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Gas Gain Measurements from a Negative Ion TPC X-ray Polarimeter  [PDF]
Z. Prieskorn,J. E. Hill,P. E. Kaaret,J. K. Black,K. Jahoda
Physics , 2011, DOI: 10.1109/TNS.2011.2155083
Abstract: Gas-based time projection chambers (TPCs) have been shown to be highly sensitive X-ray polarimeters having excellent quantum efficiency while at the same time achieving large modulation factors. To observe polarization of the prompt X-ray emission of a Gamma-ray burst (GRB), a large area detector is needed. Diffusion of the electron cloud in a standard TPC could be prohibitive to measuring good modulation when the drift distance is large. Therefore, we propose using a negative ion TPC (NITPC) with Nitromethane (CH3NO2) as the electron capture agent. The diffusion of negative ions is reduced over that of electrons due to the thermal coupling of the negative ions to the surrounding gas. This allows for larger area detectors as the drift distance can be increased without degrading polarimeter modulation. Negative ions also travel ~200 times slower than electrons, allowing the readout electronics to operate slower, resulting in a reduction of instrument power. To optimize the NITPC design, we have measured gas gain with SciEnergy gas electron multipliers (GEMs) in single and double GEM configurations. Each setup was tested with different gas combinations, concentrations and pressures: P10 700 Torr, Ne+CO2 700 Torr at varying concentrations of CO2 and Ne+CO2+CH3NO2 700 Torr. We report gain as a function of total voltage, measured from top to bottom of the GEM stack, and as a function of drift field strength for the gas concentrations listed above. Examples of photoelectron tracks at 5.9 keV are also presented.
A light readout system for gas TPCs  [PDF]
G. Giroux,M. Auger,D. Franco,M. Weber,S. Delaquis,R. Gornea,P. Lutz,J. -L. Vuilleumier,J. -M. Vuilleumier
Physics , 2013, DOI: 10.1088/1748-0221/9/01/P01005
Abstract: A novel light detection scheme has been tested for use in medium-pressure gas TPCs, in view of rare events searches in low energy particle physics. It has the advantage of minimal interference with the ionization collection system, used for track imaging. It provides an absolute time reference, which allows an absolute determination of the Z coordinate of events, along the direction of the drift field. This makes possible a fiducial cut along the Z-axis, allowing to reduce the background from the ends of the drift volume.
A Novel Forager Agent Based Approach to Capture the Future Browsing Pattern of Online Users  [cached]
Mohanraj Vijayakumar,Lakshmipathi R
Computer and Information Science , 2010, DOI: 10.5539/cis.v3n3p105
Abstract: A big challenge for the web master of any e-commerce website is to match user needs and keep them continuously to browse their site. It is easy for any unsatisfied user to reach out the counterpart site in a single click. Many Web usage mining methods were adopted to work on web server log and capture the future browsing pattern of user. However, the accuracy of the methods can’t satisfy the user especially in huge site. This paper presents the novel Forager agent based architecture that uses its collective intelligence for identifying the future browsing pattern of user. Our practical implementation shows that accuracy and coverage measures are very much improved than existing methods.
Impact of negative emotion on agent persuasion
消极情感对agent劝说的影响研究*

WU Jing-hu,ZHANG Xin-gang,DONG Xue-jie,
伍京华
,张新刚,董学杰

计算机应用研究 , 2011,
Abstract: For its characteristic of non-AI, agent persuasion can always be in deadlock when it simulate human being, which is harmful to its cooperation. To do with this and combined with the characteristic of emotion as in AI, classified emotion of agent persuasion, and constructed impact model of negative emotion on agent persuasion with the theory of formal logic, which was explained clearly through an example. Based on this model, also gave relative method of comparison after gave the concept of change degree of negative emotion, which was also verified to be effective through a calculation example. The result shows that it can bring the rational advantage of agent into play and decrease the system burden, which is good to its cooperation.
Circulating Prostate Cells Found in Men with Benign Prostate Disease Are P504S Negative: Clinical Implications  [PDF]
Nigel P. Murray,Eduardo Reyes,Leonardo Badínez,Nelson Orellana,Cynthia Fuentealba,Ruben Olivares,José Porcell,Ricardo Due?as
Journal of Oncology , 2013, DOI: 10.1155/2013/165014
Abstract: Introduction. Developments in immunological and quantitative real-time PCR-based analysis have enabled the detection, enumeration, and characterization of circulating tumor cells (CTCs). It is assumed that the detection of CTCs is associated with cancer, based on the finding that CTCs can be detected in all major cancer and not in healthy subjects or those with benign disease. Methods and Patients. Consecutive men, with suspicion of prostate cancer, had blood samples taken before prostate biopsy; mononuclear cells were obtained using differential gel centrifugation and CPCs detecting using anti-PSA immunocytochemistry. Positive samples underwent further classification with anti-P504S. Results. 329 men underwent prostate biopsy; of these men 83 underwent a second biopsy and 44 a third one. Of those with a biopsy negative for cancer, 19/226 (8.4%) had CPCs PSA (+) P504S (?) detected at first biopsy, 6/74 (8.1%) at second biopsy, and 5/33 (15.2%) at third biopsy. Men with cancer-positive biopsies did not have PSA (+) P504S (?) CPCs detected. These benign cells were associated with chronic prostatitis. Conclusions. Patients with chronic prostatitis may have circulating prostate cells detected in blood, which do not express the enzyme P504S and should be thought of as benign in nature. 1. Introduction Although the first report on circulating tumors was published by Ashworth in 1869 [1], the lack of technology precluded further investigations on their clinical use until recently. Developments in immunological and quantitative real-time PCR-based analysis have enabled the detection, enumeration and characterization of circulating tumor cells (CTCs). The monitoring of CTCs has the potential to improve therapeutic management at an early stage and also to identify patients with increased risk of tumor progression or recurrence before the onset of clinically detected metastasis. Furthermore, the molecular profiling of CTCs can provide new insights into cancer biology and systemic treatment in neoadjuvant or adjuvant settings. It is assumed that the detection of CTCs is associated with cancer, based on the finding that CTCs can be detected in all major cancers and not in healthy subjects or those with benign disease [2]. Most of the assays are based on enrichment and subsequent identification of CTCs using monoclonal antibodies directed against epithelial epitopes, for example, the transmembrane glycoprotein epithelial cell adhesion molecule (EpCAM) or cytokeratins that are expressed on both normal and malignant cells. This widely based approach is based on the
Use of carbon dioxide as negative contrast agent for magnetic resonance cholangiopancreatography  [cached]
Ching-Wen Chen,Yi-Sheng Liu,Chiung-Yu Chen,Hong-Ming Tsai
World Journal of Radiology , 2011,
Abstract: AIM: To evaluate the effects of using CO2 as negative contrast agent in decreasing the overlapping on the pancreaticobiliary system from intestinal fluids.METHODS: We evaluated the magnetic resonance cholangiopancreatography (MRCP) images in 117 patients divided into two groups (group 1, without taking gas producing crystals to produce CO2, n = 64; group 2, with CO2, n = 53) in a 1.5T unit using MRCP sequence. Anatomic locations of intestinal fluids distribution, overlapping with common bile duct (CBD) and pancreatic duct (PD), were evaluated.RESULTS: In the group with CO2, the decrease in distribution of intestinal fluids was significant in the gastric antrum (P = 0.001) and duodenal bulb (P < 0.001), but not in the gastric fundus and body and in the second portion of the duodenum (P = 1.000, P = 0.171, and P = 0.584 respectively). In the group with CO2, the decrease in overlapping with CBD was significant (P < 0.001), but the decrease in overlapping with PD was not (P = 0.106).CONCLUSION: MRCP with carbon dioxide as negative contrast agent would decrease intestinal fluids in the gastric antrum and duodenal bulb, thereby decreasing overlapping with the CBD.
Oligoclonal IgG bands in the cerebrospinal fluid of portuguese patients with multiple sclerosis: negative results indicate benign disease
, Maria José;Sequeira, Lucinda;Rio, Maria Edite;Thompson, Edward J.;
Arquivos de Neuro-Psiquiatria , 2005, DOI: 10.1590/S0004-282X2005000300001
Abstract: we assessed the frequency of cerebrospinal fluid (csf) restricted oligoclonal igg bands (igg-ocb) in portuguese multiple sclerosis (ms) patients and its relationship with outcome. paired csf/serum samples of 406 patients with neurological disorders were submitted to isoelectric focusing with immunodetection of igg. ninety-two patients had definite ms; non-ms cases were assembled in groups inflammatory/infectious diseases (id, n=141) and other/controls (od, n=173). we found in the ms group: mean duration, 38.9 months; clinically isolated syndromes, 24%; relapsing/remitting course (rr), 65%; in rr patients the mean edss was 2.1 and the mean index of progression was 0.31. positive patterns significantly predominated in ms (82.6%; id, 40.4%; od, 3.5%). the sensitivity and the specificity of positive igg-ocb for ms diagnosis was 82.6% and 79.9%, respectively. the sole statistically significant difference in the ms group was the lower progression index observed in negative cases. we conclude that the frequency of positive igg-ocb patterns in our ms patients fits most values reported in the literature, and that negative results indicate benign disease.
Efficacy of Black Tea as a Negative Oral Contrast Agent for MR Cholangiopancreatography (MRCP)
Kavous Firouznia,Hossein Ghanaati,Hadi Rokni,Firooze Abahashemi
Iranian Journal of Radiology , 2010,
Abstract: Background/Objective: Evaluation of the use of black tea as negative oral contrast agent in MR cholangiopancreatography (MRCP)."nPatients and Methods: Thirty-five patients (mean age, 50.3±19.2 years), who were referred for MRCP, entered in this study. MRCP was performed before, after 5 minutes and after 15 minutes following consumption of 300 ml of black tea. Depiction of the gall bladder, cystic duct, proximal and distal parts of the common bile duct (CBD), intra hepatic ducts, ampula of Vater, main pancreatic duct (MPD) and signal loss of the stomach and three different segments of the duodenum were investigated according to VAS and Lickert scores."nResults: Regarding visibility of seven different anatomical parts of the pancreatobiliary tree (gall bladder, cystic duct, CBD, common hepatic duct, intrahepatic duct, ampula of Vater and MPD), the post procedure images were better visualized only in the distal part of CBD, ampula of vater and MPD both in Lickert and VAS scoring (all Ps≤0.001)."nThere was no significant difference between the images 5 and 15 minutes after tea consumption. Regarding the obliteration of high signal in the stomach and three different parts of the duodenum, all post tea images of the mentioned parts showed significant disappearance of high signal in Lickert and VAS scoring systems (all Ps≤0.001). "nConclusion: Black tea is an affordable, cheap, available, safe, and efficient oral negative contrast agent for MRCP which reduces the signal intensity of fluids in the gastrointestinal tract and is also efficient for better depiction of MPD, distal part of CBD and ampula.
Feasibility of high-voltage systems for a very long drift in liquid argon TPCs  [PDF]
S. Horikawa,A. Badertscher,L. Kaufmann,M. Laffranchi,A. Marchionni,M. Messina,G. Natterer,A. Rubbia
Physics , 2010, DOI: 10.1088/1742-6596/308/1/012027
Abstract: Designs of high-voltage (HV) systems for creating a drift electric field in liquid argon TPCs are reviewed. In ongoing experiments systems capable of approx. 100 kV are realised for a drift field of 0.5-1 kV/cm over a length of up to 1.5 m. Two of them having different approaches are presented: (1) the ICARUS-T600 detector having a system consisting of an external power supply, HV feedthroughs and resistive voltage degraders and (2) the ArDM-1t detector having a cryogenic Greinacher HV multiplier inside the liquid argon volume. For a giant scale liquid argon TPC, a system providing 2 MV may be required to attain a drift length of approx. 20 m. Feasibility of such a system is evaluated by extrapolating the existing designs.
Pattern recognition techniques to reduce backgrounds in the search for the 136Xe double beta decay with gaseous TPCs  [PDF]
F. J. Iguaz,S. Cebrian,T. Dafni,H. Gomez,D. C. Herrera,I. G. Irastorza,G. Luzon,L. Segui,A. Tomas
Physics , 2013, DOI: 10.1063/1.4818074
Abstract: The observation of the neutrinoless double beta decay may provide essential information on the nature of neutrinos. Among the current experimental approaches, a high pressure gaseous TPC is an attractive option for the search of double beta decay due to its good energy resolution and the detailed topological information of each event. We present in this talk a detailed study of the ionization topology of the 136Xe double beta decay events in a High Pressure Xenon TPC, as well as that of the typical competing backgrounds. We define some observables based on graph theory concepts to develop automated discrimination algorithms. Our criteria are able to reduce the background level by about three orders of magnitude in the region of interest of the 136Xe Qbb for a signal acceptance of 40%. This result provides a quantitative assessment of the benefit of topological information offered by gaseous TPCs for double beta decay search, and proves that it is a promising feature in view of future experiments in the field. Possible ideas for further improvement in the discrimination algorithms and the dependency of these results with the gas diffusion and readout granularity will be also discussed.
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