Expressing Trust with Temporal Frequency of User Interaction in Online Communities

Reputation systems concern soft security dynamics in diverse areas. Trust dynamics in a reputation system should be stable and adaptable at the same time to serve the purpose. Many reputation mechanisms have been proposed and tested over time. However, the main drawback of reputation management is that users need to share private information to gain trust in a system such as phone numbers, reviews, and ratings. Recently, a novel model that tries to overcome this issue was presented: the Dynamic Interaction-based Reputation Model (DIBRM). This approach to trust considers only implicit information automatically deduced from the interactions of users within an online community. In this primary research study, the Reddit and MathOverflow online social communities have been selected for testing DIBRM. Results show how this novel approach to trust can mimic behaviors of the selected reputation systems, namely Reddit and MathOverflow, only with temporal information

Production of Medical Radioisotopes with High Specific Activity in Photonuclear Reactions with γ\gamma Beams of High Intensity and Large Brilliance

We study the production of radioisotopes for nuclear medicine in $(\gamma,x{\rm n}+y{\rm p})$ photonuclear reactions or ($\gamma,\gamma'$) photoexcitation reactions with high flux [($10^{13}-10^{15}$)$\gamma$/s], small diameter $\sim (100 \, \mu$m$)^2$ and small band width ($\Delta E/E \approx 10^{-3}-10^{-4}$) $\gamma$ beams produced by Compton back-scattering of laser light from relativistic brilliant electron beams. We compare them to (ion,$x$n$+ y$p) reactions with (ion=p,d,$\alpha$) from particle accelerators like cyclotrons and (n,$\gamma$) or (n,f) reactions from nuclear reactors. For photonuclear reactions with a narrow $\gamma$ beam the energy deposition in the target can be managed by using a stack of thin target foils or wires, hence avoiding direct stopping of the Compton and pair electrons (positrons). $(\gamma,\gamma')$ isomer production via specially selected $\gamma$ cascades allows to produce high specific activity in multiple excitations, where no back-pumping of the isomer to the ground state occurs. We discuss in detail many specific radioisotopes for diagnostics and therapy applications. Photonuclear reactions with $\gamma$ beams allow to produce certain radioisotopes, e.g. $^{47}$Sc, $^{44}$Ti, $^{67}$Cu, $^{103}$Pd, $^{117m}$Sn, $^{169}$Er, $^{195m}$Pt or $^{225}$Ac, with higher specific activity and/or more economically than with classical methods. This will open the way for completely new clinical applications of radioisotopes. For example $^{195m}$Pt could be used to verify the patient's response to chemotherapy with platinum compounds before a complete treatment is performed. Also innovative isotopes like $^{47}$Sc, $^{67}$Cu and $^{225}$Ac could be produced for the first time in sufficient quantities for large-scale application in targeted radionuclide therapy.Comment: submitted to Appl. Phys.

Fully human IgG and IgM antibodies directed against the carcinoembryonic antigen (CEA) Gold 4 epitope and designed for radioimmunotherapy (RIT) of colorectal cancers

BACKGROUND: Human monoclonal antibodies (MAbs) are needed for colon cancer radioimmunotherapy (RIT) to allow for repeated injections. Carcinoembryonic antigen (CEA) being the reference antigen for immunotargeting of these tumors, we developed human anti-CEA MAbs. METHODS: XenoMouse(®)-G2 animals were immunized with CEA. Among all the antibodies produced, two of them, VG-IgG2κ and VG-IgM, were selected for characterization in vitro in comparison with the human-mouse chimeric anti-CEA MAb X4 using flow cytometry, surface plasmon resonance, and binding to radiolabeled soluble CEA and in vivo in human colon carcinoma LS174T bearing nude mice. RESULTS: Flow cytometry analysis demonstrated binding of MAbs on CEA-expressing cells without any binding on NCA-expressing human granulocytes. In a competitive binding assay using five reference MAbs, directed against the five Gold CEA epitopes, VG-IgG2κ and VG-IgM were shown to be directed against the Gold 4 epitope. The affinities of purified VG-IgG2κ and VG-IgM were determined to be 0.19 ± 0.06 × 10(8 )M(-1 )and 1.30 ± 0.06 × 10(8 )M(-1), respectively, as compared with 0.61 ± 0.05 × 10(8 )M(-1 )for the reference MAb X4. In a soluble phase assay, the binding capacities of VG-IgG2κ and VG-IgM to soluble CEA were clearly lower than that of the control chimeric MAb X4. A human MAb concentration of about 10(-7 )M was needed to precipitate approximatively 1 ng (125)I-rhCEA as compared with 10(-9 )M for MAb X4, suggesting a preferential binding of the human MAbs to solid phase CEA. In vivo, 24 h post-injection, (125)I-VG-IgG2κ demonstrated a high tumor uptake (25.4 ± 7.3%ID/g), close to that of (131)I-X4 (21.7 ± 7.2%ID/g). At 72 h post-injection, (125)I-VG-IgG2κ was still concentrated in the tumor (28.4 ± 11.0%ID/g) whereas the tumor concentration of (131)I-X4 was significantly reduced (12.5 ± 4.8%ID/g). At no time after injection was there any accumulation of the radiolabeled MAbs in normal tissues. A pertinent analysis of VG-IgM biodistribution was not possible in this mouse model in which IgM displays a very short half-life due to poly-Ig receptor expression in the liver. CONCLUSION: Our human anti-CEA IgG2κ is a promising candidate for radioimmunotherapy in intact form, as F(ab')(2 )fragments, or as a bispecific antibody

[11C]acetate PET/CT Visualizes Skeletal Muscle Exercise Participation, Impaired Function, and Recovery after Hip Arthroplasty; First Results

Based on skeletal muscle acetate physiology we aimed studying muscle function after hip arthroplasty with [(11)C]acetate PET

[(18)F]Fluoroethyltyrosine- positron emission tomography-guided radiotherapy for high-grade glioma

BACKGROUND: To compare morphological gross tumor volumes (GTVs), defined as pre- and postoperative gadolinium enhancement on T1-weighted magnetic resonance imaging to biological tumor volumes (BTVs), defined by the uptake of (18)F fluoroethyltyrosine (FET) for the radiotherapy planning of high-grade glioma, using a dedicated positron emission tomography (PET)-CT scanner equipped with three triangulation lasers for patient positioning. METHODS: Nineteen patients with malignant glioma were included into a prospective protocol using FET PET-CT for radiotherapy planning. To be eligible, patients had to present with residual disease after surgery. Planning was performed using the clinical target volume (CTV = GTV union or logical sum BTV) and planning target volume (PTV = CTV + 20 mm). First, the interrater reliability for BTV delineation was assessed among three observers. Second, the BTV and GTV were quantified and compared. Finally, the geometrical relationships between GTV and BTV were assessed. RESULTS: Interrater agreement for BTV delineation was excellent (intraclass correlation coefficient 0.9). Although, BTVs and GTVs were not significantly different (p = 0.9), CTVs (mean 57.8 +/- 30.4 cm(3)) were significantly larger than BTVs (mean 42.1 +/- 24.4 cm(3); p < 0.01) or GTVs (mean 38.7 +/- 25.7 cm(3); p < 0.01). In 13 (68%) and 6 (32%) of 19 patients, FET uptake extended >or= 10 and 20 mm from the margin of the gadolinium enhancement. CONCLUSION: Using FET, the interrater reliability had excellent agreement for BTV delineation. With FET PET-CT planning, the size and geometrical location of GTVs and BTVs differed in a majority of patients

Pretargeted Radioimmunotherapy Using Genetically Engineered Antibody-Streptavidin Fusion Proteins for Treatment of Non-Hodgkin Lymphoma

Pretargeted radioimmunotherapy (PRIT) using streptavidin (SAv)-biotin technology can deliver higher therapeutic doses of radioactivity to tumors than conventional RIT. However, “endogenous” biotin can interfere with the effectiveness of this approach by blocking binding of radiolabeled biotin to SAv. We engineered a series of SAv FPs that down-modulate the affinity of SAv for biotin, while retaining high avidity for divalent DOTA-bis-biotin to circumvent this problem