Search Results (5)

The polymerization of isobutylene allows us to obtain a wide spectrum of polyisobutylenes (PIBs) which differ in their molecular weight characteristics and the chemical structure of chain-end groups. The bulk of the PIBs manufactured worldwide are highly reactive polyisobutylenes (HRPIBs) with –C(Me)=CH₂ end-groups and low-molecular weights (M_n < 5 kDa). HRPIBs are feedstocks that are in high demand in the manufacturing of additives for fuels and oils, adhesives, detergents, and other fine chemicals. In addition, HRPIBs and CMe₂Cl-terminated PIBs are intensively studied with the aim of finding biomedical applications and for the purpose of developing new materials. Both chain control (molecular weight and dispersity) and chemoselectivity (formation of exo-olefinic or –CMe₂Cl groups) should be achieved during polymerization. This review highlights the fundamental issues in the mechanisms of isobutylene polymerization and PIB analysis, examines actual catalytic approaches to PIBs, and describes recent studies on the functionalization and applications of HRPIBs and halogen-terminated PIBs. Full article

Background: Hepatitis C virus (HCV) is still common in patients with chronic kidney disease. It has been recently discovered that chronic HCV is a risk factor for increased incidence of CKD in the adult general population. According to a systematic review with a meta-analysis of clinical studies, pooling results of longitudinal studies (n = 2,299,134 unique patients) demonstrated an association between positive anti-HCV serologic status and increased incidence of CKD; the summary estimate for adjusted HR across the surveys was 1.54 (95% CI, 1.26; 1.87), (p < 0.0001). The introduction of direct-acting antiviral drugs (DAAs) has caused a paradigm shift in the management of HCV infection; recent guidelines recommend pan-genotypic drugs (i.e., drugs effective on all HCV genotypes) as the first-choice therapy for HCV, and these promise to be effective and safe even in the context of chronic kidney disease. Aim: The purpose of this narrative review is to show the most important data on pan-genotypic DAAs in advanced CKD (CKD stage 4/5). Methods: We recruited studies by electronic databases and grey literature. Numerous key-words (‘Hepatitis C’ AND ‘Chronic kidney disease’ AND ‘Pan-genotypic agents’, among others) were adopted. Results: The most important pan-genotypic combinations for HCV in advanced CKD are glecaprevir/pibrentasvir (GLE/PIB) and sofosbuvir/velpatasvir (SOF/VEL). Two clinical trials (EXPEDITION-4 and EXPEDITION-5) and some ‘real-world’ studies (n = 6) reported that GLE/PIB combinations in CKD stage 4/5 gave SVR12 rates ranging between 86 and 99%. We retrieved clinical trials (n = 1) and ‘real life’ studies (n = 6) showing the performance of SOF/VEL; according to our pooled analysis, the summary estimate of SVR rate was 100% in studies adopting SOF/VEL antiviral combinations. The drop-out rate (due to AEs) in patients on SOF/VEL ranged between 0 and 4.8%. Conclusions: Pan-genotypic combinations, such as GLE/PIB and SOF/VEL, appear effective and safe for HCV in advanced CKD, even if a limited number of studies with small sample sizes currently exist on this issue. Studies are under way to assess whether successful antiviral therapy with DAAs will translate into better survival in patients with advanced CKD. Full article

Polymerization of isobutylene (IB) for synthesizing highly reactive polyisobutylene (HRPIB) is characterized by a complicated fast intrinsic reaction rate; therefore, the features of its products exhibit a strong dependence on mixing efficiency. To provide uniform and efficient mixing, a rotating packed bed was employed as a reactor for polymerization of IB. The effects of operating parameters including polymerization temperature (T), rotating speed (N) and relative dosage of monomers and initiating systems ([M]₀/[I]₀) on number-average molecular weight (M_n) of HRPIB were studied. HRPIB with M_n of 2550 g·mol⁻¹ and exo-olefin terminal content of 85 mol% were efficiently obtained at suitable conditions as T of 283 K, N of 1600 rpm and [M]₀/[I]₀ of 49. Moreover, the M_n can be regulated by changing T, N and [M]₀/[I]₀. Based on the presumptive-steady-state analysis method and the coalescence–redispersion model, a model for prediction of the M_n was developed and validated, and the calculated M_n values agreed well with experimental results, with a deviation of ±10%. The results demonstrate that RPB is a promising reactor for synthesizing HRPIB, and the given model for M_n can be applied for the design of RPB and process optimization. Full article

Polyisobutylenes (PIB) constitute a versatile family of polymer materials that have been used mainly as fuel and lubricant additives. Particularly, the current commercial demand for highly reactive polyisobutylene (HR-PIB) products motivates the development of new processes and procedures to produce PIBs with high polymer yields, narrow molar mass distributions and high vinyl contents. For this reason, a bibliometric survey is presented here to map and discuss important technical aspects and technological trends in the field of solution cationic polymerization of isobutylenes. It is shown that investigations in this field are concentrated mainly on developed countries and that industrial initiatives indicate high commercial interest and significant investments in the field. It is also shown that use of catalyst systems based on AlCl₃ and ether cocatalysts can be very beneficial for PIB and HR-PIB manufacture. Finally, it is shown that investigations search for cheaper and environmentally friendly catalysts and solvents that can be employed at moderate temperatures, particularly for the production of HR-PIB. Full article

Wprowadzenie: Postępowanie chirurgiczne stanowi podstawową metodę leczenia niedrobnokomórkowego raka płuca. Materiał i metody: W pracy przeprowadzono retrospektywną analizę skuteczności tego leczenia w grupie 431 chorych operowanych w Klinice Chirurgii Instytutu Gruźlicy i Chorób Płuc w Warszawie w latach 1998–1999. W 218 (50%) przypadkach wykonano lobektomię, w 21 (5%)—bilobektomię, w 188 (44%)—pneumonektomię, a w 4 (1%)—resekcję klinową. U 70 (16%) chorych rozpoznano stadium zaawansowania pIA, u 112 (26%)—pIB, u 22 (5%)—pIIA, u 110 (26%)—pIIB, u 88 (20%)—pIIIA, u 13 (3%)—pIIIB i u 16 (4%)—pIV. Wyniki: Wskaźnik 5-letniego przeżycia dla całej grupy wynosił 49.1%. Analiza statystyczna wykazała wyższy odsetek odległych przeżyć w grupie wiekowej do 50. rż. (p = 0.03), u płci żeńskiej (p = 0.01, HR = 0.63), w przypadku mniej rozległego zabiegu (lobektomia) (p < 0.005). Wskaźniki odległych przeżyć wykazywały znamienną zależność od stadium zaawansowania choroby nowotworowej (p < 0.005). Pięcioletnie przeżycie pacjentów w stadium IA wynosiło 81.7%, IB—62.2%, IIA—59.1%, IIB—38%, IIIA—21.3%, IIIB—8.3% oraz IV—8.3%. Typ histopatologiczny miał również znamienny wpływ na odległe przeżycia chorych (p < 0.005). Pięcioletnie przeżycie chorych na raka płaskonabłonkowego wynosiło 53.4%, na raka gruczołowego—38.3%, na raka wielkokomórkowego—37.5%, na rakowiaka—94.7%, a na pozostałe typy raka—39.1%. Wskaźnik odległego przeżycia zależał znamiennie od cechy T (p < 0.005). Obniżone wyjściowe stężenie hemoglobiny (p < 0.005, HR = 1.52) oraz przetoczenie masy erytrocytarnej w okresie pooperacyjnym (p = 0.03) były niekorzystnymi czynnikami rokowniczymi. Znamiennie gorsze rokowanie wykazano w przypadku cechy R1 lub R2 (p = 0.01) oraz cechy M1 (p < 0.005). Dodatkowo, w analizie wielowymiarowej Coxa wartość FEV1 poniżej 80% (HR = 1.46) była zmienną negatywnie wpływającą na odległe przeżycie, a brak objawów klinicznych choroby, z wyjątkiem kaszlu (HR = 0.73)—zmienną wpływającą korzystnie. Wnioski: W analizie jednowymiarowej wyłoniono następujące czynniki ryzyka: płeć męska, wiek powyżej 50. rż., obniżone stężenie Hb, zabieg operacyjny o poszerzonym zakresie, zaawansowane stadium, utkanie raka gruczołowego i wielkokomórkowego, cecha T, N, R i M oraz przetoczenie ME w okresie pooperacyjnym. Analiza wielowymiarowa Coxa wykazała następujące negatywne czynniki prognostyczne: obniżone wyjściowe stężenie Hb, wartość FEV1 poniżej 80%, zabieg operacyjny o poszerzonym zakresie (pneumonektomia), zaawansowane stadium raka, utkanie raka gruczołowego oraz następujące korzystne rokowniczo czynniki: płeć żeńska i brak objawów klinicznych, z wyjątkiem kaszlu. Full article