1,355,191 research outputs found
Shock timing in mitogynogenesis and tetraploidization of the European sea bass Dicentrarchus labrax
No full textA two-step assay was performed under strictly controlled temperature (14±0.2 °C) to obtain mitogynogenetic and tetraploid offspring in the European sea bass (Dicentrarchus labrax L.). The first (probative) series of trials was aimed at adjusting both intensity and timing of the pressure shock to be applied for doubling chromosome set. Larval hatching (LH) (mean 1±1% for gynogenetic double haploids and 3±2% for tetraploids) was achieved only when the pressure shock was applied within 70–90 min after fertilization and the pressure intensity was set at 81–91 (MPa). Lower pressure (70–80 MPa) produced largely variable results and the lowest pressures (<70 MPa) were ineffective. The second series of trials (optimization) was performed to improve the yield in manipulated offspring by recording the time of the first cleavage in a preliminary fertilization test, and timing the application of the pressure shock accordingly. With this manipulation, mitogynogenesis and tetraploidization success rates consistently increased (mean LH 10±6% and 18±12%, respectively), producing live progeny. A significant linear regression was found between the optimal shock application time and the appearance of the first cleavage. The linear regression may be applicable to other fish species
Haematological parameters in Umbrina cirrosa (Teleostei, Sciaenidae): a comparison between diploid and triploid
No full textHaematological features were compared between diploid and triploid specimens of the ray-finned fish Umbrina cirrosa. No significant differences between diploids and triploids were reported in haematocrit and total haemoglobin concentration, but erythrocytes and thrombocytes were significantly greater in size in triploids. Glycaemia was significantly lower in diploids, whereas triploid erythrocytes were more resistant to osmotic stress. In triploids, a greater fraction of leukocytes was positive for alkaline phosphatase activity, when stimulated with Bacillus clausii spores, otherwise no significant increase of oxygen consumption was observed in triploid leukocytes after stimulation, based on assays for superoxide anions. Triploids were characterized by a lower concentration of circulating blood cells with a lower surface/volume ratio when compared with diploids. These features may lead to a general disadvantage of triploids in withstanding stress conditions: a situation that needs to be taken into account in aquaculture practice
A kinetic study of the quartz-cristobalite phase transition
No full textCristobalite is a common silica polymorph in ceramics, as it can crystallize in SiO2-rich systems during high temp. processes. Its occurrence in final traditional ceramic bodies remarkably affects their thermal expansion, thus playing an important role in the shrinkage upon cooling. The quartz-cristobalite transformation kinetics is investigated by in-situ isothermal X-ray powder diffraction expts. and then correlated to the av. particle size (〈d〉) of the starting quartz using a model here developed. An Avrami-like rate equation, i.e. α(t) = 1 - exp(- k × t)n, in which the n-term is assumed to account for the dependence on the av. particle size, has provided the best fitting of theor. to exptl. data, yielding activation energy values that range from 181 to 234 kJ mol-1, and exponential n-coeffs. from 0.9 to 1.5. Ex-situ observations have demonstrated that the formation of cristobalite from quartz after 50 min, 2, 4 and 6 h at 1200 and 1300 °C, exhibits a remarkable dependence on 〈d〉 of quartz, showing comparable behaviors in the case of 〈d〉 equal to 15.8 and 28.4 μm, but significant differences for 〈d〉 of 4.1 μm. The formation of cristobalite is boosted remarkably at temp. higher than 1200 °C, with an increase by wt. even of 500%, with respect to its content at lower temp. The method of sample prepn. (dry powder, wet powder and tablet of compressed dry powder) seems to influence the results only at temp. > 1200 °C and in the case of fine powder
Criteri per valutare la qualità delle uova in tre specie di pesci marini di allevamento.
No full textIn: Il prodotto ittico consumo, qualità , commercializzazione
Riproduzione e manipolazione gametica di Umbrina cirrosa (L.) per la diversificazione dell’acquacoltura nazionale.
No full textRelazione tecnica dell'attività scientifica IV° Piano Triennale per la Pesca e l'Acquacoltura. Ministero delle Politiche Agricole e Forestali
Eleven years of experiments in chromosome set manipulation of the European sea bass (Dicentrarchus labrax L.).
No full textInfluence of composition on some industrially relevant properties of traditional sanitary-ware glaze
No full textTwo series of glazes have been produced from different combinations of the same raw materials in the range of interest for sanitary-ware applications: they are designed to allow one to get insight into network-forming and network-modifying species. Fusibility tests and hot stage microscope observations show the influence of even low differences in the starting chemical compositions on the transformation temperatures. X-ray powder diffraction, wavelength dispersion spectrometry and scanning electron microscopy prove that: (i) zircon, the most abundant crystalline phase, is homogeneously distributed and decreases by a 3% from its starting value; (ii) the glass-phase of glaze has a quasi-uniform composition. X-ray synchrotron radiation micro-tomography shows that glaze porosity is 15% by volume, and voids are prevalently not interconnected and with size up to 50 μm. The linear thermal expansion of the glass phase of glaze ranges between 6 and 7 × 10 -6 °C -1, without apparent correlation with composition
Sanitary-ware vitreous body characterization method by optical microscopy, elemental maps, image processing and X-ray powder diffraction
No full textAbstract
The present investigation deals with a characterization method for fired body (cast piece) from a standard sanitary-ware industrial cycle, relying
upon data mainly from optical/electron microscopy and chemical mapping. Image processing techniques have been used to reconstruct the phasedistribution
throughout the body, so as to provide a phase-arrangement-sensitive description of the crystalline and amorphous components. The
results so attained are compared with those from classical X-ray powder diffraction in terms of total phase-contents. The amorphous phase-content
and its distribution can be determined by optical microscopy, and the modest level of precision of the phase quantification is improvable by
accounting for the occurrence of voids. Residual quartz is identified by means of the backscattered electron contrast differences in images, and
thereby its morphologic properties and amount are determined. The use of elemental X-ray maps allows one to attain a description of the local
composition and, on the basis of some assumptions, to quantify microcrystalline mullite and also discriminating between primary versus secondary
mullite
Mutual support groups for family caregivers of people with amyotrophic lateral sclerosis: a pilot study
No full textFamily caregivers of people with amyotrophic lateral sclerosis (ALS) live stressful lives in which they spend most of their time caring for their loved ones and managing difficult situations, thereby reducing the time spent in taking care of themselves. This situation may last several years. Previous literature has widely highlighted that this situation reduces caregivers’ quality of life and increases their psychological distress and risk of health problems, but there is a lack of studies that focus on psychological interventions for these situations. This qualitative study examined a pilot experience of two mutual support groups for family caregivers of people with ALS. The aim was to identify caregivers’ needs, the prominent aspects of their experience, and to understand whether and how this intervention strategy might help them. Six partners (four men and two women) and six adult children (five women and one man) participated in the groups, which were conducted in northern Italy. After the support groups finished, participants underwent semi‐structured interviews. The authors conducted a content analysis of the transcripts of the interviews and the 20 group sessions. The thematic areas identified were “caregiving,” “being the son/daughter of a person with ALS,” “being the partner of a person with ALS,” “group experience” and “group evaluation.” The caregiving experience was profoundly different depending on whether the caregiver was a son/daughter or a partner of a patient with ALS. Moreover, comparison with peers and mutual support helped participants to better cope with ALS and its consequences, to improve their care for their relatives and to overcome typical caregiver isolation. These results suggest the usefulness of involving communities in caregiver support in order to create new networks and activate personal and social resources for well‐being
Feldspar and firing cycle effects on the evolution of sanitary-ware vitreous body
No full textThis work is focused on the study of macroscopic and microscopic properties of traditional sanitary-ware vitreous bodies as a function of feldspar flux and firing time-temperature profile, using a fixed slip formulation (50 wt.% clay, 25 wt.% quartz and 25 wt.% feldspar). Two flux particle sizes (45 and 75 μm), three flux compositions (Na-based feldspar, K-based feldspar and a mix of them) and three firing cycles with the same soaking temperature (i.e. 1240 C) have been combined to evaluate their effects on the relevant industrial properties of water absorption and thermal expansion. The micro-scale observables, phase composition and micro-morphology, have also been investigated. Despite a general similarity exhibited by the ceramic samples, qualitative and quantitative differences in terms of feldspar dissociation temperature, phase-composition and densification trends have been observed. In particular, for a fixed firing cycle, the combination of the sodium based feldspar with the smallest flux particle size leads systematically to a water absorption value that is below the 0.5 target value and to a glass amount that approaches 70 wt.%. Thermal expansion coefficients below the quartz α-β transition are found in the 6.2-6.9×10-6 C-1 range; the highest values seem to be favoured by incorporation of potassium based
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