean to be punished twice for the same offense? What is the evil that the right guards against? The Court appears to have defined the prohibition in two ways. For years, it explained the right as a guarantee that defendants will suffer no greater punishment than that authorized by the legislature. The idea underlying this approach is that legislatures define the scope of punishments, and thus, punishment in excess of this legislative authorization is unconstitutionally multiple. Until recently, the Court seemed to have taken the position that legislative deference is the only function of the right against multiple punishments. In 1989, however, the Court held in United States v. Halpers that legislatively authorized civil sanctions cannot be imposed in a separate proceeding after the defendant has been prosecuted and punished. The Halper Court thus seemed to define multiple punishments in terms of proceedings rather than legislative maximums. These two approaches to the multiple punishments prohibition coexist uneasily. While the legislative deference model recognizes the legislature\u27s power to prescribe punishments, the separate proceedings model effectively undermines that power by prohibiting punishments within legislatively authorized maximums if they happen to be imposed in separate proceedings. Thus, some commentators have argued that the two models of multiple punishments doctrine are fundamentally inconsistent. The Court\u27s focus on separate proceedings in Halper has also caused problems by blurring the distinction between multiple punishments and multiple prosecutions cases. Thus lower courts applying Halper awkwardly import multiple prosecutions doctrine, creating even more confusion? Some point to these problems as evidence that the Double Jeopardy Clause should not be read to protect against multiple punishments at all. The most vocal of these critics, Justice Scalia, has described the multiple punishments prohibition as one of those areas where the Court\u27s jurisprudence is not only wrong but unworkable as well. \u27 This Note suggests that a double jeopardy prohibition on multiple punishments is neither wrong nor unworkable. Rather, the main problem with multiple punishments jurisprudence stems from the Court\u27s failure to identify a single double jeopardy interest under- lying its various applications of the right. While the Court sometimes states what the prohibition does, it has not articulated what it means. The Court could achieve enhanced clarity by tying its multiple punishments jurisprudence to the interest that the Double Jeopardy Clause was originally designed to serve: the interest in preserving the integrity of final judgments

Biometric surveillance in schools : cause for concern or case for curriculum?

This article critically examines the draft consultation paper issued by the Scottish Government to local authorities on the use of biometric technologies in schools in September 2008 (see http://www.scotland.gov.uk/Publications/2008/09/08135019/0). Coming at a time when a number of schools are considering using biometric systems to register and confirm the identity of pupils in a number of settings (cashless catering systems, automated registration of pupils' arrival in school and school library automation), this guidance is undoubtedly welcome. The present focus seems to be on using fingerprints, but as the guidance acknowledges, the debate in future may encompass iris prints, voice prints and facial recognition systems, which are already in use in non-educational settings. The article notes broader developments in school surveillance in Scotland and in the rest of the UK and argues that serious attention must be given to the educational considerations which arise. Schools must prepare pupils for life in the newly emergent 'surveillance society', not by uncritically habituating them to the surveillance systems installed in their schools, but by critically engaging them in thought about the way surveillance technologies work in the wider world, the various rationales given to them, and the implications - in terms of privacy, safety and inclusion - of being a 'surveilled subject'

MEMS 411: Self Lacing Shoes

For our senior design project we have chosen to design and prototype a pair of self lacing shoes with the initial target audience being people with disabilities who are limited in their ability to tie their own shoes for a variety of reasons. However, we hope that this product will catch on in popularity and become normalized for all people. These shoes will allow the wearer to easily slip them on and then secure the shoes to the foot with the push of a button rather than tying laces as in conventional shoes. This process will be driven by a mechanical motor and ratchet system hidden in the soles of the shoes. While alternatives such as Velcro, slip-ons, and even other self-lacing shoes are available on the market, each of these options have short comings which our product aims to improve on. From lack of foot support to lack of style and inaccessible prices, the current market does not provide a suitable option for people who want something other than conventional shoes

A mathematical model quantifies proliferation and motility effects of TGF--β\beta on cancer cells

Transforming growth factor (TGF) $\beta$ is known to have properties of both a tumor suppressor and a tumor promoter. While it inhibits cell proliferation, it also increases cell motility and decreases cell--cell adhesion. Coupling mathematical modeling and experiments, we investigate the growth and motility of oncogene--expressing human mammary epithelial cells under exposure to TGF--$\beta$. We use a version of the well--known Fisher--Kolmogorov equation, and prescribe a procedure for its parametrization. We quantify the simultaneous effects of TGF--$\beta$ to increase the tendency of individual cells and cell clusters to move randomly and to decrease overall population growth. We demonstrate that in experiments with TGF--$\beta$ treated cells \textit{in vitro}, TGF--$\beta$ increases cell motility by a factor of 2 and decreases cell proliferation by a factor of 1/2 in comparison with untreated cells.Comment: 15 pages, 4 figures; to appear in Computational and Mathematical Methods in Medicin