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To identify the cytosolic proteins of rat hepatocytes involved in transcellular transport of sulfated and taurine-conjugated bile salts in comparison with only taurine-conjugated bile salts, photoaffinity labeling studies were performed with [3H]-7,7-ASLCT (7,7-azi-3 alpha-sulfatolithocholyl[2'-3H(N)]taurine), [3H]-7,7-ACT ((7,7-azi-3 alpha,12 alpha-dihydroxy-5 beta-cholan-24-oyl)- 2'-[2'-3H(N)]aminoethanesulfonate), and [3H]-7,7-ALCT (7,7-azilithocholyl[2'-3H(N)]taurine) using isolated hepatocytes and intact liver tissue. Photoaffinity labeling of isolated hepatocytes with [3H]-7,7-ASLCT on the one hand and with [3H]-7,7-ACT and [3H]-7,7-ALCT on the other resulted in a different labeling pattern of cytosolic polypeptides, without a relevant incorporation of radioactivity into subunits of glutathione transferases. This suggests that glutathione transferases play no role in the transport of dianionic or of monoanionic bile salts. With [3H]-7,7-ACT and [3H]-7,7-ALCT a moderate incorporation of radioactivity was found in polypeptides with apparent M(r)s of 33,000, 38,000, and 54,000, whereas with [3H]-7,7-ASLCT, a polypeptide with an apparent M(r) of 14,000, identified as H-FABP, was markedly and almost exclusively labeled. Photoaffinity labeling of specimens of intact liver tissue resulted in a labeling pattern of cytosolic polypeptides comparable to that obtained from photolabeled isolated hepatocytes. All results suggest that transcellular transport of dianionic sulfated as well as taurine-conjugated bile salts and of monoanionic taurine-conjugated bile salts follows different pathways. In intracellular transport of taurine-conjugated bile salts, several cytosolic polypeptides may have a function, whereas, in transport of taurine-conjugated 3 alpha-sulfato bile salts, only H-FABP appears to be involved.

For the identification of proteins involved in hepatobiliary transport, the photolabile derivative 7,7-ASLCT ((7,7-azi-3 alpha-sulfato-5 beta-cholan-24-oyl)-2'-aminoethanesulfonate) was synthesized. 7,7-ASLCT is taken up into liver and excreted into bile completely unmetabolized at a rate between the excretion rate of SLCT ((3 alpha-sulfato-5 beta-cholan-24-oyl)-2'- aminoethanesulfonate) and SCCT ((7 alpha-hydroxy-3 alpha-sulfato-5 beta- cholan-24-oyl)-2'-aminoethanesulfonate). The dependency of flux rate of uptake into freshly isolated hepatocytes on the concentration of 7,7-ASLCT in presence of Na+ (143 mM) and with Na+ depletion (1 mM) is best described by the assumption of two simple transport systems, the kinetic parameters of which are similar to those of SLCT. As studied in the presence of Na+, 7,7-ASLCT and SLCT exhibit a clearly competitive cross-inhibition of uptake with inhibition constants that are similar to the corresponding half-saturation constants. Photoaffinity labeling of isolated hepatocytes using 7,7-ASLCT (400 microM) resulted in the irreversible inhibition of the uptake of 7,7-ASLCT and SLCT to similar extents, confirming the kinetic data that 7,7-ASLCT is a true competing substrate for the uptake of SLCT. Because in intact rat liver 7,7-ASLCT and SLCT mutually inhibit their biliary excretion, the photolabile derivative shares with SLCT the same pathways in uptake and in excretion. Thus, 7,7-ASLCT should be appropriate for the study of hepatobiliary transport of sulfated and taurine-conjugated bile salts by photoaffinity labeling.

During my active career as the head of the Max-Planck-Institute for Aeronomy, I had many occasions of a most fruitful cooperation with Sir Granville Beynon. I remember three of them especially well.

HF and VHF backscatter measurements carried out in Northern Germany and Scandinavia (φ = 55°–70°) from 1963–1971 were analysed and are now presented comprehensively. The daily and seasonal frequency distributions of auroral backscatter echoes are derived as well as the correlation between auroral occurrences and geomagnetic disturbances and the dependence of the echo amplitude on geomagnetic latitude. By means of a calculated equivalent current system the relation between the backscatter occurrences at different stations and the extension and strength of the polar electrojet have been investigated. All observed events when combined in a synoptic graph as a function of time and geomagnetic latitude show a spiral type structure. In addition to auroral backscatter results the daily and seasonal variation of Es -scatter and 2 × F 2 ground backscatter events are presented.

If one is asked to contribute an historical account on the occasion of an anniversary, as I see it there are two possible approaches: either to give a survey of the facts as completely as possible or to base the contribution on personal recollections which is of course much more subjective and somewhat more lively. The former I have tried to do in my written contribution to the 50th Anniversary of the Discovery of the Ionosphere in J. appl. terr. Phys , and in this paper I should like to attempt the second approach. When Appleton made his famous discovery, I was still a schoolboy but nevertheless already interested in radio propagation and what was then called the Heaviside layer. Having been a broadcast listener since 1924, and a real ‘ham ’ since 1925, I had experienced the queer propagation phenomena that occurs on medium and short waves. When I entered the Technical University at Munich in 1926, I soon became confronted in Zenneck’s institute with the literature on this new field of physics. By good fortune, Zenneck was editor of the periodical that was then called Jahrbuch der drahtlosen Telegraphie and his abstracts of the pertinent publication in the Proc. Inst Radio Engrs, Proc. R. Soc. Lond . A and The Electrician , were famous for their conciseness and clarity. Having been educated at a Bavarian humanistic Gymnasium, I had learnt Latin, Greek and French, but no English, and for this reason Zenneck’s abstracts were very helpful to me.

A review of the recent work on scattering draws attention to a number of discrepancies in the interpretation of the data. Most workers believe that the scattering is due to clouds in the E layer. The experiments described in this paper indicate that there are several types of scattering phenomena. It is concluded that the most common source of scatter is the reflection of waves from irregularities on the surface of the earth. In this case the wave path is from the sender of F layer - earth - F layer and hence to receiver, i e. is analogous to a 2×F reflection. The characteristics of the different types of scattering and their effects on the propagation of short waves are discussed.

A new-style beacon experiment for measuring the difference-differential-Doppler (DDD) effect and the Faraday effect by using signals from geostationary satellites is proposed. By using the beacon frequencies of a geostationary satellite with frequency ranges ≥ 130 MHz, it can be shown that above 5000 km the upper atmosphere does not contribute measurably to the Faraday rotation angle. This is due to the weighting function of the earth's magnetic field and the decrease in electron content with increasing altitude. The socalled differential Doppler is not affected by the above-mentioned weighting function, and therefore ∫Nds is measurable along the total range up to 36,000 km, which is the distance of the geostationary satellite. In general, the Faraday rotation and the differential Doppler only display the variation of ∫Nds as a function of time; e.g., the total amount of ∫Nds is not known. By measuring the Faraday rotation on two closely spaced frequencies, however, one can calculate the total amount of ∫Nds up to about 5000 km. This experiment was designed so that the DDD effect and the Faraday effect could be measured on two closely spaced frequencies. To measure the total electron content (TEC) up to 36,000 km, the following new method (DDD) is proposed: Over a time interval of approximately 4 minutes, the beacon frequency of 138 MHz is slowly shifted to 137.5 MHz and then slowly back to 138 MHz; simultaneously, the frequency 414 MHz is shifted to 412.5 MHz and back to 414 MHz. By designing an appropriate phase-locked receiving system, it seems possible to measure the so-called difference-differential Doppler with an accuracy of better than 5%, e.g., to calculate the total amount of ∫Nds from 0 to 36,000 km. No other known method can achieve such an accuracy. The effective radiated power of the satellite antenna never exceeds 1 watt. Taking into account navigation systems, ∫Nds represents, apart from a constant well-known factor, the total range error that is due to the ionosphere and magnetosphere. Measurements of the Faraday effect and differential-Doppler effect (137.350 and 412.050 MHz) with signals from the ATS-3 satellite displayed very sensitively traveling ionospheric disturbances (TID) at our observing station in Lindau. By using several reasonably located observing stations, dynamic processes (TID) in the upper atmosphere might be easily investigated. Regardless of whether it will be possible to determine accurately the exospheric electron content and whether this proposal will be accepted, there is an absolute necessity for any measuring method that yields ∫Nds with a much higher accuracy than can be determined by the presently used methods. The determination of ∫Nds is required with at least the above-mentioned accuracy for any thorough investigation of so-called occultation experiments. Comparisons with other methods in use for calculating ∫Nds are presented, e.g., regular group-delay measurements. The proposed method seems to yield the most accurate measurements possible for these particular experiments. It is very likely that from a technical point of view the accuracy is greater than can be obtained with the group-delay methods now used. From a theoretical point of view, however, the degrees of accuracy obtained by the two methods are comparable.

I t is well known tha t radio p ropaga t ion conditions over any distance m a y be deduced f rom the results of observ-ations a t vert ical incidence b y s imple calculations [1-2]. However , these calculations imply some assumptions, which are not complete ly certain and, perhaps as a result of those assumptions, the observat ions of radio communica t ion conditions do not complete ly agree wi th the calculations. Therefore it seems more desirable to compare radio communica t ion condit ions with direct observat ions of the different modes of propagation. Perhaps the mos t efficient sys tem to achieve this t ask is to use the pulse me thod not ~t vert ical incidence bu t to observe the pulses b y a receiver in the wanted distance f rom the t ransmi t te r . Expe r imen t s of t h a t k ind on fixed frequencies were carried out all over the globe and gave valuable informat ion about pa ths of propagat ion. Much more in format ion m a y be obta ined b y using the sweep f requency m e t hod be tween the sender ~nd a r emote receiver. A few exper iments of tha.t n~ture were carried out in Canada, Grea t ]~ritMn, Japan , USA and Germany , and some results were published recent ly [3-6]. The scarcity of those exper iments is caused wi thout ~ny doubt b y the technical difficulties of synchronisat ion between the t runsmi t te r und the receiver.

Using a typical example it is demonstrated that geostationary beacon-satellites are a useful means for recording the influence of gravity waves on the total electron content Nt of the ionosphere. By differentiation of Nt with respect to time the gravity waves become clearly visible expecially during those parts of the Nt-record with steep increases or decreases which obscure the effect of gravity waves.

By using the beacon frequencies of a geostationary satellite with frequency ranges > 130 MHz it can be shown that above 5000 km the upper atmosphere does not contribute measurably to the Faraday rotation angle. This is due to the weighting of the Earth's magnetic field and the decrease in electron content with increasing altitude. The so called differential Doppler is not affected by the above mentioned weighting function and therefore ∝ N ds is measurable along the total range up to 36,000 km—the distance of the geostationary satellite. In order to measure the total electron content up to 36,000 km a new method is proposed.

Im ersten Kapitel werden einige technische Probleme der Impulserzeugung, des Impulsempfangs und der Impulsregistrierung besprochen, soweit sie fur die Impulstechnik der Ionospharenforschung charakteristisch sind. Im zweiten Kapitel wird auf die Anwendung der Impulstechnik in der Ionospharenforschung eingegangen. In beiden Kapiteln sollen gewisse Grundtatsachen als bekannt vorausgesetzt werden, so das Prinzip der Abstandsbestimmung mit Hilfe des Echolaufzeitverfahrens, die Zusammenhange zwischen Impulsdauer, Bandbreite des Impulsspektrums und Genauigkeit der Abstandsbestimmung sowie die Zusammenhange zwischen Impulsfolgefrequenz und maximalem Abstandsmesbereich.

Observations of auroral effects on the ionosphere over Finland on Dec. 3, 1961, are reported. The daily height variations of weak, low echos (D) appearing on ionograms were studied at 70 to 90 km. (R.E.U.)

Fieldstrength records on 2.8 Mc/s between Sardinia and Italy have shown that the winter anomaly of ionospheric absorption still exists at 40° northern latitude but is less pronounced and of shorter duration than at 52°N.