[en] The influence of surface topography on the energy distribution of particles scattered from a sample was studied in a general review and investigated for specific cases. Experimentally the method consists of bombarding a sample from a particular direction with a monoenergetic beam of charged particles provided by an ion accelerator. The number of particles, which undergo large angle scattering into specific directions, and their energy within given intervals (channels) are determined. The result is called the energy spectrum. A general investigation of the interrelation between the profile of the surface and the energy spectrum was made. Although there is no one-to-one relationship, the general features of the surface topography are reflected in the specific shape of the spectrum: (1) Periodic surface profiles lead to yield oscillations in the spectrum. The oscillation length is directly related to the wavelenngth of the surface structure, and the shape is related to the type of surface undulations irradiated. (2) In case of a random surface, statistical properties such as the standard deviations from the mean level, and the correlation between surface excursions affect the spectral shape in a specific way. These results were achieved using both analytical and computer calculations. General rules were introduced first, linking the energy distribution of particles scattered from a general sample with the spectrum from a perfectly smooth surface. These rules state that the shape of the spectrum is affected but not the total yield. For periodic surfaces, the yield oscillations extend over the whole spectrum and a conservation rule applies to each oscillation. For random surfaces, the energy spectrum is most affected near maximum energy and the yield is balanced considering the whole spectrum

[en] In the two lecture volumes of the Proceedings of the International Congress on Forest Decline Research the papers are presented according to the topics of the plenary and poster sessions. The sessions had been devoted to the damage symptoms in forest decline, to the main stressors (atmosphere, climate, soil, biota), to the effects of the stressors (on rhizosphere, on decomposers, and on plants) (see vol. 1), to case studies (in Germany and abroad), to regional comparisons, to critical loads, and to silvicultural measures (see vol. 2). Additionally personal impressions about the forest decline phenomen in Germany and its causes and opinions about the perspective in regard to research needs, to silvicultural practices and to emission control are given. (orig./vhe)

[en] In the two lecture volumes of the Proceedings of the International Congress on Forest Decline Research the papers are presented according to the topics of the plenary and poster sessions. The sessions had been devoted to the damage symptoms in forest decline, to the main stressors (atmosphere, climate, soil, biota), to the effects of the stressors (on rhizosphere, on decomposers, and on plants) (see vol. 1), to case studies (in Germany and abroad), to regional comparisons, to critical loads, and to silvicultural measures (see vol. 2). Additionally personal impressions about the forest decline phenomen in Germany and its causes and opinions about the perspective in regard to research needs, to silvicultural practices and to emission control are given. (orig./vhe)

[en] A mathematic method for calculating nutrient uptake by plants was wasted through experimentation. The resulting data was not accurate enough to draw definite conclusions. However, some hypothetical conclusions were drawn mainly to get as much information as possible to improve future work. 4 refs, 2 figs, 3 tabs

[en] This paper, presented at the opening session of the congress, gives an introduction into the subject, summarizes the current state of forest decline research, and points out areas requiring further research. The following individual aspects are briefly dealt with: ecosystem perspective, criteria of forest decline, changes in chemical climate, adjustment of organism to changes in their environment, hypotheses on forest decline, predisposing effects, changes in the chemical soil state, natural and man-made soil acidification and vegetation type, changes in nutrient regimes and in forest growth, time course of soil acidification, the effect of soil acidification on trees, the water stress hypotheses of crown thinning of spruce, uncertainties in forest planning and management, deficiencies in the control of forest ecosystems, results of material balance case studies, restoration of the chemical soil state, environmental monitoring, hypothesis in respect top effects of air pollutants, missing basic knowledge, principles of self-organisation of ecosystems, the need for ecosystem research. (vhe)

[en] Purpose: For preoperative staging of colorectal cancer a CT scan is frequently performed. This report examines the sensitivity of CT for regional lymph node metastasis of colorectal cancer using different criteria. Materials and methods: Preoperative CT scans of 153 patients with colorectal cancer were analyzed using different criteria for N1. The results were then compared to the postoperative histological findings. Results: For N1=lymph nodes (LN)>1 cm the sensitivity was 47%. For N1=LN>1 cm or an increased number of LN<1 cm the sensitivity was 71%. In patients with a primary tumor seen on CT, sensitivity rose to 87%. Discussion: Evidence of regional nodal metastatic disease is only relevant for rectal cancer, colon polyps, and for locally excised tumors when considering present surgical concepts for the treatment of colorectal cancer. In these cases CT analysis using the broadened criteria for N1 proposes a valuable argument regarding possible preoperative radiotherapy or an operative revision. (orig.)

[en] Synthetic advances in the formation of ultrasmall (<10 nm) fluorescent poly(ethylene glycol)-coated (PEGylated) core–shell silica nanoparticles (SNPs), enabling improved particle size and surface chemical property control, have led to successful clinical translation of SNPs as diagnostic probes in oncology. Despite the success of such probes, details of the dye incorporation and resulting silica architecture are still poorly understood. Here, we employ afterpulse-corrected fluorescence correlation spectroscopy (FCS) to monitor fast fluorescence fluctuations (lag times <10^–5 s) of the negatively charged cyanine dye Cy5 as a probe to study such details for dye encapsulation in 5 nm silica cores of PEGylated core–shell SNPs (C dots). Upon deposition of additional silica shells over the silica core, we find that the amplitude of photoinduced cis–trans isomerization decreases, suggesting that the Cy5 dyes are located near or on the surface of the original SNP cores. In combination with time-correlated fluorescence decay measurements, we deduce radiative and nonradiative rates of the Cy5 dye in these particles. Finally, results demonstrate that FCS is a well-suited tool to investigate aspects of the photophysics of fluorescent nanoparticles, and that conformational changes of cyanine dyes like Cy5 are excellent indicators for the local dye environment within ultrasmall SNPs.

[en] We have measured with high resolution the full vector momenta of the doubly charged recoil ions produced when Ar and Ne atomic targets are ionized by intense circularly polarized few-cycle (∼8 fs) laser pulses in the sequential ionization region. The momentum spectra of the ions were found to exhibit structure which is characteristic of the relative binding energies of the two electrons and the sequential nature of the emission process. We demonstrate that the measured spectra can be used to extract subcycle time information regarding the sequential release of the two electrons

[en] We have measured angular distributions of ion fragments produced in dissociative double ionization of CO, CO₂, and C₂H₂ by intense ultrashort laser pulses. This report extends similar recent studies of O₂ and N₂ to a wider set of molecules. We found that for sub-10-fs pulses of sufficiently low intensity the fragments' angular distributions for all studied molecules are determined by angular dependence of the first ionization step. Those experimental angular distributions were in good agreement with angular dependent ionization probabilities calculated with the molecular tunneling ionization theory. The measured angular distributions directly reflect the symmetry of the corresponding molecular orbitals. For higher laser intensities and longer pulse durations, dynamic alignment and postionization alignment start to affect the angular distributions and ion fragments are preferentially ejected along the laser-polarization direction

[en] We have used momentum imaging techniques to measure in high resolution the kinetic energy release spectra and angular distributions of coincident O⁺ and N⁺ ion pairs produced by short laser pulses (8-35 fs) on targets of N₂ and O₂ at peak intensities between 1 and 12 x 10¹⁴ W cm^-2. We record the full momentum vectors of both members of each pair and achieve a kinetic energy release resolution of less than 0.3 eV. We find that the process proceeds through well-defined electronic states of the excited molecular dications. Using linear and circularly polarized light, we identify two mechanisms for the production of these states, rescattering and sequential ionization. By using 8 fs pulses, we observe that the internuclear distance can be frozen during the pulse. For low intensities and 8 fs pulses, emission from N₂ is strongly directed along the polarization vector, while that for O₂ is not, a result we interpret as being due to the different symmetries of the outer orbitals of these molecules. For high intensities and longer pulses, the distributions increasingly fold towards the polarization vector, ultimately peaking at zero degrees for both molecules. For oxygen, a local peaking for molecules aligned at right angles to the polarization vector is seen. A discussion and interpretation of the results are presented