130 research outputs found
Flows and particles with shear-free and expansion-free velocities in (L^-_n,g)- and Weyl's spaces
Conditions for the existence of flows with non-null shear-free and
expansion-free velocities in spaces with affine connections and metrics are
found. On their basis, generalized Weyl's spaces with shear-free and
expansion-free conformal Killing vectors as velocity's vectors of spinless test
particles moving in a Weyl's space are considered. The necessary and sufficient
conditions are found under which a free spinless test particle could move in
spaces with affine connections and metrics on a curve described by means of an
auto-parallel equation. In Weyl's spaces with Weyl's covector, constructed by
the use of a dilaton field, the dilaton field appears as a scaling factor for
the rest mass density of the test particle. PACS numbers: 02.40.Ky, 04.20.Cv,
04.50.+h, 04.90.+eComment: 20 pages, LaTeX, to appear in Classical and Quantum Gravity. arXiv
admin note: substantial text overlap with arXiv:gr-qc/001104
Frames of reference in spaces with affine connections and metrics
A generalized definition of a frame of reference in spaces with affine
connections and metrics is proposed based on the set of the following
differential-geometric objects:
(a) a non-null (non-isotropic) vector field,
(b) the orthogonal to the vector field sub space,
(c) an affine connection and the related to it covariant differential
operator determining a transport along the given non-null vector filed.
On the grounds of this definition other definitions related to the notions of
accelerated, inertial, proper accelerated and proper inertial frames of
reference are introduced and applied to some mathematical models for the
space-time. The auto-parallel equation is obtained as an Euler-Lagrange's
equation. Einstein's theory of gravitation appears as a theory for
determination of a special frame of reference (with the gravitational force as
inertial force) by means of the metrics and the characteristics of a material
distribution.
PACS numbers: 0490, 0450, 1210G, 0240VComment: 17 pages, LaTeX 2
Space construction system analysis. Part 2: Platform definition
The top level system requirements are summarized and the accompanying conceptual design for an engineering and technology verification platform (ETVP) system is presented. An encompassing statement of the system objectives which drive the system requirements is presented and the major mission and subsystem requirements are described with emphasis on the advanced communications technology mission payload. The platform design is defined and used as a reference configuration for an end to space construction analyses. The preferred construction methods and processes, the important interactions between the platform design and the construction system design and operation, and the technology development efforts required to support the design and space construction of the ETVP are outlined
Measuring the gravitational field in General Relativity: From deviation equations and the gravitational compass to relativistic clock gradiometry
How does one measure the gravitational field? We give explicit answers to
this fundamental question and show how all components of the curvature tensor,
which represents the gravitational field in Einstein's theory of General
Relativity, can be obtained by means of two different methods. The first method
relies on the measuring the accelerations of a suitably prepared set of test
bodies relative to the observer. The second methods utilizes a set of suitably
prepared clocks. The methods discussed here form the basis of relativistic
(clock) gradiometry and are of direct operational relevance for applications in
geodesy.Comment: To appear in "Relativistic Geodesy: Foundations and Application", D.
Puetzfeld et. al. (eds.), Fundamental Theories of Physics, Springer 2018, 52
pages, in print. arXiv admin note: text overlap with arXiv:1804.11106,
arXiv:1511.08465, arXiv:1805.1067
A retinal code for motion along the gravitational and body axes
Self-motion triggers complementary visual and vestibular reflexes supporting image-stabilization and balance. Translation through space produces one global pattern of retinal image motion (optic flow), rotation another. We examined the direction preferences of direction-sensitive ganglion cells (DSGCs) in flattened mouse retinas in vitro. Here we show that for each subtype of DSGC, direction preference varies topographically so as to align with specific translatory optic flow fields, creating a neural ensemble tuned for a specific direction of motion through space. Four cardinal translatory directions are represented, aligned with two axes of high adaptive relevance: the body and gravitational axes. One subtype maximizes its output when the mouse advances, others when it retreats, rises or falls. Two classes of DSGCs, namely, ON-DSGCs and ON-OFF-DSGCs, share the same spatial geometry but weight the four channels differently. Each subtype ensemble is also tuned for rotation. The relative activation of DSGC channels uniquely encodes every translation and rotation. Although retinal and vestibular systems both encode translatory and rotatory self-motion, their coordinate systems differ
Production, quality control, stability, and potency of cGMP-produced Plasmodium falciparum RH5.1 protein vaccine expressed in Drosophila S2 cells
Plasmodium falciparum reticulocyte-binding protein homolog 5 (PfRH5) is a leading asexual blood-stage vaccine candidate for
malaria. In preparation for clinical trials, a full-length PfRH5 protein vaccine called “RH5.1” was produced as a soluble product under
cGMP using the ExpreS2 platform (based on a Drosophila melanogaster S2 stable cell line system). Following development of a highproducing
monoclonal S2 cell line, a master cell bank was produced prior to the cGMP campaign. Culture supernatants were
processed using C-tag affinity chromatography followed by size exclusion chromatography and virus-reduction filtration. The
overall process yielded >400 mg highly pure RH5.1 protein. QC testing showed the MCB and the RH5.1 product met all specified
acceptance criteria including those for sterility, purity, and identity. The RH5.1 vaccine product was stored at −80 °C and is stable for
over 18 months. Characterization of the protein following formulation in the adjuvant system AS01B showed that RH5.1 is stable in
the timeframe needed for clinical vaccine administration, and that there was no discernible impact on the liposomal formulation of
AS01B following addition of RH5.1. Subsequent immunization of mice confirmed the RH5.1/AS01B vaccine was immunogenic and
could induce functional growth inhibitory antibodies against blood-stage P. falciparum in vitro. The RH5.1/AS01B was judged
suitable for use in humans and has since progressed to phase I/IIa clinical trial. Our data support the future use of the Drosophila S2
cell and C-tag platform technologies to enable cGMP-compliant biomanufacture of other novel and “difficult-to-express”
recombinant protein-based vaccines
Escândalos, marolas e finanças: para uma sociologia da transformação do ambiente econômico
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