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- Author or Editor: R. Wei x
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Summary
The feasibility of measuring picogram levels of actinides in a urine matrix using ion chromatography coupled on-line to an inductively coupled plasma quadrupole mass spectrometer (IC-Q-ICPMS) was investigated. A chelation column for separation of matrix ions and preconcentration of the actinides was combined with a cation-exchange column for separation of the actinides. Sample preparation required simple addition of ammonium acetate to adjust the pH of the urine matrix. Spike solutions containing 232 Th, 237Np, 238U, 239Pu, and 241Am were added to undiluted urine, diluted urine (1 : 9) and water. Results showed that this approach enhanced the signal sensitivities of all the tested actinides over two orders of magnitude in the water matrix, while certain elements (especially Am) can still be effectively concentrated in undiluted urine.
Abstract
For in vivo measurement of DNA synthesis in the patient"s tumour 3"-[18F]fluoro-3"-deoxythymidine (FLT) has been shown to be very promising. As a new labeling precursor 5"-O-(4,4"-dimethoxytrityl)-2,3"-anhydrothymidine (DMTThy) was chosen and an organic synthesis was developed including NMR and MS data for characterisation. The 18F-labeling of DMTThy can be performed within 30 minutes in radiochemical yields of almost 20% when using polar solvents such as DMF or DMSO and a temperature of 160 °C. Hydrolysis is completed with 1N HCl at 50 °C within 10 minutes without losses.
Abstract
[18F]FLT (3
-deoxy-3-[18F]fluorothymidine) turned out to be a tracer particularly suitable for PET imaging of tumor proliferation because of lacking degradation in vivo. To facilitate clinical studies with [18F]FLT, we investigated two new easily accessible precursors, 2,3-anhydrothymidine (AThy) and 5-O-(4,4-dimethoxytriphenylmethyl)-2,3-anhydrothymidine (DMTThy), using a common approach for introducing the label with nucleophilic [18F]fluoride. Radiochemical yields were determined in dependence on substrate concentration, reaction time and temperature. In the case of AThy (10 mg), best FLT yields were 5.3%±1.2 (130 °C, 30 min). Labeling of DMTThy (10 mg) gave 14.3%±3.3 at 160 °C within 10 minutes. Starting with an aqueous solution of 20 GBq [18F]fluoride the new method allows to produce 1.3 GBq [18F]FLT within 90 minutes ready for intravenous injection. The new labeling procedures allow [18F]FLT synthesis without lengthy preparation of the precursor and with high reproducibility mandatory for clinical application.
Abstract
Dielectric analysis (DEA), supported by thermogravimetric analysis (TG), differential scanning calorimetry (DSC), powder X-ray diffraction analysis (PXRD) and photomicrography, reveal the chiral difference in the amino acids. The acids are classified as dielectric materials based on their structure, relating chirality to the vector sum of the average dipole moment, composed of the constant optical (electronic) and infra-red (atomic) polarizabilities, as well as dipole orientation. This study encompasses 14 L-and D-amino acid isomers. Physical properties recorded include AC electrical conductivity, charge transfer complexes, melting, recrystallization, amorphous and crystalline phases, and relaxation spectra, activation energies and polarization times for the electrical charging process.
Abstract
The thermal analytical study of most hydrophobic and hydrophilic D/L amino acids reveals significant hydropathy index correlation between the presence of water and crystalline amino acids. The TG derivative mass profiles for arginine and lysine (hydrophilic acids) at various time intervals of atmospheric exposure, show two distinct peaks, one between 50 and 60°C (unbound water), and one close to 100°C (bound-like water). The DSC heat-cool profiles for lysine and arginine confirmed the presence of these multiple waters with two heats of vaporization. The absence of these patterns from the TG and DSC for cysteine and phenylalanine (hydrophobic acids) further supports the conclusions.
Abstract
Samples of rock, soil and seepage were collected from Yucca Mountain, USA, and analyzed for 36Cl/Cl ratios by accelerator mass spectrometry (AMS). Rock excavated from the Drill Hole Wash fault at repository horizon depths produced a ratio suggesting that small amounts of water with “bomb-pulse” 36Cl had percolated to that site over the past 50 years. Rock from four other sites within the exploratory studies facility did not yield bomb-pulse ratios. Ratios in the soil varied depending on depth and location, with some samples producing bomb-pulse signatures. Ratios for seep water were slightly elevated above the present cosmogenic background value. This paper also discusses results from a column study mimicking the passage of 36Cl through volcanic rock and from an experiment using bromide instead of chloride as a carrier in sample preparation for AMS.
Abstract
Background and aims
Self-injurious behaviors (SIBs) and problematic shopping (PS) are both prevalent in adolescents. These behaviors have been proposed as behavioral addictions and linked to impulsivity (Imp) and sensation-seeking (SS). They are also associated with negative mental health and psychosocial measures. This study examined relationships between PS and SIB in adolescents. It also examined how PS and SIB relate to Imp and SS, and interactions between PS and SIB in relation to health/functioning measures.
Methods
Survey data from 2,624 Connecticut high-school students were evaluated using chi-square analyses. Next, logistic regression models were used to assess relationships between PS and measures of SIB. T-tests compared Imp and SS in adolescents with and without PS and SIB. Interaction analyses assessed effects of PS on relationships between SIB and health/functioning measures.
Results
Adolescents with PS had 3.43-fold higher odds of endorsing lifetime SIB than those without PS, and were more likely to exhibit severe SIB and disruption due to SIB. PS and SIB were associated with elevated Imp and SS. Interaction analyses revealed that in adolescents with PS, the relationships between SIB and substance use was weaker than in adolescents without PS. This suggests PS accounts for variance in relationships between SIB and substance use.
Discussion and conclusions
PS is strongly related to SIB prevalence, severity, and impairment in adolescents, and weakens associations between SIB and substance use. PS should therefore be considered for prevention efforts for SIB. Further research should investigate mechanisms connecting PS and SIB and explore possible interventions targeting associated features like Imp and SS.
Abstract
Background and aims
Deficits in cognitive control represent a core feature of addiction. Internet Gaming Disorder (IGD) offers an ideal model to study the mechanisms underlying cognitive control deficits in addiction, eliminating the confounding effects of substance use. Studies have reported behavioral and neural deficits in reactive control in IGD, but it remains unclear whether individuals with IGD are compromised in proactive control or behavioral adjustment by learning from the changing contexts.
Methods
Here, fMRI data of 21 male young adults with IGD and 21 matched healthy controls (HC) were collected during a stop-signal task. We employed group independent component analysis to investigate group differences in temporally coherent, large-scale functional network activities during post-error slowing, the typical type of behavioral adjustments. We also employed a Bayesian belief model to quantify the trial-by-trial learning of the likelihood of stop signal – P(Stop) – a broader process underlying behavioral adjustment, and identified the alterations in functional network responses to P(Stop).
Results
The results showed diminished engagement of the fronto-parietal network during post-error slowing, and weaker activity in the ventral attention and anterior default mode network in response to P(Stop) in IGD relative to HC.
Discussion and conclusions
These results add to the literatures by suggesting deficits in updating and anticipating conflicts as well as in behavioral adjustment according to contextual information in individuals with IGD.
Partial abortion of gametes possessing S-5 j in S-5 i / S-5 j genotype at locus S-5 is responsible for hybrid sterility between indica and japonica subspecies in rice ( Oryza sativa L.), while a single wide compatibility (WC) allele S-5 n can restore normal hybrid fertility between the two groups. In this study, Pei’ai 64S, one of the most popular WC line widely used for subspecific hybrid rice breeding program in South China was studied for location of its S-5 locus. Twenty SSR (Simple Sequence Repeat) markers derived from Cornell SSR linkage map and 9 developed using sequences from GenBank database were employed to perform bulked segregant analysis of the mapping population derived from a three-way cross (Pei’ai 64S/T8//Akihikari) to tag fine location of the hybrid sterility locus, S-5 . This S-5 locus was mapped on chromosome 6 approximately 0.2 cM from GXR6 and RM276 SSR markers. This tight linkage of the markers and the S-5 locus would be very useful for efficient marker-assisted selection for WC varieties and for map-based cloning of the gene.
We report on the room temperature ferromagnetism observed in heat treated nanocrystalline diamonds. By systematic annealing of nanocrystalline diamond, graphitic nanoclusters having finite magnetization with well-defined hysteresis and coercivity, and a Curie temperature (TC) well above 400 K (estimated TC ~ 590 K), were synthesized. Using detailed analysis of the structural modification at various annealing stages, with Raman Spectroscopy and High Resolution Transmission Electron Microscopy, we show that the carbon bonding configuration has important consequence to the observed magnetism in these samples. These findings could lead to controlled fabrication of metal free magnetic carbon system.
