Enabling More Users to Benefit from Near-Field Communications: From Linear to Circular Array

Massive multiple-input multiple-output (MIMO) for 5G is evolving into the extremely large-scale antenna array (ELAA) to increase the spectrum efficiency by orders of magnitude for 6G communications. ELAA introduces spherical-wave-based near-field communications, where channel capacity can be significantly improved for single-user and multi-user scenarios. Unfortunately, the near-field region at large incidence/emergence angles is greatly reduced with the widely studied uniform linear array (ULA). Thus, many randomly distributed users may fail to benefit from near-field communications. In this paper, we leverage the rotational symmetry of uniform circular array (UCA) to provide uniform and enlarged near-field regions at all angles, enabling more users to benefit from near-field communications. Specifically, by exploiting the geometrical relationship between UCA and users, the near-field beamforming technique for UCA is developed. Based on the analysis of near-field beamforming, we reveal that UCA is able to provide a larger near-field region than ULA in terms of the effective Rayleigh distance. Moreover, a concentric-ring codebook is designed to realize efficient codebook-based beamforming in the near-field region. In addition, we find out that UCA could generate orthogonal near-field beams along the same direction when the focal point of the near-field beam is exactly the zeros of other beams, which has the potential to further improve spectrum efficiency in multi-user communications compared with ULA. Simulation results are provided to verify the effectiveness of theoretical analysis and feasibility of UCA to enable more users to benefit from near-field communications by broadening the near-field region.Comment: Accepted by IEEE TWC. In this paper, the rotational symmetry of UCA is leveraged to provide uniform and enlarged near-field regions, enabling more users to benefit from near-field communications. Simulation codes will be provided to reproduce the results in this paper: http://oa.ee.tsinghua.edu.cn/dailinglong/publications/publications.htm

Achieving quantum advantages for image filtering

Image processing is a fascinating field for exploring quantum algorithms. However, achieving quantum speedups turns out to be a significant challenge. In this work, we focus on image filtering to identify a class of images that can achieve a substantial speedup. We show that for images with efficient encoding and a lower bound on the signal-to-noise ratio, a quantum filtering algorithm can be constructed with a polynomial complexity in terms of the qubit number. Our algorithm combines the quantum Fourier transform with the amplitude amplification technique. To demonstrate the advantages of our approach, we apply it to three typical filtering problems. We highlight the importance of efficient encoding by illustrating that for images that cannot be efficiently encoded, the quantum advantage will diminish. Our work provides insights into the types of images that can achieve a substantial quantum speedup.Comment: 8 pages, 9 figure

Smoke-suppressant and flame-retardant rigid polyurethane foam obtained via processing based on saccharomycetes fungus and ammonium molybdate

The present work proposes an environmentally friendly, simple, and efficient way to impart smoke suppression and flame retardancy to rigid polyurethane foam (RPUF) by soaking the pristine RPUF for short periods in the saccharomycetes fungus (SF) solution and then in the ammonium molybdate (AM) solution. The co-addition of SF and AM exhibit good performance on smoke suppression and flame retardant. The level of flammability, thermal degradation behavior, and combustion properties of the samples are evaluated mainly via vertical burning tests, thermogravimetric analysis, and calorimetry, respectively. The proportions of 16SF/3AM/RPUF are varied to maximize the performance of the processed RPUF samples in terms of both smoke suppression and flame retardancy, which are substantially increased by the optimal sample compared to those of pristine RPUF

The Role of Sirt1 in Bile Acid Regulation during Calorie Restriction in Mice.

Sirtuin 1 (Sirt1) is an NAD+-dependent protein deacetylase that is proposed to mediate many health-promoting effects of calorie restriction (CR). We recently reported that short-term CR increased the bile acid (BA) pool size in mice, likely due to increased BA synthesis in liver. Given the important role of Sirt1 in the regulation of glucose, lipid, as well as BA metabolism, we hypothesized that the CR-induced increase in BAs is Sirt1-dependent. To address this, the present study utilized genetically-modified mice that were Sirt1 loss of function (liver knockout, LKO) or Sirt1 gain of function (whole body-transgenic, TG). Three genotypes of mice (Sirt1-LKO, wild-type, and Sirt1-TG) were each randomly divided into ad libitum or 40% CR feeding for one month. BAs were extracted from various compartments of the enterohepatic circulation, followed by BA profiling by UPLC-MS/MS. CR increased the BA pool size and total BAs in serum, gallbladder, and small intestine. The CR-induced increase in BA pool size correlated with the tendency of increase in the expression of the rate-limiting BA-synthetic enzyme Cyp7a1. However, in contrast to the hypothesis, the CR-induced increase in BA pool size and Cyp7a1 expression was still observed with ablated expression of Sirt1 in liver, and completely suppressed with whole-body overexpression of Sirt1. Furthermore, in terms of BA composition, CR increased the ratio of 12α-hydroxylated BAs regardless of Sirt1 genotypes. In conclusion, the CR-induced alterations in BA pool size, BA profiles, and expression of BA-related genes do not appear to be dependent on Sirt1

Summary of BA regulation during CR in various Sirt1 genetically-modified mice.

<p>In WT mice, CR increases the BA pool size and total BAs in serum, gallbladder, and small intestine. Additionally, the expression of Cyp7a1 also tends to be increased, suggesting more BA synthesis in liver. However, the CR-induced increase in BA pool size and Cyp7a1 expression is still observed with ablated expression of Sirt1 in liver, and completely suppressed with whole-body overexpression of Sirt1. Furthermore, CR-induced alterations in BA composition, especially the increase in the ratio of 12α- vs non-12α-hydroxylated BAs), remain similar in all three genotypes of mice.</p

The BA pool size and total BAs in various compartments of enterohepatic circulation.

<p>Sirt1-LKO, WT, and Sirt1-TG mice were given ad libitum (AL) or 40% CR feeding (n = 5) for one month. BAs were extracted from liver, gallbladder (GB), small (SI) and large intestine (LI), and twenty major individual BAs were quantified by UPLC-MS/MS. The BA pool size (A) is estimated by adding total BAs in liver, GB, and intestine (B). (C) shows total BAs in serum. Data are presented as means ± SEM of 5 mice. The triangle represents increased expression of Sirt1 in liver. # represents differences compared to WT mice, by one-way ANOVA, followed by Duncan’s post-hoc test (<i>p</i> < 0.05). * represents differences compared to AL mice of the same genotype by Student's <i>t</i>-test (<i>p</i> < 0.05).</p

Expression of Cyp7a1 transcription regulators in liver and ileum.

<p>The mRNAs of key factors that regulate basal Cyp7a1 transcription (HNF4α, LRH-1, and PGC-1α) and BA-feedback inhibition of Cyp7a1 transcription (both FXR-SHP in liver and FXR-Fgf15 in ileum) were quantified in (A) liver and (B) intestine. Data are presented as means ± SEM of 5 mice. The triangle represents increased expression of Sirt1 in liver. # represents differences compared to WT mice, by one-way ANOVA, followed by Duncan’s post-hoc test (<i>p</i> < 0.05). * represents differences compared to AL mice of the same genotype by Student's <i>t</i>-test (<i>p</i> < 0.05).</p

Body weight, liver weight, and Sirt1 expression.

<p>After one-month of 40% CR, body weight (BW) and liver weight (LW) of Sirt1-LKO, WT, and Sirt1-TG mice were recorded. (A) The ratio of LW to BW was calculated. (B) The expression of Sirt1 was quantified in liver and ileum of three genotypes of mice that were either AL- or CR-fed. Data are presented as means ± SEM of 5 mice. The triangle represents increased expression of Sirt1 in liver. # represents differences compared to WT mice, by one-way ANOVA, followed by Duncan’s post-hoc test (<i>p</i> < 0.05). * represents differences compared to AL mice of the same genotype by Student's <i>t</i>-test (<i>p</i> < 0.05).</p

Expression of BA transporters in the enterohepatic circulation.

<p>The mRNAs of proteins involved in BA transport in liver (uptake: Ntcp, Oatp1b2, and Oatp1a1; efflux: Bsep, Mrp2, and Mrp3) (A) and ileum (uptake: Asbt; intracellular transport: Ibabp; efflux: Ostα, Ostβ) (B) were quantified. Data are presented as means ± SEM of 5 mice. The triangle represents increased expression of Sirt1 in liver. # represents differences compared to WT mice, by one-way ANOVA, followed by Duncan’s post-hoc test (<i>p</i> < 0.05). * represents differences compared to AL mice of the same genotype by Student's <i>t</i>-test (<i>p</i> < 0.05).</p