Impacts of soil conditions and light availability on natural regeneration of Norway spruce Picea abies (L.) H. Karst. in low-elevation mountain forests

& Key message Natural regeneration of P. abies (L.) H. Karst. may reach high densities in lower mountain elevations. The highest densities were found in sites with moderate light availability, with low pH, and not near the riverbank. However, age-height classes differed in the predicted magnitude of response, but were consistent in response directions. Mosses and understory species typical of coniferous forests were positively correlated with regeneration density. & Context Norway spruce Picea abies (L.) H. Karst. in Central Europe is at risk under climate change scenarios, particularly in mountain regions. Little is known about the impact of environmental factors on the natural regeneration of P. abies in lowelevation mountain forests. & Aims We aimed to assess impacts of distance from the riverbank, soil pH, and light availability on natural P. abies regeneration. We hypothesized that (1) natural P. abiesregeneration would depend on light availability and soil pH and (2) there are understory plant species which may indicate the microsites suitable for natural regeneration of P. abies. & Methods The study was conducted in the Stołowe Mountains National Park (SW Poland, 600–800 m a.s.l.). We established 160 study plots (25 m2 ) for natural regeneration, light availability, soil pH, and understory vegetation assessment

Chemical vapour deposition of reactive organogermanium films by laser-induced decomposition of tetramethoxygermane

Laser-induced multiphoton and SF6-photosensitised decomposition of tetramethoxygermane has been used for chemical vapour deposition of reactive organooxogermanium polymers, which were characterised by IR, VIS, and UV spectra and ESCA and TEM techniques. The properties of the deposited layers differed depending on the mode of tetramethoxygermane decomposition. The films were reactive towards the ambient atmosphere; this is discussed in terms of the reaction of CH3OGe groups with air moisture.Peer Reviewe

Formation of nano-pyramids of layered materials with AFM

We have been able to raise squares of around 2 A in height of the layered materials Bi1.6Sb0.4Se3, Bi1.9Sb0.1Se3 and Bi2Se3 by means of contact atomic force microscopy in air. By raising squares on/beneath previously produced squares, Mayan-like pyramids have been constructed, each step of the pyramid being around 2 A in height. We neither remove matter from the surface nor produce a localized oxidation of the sample; we elevate a portion of it. When the surface is oxidized, the AFM cantilever pulls the oxide off producing holes. The raising of the squares is also possible in a nitrogen atmosphere

Charakterystyka kompozytu o osnowie ceramicznej modyfikowanej włóknami węglowymi

Carbon micro/nanofibers prepared by catalytic chemical vapor deposition have been characterized in the form of powders and in the form of filaments, intercorporated in the matrix of ZrO2. Scanning electron microscopy, transmission electron microscopy, high resolution electron microscopy, electron spectroscopy for chemical analysis and Raman spectroscopy have been used. The outer diameter of the fibers varied from 50 nm to 600 nm with an average diameter of 120 nm, length from several micrometers to several tens of micrometers and inner diameters from 20 nm to 230 nm. Two types of fibers have been identified; cylindrical which consists of a distinct graphite layers parallel to the fiber axes and bamboo - shaped fibers with walls which are built from domains with different orientations of graphite layers. The fibers contain 99.05 at.% carbon and 0.95 at.% oxygen with a binding energy of O (1s) electrons of 532.7 e V which corresponds to carbon in C-O bonds. In the first-order Raman spectra, the position of the band G was found at 1600 cm-1 and D at 1282 cm-1. The CNFs in ZrO2+ CNFs composite have been relatively well dispersed, however clusters of CNFs together with porosity are present as a result of the difficulty of dispersing, too. TEM and HREM revealed that the CNFs are usually located at the grain boundaries of ZrO2 in the form of undamaged nanofibers or disordered graphite.Włókna węglowe przygotowane metodą osadzania z par (tzw. Chemical Vapour Deposition), były badane bezpośrednio po wytworzeniu oraz po wprowadzeniu do osnowy ceramicznej metodami elektronowej mikroskopii skaningowej, transmisyjnej oraz spektroskopii ramanowskiej. Średnica włókien wahała się pomiędzy 50 nm, a 600 nm przy sredniej wartości ok.120 nm, podczas gdy ich długość wynosiła od kilku do kilkudziesięciu mikrometrów. Identyfikowano dwa rodzaje budowy włókien, tj. cylindryczne oraz z wewnętrznymi przekładkami typu „łodygi bambusa“. Włókna węglowe zawierały do 0.95 at. % tlenu o energi wiazania O (1s) ok.532.7 e V, co odpowiada wiązaniu C-O. Na pierwszym widmie Ramana pasmo G identyfikowano dla 1600 cm-1, a pasmo D dla 1282 cm-1. Badania kompozytu wykazałay równomierny rozkład włókien w ceramicznej osnowie. W sąsiedztwie większych aglomeratów stwierdzono tendencje do występowania pustek. W czasie spiekania przeważająca część włókien zachowała swoją rurkową strukturę, natomiast pozostały materiał węglowy uległ przemianie do słabo uprządkowanych struktur grafitu lub nawet uległ amorfizacji

Atomic surface characterisation and modification of the layered compounds Bi2Se3, Bi1.9Sb0.1Se3 and Bi1.6Sb0.4Se3.

In this work, we show atomic STM images of the layered compound Bi2Se3. We study the effect in the surface of the substitution of 5% and 20% of the Bi atoms for Sb in Bi1.9Sb0.1Se3 and Bi1.6Sb0.4Se3. The images of the three samples show similar trigonal structures corresponding probably to the van der Waals Se atoms. The distance measured between surface atoms in Bi2Se3 is 4.04 A, in Bi1.9Sb0.1Se3 is 4.16 A and in Bi1.6Sb0.4Se3 is 4.26 A. In Bi1.6Sb0.4Se3 some atomic sites appear brighter than others. The effect is accentuated at higher tunnelling currents and is not observed in the other compounds. Nanoscopic range depressions on the sample might be related to the skeletal crystal structure since the images show atomic corrugations that align slightly in one direction. We explain the results as the effects of the interactions between tip and sample, and discuss two interpretations: on the one hand, localised depression of the individual atomic sites, and on the other the possible elevation of the atoms of the surface due to a phase transition of the compounds induced by STM

IR laser therlomytic conversion of disiloxanes to polyoxocarbosilane phase and silicon carbide

International audienceContinuous-wave CO2 laser irradiation into gaseous methyldisiloxanes [(CH3)nH32nSi]2O (n ~ 2,3) at 1000 uC yields nanosized Si/C/O–carbon composites and at 2000 uC affords SiC–Si/C/O–carbon composites. The results demonstrate the feasibility of the direct production of silicon carbide from disiloxanes and suggest that the laser-induced homogeneous thermolysis of disiloxanes to SiC can be a preferred alternative to the earlier reported conventional thermolysis of specially synthesized polysiloxanes