Secular changes in the short-term preventive,positive, and temperature checks to population growth in Europe, 1460 to 1909     

Patrick R. Galloway 《Climatic change》1994,26(1):3-63

Annual variations in births, marriages, deaths, grain prices, and quarterly temperature series in England, France, Prussia, and Sweden are analyzed using a distributed lag model. The results provide support for the existence of the shortterm preventive, positive and temperature checks to population growth. Decreases in fertility and nuptiality are generally associated with increases in grain prices. Increases in mortality appear to be associated with high grain prices, cold winters and hot summers. Changes in these responses over time are examined within the context of economic development.The causes of a high mortality are various; but the greater number of known causes may be referred to five heads: 1) excessive cold or heat; 2) privation of food; 3) effluvial poisons generated in marshes, foul prisons, camps, cities; and epidemic diseases, such as typhus, plague, small pox, and other zymotic diseases; 4) mechanical and chemical injuries; 5) spontaneous disorders to which the structure of the human organization renders it liable. - Farr (1846, p. 164)....a foresight of the difficulties attending the rearing of a family acts as a preventive check, and the actual distresses of some of the lower classes, by which they are disabled from giving the proper food and attention to their children, acts as a positive check to the natural increase of population. - Malthus (1798, Chapter 4).The research on which this paper is based has been funded by grants R01-HD18107 and T32-HD07275 from the U.S. National Institute of Child Health and Human Development. This paper is associated with the author's Basic Patterns in Annual Variations in Fertility, Nuptiality, Mortality, and Prices in Preindustrial Europe,Population Studies 42, 2, 1988, 275-303. I thank Ronald Lee, Ulla Larsen, and Jan de Vries for helpful comments and suggestions.  相似文献   

Outcomes and policy recommendations from the IPCC/AFOS working group on climate change response strategies and emission reductions     

K. Heinloth  R. P. Karimanzira 《Climatic change》1994,27(1):139-146

The most promising response strategies are

-sustainable practices in agriculture to improve productivity on existing arable land especially in developing countries to meet the food requirements of a still rising population

-sustainable practices in forestry both in tropical forests as well as in forests of temperate and boreal zones, in the latter case to achieve sufficient fast adaption to climate change.

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Active and passive microwave remote sensing of precipitating storms during CaPE. Part I: Advanced microwave precipitation radiometer and polarimetric radar measurements and models     

J. Turk  J. Vivekanandan  F. S. Marzano  R. E. Hood  R. W. Spencer  F. J. LaFontaine 《Meteorology and Atmospheric Physics》1994,54(1-4):3-27

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Early Cretaceous volcaniclastic and quartzose sandstones from north central Nepal: composition,sedimentology and geotectonic significance     

Sören B. Dürr  Martin R. Gibling 《International Journal of Earth Sciences》1994,83(1):62-75

Early Cretaceous sandstones and shales from the Thakkhola region (Chukh and Tangbe Formations) were deposited on the subsiding northern (Tethyan) margin of Gondwana; current directions indicate a source area to the south. Whereas the Berriasian Chukh Formation is dominated by quartz arenites, volcaniclastic sandstones and minor conglomerates dominate the Tangbe Formation of Valanginian to Aptian age. Upsection, the composition of the volcaniclastic components changes from mainly basaltic to dominantly dacitic/rhyolitic. Magmatism was preceded and accompanied by strong uplift in the source area of the Chukh and Tangbe clastics, resulting in the erosion of probably more than several hundred meters of pre-Cretaceous sedimentary, metamorphic and plutonic rocks. A geochemical whole rock analysis of basaltic pebble fragments shows their alkaline character and suggests a within-plate geotectonic setting for the volcanic source. This volcanotectonic event is probably related to rifting between Australia and Greater India, where seafloor spreading began in late Valanginian/Hauterivian times.  相似文献   

Small-scale clusters of photospheric network bright points and their dependence on the solar cycle phase     

V. N. Dermendjev  R. Muller  M. S. Madjarska 《Solar physics》1994,155(1):45-55

The tendency of network bright points (NBPs) to form in their surface distribution non-random, small-scale clusters is studied by a 2-D nearest-neighbours test, based on observational data for the distance between separate NBPs. High-resolution photographs taken from long time series obtained at4308 with the 50-cm refractor of Pic du Midi Observatory are used. Three different epochs of the solar cycle were chosen. The results obtained suggest that the degree of clustering depends on the solar cycle phase. Supposing that the NBPs are good tracers of the kilogauss small-scale magnetic field, we use them to obtain information about the subphotospheric small-scale magnetic field organisation and its dependence on the solar cycle phase.  相似文献   

Solar and stellar chromospheric contrast     

Robert A. Donahue  Sergio R. Restaino  Stephen L. Keil 《Solar physics》1994,149(2):257-265

Positions of active regions estimated from observations of the whole solar disk in Caii K _iv during the period 1977–1989 at the Coimbra Astronomical Observatory are compared with the time-dependent latitudinal distribution of background solar magnetic fields and with the latitudinal shifts of boundaries of their polarities. We confirm that the sunspot groups are located near the zonal boundaries between the opposite polarities of the solar background magnetic field during different phases of the two recent consecutive cycles of activity. We demonstrate a probable connection between the increased number of groups and the commencement of poleward migration of zonal boundaries in both hemispheres. But the influence of the dominant convective rolls seems to he still unclear. A new problem of interrelation between the zonal and sector boundaries has also appeared.  相似文献   

WKB estimates for the onset of ideal MHD instabilities in solar coronal loops     

A. W. Hood  P. De Bruyne  R. A. M. Van Der Linden  M. Goossens 《Solar physics》1994,150(1-2):99-115

A WKB approach, based on the method of Connor, Hastie, and Taylor (1979), is used to obtain simple estimates of the critical conditions for the onset of ideal MHD instabilities in line-tied solar coronal loops. The method is illustrated for the constant twist, Gold-Hoyle (1960) field, and the critical conditions are compared with previous and new numerical results. For the force-free case, the WKB estimate for the critical loop length reduces to . For the sufficiently non-force-free case the critical length can be expressed in the forml ₀ +l ₁/m. The results confirm the findings of De Bruyne and Hood (1992) that for force-free fields them = 1 mode is the first mode to become unstable but for the sufficiently strong non-force-free case this reverses with them → ∞ mode being excited first.  相似文献   

Intensity oscillations in chromospheric bright points and network elements     

R. Kariyappa 《Solar physics》1994,154(1):19-27

From a 35-min time series of photographic spectra in the Caii H-line obtained at the Vacuum Tower Telescope (VTT) of the Sacramento Peak Observatory under high spatial, spectral, and temporal resolution, we have derived a large number of H-line profiles at the sites of the bright points in the interior of the supergranulation cells, and at the network elements, on a quiet region at the centre of the solar disc. It is shown that the bright points are associated with 3-min periodicity in their intensity oscillations whereas the network elements exhibit 7-min periodicity. It is surmised that the large difference in periods of the intensity oscillations, the strength of the magnetic fields, and the intensity enhancements at the sites of the bright points and the network elements themselves may probably be taken as evidence to argue that the mechanisms of heating in the two cases are dissimilar, irrespective of the sizes of these structures.  相似文献   

Strange quark matter and models of strange stars     

Yu. L. Vartanyan  A. R. Arutyunyan  A. K. Grigoryan 《Astrophysics》1994,37(3):271-280

In the framework of the MIT bag model we consider absolutely stable strange quark matter consisting of u, d, and s quarks and electrons. For a realistic range of parameters of the quark bag we compute the threshold density for the appearance of strange quark matter that is realized on the surface of self-sustaining strange stars. On the basis of twelve calculated equations of state we give a detailed study of the series of configurations of strange stars consistent with the best known observational data. We show that the binding energy of the models depends essentially on the quark-gluon interaction constant _c.Translated fromAstrofizika, Vol. 37, No. 3, 1994.The authors are grateful to E. V. Chubaryan and A. M. Atoyan for assistance in overcoming the information blockade. The present paper was written in the framework of area 46/101 93-353, supported by the Ministry of Higher Education and Science of the Republic of Armenia.  相似文献   

Paleohydrology and paleochemistry of Lake Manitoba,Canada: the isotope and ostracode records   总被引：1，自引：1，他引：0  

William M. Last  James T. Teller  Richard M. Forester 《Journal of Paleolimnology》1994,12(3):269-282

Lake Manitoba, the largest lake in the Prairie region of North America, contains a fine-grained sequence of late Pleistocene and Holocene sediment that documents a complex postglacial history. This record indicates that differential isostatic rebound and changing climate have interacted with varying drainage basin size and hydrologic budget to create significant variations in lake level and limnological conditions. During the initial depositional period in the basin, the Lake Agassiz phase (12–9 ka), ¹⁸O of ostracodes ranged from –16 to –5 (PDB), implying the lake was variously dominated by cold, dilute glacial meltwater and warm to cold, slightly saline water.Candona subtriangulata, which prefers cold, dilute water, dominates the most negative ¹⁸O intervals, when the basin was part of proglacial Lake Agassiz. At times during this early phase, the ¹⁸O of the lake abruptly shifted to higher values; euryhaline taxa such asC. rawsoni orLimnocythere ceriotuberosa, and halobiont taxa such asL. staplini orL. sappaensis are dominant in these intervals. This positive covariance of isotope and ostracode records implies that the lake level episodically fell, isolating the Lake Manitoba basin from the main glacial lake.¹⁸O values from inorganic endogenic Mg-calcite in the post-Agassiz phase of Lake Manitoba trend from –4 at 8 ka to –11 at 4.5 ka. We interpret that this trend indicates a gradually increasing influence of isotopically low (–20 SMOW) Paleozoic groundwater inflow, although periods of increased evaporation during this time may account for zones of less negative isotopic values. The ¹⁸O of this inorganic calcite abruptly shifts to higher values (–6) after 4.5 ka due to the combined effects of increased evaporative enrichment in a closed basin lake and the increased contribution of isotopically high surface water inflow on the hydrologic budget. After 2 ka, the ¹⁸O of the Mg-calcite fluctuates between –13 and –7, implying short-term variability in the lake's hydrologic budget, with values indicating the lake varied from outflow-dominated to evaporation-dominated. The ¹³C values of Mg-calcite remain nearly constant from 8 to 4.5 ka and then trend to higher values upward in the section. This pattern suggests primary productivity in the lake was initially constant but gradually increased after 4.5 ka.This is the sixth in a series of papers published in this issue on the paleolimnology of arid regions. These papers were presented at the Sixth International Palaeolimnology Symposium held 19–21 April, 1993 at the Australian National University, Canberra, Australia. Dr A. R. Chivas served as guest editor for these papers.  相似文献