Nearly Space-Filling Fractal Networks of Carbon Nanopores

URL:http://link.aps.org/doi/10.1103/PhysRevLett.88.115502 DOI:10.1103/PhysRevLett.88.115502Small-angle x-ray scattering, nitrogen adsorption, and scanning tunneling microscopy show that a series of activated carbons host an extended fractal network of channels with dimension Dp = 2.8-3.0 (pore fractal), channel width 15-20Å (lower end of scaling), network diameter 3000-3400Å (upper end of scaling), and porosity of 0.3-0.6. We interpret the network as a stack of quasiplanar invasion percolation clusters, formed by oxidative removal of walls between closed voids of diameter of ∼10Å and held in registry by fibrils of the biological precursor, and point out unique applications.This work was supported by the Petroleum Research Fund, Grant No. 30602-AC9,5 (P. P.); the Department of Energy, Contracts No. W-7405-ENG-36 (P. P.) and No. DE-AC04-00A185000 (T. P. R.); and the Ceramic and Non-Metallic Materials Program at AFOSR (W. P. H.)

LiFePO4 spray drying scale-up and carbon-cage for improved cyclability

The growing market for electrical vehicles requires inexpensive, long-lasting batteries. LiFePO4 (LFP) melt-synthesized from ore concentrate fits this role, but the manufacturing process requires additional steps that includes grinding large ingots into a nanoparticle suspension followed by a dessication step. Spray drying, rather than tray drying, creates a mesopomus powder that enhances wettability. Adding lactose and high-Mw polyvinyl alcohol (PVA) to the suspension of nanostructures followed by pyrolysis, creates a carbon-cage that interconnects the cathode nanoparticles, imparting better capacity (LiFePO4/C: 161 mA h g(-1) at 0.1C), discharge rate (flat plateau, 145 mA h g(-1) at 5C), and cyclability (91% capacity retention after 750 cycles at 1C). Particle size affects battery stability; PVA increases the suspension's viscosity and alters the powder morphology, from spherical to hollow particles. A model describes the non-Newtonian suspension's rheology changing: shear, temperature, LFP and PVA loading. Carbon precursors prevent the nanoparticles from sintering during calcination but lactose gasifies 50% of the carbon, according to the chemical and allotropic composition measurements (CS analyzer, XPS, and Raman). The carbon-cage imparts micmporosity and we correlate the SEM and TEM powder's morphology with N2 physisorption porosimetry. Ultrasonication of the suspension fragments the PVA chain, which is detrimental to the final cathode performance

Dynamic imaging of individual remyelination profiles in multiple sclerosis

Background Quantitative in vivo imaging of myelin loss and repair in patients with multiple sclerosis (MS) is essential to understand the pathogenesis of the disease and to evaluate promyelinating therapies. Selectively binding myelin in the central nervous system white matter, Pittsburgh compound B ([11C]PiB) can be used as a positron emission tomography (PET) tracer to explore myelin dynamics in MS. Methods Patients with active relapsing-remitting MS (n = 20) and healthy controls (n = 8) were included in a longitudinal trial combining PET with [11C]PiB and magnetic resonance imaging. Voxel-wise maps of [11C]PiB distribution volume ratio, reflecting myelin content, were derived. Three dynamic indices were calculated for each patient: the global index of myelin content change; the index of demyelination; and the index of remyelination. Results At baseline, there was a progressive reduction in [11C]PiB binding from the normal-appearing white matter to MS lesions, reflecting a decline in myelin content. White matter lesions were characterized by a centripetal decrease in the tracer binding at the voxel level. During follow-up, high between-patient variability was found for all indices of myelin content change. Dynamic remyelination was inversely correlated with clinical disability (p = 0.006 and beta-coefficient = -0.67 with the Expanded Disability Status Scale; p = 0.003 and beta-coefficient = -0.68 with the MS Severity Scale), whereas no significant clinical correlation was found for the demyelination index. Interpretation [11C]PiB PET allows quantification of myelin dynamics in MS and enables stratification of patients depending on their individual remyelination potential, which significantly correlates with clinical disability. This technique should be considered to assess novel promyelinating drugs. Ann Neurol 2016;79:726-73

Dark Matter and Higgs Sector

The inert doublet model is an extension of the Standard Model of Elementary Particles that is defined by the only addition of a second Higgs doublet without couplings to quarks or leptons. This minimal framework has been studied for many reasons. In particular, it has been suggested that the new degrees of freedom contained in this doublet can account for the Dark Matter of the Universe.Comment: 6 pages, 3 figures,To appear in the Proceedings of the sixth International Workshop on the Dark Side of the Universe (DSU2010) Leon, Guanajuato, Mexico 1-6 June 201

Inflation and dark matter in two Higgs doublet models

We consider the Higgs inflation in the extension of the Standard Model with two Higgs doublets coupled to gravity non-minimally. In the presence of an approximate global U(1) symmetry in the Higgs sector, both radial and angular modes of neutral Higgs bosons drive inflation where large non-Gaussianity is possible from appropriate initial conditions on the angular mode. We also discuss the case with single-field inflation for which the U(1) symmetry is broken to a Z_2 subgroup. We show that inflationary constraints, perturbativity and stability conditions restrict the parameter space of the Higgs quartic couplings at low energy in both multi- and single-field cases. Focusing on the inert doublet models where Z_2 symmetry remains unbroken at low energy, we show that the extra neutral Higgs boson can be a dark matter candidate consistent with the inflationary constraints. The doublet dark matter is always heavy in multi-field inflation while it can be light due to the suppression of the co-annihilation in single-field inflation. The implication of the extra quartic couplings on the vacuum stability bound is also discussed in the light of the recent LHC limits on the Higgs mass.Comment: (v1) 28 pages, 8 figures; (v2) 29 pages, a new subsection 3.3 added, references added and typos corrected, to appear in Journal of High Energy Physic

Hexagonal Hybrid Bismuthene by Molecular Interface Engineering

High-quality devices based on layered heterostructures are typically built from materials obtained by complex solid-state physical approaches or laborious mechanical exfoliation and transfer. Meanwhile, wet-chemically synthesized materials commonly suffer from surface residuals and intrinsic defects. Here, we synthesize using an unprecedented colloidal photocatalyzed, one-pot redox reaction a few-layers bismuth hybrid of “electronic grade” structural quality. Intriguingly, the material presents a sulfur-alkyl-functionalized reconstructed surface that prevents it from oxidation and leads to a tuned electronic structure that results from the altered arrangement of the surface. The metallic behavior of the hybrid is supported by ab initio predictions and room temperature transport measurements of individual nanoflakes. Our findings indicate how surface reconstructions in two-dimensional (2D) systems can promote unexpected properties that can pave the way to new functionalities and devices. Moreover, this scalable synthetic process opens new avenues for applications in plasmonics or electronic (and spintronic) device fabrication. Beyond electronics, this 2D hybrid material may be of interest in organic catalysis, biomedicine, or energy storage and conversion.This work has been supported by the European Union (ERC-2018-StG 804110-2D-PnictoChem & and ERC Proof of Concept Grant 101101079-2D4H2 to G.A.; ERC-2021-StG 101042680 2D-SMARTiES awarded to J.J.B.), the Spanish MICINN (PID2019-111742GA-I00, PID2020–115100GB–I00, MRR/PDC2022-133997-I00, TED2021-131347B-I00, and Excellence Unit María de Maeztu CEX2019-000919-M), and the Generalitat Valenciana (CIDEGENT/2018/001, CIDEGENT/2018/005, and CDEIGENT/2019/022). Financial support by Severo Ochoa centre of excellence program (CEX2021–001230–S) is gratefully acknowledged. M.K. and H.B.W. acknowledge support by the Deutsche Forschungsgemeinschaft (DFG), under Projektnummer 182849149 (SFB 953, projects B08 and B13). Electron microscopy work carried out at UCM (M.V., G.S.S.) sponsored by MICINN PID2021-122980OB-C51 and Comunidad de Madrid MAD2D-CM-UCM3. G.S.S. acknowledges financial support from Spanish MCI Grant Nos. RTI2018-099054-J-I00 (MCI/AEI/FEDER, UE) and IJC2018-038164-I. C.D. and Y.M.E. thank the cluster of excellence 3DMM2O funded by DFG under Germany’s Excellence Strategy – 2082/1 – 390761711 for financial support. The authors thank Lukas Grünwald and Erich Müller for helpful discussions. A.M.R. thanks the Spanish MIU (Grant No FPU21/04195). A.S.-D. thanks the Universidad de Valencia, for an ‘Atracción del talento’ predoctoral grant. F.G.-P. thanks ITQ, UPV–CSIC for concession of a contract (PAID 01-18)

Association between fat-soluble vitamins and self-reported health status: A cross-sectional analysis of the MARK-AGE cohort

Self-rated health (SRH) is associated with higher risk of death. Since low plasma levels of fat-soluble vitamins are related to mortality, we aimed to assess whether plasma concentrations of vitamins A, D and E were associated with SRH in the MARK-AGE study. We included 3158 participants (52% female) aged between 35-75 years. Cross-sectional data were collected via questionnaires. An enzyme immunoassay quantified 25-hydroxyvitamin D and HPLC determined α-tocopherol and retinol plasma concentrations. The median 25-hydroxyvitamin D and retinol concentrations differed significantly (P<0.001) between SRH categories, and were lower in the combined fair/poor category versus the excellent, very good, good categories (25-hydroxvitamin D: 40.8 vs. 51.9, 49.3, 46.7 nmol/l, respectively; retinol: 1.67 vs. 1.75, 1.74, 1.70 μmol/l, respectively). Both vitamin D and retinol status were independently associated with fair/poor SRH in multiple regression analyses: adjusted ORs (95% CI) for the vitamin D insufficiency, deficiency, severe deficiency categories were 1.33 (1.06-1.68), 1.50 (1.17-1.93), and 1.83 (1.34-2.50) respectively; P=0.015, P=0.001, P<0.001, and for the second/third/fourth retinol quartiles: 1.44 (1.18-1.75), 1.57 (1.28-1.93), 1.49 (1.20-1.84); all P<0.001. No significant associations were reported for α-tocopherol quartiles. Lower vitamin A and D status emerged as independent markers for fair/poor SRH. Further insights into the long-term implications of these modifiable nutrients on health status are warranted

Current paradigm of the 18-kDa translocator protein (TSPO) as a molecular target for PET imaging in neuroinflammation and neurodegenerative diseases

Neuroinflammation is a process characterised by drastic changes in microglial morphology and by marked upregulation of the 18-kDa translocator protein (TSPO) on the mitochondria. The continual increase in incidence of neuroinflammation and neurodegenerative diseases poses a major health issue in many countries, requiring more innovative diagnostic and monitoring tools. TSPO expression may constitute a biomarker for brain inflammation that could be monitored by using TSPO tracers as neuroimaging agents. From medical imaging perspectives, this review focuses on the current concepts related to the TSPO, and discusses briefly on the status of its PET imaging related to neuroinflammation and neurodegenerative diseases in humans