644 research outputs found
Rotation curves of UMa galaxies in the context of modified Newtonian dynamics
This is the third in a series of papers in which spiral galaxy rotation
curves are considered in the context of Milgrom's modified dynamics (MOND). The
present sample of 30 objects is drawn from a complete sample of galaxies in the
Ursa Major cluster with photometric data by Tully et al. (1996) and 21 cm line
data by Verheijen (1997). The galaxies are roughly all at the same distance (15
to 16 Mpc). The radio observations are made with the Westerbork Synthesis Array
which means that the linear resolution of all rotation curves is comparable.
The greatest advantage of this sample is the existance of K'-band surface
photometry for all galaxies; the near-infrared emission, being relatively free
of the effects of dust absorption and less sensitive to recent star formation,
is a more precise tracer of the mean radial distribution of the dominant
stellar population. The predicted rotation curves are calculated from the
K'-band surface photometry and the observed distribution of neutral hydrogen
using the simple MOND prescription where the one adjustable parameter is the
mass of the stellar disk or the implied mass-to-light ratio. The predicted
rotation curves generally agree with the observed curves and the mean M/L in
the near-infrared is about 0.9 with a small dispersion. The fitted M/L in the
B-band is correlated with B-V color in the sense predicted by population
synthesis models. Including earlier work, about 80 galaxy rotation curves are
now well-reproduced from the observed distribution of detectable matter using
the MOND formula to calculate the gravitational acceleration; this lends
considerable observational support to Milgrom's unconventional hypothesis.Comment: 19 pages, 9 figures, aas style, ApJ in press. Updated and corrected
references, content unchange
Electrodynamics of superconductors
An alternate set of equations to describe the electrodynamics of
superconductors at a macroscopic level is proposed. These equations resemble
equations originally proposed by the London brothers but later discarded by
them. Unlike the conventional London equations the alternate equations are
relativistically covariant, and they can be understood as arising from the
'rigidity' of the superfluid wave function in a relativistically covariant
microscopic theory. They predict that an internal 'spontaneous' electric field
exists in superconductors, and that externally applied electric fields, both
longitudinal and transverse, are screened over a London penetration length, as
magnetic fields are. The associated longitudinal dielectric function predicts a
much steeper plasmon dispersion relation than the conventional theory, and a
blue shift of the minimum plasmon frequency for small samples. It is argued
that the conventional London equations lead to difficulties that are removed in
the present theory, and that the proposed equations do not contradict any known
experimental facts. Experimental tests are discussed.Comment: Small changes following referee's and editor's comments; to be
published in Phys.Rev.
Incidence and survival rate of women with cervical cancer in the Greater Amsterdam area
To evaluate the effect of population-based cervical cancer screening on the occurrence of cervical cancer in The Netherlands, we investigated the incidence and survival of cervical cancer registered by a cancer registry in the Greater Amsterdam area. The incidence rate of squamous cell carcinoma decreased significantly from 9.2/100,000 women in 1988 to 5.9/100,000 in 2000 (P<0.001). The incidence rate of adenocarcinomas remained stable. After adjustment for age, stage and lymph node involvement, the relative risk of death was 1.6 times higher for patients with adenocarcinomas than for patients with squamous cell carcinoma (95% CI 1.2-2.1). The decreased survival was related to histological type, as the effect remained significant after correction for confounding factors. Over time, the prognosis of women with squamous cell carcinoma improved significantly. No significant change was observed for women diagnosed with adenocarcinoma. These results suggest that the screening programme in The Netherlands as executed in the Greater Amsterdam area is associated with a decreased incidence and increased survival of patients with squamous cell carcinoma, but fails to detect (pre)malignant lesions of adenocarcinoma. Since more than 92% of adenocarcinomas and its precursors contain high-risk HPV, adding HPV testing to cytologic screening might improve the present screening programme in detecting adenocarcinoma and its precursor lesions
A near-infrared study of the obscured 3C129 galaxy cluster
We present a catalogue of 261 new infrared selected members of the 3C129
galaxy cluster. The cluster, located at 0.02, forms part of the
Perseus-Pisces filament and is obscured at optical wavelengths due to its
location in the zone of avoidance. We identified these galaxies using the
and band imaging data provided by the UKIDSS Galactic Plane Survey within
an area with a radius of centred on the X-ray emission of the
cluster at . A total of 26 of the
identified galaxy members have known redshifts 24 of which are from our 2016
Westerbork HI survey and two are from optical spectroscopy. An analysis of the
galaxy density at the core of the 3C129 cluster shows it to be less dense than
the Coma and Norma clusters, but comparable to the galaxy density in the core
of the Perseus cluster. From an assessment of the spatial and velocity
distributions of the 3C129 cluster galaxies that have redshifts, we derived a
velocity of km/s and km/s for the
main cluster, with a substructure in the cluster outskirts at km/s with km/s. The presence of this substructure is
consistent with previous claims based on the X-ray analysis that the cluster is
not yet virialised and may have undergone a recent merger.Comment: 33 pages, 16 figures, includes an appendix, accepted for publication
in A&
The MeerKAT Fornax Survey
We present the science case and observations plan of the MeerKAT Fornax
Survey, an HI and radio continuum survey of the Fornax galaxy cluster to be
carried out with the SKA precursor MeerKAT. Fornax is the second most massive
cluster within 20 Mpc and the largest nearby cluster in the southern
hemisphere. Its low X-ray luminosity makes it representative of the environment
where most galaxies live and where substantial galaxy evolution takes place.
Fornax's ongoing growth makes it an excellent laboratory for studying the
assembly of clusters, the physics of gas accretion and stripping in galaxies
falling in the cluster, and the connection between these processes and the
neutral medium in the cosmic web.
We will observe a region of 12 deg reaching a projected distance of 1.5
Mpc from the cluster centre. This will cover a wide range of environment
density out to the outskirts of the cluster, where gas-rich in-falling groups
are found. We will: study the HI morphology of resolved galaxies down to a
column density of a few times 1e+19 cm at a resolution of 1 kpc; measure
the slope of the HI mass function down to M(HI) 5e+5 M(sun); and attempt to
detect HI in the cosmic web reaching a column density of 1e+18 cm at a
resolution of 10 kpc.Comment: Proceedings of Science, "MeerKAT Science: On the Pathway to the SKA",
Stellenbosch, 25-27 May 201
Geometry-dependent electrostatics near contact lines
Long-ranged electrostatic interactions in electrolytes modify their contact
angles on charged substrates in a scale and geometry dependent manner. For
angles measured at scales smaller than the typical Debye screening length, the
wetting geometry near the contact line must be explicitly considered. Using
variational and asymptotic methods, we derive new transcendental equations for
the contact angle that depend on the electrostatic potential only at the three
phase contact line. Analytic expressions are found in certain limits and
compared with predictions for contact angles measured with lower resolution. An
estimate for electrostatic contributions to {\it line} tension is also given.Comment: 3 .eps figures, 5p
Comparative interactomics analysis of different ALS-associated proteins identifies converging molecular pathways
Amyotrophic lateral sclerosis (ALS) is a devastating
neurological disease with no effective treatment
available. An increasing number of genetic causes of ALS
are being identified, but how these genetic defects lead to
motor neuron degeneration and to which extent they affect
common cellular pathways remains incompletely understood.
To address these questions, we performed an interactomic
analysis to identify binding partners of wild-type
(WT) and ALS-associated mutant versions of ATXN2,
C9orf72, FUS, OPTN, TDP-43 and UBQLN2 in neuronal
cells. This analysis identified several known but also many
novel binding partners of these proteins
GMRT HI observations of the Eridanus group of galaxies
The GMRT HI 21cm-line observations of galaxies in the Eridanus group are
presented. The Eridanus group, at a distance of ~23 Mpc, is a loose group of
\~200 galaxies. The group extends more than 10 Mpc in projection. The velocity
dispersion of the galaxies in the group is ~240 km/s. The galaxies are
clustered into different sub-groups. The overall population mix of the group is
30% (E+S0) and 70% (Sp+Irr). The observations of 57 Eridanus galaxies were
carried out with the GMRT for ~200 hour. HI emission was detected from 31
galaxies. The channel rms of ~1.0 mJy beam^{-1} was achieved for most of the
image-cubes made with 4 hour of data. The corresponding HI column density
sensitivity (3-sigma) is ~1x10^{20} cm^{-2} for a velocity-width of ~13.4 km/s.
The 3-sigma detection limit of HI mass is ~1.2x10^{7} M_sun for a line-width of
50 km/s. Total HI images, HI velocity fields, global HI line profiles, HI mass
surface densities, HI disk parameters and HI rotation curves are presented. The
velocity fields are analysed separately for the approaching and the receding
sides of the galaxies. This data will be used to study the HI and the radio
continuum properties, the Tully-Fisher relations, the dark matter halos, and
the kinematical and HI lopsidedness in galaxies.Comment: 75 pages including HI atlas; Accepted for publication in Journal of
Astroph. & Astron. March, 200
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