As a fundamental physical process in the ionosphere, photoionization and the associated photoelectrons play vital roles in determining the ionospheric electron density and temperature for Earth and ...other planets with atmospheres such as Mars and Venus. The production and transport of ionospheric photoelectrons have been widely examined on Earth, but relatively less studied for other terrestrial planets, such as Mars and Venus. In this study, a two‐stream photoelectron transport model for Mars and Venus is constructed, in which the photoelectron fluxes, photoelectron heating rates, primary and secondary ionization rates are calculated. The simulated photoelectron fluxes agree with Mars Atmosphere and Volatile Evolution (MAVEN) observations at various altitudes, with the input of solar spectrum irradiance, electron density and temperature, neutral density and temperature observed by MAVEN. Moreover, by parametrically fitting the simulation results for various solar zenith angles and solar activities, we obtain empirical parameterized formulas for ionization and heating efficiencies which can potentially be adapted to planetary ionospheric models for the community.
Key Points
A two‐stream model for Venus and Mars provides photoelectron flux, secondary ionization and photoelectron heating rates
The photoelectron fluxes simulated by the two‐stream model agree with the Mars Atmosphere and Volatile Evolution observations
Parameterized models of ionization and heating efficiencies are available for the community
Insulin is a peptide well known for its role in regulating glucose metabolism in peripheral tissues. Emerging evidence from human and animal studies indicate the multifactorial role of insulin in the ...brain, such as neuronal and glial metabolism, glucose regulation, and cognitive processes. Insulin resistance (IR), defined as reduced sensitivity to the action of insulin, has been consistently proposed as an important risk factor for developing neurodegeneration and cognitive impairment. Although the exact mechanism of IR‐related cognitive impairment still awaits further elucidation, neuroimaging offers a versatile set of novel contrasts to reveal the subtle cerebral abnormalities in IR. These imaging contrasts, including but not limited to brain volume, white matter (WM) microstructure, neural function and brain metabolism, are expected to unravel the nature of the link between IR, cognitive decline, and brain abnormalities, and their changes over time. This review summarizes the current neuroimaging studies with multiparametric techniques, focusing on the cerebral abnormalities related to IR and therapeutic effects of IR‐targeting treatments. According to the results, brain regions associated with IR pathophysiology include the medial temporal lobe, hippocampus, prefrontal lobe, cingulate cortex, precuneus, occipital lobe, and the WM tracts across the globe. Of these, alterations in the temporal lobe are highly reproducible across different imaging modalities. These structures have been known to be vulnerable to Alzheimer's disease (AD) pathology and are critical in cognitive processes such as memory and executive functioning. Comparing to asymptomatic subjects, results are more mixed in patients with metabolic disorders such as type 2 diabetes and obesity, which might be attributed to a multifactorial mechanism. Taken together, neuroimaging, especially MRI, is beneficial to reveal early abnormalities in cerebral structure and function in insulin‐resistant brain, providing important evidence to unravel the underlying neuronal substrate that reflects the cognitive decline in IR.
Evidence Level
5
Technical Efficacy
Stage 2
Natural killer (NK) cells play a major role in body's fighting against various types of cancers. Their infiltration in the tumor microenvironment (TME) of gastric cancer (GC) are significantly ...decreased, which has been reported as a robust prognostic marker. However, the causes leading to NK cells loss in GC TME remains poorly understood.
We constructed a non-contact co-culturing system and humanized xenograft tumor mice model to detect the influence of GC microenvironment on NK-92 or primary human NK cells viability by flow cytometry. Then through using the specific inhibitors for different types of cell death and examining the surrogate markers, we confirmed ferroptosis in NK cells. Inspired by the accidental discoveries, we constructed a NK-92 cell strain with high expression of GPX4 and treated the humanized xenograft tumor mice model with the NK-92 cells.
We found L-KYN, mainly generated through indoleamine 2, 3-dioxygenase (IDO) from GC cells, impaired NK cells viability in TME. Further analysis revealed L-KYN induced ferroptosis in NK cells via an AHR-independent way. Moreover, we found NK cells with higher GPX4 expression showed resistance to L-KYN induced ferroptosis. Based on this, we generated GPX4 over-expressed NK-92 cells, and found these cells showed therapeutic potential towards GC.
Our study revealed a novel mechanism to explain the decline of NK cell number in GC TME. Notably, we also developed a potential immunotherapy strategy, which might be beneficial in clinical treatment in the future.
Abstract
Site-selective modification of complex molecules allows for rapid accesses to their analogues and derivatives, and, therefore, offers highly valuable opportunities to probe their functions. ...However, to selectively manipulate one out of many repeatedly occurring functional groups within a substrate represents a grand challenge in chemistry. Yet more demanding is to develop methods in which alterations to the reaction conditions lead to switching of the specific site of reaction. We report herein the development of a Pd/Lewis acid co-catalytic system that achieves not only site-selective, but site-switchable mono-
O
-allylation of polyols with readily available reagents and catalysts. Through exchanging the Lewis acid additives that recognize specific hydroxyls in a polyol substrate, our system managed to install a versatile allyl group to the target in a site-switchable manner. Our design demonstrates remarkable scope, and is amenable to the direct derivatization of various complex, bioactive natural products.
This paper presents an investigation on vibration characteristics of graphene nanoplatelet (GPL) reinforced disk-shaft rotor with eccentric mass resting on elastic supports. The shaft is made of ...common metal material while the disk is made of graphene nanoplatelet reinforced material. The weight fraction of graphene nanoplatelets (GPLs) is assumed to vary smoothly and continuously along the thickness direction of the disk, which leads to a functionally gradient (FG) structure. The effective properties of the disk are determined via the Halpin-Tsai micromechanics model and the rule of mixture. In accordance with the Timoshenko beam theory and Kirchhoff plate theory, the governing equations which take into account gyroscopic effect due to rotation are derived by using the Lagrange equation. The substructure modal synthesis method and the assumed modes method are utilized to obtain the natural frequencies, and the Runge-Kutta method is adopted to solve the forced vibration response of the rotor system, where the centrifugal force and gravity of an eccentric mass in the shaft are considered as generalized forces. The present analysis is validated through comparison with both experiment and finite element (FE) results. A detailed parametric study is conducted to examine the effects of the rotating speed, GPL weight fraction, GPL distribution pattern, length-to-thickness ratio and length-to-width ratio of GPLs, disk position, disk dimension, and support stiffness on vibration behaviors of the nanocomposite disk-shaft rotor system.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, GIS, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Background
Type 2 diabetes mellitus (T2DM) is associated with cognitive decline and altered brain structure and function. However, the interhemispheric coordination of T2DM patients is unclear.
...Purpose
To investigate interhemispheric functional and anatomic connectivity in T2DM, and their associations with cognitive performance and endocrine parameters.
Study Type
Prospective.
Subjects
38 T2DM patients and 42 matched controls.
Field Strength/Sequences
3.0 T magnetic resonance imaging (MRI) scanner; magnetization‐prepared rapid acquisition gradient echo sequence; fluid‐attenuated inversion recovery sequence; single‐shot, gradient‐recalled echo‐planar imaging sequence (resting‐state functional MRI); and diffusion‐weighted spin‐echo‐based echo‐planar sequence (diffusion tensor imaging).
Assessment
Voxel‐mirrored homotopic connectivity (VMHC) value was calculated based on the functional images. Fibers passing through the regions with significant VMHC differences were identified using an atlas‐guided track recognition. The mean fractional anisotropy (FA), mean diffusivity (MD), and fiber length were extracted and compared between the two groups. Finally, correlational analyses were performed to examine the relationships between abnormal interhemispheric connectivity, cognitive performances, and endocrine parameters.
Statistical Tests
Two‐sample t‐tests were performed controlling for confounding factors, with partial correlation analysis. False discovery rate (FDR) correction was used for multiple comparisons. A P value <0.05 was considered statistically significant.
Results
T2DM patients exhibited significantly decreased VMHC between bilateral lingual gyrus and sensorimotor cortex. The fibers connecting lingual gyrus in patients showed significantly lower FA (P = 0.011) and shorter fiber length (P < 0.001), while the differences in sensorimotor fibers were insignificant (P = 0.096 for FA, P = 0.739 for fiber length and P = 0.150 for MD). The FA value in the lingual fibers was negatively correlated with insulin resistance (IR) level in T2DM group after FDR correction (R = −0.635).
Data Conclusion
We noted disruptions in interhemispheric coordination in T2DM patients, involving both functional and anatomical connectivities. IR might be a promising therapeutic target in the intervention of T2DM‐related cognitive impairment.
Level of Evidence
2
Technical Efficacy Stage
2
Abstract
It has been widely recognized that the ionosphere of the terrestrial planet responds greatly to the enhanced X-ray and extreme ultraviolet radiation during solar flares. However, little ...attention has been paid to the comparative study of the ionospheric response between different Earth-like planets. In this work, we investigate the responses of the ionospheres of Earth, Venus, and Mars to the 2017 September 6 solar flares, with self-consistent planetary ionospheric models. The result shows that the electron density increases significantly in the relatively low ionosphere region, and its maximum relative change displays profound differences between planets. The ion temperatures at Earth and Venus share a similar response to flares, but differ from those at Mars, which relates to the background atmospheric conditions. For the electron temperature response to the X9.3 flare, at Earth it increases with a maximum magnitude of 250 K, in contrast to the decrease of ∼45 K at Venus and ∼40 K at Mars. The vertical plasma velocity at all three planets exhibits enhancement during solar flares. As a result, the upward flux increases by 2.16 × 10
12
m
−2
s
−1
at 800 km of Earth, 3.79 × 10
10
m
−2
s
−1
, and 8.45 × 10
9
m
−2
s
−1
at 400 km of Venus and Mars. This is the first self-consistent simulation of the flare-induced enhancement of upward plasma flow at Venus and Mars.
The remaining useful life (RUL) prediction of bearings plays a crucial role in ensuring the safe operation of machinery and reducing costly maintenance. Sufficient degradation information contributes ...to the accuracy of RUL prediction, but the effective retention of degradation information is still a difficult task, especially for small samples. Thus, a novel RUL prediction method was proposed using data augmentation (DA) and a deep bidirectional gate recurrent unit (DBGRU). Initially, a feature selection method without consideration of the operating time that exploited the mutual information of different units, namely, the main factor correlation index (MFCI), was proposed to construct suitable feature input. In addition, a higher volume of training samples was generated with an effective DA technique, Mixup, and a bidirectional gate recurrent unit (BGRU) layer was utilized to further explore the subtle degradation information with the mixed data and the raw data, which also improved the robustness and generalization of the model. Ultimately, the advantage of the proposed method was demonstrated by a comparison with several state-of-the-art prediction models for the same circumstance. The test results showed that the proposed method was promising and that it had good prediction accuracy and robustness for different working conditions.
Traumatic brain injury (TBI) is an increasingly common emergency disease that usually leads to prolonged physical and cognitive impairments. In this study, we investigated if sevoflurane could induce ...cognitive improvement in TBI rats. Rats were subjected to head trauma induced by a fluid percussion device. A two-hour exposure to 3% sevoflurane was performed in a chamber immediately after TBI. Sevoflurane inhalation reduced the neurological and cognitive deficits induced by TBI with ameliorated synaptic injuries in the hippocampus. Moreover, after sevoflurane treatment, the expression of nuclear factor erythroid-2-related factor-2 (Nrf-2) and hemeoxygenase-1 (HO-1) in the hippocampus was enhanced 1 d after TBI and maintained at high levels 14 days later, and oxidative stress induced by TBI was inhibited. However, the HO-1 inhibitor, Zinc protoporphyrin (ZnPP), used to demonstrate the involvement of HO-1, suppressed the protective effect of sevoflurane. These results indicate that sevoflurane administered immediately after TBI may protect against TBI-induced synaptic and cognitive impairments by promoting the antioxidant Nrf-2/HO-1 pathway. Sevoflurane may be a promising anesthetic for patients with TBI.
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