2,185 research outputs found
Variational quantum algorithms for scanning the complex spectrum of non-Hermitian systems
Solving non-Hermitian quantum many-body systems on a quantum computer by
minimizing the variational energy is challenging as the energy can be complex.
Here, based on energy variance, we propose a variational method for solving the
non-Hermitian Hamiltonian, as zero variance can naturally determine the
eigenvalues and the associated left and right eigenstates. Moreover, the energy
is set as a parameter in the cost function and can be tuned to obtain the whole
spectrum, where each eigenstate can be efficiently obtained using a two-step
optimization scheme. Through numerical simulations, we demonstrate the
algorithm for preparing the left and right eigenstates, verifying the
biorthogonal relations, as well as evaluating the observables. We also
investigate the impact of quantum noise on our algorithm and show that its
performance can be largely improved using error mitigation techniques.
Therefore, our work suggests an avenue for solving non-Hermitian quantum
many-body systems with variational quantum algorithms on near-term noisy
quantum computers
Variational quantum simulation of the quantum critical regime
The quantum critical regime marks a zone in the phase diagram where quantum
fluctuation around the critical point plays a significant role at finite
temperatures. While it is of great physical interest, simulation of the quantum
critical regime can be difficult on a classical computer due to its intrinsic
complexity. In this paper, we propose a variational approach, which minimizes
the variational free energy, to simulate and locate the quantum critical regime
on a quantum computer. The variational quantum algorithm adopts an ansatz by
performing an unitary operator on a product of a single-qubit mixed state, in
which the entropy can be analytically obtained from the initial state, and thus
the free energy can be accessed conveniently. With numeral simulation, we show,
using the one-dimensional Kitaev model as a demonstration, the quantum critical
regime can be identified by accurately evaluating the temperature crossover
line. Moreover, the dependence of both the correlation length and the phase
coherence time with the temperature are evaluated for the thermal states. Our
work suggests a practical way as well as a first step for investigating quantum
critical systems at finite temperatures on quantum devices with few qubits
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Hyperspectral Imaging with Stimulated Raman Scattering by Chirped Femtosecond Lasers
Raman microscopy is a quantitative, label-free, and noninvasive optical imaging technique for studying inhomogeneous systems. However, the feebleness of Raman scattering significantly limits the use of Raman microscopy to low time resolutions and primarily static samples. Recent developments in narrowband stimulated Raman scattering (SRS) microscopy have significantly increased the acquisition speed of Raman based label-free imaging by a few orders of magnitude, at the expense of reduced spectroscopic information. On the basis of a spectral focusing approach, we present a fast SRS hyperspectral imaging system using chirped femtosecond lasers to achieve rapid Raman spectra acquisition while retaining the full speed and image quality of narrowband SRS imaging. We demonstrate that quantitative concentration determination of cholesterol in the presence of interfering chemical species can be achieved with sensitivity down to 4 mM. For imaging purposes, hyperspectral imaging data in the C–H stretching region is obtained within a minute. We show that mammalian cell SRS hyperspectral imaging reveals the spatially inhomogeneous distribution of saturated lipids, unsaturated lipids, cholesterol, and protein. The combination of fast spectroscopy and label-free chemical imaging will enable new applications in studying biological systems and material systems.Chemistry and Chemical BiologyEngineering and Applied Science
Geometry-Aware Video Object Detection for Static Cameras
In this paper we propose a geometry-aware model for video object detection.
Specifically, we consider the setting that cameras can be well approximated as
static, e.g. in video surveillance scenarios, and scene pseudo depth maps can
therefore be inferred easily from the object scale on the image plane. We make
the following contributions: First, we extend the recent anchor-free detector
(CornerNet [17]) to video object detections. In order to exploit the
spatial-temporal information while maintaining high efficiency, the proposed
model accepts video clips as input, and only makes predictions for the starting
and the ending frames, i.e. heatmaps of object bounding box corners and the
corresponding embeddings for grouping. Second, to tackle the challenge from
scale variations in object detection, scene geometry information, e.g. derived
depth maps, is explicitly incorporated into deep networks for multi-scale
feature selection and for the network prediction. Third, we validate the
proposed architectures on an autonomous driving dataset generated from the
Carla simulator [5], and on a real dataset for human detection (DukeMTMC
dataset [28]). When comparing with the existing competitive single-stage or
two-stage detectors, the proposed geometry-aware spatio-temporal network
achieves significantly better results.Comment: Accepted at BMVC 2019 as ORA
Epi-illumination SPIM for volumetric imaging with high spatial-temporal resolution.
We designed an epi-illumination SPIM system that uses a single objective and has a sample interface identical to that of an inverted fluorescence microscope with no additional reflection elements. It achieves subcellular resolution and single-molecule sensitivity, and is compatible with common biological sample holders, including multi-well plates. We demonstrated multicolor fast volumetric imaging, single-molecule localization microscopy, parallel imaging of 16 cell lines and parallel recording of cellular responses to perturbations
Aldosterone defects in infants and young children with hyperkalemia: A single center retrospective study
IntroductionHyperkalemia is a rare but severe condition in young children and usually discovered as a result of hemolysis of the blood samples taken. However, patients with defects in either aldosterone biosynthesis or function can also present with hyperkalemia- as well hyponatremia-associated, and metabolic acidosis. It is a challenge to make an accurate diagnosis of these clinical conditions. We conducted this study to investigate the clinical and genetic features of aldosterone signaling defects associated hyperkalemia in young children.MethodA retrospective review was conducted at the pediatric department of the First Affiliated Hospital of Guangxi Medical University from 2012 to 2022.Results47 patients with hyperkalemia were enrolled, of which 80.9% (n = 38) were diagnosed with primary hypoaldosteronism, including congenital adrenal hyperplasia due to 21-hydroxylase deficiency (n = 32), isolated hypoaldosteronism (n = 1) due to CYP11B2 gene mutation and Xp21 contiguous gene deletion syndrome (n = 1). Additionally, 4 patients were clinically-diagnosed with primary adrenal insufficiency. Nine patients were confirmed with aldosterone resistance, of which one child was diagnosed with pseudohypoaldosteronism (PHA) type 1 with a mutation in the NR3C2 gene and 3 children were identified with PHA type 2 due to novel mutations in either the CUL3 or KLHL3 genes. Five patients had PHA type 3 because of pathologies of either the urinary or intestinal tracts.ConclusionsThe etiologies of infants with hyperkalemia associated with aldosterone defects were mostly due to primary hypoaldosteronism. An elevated plasma aldosterone level may be a useful biomarker for the diagnosis an aldosterone functional defect in patients presented with hyperkalemia. However, a normal plasma aldosterone level does rule out an aldosterone defect in either its biosynthesis or function, especially in young infants. Molecular genetic analyses can greatly help to clarify the complexity of disorders and can be used to confirm the diagnosis
Bis[1,1′-(1,3-phenylÂenedimethylÂene)di(1H-imidazol-3-ium)] β-octaÂmolybdate
In the title compound, (C14H16N4)2[Mo8O26], the β-octaÂmolybdate anion is centrosymmetric. N—Hâ‹ŻO hydrogen bonds link the diimidazolium cations and the polyoxidoanions into a chain structure along [100]. π–π interÂactions between the imidazole rings and between the imidazole and benzene rings [centroid–centroid distances = 3.611 (2) and 3.689 (3) Å, respectively] connect the chains
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Quantitative Chemical Imaging with Multiplex Stimulated Raman Scattering Microscopy
Stimulated Raman scattering (SRS) microscopy is a newly developed label-free chemical imaging technique that overcomes the speed limitation of confocal Raman microscopy while avoiding the nonresonant background problem of coherent anti-Stokes Raman scattering (CARS) microscopy. Previous demonstrations have been limited to single Raman band measurements. We present a novel modulation multiplexing approach that allows real-time detection of multiple species using the fast Fourier transform. We demonstrate the quantitative determination of chemical concentrations in a ternary mixture. Furthermore, two imaging applications are pursued: (1) quantitative determination of oil content as well as pigment and protein concentration in microalgae cultures; and (2) 3D high-resolution imaging of blood, lipids, and protein distribution in ex vivo mouse skin tissue. We believe that quantitative multiplex SRS uniquely combines the advantage of fast label-free imaging with the fingerprinting capability of Raman spectroscopy and enables numerous applications in lipid biology as well as biomedical imaging.Chemistry and Chemical BiologyEngineering and Applied Science
Hyponatremia in babies: a 11-year single-center study
IntroductionHyponatremia is one of the most prevalent water-electrolyte disturbances encountered in clinical practice in pediatrics and can arise from various conditions. However, there are limited reports on hyponatremia in hospitalized infants. The objective of this study was to provide an overview of the incidence, etiologies, and clinical characteristics of hyponatremia in hospitalized babies (from birth to 3 years old) at a tertiary hospital.MethodComputer records of all hospitalized babies (from birth to 3 years old) with hyponatremia were extracted from the First Affiliated Hospital of Guangxi Medical University's clinical databases.Results801 patients from 39,019 hospital admissions were found to have hyponatremia and the overall prevalence of this condition was 2.05% in babies. Patients with hyponatremia due to aldosterone signaling abnormalities, neurological disorders, and liver diseases exhibited more severe outcomes than those with other etiologies.ConclusionsVarious conditions can result in hyponatremia in hospitalized babies. Aldosterone signaling abnormalities were not that uncommon and it could lead to severe hyponatremia in babies
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