Abstract
We report the observations of FRB 20220912A using the Five-hundred-meter Aperture Spherical radio Telescope. We conducted 17 observations totaling 8.67 hr and detected a total of 1076 bursts ...with an event rate up to 390 hr
−1
. The cumulative energy distribution can be well described using a broken power-law function with the lower- and higher-energy slopes of −0.38 ± 0.02 and −2.07 ± 0.07, respectively. We also report the
L
-band (1–1.5 GHz) spectral index of the synthetic spectrum of FRB 20220912A bursts, which is −2.6 ± 0.21. The average rotation measure value of the bursts from FRB 20220912A is −0.08 ± 5.39 rad m
−2
, close to 0 rad m
−2
and was relatively stable over 2 months. Most bursts have nearly 100% linear polarization. About 45% of the bursts have circular polarization with Signal-to-Noise ratio > 3, and the highest circular polarization degree can reach 70%. Our observations suggest that FRB 20220912A is located in a relatively clean local environment with complex circular polarization characteristics. These various behaviors imply that the mechanism of circular polarization of FRBs likely originates from an intrinsic radiation mechanism, such as coherent curvature radiation or inverse Compton scattering inside the magnetosphere of the FRB engine source (e.g., a magnetar).
The air flow and pollutant dispersion within a group of street canyons ventilated merely by thermal buoyancy force induced by heated building surfaces are examined by CFD model using SST k-ω ...turbulence model for different urban skyline configurations. Pollutants emitted from the bottom of street canyon roughly mimic the traffic exhaust releasing. Numerical results are validated well with former theoretical results on thermal boundary flow adjacent to a heated vertical wall. The air exchange rate per hour (ACH) and pollutant retention time are adopted to evaluate the canyon ventilation performance. An exponential relationship could be established between the pollutant retention time and the thermal boundary flow rate. A semi-empirical formula is proposed by using the theoretical results of thermal boundary layer and two empirical constants derived from the present simulation results, which could be used to evaluate the ventilation performance at the urban design. As the convergence flow at the street canyon roof decays from urban rim to urban center, the pollutant retention time differs from canyon to canyon. The “protuberant” skyline configuration is found more effectively in purifying the street canyons at urban edge, in contrast, the “concave” skyline configuration shows higher purification efficiency at urban center. Present research could benefit for design purpose and environmental impact assessment.
•Canyon dispersion was modelled under the regime of pure buoyancy driven flows.•Theoretical evaluation on the air exchange rate at canyon roof was presented.•Air exchange rates were of linear relationships with thermal boundary flow rates.•Thermal plume merging was a key pattern for near-ground level pollutant dilution.•Pollutant retention time reduces exponentially with the increase of boundary flow rate.
•Urban morphology with unique packaging density and multiple frontal area densities.•Channeling flow rates at block arrays are hardly influenced by the frontal area density.•Air exchange at canopy ...top region plays a key role in pedestrian level ventilation.•Linear relationship is found between AER of the canopy and PFR of urban array.•Reduction of building frontal area density could enhance urban neighborhood ventilation.
Improved ventilation in an urban residential neighborhood is a determinant for better energy efficiency and air quality of the neighborhood. This is particularly important for the real estimates recently developed in many cities in China, as these neighborhoods are built with high density. In this paper, we consider in an idealized neighborhood with two categories of packaging building densities (λp) of 0.25 and 0.44, which respectively represent medium and compact urban development. For each packaging density, the frontal area density of arrays is varied from 0.125 to 0.5 through adding building blocks and reducing building size simultaneously. Computational fluid dynamics simulations are carried out to predict the wind flow through the building arrays by the use of renormalization group (RNG) k-ε turbulence model. Our predictions are validated by comparing with experimental data. Numerical results reveal that ventilation rate could be greatly enhanced when a low level of packaging building density is maintained. The momentum exchange rate at the canopy roof level is effectively strengthened when the frontal area density decreases, together with a reduction of ventilation in the urban canopy layer (UCL). Additionally, a linear relationship is found between the UCL ventilation rate and the momentum exchange rate at the urban canopy roof level. For a constant packaging density, reducing frontal area density improves the city block ventilation by enhancing the air exchange rate at the roof level rather than increasing horizontal drag. This paper also illustrates a practical strategy in optimum neighborhood building layout design to minimize the pollutant level.
During the sunny days with very weak wind, thermal buoyancy forces will play a crucial role in the airflow and urban thermal environment. The merging effect of urban building plumes is particularly ...investigated by the use of unsteady Reynolds-averaged Navier Stokes (URANS) methodology. After testing against benchmark theoretical results, the SST k-ω model showing better performance in capturing the near wall processes and it was adopted to simulate the urban turbulent flows. The airflow patterns and temperature fields are analyzed for seven urban sizes ranging from 3 to 10 rows of buildings and six aspect ratios ranging from 0.5 to 3.0. The merging of thermal plumes induces a horizontal convergence flow, resulting in stagnant region at the urban center. A typical urban heat island temperature distribution with a peak value at the urban center is then found. Additionally, with the increase of urban size, the averaged velocity with the canyon decreases and averaged temperature increases. The average velocity within the street canyon decreases monotonously and the vortices number increases with the aspect ratio (building height H to the street width W). The average temperature also increases with aspect ratio, except when the aspect ratio increases from 2.0 to 2.5, where the flow structure within the street canyon changes from a three vortices structure into a four vortices structure. This research could provide a new idea about how urban heat island is formed and the relation between its intensity with urban size and geometry.
•The urban building plumes merging is numerically investigated.•UHI temperature distribution is observed under very weak synoptic wind.•Hot air is trapped within urban canyons due to plume merging and vortices.•Temperature level in the city centre increases monotonously with urban size.•Thermal environment within street canyons is directly related to the flow structure.
This paper presents the result of the search for pulses from the fast radio burst FRB 20220912A with the LPA LPI antenna at a frequency of 111 MHz during the period of activity in October–November ...2022. As a result of observations, pulses were recorded on October 18, 30 and November 12 with a dispersion measure of
pc/cm
3
and a peak flux density of 626, 354, and 203 Jy, respectively. The registration of the FRB 20220912A radio burst with the FAST radio telescope on October 28 in the frequency range of 1–1.5 GHz is also reported. The data at other frequencies are analyzed, the dependence of the pulse width on the frequency
is obtained.
The pedestrian level pollutant transport in street canyons with multiple aspect ratios (H/W) is numerically investigated in the present work, regarding of various unstable thermal stratification ...scenarios and plain surrounding. Non-isothermal turbulent wind flow, temperature field and pollutant spread within and above the street canyons are solved by the realizable k-ε turbulence model along with the enhanced wall treatment. One-vortex flow regime is observed for shallow canyons with H/W=0.5, whereas multi-vortex flow regime is observed for deep canyons with H/W=2.0. Both one-vortex and multi-vortex regimes could be observed for the street canyons with H/W=1.0, where the secondary vortex could be initiated by the flow separation and intensified by unstable thermal stratification. Air exchange rate (AER) and pollutant retention time are adopted to respectively evaluate the street canyon ventilation and pollutant removal performance. A second-order polynomial functional relationship is established between AER and Richardson number (Ri). Similar functional relationship could be established between retention time and Ri, and it is only valid for canyons with one-vortex flow regime. In addition, retention time could be prolonged abruptly for canyons with multi-vortex flow regime. Very weak secondary vortex is presented at the ground level of deep canyons with mild stratification, where pollutants are highly accumulated. However, with the decrease of Ri, pollutant concentration adjacent to the ground reduces accordingly. Present research could be applied to guide the urban design and city planning for enhancing pedestrian environment.
The pedestrian level pollutant transport in street canyons with multiple aspect ratios (H/W) is numerically investigated in the present work, regarding of various unstable thermal stratification scenarios and plain surrounding. Air exchange rate (AER) and pollutant retention time are adopted to evaluate the street canyon ventilation and pollutant removal performance, respectively. A second-order polynomial functional relationship is established between AER and Richardson number (Ri). Similar functional relationship could be established between retention time and Ri, and it is only valid for canyons with one-vortex flow regime. In addition, retention time could be delayed abruptly for canyons with multi-vortex flow regime. Very weak secondary vortex is presented at the ground level of deep canyons with mild stratification, where pollutants are highly accumulated. However, with the decrease of Ri, pollutant concentration adjacent to the ground reduces accordingly. Display omitted
•Ground secondary vortex produced by the flow separation and stratification•Pollutants are accumulated at ground level due to the intervals of buildings.•Multi-vortex flow regime could delay pedestrian level pollutant dilution.•AER and Ri could be correlated by the polynomial functions.•Retention time and Ri could be correlated for one-vortex flow regime.
Non-alcoholic fatty liver disease (NAFLD) and alcohol-related liver disease (ArLD) constitute the primary forms of chronic liver disease, and their incidence is progressively increasing with changes ...in lifestyle habits. Earlier studies have documented a correlation between the occurrence and development of prevalent mental disorders and fatty liver.
To investigate the correlation between fatty liver and mental disorders, thus necessitating the implementation of a mendelian randomization (MR) study to elucidate this association.
Data on NAFLD and ArLD were retrieved from the genome-wide association studies catalog, while information on mental disorders, including Alzheimer's disease, schizophrenia, anxiety disorder, attention deficit hyperactivity disorder (ADHD), bipolar disorder, major depressive disorder, multiple personality disorder, obsessive-compulsive disorder (OCD), post-traumatic stress disorder (PTSD), and schizophrenia was acquired from the psychiatric genomics consortium. A two-sample MR method was applied to investigate mediators in significant associations.
After excluding weak instrumental variables, a causal relationship was identified between fatty liver disease and the occurrence and development of some psychiatric disorders. Specifically, the findings indicated that ArLD was associated with a significantly elevated risk of developing ADHD (OR: 5.81, 95%CI: 5.59-6.03,
< 0.01), bipolar disorder (OR: 5.73, 95%CI: 5.42-6.05,
= 0.03), OCD (OR: 6.42, 95%CI: 5.60-7.36,
< 0.01), and PTSD (OR: 5.66, 95%CI: 5.33-6.01,
< 0.01). Meanwhile, NAFLD significantly increased the risk of developing bipolar disorder (OR: 55.08, 95%CI: 3.59-845.51,
< 0.01), OCD (OR: 61.50, 95%CI: 6.69-565.45,
< 0.01), and PTSD (OR: 52.09, 95%CI: 4.24-639.32,
< 0.01).
Associations were found between genetic predisposition to fatty liver disease and an increased risk of a broad range of psychiatric disorders, namely bipolar disorder, OCD, and PTSD, highlighting the significance of preventive measures against psychiatric disorders in patients with fatty liver disease.
Hypertriglyceridemia is the third leading cause of acute pancreatitis (AP), and its incidence is increasing. Due to its relatively insidious etiology, it is easy to be ignored in the early stages. In ...China, Chaiqin Chengqi Decoction (CQCQD) has long been employed for treating AP.
To evaluate the effectiveness of CQCQD in patients diagnosed with mild/ moderately severe hypertriglyceridemic AP (HTG-AP).
In this study, the clinical data of 39 patients with HTG-AP admitted from January 2019 to November 2022 were collected. The changes of blood lipids, gastrointestinal symptoms, and abdominal pain before and after treatment were analyzed and compared between the two groups.
Twenty patients were treated with the conventional HTG-AP regimen, and 19 patients were additionally treated with CQCQD. After receiving treatment, the triglycerides (TG) level of the CQCQD group was lower than that of the CQCQD group (3.14 ± 0.25 mmol/L
4.96 ± 0.47 mmol/L,
< 0.01). After 3 d of treatment, the patients in the CQCQD group had more bowel movements than the control group (2.51 ± 0.25 times
1.00 ± 0.17 times,
= 0.01). The gastrointestinal function of most patients returned to normal, and the acute gastrointestinal injury score was significantly lower than that of the control group (0.11 ± 0.07
0.42 ± 0.11,
< 0.01).
In patients with HTG-AP, CQCQD can significantly reduce the TG level, shorten the recovery time of defecation, significantly improve the gastrointestinal function.
Magnesium and its alloys as biodegradable implant materials can be potentially used in cardiovascular and orthopedic devices. However, few studies have focused on its application in esophageal ...stents. In this paper, time-lapse degradation characteristics of pure Mg were analyzed by scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, hydrogen evolution, pH and electrochemical measurements after immersion in artificial saliva for different times. Results revealed that a dense degradation product film formed on samples, which mainly consisted of two kinds of layers： one was calcium phosphate compounds with different structures; the other was thin magnesium hydrate layer close to the substrate. Less pH increase and low degradation rate were ob- served in the first 5 days of immersion, which can be ascribed to the formation of a thicker and denser layer on the sample surface with increasing immersion time. And then there was an increase in degradation rate and pH values; the deposition layer remained almost intact after immersion for 6 and 8 days. After 10 days of immersion, the degradation rate and pH value remained stable, and the calcium phosphate layer was delaminated and the inner magnesium hydrate layer was exposed. This study indicated that pure Mg exhibited desirable degradation resistance in artificial saliva, which provided magnesiumbased materials with the potential to be used as esophageal stents.
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