The effect of hydrogen on the mechanical properties of an A7075 aluminum alloy and hydrogen diffusivity are investigated using the electrochemical cathode charge method. The apparent hydrogen ...diffusivity in the A7075 alloy is 4.4
×
10
−12
m
2/s at 318
K. Hydrogen charging induces a decrease of both the tensile strength and the elongation to fracture in comparison to tests performed in atmospheric environment. In both cases, dimples and intergranular cracks were observed on the fracture surfaces. A striation-like pattern, which is characteristic of fracture surfaces in hydrogen embrittled iron and steels, is also observed.
Abstract The aim of this study was to analyze and describe the intrapapillary capillary loops (IPCL), which are a feature of early oral neoplastic lesions, using a narrowband imaging (NBI) system. ...Forty-one patients (26 men, 15 women; mean age, 52.34 years; range, 23–83 years) presenting with non-neoplastic or neoplastic lesions, and normal cases, were examined using the prototype Evis Lucera Spectrum (Olympus Co.). The images were analyzed and an IPCL classification was devised. All normal cases ( n = 10) had regularly distributed capillary loops of the same shape (type I). Non-neoplastic lesions ( n = 8) had mild changes of the capillary loops (types II and III) and neoplastic lesions ( n = 23) were irregularly distributed and had several loop shapes (types III and IV). The microvascular organization of non-neoplastic lesions was notably different from that of neoplastic lesions. A brownish area was found in five cases of early carcinoma. The narrowband imaging system is a potential approach for clinically analyzing microvascular organization and IPCL. It could be useful for diagnosing oral squamous cell carcinoma at an earlier stage and for determining the margin of resection.
Synthetic MR imaging enables the creation of various contrast-weighted images including double inversion recovery and phase-sensitive inversion recovery from a single MR imaging quantification scan. ...Here, we assessed whether synthetic MR imaging is suitable for detecting MS plaques.
Quantitative and conventional MR imaging data on 12 patients with MS were retrospectively analyzed. Synthetic T2-weighted, FLAIR, double inversion recovery, and phase-sensitive inversion recovery images were produced after quantification of T1 and T2 values and proton density. Double inversion recovery images were optimized for each patient by adjusting the TI. The number of visible plaques was determined by a radiologist for a set of these 4 types of synthetic MR images and a set of conventional T1-weighted inversion recovery, T2-weighted, and FLAIR images. Conventional 3D double inversion recovery and other available images were used as the criterion standard. The total acquisition time of synthetic MR imaging was 7 minutes 12 seconds and that of conventional MR imaging was 6 minutes 29 seconds The lesion-to-WM contrast and lesion-to-WM contrast-to-noise ratio were calculated and compared between synthetic and conventional double inversion recovery images.
The total plaques detected by synthetic and conventional MR images were 157 and 139, respectively (
= .014). The lesion-to-WM contrast and contrast-to-noise ratio on synthetic double inversion recovery images were superior to those on conventional double inversion recovery images (
= .001 and < 0.001, respectively).
Synthetic MR imaging enabled detection of more MS plaques than conventional MR imaging in a comparable acquisition time. The contrast for MS plaques on synthetic double inversion recovery images was better than on conventional double inversion recovery images.
Y-configuration stent-assisted coil embolization is used for treating wide-neck aneurysms. Noninvasive alternatives to x-ray DSA for follow-up after Y-configuration stent-assisted coil embolization ...treatment are required. This study aimed to assess the usefulness of non-contrast-enhanced MRA by using a Silent Scan (silent MRA) for follow-up after Y-configuration stent-assisted coil embolization for basilar tip aneurysms.
Seven patients treated with Y-configuration stent-assisted coil embolization for basilar tip aneurysms underwent silent MRA, 3D TOF-MRA, and DSA. Silent MRA and 3D TOF-MRA images were obtained during the same scan session on a 3T MR imaging system. Two neuroradiologists independently reviewed both types of MRA images and subjectively scored the flow in the stents on a scale of 1 (not visible) to 5 (nearly equal to DSA) by referring to the latest DSA image as a criterion standard. Furthermore, we evaluated the visualization of the neck remnant.
In all patients, the 2 observers gave a higher score for the flow in the stents on silent MRA than on 3D TOF-MRA. The average score ± standard deviation was 4.07 ± 0.70 for silent MRA and 1.93 ± 0.80 (
< .05) for 3D TOF-MRA. Neck remnants were depicted by DSA in 5 patients. In silent MRA, neck remnants were depicted in 5 patients, and visualization was similar to DSA; however, in 3D TOF-MRA, neck remnants were depicted in only 1 patient.
Silent MRA might be useful for follow-up after Y-configuration stent-assisted coil embolization.
Blood flow in an intracranial stent cannot be visualized with 3D time-of-flight MR angiography owing to magnetic susceptibility and radiofrequency shielding. As a novel follow-up tool after ...stent-assisted coil embolization, we applied MRA by using a Silent Scan algorithm that contains an ultrashort TE combined with an arterial spin-labeling technique (Silent MRA). The purpose of this study was to determine whether Silent MRA could visualize flow in an intracranial stent placed in the anterior circulation.
Nine patients treated with stent-assisted coil embolization for anterior circulation aneurysms underwent MRAs (Silent MRA and TOF MRA) and x-ray digital subtraction angiography. MRAs were performed in the same session on a 3T unit. Two neuroradiologists independently reviewed the MRA images and subjectively scored flow in a stent as 1 (not visible) to 4 (excellent) by referring to the latest x-ray digital subtraction angiography image as a criterion standard.
Both observers gave MRA higher scores than TOF MRA for flow in a stent in all cases. The mean score for Silent MRA was 3.44 ± 0.53, and for TOF MRA, it was 1.44 ± 0.46 (P < .001).
Silent MRA was able to visualize flow in an intracranial stent more effectively than TOF MRA. Silent MRA might be useful for follow-up imaging after stent-assisted coil embolization, though these study results may be only preliminary due to some limitations.
The flow-diverter device has been established as a treatment procedure for large unruptured intracranial aneurysms. The purpose of this study was to compare the usefulness of Silent MR angiography ...and time-of-flight MRA to assess the parent artery and the embolization state of the aneurysm after a flow-diverter placement.
Seventy-eight large, unruptured internal carotid aneurysms in 78 patients were the subjects of this study. After 6 months of treatment, they underwent follow-up digital subtraction angiography, Silent MRA, and TOF-MRA, performed simultaneously. All images were independently reviewed by 2 neurosurgeons and 1 radiologist and rated on a 4-point scale from 1 (not visible) to 4 (excellent) to evaluate the parent artery. The aneurysmal embolization status was assessed with 2 ratings: complete or incomplete occlusion.
The mean scores of Silent MRA and TOF-MRA regarding the parent artery were 3.18 ± 0.72 and 2.31 ± 0.86, respectively, showing a significantly better score with Silent MRA (
< .01). In the assessment of the embolization of aneurysms on Silent MRA and TOF-MRA compared with DSA, the percentages of agreement were 91.0% and 80.8%, respectively.
Silent MRA is superior for visualizing blood flow images inside flow-diverter devices compared with TOF-MRA. Furthermore, Silent MRA enables the assessment of aneurysmal embolization status. Silent MRA is useful for assessing the status of large and giant unruptured internal carotid aneurysms after flow-diverter placement.
T1 and T2 values and proton density can now be quantified on the basis of a single MR acquisition. The myelin and edema in a voxel can also be estimated from these values. The purpose of this study ...was to evaluate a multiparametric quantitative MR imaging model that assesses myelin and edema for characterizing plaques, periplaque white matter, and normal-appearing white matter in patients with MS.
We examined 3T quantitative MR imaging data from 21 patients with MS. The myelin partial volume, excess parenchymal water partial volume, the inverse of T1 and transverse T2 relaxation times (R1, R2), and proton density were compared among plaques, periplaque white matter, and normal-appearing white matter.
All metrics differed significantly across the 3 groups (
< .001). Those in plaques differed most from those in normal-appearing white matter. The percentage changes of the metrics in plaques and periplaque white matter relative to normal-appearing white matter were significantly more different from zero for myelin partial volume (mean, -61.59 ± 20.28% plaque relative to normal-appearing white matter, and mean, -10.51 ± 11.41% periplaque white matter relative to normal-appearing white matter), and excess parenchymal water partial volume (13.82 × 10
± 49.47 × 10
% and 51.33 × 10
± 155.31 × 10
%) than for R1 (-35.23 ± 13.93% and -6.08 ± 8.66%), R2 (-21.06 ± 11.39% and -4.79 ± 6.79%), and proton density (23.37 ± 10.30% and 3.37 ± 4.24%).
Multiparametric quantitative MR imaging captures white matter damage in MS. Myelin partial volume and excess parenchymal water partial volume are more sensitive to the MS disease process than R1, R2, and proton density.
The Low-Profile Visualized Intraluminal Support Device comprises a small-cell nitinol structure and a single-wire braided stent that provides greater metal coverage than previously reported ...intracranial stents, as well as assumed strong susceptibility artifacts. This study aimed to assess the benefits of non-contrast-enhanced MRA by using a Silent Scan (Silent MRA) for intracranial anterior circulation aneurysms treated with Low-Profile Visualized Intraluminal Support Device stents.
Thirty-one aneurysms treated with Low-Profile Visualized Intraluminal Support Device stents were assessed by using Silent MRA, 3D TOF-MRA, and x-ray DSA. The quality of MRA visualization of the reconstructed artery was graded on a 4-point scale from 1 (not visible) to 4 (excellent). Aneurysm occlusion status was evaluated by using a 2-grade scale (total occlusion/remnant neck or aneurysm). Weighted κ statistics were used to evaluate interobserver and intermodality agreement.
The mean scores ± SDs for Silent MRA and 3D TOF-MRA were 3.16 ± 0.79 and 1.48 ± 0.67 (
< .05), respectively, with substantial interobserver agreement (κ = 0.66). The aneurysm occlusion rates of the 2-grade scale (total occlusion/remnant neck or aneurysm) were 69%/31% for DSA, 65%/35% for Silent MRA, and 92%/8% for 3D TOF-MRA, respectively. The intermodality agreements were 0.88 and 0.30 for DSA/Silent MRA and DSA/3D TOF-MRA, respectively.
Silent MRA seems to be useful for visualizing intracranial anterior circulation aneurysms treated with Low-Profile Visualized Intraluminal Support Device stents.
Multiscale analysis of a semi-periodically perforated plate based on a homogenization theory is experimentally validated both macroscopically and microscopically, using a full-field strain ...measurement. To do this, a plate-fin-type perforated plate with a misaligned microstructure is considered as a semi-periodically perforated plate. Then, a homogenization theory that can analyze macroscopic behavior and microscopic stress and strain distributions of the perforated plate is presented. To validate the theory, a tensile test of a plate-fin-type semi-periodically perforated plate made of epoxy resin is conducted. During the test, the microscopic deformation of the specimen is observed with a digital image correlation (DIC) full-field measurement system, from which microscopic strain distribution of the specimen is calculated. It is shown that the obtained strain distribution satisfies the unit-cell periodicity except at edges of the periodic structure, and that the strain distribution is in good agreement with the result of analysis using the homogenization theory. It is also shown that the macroscopic stress–strain relationships obtained by the experiment and analysis agree well, supporting the macroscopic and microscopic validity of the multiscale analysis using the homogenization theory.
•Multiscale analysis is experimentally validated macroscopically and microscopically.•A tensile test of a plate-fin-type semi-periodically perforated plate is conducted.•Microscopic strain distribution is observed with a DIC full-field measurement system.•Multiscale analysis for the plate is performed based on a homogenization theory.•Results of the experiment and analysis agree well in both macro- and micro-scales.
Summary
Background Nerve growth factor (NGF) is an important substance in the skin, where it modulates nerve maintenance and repair. However, the direct link between NGF and pruritic diseases such ...as atopic dermatitis is not yet fully understood. Our previous study showed that NGF plays an important role in the pathogenesis of atopic dermatitis‐like skin lesions in NC/Nga mice. NGF mediates its effects by binding to two classes of transmembrane receptors, a high‐affinity receptor (tropomyosin‐related kinase A, TrkA) and a low‐affinity receptor (p75).
Objectives To determine the significance of NGF receptors in the pathogenesis of atopic dermatitis, the effects of TrkA inhibitors AG879 and K252a on the symptoms of NC/Nga mice were evaluated.
Methods Male NC/Nga mice with severe skin lesions were used. AG879 or K252a was applied to the rostral part of the back of mice five times a week. The dermatitis score for the rostral back was assessed once a week. The scratching behaviour was measured using an apparatus, MicroAct (Neuroscience, Tokyo, Japan). Immunofluorescence examinations were made in the rostral back skin for nerve fibres, NGF and TrkA receptor.
Results Repeated applications of AG879 or K252a significantly improved the established dermatitis and scratching behaviour, and decreased nerve fibres in the epidermis. NGF was observed more weakly in keratinocytes, and a lower expression of TrkA was observed in stratum germinativum of the epidermis of mice treated with AG879 or K252a compared with those treated with vehicle.
Conclusions We suggest that NGF plays an important role in the pathogenesis of atopic dermatitis‐like skin lesions via the high‐affinity NGF receptor. These findings provide a new potential therapeutic approach for the amelioration of symptoms of atopic dermatitis.
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