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Although successful in the structural determination of ordered biomolecules, the spectroscopic investigation of oligopeptides in solution is hindered by their complex and rapidly changing conformational ensemble. The measured circular dichroism (CD) spectrum of an oligopeptide is an ensemble average over all microstates, severely limiting its interpretation, in contrast to ordered biomolecules. Spectral deconvolution methods to estimate the secondary structure contributions in the ensemble are still mostly based on databases of larger ordered proteins. Here, we establish how the interpretation of CD spectra of oligopeptides can be enhanced by the ability to compute the same observable from a set of atomic coordinates. Focusing on two representative oligopeptides featuring a known propensity toward an α-helical and β-hairpin motif, respectively, we compare and cross-validate the structural information coming from deconvolution of the experimental CD spectra, sequence-based de novo structure prediction, and molecular dynamics simulations based on enhanced sampling methods. We find that small conformational variations can give rise to significant changes in the CD signals. While for the simpler conformational landscape of the α-helical peptide de novo structure prediction can already give reasonable agreement with the experiment, an extended ensemble of conformers needs to be considered for the β-hairpin sequence.

The objectives of the present study were: (1) to evaluate the predicting value of the most important European soil P tests for P leaching losses; and (2) to investigate how these soil P tests reflect the development of P depth profiles in original homogeneous soils of lysimeters. The study included more than 100 lysimeters, located at the Lysimeter Station Falkenberg/Saxony-Anhalt, UFZ-Centre for Environmental Research Leipzig-Halle GmbH, Germany. Soil textures were sand, sandy loam, loam and silt. The management forms were arable land, grassland and fallow with various variation in fertilisation, crop rotation and irrigation. Samples were collected from the A-horizons and from the whole profiles of eight set-aside and dismantled lysimeters at 10-cm sections. The concentrations of total P were determined monthly in the leachates and evaluated for a three-year period. The concentrations of P extracted by ammonium acetate lactate (AL-P), double lactate (DL-P), sodium bicarbonate (Olsen-P) and ammonium oxalate (OX-P) as well as Ptwere significantly correlated with each other (P<0.05–P<0.001) for arable soils. The relevant regression coefficients were strongly influenced by soil texture, soil use and management. The mean annual P concentrations of the leachates were in the range 0.4–1.2 mg l−1for sands and <0.001–0.1 mg l−1for the textures sandy loam, loam and silt. These corresponded to P leaching losses of 0.001–2846 g ha−1yr−1. Mean annual and maximum P concentrations and leaching losses were significantly (r>0.954, P<0.001) predicted by the OX-P concentrations of arable topsoils in lysimeters filled with sand. For sandy loam under grass the agronomic soil P tests (AL-P, DL-P and Olsen-P) enabled reasonable predictions of P in leachate. Under arable use, factors such as fertilisation, management intensity, depth of tillage and irrigation resulted in weak correlations between soil P concentrations and P in leachate. It was shown for the first time that all P extractants reflected P enrichments in topsoils and subsoils and the development of distinct depth profiles. Influence of soil use on the depth distribution of P was more pronounced in the 0–20 cm layer than in the subsoils. Here, the original homogeneous substrate had oscillating P concentrations at 10-cm increments under all soil uses. These could not be explained by Aloxand Feoxbut were significantly correlated with the Ctcontents and bulk density. This indicates that vertical movement of P containing organic matter along with differences in porosity contributed to the heterogeneous P distribution in the lysimeter subsoils. This new evidence must be considered if data sets from long-term lysimeter experiments are used to calibrate and validate P leaching models.

3(S)-(6-Methoxypyridin-3-yl)-3-{2-oxo-3-[3-(5,6,7,8-tetrahydro-[1,8]-naphthyridin-2-yl)propyl]imidazolidin-1-yl}propionic acid 6 was identified as a potent and selective antagonist of the αvβ3 receptor. This compound has an excellent in vitro profile (IC50 = 0.08 nM), a significant unbound fraction in human plasma (12%), and good pharmacokinetics in rat, dog, and rhesus monkey. On the basis of the efficacy shown in three in vivo models of bone turnover, the compound was selected for clinical development. To support the ongoing metabolism and safety studies, a novel strategy was employed in which a series of oxidized derivatives of 6 were prepared by exposure of 6 (or the methyl ester) to chemical oxidizing agents. These products proved useful in the identification of active metabolites generated by either in vitro or in vivo metabolism.

Lysimeter trials carried out over several years showed that cutting mineral fertilizer by 50% does not immediately result in a reduction of the leaching losses of relevant macronutrients (N, P, K). Land usage changes in the form of 1‐year rotating set‐asides entail greater N‐leaching compared to best management practices (BMP). By contrast, after set‐aside lasting 3–5 years, reductions in N‐leaching of 25–45% must be expected. Lysimeter trials of reintegrating land set‐aside for a number of years into intensive agriculture without increasing N‐leaching losses are presented. Ways of scaling up lysimeter results to fields and small catchments are described, as well as areas where research still needs to be carried out are discussed. Copyright © 2002 John Wiley & Sons, Ltd.

—Reflectivity of the continental crust displays many different patterns. The DEKORP lines are used as a basis for comparing and reviewing reflectivity in different tectonic units. The (brittle) upper crust generally exhibits only two types of reflectivity. It is either rather "transparent," preferably in some extensional provinces, or/and it shows traces of thrust and shear zones of former or present ruptures. As these zones have a low impedance interior (with few exceptions), their first reflection onsets have a negative polarity and evince strong, but short signals, which sometimes can be correlated over several kilometers. The (generally ductile) lower crust displays a completely different reflectivity. In warm, extensional and thin crusts the lower part is full of reflecting lamellae. It is suggested that this type of reflectivity has a thermo-rheological origin. The creation of lamellae must take place in a ductile material with contrasting impedance under extensional stresses. It can be associated with mineral alignment and corresponding seismic anisotropy. Destruction of lamellae may take place by a cooling process, transforming parts of the lower crust into a brittle regime. Small stresses might deform or break the lamellae and leave a certain dispersed reflectivity like that in some old (and cold) shields. There are no observations of reflecting lamellae in the upper crust or in the upper mantle. In all areas the Moho is the last reflecting band (reflection Moho), which most often is identical with the classical refraction Moho. There are isolated, mostly dipping, reflections in the uppermost mantle in zones where the last tectonic event, a delamination or subduction, was not succeeded by a heating process. The uppermost mantle is brittle again in most areas and may keep the memory of a (cold) collision over billions of years.

A marine seismic reflection survey was carried out in 1996 by DEKORP, Potsdam, and BGR, Hannover in the SW Baltic Sea. Several tectonic lineaments were crossed nearly perpendicularly, for example, the Caledonian Deformation Front which is assumed to mark the northern boundary of the terrane Avalonia which accreted to Baltica ca. 400Ma. Here, a bivergent collision is clearly observed, confirming early ideas from the BABEL survey. The NE-dipping reflections in the uppermost mantle are interpreted as signs of the subducted Tornquist Ocean. A similar tectonic style of compression and indentation is observed in the Proterozoic crust northeast of Bornholm, where in addition a remarkable crustal thickening and a strong increase of reflection power is observed. The three DEKORP lines in this area provide a certain three-dimensional control and allows extension of similar observations from the BABEL line A southward. This Proterozoic terrane accretion seems to be connected to major tectonic lineaments in southern Sweden, either to the Gothian Thrust or the Sveconorwegian Front.

Based on the strong heat flow in the Archaean and Proterozoic a concept for dynamical processes is developed that agrees with observation of low and high pressure metamorphism in ensialic belt of the Precambrian in Scandinavia and other old shield areas. Heat release is considered to have taken place predominantly at fast spreading oceanic ridges, some of them certainly adjacent to continental margins. Thinner, warmer, lighter, and faster oceanic plates descended with very small dip below the continent, leading to an underplating, to a decrease of the continental thermal gradient, and to a compressive stress with the tendency to keep the growing Archaean supercontinent together. Ensialic belts may have partly been created by a shallow secondary back-arc creep pattern. The general decrease of heat production and heat release continuously slowed all creep processes. At around 1000 ± 300 Ma, oceanic plates must have reached critical values of thickness, weight, and density to perform a real steep angle subduction, reinforced by sediment loads and phase transition at depth. A well developed plate tectonic pattern with an opening and closing of the lapetus ocean, with subduction, and a subsequent continent-continent collision can be inferred for the forming of the Caledonian-Appalachian mountain range. Even today, dynamical movements at asthenospheric levels below Fennoscandia are still present as indicated by observations of seismic travel time residuals, deep seismic soundings, gravity, compressive stresses, and theoretical calculations of temperature and viscosity.

A modified assay for the detection of DNA single-strand breaks (SSBs) in human mononucleated white blood cells (MWBCs) based on the nick translation (NT) reaction was developed and combined with the test for unscheduled DNA synthesis (UDS). Both assays were performed on disposable 96-well filtration plates and therefore allowed rapid and sensitive examination of SSBs and UDS. Only 5–8 ml of heparinized blood is required for an eightfold determination in both assays. The uptake of radioactive nucleotide precursors was demonstrated to depend linearly upon the NT reaction time and in both assay systems on the number of investigated cells. The best results and the lowest signal to noise ratio were obtained when the NT assay was performed at 25°C for 20 min. The test was standardized for 150000MWBCs/well and a polymerase I concentration of 20 U/ml. The same number of cells were used to measure UDS during a 4-h incubation at 37°C. We observed a dose-dependent increase in SSBs after in vitro incubation with N-methyl-N-nitrosoguanidine (MNNG), with a detection limit of 50 µM when MNNG was present for 1 h and of 5µM after 20-h incubation period. UDS in MWBCs was increased after treatment for 1 h with MNNG (200 µM) only if poly(ADP)ribose synthesis was inhibited by 3-aminobenzamide. UDS was induced by 320 µM methyl methanesulfonate, but SSBs could only be detected after inhibition of UDS by 100 µM hydroxyurea. The described modification of the NT procedure for the detection of SSBs in DNA of human MWBCs and its combination with the detection of UDS could serve as a useful tool for biological monitoring in occupational or environmental medicine.

Based on observations of reflectivity and lengths of reflecting boundaries in various geological units a consistent picture for explaining the different reflectivity patterns is derived. Whereas in the upper, brittle part of old crusts reflectivity concentrates on fault zones of former or present compressional zones it is absent in warm extensional areas, where in addition, granitic plutons may disturb any upper crustal “layering”. The lower crust of these young and warm areas with its reflecting lamellae is dominated by strain and shear processes i.e. by an ordering process in a low-viscosity environment.

Fur ein grosseres Gebiet im Lockergesteinsbereich Nordost- und Mitteldeutschlands wurden verschiedene Verfahren zur Abschatzung des mittleren Gebietsabflusses gepruft und mit gemessenen Abflussen verglichen. Die Ansatze von Renger und Strebel (1980) sowie Bagrov, mod. von Glugla (1985) berucksichtigen die Einflusse von Boden und Landnutzung auf den Gebietsabfluss und zeigen gute Ubereinstimmung mit Messwerten fur Einzugsgebiete > 100 km2.Der Gebietsniederschlag ist die dominierende Bilanzgrosse. Aufgrund Niederschlagsmangels kommt es im uberwiegenden Teil des Beispielsgebietes in etwa 20% der Jahre zu extremer Verminderung und unter Nadelwald bereits zum Erliegen der Abflussbildung.Setzt man fur die erste Halfte des nachsten Jahrhunderts eine Erhohung der Temperatur um 1,5 K, eine Zunahme der Winterniederschlage um 6% und eine Abnahme der Sommerniederschlage um 2% an (mittlerer Erwartungswert auf der Grundlage von Prognosen von Kenny et al. 1993), so sind nur sehr geringe Anderungen des mittleren Abflusses zu erwarten. Grobszenarien auf der Basis extremerer Abweichungen von diesem mittleren Erwartungswert lassen jedoch deutliche Auswirkungen auf den Landschaftswasserhaushalt erkennen.Weitere Arbeiten sollten neben der zeitlich und raumlich differenzierteren Aufklarung von Abflussbildungsprozessen eine Prazisierung der mittleren Gebietsabflusse in verschiedenen Massstaben unter Einbeziehung aktueller Ergebnisse von bodenhydrologischen Messplatzen und Lysimetern beinhalten.

The restoration of peripher labyrinthine excitability after sudden unilateral isolated vestibular loss shows a different behaviour: It can happen with or without recovery nystagmus with a numerical nearly equal frequency. In a follow-up of 44 patients with unilateral vestibular loss of vascular genetics the objective and subjective characteristics of both states are described. In explanation of it a lesion of variable etiology in the region of the vestibular artery and a supposition of a not yet or already occured compensation of the disturbed tonus balance in the nuclear area are not sufficient. Rather the origin of the different clinical states of recovery phenomenon must be presumed in all probability as the result of a primary and secondary retrograde degeneration of the vestibular neurons. Thereby the distance of the lesion from the Scarpa ganglion is presumably of decisive importance.

Based on the selenothermsT(z) (= temperature-depth functions) and melting point-depth functionsTm(z) viscosity values?(z) are calculated. According to two different creep laws used, two sets of viscosity values are obtained. Viscosities in the outer part of the Moon are found to be larger than those anywhere on Earth. These high values of? explain the large elasticityQ found in lunar seismograms. Viscosities below about 500 km in depth are so small that, at present, some kind of convection or a flow of matter is possible. Tidegenerated moonquakes at depths of around 1000 km seem to be connected with some viscous process. From considerations of viscosities at the time period of mare filling, some selection of ancient selenotherms may be performed.

Further evidence for the existence of the terrane East Avalonia (Cadomia) in north-west Europe, its boundaries and its role in the Caledonian collisional processes comes from studies of deep seismic reflection data at sea and on land. Various sutures are found in the north-east and the north-west, and a generally poor reflectivity dominates in the major part. Further details of reflectivity patterns support the idea that a huge terrane which split from the northern rim of Gondwana moved northward and collided with the merging plates Laurentia-Baltica. Its docking features are analysed.

The first publications on the use of magnetic resonance for breast imaging (MRBI) appeared more than 10 years ago. According to the literature between 14% and 47% of all breast carcinomas are multicentric carcinoma (MCC), a substantial number of which are not detected by conventional mammography. In a prospective study our purpose was to establish a clinically relevant procedure with MRBI for women with a single suspect lesion on mammography. Eight (32%) of 25 patients with histologically confirmed carcinoma had an MCC. Seven MCC were detected with MRBI and only one was diagnosed by mammography; one was discovered with neither MRBI nor mammography. MRBI proved to be the superior technique, with a sensitivity of 0.88 compared with 0.13 for mammography.

Crustal isovelocity lines are constructed along the European Geotraverse for the seismic velocities 6.0, 6.4, 7.1 and 7.8 km/s. Using this velocity structure and a correlation between heat generation and seismic velocity for crustal rocks, the contribution of the crust to the surface heat flow density value is calculated. The heat flow density at the Moho varies from 5 to 40 mW/m 2from Paleo-Europe in the north to Neo-Europe in the south, while the mantle heat flow density is close to zero beneath the Alps; the temperatures calculated for the Moho are 260°–390°C for Paleo- to Meso-Europe, 420°–520°C for Neo-Europe and 700°C for the mountain-root beneath the Alps.

The Antarctic Peninsula has a remarkable record of active margin processes, which include subduction with progressive ridge-trench collisions, margin segmentation by major fracture zones, rifting in a hybrid back-arc and sheared plate margin context, fore-arc basin development and glacial-marine controlled trench fill processes.

Deep reflection seismic data collected in Germany during the last three decades allow an insight into the structure of the Variscan crust in Germany. Although the crustal thickness is relatively constant, reflection data revealed important internal structures. Most profiles show a poorly reflective upper crust (disregarding fault zones) while its lower part is characterized by many flat-lying reflections. But also dipping reflections in the upper and lower crust have been observed on DEKORP reflection lines. Beneath the geothermal anomaly of Urach an updoming of the reflective lower crust coinciding with a pronounced low-velocity body can be observed. Near the suture zones between Moldanubian, Saxothuringian and Rhenohercynian abundant diffractions appear in the middle and lower crust. One exception is found in the west where post-Variscan developments created the deep Saar-Nahe-trough.

The creep properties of the asthenosphere and the lithosphere are considered important parameters in controlling vertical and horizontal movements. The boundary between lithosphere and asthenosphere is not well defined, whereas a relatively abrupt chemical boundary like the Mohorovićić-discontinuity (= Moho) can be well traced by seismic methods. In the Fennoscandian area weak reflected waves P mP but strong “head”-waves P nwere detected in contrast to the observations within the Rhenish shield where strong P mP and sometimes intracrustal reflections, but only very weak P n-waves are observed. In general, high temperatures in quartz-bearing rocks result in a low-velocity lower crust. A low velocity should increase the reflection coefficient at the Moho considerably — producing strong P mP-waves. A high temperature also produces a negative velocity gradient below the Moho, leading to weak or missing P n-waves, as observed in the Rhenish shield.

In a controlled study, ten male volunteers (five smokers and five nonsmokers) were subjected to different smoking conditions and compared to five non-smokers, not exposed to cigarette smoke. During the 4 days of the study, nonsmoking periods were strictly controlled. On the first day the ten subjects were sham exposed. On the second day the five smokers smoked 24 cigarettes in 8 h, while the five nonsmokers were exposed to the environmental tobacco smoke. After another day of sham exposure the smoke exposure was repeated under the same conditions. Blood was drawn before and after exposure and DNA single-strand breaks (SSBs) were analyzed in lymphocytes immediately (1 h) after isolation of cells and after 4 h incubation at 37°C, using a modified assay based on the nick translation reaction. Base levels of unscheduled DNA synthesis (UDS) and UDS levels were determined after 1 h incubation with methyl methanesulfonate. Duplicate analysis using the same method was performed in a second laboratory after transportation of blood samples at 0°C on a train from Munich to Hamburg. Tobacco smoke exposure of the subjects increased COHb and plasma cotinine levels. SSBs could be detected in all probands with some inter-individual day-to-day and morning-to-evening variations. In four of five active smokers, SSB increases were found after smoking. In nonsmokers exposed to tobacco smoke no exposure-related variation in SSB levels could be detected. In lymphocytes which were incubated in culture medium (DME/H) for 4 h at 37°C, SSBs correlated significantly with the SSBs of fresh (NT1) samples but the SSB level was lower in almost all cases and the effect of smoking was not as pronounced as in the NT1 samples. Larger interindividual variations and higher values in general were detected after 8–9h of transportation. Therefore, we recommend immediate determination of SSBs as soon as possible after blood sampling. We conclude that the modified nick translation assay is sensitive enough to detect SSBs caused by an in vivo genotoxic exposure when possible interindividual differences are considered in the study design and could therefore be used in biological monitoring of exposures at the workplace.

Fortlaufende Kontrollen des Nystagmus vom Beginn des Menière-Anfalls an wurden durchgeführt. Es lassen sich vier Verlaufsformen unterscheiden. Hinsichtlich der Schlagrichtung des Nystagmus bzw. des Schlagrichtungswechsels während eines Anfalls wird eine mögliche neurophysiologische Erklärung gegeben: Infolge einer erhöhten Kaliumkonzentration im Perilymphraum während eines Menière-Anfalls kommt es zur Depolarisation der Synapse zwischen vestibulärer Rezeptorzelle und afferenter Nervenfaser. Die Größe der Kaliumkonzentration bestimmt das Ausmaß der Depolarisation und somit die Nystagmusschlagrichtung.

Seventy-three of 172 patients with sudden deafness had a vestibular participation. The found forms of spontaneous and provoked nystagmus, their partial combination with thermic under- or unexcitability of the labyrinth as well as vertigo complaints of the patients are described, especially in their temporal course during the illness. The frequent vestibular particapation during sudden deafness entitles to introduce the term “range of forms of peripheral-vasculary conditioned labyrinthine disturbances”, whose cornerstones are the sudden isolated peripheral deafness and the sudden isolated peripheral vestibular loss with a number of intermediate forms. In addition to this, the stronger consideration of the vestibular findings during sudden deafness facilitates the otherwise often difficult differential diagnosis of Menière's syndrome: that one differs by the lacking increase of direction-fixed spontaneous or positional nystagmus to the cochlearly injured ear, incidences of central forms of nystagmus, and the possibility of temporal occurrence of the vestibular findings after the cochlear damage.

A grid of deep seismic reflection profiles recorded in the Oberpfalz, West Germany for DEKORP and the West German Deep Drilling Project (KTB) provides an opportunity to study the three-dimensional structure of a small part of the Variscan fold belt. The grid straddles the Erbendorf Line (the surface expression of the suture between the Moldanubian and the Saxuthuringian zones of the Variscides), and the edge of the Bohemian Massif, marked by the Franconian Line. The principal features that can be recognised on the data are a series of gently SE-dipping reflections that may be thrusts, one of which seems to correspond to a high-velocity zone that is one of the specific targets of the deep borehole. This thrust has been traced as a characteristic reflection and mapped out over five of the profiles, including the intersection that is the proposed drill site. It appears to be disrupted by steep NW-SE trending faults that are interpreted as dextral strike-slip faults, expressed, in effect, as positive and negative flower structures. The pattern of transpression and transtension shown by these flowers is consistent with dextral shear parallel to the Bayerischer Pfahl, a dextral shear zone more than 150 km long.

The detection of DNA single-strand breaks (SSB) in human mononucleated white blood cells (MWBC) using a modified version of the nick translation assay is presented. This assay allows rapid and sensitive examination of SSB using only 5 ml heparinized blood for an eightfold determination. The assay was standardized by incubation of MBWC in vitro with N-methyl-N'-nitro-N-nitro-soguanidine (MNNG), a known genotoxic agent. In vitro incubation of MWBC with MNNG induced a dose-dependent increase in DNA-SSB at doses between 5 and 500 µM MNNG. The detection limit for the assay was 5 µM MNNG. To assess the suitability of this assay to detect SSB in vivo a controlled study was performed in which volunteer smokers (n = 5), nonsmokers (n = 5) exposed to environmental tobacco smoke (ETS), and nonsmoker controls (n = 5) were compared. The study lasted 4 experimental days, 2 control and 2 exposure days. On control days (days 1 and 3) smokers and nonsmokers sat in an unventilated 45 m3 room for 8 h. On the exposure days (days 2 and 4) each of the five smokers smoked 24 cigarettes in 8 h, while the five nonsmokers were exposed to the ETS generated by the smoking volunteers. High exposure to tobacco smoke was confirmed by dosimetry of carboxyhemoglobin (COHb), plasma nicotine and cotinine levels. Blood was drawn before and after each exposure on all 4 experimental days for determination of DNA-SSB in lymphocytes immediately after isolation of blood cells. COHb, plasma nicotine, and cotinine levels were considerably increased in both smokers and nonsmokers exposed to ETS on days 2 and 4. DNA-SSB were detected in all volunteers with intra-and interindividual day to day and morning to evening variations. After smoking, SSB increased on day 2 and on day 4 in smokers. In nonsmokers exposed to ETS no exposure-related variation in SSB levels was found. We conclude that the modified nick translation assay is sensitive enough to detect SSB induced in vivo by exposure to a genotoxic agent and could therefore be used in biological monitoring at the workplace.

Geo-scientific planetary research of the last 25 years has revealed the global structure and evolution of the terrestrial planets Moon, Mercury, Venus and Mars. The evolution of the terrestrial bodies involves a differentiation into heavy metallic cores, Fe-and Mg-rich silicate mantles and light Ca, Al-rich silicate crusts early in the history of the solar system. Magnetic measurements yield a weak dipole field for Mercury, a very weak field (and local anomalies) for the Moon and no measurable field for Venus and mars. Seismic studies of the Moon show a crust-mantle boundary at an average depth of 60 km for the front side, P- and S-wave velocities around 8 respectively 4.5 km s−1 in the mantle and a considerable S-wave attenuation below a depth of 1000 km. Satellite gravity permits the study of lateral density variations in the lithosphere. Additional contributions come from photogeology, orbital particle, x-and ψ-ray measurements, radar and petrology.

Although now four seismic stations are operating on the Moon the determination of epicenters and mechanisms of moonquakes is still problematic. On the Moon no decoupling of compressional, transverse, and surface waves takes place, no clear first arrivals can be found, and coherence between vertical and horizontal components of a seismograph station is poor. New methods of locating epicenters are presented. They consist of a statistical analysis of the first arrival groups and correlation of components of tidal forces to arrival times in relation to perigee. Certain regions of the Moon, as for instance the Eastern boundary of Mare Nubium, can be considered highly suspicious as possible source region; others have to be ruled out as here triggering by tidal stress seems highly improbable. From various possible mechanisms a connection with a degassing of the Moon seems to offer an acceptable explanation.

Results of deep seismic soundings from various areas of the world are presented. Much weight is put on recent European investigations. Seismic refraction surveys are found to yield reliable information on the depth and undulation of the Mohorovicic discontinuity (Moho). Wide angle reflection data are used for the derivation of an overall velocity gradient zone of a few kilometers in many continental areas. From near vertical and subcritical reflection data a stepwise character of the gradient zone is deduced. The overall picture from different seismic investigations shows the Moho as a laminar transition zone of a few kilometer thickness. There is a general stepwise increase in the velocity of compressional (P) and shear waves (S), possibly often interrupted by layers with lower velocities, until values around 8 km/s are reached for theP-waves in the uppermost part of the mantle. Petrologic explanations of these features deal with layers of partial melts, crystallisation seams, intrusions and some peeling of mantle matter. Problems of the evolution, shifting, and subduction of the Moho are discussed in the light of plate tectonics.

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