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We present the status of an ongoing study for a high-resolution near-infrared echelle spectrograph for the 10.4-m GTC (Gran Telescopio de Canarias) which will soon start operating at the Observatorio del Roque de los Muchachos on the island of La Palma. The main science driver of this instrument, which we have baptized NAHUAL, is to carry out a high precision radial velocity survey of exoplanets around ultracool dwarfs. NAHUAL is being especially designed to achieve the highest possible accuracy for radial velocity measurements. The goal is to reach an accuracy of a few m/s. It is thus required that the instrument is cross-dispersed and that it covers simultaneously a wide wavelength range. Absorption cells will be placed in front of the slit which will allow a simultaneous self-reference similar to an iodine-cell in the optical regime. It is planned to place the instrument at one of the Nasmyth platform of the GTC behind the Adaptive Optics system. Our current design reaches a maximum spectral resolution of λ/Δλ = 50000 with a slit width of 0.175 arcsec, and gives nearly complete spectral coverage from 900 to 2400 nm. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The desire of astronomers for wide field telescope systems which surpass the RCC (1:8 max. 1.5 degree) in light gathering power and field of view are relative concrete today. For this type of telescope, detectors planned ARE CCDs in multichip arrangement.

We present an empirical model of global exospheric temperatures and densities of neutral constituents, based on data from 228 geomagnetically quiet days during the operation of the Esro 4 gas analyzer (mean Ap = 7). By means of an expansion in spherical harmonics the model infers exospheric temperatures from both the measured N2 and Ar densities. O and He densities are presented as extrapolated density distributions at 120 km altitude. The Esro 4 model complements the similar Ogo 6 mass spectrometer model with observations at considerably lower altitudes (240-320 km) and lower levels of solar activity Inferred exospheric temperatures are typically 5-9% below Ogo 6 model values for F10.7 = 120.

Molecular oxygen and nitrogen number densities in the altitude range 115–220 km above Sardinia were measured in two sounding rocket experiments (Esro payloads S84 and S90) in February 1972 by a combination of UV monochromators and mass spectrometers. The measured values agree closely with the Cira (1972) values for the 120-km altitude region. At higher altitudes the O2 profiles measured by UV monochromators indicate deviations from diffusive equilibrium with respect to the N2 profile measured by the mass spectrometers.

Neutral atmospheric composition measurements were obtained by the Esro 4 gas analyzer during a series of geomagnetic storms in late February 1973. Complemented by ground-based ionosonde data, these measurements show a complex latitudinal and longitudinal structure of the storm-associated disturbances in the upper atmosphere. Specifically, a strong depression of the O/N2 ratio developed and persisted for several consecutive days above the Australian-African area. It was distinguished by a fairly sharp eastward boundary near 180°E longitude. This mid-latitude disturbance zone was distinctly separated from strongly disturbed regions at higher latitudes. It is suggested that the energy causing this mid-latitude disturbance was deposited primarily at altitudes below 150 km. Because of the long diffusion time constants in the lower thermosphere this can account for the persistence of the phenomena observed at F2 layer heights.

Aufgrund umfangreicher Arbeiten, insbesondere von Hayreh (1969, 1975), wissen wir heute, das die Blutversorgung des Sehnervenkopfes fast ausschlieslich dem Ziliarkreis-lauf entspringt. Die Zirkulationsverhaltnisse in den kurzen hinteren Ziliararterien und im Aderhautkreislauf sind damit entscheidend wichtig fur die Deutung von Erkrankungen des Sehnervenkopfes wie Glaukoma chronicum simplex, insbesondere aber „Glaukom ohne Hochdruck“und Papillomalazie. Entsprechend zahlreich sind Veroffentlichungen, die sich mit Veranderungen des Fluores-zenzangiogrammes von Papille und Aderhaut bei diesen Erkrankungen befassen.

Maximal initial dye concentration in the retinal arteries is desirable for high quality fluorescein Angiograms and is essential for circulation studies. Such high initial dye concentrations can only be achieved by a very rapid fluorescein injection technique necessitating an automatic injector. A reliable easy to use "spring-injector" has been designed for clinical use (Figs. 1 and 2). A disposable syringe is driven by a spring contained in a metal cylinder. Microswitches are activated by the piston of the injector triggering one exposure each at the beginning and at the end of the injection. Time and duration of the injection are therby permanently documented on the film. The "Terumo Disposable Syringe 10 cc" is used routinely. By interposing a plastic connector between syringe and injector-piston the injection-volume can be reduced to 5 ml. With diffferent connectors one can inject an volume desired up to 10 ml. The duration of the injection can be varied by using different intravenous catheters. Routinely the "VYGON Trocaflex catheter Nr. 125.16" with a needle diameter of 1.1 mm and a length of 30 cm is used resulting in an injection time of 10 ml/1.0 sec or 5 ml/0.5 sec. The largest Trocaflex catheter (No. 125.20) will shorten the injection time to 10 ml/0.5 sec and 5 ml/0.25 sec respectively. Even faster injections can be achieved by shortening the catheter or by using a stronger spring. With the described injector, high-speed, well-standardized fluorescein injections are possible. The intravenous catheter makes parvenous injections impossible and will allow for repeated angiograms even on different days without the need for a new venous puncture.

Es gibt eine sehr umfangreiche Literatur uber die Zentralgefasverschlusse des Auges und dennoch kaum Untersuchungen, die sich mit den veranderten retinalen Zirkulationszeiten in diesen Fallen beschaftigen. Wegen der standig wechselnden allgemeinen Kreislaufdynamik lassen sich verlasliche Resultate nur aus dem Vergleich mit dem gesunden Partnerauge erzielen. Derartige Vergleichsmessungen sind mit Hilfe der synchronen Fluoreszenzangiographie beider Augen moglich geworden. Uber die mit dieser Methode erhaltenen Ergebnisse an Gesunden habe ich vor dieser Gesellschaft bereits berichtet (Laux 1975, 1977). In der vorliegenden Arbeit wurde bei 44 Patienten mit einseitigen arteriellen und venosen bzw. kombinierten Verschlussen — immer unter Bezug auf das gesunde Partnerauge — der Zeitpunkt der arteriellen Farbstoffanflutung und des fruhvenosen Ruckstromes jeweils am Papillenrand gemessen.

Large and complex heat pipe systems must be installed to thermally control the high dissipating repeater equipment of direct broadcasting TV-satellites, such as the TV-SAT/TDF-1 spacecrafts which are now under development. This paper aims to identify the extent of similarity between ground testing and O-g operation of such systems in terms of transport capability and temperature distribution. The investigation concentrates mainly on the performance limits due to gravitational forces during ground testing and is supported by a number of individual heat pipe tests. The results show that higher temperatures of the heat pipe and/or heat source must be expected during ground testing due to the following mechanism: layer of excess liquid in the condenser zone during adverse tilt operation, partial dry out of grooves in the heating zone (pronounced in cases with one-sided heat input) and pool boiling with a consequent overheating of the evaporator in reflux mode operation of straight heat pipes. The sharp decrease in transport capability in adverse tilt positions may be partially offset by the performance improvement due to excess liquid. However, assessment of this effect is marginal because the contribution of groove drainage to the excess liquid volume for different heat pipe configurations and operation modes is unknown.

A heat pipe flight experiment on SPAS 01 was performed in February 1984 to investigate the function of excess liquid within heat pipes. The pipes were to be used for the Franco-German direct broadcasting satellite TVSAT/TDF-1. The aim of the experiment was to prove the hypothesis that slug formation represents the more stable configuration contrary to film formation in 0-g conditions. Computer models had been developed to derive the slug formation from temperature distribution along the condenser zones. Described are the experimental setup, the test results, and the method used to derive the slug length from the available data.

Rapid-sequence fluorescein angiograms of 127 healthy eyes with cilioretinal arteries were analyzed with regard to the time of dye entry into the central retinal artery, the cilioretinal artery and the choroid. In younger patients up to age 49) the cilioretinal artery filled simultaneously just as often as prior to the central retinal artery (42.9% and 41.4%, respectively); only rarely (15.7%) was a later filling noticed. In older persons (50 years of age and older) this filling pattern was reversed. The cilioretinal artery most frequently filled later than the central retinal artery (48.7%) and only rarely prior to it (15.8%). Similar results were obtained when comparing the filling time of the central retinal artery with the first choroidal fluorescein. With increasing age the circulation in the choroid and the cilioretinal arteries slows down in comparison to the central retinal artery, due to sclerotic vessel changes which have been shown to be much more pronounced in the choroidal vessels than in the retinal vessels. These findings are important for the understanding of age-related diseases of the optic nerve head, which derives almost all its blood supply from the choroidal circulation.

Using a standardized technique of rapid fluorescein angiography applying a special diaphragm in the camera to reduce the patient stress by the frequent flashes and an automatic dye injection retinal circulation times of 173 healthy eyes were measured and statistically analysed. Circulation time was defined as the time interval between first visible arterial and venous fluorescence of corresponding vessels near the disc margin. The circulation time for the temporal vessels (1.1--1.2 s) was significantly faster than that of the nasal vessels (1.3 s) whereas there was no significant difference between the upper and lower main vessels. The very short circulation times are caused by short circuits near the disc. The difference between the shorter temporal and longer nasal times is caused by the macular circulation. It would therefore be more accurate to speak of peripapillary circulation times or of circulation times of the posterior pole of the fundus.

Investigations of the initial phase of the angiogram and measurements of retinal circulation times require a rapid sequence angiography. Although almost all of the available cameras allow for 2 or 3 exposures per second, such rapid sequence angiograms are not performed routinely. Especially the patient's stress from 2 or 3 flashes per second is considerable making these investigations very difficult. We have introduced 3 modifications of the regular technique of rapid sequence angiography that greatly facilitate the procedure so that large numbers of patients can easily be investigated in clinical routine. 1. The regular fixation target in the Zeiss fundus camera has been replaced by a special diaphragm (Fig. 1) which will exclude part of the fundus from exposure to light. This way pictures are taken only of the disc and the peripapillary area which are most important for circulation studies. After completion of the rapid sequence the diaphragm can easily be removed and further pictures taken of regular size. 2. The fluorescein is injected by means of an automatic injector (Fig. 2) in order to obtain a concentrated dye bolus. 3. The sequence of the angiogram is controlled by an electronic timer (Fig. 3 a and b). The photographer can thus fully concentrate on the camera adjustment without worrying about dye injection or triggering the camera. The perfect standardisation obtained will facilitate the measurement of different circulation parameters later on the film.

300 rabbit corneas were burned for 1 minute by applying a filter paper of 10 mm diameter soaked in different concentrations of NaOH. The aqueous humor pH was then measured at certain time intervals and after different treatment methods until the physiologic pH of 7.6 was reached. The results were statistically analysed. Group 1, 2 and 3 were burned in 1n NaOH, 3n NaOH, and 6n NaOH respectively without any treatment. In these groups a "therapeutic" pH-level of 8.5 was measured on an average 0.5, 2.5 and 5 hours after the burn (Table 1 and Fig. 2). Group 4 and 5 again were burned with 6n NaOH. In group 4 the burn was followed by constant irrigation with physiologic saline solution by means of the Morgan Therapeutic Lens (Fig. 1a and b). With this regimen a pH of 8.5 was reached after 2.5 hours (Table 1 and Fig. 3). In group 5 the physiologic saline solutions was replaced by a buffer solution (Isogutt) and a pH of 8.5 was measured after only one hour (Table 1 and Fig. 3). Based upon these results it is felt that severe lye burns should be treated by constant irrigation with a buffer solution for several hours. A treatment that can easily be performed by use of the Morgan Therapeutic Lens.

Der Film zeigt den Fall eines willkurlich auslosbaren Nystagmus. Es handelt sich um eine 26jahrige Frau, die niemals ernstlich krank war. Insbesondere bestehen keinerlei krankhafte Augenveranderungen. Sie hat auf beiden Augen immer gut gesehen und nie geschielt. Mit 12 Jahren hat sie eine Brille bekommen, die sie jedoch nur ein Jahr lang getragen hat. Seit dem 11. Lebensjahr ist sie imstande, einen willkurlichen Nystagmus bei sich auszulosen, ohne das sie angeben kann, wie sie dieses „Kunststuck“ erlernt hat oder „wie man es macht“. Sie hat das Zittern nur selten vorgefuhrt, da sie furchtete, die Augen konnten in einer abnormen Stellung stehen bleiben. Die einschlagige Familienanamnese ist negativ, die Patientin selbst hat nie an einem unwillkurlichen Augenzittern gelitten.

Es wurde die in der Abteilung fur Augenheilkunde der Universitat Ulm entwickelte Untersuchungseinheit zur simultanen Fluoreszenz-Angiographie beider Augen dargestellt (Abb. 1). Das Gerat besteht aus zwei Zeiss-Funduskameras mit je einem Schnellblitzgenerator. Die Kameras sind voll synchronisiert und mechanisch getrennt montiert, so das eine unabhangige Einstellung auf das jeweilige Patientenauge erfolgen kann. Die Einheit ermoglicht simultane Fluoreszenz-Angiogramme beider Augen mit einer Aufnahmefrequenz von 0,6 Sekunden. Der Farbstoff wird mit einer automatischen Injektionsspritze innerhalb einer Sekunde in die Kubitalvene eingespritzt. Bei Beginn der Injektion startet die automatische Spritze einen elektronischen Zeitgeber, der den weiteren Ablauf der Serie steuert.

Unilateral ligation of the common carotid artery was performed in rabbits. Before ligation, immediately thereafter, and 6 weeks later the ophthalmic artery pressure was determined and at the same time a synchronous measurement of the ear to retina time was done on both sides. The results were statistically analyzed (Tables 1-4). Ligation of the right common carotid artery resulted in a highly significant difference in systolic ophthalmic artery pressure between the two eyes of 16.4 mm Hg, and in diastolic pressure one of 13.0 mm Hg. After ligation of the left similar pressure differences of (systolic) 17.8 mm Hg and (diastolic) 15.2 mm Hg were shown. During the following 6 weeks these differences decreased considerably, to 41.5% and 29.2% after ligation on the right and to 33.5% and 36.6% after ligation on the left. The ear to retina time was markedly prolonged on the side of the ligation. This resulted in a highly significant side difference of 0.42 s immediately after ligation on the right common carotid artery and 0.4 s immediately after ligation on the left side. After 6 weeks these differences were only slightly reduced, to 80% and 72.7% respectively. These animal experiments demonstrate clearly that an acute occlusion of one common carotid artery in rabbits can easily be diagnosed by ophthalmodynamometry as well as by synchronous measurement of the ear to retina time. In chronic occlusions determination of the ear to retina time is superior to pressure measurement. This is of particular interest since in these experiments an ophthalmodynamometric method was used that is much superior to the clinical method of ophthalmodynamometry.

Rapid-sequence fluorescein angiography was performed simultaneously on both eyes of each of 241 healthy individuals in order to analyze and compare dye inflow patterns in the eyes of each subject. The many uncertainties of successive investigations resulting from uncontrollable changes in systemic circulation parameters between the two angiographies were thus eliminated. In over 90% of the subjects there was no difference between the two eyes in respect of arm-fundus time nor the filling pattern of choroid and retina. A few subjects did show a difference, but this lasted for only one exposure and was normalized on the second exposure of the sequence. It is therefore concluded that side differences of the fluorescein inflow pattern on simultaneous bilateral angiography are highly suggestive of unilateral circulatory disturbances in the cervical, retinal or choroidal vessel. Such disturbances are practically certain if side differences last for more than just one exposure. In contrast, the filling pattern in cilioretinal arteries was very variable and over one third of the subjects presented with side differences between their two eyes. Therefore the filling pattern of these vessels cannot be used for diagnostic purposes.

A case is presented with large anomalous retinal veins arising above the macula and running across it downwards, towards and into the inferior temporal vein. There was a decreased visual acuity which could not be accounted for. The literature dealing with this rare anomaly is discussed. This is the first case in which the vascular anomaly was associated with deuteranopia.

Measurements of N2, Ar, O, and He densities obtained by the gas analyzer on board the satellite Esro 4 indicate in both hemispheres a persistent longitudinal variation of thermospheric composition in middle and high latitudes. Increases of N2 and Ar densities are strongly correlated with a reduction of He and O densities. The amplitudes of the variations are higher in the southern hemisphere than in the northern hemisphere. Universal time variations are only weakly observed in polar latitudes. We present an empirical model, which describes the latitudinal dependence of longitudinal composition variations under quiet geomagnetic conditions.

To the Editor .–I would like to stress the fact that I had no knowledge of the work being done by Dutch authors on simultaneous bilateral fluorescein angiography (Archives95:1274-1280, 1977). Their method was apparently first shown at a scientific exhibition during the 22nd International Congress of Ophthalmology in Paris in May 1974 and in the same year their paper was read before the international meeting on fluorescein angiography in Leiden, The Netherlands. As I did not participate in either congress, I had no way of knowing about their work. My work was first reported at the International Symposium on Fluorescein Angiography in Ghent in March 1976. Apparently, this method has been simultaneously developed in The Netherlands and in Germany and neither one of the two groups knew of the other one.