Diffusion MRI tractography has emerged as a useful and popular tool for mapping connections between brain regions. In this study, we examined the performance of quantitative anisotropy (QA) in ...facilitating deterministic fiber tracking. Two phantom studies were conducted. The first phantom study examined the susceptibility of fractional anisotropy (FA), generalized factional anisotropy (GFA), and QA to various partial volume effects. The second phantom study examined the spatial resolution of the FA-aided, GFA-aided, and QA-aided tractographies. An in vivo study was conducted to track the arcuate fasciculus, and two neurosurgeons blind to the acquisition and analysis settings were invited to identify false tracks. The performance of QA in assisting fiber tracking was compared with FA, GFA, and anatomical information from T1-weighted images. Our first phantom study showed that QA is less sensitive to the partial volume effects of crossing fibers and free water, suggesting that it is a robust index. The second phantom study showed that the QA-aided tractography has better resolution than the FA-aided and GFA-aided tractography. Our in vivo study further showed that the QA-aided tractography outperforms the FA-aided, GFA-aided, and anatomy-aided tractographies. In the shell scheme (HARDI), the FA-aided, GFA-aided, and anatomy-aided tractographies have 30.7%, 32.6%, and 24.45% of the false tracks, respectively, while the QA-aided tractography has 16.2%. In the grid scheme (DSI), the FA-aided, GFA-aided, and anatomy-aided tractographies have 12.3%, 9.0%, and 10.93% of the false tracks, respectively, while the QA-aided tractography has 4.43%. The QA-aided deterministic fiber tracking may assist fiber tracking studies and facilitate the advancement of human connectomics.
The Geometric Structure of the Brain Fiber Pathways Van J. Wedeen; Rosene, Douglas L.; Wang, Ruopeng ...
Science (American Association for the Advancement of Science),
03/2012, Letnik:
335, Številka:
6076
Journal Article
Recenzirano
Odprti dostop
The structure of the brain as a product of morphogenesis is difficult to reconcile with the observed complexity of cerebral connectivity. We therefore analyzed relationships of adjacency and crossing ...between cerebral fiber pathways in four nonhuman primate species and in humans by using diffusion magnetic resonance imaging. The cerebral fiber pathways formed a rectilinear three-dimensional grid continuous with the three principal axes of development. Cortico-cortical pathways formed parallel sheets of interwoven paths in the longitudinal and medio-lateral axes, in which major pathways were local condensations. Cross-species homology was strong and showed emergence of complex gyral connectivity by continuous elaboration of this grid structure. This architecture naturally supports functional spatio-temporal coherence, developmental path-finding, and incremental rewiring with correlated adaptation of structure and function in cerebral plasticity and evolution.
The pressure elevation related to the variances in temperature for cylinder Li-ion cells including LiCoO
2
, LiMnO
2
, LiFePO
4,
and LiNi
1/3
Mn
1/3
Co
1/3
O
2
cathodes was compared with their ...explosive behaviors. 50 and 100% state of charges Li-ion cells were examined the pressure rising rates in an open-circuit voltage condition using adiabatic calorimetry. A charged cell underwent an extremely runaway reaction at elevated temperatures and caused a thermal explosion due to high potential energy of the battery system and interaction with the components. This study presented the relationships between temperature and pressure in a Li-ion cell proceeding on a thermal explosion in the adiabatic confinement testing. The layer-structure LiCoO
2
cell has the significant deflagration potential for condensed phase explosion. Moreover, the considerable quantities of gas eruption from a charged cell can be resulted in battery rupture and flames from a confined energy storage system. The critical temperature to thermal explosion model for a cylinder Li-ion cell was evaluated to classify their runaway reaction and deflagration potential.
Emulsion polymerization is the most applied method in the vinyl acetate monomer (VAM)–polyvinyl acetate (PVAc) process. However, the flammable property and unexpected bulk polymerization for the ...reactant and product may occur in the batch reactor or storage tank. VAM is reactive enough to decompose readily into free radicals and then, initiate the polymerization, which may contribute to heat accumulation due to the monomer, initiator, and solvent mixtures. This study attempts to analyze the exothermic reaction and compare the thermal runaway potential for various VAM solutions during PVAc polymerizations. Summarily, 50%, 70%, and 100% of VAM solutions reacting with 2,2’–azobis(2-methylpropionitrile) readily increase the self-heating rate with their concentration from adiabatic calorimetric tests. Furthermore, kinetic parameters of 50, 70, and 100 mass% VAM solutions were evaluated to elucidate the self-heating model associated with thermal analysis and to determine heat production mechanisms that are practical to proactive safety protocol for the PVAc emulsion process.
Use of adiabatic calorimetry to characterise thermal runaway of Li-ion cells is a crucial technique in battery safety testing. Various states of charge (SoC) of Li-ion cells were investigated to ...ascertain their thermal runaway features using a Vent Sizing Package 2 (VSP2) adiabatic calorimeter. To evaluate the thermal runaway characteristics, the temperature-pressure-time trajectories of commercial cylindrical cells were tested, and it was found that cells at a SoC of greater than 50% were subject to thermal explosion at elevated temperatures. Calorimetry data from various 18650 Li-ion cells with different SoC were used to calculate the thermal explosion energies and chemical kinetics; furthermore, a novel self-heating model based on a pseudo-zero-order reaction that follows the Arrhenius equation was found to be applicable for studying the exothermic reaction of a charged cell.
•Adiabatic calorimetry is applied to the study of thermal runaway in Li-ion cells.•A self-heating model was developed based on pseudo-zero-order Arrhenius kinetics.•Thermal explosion energy increases exponentially with SoC.
Epigenetic regulation is important for cancer progression; however, the underlying mechanisms, particularly those involving protein acetylation, remain to be fully understood. Here, we show that ...p300/CBP‐associated factor (PCAF)‐dependent acetylation of the transcription factor intestine‐specific homeobox (ISX) regulates epithelial–mesenchymal transition (EMT) and promotes cancer metastasis. Mechanistically, PCAF acetylation of ISX at lysine 69 promotes the interaction with acetylated bromodomain‐containing protein 4 (BRD4) at lysine 332 in tumor cells, and the translocation of the resulting complex into the nucleus. There, it binds to promoters of EMT genes, where acetylation of histone 3 at lysines 9, 14, and 18 initiates chromatin remodeling and subsequent transcriptional activation. Ectopic ISX expression enhances EMT marker expression, including TWIST1, Snail1, and VEGF, induces cancer metastasis, but suppresses E‐cadherin expression. In lung cancer, ectopic expression of PCAF–ISX–BRD4 axis components correlates with clinical metastatic features and poor prognosis. These results suggest that the PCAF–ISX–BRD4 axis mediates EMT signaling and regulates tumor initiation and metastasis.
Synopsis
The PCAF–ISX–BRD4 axis is an important regulator of tumor metastasis and cell plasticity. PCAF‐mediated acetylation of the transcription factor ISX promotes translocation of ISX‐BRD4 to the nucleus to activate EMT genes and to induce metastasis.
ISX transactivates genes encoding EMT regulators and promotes EMT.
PCAF acetylation of ISX is essential for ISX–BRD4 complex formation, and induces EMT and cancer cell metastasis.
PCA, ISX and BRD4 show high expression correlation with clinical outcomes and prognosis in patients with NSCLC.
The PCAF–ISX–BRD4 axis is an important regulator of tumor metastasis and cell plasticity. PCAF‐mediated acetylation of the transcription factor ISX promotes translocation of ISX‐BRD4 to the nucleus to activate EMT genes and to induce metastasis.
The wet-etching process has been used to manufacture electronic devices including wafers, panels, and printed circuit boards, since it is economical and effective. In the high-tech industry, graphene ...or carbonated films that have undergone chemical vapor deposition are frequently employed. The copper residue or foil on these films is removed using a Cu etchant. The Cu etchant composition, on the other hand, has corrosive and thermally unstable properties, which must conduct its hazardous properties and thermal runaway potential during the metal-etching process. This study aims to assess the thermophysical information of the Cu etchant reacting with copper powder, cupric sulfate, and cupric chloride using an adiabatic calorimetric approach. To fit the self-heating rates of different Cu-etching solutions, the thermokinetic data are first evaluated. The self-heating models are then simulated to evaluate thermal incompatibility for the Cu-etching process. The Cu etchant-involving copper shows the most incompatible hazard among the etching solutions. As a result, the thermal incompatibility analysis can determine the design for a safe etching process.
► Thermal analysis is employed to classify hazardous rating for Li-ion cell cathodes. ► The thermal hazards of the LiCoO2 cathode at elevated temperatures is significant. ► VSP2 is an alternative ...measurement of a battery thermal stability evaluation. ► Calorimetry method provide the safety design considerations of Li-ion batteries.
Thermal runaway hazards related to adiabatic runaway reactions in various 18650 Li-ion batteries were studied in an adiabatic calorimeter with vent sizing package 2 (VSP2). We selected two cathode types, LiCoO2 and Li(Ni1/3Co1/3Mn1/3)O2, and tested Li-ion batteries to determine the thermal runaway features. The charged 18650 Li-ion batteries were tested to evaluate the thermal hazard characteristics, such as the initial exothermic temperature (T0), self-heating rate (dT/dt), pressure rise rate (dP/dt), pressure–temperature profiles, maximum temperature (Tmax) and pressure (Pmax), which are measured by VSP2 with a customized stainless steel test can. The thermal reaction behaviors of the Li-ion battery packs were shown to be an important safety concern for energy storage systems for power supply applications. The thermal abuse trials of the adiabatic calorimetry methodology used to classify the self-reactive ratings of the various cathodes for Li-ion batteries provided the safety design considerations.
•Adiabatic calorimetry is applied to study thermal runaway for PAA.•The concentrated PAA could cause the thermal explosion after a runaway reaction.•A self-heating model with nth-order kinetic ...equation of PAA is proposed.
Thermal analysis of peracetic acid (PAA) with respect to the explosive properties was performed using calorimetry. The exothermic characteristics and thermal runaway profiles of PAA solutions were acquired through differential scanning calorimetry (DSC) and vent sizing package 2 (VSP2). The results revealed significant enthalpy changes and gas eruption for PAA solutions that were subjected to free-radical induced and autocatalytic reactions. The reaction kinetics and order of various PAA solutions were elucidated using calorimetry.
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