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The pure y-form of isotactic poly(propy1ene) can be obtained by melt-crystallization starting from a fraction of a random ethylene-propene copolymer (ethylene content 4 wt.4'0) soluble in p-xylene at 28 "C). Some structural models previously reported are tested by comparing calculated wide-angle X-ray diffraction patterns with the experimental ones. A method for the quantitative determination of the y-form crystallinity by X-ray line profiles is proposed. The original copolymer and its fractions are characterized by differential scanning calorimetry and l 3 C NMR techniques.

Febrile neutropenia (FN) is a common complication in pediatric patients receiving allogeneic hematopoietic stem cell transplantation (HSCT). Frequently, a precise cause cannot be identified, and many factors can contribute to its genesis. Gut microbiota (GM) has been recently linked to many transplant-related complications, and may also play a role in the pathogenesis of FN. Here, we conducted a longitudinal study in pediatric patients receiving HSCT from three centers in Europe profiling their GM during the transplant course, particularly at FN onset. We found that a more stable GM configuration over time is associated with a shorter duration of fever. Moreover, patients with longer lasting fever exhibited higher pre-HSCT levels of Collinsella, Megasphaera, Prevotella and Roseburia and increased proportions of Eggerthella and Akkermansia at the engraftment. These results suggest a possible association of the GM with the genesis and course of FN. Data seem consistent with previous reports on the relationship of a so-called “healthy” GM and the reduction of transplant complications. To our knowledge, this is the first report in the pediatric HSCT setting. Future studies are warranted to define the underling biological mechanisms and possible clinical implications.

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