Channel Coding for Future Space Missions: New Requirements and Trends

Future space missions will put severe constraints on communication links in terms of data rates, bandwidth occupancy, complexity, and performance. The requirements imposed by the new missions and their consequences on channel code design are presented in the first part of the paper. All relevant issues, including code rates, frame lengths, modulation formats, performance metrics, complexity, and others, are discussed. In the second part of the paper, long erasure correcting codes are presented and their properties explained. These codes operate at the upper layers of the space link protocol and constitute an attractive new frontier for zero packet loss in future space communications.     

A new generation of getter‐coated sputter ion pumps for XHV applications

A new concept of sputtered ion getter pump is presented. The body of this pump is internally coated by a getter thin film constituted by a layer of TiZrV together with a protective covering of palladium, according to a technology that CERN (European Center for Nuclear Research) licensed us. TiZrV is a well‐known alloy able to pump getterable gases such as hydrogen, oxygen, nitrogen, carbon monoxide and dioxide. With the exception of H², the sorption of these gases is not reversible and it causes a progressive contamination of the bulk of the material. With the addition of the palladium overlayer, the pumping action is limited to hydrogen and carbon monoxide, but the lifetime of the film is strongly enhanced, thanks to the possibility of an unlimited number of thermal activations, which restore the initial performances of the film. An innovative sputter ion pump design, optimized for both pumping speed in ultra high vacuum and getter film sputtering, will be introduced. Moreover, pumping speed measurements and ultimate pressure data, obtained after a relatively short bake‐out at temperature lower than standard procedures, will be reported.     

Expansive properties of the mixture C4A H12−2C II. Effects of lime, porosity and liquid/solid ratio

The effects of solid lime, initial porosity and liquid-solid ratio on the reaction of ettringite formation and on the expansion of uniaxially unrestrained comapacts of C₄A H₁₂-2C mixture have been studied at 20°C. A reaction and an expansion mechanism are proposed, based on the effect of the solid lime on the formation of an ettringite layer coating the reacting surface of the solids, on the surface area of the reaction product, on the crystallization pressure, on the water adsorption and the repulsion due to high zeta potential values.     

NPM1-Mutated Myeloid Neoplasms with <20% Blasts: A Really Distinct Clinico-Pathologic Entity?

Nucleophosmin (NPM1) gene mutations rarely occur in non-acute myeloid neoplasms (MNs) with <20% blasts. Among nearly 10,000 patients investigated so far, molecular analyses documented NPM1 mutations in around 2% of myelodysplastic syndrome (MDS) cases, mainly belonging to MDS with excess of blasts, and 3% of myelodysplastic/myeloproliferative neoplasm (MDS/MPN) cases, prevalently classified as chronic myelomonocytic leukemia. These uncommon malignancies are associated with an aggressive clinical course, relatively rapid progression to overt acute myeloid leukemia (AML) and poor survival outcomes, raising controversies on their classification as distinct clinico-pathologic entities. Furthermore, fit patients with NPM1-mutated MNs with <20% blasts could benefit most from upfront intensive chemotherapy for AML rather than from moderate intensity MDS-directed therapies, although no firm conclusion can currently be drawn on best therapeutic approaches, due to the limited available data, obtained from small and mainly retrospective series. Caution is also suggested in definitely diagnosing NPM1-mutated MNs with blast count <20%, since NPM1-mutated AML cases frequently present dysplastic features and multilineage bone marrow cells showing abnormal cytoplasmic NPM1 protein delocalization by immunohistochemical staining, therefore belonging to NPM1-mutated clone regardless of blast morphology. Further prospective studies are warranted to definitely assess whether NPM1 mutations may become sufficient to diagnose AML, irrespective of blast percentage.     

Inflammatory Microenvironment and Specific T Cells in Myeloproliferative Neoplasms: Immunopathogenesis and Novel Immunotherapies

The Philadelphia-negative myeloproliferative neoplasms (MPNs) are malignancies of the hematopoietic stem cell (HSC) arising as a consequence of clonal proliferation driven by somatically acquired driver mutations in discrete genes (JAK2, CALR, MPL). In recent years, along with the advances in molecular characterization, the role of immune dysregulation has been achieving increasing relevance in the pathogenesis and evolution of MPNs. In particular, a growing number of studies have shown that MPNs are often associated with detrimental cytokine milieu, expansion of the monocyte/macrophage compartment and myeloid-derived suppressor cells, as well as altered functions of T cells, dendritic cells and NK cells. Moreover, akin to solid tumors and other hematological malignancies, MPNs are able to evade T cell immune surveillance by engaging the PD-1/PD-L1 axis, whose pharmacological blockade with checkpoint inhibitors can successfully restore effective antitumor responses. A further interesting cue is provided by the recent discovery of the high immunogenic potential of JAK2V617F and CALR exon 9 mutations, that could be harnessed as intriguing targets for innovative adoptive immunotherapies. This review focuses on the recent insights in the immunological dysfunctions contributing to the pathogenesis of MPNs and outlines the potential impact of related immunotherapeutic approaches.     

Generalized IRA Erasure Correcting Codes for Hybrid Iterative/Maximum Likelihood Decoding

The design of low-density parity-check (LDPC) codes under hybrid iterative / maximum likelihood decoding is addressed for the binary erasure channel (BEC). Specifically, we focus on generalized irregular repeat-accumulate (GeIRA) codes, which offer both efficient encoding and design flexibility. We show that properly designed GeIRA codes tightly approach the performance of an ideal maximum distance separable (MDS) code, even for short block sizes. For example, our (2048,1024) code reaches a codeword error rate of 10^-5 at channel erasure probability isin= 0.450, where an ideal (2048,1024) MDS code would reach the same error rate at isin = 0.453.     

Simple reconfigurable low-density parity-check codes

Low-density parity-check codes (LDPCC) have been recently investigated as a possible solution for high data rate applications, for both space and terrestrial wireless communications. A main issue is the research of low complexity encoding and decoding schemes. In this letter we present a class of reconfigurable LDPCC characterized by low encoding and decoding complexity: we call them generalized irregular repeat-accumulate (GeIRA) codes.     

Expansive properties of the mixture C4AS̄H12 - 2CS̄ I. An hypothesis on the expansion mechanism

Hydration and expansion of uniaxially unrestrained compacts of C₄AS?H₁₂ - 2CS? mixture have been studied at 20°C in different contact solutions. The highest reaction rates and final expansions were observed in the saturated lime solution. A mechanism of expansion, based on the concurrence of the increase in volume of solids, crystallization pressure, water adsorption and zeta potential variations of ettringite crystals has been proposed to account for the different expansions.     

Proposal for using mechanical staplers with Polysorb in creation of orthotopic neobladder

After radical cysto-prostatectomy the bladder substitute is made from an ileal segment, opened along its antimesenteric border and folded; the results are in general good. The success of this procedure demands attention to detail, hemostasis and gentle handling of tissue so this surgery depends an unusual degree of commitment to meticulous technique. The very low rate complications, obtained with mechanical sutures in gastrointestinal surgery, incited the Authors using the staplers GIA and TA Polysorb for detubularized ileal segment. They are very manageable, easy to use and the follow-up shows the absence of urinary stone; so the team approach is less tedious and strenuous. The Authors present their results of 11 neobladder-staplers made with 35 cm of detubularized ileal segment without folding.     

Influence of period‐doubling bifurcations in the appearance of border collisions for a ZAD‐strategy‐controlled buck converter

The first period‐doubling bifurcation of a dc–dc buck converter controlled by a zero‐average dynamic strategy is studied in detail. Owing to the saturation of the duty cycle, this bifurcation is followed by a border‐collision bifurcation, which is the main mechanism to introduce instability and chaos in the circuit. The multiparameter analysis presented here leads to a complete knowledge of the relatioship between these two bifurcations. The results are obtained by using a frequency‐domain approach for the study of period‐two oscillations in maps. Copyright © 2010 John Wiley & Sons, Ltd.