Optically polarized He3 Gentile, T R; Nacher, P J; Saam, B ...
Reviews of modern physics,
12/2017, Letnik:
89, Številka:
4
Journal Article
Recenzirano
This article reviews the physics and technology of producing large quantities of highly spin-polarized He3 nuclei using spin-exchange (SEOP) and metastability-exchange (MEOP) optical pumping. Both ...technical developments and deeper understanding of the physical processes involved have led to substantial improvements in the capabilities of both methods. For SEOP, the use of spectrally narrowed lasers and K-Rb mixtures has substantially increased the achievable polarization and polarizing rate. For MEOP nearly lossless compression allows for rapid production of polarized He3 and operation in high magnetic fields has likewise significantly increased the pressure at which this method can be performed, and revealed new phenomena. Both methods have benefitted from development of storage methods that allow for spin-relaxation times of hundreds of hours, and specialized precision methods for polarimetry. SEOP and MEOP are now widely applied for spin-polarized targets, neutron spin filters, magnetic resonance imaging, and precision measurements.
The standard model predicts that, in addition to a proton, an electron, and an antineutrino, a continuous spectrum of photons is emitted in the β decay of the free neutron. We report on the RDK II ...experiment which measured the photon spectrum using two different detector arrays. An annular array of bismuth germanium oxide scintillators detected photons from 14 to 782 keV. The spectral shape was consistent with theory, and we determined a branching ratio of 0.00335±0.00005stat±0.00015syst. A second detector array of large area avalanche photodiodes directly detected photons from 0.4 to 14 keV. For this array, the spectral shape was consistent with theory, and the branching ratio was determined to be 0.00582±0.00023stat±0.00062syst. We report the first precision test of the shape of the photon energy spectrum from neutron radiative decay and a substantially improved determination of the branching ratio over a broad range of photon energies.
Humans are estimated to consume several grams per week of nanoplastics (NPs) through exposure to a variety of contamination sources. Nonetheless, the effects of these polymeric particles on living ...systems are still mostly unknown. Here, by means of CD, NMR and TEM analyses, we describe at an atomic resolution the interaction of ubiquitin with polystyrene NPs (PS-NPs), showing how a hard protein corona is formed. Moreover, we report that in human HeLa cells exposure to PS-NPs leads to a sensible reduction of ubiquitination. Our study overall indicates that PS-NPs cause significant structural effects on ubiquitin, thereby influencing one of the key metabolic processes at the base of cell viability.
A high-resolution study of ubiquitin-polystyrene nanoparticle (PS-NP) interaction is reported. We also show the effects of PS-NPs on ubiquitination in HeLa cells.
In Pawlak’s theory of information systems, one has a collection of objects and knows the values of any object with respect a certain class of properties, usually called attributes. An implicit ...assumption of this theory is that the difference between the nature of objects and attributes is well outlined. In our paper we generalize the concept of information system by analyzing the case in which there is no a priori distinction in the nature of objects and attributes and, hence, both the interpretations are admissible. We call the structure arising in the previous context knowledge pairing system. We study the indiscernibility relations induced in both the admissible interpretations by means of up-down operators, in such a way to have a direct analogy with the extent and intent operators used in Formal Context Analysis. In particular, we investigate three models of knowledge pairing systems arising from real contexts and modeled respectively by graphs, digraphs and hypergraphs. We show the real convenience to use the notion of knowledge pairing system focusing on interpretation of this structure and discussing the two admissible perspectives obtained by avoiding the difference between the roles of objects and attributes.
A new development in small-angle neutron scattering with polarization analysis allows us to directly extract the average spatial distributions of magnetic moments and their correlations with ...three-dimensional directional sensitivity in any magnetic field. Applied to a collection of spherical magnetite nanoparticles 9.0 nm in diameter, this enhanced method reveals uniformly canted, magnetically active shells in a nominally saturating field of 1.2 T. The shell thickness depends on temperature, and it disappears altogether when the external field is removed, confirming that these canted nanoparticle shells are magnetic, rather than structural, in origin.
Oral mucositis can be a debilitating and dangerous adverse effect of the chemoradiation used to prepare patients for bone marrow transplantation. Palifermin, a recombinant keratinocyte growth factor, ...was shown in this study to reduce the incidence and duration of severe oral mucositis after high-dose chemoradiation.
Palifermin shows promise as a means of preventing oral mucositis, which can be a dangerous adverse effect of the chemoradiation.
High-dose chemotherapy and radiotherapy followed by hematopoietic stem-cell support is a well-established treatment for hematologic cancers. Oral mucositis develops and requires treatment in approximately 70 to 80 percent of patients receiving radiation-based conditioning treatments.
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The incidence and severity of oral mucositis vary with the conditioning regimen.
Oral mucositis results from injury to epithelial cells that line the oral cavity. The damage causes changes ranging from mild atrophy to severe ulceration. Serious consequences include pain requiring opioid analgesia, potentially life-threatening infections, inadequate nutrition requiring parenteral feeding, and prolonged hospitalization.
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Currently, no standard therapy prevents or treats severe oral mucositis. . . .
In this paper we complete and generalize some previous results concerning the computing of the sequential and parallel convergent time for two discrete dynamical system of signed integer partitions. ...We also refine the concept of parallel convergent time for a finite graded partially ordered set (briefly poset) X which is also a discrete dynamical model. To this aim we define the concept of fundamental sequence of X and we compute this sequence in two particularly important cases. In the first case, when X is the finite lattice S(n,r) of all the signed integer partitions ar,…,a1,b1,…,bn-r such that r⩾ar⩾⋯⩾a1⩾0⩾b1⩾⋯⩾bn-r⩾-(n-r), where n⩾r⩾0 and the unique part that can be repeated is 0. In the second case, when X is the sub-lattice S(n,d,r) of all the signed integer partitions of S(n,r) having exactly d non-zero parts. The relevance of the previous lattices as discrete dynamical models is related to their link with some unsolved extremal combinatorial sum problems.
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