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RISS 인기검색어
- 검색키워드
- 저자 : Emami Arash (검색결과 3 건)
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Arash Shams,Mohammadreza Mehdizadeh,HamidReza Teimoury,Mehrsa Emami,Seyed Amin Mirmohammadi,Samahe Sadjadi,Eduard Bardají,Albert Poater,Naeimeh Bahri-Laleh 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.116 No.-
The role of the pore architecture of the Ziegler-Natta (ZN) catalysts in the propylene polymerizations isunveiled, towards the catalyst activity, H2– and comonomer-response, and final properties of the synthesizedpolymer. In this regard, two commercially available ZN catalysts (Cat-A and Cat-B belong to the 4thgeneration, containing diisobutyl phthalate as internal donor) with a similar composition but with differentpore structures were employed in propylene/1-hexene copolymerizations in the presence of H2 as achain transfer agent. Although pore diameter does not alter H2-response noticeably, it significantly affectsthe comonomer incorporation as well as the distribution of the isotactic sequence length in the copolymerbackbone. Cat-A with a lower surface area, a larger pore diameter, and a wider inlet showed slightlyhigher activities in homopolymerization and copolymerization experiments. According to the selfnucleationand annealing (SSA) results, the copolymer produced from Cat-A demonstrated lower isotacticsequence length and lamellar thickness contents owing to its larger pore diameter with wider inlets. Moreover, Temperature Rising Elution Fractionation (TREF) profiles asserted SSA data in which thecopolymer from Cat-A represented a higher content of low elution temperatures fractions, due to itshigher comonomer content. These findings will lead to catalysts for different polypropylene grades.
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Conor Dunn,Michael Faloon,Edward Milman,Sina Pourtaheri,Kumar Sinah,Ki Hwang,Arash Emami 대한척추외과학회 2018 Asian Spine Journal Vol.12 No.2
Study Design: Retrospective case series with prospective arm. Purpose: To assess the safety and accuracy of percutaneous lumbosacral pedicle screw placement (PLPSP) in the lumbosacral spine using intraoperative dual-planar fluoroscopy (DPF). Overview of Literature: There are several techniques available for achieving consistent, safe, and accurate results with PLPSP. There is a paucity of literature describing the beneficial operative, economic, and clinical outcomes of DPF, the most readily accessible image guidance system. Methods: From 2004 to 2014, 451 consecutive patients underwent PLPSP using DPF, for a total of 2,345 screw placement. The results of prospectively obtained postoperative computed tomography (CT) examinations of an additional 41 consecutive patients were compared with the results of 104 CT examinations obtained postoperatively due to clinical symptomatology; these results were interpreted by three reviewers. The rates of revision indicated by misplaced screws with consistent clinical symptomatology were compared between groups. Pedicle screw placement was graded according to 2-mm increments in medial pedicle wall breach and measurement of screw axis placement. Results: Seven of the 2,345 pedicle screws placed percutaneously with the use of the dual-planar fluoroscopic technique required revision because of a symptomatic misplaced screw, for a screw revision rate of 0.3%. There were no statistically significant demographic differences between patients who had screws revised and those who did not. All screws registered greater than 10 mA on electromyographic stimulation. In the 41 prospectively obtained CT examinations, one out of 141 screws (0.7%) was revised due to pedicle wall breach; whereas among the 104 patients with 352 screws, three screws were revised (0.9%). Conclusions: DPF is an extremely accurate, safe, and reproducible technique for placement of percutaneous pedicle screws and is a readily available and cost-effective alternative to CT-guided pedicle screw placement techniques. Postoperative CT evaluation is not necessary with PLPSP unless the patient is symptomatic. Acceptable electromyographic thresholds may need to be reevaluated.
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Changoor Stuart,Faloon Michael Joseph,Dunn Conor John,Sahai Nikhil,Issa Kimona,Sinha Kumar,Hwang Ki Soo,Emami Arash 대한척추외과학회 2021 Asian Spine Journal Vol.15 No.3
Study Design: Retrospective cohort study. Purpose: To assess long-term clinical outcomes of adjacent segment disease (ASD) in patients who underwent lumbar interbody fusion with percutaneous pedicle screw (PS) instrumentation. Overview of Literature: ASD is a well-known sequela of spinal fusion, and is reported to occur at a rate of 2%–3% per year. There is debate as to whether ASD is a result of the instrumentation and fusion method or is the natural history of the patient’s disease. Minimally invasive percutaneous PS augmentation of lumbar interbody fusion aims to prevent the disruption of posterior soft tissue stabilizers. Methods: From 2004–2014, 419 consecutive patients underwent anterior, lateral, or minimally invasive transforaminal lumbar interbody fusion with percutaneous PS placement at a single institution. The mean follow-up was 4.5 years. The primary outcome measure was reoperation due to ASD. Patients were divided into two cohorts: those who underwent revision surgery secondary to ASD and those who did not require further surgery. Radiographic parameters were performed using postoperative radiographs. Patients with a pelvic incidence–lumbar lordosis (PI–LL) mismatch >10° were noted. Results: Revision proportion secondary to ASD was 4.77% (n=20). Mean time to revision surgery was 2.5 years. Revision rate secondary to ASD was 1.1% per year. Patients who developed ASD were younger than those who did not (50.5 vs. 56.9 years, p=0.015). There was no difference in number of levels fused between cohorts. Revision proportion secondary to ASD was similar between approaches (anterior, lateral, minimally invasive). There was no significant difference in PI–LL mismatch between those who underwent revision for ASD and those who did not (22.2% vs. 18.8%, p=0.758). Conclusions: ASD rates in patients who underwent percutaneous PS placement were lower than those previously published after open PS placement, possibly related to greater preservation of the posterior stabilizing elements of the lumbar spine.
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