Approximated cauchy problem for linear,first order,overdetermined systems

Sunto Le soluzioni di certi sistemi differenziali sono dense tra le funzioni C^∞ di una superficie non caratteristica.

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Entrata in Redazione l'11 ottobre 1978.

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Supported by C.N.R. Research groups.     

Crocetin Mitigates Irradiation Injury in an In Vitro Model of the Pubertal Testis: Focus on Biological Effects and Molecular Mechanisms

Infertility is a potential side effect of radiotherapy and significantly affects the quality of life for adolescent cancer survivors. Very few studies have addressed in pubertal models the mechanistic events that could be targeted to provide protection from gonadotoxicity and data on potential radioprotective treatments in this peculiar period of life are elusive. In this study, we utilized an in vitro model of the mouse pubertal testis to investigate the efficacy of crocetin to counteract ionizing radiation (IR)-induced injury and potential underlying mechanisms. Present experiments provide evidence that exposure of testis fragments from pubertal mice to 2 Gy X-rays induced extensive structural and cellular damage associated with overexpression of PARP1, PCNA, SOD2 and HuR and decreased levels of SIRT1 and catalase. A twenty-four hr exposure to 50 μM crocetin pre- and post-IR significantly reduced testis injury and modulated the response to DNA damage and oxidative stress. Nevertheless, crocetin treatment did not counteract the radiation-induced changes in the expression of SIRT1, p62 and LC3II. These results increase the knowledge of mechanisms underlying radiation damage in pubertal testis and establish the use of crocetin as a fertoprotective agent against IR deleterious effects in pubertal period.     

Application of capillary gas chromatography to automated on-line quantitative analysis of solvent vapors

Solvent vapors in air may be measured with capillary gas chromatographic columns. By using large diameter columns and sample loops of approximately the same internal diameter, the column may be connected directly to the gas sampling valve. This approach eliminates the use of a splitter or cryogenic trapping and allows low levels to be measured. By operating the column at high velocity, column efficiency is sacrificed for increase in speed.     

Synthesis of tetrahydro-1,4-benzodiazepine-2-ones on hydrophilic polyamide SynPhase lanterns

Solid-phase synthesis is greatly dependent on the solid support. Here, we report the use of a new hydrophilic grafted surface on SynPhase lanterns in solid-phase organic chemistry. A convenient and facile solid-phase synthesis of disubstituted 1,4-benzodiazepine-2-ones on polyamide SynPhase lanterns is described. The key step of the synthesis involved a reduction-cyclization of a nitroaryl methyl ester with a mixture of tin(II) chloride dihydrate and ammonium acetate in water and ethanol at elevated temperature to give the desired target compounds. A library of 21 disubstituted 1,4-benzodiazepine-2-ones was prepared.     

Synthesis new Co–Mn mixed oxide catalyst for the production of light olefins by tuning the catalyst structure

In order to increase the catalyst activity for Fischer–Tropsch synthesis (FTS), the preparation methods of two new catalysts were studied. The chemically identical bimetallic Co–Mn/Al₂O₃ catalysts were synthesized by different synthetic methods: (a) via thermal decomposition of the complex [Co_1.33Mn_0.667(C₇H₃NO₄)₂(H₂O)₅].2H₂O ( 1 ) and (b) by the impregnation technique. The complex was characterized by the single‐crystal analysis, elemental analysis, and Fourier‐transform infrared (FT‐IR) spectroscopy. Both catalysts were characterized by powder X‐ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X‐ray spectrometry (EDS), Brunauer–Emmett–Teller (BET) specific surface area, hydrogen temperature‐programmed reduction (H₂‐TPR), and H₂‐chemisorption. The catalysts' activity was investigated for the Fischer–Tropsch synthesis in a fixed bed microreactor. Higher activity was obtained for the catalyst prepared by thermal decomposition of the inorganic precursor due to its small particle size, superior dispersion, and higher surface area. The results show that the catalyst prepared thermal decomposition has 21% ethylene, 10% propylene, and 50% C₅⁺ selectivity, while methane selectivity of this catalyst is 11% at 250°C. On the other hand, the catalyst obtained by the impregnation method displays 15% ethylene, 8% propylene, 29% C₅⁺_, and 29% methane selectivity at the same temperature.     

Synthesis of C-Ring Hydroxylated Neoflavonoids by Ligand Coupling Reactions

Reaction of 4-trifluoromethanesulfonyloxycoumarin derivatives with benzyloxyphenylboronic acid derivatives under modified Suzuki reaction conditions afforded the corresponding neoflavones. Selective debenzylation took place in high yields when the palladium-catalysed hydrogenolysis was performed in the presence of acetic acid.     

Continuous thermal collapse of the intrinsically disordered protein tau is driven by its entropic flexible domain

The tau protein belongs to the category of Intrinsically Disordered Proteins (IDP), which in their native state lack a folded structure and fluctuate between many conformations. In its physiological state, tau helps nucleating and stabilizing the microtubules' (MTs) surfaces in the axons of the neurons. Tau is mainly composed by two domains: (i) the binding domain that tightly bounds the MT surfaces and (ii) the projection domain that exerts a long-range entropic repulsive force and thus provides the proper spacing between adjacent MTs. Tau is also involved in the genesis and in the development of the Alzheimer disease when it detaches from MT surfaces and aggregates in paired helical filaments. Unfortunately, the molecular mechanisms behind these phenomena are still unclear. Temperature variation, rarely considered in biological studies, is here used to provide structural information on tau correlated to its role as an entropic spacer between adjacent MTs surfaces. In this paper, by means of small-angle X-ray scattering and molecular dynamics simulation, we demonstrate that tau undergoes a counterintuitive collapse phenomenon with increasing temperature. A detailed analysis of our results, performed by the Ensemble Optimization Method, shows that the thermal collapse is coupled to the occurrence of a transient long-range contact between a region encompassing the end of the proline-rich domain P2 and the first part of the repeats domain, and the region of the N-terminal domain entailing residues 80-150. Interestingly these two regions involved in the tau temperature collapse belong to the flexible projection domain that acts as an entropic bristle and regulates the MTs' architecture. Our results show that temperature is an important parameter that influences the dynamics of the tau projection domain, and hence its entropic behavior.     

Unraveling the Mechanism of the Photodeprotection Reaction of 8‐Bromo‐ and 8‐Chloro‐7‐hydroxyquinoline Caged Acetates

Photoremovable protecting groups (PPGs) when conjugated to biological effectors forming “caged compounds” are a powerful means to regulate the action of physiologically active messengers in vivo through 1‐photon excitation (1PE) and 2‐photon excitation (2PE). Understanding the photodeprotection mechanism is important for their physiological use. We compared the quantum efficiencies and product outcomes in different solvent and pH conditions for the photolysis reactions of (8‐chloro‐7‐hydroxyquinolin‐2‐yl)methyl acetate (CHQ‐OAc) and (8‐bromo‐7‐hydroxyquinolin‐2‐yl)methyl acetate (BHQ‐OAc), representatives of the quinoline class of phototriggers for biological use, and conducted nanosecond time‐resolved spectroscopic studies using transient emission (ns‐EM), transient absorption (ns‐TA), transient resonance Raman (ns‐TR²), and time‐resolved resonance Raman (ns‐TR³) spectroscopies. The results indicate differences in the photochemical mechanisms and product outcomes, and reveal that the triplet excited state is most likely on the pathway to the product and that dehalogenation competes with release of acetate from BHQ‐OAc, but not CHQ‐OAc. A high fluorescence quantum yield and a more efficient excited‐state proton transfer (ESPT) in CHQ‐OAc compared to BHQ‐OAc explain the lower quantum efficiency of CHQ‐OAc relative to BHQ‐OAc.     

Light-Activated Serotonin for Exploring Its Action in Biological Systems

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