Effect of lower energy threshold on single and multiple scatter distributions in positron volume imaging

1999 ◽  
Vol 46 (4) ◽  
pp. 1129-1135 ◽  
Author(s):  
T.K. Lewellen ◽  
R.L. Harrison ◽  
S.G. Kohlmyer
Keyword(s):  
Lower Energy ◽  
Energy Threshold ◽  
Multiple Scatter ◽  
Volume Imaging ◽  
Lower Energy Threshold

A New Sum Trigger to Provide a Lower Energy Threshold for the MAGIC Telescope

2009 ◽  
Vol 56 (6) ◽  
pp. 3840-3843 ◽  
Author(s):  
Michael Rissi ◽  
Nepomuk Otte ◽  
Thomas Schweizer ◽  
Maxim Shayduk
Keyword(s):  
Lower Energy ◽  
Energy Threshold ◽  
Lower Energy Threshold

Impact of the lower energy threshold on the NEMA NU2-2001 count-rate performance of a LSO based PET-CT scanner

2008 ◽  
Vol 47 (05) ◽  
pp. 210-214 ◽  
Author(s):  
H. Herzog ◽  
K. P. Schäfers ◽  
S. Käpplinger ◽  
O. Schober ◽  
J. Eckardt
Keyword(s):  
Count Rate ◽  
Lower Energy ◽  
Energy Threshold ◽  
Global Maximum ◽  
Rate Performance ◽  
Radioactivity Concentration ◽  
Scatter Fraction ◽  
Pet Ct ◽  
Lower Energy Threshold ◽  
The Impact

SummaryThe aim of this study was to investigate the impact of the lower energy threshold (LET) on the NEMA NU2–2001 count-rate performance of a LSO-based PET scanner (Siemens PET-CT Biograph Sensation 16). The quantitative measurements were focused on three different aspects: noise equivalent count rate (NEC), scatter fraction, and absolute sensitivity. Methods: According to the NEMA-NU2–2001 protocol count-rate-performance (NEC-2R, scatter fraction) and sensitivity were evaluated performing serial measurements at LETs of 350, 375, 400, 410, 420, 430, 440, and 450 keV (the upper energy threshold was fixed to 650 keV). NEMA protocols were adapted to account for the intrinsic radioactivity of 176Lu in the LSO crystals. Results: Up to a radioactivity concentration of 8 kBq/ml the highest NECrates were obtained at an LET of 410 keV, between 8 and 20 kBq/ml at an LET of 420 keV and above 20 kBq/ml at an LET of 430 keV. The overall NEC maximum was 67 kcps at 430 keV (at 28 kBq/ml). The minimum scatter fraction was measured at a radioactivity concentration of ~ 0.5 kBq/ml. The scatter fraction decreased continuously from 45% at an energy threshold of 350 keV to 24% at 450 keV. The maximum sensitivity of 5.8 kcps/MBq, was obtained at an LET of 350 keV and the minimum sensitivity of 4.2 kcps/MBq at an LET of 450 keV. At the LET with the maximum NEC-rate (430 keV) the sensitivity was 4.8 kcps/MBq. Conclusion: The optimal count-rate performance of the LSO-based PET system was found at LETs between 410 keV and 430 keV depending on the actual radioactivity concentration placed in the scanner. A global maximum in NEC count rate was obtained at an LET of 430 keV.

scholarly journals The IceCube Neutrino Telescope

2012 ◽  
Vol 8 (S288) ◽  
pp. 105-114
Author(s):  
Thomas K. Gaisser ◽  
Keyword(s):  
Lower Energy ◽  
Data Acquisition System ◽  
Neutrino Telescope ◽  
South Pole ◽  
Fully Integrated ◽  
Air Shower ◽  
System Data ◽  
Lower Energy Threshold ◽  
Single Data ◽  
Shower Array

AbstractConstruction of IceCube at the Amundsen-Scott South Pole Station was completed at the end of 2010 after eight construction seasons. The detector consists of 5,160 digital optical modules on 86 cables with 60 modules each, viewing in total a cubic kilometer of ice between 1,450 and 2,450 meters below the surface. IceCube includes a sub-array called DeepCore consisting of 8 special cables, and providing a more densely instrumented region with a lower energy threshold in the deep center of the array. IceCube also includes an air shower array called IceTop directly above the deep detector. Optical modules in all three components of the detector are fully integrated into a single data acquisition system. Data taking and analysis began during construction and continues with the completed detector. This paper describes recent results from IceCube.

Determination of the lattice translation across {110} APBs in GaAs

1988 ◽  
Vol 46 ◽  
pp. 600-601
Author(s):  
D.R. Rasmussen ◽  
N.-H. Cho ◽  
C.B. Carter
Keyword(s):  
Grain Boundaries ◽  
Lower Energy ◽  
Antiphase Boundary ◽  
The Other ◽  
Boundary Structure ◽  
Interface Plane ◽  
Inversion Symmetry ◽  
High Angle ◽  
Equilibrium Distance

Domains in GaAs can exist which are related to one another by the inversion symmetry, i.e., the sites of gallium and arsenic in one domain are interchanged in the other domain. The boundary between these two different domains is known as an antiphase boundary [1], In the terminology used to describe grain boundaries, the grains on either side of this boundary can be regarded as being Σ=1-related. For the {110} interface plane, in particular, there are equal numbers of GaGa and As-As anti-site bonds across the interface. The equilibrium distance between two atoms of the same kind crossing the boundary is expected to be different from the length of normal GaAs bonds in the bulk. Therefore, the relative position of each grain on either side of an APB may be translated such that the boundary can have a lower energy situation. This translation does not affect the perfect Σ=1 coincidence site relationship. Such a lattice translation is expected for all high-angle grain boundaries as a way of relaxation of the boundary structure.

An Alternate Energy-Conserved Pathway for the Morita-Baylis-Hillman (MBH) Reaction

2020 ◽  
Author(s):  
Veejendra Yadav
Keyword(s):  
Proton Transfer ◽  
Transition State ◽  
Lower Energy ◽  
Aldol Reaction ◽  
Membered Ring ◽  
Ammonium Ion ◽  
Alternate Energy ◽  
Ring Transition State ◽  
Mbh Reaction

An new overall lower energy pathway for the amine-catalysed Morita-Baylis-Hillman reaction is proposed from computations at the M06-2X/6-311++G(d,p) level. The pathway involves proton-transfer from the ammonium ion to the alkoxide formed from the aldol reaction through a seven-membered ring transition state (TS) structure followed by highly exothermic Hofmann<i> </i>elimination through a five-membered ring TS structure to form the product and also release the catalyst to carry on with the process all over again.

An Alternate Energy-Conserved Pathway for the Morita-Baylis-Hillman (MBH) Reaction

2020 ◽  
Author(s):  
Veejendra Yadav
Keyword(s):  
Proton Transfer ◽  
Transition State ◽  
Lower Energy ◽  
Aldol Reaction ◽  
Membered Ring ◽  
Ammonium Ion ◽  
Alternate Energy ◽  
Ring Transition State ◽  
Mbh Reaction

An new overall lower energy pathway for the amine-catalysed Morita-Baylis-Hillman reaction is proposed from computations at the M06-2X/6-311++G(d,p) level. The pathway involves proton-transfer from the ammonium ion to the alkoxide formed from the aldol reaction through a seven-membered ring transition state (TS) structure followed by highly exothermic Hofmann<i> </i>elimination through a five-membered ring TS structure to form the product and also release the catalyst to carry on with the process all over again.

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