The importance of the isoelectric point for the preparation and characterization of functional materials to understand their behavior and optimize their performance is highlighted, with especial ...focus on industrial catalysts. In different liquid-phase steps involved in materials synthesis, the knowledge of the surface charge as a function of the pH of the medium is fundamental, since it is the dynamizing agent of processes such as gelation, peptization, coagulation and agglomeration to form solid particles. Therefore, zeta potential (ζ) measurements, often based on electrophoretic migration techniques, are a powerful source of information. The basic principles are introduced to explain through relevant examples the possibilities for materials design. Regarding materials preparation, the measurement of the zeta potential to control the synthesis and coating of supports is reviewed, with special attention to shaped supports. Aspects as the influence of the binders on the supports properties depending on their mutual interaction are analyzed, with example systems based on TiO2 or Al2O3 and natural silicates such as sepiolite. Also, how the knowledge of ζ as a function of pH allows, by choosing the appropriate pH, the preferential impregnation of noble metals on porous supports, as well as the washcoating of dense ceramic monoliths with porous supports. Special attention has been paid to surfaces characterization based on the use of zeta potential measurements to estimate the formation and relative location of species, the apparent surface coverage, or the adsorption and reactivity, to establish synthesis strategies to achieve specific properties.
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•Zeta potential measurements help defining synthesis and coating strategies.•Explanation of the relative distribution and apparent surface coverage of active species in shaped supports.•Estimation of active phase dispersion on a support until multilayers or agglomerated crystals start to form.•Prediction of nanomaterials reactivity in the human body and the environment for grouping and a safe and sustainable design.
We investigated the metabolomic profile associated with exposure to trihalomethanes (THMs) and nitrate in drinking water and with colorectal cancer risk in 296 cases and 295 controls from the Multi ...Case-Control Spain project. Untargeted metabolomic analysis was conducted in blood samples using ultrahigh-performance liquid chromatography-quadrupole time-of-flight mass spectrometry. A variety of univariate and multivariate association analyses were conducted after data quality control, normalization, and imputation. Linear regression and partial least-squares analyses were conducted for chloroform, brominated THMs, total THMs, and nitrate among controls and for case-control status, together with a N-integration model discriminating colorectal cancer cases from controls through interrogation of correlations between the exposure variables and the metabolomic features. Results revealed a total of 568 metabolomic features associated with at least one water contaminant or colorectal cancer. Annotated metabolites and pathway analysis suggest a number of pathways as potentially involved in the link between exposure to these water contaminants and colorectal cancer, including nicotinamide, cytochrome P-450, and tyrosine metabolism. These findings provide insights into the underlying biological mechanisms and potential biomarkers associated with water contaminant exposure and colorectal cancer risk. Further research in this area is needed to better understand the causal relationship and the public health implications.
The transference of the nutritional function from the VYS to the chorioallantoic placenta during middle pregnancy is a key event for the activation of embryo oxidative metabolism. However, the ...metabolic adaptations occurring in these tissues during this critical period have not been studied to date. Herein, we investigate the VYS and placenta mitochondrial adaptations throughout gestational days 11, 12 and 13. The results reflect that, during the placentation period, mitochondrial proliferation predominates over differentiation in placenta. Besides, VYS development and mitochondriogenesis show a slowdown despite maintaining the mitochondrial OXPHOS capacities, hence becoming a supporting tissue until the placenta functions are completely available.
Slimak
challenge the reliability of our oldest (>65,000 years) U-Th dates on carbonates associated with cave paintings in Spain. They cite a supposed lack of parietal art for the 25,000 years ...following this date, along with potential methodological issues relating to open-system behavior and corrections to detrital or source water
Th. We show that their criticisms are unfounded.
•The optimal conditions for synthesis of pure NiFe2O4 samples with the smallest particle size were determined.•The effect of urea/KOH concentration, temperature and time on the crystal size was ...analyzed.•The improvement of the silica coating and functionalization on the ions adsorption capacity was established.•The almost superparamagnetic behavior of the samples was verified by several techniques.
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Nickel ferrite samples are currently investigated due to their potential technological applications. For this reason, the optimal synthesis conditions of nickel ferrite samples with small particle size were investigated here. First, a systematic study was carried out using urea as an additive, and varying reaction parameter such as the amount of urea added or the reaction temperature and time. For comparison purposes, another sample was synthesized using potassium hydroxide as an additive. The two pure nickel ferrite samples were coated with silica, functionalizing them with APTES and AEPMDS. X-rays, FTIR, Mössbauer spectroscopy, TEM and Ms vs. H and FC/ZFC curves were used for the characterization of samples and the evaluation of their properties. Square particles with an average size of 21.2 nm were observed in the TEM images of the sample synthesized with urea, while these are spherical of 6.2 nm in the sample prepared with potash. Their subsequent coating and functionalization give rise to an arrangement of particles within interlocking strands whose thickness increases with their size. Ms vs. H curves confirm the almost superparamagnetic behavior of all synthesized powders, although with a slight increase in the coercivity value of the samples prepared with urea. Preliminary tests carried out on the functionalized samples to evaluate the adsorption capacity in aqueous solution and their easy separation in presence of an external magnetic field, confirm that the sample synthesized with urea and functionalized with AEPDMS is the most efficient for the Cu2+ ions removal.
Context.
Fast outflows and their interaction with slow shells (generally known as the fossil circumstellar envelope of asymptotic giant branch stars) play an important role in the structure and ...kinematics of protoplanetary and planetary nebulae (pPNe, PNe). To properly study their effects within these objects, we also need to observe the intermediate-temperature gas, which is only detectable in the far-infrared and submillimetre (submm) transitions.
Aims.
We study the physical conditions of the outflows presented in a number of pPNe and PNe, with a focus on their temperature and excitation states.
Methods.
We carried out
Herschel
/HIFI observations in the submm lines of
12
CO in nine pPNe and nine PNe and complemented them with low-
J
CO spectra obtained with the IRAM 30m telescope and taken from the literature. The spectral resolution of HIFI allows us to identify and measure the different nebular components in the line profiles. The comparison with large velocity gradient model predictions was used to estimate the physical conditions of the warm gas in the nebulae, such as excitation conditions, temperature, and density.
Results.
We found high kinetic temperatures for the fast winds of pPNe, typically reaching between 75 K and 200 K. In contrast, the high-velocity gas in the sampled PNe is colder, with characteristic temperatures between 25 K and 75 K, and it is found in a lower excitation state. We interpret this correlation of the kinetic temperature and excitation state of fast outflows with the amount of time elapsed since their acceleration (probably driven by shocks) as a consequence of the cooling that occurred during the pPN phase.
CONTEXTSilicon carbide dust is ubiquitous in circumstellar envelopes around C-rich AGB stars. However, the main gas-phase precursors leading to the formation of SiC dust have not yet been identified. ...The most obvious candidates among the molecules containing an Si-C bond detected in C-rich AGB stars are SiC2, SiC, and Si2C. To date, the ring molecule SiC2 has been observed in a handful of evolved stars, while SiC and Si2C have only been detected in the C-star envelope IRC +10216.AIMSWe aim to study how widespread and abundant SiC2, SiC, and Si2C are in envelopes around C-rich AGB stars and whether or not these species play an active role as gas-phase precursors of silicon carbide dust in the ejecta of carbon stars.METHODSWe carried out sensitive observations with the IRAM 30m telescope of a sample of 25 C-rich AGB stars to search for emission lines of SiC2, SiC, and Si2C in the λ 2 mm band. We performed non-LTE excitation and radiative transfer calculations based on the LVG method to model the observed lines of SiC2 and to derive SiC2 fractional abundances in the observed envelopes.RESULTSWe detect SiC2 in most of the sources, SiC in about half of them, and do not detect Si2C in any source, at the exception of IRC +10216. Most of these detections are reported for the first time in this work. We find a positive correlation between the SiC and SiC2 line emission, which suggests that both species are chemically linked, the SiC radical probably being the photodissociation product of SiC2 in the external layer of the envelope. We find a clear trend in which the denser the envelope, the less abundant SiC2 is. The observed trend is interpreted as an evidence of efficient incorporation of SiC2 onto dust grains, a process which is favored at high densities owing to the higher rate at which collisions between particles take place.CONCLUSIONSThe observed behavior of a decline in the SiC2 abundance with increasing density strongly suggests that SiC2 is an important gas-phase precursor of SiC dust in envelopes around carbon stars.
Within-person trajectories of cerebrospinal fluid (CSF) biomarkers in Alzheimer's disease (AD) are not well defined.
We included 467 subjects from the BIOMARKAPD study with at least two serial CSF ...samples. Diagnoses were subjective cognitive decline (n = 75), mild cognitive impairment (n = 128), and AD dementia (n = 110), and a group of cognitively unimpaired subjects (n = 154) were also included. We measured baseline and follow-up CSF levels of total tau (t-tau), phosphorylated tau (p-tau), YKL-40, and neurofilament light (NfL). Median CSF sampling interval was 2.1 years.
CSF levels of t-tau, p-tau, NfL, and YKL-40 were 2% higher per each year of baseline age in controls (P <.001). In AD, t-tau levels were 1% lower (P <.001) and p-tau levels did not change per each year of baseline age. Longitudinally, only NfL (P <.001) and YKL-40 (P <.02) increased during the study period.
All four CSF biomarkers increase with age, but this effect deviates in AD for t-tau and p-tau.
•In this large longitudinal multicenter cerebrospinal fluid (CSF) study each year of increase at baseline age was significantly associated with 2% higher mean CSF t-tau and p-tau levels in controls. Within the Alzheimer's disease group, each year of increase at baseline age was significantly associated with 1% lower mean CSF t-tau levels, and p-tau levels did not change with age.•Each year of increase at baseline age was significantly associated with 2% higher mean CSF neurofilament light (NfL) and YKL-40 levels in controls without differences among groups.•Longitudinally, after adjusting for baseline age, only NfL and YKL-40 levels significantly increased during the study period in all groups.•The pattern of change of CSF tau, NfL, and YKL-40 is different in Alzheimer's disease.
The laser Raman and IR spectra of 5-chlorocytosine have been recorded and accurately assigned in the solid state using Density functional calculations (DFT) together with the linear scaling equation ...procedure (LSE) and the solid state simulation of the crystal unit cell through a tetramer form. These results remarkably improve those reported previously by other authors. Several new scaling equations were proposed to be used in related molecules. The six main tautomers of the biomolecule 5-chlorocytosine were determined and optimized at the MP2 and CCSD levels, using different basis sets. The relative stabilities were compared with those obtained in cytosine and their 5-halo derivatives. Several relationships between energies, geometric parameters and NBO atomic charges were established. The effect of the chlorine substitution in the fifth position was evaluated through the stability of the Watson-Crick (WC) base pair of 5-chlorodeoxycytidine with deoxyguanosine, and through their vibrational spectra.
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•The stabilities of the main tautomers of 5-halo-cytosine derivatives were determined.•The crystal unit cell was simulated by a tetramer form and obtained its spectra.•A reassignment of the IR and Raman bands was carried out by DFT methods and scaling.•The effect of the chlorine atom in the Watson-Crick base pair was determined.
Introduction
The evidence for characteristics of persons with subjective cognitive decline (SCD) associated with amyloid positivity is limited.
Methods
In 1640 persons with SCD from 20 Amyloid ...Biomarker Study cohort, we investigated the associations of SCD‐specific characteristics (informant confirmation, domain‐specific complaints, concerns, feelings of worse performance) demographics, setting, apolipoprotein E gene (APOE) ε4 carriership, and neuropsychiatric symptoms with amyloid positivity.
Results
Between cohorts, amyloid positivity in 70‐year‐olds varied from 10% to 76%. Only older age, clinical setting, and APOE ε4 carriership showed univariate associations with increased amyloid positivity. After adjusting for these, lower education was also associated with increased amyloid positivity. Only within a research setting, informant‐confirmed complaints, memory complaints, attention/concentration complaints, and no depressive symptoms were associated with increased amyloid positivity. Feelings of worse performance were associated with less amyloid positivity at younger ages and more at older ages.
Discussion
Next to age, setting, and APOE ε4 carriership, SCD‐specific characteristics may facilitate the identification of amyloid‐positive individuals.
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