Occurrence and distribution of shortnose sturgeon,Acipenser brevirostrum,in the upper tidal Delaware River

Sampling in the upper tidal Delaware River between Trenton, New Jersey, and Philadelphia, Pennsylvania, from July 1981 through December 1984 demonstrated the existence of a significant population of shortnose sturgeon. The sturgeon aggregate in the river channel during daylight hours, especially in the area between Trenton and Florence, New Jersey (river km 211.8 to 198.8). Occurrence in the river downstream of Florence appears to be restricted by poor water quality during summer months. Sturgeon were present in the study area throughout the year, but largest numbers were collected from May though November. No spawning was observed during this study, but presence of males with milt suggests that spawning possibly occurs in the Trenton area. Preliminary population estimates (Peterson, Schnabel and Seber-Jolly) indicate an adult population of approximately 6,000–14,000 shortnose sturgeon occupying the upper tidal Delaware River.     

Theoretical field configurations for thundercloud models with volume charge distributions

The potential gradient at ground level due to a charge volume is obtained in terms of integrals, some values of which are computed as functions of normalized vertical and horizontal distances. Using these values the vertical potential gradients at points on the ground below some simple cloud volumes, built up of cylindrical slices of uniform charge densities, are calculated. The results consitute definite improvements on those provided by conventional point-charge models.     

On the spiral structure of atmospheric vortices

a au au a ¶rt;am m ¶rt;uauu n¶rt;nu mau nua am u nu uu, m n amu n nua n uau mua mu.     

A simple model of a building cumulus cloud

Summary A model of a building cumulus structure is described. The one-stage model published in[1] was used to describe ascent of two cloudy parcels that a cloud is supposed to be formed of. The other ascent is assumed to take place after the first cloud element sinks back as a result of evaporative cooling. The numerical results and their evaluation are given for various rates of mixing at the cloud top level of the first cloud volume.     

On the propagation of streamers through a large population of neutral droplets

Streamers were injected into a large population of small droplets, of radii about 20 m, confined to a given region of pre-determined shape on a photographic film, and situated in a gap between which a variable electric field can be applied. Results showed that the droplet region behaves like a dipole discharging from both ends if its inclination to the electric field is less than 45° and the field is not less than –230 kV/m at atmospheric pressure.We deduced that streamer intensification will occur at relatively low fields if there exists pockets of large number density of small droplets.     

Geodetic and geophysical implications of the homogeneous reduction of pole coordinates (1899–1979)

The new series ILS (H) of pole coordinates (1899.9–1979.0) computed in a homogeneous system has been employed for the determination of the period of Chandler's component of polar motion. The comparison with a value derived from a previous series ILS (VY) shows there is no significant variation in the period in spite of the known systematic errors affecting the ILS (VY) series. Any high precision geodetic network adjustment has to take account of the pole coordinates defined by the ILS (H) series. Such long series permitted the identification of another component of polar motion with a period of about 30 years. The polhode derived from the ILS (H) series shows greater regularity than previously deduced polhodes and, therefore, we can conclude that past investigations in geodesy and geophysics trying to correlated the irregularities of the polhode with different geophysical phenomena, for instance, earthquakes, may have to be revised.     

AN ALGORITHM FOR THE CALIBRATION OF AERIAL PHOTOGRAPHIC SYSTEMS

The algorithm presented assumes a preliminary determination of the elements of inner orientation and bases its mathematical model on the collinearity condition, from which projective equations are derived. Linearisation of condition equations is based on Taylor's expansion, whilst the subsequent solution follows iteration cycles. The method aims to derive composite corrections to image coordinates, with the aid of test field data.

Résumé

L'auteur présente un algorithme oú l'on suppose déterminés au préalable les éléments d'orientation interne. La modélisation mathématique s'appuie sur les conditions de co-linéarité et sur les équations qui en résultent en projection. On linéarise les équations de conditions en utilisant un développement en série de Taylor, et l'on obtient la solution correspondante par itération. La méthode vise à apporter des corrections aux coordonnées images en utilisant les données d'un polygone d'essai.

Zusammenfassung

Bei dem dargestellten Algorithmus wird die vorläufige Bestimmung der Elemente der inneren Orientierung angenommen, und das mathematische Modell basiert aufder Kollinearitätsgleichung, woraus perspektive Gleichungen abgeleitet werden. Die Linearisierung der Bedingungsgleichungen erfolgt durch Anwendung der Taylor-Reihe, was für die folgenden Berechnungen einen iterativen Prozess bedingt. Mit der Methode wird angestrebt, Bildkoordinaten mit Hilfe von Testfelddaten zu verbessern.     

Results of a semi-implicit two-step method for the simulation of markedly nonlinear flow in coastal seas

Results of a numerical method for the simulation of nonlinear flow in coastal seas are presented. The method is based on a neutral semi-implicit scheme which is modified into a stability-enhancing two-step algorithm. By means of this method the simulation of highly nonlinear flow patterns is possible in a stable and economic way. Three examples of models of different North Sea coastal regions are discussed under certain aspects to demonstrate the reliability of the method.     

Kulkeite,a new metamorphic phyllosilicate mineral: Ordered 1∶1 chlorite/talc mixed-layer

Kulkeite occurs as platy, colorless, porphyroblastic, single crystals up to 2 mm in size in a low-grade dolomite rock associated with a Triassic meta-evaporite series at Derrag, Tell Atlas, Algeria, It is associated with sodian aluminian talc, unusual chlorite polytypes, and both K and Na phlogopite. Kulkeite is optically biaxial, negative, n _x=1.552, n _y=1.5605, n _z=1.5610, 2V_z=24° (obs.). Based on microprobe analysis the empirical formula is (Na_0.38K_0.01Ca_0.01)(Mg_8.02Al_0.99)[Al_1.43Si_6.57O₂₀](OH)₁₀ with some variation in Na, Si, and tetrahedral Al. The crystals are monoclinic with a=5.319(1), b=9.195(2), c=23.897(10) Å, β=97° 1(3)′; Z=2; the calculated density is 2.70 g cm^?3. The four strongest lines in the X-ray powder pattern are (d, I, hkl): 7.90, 100, 003; 1.533, 100, 060; 7.42, 80, 002; 3.38, 80, 007; the 001 reflection with 23.7 Å has intensity 10. Transmission electron microscopy confirms the nature of a regular 1∶1 mixed-layer, which consists of 14 Å chlorite (clinochlore) sheets alternating with sheets of one-layer (9.5 Å) talc characterized by the lattice substitution NaAl→Si just as in the talc occurring as a discrete mineral co-existing with kulkeite. Kulkeite is intergrown with lamellae of clinochlore that represent two-layer and five-layer (70 Å) polytypes with optical birefringence exceeding the normal value for clinochlore by a factor of 3. The origin of kulkeite is due to low-grade metamorphism with temperatures probably not exceeding 400° C. As the clinochlore lamellae and sodian aluminian talc are found in mutual contact, kulkeite seems to represent a metastable mineral at least during the latest phase of metamorphism. However, at an earlier stage, prior to clinochlore formation, kulkeite might have been stable, and the incorporation of Na and Al into its talc component could indeed be the decisive factor for the formation of the mixed-layer.