Postharvest dehydration of red grapes: impact of temperature and water-loss conditions on free and glycosylated volatile metabolites of exocarp and epicarp of Nebbiolo and Aleatico varieties.

BACKGROUND: Postharvest dehydration affects the metabolism of grapes, impacting odorous secondary metabolites and therefore the features of the corresponding passito wines - high-quality products with winemaking practices linked to specific territories and related autochthonous grape varieties. Water loss and temperature conditions are the main variables of the dehydration process. This study assessed how they impacted the patterns of free and glycosylated volatile organic compounds (VOCs) of the exocarp (pulp) and epicarp (skin) in Nebbiolo and Aleatico, a neutral and semi-aromatic red grape variety, respectively. Dehydration parameters were set in tunnel conditions, and VOCs were quantitatively analyzed by solid phase extraction-gas chromatography-mass spectrometry. RESULTS: For Nebbiolo grapes, weight loss had a greater impact on free volatiles than dehydration temperature, with a 20% weight loss increasing total VOCs in both exocarp and epicarp. Low temperature (10 °C) significantly increased (P < 0.05) the glycosylated VOCs' terpene content. In Aleatico grapes, weight loss was key in modulating free volatiles, with 30% weight loss and 15 °C leading to significant increases in VOCs, especially exocarp terpenes, acids and benzenoids. More stressful dehydration (30% weight loss at 25 °C) resulted in higher aroma precursor concentrations. CONCLUSION: These findings can assist passito wine production in preserving varietal aromas of original grapes trough optimized dehydration conditions, preventing sensory homologation occurring because of strong uncontrolled dehydration. They can also promote optimization of energy consumption, thus fostering financial and environmental sustainability. © 2024 The Author(s). Journal of the Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Profiling the specificity of clonally expanded plasma cells during chronic viral infection by single-cell analysis.

Plasma cells and their secreted antibodies play a central role in the long-term protection against chronic viral infection. However, due to experimental limitations, a comprehensive description of linked genotypic, phenotypic, and antibody repertoire features of plasma cells (gene expression, clonal frequency, virus specificity, and affinity) has been challenging to obtain. To address this, we performed single-cell transcriptome and antibody repertoire sequencing of the murine BM plasma cell population following chronic lymphocytic choriomeningitis virus infection. Our single-cell sequencing approach recovered full-length and paired heavy- and light-chain sequence information for thousands of plasma cells and enabled us to perform recombinant antibody expression and specificity screening. Antibody repertoire analysis revealed that, relative to protein immunization, chronic infection led to increased levels of clonal expansion, class-switching, and somatic variants. Furthermore, antibodies from the highly expanded and class-switched (IgG) plasma cells were found to be specific for multiple viral antigens and a subset of clones exhibited cross-reactivity to nonviral and autoantigens. Integrating single-cell transcriptome data with antibody specificity suggested that plasma cell transcriptional phenotype was correlated to viral antigen specificity. Our findings demonstrate that chronic viral infection can induce and sustain plasma cell clonal expansion, combined with significant somatic hypermutation, and can generate cross-reactive antibodies.

Persistent virus-specific and clonally expanded antibody-secreting cells respond to induced self-antigen in the CNS.

B cells contribute to the pathogenesis of both cellular- and humoral-mediated central nervous system (CNS) inflammatory diseases through a variety of mechanisms. In such conditions, B cells may enter the CNS parenchyma and contribute to local tissue destruction. It remains unexplored, however, how infection and autoimmunity drive transcriptional phenotypes, repertoire features, and antibody functionality. Here, we profiled B cells from the CNS of murine models of intracranial (i.c.) viral infections and autoimmunity. We identified a population of clonally expanded, antibody-secreting cells (ASCs) that had undergone class-switch recombination and extensive somatic hypermutation following i.c. infection with attenuated lymphocytic choriomeningitis virus (rLCMV). Recombinant expression and characterisation of these antibodies revealed specificity to viral antigens (LCMV glycoprotein GP), correlating with ASC persistence in the brain weeks after resolved infection. Furthermore, these virus-specific ASCs upregulated proliferation and expansion programs in response to the conditional and transient induction of the LCMV GP as a neo-self antigen by astrocytes. This class-switched, clonally expanded, and mutated population persisted and was even more pronounced when peripheral B cells were depleted prior to autoantigen induction in the CNS. In contrast, the most expanded B cell clones in mice with persistent expression of LCMV GP in the CNS did not exhibit neo-self antigen specificity, potentially a consequence of local tolerance induction. Finally, a comparable population of clonally expanded, class-switched, and proliferating ASCs was detected in the cerebrospinal fluid of relapsing multiple sclerosis (RMS) patients. Taken together, our findings support the existence of B cells that populate the CNS and are capable of responding to locally encountered autoantigens.

Lecithin Capping Ligands Enable Ultrastable Perovskite-Phase CsPbI3 Quantum Dots for Rec. 2020 Bright-Red Light-Emitting Diodes.

Bright-red light-emitting diodes (LEDs) with a narrow emission line width that emit between 620 and 635 nm are needed to meet the latest industry color standard for wide color gamut displays, Rec. 2020. CsPbI3 perovskite quantum dots (QDs) are one of the few known materials that are ideally suited to meet these criteria. Unfortunately, CsPbI3 perovskite QDs are prone to transform into a non-red-emitting phase and are subject to further degradation mechanisms when their luminescence wavelength is tuned to match that of the Rec. 2020 standard. Here, we show that zwitterionic lecithin ligands can stabilize the perovskite phase of CsPbI3 QDs for long periods in air for at least 6 months compared to a few days for control samples. LEDs fabricated with our ultrastable lecithin-capped CsPbI3 QDs exhibit an external quantum efficiency (EQE) of 7.1% for electroluminescence centered at 634 nm─a record for all-inorganic perovskite nanocrystals in Rec. 2020 red. Our devices achieve a maximum luminance of 1391 cd/m2 at 7.5 V, and their operational half-life is 33 min (T50) at 200 cd/m2─a 10-fold enhancement compared to control samples. Density functional theory results suggest that the surface strain in CsPbI3 QDs capped with the conventional ligands, oleic acid and oleylamine, contributes to the instability of the perovskite structural phase. On the other hand, lecithin binding induces virtually no surface strain and shows a stronger binding tendency for the CsPbI3 surface. Our study highlights the tremendous potential of zwitterionic ligands in stabilizing the perovskite phase and particle size of CsPbI3 QDs for various optoelectronic applications.

Effect of Salt Addition and Fermentation Time on Phenolics, Microbial Dynamics, Volatile Organic Compounds, and Sensory Properties of the PDO Table Olives of Gaeta (Italy).

'Oliva di Gaeta' is almost certainly the most important and well-known PDO denomination for table olives in Italy. Their production is based on a specific two-stage trade preparation called the 'Itrana' method. In this work, we investigated how variations in the duration of the initial water fermentation (i.e., 15 and 30 days) and the salt concentration (i.e., 6% and 8% NaCl) influence the chemical features, microbial dynamics, polyphenols, volatile organic compounds, and sensory features of 'Oliva di Gaeta'. The time of the addition of salt did not affect the final concentration in the brine, but a longer initial water fermentation (before salt addition) led to lower pH values. The bacterial count constantly increased until the salt addition (i.e., either 15 or 30 days), while the yeast population peaked on day 30. Generally, the two different salt concentrations did not affect the count of microorganisms at the end of fermentation, with the only exception being a higher lactic acid bacteria count for the treatment with 6% salt added at 30 days. At commercial maturity, the crucial bitter tastant oleuropein was not completely removed from the drupes, and differences in salt concentration and the length of the first-stage water fermentation did not influence its content at the end of olive curing. Richer volatile profiles of olives were detected with higher-salt treatments, while the combination of low salt and early saline treatment provided a more distinct profile. Longer initial water fermentation caused a small increase in some phenolic compounds (e.g., iso-verbascoside, verbascoside, and hydroxytyrosol-glucoside). A panel test indicated that salt application at 30 days resulted in a more "Sour" and "Bitter" taste, irrespective of the salt concentration. The low salt concentration coupled with the late saline treatment resulted in more "Fruity" notes, probably due to the higher production of esters by lactobacilli. The slightly bitter perception of the olives was consistent with the partial removal of oleuropein. Our work revealed the characteristics of the 'Itrana' method and that the variation in salt concentration and its time of application changes parameters ranging from the microbial dynamics to the sensory profile. Specifically, our data indicate that 6% NaCl coupled with a longer initial water fermentation is the most different condition: it is less effective in blocking microbial growth but, at the same time, is more potent in altering the nutritional (e.g., polyphenols) and sensorial qualities (e.g., bitterness and fruitiness) of 'Oliva di Gaeta'.

Fast, wafer-scale growth of a nanometer-thick graphite film on Ni foil and its structural analysis.

The growth of graphite on polycrystalline Ni by chemical vapor deposition (CVD) and the microstructural relation of the graphitic films and the metallic substrate continues to puzzle the scientific community. Here, we report the wafer-scale growth of a nanometer-thick graphite film (∼100 nm, NGF) on Ni foil via a fast-thermal CVD approach (5 min growth). Moreover, we shed light on how localized thickness variations of the NGF relate to the Ni surface topography and grain characteristics. While on a macro-scale (mm2), the NGF film looks uniform-with a few hundred highly ordered graphene layers (d0002 = 0.335 nm), when studied at the micro- and nano-scales, few-layer graphene sections can be identified. These are present at a density of 0.1%-3% areas in 100 µ m2, can be as thin as two layers, and follow an epitaxial relation with the {111} fcc-Ni planes. Throughout the 50 cm2 NGF, the sharp graphite/substrate interfaces are either composed of a couple of NiCx layers or a graphene layer. Moreover, the NGF was successfully transferred on SiO2/Si substrate by a wet chemical etching method. The as-produced NGFs could complement or offer an alternative to the mm-thick films produced from natural graphite flakes or polymer sheets.

Biophenolic Compounds Influence the In-Mouth Perceived Intensity of Virgin Olive Oil Flavours and Off-Flavours.

In this study, the influence of phenolic compounds on the sensory scores attributed to extra virgin olive oil (EVOO) by panel test was investigated. Two model olive oils (MOOs) with identical concentrations of volatile compounds, differing only in the amount of biophenols (297 vs. 511 mg kg-1), were analysed by two official panels and by SPME-GC/MS. Six other MOOs set up by the two previous models were also tested and analysed. They were formulated separately with the addition of three off-flavours ('rancid', 'winey-vinegary' and 'fusty-muddy'). While high levels of EVOO phenolic compounds did not produce any effect on the headspace concentration of volatile compounds, they did affect the scores of both positive and negative sensory attributes of EVOO, due to the well-known in-mouth interactions between EVOO phenols, saliva and volatile compounds. In particular, a decrease of about 39% in the positive fruity score was found in the presence of a higher concentration of phenols. Regarding EVOO off-flavours, the higher level of phenolic compounds decreased by about 23% the score of 'fusty-muddy' defect and increased the score of 'winey-vinegary' defect about 733%. No important effect of EVOO phenolics on the perceived intensity of the 'rancid' defect was found. These findings could be helpful in explaining some discrepancies of panel test responses observed during extra virgin olive oil shelf life.

Effects of Inclusion of Fresh Forage in the Diet for Lactating Buffaloes on Volatile Organic Compounds of Milk and Mozzarella Cheese.

This paper aimed to assess the effects of feeding fresh forage on volatile organic compounds (VOCs) of buffalo milk and mozzarella cheese. Sixteen lactating buffaloes were equally allotted into two groups fed diets containing (experimental (Exp) group) or not (control (Ctl) group) 20 kg/d of fresh sorghum. Milk from the groups was separately collected and transformed in the traditional 'Mozzarella di Bufala Campana' Protected Denomination of Origin (PDO). Three batches of mozzarella were produced for each diet and they were analyzed, along with the two bulks of milk, for VOC composition, by using solid phase micro-extraction (SPME) coupled with gas-chromatography/mass spectrometry (GC/MS). The use of fresh forage increased the levels of long chain fatty acids along with the contents of aldehydes, and this could be responsible for an increase in green notes of milk. The use of the Ctl diet, containing a higher proportion of silage, increased the ketones, acids, and esters, which are compounds that could raise the cheese and fruity notes of milk. The mozzarella was less affected by the dietary treatment than milk. The use of fresh forage (sorghum) enhanced the green notes of milk and induced a few changes in the VOC profile of the typical PDO Mozzarella di Bufala Campana cheese, that were nonetheless detectable by sensory analysis. The low level found for butanoic acid, 2,3-pentanedione, and propyl acetate in mozzarella cheese obtained with fresh forage diet can lead to perceive less the olfactory notes of cheese, cream, and fruit.

Volatile compounds, physicochemical and sensory characteristics of Colatura di Alici, a traditional Italian fish sauce.

BACKGROUND: The present study reports for the first time the physical, chemical and sensory characterization of a traditional fish sauce from Italy, called 'Colatura di Alici', which is considered to be the direct descendant of the ancient roman sauce 'Garum'. RESULTS: Among the volatile compounds, carboxylic acids, aldehydes, sulphuric compounds and pyrazines were identified. The most abundant compounds identified were 3-methyl-butanoic acid, nonanal and 3-methyl-butanal. The sample A had the highest amount of volatile fatty acids (>250 µg kg-1 ) and sample B had the highest concentration of aldehydes (>80 µg kg-1 ). These volatile compounds arise from the long fermentation activity and oxidation of fatty acids of the fish flesh and are responsible for the strong cheesy and fishy aroma. The protein content ranged from 90 to 130 g kg-1 , and the soluble solids ranged from 30 to 38 °Brix, as a result of the high amount of NaCl used during processing. The sensory analysis showed a great intensity for the cheesy, fishy and umami attributes, and a medium intensity for the roasted and meaty attributes. CONCLUSION: For the first time, the volatile compounds and sensory characteristics of this traditional fish sauce are reported. The samples differ in terms of sensory and aromatic profiles. These differences are probably linked to the poorly standardized methods used in the production process. Overall, the results of the present study could be used by local fish sauce producers to monitor the quality of the product and to improve the production process. © 2020 Society of Chemical Industry.

Volatile Organic Compound and Fatty Acid Profile of Milk from Cows and Buffaloes Fed Mycorrhizal or Nonmycorrhizal Ensiled Forage.

Seed inoculation of forage crops by arbuscular mycorrhizal fungi (AMF) generally results in higher profitability, but also modifies the chemical composition of silage in terms of increased biomass, protein, and dry matter. Raw milk aroma is affected by the type of feed. This work investigated the influence of ensiled forage obtained by seed inoculation with AMF on the volatile fractions and fatty acid composition of milk. Two experiments were carried out: in the first, buffaloes were fed maize silage, and in the second, cows were fed sorghum silage. The volatile fractions of milk were quantified by headspace solid-phase micro-extraction (HS-SPME), combined with gas chromatography-mass spectrometry (GC-MS), and fatty acids by gas chromatography (GC). The ensiled forage obtained with AMF increased saturated fatty acids (SFAs), and decreased monounsaturated fatty acids (MUFAs) and polyunsaturated fatty acids (PUFAs) in both experiments. The volatile fraction in milk samples obtained from bovines fed mycorrhizal ensiled forage showed an increase of free fatty acids and ketones, responsible for cheesy and fruity odors. Aldehydes, responsible for green and grassy notes, increased only in the milk from buffaloes fed ensiled maize. Our results suggest that inoculation of maize and sorghum seed with AMF, combined with a low rate of fertilizers, leads to ensiled forage that could slightly affect the FA profile and odor quality of milk.

Use of odorant series for extra virgin olive oil aroma characterisation.

BACKGROUND: Extra virgin olive oil (EVOO) volatile composition is mainly used as a means of characterisation and authentication, especially for protected denomination of origin (PDO) products. This work investigated the volatile compounds from 25 EVOOs from four Spanish (Cornicabra, Manzanilla Castellana, Picual and Manzanilla Cacereña) and four Italian (Ortice, Ravece, Nocellara del Belice and Itrana) cultivars in terms of odour activity value (OAV). Forty-seven volatile compounds were analysed by solid phase microextraction gas chromatography/mass spectrometry (SPME-GC/MS). OAVs of volatile compounds with similar descriptors were grouped in order to establish eight odorant series: fruity, grass, apple, tomato, floral, woody-spicy, fatty and mushroom. RESULTS: No differences in sensory descriptors were observed among the EVOOs analysed by official VOO sensory analysis. The method of odorant series applied herein was demonstrated to successfully characterise EVOO odour as expected from a sensory panel but using only instrumental analysis of volatile compounds, and giving additional reliable quantitative information. The results can be presented as a 'barcode', providing a visual and effective graphical representation allowing an easy and rapid description of EVOO sensory attributes using instrumental data. CONCLUSION: The odorant series have the potential to better differentiate the aroma of food products, opening new possibilities allowing a schematic and effective visual representation to be used for EVOO quality control and consumer information, especially in new olive oil consuming countries. © 2018 Society of Chemical Industry.

Use of phenolic compounds from olive mill wastewater as valuable ingredients for functional foods.

Olive mill wastewater (OMW) is a pollutant by-product from the virgin olive oil production. Its high content in phenolic compounds makes them play an important role for their use in foods, for their high antioxidant significance. The present paper gives an overview on the techniques for OMW valuable ingredient separation, focusing on the most effective ones for their use in food products as functional ingredients. We report on effective methods to recover OMW phenolics, and give several examples on the use these extracts in foods. When added into vegetable oils, their effect on retarding lipid oxidation improves the oxidative status of the product, whilst several challenges need to be faced. OMW phenolic extracts were also used in food emulsions, milk products or other model systems, showing promising results and little or no negative impact on the sensory characteristics or other properties. Their possible use as antimicrobial agents is also another promising approach, as positive results were obtained when applied in meat products. Other examples of using natural phenolic extracts from other sources are suggested also for OMW extracts, to expand their use and thus to improve the nutritional and technological quality of foods.

Extra virgin olive oil aroma release after interaction with human saliva from individuals with different body mass index.

BACKGROUND: The interindividual variability observed in saliva characteristics raises the question of its relationship with variability in fat sensory perception, particularly in aroma compounds. In the present study, which aimed to measure aroma release from different individuals, eleven key aroma compounds of extra virgin olive oil (EVOO) were monitored and quantified in dynamic headspace after an in vitro interaction between EVOO and human saliva. Therefore, 60 individuals were studied from those who were normal weight (NW), overweight (OW) and obese (O). RESULTS: OW and O demonstrate a higher release of C6 compounds compared to NW. By contrast, NW have a higher release of C5 compounds. Pentanal and hexanal also increased after saliva interaction in a refined olive oil that is free from volatiles. Among the saliva samples with a higher release in NW individuals, only pentanal was different. However, the low levels of these lipid oxidation end-products do not appear to be very important with respect to increasing odorous fat sensitivity. CONCLUSION: The results obtained in the present study demonstrate the important role of saliva in the aroma release of EVOO, indicating that humans can perceive it differently in relation to their body mass index. © 2017 Society of Chemical Industry.

Sn cation valency dependence in cation exchange reactions involving Cu(2-x)Se nanocrystals.

We studied cation exchange reactions in colloidal Cu(2-x)Se nanocrystals (NCs) involving the replacement of Cu(+) cations with either Sn(2+) or Sn(4+) cations. This is a model system in several aspects: first, the +2 and +4 oxidation states for tin are relatively stable; in addition, the phase of the Cu(2-x)Se NCs remains cubic regardless of the degree of copper deficiency (that is, "x") in the NC lattice. Also, Sn(4+) ions are comparable in size to the Cu(+) ions, while Sn(2+) ones are much larger. We show here that the valency of the entering Sn ions dictates the structure and composition not only of the final products but also of the intermediate steps of the exchange. When Sn(4+) cations are used, alloyed Cu(2-4y)Sn(y)Se NCs (with y ≤ 0.33) are formed as intermediates, with almost no distortion of the anion framework, apart from a small contraction. In this exchange reaction the final stoichiometry of the NCs cannot go beyond Cu0.66Sn0.33Se (that is Cu2SnSe3), as any further replacement of Cu(+) cations with Sn(4+) cations would require a drastic reorganization of the anion framework, which is not possible at the reaction conditions of the experiments. When instead Sn(2+) cations are employed, SnSe NCs are formed, mostly in the orthorhombic phase, with significant, albeit not drastic, distortion of the anion framework. Intermediate steps in this exchange reaction are represented by Janus-type Cu(2-x)Se/SnSe heterostructures, with no Cu-Sn-Se alloys.

CO oxidation on colloidal Au(0.80)Pd(0.20)-Fe(x)O(y) dumbbell nanocrystals.

We report a colloidal synthesis of Au(0.80)Pd(0.20)-Fe(x)O(y) dumbbell nanocrystals (NCs) derived from Au(0.75)Pd(0.25) NCs by metal oxide overgrowth. We compared the catalytic activity of the two types of NCs in the CO oxidation reaction (CO + 1/2O(2) → CO(2)), after they had been dispersed on an alumina nanopowder support. In both cases, the surface active sites were identified by means of in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The enhanced catalytic performance of the dumbbell NCs (Au(0.80)Pd(0.20)-Fe(x)O(y)) catalyst over that of the initial Au(0.75)Pd(0.25) NCs could be correlated to the presence of the epitaxial connection between the Fe(x)O(y) and the Au(0.80)Pd(0.20) domains (as the main factor). Such connection should result in an electron flow from the metal oxide (Fe(x)O(y)) domain to the noble metal (Au(0.80)Pd(0.20)) domain and appears to influence favorably the nature and composition of the catalytically active surface sites of the dumbbells. Our experiments indicate indeed that, when the metal alloy domain is attached to the metal oxide domain (that is, in the dumbbell), surface Pd species are more active than in the case of the initial Au(0.75)Pd(0.25) NCs and also Au(δ-) sites are formed that were not present on the initial Au(0.75)Pd(0.25) NCs.

Microbiome signatures associated with flavor development differentiate Protected Designation of origin water Buffalo Mozzarella cheese from different production areas.

Water Buffalo Mozzarella (BM) is a typical cheese from Southern Italy with unique flavor profile and texture. It is produced following a traditional back-slopping procedure and received the Protected Designation of Origin (PDO) label. To better understand the link between the production area, the microbiome composition and the flavor profile of the products, we performed a multiomic characterization of PDO BM collected from 57 different dairies located in the two main PDO production area, i.e. Caserta (n = 35) and Salerno (n = 22). Thus, we assessed the microbiome by high-throughput shotgun metagenomic sequencing and the Volatile Organic Compounds (VOCs) by gas chromatography/mass spectrometry (GC/MS). Streptococcus thermophilus, Lactobacillus helveticus, and Lactobacillus delbrueckii subsp. delbrueckii were identified as the core microbiome present in all samples. However, the microbiome taxonomic profiles resulted in a clustering of the samples based on their geographical origin, also showing that BM from Caserta had a greater microbial diversity. Consistently, Caserta and Salerno samples also showed different VOC profiles. These results suggest that the microbiome and its specific metabolic activity are part of the terroir that shape BM specific features, linking this traditional product with the area of production, thus opening new clues for improving traceability and fraud protection of traditional products.

Copper sulfide nanocrystals with tunable composition by reduction of covellite nanocrystals with Cu+ ions.

Platelet-shaped copper sulfide nanocrystals (NCs) with tunable Cu stoichiometry were prepared from Cu-rich covellite (Cu1.1S) nanoplates through their reaction with a Cu(I) complex ([Cu(CH3CN)4]PF6) at room temperature. Starting from a common sample, by this approach it is possible to access a range of compositions in these NCs, varying from Cu1.1S up to Cu2S, each characterized by a different optical response: from the metallic covellite, with a high density of free carriers and strong localized surface plasmon resonance (LSPR), up to Cu2S NCs with no LSPR. In all these NCs the valency of Cu in the lattice stays always close to +1, while the average -1 valency of S in covellite gradually evolves to -2 with increasing Cu content; i.e., sulfur is progressively reduced. The addition of copper to the starting covellite NCs is similar to the intercalation of metal species in layered transition metal dichalcogenides (TMDCs); i.e., the chalcogen-chalcogen bonds holding the layers are progressively broken to make room for the intercalated metals, while their overall anion sublattice does not change much. However, differently from the TMDCs, the intercalation in covellite NCs is sustained by a change in the redox state of the anion framework. Furthermore, the amount of Cu incorporated in the NCs upon reaction is associated with the formation of an equimolar amount of Cu(II) species in solution. Therefore, the reaction scheme can be written as: Cu1.1S + 2γCu(I) → Cu1.1+γS + γCu(II).

Effects of Leaf Removal on Free and Glycoconjugate Aromas of Skins and Pulps of Two Italian Red Grapevine Varieties.

Leaf removal is a cultural practice mainly aimed at improving cluster zone microclimates and impacting primary and secondary metabolites, such as volatiles. This research aimed to assess the impact of defoliation on free and glycosylated aromas of a neutral ('Nebbiolo') and a semi-aromatic ('Aleatico') red variety. Defoliation was performed at fruit set (BBCH 71) and, for 'Nebbiolo', also at berries touch (BBCH 81) phenological stages. Skins and pulps were separately analyzed by Solid Phase Extraction-Gas Chromatography/Mass Spectrometry. Results showed that the response to defoliation was variety-dependent. For 'Nebbiolo', especially when performed at the berries' touch stage, defoliation had a significant effect on the accumulation of free volatiles and glycosidic precursors. Differently, free and bound 'Aleatico' volatiles were less impacted by defoliation. Interestingly, in both grapevine varieties, defoliation significantly enhanced the accumulation of aroma precursors in grapes' skins, which is of particular relevance for red wine production and their aging potential. Moreover, results could be helpful for the management of grape quality, as defoliation is currently considered as a strategy to address climate change issues.

Simultaneous Growth Strategy of High-Optical-Efficiency GaN NWs on a Wide Range of Substrates by Pulsed Laser Deposition.

Here, we explore a catalyst-free single-step growth strategy that results in high-quality self-assembled single-crystal vertical GaN nanowires (NWs) grown on a wide range of common and novel substrates (including GaN, Ga2O3, and monolayer two-dimensional (2D) transition-metal dichalcogenide (TMD)) within the same chamber and thus under identical conditions by pulsed laser deposition. High-resolution transmission electron microscopy and scanning transmission electron microscopy (HR-STEM) and grazing incidence X-ray diffraction measurements confirm the single-crystalline nature of the obtained NWs, whereas advanced optical and cathodoluminescence measurements provide evidence of their high optical quality. Further analyses reveal that the growth is initiated by an in situ polycrystalline layer formed between the NWs and substrates during growth, while as its thickness increases, the growth mode transforms into single-crystalline NW nucleation. HR-STEM and corresponding energy-dispersive X-ray compositional analyses indicate possible growth mechanisms. All samples exhibit strong band edge UV emission (with a negligible defect band) dominated by radiative recombination with a high optical efficiency (∼65%). As all NWs have similar structural and optical qualities irrespective of the substrate used, this strategy will open new horizons for developing III-nitride-based devices.

The big impact of a small detail: cobalt nanocrystal polymorphism as a result of precursor addition rate during stock solution preparation.

The control of nanocrystal structures at will is still a challenge, despite the recent progress of colloidal synthetic procedures. It is common knowledge that even small modifications of the reaction parameters during synthesis can alter the characteristics of the resulting nano-objects. In this work we report an unexpected factor which determines the structure of cobalt nanoparticles. Nanocrystals of distinctly different sizes and shapes have resulted from stock solutions containing exactly the same concentrations of [Co{N(SiMe(3))(2)}(2)(thf)], hexadecylamine, and lauric acid. The reduction reaction itself has been performed under identical conditions. In an effort to explain these differences and to analyze the reaction components and any molecular intermediates, we have discovered that the rate at which the cobalt precursor is added to the ligand solution during the stock solution preparation at room temperature becomes determinant by triggering off a nonanticipated side reaction which consumes part of the lauric acid, the main stabilizing ligand, transforming it to a silyl ester. Thus, an innocent mixing, apparently not related to the main reaction which produces the nanoparticles, becomes the parameter which in fine defines nanocrystal characteristics. This side reaction affects in a similar way the morphology of iron nanoparticles prepared from an analogous iron precursor and the same long chain stabilizing ligands. Side reactions are potentially operational in a great number of systems yielding nanocrystals, despite the fact that they are very rarely mentioned in the literature.