442 research outputs found
Snake states and their symmetries in graphene
Snake states are open trajectories for charged particles propagating in two
dimensions under the influence of a spatially varying perpendicular magnetic
field. In the quantum limit they are protected edge modes that separate
topologically inequivalent ground states and can also occur when the particle
density rather than the field is made nonuniform. We examine the correspondence
of snake trajectories in single-layer graphene in the quantum limit for two
families of domain walls: (a) a uniform doped carrier density in an
antisymmetric field profile and (b) antisymmetric carrier distribution in a
uniform field. These families support different internal symmetries but the
same pattern of boundary and interface currents. We demonstrate that these
physically different situations are gauge equivalent when rewritten in a Nambu
doubled formulation of the two limiting problems. Using gauge transformations
in particle-hole space to connect these problems, we map the protected
interfacial modes to the Bogoliubov quasiparticles of an interfacial
one-dimensional p-wave paired state. A variational model is introduced to
interpret the interfacial solutions of both domain wall problems
Radiofrequency ablation and chemotherapy versus chemotherapy alone for locally advanced pancreatic cancer (PELICAN): study protocol for a randomized controlled trial
Quimioteràpia; Càncer de pàncrees localment avançat; Ablació per radiofreqüènciaQuimioterapia; Cáncer de páncreas localmente avanzado; Ablación por radiofrecuenciaChemotherapy; Locally advanced pancreatic cancer; Radiofrequency ablationBackground
Approximately 80% of patients with locally advanced pancreatic cancer (LAPC) are treated with chemotherapy, of whom approximately 10% undergo a resection. Cohort studies investigating local tumor ablation with radiofrequency ablation (RFA) have reported a promising overall survival of 26–34 months when given in a multimodal setting. However, randomized controlled trials (RCTs) investigating the effect of RFA in combination with chemotherapy in patients with LAPC are lacking.
Methods
The “Pancreatic Locally Advanced Unresectable Cancer Ablation” (PELICAN) trial is an international multicenter superiority RCT, initiated by the Dutch Pancreatic Cancer Group (DPCG). All patients with LAPC according to DPCG criteria, who start with FOLFIRINOX or (nab-paclitaxel/)gemcitabine, are screened for eligibility. Restaging is performed after completion of four cycles of FOLFIRINOX or two cycles of (nab-paclitaxel/)gemcitabine (i.e., 2 months of treatment), and the results are assessed within a nationwide online expert panel. Eligible patients with RECIST stable disease or objective response, in whom resection is not feasible, are randomized to RFA followed by chemotherapy or chemotherapy alone. In total, 228 patients will be included in 16 centers in The Netherlands and four other European centers. The primary endpoint is overall survival. Secondary endpoints include progression-free survival, RECIST response, CA 19.9 and CEA response, toxicity, quality of life, pain, costs, and immunomodulatory effects of RFA.
Discussion
The PELICAN RCT aims to assess whether the combination of chemotherapy and RFA improves the overall survival when compared to chemotherapy alone, in patients with LAPC with no progression of disease following 2 months of systemic treatment.Olympus Netherlands BV supported the investigator-initiated PELICAN trial with material support by providing the RFA generators and electrodes for the study. They did not have and will not have any influence on the trial design, data collection, interpretation of the data, manuscript development, or decision to publish. Furthermore, the study protocol has undergone full external peer review and received a data management and monitoring grant from the Dutch Cancer Society (grant number 2014-7244)
Axisymmetric and triaxial MOND density-potential pairs
We present a simple method, based on the deformation of spherically symmetric
potentials, to construct explicit axisymmetric and triaxial MOND
density-potential pairs. General guidelines to the choice of suitable
deformations, so that the resulting density distribution is nowhere negative,
are presented. This flexible method offers for the first time the possibility
to study the MOND gravitational field for sufficiently general and realistic
density distributions without resorting to sophisticated numerical codes. The
technique is illustrated by constructing the MOND density-potential pair for a
triaxial galaxy model that, in the absence of deformation, reduces to the
Hernquist sphere. Such analytical solutions are also relevant to test and
validate numerical codes. Here we present a new numerical potential solver
designed to solve the MOND field equation for arbitrary density distributions:
the code is tested with excellent results against the analytic MOND triaxial
Hernquist model and the MOND razor-thin Kuzmin disk, and a simple application
is finally presented.Comment: 21 pages, 5 figures. Accepted for publication in the Astrophysical
Journa
Constraining Lyman-alpha spatial offsets at from VANDELS slit spectroscopy
We constrain the distribution of spatially offset Lyman-alpha emission
(Ly) relative to rest-frame ultraviolet emission in high
redshift () Lyman-break galaxies (LBGs) exhibiting Ly emission
from VANDELS, a VLT/VIMOS slit-spectroscopic survey of the CANDELS Ultra Deep
Survey and Chandra Deep Field South fields (
total). Because slit spectroscopy compresses two-dimensional spatial
information into one spatial dimension, we use Bayesian inference to recover
the underlying Ly spatial offset distribution. We model the
distribution using a 2D circular Gaussian, defined by a single parameter
, the standard deviation expressed in polar
coordinates. Over the entire redshift range of our sample (), we find
kpc ( conf.),
corresponding to arcsec at . We also find that
decreases significantly with redshift. Because
Ly spatial offsets can cause slit-losses, the decrease in
with redshift can partially explain the increase
in the fraction of Ly emitters observed in the literature over this
same interval, although uncertainties are still too large to reach a strong
conclusion. If continues to decrease into the
reionization epoch, then the decrease in Ly transmission from galaxies
observed during this epoch might require an even higher neutral hydrogen
fraction than what is currently inferred. Conversely, if spatial offsets
increase with the increasing opacity of the IGM, slit losses may explain some
of the drop in Ly transmission observed at . Spatially resolved
observations of Ly and UV continuum at are needed to settle the
issue.Comment: Submitted to MNRA
Glioblastoma adaptation traced through decline of an IDH1 clonal driver and macro-evolution of a double-minute chromosome
In a glioblastoma tumour with multi-region sequencing before and after recurrence, we find an IDH1 mutation that is clonal in the primary but lost at recurrence. We also describe the evolution of a double-minute chromosome encoding regulators of the PI3K signalling axis that dominates at recurrence, emphasizing the challenges of an evolving and dynamic oncogenic landscape for precision medicin
A rapid and systematic review of the effectiveness of temozolomide for the treatment of recurrent malignant glioma
A rapid and systematic review of the effectiveness and cost-effectiveness of temozolomide in the treatment of recurrent malignant glioma was commissioned by the NHS HTA Programme on behalf of NICE. The full report has been published elsewhere. This paper summarizes the results for the effectiveness of temozolomide in people with recurrent glioblastoma multiforme and anaplastic astrocytoma. The review was conducted using standard systematic review methodology involving a systematic literature search, quality assessment of included studies with systematic data extraction and data synthesis. One randomized controlled trial and four uncontrolled studies were identified for inclusion. The key results were that temozolomide may increase progression-free survival but has no significant impact on overall length of survival. The main effect from temozolomide may have been in those patients who had not received any prior chemotherapy regimens, however further randomized controlled trials are required to confirm this suggestion. Temozolomide appears to produce few serious adverse effects and may also have a positive impact on health-related quality of life. Overall the evidence-base is weak and few strong conclusions can be drawn regarding the effectiveness of temozolomide. Large, well-designed randomized controlled trails conducted in a wider patient population are needed
Dynamic scaling for 2D superconductors, Josephson junction arrays and superfluids
The value of the dynamic critical exponent is studied for two-dimensional
superconducting, superfluid, and Josephson Junction array systems in zero
magnetic field via the Fisher-Fisher-Huse dynamic scaling. We find
, a relatively large value indicative of non-diffusive
dynamics. Universality of the scaling function is tested and confirmed for the
thinnest samples. We discuss the validity of the dynamic scaling analysis as
well as the previous studies of the Kosterlitz-Thouless-Berezinskii transition
in these systems, the results of which seem to be consistent with simple
diffusion (). Further studies are discussed and encouraged.Comment: 19 pages in two-column RevTex, 8 embedded EPS figure
The thickness of HI in galactic discs under MOND: theory and application to the Galaxy
The outskirts of galaxies are a very good laboratory for testing the nature
of the gravitational field at low accelerations. By assuming that the neutral
hydrogen gas is in hydrostatic equilibrium in the gravitational potential of
the host galaxy, the observed flaring of the gas layer can be used to test
modified gravities. For the first time we construct a simple framework to
derive the scaleheight of the neutral hydrogen gas disc in the MOND scenario
and apply this to the Milky Way. It is shown that using a constant gas velocity
dispersion of ~9 km/s, MOND is able to give a very good fit to the observed HI
flaring beyond a galactocentric distance of 17 kpc up to the last measured
point (~40 kpc). Between 10 and 16 kpc, however, the observed scaleheight is
about 40% more than what MOND predicts for the standard interpolating function
and 70% for the form suggested by Famaey & Binney. Given the uncertainties in
the non-thermal pressure support by cosmic rays and magnetic fields, MOND seems
to be a plausible alternative to dark matter in explaining the Milky Way
flaring. Studying the flaring of extended HI discs in external edge-on galaxies
may be a promising approach to assess the viability of MOND.Comment: 13 pages, 4 figure
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