Gaps In Series Research Articles

Fiber-optic-triggered high-power low-pressure glow discharge switches

The development of a novel version of an optically triggered low-pressure high-power glow discharge switch is reported. Characteristic of these type of switches are high-voltage hold-off, high peak current capability, excellent current rise rate, low delay and jitter, and a simple device geometry. This method of triggering guides a UV light pulse through a fiber-optic cable to the aperture in the cathode electrode. Photoelectrons are produced and quickly avalanche to initiate the discharge, and a glow discharge is formed. Jitter and delay of 0.4 ns half-width half-maximum (HWHM) and 78 ns, respectively, have been obtained and reliable triggering has been demonstrated with energies as low as 10 mu J of UV light. This device is considered suitable for scaling switches to very high current and voltages by simultaneously triggering multiple gaps in parallel or series.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Interprétation de la déglaciation rhodanienne au Würm, des moraines « internes » à la cuvette lémanique

Between the "inner moraines" and the upperside of the Leman Lake, we observe the following elements : — two generations of "inner moraines" of as yet undetermined age, the oldest being over 241 10 ±900 B.P.; — a series of over-deepened basins now either wholly filled up with lacustrine deposits (Malville, Le Bouchage) or not (Le Bourget, Annecy, Léman), with thicknesses of several hundred meters; — a series of paraglacial or glacio-lacustrine supra-morainic deposits directly related to the déglaciation, which are disposed "en echelon" from the downstream side to the upstream side; — on single till cover to the downstream side of the Geneva basin, directly superposed to the substratum or to a wurmian ante-morainic complex; — a thick complex of superposed morainic, lacustrine and marshy deposits in which several interstadials were dated from 34550 to 23500 B.P. in the Leman basin only (Chablais, Vaud). Present chrono-stratigraphic conclusions, notably concerning the age of the maximum glacial advance, differ between the frontal area (early Wùrm) and the upstream side of the Leman basin (late Wùrm). Now, we note that : — undoubted, dated interstadial deposits only occur in the Leman basin, far upstream from the "inner moraines"; — between the "inner moraines" and the Leman basin, there is only one single till cover as well as déglaciation deposits, without any evidence of interstadial formations or of true glacial stops. Therefore, in all likelihood, the morainic deposit of the Plateau Savoyard represents one single glacial phase, predating the oldest Leman interstadials (34600 ± 2700 B. P.). One indétermination still subsists, regarding its age, in relation with both the sedimentary gaps in the glacial-interstadial series and the duration of the sedimentation process of the déglaciation and of later lacustrine deposits.

A bias in the satellite‐observed low‐level cloud motion winds over the central tropical Pacific

Island wind data from the central tropical Pacific are compared with satellite‐observed low‐level cloud motion winds over the same area during 1976–1980. The purpose of the comparison is to investigate the effect of gaps in the satellite wind series. It is found that the distribution of the gaps is such that the resulting time series is biased from the complete time series because of undersampling of the strongest westerly and northerly wind anomalies. This bias is strong enough, at least in this geographical region, to cause difficulties in estimating accurate mean fields from the cloud motion winds alone. The gaps leading to this bias occur on time scales of days to weeks and are most common during the northern hemisphere winter. Further, the gaps can be attributed to the presence of heavy, high cloud cover typical of strong convective events. The bias follows from the fact that the wind anomalies are also strongest at these times.

Mantle metasomatism—perspective and prospect

Summary Mantle replenishment in lithophile elements has been discerned in the patterns of trace elements and isotopes in lavas. One replenishment process is identified as metasomatic replacement, seen in ultramafic xenoliths brought up in high-velocity alkaline eruptions. Thus alkaline magmatism provides the best prima facie evidence of metasomatism and open-system conditions in the upper mantle. The list of added lithophile elements includes the following: H, C, F, Na, Al, P, S, Cl, K, Ca, Ti, Fe, Rb, Y, Zr, Nb, Ba and rare earths. Some metasomatism may be due to wall-rock alteration near magma bodies, but the evidence for metasomatism prior to melting opens the possibility that the process is a precursor to alkaline magmatism, giving the necessary source enrichment in lithophile elements. In some igneous provinces the metasomatism is widespread, intensive and pervasive; in others it appears as veining of variable intensity. Metasomatism as a large-scale process is best indicated by the widespread distribution of alkaline magmatism in space and time: volatile flux through the lithosphere would then be the necessary precursor of metasomatism and magmatism. Volatile activity, metasomatism and melt enrichment clearly widen the scope for mafic magma generation in the mantle, but some long-standing problems of the alkaline associations (and indeed the calc-alkaline) also call for re-examination in terms of volatile activity in the lithosphere mantle. These include the diversity of magmas, the generation of large felsic volumes, and composition gaps in magma series. Experiments show that felsic minerals are stable to 30 kb, indicating the possibility of felsic-melt generation in the upper part of the mantle. A combination of volatile flux and melt percolation along geotherms that intersect the solidus at depths of less than 80 km would lead to enrichment and metasomatism, providing distinct mantle sources for felsic magmas. Initial (or residual) melts from such a region, as distinct from those from greater depths, would be constrained by equilibria involving felsic minerals. Thus an igneous cycle could generate a bimodal association, with felsic melts forming in the upper regime and the mafic melts originating at depths below the range of felsic-mineral stabilities. Such a magma system is consistent with the observed eruptive characteristics, explains the typical ultramafic nodule and megacryst suites in the alkali olivine-basalt association and is free of difficulties with relative volumes of melts, with eruption timing and with rapid changes in erupted compositions.

Adequacy of the Rawinsonde Network for Global Circulation Studies Tested through Numerical Model Output

Abstract Numerical output from a GFDL global climate model was used to determine whether the present distribution of rawinsonde stations is adequate to deduce the atmospheric structure and its variability in space and time over the globe. Spatial data gaps were found to cause typical rms wind errors averaged over a hemisphere of 2 to 3 m s−1, increasing for the zonal wind component to 5 or 6 m s−1 at jet stream levels. In temperature the spatial data gaps led to rms errors on the order of 0.5 to 1°C in the free atmosphere, in geopotential height between 20 and 30 gpm in, the upper troposphere, and in specific humidity between 1 and 2 g kg−1 near the surface and about 0.3 g kg−1 at 500 mb. Errors due to instrumental deficiencies, unrepresentativeness of the local soudings, deficiencies in the analysis technique and gaps in the time series were found to he less important than those due to the, spatial gaps, even in the Northern Hemisphere. In the Northern Hemisphere, the rawinsonde network was found to be g...

Plagioclase and other mineral equilibria in a contact metamorphic aureole

Plagioclase, microcline, amphibole, clinozoisite, clinopyroxene and biotite from alternating pelitic and calcareous hornfelses of the Wyman Formation, Blanco Mountain Quadrangle, California, were analyzed using an electron microprobe. The metamorphic aureole formed at temperatures of 300–600° C, total pressure 2–3 Kb, and low but variable partial pressure of CO2. The minerals show some compositional changes with metamorphic grade as well as differences from one assemblage to another. The plagioclases developed in the aureole do not form a continuous series. Rather, coexisting grains of plagioclase in individual rock layers form at certain distinct compositions: An 1–3, 15–17, 28–32, 38–45, 51–55, 59–65, 75 and 80. There is no evidence of disequilibrium in the rocks, although diffusion was limited; the volume for chemical equilibrium for most samples was less than 1 mm. Inspection of the changes in mineral assemblages with increasing degree of metamorphism and with changes in fluid composition suggests a number of reactions between the phases. Neither these reactions nor the compositions of coexisting minerals provide an obvious explanation for the observed gaps in the plagioclase series. Therefore it is postulated that the compositional clustering is structurally controlled.

Dielectric properties of the hydrates of argon and nitrogen

The dielectric relaxation of water in the structure I clathrate hydrates of argon and nitrogen was studied over a range of temperature and pressure. Hydrates were slowly grown at pressures of 1 to 2 kbar in a coaxial cell enclosed in a pressure vessel. The complex permittivity loci resemble circular arcs with static dielectric constants of ~56 at 0 °C and high-frequency dielectric constants of 2.85 ± 0.05. Relaxation near 0 °C is about as slow as in ice I, but activation energies and entropies are much smaller. Formation of Bjerrum defects probably takes place preferentially near the occasional sites at which argon and nitrogen molecules have replaced water molecules in the lattice. The much faster relaxations found previously in the isostructural hydrates of ethers arise from orientational defects induced in the water lattice by the encaged molecules, a small proportion of which may form hydrogen bonds with water. The effect of small gaps in series with samples showing circular-arc dispersion behavior was evaluated.

A Tripping Circuit for a Multi-stage Surge Generator

The sphere gap in the first stage of an existing multistage surge generator has been replaced by two equal gaps in series by introducing a third sphere. By applying an impulse to the centre sphere when the gaps are charged nearly to the breakdown voltage, breakdown can be initiated at a desired instant. This tripping impulse is generated by a thyratron becoming ionized when a low voltage impulse is applied to its grid, and simultaneously to the sweep circuit of the oscillograph. On account of the inherent time delay in the ionization of a thyratron, the sweep circuit is initiated before the surge generator. A delay cable in the measuring circuit is thus rendered unnecessary. Visual or automatic methods of controlling the output voltage of the generator can be used.

SHORT REVIEWS AND NOTICES

A. K. B. ROBERTS. St George's Chapel, Windsor Castle, 1348-1416: A Study in early Collegiate Administration. (Historical Monographs relating to St George's Chapel, Windsor Castle. Windsor: Oxley and Son (Windsor) Ltd. I948. From the records at Windsor, Dr Roberts has reconstructed the economy and financial administration of the college of canons of St George's Chapel during the first sixty-eight years of its existence. Account-rolls are inevitably the foundation of such a study, and there are large gaps in the Windsor series. Treasurers' Rolls and Precentors' Rolls survive for about one year in every three; but Stewards' Rolls and estate accounts are much more defective. Dr Roberts's work, however, has been done with care and skill, and the pattern of central administration (which changed little during this period) emerges clearly. The three principal financial offices of the Chapter were the Treasurership, the Stewardship and the Precentorship. These were held by canons elected in Chapter; they were burdensome offices, and refusal to serve was punishable with heavy loss of emolument; they circulated fairly rapidly, and there was little continuity. The Steward (and Receiver-general, as he also termed himself) was responsible for the estates. He supervised the cultivation of manors by bailiffs or reeves. He negotiated leases, and collected the estate revenues. The Treasurer received these revenues from the Steward, and his main concern was with expenditure. The Precentor received and accounted for offerings, and was responsible for the upkeep of the chapel and its services. Until I393, his office seems to have enjoyed a considerable measure of financial independence. Changes in estate management, and in the financial fortunes of the Chapter, are not so clear to sight. They can be observed from time to time, but they cannot be followed continuously, and they cannot always be explained. Most of the endowments of St George's were impropriated churches, granted by Edward III between I348 and I35i, and widely scattered, from Saltash in Cornwall to Simonburn in Northumberland. It was natural that most of these churches, being distant, should be farmed from the beginning. In early years, however, a few churches and manors, most of them within easy reach of Windsor, were directly managed by the Chapter. Probably, as Dr Roberts suggests, this was because the Chapter at first maintained a common table, to which provisions were sent. After I 355, when the building of the canons' chambers was completed, the common table was given up; and after I 36 I, at the latest, all the estates were at farm except the two manors of Iver and Craswell, both very close to Windsor. These long remained in hand: Craswell till I4I5, Iver till some date between I4I 7 and I422. When they were farmed at last, the result seems to have been, not only a great saving of trouble, but some increase in revenue. Dr Roberts has found several auditors' estimates of the annual values of Craswell and Iver, made at various dates while the two manors were in hand. The farms received under the leases made in Henry V's reign were slightly higher than the highest of these. The reign of Henry V was a time of financial reconstruction at St George's. For reasons which are not very clear, from I400 onwards the financial situation of the college had been deteriorating; simultaneously its accounts had been becoming more and more involved. The canons should have been expert administrators, for Windsor canonries were fat, and convenient for London, and therefore commonly the perquisites of eminent civil servants,

On the connection between gaps in power series and the roots of their partial sums

On the connection between gaps in power series and the roots of their partial sums

Dust figures formed by an electric spark

The dust figures produced by the sound waves generated by electric sparks passing between a pair of spark gaps in series show interference. Measurements of the patterns made when the distance between the gaps ranged from 15 cm. to 3 cm. show that the wave-length of the sound is constant. When a single spark gap was placed between walls, the sparks produced modified patterns. These are explained by the method of images. The patterns may be regarded as sound maps, and should prove useful in illustrating acoustical phenomena such as the directive properties of cones for high-frequency sound.