The Fourier inversion method recently introduced to the EXAFS analyses has enabled to give the information on the local atomic arrangement around the absorbing atoms. This method, complimentary to the traditional X-ray structure analysis one, has proved to be very useful to get information about the local structure in both amorphous and crystalline materials.
The present review mainly describes the followings: 1) Why is EXAFS observed?
2) Why is the new method of analysis effective? 3) How to analyze the data? 4) What are the remaining difficulties? 5) What are variational methods?
In view of the fact that synchrotron radiation sources with an intensive continuous X-ray spectrum soon become popular, the above method will be widely used in various fields including biophysics.

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In the near future, powerful X-ray source (Synchrotron Orbital Radiation, SOR) will be available at National Laboratory for High Energy Physics (Tsukuba). One of the most promising researches using SOR system is its application to biomedical problems. The objective of this report is to review the EXAFS studies on biological system. EXAFS can probe the local structure just around the X-ray absorbing atom. In this paper we describe the analysis of EXAFS spectrum of iron atom in rubredoxin, one of the simplest metalloproteins, and then we summarize the results of structural analysis on various metallo-proteins and enzymes such as nitrogenase, cytochrome P-450, hemoglobin, cytochrome c oxidase and so on.

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Giant transitory excitation, as is familiar in nerve impulse propagation, is derived from a simple thermokinetic model. Excitations of all-or-none type, the graded type, and also the repetitive pulsing have been derived from a single model depending on the value of control parameter. The temperature, or the concentration of enetgy is included as an independent reference variable which is affected by the reaction heat. The rate of reaction is affected in turn by the temperature through Arrhenius' formula. The strong nonlinearity involved in the Arrhenius' formula leads to a multiple steady state which is connected with the existence of a threshold for the excitation. The dynamic large excursion along an almost closed path in phase space is related to the existence of a nearby limit cycle, which is generated by an inverted bifurcation. Thus the interplay of the soft-and hard-mode instabilities is shown to form the background of the giant transitory excitation.
The transition into repetitive pulsing is also investigated from the point of view of fluctuation which reflects the difference between normal and inverted bifurcation.

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Three main approaches are commonly used in dectecting axonal transport; (a) accumulation of substances in dammed nerves; (b) direct observation of the movement of organelles in nerves; and (c) transport of radioactive substances along nerves. Most phenomena of axonal transport are classified into three types; (a) slow anterograde; (b) fast anterograde; (c) fast retrograde. phases. Pressure injection technique to introduce radioactive substances into some exceptionally large cell bodies in Aplysia neurones is useful because the study of transmitter specificity can be realyzed in an identified neurone. Some hypothetical models of axonal transport machinery were introduced. Recent progress of axonal transport was described from biophysical point of view. One is application of modern radiation detectors for measurement of tracer profiles in neurones, such as semiconducter detector and multiwire proportional chamber. The second is artificial cell model such as skinned axon and introduction of artificial panticles which simulate transported vesicles. The third is theoretical studies of axonal transport; time dependent tracer profiles were simulated by using a digital computer. Some physiological significance of axonal transport was also discussed.

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