1,721,624 research outputs found
Autologous stem cell transplantation for T-cell lymphomas
No full textPeripheral T-cell lymphomas (PTCLs) are a rare and heterogeneous group of T-cell malignancies characterized by a very poor outcome. The optimal treatment for PTCLs remains controversial. The role of stem cell transplantation in PTCLs has been investigated; however, no randomized control studies specifically dedicated to PTCLs are currently available. Several retrospective and prospective studies have suggested that high-dose chemotherapy (HDT) followed by autologous stem cell transplantation (ASCT) may improve the survival in patients with chemosensitive T-cell lymphoma, either upfront or as salvage treatment. This review provides a summary of the current literature with the intent to explore the role of ASCT in various clinical scenario
Crystal-structure of Syndiotactic Polypropylene
No full textAn analysis of the crystal structure on unoriented and oriented samples of syndiotactic polypropylene is presented, on the basis of a comparison between calculated structure factors and experimental X-ray diffraction intensities. According to the present analysis, syndiotactic polypropylene can exist in different orthorhombic modifications having chains in helical conformation. Stretched samples may contain, at least in part, the C-centered structure proposed by Corradini et al. (limit space group C222(1)), while single crystals and polycrystalline samples are generally in the structure proposed by Lotz, Lovinger, Cais, and Davis (limit space group Ibca). Calculations of structure factors indicate that the two polymorphic forms of s-PP may be characterized by various degrees of disorder depending on the chemical and physical history of the sample. A possible disorder present is related to the statistical substitution of right and left handed helices along the same lattice axes. The space groups for the two limit statistical structures are Cmcm and Bmcm
CRYSTALLINE STRUCTURE OF SOME ALTERNATE COPOLYMERS BETWEEN CARBON MONOXIDE AND STYRENE DERIVATIVES
No full textThe crystal structure of some alternate copolymers of styrene and styrene derivatives with carbon monoxide is presented. We start from the crystal structure previously solved in the case of poly(1-oxo-2-phenyltrimethylene) (STCO), which gave clear evidences of the syndiotactic nature of this copolymer. The very close analogies between the X-ray powder diffraction spectra of copolymers of CO with p-fluorostyrene (pFSTCO), m-methylstyrene (mMSTCO), and p-methylstyrene (pMSTCO) with the spectrum of STCO allow us to postulate an analogous syndiotactic structure and a very similar chain conformation and packing model for them. The structural models have been refined for all four copolymers through the Rietveld method, giving the following results. (a) For STCO: space group P2(1)/c, a = 15.20 angstrom, b = 6.166 angstrom, c = 7.59 angstrom, beta = 102.5-degrees. (b) For pFSTCO: space group P2(1)/c, a = 15.59 angstrom, b = 6.168 angstrom, c = 7.551 angstrom, beta = 98.8-degrees. (c) For mMSTCO: space group P2(1)/c, a = 16.14 angstrom, b = 6.816 angstrom, c = 7.580 angstrom, beta = 100.3-degrees (d) For pMSTCO: space group C2/c, a = 35.54 angstrom, b = 6.262 angstrom, c = 7.536 angstrom, beta = 96.0-degrees. All the studied copolymers crystallize with the chain backbone in a nearly extended conformation, with very similar values of the dihedral angles. Roughly speaking, also the packing models are very similar. In all crystal structures the chains are arranged to form layers parallel to the bc plane piled along a. The packing models for the various copolymers present the most relevant differences in the stacking along a of these bc layers
Current state of art for transplantation paradigms in peripheral T-cell lymphomas
No full textPeripheral T-cell lymphomas (PTCLs) are a rare and aggressive lymphoproliferative disorder characterized, with few exception, by poor prognosis. A correct diagnosis is still hampered by the heterogeneity and rarity of disease. Historically, PTCLs were treated like aggressive B-cell lymphoma with anthracycline-based combination chemotherapy with disappointing results. Neither dose intensification nor dose escalation of chemotherapy has been successful in prolonging the survival of PTCL patients. Due to this discouraging scenario, new therapeutic strategies have been tested. A therapeutic program including hematopoietic stem-cell transplantation (SCT) may represent an interesting strategy for high-risk patients. Although no randomized trials are available, autologous SCT may offer a chance of cure in chemosensitive disease. Nonmyeloablative allogeneic SCT has shown a curative potential with limited toxicity, and it is actively being investigated. We will review the role of the current therapeutic approach to PTCL focusing on the most recent advances in SCT
Conformational and packing energy calculations for isotactic poly(vinylcyclohexane): Crystal structure of form I
No full textThe polymorphic behavior of poly(vinylcyclohexane) is discussed on the basis of conformational energy calculations on an isolated chain. The presence of two different modifications is in accordance with the energy minima present in the conformational energy maps. The packing of the chains in form I is analyzed on the basis of packing energy and structure factor calculations
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