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排序方式: 共有368条查询结果,搜索用时 15 毫秒
111.
Anis Fadhlina Izyani Awang Qamar Uddin Ahmed Syed Adnan Ali Shah Juliana Md. Jaffri Kashif Ghafoor A. B. M. Helal Uddin 《Natural product research》2020,34(5):629-637
AbstractStereospermum fimbriatum or locally known as “Chicha” is traditionally used for itchy skin, earache, stomachache and postpartum treatments. This study was designed to evaluate the antimicrobial potential of S. fimbriatum’s stem bark against 11 pathogens and isolate its bioactive compound. Successive soxhlet extraction was conducted using n-hexane, dichloromethane (DCM) and methanol. Disc diffusion, minimum inhibitory and bactericidal concentration (MIC & MBC) assays were done to examine the antimicrobial activity. Bioassay-guided isolation was conducted on S. fimbriatum’s extract. The DCM extract of stem bark (DS) was the most potent extract followed by n-hexane extract of the stem bark (NS). A novel compound was isolated and coded as C1 which demonstrated potent antibacterial effects with the MIC values as low as 3.13?µg/mL to 6.25?µg/mL, against S. epidermidis, MRSA and S. aureus. Thus, S. fimbriatum could be a potential source of antimicrobial agents for the treatment of skin infections, specifically, MRSA. 相似文献
112.
Tutita M. Casa Juliana R. MacSwan Kara E. LaMonica Madelyn W. Colonnese Janine M. Firmender 《School science and mathematics》2019,119(4):176-189
Curriculum guidelines and professional organizations’ recommendations lack details about how often and how much students should write in mathematics and what characteristics should define their writing. This study presents an analytic framework that addresses how often students are prompted in student mathematics books to write, how much they may be encouraged to write, and the characteristics of the writing prompts. Consequently, 2,095 writing prompts in student books across 10 comprehensive Grade 3 resources were analyzed. Findings indicate a marked variation in how often and how much students are positioned to write. Most prompts have students explain what they did to solve a problem and why about number concepts, with most pressing for procedures. The greatest percentage of prompts had students write about their own solutions and do not urge them to include specific writing features. 相似文献
113.
A simple method is described for the determination of Cd, Cu, Mn, Ni, Pb and Zn in nails by using inductively coupled plasma mass spectrometry (ICP-MS) or electrothermal atomic absorption spectrometry (ETAAS). Prior to analysis, 10-20 mg of nail samples were accurately weighed into (15 mL) conical tubes. Then, 1 mL of 25% (w/v) tetramethylammonium hydroxide (TMAH) solution was added to the samples, incubated at room temperature overnight and then further diluted to 10 mL with 1% (v/v) HNO(3). After that, samples were directly analyzed. Rhodium was used as internal standard for ICP-MS analysis. Method detection limits (3 s, n=20) were 0.1, 3.0, 1.0, 4.5, 1.5, 5.0 ng g(-1) for Cd, Cu, Mn, Ni, Pb and Zn, respectively for ICP-MS, and 24, 26, 30, 143, 130 and 1000 ng g(-1), respectively for ETAAS. The key issue addressed here is the elimination of the acid digestion prior to analysis. Moreover, with the use of the proposed method there is a considerable improvement in the sample throughput comparing to the traditional methods using microwave-assisted acid sample digestion prior to analysis. For validation purposes, six ordinary nail samples were solubilized and then directly analyzed by ICP-MS and ETAAS, with no statistical difference between the two techniques at 95% level on applying the t-test. 相似文献
114.
Dutra JC da C Terzi S Bevilaqua JV Damaso MC Couri S Langone MA Senna LF 《Applied biochemistry and biotechnology》2008,147(1-3):63-75
The aim of this study was to monitor the biomass growth of Aspergillus niger in solid-state fermentation (SSF) for lipase production using digital image processing technique. The strain A. niger 11T53A14 was cultivated in SSF using wheat bran as support, which was enriched with 0.91% (m/v) of ammonium sulfate. The addition of several vegetable oils (castor, soybean, olive, corn, and palm oils) was investigated
to enhance lipase production. The maximum lipase activity was obtained using 2% (m/m) castor oil. In these conditions, the growth was evaluated each 24 h for 5 days by the glycosamine content analysis and digital
image processing. Lipase activity was also determined. The results indicated that the digital image process technique can
be used to monitor biomass growth in a SSF process and to correlate biomass growth and enzyme activity. In addition, the immobilized
esterification lipase activity was determined for the butyl oleate synthesis, with and without 50% v/v hexane, resulting in 650 and 120 U/g, respectively. The enzyme was also used for transesterification of soybean oil and ethanol
with maximum yield of 2.4%, after 30 min of reaction. 相似文献
115.
Cunha AG Fernández-Lorente G Bevilaqua JV Destain J Paiva LM Freire DM Fernández-Lafuente R Guisán JM 《Applied biochemistry and biotechnology》2008,146(1-3):49-56
Lipase immobilization offers unique advantages in terms of better process control, enhanced stability, predictable decay rates
and improved economics. This work evaluated the immobilization of a highly active Yarrowia lipolytica lipase (YLL) by physical adsorption and covalent attachment. The enzyme was adsorbed on octyl–agarose and octadecyl–sepabeads
supports by hydrophobic adsorption at low ionic strength and on MANAE–agarose support by ionic adsorption. CNBr–agarose was
used as support for the covalent attachment immobilization. Immobilization yields of 71, 90 and 97% were obtained when Y. lipolytica lipase was immobilized into octyl–agarose, octadecyl–sepabeads and MANAE–agarose, respectively. However, the activity retention
was lower (34% for octyl–agarose, 50% for octadecyl–sepabeads and 61% for MANAE–agarose), indicating that the immobilized
lipase lost activity during immobilization procedures. Furthermore, immobilization by covalent attachment led to complete
enzyme inactivation. Thermal deactivation was studied at a temperature range from 25 to 45°C and pH varying from 5.0 to 9.0
and revealed that the hydrophobic adsorption on octadecyl–sepabeads produced an appreciable stabilization of the biocatalyst.
The octadecyl–sepabeads biocatalyst was almost tenfold more stable than free lipase, and its thermal deactivation profile
was also modified. On the other hand, the Y. lipolytica lipase immobilized on octyl–agarose and MANAE–agarose supports presented low stability, even less than the free enzyme. 相似文献
116.
A new high-performance liquid chromatographic method was developed and validated for clopidogrel determination in pharmaceutical formulations. The system consisted of an ACE 5 octadecylsilane (C18; 150 x 4.6 mm id), 5.0 microm particle size column; methanol-0.1% triethylamine (75 + 25, v/v), pH 5.3, mobile phase at a flow rate of 1.2 mL/min; and a diode array detector set at 220 nm. Specificity, linearity, precision, accuracy, and robustness were the parameters evaluated. The retention time for clopidogrel was 6.8 min. To estimate specificity, an aqueous sample solution was subjected to degradation by ultraviolet light and by acid, alkaline, and oxidation media. The peaks of degradation products did not interfere with the compound signal, and there was no interference when a placebo solution was analyzed. Linearity over a concentration range of 10.0 to 90.0 microg/mL was shown (correlation coefficient = 0.9998). Low values of relative standard deviation indicated the adequate intraday and interday precision. The average recovery was found as 99.16%. In the robustness test, small modifications to the mobile phase composition did not affect the determination of clopidogrel. The proposed method proved to be simple, fast, and cost efficient for the intended use. 相似文献
117.
Lucia Caporaso Juliana Coelho Eduardo Esteves 《Rendiconti del Circolo Matematico di Palermo》2008,57(1):33-59
Abstract For a Gorenstein curve X and a nonsingular point P∈ X, we construct Abel maps
and
, where JXi is the moduli scheme for simple, torsion-free, rank-1 sheaves on X of degree i. The image curves of A and AP are shown to have the same arithmetic genus of X. Also, A and AP are shown to be embeddings away from rational subcurves L⊂ X meeting
in separating nodes. Finally we establish a connection with Seshadri’s moduli scheme UX(1) for semistable, torsion-free, rank-1 sheaves on X, obtaining an embedding of A(X) into UX(1).
Keywords Abel map, Torsion-free rank-1 sheaf, Compactified Jacobian, Gorenstein singularity
Mathematics Subject Classification (2000) 14H40, 14H60 相似文献
118.
Dr. Juliana S. A. Carneiro Dr. Giada Innocenti Hyun June Moon Yoseph Guta Laura Proaño Prof. Dr. Carsten Sievers Dr. Miles A. Sakwa-Novak Dr. Eric W. Ping Prof. Dr. Christopher W. Jones 《Angewandte Chemie (International ed. in English)》2023,62(24):e202302887
Direct air capture (DAC) processes for extraction of CO2 from ambient air are unique among chemical processes in that they operate outdoors with minimal feed pretreatments. Here, the impact of humidity on the oxidative degradation of a prototypical solid supported amine sorbent, poly(ethylenimine) (PEI) supported on Al2O3, is explored in detail. By combining CO2 adsorption measurements, oxidative degradation rates, elemental analyses, solid-state NMR and in situ IR spectroscopic analysis in conjunction with 18O labeling of water, a comprehensive picture of sorbent oxidation is achieved under accelerated conditions. We demonstrated that the presence of water vapor can play an important role in accelerating the degradation reactions. From the study we inferred the identity and kinetics of formation of the major oxidative products, and the role(s) of humidity. Our data are consistent with a radical mediated autooxidative degradation mechanism. 相似文献
119.
Christine Moseley Juliana Utley Julie Angle Mwarumba Mwavita 《School science and mathematics》2016,116(7):389-398
The increasing popularity of including environmental topics and issues in school curricula has created a need for effective environmental education teachers. One way to evaluate teacher effectiveness is through teacher efficacy, a belief measure that evaluates a teacher's perception that he/she can teach effectively. Research suggests that teachers’ instructional decisions are influenced by their beliefs, which are framed by their personal experiences. Because teacher efficacy is content specific, the purpose of this study was to develop a survey, the Environmental Education Teacher Efficacy Belief Instrument (EETEBI), to measure the teacher efficacy beliefs of preservice teachers as they relate to environmental education teaching strategies and outcomes. 相似文献
120.
Biodiesel fuel production by the transesterification reaction of soybean oil using immobilized lipase 总被引:1,自引:0,他引:1
Bernardes OL Bevilaqua JV Leal MC Freire DM Langone MA 《Applied biochemistry and biotechnology》2007,137(1-12):105-114
The enzymatic alcoholysis of soybean oil with methanol and ethanol was investigated using a commercial, immobilized lipase (Lipozyme RMIM). The effect of alcohol (methanol or ethanol), enzyme concentration, molar ratio of alcohol to soybean oil, solvent, and temperature on biodiesel production was determined. The best conditions were obtained in a solvent-free system with ethanol/oil molar ratio of 3.0, temperature of 50 degrees C, and enzyme concentration of 7.0% (w/w). Three-step batch ethanolysis was most effective for the production of biodiesel. Ethyl esters yield was about 60% after 4 h of reaction. 相似文献