121 research outputs found
Biocompatible Nanocomplexes for Molecular Targeted MRI Contrast Agent
Accurate diagnosis in early stage is vital for the treatment of Hepatocellular carcinoma. The aim of this study was to investigate the potential of poly lactic acidâpolyethylene glycol/gadoliniumâdiethylenetriamine-pentaacetic acid (PLAâPEG/GdâDTPA) nanocomplexes using as biocompatible molecular magnetic resonance imaging (MRI) contrast agent. The PLAâPEG/GdâDTPA nanocomplexes were obtained using self-assembly nanotechnology by incubation of PLAâPEG nanoparticles and the commercial contrast agent, GdâDTPA. The physicochemical properties of nanocomplexes were measured by atomic force microscopy and photon correlation spectroscopy. The T1-weighted MR images of the nanocomplexes were obtained in a 3.0 T clinical MR imager. The stability study was carried out in human plasma and the distribution in vivo was investigated in rats. The mean size of the PLAâPEG/GdâDTPA nanocomplexes was 187.9 ± 2.30 nm, and the polydispersity index was 0.108, and the zeta potential was â12.36 ± 3.58 mV. The results of MRI test confirmed that the PLAâPEG/GdâDTPA nanocomplexes possessed the ability of MRI, and the direct correlation between the MRI imaging intensities and the nano-complex concentrations was observed (r = 0.987). The signal intensity was still stable within 2 h after incubation of the nanocomplexes in human plasma. The nanocomplexes gave much better image contrast effects and longer stagnation time than that of commercial contrast agent in rat liver. A dose of 0.04 mmol of gadolinium per kilogram of body weight was sufficient to increase the MRI imaging intensities in rat livers by five-fold compared with the commercial GdâDTPA. PLAâPEG/GdâDTPA nanocomplexes could be prepared easily with small particle sizes. The nanocomplexes had high plasma stability, better image contrast effect, and liver targeting property. These results indicated that the PLAâPEG/GdâDTPA nanocomplexes might be potential as molecular targeted imaging contrast agent
Development of CVD diamond radiation detectors
Diamond is a nearly ideal material for detecting ionizing radiation. Its outstanding radiation hardness, fast charge collection and low leakage current allow a diamond detector to be used in high ra diation, high temperature and in aggressive chemical media. We have constructed charged particle detectors using high quality CVD diamond. Characterization of the diamond samples and various detect ors are presented in terms of collection distance, , the average distance electron-hole pairs move apart under the influence of an electric field, where is the sum of carrier mo bilities, is the applied electric field, and is the mobility weighted carrier lifetime. Over the last two years the collection distance increased from 75 m to over 200 m. With this high quality CVD diamond a series of micro-strip and pixel particle detectors have been constructed. These devices were tested to determine their position resolution and signal to n oise performance. Diamond detectors were exposed to large fluences of pions, protons and neutrons to establish their radiation hardness properties. The results of these tests and their correlati on with the characterization studies are presented
Proton Irradiation of CVD Diamond Detectors for High Luminosity Experiments at the LHC
CVD diamond shows promising properties for use as a position sensitive detector for experiments in the highest radiation areas at the Large Hadron Collider. In order to study the radiation hardn ess of diamond we exposed CVD diamond detector samples to 24~GeV/ and 500~MeV protons up to a fluence of . We measured the charge collection distance, the ave rage distance electron hole pairs move apart in an external electric field, and leakage currents before, during, and after irradiation. The charge collection distance remains unchanged up to and decreases by 40~\% at . Leakage currents of diamond samples were below 1~pA before and after irradiation. The particle indu ced currents during irradiation correlate well with the proton flux. In contrast to diamond, a silicon diode, which was irradiated for comparison, shows the known large increase in leakage curren t. We conclude that CVD diamond detectors are radiation hard to 24~GeV/ and 500~MeV protons up to at least without signal loss
Proton irradiation of CVD diamond detectors for high-luminosity experiments at the LHC
CVD diamond shows promising properties for use as a position sensitive detector for experiments in the highest radiation areas at the Large Hadron Collider. In order to study the radiation hardn ess of diamond we exposed CVD diamond detector samples to 24~GeV/ and 500~MeV protons up to a fluence of . We measured the charge collection distance, the ave rage distance electron hole pairs move apart in an external electric field, and leakage currents before, during, and after irradiation. The charge collection distance remains unchanged up to and decreases by 40~\% at . Leakage currents of diamond samples were below 1~pA before and after irradiation. The particle indu ced currents during irradiation correlate well with the proton flux. In contrast to diamond, a silicon diode, which was irradiated for comparison, shows the known large increase in leakage curren t. We conclude that CVD diamond detectors are radiation hard to 24~GeV/ and 500~MeV protons up to at least without signal loss
Development of diamond tracking detectors for high luminosity experiments at the LHC: addendum
Micro-strip sensors based on CVD Diamond
In this article we present the performance of recent chemical vapour deposition (CVD) diamond micro-strip sensors in beam tests. In addition we present the first comparison of a CVD diamond micro-strip sensor before and after proton irradiation
Performance of irradiated CVD diamond micro-strip sensors
CVD diamond detectors are of interest for charged particle detection and tracking due to their high radiation tolerance. In this article we present, for the first time, beam test results from recently manufactured CVD diamond strip detectors and their behavior under low doses of electrons from a -source and the performance before and after intense () proton- and pion-irradiations. We find that low dose irradiations increase the signal-to-noise ratio (pumping of the signal) and slightly deteriorate the spatial resolution. Intense irradiations with protons () lowers the signal-to-noise ratio slightly. Intense irradiation with pions () lowers the signal-to-noise ratio more. The spatial resolution of the diamond sensors improves after irradiations
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