179 research outputs found
Doping evolution of antiferromagnetism and transport properties in the non-superconducting BaFe2-2xNixCrxAs2
We report elastic neutron scattering and transport measurements on the Ni and
Cr equivalently doped iron pnictide BaFeNiCrAs.
Compared with the electron-doped BaFeNiAs, the long-range
antiferromagnetic (AF) order in BaFeNiCrAs is
gradually suppressed with vanishing ordered moment and N\'{e}el temperature
near without the appearance of superconductivity. A detailed analysis
on the transport properties of BaFeNiAs and
BaFeNiCrAs suggests that the non-Fermi-liquid
behavior associated with the linear resistivity as a function of temperature
may not correspond to the disappearance of the static AF order. From the
temperature dependence of the resistivity in overdoped compounds without static
AF order, we find that the transport properties are actually affected by Cr
impurity scattering, which may induce a metal-to-insulator crossover in highly
doped BaFeNiCrAs.Comment: 10 pages, 12 figure
Electron doping evolution of the magnetic excitations in BaFe2-xNixAs2
We use inelastic neutron scattering (INS) spectroscopy to study the magnetic
excitations spectra throughout the Brioullion zone in electron-doped iron
pnictide superconductors BaFeNiAs with .
While the sample is near optimal superconductivity with K
and has coexisting static incommensurate magnetic order, the
samples are electron-overdoped with reduced of 14 K and 8 K,
respectively, and have no static antiferromagnetic (AF) order. In previous INS
work on undoped () and electron optimally doped () samples, the
effect of electron-doping was found to modify spin waves in the parent compound
BaFeAs below 100 meV and induce a neutron spin resonance at the
commensurate AF ordering wave vector that couples with superconductivity. While
the new data collected on the sample confirms the overall features of
the earlier work, our careful temperature dependent study of the resonance
reveals that the resonance suddenly changes its -width below similar
to that of the optimally hole-doped iron pnictides
BaKFeAs. In addition, we establish the dispersion of
the resonance and find it to change from commensurate to transversely
incommensurate with increasing energy. Upon further electron-doping to
overdoped iron pnictides with and 0.18, the resonance becomes weaker
and transversely incommensurate at all energies, while spin excitations above
100 meV are still not much affected. Our absolute spin excitation
intensity measurements throughout the Brillouin zone for
confirm the notion that the low-energy spin excitation coupling with itinerant
electron is important for superconductivity in these materials, even though the
high-energy spin excitations are weakly doping dependent.Comment: 16 pages, 16 figure
A MIC-LSTM based parameter extraction method for single-diode PV model
In recent years, the installed capacity of renewable energy systems has seen rapid growth, particularly in photovoltaic (PV) power. Photovoltaic modules, being the fundamental elements of the PV system, play a crucial role in determining system performance. However, the challenge arises from the inconsistent decay rates of PV modules, which significantly impact the accuracy of PV system modeling. To address this issue, this paper introduces a novel MIC-LSTM based parameter extraction method for the single-diode PV model. This method focuses on accurately deriving PV module model parameters under various decay rates. By establishing a mapping relationship between the current-voltage (I-V) curve characteristics and the five unknown parameters in the photovoltaic module model, the proposed method demonstrates high precision in parameter extraction. Simulation and experimental verifications are carried out to validate the proposed method, where the extraction accuracy is 99.3%, 98.39%, 98.85%, 97.91%, and 98.36% for the five unknown model parameters
Precursory Cooper Flow in Ultralow-Temperature Superconductors
Superconductivity at low temperature -- observed in lithium and bismuth, as
well as in various low-density superconductors -- calls for developing reliable
theoretical and experimental tools for predicting ultralow critical
temperatures, , of Cooper instability in a system demonstrating nothing
but normal Fermi liquid behavior in a broad range of temperatures below the
Fermi energy, . Equally important are controlled predictions of
stability in a given Cooper channel. We identify such a protocol within the
paradigm of precursory Cooper flow -- a universal ansatz describing
logarithmically slow temperature evolution of the linear response of the normal
state to the pair-creating perturbation. Applying this framework to the
two-dimensional uniform electron gas, we reveal a series of exotic
superconducting states, pushing controlled theoretical predictions of to
the unprecedentedly low scale of
Enhancing Medical Task Performance in GPT-4V: A Comprehensive Study on Prompt Engineering Strategies
OpenAI's latest large vision-language model (LVLM), GPT-4V(ision), has piqued
considerable interest for its potential in medical applications. Despite its
promise, recent studies and internal reviews highlight its underperformance in
specialized medical tasks. This paper explores the boundary of GPT-4V's
capabilities in medicine, particularly in processing complex imaging data from
endoscopies, CT scans, and MRIs etc. Leveraging open-source datasets, we
assessed its foundational competencies, identifying substantial areas for
enhancement. Our research emphasizes prompt engineering, an often-underutilized
strategy for improving AI responsiveness. Through iterative testing, we refined
the model's prompts, significantly improving its interpretative accuracy and
relevance in medical imaging. From our comprehensive evaluations, we distilled
10 effective prompt engineering techniques, each fortifying GPT-4V's medical
acumen. These methodical enhancements facilitate more reliable, precise, and
clinically valuable insights from GPT-4V, advancing its operability in critical
healthcare environments. Our findings are pivotal for those employing AI in
medicine, providing clear, actionable guidance on harnessing GPT-4V's full
diagnostic potential
Label-free timing analysis of modularized nuclear detectors with physics-constrained deep learning
Pulse timing is an important topic in nuclear instrumentation, with
far-reaching applications from high energy physics to radiation imaging. While
high-speed analog-to-digital converters become more and more developed and
accessible, their potential uses and merits in nuclear detector signal
processing are still uncertain, partially due to associated timing algorithms
which are not fully understood and utilized. In this paper, we propose a novel
method based on deep learning for timing analysis of modularized nuclear
detectors without explicit needs of labelling event data. By taking advantage
of the inner time correlation of individual detectors, a label-free loss
function with a specially designed regularizer is formed to supervise the
training of neural networks towards a meaningful and accurate mapping function.
We mathematically demonstrate the existence of the optimal function desired by
the method, and give a systematic algorithm for training and calibration of the
model. The proposed method is validated on two experimental datasets. In the
toy experiment, the neural network model achieves the single-channel time
resolution of 8.8 ps and exhibits robustness against concept drift in the
dataset. In the electromagnetic calorimeter experiment, several neural network
models (FC, CNN and LSTM) are tested to show their conformance to the
underlying physical constraint and to judge their performance against
traditional methods. In total, the proposed method works well in either ideal
or noisy experimental condition and recovers the time information from waveform
samples successfully and precisely.Comment: 25 pages, 10 figure
Low dose triptolide reverses chemoresistance in adult acute lymphoblastic leukemia cells via reactive oxygen species generation and DNA damage response disruption
Chemoresistance represents a major challenge for treatment of acute lymphoblastic leukemia (ALL). Thus, new drugs to overcome chemoresistance in ALL are urgently needed. To this end, we established a cytarabine (araC)-resistant ALL cell line (NALM-6/R), which interestingly displayed cross-resistance towards doxorubicin (ADM). Here we report that low dose of triptolide (TPL), a natural product used for treating inflammatory diseases such as arthritis, could reverse araC and ADM resistance and in NALM-6/R cells as well as primary cells from patients with relapsed or refractory (R/R) ALL, reflected by inhibition of cell proliferation and induction of apoptosis in vitro, and repression of tumor growth in vivo in a mouse xenograft model. Mechanistically, these events were associated with impaired mitochondrial membrane potential and increased reactive oxygen species (ROS) production. Co-treatment with TPL and araC or ADM upregulated pro-apoptotic caspase-9 protein, inhibited checkpoint kinase 1 (Chk1) and 2 (Chk2) phosphorylation, and induced γH2A.X (a DNA damage marker). Notably, the combination regimen of TPL and conventional chemotherapeutics also rapidly diminished tumor burden in a patient with R/R ALL. Together, these findings provide preclinical evidence for repurposing use of TPL in combination with chemotherapeutic agents to treat R/R ALL as an alternative salvage regimen
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