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71.
In this paper, we present a method for using rational expectations in a stochastic linear-quadratic optimization framework in which the unknown parameters are updated through a learning scheme. We use the QZ decomposition as suggested by Sims (Ref. 1) to solve the rational expectations part of the model. The parameter updating is done with the Kalman filter and the optimal control is calculated using the covariance matrix of the uncertain parameter. 相似文献
72.
Geng S Fang J Turner KB Daunert S Wei Y 《Analytical and bioanalytical chemistry》2012,403(8):2403-2409
Polychlorinated biphenyls (PCBs) are environmental pollutants that have been associated with numerous adverse health effects in human and animals. Hydroxylated PCBs (HPCBs) are the product of the oxidative metabolism of PCBs. The presence of hydroxyl groups in HPCBs makes these compounds more hydrophilic than the parent PCBs. One of the best approaches to break down and remove these contaminants is bioremediation; an environmentally friendly process that uses microorganisms to degrade hazardous chemicals into non-toxic ones. In this study, we investigated the cellular accumulation and toxicity of selected PCBs and HPCBs in Gram-negative bacteria, using Escherichia coli as a model organism. We found that none of the five PCBs tested were toxic to E. coli, presumably due to their limited bioavailability. Nevertheless, different HPCBs tested showed different levels of toxicity. Furthermore, we demonstrated that the primary multidrug efflux system in E. coli, AcrAB-TolC, facilitated the efflux of HPCBs out of the cell. Since AcrAB-TolC is constitutively expressed in E. coli and is conserved in all sequenced Gram-negative bacterial genomes, our results suggest that the efflux activities of multidrug resistant pumps may affect the accumulation and degradation of PCBs in Gram-negative bacteria. 相似文献
73.
Orera A Baikie T Kendrick E Shin JF Pramana S Smith R White TJ Sanjuán ML Slater PR 《Dalton transactions (Cambridge, England : 2003)》2011,40(15):3903-3908
High oxygen content apatite germanates, La(10)Ge(6-x)W(x)O(27+x), have been prepared by doping on the Ge site with W. In addition to increasing the oxygen content, this doping strategy is shown to result in stabilisation of the hexagonal lattice, and yield high conductivities. Structural studies of La(10)Ge(5.5)W(0.5)O(27.5) show that the interstitial oxygen sites are associated to a different degree with the Ge/WO(4) tetrahedra, leading to five coordinate Ge/W and significant disorder for the oxygen sites associated with these units. Raman spectroscopy studies suggest that in the case of the WO(5) units, the interstitial oxygen is more tightly bonded and therefore not as mobile as in the case of the GeO(5) units, thus not contributing significantly to the conduction process. 相似文献
74.
We have performed extensive small-angle neutron scattering (SANS) diffraction studies of the vortex lattice in single crystal
YNi2B2C for B‖c. High-resolution SANS, combined with a field-oscillation vortex lattice preparation technique, allows us to separate Bragg
scattered intensities from two orthogonal domains and accurately determine the unit cell angle, β. The data suggest that upon increasing field there is a finite transition width where both low- and high-field distorted
hexagonal vortex lattice phases, mutually rotated by 45°, coexist. The smooth variation of diffracted intensity from each
phase through the transition corresponds to a redistribution of populations between the two types of domains. 相似文献
75.
Brodie CR Heaton TH Leng MJ Kendrick CP Casford JS Lloyd JM 《Rapid communications in mass spectrometry : RCM》2011,25(8):1089-1099
We investigate the effect of acid treatment methods on δ(15)N values from a range of environmental organic materials in the context of the increased application of 'dual-mode' isotope analysis (the simultaneous measurement of δ(13)C and δ(15)N from the same acid-treated sample). Three common methods are compared; (i) untreated samples; (ii) acidification followed by sequential water rinse (rinse method); and (iii) acidification in silver capsules (capsule method). The influence of capsule type (silver and tin) on δ(15)N is also independently assessed (as the capsule and rinse methods combust samples in different capsules; silver and tin, respectively). We find significant differences in δ(15)N values between methods and the precision of any one method varies significantly between sample materials and above the instrument precision (>0.3‰). The δ(15)N values of untreated samples did not produce the most consistent data on all sample materials. In addition, the capsule type appears to influence the measured δ(15)N value of some materials, particularly those combusted only in silver capsules. We also compare the new δ(15)N data with previously published δ(13)C data on the same materials. The response of δ(13)C and δ(15)N within and between methods and sample materials to acidification appears to be relatively disproportionate, which can influence the environmental interpretation of the measured data. In addition, statistical methods used to estimate inorganic nitrogen are shown to be seriously flawed. 相似文献
76.
Harry Smith Matthew Turnbull Richard E. Kendrick 《Photochemistry and photobiology》1992,56(5):607-610
Seedlings of wild type (WT) and the lh mutant of Cucumis sativus were grown in white light and given supplementary far-red radiation either to the whole plant, or via fiber-optic probes directed at the apical region of the hypocotyl. In both WT and mutant seedlings, reducing the ratio of red to far-red radiation resulted in significant increases in extension growth. Direct measurement of extension rate by transducer techniques revealed that the mutant seedlings responded to additional far-red radiation by an increment in extension rate that was equivalent to that observed with the WT seedlings. Assuming that the lh mutant is deficient in phytochrome B (Kendrick and Nagatani, The Plant Journal 1: 133–139, 1991), these results indicate that although phytochrome B clearly has an important role in the induction of the shade avoidance syndrome, it is unlikely to be the sole responsible receptor. 相似文献
77.
78.
79.
An axisymmetric magnetic field is applied to a spherical, turbulent flow of liquid sodium. An induced magnetic dipole moment is measured which cannot be generated by the interaction of the axisymmetric mean flow with the applied field, indicating the presence of a turbulent electromotive force. It is shown that the induced dipole moment should vanish for any axisymmetric laminar flow. Also observed is the production of toroidal magnetic field from applied poloidal magnetic field (the omega effect). Its potential role in the production of the induced dipole is discussed. 相似文献
80.
Kendrick P Cox TJ Li FF Zhang Y Chambers JA 《The Journal of the Acoustical Society of America》2008,124(1):278-287
This paper compares two methods for extracting room acoustic parameters from reverberated speech and music. An approach which uses statistical machine learning, previously developed for speech, is extended to work with music. For speech, reverberation time estimations are within a perceptual difference limen of the true value. For music, virtually all early decay time estimations are within a difference limen of the true value. The estimation accuracy is not good enough in other cases due to differences between the simulated data set used to develop the empirical model and real rooms. The second method carries out a maximum likelihood estimation on decay phases at the end of notes or speech utterances. This paper extends the method to estimate parameters relating to the balance of early and late energies in the impulse response. For reverberation time and speech, the method provides estimations which are within the perceptual difference limen of the true value. For other parameters such as clarity, the estimations are not sufficiently accurate due to the natural reverberance of the excitation signals. Speech is a better test signal than music because of the greater periods of silence in the signal, although music is needed for low frequency measurement. 相似文献