Terahertz (THz) wideband ultra-massive multiple-input multiple-output (UM-MIMO) systems are critical for the upcoming 6G. The far- and near-field regions always coexist as the hybrid-field regions in ...the THz wideband UM-MIMO systems, but the existing hybrid-field estimation schemes can not perform well for the wideband channel without prior knowledge of user location information. In this work, we propose an efficient subarray-based hybrid-field channel estimation algorithm for the THz wideband UM-MIMO systems without prior knowledge of user location. The estimation problem is decomposed into a series of sub-problems, each of which considers only one subarray for channel estimation in combination with the wideband sparse detection. Then, the hybrid-field channel is recovered by combining all the subarray channels. Simulation results show that the proposed algorithm is able to recover the hybrid-field wideband channel accurately at a low pilot overhead and the bandwidth has little effect on the performance of the proposed.
The unprecedented increase in wireless data traffic has motivated the development of terahertz communications (THzCom) over the years. Since THzCom would suffer from performance degradation and even ...link outage in mobile scenarios, the integrated sensing and communications (ISAC) are promised to settle the mobility challenges by extracting information from wireless channels. The emerging technique so-called THz-ISAC (T-ISAC) is in the initial stage of theoretical evaluation, yet the existing ISAC theory performs unsatisfactorily without considering THz natures. To this ends, the performance of sensing and communication (S&C) functionalities in T-ISAC systems is researched in this work. Firstly, T-ISAC performance frameworks containing metrics and models are summarized. Combining ISAC theory with THz natures, three aspects of S&C metric correlation in coexistence, coordination and cooperation are orderly elaborated. And the limits of performance in resource-sharing, waveform-integrating and functionality-beneficial gains in T-ISAC systems are accordingly discussed. The challenges and roads ahead of T-ISAC theory efforts are hence concluded into issues on performance models, analysis approaches and metric optimizations.
In this article, a technique based on artificial neural networks (ANNs) is proposed to extract stable complex permittivity and permeability of low-loss materials from transmission/reflection (T/R) ...measurements. The equations of attenuation constant α and phase constant β of a sample-filled transmission line are derived. The calculated α and β are put into an ANN model. The outputs of the ANN model are stable complex permittivity and permeability over the whole measurement frequency range, while the values extracted by other techniques are resonant at the frequencies corresponding to integer multiples of one-half wavelength in the sample materials. Two low-loss materials with substantial thickness are measured in X-band to validate the proposed technique. Compared with the Nicolson-Ross-Weir (NRW) technique, the short-circuited technique, and an ANN technique without the derived equations, the proposed technique provides stable results for the two samples. In addition, the extracted values are compared with the "true values" measured from the thinner samples to further present the advantages of the proposed technique.
Endoscopic sphincterotomy (ES) is the standard treatment for common bile duct stones. The reported findings regarding complications, such as biliary pancreatitis and cholangitis, differ between ...cholecystectomy after ES. The purpose of this study is to compare cholecystectomy outcomes after endoscopic treatment of common bile duct stones whether or not the incidence of recurrent pancreatitis and cholangitis is reduced, especially in high-risk patients.
We analyzed 8 studies, including 7 randomized controlled trials retrieved from the PubMed (1990-2019), Embase (1990-2019), and Cochrane (1990-2019) databases for trials comparing the two strategies for treatment of gallstones after ES. A related study on gallbladder removal after ES was acquired, followed by analysis of each group using RevMan. Risk ratios (RRs) were calculated for categorical variables and differences in means were calculated for continuous variables.
We retrieved a total of 8 studies, including seven randomized controlled trials and one retrospective study. A total of 12,717 patients were included in the study (4922 in the early cholecystectomy group and 7795 in the gallbladder in situ group). During the follow-up period, 41 patients had pancreatitis after ES in the cholecystectomy group and 177 patients in the wait-and-see group. The incidence of pancreatitis in the cholecystectomy group was significantly reduced (RR, 0.38; 95% CI, 0.27-0.53; P < 0.00001; I
= 0%). The incidence of cholangitis and jaundice in the cholecystectomy group was also less than the preserved gallbladder group (RR, 0.31; 95% CI, 0.26-0.38; P < 0.00001; I
= 0%). There was no significant difference in mortality between the two groups (RR, 0.73; 95% CI, 0.52-1.02; P = 0.07; I
= 14%). There was a significant difference in cholecystitis and biliary colic (RR, 0.28; 95% CI, 0.24-0.32; P < 0.00001; I
= 17%).
Early cholecystectomy after removal of common bile duct stones can effectively reduce biliary complications. This is still true for high-risk patients and has no significant effect on the mortality of patients. Laparoscopic cholecystectomy is recommended after ES.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Soft lattice and strong exciton–phonon coupling have been demonstrated in layered double perovskites (LDPs) recently; therefore, LDPs represents a promising class of compounds as excellent ...self‐trapped exciton (STE) emitters for applications in solid‐state lighting. However, few LDPs with outstanding STE emissions have been discovered, and their optoelectronic properties are still unclear. Based on the three‐dimensional (3D) Cs2NaInCl6, we synthesized two 2D derivatives (PEA)4NaInCl8:Sb (PEA=phenethylamine) and (PEA)2CsNaInCl7:Sb with monolayer and bilayer inorganic sheets by a combination of dimensional reduction and Sb‐doping. Bright broadband emissions were obtained for the first time under ambient temperature and pressure, with photoluminescence quantum efficiency (PLQE) of 48.7 % (monolayer) and 29.3 % (bilayer), superior to current known LDPs. Spectroscopic characterizations and first‐principles calculations of excited state indicate the broadband emissions originate from STEs trapped at the introduced SbCl63− octahedron.
Two layered double perovskites of (PEA)4NaInCl8 and (PEA)2CsNaInCl7, with the highest efficiency under ambient temperature and pressure, were successfully prepared. This study clearly presents the origin of self‐trapped exciton emission and provides a feasible strategy to explore new layered perovskite emitters.
Hepatic alveolar echinococcosis (HAE) is a potentially fatal disease caused by the larval growth of Echinococcus multilocularis. We analysed the clinical data of 178 consecutive HAE patients treated ...with definitive radical surgery at our institution. According to the surgical approach: group A patients underwent direct radical hepatic resection; group B patients first underwent percutaneous puncture external drainage, followed by radical hepatic resection 2 months later; group C patients underwent a two-step hepatic resection; and group D patients underwent liver transplantation. The baseline characteristics, mortality, postoperative complications and recurrence rates were evaluated. Symptoms were present in 79.8% (142/178) patients. Bi-lobar lesion was found in 34 (19.1%, 34/178) patients, 47.2% (84/178) of whom had ⩾2 lesions each. There were no intraoperative deaths. The postoperative mortality was 2.29% in group A, 8.62% in group D and 0% in groups B and C. The main cause of death was a serious postoperative complication (Clavien-Dindo grades III-V). Patients were followed-up systematically for a median of 35.8 months (8-72) without recurrence. Active HAE should be treated by radical liver resection, and the complicated alveolar echinococcosis of the liver has been managed whenever possible using principles of radical liver resection by experienced hepatic surgeons.
Histopathological level imaging in a non-invasive manner is important for clinical diagnosis, which has been a tremendous challenge for current imaging modalities. Recent development of ...ultra-high-field (UHF) magnetic resonance imaging (MRI) represents a large step toward this goal. Nevertheless, there is a lack of proper contrast agents that can provide superior imaging sensitivity at UHF for disease detection, because conventional contrast agents generally induce T2 decaying effects that are too strong and thus limit the imaging performance. Herein, by rationally engineering the size, spin alignment, and magnetic moment of the nanoparticles, we develop an UHF MRI-tailored ultra-sensitive antiferromagnetic nanoparticle probe (AFNP), which possesses exceptionally small magnetisation to minimize T2 decaying effect. Under the applied magnetic field of 9 T with mice dedicated hardware, the nanoprobe exhibits the ultralow r
/r
value (~1.93), enabling the sensitive detection of microscopic primary tumours (<0.60 mm) and micrometastases (down to 0.20 mm) in mice. The sensitivity and accuracy of AFNP-enhanced UHF MRI are comparable to those of the histopathological examination, enabling the development of non-invasive visualization of previously undetectable biological entities critical to medical diagnosis and therapy.
Field reconnaissance reports reveal the seismic vulnerability of bridge abutment foundations. To reduce the time and cost of postearthquake repair, modern seismic design specifications allow abutment ...backwalls to fracture before the supporting abutment foundations reach their maximum strength. This design strategy enables abutment backwalls to function as a fuse, thus protecting the abutment foundations from experiencing excessive forces and damage. This paper introduces a new abutment modeling scheme to capture the shear fracture mechanism of straight backwalls in seat abutments. To this end, a backwall connection spring is developed and incorporated into a spring system that simulates the behavior of various abutment components. The importance of considering the backwall fracture is examined by reviewing conventional modeling methodologies for abutments and building companion numerical models. Static pushover and incremental dynamic analyses (IDAs) were conducted for two bridges (single‐ and two‐span) modeled by both the proposed and conventional abutment modeling schemes. Moreover, component‐level fragility curves are developed using IDA results. The comparisons show that the conventional abutment modeling schemes significantly overestimate abutment foundation damage and underestimate the likelihood of deck unseating, column damage, and bearing displacement in the passive direction. Conversely, the proposed modeling scheme is able to capture the essential seismic responses of various components in seat abutment bridges. The consideration of backwall fracture in the modeling of abutment components enables a more rational seismic response assessment of bridges with backwalls, which are likely to be damaged during earthquakes, particularly for bridges which are seismically designed to protect abutment foundations.
Li metal is the ultimate choice for the anode in next‐generation high energy density rechargeable batteries. However, undesired dendrite growth, dead Li formation, and a large volume change of the ...lithium metal anode lead to severe safety hazards such as short‐circuiting, fire, or even explosion. Graphene oxide (GO) in large areas has been prepared as the Li metal host via a continuous centrifugal casting method. Aligned microchannels are then fabricated in it by a simple punching method using 3D printed templates. The GO matrix effectively regulates the lithium plating/stripping behavior while the aligned channels uniformly distributes the Li‐ion flux and provides short Li‐ion diffusion paths. The Li/ holey GO composite is flexible with a controllable thickness from 50 to 150 µm, which corresponds to capacities from 9.881 to 27.601 mAh cm−2. As a result, the anode has a low overpotential of 30 mV after 100 h, a high capacity of ≈3538 mAh g−1 (91.4% of the theoretical capacity), and a superior rate ability of up to 50 C with a LiFePO4 cathode. The holey GO/Li electrode is also paired with other cathodes and used in pouch cells, indicating its suitability for various high‐energy battery systems.
Graphene oxide (GO) in large areas has been prepared as the Li metal host via a continuous centrifugal casting method. Aligned microchannels are fabricated in it by a simple punching method using 3D printed templates. The GO matrix effectively regulates the lithium plating/stripping behavior while the aligned channels uniformly distribute the Li‐ion flux and provide short Li‐ion diffusion paths.
PDF
