Characterization of the supercontinuum radiation generated by self-focusing of few-cycle 800 nm pulses in argon

Self-focusing of few-cycle pulses in atmospheric-pressure argon results in a supercontinuum which differs remarkably from the case of longer pulses: under single-filament conditions it extends to 200 nm and 250 nm with 6 fs and 10 fs pulses, respectively; the radiation, including the shortest wavelengths, is collimated and shows no conical emission. The short-wavelength part is intrinsically at least as short as the incoming fundamental pulse. These features make the few-cycle supercontinuum attractive as a source of widely tunable 10 fs pump pulses for spectroscopic applications. We present extensive experimental results including the dependence of the spectrum on pulse energy, duration and chirp, filament length, gas pressure and a comparison with nitrogen and air. We discuss them and other features including the role of the third harmonic and identify the conditions required to get a single highly stable filament. We also present a model, based on self-guiding, which predicts useful scaling rules.     

Synthetic Neoglycoconjugates of Hepta- and Nonamannoside Ligands for Eliciting Oligomannose-Specific HIV-1-Neutralizing Antibodies

Oligomannose-type glycans on the spike protein of HIV-1 constitute relevant epitopes to elicit broadly neutralizing antibodies (bnAbs). Herein we describe an improved synthesis of α- and β-linked hepta- and nonamannosyl ligands that were subsequently converted into BSA and CRM₁₉₇ neoglycoconjugates. We assembled the ligands from anomeric 3-azidopropyl spacer glycosides from select 3-O-protected thiocresyl mannoside donors. Chain extensions were achieved using [4+3] or [4+5] block synthesis of thiocresyl and trichloroacetimidate glycosyl donors. Subsequent global deprotection generated the 3-aminopropyl oligosaccharide ligands. ELISA binding data obtained with the β-anomeric hepta- and nonamannosyl conjugates with a selection of HIV-1 bnAbs showed comparable binding of both mannosyl ligands by Fab fragments yet lesser binding of the nonasaccharide conjugate by the corresponding IgG antibodies. These results support previous observations that a complete Man₉ structure might not be the preferred antigenic binding motif for some oligomannose-specific antibodies, and have implications for glycoside designs to elicit oligomannose-targeted HIV-1-neutralizing antibodies.     

Synthesis of allyl O-[sodium(alpha-D-glycero-D-talo-2- octulopyranosyl)onate]-(2-->6)-2-acetamido-2-deoxy-beta-D-glucopyranosi de, a core constituent of the lipopolysaccharide from Acinetobacter calcoaceticus NCTC 10305

Reaction of methyl 2,6-anhydro-2,3-dideoxy-D-manno-2-octenoate 1 with 3-chloroperoxybenzoic acid gave the 2,3-anhydro derivative 2, which was converted into the per-O-acetylated anomeric methyl glycosides of D-glycero-D-galacto-2-octulopyranosylonic acid in good yield. Subsequent inversion of the configuration at C-3 and deprotection afforded sodium (methyl beta-D-glycero-D-talo-2-octulopyranosid)onate. Alternatively, 2 was transformed into methyl (alpha-D-glycero-D-talo-2- octulopyranosyl bromide(onate derivatives. Reaction with methanol or allyl 2-acetamido-2-deoxy- 3,4-O-(1,1,3,3-tetraisopropyldisiloxan-1,3-diyl)-beta-D-g lycopyranoside, promoted by silver triflate, gave good yields of the corresponding orthoester derivatives. Me3Si triflate-catalyzed orthoester rearrangement and removal of the protecting groups afforded sodium O-(methyl alpha-D-glycero- D-talo-2-octulopyranosid)onate and the disacchanide, allyl O-[sodium(alpha-D-glycero-D-talo-2- octulopyranosyl)onate]-(2-->6)-2-acetamido-2-deoxy-beta-D-gl ucopyranoside in high yield.     

Anomalous dilatation-temperature curves of PZT-ZrO2 composites

The dilatation-temperature curves of the PZT-ZrO₂ composites, containing 1.3–13.2 vol% ZrO₂ were studied. The course of martensitic transformation (MT) of dispersed ZrO₂ particles in the PZT matrix was followed. Upon cooling, a spontaneous microcrack formation occurred during the MT from tetragonal to monoclinic crystal phase of ZrO₂. The phenomenon of intensive shrinkage above 800 °C upon heating is explained as a process of microcrack healing in the presence of the PbO-rich liquid phase.     

Hydrolytic processes and condensation reactions in the cellulose solvent system N,N-dimethylacetamide/lithium chloride. Part 2: degradation of cellulose

Certain cellulose samples, especially those of higher molecular weight, are initially insoluble in N,N-dimethylacetamide (DMAc, 1)/lithium chloride, which is a very common solvent system for cellulosic materials. According to a common protocol, heating or refluxing these samples in DMAc, or in DMAc containing dissolved LiCl, represents one of several so-called ‘activation’ procedures, which are aimed at facilitating subsequent dissolution. In the present work, it is shown that the improved solubility achieved by this method is not only caused by a better activation or improved accessibility of the pulp, but also by a progressing degradation of the cellulosic material (DP loss).The degradation of cellulose in DMAc or DMAc/LiCl is due to two separate chemical processes. The first one, involving N,N-dimethylacetoacetamide (2) which is the primary condensation product of DMAc, causes a slow degradation by thermal endwise peeling. The glucose units peeled off the reducing end are released as furan structures (3). The mechanism appears to be a thermal cleavage of the glycosidic bond, which becomes quite selective towards the proximal anhydroglucose unit by a neighbor group-assisted effect according to quantum-chemical calculations. Due to its stepwise and thus slow mechanism, this pathway contributes only insignificantly to the overall cellulose degradation.The second degradation mechanism causes random chain cleavage and thus pronounced and rather fast changes in the molecular weight distribution. It involves N,N-dimethylketeniminium ions (5), whose presence in DMAc/LiCl at temperatures above 80 °C—the coalescence temperature of DMAc as determined by dynamic NMR—was unambiguously demonstrated by specific trapping in a thermal [2+2]-cycloaddition with lipophilic olefins. The keteniminium ion is an extremely reactive electrophile, which is able to directly cleave glycosidic bonds. The detrimental effect of this intermediate on the integrity of cellulosic pulps was confirmed by addition of an external degrading agent of the keteniminium type. Also the precursor compound, a ketene aminal, was confirmed to be present in heated DMAc or DMAc/LiCl by trapping with allyl alcohol in a spontaneous Claisen-type rearrangement.     

Clinical relevance of p53 index and expression of proliferating cell nuclear antigen and Ki-67 in gastric cancer

To improve the therapeutic outcome for inoperable non-small-cell lung cancer, we applied definitive thoracic radiotherapy combined with concurrent administration of carboplatin and etoposide. We retrospectively analyzed 55 eligible patients with Stage III disease. The one-year rate of overall survival (OAS) and distant metastasis-free survival (DMFS) of the total group were 46.1% and 36.1%, respectively. Twenty-nine patients developed thoracic failures (52.7%) and 23 (41.8%) distant failures. Using univariate and multivariate analyses, radiation dose, performance status and LDH were revealed as significant prognostic factors of OAS, and LDH had a strong adverse effect on DMFS. Leucopenia of Grade 3 or higher was noted in 75.9%, anemia in 55.6%, thrombocytopenia in 59.3%, esophagitis in 20.4%, and lung injury in 10.9%. Sufficient gain was not obtained by our strategy, and higher morbidity, especially of lung, was noted than was expected. It was suspected that simultaneous use of oral etoposide might increase radiation pneumonitis, so one should take special care of unexpected toxicity in concurrent chemoradiotherapy. Both the hyperfractionated technique of radiotherapy and the time-dose modification of anti-tumor drugs should be considered in further steps.     

Characterization and Classification of Extra Virgin Olive Oil from Five Less Well-Known Greek Olive Cultivars

The present study comprises the second part of an ongoing study focusing on olive oil from five less well‐known Greek cultivars for three of which there are no data available in the literature regarding their chemical composition. A total of 74 olive oil samples were collected during the harvesting periods 2012–2013 and 2013–2014. Headspace‐solid phase microextraction was applied to determine the olive oil volatile profile. Fifty‐six compounds were identified and semi‐quantified by CG–MS. Furthermore, fatty acid composition, conventional quality parameters and color parameters were determined in an effort to characterize and differentiate olive oils according to cultivar. All samples were characterized as extra virgin olive oils. Data obtained showed significant differences between the cultivars. Multi‐element analysis in combination with chemometrics resulted in a high classification rate of 86.5 % for the combination of volatiles plus color, 89.2 % for the combination of VC plus FA, and 91.9 % for the combination of FA composition plus color plus CQP.     

Ageing of dental zirconia ceramics

An in vitro study was designed to monitor the t–m transformation of biomedical grade 3Y-TZP ceramics produced from two ready-to-press granulated powders of the same nominal chemical composition, but differing in their specific surface area. Disc-shaped specimens were formed by uni-axial dry-pressing and sintering in air for 2 h in the temperature range 1400–1550 °C, resulting in a mean grain size of 0.26–0.57 μm. The sintered specimens were subjected to accelerated ageing in deionized water at 134 °C for up to 48 h and verified in terms of the amount of the transformed monoclinic fraction, the thickness of the transformed layer, and the bi-axial flexural strength. The sintering-temperature-dependent transformability during ageing was confirmed, whereby the role of the starting-powder characteristics was more pronounced at lower sintering temperatures and was almost negligible at higher sintering temperatures.     

Solution growth of spherulitic rod and platelet calcium phosphate assemblies through polymer-assisted mesoscopic transformations

Solution growth of apatite its precursors in the presence of urea commercial gelatin is found to lead, under appropriate conditions, to a rich spectrum of morphologies, among them high aspect ratio needles in uniform sturdy spherulitic assemblies resulting from a herein documented morphological ‘Chrysalis Transformation’; the latter transformation involves the growth of parallel arrays of high aspect ratio needles within micron-scale tablets the formation of a radial needle arrangement upon disruption of tablet wrapping. A different level of gelatin leads to the formation of sturdy platelet-based spherulites through another morphological transformation. We also probe the role of four simple synthetic water-soluble polymers; we find that three of them (poly(vinyl alcohol), polyvinylpyrrolidone and polyacrylamide)) also affect substantially the assembly habits of apatite; the effect is similar to that of gelatin but the attained control is less perfect/complete. The case of poly(vinyl alcohol) provides, through variation of the degree of hydrolysis, insights as regards the chain architecture features that might favor morphological transformations. Morphological transformations of particle assemblies documented herein constitute novel ways of generating dense quasi-isotropic reinforcements with high aspect ratio ceramic particles; it becomes possible to tailor calcium phosphate phases at the structural level of crystal assembly.