(2, 1)-Separating systems beyond the probabilistic bound

Building on previous results of Xing, we give new lower bounds on the rate of linear intersecting codes over large alphabets. The proof is constructive, and uses algebraic geometry (although nothing beyond the basic theory of linear systems on curves). Then, using these new bounds within a concatenation argument, we construct binary (2,1)-separating systems of asymptotic rate exceeding the one given by the probabilistic method, which was the best lower bound available up to now. This answers (negatively) the question of whether this probabilistic bound was exact, which has remained open for more than 30 years.     

A Combined Kinetic and Thermodynamic Approach for the Interpretation of Continuous‐Flow Heterogeneous Catalytic Processes

The heterogeneous proline‐catalyzed aldol reaction was investigated under continuous‐flow conditions by means of a packed‐bed microreactor. Reaction‐progress kinetic analysis (RPKA) was used in combination with nonlinear chromatography for the interpretation, under synthetically relevant conditions, of important mechanistic aspects of the heterogeneous catalytic process at a molecular level. The information gathered by RPKA and nonlinear chromatography proved to be highly complementary and allowed for the assessment of optimal operating variables. In particular, the determination of the rate‐determining step was pivotal for optimizing the feed composition. On the other hand, the competitive product inhibition was responsible for the unexpected decrease in the reaction yield following an apparently obvious variation in the feed composition. The study was facilitated by a suitable 2D instrumental arrangement for simultaneous flow reaction and online flow‐injection analysis.     

Aloe djiboutiensis: Antioxidant Activity,Molecular Networking-Based Approach and In Vivo Toxicity of This Endemic Species in Djibouti

For the first time, the study of the antioxidant activity, the characterization of the phytoconstituants, and the evaluation of in vitro and in vivo toxicity of A. djiboutiensis leave and latex are performed. The antioxidant activity of both latex (ADL) and the methanolic extract of leaves (ADM) is determined using 1-diphenyl-2-picrylhydrazyl (DPPH), 2,2′-azino-bis 3-ethylbenzothiazoline-6-sulphonic acid (ABTS) scavenging radical methods and ferric reducing/antioxidant power (FRAP) assay. The phytochemical study of latex is done using Liquid Chromatography-Mass Spectrometry (LC-MS/MS) and a molecular networking-based approach. The evaluation of in vivo toxicity is performed on mice by oral gavage with a suspension of ADL. Our results show that weak antioxidant activity of ADL and ADM in opposition to their high polyphenol, 83.01 mg and 46.4 mg expressed in gallic acid equivalent (GAE)/g of dry weight (DW), respectively, and flavonoid contents 13.12 mg and 4.25 mg expressed in quercetin equivalent (QE)/g dry weight (DW), respectively. Using the Global Natural Products Social Molecular Networking (GNPS) website, nine (9) anthraquinones derivatives, ten (10) chromones derivatives, two (2) flavonols/ chromones isomers are annotated in the molecular network. The treated mice do not display abnormalities in their general physical appearance and biochemistry parameters, compared to the controls. Only glucose and calcium levels are slightly higher in male treated mice compared to the vehicles.     

Two‐Photon‐Induced Fluorescence in New π‐Expanded Diketopyrrolopyrroles

Structurally unique π‐expanded diketopyrrolopyrroles (EDPP) were designed and synthesized. Strategic placement of a fluorene scaffold at the periphery of a diketopyrrolopyrrole through tandem Friedel–Crafts‐dehydration reactions resulted in dyes with supreme solubility. The structure of the dyes was confirmed by X‐ray crystallography verifying a nearly flattened arrangement of the ten fused rings. Despite the extended ring system, the dye still preserved good solubility and was further functionalized by using Pd‐catalyzed coupling reactions, such as the Buchwald–Hartwig amination. Photophysical studies of these new functional dyes revealed that they possess enhanced properties when compared with expanded DPPs in terms of two‐photon absorption cross‐section. It is further demonstrated that in addition to the initial diacetals, the final electrophilic cyclization step can also be applied to diketones. By placing two amine groups at peripheral positions of the resulting dyes, values of two‐photon absorption cross‐section on the level of 2000 GM around 1000 nm were achieved, which in combination with high fluorescence quantum yield (Φ_fl), generated a two‐photon brightness of approximately 1600 GM. These characteristics in combination with strong red emission (665 nm) make these new π‐expanded diketopyrrolopyrroles of major promise as two‐photon dyes for bioimaging applications. Finally, the corresponding N‐alkylated DPPs displayed a solid‐state fluorescence.     

Investigating aroma diversity combining purge‐and‐trap,comprehensive two‐dimensional gas chromatography,and mass spectrometry

Headspace gas chromatography is frequently used for aroma profiling thanks to its ability to naturally exploit the volatility of aroma compounds, and also to provide chemical information on sample composition. Its main advantages rely on simplicity, no use of solvent, amenability to automation, and the cleanliness of the extract. In the present contribution, the most effective sampling (dynamic extraction), separation (multidimensional gas chromatography), and detection (mass spectrometry) techniques for untargeted analysis are exploited in combination, showing their potential in unraveling aroma profiles in fruit beers. To complete the overall analytical process, a neat workflow for data analysis is discussed and used for the successful characterization and identification of five different beer flavors (berries, cherry, banana, apple, and peach). From the technical viewpoint, the coupling of purge‐and‐trap, comprehensive two‐dimensional gas chromatography, and mass spectrometry makes the global methodology unique, and it is for the first time discussed. A (low‐)flow modulation approach allowed for the full transfer into the second dimension with mass‐spectrometry compatible flow (< 7 mL/min), avoiding the need of splitting before detection and making the overall method sensitive (1.2–5.2‐fold higher signal to noise ratio compared to unmodulated gas chromatography conditions) and selective.     

The acoustical characterization of orchestra platforms and uncertainty estimation of the results

Measurements have been carried out on furnished orchestra platforms in four concert halls in Italy in order to describe the sound field perceived by musicians. The heterogeneous nature of the orchestra suggested a procedure able to take into account the mutual hearing between instrumental sections. The measured parameters were the early, late and total support, the reverberation time, the early decay time and the clarity index. A part of the study has been devoted to the measurement uncertainty estimation. The source directivity and the small displacements of the microphone influence the early decay time to a great extent while the on-platform spatial variability affects both the early decay time and the clarity index. Per-section early support shows differences that render the overall spatial mean inappropriate to describe the stage as a whole. For the other parameters an overall mean platform value can instead be suitable, even though, for the case of clarity a more evident group variability is observed. The values of late support, reverberation time, early decay time and clarity index, proposed in literature as suitable measures of reverberance for musicians, are not all intercorrelated, indicating that not all these parameters can be associated to the same subjective impression.     

Ammonium chloride-promoted four-component synthesis of pyrrolo[3,4-b]pyridin-5-one

A novel multicomponent synthesis of 5-aminooxazole starting from simple and readily available inputs is described. Thus, simply heating a methanol solution of an aldehyde 3, an amine 4, and an alpha-isocyanoacetamide 5 provided the 5-aminooxazole (1) in good to excellent yield. The reaction of 1 with alpha,beta-unsaturated acyl chloride 13 lead to the formation of pyrrolo[3,4-b]pyridin-5-one (2) in a single operation. A triple domino sequence, acylation/IMDA/retro-Michael cycloreversion, is involved in this new scaffold-generating reaction. After the observation that ammonium chloride can significantly accelerate the oxazole formation in toluene, a one-pot four-component synthesis of 2 is developed.     

Multiplicity distributions in a thermodynamical model of hadron production ine + e − collisions

Predictions of a thermodynamical model of hadron production for multiplicity distribution ine ⁺ e ^? annihilations at LEP and PEP-PETRA centre of mass energies are shown. The production process is described as a two-step process in which primary hadrons emitted from the thermal source decay into final observable particles. The final charged tracks multiplicity distributions turn out to be of Negative Binomial type and are in quite good agreement with experimental observations. The average number of clans calculated from fitted Negative Binomial coincides with the average number of primary hadrons predicted by the thermodynamical model, suggesting that clans should be identified with primary hadrons.     

α'β-Elimination and wittig rearrangement of the carbanion from benzyl cyclooctyl ether

Beside the Wittig rearrangement and the migration of the cyclooctyl radical to the para position, the title carbanion gives rise to an elimination in a syn process.