3,910 research outputs found
Sensitive detection of methane at 3.3 μm using an integrating sphere and interband cascade laser
Detection of methane at 3.3μm using a DFB Interband Cascade Laser and gold coated integrating sphere is performed. A 10cm diameter sphere with effective path length of 54.5cm was adapted for use as a gas cell. A comparison between this system and one using a 25cm path length single-pass gas cell is made using direct TDLS and methane concentrations between 0 and 1000 ppm. Initial investigations suggest a limit of detection of 1.0ppm for the integrating sphere and 2.2ppm for the single pass gas cell. The system has potential applications in challenging or industrial environments subject to high levels of vibration
Vertical Orientation in a New Gobioid Fish from New Britain
While visiting Rabaul, New Britain, during
Cruise 6 of the Stanford University vessel "Te
Vega" we observed and collected specimens of
a small gobioid fish that swam and hovered
vertically, with its head up, in midwater close to
pockets in the wall of an underwater cliff at
depths below 30 feet. Many kinds of fishes, for
example scorpaenids and cottoids, are known to
orient vertically in contact with a substrate.
There are fewer examples of vertically oriented
fishes in midwater; among the best known are
the seahorses and centriscids. Observations have
also been made on vertically oriented mesopelagic
fishes. Barham (1966) has seen myctophids
hovering vertically, as well as swimming
upward and downward. Paralepidids are also
known to be vertical swimmers (Peres, 1958;
Bernard, 1958; Cohen, personal observations).
We have found, however, no previous record of
this habit in gobioid fishes and our observations
are presented herewith. We have been unable to
identify the fish with any known form, and we
describe it as a ne
Dark Energy and Modified Gravity
Despite two decades of tremendous experimental and theoretical progress, the
riddle of the accelerated expansion of the Universe remains to be solved. On
the experimental side, our understanding of the possibilities and limitations
of the major dark energy probes has evolved; here we summarize the major probes
and their crucial challenges. On the theoretical side, the taxonomy of
explanations for the accelerated expansion rate is better understood, providing
clear guidance to the relevant observables. We argue that: i) improving
statistical precision and systematic control by taking more data, supporting
research efforts to address crucial challenges for each probe, using
complementary methods, and relying on cross-correlations is well motivated; ii)
blinding of analyses is difficult but ever more important; iii) studies of dark
energy and modified gravity are related; and iv) it is crucial that R&D for a
vibrant dark energy program in the 2030s be started now by supporting studies
and technical R&D that will allow embryonic proposals to mature. Understanding
dark energy, arguably the biggest unsolved mystery in both fundamental particle
physics and cosmology, will remain one of the focal points of cosmology in the
forthcoming decade.Comment: 5 pages + references; science white paper submitted to the Astro2020
decadal surve
Hidden variable interpretation of spontaneous localization theory
The spontaneous localization theory of Ghirardi, Rimini, and Weber (GRW) is a
theory in which wavepacket reduction is treated as a genuine physical process.
Here it is shown that the mathematical formalism of GRW can be given an
interpretation in terms of an evolving distribution of particles on
configuration space similar to Bohmian mechanics (BM). The GRW wavefunction
acts as a pilot wave for the set of particles. In addition, a continuous stream
of noisy information concerning the precise whereabouts of the particles must
be specified. Nonlinear filtering techniques are used to determine the dynamics
of the distribution of particles conditional on this noisy information and
consistency with the GRW wavefunction dynamics is demonstrated. Viewing this
development as a hybrid BM-GRW theory, it is argued that, besides helping to
clarify the relationship between the GRW theory and BM, its merits make it
worth considering in its own right.Comment: 13 page
Correspondence between solar fine-scale structures in the corona, transition region, and lower atmosphere from collaborative observations
The Soft X-Ray Imaging Payload and the High Resolution Telescope and Spectrograph (HRTS) instrument were launched from White Sands on 11 December 1987 in coordinated sounding rocket flights to investigate the correspondence of coronal and transition region structures, especially the relationship between X-ray bright points (XBPs) and transition region small spatial scale energetic events. The coaligned data from X-ray images are presented along with maps of sites of transition region energetic events observed in C IV (100,000 K), HRTS 1600 A spectroheliograms of the T sub min region and ground based magnetogram and He I 10830 A images
Constraints on the perturbed mutual motion in Didymos due to impact-induced deformation of its primary after the DART impact
Binary near-Earth asteroid (65803) Didymos is the target of the proposed NASA
Double Asteroid Redirection Test (DART), part of the Asteroid Impact &
Deflection Assessment (AIDA) mission concept. In this mission, the DART
spacecraft is planned to impact the secondary body of Didymos, perturbing
mutual dynamics of the system. The primary body is currently rotating at a spin
period close to the spin barrier of asteroids, and materials ejected from the
secondary due to the DART impact are likely to reach the primary. These
conditions may cause the primary to reshape, due to landslides, or internal
deformation, changing the permanent gravity field. Here, we propose that if
shape deformation of the primary occurs, the mutual orbit of the system would
be perturbed due to a change in the gravity field. We use a numerical
simulation technique based on the full two-body problem to investigate the
shape effect on the mutual dynamics in Didymos after the DART impact. The
results show that under constant volume, shape deformation induces strong
perturbation in the mutual motion. We find that the deformation process always
causes the orbital period of the system to become shorter. If surface layers
with a thickness greater than ~0.4 m on the poles of the primary move down to
the equatorial region due to the DART impact, a change in the orbital period of
the system and in the spin period of the primary will be detected by
ground-based measurement.Comment: 8 pages, 7 figures, 2 tables, accepted for publication in MNRA
Schrieffer-Wolff transformation for quantum many-body systems
The Schrieffer-Wolff (SW) method is a version of degenerate perturbation
theory in which the low-energy effective Hamiltonian H_{eff} is obtained from
the exact Hamiltonian by a unitary transformation decoupling the low-energy and
high-energy subspaces. We give a self-contained summary of the SW method with a
focus on rigorous results. We begin with an exact definition of the SW
transformation in terms of the so-called direct rotation between linear
subspaces. From this we obtain elementary proofs of several important
properties of H_{eff} such as the linked cluster theorem. We then study the
perturbative version of the SW transformation obtained from a Taylor series
representation of the direct rotation. Our perturbative approach provides a
systematic diagram technique for computing high-order corrections to H_{eff}.
We then specialize the SW method to quantum spin lattices with short-range
interactions. We establish unitary equivalence between effective low-energy
Hamiltonians obtained using two different versions of the SW method studied in
the literature. Finally, we derive an upper bound on the precision up to which
the ground state energy of the n-th order effective Hamiltonian approximates
the exact ground state energy.Comment: 47 pages, 3 figure
First-in-human phase I/II, open-label study of the anti-OX40 agonist INCAGN01949 in patients with advanced solid tumors
Inmunomodulación; Linfocitos T; Microambiente tumoralImmunomodulació; Limfòcits T; Microambient tumoralImmunomodulation; T-Lymphocytes; Tumor microenvironmentBackground OX40 is a costimulatory receptor upregulated on antigen-activated T cells and constitutively expressed on regulatory T cells (Tregs). INCAGN01949, a fully human immunoglobulin G1κ anti-OX40 agonist monoclonal antibody, was designed to promote tumor-specific immunity by effector T-cell activation and Fcγ receptor-mediated Treg depletion. This first-in-human study was conducted to determine the safety, tolerability, and preliminary efficacy of INCAGN01949.
Methods Phase I/II, open-label, non-randomized, dose-escalation and dose-expansion study conducted in patients with advanced or metastatic solid tumors. Patients received INCAGN01949 monotherapy (7–1400 mg) in 14-day cycles while deriving benefit. Safety measures, clinical activity, pharmacokinetics, and pharmacodynamic effects were assessed and summarized with descriptive statistics.
Results Eighty-seven patients were enrolled; most common tumor types were colorectal (17.2%), ovarian (8.0%), and non-small cell lung (6.9%) cancers. Patients received a median three (range 1–9) prior therapies, including immunotherapy in 24 patients (27.6%). Maximum tolerated dose was not reached; one patient (1.1%) receiving 350 mg dose reported dose-limiting toxicity of grade 3 colitis. Treatment-related adverse events were reported in 45 patients (51.7%), with fatigue (16 (18.4%)), rash (6 (6.9%)), and diarrhea (6 (6.9%)) being most frequent. One patient (1.1%) with metastatic gallbladder cancer achieved a partial response (duration of 6.3 months), and 23 patients (26.4%) achieved stable disease (lasting >6 months in one patient). OX40 receptor occupancy was maintained over 90% among all patients receiving doses of ≥200 mg, while no treatment-emergent antidrug antibodies were detected across all dose levels. Pharmacodynamic results demonstrated that treatment with INCAGN01949 did not enhance proliferation or activation of T cells in peripheral blood or reduce circulating Tregs, and analyses of tumor biopsies did not demonstrate any consistent increase in effector T-cell infiltration or function, or decrease in infiltrating Tregs.
Conclusion No safety concerns were observed with INCAGN01949 monotherapy in patients with metastatic or advanced solid tumors. However, tumor responses and pharmacodynamic effects on T cells in peripheral blood and post-therapy tumor biopsies were limited. Studies evaluating INCAGN01949 in combination with other therapies are needed to further evaluate the potential of OX40 agonism as a therapeutic approach in patients with advanced solid tumors.This study was funded by Incyte Corporation (Wilmington, USA)
Electrophysiological Signatures of Spatial Boundaries in the Human Subiculum.
Environmental boundaries play a crucial role in spatial navigation and memory across a wide range of distantly related species. In rodents, boundary representations have been identified at the single-cell level in the subiculum and entorhinal cortex of the hippocampal formation. Although studies of hippocampal function and spatial behavior suggest that similar representations might exist in humans, boundary-related neural activity has not been identified electrophysiologically in humans until now. To address this gap in the literature, we analyzed intracranial recordings from the hippocampal formation of surgical epilepsy patients (of both sexes) while they performed a virtual spatial navigation task and compared the power in three frequency bands (1-4, 4-10, and 30-90 Hz) for target locations near and far from the environmental boundaries. Our results suggest that encoding locations near boundaries elicited stronger theta oscillations than for target locations near the center of the environment and that this difference cannot be explained by variables such as trial length, speed, movement, or performance. These findings provide direct evidence of boundary-dependent neural activity localized in humans to the subiculum, the homolog of the hippocampal subregion in which most boundary cells are found in rodents, and indicate that this system can represent attended locations that rather than the position of one\u27s own body
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