Synthesis and structure of stable 1,2-diaryldisilyne

Sasamori, Takahiro,Han, Joon Soo,Hironaka, Koji,Takagi, Nozomi,Nagase, Shigeru,Tokitoh, Norihiro De Gruyter 2010 Pure and Applied Chemistry Vol.82 No.3

<P>A novel 1,2-diaryldisilyne, BbtSi≡SiBbt (Bbt = 2,6-bis[bis(trimethylsilyl)methyl]-4-[tris(trimethylsilyl)methyl]phenyl), was synthesized as a stable compound by reduction of the corresponding 1,2-dibromodisilene, Bbt(Br)Si=Si(Br)Bbt. The spectral and structural features of this first stable 1,2-diaryldisilyne are revealed, and the Si≡Si triple-bond character is evaluated with the aid of detailed theoretical calculations. The triple-bond characters of BbtSi≡SiBbt and BbtGe≡GeBbt are compared based on experimental and theoretical results.</P>

Reactivity of an Aryl-Substituted Silicon−Silicon Triple Bond: Reactions of a 1,2-Diaryldisilyne with Alkenes

Han, Joon Soo,Sasamori, Takahiro,Mizuhata, Yoshiyuki,Tokitoh, Norihiro American Chemical Society 2010 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.132 No.8

<P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2010/jacsat.2010.132.issue-8/ja9108566/production/images/medium/ja-2009-108566_0005.gif'> <P>The reactivity of a bulky, diaryl-substituted disilyne, Ar−Si?Si−Ar, was examined for the first time. Reaction of the disilyne with ethylene yielded an ethylene-bridged bis(silacyclopropane), which is interpreted as a further reaction product of the initially formed 1,2-disilacyclobutene species with ethylene. A cyclohexane fused with a 1,2-disilacyclobutene was obtained in the reaction with cyclohexene. In the reaction with 2,3-dimethyl-1,3-butadiene, a tricyclo derivative was isolated from the complex product mixture.</P></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja9108566'>ACS Electronic Supporting Info</A></P>

Evidence for LiBr-Assisted Generation of a Silylene from a 1,2-Diaryl-1,2-dibromodisilene

Han, Joon Soo,Sasamori, Takahiro,Mizuhata, Yoshiyuki,Tokitoh, Norihiro Wiley (John WileySons) 2012 Chemistry, an Asian journal Vol.7 No.2

Closed Form Expression for BER Performance of Decode-and-Forward Relaying over Different Time Selective Fading Channel

Shintaro UCHIDA,Fumihito SASAMORI,Fumiaki MAEHARA 대한전자공학회 2009 ITC-CSCC :International Technical Conference on Ci Vol.2009 No.7

This paper presents a closed form expression for the theoretical BER of decode-and-forward (DF) relaying over time selective fading channels. In our derivation, DBPSK is chosen as a modulation scheme and radio channels between nodes are assumed to be different time selectivity and therefore, the proposed theoretical formula provides the BER at any arbitrary Doppler effect due to the mobile nodes. The validity of the proposed theoretical approach is confirmed by comparing with the computer simulation results.

Reactivity of an aryl-substituted silicon–silicon triple bond: 1,2-disilabenzenes from the reactions of a 1,2-diaryldisilyne with alkynes

Han, Joon Soo,Sasamori, Takahiro,Mizuhata, Yoshiyuki,Tokitoh, Norihiro Royal Society of Chemistry 2010 Dalton Transactions Vol.39 No.39

<P>The reactivity of a diaryl-substituted disilyne, Ar–Si&z.tbd;Si–Ar, with alkynes was examined. Reaction of the disilyne with acetylene yielded a 1,2-disilabenzene as the sole product.</P> <P>Graphic Abstract</P><P>A 1,2-disilabenzene was obtained from the reaction of a 1,2-diaryldisilyne with acetylene and evidence for its aromaticity was collected. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c0dt00115e'> </P>

Surgical Outcome of Children and Adolescents with Tethered Cord Syndrome

Toshitaka Seki,Kazutoshi Hida,Shunsuke Yano,Toru Sasamori,Shuji Hamauchi,Izumi Koyanagi,Kiyohiro Houkin 대한척추외과학회 2016 Asian Spine Journal Vol.10 No.5

Study Design: Retrospective cohort study. Purpose: To compare long-term results of surgery with the outcomes of symptomatic and asymptomatic tethered cord syndrome (TCS) in children and adolescents and to assess the surgery duration for those with TCS. Overview of Literature: Pediatric patients with TCS continue to pose significant diagnostic and management challenges. Methods: We retrospectively analyzed the outcomes of 31 patients (16 males, 15 females) with TCS, including 21 with lumbosacral lipoma. All were surgically treated between 1989 and 2015. They were divided into symptomatic and asymptomatic TCS groups. The results of the treatment were summarized and analyzed using a non-parametric Mann–Whitney U test. Results: Nineteen patients had symptomatic TCS and 12 had asymptomatic TCS. Patients had a median age of 34 months (range, 0–201 months). The median follow-up period was 116 months (range, 7–223 months). Of the 19 symptomatic TCS patients, preoperative deficits improved after surgery in two (10.5%) and remained stable in 17 (89.5%) patients. One of the 12 asymptomatic TCS (8.3%) patients showed an exacerbated illness after surgery, and one in 11 patients remained stable (11.7%). There were significant differences in monthly age at surgery, preoperative bowel and bladder dysfunction, neurological function, presence/absence of clean intermittent catheterization introduction, and presence/absence of motor disorder at final follow-up (all p <0.05). In the univariate analysis, the presence/absence of preoperative bowel and bladder dysfunction, and symptoms were strongly associated with the risk of children and adolescents with TCS (p <0.05). Conclusions: Early accurate diagnosis and adequate surgical release might lead to successful outcomes in children and adolescents with TCS. Surgical untethering is a safe and effective method for treatment of children with TCS.

Intramedullary Schwannoma of the Spinal Cord: A Nationwide Analysis by the Neurospinal Society of Japan

Takeshi Hara,Masaki Mizuno,Kazutoshi Hida,Toru Sasamori,Yasuyuki Miyoshi,Hisaaki Uchikado,Hiroki Ohashi,Taku Sugawara,Yasuhiro Takeshima,Yukoh Ohara,Akihide Kondo,Toshiki Endo 대한척추신경외과학회 2023 Neurospine Vol.20 No.3

Objective: This study was aimed to report the clinical characteristics of intramedullary schwannomas and discuss imaging findings and treatment strategies. Methods: The inclusion criterion was consecutive patients with intramedullary schwannomas who were surgically treated at 8 centers between 2009 and 2020. Clinical characteristics included age, sex, clinical presentation, disease duration, and follow-up period. The modified McCormick scale was used to compare the preoperative and postoperative conditions. Pre- and postoperative magnetic resonance images (MRI) of each case were analyzed. Results: The mean age of the total 11 patients at the operation was 50.2 years. The mean duration of the symptoms was 23 months, with limb paresthesia being the most common clinical presentation. The cervical spine was the most common localization level of the tumor in 6 cases. The mean follow-up duration was 49.4 months. Gross total resection (GTR) and subtotal resection (STR) was achieved in 9 and 2 cases, respectively. According to the modified McCormick scale at 6 months postoperatively, 7 cases (63.6%) had improved and 4 cases (36.3%) had unchanged grades. Typical MRI findings of the intramedullary schwannoma included ring-like enhancement, syringomyelia, cystic formation, intramedullary edema, and hemosiderin deposition. Gadolinium enhancement was homogenous in 8 cases (72.7%). The tumor margins were well demarcated in all cases. Conclusion: Intramedullary schwannoma should be considered when sharp margins and well-enhanced tumors are present at the cervical spine level and the initial symptoms are relatively mild, such as dysesthesia. When GTR cannot be achieved, STR for tumor decompression is recommended.

Clinical Factors for Prognosis and Treatment Guidance of Spinal Cord Astrocytoma

Toshitaka Seki,Kazutoshi Hida,Shunsuke Yano,Takeshi Aoyama,Izumi Koyanagi,Toru Sasamori,Shuji Hamauchi,Kiyohiro Houkin 대한척추외과학회 2016 Asian Spine Journal Vol.10 No.4

Study Design: Retrospective study. Purpose: To obtain information useful in establishing treatment guidelines by evaluating baseline clinical features and treatment outcomes of patients with spinal cord astrocytoma (SCA). Overview of Literature: The optimal management of SCA remains controversial, and there are no standard guidelines. Methods: The study included 20 patients with low-grade and 13 with high-grade SCA surgically treated between 1989 and 2014. Patients were classified according to the extent of surgical resection. Survival was assessed using Kaplan–Meier plots and compared between groups by log-rank tests. Neurological status was defined by the modified McCormick scale and compared between groups by Mann–Whitney U tests. Results: Surgical resection was performed for 19 of 20 low-grade (95%) and 10 of 13 high-grade (76.9%) SCA patients. Only nine patients (27.3%) underwent gross total resection, all of whom had low-grade SCA. Of all patients, 51.5% showed deteriorated neurological status compared to preoperative baseline. Median overall survival was significantly longer for low-grade SCA than that for high-grade SCA (91 months, 78% at 5 years vs. 15 months, 31% at 5 years; p =0.007). Low-grade SCA patients benefited from more aggressive resection, whereas high-grade SCA patients did not. Multivariate analysis revealed histology status (hazard ratio [HR], 0.30; 95% confidence interval [CI], 0.09–0.98; p <0.05) and postoperative neurological status (HR, 0.12; CI, 0.02–0.95; p <0.05) as independent predictors of longer overall survival. Adjuvant radiotherapy had no significant impact on survival rate. However, a trend for increased survival was observed with radiation cordotomy (RCT) in high-grade SCA patients. Conclusions: Aggressive resection for low-grade and RCT for high-grade SCA may prolong survival. Preservation of neurological status is an important treatment goal. Given the low incidence of SCA, establishing strong collaborative, interdisciplinary, and multiinstitutional study groups is necessary to define optimal treatments.