A user evaluation of hierarchical phrase browsing

Phrase browsing interfaces based on hierarchies of phrases extracted automatically from document collections offer a useful compromise between automatic full-text searching and manually-created subject indexes. The literature contains descriptions of such systems that many find compelling and persuasive. However, evaluation studies have either been anecdotal, or focused on objective measures of the quality of automatically-extracted index terms, or restricted to questions of computational efficiency and feasibility. This paper reports on an empirical, controlled user study that compares hierarchical phrase browsing with full-text searching over a range of information seeking tasks. Users found the results located via phrase browsing to be relevant and useful but preferred keyword searching for certain types of queries. Users experiences were marred by interface details, including inconsistencies between the phrase browser and the surrounding digital library interface

Point-spread function and photon transfer of a CCD for space-based astronomy

A front-illuminated development Euclid charge-coupled device (CCD) is tested to observe the CCD point-spread function (PSF) relative to signal size using a single-pixel photon transfer curve (SP-PTC) technique. In the process of generating a SP-PTC charge redistribution effects were observed. In attempting to show that charge redistribution can be caused by exposing a charge-populated well in the CCD array to further illumination, excess charge became apparent in recorded data. Excess charge is suggested to be proportionally generated in the CCD array if existing charge is subjected to further illumination before transfer and readout. The construction of an optical test bench and CCD operating variables are discussed alongside systematic error concerns and mitigation techniques

Thermophysical Properties of CeB 6 and PrB 6 at Subambient Temperatures

Equilibrium adiabatic heat-capacity measurements have been made on zone refined samples of CeB 6 and PrB 6 . Companion measurements made on LaB 6 , NdB 6 , and GdB 6 have been reported elsewhere. These show cooperative lambda-type anomalies associated with antiferro-magnetic ordering. Except for lanthanum hexaboride, Schottky internal crystal field levels result in significant contributions to the thermodynamic functions. The gross thermodynamic properties at 298.15 K heat capacity ( C p / R ), entropy increment (Δ 0,m T S 0 / R ), and Gibbs energy function are correlated with the nature of the lanthanide. For LaB 6 , CeB 6 , PrB 6 , NdB 6 , and GdB 6 the three properties are, respectively: {11.654, 12.014, 11.997, 11.916, 11.695} C p / R ; {10.001, 11.803, 12.430, 12.558, 13.982} S 0 /R, and finally {4.379, 5.912, 6.232, 6.451, 7.905} Φ m 0 / R .Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43146/1/10973_2004_Article_5116049.pd

Impaired platelet-dependent thrombin generation associated with thrombocytopenia is improved by prothrombin complex concentrates in vitro.

BACKGROUND: Impaired thrombin generation (TG) in patients with acquired coagulopathy, is due to low coagulation factors and thrombocytopenia. The latter is typically treated with platelet transfusions and the former with plasma and occasionally with prothrombin complex concentrates (PCCs). We hypothesized that manipulating the concentrations of coagulation factors might result in restoration of platelet-dependent TG over and above that of simple replacement therapy. OBJECTIVE: To investigate the influence of PCCs on impaired TG secondary to thrombocytopenia. METHODS: TG was evaluated by thrombin generation assay using a thrombocytopenia model in which normal plasma samples with varying platelet counts (20-300 × 109/L) were spiked with PCCs (25%-150% increase in plasma PCC levels). RESULTS: PCCs and platelets significantly increased TG in a dose-dependent manner in vitro. Two-way repeated measures of analysis of variance showed variance in peak height, area under the curve, time to peak, and velocity. This variance explained, respectively, by levels of PCC was 47, 59, 25 and 53%; by platelet count was 45, 28, 44, and 14%; by the combination was 80, 67, 70, and 62% variance; and a combination with additional interaction was 91, 84, 76, and 68%. TG at a platelet count 40 × 109/L with an approximate 25% increase in PCC concentration was similar to TG at 150 × 109/L. Similarly, patient samples spiked ex vivo with PCCs also showed highly significant improvements in TG. CONCLUSIONS: Impaired TG of thrombocytopenia is improved by PCCs, supporting the need for additional studies in complex coagulopathies characterized by mild to moderate thrombocytopenia and abnormal coagulation

Multi-level parallel clocking of CCDs for: improving charge transfer efficiency, clearing persistence, clocked anti-blooming, and generating low-noise backgrounds for pumping

A multi-level clocking scheme has been developed to improve the parallel CTE of four-phase CCDs by suppressing the effects of traps located in the transport channel under barrier phases by inverting one of these phases throughout the transfer sequence. In parallel it was apparent that persistence following optical overload in Euclid VIS detectors would lead to undesirable signal released in subsequent rows and frames and that a suitable scheme for flushing this signal would be required. With care, the negatively biased electrodes during the multi-level transfer sequence can be made to pin the entire surface, row-by-row, and annihilate the problematic charges. This process can also be extended for use during integration to significantly reduce the unusable area of the detector, as per the clocked anti-blooming techniques developed many years ago; however, with the four-phase electrodes architecture of modern CCDs, we can take precautionary measures to avoid the problem of charge pumping and clock induced charge within the science frames. Clock induced charge is not all bad! We also propose the use of on-orbit trap-pumping for Euclid VIS to provide calibration input to ground based correction algorithms and as such a uniform, low noise background is require. Clock induced charge can be manipulated to provide a very suitable, low signal and noise background to the imaging array. Here we describe and present results of multi-level parallel clocking schemes for use in four-phase CCDs that could improve performance of high precision astronomy applications such as Euclid VIS