1,559 research outputs found
Quantum state conversion between continuous variable and qubits systems
We investigate how quantum state can be converted between continuous variable
and qubits systems. Non-linear Jaynes-Cumings interaction Hamiltonian is
introduced to accomplish the conversion. Detail analysis on the conversion of
thermal state exhibits that pretty good fidelity can be achieved.Comment: 6 page
Locally Optimal Estimation and Control of Cable Driven Parallel Robots using Time Varying Linear Quadratic Gaussian Control
We present a locally optimal tracking controller for Cable Driven Parallel
Robot (CDPR) control based on a time-varying Linear Quadratic Gaussian (TV-LQG)
controller. In contrast to many methods which use fixed feedback gains, our
time-varying controller computes the optimal gains depending on the location in
the workspace and the future trajectory. Meanwhile, we rely heavily on offline
computation to reduce the burden of online implementation and feasibility
checking. Following the growing popularity of probabilistic graphical models
for optimal control, we use factor graphs as a tool to formulate our controller
for their efficiency, intuitiveness, and modularity. The topology of a factor
graph encodes the relevant structural properties of equations in a way that
facilitates insight and efficient computation using sparse linear algebra
solvers. We first use factor graph optimization to compute a nominal
trajectory, then linearize the graph and apply variable elimination to compute
the locally optimal, time varying linear feedback gains. Next, we leverage the
factor graph formulation to compute the locally optimal, time-varying Kalman
Filter gains, and finally combine the locally optimal linear control and
estimation laws to form a TV-LQG controller. We compare the tracking accuracy
of our TV-LQG controller to a state-of-the-art dual-space feed-forward
controller on a 2.9m x 2.3m, 4-cable planar robot and demonstrate improved
tracking accuracies of 0.8{\deg} and 11.6mm root mean square error in rotation
and translation respectively.Comment: 8 pages, 11 figures, accepted to IEEE International Conference on
Intelligent Robotics and Systems (IROS) 202
A Hybrid Cable-Driven Robot for Non-Destructive Leafy Plant Monitoring and Mass Estimation using Structure from Motion
We propose a novel hybrid cable-based robot with manipulator and camera for
high-accuracy, medium-throughput plant monitoring in a vertical hydroponic farm
and, as an example application, demonstrate non-destructive plant mass
estimation. Plant monitoring with high temporal and spatial resolution is
important to both farmers and researchers to detect anomalies and develop
predictive models for plant growth. The availability of high-quality,
off-the-shelf structure-from-motion (SfM) and photogrammetry packages has
enabled a vibrant community of roboticists to apply computer vision for
non-destructive plant monitoring. While existing approaches tend to focus on
either high-throughput (e.g. satellite, unmanned aerial vehicle (UAV),
vehicle-mounted, conveyor-belt imagery) or high-accuracy/robustness to
occlusions (e.g. turn-table scanner or robot arm), we propose a middle-ground
that achieves high accuracy with a medium-throughput, highly automated robot.
Our design pairs the workspace scalability of a cable-driven parallel robot
(CDPR) with the dexterity of a 4 degree-of-freedom (DoF) robot arm to
autonomously image many plants from a variety of viewpoints. We describe our
robot design and demonstrate it experimentally by collecting daily photographs
of 54 plants from 64 viewpoints each. We show that our approach can produce
scientifically useful measurements, operate fully autonomously after initial
calibration, and produce better reconstructions and plant property estimates
than those of over-canopy methods (e.g. UAV). As example applications, we show
that our system can successfully estimate plant mass with a Mean Absolute Error
(MAE) of 0.586g and, when used to perform hypothesis testing on the
relationship between mass and age, produces p-values comparable to ground-truth
data (p=0.0020 and p=0.0016, respectively).Comment: 8 pages (6-content, 2-citations), 10 figures, 4 tables, submitted to
ICRA 202
Switchable resolution in soft x-ray tomography of single cells.
The diversity of living cells, in both size and internal complexity, calls for imaging methods with adaptable spatial resolution. Soft x-ray tomography (SXT) is a three-dimensional imaging technique ideally suited to visualizing and quantifying the internal organization of single cells of varying sizes in a near-native state. The achievable resolution of the soft x-ray microscope is largely determined by the objective lens, but switching between objectives is extremely time-consuming and typically undertaken only during microscope maintenance procedures. Since the resolution of the optic is inversely proportional to the depth of focus, an optic capable of imaging the thickest cells is routinely selected. This unnecessarily limits the achievable resolution in smaller cells and eliminates the ability to obtain high-resolution images of regions of interest in larger cells. Here, we describe developments to overcome this shortfall and allow selection of microscope optics best suited to the specimen characteristics and data requirements. We demonstrate that switchable objective capability advances the flexibility of SXT to enable imaging cells ranging in size from bacteria to yeast and mammalian cells without physically modifying the microscope, and we demonstrate the use of this technology to image the same specimen with both optics
Entanglement of bosonic modes of nonplanar molecules
Entanglement of bosonic modes of material oscillators is studied in the
context of two bilinearly coupled, nonlinear oscillators. These oscillators are
realizable in the vibrational-cum-bending motions of C-H bonds in
dihalomethanes. The bilinear coupling gives rise to invariant subspaces in the
Hilbert space of the two oscillators. The number of separable states in any
invariant subspace is one more than the dimension of the space. The dynamics of
the oscillators when the initial state belongs to an invariant subspace is
studied. In particular, the dynamics of the system when the initial state is
such that the total energy is concentrated in one of the modes is studied and
compared with the evolution of the system when the initial state is such
wherein the modes share the total energy. The dynamics of quantities such as
entropy, mean of number of quanta in the two modes and variances in the
quadratures of the two modes are studied. Possibility of generating maximally
entangled states is indicated.Comment: 21 pages, 6 figure
A Genome-Wide Association Study of Hypertension and Blood Pressure in African Americans
The evidence for the existence of genetic susceptibility variants for the common form of hypertension (“essential hypertension”) remains weak and inconsistent. We sought genetic variants underlying blood pressure (BP) by conducting a genome-wide association study (GWAS) among African Americans, a population group in the United States that is disproportionately affected by hypertension and associated complications, including stroke and kidney diseases. Using a dense panel of over 800,000 SNPs in a discovery sample of 1,017 African Americans from the Washington, D.C., metropolitan region, we identified multiple SNPs reaching genome-wide significance for systolic BP in or near the genes: PMS1, SLC24A4, YWHA7, IPO7, and CACANA1H. Two of these genes, SLC24A4 (a sodium/potassium/calcium exchanger) and CACNA1H (a voltage-dependent calcium channel), are potential candidate genes for BP regulation and the latter is a drug target for a class of calcium channel blockers. No variant reached genome wide significance for association with diastolic BP (top scoring SNP rs1867226, p = 5.8×10−7) or with hypertension as a binary trait (top scoring SNP rs9791170, p = 5.1×10−7). We replicated some of the significant SNPs in a sample of West Africans. Pathway analysis revealed that genes harboring top-scoring variants cluster in pathways and networks of biologic relevance to hypertension and BP regulation. This is the first GWAS for hypertension and BP in an African American population. The findings suggests that, in addition to or in lieu of relying solely on replicated variants of moderate-to-large effect reaching genome-wide significance, pathway and network approaches may be useful in identifying and prioritizing candidate genes/loci for further experiments
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COVID-19 infection: the China and Italy perspectives.
The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is responsible for the COVID-19 pandemic. Since its first report in December 2019, despite great efforts made in almost every country worldwide, this disease continues to spread globally, especially in most parts of Europe, Iran, and the United States. Here, we update the recent understanding in clinical characteristics, diagnosis strategies, as well as clinical management of COVID-19 in China as compared to Italy, with the purpose to integrate the China experience with the global efforts to outline references for prevention, basic research, treatment as well as final control of the disease. Being the first two countries we feel appropriate to evaluate the evolution of the disease as well as the early result of the treatment, in order to offer a different baseline to other countries. It is also interesting to compare two countries, with a very significant difference in population, where the morbidity and mortality has been so different, and unrelated to the size of the country
Equine grass sickness (a multiple systems neuropathy) is associated with alterations in the gastrointestinal mycobiome
Background: Equine grass sickness (EGS) is a multiple systems neuropathy of grazing horses of unknown aetiology. An apparently identical disease occurs in cats, dogs, rabbits, hares, sheep, alpacas and llamas. Many of the risk factors for EGS are consistent with it being a pasture mycotoxicosis. To identify potential causal fungi, the gastrointestinal mycobiota of EGS horses were evaluated using targeted amplicon sequencing, and compared with those of two control groups. Samples were collected post mortem from up to 5 sites in the gastrointestinal tracts of EGS horses (EGS group; 150 samples from 54 horses) and from control horses that were not grazing EGS pastures and that had been euthanased for reasons other than neurologic and gastrointestinal diseases (CTRL group; 67 samples from 31 horses). Faecal samples were also collected from healthy control horses that were co-grazing pastures with EGS horses at disease onset (CoG group; 48 samples from 48 horses).
Results: Mycobiota at all 5 gastrointestinal sites comprised large numbers of fungi exhibiting diverse taxonomy, growth morphology, trophic mode and ecological guild. FUNGuild analysis parsed most phylotypes as ingested environmental microfungi, agaricoids and yeasts, with only 1% as gastrointestinal adapted animal endosymbionts. Indices of alpha-diversity indicated that mycobiota richness and diversity varied throughout the gastrointestinal tract and were greater in EGS horses. There were significant inter-group and inter-site differences in mycobiota structure. A large number of phylotypes were differentially abundant among groups. Key phylotypes (n=56) associated with EGS were identified that had high abundance and high prevalence in EGS samples, significantly increased abundance in EGS samples, and were important determinants of the inter-group differences in mycobiota structure. Many key phylotypes were extremophiles and/or were predicted to produce cytotoxic and/or neurotoxic extrolites.
Conclusions: This is the first reported molecular characterisation of the gastrointestinal mycobiota of grazing horses. Key phylotypes associated with EGS were identified. Further work is required to determine whether neurotoxic extrolites from key phylotypes contribute to EGS aetiology or whether the association of key phylotypes and EGS is a consequence of disease or is non-causal
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