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81.
This paper investigates the relationship between airway closure dynamics and acoustic fluctuations in expiratory crackles using direct numerical simulation. A unified mathematical model is proposed to deal with flow in an airway, elastic deformation of the airway wall, surface tension driven motion of the liquid film that lines the airway, and their acoustic fluctuations because of material compressibility. Airway closure is induced by increasing the surrounding pressure, then the source of the pressure fluctuations is measured over time. Our results show that the airway closure occurs suddenly because of a bridge formation of the liquid film, and high energy transfer occurs between the kinetic energy, the surface energy of the liquid interface, and the elastic energy of the airway wall, invoking a large acoustic fluctuation that causes the expiratory crackles. Nonlinear behavior is observed in terms of the airway wall stiffness; the dynamic motion of the airway closure becomes moderate and both the energy transfer and acoustic fluctuations are dramatically reduced with an increase in airway wall stiffness. 相似文献
82.
Gerhard Tutz 《Biometrical journal. Biometrische Zeitschrift》1991,33(5):519-527
Direct kernels, due to LAUDER (1983), as an alternative to the indirect kernel method in discriminant analysis are considered. It is shown that direct kernels may be based on any kernel function known in discrete density estimation. The choice of smoothing parameters is based on general loss functions and a family of loss functions which are specific for the discrimination problem is introduced. Examples with distance dependent and distance independent smoothing parameters are given to illustrate the applicability. 相似文献
83.
Teppei Ikeya David Ban Donghan Lee Yutaka Ito Koichi Kato Christian Griesinger 《Biochimica et Biophysica Acta (BBA)/General Subjects》2018,1862(2):287-306
Background
To understand the mechanisms related to the ‘dynamical ordering’ of macromolecules and biological systems, it is crucial to monitor, in detail, molecular interactions and their dynamics across multiple timescales. Solution nuclear magnetic resonance (NMR) spectroscopy is an ideal tool that can investigate biophysical events at the atomic level, in near-physiological buffer solutions, or even inside cells.Scope of review
In the past several decades, progress in solution NMR has significantly contributed to the elucidation of three-dimensional structures, the understanding of conformational motions, and the underlying thermodynamic and kinetic properties of biomacromolecules. This review discusses recent methodological development of NMR, their applications and some of the remaining challenges.Major conclusions
Although a major drawback of NMR is its difficulty in studying the dynamical ordering of larger biomolecular systems, current technologies have achieved considerable success in the structural analysis of substantially large proteins and biomolecular complexes over 1 MDa and have characterised a wide range of timescales across which biomolecular motion exists. While NMR is well suited to obtain local structure information in detail, it contributes valuable and unique information within hybrid approaches that combine complementary methodologies, including solution scattering and microscopic techniques.General significance
For living systems, the dynamic assembly and disassembly of macromolecular complexes is of utmost importance for cellular homeostasis and, if dysregulated, implied in human disease. It is thus instructive for the advancement of the study of the dynamical ordering to discuss the potential possibilities of solution NMR spectroscopy and its applications. This article is part of a Special Issue entitled “Biophysical Exploration of Dynamical Ordering of Biomolecular Systems” edited by Dr. Koichi Kato. 相似文献84.
An increase in urban population and the reduced number of suitable lands for construction projects have necessitated the need for ground improvement methods with no environmentally detrimental effects. Microbial-induced calcite precipitation (MICP) is a relatively environmentally friendly method for soil regeneration. In the present paper, X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses were performed to investigate the type and method of cement formation in loose quartz sand with different densities stabilized using bacteria. The results showed that the highest content of calcium carbonate cement was produced in the sample with the lowest density. Moreover, after microbial stabilization, the shear strength measured in the direct shear test was increased in the specimen with a lower density. We observed an increase in shear strength from 0.63 kg/cm2 before injection for loose sand (γ = 1.5 g/cm3) to 3.92 kg/cm2 after injection. In addition, the effect of injection time was investigated and found that shear strength in the two-stage injection per day is greater than that in one- and three-stage injections per day. With prolonging the injection time from one to five days, shear strength was significantly increased from 2.07 to 4.54 kg/cm2. Furthermore, prolonging the bacterial treatment period led to a significant increase in the produced carbonate cement and, consequently, enhanced soil shear strength. 相似文献
85.
火炬松成熟合子胚培养直接器官发生和植株再生 总被引:11,自引:0,他引:11
基因型Hb,Ma和Mc的火炬松成熟合子胚在附加1.0mg/LNAA,4.0mg/LBA,500mg/LLH和500mg/L谷氨酰胺的TE培养基上培养12周后,在子叶和胚轴部位形成不定芽原基。然后将合子胚转移到附加0.5mg//LNAA,0.05mg/LIBA,2mg/LBA,500mg/LLH和500mg/L谷氨酰胺的TE不定芽分化培养基上,6周后分化产生大量不定芽,3种基因型中,Hb的直接不定芽 相似文献
86.
赵世民 徐金相 刘根齐 刘承宪 李雪梅ZHAO Shi-Min XU Jin-Xiang LIU Gen-Qi LIU Cheng-Xian li Xue-Mei 《遗传》1997,19(6):18-20
在较长的时间内,可保持正常生理状态与细胞活性的原生质体的制备及保存技术是进行空间细胞融合实验的前提条件。本研究以0.7ml/L的葡萄糖作渗透压,在6-8℃低温条件下经过72小时保存后,供试原生质体的存活率仍可达81%,并保持了其长壁与分裂的特性。
Abstract:Storage duration and acativity of isolated protoplasts are important problem for experiment on plant cell fusion in space.We have achieved preliminary success using glucose as osmotic reagent,The survival protopasts after 72 hour storage in 0.7mol/L glucose at 6~8℃ reached 81% and maintained a very high activity of division. 相似文献
87.
The influence of salt and nitrogen on herbivore abundance: direct and indirect effects 总被引:4,自引:0,他引:4
We report on the influence of experimentally increased interstitial salinity and plant nitrogen on the abundance of the delphacid
planthopper, Prokelisia marginata (Van Duzee) (Homoptera: Delphacidae), which feeds on salt marsh cordgrass, Spartina alterniflora. We also report the effects of these treatments on parasitism of P. marginata eggs by the fairyfly parasitoid, Anagrus sophiae (Hymenoptera: Mymaridae). Soil salinity was significantly elevated following the addition of salt pellets broadcast over
the ground and plant foliar nitrogen was significantly increased after the addition of fertilizer. The addition of fertilizer
increased P. marginata densities on Spartina but addition of salt did not. Neither treatment significantly affected levels of egg parasitism by A. sophiae. In this system direct effects of plants on their herbivores via changes in plant chemistry appear more important than indirect
effects of plants on herbivores via their natural enemies.
Received: 1 August 1997 / Accepted: 29 September 1997 相似文献
88.
In the 3- to 4-day embryonic avian limb bud, a unique zone of mesodermal tissue is located posteriorly at the junction of bud and body wall. Appropriately grafted to a host limb bud, it induces the formation of a supernumerary limb outgrowth from preaxial tissue and determines that its posterior side will face the graft. It is called the zone of polarizing activity (ZPA).When limb-bud mesoderm is isolated, dissociated, reaggregated centrifugally, jacketed in the mesoderm-free hull of another limb bud, and grown as a graft on a host embryo, the recombinant frequently forms a limb-like structure terminating in digits that fail to show differentiation with respect to the anteroposterior axis. When, however, a bit of ZPA tissue is implanted in the recombinant subjacent to the anterior or posterior margin of the ectoderm, the resulting outgrowth shows a characteristic anteroposterior order of digits that corresponds to the placement of the implant, regardless of its relationship with the anteroposterior axis of the ectoderm or of the host embryo.Dorsoventral differentials have been recognized only in limbs formed from reaggregated leg-bud mesoderm. The direction of the dorsoventral axis always corresponds to the original axis of the ectodermal jacket regardless of the orientation of the recombinant on the host. 相似文献
89.
Ludivina Avila Marc Wirtz Richard A. Bunce Mario Rivera 《Journal of biological inorganic chemistry》1999,4(5):664-674
The gene coding for putidaredoxin has been synthesized using a combination of chemical and enzymatic methods and subsequently
expressed in Escherichia coli. The recombinant protein characterized by electronic spectroscopy, mass spectrometry, and electrochemistry was found to be
identical to putidaredoxin obtained from Pseudomonas putida. Polylysine was found to promote the fast and reversible electrochemistry of putidaredoxin at negatively charged electrodes
such as indium-doped tin oxide or gold surfaces modified with mercaptoalkanoate groups. The value of the heterogeneous electron
transfer rate constant obtained from solutions containing a mixture of putidaredoxin and polylysine (k
s
=1.3×10–3 cm/s) is one order of magnitude larger than the values reported previously at gold electrodes modified with mercaptoethylamine
or at antimony-doped tin oxide semiconductor electrodes. It was observed that when the reduction potential of putidaredoxin
is measured by cyclic voltammetry, the resultant value is consistently more positive (64 mV) than the reduction potential
measured with potentiometric titrations. A comparison between the electrochemical responses of putidaredoxin and spinach ferredoxin,
combined with the examination of their corresponding three-dimensional structures, indicates that the positive shift in the
reduction potential of putidaredoxin originates from the formation of a transient complex between putidaredoxin and polylysine
at the electrode surface. The formation of this transient complex modulates the reduction potential of putidaredoxin by lowering
the value of the dielectric constant around its iron-sulfur cluster microenvironment, specifically by neutralizing negative
charges surrounding the active site and by excluding water from the solvent exposed iron sulfur cluster. The observed positive
shift in E°′, which is induced by complexation with polylysine at the electrode-surface, suggests that similar factors are
likely to contribute to the anodic shift in the E°′ of cytochrome P450cam-bound putidaredoxin (+44 mV) with respect to the E°′ measured for free putidaredoxin.
Received: 14 June 1999 / Accepted: 6 August 1999 相似文献
90.
Fabrizio Briganti Demetrio Randazzo Andrea Scozzafava Debora Berti Piero Baglioni Patrizia Di Gennaro Enrica Galli Giuseppina Bestetti 《Journal of Molecular Catalysis .B, Enzymatic》1999,7(5-6):263-272
The whole cell biological conversion of naphthalene to (+)-cis-(1R,2S)-dihydroxy-1,2-dihydronaphthalene by the E. coli JM109(pPS1778) recombinant strain carrying the naphthalene dioxygenase and regulatory genes cloned from Pseudomonas fluorescens N3 in micellar systems has been investigated using biochemical and chemico-physical techniques. Reverse and direct micellar systems have been tested. Non-ionic surfactants (Tween and Triton X series) were found not to inhibit either the growth of the bacteria and the expression of the hydroxylating dioxygenase enzyme in such systems and were utilized in order to speed up the naphthalene conversion by increasing its solubility and also its bioavailability. The phase behavior of the direct micellar system was characterized through light scattering and other chemico-physical techniques. Further addition of isopropyl-palmitate 1–2% v/v to the micellar systems resulted in an increase of the apparent substrate concentration in solution and particularly its bioavailability thus allowing faster catalytic conversions resulting in an increase in productivity for the process. Since the cis-dihydrodiols are acquiring considerable potential as chiral pool synthons in asymmetric synthesis for a variety of industrial processes, possible applications for efficient small and large-scale production of such compounds are discussed. 相似文献