Anthropogenic regulation of the phosphorus balance in the Thau catchment-coastal lagoon system (Mediterraean Sea, France) over 24 years

In the Thau lagoon, despite there being no phosphate limitation policy, the annual mean phosphate concentrations decreased by 90% between 1971 and 1994. The present study indicates a relationship between the decrease of phosphate concentrations and changes in urban, industrial and agricultural activities within the catchment generating phosphorus (P) inputs; and shellfish farming leading to phosphorus storage and export. The relationship (tonnes of P) is: P-PO(4)(3-) in the lagoon waters=1.0124 anthropogenic phosphorus balance--47.62 (r(2) = 0.824, p < 0.000). As population growth is expected in coastal zones, sustainable development requires the need for addressing the role played by human activities and the multi-scale regulation of them. As an element of integrated coastal zone management, the present study provides a regional scale analysis of these aspects.     

Definition and Determination of Laminae in Ozone Profiles

Ozone profiles measured by sondes often display thin layers of substantially enhanced or depressed ozone concentration, which are called laminae. Laminae are important because they reveal much stronger long-term trends than the ozone concentration itself and seem to be more sensitive to various factors. The paper presents our definition and method of determination of laminae in comparison with other methods of lamina definition. This is important for clarifying some differences between the lamina-related results of different authors and for examination of long-term trends in lamina characteristics. The sensitivity of long-term trends to changes of methods of lamina determination is tested and found small, without a noticeable influence of changes of methods on trends.     

An Overview of Long-Term Trends in the Lower Ionosphere Below 120 km

The increasing concentration of greenhouse gases in the atmosphere is expectedalso to modify the mesosphere and lower thermosphere (MLT region). However,the greenhouse cooling – instead of heating – at these heights is revealed by modelsand generally confirmed by observations. This should more or less affect variousionospheric parameters at these heights. The spatial and temporal structure oftemperature trends in the MLT region is quite complex and, therefore, such structureshould occur for trends in the lower ionosphere as well. In the lower part of theionosphere below about 90 km, the rocket measurements of electron density, theindirect phase reflection height measurements and the A3 radio wave absorptionmeasurements reveal trends corresponding to cooling and shrinking of the mesosphere,while riometric measurements of cosmic noise absorption provide inconclusive results.The radio wave absorption and rocket electron density measurements clearly display asubstantial dependence of trends on height. Ionosonde data show that there is amodel-expected trend in the maximum electron concentration of the E region ionosphere;foE is slightly increasing. On the other hand, the height of the normal E layer, h'E, isslightly decreasing. The nighttime LF radio wave reflection height measurements near95 km support an idea of increasing electron density. However, rather scarce rocketmeasurements display a negative trend in electron density at 90–120 km. The role ofthe solar cycle and other longer-term variability of natural origin in the determinationof observational trends must not be neglected. In spite of the general qualitativeagreement with model expectations, there is still some controversy between variousobservational trend results (hopefully, apparent rather than real), which needs to beclarified.     

An explanation of discrepancy in mesospheric temperature trends derived from ground-based LF phase-height observations

Bremer and Berger (J. Atmos. Solar Terr. Phys. 64 (2002) 805) applied a correction for trends in the NO concentration and α_eff in the interpretation of trends in the low frequency (LF) phase height measurements and obtained results less consistent with model simulations as well as the observed trends in mesospheric temperatures. The correction is shown to be too large most probably due to the application of inappropriate trends in α_eff of Chakrabarty (Adv. Space Res. 20 (1997) 2117), which yield a trend in electron density opposite to that which is observed. The discrepancy between the observational data and model-simulated trends of Bremer and Berger (J. Atoms. Solar. Terr. Phys. 64 (2002) 805) in the LF phase heights can be largely removed. Even more important, the trends in mesospheric temperatures inferred by Bremer and Berger (J. Atmos. Solar Terr. Phys. 64 (2002) 805) from trends in the LF phase heights without the inappropriate correction agree well with the results of analysis of a global set of results on trends in the mesospheric temperatures by Beig et al. (Rev. Geophys. 41 (2003) 1015).     

Singularly weighted symplectic forms and applications to asteroid motion

New techniques to study Hamiltonian systems with Hamiltonian forcing are proposed. They are based on singularly weighted symplectic forms and transformations which preserve these forms. Applications pertaining to asteroid motion are outlined. These involve the presence of both Jupiter and Saturn.     

Hysteresis of foF2 at European middle latitudes

The hysteresis of foF2 is studied for several European stations over the whole 24-hour diurnal interval for the equinoctial months of the years just before and just after the solar cycle minimum for solar cycles 20 and 21. Based on previous results, the hysteresis is expected to develop best just for the equinoctial months and near the solar cycle minimum. The hysteresis is generally found to be negative, i.e. higher foF2 for the rising branch compared to the falling branch of solar cycle. However, this is not the case in some individual months of some years. The noontime hysteresis represents the hysteresis at other times of the day qualitatively (as to sign) but not quantitatively. The hysteresis appears to be relatively persistent from one solar cycle to another solar cycle in spring but not in autumn. A typical value for springtime hysteresis is about 0.5 MHz. The inclusion of hysteresis into long-term ionospheric and radio wave propagation predictions remains questionable.     

The BeppoSAX High Energy Large Area Survey (HELLAS) – III. Testing synthesis models for the X-ray background

The BeppoSAX High Energy Large Area Survey (HELLAS) has surveyed several tens of deg² of the sky in the     band down to a flux of about     . The source surface density of     at the survey limit corresponds to a resolved fraction of the     X-ray background (XRB) of the order of     per cent. The extrapolation of the HELLAS     towards fainter fluxes with a Euclidean slope is consistent with the first XMM–Newton measurements, in the same energy band, which are a factor of 20 times more sensitive. The source counts in the hardest band so far surveyed by X-ray satellites are used to constrain XRB models. It is shown that in order to reproduce the     counts over the range of fluxes covered by BeppoSAX and XMM–Newton a large fraction of highly absorbed     , luminous     active galactic nuclei is needed. A sizeable number of more heavily obscured, Compton-thick, objects cannot be ruled out but they are not required by the present data. The model predicts an absorption distribution consistent with that found from the hardness ratios analysis of the so far identified HELLAS sources. Interestingly enough, there is evidence of a decoupling between X-ray absorption and optical reddening indicators, especially at high redshifts/luminosities where several broad-line quasars show hardness ratios typical of absorbed power-law models with     .     

Comparison of ozone vertical distributions measured by different techniques at mesospheric altitudes

A comparison is done between the ozone vertical profiles obtained by a microwave technique at the Bordeaux Observatory and by a short Umkehr method at the Chiran station of the Observatoire de Haute-Provence, on 19 June 1981. There is a good agreement between the results obtained by both methods in spite of the distance between both sites.     

关于有限断层计算模型的研究——考虑位错时、空不均匀分布的滑动时间函数

断层面上某一点的滑动时间函数需要用三个参数来表达:断层的平均位错量、上升时间和破裂传播的时间延迟。本文基于有限断层模型,根据断层面上每个子源的位错量时、空不均匀分布特征,采用Brune模型系统确定了相应滑动时间函数的三个参数,构建了位错量呈时、空不均匀分布的有限断层滑动模型。该方法可以表现破裂面上断层位错量在时间和空间上分布的不均匀特征,既能够表现震源的复杂性同时又能够简化震源模型的构建过程,为考虑断层附近的强地震动数值模拟计算提供了有效的途径。     

Three Reflection Telescopes for Wide Field Space Astronomy. First Results from a 30 cm Prototype and Prospects

We present the basic concepts of the two-mirror, three-reflection optical system (2MTRT), and discuss the important benefits of such a system for space projects: wide ( 2^°) correctedand unvignetted FOV, without the use of refractive optics for thefield correction, planarity of the focal surface for an optimizedinstallation of wide area detectors, easy telescope adjustement, small volume and little mass.We also report the results of optical tests made with a 30 cm prototype,equipped with a 2k × 2k CCD camera, and give examples of scientific programmes which can be performed from space and in hostile terrestrial sites such as the Antarctic Plateau.