Search

To reduce manufacturing costs, high-quality 150 mm 4H-SiC wafers were grown at over 1.5 mm/h by high-temperature chemical vapor deposition. The dislocations in the initial growth stage did not increase compared with those in the seed crystal. The dislocation densities decreased during crystal growth, and the densities of threading dislocations and basal plane dislocations at the growth thickness of 7.1 mm were 1186 and 211 /cm2, respectively. The resolved shear stress, which is the cause of the increase in dislocations during growth, was calculated based on thermal fluid simulations; the shear stress of the grown crystal with a flat surface was small compared with that of the convex-shaped crystal. The dislocations did not increase likely because the crystals grown at high speeds were relatively flat. In addition, the decrease in dislocations was attributed to the frequent annihilation of dislocations due to the growth at a high temperature (2490 °C).

Bevacizumab, a monoclonal antibody against vascular endothelial growth factor, may be associated with arterial embolisms. We herein report a case of acute myocardial infarction caused by coronary embolism during combination chemotherapy with mFOLFOX-6 and bevacizumab in a patient with metastatic colon cancer. Thromboembolism occurred only in the distal right posterolateral branch without stenotic lesions or plaque rupture in the proximal branch of the right coronary artery. Sole thromboaspiration was successfully performed; the final angiogram demonstrated no stenosis in the right coronary artery. Bevacizumab may be associated with acute coronary syndrome in patients with coronary risk factors, despite no significant coronary narrowing.

Purpose Obstructive sleep apnea (OSA) is associated with various cardiovascular disorders. This study aimed to investigate the effects of OSA on left ventricular (LV) function in patients with OSA who were at risk for heart failure but who had not yet developed structural heart changes. The study also sought to determine the effects of continuous positive airway pressure (CPAP) in these patients. Methods In a retrospective study, consecutive patients with polysomnographic OSA (apnea-hypopnea index [AHI] >5) were categorized into mild (AHI < 15), moderate (15 ≤ AHI < 30), and severe OSA (AHI ≥ 30) groups. The subjects were patients with OSA and at risk for heart failure who had not yet developed structural heart changes. All study participants underwent echocardiography and two-dimensional speckle tracking analysis, and their global longitudinal strain (GLS) was calculated. Results Of 275 patients, there were 31 with mild, 92 with moderate, and 152 with severe OSA. Of patients with moderate to severe OSA (AHI ≥ 20), 206 started CPAP and 92 patients underwent follow-up echocardiogram and speckle tracking echo analysis (median period of CPAP use: 283 days [258 to 391]). GLS was significantly reduced in patients with moderate and severe OSA compared with mild OSA (−17.8±3.1 vs. −18.0±2.6 vs. −19.3±2.8%, p=0.038). The proportion of patients with GLS ≥ −18% was significantly higher among the patients with moderate to severe OSA than among those with mild OSA. GLS improved after CPAP therapy in patients with moderate to severe OSA (GLS: −18.1±2.7% to −19.0±2.8%, p=0.004). Significant improvement in GLS was confirmed, particularly among patients with good CPAP adherence. Conclusion Moderate to severe OSA is associated with LV dysfunction and can be significantly improved by CPAP therapy.

Bioprosthetic aortic valves have limited durability. We herein report sudden progression of structural valve deterioration (SVD) and a successful case of emergency transcatheter aortic valve (TAV) implantation for acute decompensated heart failure (ADHF) caused by SVD. A 79-year-old man who had undergone a Bentall operation 11 years prior was diagnosed with ADHF due to suddenly progressive SVD. Emergency TAV implantation in the surgical bioprosthetic valve was selected based on the surgical risk. Ours and previous case reports suggest that SVD can progress suddenly, even after months of stability, and that emergency TAV implantation is effective.

To reduce the cost of silicon carbide (SiC) substrates, we have developed a high-temperature chemical vapor deposition (HTCVD) method for high-productivity crystal growth. We have conducted research using crystals of diameter 4 inches or less. In order to further reduce the cost, development of a 150-mm substrate has been demanded. With increasing crystal diameter, the occurrence of cracks should be suppressed efficiently. The internal structure of the furnace was designed to reduce the distribution of temperature in the radial direction of the crystal, ultimately reducing the stress responsible for the formation cracks. We demonstrated a 150-mm 4H-SiC substrate without cracks using by HTCVD method.

The process conditions for fast growth of 4 in. 4H-polytype SiC (4H-SiC) single crystals were studied for high-temperature gas source method. Prior to experiments, crystal growth simulations were conducted to investigate the influence of vertical gas-flow velocity on the radial distribution of the growth rate. Crystal growth experiments were performed using the crucibles designed for 4 in. crystal growth following the simulation studies. By investigating growth rate as functions of the input partial pressure of source gases and temperatures of growing surfaces, expressions for the growth rate of 4-in. crystals were derived. We also clarified the optimal conditions for single-crystal growth. Finally, fast growth of 4 in. 4H-SiC crystals with uniform shape was demonstrated.

Methotrexate (MTX) is an immunosuppressor that is widely used to treat autoimmune diseases, including rheumatoid arthritis (RA). However, it can have serious adverse effects including a lymphoma: MTX-associated lymphoproliferative disorder (MTX-LPD). Extranodal lesions are common in MTX-LPD patients. However, MTX-LPD in the central nervous system (CNS) is extremely rare with few reported cases. Here, we describe a case of primary CNS MTX-LPD in a patient with RA, with a review of the literature. A 68-year-old woman who had received MTX for her RA for more than 10 years was referred to our hospital. Head magnetic resonance imaging (MRI) showed multiple lesions with heterogeneous contrast enhancement scattered throughout both hemispheres. As immunosuppression caused by MTX was suspected, MTX was discontinued, based on a working diagnosis of MTX-LPD. We performed an open biopsy of her right temporal lesion. Histopathologic examination showed atypical CD20+ lymphoid cells, leading to a definitive diagnosis of diffuse large B-cell lymphoma (DLBCL). In situ hybridization of an Epstein-Barr virus-encoded small RNA (EBER) was positive. Sanger sequencing confirmed that both MYD88 L265 and CD79B Y196 mutations were absent. The LPD regressed after stopping MTX. Follow-up head MRI at 8 months after surgery showed no evidence of recurrence. Although primary CNS MTX-LPD is extremely rare, it should be included in the differential diagnosis when a patient receiving MTX develops CNS lesions. Diagnosis by biopsy and MTX discontinuation are required as soon as possible.

Objective PET scans are useful for the diagnosis and treatment planning of glioma. Introduced in 2013, bevacizumab (Bev) treatment efficacy can be difficult to determine using MRI imaging. We instead performed PET scans to determine the efficacy of Bev-based glioblastoma treatment. Methods Eighty glioblastoma patients treated with Bev from July 2013 to December 2021 were included. The patients were divided into the following three groups: the first group received Bev added to the Stupp regimen after biopsy or subtotal resection (first-dose group), the second group received Bev added to the Stupp regimen after biopsy followed by tumor resection (neoadjuvant group), and the third group received the Stupp regimen after tumor resection followed by TMZ + Bev at recurrence (recurrent group). PET scans (FDG, MET, FLT, and FMISO) were performed before and 4 weeks after the start of the Bev treatment. FDG, MET, and FLT measured tumor-to-normal ratio (TNR), and FMISO measured tumor-to-blood ratio (TBR), as well as the percent change in SUVmax, TNR, TBR, and MTV before and after Bev treatment. Using the Cox proportional hazards model, we examined which of these rates of change were the prognostic factors. Results The median PFS (months) and median OS from Bev treatment were 8.87, 16.53, and 4.0 and 12.53, 22.13, and 8.0, respectively. Significant differences in the percent change in MTV for MET, FLT, and FMISO in the first-line group, the percent change in MTV for FDG and MET, the percent change in FDG TNR and FMISO TBR in the recurrent group, and the percent change in MTV for MET and FLT in the neoadjuvant group were shown in the Cox proportional hazards model. Conclusion Neoadjuvant treatment with Bev prolonged PFS and OS. The decrease in MET MTV change rate and FMISO TBR.

Acute type A aortic dissection is a potentially fatal disease, and emergency surgery should be considered when it is diagnosed. We herein report two cases of retrograde type A aortic dissection with intramural hematoma, followed by re-dissection, rupture, and cardiac tamponade. The diagnoses in these cases had to be made carefully, as the false lumen of the ascending aorta was sometimes unclear on contrast-enhanced computed tomography.

Lumbar spondylolysis is commonly recognized at a single-level of the lumbar spine and frequently affects the L5 pars interarticularis unilaterally or bilaterally. Some reports have described multiple-level spondylolysis, most cases of which occur at consecutive lumbar segments. We herein present a rare case of lumbar spondylolysis involving nonconsecutive multiple-level segments; only eight such cases have been reported previously. A 38-year-old man presented with a 10-month history of chronic severe low back pain. Lumbar flexion-extension radiographs and computed tomography revealed spondylolysis at the level of L3 and L5, whereas no spondylolisthesis was present and the intervertebral disc spaces were maintained at all levels. Because 6 months of conservative management failed and repeated diagnostic blocks confirmed that the fracture of the L3 pars interarticularis was generating pain, repair of the bilateral L3 pars interarticularis with the smiley face rod method was performed. At the last follow-up 1 year after surgery, the patient had resumed normal life as a laborer and reported no back pain.

In surgical treatment of acute subdural hematoma (ASDH), neurosurgeons frequently encounter bleeding from cortical arteries, which is usually controlled with bipolar coagulation. However, bipolar coagulation is associated with a risk of sacrificing the cortical artery, which may affect the prognosis of neurological symptoms when these cortical arteries supply critical areas. In this article, we describe microsurgical repair of damaged cortical arteries using a 10-0 nylon micro-suture in patients with arterial-origin ASDH. After removal of the subdural hematoma, the exact bleeding point of the cortical artery was identified, and the 10-0 nylon suture stitches were placed on the arterial tear under a microscope. After completion of the micro-suture, vascular patency was confirmed by indocyanine green (ICG) videoangiography. From June 2015 through February 2017, microsurgical repair was performed for seven cortical arteries in six patients. All damaged arteries were located near the Sylvian fissure, and all tears were pinhole tears. The average blood flow occlusion time was 8 min (range, 0–15 min). The patency of all seven repaired arteries was successfully confirmed by ICG videoangiography. Postoperative cerebral infarction was not observed except in one patient with cerebral contusion and a history of severe head trauma. The present report demonstrates that repair of a cortical artery by the 10-0 nylon micro-suture is a simple and safe method with a low risk of sacrificing the artery. This technique may be a good option in the surgical treatment of arterial-origin ASDH, especially when the accompanying cerebral contusion is minimal.

Synchrotron X-ray topography was carried out for 4H-SiC crystals grown by high-temperature gas source method, and transmission topography analysis with g= or 0004 was carried out for the cross-sectional samples. Dislocation contrasts extended in the growth direction were observed and the propagation behavior of threading screw dislocations (TSDs), threading edge dislocations (TEDs), basal plane dislocations (BPDs) and stacking faults (SFs) in the facet and step-flow regions were discussed. The propagation of dislocations in the fast grown crystal with a growth rate of 3.1mm/h was also evaluated by cross-sectional topography.

Spontaneous coronary artery dissection (SCAD) is rare, but it frequently presents as acute myocardial infarction. It is frequently fatal and most cases are diagnosed at autopsy. We herein present the case of a 65-year-old woman with ST-elevation and myocardial infarction due to SCAD. Optical coherence tomography (OCT) helped us to confirm the diagnosis. The information on the intravascular morphology provided by OCT imaging is much more detailed in comparison to that provided by coronary angiography (CAG) and intravascular ultrasound (IVUS).

Fast growth of n-type 4H-SiC crystals was attempted using a high-temperature gas-source method. High growth rates exceeding 9 mm/h were archived at a seed temperature of 2550 °C, although the formation of macro-step bunching caused doping fluctuation and voids in the grown crystal. We investigated a trade-off between growth-rate enhancement and macro-step formation and how to improve the trade-off. By controlling the growth conditions, the growth of highly nitrogen-doped 4H-SiC crystals without the doping fluctuation and void formation were accomplished under a high growth rate exceeding 3 mm/h, maintaining the density of threading screw dislocations in the same level with the seed crystal. The influence of growth parameters on nitrogen incorporations into grown crystals was also surveyed.

Ischemic tolerance is an endogenous neuroprotective phenomenon induced by sublethal ischemia. Ischemic preconditioning (IPC), the first discovered form of ischemic tolerance, is widely seen in many species and in various organs including the brain and the spinal cord. Ischemic tolerance of the spinal cord is less familiar among neurosurgeons, although it has been reported from the viewpoint of preventing ischemic spinal cord injury during aortic surgery. It is important for neurosurgeons to have opportunities to see patients with spinal cord ischemia, and to understand ischemic tolerance of the spinal cord as well as the brain. IPC has a strong neuroprotective effect in animal models of ischemia; however, clinical application of IPC for ischemic brain and spinal diseases is difficult because they cannot be predicted. In addition, one drawback of preconditioning stimuli is that they are also capable of producing injury with only minor changes to their intensity or duration. Numerous methods to induce ischemic tolerance have been discovered that vary in their timing and the site at which short-term ischemia occurs. These methods include ischemic postconditioning (IPoC), remote ischemic preconditioning (RIPC), remote ischemic perconditioning (RIPerC) and remote ischemic postconditioning (RIPoC), which has had a great impact on clinical approaches to treatment of ischemic brain and spinal cord injury. Especially RIPerC and RIPoC to induce spinal cord tolerance are considered clinically useful, however the evidence supporting these methods is currently insufficient; further experimental or clinical research in this area is thus necessary.

A case of delayed occurrence of C3 vertebra anterior subluxation diagnosed 10 days after surgery for epidural hematoma is herein described. A 56-year-old man underwent surgery for right epidural hematoma. No spinal fracture was identified on the cervical–spinal computed tomography (CT) on arrival. The patient developed neck pain after the craniotomy, and cervical magnetic resonance imaging 5 days postoperatively revealed a disruption of the C3–C4 posterior ligament complex. The patient was conservatively treated with immobilization. Cervical CT 10 days postoperatively revealed C3 vertebra anterior subluxation. Posterior fixation surgery was performed 21 days after admission, and the postoperative course was uneventful. This case suggests that awareness of delayed occurrence of cervical dislocation after traumatic intracranial hemorrhage should be increased among neurosurgeons.

Idiopathic carpal tunnel syndrome (CTS) is a common complaint, reflecting entrapment neuropathy of the upper extremity. CTS produces symptoms similar to those of other conditions, such as cervical spondylosis or ischemic or neoplastic intracranial disease. Because of these overlaps, patients with CTS are often referred to a neurosurgeon. Surgical treatment of CTS was started recently in our department. Through this experience, we realized that neurosurgeons should have an increased awareness of this condition so they can knowledgeably assess patients with a differential diagnosis that includes CTS and cervical spinal and cerebral disease. We conducted a literature review to gain the information needed to summarize current knowledge on the clinical, pathogenetic, and therapeutic aspects of CTS. Because the optimal diagnostic criteria for this disease are still undetermined, its diagnosis is based on the patient’s history and physical examination, which should be confirmed by nerve conduction studies and imaging modalities such as magnetic resonance imaging and ultrasonography. Treatment methods include observation, medication, splinting, steroid injections, and surgical intervention. Understanding the clinical features and pathogenesis of CTS, as well as the therapeutic options available to treat it, is important for neurosurgeons if they are to provide the correct management of patients with this disease.

We performed fast growth of a 4H-SiC crystal using the gas-source method and investigated the crystal to reveal changes in dislocation densities along the growth direction. The remarkable reduction in densities of threading and basal plane dislocations to be less than 1/10 and 1/20, respectively, was confirmed in the crystal grown at ∼3 mm h−1. The change in radial distribution of threading dislocations indicates enhanced reduction in dislocation densities within an area containing high density dislocations. We discussed possible mechanisms which could explain declining densities of threading dislocations according to the results obtained by classifying threading dislocations into each Burgers vector.

Computed tomographic angiography (CTA) is a quick and accurate method in triage to determine recanalization therapies for acute ischemic stroke. To minimize delay in the start of recanalization therapies, performance of CTA immediately after unenhanced brain computed tomography (CT) is recommended as the minimum standard. However, there are some pitfalls related to image interpretation of CTA in acute stroke, such as false patency sign. We describe the case of a 66-year-old man who presented with acute middle cerebral artery (MCA) occlusion by a calcified embolus with false patency sign on CTA after coronary angiography. We misinterpreted the CTA image as a patent MCA, and unnecessary brain magnetic resonance imaging caused delay in the start of endovascular thrombectomy. Our findings suggest that calcified cerebral emboli can present with false patency sign on CTA. To avoid misinterpretation of the CTA image and start recanalization therapy as soon as possible, physicians should be aware of false patency sign, especially when unenhanced CT shows hyperdense emboli and CTA findings do not correspond with patients' symptoms in acute ischemic stroke.

In Japan, hepatic arterial infusion chemotherapy (HAIC) using reservoir system is recommended for patients with hepatocellular carcinoma (HCC) whose hepatic spare ability is favorable. Arterial infusion catheter is commonly detained in hepatic artery via femoral or brachial artery. In our hospital, catheter is often inserted by puncturing the left subclavian or brachial artery considering the patient's activities of daily living (ADL) during long-term detaining. However, it rarely causes posterior circulation ischemic stroke because of the left vertebral artery branches on the path of catheter. We herein report a case of posterior circulation ischemic stroke caused by heparin-induced thrombosis (HIT) after detaining hepatic arterial infusion catheter. A 63-year-old man who is under HAIC treatment for HCC was introduced to the department of neurological surgery because of vertigo and vomiting. Magnetic resonance imaging revealed sporadic fresh cerebral infarction in the bilateral cerebellar hemisphere. Carotid ultrasonography detected a floating thrombus around the part of the left vertebral subclavian artery bifurcation. Detained catheter was removed and continuous heparin administration was started immediately. However, thrombocytopenia occurred 5 days after the injection. Because 4T's score was 6 points, HIT was strongly suspected. We stopped heparin injection immediately and observed the patient's physical status strictly. After that, platelet value improved naturally. At the late date, antibodies specific for platelet factor 4/heparin complexes were positive and he was diagnosed with HIT.

(6–4) photolyases [(6–4)PLs] are flavoproteins that use blue light to repair the ultraviolet-induced pyrimidine(6–4)pyrimidone photoproduct in DNA. Their flavin adenine dinucleotide (FAD) cofactor can be reduced to its repair-active FADH– form by a photoinduced electron transfer reaction. In animal (6–4)PLs, a chain of four Trp residues was suggested to be involved in a stepwise transfer of an oxidation hole from the flavin to the surface of the protein. Here, we investigated the effect of mutation of the fourth Trp on the DNA photorepair activity of Xenopus laevis (6–4)PL (Xl64) in bacterial cells. The photoreduction and photorepair properties of this mutant protein were independently characterized in vitro. Our results demonstrate that the mutation of the fourth Trp in Xl64 drastically impairs the DNA repair activity in cells and that this effect is due to the inhibition of the photoreduction process. We thereby show that the photoreductive formation of FADH– through the Trp tetrad is essential for the ...

Intracranial cavernous angiomas (cavernomas, cavernous hemangiomas, cavernous malformations) usually cause intraparenchymal hemorrhage but are rarely described as a cause of isolated subarachnoid hemorrhage (SAH).[2,6,10] Some cases of intracranial cavernous angiomas presenting with isolated SAH have been reported.[3,7,9,10,12] However, cavernous angiomas presenting with so-called angiographically negative aneurysmal-like SAH are rare. To our knowledge, only one case of cavernous angioma presenting with perimesencephalic SAH has been reported.[11] We describe a case of cavernous angioma presenting with SAH, which was diffusely distributed in the basal cisterns and mimicked intracranial aneurysm rupture.

In contrast to other levels of upper disc spaces, the Luschka joints are usually absent at the C7/T1 disc space. Therefore, it has been reported that the C7/T1 disc herniation is prone to herniate laterally rather than centrally. In this manuscript, we describe an extremely rare central-type disc herniation at the C7/T1 level presented with myelopathy. A 76-year-old man presented with a 20-day history of progressive gait disturbance. Physical examination revealed bilateral lower extremity hyperreflexia and mild foot numbness with no upper extremity motor weakness or sensory disturbance. Cervical magnetic resonance imaging(MRI)revealed severe spinal cord compression at the C7/T1 level caused by a central-type disc herniation. We removed the herniated disc and performed anterior fusion with a titanium box cage. Lower extremity numbness and weakness diminished rapidly. Three weeks later, cervical MRI showed a well-decompressed spinal cord and almost normal gait. We reevaluated the preoperative computed tomography of this patient and confirmed the absence of Luschka joints at the C7/T1 level. Although the condition is rare, clinicians should consider the possibility of C7/T1 disc herniation in patients with leg weakness or numbness but no or few hand-related symptoms.

The synthesis of 3-pyridinols carrying alkyltelluro, alkylseleno, and alkylthio groups is described together with a detailed kinetic, thermodynamic, and mechanistic study of their antioxidant activity. When assayed for their capacity to inhibit azo-initiated peroxidation of linoleic acid in a water/chlorobenzene two-phase system, tellurium-containing 3-pyridinols were readily regenerable by N-acetylcysteine contained in the aqueous phase. The best inhibitors quenched peroxyl radicals more efficiently than alpha-tocopherol, and the duration of inhibition was limited only by the availability of the thiol reducing agent. In homogeneous phase, inhibition of styrene autoxidation absolute rate constants k(inh) for quenching of peroxyl radical were as large as 1 x 10(7) M(-1) s(-1), thus outperforming the best phenolic antioxidants including alpha-tocopherol. Tellurium-containing 3-pyridinols could be quantitatively regenerated in homogeneous phase by N-tert-butoxycarbonyl cysteine methyl ester, a lipid-soluble analogue of N-acetylcysteine. In the presence of an excess of the thiol, a catalytic mode of action was observed, similar to the one in the two-phase system. Overall, compounds bearing the alkyltelluro moiety ortho to the OH group were much more effective antioxidants than the corresponding para isomers. The origin of the high reactivity of these compounds was explored using pulse-radiolysis thermodynamic measurements, and a mechanism for their unusual antioxidant activity was proposed. The tellurium-containing 3-pyridinols were also found to catalyze reduction of hydrogen peroxide in the presence of thiol reducing agents, thereby acting as multifunctional (preventive and chain-breaking) catalytic antioxidants.

We propose a simplified reaction model for SiGe epitaxial growth by chemical vapor deposition (CVD). The SiH4 and GeH4 adsorption at vacant sites, the exchange reaction between SiH and GeH at the surface, and the decomposition of SiH and GeH are considered in the model. The decomposition of SiH4 or GeH4 into SiH2 or GeH2 is representative of complicated reactions in the gas phase. SiGe growth is carried out on a 300 mm Si substrate by reduced-pressure CVD from the SiH4–GeH4–H2 system in the original epitaxial furnace. The dependences of the growth rate and Ge content in the SiGe layer on the temperature and GeH4 flow rate are determined by the characterization of specimens cut from certain positions in 300 mm wafers. By using the chemical reaction analysis software package chemkin, the rate constants in the proposed model are determined by comparison with experimental results. In this report, we validate that the model can explain the behavior of SiGe CVD.

OBJECT: Neuroendocrine carcinoma (NEC) is a malignant tumor that usually arises in the lung, pancreas and gastrointestinal tract. Brain metastasis of NEC is merely reported. Herein, we report two cases of NEC in the brain mimicking glioblastoma (GBM). CASES: Both patients were in their 60s, cystic lesions with peritumoral edema affected the temporal lobe. Cyst walls were thin but hyperintense in diffusion weighted images implying increased cellularity. Positron emission tomography (PET) revealed malignant nature by strong uptake of methionine (MET), fluorothymidine (FLT) and fluoromisonidazole likewise GBM. However, fluorodeoxyglucose (FDG) indicated relatively weak uptakes compared as GBM. Both tumors were resected under the preoperative diagnosis of GBM, however, pathological diagnoses were NEC by immunohistochemical finding of negative GFAP and positive markers of neuroendocrine differentiation. Systemic examination failed to reveal the origin. Both cases underwent radiotherapy. One case was lost by spinal dissemination 11 months after the operation. DISCUSSION: FDG-PET of neuroendocrine tumor in the extracranial lesion does not always demonstrate strong uptake. FDG-PET for NEC in the brain could be less accumulated than GBM, while it should be evaluated keeping in mind that the background level of FDG would be high in the brain tissue. In case of malignant tumors endorsed by other tracer such as MET and FLT, inconsistent FDG-PET finding might be useful for the diagnosis of NEC in the brain.

Group 14 element derivatives of carbotelluroates, RCOTeMPh 3 (M = Ge, Sn, Pb), were synthesized as stable compounds by reacting sodium carbotelluroates with Ph 3 MCl and were characterized by IR and 1 3 C and 1 2 5 Te NMR spectra. Their molecular structures were revealed by X-ray molecular analysis. The C=O...Sn distance in RCOTeSnPh 3 was found to be shorter than the C=O...Ge distance in RCOTeGePh 3 , despite the fact that the atomic radius of Sn is larger than that of Ge. A similar shortening of the nonbonding distance was observed for the corresponding selenium derivatives. Molecular orbital calculations of model compounds, i.e., CH 3 COEM(CH 3 ) 3 (E = Se, Te; M = Ge, Sn, Pb), at the B3LYP/LANL2DZ+p level also supported this shortening of the C=O...Sn distance. NBO (natural bond orbital) analyses of the model compounds showed that two types of orbital interactions, n O →σ * M E and n O →σ * M C (E = S, Se, Te; M = Ge, Sn, Pb), are important in these carbochalcogenoates. Furthermore, the former interaction has a greater role in the case of carbothioates, whereas the latter is dominant in carbotelluroates.

Selenocarboxylic acids [RC(=O)SeH] were found to readily react with aryl, acyl, and arenesulfonyl isocyanates to give the corresponding acyl carbamoyl selenides 3 [RC(=O)SeC(=O)NHR′, R′ = aryl, C6H5CO, and 4-MeC6H4SO2] in good yields. Their tautomers [RC(=O)SeC(=NR′)OH] were also detected by 1H, 13C, and 77Se NMR spectroscopies. The structure of 3 [R = 2,6-(MeO)2C6H3, R′ = 4-MeC6H4] was characterized by X-ray crystallography, which showed that this molecule is stabilized by an intramolecular hydrogen bond between the carbonyl oxygen and the NH hydrogen to form a planar six-membered ring and by nonbonded interaction of the ortho methoxy oxygen with the carbonyl oxygen or the selenium atoms. 4-Methoxybenzoyl and 4-methoxythiobenzoyl N-(4-methylphenyl)carbamoyl sulfides (4 and 5) were shown by X-ray crystallography to similarly have a planar intramolecular six-membered ring formed by a hydrogen bond between the carbonyl oxygen or thiocarbonyl sulfur and NH hydrogen atoms. The tautomers [RC(=E)SC(=NR′)OH; E = O or S] of 4 and 5 also were detected spectroscopically. The reactions of 3h (R = 4-MeOC6H4, R′ = Ph) with sodium methoxide and p-toluidine gave sodium selenocarboxylate and the corresponding amides and urea as main products, respectively. © 2001 John Wiley & Sons, Inc. Heteroatom Chem 12:250–258, 2001

Work Index is an important factor in designing grinding processes. In previous papers, the authors proposed a Corresponding Work Index which is proportional to the Work Index. The Corresponding Work Index could be estimated by examination of the zero-order grinding rate constant using various grinding mills.In this study, grinding experiments were carried out with five types of solid materials using a ball mill, a vibration mill and a planetary mill. The relationships between the Corresponding Work Index and particle size were evaluated. For these mills, the Corresponding Work Indices of silica glass, quartz and feldspar increased up to a certain particle size and became approximately constant. However, the Indices of limestone and gypsum had a minimum when the evaluated size was nearly the same as that of grain size. The Corresponding Work Index can be useful for evaluating the fine grindability of solid materials in these mills.

Bis(phosphine)bis(tellurocarboxylato)-palladium(II) and -platinum(II), [M(RCOTe)2(PR′3)2] (M = Pd or Pt; R = But, Ph, 4-MeC6H4, etc.; R′ = Et or Ph), were synthesized in moderate to good yields by treating sodium tellurocarboxylates or O-trimethylsilyl telluroesters with [MCl2(PR′3)2]. The platinum complexes with 2-methoxybenzenecarbotelluroato ligands also were synthesized from [Pt(PR′3)4] with the corresponding diacyl ditelluride. The tellurocarboxylato complexes are yellow to orange or red crystals, and labile thermally and toward oxygen. The nickel analogues [Ni(RCOTe)2(PR′3)2] (R′ = Et or Ph) were obtained by similar fashion, but were too labile to isolate. X-Ray diffraction analysis of trans-[Pt(4-MeC6H4COTe)2(PEt3)2] was carried out, and compared with those of the corresponding thio- and seleno-carboxylato complexes. These complexes crystallized in the same space group (P21/c) and are isostructural having a square-planar co-ordination geometry with thio- or telluro-carboxylato ligands which are unidentate.

A series of selenocarboxylic acids and their alkali metal salts were prepared. The potassium, rubidium and cesium salts are foundamentaly dimeric structure. Selenocarboxylic acids exist predominantly in selenon acid (selon acid) at low temperature in polar solvent. Selenocarboxylic acids readily react with aryl isocyanates to acyl carbamoyl selenides in good yields.

Selenothioic acid S-alkyl esters were synthesized from the reaction of terminal acetylenes with n-butyllithium, selenium, and alkanethiols in moderate to high yields. The use of substituted benzene...

The reaction of lithium alkyneselenolates generated from terminal acetylenes with thiols gave rise to lithium eneselenolates with high stereoselectivity. The trapping with alkyl halides afforded ketene selenothioacetals, whereas the trapping with allylic bromides yielded γ,δ-unsaturated selenothioesters via seleno-Claisen rearrangement.

Thiocarboxylic acids, such as selenocarboxylic acids, exist predominantly in the thioxo form (RCSOH, thion acid) in polar solvents such as tetrahydrofuran (THF) at temperatures below −50 °C. Tellurocarboxylic acids (5) were observed for the first time by acidolysis of the corresponding cesium tellurocarboxylates with hydrogen chloride. The telluroic acids (6) exist predominantly in the telluroxo form (RCTeOH, telluron acid) in THF at temperatures below −70 °C. Telluron acids were reddish to blue violet for the aliphatics (R = alkyl) and dark green for the aromatics (R = aryl) and reacted with aryl isocyanates at −70 °C to give crystalline acyl carbamoyl tellurides in good yields.

A series of rubidium and cesium tellurocarboxylates (2 and 3) were synthesized from the reaction of O-trimethylsilyl tellurocarboxylates (1) with rubidium and cesium fluorides in moderate isolated yields and characterized by 1H, 13C, and 125Te NMR spectroscopy and X-ray diffraction. The carbon–oxygen distance [1.235(6) A] of the tellurocarboxyl group of crystalline cesium 2-methoxybenzenecarbotelluroate (3f) showed a typical value of the carbon–oxygen double bond. The crystal packing of 3f shows the possibility of an interaction between the cesium cation and the aromatic ring carbon. The thio- and selenocarboxyl groups of the corresponding sulfur and selenium isologues (4 and 5) also indicate a double bond [1.231(4) and 1.226(5) A] between the carbon and oxygen, respectively. The salts (2 and 3) readily react with iodomethane to afford the corresponding Te-methyl tellurocarboxylates in good yields. The reaction between 3 and tetramethylammonium chloride was found to give a novel quaternary ammonium salt (...

Aromatic diselenoic acid Se-methyl esters 1 react with amines at 0°C in tetrahydrofuran (THF) to yield selenoamides in moderate to good yields. The reaction course is highly dependent on the steric requirements of both starting materials. In the reactions of the ester 1a with 2-methylpiperidine and of the ester 1b with piperidine, the starting materials disappear within 1 hour with the liberation of black selenium, but the corresponding selenoamides are not produced. These results may be ascribed to the steric congestion caused by the formation of the selenoamide group from the tetrahedral intermediate 15. X-ray crystal structure analyses of the selenoamides 3 and 9 have been performed. The bond length of C(Se)N is shorter than a carbon nitrogen single bond. On the other hand, the CSe bond is longer than that of the ordinary carbon-selenium double bond. These results are indicative of the efficient delocalization of the electrons of nitrogen to the carbon–selenium double bond. The double bond character between the carbon attached to selenium and the nitrogen is also supported by the nitrogen atom showing sp2 character. When a methyl group is introduced at the meta position of the aromatic ring, the deviation of the aromatic ring from the plane involving the carbon–selenium double bond and nitrogen atom becomes substantially large, perhaps due to the steric bulkiness of the selenium atom.