6,130 research outputs found
Whewell\'s Wager: The Continuing Dialogue of Metaphysics and Physics in Science
In his library at Trinity College, Cambridge University, around the year I860, William
Whewell (1794-1866) engages in conversation with a company of thinkers on the province
of metaphysics and physics, to form a comprehensive scientific belief. In attendance with him are Lord Francis Bacon (1561-1626), Sir Robert Boyle (1627-1691 ), Sir Isaac Newton (1642-1727) , John Henry Cardinal Newman (1801-1890), Professor Alfred North Whitehead (1861-1947), and Pope John Paul II (b. 1920). Whewell proposes a wager: Is there a possible remedy to be found for the schism between the metaphysical and the physical
elements of science
Single-color two-photon spectroscopy of Rydberg states in electric fields
Rydberg states of atomic helium with principal quantum numbers ranging from
n=20 to n=100 have been prepared by non-resonance-enhanced single-color
two-photon excitation from the metastable 2 {^3}S{_1} state. Photoexcitation
was carried out using linearly and circularly polarized pulsed laser radiation.
In the case of excitation with circularly polarized radiation, Rydberg states
with azimuthal quantum number |m_{\ell}|=2 were prepared in zero electric
field, and in homogeneous electric fields oriented parallel to the propagation
axis of the laser radiation. In sufficiently strong electric fields, individual
Rydberg-Stark states were resolved spectroscopically, highlighting the
suitability of non-resonance-enhanced multiphoton excitation schemes for the
preparation of long-lived high-|m_{\ell}| hydrogenic Rydberg states for
deceleration and trapping experiments. Applications of similar schemes for
Doppler-free excitation of positronium atoms to Rydberg states are also
discussed
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Genetic Suppression of Basement Membrane Defects in Caenorhabditis elegans by Gain of Function in Extracellular Matrix and Cell-Matrix Attachment Genes.
Basement membranes are extracellular matrices essential for embryonic development in animals. Peroxidasins are extracellular peroxidases implicated in the unique sulfilimine cross-links between type IV basement membrane collagens. Loss of function in the Caenorhabditis elegans peroxidasin PXN-2 results in fully penetrant embryonic or larval lethality. Using genetic suppressor screening, we find that the requirement for PXN-2 in development can be bypassed by gain of function in multiple genes encoding other basement membrane components, or proteins implicated in cell-matrix attachment. We identify multiple alleles of let-805, encoding the transmembrane protein myotactin, which suppress phenotypes of pxn-2 null mutants and of other basement membrane mutants such as F-spondin/spon-1 These let-805 suppressor alleles cause missense alterations in two pairs of FNIII repeats in the extracellular domain; they act dominantly and have no detectable phenotypes alone, suggesting they cause gain of function. We also identify suppressor missense mutations affecting basement membrane components type IV collagen (emb-9, let-2) and perlecan (unc-52), as well as a mutation affecting spectraplakin (vab-10), a component of the epidermal cytoskeleton. These suppressor alleles do not bypass the developmental requirement for core structural proteins of the basement membrane such as laminin or type IV collagen. In conclusion, putative gain-of-function alterations in matrix proteins or in cell-matrix receptors can overcome the requirement for certain basement membrane proteins in embryonic development, revealing previously unknown plasticity in the genetic requirements for the extracellular matrix
Historical costume simulation
The aim of this study is to produce accurate reproductions of digital clothing from historical sources and to investigate the implications of developing it for online museum exhibits. In order to achieve this, the study is going through several stages. Firstly, the theoretical background of the main issues will be established through the review of various published papers on 3D apparel CAD, drape and digital curation. Next, using a 3D apparel CAD system, this study attempts the realistic visualization of the costumes based on the establishment of a valid simulation reference. This paper reports the pilot exercise carried out to scope the requirements for going forward
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CELL BIOLOGY. GATA get a hold on senescence.
A transcription factor's abundance connects autophagy to cellular senescence and a secretory phenotype
[Also see Research Article by
Kang
et al.
]
This is the author accepted manuscript. The final version is available from AAAS via http://dx.doi.org/10.1126/science.aad250
Tweets as impact indicators: Examining the implications of automated bot accounts on Twitter
This brief communication presents preliminary findings on automated Twitter
accounts distributing links to scientific papers deposited on the preprint
repository arXiv. It discusses the implication of the presence of such bots
from the perspective of social media metrics (altmetrics), where mentions of
scholarly documents on Twitter have been suggested as a means of measuring
impact that is both broader and timelier than citations. We present preliminary
findings that automated Twitter accounts create a considerable amount of tweets
to scientific papers and that they behave differently than common social bots,
which has critical implications for the use of raw tweet counts in research
evaluation and assessment. We discuss some definitions of Twitter cyborgs and
bots in scholarly communication and propose differentiating between different
levels of engagement from tweeting only bibliographic information to discussing
or commenting on the content of a paper.Comment: 9 pages, 4 figures, 1 tabl
In-vivo magnetic resonance imaging of hyperpolarized silicon particles
Silicon-based micro and nanoparticles have gained popularity in a wide range
of biomedical applications due to their biocompatibility and biodegradability
in-vivo, as well as a flexible surface chemistry, which allows drug loading,
functionalization and targeting. Here we report direct in-vivo imaging of
hyperpolarized 29Si nuclei in silicon microparticles by MRI. Natural physical
properties of silicon provide surface electronic states for dynamic nuclear
polarization (DNP), extremely long depolarization times, insensitivity to the
in-vivo environment or particle tumbling, and surfaces favorable for
functionalization. Potential applications to gastrointestinal, intravascular,
and tumor perfusion imaging at sub-picomolar concentrations are presented.
These results demonstrate a new background-free imaging modality applicable to
a range of inexpensive, readily available, and biocompatible Si particles.Comment: Supplemental Material include
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