Advanced numerical models used for climate prediction are known to exhibit biases in their simulated climate response to variable concentrations of the atmospheric greenhouse gases and aerosols that ...force a non-uniform, in space and time, secular global warming. We argue here that these biases can be particularly pronounced due to misrepresentation, in these models, of the multidecadal internal climate variability characterized by large-scale, hemispheric-to-global patterns. This point is illustrated through the development and analysis of a prototype climate model comprised of two damped linear oscillators, which mimic interannual and multidecadal internal climate dynamics and are set into motion via a combination of stochastic driving, representing weather noise, and deterministic external forcing inducing a secular climate change. The model time series are paired with pre-specified patterns in the physical space and form, conceptually, a spatially extended time series of the zonal-mean near-surface temperature, which is further contaminated by a spatiotemporal noise simulating the rest of climate variability. The choices of patterns and model parameters were informed by observations and climate-model simulations of the 20th century near-surface air temperature. Our main finding is that the intensity and spatial patterns of the internal multidecadal variability associated with the slow-oscillator model component greatly affect (i) the ability of modern pattern-recognition/fingerprinting methods to isolate the forced response of the climate system in the 20th century ensemble simulations and (ii) climate-system predictability, especially decadal predictability, as well as the estimates of this predictability using climate models in which the internal multidecadal variability is underestimated or otherwise misrepresented.
The neural basis for the transition from preclinical to symptomatic Huntington's disease (HD) is unknown. We used serial positron emission tomography (PET) imaging in preclinical HD gene carriers ...(p-HD) to assess the metabolic changes that occur during this period. Twelve p-HD subjects were followed longitudinally with 11C-raclopride and 18F-fluorodeoxyglucose PET imaging, with scans at baseline, 18 and 44 months. Progressive declines in striatal D2-receptor binding were correlated with concurrent changes in regional metabolism and in the activity of an HD-related metabolic network. We found that striatal D2 binding declined over time (P < 0.005). The activity of a reproducible HD-related metabolic covariance pattern increased between baseline and 18 months (P < 0.003) but declined at 44 months (P < 0.04). These network changes coincided with progressive declines in striatal and thalamic metabolic activity (P < 0.01). Striatal metabolism was abnormally low at all time points (P < 0.005). By contrast, thalamic metabolism was elevated at baseline (P < 0.01), but fell to subnormal levels in the p-HD subjects who developed symptoms. These findings were confirmed with an MRI-based atrophy correction for each individual PET scan. Increases in network expression and thalamic glucose metabolism may be compensatory for early neuronal losses in p-HD. Declines in these measures may herald the onset of symptoms in gene carriers.
In this study, the criterion for validity of the nighttime ozone chemical equilibrium assumption in the mesopause region is applied to Sounding of the Atmosphere using Broadband Emission Radiometry ...data for the year 2004 to define the boundary of this equilibrium. We demonstrate that the boundary varies within the range of 77–86 km depending on season and latitude and the retrieval of atomic oxygen from the equilibrium assumption below this boundary leads to significant (up to 5–8 times) underestimation of this component's concentration in the range of 80–85 km. However, this fact does not influence the subsequent atomic hydrogen retrieval.
Plain Language Summary
The chemical equilibrium of nighttime ozone in the mesopause region is one of the main assumption which has been employed for several decades for determining distributions of atomic oxygen and atomic hydrogen via satellite and rocket measurements of ozone and airglow emissions. Usually, this assumption is used in the range of 80–105 km. In this paper, we demonstrate for the first time from experimental data that the lower boundary, where the chemical equilibrium of nighttime ozone is valid, varies within the range of 77–86 km depending on season and latitude. The use of the equilibrium assumption under that boundary can lead to a great (up to 5–8 times) underestimation of O concentration in the range of 80–85 km but does not influence atomic hydrogen derivation.
Key Points
The boundary of the nighttime ozone chemical equilibrium area in the mesopause region varies within the range of 77‐86 km
Derivation of atomic oxygen below the boundary leads to significant underestimation in the range of 80‐85 km
Invalidity of nighttime ozone chemical equilibrium assumption does not influence atomic hydrogen retrieval
To identify metabolic brain networks that are associated with Tourette syndrome (TS) and comorbid obsessive-compulsive disorder (OCD).
We utilized (18)F-fluorodeoxyglucose and PET imaging to examine ...brain metabolism in 12 unmedicated patients with TS and 12 age-matched controls. We utilized a spatial covariance analysis to identify 2 disease-related metabolic brain networks, one associated with TS in general (distinguishing TS subjects from controls), and another correlating with OCD severity (within the TS group alone).
Analysis of the combined group of patients with TS and healthy subjects revealed an abnormal spatial covariance pattern that completely separated patients from controls (p < 0.0001). This TS-related pattern (TSRP) was characterized by reduced resting metabolic activity of the striatum and orbitofrontal cortex associated with relative increases in premotor cortex and cerebellum. Analysis of the TS cohort alone revealed the presence of a second metabolic pattern that correlated with OCD in these patients. This OCD-related pattern (OCDRP) was characterized by reduced activity of the anterior cingulate and dorsolateral prefrontal cortical regions associated with relative increases in primary motor cortex and precuneus. Subject expression of OCDRP correlated with the severity of this symptom (r = 0.79, p < 0.005).
These findings suggest that the different clinical manifestations of TS are associated with the expression of 2 distinct abnormal metabolic brain networks. These, and potentially other disease-related spatial covariance patterns, may prove useful as biomarkers for assessing responses to new therapies for TS and related comorbidities.
Radiotracer imaging (RTI) of the nigrostriatal dopaminergic system is a widely used but controversial biomarker in Parkinson disease (PD). Here the authors review the concepts of biomarker ...development and the evidence to support the use of four radiotracers as biomarkers in PD: 18Ffluorodopa PET, (+)-11Cdihydrotetrabenazine PET, 123Ibeta-CIT SPECT, and 18Ffluorodeoxyglucose PET. Biomarkers used to study disease biology and facilitate drug discovery and early human trials rely on evidence that they are measuring relevant biologic processes. The four tracers fulfill this criterion, although they do not measure the number or density of dopaminergic neurons. Biomarkers used as diagnostic tests, prognostic tools, or surrogate endpoints must not only have biologic relevance but also a strong linkage to the clinical outcome of interest. No radiotracers fulfill these criteria, and current evidence does not support the use of imaging as a diagnostic tool in clinical practice or as a surrogate endpoint in clinical trials. Mechanistic information added by RTI to clinical trials may be difficult to interpret because of uncertainty about the interaction between the interventions and the tracer.
The database of the SABER/TIMED satellite campaign includes the reconstruction results of nighttime distributions of O, H, and some other characteristics at heights of the mesosphere–lower ...thermosphere from measurements of volume emission rate ofOH* profiles near 2 μm, temperature, and ozone. The retrieval procedure is based on the chemical equilibrium approximation of nighttime ozone and a model of two excited OH states (ν = 9.8) forming the indicated radiation. In this work, a modernized model of these levels with the corrected constants corresponding to published data is used to retrieve O, H, OH, HO
2
, and the chemical heating rate at altitudes of 80–100 km according to SABER/TIMED measurements in 2002–2021. It is found that the new parameters of the retrieval procedure lead to significant (up to 2 times or more) changes in the spatial distributions of O, H, and chemical heating rate, but only a slight change in OH and HO
2
distributions.
A series of carbosilane dendrimers of the 4th, 6th, and 7th generations with a terminal trimethylsilylsiloxane layer was synthesized. Theoretical models of these dendrimers were developed, and ...equilibrium dendrimer conformations obtained via molecular dynamics simulations were in a good agreement with experimental small-angle X-ray scattering (SAXS) data demonstrating molecule monodispersity and an almost spherical shape. It was confirmed that the glass transition temperature is independent of the dendrimer generation, but is greatly affected by the chemical nature of the dendrimer terminal groups. A sharp increase in the zero-shear viscosity of dendrimer melts was found between the 5th and the 7th dendrimer generations, which was qualitatively identical to that previously reported for polycarbosilane dendrimers with butyl terminal groups. The viscoelastic properties of high-generation dendrimers seem to follow some general trends with an increase in the generation number, which are determined by the regular branching structure of dendrimers.
The analysis of the state of two patients with congenital cerebral hernias was carried out, which made it possible to establish differences in the effect of hernias on the state of the body. In the ...first case, the hernia is localized in the nasal cavity, and after its removal, the postoperative cerebrospinal fluid (CSF) leakage was stopped by a flap of the mucous membrane from the opposite side of the nasal septum. In the second case clinical analysis and computed tomography made it possible to state that the hernia was in the retromaxillary space and did not affect the patient's condition. Computed tomography shows signs of moderate blood pressure on the adjacent formations, and removal of the hernia and stopping the subsequent CSF leakage were impossible. The presented observations demonstrate an ambiguous approach to resolving the issue of surgical intervention in such cases.
CNFC process codes Schmidt, O V; Feigin, A I; Makeeva, I R ...
Journal of physics. Conference series,
03/2020, Letnik:
1475, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The following models and codes for technological stages of CNFC are being developed in the frames of "Proryv" project * Mathematical models of technological processes describing physical and ...chemical, gas/hydrodynamic, kinetic and phase processes occurring in apparatus. The models are focused on reasoning the range of technical parameters under normal, transitional and abnormal modes and on reasoning and optimization of mass-dimensional characteristics of the equipment and calculation of separate units lifetime; * KOD TP code is intended for real-time simulation of the operation of technological schemes in order to define the functionality, controllability and to optimize the technology including control systems and simulation of accidents; * Kinematic model of processing lines is intended for virtual definition of commutated workability both separate processes, nodes and facilities and processing lines in all. Starting, transitional, stationary modes are considered as 4D-models taking into account kinematic and technological features and restrictions. Developing models and codes are currently used when technologies for closing stages of CNFC are designed (preparing initial data for equipment design and construction). Calculation models allow to detect collisions on early stages and to correct technological, design and engineering documentation; to perform polyvariant calculations to define the efficiency of separate nodes and the scheme in whole; to reason technical and design solutions and to evaluate the fission and nuclear materials during all the stages of the technological process including the in-process one. Currently the integrated system of models and codes is being developed for consistent simulation of heterogeneous processes and phenomena that are required to consider under calculating maintaining and reasoning the safety of CNFC technologies. The integrated system includes the existing and newly developed models and codes intended to describe technologic processes and apparatus, nuclear and radiation safety, ignition criteria, combustion, construction and engineering system behavior under critical loading and so on. The use of modern computational systems allows to perform associate calculations with date exchange between different codes from simple engineering to CFD- codes and to provide the solution of the complex problem of CNFC technology simulation.
In a randomized, double-blind, placebo-controlled study in 64 subjects with Huntington disease (HD), 8 g/day of creatine administered for 16 weeks was well tolerated and safe. Serum and brain ...creatine concentrations increased in the creatine-treated group and returned to baseline after washout. Serum 8-hydroxy-2'-deoxyguanosine (8OH2'dG) levels, an indicator of oxidative injury to DNA, were markedly elevated in HD and reduced by creatine treatment.
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