1,721,497 research outputs found
Study of the contrast in electric force microscopy images of RuO2-based thick-film resistors
No full textThe contrast mechanism of electric force microscopy (EFM) operating in static and dynamic modes have been investigated and applied to the clarification of the electrical conduction properties of RuO2-based thick-film resistors. Both the magnetic and the electrical contributions to the overall EFM signal and the corresponding contrast have been analysed and compared by using different types of atomic force microscopy tip (with a magnetic coating and with a Pt/Ir coating). It has been found that the EFM contrast changes on inverting the voltage polarity of the samples. The regions surrounding the RuO2 grains present an EFM signal which is lower for a negative bias than for a positive bias at low values of the applied voltage; this signal difference tends to disappear on increasing the absolute bias value. This behaviour, typical of semiconductors, ascribes to the above regions semiconducting properties
Work function dependence on the thickness and substrate of carbon contamination layers by Kelvin probe force microscopy
No full textThe contact potential difference (CPD) between carbon contamination (CC) layers and the several substrates on which they were deposited has been measured as a function of the film thickness by means of Kelvin probe force microscopy (KPFM). The observed CPD trends may be divided into three categories: (i) an increase, or decrease, in CPD with thickness up to a saturation value with sign inversion with respect to the substrates (Al and Si); (ii) an oscillation with no sign inversion (substrates, gold and platinum); (iii) an oscillation through sign inversion (palladium substrate). Effects (ii) and (iii) seem to be typical of CC, since they have not been observed for other materials, including evaporated carbon. Several possible causes of the above two effects are examined, but a satisfactory interpretation has not been found yet. The sensitivity of KPFM is such that CC layers 10 nm thick are easily visible, whereas they are hardly detectable by topography
Notula 1474. Aquilegia einseleana F.W. Schultz in NEPI C., PERUZZI L., SCOPPOLA A. (eds.), Notulae alla checklist della flora vascolare italiana: 5.
No full textThe collagen fibril surface: TMAFM, FEG-SEM and freeze-etching observations
No full textNative, unfixed collagen fibrils from rat tail tendon were dehydrated following
different procedures and observed under a FEG-SEM and an AFM operated in Tapping Mode
(TMAFM). Freeze-etched, untreated fibrils from the same tissue were also observed for comparison.
The most notable features of the fibril surface, i.e., the gap/overlap alternation and three prominent
intraperiod ridges, were simultaneously visible only in freeze-etched specimens, while under the
SEM and the TMAFM their appearance was dependent on both the dehydration procedure and the
visualization technique. The different susceptibility of the collagen fibril surface structures to
various treatments clearly implies the existence of domains of different composition. Moreover,
identical specimens were imaged differently by SEM and TMAFM, highlighting instrument-specific
advantages and limitations. The onset of dehydration-dependent, procedure-specific artifacts
should be considered in high-resolution studies of connective tissues. As for any biological specimen,
the final aspect of collagen fibrils is determined no less by the preliminary treatments than
by the visualization approach
Direct visualization of collagen-bound proteoglycans by tapping-mode atomic force microscopy
No full textMost studies on the interaction of collagen with proteoglycans, two universal components of connective tissues, use technical approaches which substantially modify the shape and size of the proteoglycans themselves. In the present study unfixed, untreated collagen fibrils from rat tail tendon were dehydrated and observed by tapping-mode atomic force microscopy. The surface of collagen fibrils immediately reveals a periodic alternation of gap and overlap zones. A thin, transverse ridge decorates the gap zone, while other filamentous structures run on the fibril surface, either parallel or perpendicular to the fibril axis. These surface structures are much enhanced by Cupromeronic Blue preincubation, while pretreatment with chondroitinase ABC removes them completely, leaving barely detectable transverse ridges. The ridge and filaments are likely to represent, respectively, the core protein and the glycosaminoglycan side chains of proteoglycans, displayed with a far better resolution than with conventional histochemical or immunohistochemical techniques. Our data suggest that proteoglycan molecules are capable of different, multiple interactions with the collagen fibril surface as well as with each other
Per il Centenario di Ulisse Aldrovandi (1522-1605)
No full textIl contributo esamina i caratteri del museo naturalistico di Ulisse Aldrovandi e li colloca nel quadro della cultura scientifica europea tardo-rinascimental
Tridimensional imaging of the collagen fibril: a comparative evaluation of different techniques.
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