Preterm birth is associated with impairments in self-regulation and altered white-matter fibre properties of brain areas linked to self-regulation in childhood, which may extend into adolescence. As self-regulation can be effectively targeted by interventions, it is important to understand such potential disadvantages and their neural sources in vulnerable groups. We examined associations between gestational age (GA) at birth, white-matter fibre properties (e.g. fractional anisotropy (FA)) and self-regulation, as well as brain-behaviour associations at the onset of adolescence. We hypothesized that lower GA relates to poorer self-regulation ability and reduced FA in brain fibres connecting self-regulation hubs, and that self-regulation correlates positively with FA. Participants were drawn from the Adolescent Brain Cognitive Development (ABCD) study: 1695 preterm and 1693 term-born adolescents for behavioural analyses and 1304 preterm and 1379 term-born adolescents for neural analyses. Associations between GA, self-regulation and fibre properties were tested using local structural equation modelling (SEM), and brain-behaviour associations were estimated via regularized SEM. None of the hypotheses was supported by the data. We suspect a sampling bias in the ABCD preterm cohort towards better adapted individuals, highlighting the importance of considering cohort characteristics when generalizing results from this cohort to the broader preterm population.
In this study, we investigate how variations in precursor composition and partial vapor-assisted substitution of Sn by Ge affect the material quality and device performance of CZTGSe solar cells. Precursor films with different Cu-Sn alloy ratios were selenized under controlled SnSe2-x and GeSe2-x vapor conditions, enabling the synthesis of Cu2ZnSn1-xGexSe4 absorber layers with Ge/(Ge + Sn) ratios ranging from 0 to 36%. Despite the initial variations, the final absorber compositions converged due to in-process shifts driven by Sn and/or Ge incorporation and loss during the reaction. Beyond the established role of the absorber composition, we show that the reaction pathway, determined by the precursor composition, strongly influences the defect concentration, material quality, and device performance. A Cu-rich and Sn-poor (Cu/Sn > 2) starting composition that evolves into a Cu-poor Sn-rich kesterite absorber is found to be particularly beneficial. Furthermore, prolonged post deposition treatment revealed distinct stability trends: Ge-free devices degraded steadily, whereas Ge-containing devices continued to improve over similar to 430 hours. We attribute this to stabilization of [V-Cu + Zn-Cu] defect clusters and re-distribution of Ge atoms. The best-performing device, with Ge/(Ge + Sn) = 9% achieved 12.5% efficiency with enhanced long-term stability, underscoring the potential of vapor-phase Ge integration for advancing physically synthesized kesterite solar cells.
$A$ be an abelian variety over a number field $K$ of dimension $r$, $a_1, \dots, a_g \in A(K)$ and $F/K$ a finite Galois extension. We consider the density of primes $\frak p$ of $K$ such that the quotient $\bar{A}(k({\frak p}))/\langle \bar{a}_1,\dots,\bar{a}_g\rangle$ has at most $2r-1$ cyclic components and $\frak p$ satisfies a Frobenius condition with respect to $F/K$, where $\bar{A}$ is the reduction of $A$ modulo $\frak p$, $k(\frak p)$ is the residue class field of $\frak p$ and $\langle \bar{a}_1,\dots,\bar{a}_g\rangle$ is the subgroup generated by the reductions $\bar{a}_1,\dots,\bar{a}_g$. We develop a general framework to prove the existence of the density under the Generalized Riemann Hypothesis.
Bimetallic platinum-iridium electrocatalysts for oxygen reduction/evolution reactions (ORR/OER) are of great interest for unitized regenerative fuel cells. The potential-dependent formation of catalytically active Pt-Ir species and their resulting electronic structure to accelerate both the ORR and OER are still unknown. Raman spectroscopy is used to monitor in situ the potential-resolved electronic and structural interactions of Pt and Ir in sputtered Pt-Ir thin films as model catalyst systems for the ORR and OER. The low coverage of oxygen-based intermediates on the Pt surface sites for Pt-Ir films correlates with enhanced ORR activity. At potentials before and during the OER, further electrochemical oxidation of the Pt-Ir thin films occurs that clearly differs from that of the monometallic films. DFT calculations indicate the formation of hydrous PtO6-IrO6 edge-sharing chains with & micro;-oxo bond linkages to couple Pt and Ir centers electronically. The theoretical stretching and bending motions of these Pt-O-Ir bonds are the most intense vibrations at 494, 542 and 682 cm-1 and are in very good agreement with the experimental data (similar to 510, similar to 540 and 657 cm-1). Very remarkably, theoretical and experimental data uncover a clear shift to lower energy by similar to 38 cm-1 for symmetric stretching of Ir-O-Pt (657 cm-1) compared to Ir-O-Ir (695 cm-1) under OER conditions. In other words, this change in bond strength can be correlated with lower OER activity and indicates a weakening of the Ir-O-Pt bond by similar to 0.48 kJ mol-1 compared to IrOx. Overall, our comprehensive in situ Raman and DFT investigations provide new mechanistic insights into the potential-resolved formation of catalytically active Pt-Ir sites for both the ORR and OER.
Permeable sands on continental shelves host microbial communities that drive organic carbon turnover, oxygen fluxes and nitrogen loss. Advective porewater flow associated with sedimentary bedforms maintains these rates and fluxes. Modeling and laboratory studies suggest that advective porewater flow is tightly coupled to bedform stability. However, the impacts of in situ bedform stability on biogeochemical fluxes in subtidal sands remain unconstrained. We deployed a benthic lander at six stations in the North Sea to measure in situ bedform geometries, oxygen fluxes and primary productivity accompanied with ex situ incubations, glycan extraction and microscopy. We observed bedform migration velocities ranging between 0 and 3.2 cm h(-1), which were only 9-16% of expected values from mechanistic models. Bedform stability may be enhanced by high interstitial colloidal and particulate algal glycans concentrations (2-52 mmol C L-1) that are a representative component of extracellular polymeric substances. Benthic primary productivity as a source of carbon was negligible (< 0.003 mmol C m(-2) d(-1)). Pore space glycan accumulation was attributed to algal biomass filtered out of the overlying water column by advective flow through the permeable sediment. Benthic glycan concentrations correlated significantly with oxygen consumption rates per volume porewater (17-207 mu mol L-PW(-1) h(-1)), whereas sediment oxygen fluxes (6-17 mmol m(-2) d(-1)) significantly correlated with modeled porewater velocities. Overall, the impact of glycans as a proxy for pelagically derived algal biomass was twofold: (1) they drove higher oxygen consumption rates in surface sediments and (2) contributed to stabilization of bedforms, which almost doubled oxygen fluxes into the sediment.
