•CNC reinforced PVA bio-nanocomposites were prepared.•IR, 2D correlation spectroscopy and XRD methods evidenced the H-bond formation.•Gravimetric method coupled with NIR and 2D COS indicated the ...reduction of water sorption in the reinforced films.
Bio-nanocomposite films based on cellulose nanocrystals reinforced poly(vinyl alcohol) were obtained by solvent casting method. To assess the structural features of the films, different spectral techniques (FTIR, 2D COS and XRD) have been used. Infrared and 2D correlation spectroscopy evidenced the presence of H-bond interactions between the PVA and CNC, and the variation in the conformational rearrangements, while XRD showed that the crystallite size and the crystallinity degree were affected by the incorporation of CNC. At low content of CNC in the PVA matrix, the crystallinity degree decreased to 29.9%, while at higher CNC content increased to 80.6%, comparing to PVA (35.4%). To evaluate the interaction with water, contact angle measurement, water sorption and NIR spectroscopy were used, respectively. The increase of the CNC content induced a reduction in water sorption ability from 93% for PVA to 75% for PVA/CNC films, indicating the involvement of the hydroxyl groups in new hydrogen bonded interactions. By analyzing the variation of the NIR bands from 1930, 1902 and 1985nm, was observed that the water molecules interact with the polymer matrix through moderate hydrogen bond before diffusing into the free volume of the matrix and form stronger hydrogen bonds.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPUK, ZRSKP
The aim of this study is to find the most convenient procedure to make an easy differentiation between various kinds of wood. The wood samples used were: fir (Acer alba), poplar (Populus tremula), ...lime (Tillia cordata), sycamore (Acer pseudoplatanus), sweet cherry (Prunus avium), hornbeam (Carpinus betulus), walnut (Juglans regia), beech (Fagus sylvatica), oak (Quercus robur). The methods of investigation used were FT-IR spectroscopy, X-ray diffraction and thermogravimetry.
By FT-IR spectroscopy, was observed that the ratio values of lignin/carbohydrate IR bands for wood decreases with increasing the average wood density, showing a decrease in lignin content. Also, the calculated values of lignin percentage from the FT-IR spectra are in very good correlation with the values from literature.
Following the deconvolution process of the X-ray diffraction patterns, it was found that the degree of crystallinity, the apparent lateral crystallite size, the proportion of crystallite interior chains and cellulose fraction tend to increase with increasing of the wood density.
Thermal analysis is able to give information about degradation temperatures for the principal components of different wood samples. The shape of DTG curves depends on the wood species that cause the enlargement of the peaks or the maxima of the decomposition step varies at larger or smaller temperatures ranges. The temperatures and weight loss percentage are particular for each kind of wood.
This study showed that analytical methods used have the potential to be important sources of information for a quick evaluation of the chemical composition of wood samples.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPUK
Nanocomposite films containing cellulose nanocrystals (CNC), as the reinforcing phase, and poly(vinyl alcohol) (PVA)/starch (S) blend, as the matrix, were prepared by solution casting technique. For ...the preparation, 5, 10, 15 wt% CNC suspension were incorporated in blends containing 90 wt% PVA/10 wt% S, 75 wt% PVA/25 wt% S and 50 wt% PVA/50 wt% S. Structural evaluation was done by Fourier transform infrared spectrometry and X-ray diffraction, and the morphological aspects by atomic force microscopy. Infrared spectroscopy evidenced the presence of H-bond interactions between the PVA and S and between PVA/S blend and CNC, and also variation in the conformational rearrangement, while the X-ray diffraction showed that the crystallite size and the degree of crystallinity were strongly affected by blending of PVA with S and also by the incorporation of CNC in the nanocomposite films. The surface roughness of studied samples increased with the increasing of S and filler content.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPUK, ZRSKP
► Evaluation of structural behaviour of Tilia wood heat treatment with low temperature and humidity. ► Chemical modifications were investigated by FT-IR, PCA and 2D-COS spectroscopy. ► HT treatment ...of wood revealed the formation of acetic acid, which catalyse the hydrolysis of carbohydrates. ► At the beginning a higher extent of carbohydrates, then an increase of the lignin degradation was observed.
It is known that heat treatment of wood combined with a low percent of relative humidity causes transformations in the chemical composition of it. The modifications and/or degradation of wood components occur by hydrolysis, oxidation, and decarboxylation reactions. The aim of this study was to give better insights on wood chemical modifications during wood heat treatment under low temperature at about 140°C and 10% percentage of relative humidity, by infrared, principal component analysis and two dimensional infrared correlation spectroscopy. For this purpose, hardwood samples of lime (Tilia cordata) were investigated and analysed.
The infrared spectra of treated samples were compared with the reference ones, the most important differences being observed in the “fingerprint” region. Due to the complexity of this region, which have contributions from all the wood constituents the chemical changes during hydro-thermal treatment were examined in detail using principal component analysis and 2D IR correlation spectroscopy.
By hydro-thermal treatment of wood results the formation of acetic acid, which catalyse the hydrolysis reactions of hemicelluloses and amorphous cellulose. The cleavage of the β-O-4 linkages and splitting of the aliphatic methoxyl chains from the aromatic lignin ring was also observed. For the first treatment interval, a higher extent of carbohydrates degradation was observed, then an increase of the extent of the lignin degradation also took place.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPUK
Degraded sensory experience during critical periods of development can have adverse effects on brain function. In the auditory system, conductive hearing loss associated with childhood ear infections ...can produce long-lasting deficits in auditory perceptual acuity, much like amblyopia in the visual system. Here we explore the neural mechanisms that may underlie “amblyaudio” by inducing reversible monaural deprivation (MD) in infant, juvenile, and adult rats. MD distorted tonotopic maps, weakened the deprived ear's representation, strengthened the open ear's representation, and disrupted binaural integration of interaural level differences (ILD). Bidirectional plasticity effects were strictly governed by critical periods, were more strongly expressed in primary auditory cortex than inferior colliculus, and directly impacted neural coding accuracy. These findings highlight a remarkable degree of competitive plasticity between aural representations and suggest that the enduring perceptual sequelae of childhood hearing loss might be traced to maladaptive plasticity during critical periods of auditory cortex development.
► Reversible monaural hearing loss induced at various stages of development in rats ► Recordings show bidirectional plasticity in monaural and binaural representations ► Reorganization greater in cortex than midbrain, greater in infancy than later life ► Plasticity causes shift in encoding accuracy assessed with a computational model
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPUK, ZAGLJ, ZRSKP
Biobased materials present a great interest due to their properties and biodegradability. Cellulose nanocrystals (CNC) nanofiller, in various amounts, was incorporated into a carboxymethyl cellulose ...(CMC)–glycerol (G) matrix in order to obtain nanocomposite systems with improved properties. The effect of the nanofiller on the structural features was investigated by Fourier transform infrared (FT-IR) spectroscopy, principal component analysis (PCA), two-dimensional correlation spectroscopy (2D-COS), and X-ray diffraction, while the sorption properties were evaluated by water vapor isotherms using the gravimetric method coupled with infrared spectroscopy. We observed the presence of the interactions taking place between the CMC-G and CNC involving the hydroxyl and carboxylate groups, which decreased the number of water sorption sites. Following this, the moisture content in the nanocomposite films decreased with the increase in the amount of CNC. Moreover, the bands associated to water molecules presented different wavenumber values separated for CMC-G and CNC components.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
An investigation of the constitutional adaptive gelation process of chitosan/cinnamaldehyde (C/Cy) dynagels is reported. These gels generate timely variant macroscopic organization across extended ...scales. In the first stage, imine‐bond formation takes place “in‐water” and generates low‐ordered hydrogels. The progressive formation of imine bonds further induces “out‐of‐water” increased reactivity within interdigitated hydrophobic self‐assembled layers of Cy, with a protecting environmental effect against hydrolysis and that leads to the stabilization of the imine bonds. The hydrophobic swelling due to Cy layers at the interfaces reaches a critical step when lamellar self‐organized hybrids are generated (24 hours). This induces an important restructuration of the hydrogels on the micrometric scale, thus resulting in the formation of highly ordered microporous xerogel morphologies of high potential interest for chemical separations, drug delivery, and sensors.
Dynamic constitutional gelation of chitosan/cinnamaldehyde (C/Cy) generates variant‐adaptive macroscopic organization across extended scales (see figure). The resulting highly ordered microporous xerogel morphologies are of high potential interest for chemical separation, drug delivery, and sensors.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
The main difficulties in wood and pulp analyses arise principally from their numerous components with different chemical structures. Therefore, the basic problem in a specific analytical procedure ...may be the selective separation of the main carbohydrate-derived components from lignin due to their chemical association and structural coexistence. The processing of the wood determines some structural modification in its components depending on the type of wood and the applied procedure. Fourier transform infrared (FT-IR) spectrometry and X-ray diffraction have been applied to analyze Eucalyptus g. wood chips and unbleached and chloritebleached pulp. The differences between samples have been established by examination of the spectra of the fractions obtained by successive extraction (acetone extractives, acetone free extractive samples, hemicelluloses, and lignins) by evaluating the derivative spectra, band deconvolution, etc. The energy and the hydrogen bonding distance have been evaluated. The relationship between spectral characteristics and sample composition has been established, as well as the variation of the degree of crystallinity after pulping and bleaching. The integral absorption and lignin/carbohydrate ratios calculated from FT-IR spectra of the IR bands assigned to different bending or stretching in lignin groups are stronger in the spectrum of eucalyptus chips than those from brown stock (BS) pulp spectra because of the smaller total amount of lignin in the latter. FT-IR spectra clearly show that after chlorite bleaching the structure of the wood components is partially modified or removed. Along with FT-IR data, the X-ray results confirmed the low content of lignin in the pulp samples by increasing the calculated values of the crystalline parameters. It was concluded that FT-IR spectroscopy can be used as a quick method to differentiate Eucalyptus globulus samples.
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NUK, OILJ, SAZU, UKNU, UL, UM, UPUK
In this study the weathering behavior of lime wood (Tillia cordata Mill.) has been examined using FT-IR and 2D IR correlation spectroscopy, which evidenced chemical changes induced by exposure to ...weathering conditions. It was showed that lignin is most sensitive component to the photodegradation processes as indicated by considerable decreases in the intensities of the characteristic aromatic lignin band at 1505cm−1 and other associated bands.
By 2D correlation spectroscopy has been demonstrated that the moment of CO from carboxyl and acetyl groups in hemicelluloses is changing first, followed by the CC of aromatic skeletal, CO in non-conjugated ketones, carboxyl groups and lactones, absorbed O–H and conjugated C–O groups in quinones.
The carbonyl formation corresponded well with lignin degradation, indicating a close relationship between them. Comparing the rate of carbonyl formation and lignin decay clearly showed that the former is remarkably higher than the latter, indicating the formation of carbonyl bands at 1738cm−1 probably resulted from not only lignin oxidation but also from reactions occurring in other components of the wood. Quinine formation is combined with the decay of aromatic structures and the formation of conjugated carbonyl groups.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPUK
Aim
Past pollen records reveal the changes in latitudinal distribution of plants in relation to climate, particularly their expansion in response to global warming. The maximum northward expansion of ...the mangrove genus Avicennia since the Early Eocene is known, but this information is missing for other mangrove taxa. Here, we evaluate the diversity of past mangroves with respect to latitude during three Cenozoic thermal maxima (PETM: 56 Ma; EECO: 54–49 Ma; MMCO: 17–14 Ma).
Location
North Atlantic, Mediterranean.
Taxa
Avicennia, other mangrove taxa (Rhizophoraceae, Nypa, Xylocarpus, Pelliciera, etc.).
Method
We collected well‐dated marine sediments along a Northern Hemisphere latitudinal transect and we analysed their pollen content in order to compare the past distribution of mangrove taxa with the present. The analysis of 89 samples (PETM: 13; EECO: 31; MMCO: 45) was performed and interpreted using a robust botanical background for identification of pollen grains and their representativeness in marine sediments.
Results
During the Early Eocene, two palaeolatitudinal thresholds at 65–70°N and 35°N, respectively, delimited the Avicennia‐only mangrove from a diversified but scrawny mangrove and finally from a diversified and well‐developed mangrove. The Avicennia threshold was selective at 40°N during the Mid‐Miocene. The Avicennia range limit was up to 10–15° poleward of the limit for other mangrove taxa during the Early Eocene and the Mid‐Miocene compared with 9° at present.
Main conclusions
A buffer zone characterised by a diversified but scrawny mangrove co‐occurring with a few megathermal plants occurred in the Early Eocene between 35°N and 65–70°N. This finding questions the relative influence of a more ‘equable’ climate and/or the ability of some taxa to expand towards areas with cooler conditions in the past. Mangrove provincialism, which was established progressively after the Early Eocene, was probably forced by plate tectonics. The taxonomic impoverishment of the Atlantic East Pacific province was probably caused by successive periods of global cooling. These results support the Tethyan origin of the mangroves.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
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