334 research outputs found
Clinical ROC Studies of Digital Stereo Mammography
The objective of this study was to explore and document the diagnostic utility of digital stereo mammography for the detection of localized breast cancer in women. In it we characterized the ability of experienced mammographers, general radiologists, and non-radiologists to detect three types of tumor masses embedded within a heterogeneous background of normal tissue elements in numerically simulated digital mammograms. The simulated mammograms were displayed to the subjects on a high resolution video display, both in stereo mode and in mono mode. Half of the mammograms contained a single tumor, ranging from 0.3 to 0.8 cm in maximal diameter. Each reader rated 120 images (60 in stereo and 60 in mono) as to the probability of abnormality on scale of 1-5. Observer responses were evaluated using receiver operating characteristic (ROC) analysis to characterize any difference in diagnostic performance between the two viewing modes. The synthesized mammograms and the digital display were highly rated by the participant radiologists as promising tools for future research. The results of ROC analysis, however, indicated no significant difference in tumor detection when the same readers utilized the stereo mode versus the mono mode (Az mono = 0.833 versus, Az stereo = 0.826). The results were similar for readers of all 3 experience levels--mammographers, general radiologists, and non-radiologists
The function of visual search and memory in sequential looking tasks
Eye and head movements were recorded as unrestrained subjects tapped or only looked at nearby targets. Scanning patterns were the same in both tasks: subjects looked at each target before tapping it; visual search had similar speeds and gaze-shift accuracies. Looking however, took longer and, unlike tapping, benefitted little from practice. Looking speeded up more than tapping when memory load was reduced: memory was more efficient during tapping. Conclusion: eye movements made when only looking are different from those made when tapping. Visual search functions as a separate process, incorporated into both tasks: it can be used to improve performance when memory load is heavy
Universal Constraints on Low-Energy Flavour Models
It is pointed out that in a general class of flavour models one can identify
certain universally present FCNC operators, induced by the exchange of heavy
flavour messengers. Their coefficients depend on the rotation angles that
connect flavour and fermion mass basis. The lower bounds on the messenger scale
are derived using updated experimental constraints on the FCNC operators. The
obtained bounds are different for different operators and in addition they
depend on the chosen set of rotations. Given the sensitivity expected in the
forthcoming experiments, the present analysis suggests interesting room for
discovering new physics. As the highlights emerge the leptonic processes,
, and
conversion in nuclei.Comment: 18 pages, 3 figures; v2 matches published versio
Cosmological vacuum selection and metastable susy breaking
We study gauge mediation in a wide class of O'Raifeartaigh type models where
supersymmetry breaking metastable vacuum is created by gravity and/or quantum
corrections. We examine their thermal evolution in the early universe and the
conditions under which the susy breaking vacuum can be selected. It is
demonstrated that thermalization typically makes the metastable supersymmetry
breaking cosmologically disfavoured but this is not always the case. Initial
conditions with the spurion displaced from the symmetric thermal minimum and a
small coupling to the messenger sector can result in the realization of the
susy breaking vacuum even if the reheating temperature is high. We show that
this can be achieved without jeopardizing the low energy phenomenology. In
addition, we have found that deforming the models by a supersymmetric mass term
for messengers in such a way that the susy breaking minimum and the susy
preserving minima are all far away from the origin does not change the
conclusions. The basic observations are expected to hold also in the case of
models with an anomalous U(1) group.Comment: 28 pages, 4 figures, plain Latex, journal versio
The Messenger Sector of SUSY Flavour Models and Radiative Breaking of Flavour Universality
The flavour messenger sectors and their impact on the soft SUSY breaking
terms are investigated in SUSY flavour models. In the case when the flavour
scale M is below the SUSY breaking mediation scale M_S, the universality of
soft terms, even if assumed at M_S, is radiatively broken. We estimate this
effect in a broad class of models. In the CKM basis that effect gives flavour
off-diagonal soft masses comparable to the tree-level estimate based on the
flavour symmetry.Comment: 24 pages, 3 figures. v3: minor changes in the text, typos corrected,
version accepted for publication in JHE
Analyzing split channel medium access control schemes,”
Abstract: In order to improve the throughput performance of Medium Access Control (MAC) schemes in wireless communication networks, some researchers proposed to divide a single shared channel into several subchannels: one as control sub-channel and the others as data sub-channels. In this paper, we analyze and evaluate the maximum achievable throughput of a class of generic multi-channel MAC schemes that are based on the RTS/CTS (Ready-To-Send/Clear-To-Send) dialogue and on ALOHA contention resolution. We study these multichannel MAC schemes under two split-channel scenarios: the fixed-total-bandwidth scenario and the fixed-channel-bandwidth scenario. In the fixed-total-bandwidth scenario, we show that the throughput of the multi-channel MAC schemes is inferior to that of the corresponding single-channel MAC scheme, which sends the RTS/CTS packets and DATA packets on a single shared channel. For the fixed-channel-bandwidth scenario, where CDMA or similar techniques can be applied, we derive the optimal number of the data subchannels that maximizes the throughput. The analytical framework that we derive in this paper can also be used to evaluate other contention resolution technique, when the average contention period is known. Index Terms: medium access control, MAC, shared channel, multiple channels, ALOHA, contention resolution, RTS/CTS dialogue Article: I. INTRODUCTION In wireless communication networks, Medium Access Control (MAC) schemes are used to manage the access of active nodes to a shared channel Even though there are many multi-channel MAC schemes proposed in the technical literature, to the best of our knowledge, systematic comparison of these multi-channel MAC schemes with the corresponding single-channel schemes is not available except i
Novel and promising compounds to treat Cryptosporidium parvum infections
No fully effective approved drug therapy exists for Cryptosporidium infections of immunocompetent and immunocompromised patients. Here, we investigated 11 benzimidazole derivatives carrying substituted thioalkyl and thiobenzyl groups at position 2 of benzimidazole nucleus and additional substituents at the benzene part of benzimidazole for inhibition of the in vitro growth of the intestinal protozoan parasite, Cryptosporidium parvum. Three of them, i.e., 5-carboxy-2-(4-nitrobenzylthio)-1H-benzimidazole, 5,6-dichloro-2-(4-nitrobenzylthio)-1H-benzimidazole, and 4,6-dichloro-2-(4-nitrobenzylthio)-1H-benzimidazole, (compounds 5, 7, and 8) were the most active (IC50 28–31 μM). The concentration of compounds 5, 7, and 8 that caused 50% growth inhibition in human enterocytic HCT-8 cells by a quantitative alkaline phosphatase immunoassay was comparable with those obtained for paromomycin
Novel and promising compounds to treat Cryptosporidium parvum infections
No fully effective approved drug therapy exists for Cryptosporidium infections of immunocompetent and immunocompromised patients. Here, we investigated 11 benzimidazole derivatives carrying substituted thioalkyl and thiobenzyl groups at position 2 of benzimidazole nucleus and additional substituents at the benzene part of benzimidazole for inhibition of the in vitro growth of the intestinal protozoan parasite, Cryptosporidium parvum. Three of them, i.e., 5-carboxy-2-(4-nitrobenzylthio)-1H-benzimidazole, 5,6-dichloro-2-(4-nitrobenzylthio)-1H-benzimidazole, and 4,6-dichloro-2-(4-nitrobenzylthio)-1H-benzimidazole, (compounds 5, 7, and 8) were the most active (IC50 28–31 μM). The concentration of compounds 5, 7, and 8 that caused 50% growth inhibition in human enterocytic HCT-8 cells by a quantitative alkaline phosphatase immunoassay was comparable with those obtained for paromomycin
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