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This study is focused on the historical evolution of a heavily eroded field with discontinuous grass cover on a major thalweg (ephemeral gully). Tens of parcels originally formed a protective pattern in the study area, and the thalweg was permanently covered with grass. During the period of collectivization, the field structure had been unified into a compact 34 ha parcel, which resulted in the formation of ephemeral gullies after every heavy rainfall event. Historical and recent aerial photographs were used to analyze the erosion occurrences, vegetation degradation connected with the erosion processes, and the land-use pattern. The visual erosion pattern assessment has indicated that in this field, rills and other erosion objects have repeatedly developed in the same locations in different time periods. The soil erosion hazard was also modelled by the new Czech erosion model Atlas EROZE. A comparison between the modelling results and the assessment of real visual data shows that areas at risk can be identified by both these methods. In addition, the land-use pattern was modelled using two different scenarios. The results suggest that soil erosion can be significantly reduced by segmentation of the field into smaller plots. [ABSTRACT FROM AUTHOR]

Number of erosive rains, kinetic energy of erosive rains and factor of erosive efficiency of rains according to the USLE methodology were assessed by two methods of erosive rains determination. The first method (VAR1) defined erosive rains by intensity ≥ 0.4 mm· min-1; total ≥ 12.5 mm and the second method (VAR2) by intensity ≥ 6 mm· 15 min-1; total ≥ 12.5 mm. Database contained one minute precipitation data from four automatic stations in the Czech Republic for the period of 2000-2005. Two-way analysis of variance (ANOVA) showed a statistically highly significant difference between the annual number of erosive rains determined by the two methods. The rains simultaneously complying with two following criteria (30 min intensity lower than 15 mm·h−1 and sum of 40 mm) were not generally classified as erosive rains according to VAR2. The number of erosive rains determined by VAR2 most often reached 40 to 50% of VAR1 results. Two-way ANOVA proved highly significant differences between the kinetic energy values for the erosive rains determined by VAR1 a VAR2. According to VAR2 the rains with kinetic energy lower than 3 MJ·ha −1 are generally not considered as erosive rains. The results of kinetic energy of the erosive rains determined by VAR2 most often reached 60 to 70% of VAR1 results. Two-way ANOVA has not proved a statistical difference between annual values of R factor of erosive rains determined by the two methods. According to VAR2 the rains with R factor lower than 5 are in general not included into annual R factor value. The results of annual R factor values of erosive rains determined by VAR2 are about 25% lower than the results of VAR1. Correlation between number of erosive rains, kinetic energy of erosive rains and annual R factor value assessed by both methods showed a statistically significant relationship. The conversion formulas between results of the two methods (VAR1 and VAR2) were derived by linear regression. As conclusion we can state that when using present automatic stations in R factor analyses, we have to be aware of overestimating the erosivities compared to historical data based on ombrograms, where only low temporal resolution data were available. [ABSTRACT FROM AUTHOR]

Abstract: A new classification of laser ion sources concerning their pulse-to-pulse reproducibility in the ion emission is proposed. In particular, we distinguish between plasmas according to the electron distribution and changing its characteristics at a laser intensity threshold of 1014 W/cm2. Well reproducible continuous pulsed ion currents are typical for the intensity below the threshold. In contrast to this plasma the “two-temperature” plasma arising for the intensity above this threshold shows not only a separation of charges in space and time during the expansion but it also shows outbursts of ions similar to a self-pulsing instability leading to a chaos. The sequence of fast ion outbursts visible on the time-resolved ion currents is sensitive to the details of non-linear interaction of the laser beam with the generated plasma. Analysis of ion sources based on a time-of-flight signal function is applied to quantify their emission characteristics as the hidden partial currents of the ionized species constituting, the total measured current, the centre-of-mass velocity of individual charge states, their abundance and the ion temperature. [ABSTRACT FROM AUTHOR]

Abstract: A novel analysis of ion currents, which is based on the use of shifted Maxwell–Boltzmann velocity distribution, is applied to quantify the properties of expanding laser-produced plasmas into the vacuum. The ion currents were measured outside the critical zone where the recombination and collisional excitation processes are not important and the charge-states of ions are frozen. The deconvolution of single-shot ion currents is applied for recovering the partial currents of participating ion species in the measured ion currents in carbon, copper and polyethylene plasmas created by various pulsed laser beams. This method allows determining the plasma temperature, the centre-of-mass velocities of individual charge-states and their abundance. The obtained charge-state dependencies of the centre-of-mass velocities render important details in establishing the mechanisms responsible for the ion emission, which has fundamental importance in applications of laser ion sources. [Copyright &y& Elsevier]

Ablation behavior of organic polymer (polymethylmethacrylate) and elemental solid (silicon) irradiated by single pulses of XUV radiation emitted from Z-pinch, plasma-focus, and laser-produced plasmas was investigated. The ablation characteristics measured for these plasma-based sources will be compared with those obtained for irradiation of samples with XUV radiation generated by a free-electron laser. [Copyright &y& Elsevier]

Emission of multiply charged ions and soft x-rays from the plasmas produced by laser pulses focused on (111) surface of Fe and Fe-2 mass % Si single crystals is investigated for wavelengths of 1064 and 248 nm and intensities up to ≈1×1010 W/cm2. It is demonstrated that the Si admixture in the Fe plasma results in a higher emission of Feq+ ions (1≤q≤4) but in a markedly lower x-ray emission. The relation of wavelengths and pulse durations of laser beams used is figured in the fluence dependence of the ion emission. [ABSTRACT FROM AUTHOR]

The emission of multiply charged Cuq+ ions from a plasma produced by 308 nm excimer laser is analyzed with respect to the distance from the irradiated target. The critical zone, outside which the charge states of ions of the expanding plasma are frozen, was determined to be approximately 20 cm from the target. This value was estimated using a charge-freezing criterion expressed by a distance dependence of the total charge carried by the ions Q∝L-2, which describes the dilution of plasma by its expansion into a vacuum without collisional recombination processes. [ABSTRACT FROM AUTHOR]

The interaction of an intense laser pulse with a solid target produces large number of fast free electrons. This emission gives rise to two distinct sources of the electromagnetic pulse (EMP): the pulsed return current through the holder of the target and the outflow of electrons into the vacuum. A relation between the characteristics of laser-produced plasma, the target return current and the EMP emission are presented in the case of a massive Au target irradiated with the intensity of up to 3 × 1016 W/cm2. The emission of the EMP was recorded using a 12 cm diameter Moebius loop antennas, and the target return current was measured using a new type of inductive target probe (T-probe). The simultaneous use of the inductive target probe and the Moebius loop antenna represents a new useful way of diagnosing the laser-matter interaction, which was employed to distinguish between laser-generated ion sources driven by low and high contrast laser pulses. [ABSTRACT FROM AUTHOR]

This paper provides an up-to-date review of the problems related to the generation, detection and mitigation of strong electromagnetic pulses created in the interaction of high-power, high-energy laser pulses with different types of solid targets. It includes new experimental data obtained independently at several international laboratories. The mechanisms of electromagnetic field generation are analyzed and considered as a function of the intensity and the spectral range of emissions they produce. The major emphasis is put on the GHz frequency domain, which is the most damaging for electronics and may have important applications. The physics of electromagnetic emissions in other spectral domains, in particular THz and MHz, is also discussed. The theoretical models and numerical simulations are compared with the results of experimental measurements, with special attention to the methodology of measurements and complementary diagnostics. Understanding the underlying physical processes is the basis for developing techniques to mitigate the electromagnetic threat and to harness electromagnetic emissions, which may have promising applications. [ABSTRACT FROM AUTHOR]

It is known that exposure of a target to a focused laser beam results in the occurrence of a time-varying current between the target and the grounded vacuum chamber. This current is composed by three distinct phases, namely, the ignition phase, in which the laser pulse drives the electron emission, while electrons coming from the ground through the target holder balance the positive charge generated on the target. The active phase appears at post-pulse times and it is characterized by the presence of peaked structures in the time-resolved current, representing characteristics of the target composition. Finally, the afterglow phase is determined by a current of electrons flowing from the target to the ground. In the active phase of target current resulting from polymers ablation with an UV KrF laser, negative target current peaks have been observed, whose origin is still unknown. We investigate the dependence of these current structures on the dimensions of the target, using ultra-high molecular weight polyethylene disks of different thickness. We provide evidence to explain the origin of such negative peaks. We found, indeed, that target initially charges positively under the action of the laser pulse, leading to a first negative target current peak. Then, a net charge unbalance is produced that further attracts free electrons on target surface. This behavior is enhanced if an opportune static electric field is imposed between the target and an opposite electrode. [ABSTRACT FROM AUTHOR]

Land use is one of the important factors affecting the water quality in catchments. This study evaluates differences in water quality due to land use in the upper transboundary catchment of the river Nisa (694 km 2 ) in the Czech-German-Polish triangle. Water samples collected weekly from the river and its tributaries at 29 sampling sites were analysed for a total of 25 parameters, including nutrients, major ions, major elements and traces of heavy metals. Each sampling site represents a sub catchment characterized by a specific composition of 8 land-use categories. Cluster analysis has been applied to divide the sub catchments into five land-use classes. When all measured parameters were taken into account, this statistical method resulted in six groups of sampling sites that are similar in their chemical water composition and that, at the same time, reflects the land use, regardless of sub-catchment size. Water quality was particularly affected by the portions of settlement areas and arable land. Sub catchments which were mainly forested (above 70%) show the smallest level of concentration for all monitored parameters (except Cd, Mn, SO 4 ). Densely populated areas reduce water quality despite high proportions of forest. [ABSTRACT FROM AUTHOR]

• Linkage between soil surface microrelief and overland flow was examined. • Differently oriented wheel tracks served as water flow paths or as sediment sinks. • Increase of surface connectivity after a rain was shown by functional connectivity. • Structural connectivity showed reorganization of the surface runoff pathways. Although wheel tracks cover only a small portion of the surface of agricultural fields, their effect on surface runoff and sediment transport is substantial. Wheel tracks change the microrelief of the soil surface, and influence how the surface is further altered by rainfall and runoff. This study presents a plot-scale microrelief analysis of a tilled surface with wheel tracks under simulated rainfall. Digital elevation models of the microrelief with 1 cm spatial resolution were obtained using the Structure from Motion method. The random roughness, the structural connectivity, and functional connectivity were calculated for before-rainfall and after-rainfall soil surface conditions. The experiments were carried out on inclined, freshly-tilled plots (8 m long, 2 m wide). The wheel tracks were created by four passages of machinery in the slope direction (SWT) and in the contour-line direction (CWT). The experiments were compared to reference plots without wheel tracks (NWT). The wheel tracks increase water and sediment connectivity if they are oriented in slope-wise direction. Microrelief analysis shows that SWT drains water from the surrounding soil. The soil surface adjacent to SWT can also become more connected with the wheel track, due to changes in microrelief introduced by rainfall and runoff. The calculated higher connectivity in the SWT plot corresponded to the measured increased sediment loads. This suggests faster overland flow and therefore shorter flow pathways on the soil surface microrelief. CWT leads to a decrease in the water and sediment connectivity compared to the NWT and SWT plots. Although the surface runoff can overflow the CWT, the network of flow paths results in decreased flow velocity and a slower sediment transport rate. However, the CWT effect is not permanent, and declines as the wheel tracks become silted with the deposited sediment. It is shown that detailed microrelief data provide relevant information for a study of the changes in flow routing in a tilled agricultural field with the presence of a wheel track. SWT accelerates the runoff and especially the sediment transport. During a rainfall event, the hydraulic connection between the wheel track and the surrounding soil increases dramatically. CWT reduces the surface runoff and also the sediment transport. In the long term, rainfall events and surface runoff alter the microrelief connectivity, causing the soil surface to be more hydraulically connected, irrespective of the wheel track orientation. This study demonstrates the effect of wheel tracks on water and sediment transport. The results draw attention to the importance of appropriate soil protection measures, as a bare unprotected surface microrelief exposed to rainfall leads to increased sediment connectivity. [ABSTRACT FROM AUTHOR]

Recent progress in ultrashort-pulse high-power laser technology has resulted in the production of extremely high light intensities approaching 1020 W/cm². The great non-linear forces generated by the laser pulse during its interaction with plasma can be used to accelerate electrons and ions to energies from hundreds of keV to hundreds of MeV over distances of only microns. This creates the prospect of construction of compact laser-based particle accelerators and their application in material science, medicine, nuclear physics, and inertial confinement fusion. In this paper, the results of our recent studies on fast ion generation in plasma produced by an intense 1-ps laser pulse, performed using the terawatt Nd:glass laser at Institute of Plasma Physics and Laser Microfusion (IPPLM) in Warsaw, are briefly reviewed. The properties of fast proton beams generated from thin foil targets of various structures as well as the heavy ion fluxes emitted from massive high-Z targets are discussed. The possibility of producing picosecond ion beams of ultrahigh ion current densities (> 1010 A/cm² close to the target) is considered. The most important features of fast ion generation in the plasmas produced by ultrashort (1 ps) and long (0.5 ns) laser pulses are also compared. [ABSTRACT FROM AUTHOR]

In a mixture of molecular gases with compositions (CO2–N2–H2O and CO–N2–H2O) and total pressure close to that of the Earth’s early atmospheres, a centimeter-sized plasma was created by focusing a single 85-J, 450-ps near-infrared laser pulse in a center of 15-L gas cell. Chemical consequences of the laser-produced plasma generation in such a mixture were investigated using high-performance liquid chromatography with mass-spectrometric detection (HPLC/MS). Amino acids were identified in the reaction mixture containing CO2 as well as in that one based on CO, both exposed to 10 laser shots. [Copyright &y& Elsevier]