In this study, the super-resolution convolutional neural network (SRCNN) scheme, which is the emerging deep-learning-based super-resolution method for enhancing image resolution in chest CT images, ...was applied and evaluated using the post-processing approach. For evaluation, 89 chest CT cases were sampled from The Cancer Imaging Archive. The 89 CT cases were divided randomly into 45 training cases and 44 external test cases. The SRCNN was trained using the training dataset. With the trained SRCNN, a high-resolution image was reconstructed from a low-resolution image, which was down-sampled from an original test image. For quantitative evaluation, two image quality metrics were measured and compared to those of the conventional linear interpolation methods. The image restoration quality of the SRCNN scheme was significantly higher than that of the linear interpolation methods (
p
< 0.001 or
p
< 0.05). The high-resolution image reconstructed by the SRCNN scheme was highly restored and comparable to the original reference image, in particular, for a ×2 magnification. These results indicate that the SRCNN scheme significantly outperforms the linear interpolation methods for enhancing image resolution in chest CT images. The results also suggest that SRCNN may become a potential solution for generating high-resolution CT images from standard CT images.
Ground triplet 4,6-bis(trifluoromethyl)-1,3-phenylene bis(
-butyl nitroxide) (TF2PBN) reacted with Y(hfac)
(H
O)
(hfac = 1,1,1,5,5,5-hexafluoropentane-2,4-dionate), affording a doubly ...hydrogen-bonded adduct Y(hfac)
(H
O)
(TF2PBN). The biradical was recovered from the adduct through recrystallization. Crystallographic analysis indicates that the torsion angles (|
| ≤ 90°) between the benzene ring and nitroxide groups were 74.9 and 84.8° in the adduct, which are larger than those of the starting material TF2PBN. Steric congestion due to
-trifluoromethyl groups gives rise to the reduction of π-conjugation. Two hydrogen bonds enhance this deformation. Susceptometry of the adduct indicates a ground singlet with 2
/
= -128(2) K, where 2
corresponds to the singlet-triplet gap. The observed magneto-structure relation is qualitatively consistent with Rajca's pioneering work. A density functional theory calculation at the UB3LYP/6-311+G(2d,p) level using the atomic coordinates determined provided a result of 2
/
= -162.3 K for the adduct, whilst the corresponding calculation on intact TF2PBN provided +87.2 K. After a comparison among a few known compounds, the 2
vs. |
| plot shows a negative slope with a critical torsion of 65(3)°. The ferro- and antiferromagnetic coupling contributions are balanced in TF2PBN, being responsible for ground-state interconversion by means of small structural perturbation like hydrogen bonds.
Radiomics has potential for reflecting the differences in glioma perfusion heterogeneity between arterial spin labeling (ASL) and dynamic susceptibility contrast (DSC) imaging. The aim of this study ...was to compare radiomic features of ASL and DSC imaging-derived parameters (cerebral blood flow, CBF) and assess radiomics-based classification models for low-grade gliomas (LGGs) and high-grade gliomas (HGGs) using their parameters. The ASL-CBF and DSC-relative CBF of 46 glioma patients were normalized (ASL-nCBF and DSC-nrCBF) for data analysis. For each map, 91 radiomic features were extracted from the tumor volume. Seventy-five radiomic features were significantly different (P < 0.00055) between ASL-nCBF and DSC-nrCBF. Positive correlations were observed in 75 radiomic features between ASL-nCBF and DSC-nrCBF. Even though ASL imaging underestimated CBF compared with DSC imaging, there were significant correlations (P < 0.00055) in the first-order-based mean, median, 90
percentile, and maximum. Texture analysis showed that ASL-nCBF and DSC-nrCBF characterized similar perfusion patterns, while ASL-nCBF could evaluate perfusion heterogeneity better. The areas under the curve of the ASL-nCBF and DSC-nrCBF radiomics-based classification models for gliomas were 0.888 and 0.962, respectively. Radiomics in ASL and DSC imaging is useful for characterizing glioma perfusion patterns quantitatively and for classifying LGGs and HGGs.
Magnetic switches working in solid states are of recent interest for applications to sensor, memory, etc. The author and co-workers have developed various unconventional spin transition/crossover ...materials. The first example is a supramolecular chemistry consisting of genuine organic nitroxide biradicals with a triplet ground state. Each nitroxide group is located close to each other to form weak covalent bonds in an intermolecular fashion. Biradicals are polymerized/depolymerized stepwise. The second example belongs to 3d-2p heterospin systems where the nitroxide oxygen atom is directly bonded to a nickel(II) or copper(II) ion. The planar/nonplanar chelate structure changes, accompanied by high-/low-spin transition due to a 3d-2p exchange-coupling switch. A novel entropy-driven spin crossover scenario has been established. The third example is a 3d iron(II) spin crossover material carrying a stearyl (C18) group. An order-disorder-type structural transition appears with respect to the alkyl conformation. As these examples show, single-crystal-to-single-crystal structural transitions are often observed. It is because the spin entropy term regulates the atomic dislocation enthalpy, and the entropy change due to the spin multiplicity is basically small. These molecular motions clarified by means of detailed crystallography afford one of the most convincing evidence for the spin transition phenomenon.
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•We designed bisnitroxide compounds where the radical groups are near and far.•The crystal structure analysis clarified the linear and U-shaped molecular structures.•The exchange ...coupling constants were semiquantitatively evaluated in solution.•The solution ESR spectra were satisfactorily reproduced with simulation.
Two new pincer-type bisnitroxides have been synthesized, where tetramethylenedioxy and o-xylylenedioxy are chosen as a bridge between the p-position of two tert-butyl phenyl nitroxide moieties. The X-ray crystal structure analysis clarified the linear and U-shaped molecular structures for the former and latter compounds, respectively. In the toluene solution ESR of the tetramethylenedioxy derivative, five hyperfine splitting lines were recorded, but a center signal was somewhat lowered. The ESR spectra of the o-xylylenedioxy derivative displayed a typical 1/2/3/2/1 five-line pattern at 370 K, and an “alternating line-width” effect appeared in 210–230 K. These spectra were reproduced by simulation, based on the proposed model where a few conformers have differing exchange couplings. The contribution showing strong exchange is reasonably ascribable to the U-shaped conformer. Thus, the solid and solution experimental results are compatible with each other.
Keywards: biradical, nitroxide, aminoxyl, ESR, exchange interaction.
Reaction of nickel(
ii
) thiocyanate and
tert
-butyl 5-phenyl-2-pyridyl nitroxide (phpyNO) afforded a 2p-3d-2p heterospin triad Ni(phpyNO)
2
(NCS)
2
. The compound crystallizes in the orthorhombic
...Pbcn
space group. The whole molecule is crystallographically independent. The torsion angles around Ni-O-N-C
2py
are 26.8(4) and 27.3(4)° at 400 K, indicating appreciable orbital overlaps of the radical π* and nickel(
ii
) 3d
x
2
−
y
2
/3d
z
2
orbitals. In a low-temperature region, the torsion was enhanced, and the space group changed to monoclinic
P
2
1
/
c
with a doubled asymmetric unit volume. The
χ
m
T
value was practically null below
ca.
140 K and, on heating to 400 K, gradually increased and reached 1.30 cm
3
K mol
−1
. A van't Hoff analysis suggests a spin transition at
T
1/2
= 530(20) K. Density functional theory calculation reproduced ground
S
total
= 0 with singlet-triplet gaps of 910 and 1263 K for the 140 K structure, and the gap was reduced to 297 K at 400 K. Consequently, the present compound can be considered as an incomplete spin-crossover material, as a result of
T
1/2
located above the experimental temperature window.
The exchange coupling in Ni(phpyNO)
2
(NCS)
2
is strongly antiferromagnetic in a low-temperature structure whilst moderately antiferromagnetic in a high-temperature structure.
Purpose
This study aimed at developing a deep learning-based method for multi-label thoracic abnormality classification on frontal view chest X-ray (CXR). To improve the performance of ...classification, issues of class imbalance, noisy labels and ensemble of networks are addressed in the paper.
Methods
The experiments were performed on a public dataset called Chest X-ray 14 (CXR14), which includes 112,120 frontal view CXRs from 30,805 patients. We came up with an ensemble learning framework to improve the classification and a noisy label detection method to detect the CXRs with noisy labels. The detected CXRs were reviewed by two board-certificated radiologists in a consensus fashion to evaluate detected noisy labels. The classification was assessed on CXR14 with area under the receiver operating characteristic curve (AUC).
Results
Report from the radiologists indicated that detected noisy labels had high possibility to be true positives. A notable improvement from baseline in performance of classification was observed with the ensemble learning framework. After removing the CXRs with detected noisy labels, 8 out of 14 abnormalities improved significantly on CXR14. The suggested framework achieved AUC score of 0.827 on CXR14.
Conclusion
The methods of this study boost the classification on CXR with awareness of the label noise. Expanded experimental results show that all of them were able to improve multi-label thoracic abnormality classification performance, respectively. A new state-of-the-art is achieved in this study.
Spin-crossover (SCO) is a reversible transition between low and high spin states by external stimuli such as heat. The SCO behavior and transition temperature (T 1/2) of a series of ...FeII(X-pybox)2(ClO4)2 were studied to establish a methodology for ligand-field engineering, where X-pybox stands for 2,6-bis(oxazolin-2-yl)pyridine substituted with X at the 4-position of the pyridine ring. We utilized X = MeO, Me, 3-thienyl, Ph, H, MeS, 2-thienyl, N3, Cl, Br, 3-pyridyl, and 4-pyridyl. The solution susceptometry on five new derivatives with X = Me, 2-thienyl, N3, Br, and 3-pyridyl was performed in acetone, giving the SCO temperatures of 220, 260, 215, 280, and 270 K, respectively. The density-functional-theory molecular orbital (MO) calculation was performed on the ligands with geometry optimization. The atomic charge on the pyridine nitrogen atom ρ(Npy) was extracted from the natural orbital population analysis. Positive correlation appeared in the T 1/2 versus ρ(Npy) plot with R 2 = 0.734, being consistent with the analysis using the Hammett substituent constants (σp and σp +). This finding well agrees with the mechanism proposed: the rich electron density lifts the t2g energy level through the dπ–pπ interaction, resulting in a narrow t2g–eg energy gap and favoring the high-spin state and low T 1/2. The MO method was successfully applied to the known SCO-active iron(II) compounds involving 4-substituted 2,6-bis(pyrazol-1-yl)pyridines. A distinct positive correlation appeared in the T 1/2 versus ρ(Npy) plot. The comparison of correlation coefficients indicates that ρ(Npy) is a more reliable parameter than σp or σp + to predict a shift of T 1/2. Furthermore, this method can be more generalized by application to another known SCO family having 3-azinyl-4-p-tolyl-5-phenyl-1,2,4-triazole ligand series, where azinyl stands for a 2-azaaromatic ring. A good linear correlation was found in the T 1/2 versus ρ(NA) plot (NA is the ligating nitrogen atom in the azaaromatic ring). Finally, we will state a reason why the present treatment is competent to predict the SCO equilibrium position only by consideration on the electronic perturbation.
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