Ductile-Brittle Transition Temperature shift controlled by grain boundary decohesion and thermally activated energy and hydrogen GB embrittlement

Classical structural problems of temper embrittlement are evaluated in terms of changes in the ductile-brittle transition temperature (DBTT). Experimentally, DBTT is not only strongly dependent on the effects of the type and amount of segregated solute at grain boundary (GB) but also on the hardness of the steel and strain rate. Recent first-principles calculations provide the decohesion of the GB based on the concentration of different elements on the GB. The decohesion, , is difference between the energy of the fracture surfaces and the energy of the GB () The calculations show that the decohesion is linearly related to the concentration of metalloids on the GB. The calculations show that the embrittling potency () of the different metalloids, Sb, Sn, and P, are ranked as follows: . This study reanalyzes earlier experimental data and attempts to correlate the effect of strain rate and hardness to DBTT on samples with GB embrittled with different concentrations of Sb, Sn and P. Charpy notched and cantilever static bending tests on 3.5 Ni – 1.7 Cr steels were performed at two different strain rates and at two different hardness. It is found that DBTT is linearly related to when the strain rate and hardness are not changed. That is , where c and α are constants that vary with strain rate and hardness. The constant c is function related to DBTT for cleavage fracture but the slope, α, is a function of strain rate only for the medium hardness steel, but is independent of strain rate for the hard steel. The activation energy for the motion of dislocations that is responsible for the plasticity is estimated by relating the strain rate to activation energy and DBTT through an Arrhenius relationship. This activation energy then is correlated with the and . The activation energy is strongly dependent on GB decohesion and high hardness sample In addition, hydrogen GB embrittlement is linked with decohesion and analyzed in terms of micro- and macro-fracture mechanics

Low-grade metamorphism around the down-dip limit of seismogenic subduction zones: Example from an ancient accretionary complex in the Shimanto Belt, Japan

International audienceReactions involving clay minerals during low-grade metamorphism at the depth of an ancient accretionary complex in the Shimanto Belt, Kyushu, Japan, were studied by integrated transmission electron microscopy-energy dispersive X-ray spectroscopy and X-ray diffraction analyses of the bulk rock and clay fraction. The analyzed metasediment (the Kitagawa unit) contain an incipient sub-horizontal slaty cleavage. Illite crystallinity data and mica b dimensions indicate that the conditions of metamorphic deformation were anchizone-epizone grade and intermediate pressure. Cleavage formation was linked to two reactions involving clay minerals: (1) the recrystallization of 1M-dominant matrix mica, inherited from the original sedimentary fabric, into thick, defect-free 2M1 packets along cleavage planes; and (2) the formation of chlorite from 7 Å berthierine. Balanced equations among the clay phases, based on compositional data and their relative abundance, suggest that the decomposition of matrix mica resulted in the formation of paragenetic mica and chlorite along the cleavage planes, without significant elemental outflux. Although a modal increase in phyllosilicates is not indicated by the data, the growth of chlorite and mica along cleavage planes may have a large influence on the rheological properties of a décollement and may be related to the occurrence of the seismic-aseismic transition at ~ 350 °C

Use of High Strength Steel for Hydrogen Containment

The research involves experiments on model lab heats of an ultra-high-strength steel (high C, low Ni ) and a high-toughness, high-strength steel (high Ni, low C) to determine the limits of toughness as a function of yield strength, grain-boundary purity, and hydrogen fugacity. In addition, the existence and mechanism of brittle intergranular cracking in ideally pure steels is being investigated

Development of P450-BM3 using molecular dynamics simulations- A tribute to the late Professor Hideaki Yamada

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Spinal Surgery after Bilateral Subthalamic Stimulation for Patients with Parkinson's Disease: A Retrospective Outcome Analysis of Pain and Functional Control

Parkinson's disease (PD) patients often suffer from spinal diseases requiring surgeries, although the risk of complications is high. There are few reports on outcomes after spinal surgery for PD patients with deep brain stimulation (DBS). The objective of this study was to explore the data on spinal surgery for PD patients with precedent DBS. We evaluated 24 consecutive PD patients with 28 spinal surgeries from 2007 to 2017 who received at least a 2-year follow-up. The characteristics and outcomes of PD patients after spinal surgery were compared to those of 156 non-PD patients with degenerative spinal diseases treated in 2013-2017. Then, the characteristics, outcomes, and spinal alignment of PD patients receiving DBS were analyzed in degenerative spinal/ lumbar diseases. The mean age at the time of spinal surgery was 68 years. The Hoehn and Yahr score regarding PD was stage 1 for 8 patients, stage 2 for 2 patients, stage 3 for 8 patients, stage 4 for 10 patients, and stage 5 for 0 patient. The median preoperative L-DOPA equivalent daily dose was 410 mg. Thirteen patients (46%) received precedent subthalamic nucleus (STN) DBS. Lumbar lesions with pain were common, and operation and anesthesia times were long in PD patients. Pain and functional improvement of PD patients persisted for 2 years after surgery with a higher complication rate than for non-PD patients. PD patients with STN DBS maintained better lumbar lordosis for 2 years after spinal surgery. STN DBS significantly maintained spinal alignment with subsequent pain and functional amelioration 2 years after surgery. The outcomes of spinal surgery for PD patients might be favorably affected by thorough treatment for PD including DBS

Successful laparoscopic resection of virilizing ovarian steroid cell tumor, not otherwise specified, in a 22-year-old woman: a case report and evaluation of the steroidogenic pathway

Objective: Ovarian steroid cell tumor (SCT) is a rare tumor with steroid-producing ability. We report a 22-year-old woman with secondary amenorrhea and hirsutism caused by an ovarian SCT-not otherwise specified (NOS), who underwent successfully laparoscopic resection of the tumor. Case report: A 22-year-old null gravida woman presented to a hospital, having amenorrhea for 18 months and increasing facial hair. Physical examination revealed obesity (body mass index, 37.3 kg/m2) with evident facial and trunk hair. Total and free serum testosterone, and dehydroepiandrosterone sulfate levels were found to be elevated. Levels of serum adrenocorticotropic hormone, gonadotropins, cortisol, aldosterone, and ovarian steroids were observed to be within reference intervals. Although polycystic ovaries were not found, a hyperechogenic solid tumor (3 cm) was detected on transvaginal ultrasonography. Laparoscopic resection of the tumor was performed. One month post-surgery, total and free testosterone levels were observed to have decreased, and menstruation resumed two months thereafter. The patient was histologically diagnosed with ovarian SCT-NOS. Expression of ovarian steroidogenic enzymes, which are related to hyperandrogenism, was observed. No disease recurrence has been reported for more than 5 years post-surgery

Long-Term Continuous Cervical Spinal Cord Stimulation Exerts Neuroprotective Effects in Experimental Parkinson's Disease

Background: Spinal cord stimulation (SCS) exerts neuroprotective effects in animal models of Parkinson’s disease (PD). Conventional stimulation techniques entail limited stimulation time and restricted movement of animals, warranting the need for optimizing the SCS regimen to address the progressive nature of the disease and to improve its clinical translation to PD patients. Objective: Recognizing the limitations of conventional stimulation, we now investigated the effects of continuous SCS in freely moving parkinsonian rats. Methods: We developed a small device that could deliver continuous SCS. At the start of the experiment, thirty female Sprague-Dawley rats received the dopamine (DA)-depleting neurotoxin, 6-hydroxydopamine, into the right striatum. The SCS device was fixed below the shoulder area of the back of the animal, and a line from this device was passed under the skin to an electrode that was then implanted epidurally over the dorsal column. The rats were divided into three groups: control, 8-h stimulation, and 24-h stimulation, and behaviorally tested then euthanized for immunohistochemical analysis. Results: The 8- and 24-h stimulation groups displayed significant behavioral improvement compared to the control group. Both SCS-stimulated groups exhibited significantly preserved tyrosine hydroxylase (TH)-positive fibers and neurons in the striatum and substantia nigra pars compacta (SNc), respectively, compared to the control group. Notably, the 24-h stimulation group showed significantly pronounced preservation of the striatal TH-positive fibers compared to the 8-h stimulation group. Moreover, the 24-h group demonstrated significantly reduced number of microglia in the striatum and SNc and increased laminin-positive area of the cerebral cortex compared to the control group. Conclusions: This study demonstrated the behavioral and histological benefits of continuous SCS in a time-dependent manner in freely moving PD animals, possibly mediated by anti-inflammatory and angiogenic mechanisms

Vagus Nerve Stimulation with Mild Stimulation Intensity Exerts Anti-Inflammatory and Neuroprotective Effects in Parkinson's Disease Model Rats

Background: The major surgical treatment for Parkinson's disease (PD) is deep brain stimulation (DBS), but a less invasive treatment is desired. Vagus nerve stimulation (VNS) is a relatively safe treatment without cerebral invasiveness. In this study, we developed a wireless controllable electrical stimulator to examine the efficacy of VNS on PD model rats. Methods: Adult female Sprague-Dawley rats underwent placement of a cuff-type electrode and stimulator on the vagus nerve. Following which, 6-hydroxydopamine (6-OHDA) was administered into the left striatum to prepare a PD model. VNS was started immediately after 6-OHDA administration and continued for 14 days. We evaluated the therapeutic effects of VNS with behavioral and immunohistochemical outcome assays under different stimulation intensity (0.1, 0.25, 0.5 and 1 mA). Results: VNS with 0.25-0.5 mA intensity remarkably improved behavioral impairment, preserved dopamine neurons, reduced inflammatory glial cells, and increased noradrenergic neurons. On the other hand, VNS with 0.1 mA and 1 mA intensity did not display significant therapeutic efficacy. Conclusions: VNS with 0.25-0.5 mA intensity has anti-inflammatory and neuroprotective effects on PD model rats induced by 6-OHDA administration. In addition, we were able to confirm the practicality and effectiveness of the new experimental device