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1.
Maria do Carmo B. Pimentel Eduardo Henrique M. Melo José Luiz Lima Filho William M. Ledingham Nelson Durán 《Applied biochemistry and biotechnology》1997,66(2):185-195
This work is a study of lipase production by a Brazilian strain ofPenicillium citrinum using an inexpensive and simple medium without organic nitrogen sources and of some important industrial properties, including
thermostability in relation to ionic strength. The maximal lipase activity (1585 U/L) was obtained whenPenicillium citrinum was cultured on 0.75% ammonium sulfate complemented with minerals salts instead of yeast extract. Although this activity
was about 55% lower than that produced in medium with yeast extract (2850 U/L), the specific activity (7.8 U/mg proteins)
was higher than that obtained with the yeast extract (4.9 U/mg proteins). The morphology of fungus changed totally, with yeast
extract there are smooth, solid, and spherical pellets whereas on ammonium sulfate there are small “hairy” pellets uniformly
suspended in the medium. The effect of ferrous (Fe++) ions was carried out using medium MA with and without Fe++ ions. Lipase production byPenicillium citrinum in medium MA requires Fe++ ions, the absence of which caused a decreased of about 50% in the specific activity (3.5 U/mg proteins). The utilization
of commercial, locally available oils as carbon sources, such as soybean oil (236 U/L) and corn oil (74 U/L) resulted in lower
activity compared to olive oil, showing that lipase production byPenicillium citrinum is specifically induced by olive oil. Potassium concentration in the medium can effects the production of lipase (1 mM (1585
U/L), 10 mM (1290 U/L), and 30 mM (1238 U/L), 50 mM (195 U/L), and 100 mM (2 U/L). The crude culture filtered was susceptable
to thermal deactivation. It was stable at pH 6.0, but was not stable at the optimum pH (8.0-8.5) at 50 mM. At the low ionic
concentration (1-25 mM) this lipase was stable at low pH (3.5-4.0). The activation energy was 22.4 ±2.2 Kcal. mol 1. 相似文献
2.
3.
M. Campbell K.W.D. Ledingham A.D. Baillie M.L. Fitzpatrick J.Y. Gourlay J.G. Lynch 《Nuclear Physics A》1975,249(2):349-365
Recent review papers have indicated that experimental K.-capture to positon emission ratios in allowed decays disagree with theory especially for high-Z nuclei. The experimental error has never been sufficiently small to verify this with certainty. The K-capture to positon emission ratio, , in 120Sb has been measured with an uncertainty of about 3% and found to lie about 16% lower than the most recent theoretical predictions. 相似文献
4.
The trace element Zn in the Zn-doped multi-layer ш - V group compound semiconductor was detected by means of Resonant Laser Ablation/lomzation(RLA). A detection limit of 2. 5 X 1017 atoms/cm3 (about 5 ppm) has been estimated. The mass spectra and the optical resonant ionization spectrum around 214 nm are given in this paper. 相似文献
5.
本文简要地描述了激光共振电离质谱的实验装置和测量方法,给出了用共振电离质谱方法对锌掺杂化合物半导体材料进行分析的光谱和质谱图,并估计了用这种方法进行痕量分析可能达到的检测限. 相似文献
6.
K. W. D. Ledingham 《Hyperfine Interactions》2006,171(1-3):69-81
High intensity lasers interacting with solid and gas targets can produce energetic beams of electrons, protons, heavy ions,
photons and neutrons. There is the potential for producing “table top” sources of radiation for many different applications. 相似文献
7.
N. L. C. Licinio Da Silva A. A. Salgueiro W. M. Ledingham E. H. M. Melo J. L. Lima Filho 《Applied biochemistry and biotechnology》1992,37(1):1-10
The influence of potassium on ethanol production bySaccharomyces cerevisiae wild type and AR5 cells carrying the plasmid pCYG4 was investigated. This plasmid carries the glutamate dehydrogenase gene
conferring an 11-fold higher level of expressed enzyme activity over the wild type cells. All experiments were carried out
in batch culture with medium supplemented to different potassium concentrations up to 180 mM. Maximum ethanol production rate
was observed in the AR5 cells grown in medium supplemented with 3.5 mM of potassium ions. Glucose uptake rate increased with
increasing potassium up to 60 mM, but higher concentrations depressed glucose uptake rate in both strains. Furthermore, the
wild type cells showed higher growth rate, ethanol production, and glucose consumption rate than the AR5 cells. These lower
rates in the AR5 cells could be explained by repression of potassium uptake by an enhancement of ammonium feeding, and greater
energy requirements by these cells due the presence of the plasmid. 相似文献
8.
Robson L Ledingham KW McKenna P McCanny T Shimizu S Yang JM Wahlström CG Lopez-Martens R Varju K Johnsson P Mauritsson J 《Journal of the American Society for Mass Spectrometry》2005,16(1):82-89
The mechanism of atomic and molecular ionization in intense, ultra-short laser fields is a subject which continues to receive considerable attention. An inherent difficulty with techniques involving the tight focus of a laser beam is the continuous distribution of intensities contained within the focus, which can vary over several orders of magnitude. The present study adopts time of flight mass spectrometry coupled with a high intensity (8 x 10(15) Wcm(-2)), ultra-short (20 fs) pulse laser in order to investigate the ionization and dissociation of the aromatic molecule benzene-d1 (C(6)H(5)D) as a function of intensity within a focused laser beam, by scanning the laser focus in the direction of propagation, while detecting ions produced only in a "thin" slice (400 and 800 microm) of the focus. The resultant TOF mass spectra varies significantly, highlighting the dependence on the range of specific intensities accessed and their volumetric weightings on the ionization/dissociation pathways accessed. 相似文献
9.
Michael J. Epton Katherine Ledingham Jack Dummer Wan‐Ping Hu Bronwen Rhodes Senti T. Senthilmohan Jennifer M. Scotter Randall Allardyce Julie Cook Maureen P. Swanney 《Rapid communications in mass spectrometry : RCM》2009,23(3):443-447
Selected ion flow tube mass spectrometry (SIFT-MS) is a sensitive technique capable of measuring volatile compounds (VCs) in complex gas mixtures in real time; it is now being applied to breath analysis. We investigated the effect of inhalers containing chlorofluorocarbons (CFCs) on the detection and measurement of haloamines in human breath. SIFT-MS mass scans (MS) and selected ion monitoring (SIM) scans were performed on three healthy non-smoking volunteers before and after inhalation of the following medications: Combivent™ metered-dose inhaler (MDI) (CFC-containing); Ventolin™ MDI (CFC-free); Atrovent™ MDI (CFC-free), Beclazone™ MDI (CFC-containing); Duolin™ nebuliser. In addition, the duration of the persistence of the mass/charge ratios was measured for 20 h. Inhalers containing CFCs generated large peaks at m/z 85, 87, 101, 103 and 105 in vitro and in vivo, consistent with the predicted product ions of CFCs 12, 114 and 11. No such peaks were seen with Duolin™ via nebuliser, or CFC-free MDIs. We conclude that measurement of VCs, such as haloamines, with product ions of similar m/z values to the ions found for CFCs would be significantly affected by the presence of CFCs in inhalers. This issue needs to be accounted for prior to the measurement of VCs in breath in people using inhalers containing CFCs. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
10.
McKenna P Ledingham KW Shimizu S Yang JM Robson L McCanny T Galy J Magill J Clarke RJ Neely D Norreys PA Singhal RP Krushelnick K Wei MS 《Physical review letters》2005,94(8):084801
A beam of MeV protons, accelerated by ultraintense laser-pulse interactions with a thin target foil, is used to investigate nuclear reactions of interest for spallation physics. The laser-generated proton beam is shown (protons were measured) to have a broad energy distribution, which closely resembles the expected energy spectrum of evaporative protons (below 50 MeV) produced in GeV-proton-induced spallation reactions. The protons are used to quantify the distribution of residual radioisotopes produced in a representative spallation target (Pb), and the results are compared with calculated predictions based on spectra modeled with nuclear Monte Carlo codes. Laser-plasma particle accelerators are shown to provide data relevant to the design and development of accelerator driven systems. 相似文献