12,691 research outputs found
Implications of coral reef buildup for the controls on atmospheric CO2 since the Last Glacial Maximum
We examine the effect on atmospheric CO2 of the occurrence of increased shallow water carbonate deposition and regrowth of the terrestrial biosphere following the last glacial. We find that contrary to recent speculations that changes in terrestrial carbon storage were primarily responsible for the observed similar to20 ppmv late Holocene CO2 rise, a more likely explanation is coral reef buildup and other forms of shallow water carbonate deposition during this time. The importance of a responsive terrestrial carbon reservoir may instead be as a negative feedback restricting the rate of CO2 rise possible in the early stages of the deglacial transition. This separation in time of the primary impacts of regrowth of the terrestrial biosphere and increased shallow water carbonate deposition explains the occurrence of an early Holocene carbonate preservation event observed in deep-sea sediments. We demonstrate that their combined influence is also consistent with available proxy estimates of deep ocean carbonate ion concentration changes over the last 21 kyr. Accounting for the processes that act on the carbonate chemistry of the ocean as a whole then allows us to place strong constraints on the nature of the remaining processes that must be operating at the deglacial transition. By subtracting the net CO2 effect of coral reef buildup and terrestrial biosphere regrowth from recent high-resolution ice core data, we highlight two periods, from 17.0 to 13.8 kyr and 12.3 to 11.2 kyr BP characterized by sustained rapid rates of CO2 increase (> 12 ppmv kyr(-1)). Because these periods are coincident with Southern Hemisphere "deglaciation,'' we argue that changes in the biogeochemical properties of the Southern Ocean surface are the most likely cause
Gauged B-3L_\tau, low-energy unification and proton decay
We point out that if there is a gauged symmetry at low energy, it
can prevent fast proton decay. This may help building models with theories with
extra dimensions at the TeV scale. For purpose of illustration we present an
explicit model with large extra dimensions. The Higgs required for a realistic
fermion masses and mixing are included. The problem of neutrino masses are
solved with triplet Higgs scalars. The proton remains stable even after the
symmetry breaking.Comment: 8 pages, Late
Connecting Dark Energy to Neutrinos with an Observable Higgs Triplet
To connect the scalar field (acceleron) responsible for dark energy to
neutrinos, the usual strategy is to add unnaturally light neutral singlet
fermions (right-handed neutrinos) to the Standard Model. A better choice is
actually a Higgs triplet, through the coupling of the acceleron to the
trilinear Higgs triplet-double-doublet interaction. This hypothesis predicts an
easily observable doubly-charged Higgs boson at the forthcoming Large Hadron
Collider (LHC).Comment: 9 page
A randomized controlled trial for families with preschool children - promoting healthy eating and active playtime by connecting to nature
published_or_final_versio
Majorana neutrinos with split fermions in extra dimensions
We propose new solutions to the neutrino mass problem in theories with large
extra dimensions in a thick wall scenario. It has recently been argued that our
3-brane could be a thick wall at the boundary of the bulk. The gauge bosons and
the Higgs scalars have an almost flat profile on this wall, while fermions
could have localized profile with left-handed and right-handed components
displaced with respect to each other. We point out that with split fermions it
is possible to generate Majorana neutrino masses contributing to the
neutrinoless double beta decay. The almost degenerate neutrinos can also come
out naturally in this case. Unlike other models of neutrino masses in extra
dimensions there are no bulk fields in this scenario.Comment: 12 pages, 1 figure, revise
Prolonged survival of patients receiving trastuzumab beyond disease progression for HER2 overexpressing metastatic breast cancer (MBC)
Background: The aim of this retrospective analysis was to evaluate the impact of trastuzumab-based regimens on the survival of patients with HER2-overexpressing metastatic breast cancer (MBC). The study specifically focussed on the influence of the continuation of trastuzumab-based treatment despite tumor progression on survival. Patients and Methods: Patients with HER2 overexpressing MBC were included in this retrospective analysis. HER2 overexpression was determined by the immunohistochemical staining score (DAKO Hercep Test (TM)). Trastuzumab was applied at a loading dose of 4 mg/kg and a maintenance dose of 2 mg/kg. Results: Among 136 HER2 overexpressing patients (DAKO score 3+), 66 patients received first-line trastuzumab, 47 patients received trastuzumab as second-line therapy and 23 patients received trastuzumab beyond disease progression. There was no significant difference regarding the duration of trastuzumab-based treatment (first-line: 29.5 weeks vs. second-line: 25 weeks). Moreover, there was no difference in the response rate (first-line: 37.9% vs. second-line: 35.7%) or the median survival (p = 0.47 log rank). Patients who received >= 2 trastuzumab-based regimens for MBC survived significantly longer compared to those who had received only 1 regimen (>= 2 regimens: 62.4 months vs. 1 regimen: 38.5 months; p = 0.01 log rank). Conclusions: Trastuzumab is highly effective in the treatment of HER2 overexpressing MBC. Compared to historical controls, overall survival appears to be markedly prolonged, particularly in patients who received sequential trastuzumab-based treatment beyond disease progression
Near Threshold Enhancement of p pbar System and p pbar Elastic Scattering
The observed enhancement of -production near the threshold in
radiative decays of and -annihilations can be explained with
final state interactions among the produced system, where the
enhancement is essentially determined by elastic scattering
amplitudes. We propose to use an effective theory for interactions in a system near its threshold. The effective theory is similar to the well-known
one for interactions in a system but with distinctions. It is interesting
to note that in the effective theory some corrections to scattering amplitudes
at tree-level can systematically be summed into a simple form. These
corrections are from rescattering processes. With these corrected amplitudes we
are able to describe the enhancement near the threshold in radiative decays of
and -annihilations, and the elastic scattering near
the threshold.Comment: Discussions and References added, Fig.2 redrawn. Published version in
Phys. Lett.
QEnclave - A practical solution for secure quantum cloud computing
We introduce a secure hardware device named a QEnclave that can secure the
remote execution of quantum operations while only using classical controls.
This device extends to quantum computing the classical concept of a secure
enclave which isolates a computation from its environment to provide privacy
and tamper-resistance. Remarkably, our QEnclave only performs single-qubit
rotations, but can nevertheless be used to secure an arbitrary quantum
computation even if the qubit source is controlled by an adversary. More
precisely, attaching a QEnclave to a quantum computer, a remote client
controlling the QEnclave can securely delegate its computation to the server
solely using classical communication. We investigate the security of our
QEnclave by modeling it as an ideal functionality named Remote State Rotation.
We show that this resource, similar to previously introduced functionality of
remote state preparation, allows blind delegated quantum computing with perfect
security. Our proof relies on standard tools from delegated quantum computing.
Working in the Abstract Cryptography framework, we show a construction of
remote state preparation from remote state rotation preserving the security. An
immediate consequence is the weakening of the requirements for blind delegated
computation. While previous delegated protocols were relying on a client that
can either generate or measure quantum states, we show that this same
functionality can be achieved with a client that only transforms quantum states
without generating or measuring them.Comment: 25 pages, 5 figure
Distribution of particles and bubbles in turbulence at small Stokes number
The inertia of particles driven by the turbulent flow of the surrounding
fluid makes them prefer certain regions of the flow. The heavy particles lag
behind the flow and tend to accumulate in the regions with less vorticity,
while the light particles do the opposite. As a result of the long-time
evolution, the particles distribute over a multi-fractal attractor in space. We
consider this distribution using our recent results on the steady states of
chaotic dynamics. We describe the preferential concentration analytically and
derive the correlation functions of density and the fractal dimensions of the
attractor. The results are obtained for real turbulence and are testable
experimentally.Comment: 4 page
Leptogenesis from Neutralino Decay with Nonholomorphic R-Parity Violation
In supersymmetric models with lepton-number violation, hence also R-parity
violation, it is easy to have realistic neutrino masses, but then leptogenesis
becomes difficult to achieve. After explaining the general problems involved,
we study the details of a model which escapes these constraints and generates a
lepton asymmetry, which gets converted into the present observed baryon
asymmetry of the Universe through the electroweak sphalerons. This model
requires the presence of certain nonholomorphic R-parity violating terms. For
completeness we also present the most general R-parity violating Lagrangian
with soft nonholomorphic terms and study their consequences for the
charged-scalar mass matrix. New contributions to neutrino masses in this
scenario are discussed.Comment: 30 pages, 6 figure
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