In Ar-rich Ar–H2–CH4 gas mixture the presence of H2 is found to be beneficial to the plasma stability. On the other hand, too high H2 percentages lead to materials showing a high surface roughness. ...In the present work, diamond films were grown on p-type Si (100) substrates screening different quantities of H2. The plasma phase and plasma–substrate interface were investigated by in-situ optical emission spectroscopy and pyrometric interferometry to determine the behavior of emitting species and the deposition rates, respectively. The obtained films were characterized by Raman micro-spectroscopy, AFM and SEM techniques. For H2 percentages between 6.3 and 10%, the structure and morphology are characteristic of nanocrystalline films, affording low roughness values when a buffer layer was grown between the diamond coating and the treated silicon surface.
► We explore the limits of the hydrogen percentage in Ar–H2–CH4 gas mixtures. ► We develop a new kind of buffer layer between the diamond films and treated silicon substrate. ► We obtain a low roughness of the coatings without modifying the Astex-type reactor.
Raman spectroscopy is a powerful technique for studying cellular biochemistry. In fact, each toxic chemical induces biochemical changes related to the own action mechanism. In this investigation ...Raman microspectroscopy has been used, in correlation with atomic force microscopy images, to detect biochemical and structural damages occurring in cultured human cells as a consequence of deltamethrin exposure. Cultured human keratinocyte cells have been exposed at increasing concentrations of deltamethrin from 10
−3
M to 10
−6
M for 24
h. A viability test indicated that the cytotoxic dose corresponds to exposure at deltamethrin solution for 24
h with the chemical concentration between 10
−4
M and 2.5
10
−4
M. The compared analysis of Raman spectra and AFM images allows to state that an evident damage occurs in the plasmatic membrane and it is already detectable after exposure of keratinocytes at the lowest investigated deltamethrin concentration (10
−6
M). The most important modifications are related to the breakdown of CH
2 bonds of lipidic chains, whereas proteineous bonds are less involved in the deltamethrin action. On the whole, cellular damage starts after exposure to deltamethrin doses well lower than that established as cytotoxic.
Aims: Lactobacillus brevis IOEB 9809 is able to produce both tyramine and putrescine via tyrosine decarboxylase and agmatine deiminase enzymes, respectively, when cultured on synthetic media. The ...aims of this study were to assess the expression of L. brevis IOEB 9809 tdc and aguA1 genes, during wine fermentation and to evaluate the effect of substrate availability and pH on tdc and aguA1 expression, as well as on biogenic amine production and L. brevis viability.
Methods and Results: The relative expression of L. brevis IOEB 9809 tdc and aguA1 genes was analysed in wine by quantitative real‐time RT‐PCR (qRT‐PCR) during a period of incubation of 30 days. Cell viability, pH values, putrescine and tyramine concentration were monitored throughout the experiments.
Conclusions: The wine trials indicated that L. brevis IOEB 9809 is able to produce both tyramine and putrescine during wine fermentation. Increased cell viability was also observed in wine supplemented with tyrosine or agmatine. qRT‐PCR analysis suggests a strong influence of substrate availability on the expression of genes coding for tyrosine decarboxylase and agmatine deiminase in L. brevis IOEB 9809. Less evident is the relationship between putrescine and tyramine production and tolerance to wine pH.
Significance and Impact of Study: To our knowledge, this study represents the first assessment of relative expression of L. brevis IOEB 9809 genes involved in biogenic amine production in wine. Furthermore, an effect of biogenic amine production on viability of L. brevis during wine fermentation was established.
The mechanical properties of polycrystalline diamond coatings with thickness varying from 0.92 to 44.65
μm have been analysed. The tested samples have been grown on silicon substrates via microwave ...plasma enhanced chemical vapour deposition from highly diluted gas mixtures CH
4–H
2 (1% CH
4 in H
2). Reliable hardness and elastic modulus values have been assessed on lightly polished surface of polycrystalline diamond films.
The effect of the coating thickness on mechanical, morphological and chemical-structural properties is presented and discussed. In particular, the hardness increases from a value of about 52 to 95
GPa and the elastic modulus from 438 to 768
GPa by varying the coating thickness from 0.92 to 4.85
μm, while the values closer to those of natural diamond (H
=
103
GPa and E
=
1200
GPa) are reached for thicker films (>
5
μm). Additionally, the different thickness of the diamond coatings permits to select the significance of results and to highlight when the soft silicon substrate may affect the measured mechanical data. Thus, the nanoindentation experiments were made within the range from 0.65% to 10% of the film thickness by varying the maximum load from 3 to 80
mN.
► 190: diamond film. ► 560: plasma CVD. ► 430: mechanical properties characterization. ► 450: morphology.
Melanin obtained from the liver of
Rana esculenta L., was isolated from melanosomes and deposited as thin film on quartz substrate, in order to perform Raman, absorption and photoluminescence ...measurements at room temperature. The Raman spectrum was analysed by considering the contribution of the vibrational modes from different functional groups of the melanin structure. The absorption and photoluminescence measurements support the model that melanin consists of nano-aggregates of oligomeric structures rather than extended heteropolymer. An optical gap value of about 0.6
eV was estimated by considering the Tauc model. The largest size group of clusters mainly contribute to determine the optical gap value, whereas the PL emission is due to groups of clusters which are selectively pumped.
We report a detailed investigation of fluorescence properties of synthetic eumelanin pigment in solution. A complete set of fluorescence spectra in the near-UV and visible range is analysed. ...Excitation spectra at a few selected emission energies are also investigated. Our measurements support the hypothesis that fluorescence in eumelanin is related to chemically distinct oligomeric units that can be selectively excited. Fluorescence due to large oligomer systems is spectrally differentiated from that due to monomers and small oligomer systems. Fluorescence excitation measurements show the contribution of 5,6-dihydroxyndole-2-carboxylic acid and 5,6-dihydroxyndole monomers to the emission of small-size oligomers.
This work presents a new, very long snowfall time series collected in a remote site of Italian Apennine mountains (Montevergine Observatory, 1280 m above sea level). After a careful check, based on ...quality control tests and homogenization procedures, the available data (i.e. daily height of new snow) have been aggregated over winter season (December-February) to study the long-term variability for the period 1884-2020. The main evidence emerging from this analysis lies in (i) the strong interannual variability of winter snowfall amounts, (ii) the absence of a relevant trend from the late 19th century to the mid-1970s, (iii) the strong reduction in the snowfall amount and frequency of occurrence from the mid-1970s to the end of the 1990s and (iv) the increase in average snowfall amount and frequency of occurrence in the past 20 years.
Aim: Understanding the molecular response to stress tolerance of wine Lactobacillus plantarum.
Methods and Results: Two genes codifying for heat shock proteins were cloned from wine L. plantarum. ...The coding regions of the two heat shock genes are 420 and 444 nucleotides long, and started with an ATG codon suggesting that they were translated. The protein sequences deduced from the isolated genes have a molecular mass of 18·483 and 19·282 kDa, respectively, and were therefore named hsp18·5 and hsp19·3. The expression of small heat shock genes was analysed by RT‐PCR analysis. Moreover, the 5′ and 3′ noncoding regions were cloned and sequenced.
Conclusions: The expression of the heat shock genes was strongly induced by heat, cold and ethanol stress. Analysis of the 5′ and 3′ flanking regions of hsp18·5 and hsp19·3 genes, revealed the presence of an inverted repeat sequence (TTAGCACTC‐N9‐GAGTGCTAA) homologue to the CIRCE elements found to the upstream regulatory region of heat shock operons, and an inverted sequence that could form a stem and loop structure that it is likely to function as a transcriptional terminator. Based on their structures, the genes were classified as belonging to Class I of heat shock genes according to the B. subtilis nomenclature of heat response genes.
Significance and Impact of the Study: Small heat shock genes isolated from wine L. plantarum might have a role in preventing damage by cold stress.
Summary
Morphological changes of normal human keratinocyte cells have been monitored by means of atomic force microscopy after the exposure at a mercury solution containing HgCl2 at 10−7 M. The ...measurements have been carried out in contact mode in a thermostated liquid cell, to reproduce a cellular environment similar to the physiologic one. Remarkable alterations of the cellular morphology and volume have been revealed after few minutes from starting the exposure experiment, although the HgCl2 concentration is several orders of magnitudes lower than the cytotoxic value (10−4 M). The atomic force microscopy technique results to be a powerful mean to investigate modifications induced in the cell morphology by external chemical agents.
Undoped CdSe and CdSe:Zn thin films have been grown on silicon substrate by using pulsed laser deposition technique. The electrical, structural and optical properties have been investigated. The ...films grow crystalline and highly oriented. Electrical measurements show that they are n-type doped. The reflectivity and photoluminescence are consistent and point out that the undoped CdSe film present excitonic features at low temperature, differently from CdSe:Zn films, whose spectral features are related to band–band transition. The luminescence efficiency of CdSe:Zn persists up to room temperature, whereas the luminescence of undoped CdSe is scarcely visible above 250
K.
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