We investigate the high-pressure phase diagram of the hydrous mineral brucite, Mg(OH)₂, using structure search algorithms and ab initio simulations. We predict a high-pressure phase stable at ...pressure and temperature conditions found in cold subducting slabs in Earth’s mantle transition zone and lower mantle. This prediction implies that brucite can play a much more important role in water transport and storage in Earth’s interior than hitherto thought. The predicted high-pressure phase, stable in calculations between 20 and 35 GPa and up to 800 K, features MgO₆ octahedral units arranged in the anatase–TiO₂ structure. Our findings suggest that brucite will transform from a layered to a compact 3D network structure before eventual decomposition into periclase and ice. We show that the high-pressure phase has unique spectroscopic fingerprints that should allow for straightforward detection in experiments. The phase also has distinct elastic properties that might make its direct detection in the deep Earth possible with geophysical methods.
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The interiors of giant icy planets depend on the properties of hot, dense mixtures of the molecular ices water, ammonia, and methane. Here, we discuss results from first-principles molecular dynamics ...simulations up to 500 GPa and 7000 K for four different ammonia-water mixtures that correspond to the stable stoichiometries found in solid ammonia hydrates. We show that all mixtures support the formation of plastic and superionic phases at elevated pressures and temperatures, before eventually melting into molecular or ionic liquids. All mixtures' melting lines are found to be close to the isentropes of Uranus and Neptune. Through local structure analyses we trace and compare the evolution of chemical composition and longevity of chemical species across the thermally activated states. Under specific conditions we find that protons can be less mobile in the fluid state than in the (colder, solid) superionic regime.
Neuroacanthocytosis (NA) syndromes are a group of rare diseases characterized by neurological disorders and misshaped spiky red blood cells (acanthocytes) including Chorea-Acanthocytosis (ChAc), ...McLeod syndrome (MLS), Huntington disease-like 2 (HDL 2), pantothenate kinase-associated neurodegeneration (PKAN), abeta- and hypobetalipoproteinemia and aceruloplasminemia. This clinically and genetically heterogeneous group of diseases shares main clinical features presenting most often as a hyperkinetic movement disorder. Even though these are long noted disease conditions, we still know only little on the underlying disease mechanisms.
The current review focuses upon ChAc as the core entity of NA syndromes caused by mutations in the VPS13A gene. The support of patient organizations and the ERA-NET initiative yielded to different multidisciplinary efforts with significant progress on our understanding of ChAc. Disturbances in two pathways are currently considered to be significantly involved in the pathophysiology of ChAc, namely elevated Lyn kinase phosphorylation and decreased signaling via Phosphoinositide 3-kinase (PI3K). These recent developments may reveal potential drugable targets for causative therapies of ChAc.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
The structures and electronic properties of low-energy neutral and anionic Mg n (n = 3–20) clusters have been studied by utilizing a widely adopted CALYPSO structure searching method coupled with ...density functional theory calculations. A large number of low-energy isomers are optimized at the B3PW91 functional with the 6-311+G(d) basis set. The optimized geometries clearly indicate that a structural transition from hollow three-dimensional configurations to filled-cage-like structures occurs at n = 16 for both neutral and anionic clusters. Based on the anionic ground state structures, photoelectron spectra are simulated using time-dependent density functional theory (TD-DFT) and compared with experimental results. The good agreement validates that the current ground state structures, obtained from the symmetry-unconstrained searches, are true global minima. A detailed chemical bonding analysis distinctly indicates that the Mg17 cluster is the first neutral locally π-aromatic homonuclear all-metal cluster, which perfectly satisfies Hückel’s well-known 4N + 2 rule.
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Objective
Weight loss has been identified as a negative prognostic factor in amyotrophic lateral sclerosis, but there is no evidence regarding whether a high‐caloric diet increases survival. ...Therefore, we sought to evaluate the efficacy of a high‐caloric fatty diet (HCFD) for increasing survival.
Methods
A 1:1 randomized, placebo‐controlled, parallel‐group, double‐blinded trial (LIPCAL‐ALS study) was conducted between February 2015 and September 2018. Patients were followed up at 3, 6, 9, 12, 15, and 18 months after randomization. The study was performed at 12 sites of the clinical and scientific network of German motor neuron disease centers (ALS/MND‐NET). Eligible patients were randomly assigned (1:1) to receive either HCFD (405kcal/day, 100% fat) or placebo in addition to riluzole (100mg/day). The primary endpoint was survival time, defined as time to death or time to study cutoff date.
Results
Two hundred one patients (80 female, 121 male, age = 62.4 ± 10.8 years) were included. The confirmatory analysis of the primary outcome survival showed a survival probability of 0.39 (95% confidence interval CI = 0.27–0.51) in the placebo group and 0.37 (95% CI = 0.25–0.49) in the HCFD group, both after 28 months (point in time of the last event). The hazard ratio was 0.97, 1‐sided 97.5% CI = −∞ to 1.44, p = 0.44.
Interpretation
The results provide no evidence for a life‐prolonging effect of HCFD for the whole amyotrophic lateral sclerosis population. However, post hoc analysis revealed a significant survival benefit for the subgroup of fast‐progressing patients. ANN NEUROL 2020;87:206–216
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Sodium is one of the best examples of a free-electron-like metal and of a certain technological interest. However, an unambiguous determination of the structural evolution of sodium clusters is ...challenging. Here, we performed an unbiased structure search among neutral and anionic sodium clusters in the medium size range of 10–25 atoms, using the Crystal structure AnaLYsis by Particle Swarm Optimization (CALYPSO) method. Geometries are determined by CALYPSO structure searches, followed by reoptimization of a large number of candidate structures. For most cluster sizes the simulated photoelectron spectra of the lowest-energy structures are in excellent agreement with the experimental data, indicating that the current ground-state structures are the true minima. The equilibrium geometries show that, for both neutral and anionic species, the structural evolution from bilayer structures to layered outsides with interior atoms occurs at n = 16. A novel unprecedented honeycomb-like structure of Na20 cluster with C 3 symmetry is uncovered, which is more stable than the prior suggested structure based on pentagonal structural motifs.
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Amyotrophic lateral sclerosis (ALS) is the most frequent motor neuron disease. Cytoplasmic fused in sarcoma (FUS) aggregates are pathological hallmarks of FUS-ALS. Proper shuttling between the ...nucleus and cytoplasm is essential for physiological cell function. However, the initial event in the pathophysiology of FUS-ALS remains enigmatic. Using human induced pluripotent stem cell (hiPSCs)-derived motor neurons (MNs), we show that impairment of poly(ADP-ribose) polymerase (PARP)-dependent DNA damage response (DDR) signaling due to mutations in the FUS nuclear localization sequence (NLS) induces additional cytoplasmic FUS mislocalization which in turn results in neurodegeneration and FUS aggregate formation. Our work suggests that a key pathophysiologic event in ALS is upstream of aggregate formation. Targeting DDR signaling could lead to novel therapeutic routes for ameliorating ALS.
The interior structure of the giant ice planets Uranus and Neptune, but also of newly discovered exoplanets, is loosely constrained, because limited observational data can be satisfied with various ...interior models. Although it is known that their mantles comprise large amounts of water, ammonia, and methane ices, it is unclear how these organize themselves within the planets—as homogeneous mixtures, with continuous concentration gradients, or as well-separated layers of specific composition. While individual ices have been studied in great detail under pressure, the properties of their mixtures are much less explored. We show here, using first-principles calculations, that the 2:1 ammonia hydrate, (H₂O)(NH₃)₂, is stabilized at icy planet mantle conditions due to a remarkable structural evolution. Above 65 GPa, we predict it will transform from a hydrogen-bonded molecular solid into a fully ionic phase
O
2
−
(
NH
4
+
)
2
, where all water molecules are completely deprotonated, an unexpected bonding phenomenon not seen before. Ammonia hemihydrate is stable in a sequence of ionic phases up to 500 GPa, pressures found deep within Neptune-like planets, and thus at higher pressures than any other ammonia–water mixture. This suggests it precipitates out of any ammonia–water mixture at sufficiently high pressures and thus forms an important component of icy planets.
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•Hand muscle denervation was studied in adult spinal muscular atrophy (SMA) patients with MUNIX.•Adult SMA patients had a pathophysiological remarkable denervation pattern of hand muscles, a ...‘reversed split hand’.•MUNIX is a biomarker for upcoming questions in adult SMA.
There is still insufficient knowledge about natural history in adult spinal muscular atrophy, thus valid markers for treatment and disease monitoring are urgently needed.
We studied hand muscle innervation pattern of 38 adult genetically confirmed 5q spinal muscular atrophy (SMA) patients by the motor unit number index (MUNIX) method. Data were compared to healthy controls and amyotrophic lateral sclerosis (ALS) patients and systematically correlated to typical disease-relevant scores and other clinical as well as demographic characteristics.
Denervation of hand muscles in adult SMA was not evenly distributed. By calculation of the MUNIX ratios, we identified a specific hand muscle wasting pattern for SMA which is different to the split hand in ALS. Furthermore, MUNIX parameters strongly correlated with established disease course parameters independent of disease stages.
We found a pathophysiological remarkable denervation pattern of hand muscles, a ‘reversed split hand’. MUNIX of single hand muscles correlated well with disease severity and thus represents an easily available biomarker for adult SMA.
Our data show the power of the MUNIX method as a biomarker for upcoming questions in adult SMA.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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