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1.
This paper is concerned with the study of the stationary solutions of the equationwhere the diffusion matrix A and the reaction term f are periodic in x. We prove existence and uniqueness results for the stationary equation and we then analyze the behaviour of the solutions of the evolution equation for large times. These results are expressed by a condition on the sign of the first eigenvalue of the associated linearized problem with periodicity condition. We explain the biological motivation and we also interpret the results in terms of species persistence in periodic environment. The effects of various aspects of heterogeneities, such as environmental fragmentation are also discussed.  相似文献   

2.
A bacterium, Aeromonas sp. GJ-18, having strong chitinolytic activity was isolated from coastal soil and used for crude enzyme preparations. This enzyme preparation contained N-acetyl-D-glucosaminidase and N,N-diacetylchitobiohydrolase. N-Acetyl-D-glucosaminidase was inactive above 50 °C, but N,N-diacetylchitobiohydrolase was stable at this temperature. Utilizing the temperature sensitivities of the chitin degradation enzymes in crude enzyme preparation, N-acetyl-D-glucosamine (GlcNAc) and N,N-diacetylchitobiose [(GlcNAc)2] were selectively produced from chitin. At 45 °C, GlcNAc was produced as a major hydrolytic product (94% composition) with a yield of 74% in 5 d, meanwhile at 55 °C (GlcNAc)2 was the major product (86%) with a yield of 35% within 5 d.Revisions requested 29 September 2004; Revisions received 1 November 2004  相似文献   

3.
In this note it is shown that the block design with incidence matrix Ñ = [NNN], where N = c1hNh + coh (11′–Nh). coh and c1h are any non-negative integers and Nh,h = 1, 2,…,p, are incidence matrices of balanced incomplete block designs with the same number of treatments t, is a balanced block design with the block sizes exceeding the number of treatments. In derivation the matrix M0, introduced by CALIński (1971) is utilized.  相似文献   

4.
To investigate, the effects of hydrostatic pressure on transmembrane signaling in cold-adapted marine fishes, we examined the high-affinity GTPase activity in two congeneric marine fishes, Sebastolobus alascanus and S. altivelis. In brain membranes there are two GTPase activities, one with a low K m and one with a high K m for GTP. The high-affinity GTPase activity, characteristic of the subunits of the guanine nucleotide binding protein pool, was stimulated by the A1 adenosine receptor agonists N 6(R-phenylisopropyl)adenosine and N 6-cyclopentyladenosine, and the muscarinic cholinergic agonist carbamyl choline. Pertussis toxin-catalyzed ADP-ribosylation of the membranes for 2 h at 5°C prior to the GTPase assay decreased the basal GTPase activity 30–40% and abolished N 6 (R-phenylisopropyl)adenosine stimulation of GTP hydrolysis. Basal high-affinity hydrolysis of GTP, measured at 0.3 mol·1-1GTP, was stimulated 22% in both species by 340 atm pressure. At 340 atm pressure, the apparent K m of GTP is decreased approximately 10% in each of the species, and the V max values are increased 11 and 15.9% in S. alascanus and S. altivelis, respectively. The apparent volume changes associated with the decreased K m of GTP and the increased V max ranged from-7.0 to-9.9 ml·mol-1. Increased pressure markedly decreased the efficacy of N 6 (R-phenylisopropyl) adenosine, N 6-cylcopentyladenosine and carbamyl choline in stimulating GTPase activity. The effects of increased hydrostatic pressure on transmembrane signal transduction by the A1 adenosine receptor-inhibitory guanine nucleotide binding protein-adenylyl cyclase system may stem, at least in part, from pressure-increased GTP hydrolysis and the concomitant termination of inhibitory signal transduction.Abbreviations [3H] DPCPX 3H cyclopentyl-1, 3-dipropylxanthine - AppNHp 5-adenylylimidodiphosphate - cpm counts per minute - CPA N 6-cyclopentyladenosine - EDTA ethylenediaminetetra acetic acid - EGTA ethyleneglycol-bis (-aminoethylether) N, N, N, N-totra-acctic acid - G protein guanine nucleotide binding protein - Gi inhibitory G protein - Go other G protein, common in brain membranes - Gs stimulatory G protein - GTPase guanosine triphosphatase - K i inhibition constant - K m Michaelis constant - pK a log of the dissociation constant - R-PIA N 6 (R-phenylisopropyl) adenosine - TRIS tris[hydroxymethyl]aminomethane - Vmax maximal velocity - [-32P]GTP [-32P] guanosine 5-triphosphate (tetra (triethylammonium) salt)  相似文献   

5.
This paper considers a model of the human cardiovascular-respiratory control system with one and two transport delays in the state equations describing the respiratory system. The effectiveness of the control of the ventilation rate is influenced by such transport delays because blood gases must be transported a physical distance from the lungs to the sensory sites where these gases are measured. The short term cardiovascular control system does not involve such transport delays although delays do arise in other contexts such as the baroreflex loop (see [46]) for example. This baroreflex delay is not considered here. The interaction between heart rate, blood pressure, cardiac output, and blood vessel resistance is quite complex and given the limited knowledge available of this interaction, we will model the cardiovascular control mechanism via an optimal control derived from control theory. This control will be stabilizing and is a reasonable approach based on mathematical considerations as well as being further motivated by the observation that many physiologists cite optimization as a potential influence in the evolution of biological systems (see, e.g., Kenner [29] or Swan [62]). In this paper we adapt a model, previously considered (Timischl [63] and Timischl et al. [64]), to include the effects of one and two transport delays. We will first implement an optimal control for the combined cardiovascular-respiratory model with one state space delay. We will then consider the effects of a second delay in the state space by modeling the respiratory control via an empirical formula with delay while the the complex relationships in the cardiovascular control will still be modeled by optimal control. This second transport delay associated with the sensory system of the respiratory control plays an important role in respiratory stability. As an application of this model we will consider congestive heart failure where this transport delay is larger than normal and the transition from the quiet awake state to stage 4 (NREM) sleep. The model can be used to study the interaction between cardiovascular and respiratory function in various situations as well as to consider the influence of optimal function in physiological control system performance.Supported by FWF (Austria) under grant F310 as a subproject of the Special Research Center F003 Optimization and ControlMathematics Subject Classification (2000): 92C30, 49J15  相似文献   

6.
Cotyledonary node explants of Acacia nilotica subspecies indica Brenan, differentiated multiple shoots on Gamborg et al.' s medium (B5, Gamborg et al. 1968) supplemented with cytokinins like N6-benzyladenine, 6-(, -Dimethylallylamino)-purine, kinetin or zeatin. Of the four, BA supported maximum multiple shoot differentiation; the highest average number of shoots (6.3) per expiant was in 1.5 mg/l. The number of shoots was further enhanced by (i) using nodal explants of in vitro regenerated shoots as microcuttings, and (ii) repeated subculture of the original expiants (stumps) on the same medium after excising the shoots. Thus, over seven hundred shoots could be obtained from a single cotyledonary node explant. Individual shoots, when transferred to 2 mg/l indole-3-acetic acid augmented medium organised healthy roots in 100% cultures. Such test tube grown plantlets have been successfully transferred to soil, where they grow well up to eight weeks.Abbreviations 2iP 6-(, -Dimethylallylamino)-purine - AC activated charcoal - B5 Gamborg et al. 's medium with 0.8% agar + 3 % sucrose - BA,N6 benzyladenine - CW coconut water - FAA formalin-aceticacid-alcohol - IAA indole-3-acetic acid - IBA indole-3-butyric acid - Kn kinetin - NAA -naphthaleneacetic acid - NOA -naphthoxyacetic acid  相似文献   

7.
A method for plant regeneration of Iris via somatic embryogenesis is described. Root and leaf pieces from in vitro-grown plants of several genotypes of rhizomatous Iris sp. were cultured in vitro. Callus induction occurred only on root cultures incubated under low light intensity (35 mol m-2 s-1) on two induction media containing 2,4-D (4.5 or 22.5 M), NAA (5.4 M) and kinetin (0.5 M). Somatic embryos developed after transfer of callus onto four regeneration media containing 9 or 22 M BA, or 5 M kinetin and 2 M TIBA or 9 M BA and 4 M TIBA. Plantlets could be obtained from these somatic embryos. Genotypic differences were found both in callus induction and somatic embryo formation, with I. pseudacorus responding better than I. versicolor or I. setosa. Cytological analysis performed on root tips of 80 regenerated plants revealed that two of the I. pseudacorus regenerants were tetraploid.Abbreviations 2,4-D dichlorophenoxy acetic acid - NAA naphthaleneacetic acid - BA 6-benzyladenine - TIBA 2,3,5-triiodobenzoic acid - IBA indolebutyric acid  相似文献   

8.
Book reviews     
Consider the perturbed harmonic oscillator Ty=-y+x2y+q(x)y in L2(), where the real potential q belongs to the Hilbert space H={q, xq L2()}. The spectrum of T is an increasing sequence of simple eigenvalues n(q)=1+2n+n, n 0, such that n 0 as n. Let n(x,q) be the corresponding eigenfunctions. Define the norming constants n(q)=limxlog |n (x,q)/n (-x,q)|. We show that for some real Hilbert space and some subspace Furthermore, the mapping :q(q)=({n(q)}0, {n(q)}0) is a real analytic isomorphism between H and is the set of all strictly increasing sequences s={sn}0 such that The proof is based on nonlinear functional analysis combined with sharp asymptotics of spectral data in the high energy limit for complex potentials. We use ideas from the analysis of the inverse problem for the operator -ypy, p L2(0,1), with Dirichlet boundary conditions on the unit interval. There is no literature about the spaces We obtain their basic properties, using their representation as spaces of analytic functions in the disk.  相似文献   

9.
Oxygen mass transfer represents the most important parameter involved in the design and operation of mixing-sparging equipment for bioreactors. It can be described and analyzed by means of the mass transfer coefficient, kLa. The kLa values are affected by many factors such as geometrical and operational characteristics of the vessels, media composition, type, concentration and microorganism morphology, and biocatalysts properties. The efficiency of oxygen transfer could be enhanced by adding oxygen-vectors in broths, such as hydrocarbons or fluorocarbons, without increasing the energy consumption for mixing or aeration. The experimental results obtained for simulated broths indicated a considerable increase of kLa in the presence of n-dodecane, and the existence of a certain value of n-dodecane concentration that corresponds to a maximum mass transfer rate of oxygen. The magnitude of the positive effect of n-dodecane depends both on the broths characteristics and operational conditions of the bioreactor.Notation d stirrer diameter, mm - d oxygen electrode diameter, mm - D bioreactor diameter, mm - h distance from the inferior stirrer to the bioreactor bottom, mm - H bioreactor height, mm - kLa oxygen mass transfer coefficient, s-1 - l impeller blade length, mm - I oxygen electrode immersed length, mm - P power consumption for mixing of non-aerated broths, W - Pa power consumption for mixing of aerated broths, W - (Pa/V) specific power input, W/m3 - s baffle width, mm - vS superficial air velocity, m/s - V volume of medium, m3 - w impeller blade height, mm - volumetric fraction of oxygen-vector - a apparent viscosity, Pa*s - density, kg/m3  相似文献   

10.
The rate of CO2- and p-benzoquione-dependent photosynthetic O2 evolution by Anabaena variabilis cells remained unaltered and the rate of O2 uptake observed after switching off the light (endogenous respiration) was enhanced by a factor of 6–8 when the O2 concentration was increased from 200 to 400 M. Photosystem-I-linked O2 uptake and respiration of the cells incubated with ascorbate and N,N,NN-tetramethyl-p-phenylenediamine was not appreciable influenced by the O2 concentration. 2-Iodo-6-isopropyl-3-methyl-2,4,4-trinitrodiphenyl ether, blocking electron transfer at the plastoquinone level, suppressed O2 evolution and had no influence on endogenous respiration. 2-n-Heptyl-4-hydroxyquinoline-N-oxide, an inhibitor of electron transfer between photosystems II and I, as well as the cytochrome-oxidase inhibitors N 3 - , CN- and NH2OH, caused a 35–50% retardation of endogenous respiration and blocked photosynthetic O2 evolution. The molar ratio of cytochromes b6, f, c-553, aa3 and photosystem-I reaction centers in the isolated membranes equalled approx. 2:1:2:0.7:2. It is inferred that endogenous respiration of A. variabilis cells is inhibited by the light-induced electron flow through both photosystems at the level of the plastoquinone-plastocyanin-oxidoreductase complex.Abbreviations DCMU 3-(3,4-dichlorophenyl)-1,1-dimethylurea - DNP-INT 2-iodo-6-isopropyl-3-methyl-2,4,4-trinitrodiphenyl ether - Hepes 4-(2-hydroxyethyl)-1-piperazine ethansulfonic acid - TMPD N,N,NN-tetramethyl-p-phenylenediamine  相似文献   

11.
Local molecular properties and their use in predicting reactivity   总被引:1,自引:0,他引:1  
Expressions for the local electron affinity, electronegativity and hardness are derived in analogy to the local ionization energy introduced by Sjoberg, Murray and Politzer. The local polarizability is also defined based on an additive atomic orbital polarizability model that uses Rivail's variational technique. The characteristics of these local properties at molecular surfaces and their relevance to electrophilic aromatic substitution, to SN2 reactivity and to the nucleophilicity of enolate ions are discussed.Figure The local ionization energy at the SES surfaces of methyl benzoate. The color scale ranges from 375 (blue) to 550 kcal mol–1 (red). The blue areas are those for which interaction with an acceptor is most favorable.  相似文献   

12.
We show that explicit mathematical and biological relationships exist among the scaling exponents and the allometric constants (α and β, respectively) of log–log linear tree‐community size frequency distributions, plant density NT, and minimum, maximum and average stem diameters (Dmin, Dmax, and , respectively). As individuals grow in size and Dmax increases, NT is predicted to decrease as reflected by a decrease in the numerical value of α and an increase in the value of β. Our derivations further show that NT decreases as increases even if Dmin or Dmax remain unchanged. Because Dmax and the age of the largest individuals in a community are correlated, albeit weakly, we argue that the interdependent relationships among the numerical values of α, β, NT, and shed light on the extent to which communities have experienced recent global disturbance. These predicted relationships receive strong statistical support using two large datasets spanning a broad spectrum of tree‐dominated communities.  相似文献   

13.
Summary The liquid and solids mixing in fluidized bed bio-reactors containing particles with a density only slightly higher than water (1100 kg/m3) is generally consistent with the results found in previous studies for reactors with particles of higher density. The liquid mixing can be described by an axial dispersion model for a large variety of conditions while the solids follow the streamlines of the liquid. In the presence of a gas phase the degree of mixing of both the liquid and the solid phase increased. This effect became larger with increasing reactor diameter. In the extrapolation of laboratory data of three phase fluidized bed bio-reactors to pilot plant systems this effect should be taken into account. The liquid and solids mixing may have a substantial effect on overall conversion rates and on possible microbial stratification in the reactor.Nomenclature Bo Bodenstein number v L/D (-) - D r diameter of the fluidized bed reactor (m) - D 1 Dispersion coefficient of the liquid phase (m2/s) - D g dispersion coefficient of the solid phase (m2/s) - E(in) normalized dye concentration function entering the ideally mixed tank reactor (-) - E(t) normalized dye concentration function as measured (-) - L length of the axial dispersed reactor (m) - t time after dye injection (s) - t m time constant for microbial selection (s) - t s solid mixing time constant (s) - t time interval in which a particle migrates within the bed (s) - v t superficial gas velocity (m/s) - v g superficial liquid velocity (m/s) - z migration distance of a particle in the bed (m) - 1 in situ growth rate of a dominant organism (s-1) - 2 in situ growth rate of a recessive organism (s-1) - average residence time in the axial dispersed reactor (s) - t average residence time in the ideally mixed tank reactor (s)  相似文献   

14.
Sixteen asparagine-linked oligosaccharides ranging in size from (Man)2(GlcNAc)2 (Fuc)1 to (GlcNAc)6(Man)3(GlcNAc)2 were obtained from human 1-acid glycoprotein and fibrinogen, hen ovomucoid and ovalbumin, and bovine fetuin, fibrin and thyroglobulin by hydrazinolysis, mild acid hydrolysis and glycosidase treatment. The oligosaccharides hadN-acetylglucosamine at the reducing termini and mannose andN-acetylglucosamine residues at the non-reducing termini and were prepared for use asN-acetylglucosaminyltransferase substrates. Purification of the oligosaccharides involved gel filtration and high performance liquid chromatography on reverse phase and amine-bonded silica columns. Structures were determined by 360 MHz and 500 MHz proton nuclear magnetic resonance spectroscopy, fast atom bombardment-mass spectrometry and methylation analysis. Several of these oligosaccharides have not previously been well characterized.Abbreviations bis bisecting GlcNAc - DMSO dimethylsulfoxide - FAB fast atom bombardment - Fuc l-fucose - Gal d-galactose - GLC gas-liquid chromatography - GlcNAc or Gn N-acetyl-d-glucosamine - HPLC high performance liquid chromatography - Man or M d-mannose - MES 2-(N-morpholino)ethanesulfonate - MS mass spectrometry - NMR nuclear magnetic resonance - PIPES piperazine-N,N-bis(2-ethane sulfonic acid) the nomenclature of the oligosaccharides is shown in Table 1.  相似文献   

15.
F. Grolig  I. Just  K. Aktories 《Protoplasma》1996,193(1-4):77-81
Summary The ability of two bacterial toxins to modify a plant actin by covalent ADP-ribosylation was tested in the green algaChara corallina. Using [32P]NAD, bothClostridium botulinum C2 toxin andClostridium perfringens iota toxin labelled a protein of Mr 42 kDa which comigrated with actin and was immunoprecipitated by a monoclonal anti-actin antibody. ADP-ribosylation ofChara actin was more efficient with iota toxin than with C2 toxin. The actin bundles in perfusedChara cells were not affected by toxin-containing media competent for ADP-ribosylation. The data indicate that monomeric plant actin is substrate for ADP-ribosylation by the bacterial toxins.Abbreviations ADP adenosine-diphosphate - EGTA ethyleneglycol-bis-(-aminoethyl)N,N,N,N-tetraacetic acid - NAD nicotinamide dinucleotide - pCA -log [Ca2+] - PIPES piperazine-N,N-bis(2-ethanesulfonic acid) Dedicated to Prof. Dr. Dr. h.c. Eberhard Schnepf on the occasion of his retirement  相似文献   

16.
Glycyrrhizic acid and its 30-methyl ester were conjugated with 2-amino-1,3,4,6-tetra-O-acetyl-2-deoxy--D-glucopyranose, 2,3,4,6-tetra-O-acetyl--D-glucopyranosyl amine, 2,3,4-tri-O-acetyl--L-arabinopyranosyl amine, 2-acetamido-2-deoxy--D-glucopyranosyl amine, and -D-galactopyranosyl amine using N,N-dicyclohexylcarbodiimide and its mixtures with N-hydroxybenzotriazole. Structures of the conjugates were confirmed by IR, UV, 1H, and 13C NMR spectroscopy. The glycoconjugate with the residues of 2-acetamido-2-deoxy--D-glucopyranosyl amine in the carbohydrate part of its molecule exhibited antiviral activity (ID50 4 g/ml) toward the herpes simplex type 1 virus (HSV-1) in the VERO cell culture. Two compounds demonstrated anti-HIV-1 activity (50–70% inhibition of p24) in a culture of MT-4 cells at concentrations of 0.5–20 g/ml.  相似文献   

17.
The cyanobacterium Spirulina platensis was used to verify the possibility of employing microalgal biomass to reduce the contents of nitrate and phosphate in wastewaters. Batch tests were carried out in 0.5 dm3 Erlenmeyer flasks under conditions of light limitation (40 mol quanta m–2 s–1) at a starting biomass level of 0.50 g/dm3 and varying temperature in the range 23–40°C. In this way, the best temperature for the growth of this microalga (30°C) was determined and the related thermodynamic parameters were estimated. All removed nitrate was used for biomass growth (biotic removal), whereas phosphate appeared to be removed mainly by chemical precipitation (abiotic removal). The best results in terms of specific and volumetric growth rates ( =0.044 day–1, Q x =33.2 mg dm–3 day–1) as well as volumetric rate and final yield of nitrogen removal ( =3.26 mg dm–3 day–1, =0.739) were obtained at 30°C, whereas phosphorus was more effectively removed at a lower temperature. In order to simulate full-scale studies, batch tests of nitrate and phosphate removal were also performed in 5.0 dm3 vessels (mini-ponds) at the optimum temperature (30°C) but increasing the photon fluence rate to 80 mol quanta m–2 s–1 and varying the initial biomass concentration from 0.25 to 0.86 g/dm3. These additional tests demonstrated that an increase in the inoculum level up to 0.75 g/dm3 enhanced both NO3 and PO4 3– removal, confirming a strict dependence of these processes on biomass activity. In addition, the larger surface area of the ponds and the higher light intensity improved removal yields and kinetics compared to the flasks, particularly concerning phosphorus removal ( =0.032–0.050 day–1, Q x =34.7–42.4 mg dm–3 day–1, =3.24–4.06 mg dm–3 day–1, =0.750–0.879, =0.312–0.623 mg dm–3 day–1, and =0.224–0.440).  相似文献   

18.
We have used density functional theory to study palladium-based catalysts commonly used for the polymerization of norbornene derivatives with an ester group. Exoexo, exoendo, and endoendo isomers of catalyst complexes were investigated; the endoendo isomer was the most stable and inactive due to an intramolecular interaction between Pd and O of the carbonyl group. Phosphine groups are effective in minimizing the Pd–O interaction in the endoendo isomer and P(C6H11)3 was found to be the most efficient reagent. The intramolecular Pd–O interactions were estimated using model complexes, and it was demonstrated that they play a crucial role in stabilizing the endoendo isomer.Figure Methyl ester norbornene complex for endoendo isomers with P(C6H11)3  相似文献   

19.
1-(2,3,5-Tri-O-acetyl)--D-ribofuranosyl indole, the key compound in the synthesis of glycosides with the bis(indole) aglycone, was obtained for the first time by the indoline–indole method. There were synthesized 3-(1-methylindol-3-yl)-4-(1-glycosylindol-3-yl)furan(or pyrrole)-2,5-diones containing the residue of -D-ribofuranose or 2-deoxy--D-ribofuranose and analogous glycosides of indolo[2,3-a]furano(or pyrrolo)[3,4-]carbazol-5,7-diones, which are structurally relative to the antitumor antibiotic rebeccamycin. Their cytotoxicities toward a number of human tumor cell lines were studied in vitro, and the carbazole N-glycosides were shown to be more active than the bis(indole) glycosides. At the same time, the ribofuranosides were found to be less active than the corresponding ribopyranosides synthesized previously.  相似文献   

20.
New triterpene glycosides, ulososides C, (20S,22S,23R,24S)-3,22,23-trihydroxy-3-O-(-D-glucopyranosyl)-32-nor-24-methyllanost-8(9)-ene-30-oic acid, D, (20S,22S,23R,24S)-3,22,23-trihydroxy-3-O-(-D-N-acetylglucosaminopyranosyl)-32-nor-24-methyllanost-8(9)-ene-30-oic acid, and E, (20S,22S,23R,24S)-3,22,23-trihydroxy-3-O-(-D-glucuronopyranosyl-(1 2)--D-arabinopyranosyl-32-nor-24-methyllanost-8(9)-ene-30-oic acid, were isolated from an Ulosa sp. sponge. Their structures were determined by spectral methods and chemical transformations. Specific features of their structures are discussed.  相似文献   

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