6,516 research outputs found

    \eta - \eta' Mixing -- From Electromagnetic Transitions to Weak Decays of Charm and Beauty Hadrons (presented at Hadron 2011)

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    It has been realized for a long time that knowing the \eta and \eta' wave functions in terms of quark and gluon components probes our understanding of non-perturbative QCD dynamics. Great effort has been given to this challenge -- yet no clear picture has emerged even with the most recent KLOE data. We point out which measurements would be most helpful in arriving at a more definite conclusion. A better knowledge of these wave functions will significantly help to disentangle the weight of different decay subprocesses in semi-leptonic decays of D^+, D_s^+ and B^+ mesons. The resulting insights will be instrumental in treating even non-leptonic B transitions involving η\eta and η\eta^{\prime} and their CP asymmetries; thus they can sharpen the case for or against New Physics intervening there.Comment: Prepared for HADRON 201

    Analysis of fossil planktonic foraminifera: the sieve mesh effect

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    The choice of the sediment size fraction in the analysis of fossil planktonic foraminifera is of great importance in determining the composition of assemblages. In past studies several size fractions have been utilised. Imbrie and Kipp (1971) stated that “smaller fractions give rise to too many uncertainties in the identification of small specimens and require too long to process. Large mesh size yield undesiderable loss of small species, and small specimens of larger species”. The adoption of coarser sieve meshes has the effect to reduce the percentages of small sized (usually living in cold waters) species (Bé and Hutson, 1977). In a comparison between >63 μm and >150 μm size-fraction of planktonic foraminifera assemblages from NW Atlantic Ocean, Smart (2002), stated that because particular smaller species are either under-represented or even absent from the larger (>150 μm) size-fraction, the smaller (>63 μm) size-fraction must be included in studies of planktonic foraminifera. Di Donato et al. (2008) highlighted in the >150 μm size fraction of a core from the Tyrrhenian Sea, a great loss of the small-sized species Turborotalita quinqueloba in glacial samples, where this species is very abundant. This caused an increase in warm water species such as Globigerinoides ruber, apparently reaching typical Holocene values in some full glacial levels. From the above mentioned statements, it is clear that treatment changes can strongly influence the results of palaeoclimatic reconstructions based on planktonic foraminiferal assemblages. As stated by Aitchison (1986, 1992) scale invariance and subcompositional coherence are fundamental properties of the compositional data analysis (CODA). The main goal of this paper is to verify if the variable relationships pointing out from CODA of foraminiferal assemblages are or not influenced by the size fraction and, more in general, to test the robustness of CODA respect to treatment changes related to different preparation techniques for the analysis of planktonic foraminifera

    Biomass valorization: Sustainable methods for the production of hemicellulolytic catalysts from thermoanaerobacterium thermostercoris strain buff

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    Processing and selection of fruits and vegetables generate high quantities of wastes that represent an economic and environmental issue for the agroindustry sector. According to the so-called “biorefinery” approach, this biomass can be exploited for the recovery of value-added molecules. In this study, the residues of industrial processing of tomato (Lycopersicon esculentum variety “Hybrid Rome”), fennel (Foeniculum vulgare), potato (Solanum tuberosum) and carrot (Daucus carota) were used as sole carbon sources to support cheap and sustainable microbial growth as well as the production of secondary metabolites (hydrogen and ethanol) by Thermoanaerobacterium thermostercoris strain BUFF, a thermophilic anaerobic microorganism isolated from buffalo-dung compost. Moreover, the use of hemicellulolytic enzymes of T. thermostercoris was assayed in the bioconversion reaction of the polymer fraction extracted from the rhizome of giant reed (Arundo donax) and of the leaves and stems of cardoon (Cynara cardunculus), dedicated non-food crops employed in energy supply

    Parageobacillus thermantarcticus, an Antarctic Cell Factory: From Crop Residue Valorization by Green Chemistry to Astrobiology Studies

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    Knowledge of Antarctic habitat biodiversity, both marine and terrestrial, has increased considerably in recent years, causing considerable development in the studies of life science related to Antarctica. In the Austral summer 1986–1987, a new thermophilic bacterium, Parageobacillus thermantarcticus strain M1 was isolated from geothermal soil of the crater of Mount Melbourne (74°22′ S, 164°40′ E) during the Italian Antarctic Expedition. In addition to the biotechnological potential due to the production of exopolysaccharides and thermostable enzymes, successful studies have demonstrated its use in the green chemistry for the transformation and valorization of residual biomass and its employment as a suitable microbial model for astrobiology studies. The recent acquisition of its genome sequence opens up new opportunities for the use of this versatile bacterium in still unexplored biotechnology sectors

    Investigation of the skin contamination predictability by means of QForm UK extrusion code

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    The paper presents an innovative approach implemented in QForm UK Extrusion FEM software to analyse one of the core defects encountered in profile extrusion known as billet skin defect. The validation of the algorithm has been performed based on a number of experimental case studies taken from the literature [1,2]. Additionally, the sensitivity of the accuracy of the results to the variation in initial parameters has been analysed for both types of profile shapes: solid and hollow. Based on this, practical recommendations have been formalised for the successful industrial use of the presented algorithm

    Effects of Ionizing Radiation and Long-Term Storage on Hydrated vs. Dried Cell Samples of Extremophilic Microorganisms

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    A main factor hampering life in space is represented by high atomic number nuclei and energy (HZE) ions that constitute about 1% of the galactic cosmic rays. In the frame of the “STARLIFE” project, we accessed the Heavy Ion Medical Accelerator (HIMAC) facility of the National Institute of Radiological Sciences (NIRS) in Chiba, Japan. By means of this facility, the extremophilic species Haloterrigena hispanica and Parageobacillus thermantarcticus were irradiated with high LET ions (i.e., Fe, Ar, and He ions) at doses corresponding to long permanence in the space environment. The survivability of HZE-treated cells depended upon either the storage time and the hydration state during irradiation; indeed, dry samples were shown to be more resistant than hydrated ones. With particular regard to spores of the species P. thermantarcticus, they were the most resistant to irradiation in a water medium: an analysis of the changes in their biochemical fingerprinting during irradiation showed that, below the survivability threshold, the spores undergo to a germination-like process, while for higher doses, inactivation takes place as a consequence of the concomitant release of the core’s content and a loss of integrity of the main cellular components. Overall, the results reported here suggest that the selected extremophilic microorganisms could serve as biological model for space simulation and/or real space condition exposure, since they showed good resistance to ionizing radiation exposure and were able to resume cellular growth after long-term storage

    Novel psychrophiles and exopolymers from permafrost thaw lake sediments

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    Thermokarst lakes are one of the most abundant types of microbial ecosystems in the circumpolar North. These shallow basins are formed by the thawing and collapse of ice-rich permafrost, with subsequent filling by snow and ice melt. Until now, permafrost thaw lakes have received little attention for isolation of microorganisms by culture-based analysis. The discovery of novel psychrophiles and their biomolecules makes these extreme environments suitable sources for the isolation of new strains, including for potential biotechnological applications. In this study, samples of bottom sediments were collected from three permafrost thaw lakes in subarctic Québec, Canada. Their diverse microbial communities were characterized by 16S rRNA gene amplicon analysis, and subsamples were cultured for the isolation of bacterial strains. Phenotypic and genetic characterization of the isolates revealed affinities to the genera Pseudomonas, Paenibacillus, Acinetobacter, Staphylococcus and Sphingomonas. The isolates were then evaluated for their production of extracellular enzymes and exopolymers. Enzymes of potential biotechnological interest included α and β-glucosidase, α and β-maltosidase, β-xylosidase and cellobiohydrolase. One isolate, Pseudomonas extremaustralis strain 2ASCA, also showed the capability to produce, in the loosely bound cell fraction, a levan-type polysaccharide with a yield of 613 mg/L of culture, suggesting its suitability as a candidate for eco-sustainable alternatives to commercial polymers

    Ovarian cancer metastasis to the breast: a case report and review of the literature

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    Although ovarian cancer often presents as a widespread disease, metastases to the breast and/or axillary lymph nodes are a very rare event, accounting for only 0.03-0.6% of all breast cancers. Its early recognition and accurate distinction from primary breast cancer are of crucial importance to choose an adequate systemic therapy over unnecessary surgeries. We presented the case of a 53-year-old woman who was diagnosed with breast metastases 2 years after the diagnosis of advanced primary serous ovarian cancer. The patient underwent primary cytoreductive surgery and platinum-based chemotherapy in combination with bevacizumab, followed by bevacizumab maintenance for 18 months. After 2 years of negative follow-ups, the disease unexpectedly spread to the left breast and axillary lymph nodes. No axillary lymph node dissection or breast surgery was performed. The patient received axillary radiotherapy and multiple chemotherapy lines: gemcitabine/cisplatin, liposomal doxorubicin, topotecan, olaparib/cediranib, paclitaxel, and cisplatin. Unfortunately, none of these treatments improved her prognosis and she died 3 years after the disease recurrence. Ovarian cancer metastasis to the breast reveals a disseminated disease with a poor prognosis. Currently, no valid treatment options are available as the disease shows multidrug chemoresistance. In the era of precision medicine, the characterization of genetic and molecular markers may play a role in offering new promising targeted therapies

    Extremely fast triplet formation by charge recombination in a Nile Red/fullerene flexible dyad

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    A donor/acceptor dyad was obtained by linking Nile Red and fullerene to a calix[4]arene scaffold. The dyad was spectroscopically characterized, both with steady-state and ultrafast transient absorption experiments, as well as with electrochemical and spectroelectrochemical techniques. We demonstrate extremely fast and efficient formation of a long-lived excited triplet localized on the fullerene moiety in this system, occurring in about 80 ps in toluene and 220 ps in chloroform. The mechanism of this process is investigated and discussed. The spectroscopic and electrochemical characterization suggests the occurrence of electron transfer from Nile Red to fullerene, leading to the formation of a charge-separated state. This state lives very briefly and, because of the small interaction between the electron donor and acceptor, promotes a singlet/triplet state mixing, inducing charge recombination and efficient triplet formation

    Mechanistic Basis for Red Light Switching of Azonium Ions

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    Azonium ions formed by the protonation of tetra-ortho-methoxy-substituted aminoazobenzenes photoisomerize with red light under physiological conditions. This property makes them attractive as molecular tools for the photocontrol of physiological processes, for example, in photopharmacology. However, a mechanistic understanding of the photoisomerization process and subsequent thermal relaxation is necessary for the rational application of these compounds as well as for guiding the design of derivatives with improved properties. Using a combination of sub-ps/ns transient absorption measurements and quantum chemical calculations, we show that the absorption of a photon by the protonated E-H+ form of the photoswitch causes rapid (ps) isomerization to the protonated Z-H+ form, which can also absorb red light. Proton transfer to solvent then occurs on a microsecond time scale, leading to an equilibrium between Z and Z-H+ species, the position of which depends on the solution pH. Whereas thermal isomerization of the neutral Z form to the neutral E form is slow (∼0.001 s-1), thermal isomerization of Z-H+ to E-H+ is rapid (∼100 s-1), so the solution pH also governs the rate at which E/E-H+ concentrations are restored after a light pulse. This analysis provides the first complete mechanistic picture that explains the observed intricate photoswitching behavior of azonium ions at a range of pH values. It further suggests features of azonium ions that could be targeted for improvement to enhance the applicability of these compounds for the photocontrol of biomolecules.</p
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