990 research outputs found
Static compression of porous dust aggregates
Context: In protoplanetary disks, dust grains coagulate with each other and
grow to form aggregates. As these aggregates grow by coagulation, their filling
factor \phi decreases down to \phi << 1. However, comets, the remnants of these
early planetesimals, have \phi ~ 0.1. Thus, static compression of porous dust
aggregates is important in planetesimal formation. However, the static
compression strength has been investigated only for relatively high density
aggregates (\phi > 0.1). Aims: We investigate and find the compression strength
of highly porous aggregates (\phi << 1). Methods: We perform three dimensional
N-body simulations of aggregate compression with a particle-particle
interaction model. We introduce a new method of static compression: the
periodic boundary condition is adopted and the boundaries move with low speed
to get closer. The dust aggregate is compressed uniformly and isotropically by
themselves over the periodic boundaries. Results: We empirically derive a
formula of the compression strength of highly porous aggregates (\phi << 1). We
check the validity of the compression strength formula for wide ranges of
numerical parameters, such as the size of initial aggregates, the boundary
speed, the normal damping force, and material. We also compare our results to
the previous studies of static compression in the relatively high density
region (\phi > 0.1) and confirm that our results consistently connect to those
in the high density region. The compression strength formula is also derived
analytically.Comment: 12 pages, 14 figures, accepted for publication in A&
Public views of health insurance in Japan during the era of attaining universal health coverage: a secondary analysis of an opinion poll on health insurance in 1967
While Japan’s success in achieving universal health insurance over a short period with controlled healthcare costs has been studied from various perspectives, that of beneficiaries have been overlooked. We conducted a secondary analysis of an opinion poll on health insurance in 1967, immediately after reaching universal coverage. We found that people continued to face a slight barrier to healthcare access (26.8% felt medical expenses were a heavy burden) and had high expectations for health insurance (60.5% were satisfied with insured medical services and 82.4% were willing to pay a premium). In our study, younger age, having children before school age, lower living standards, and the health insurance scheme were factors that were associated with a willingness to pay premiums. Involving high-income groups in public insurance is considered to be the key to ensuring universal coverage of social insurance
Challenges in decision-making support processes regarding living kidney donation: A qualitative study
Wada Y., Ueno T., Umeshita K., et al. Challenges in decision-making support processes regarding living kidney donation: A qualitative study. Journal of Renal Care , (2024); https://doi.org/10.1111/jorc.12494.Background: Previous studies on decision-making of living kidney donors have indicated issues regarding donors' autonomy is inherent in decision-making to donate their kidney. Establishing effective decision-making support that guarantees autonomy of living kidney donor candidates is important. Objectives: The aim of this study was to identify the difficulties in the decision-making support when clinical transplant coordinators advocating for the autonomy of donor candidates of living donor kidney transplantation and to identify the methods to deal with these difficulties. Design: A qualitative descriptive study. Participants: Ten clinical transplant coordinators supporting living kidney donors. Approach: Semi-structured interviews were conducted using an interview guide. The modified grounded theory approach was utilised to analyse. Results: Three categories related to difficulties were as follows: issues inherent to the interaction between coordinators, donor candidates and their families; issues regarding the environment and institutional background in which coordinators operate; and emotional labour undertaken by coordinators in the decision-making support process. Additionally, five categories related to methods were as follows: assessing the autonomy of donor candidates based on the coordinators nursing experience; interventions for the donor candidates and their family members based on the coordinators nursing experience; smooth coordination with medical staff; clarifying and asserting their views as coordinators; and readiness to protect the donor candidates. Conclusion: The involvement of highly experienced coordinators with excellent and assertive communication skills as well as the ability to reflect on their own practices is essential. Moreover, we may need to fundamentally review the transplant community, where power domination is inherent
Geometrical Cross Sections of Dust Aggregates and a Compression Model for Aggregate Collisions
Geometrical cross sections of dust aggregates determine their coupling with
disk gas, which governs their motions in protoplanetary disks. Collisional
outcomes also depend on geometrical cross sections of initial aggregates. In
the previous paper, we performed three-dimensional N-body simulations of
sequential collisions of aggregates composed of a number of sub-micron-sized
icy particles and examined radii of gyration (and bulk densities) of the
obtained aggregates. We showed that collisional compression of aggregates is
not efficient and that aggregates remain fluffy. In the present study, we
examine geometrical cross sections of the aggregates. Their cross sections
decreases due to the compression as well as their gyration radii. It is found
that a relation between the cross section and the gyration radius proposed by
Okuzumi et al. is valid for the compressed aggregates. We also refine the
compression model proposed in our previous paper. The refined model enables us
to calculate the evolution of both gyration radii and cross sections of growing
aggregates and reproduces well our numerical results of sequential aggregate
collisions. The refined model can describe non-equal-mass collisions as well as
equal-mass case. Although we do not take into account oblique collisions in the
present study, oblique collisions would further hinder compression of
aggregates
Comet 9P/Tempel 1: Interpretation with the Deep Impact Results
According to our common understandings, the original surface of a
short-period comet nucleus has been lost by sublimation processes during its
close approaches to the Sun. Sublimation results in the formation of a dust
mantle on the retreated surface and in chemical differentiation of ices over
tens or hundreds of meters below the mantle. In the course of NASA's Deep
Impact mission, optical and infrared imaging observations of the ejecta plume
were conducted by several researchers, but their interpretations of the data
came as a big surprise: (1) The nucleus of comet 9P/Tempel 1 is free of a dust
mantle, but maintains its pristine crust of submicron-sized carbonaceous
grains; (2) Primordial materials are accessible already at a depth of several
tens of cm with abundant silicate grains of submicrometer sizes. In this study,
we demonstrate that a standard model of cometary nuclei explains well available
observational data: (1) A dust mantle with a thickness of ~1-2 m builds up on
the surface, where compact aggregates larger than tens of micrometers dominate;
(2) Large fluffy aggregates are embedded in chemically differentiated layers as
well as in the deepest part of the nucleus with primordial materials. We
conclude that the Deep Impact results do not need any peculiar view of a comet
nucleus.Comment: 11 pages, 1 figure, 1 table. ApJ letters, 673, L199-20
Immunoglobulin Production by Peripheral Blood Mononuclear Cells in IgA Nephropathy Patients and their Relatives
Immunoglobulin production by peripheral blood mononuclear cells of 27 patients of IgA nephropathy and 11 relatives was determined. In comparison with 15 healthy controls, no significant difference could be observed in both IgA nephropathy patients and relatives of the group not stimulated with PWM, but in the group stimulated with PWM a significant elevation in the production of IgA, IgG and IgM was seen in IgA nephropathy patients, while in the relatives a significant elevation in production of IgA and IgG was observed. It is speculated that immune complexes mainly IgA are the chief cause of development and progression of IgA nephropathy and that IgG and IgM are also involved. In also relatives, the presence of immunological abnormalities similar to those of IgA nephropathy patients is suggested
Regeneration of the acorn worm pygochord with the implication for its convergent evolution with the notochord
The origin of the notochord is a central issue in chordate evolution. This study examined the development of the acorn worm pygochord, a putative homologue of the notochord. Because the pygochord differentiates only after metamorphosis, the developmental was followed process by inducing regeneration after artificial amputation in Ptychodera flava. It was found that although the regeneration of the posterior part of the body did not proceed via formation of an obvious regeneration bud, pygochord regeneration was observed within a few weeks, possibly via trans‐differentiation of endoderm cells. The expression of the fibrillary collagen gene (Fcol) and elav in the pygochord during regeneration was detected. This indicates that pygochord cells are not part of gut epithelial cells, but that they differentiated as a distinct cell type. Our gene expression analyses do not provide supporting evidence for the homology between the pygochord and notochord, but rather favored the convergent evolution between them
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