Journal of the American Chemical Society, Jan 18, 2016
We report a concise and highly enantioselective total synthesis of (-)-alstoscholarisine A (1), a... more We report a concise and highly enantioselective total synthesis of (-)-alstoscholarisine A (1), a recently isolated monoterpenoid indole alkaloid that has significant bioactivity in promoting adult neuronal stem cells proliferation. A highly enantioselective (99% ee), intramolecular Ir-catalyzed Friedel-Crafts alkylation of indole 9 with a secondary allylic alcohol was utilized to establish the first stereogenic center upon which the other three contiguous chiral centers were readily set by a highly stereoselective tandem 1,4-addition and aldol reaction. The key tetrahydropyran was constructed through a hemiacetal reduction, and the final aminal bridge was forged by a one-pot reductive amination/cyclization. The conciseness of this approach was highlighted by building core bonds in each step with a minimalist protecting group strategy.
Angewandte Chemie (International ed. in English), Jan 17, 2016
The first enantioselective total synthesis of (-)-aspidophylline A, including assignment of its a... more The first enantioselective total synthesis of (-)-aspidophylline A, including assignment of its absolute configuration has been accomplished. A key element of the synthesis is a highly enantioselective indole allylic alkylation/iminium cyclization cascade which was developed by employing a combination of Lewis acid activation and an iridium/ligand catalyst. This strategy relies on the direct use of 2,3-disubstituted indoles with secondary allylic alcohols appended at C2 and heteronucleophiles appended at C3, indoles which are easily prepared from simple starting materials under C-H activation conditions.
2010 IEEE Antennas and Propagation Society International Symposium, 2010
A dual-port conformal diversity patch antenna with different radiation characteristics has been p... more A dual-port conformal diversity patch antenna with different radiation characteristics has been presented. By making use of hybrid feeds, the conical TM01 mode and the broadside TM11 mode of the antenna could be excited at the same frequencies. With this feeding scheme, both pattern and polarization diversities can be exploited and high isolation (<;-55dB) between the two ports can be achieved for WLAN application. From the simulated results, it is found that the main-beam positions of the radiation patterns are directed at the elevation angles of 50° and 0° for both modes, respectively. This characteristic makes the antenna to be a good candidate for future pattern or polarization diversity applications in the WLAN and MIMO communications systems.
Little is known about the antimicrobial resistance mechanisms in Klebsiella pneumoniae from swine... more Little is known about the antimicrobial resistance mechanisms in Klebsiella pneumoniae from swine in China. Thus, this paper aims to demonstrate the β-lactam resistance phenotypes and genotypes of K. pneumoniae isolates from swine in southwestern China, detect possible new β-lactamase variants, and determine whether or not the variants differ in their antibiotic resistance. Isolates from 58 unrelated diseased swine were collected from 61 pig farms in southwestern China from 2007 to 2009. Among the 58 isolates, 75.8–100% were resistant to β-lactam, 62.0–68.97% to fluoroquinolone, 44.8–46.55% to aminoglycoside, and 8.62–17.24% to β-lactam inhibitors. PCR amplification and DNA sequencing showed that blaTEM-1 was detected in 100% (n = 58) of the isolates, blaSHV in 82.76% (n = 48), blaCTX-M in 39.66% (n = 23), and blaOKP in 17.24% (n = 10). The blaSHV types included blaSHV-1, blaSHV-11, blaSHV-12, and blaSHV-27. None of the isolates harbored blaKPC, blaLEN, or blaGES gene. Four novel variants (blaOKP-A-13, blaOKP-A-14, blaOKP-A-15, and blaOKP-A-16) were identified among the 10 OKP β-lactamase-producing K. pneumoniae isolates resistant to ampicillin, amoxicillin, oxacillin, cefalexin, and cefadroxil. Plasmid analysis and PCR amplification indicated that blaTEM-1 genes were detected in the total plasmid. Molecular typing by pulsed-field gel electrophoresis revealed the presence of 10 distinct pulsotypes of OKP producer isolates. Plasmid DNA digested with XbaI yielded two to six bands of ca. 0.15–30 kb. Transformants of the 10 OKP producer isolates showed no differences in their antibiotic susceptibility, except for the pulsotype B transformant, which carried blaCTX-M. In China, β-lactam resistance appeared to be common among K. pneumoniae isolates from swine, suggesting that K. pneumoniae may be a reservoir for the dissemination of β-lactam resistance among Chinese pig farms.
ABSTRACT The influence of friction on deformation behavior of copper rods during the continuous E... more ABSTRACT The influence of friction on deformation behavior of copper rods during the continuous ECAP process (a modified C2S2 for the processing of rods and wires) was analyzed by using DEFORM-2D finite element method. The effect of friction on the stress and strain distribution, strain homogeneity and the torque-time curves was investigated. In the modified C2S2 process, the effective stress distributions are symmetrically concentrated on the shear plane, but there is an inadequate length of the plastic deformation zone. The effective strain shows a distorted fan shape in the shear deformation zone. As the friction factor increases the distorted fan shape tends to be normal and thinner, indicating that the bigger the friction factor, the more homogeneous the shear deformation. The effective strain is uniform across more than 70 thickness of the specimen. The assumed shear deformation is further divided into three stages, which can be explained by the torque-time curves.
Poly(ɛ-caprolactone) (PCL) microspheres loaded two model compounds (p-nitroaniline and rhodamine ... more Poly(ɛ-caprolactone) (PCL) microspheres loaded two model compounds (p-nitroaniline and rhodamine B) with different water solubilities were prepared by an s/o/w single emulsion solvent evaporation method. The microspheres morphology was investigated by scanning electron microscopy, drug loading and encapsulation efficiency were calculated. Drug distribution within microsphere matrix was studied by confocal laser scanning microscopy. p-Nitroaniline, as a more hydrophobic compound, distributed more evenly in the matrix, while the more hydrophilic compound rhodamine distributed close to the surfaces of microspheres. The in vitro release profiles therefore were different. This study helps to further understand the drug release mechanism from microsphere matrix, and design effective long-term drug delivery system.
A novel algorithm is proposed to extract cloud systems and spiral pattern of tropical cyclones (T... more A novel algorithm is proposed to extract cloud systems and spiral pattern of tropical cyclones (TCs) in infrared (IR) images. This mountain-climbing algorithm, inspired by mountain-climbing, defines cloud-system extraction as the problem of traversing all the peaks of the "cloud mountain" formed by a TC's cloud system. Several moving rules and stop criteria are made to define the search behaviors and constrain the traversal process. Six examples are used to validate the algorithm.
Abstract. We present an embedding of the stable failures model of CSP in the PVS theorem prover. ... more Abstract. We present an embedding of the stable failures model of CSP in the PVS theorem prover. Our work, extending a previous embedding of the traces model of CSP in [6], provides a platform for the formal verification not only of safety specifications, but also of liveness ...
Journal of the American Chemical Society, Jan 18, 2016
We report a concise and highly enantioselective total synthesis of (-)-alstoscholarisine A (1), a... more We report a concise and highly enantioselective total synthesis of (-)-alstoscholarisine A (1), a recently isolated monoterpenoid indole alkaloid that has significant bioactivity in promoting adult neuronal stem cells proliferation. A highly enantioselective (99% ee), intramolecular Ir-catalyzed Friedel-Crafts alkylation of indole 9 with a secondary allylic alcohol was utilized to establish the first stereogenic center upon which the other three contiguous chiral centers were readily set by a highly stereoselective tandem 1,4-addition and aldol reaction. The key tetrahydropyran was constructed through a hemiacetal reduction, and the final aminal bridge was forged by a one-pot reductive amination/cyclization. The conciseness of this approach was highlighted by building core bonds in each step with a minimalist protecting group strategy.
Angewandte Chemie (International ed. in English), Jan 17, 2016
The first enantioselective total synthesis of (-)-aspidophylline A, including assignment of its a... more The first enantioselective total synthesis of (-)-aspidophylline A, including assignment of its absolute configuration has been accomplished. A key element of the synthesis is a highly enantioselective indole allylic alkylation/iminium cyclization cascade which was developed by employing a combination of Lewis acid activation and an iridium/ligand catalyst. This strategy relies on the direct use of 2,3-disubstituted indoles with secondary allylic alcohols appended at C2 and heteronucleophiles appended at C3, indoles which are easily prepared from simple starting materials under C-H activation conditions.
2010 IEEE Antennas and Propagation Society International Symposium, 2010
A dual-port conformal diversity patch antenna with different radiation characteristics has been p... more A dual-port conformal diversity patch antenna with different radiation characteristics has been presented. By making use of hybrid feeds, the conical TM01 mode and the broadside TM11 mode of the antenna could be excited at the same frequencies. With this feeding scheme, both pattern and polarization diversities can be exploited and high isolation (<;-55dB) between the two ports can be achieved for WLAN application. From the simulated results, it is found that the main-beam positions of the radiation patterns are directed at the elevation angles of 50° and 0° for both modes, respectively. This characteristic makes the antenna to be a good candidate for future pattern or polarization diversity applications in the WLAN and MIMO communications systems.
Little is known about the antimicrobial resistance mechanisms in Klebsiella pneumoniae from swine... more Little is known about the antimicrobial resistance mechanisms in Klebsiella pneumoniae from swine in China. Thus, this paper aims to demonstrate the β-lactam resistance phenotypes and genotypes of K. pneumoniae isolates from swine in southwestern China, detect possible new β-lactamase variants, and determine whether or not the variants differ in their antibiotic resistance. Isolates from 58 unrelated diseased swine were collected from 61 pig farms in southwestern China from 2007 to 2009. Among the 58 isolates, 75.8–100% were resistant to β-lactam, 62.0–68.97% to fluoroquinolone, 44.8–46.55% to aminoglycoside, and 8.62–17.24% to β-lactam inhibitors. PCR amplification and DNA sequencing showed that blaTEM-1 was detected in 100% (n = 58) of the isolates, blaSHV in 82.76% (n = 48), blaCTX-M in 39.66% (n = 23), and blaOKP in 17.24% (n = 10). The blaSHV types included blaSHV-1, blaSHV-11, blaSHV-12, and blaSHV-27. None of the isolates harbored blaKPC, blaLEN, or blaGES gene. Four novel variants (blaOKP-A-13, blaOKP-A-14, blaOKP-A-15, and blaOKP-A-16) were identified among the 10 OKP β-lactamase-producing K. pneumoniae isolates resistant to ampicillin, amoxicillin, oxacillin, cefalexin, and cefadroxil. Plasmid analysis and PCR amplification indicated that blaTEM-1 genes were detected in the total plasmid. Molecular typing by pulsed-field gel electrophoresis revealed the presence of 10 distinct pulsotypes of OKP producer isolates. Plasmid DNA digested with XbaI yielded two to six bands of ca. 0.15–30 kb. Transformants of the 10 OKP producer isolates showed no differences in their antibiotic susceptibility, except for the pulsotype B transformant, which carried blaCTX-M. In China, β-lactam resistance appeared to be common among K. pneumoniae isolates from swine, suggesting that K. pneumoniae may be a reservoir for the dissemination of β-lactam resistance among Chinese pig farms.
ABSTRACT The influence of friction on deformation behavior of copper rods during the continuous E... more ABSTRACT The influence of friction on deformation behavior of copper rods during the continuous ECAP process (a modified C2S2 for the processing of rods and wires) was analyzed by using DEFORM-2D finite element method. The effect of friction on the stress and strain distribution, strain homogeneity and the torque-time curves was investigated. In the modified C2S2 process, the effective stress distributions are symmetrically concentrated on the shear plane, but there is an inadequate length of the plastic deformation zone. The effective strain shows a distorted fan shape in the shear deformation zone. As the friction factor increases the distorted fan shape tends to be normal and thinner, indicating that the bigger the friction factor, the more homogeneous the shear deformation. The effective strain is uniform across more than 70 thickness of the specimen. The assumed shear deformation is further divided into three stages, which can be explained by the torque-time curves.
Poly(ɛ-caprolactone) (PCL) microspheres loaded two model compounds (p-nitroaniline and rhodamine ... more Poly(ɛ-caprolactone) (PCL) microspheres loaded two model compounds (p-nitroaniline and rhodamine B) with different water solubilities were prepared by an s/o/w single emulsion solvent evaporation method. The microspheres morphology was investigated by scanning electron microscopy, drug loading and encapsulation efficiency were calculated. Drug distribution within microsphere matrix was studied by confocal laser scanning microscopy. p-Nitroaniline, as a more hydrophobic compound, distributed more evenly in the matrix, while the more hydrophilic compound rhodamine distributed close to the surfaces of microspheres. The in vitro release profiles therefore were different. This study helps to further understand the drug release mechanism from microsphere matrix, and design effective long-term drug delivery system.
A novel algorithm is proposed to extract cloud systems and spiral pattern of tropical cyclones (T... more A novel algorithm is proposed to extract cloud systems and spiral pattern of tropical cyclones (TCs) in infrared (IR) images. This mountain-climbing algorithm, inspired by mountain-climbing, defines cloud-system extraction as the problem of traversing all the peaks of the "cloud mountain" formed by a TC's cloud system. Several moving rules and stop criteria are made to define the search behaviors and constrain the traversal process. Six examples are used to validate the algorithm.
Abstract. We present an embedding of the stable failures model of CSP in the PVS theorem prover. ... more Abstract. We present an embedding of the stable failures model of CSP in the PVS theorem prover. Our work, extending a previous embedding of the traces model of CSP in [6], provides a platform for the formal verification not only of safety specifications, but also of liveness ...
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