169,852 research outputs found
Valutazione delle conoscenze in tema di AIDS in un gruppo di giiovani milanesi
No full textVerrà inserito in seguit
Early age evolution of rheological properties of over-stabilized bitumen emulsion-cement pastes
No full textThis paper focuses on the early age evolution of consistency and rheological properties of fresh bitumen emulsion-cement (BEC) pastes. The tested BEC pastes were fabricated using a Portland limestone cement and an over-stabilized bitumen emulsion and were characterized by water to cement ratio ranging between 0.33 and 1 and by bitumen to cement ratio ranging between 0 and 1. The testing plan included the measurement of sedimentation tendency, setting time and evolution of viscosity with increasing storage time. Rheological measurements were also carried out on bitumen emulsion-filler mastics prepared with a reference filler. Results showed that, regardless of water content, the initial and final setting time of BEC pastes increased when the proportion of bitumen with respect to cement was increased. When the total concentration of the dispersed phases was low, the increase in bitumen concentration with respect to cement led to a reduction in the rate of viscosity increase with storage time; on the other hand, when the total concentration of the dispersed phases was high the increase of storage time led to a change in the physical state of the pastes (from fluid to plastic) due to coalescence of bitumen droplets
Immunohistochemical study of solid cell nests of the thyroid gland found from an autopsy study
No full textAn immunohistochemical study was performed to identify the histogenesis of solid cell nests (SCN) found in 30 of 202 thyroids obtained at autopsy. Immunoperoxidase staining was used to detect the presence of calcitonin, thyroglobulin, thyroxin, low and high molecular weight keratins, and carcinoembryonic antigen (CEA). Results showed that cells forming solid nests had immunoreactivity for calcitonin, low molecular weight keratin, and CEA, but not for thyroglobulin, thyroxin and high molecular weight keratin. Thus, SCN do not result from tangentially cut thyroid follicles (absence of staining for thyroglobulin and thyroxin), nor from a squamous metaplastic process (absence of staining for high molecular weight keratin), but instead they are formed by C-cells because they showed calcitonin immunoreactivity, and neurosecretory granules
Thermomechanical behaviour of airfield concrete pads supporting joint strike fighter F-35B
No full textThe Lockheed Martin F-35B Lightning II is the Short Take-Off/Vertical Landing (STOVL) aircraft variant of the joint strike fighter. The new dual-cycle propulsion system, which permits the STOVL operations, exposes the airfield pavements to extremely critical thermal conditions (temperatures exceeding 930°C and heating rate of about 85°C s−1). This study permitted to analyse the thermomechanical behaviour of an ordinary concrete pad during the F-35B aircraft vertical landing. The numerical analysis provided a detailed picture of the pavement stress state generated by the jet gases, opening the scenario to different planning solutions. The results highlighted how the damage, in the form of thermomechanical spalling, occurred in the top 2–5 mm of the pavement surface. One of the possible design solutions for high-performance vertical landing pads, supporting the F-35B aircraft, could be a two-layered pavement characterised by a thin (2.5 cm) fibre-reinforced Very High-Strength Concrete overlay
Early age evolution of rheological properties of over-stabilized bitumen emulsion-cement pastes
No full textThis paper focuses on the early age evolution of consistency and rheological properties of fresh bitumen emulsion-cement (BEC) pastes. The tested BEC pastes were fabricated using a Portland limestone cement and an over-stabilized bitumen emulsion and were characterized by water to cement ratio ranging between 0.33 and 1 and by bitumen to cement ratio ranging between 0 and 1. The testing plan included the measurement of sedimentation tendency, setting time and evolution of viscosity with increasing storage time. Rheological measurements were also carried out on bitumen emulsion-filler mastics prepared with a reference filler. Results showed that, regardless of water content, the initial and final setting time of BEC pastes increased when the proportion of bitumen with respect to cement was increased. When the total concentration of the dispersed phases was low, the increase in bitumen concentration with respect to cement led to a reduction in the rate of viscosity increase with storage time; on the other hand, when the total concentration of the dispersed phases was high the increase of storage time led to a change in the physical state of the pastes (from fluid to plastic) due to coalescence of bitumen droplets
[Latent pathology of the thyroid: an epidemiological and statistical study of thyroids sampled during 507 consecutive autopsies]
No full textIn order to highlight the occult pathology of the thyroid in the aged, the authors examined all the glands withdrawn from 507 consecutive autopsies on subjects of 67.10 years of median age. In 10 tables there are weight and measurements of the thyroids, macro and microscopic details and pathologic appearances. Adenomas were found in 17.1% of cases and histologically besides the known cases referred also to the Hürtle cells type, 4 clear cells adenomas and 5 adenolipomas were found. In 27.42% the subjects were affected or were dead for a malignant extrathyroidal neoplasm, and in 26% of these there was a metastasis in the thyroid. Never a primitive thyroid carcinoma, macroscopically and clinically evident, but in 53 thyroid glands, 54 occult carcinomas (OC) were found, particularly 37 papillary and 17 medullary. IN 57% of 165 histologically treated thyroids, to evidence C-cells, hyperplasia of these cells was found associated with various pathologic conditions, more in aged subjects. In 147 glands were found 170 nodules of various number of cells, at times positive for calcitonin. These solid cellular nodes (SCN) were evaluated as nodular C-cells hyperplasia. Besides isolated cases of acute thyroiditis (also the mycotic type), of tubercular thyroiditis and Hashimoto's, in 12% of the glands a lymphocytic chronic thyroiditis was found, frequently with Hürtle cells. Others observations were: basophilic thickening of colloid also with calcium oxalate crystals, lipoid degeneration of follicular cells and fat interfollicular and interlobular infiltration, thyroid amyloidosis, inner and media elastic calcification of thyroid arteries, presence of cysts with squamous cells coating, parathyroid glands and cartilage intrathyroidal plaques
Airborne emissions of asphalt/wax blends for warm mix asphalt production
No full textDuring the asphalt heating process in the various stages of hot mix asphalt (HMA) production and paving operations a complex mixture of hydrocarbon aerosols, vapors and gases, generally composed of products of combustion, volatile organic compounds (VOCs) and polycyclic aromatic hydrocarbons (PAHs), is emitted into the atmosphere. The reduction of these airborne asphalt emissions is a continuous issue and challenge for asphalt industry and road agencies. Thus, a number of new sustainable and cleaner technologies, generally referred to as warm mix asphalts (WMA), that significantly reduce the manufacturing and application temperatures, had been developed. Despite the great number of reported WMA methodologies, organic waxes are widely used for reducing the binder viscosity and for enhancing the asphalt mixture workability already at lower temperatures (90â140 °C). The manuscript presents a detailed laboratory investigation, based on headspace gas chromatography-mass spectrometry (HS-GC/MS) and photoionization detection (PID), which aimed to assess the content of VOCs and PAHs in the asphalt emissions, taking into account the effective contribution of binder or binder/wax blend. The characterization of asphalt fume composition has allowed the identification of more than 200 volatile compounds, highlighting at the same time a hierarchy of their appearance in relation to the temperature. The detection of the less volatile compounds was feasible only at temperatures higher than 160 °C, temperature range in which the HMA is generally produced. The study of the binary asphalt/wax mixtures highlighted the twofold way in which the waxes perform in reducing emissions: on the one hand they act as flow improvers (reduction of production and paving temperatures) and on the other as fume suppressants
Half-warm mix asphalt with emulsion. An experimental study on workability and mechanical performances
No full textOne of the major sustainability-related challenge facing materials for asphalt pavements is the energy consumption and the release of harmful and odorous fumes. Reductions in these emission levels have been progressively achieved by a number of cleaner and low-temperature technologies. Recently, a further step towards an improved road pavement sustainability is represented by the half-warm mix asphalt (HWMA) mixtures, which are produced between 70 °C and 100 °C without negatively affecting their final performances. Among these methodological approaches, a very interesting solution for urban or low volume traffic roads is represented by HWMA mixtures prepared with a conventional warm emulsion and heated aggregates. Although this technique is capable of combining the advantages of hot and cold mixes, limiting some drawbacks, it is still little known and remains confined only to some regional areas (in Spain with the term mezclas templadas). There are no standards or specifications, but only some construction practices resulting from the experience gained in the field. Thus, a laboratory-scale experimental study was set up to analyze in detail the behavior of dense-graded HWMA mixes prepared with emulsion intended for a surface course layer of a low or medium traffic road. The objective was to evaluate the influence of three mix-design variables, such as compaction temperature, binder content and aggregate gradation on the volumetric and mechanical, i.e. indirect tensile strength and moisture susceptibility, properties of these mixtures. The rank comparison between the selected mixtures represented the starting point for improving on the one hand the mix-design process and on the other the operational procedures of production, transportation and placement
- …
