TANK-binding kinase 1(TBK1)is an important enzyme in the regulation of cellular antiviral effects.TBK1 regulates the activity of the interferon regulatory factors IRF3 and IRF7,thereby playing a key role in type I int...TANK-binding kinase 1(TBK1)is an important enzyme in the regulation of cellular antiviral effects.TBK1 regulates the activity of the interferon regulatory factors IRF3 and IRF7,thereby playing a key role in type I interferon(IFN)signaling pathways.The structure of TBK1 consists of an N-terminal kinase domain,a middle ubiquitin-like domain(ULD),and a C-terminal elongated helical domain.It has been reported that the ULD of TBK1 regulates kinase activity,playing an important role in signaling and mediating interactions with other molecules in the IFN pathway.In this study,we present the crystal structure of the ULD of human TBK1 and identify several con-served residues by multiple sequence alignment.We found that a hydrophobic patch in TBK1,containing residues Leu316,Ile353,and Val382,corresponding to the“Ile44 hydrophobic patch”observed in ubiquitin,was conserved in TBK1,IκB kinase epsilon(IKKε/IKKi),IκB kinase alpha(IKKα),and IκB kinase beta(IKKβ).In com-parison with the structure of the IKKβULD domain of Xenopus laevis,we speculate that the Ile44 hydrophobic patch of TBK1 is present in an intramolecular binding surface between ULD and the C-terminal elongated heli-ces.The varying surface charge distributions in the ULD domains of IKK and IKK-related kinases may be relevant to their specificity for specific partners.展开更多
We investigated the plant population structure and the phy- tosociological and regeneration status in two disturbed tropical forests in Assam Province, the Hojai Reserve Forest and Kumorakata Reserve Forest. A total o...We investigated the plant population structure and the phy- tosociological and regeneration status in two disturbed tropical forests in Assam Province, the Hojai Reserve Forest and Kumorakata Reserve Forest. A total of 166 species （80 trees, 20 shrubs and 66 herbs） of 136 genera and 63 families were recorded in both study sites. The disturbance index at the two sites, Kumorakata Reserve Forest and Hojai Reserve Forest, were recorded at 11.4% and 3.70% respectively. Reverse J-shaped population curve and exploitation of tree species in higher girth classes were recorded at both study sites. In the girth classes （10-30 cm, 30-60 cm, 60-90 cm and 90-120 cm in size） the percentage of cut stump density was higher than the percentage of individual living trees. The 18% （Kumorakata Reserve Forest） and 7% （Hojai Reserve Forest） spe- cies were recorded as not regenerating. Illegal felling and over-exploitation of forest resources may lead to species-specific changes in the population structure and can alter the future structure and composi- tion of the forests.展开更多
Riemann hypothesis (RH) is a difficult problem. So far one doesn’t know how to go about it. Studying <i>ζ</i> and using analysis method likely are two incor-rect guides. Actually, a unique hope may study...Riemann hypothesis (RH) is a difficult problem. So far one doesn’t know how to go about it. Studying <i>ζ</i> and using analysis method likely are two incor-rect guides. Actually, a unique hope may study Riemann function <img alt="" src="Edit_8fcdfff5-6b95-42a4-8f47-2cabe2723dfc.bmp" />, <img alt="" src="Edit_6ce3a4bd-4c68-49e5-aabe-dec3e904e282.bmp" />, <img alt="" src="Edit_29ea252e-a81e-4b21-a41c-09209c780bb2.bmp" /> by geometric analysis, which has the symmetry: v=0 if <i>β</i>=0, and basic expression <img alt="" src="Edit_bc7a883f-312d-44fd-bcdd-00f25c92f80a.bmp" />. We show that |u| is single peak in each root-interval <img alt="" src="Edit_d7ca54c7-4866-4419-a4bd-cbb808b365af.bmp" /> of <i>u</i> for fixed <em>β</em> ∈(0,1/2]. Using the slope u<sub>t</sub>, we prove that <i>v</i> has opposite signs at two end-points of I<sub>j</sub>. There surely exists an inner point such that , so {|u|,|v|/<em>β</em>} form a local peak-valley structure, and have positive lower bound <img alt="" src="Edit_bac1a5f6-673e-49b6-892c-5adff0141376.bmp" /> in I<sub>j</sub>. Because each <i>t</i> must lie in some I<sub>j</sub>, then ||<em>ξ</em>|| > 0 is valid for any <i>t</i> (<i>i.e.</i> RH is true). Using the positivity <img alt="" src="Edit_83c3d2cf-aa7e-4aba-89f5-0eb44659918a.bmp" /> of Lagarias (1999), we show the strict monotone <img alt="" src="Edit_87eb4e9e-bc7b-43e3-b316-5dcf0efaf0d5.bmp" /> for <i>β</i> > <i>β</i><sub>0</sub> ≥ 0 , and the peak-valley structure is equiva-lent to RH, which may be the geometric model expected by Bombieri (2000). This research follows Liuhui’s methodology: “Computing can detect the un-known and method”.</i>展开更多
Guanidimium-4,4-azo-l-hydro-1,2,4-triazol-5-one （GZTO·H2O） was synthesized from 4-amino-1,2,4-triazol- 5-one as a starting material by two-step including oxidation coupling using acid KMnO4 and reaction with （...Guanidimium-4,4-azo-l-hydro-1,2,4-triazol-5-one （GZTO·H2O） was synthesized from 4-amino-1,2,4-triazol- 5-one as a starting material by two-step including oxidation coupling using acid KMnO4 and reaction with （NH2）2C=NHoHNO3 （GN） in KOH solution. The single crystal of the title compound was obtained by slow evapo- ration method at room temperature, and its structure was firstly determined with X-ray single-crystal diffractometer. It is a orthorhombic crystal, space group Pbca with cell dimensions of a = 1.0459（2） nm, b =- 1.3584（3） nm, c= 1.6103（3） nm, a= 90.00（10）°, β=90.00（11）°,γ=90.00（11）°, V=2.2878（8） nm3, Z=8, De= 1.587 gocm-3, F（000） = 1136,/l = 0.132 mm- 1, R1 = 0.0455, wR2 = 0. 1397. The thermal behavior of GZTO·H2O was studied under a non-isothermal condition by DSC-TGA method, and its thermal decomposition process can be divided into three stages, and the first stage is an intense exothermic decomposition process. The second stage and the third stage are slow exothermic decomposition processes. The critical temperature of thermal explosion is 237.74℃.展开更多
目的研究群体感应(QS)系统在铜绿假单胞菌生物膜(BF)形成中的作用。方法体外建立3 d QS系统完整的铜绿假单胞菌野生型PA01菌株与QS系统缺陷(lasRrhlR基因缺陷△lasR△rhlR)型菌株生物模型,通过SYT09/PI荧光探针标记,结合激光共聚焦显微...目的研究群体感应(QS)系统在铜绿假单胞菌生物膜(BF)形成中的作用。方法体外建立3 d QS系统完整的铜绿假单胞菌野生型PA01菌株与QS系统缺陷(lasRrhlR基因缺陷△lasR△rhlR)型菌株生物模型,通过SYT09/PI荧光探针标记,结合激光共聚焦显微镜摄取BF不同层面的图片,经图像结构分析(ISA)软件分析获得QS系统lasRrhlR缺陷株,PA01菌株BF相关空间结构参数。结果培养第3天PA01菌株可形成较厚、有孔状通道的成熟BF结构,而△lasR△rhlR菌株仅形成明显稀薄的早期BF结构,△lasR△rhlR菌株的3 d BF厚度为(7.36±0.2)μm,PA01菌株为(21.64±0.57)μm(P<0.05),区域孔率(areal porosity,AP)分别为:(0.902±0.006)、(0.928±0.002);平均扩散距离(average diffusion distance,ADD)和结构熵(textural entropy,TE)在△lasR△rhlR菌株分别为:(1.503±0.029)和(5.706±0.190);在PA01菌株分别为:(1.467±0.015)和(5.213±0.111),△lasR△rhlR菌株AP较PA01菌株低(P<0.05);而ADD、TE较PA01菌株高(P<0.05)。结论△lasR△rhlR基因缺陷明显影响铜绿假单胞菌的BF形成能力,QS系统lasRrhlR基因在铜绿假单胞菌BF形成中发挥重要作用。展开更多
Viologens (<i>N,N'</i>-dimethyl-4,4-bipyridinium) are advanced functional materials, found important applications in electrochromic devices, molecular machines, organic batteries, and carbohydrate oxid...Viologens (<i>N,N'</i>-dimethyl-4,4-bipyridinium) are advanced functional materials, found important applications in electrochromic devices, molecular machines, organic batteries, and carbohydrate oxidation catalysts in alkaline fuel. In this article, we investigated the design, synthesis and photophysical properties of <i>N,N'</i>-dimethyl-2,5-Bis(pyridinium)oxadiazole <b>4</b> and its precursor 2,5- Bis(pyridine)oxadiazole<b> 2</b>. The crystal structure and photophysical properties of viologen <b>4</b> and precursor <b>2</b> have been determined. The viologen molecule <b>4</b> crystallized in monoclinic form, space group <i>P</i>2<sub>1</sub>/<i>n</i> with four molecules in unit cell. Precursor molecule <b>2</b> also crystalized in monoclinic form, space group <i>C</i>2/<i>c</i> with four molecules in unit cell. From X-rd data, we found three cations in the molecular structure of viologen molecule <b>4</b>, which is unusual in viologens. In the three-dimensional molecular packing diagram of molecule <b>4</b>, the three cations and iodate anions are stabilized by C···C, C···I, N···I, N···H, H···I, N—H···I and C—H···I. The dihedral angle between planes having oxadiazole and two benzene rings are 5°and 8°, suggesting the molecule <b>4</b> is a slightly strained one. The molecular structure of precursor molecule <b>2</b> stabilized by C···C and N···H short contacts between the molecules. The molecule <b>4</b> displayed strong absorbance at 315 nm and emissions between 390 - 410 nm.展开更多
The techniques of oxygen electrode polarogra-phy and Fourier transform infrared (FT-IR) spectroscopy were employed to explore the roles of polar head-group of phosphatidylglycerol (PG) molecules in the functional and ...The techniques of oxygen electrode polarogra-phy and Fourier transform infrared (FT-IR) spectroscopy were employed to explore the roles of polar head-group of phosphatidylglycerol (PG) molecules in the functional and structural aspects of photosystem Ⅱ (PS Ⅱ) through enzymatic approach. It was shown that the depletion of PG by treatment of phospholipase C (PLC) on PS Ⅱ particles caused the inhibition of oxygen evolving activity in PS Ⅱ. This effect also gave rise to changes in the protein secondary structures of PS Ⅱ, that is, an increase in a-helical conformation which is compensated by the loss of p-strand structures. It revealed that the head-group of PG molecules plays an important structural role in the maintenance of normal structure of PS Ⅱ proteins, which is required to maintain the appropriate physiological activity of the PS Ⅱ complex such as the oxygen evolving activity. It is suggested that there most probably exist hydrogen-bonding interactions between PG molecules and PS Ⅱ proteins.展开更多
Al-12Zn-3Mg-2.5Cu alloy was prepared using a liquid metallurgy route under the optimized conditions. A sample cut from the ingot was rolled non-isothermally from 400℃ to 100℃ in 100℃ steps, with 15% reduction in th...Al-12Zn-3Mg-2.5Cu alloy was prepared using a liquid metallurgy route under the optimized conditions. A sample cut from the ingot was rolled non-isothermally from 400℃ to 100℃ in 100℃ steps, with 15% reduction in thickness; it was then cold rolled isothermally at room temperature for 85% reduction. The cold-rolled alloys were characterized by electron microscopy, hardness test, and tensile test to elucidate their structural evolution and evaluate their mechanical behavior. In the results, the cast alloy consists of a-aluminum and various intermetallic compounds. These compounds are segregated along the grain boundaries, which makes the alloy difficult to roll at room tem- perature. The combined effect of non-isothermal step rolling and cold rolling results in the nano/microsized compounds distributed uniformly in the matrix. The hardness is substantially increased after rolling. This increase in hardness is attributed to the ultra-fine grain size, fine-scale intermetallic compounds, and structural defects （e.g., dislocations, stacking faults, and sub-grains）. The ultimate tensile strength of the rolled alloy is approximately 628 MPa with 7% ductility.展开更多
Based on a general isospectral problem of fractional order and the fractional quadratic-form identity by Yue and Xia, the new integrable coupling of fractional coupled Burgers hierarchy and its fractional bi-Hamiltoni...Based on a general isospectral problem of fractional order and the fractional quadratic-form identity by Yue and Xia, the new integrable coupling of fractional coupled Burgers hierarchy and its fractional bi-Hamiltonian structures are obtained.展开更多
T<span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">his paper aims to analyze the competitive position of Port of D...T<span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">his paper aims to analyze the competitive position of Port of Douala in Central African ports market structure. In other words, it consists of measuring port market level and competitiveness through an assessment of their growth rate and market share. </span></span></span><span><span><span style="font-family:""><span style="font-family:Verdana;">The purpose of the paper is to </span><span style="font-family:Verdana;">provide us with information on periodical changing status of ports competing with each other. It also provides us with an effective managerial tool to port operators in the assessment of ports market share and position. </span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">For doing so, the measurement technique as Shift-Share Analysis was applied in the study by using a panel dataset of the 7 selected ports of Central Africa sub-region from 2008 to 2018. The paper used the recent dynamics and characteristics of port market in terms of port throughputs to compare the yearly trend and market share. By conducting the study of the market growth rate model, the findings showed that the Port of Douala was the top leader of the market in 2009, 2015, 2016 and 2018. The findings also revealed the competitive positions of these ports under study have changed over the period of study due to the significant change of their market share with average growth rates. The final results showed that several determinant factors have affected the present hierarchy of competitiveness level in the selected ports market especially with small and medium size ports that are strengthening their positions vis-a-vis larger ones. However, the results could be used for analyzing the relative efficiency and overall performance of the Central African Sub-regional seaports including the Cameroonian ports.</span></span></span>展开更多
A review is presented of studies of polymeric membranes by applying positron annihilation lifetime spectroscopy （PALS）. PALS has been used to study subnanometer-sized holes, to determine their size distribution and ...A review is presented of studies of polymeric membranes by applying positron annihilation lifetime spectroscopy （PALS）. PALS has been used to study subnanometer-sized holes, to determine their size distribution and free-volume fractions, and to probe molecular-sized vacancies in glassy polymers. At present, PALS is believed to be a highly effective physical method for the examination of polymeric membranes.展开更多
基金supported by grants from the State Key Development Program for Basic Research of the Ministry of Science and Technology of China(973 Program)(Grant Nos.2011CB910304 and 2012CB910204)to YLthe National Natural Science Foundation of China(Grant Nos.30925011,31030024 and 31021062).
文摘TANK-binding kinase 1(TBK1)is an important enzyme in the regulation of cellular antiviral effects.TBK1 regulates the activity of the interferon regulatory factors IRF3 and IRF7,thereby playing a key role in type I interferon(IFN)signaling pathways.The structure of TBK1 consists of an N-terminal kinase domain,a middle ubiquitin-like domain(ULD),and a C-terminal elongated helical domain.It has been reported that the ULD of TBK1 regulates kinase activity,playing an important role in signaling and mediating interactions with other molecules in the IFN pathway.In this study,we present the crystal structure of the ULD of human TBK1 and identify several con-served residues by multiple sequence alignment.We found that a hydrophobic patch in TBK1,containing residues Leu316,Ile353,and Val382,corresponding to the“Ile44 hydrophobic patch”observed in ubiquitin,was conserved in TBK1,IκB kinase epsilon(IKKε/IKKi),IκB kinase alpha(IKKα),and IκB kinase beta(IKKβ).In com-parison with the structure of the IKKβULD domain of Xenopus laevis,we speculate that the Ile44 hydrophobic patch of TBK1 is present in an intramolecular binding surface between ULD and the C-terminal elongated heli-ces.The varying surface charge distributions in the ULD domains of IKK and IKK-related kinases may be relevant to their specificity for specific partners.
文摘We investigated the plant population structure and the phy- tosociological and regeneration status in two disturbed tropical forests in Assam Province, the Hojai Reserve Forest and Kumorakata Reserve Forest. A total of 166 species （80 trees, 20 shrubs and 66 herbs） of 136 genera and 63 families were recorded in both study sites. The disturbance index at the two sites, Kumorakata Reserve Forest and Hojai Reserve Forest, were recorded at 11.4% and 3.70% respectively. Reverse J-shaped population curve and exploitation of tree species in higher girth classes were recorded at both study sites. In the girth classes （10-30 cm, 30-60 cm, 60-90 cm and 90-120 cm in size） the percentage of cut stump density was higher than the percentage of individual living trees. The 18% （Kumorakata Reserve Forest） and 7% （Hojai Reserve Forest） spe- cies were recorded as not regenerating. Illegal felling and over-exploitation of forest resources may lead to species-specific changes in the population structure and can alter the future structure and composi- tion of the forests.
文摘Riemann hypothesis (RH) is a difficult problem. So far one doesn’t know how to go about it. Studying <i>ζ</i> and using analysis method likely are two incor-rect guides. Actually, a unique hope may study Riemann function <img alt="" src="Edit_8fcdfff5-6b95-42a4-8f47-2cabe2723dfc.bmp" />, <img alt="" src="Edit_6ce3a4bd-4c68-49e5-aabe-dec3e904e282.bmp" />, <img alt="" src="Edit_29ea252e-a81e-4b21-a41c-09209c780bb2.bmp" /> by geometric analysis, which has the symmetry: v=0 if <i>β</i>=0, and basic expression <img alt="" src="Edit_bc7a883f-312d-44fd-bcdd-00f25c92f80a.bmp" />. We show that |u| is single peak in each root-interval <img alt="" src="Edit_d7ca54c7-4866-4419-a4bd-cbb808b365af.bmp" /> of <i>u</i> for fixed <em>β</em> ∈(0,1/2]. Using the slope u<sub>t</sub>, we prove that <i>v</i> has opposite signs at two end-points of I<sub>j</sub>. There surely exists an inner point such that , so {|u|,|v|/<em>β</em>} form a local peak-valley structure, and have positive lower bound <img alt="" src="Edit_bac1a5f6-673e-49b6-892c-5adff0141376.bmp" /> in I<sub>j</sub>. Because each <i>t</i> must lie in some I<sub>j</sub>, then ||<em>ξ</em>|| > 0 is valid for any <i>t</i> (<i>i.e.</i> RH is true). Using the positivity <img alt="" src="Edit_83c3d2cf-aa7e-4aba-89f5-0eb44659918a.bmp" /> of Lagarias (1999), we show the strict monotone <img alt="" src="Edit_87eb4e9e-bc7b-43e3-b316-5dcf0efaf0d5.bmp" /> for <i>β</i> > <i>β</i><sub>0</sub> ≥ 0 , and the peak-valley structure is equiva-lent to RH, which may be the geometric model expected by Bombieri (2000). This research follows Liuhui’s methodology: “Computing can detect the un-known and method”.</i>
基金Project Supported by the National Natural Science Foundation of China （No. 20803058） and the Natural Science Foundation of Shaanxi Province （No. 2007B08）.
文摘Guanidimium-4,4-azo-l-hydro-1,2,4-triazol-5-one （GZTO·H2O） was synthesized from 4-amino-1,2,4-triazol- 5-one as a starting material by two-step including oxidation coupling using acid KMnO4 and reaction with （NH2）2C=NHoHNO3 （GN） in KOH solution. The single crystal of the title compound was obtained by slow evapo- ration method at room temperature, and its structure was firstly determined with X-ray single-crystal diffractometer. It is a orthorhombic crystal, space group Pbca with cell dimensions of a = 1.0459（2） nm, b =- 1.3584（3） nm, c= 1.6103（3） nm, a= 90.00（10）°, β=90.00（11）°,γ=90.00（11）°, V=2.2878（8） nm3, Z=8, De= 1.587 gocm-3, F（000） = 1136,/l = 0.132 mm- 1, R1 = 0.0455, wR2 = 0. 1397. The thermal behavior of GZTO·H2O was studied under a non-isothermal condition by DSC-TGA method, and its thermal decomposition process can be divided into three stages, and the first stage is an intense exothermic decomposition process. The second stage and the third stage are slow exothermic decomposition processes. The critical temperature of thermal explosion is 237.74℃.
文摘目的研究群体感应(QS)系统在铜绿假单胞菌生物膜(BF)形成中的作用。方法体外建立3 d QS系统完整的铜绿假单胞菌野生型PA01菌株与QS系统缺陷(lasRrhlR基因缺陷△lasR△rhlR)型菌株生物模型,通过SYT09/PI荧光探针标记,结合激光共聚焦显微镜摄取BF不同层面的图片,经图像结构分析(ISA)软件分析获得QS系统lasRrhlR缺陷株,PA01菌株BF相关空间结构参数。结果培养第3天PA01菌株可形成较厚、有孔状通道的成熟BF结构,而△lasR△rhlR菌株仅形成明显稀薄的早期BF结构,△lasR△rhlR菌株的3 d BF厚度为(7.36±0.2)μm,PA01菌株为(21.64±0.57)μm(P<0.05),区域孔率(areal porosity,AP)分别为:(0.902±0.006)、(0.928±0.002);平均扩散距离(average diffusion distance,ADD)和结构熵(textural entropy,TE)在△lasR△rhlR菌株分别为:(1.503±0.029)和(5.706±0.190);在PA01菌株分别为:(1.467±0.015)和(5.213±0.111),△lasR△rhlR菌株AP较PA01菌株低(P<0.05);而ADD、TE较PA01菌株高(P<0.05)。结论△lasR△rhlR基因缺陷明显影响铜绿假单胞菌的BF形成能力,QS系统lasRrhlR基因在铜绿假单胞菌BF形成中发挥重要作用。
文摘Viologens (<i>N,N'</i>-dimethyl-4,4-bipyridinium) are advanced functional materials, found important applications in electrochromic devices, molecular machines, organic batteries, and carbohydrate oxidation catalysts in alkaline fuel. In this article, we investigated the design, synthesis and photophysical properties of <i>N,N'</i>-dimethyl-2,5-Bis(pyridinium)oxadiazole <b>4</b> and its precursor 2,5- Bis(pyridine)oxadiazole<b> 2</b>. The crystal structure and photophysical properties of viologen <b>4</b> and precursor <b>2</b> have been determined. The viologen molecule <b>4</b> crystallized in monoclinic form, space group <i>P</i>2<sub>1</sub>/<i>n</i> with four molecules in unit cell. Precursor molecule <b>2</b> also crystalized in monoclinic form, space group <i>C</i>2/<i>c</i> with four molecules in unit cell. From X-rd data, we found three cations in the molecular structure of viologen molecule <b>4</b>, which is unusual in viologens. In the three-dimensional molecular packing diagram of molecule <b>4</b>, the three cations and iodate anions are stabilized by C···C, C···I, N···I, N···H, H···I, N—H···I and C—H···I. The dihedral angle between planes having oxadiazole and two benzene rings are 5°and 8°, suggesting the molecule <b>4</b> is a slightly strained one. The molecular structure of precursor molecule <b>2</b> stabilized by C···C and N···H short contacts between the molecules. The molecule <b>4</b> displayed strong absorbance at 315 nm and emissions between 390 - 410 nm.
基金This work was supported by the National Natural Science Foundation of China (Grant No. 39890390) the State Basic Research Development Plan of China (Grant No. G1998010100)the Innovative Foundation of Laboratory of Photosynthesis Basic Research, Insti
文摘The techniques of oxygen electrode polarogra-phy and Fourier transform infrared (FT-IR) spectroscopy were employed to explore the roles of polar head-group of phosphatidylglycerol (PG) molecules in the functional and structural aspects of photosystem Ⅱ (PS Ⅱ) through enzymatic approach. It was shown that the depletion of PG by treatment of phospholipase C (PLC) on PS Ⅱ particles caused the inhibition of oxygen evolving activity in PS Ⅱ. This effect also gave rise to changes in the protein secondary structures of PS Ⅱ, that is, an increase in a-helical conformation which is compensated by the loss of p-strand structures. It revealed that the head-group of PG molecules plays an important structural role in the maintenance of normal structure of PS Ⅱ proteins, which is required to maintain the appropriate physiological activity of the PS Ⅱ complex such as the oxygen evolving activity. It is suggested that there most probably exist hydrogen-bonding interactions between PG molecules and PS Ⅱ proteins.
文摘Al-12Zn-3Mg-2.5Cu alloy was prepared using a liquid metallurgy route under the optimized conditions. A sample cut from the ingot was rolled non-isothermally from 400℃ to 100℃ in 100℃ steps, with 15% reduction in thickness; it was then cold rolled isothermally at room temperature for 85% reduction. The cold-rolled alloys were characterized by electron microscopy, hardness test, and tensile test to elucidate their structural evolution and evaluate their mechanical behavior. In the results, the cast alloy consists of a-aluminum and various intermetallic compounds. These compounds are segregated along the grain boundaries, which makes the alloy difficult to roll at room tem- perature. The combined effect of non-isothermal step rolling and cold rolling results in the nano/microsized compounds distributed uniformly in the matrix. The hardness is substantially increased after rolling. This increase in hardness is attributed to the ultra-fine grain size, fine-scale intermetallic compounds, and structural defects （e.g., dislocations, stacking faults, and sub-grains）. The ultimate tensile strength of the rolled alloy is approximately 628 MPa with 7% ductility.
基金in part supported by the Natural Science Foundation of China(GrantNo.11271008)the First-class Discipline of University in Shanghai and the Shanghai Univ.Leading Academic Discipline Project(A.13-0101-12-004)
文摘Based on a general isospectral problem of fractional order and the fractional quadratic-form identity by Yue and Xia, the new integrable coupling of fractional coupled Burgers hierarchy and its fractional bi-Hamiltonian structures are obtained.
文摘T<span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">his paper aims to analyze the competitive position of Port of Douala in Central African ports market structure. In other words, it consists of measuring port market level and competitiveness through an assessment of their growth rate and market share. </span></span></span><span><span><span style="font-family:""><span style="font-family:Verdana;">The purpose of the paper is to </span><span style="font-family:Verdana;">provide us with information on periodical changing status of ports competing with each other. It also provides us with an effective managerial tool to port operators in the assessment of ports market share and position. </span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">For doing so, the measurement technique as Shift-Share Analysis was applied in the study by using a panel dataset of the 7 selected ports of Central Africa sub-region from 2008 to 2018. The paper used the recent dynamics and characteristics of port market in terms of port throughputs to compare the yearly trend and market share. By conducting the study of the market growth rate model, the findings showed that the Port of Douala was the top leader of the market in 2009, 2015, 2016 and 2018. The findings also revealed the competitive positions of these ports under study have changed over the period of study due to the significant change of their market share with average growth rates. The final results showed that several determinant factors have affected the present hierarchy of competitiveness level in the selected ports market especially with small and medium size ports that are strengthening their positions vis-a-vis larger ones. However, the results could be used for analyzing the relative efficiency and overall performance of the Central African Sub-regional seaports including the Cameroonian ports.</span></span></span>
基金The project supported by the Hundred-Persons Plan Foundation of Chinese Academy of Sciences in 2003
文摘A review is presented of studies of polymeric membranes by applying positron annihilation lifetime spectroscopy （PALS）. PALS has been used to study subnanometer-sized holes, to determine their size distribution and free-volume fractions, and to probe molecular-sized vacancies in glassy polymers. At present, PALS is believed to be a highly effective physical method for the examination of polymeric membranes.
