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排序方式: 共有140条查询结果,搜索用时 15 毫秒
131.
We report the performance of a flashlamp-pumped Cr:LiSrAlF(6) (Cr:LiSAF) laser developed and built by us. The pumping cavity incorporates filters that select the flashlamps' emission spectrum to match the absorption bands of the gain medium, allowing control of the amount of nonradiactive decay heat contribution of the optical cycle, minimizing thermal effects on the laser operation. The laser generated 2 J pulses at 15 Hz, resulting in 30 W of average power, the highest power extracted from a Cr:LiSAF rod laser to our knowledge. We were able to conclude that the laser efficiency is affected by resonator configuration changes due to thermal lens effects, and not to thermal quenching of the Cr:LiSAF luminescence. 相似文献
132.
Samad N. Ebrahimi Frank Gafner Giorgio Dell'Acqua Kuno Schweikert Matthias Hamburger 《Helvetica chimica acta》2011,94(1):38-45
Phytochemical profiling of a MeOH extract from Haberlea rhodopensis by a combination of liquid/liquid extraction, and preparative and semi‐preparative HPLC afforded three new flavone C‐glycosides, hispidulin‐8‐C‐(2″‐O‐syringoyl)‐β‐glucopyranoside ( 3 ), hispidulin 8‐C‐(6‐O‐acetyl‐β‐glucopyranoside) ( 4 ), and hispidulin 8‐C‐(6‐O‐acetyl‐2‐O‐syringoyl‐β‐glucopyranoside) ( 5 ), along with two known phenolic glycosides, myconoside ( 1 ) and paucifloside ( 2 ). The structures were established by extensive spectroscopic analyses including 1D‐ and 2D‐NMR (COSY, HSQC, and HMBC), and HR‐ESI‐TOF‐MS, and by comparison with published data. 相似文献
133.
Naser Montazeri Samad Khaksar Akbar Nazari Seyed Mohammad Vahdat 《Journal of fluorine chemistry》2011,132(7):450-5946
Pentafluorophenylammonium triflate (PFPAT) is used as an efficient catalyst in the von Pechmann condensation of phenols with β-ketoesters leading to the formation of coumarin derivatives. Short reaction times, easy and quick isolation of the products, excellent chemoselectivity, excellent yields and ease of catalyst recovery with consistent activity makes this protocol efficient and environmentally benign. 相似文献
134.
M. A. Kalam A. Samad Asgar Ali M. Aqil M. Sharma 《Journal of Dispersion Science and Technology》2013,34(1):89-96
The conventional ophthalmic solutions have demonstrated poor bioavailability and low therapeutic response due to rapid precorneal elimination of drug, which could be overcome by the use of in situ gelling systems that are instilled as drops into the eye and undergo a sol‐gel transition in the cul‐de‐sac. The present work describes the formulation of an ophthalmic delivery system of an antibacterial agent, Gatifloxacin, based on the concept of ion‐activated in situ gelation; the rheological properties of the formulation and in vitro release of the drug were evaluated. Gelrite gellan gum, a novel vehicle for ophthalmic delivery system, which gels in the presence of mono/divalent cations present in the tear fluid, was used as the gelling agent. The developed formulation showed pseudoplastic rheology and was therapeutically efficacious and provides sustained release of the drug over a 12‐hour period. The developed system is thus a viable alternative to conventional eye drops. 相似文献
135.
Olivier Potterat Carmela Herzog Melanie Raith Samad Nejad Ebrahimi Matthias Hamburger 《Helvetica chimica acta》2014,97(1):32-38
A new iridal, irigermanone ( 1 ) and nine known congeners, 2 – 10 , respectively, have been isolated from the dried rhizomes of German iris (Iris germanica). The structure of 1 was established by spectroscopic methods including HR‐ESI‐MS, 1D‐ and 2D‐NMR, and electronic circular dichroism (ECD) spectroscopy. Compound 1 is a structurally unique noriridal, and it possesses an unprecedented methylcarbonyl group instead of the α,β‐unsaturated aldehyde function typical for this group of triterpenes. 相似文献
136.
Peyman Salehi Mahdi Ayyari Morteza Bararjanian Samad Nejad Ebrahimi Atousa Aliahmadi 《Journal of the Iranian Chemical Society》2014,11(3):607-613
A series of novel 2,3-dihydroquinazolin-4(1H)-ones was synthesized by a three-component reaction between dehydroabietylamine (DHA) diterpene, isatoic anhydride and different aromatic aldehydes in the presence of a catalytic amount of p-toluenesulfonic acid (13 mol%). Diastereomeric products were separated by preparative thin-layer chromatography and their structures were characterized by 1H and 13C NMR, HMQC, IR and HR-ESI-MS. Antioxidant activities of the synthesized compounds were assessed by two different methods including DPPH and β-carotene-linoleic acid bleaching assays. Antibacterial activities of the compounds were also evaluated against two Gram-positive and one Gram-negative bacterial strains and in the case of Bacillus cereus a considerable inhibitory effect (MIC 4–16 μg/ml) was observed. 相似文献
137.
Khan MS Kannangara D Shen W Garnier G 《Langmuir : the ACS journal of surfaces and colloids》2008,24(7):3199-3204
The mechanism of the generation and sustainability of noncoalescent droplets (NCDs) was investigated at the liquid-air interface of the same liquids in the context of inkjet printing. The Weber number (We) was used to correlate and predict the generation of NCDs in a falling-drop experiment. This study found that NCDs can be generated for We higher than 130. We values of this magnitude are relevant to inkjet printing. The formation of NCD can reduce the print quality because the NCD droplets roll away uncontrollably from the print target, thus reducing print resolution. This study also used a simple experiment to demonstrate the physical origin of the NCD, which is the existence of a gaseous cushion between the liquid drop and the liquid-air interface that supports the drop. The gaseous cushion has a thickness greater than the van der Waals attraction range (around 10 nm). 相似文献
138.
Gerhard Post Samad Ahmadi Sophia Daskalaki Jeffrey H. Kingston Jari Kyngas Cimmo Nurmi David Ranson 《Annals of Operations Research》2012,194(1):385-397
The High School Timetabling Problem is amongst the most widely used timetabling problems. This problem has varying structures
in different high schools even within the same country or educational system. Due to lack of standard benchmarks and data
formats this problem has been studied less than other timetabling problems in the literature. In this paper we describe the
High School Timetabling Problem in several countries in order to find a common set of constraints and objectives. Our main
goal is to provide exchangeable benchmarks for this problem. To achieve this we propose a standard data format suitable for
different countries and educational systems, defined by an XML schema. The schema and datasets are available online. 相似文献
139.
Kin Hong Liew Wan Zurina Samad Norazzizi Nordin Poh Lee Loh Joon Ching Juan Mohd Ambar Yarmo Badrul Hisham Yahay Rahimi M.Yusop 《催化学报》2015,(5):771-777
A new heterogeneous catalyst composed of Pd nanoparticles immobilized within a HypoG el resin has been prepared in the absence of any ligands using an extensive cross-linking method.This newly developed nanocatalyst was characterized by N_2 adsorption-desorption,X-ray diffraction(XRD),transmission electron microscopy(TEM),scanning electron microscopy(SEM),energy dispersive X-ray(EDX),Fourier transform infrared spectroscopy and inductively coupled plasma-mass spectrometer(ICP-MS)techniques.TEM and XRD results revealed that the Pd nanoparticles were well dispersed with diameters in the range of 4–12 nm,and an average size of about 8 nm.The cross-linked Pd catalyst demonstrated excellent catalytic activity towards the synthesis of a series of biaryl compounds by the reaction of various aryl halides(e.g.,bromides andiodides)with phenylboronic acid in the presence of tetrabutylammonium bromide.ICP-MS analysis indicated that there was only 0.25%weight loss of Pd(0.55±0.02 ppm)from the supported catalyst after the first cycle reaction.Furthermore,the catalyst showed excellent reusability(up to five uses)with consistently high levels of catalytic activity following its recovery by filtration. 相似文献
140.
Natan Roberto de Barros Mohammad Ali Darabi Xin Ma Sibel Emir Diltemiz Menekse Ermis Alireza Hassani Najafabadi Sara Nadine Ethan A. Banton Kalpana Mandal Reza Abbasgholizadeh Natashya Falcone João F. Mano Rohollah Nasiri Rondinelli Donizetti Herculano Yangzhi Zhu Serge Ostrovidov Junmin Lee Han-Jun Kim Vahid Hosseini Mehmet R. Dokmeci Samad Ahadian Ali Khademhosseini 《Macromolecular bioscience》2023,23(12):2370037
Several microfabrication technologies have been used to engineer native-like skeletal muscle tissues. However, the successful development of muscle remains a significant challenge in the tissue engineering field. Muscle tissue engineering aims to combine muscle precursor cells aligned within a highly organized 3D structure and biological factors crucial to support cell differentiation and maturation into functional myotubes and myofibers. In this study, the use of 3D bioprinting is proposed for the fabrication of muscle tissues using gelatin methacryloyl (GelMA) incorporating sustained insulin-like growth factor-1 (IGF-1)-releasing microparticles and myoblast cells. This study hypothesizes that functional and mature myotubes will be obtained more efficiently using a bioink that can release IGF-1 sustainably for in vitro muscle engineering. Synthesized microfluidic-assisted polymeric microparticles demonstrate successful adsorption of IGF-1 and sustained release of IGF-1 at physiological pH for at least 21 days. Incorporating the IGF-1-releasing microparticles in the GelMA bioink assisted in promoting the alignment of myoblasts and differentiation into myotubes. Furthermore, the myotubes show spontaneous contraction in the muscle constructs bioprinted with IGF-1-releasing bioink. The proposed bioprinting strategy aims to improve the development of new therapies applied to the regeneration and maturation of muscle tissues. 相似文献