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91.
Zusammenfassung Um der oft gehörten Meinung entgegenzutreten, die energetischen Wirkungsgrade lebender Organismen seien wesentlich höher als die technischer Verfahren, werden entsprechende Werte miteinander verglichen. Der sehr niedrige Wirkungsgrad der Photosynthese zusammen mit der kleinen Energiedichte der Sonnenstrahlung erzwang ab einer kritischen Größe die Aufspaltung in Energiesammler, die Pflanzen, und Verbraucher chemischer Energie, den Tieren. Dank den 10 mal höheren Wirkungsgraden in der Technik, lassen sich Solarmobile bauen, die von der auf sie fallenden Sonnenstrahlung angetrieben werden. Wegen des Multiplikationsgesetzes der Teilwirkungsgrade ergeben sich sowohl für die Speicherung der Sonnenenergie in den fossilen Brennstoffen wie in der Nahrungskette extrem niedrige Wirkungsgrade.
Herrn Prof. Dr.-Ing. U. Grigull zum 75. Geburtstag gewidmet 相似文献
Efficiencies in the world of life and in engineering
One often hears the opinion, that the efficiencies in the world of life are higher than in engineering. To disprove this, many values of efficiency of corresponding processes are compared. The very low efficiency of photosynthesis in living plants together with the low density of solar radiation has led the world of life to split into collectors of energy, the plants, and consumers of chemical energy, the animals. Thanks to the ten times higher efficiencies of solar cells, it is possible, to produce solar mobiles, vehicles that move driven by solar radiation.
Herrn Prof. Dr.-Ing. U. Grigull zum 75. Geburtstag gewidmet 相似文献
92.
Peter Šemrl 《Aequationes Mathematicae》1986,31(1):184-190
LetX be a leftA-module, whereA is either a complex Banach *-algebra with an identity element or the field of quaternions. The main result of this note is that forQ, anA-quadratic functional defined onX, there exists a sesquilinear functionalB such thatB(x,x)=Q(x) holds for allxX. 相似文献
93.
Summary Nearest neighbour random walks on the homogeneous tree representing a free group withs generators (2s) are investigated. By use of generating functions and their analytic properties a local limit theorem is derived. A study of the harmonic functions corresponding to the random walk leads to properties that characterize ther-harmonic function connected with the local limits. 相似文献
94.
LetG be a graph andr a cardinal number. Extending the theorem of J. Folkman we show that if eitherr or clG are finite then there existsH with clH = clG andH (G)
r
1
. Answering a question of A. Hajnal we show that countably universal graphU
3 satisfiesU
3 (U3)
r
1
for every finiter. 相似文献
95.
Peter Schmitt 《Geometriae Dedicata》1986,21(2):123-144
Summary For every k2 and r1 there exists a set of k prototiles that admits exactly r distinct tilings. All the tilings obtained are periodic. 相似文献
96.
Dr. F. C. Goodrich 《Colloid and polymer science》1967,219(2):156-159
Summary Under steady state conditions the reduction in the diffusive flux into a sphere due the presence of a neighboring, identical sphere is calculated. Taking the flux into a sphere as 1 when the particles are at infinite separation, the flux decreases to a minimum value of 0.693 when the spheres are touching.
With 2 figures 相似文献
Zusammenfassung Unter stationären Bedingungen wird die Abnahme des Diffusionsflusses in eine Kugel, bedingt durch eine benachbarte identische Kugel, berechnet.Wird der Diffusionsfluß in eine Kugel gleich 1 gesetzt, wenn die Partikel unendlich weit voneinander entfernt sind, so nimmt der Diffusionsfluß auf einen Minimalwert von 0,693 ab, wenn sich die Kugeln berühren.
With 2 figures 相似文献
97.
Dr. H. Demel Dipl.-Ing H. J. Grießer Prof. Dr. K. Hummel 《Colloid and polymer science》1977,255(11):1131-1132
Ohne ZusammenfassungMit 1 Abbildung und 1 Tabelle 相似文献
98.
Dr. Ulrich Mayer 《Monatshefte für Chemie / Chemical Monthly》1978,109(2):421-433
A model has been developed for calculating the enthalpy, entropy and free energy change associated with the creation of cavities in a liquid the size of which corresponds to the volume occupied by a solvent molecule. The molar enthalpy change H
cav equals the molar enthalpy of vaporization of the liquid, the free energy change G
cav is given by G
cav=–RT ln (V
m
·p
eq
/RT) (V
m
=molar volume,p
eq
=equilibrium vapor pressure) and is related to the standard free energy of vaporization. This relationship provides an estimate of the free energy of cavity formation required to accomodate a substrate in the liquid. It has been shown, that the free energy of solvation of a substrate can be dissected into different contributions accounting for (1) the concentration dependence of partial molar free energy quantities, (2) the formation of holes in the solvent, (3) the existence of specific, short range solute-solvent interactions and (4) the dielectric polarization of the medium. Application of this concept leads to an equation of the general form G
S
–G
R
=a(DN
S
–DN
R
)+b(AN
S
–AN
R
)+c(G
vp
oS
–G
vp
oR
), where G represents the free energy of reaction or activation,DN the donor number,AN the acceptor number and G
vp
o
the standard free energy of vaporization of a solventS and a reference solventR, resp.
Mit 3 Abbildungen 相似文献
Mit 3 Abbildungen 相似文献
99.
Seeberger PH 《Chemical communications (Cambridge, England)》2003,(10):1115-1121
This feature article describes the development of the first automated solid-phase oligosaccharide synthesizer. A series of chemical challenges had to be addressed to accomplish this breakthrough and provide rapid access to oligosaccharides of biological significance. Accelerated synthesis of glycoconjugates promises to greatly impact the emerging field of glycobiology. Chemical glycomics uses synthetic carbohydrates and analogs to study their role in recognition, signal transduction pathways and other events of fundamental biomedical significance and shapes up to become the next major wave in biomedical research. The automated synthesis of a novel malaria vaccine candidate is discussed to illustrate the medical potential of chemical glycomics. 相似文献
100.
[reaction: see text] Hydrozirconation of alkynes followed by in situ transmetalation to dimethylzinc and 1,2-addition to activated ketones and N-diphenylphosphinoylimines leads to tertiary allylic alcohols and amines in high overall yield. With 8-phenylmenthol as the chiral auxiliary, si-face attack proceeds in good to excellent diastereoselectivities. 相似文献