Alkaline persulfate oxidation as an intermediate step for the development of a wet chemical oxidation interface for compound-specific δN analysis by LC-IRMS.

For the measurement of compound-specific isotope ratios by liquid chromatography isotope ratio mass spectrometry (LC-IRMS), complete mineralization of organic compounds to a single species of measurement gas is required so that isotopic fractionation can be minimized and corrected by identical treatment with standards. The established use of peroxydisulfate in an acidic environment has its limitations, especially when it comes to the complete oxidation of nitrogen-containing compounds with aromatic ring systems. Under acidic oxidation conditions, ammonium and nitrate were identified as the main nitrogen containing mineralization products of the oxidation of different model compounds.

Intact embodiment during perspective-taking in older adults is not affected by focal tDCS.

Embodied processing is crucial for visual perspective taking (VPT), with evidence from non-invasive transcranial direct current stimulation (tDCS) suggesting a causal role of the right temporoparietal junction (rTPJ). However, it is not known whether such embodied factors are maintained in older adults or whether rTPJ-tDCS has comparable effects in advanced age. We employed a balanced and sham-tDCS controlled, double-blinded, cross-over design, including two randomized experimental groups of healthy older adults, receiving focal tDCS over either the rTPJ (n = 30), or a control region in the dorsomedial prefrontal cortex (dmPFC, n = 30).

Neuronavigated Focalized Transcranial Direct Current Stimulation Administered During Functional Magnetic Resonance Imaging.

Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation technique that allows the modulation of the excitability and plasticity of the human brain. Focalized tDCS setups use specific electrode arrangements to constrain the current flow to circumscribed brain regions. However, the effectiveness of focalized tDCS can be compromised by electrode positioning errors on the scalp, resulting in significant reductions of the current dose reaching the target brain regions for tDCS.

A Proof-of-Principle Study for δN Measurements of Aqueous Dissolved Nitrate With a Modified LC-IRMS Interface.

Rationale: The analysis of nitrogen isotopes in aqueous dissolved nitrate is an effective method for identifying pollution sources and offers the potential to study the nitrogen cycle. However, the measurement of nitrogen isotope ratios of nitrate still requires extensive sample preparation or derivatization.

Methods: In this study, a modified commercially available liquid chromatography-isotope ratio mass spectrometer (LC-IRMS) interface is presented that enables automated measurement of δN signatures from nitrate by online reduction of nitrate in two consecutive steps.

Circulating tumor DNA in diffuse large B-cell lymphoma: analysis of response assessment, correlation with PET/CT and clone evolution.

Introduction: Circulating tumor DNA (ctDNA) can be obtained from cell-free DNA (cfDNA) andis a new technique for genotyping, response assessment and prognosis in lymphoma.

Methods: Eighteen patients with samples at diagnosis (ctDNA1), after treatment (ctDNA2) and extracted from diagnostic tissue (FFPE) were evaluated.

Results: In all patients, at least one mutation in cfDNA was detected at diagnosis.