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51.
OPTIMAL FISH HARVESTING FOR A POPULATION MODELED BY A NONLINEAR PARABOLIC PARTIAL DIFFERENTIAL EQUATION
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As the human population continues to grow, there is a need for better management of our natural resources in order for our planet to be able to produce enough to sustain us. One important resource we must consider is marine fish populations. We use the tool of optimal control to investigate harvesting strategies for maximizing yield of a fish population in a heterogeneous, finite domain. We determine whether these solutions include no‐take marine reserves as part of the optimal solution. The fishery stock is modeled using a nonlinear, parabolic partial differential equation with logistic growth, movement by diffusion and advection, and with Robin boundary conditions. The objective for the problem is to find the harvest rate that maximizes the discounted yield. Optimal harvesting strategies are found numerically. 相似文献
52.
By the use of glycosyl donors containing aromatic leaving groups linked with opposite anomeric configurations compared to those of the natural donor substrates, an inverting (Cst II) and a retaining (LgtC) glycosyltransferase were found to catalyse glycosylation reactions of natural acceptor substrates in the presence of the corresponding nucleotide. 相似文献
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54.
Manuel Scherer Andrs G. Santana Kyle Robinson Steven Zhou Hermen S. Overkleeft Lorne Clarke Stephen G. Withers 《Chemical science》2021,12(41):13909
Gaucher''s disease, the most prevalent lysosomal storage disorder, is caused by missense mutation of the GBA gene, ultimately resulting in deficient GCase activity, hence the excessive build-up of cellular glucosylceramide. Among different therapeutic strategies, pharmacological chaperoning of mutant GCase represents an attractive approach that relies on small organic molecules acting as protein stabilizers. Herein, we expand upon a new class of transient GCase inactivators based on a reactive 2-deoxy-2-fluoro-β-d-glucoside tethered to an array of lipid-mimicking phosphorus-based aglycones, which not only improve the selectivity and inactivation efficiency, but also the stability of these compounds in aqueous media. This hypothesis was further validated with kinetic and cellular studies confirming restoration of catalytic activity in Gaucher cells after treatment with these pharmacological chaperones.Engineered 2-fluoroglucosides containing a phosphorus-based leaving group rapidly form a stable covalent intermediate with GCase, thus stabilising the enzyme during transit to the lysosome, where it is released on a clinically appropriate timescale. 相似文献
55.
56.
Multilayered BaTiO3(BTO)/Bi0.5K0.5TiO3 (BKT) thin films have been fabricated on Pt/Ti/SiO2/Si substrates using a metalloorganic decomposition process. XRD investigation of the resultant BTO/BKT multilayered thin films shows that they retain a perovskite-related structure type. They also exhibit a well-defined, polarization–electric field hysteresis loop with a measured remnant polarization (2Pr) of 5 µC/cm2 at an applied electric field of 250 kV/cm. The measured dielectric constant and dielectric loss at 10 kHz is 470 and 0.07 respectively. These multilayer BTO/BKT films maintain an excellent fatigue-free character even after 109 switching cycles. The mechanism associated with the enhancement of the electrical properties of the synthesized BTO/BKT films is also discussed. 相似文献
57.
Withers JR Li D Triplet J Ruschman C Parkin S Wang G Yee GT Holmes SM 《Inorganic chemistry》2006,45(11):4307-4309
Treatment of [HNBu3]3[Mo(V)(CN)8] with manganese(II) p-toluenesulfonate in N,N'-dimethylformamide (DMF) affords {[Mn(II)(DMF)4]3[Mo(V)(CN)8]2}n (1) as a two-dimensional network. The structure of 1 consists of [cis-Mn(II)(DMF)4(mu-NC)2]2+ and [trans-Mn(II)(DMF)4(mu-NC)2]2+ units that are linked via cyanides to three-connected [Mo(V)(CN)5(mu-CN)3]3- centers in a 4:2:6 ratio, forming 12-membered rings. Magnetic measurements indicate that 1 is a ferrimagnet (TN = 8 K) that exhibits frequency-dependent behavior in chi". Heating of 1 affords an additional magnetic phase (TN = 21 K) that is absent of linkage isomerism. 相似文献
58.
Micron-Scale Residual Stress Measurement by Micro-Hole Drilling and Digital Image Correlation 总被引:1,自引:0,他引:1
This paper reports a new technique, namely the incremental micro-hole-drilling method (IμHD) for mapping in-plane residual
or applied stresses incrementally as a function of depth at the micron-scale laterally and the sub-micron scale depth-wise.
Analogous to its macroscale counterpart, it is applicable either to crystalline or amorphous materials, but at the sub-micron
scale. Our method involves micro-hole milling using the focused ion beam (FIB) of a dual beam FEGSEM/FIB microscope. The resulting
surface displacements are recorded by digital image correlation of SEM images recorded during milling. The displacement fields
recorded around the hole are used to reconstruct the stress profile as a function of depth. In this way residual stresses
have been characterized around a drilled hole of 1.8microns. diameter, enabling the profiling of the stress variation at the
sub-micron scale to a depth of 1.8 microns. The new method is used to determine the near surface stresses in a (peened) surface-severe-plastically-deformed
(S2PD) Zr50Cu40Al10 (in atomic percent, at.%) bulk metallic glass bar. In plane principal stresses of -800 MPa ± 90 MPa and −600 MPa ± 90 MPa
were measured, the maximum compressive stress being oriented 15° to the axis of the bar. 相似文献
59.
An LLG-3 oligosaccharide-fluoride can be assembled chemoenzymatically and readily coupled with various sphingosines by an engineered endoglycoceramidase glycosynthase. The lyso?ganglioside products are acylated to generate the individual isomers identified in the heterogeneous natural isolates, as well as modified glycosphingolipids. 相似文献
60.
Christopher S. Withers Saralees Nadarajah 《Statistical Inference for Stochastic Processes》2012,15(2):127-132
Suppose ${\widehat{\theta}_1}$ and ${\widehat{\theta}_2}$ are asymptotically independent non-lattice with a joint second order Edgeworth expansion in n ?1/2. Then the ?? dependency coefficient is $$\alpha \left(\widehat{\theta}_1, \widehat{\theta}_2 \right) = n^{-1/2} C + O \left(n^{-1} \right),$$ where ${C = (4 \pi)^{-1}\exp (-1/2) (\tau^2_1 + \tau^2_2) ^{1/2}}$ for ${\tau_1, \tau_2}$ their joint skewness coefficients. 相似文献