1,721,285 research outputs found
Reduced-order condensed-phase kinetic models for polyethylene, polypropylene and polystyrene thermochemical recycling
No full textThermochemical recycling of plastic waste (PW) into chemicals and energy vectors requires coupling particle and reactor-scale simulations to accurate condensed phase pyrolysis mechanisms for each constituent. This work proposes a methodology to derive reduced-order condensed-phase kinetic models from validated semi-detailed kinetic mechanisms. Two types of kinetic models are obtained for polyethylene (PE), polypropylene (PP) and polystyrene (PS): reduced semi-detailed models and multi-step fully lumped ones. These families offer different compromises between accuracy and computational cost. The former employ 50-100 gas + liquid species and describe both the radical degradation and the detailed carbon distribution of the products. Conversely, the latter involves 5-10 species per polymer tracking only the main petroleum cuts. The kinetic mechanisms are complemented by the definition of thermochemical properties of gas, liquid, and solid-phase species, accounting for phase-transitions through pseudo-chemical reactions. Model validations are performed by comparison with experimental data and the original semi-detailed mechanisms in terms of mass loss, heat fluxes and product distribution profiles. The resulting CHEMKIN-like condensed-phase models are attached as Supplementary Material and as a GitHub repository. Extending the proposed approach to other polymers and coupling it with existing subsets in the CRECK kinetic framework (e.g., biomass, PVC, PET) offers a powerful tool to model thermochemical recycling of PW and biomass/PW mixtures
Aromatase inhibitors in the adjuvant treatment of postmenopausal women with early breast cancer: Putting safety issues into perspectives.
No full textTamoxifen has been the gold standard adjuvant therapy for the treatment of postmenopausal women with hormone-receptor-positive (HR+) early breast cancer for many years. Tamoxifen treatment is limited to 5 years because of the development of de novo and acquired resistance, and an ongoing risk of adverse events, including endometrial cancer, thromboembolic events, and gynecological symptoms with long-term use. The third-generation aromatase inhibitors (Als), letrozole, anastrozole, and exemestane, are displacing tamoxifen as the first-choice therapy for HR+ early breast cancer, and are now recommended as the preferred therapy by national and international guidelines. Recent randomized trials have demonstrated that the Als are more effective than tamoxifen in preventing disease recurrence when used in substitution and sequential strategies in the early adjuvant setting, and letrozole has been shown to be more effective than placebo in the extended adjuvant setting (after 5 years of tamoxifen therapy). Trial safety data show that the overall tolerability of Als is similar to that of tamoxifen, with adverse events being predictably characteristic of estrogen deprivation; however, some important differences in adverse event profiles between tamoxifen and the Als have been demonstrated. In addition to antiestrogenic effects, tamoxifen acts as an estrogen agonist in some tissues, which can lead to serious side effects not associated with the Als, which prevent estrogen biosynthesis. A lower incidence of gynecological and thromboembolic events is observed in patients taking Als, and fewer cases of endometrial cancer are seen compared with tamoxifen. Adverse events that are more frequent with adjuvant AI therapy compared with tamoxifen include arthralgia and myalgia, bone loss, and effects on the cardiovascular system and blood lipids. The effects of Als on bone are predictable and may be easily managed, where necessary, with bisphosphonates. Studies examining the effects of Als on the cardiovascular system and lipid profiles, including in the extended adjuvant setting, suggest that these adverse events may be due to the absence of a protective effect of tamoxifen rather than true AI toxicity. Further studies are required to determine the long-term safety of AI therapy in postmenopausal women with HR+ early breast cancer
Numerical predictions of flashback limits of H2-enriched methane/air premixed laminar flames
Full text linkHydrogen is considered as a promising resource for decarbonizing not just the industrial sector but also domestic heating systems. By partially substituting natural gas with hydrogen, domestic combustion-based conversion systems have the potential to enhance efficiency, decrease carbon emissions, and achieve cleaner combustion, specifically reducing levels of particulate matter. Nevertheless, hydrogen possesses properties that differ significantly from natural gas. In particular, due to its higher laminar flame speed, hydrogen has a much higher propensity to flashback than natural gas, raising notable safety concerns. This study aims to examine the impact of H2 addition (up to 100%) to natural gas on the combustion process in domestic condensing boilers. To achieve this objective, 3D numerical simulations are conducted, modeling the multi-hole geometry that emulate perforated burners commonly found in these appliances. The simulations incorporate detailed kinetics and conjugate heat transfer with the burner plate and consider various hole-to-hole distances for a more comprehensive analysis. Flashback limits are found for a wide range of operating conditions of interest for domestic applications, with equivalence ratios from 0.5 to 1 and hydrogen fractions from 0 (pure methane) to 1 (pure hydrogen). The results confirm the observations of previous works on planar, multi-slit configurations. More specifically, the results shows that the conventional flashback correlation based on the concept of critical velocity gradient becomes inaccurate for H2 fractions larger than 0.50 as it does not take into account stretch induced preferential diffusion effects, which are especially large in the multi-hole configuration here investigated
Ruolo attuale della chemioterapia nel carcinoma transizionale della vescica muscolo-invasivo
No full textThe present role of chemotherapy in the mana. gement of muscle-invasive transitional cell bladder cancer. The results obtained with chemotherapy (CT) in the management of muscle-infiltrating transitional cell bladder carcinoma (TCBC) are compared with those of radiotherapy (RT) and surgery (S)_ Cisplatin and methotrexate are the most effective agents, with an overall response rate ranging from 20 to 45 % when administered singly. Other chemotherapeutic drugs whichproved of some antitumor activity in TCBC are doxorubicin and vinblastine, with an overall response rate of approximately IS % (range 4-28 %)_ With each drug used singly, however,complete response (CR) is uncommon. Combination CT regimens (cisplatin+methotrexate, cisplatill+methotrexate+vinblastine, methotrexate+vinblastine+doxorubicin+cisplatin) are inducing a higher number of CR with an overall response rate between 40 and 70 %. CT, previously used as adjuvant or salvagetherapy in advanced TCBC, is now given in neo-adjuvant fashion in order to achieve tumor size reduction and control of micrometastases.With these multiagent regimens a significant down-staging can be obtained without major toxicity in over SO % of patients withmuscle-infiltrating TCBC, thus increasing the number of patients which can be cured by surgery. These neo-adjuvant programs suggests potential benefit, yet randomized studies andprolonged observations are required to provide definitive results
Definizione dell'interessamento vertebrale in corso di mieloma multiplo attraverso la risonanza magnetica nucleare
No full textNO ABSTRAC
Gruppi-SH sierici in pazienti con emolinfoblastosi fuori terapia
No full textDa vari contributi è stata sottolineata l'importanza che i gruppi sulfidrilici (gruppi -SH reattivi) delle proteine rivestono in numerosi processi biologici quali la coagulazione del sangue, la mitosi cellulare, le funzioni delle membrane cellulari, il metabolismno proteico (1,2).Studi recenti hanno focalizzato il rilevante ruolo svolto dai gruppi -SH oltre che nei fenomeni immunitari con la modulazione della linfopoiesi e della funzionalità linfocitaria, anche come prima barriera endogena preposta ad antagonizzare i danni biologici dei radicali liberi ossidanti potenzialmente mutageni (3,4).E' già stata da noi segnalata una significativa diminuzione della concentrazione sierica dei gruppi -SH in pazienti con malattie neoplastiche in fase di attività (5,6), mentre il presente studio è stato condotto anche su una casistica di emolinfoblastosi in remissione completa (RC) fuori terapia
Improvements in the simulation of liquid fuel combustion in a low-temperature fluidized bed
No full textGoing Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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