| 1. |
- Abbasian, Saeid, et al.
(author)
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The determinant of external financing at the start-up stage : Empirical evidences from Swedish data
- 2014
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In: World Review of Entrepreneurship, Management and Sustainable Development. - Switzerland : InderScience Publishers. - 1746-0573 .- 1746-0581. ; 10:1, s. 124-141
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Journal article (peer-reviewed)abstract
- Small firms in general have limited access to funding, which is a major problem for entrepreneurs. In particular, this problem is evident for women and ethnic minority groups. The purpose of the study is to examine empirically the impact of gender, ethnicity and other relevant variables on the access to external financing of new small firms. A sample of 2,764 female– and male–owned small businesses, based on a unique and large database gathered through interviews, was investigated employing binary logistic regression models. The results suggest that both gender and ethnicity are significant explanatory variables influencing the access to external capital at the start–up stage. Entrepreneurs' age, experience of starting businesses and education, as well as additional jobs beside their own business, are other variables that influence the way in which entrepreneurs finance their business. Moreover, firm characteristics in terms of personal start–up capital, firm size and legal form have an impact on financing behaviour at start–up. Since the knowledge about this issue is limited, the results of this study add to our understanding of the variables affecting the behaviour of small business endeavours in seeking funding at start–up
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| 2. |
- Abbaszad Rafi, Abdolrahim, et al.
(author)
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A facile route for concurrent fabrication and surface selective functionalization of cellulose nanofibers by lactic acid mediated catalysis
- 2023
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In: Scientific Reports. - : Springer Nature. - 2045-2322 .- 2045-2322. ; 13:1
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Journal article (peer-reviewed)abstract
- Celulose nanofibers are lightweight, recycable, biodegradable, and renewable. Hence, there is a great interest of using them instead of fossil-based components in new materials and biocomposites. In this study, we disclose an environmentally benign (green) one-step reaction approach to fabricate lactic acid ester functionalized cellulose nanofibrils from wood-derived pulp fibers in high yields. This was accomplished by converting wood-derived pulp fibers to nanofibrillated “cellulose lactate” under mild conditions using lactic acid as both the reaction media and catalyst. Thus, in parallel to the cellulose nanofibril production, concurrent lactic acid-catalyzed esterification of lactic acid to the cellulose nanofibers surface occured. The direct lactic acid esterification, which is a surface selective functionalization and reversible (de-attaching the ester groups by cleavage of the ester bonds), of the cellulose nanofibrils was confirmed by low numbers of degree of substitution, and FT-IR analyses. Thus, autocatalytic esterification and cellulose hydrolysis occurred without the need of metal based or a harsh mineral acid catalysts, which has disadvantages such as acid corrosiveness and high recovery cost of acid. Moreover, adding a mineral acid as a co-catalyst significantly decreased the yield of the nanocellulose. The lactic acid media is successfully recycled in multiple reaction cycles producing the corresponding nanocellulose fibers in high yields. The disclosed green cellulose nanofibril production route is industrial relevant and gives direct access to nanocellulose for use in variety of applications such as sustainable filaments, composites, packaging and strengthening of recycled fibers.
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| 3. |
- Abulaiti, Yiming, et al.
(author)
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Search for the Standard Model Higgs boson produced by vector-boson fusion and decaying to bottom quarks in root s=8TeV pp collisions with the ATLAS detector
- 2016
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In: Journal of High Energy Physics (JHEP). - : Springer. - 1126-6708 .- 1029-8479. ; :11
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Journal article (peer-reviewed)abstract
- A search with the ATLAS detector is presented for the Standard Model Higgs boson produced by vector-boson fusion and decaying to a pair of bottom quarks, using 20.2 fb(-1) of LHC proton-proton collision data at root s - 8 TeV. The signal is searched for as a resonance in the invariant mass distribution of a pair of jets containing b-hadrons in vector-boson-fusion candidate events. The yield is measured to be -0.8 +/- 2.3 times the Standard Model cross-section for a Higgs boson mass of 125 GeV. The upper limit on the cross-section times the branching ratio is found to be 4.4 times the Standard Model cross-section at the 95% confidence level, consistent with the expected limit value of 5.4 (5.7) in the background-only (Standard Model production) hypothesis.
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| 4. |
- Afewerki, Samson, et al.
(author)
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Combinations of Aminocatalysts and Metal Catalysts : A Powerful Cooperative Approach in Selective Organic Synthesis
- 2016
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In: Chemical Reviews. - : American Chemical Society (ACS). - 0009-2665 .- 1520-6890. ; 116:22, s. 13512-13570
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Research review (peer-reviewed)abstract
- The cooperation and interplay between organic and metal catalyst Arninocatalysis systems is of utmost importance in nature and chemical synthesis. Here innovative and selective cooperative catalyst systems can be designed by combining two catalysts that complement rather than inhibit one another. This refined strategy can permit chemical transformations unmanageable by either of the catalysts alone. This review summarizes innovations and developments in selective organic synthesis that have used cooperative dual catalysis by combining simple aminocatalysts with metal catalysts. Considerable efforts have been devoted to this fruitful field. This emerging area employs the different activation modes of amine and metal catalysts as a platform to address challenging reactions. Here, aminocatalysis (e.g., enamine activation catalysis, iminium activation catalysis, single occupied molecular orbital (SOMO) activation catalysis, and photoredox activation catalysis) is employed to activate unreactive carbonyl substrates. The transition metal catalyst complements by activating a variety of substrates through a range of interactions (e.g., electrophilic pi-allyl complex formation, Lewis acid activation, allenylidene complex formation, photoredox activation, C-H activation, etc.), and thereby novel concepts within catalysis are created. The inclusion of heterogeneous catalysis strategies allows for green chemistry development, catalyst recyclability, and the more eco-friendly synthesis of valuable compounds.
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| 5. |
- Afewerki, Samson, et al.
(author)
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Direct Regiospecific and Highly Enantioselective Intermolecular α-Allylic Alkylation of Aldehydes by a Combination of Transition-Metal and Chiral Amine Catalysts
- 2012
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In: Chemistry - A European Journal. - : Wiley. - 0947-6539 .- 1521-3765. ; 18:10, s. 2972-2977
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Journal article (peer-reviewed)abstract
- The first direct intermolecular regiospecific and highly enantioselective a-allylic alkylation of linear aldehydes by a combination of achiral bench-stable Pd0 complexes and simple chiral amines as co-catalysts is disclosed. The co-catalytic asymmetric chemoselective and regiospecific a-allylic alkylation reaction is linked in tandem with in situ reduction to give the corresponding 2-alkyl alcohols with high enantiomeric ratios (up to 98:2 e.r.; e.r.=enantiomeric ratio). It is also an expeditious entry to valuable 2-alkyl substituted hemiacetals, 2-alkyl-butane-1,4-diols, and amines. The concise co-catalytic asymmetric total syntheses of biologically active natural products (e.g., Arundic acid) are disclosed.
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| 6. |
- Afewerki, Samson, et al.
(author)
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Highly Enantioselective Control of Dynamic Cascade Transformations by Dual Catalysis : Asymmetric Synthesis of Polysubstituted Spirocyclic Oxindoles
- 2015
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In: ACS Catalysis. - : American Chemical Society (ACS). - 2155-5435 .- 2155-5435. ; 5:2, s. 1266-1272
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Journal article (peer-reviewed)abstract
- The highly enantioselective (up to >99.5:0.5 er) synthesis of polysubstituted spirocyclic oxindoles with four new contiguous stereocenters, including the spiro all-carbon quaternary center, is disclosed. It is accomplished by the highly stereoselective control of a dynamic conjugate/intramolecular allylic alkylation relay sequence based on the synergistic cooperation of metal and chiral amine catalysts in which the careful selection of organic Nand, metal complex, and chiral amine is essential. The intermolecular C-C bond-forming step occurred only when both the metal and chiral amine catalysts were present.
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| 7. |
- Afewerki, Samson, et al.
(author)
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Off-Cycle Catalyst Cooperativity in Amine/Transition Metal Combined Catalysis : Bicyclo[3.2.0]heptanes as Key Species in Co-Catalytic Enantioselective Carbocyclizations
- 2022
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In: Advanced Synthesis and Catalysis. - : Wiley. - 1615-4150 .- 1615-4169. ; 364:8, s. 1394-1401
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Journal article (peer-reviewed)abstract
- The existence of off-cycle catalyst cooperativity in amine/metal combined catalysis is disclosed. The experimental and density functional theory study of the amine/metal co-catalyzed enantioselective Michael/carbocyclization cascade reaction between allenes and α,β-unsaturated aldehydes reveals that the dual catalysts can perform off-cycle cooperativity that gives access to stable bicyclo[3.2.0]heptane species that limits the carbocycle product formation. Insight into this mode of co-catalyst cooperativity sheds new light on the chiral amine/metal co-catalyzed reactions of to date and gives deeper understanding for improved future design of this type of enantioselective reactions.
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| 8. |
- Afewerki, Samson, 1985-, et al.
(author)
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Sustainable and recyclable heterogenous palladium catalysts from rice husk-derived biosilicates for Suzuki-Miyaura cross-couplings, aerobic oxidations and stereoselective cascade carbocyclizations
- 2020
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In: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 10
-
Journal article (peer-reviewed)abstract
- A new eco-friendly approach for the preparation of sustainable heterogeneous palladium catalysts from rice husk-derived biogenic silica (RHP-Si and RHU-Si). The designed heterogeneously supported palladium species (RHP-Si-NH2-Pd and RHU-Si-NH2-Pd) were fully characterized and successfully employed as catalysts for various chemical transformations (C–C bond-forming reactions, aerobic oxidations and carbocyclizations). Suzuki-Miyaura transformations were highly efficient in a green solvent system (H2O:EtOH (1:1) with excellent recyclability, providing the cross-coupling products with a wide range of functionalities in high isolated yields (up to 99%). Palladium species (Pd(0)-nanoparticles or Pd(II)) were also efficient catalysts in the green aerobic oxidation of an allylic alcohol and a co-catalytic stereoselective cascade carbocyclization transformation. In the latter case, a quaternary stereocenter was formed with excellent stereoselectivity (up to 27:1 dr).
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| 9. |
- Afewerki, Samson, 1985-, et al.
(author)
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Sustainable Design for the Direct Fabrication and Highly Versatile Functionalization of Nanocelluloses
- 2017
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In: Global Challenges. - Weinheim : Wiley. - 2056-6646. ; 1:7
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Journal article (peer-reviewed)abstract
- This study describes a novel sustainable concept for the scalable direct fabrication and functionalization of nanocellulose from wood pulp with reduced energy consumption. A central concept is the use of metal-free small organic molecules as mediators and catalysts for the production and subsequent versatile surface engineering of the cellulosic nanomaterials via organocatalysis and click chemistry. Here, organoclick chemistry enables the selective functionalization of nanocelluloses with different organic molecules as well as the binding of palladium ions or nanoparticles. The nanocellulosic material is also shown to function as a sustainable support for heterogeneous catalysis in modern organic synthesis (e.g., Suzuki cross-coupling transformations in water). The reported strategy not only addresses obstacles and challenges for the future utilization of nanocellulose (e.g., low moisture resistance, the need for green chemistry, and energy-intensive production) but also enables new applications for nanocellulosic materials in different areas.
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| 10. |
- Ali, Safdar, et al.
(author)
-
Electron-ion recombination rate coefficients for C II forming C I
- 2012
-
In: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 753:2, s. 132-
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Journal article (peer-reviewed)abstract
- We have determined absolute dielectronic recombination rate coefficients for C II, using the CRYRING heavy-ions storage ring. The resonances due to 2s-2p (∆n = 0) core excitations are detected in the center-of-mass energy range of 0-15 eV. The experimental results are compared with intermediate coupling AUTOSTRUCTURE calculations. Plasma rate coefficients are obtained from the DR spectrum by convoluting it with a Maxwell-Boltzmann energy distribution for temperatures in the range of 103-106 K. The derived temperature dependent plasma recombination rate coefficients are presented graphically to compare with the theoretical data available in literature and parameterized by using a fit formula for convenient use in plasma modelling codes. In the temperature range of 103-2×104 K, our experimental results show that previous calculations severely underestimate the plasma rate coefficients and also our AUTOSTRUCTURE calculation does not reproduce the experimental plasma rate coefficients well. Above 2×104 K the agreement between the experimental and theoretical rate coefficients is much better, and the deviations are smaller than the estimated uncertainties.
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