Search

Silica polymorphs occur under various pressures and temperature conditions, and their characteristics can be used to better understand the complex metamorphic history of planetary materials. Here, we conducted isothermal heating experiments of silica polymorphs in basaltic eucrites to assess their formation and stability. We revealed that each silica polymorph exhibits different metamorphic responses: (1) Quartz recrystallizes into cristobalite when heated at ≥ 1040 °C. (2) Monoclinic (MC) tridymite recrystallizes into no other polymorphs when heated at ≤ 1070 °C. (3) Silica glass recrystallizes into quartz when heated at 900-1010 °C, and recrystallize into cristobalite when heated at ≥ 1040 °C. These results suggest that MC tridymite in eucrites does not recrystallize into other polymorphs during the reheating events, nor does it recrystallize from other silica phases below the solidus temperature of eucrite (~ 1060 °C). Additionally, we found that pseudo-orthorhombic (PO) tridymite crystallizes from quenched melts in the samples heated at ≥ 1070 °C. Previously, cristobalite has been considered as the initial silica phase, which crystallizes from eucritic magma. Our findings suggest that the first crystallizing silica minerals may not always be cristobalite. These require a reconsideration of the formation process of silica minerals in eucrites., (© 2024. The Author(s).)

Chibaite, a silica-framework structure with cage-like voids occupied by gaseous molecules, was found in marine sediments. Its formation age could be evaluated using electron spin resonance (ESR) if the radicals formed by natural radiation can be assumed to accumulate over time. To investigate whether hydrogen transfer reactions, where organic radicals withdraw hydrogen atoms from other molecules in adjacent cages, occur in chibaite and affect ESR dating, gamma-irradiated chibaite was measured by ESR. Methyl, ethyl, n-propyl, isopropyl, tert-butyl radicals and hydrogen atoms were created by gamma irradiation at 77 K. The amount of tert-butyl radicals increased around 240 K and the similar amount of the other organic radicals decreased simultaneously, implying that hydrogen transfer reactions occur between isobutane and the organic radicals in chibaite around 240 K and therefore would have no influence on ESR dating because the reactions are completed at the environmental temperature., (© The Author(s) 2023. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Patients with massive brain swelling undergo external decompressive craniectomy to manage intracranial pressure. Following supratentorial craniectomy, and after the brain swelling is relieved, cranioplasty is performed. Although feasibility of the surgery is usually assessed by CT scanning in a supine position, it is sometimes difficult to determine whether the surgery can be performed safely. Although nine patients underwent a decompressive craniectomy during the study period, only six patients could undergo brain CT-first in a supine position and next in a lateral decubitus position with the surgical side upward-before cranioplasty. On CT images, the distance from the midline to the brain surface was measured on the image where brain bulging was maximal, and the bulging was calculated by comparing the image with the distance measured on the contralateral side. In all cases, brain bulging decreased with this change in position. The decrease ranged from 5.5-9.2mm(mean 7.1mm). Patients with brain bulging of 2.8-3.6mm in the lateral decubitus position needed no additional procedure, or only required drainage of a very small amount of cerebrospinal fluid(CSF)from the brain surface. Those with brain bulging of 5.1-12mm showed ventricular dilatation on CT images, and required ventricular puncture or spinal CSF drainage to decrease brain bulging for cranioplasty. We believe that the lateral decubitus position, with the surgical side upward, ameliorates the local brain shift induced by gravity. A lateral position during CT simulates the surgical head position for cranioplasty and can help to assess whether cranioplasty is feasible.

Our objective is to study a 53-year-old woman with Down syndrome presented with massive lobar hematoma in the left fronto-parietal lobe, and who underwent craniotomy and hematoma evacuation. Histopathological diagnosis of surgical specimen was amyloid angiopathy. Postoperative magnetic resonance studies were performed. The lesion this time showed mixed intensity on susceptibility-weighted imaging. In addition, multiple hypointense lesions were evident. An old previously unidentified hemorrhage in the right temporo-parietal lobe was accompanied by superficial cortical siderosis. Old bleeds were apparent in subcortical areas. These various kinds of hemorrhagic lesion were consistent with findings of amyloid angiopathy reported in the elderly. Most reported cases of Down syndrome associated with intracerebral hemorrhage have involved middle-aged patients. Magnetic resonance studies for Down syndrome patients before old age may disclose the degree to which amyloid angiopathy progresses in the brain of these patients., (Copyright © 2019. Published by Elsevier Inc.)

We report a systematic spectroscopical investigation of three plagioclase particles (RB-QD04-0022, RA-QD02-0025-01, and RA-QD02-0025-02) returned by the Hayabusa spacecraft from the asteroid Itokawa, by means of scanning electron microscopy, cathodoluminescence microscopy/spectroscopy, and micro-Raman spectroscopy. The cathodoluminescence properties are used to evaluate the crystallization effects and the degree of space weathering processes, especially the shock-wave history of Itokawa. They provide new insights regarding spectral changes of asteroidal bodies due to space weathering processes. The cathodoluminescence spectra of the plagioclase particles from Itokawa show a defect-related broad band centered at around 450 nm, with a shoulder peak at 425 nm in the blue region, but there are no Mn- or Fe-related emission peaks. The absence of these crystal field-related activators indicates that the plagioclase was formed during thermal metamorphism at subsolidus temperature and extreme low oxygen fugacity. Luminescence characteristics of the selected samples do not show any signatures of the shock-induced microstructures or amorphization, indicating that these plagioclase samples suffered no (or low-shock pressure regime) shock metamorphism. Cathodoluminescence can play a key role as a powerful tool to determine mineralogy of fine-grained astromaterials.

Background: Osteogenesis imperfecta (OI) is a heterogeneous group of inherited disorders that occur owing to the abnormalities in type 1 collagen, and is characterized by increased bone fragility and other extraskeletal manifestations. We report the case of a patient who was diagnosed with OI following subarachnoid hemorrhage (SAH) secondary to a ruptured saccular intracranial aneurysm (IA)., Case Presentation: A 37-year-old woman was referred to our hospital because of sudden headache and vomiting. She was diagnosed with SAH (World Federation of Neurosurgical Society grade 2) owing to an aneurysm of the middle cerebral artery. She then underwent surgical clipping of the aneurysm successfully. She had blue sclerae, a history of several fractures of the extremities, and a family history of bone fragility and blue sclerae in her son. According to these findings, she was diagnosed with OI type 1. We performed genetic analysis for a single nucleotide G/C polymorphism (SNP) of exon 28 of the gene encoding for alpha-2 polypeptide of collagen 1, which is a potential risk factor for IA. However, this SNP was not detected in this patient or in five normal control subjects. Other genetic analyses did not reveal any mutations of the COL1A1 or COL1A2 gene. The cerebrovascular system is less frequently involved in OI. OI is associated with increased vascular weakness owing to collagen deficiency in and around the blood vessels. SAH secondary to a ruptured IA with OI has been reported in only six cases., Conclusion: The patient followed a good clinical course after surgery. It remains controversial whether IAs are caused by OI or IAs are coincidentally complicated with OI.

There have been several reports of temozolomide (TMZ) treatment of pituitary carcinomas and atypical adenomas. O(6)-methyl-guanine-DNA methyltransferase is not the sole molecule determining the sensitivity to TMZ in pituitary carcinomas and atypical adenomas. The Japan Society of Hypothalamic and Pituitary Tumors study suggests that MSH6, one of mismatch repair pathway enzyme, fulfills a contributory role to the efficacy of TMZ treatment for pituitary carcinomas and atypical adenomas. The preserved MSH6 function might be essential for the responsiveness to TMZ treatment in pituitary carcinomas and atypical adenomas.

Background and Purpose: Stent-assisted coiling has expanded the treatment of intracranial aneurysms. With the use of continuously compiled data, we reviewed the role and drawbacks of stent-assisted coiling., Materials and Methods: We compiled data from consecutive patients from 2003-2012 who underwent coiling, with or without stent assistance. Clinical and angiographic results were analyzed retrospectively., Results: Of 1815 saccular aneurysms in 1505 patients, 323 (17.8%) were treated with stents (299 procedures) and 1492 (82.2%) without stents (1400 procedures). Procedure-related complications occurred in 9.4% with stents versus 5.6% without stents (P = .016, relative risk 1.5; 95% CI, 1.1-2.7). Ischemic complications were more frequent in the stent group than in the no-stent group (7.0% versus 3.5%; P = .005; relative risk, 1.7; 95% CI 1.2-2.5), as were hemorrhagic complications (2.3% versus 1.9%, P = .64). Procedure-induced mortality occurred in 2.7% (8/299) with stents versus 1.1% (15/1400) without stents (P = .029; relative risk, 2.0; 95% CI, 1.1-3.5). Logistic regression analysis identified wide-neck aneurysms as the most significant independent predictor of complications. A total of 64.1% (207/323) of aneurysms treated with stents and 70.3% (1049/1492) treated without stents have been followed, disclosing angiographic recurrence in 15.5% (32/207) versus 35.5% (372/1049), respectively (P < .0001). Logistic regression analysis showed that the presence of a stent was the most important factor for the reduction of angiographic recurrence (P < .0001; relative risk, 2.3; 95% CI, 1.6-3.3)., Conclusions: The stent-assisted coiling technique is associated with a significant decrease in recurrences but a significant increase in complications. The treatment of wide-neck aneurysms remains hazardous.

Skull base metastasis from differentiated thyroid carcinoma including follicular thyroid carcinoma (FTC) and papillary thyroid carcinoma (PTC) is a rare clinical entity. Eighteen FTC cases and 10 PTC cases showing skull base metastasis have been reported. The most common symptom of skull base metastasis from FTC and PTC is cranial nerve dysfunction. Bone destruction and local invasion to the surrounding soft tissues are common on radiological imaging. Skull base metastases can be the initial clinical presentation of FTC and PTC in the presence of silent primary sites. The possibility of skull base metastasis from FTC and PTC should be considered in patients with the clinical symptoms of cranial nerve dysfunction and radiological findings of bone destruction. A variety of genetic alterations in thyroid tumors have been identified to have a fundamental role in their tumorigenesis. Molecular histochemical studies are useful for elucidating the histopathological features of thyroid carcinoma. Recent molecular findings may provide novel molecular-based treatment strategies for thyroid carcinoma.

Many craters and thick regoliths of the moon imply that it has experienced heavy meteorite bombardments. Although the existence of a high-pressure polymorph is a stark evidence for a dynamic event, few high-pressure polymorphs are found in a lunar sample. α-PbO₂-type silica (seifertite) is an ultrahigh-pressure polymorph of silica, and is found only in a heavily shocked Martian meteorite. Here we show evidence for seifertite in a shocked lunar meteorite, Northwest Africa 4734. Cristobalite transforms to seifertite by high-pressure and -temperature condition induced by a dynamic event. Considering radio-isotopic ages determined previously, the dynamic event formed seifertite on the moon, accompanying the complete resetting of radio-isotopic ages, is ~2.7 Ga ago. Our finding allows us to infer that such intense planetary collisions occurred on the moon until at least ~2.7 Ga ago.

Color centers in selected micro- and nanodiamond samples were investigated by cathodoluminescence (CL) microscopy and spectroscopy at 298 K [room temperature (RT)] and 77 K [liquid-nitrogen temperature (LNT)] to assess the value of the technique for astrophysics. Nanodiamonds from meteorites were compared with synthetic diamonds made with different processes involving distinct synthesis mechanisms (chemical vapor deposition, static high pressure high temperature, detonation). A CL emission peak centered at around 540 nm at 77 K was observed in almost all of the selected diamond samples and is assigned to the dislocation defect with nitrogen atoms. Additional peaks were identified at 387 and 452 nm, which are related to the vacancy defect. In general, peak intensity at LNT at the samples was increased in comparison to RT. The results indicate a clear temperature-dependence of the spectroscopic properties of diamond. This suggests the method is a useful tool in laboratory astrophysics.

Object: Digital subtraction (DS) angiography is the gold standard for diagnosing spinal vascular malformations. Recently, multidetectorrow spiral CT and contrast-enhanced MR angiography have been introduced as screening examinations before DS angiography. These methods, however, do not always determine the accurate location of an arteriovenous shunt because the resulting images lack information about the spinal cord or the dura mater., Methods: Between April 2009 and December 2010, 13 patients underwent imaging evaluations for spinal vascular malformations at the authors' university hospital. This group included 8 patients with spinal dural arteriovenous fistulas (AVFs), 3 with perimedullary AVFs, and 2 with intramedullary arteriovenous malformations. Using data from these patients, the authors attempted to develop 3D computer graphics (CG) based upon the fusion of 3D rotational angiography and postmyelographic CT. They subsequently verified the accuracy of this imaging method. Ten of these 13 patients underwent surgical treatment for their lesions (11 AVFs), and for these 11 lesions the authors compared the diagnoses obtained using 3D CG with those obtained using conventional DS angiography., Results: In all 13 cases, 3D CG images of the spinal lesions were successfully developed using the patients' actual data. Four (36%) of 11 AVFs were correctly identified using DS angiography, whereas 10 (91%) were correctly identified using 3D CG. Results from 3D CG of spinal AVFs corresponded well with operative findings, and 3D CG was significantly better than conventional DS angiography at predicting AVF location (p = 0.024, Fisher exact test)., Conclusions: To the authors' knowledge, this is the first reported case series in which 3D CG of spinal vascular malformations was used to provide simultaneous, stereoscopic visualization of the spinal vascular system, spinal cord, dura mater, and bone. The 3D CG method provides precise visual images for the diagnosis and treatment of these lesions.

Extradural removal of the anterior clinoid process (ACP) is useful and essential for approaching aneurysmal and tumor lesions in and around the cavernous sinus. A safe, rapid and less invasive technique is beneficial for this basic skull base surgery. We developed a new technique by sharply cutting the ACP together with the part of the sphenoid ridge bone followed by complete replacement. A series of patients with either basilar top or internal carotid artery aneurysms underwent the present technique. After frontotemporal craniotomy, the lateral frontal and anterior middle cranial fossae are exposed extradurally. The bone was cut using a cutting steel burr from the sphenoid ridge to the superior orbital fissure and to the optic canal. By sharply separating the meningo-orbital band between the dura propria and the periorbital fascia, the ACP is exposed. The cutting burr runs underneath the ACP. By leaving a very thin sheet of bone, the entire bone piece was elevated after fracturing the thin bone using a chisel. By severing the carotid ring, the internal carotid artery is freed and mobile either laterally or medially to obtain an ample basal cistern. After operation, the once removed clinoid process is replaced in situ using a titanium plate screw. Extradural en bloc removal and in situ replacement of the ACP can be safely done by this cutting procedure. This can provide a good cosmetic result without causing enophthalmos or transient oculomotor palsy.

A unique transposition technique in microvascular decompression for hemifacial spasm (HFS) was employed in patients with compression by either the peripheral artery or the main trunk of the vertebral artery. Complete transposition that secured free space between the offending artery and the root exit zone (REZ) was accomplished by introducing GORE-TEX tape around the artery and suturing it to the petrous dura. An adequate working space, as if operating in a shallow basin, was essential. Throughout the procedure, it was not necessary to use a brain retractor. Instead, a gentle wrapping retraction technique using a sucker was employed over the brain covered by a sheet of Gelfoam (Pfizer Japan Inc., Tokyo) and cotton. All patients showed complete cure of HFS immediately after surgery with this technique. The difficulty of transposing the vertebral artery can be overcome by well-designed surgical strategy and skillfulness.