Feature ghost imaging for color identification.

On the basis of computational ghost imaging (CGI), we present a new imaging technique, feature ghost imaging (FGI), which can convert the color information into distinguishable edge features in retrieved grayscale images. With the edge features extracted by different order operators, FGI can obtain the shape and the color information of objects simultaneously in a single-round detection using one single-pixel detector. The feature distinction of rainbow colors is presented in numerical simulations and the verification of FGI's practical performance is conducted in experiments. Furnishing a new perspective to the imaging of colored objects, our FGI extends the function and the application fields of traditional CGI while sustaining the simplicity of the experimental setup.

Anti-loss-compression image encryption based on computational ghost imaging using discrete cosine transform and orthogonal patterns.

As an emerging imaging technique, computational ghost imaging (CGI) has its unique application in image encryption. However, the long imaging time and high requirement of transmitting data, both in the size of data and vulnerability of lossy compression, limit its application in the practical communications. Using discrete cosine transform to sparse bucket signals of CGI, we here propose a method by transforming the bucket signals from the sensing matrix domain to the space domain, enhancing the ability of the bucket signals (i.e., encrypted image) to resist the lossy compression. Based on the principle of CGI, we first propose to use gradient descent to find an orthogonal matrix as the encryption key, then test the performance of our method at different quality factors and undersampling rates. Both simulations and experimental results demonstrate that our encryption method shows great resistance to the traditional lossy compression methods and has good performance in the undersampling conditions. Our method provides a convenient way to transmit the bucket signals of CGI by the format that involves lossy compression and thus camouflages itself while significantly reducing the amount of data being transmitted.

Computational ghost imaging encryption with a pattern compression from 3D to 0D.

The principle of computational ghost imaging (GI) offers a potential application in optical encryption. Nevertheless, large numbers of keys composed of random or specific patterns set an obstacle to its application. Here, we propose a series of pattern compression methods based on computational GI, in which thousands of patterns are replaced by a single standard image (i.e., two-dimensional data), a sequence of numbers (i.e., one-dimensional data) or the fractional part of an irrational number (i.e., zero-dimensional data). Different pattern compression methods are tested in both simulations and experiments, and their error tolerances in encryption are further discussed. Our proposed methods can greatly reduce the pattern amount and enhance encryption security, which pushes forward the application of computational GI, especially in optical encryption.

Single-pixel imaging with Gao-Boole patterns.

Single-pixel imaging (SPI) can perceive the world using only a single-pixel detector, but long sampling times with a series of patterns are inevitable for SPI, which is the bottleneck for its practical application. Developing new patterns to reduce the sampling times might provide opportunities to address this challenge. Based on the Kronecker product of Hadamard matrix, we here design a complete set of new patterns, called Gao-Boole patterns, for SPI. Compared to orthogonal Hadamard basis patterns with elements valued as +1 or -1, our Gao-Boole patterns are non-orthogonal ones and the element values are designed as +1 or 0. Using our Gao-Boole patterns, the reconstructed quality of a target image (N × N pixels) is as high as the Hadamard one but only with half pattern numbers of the Hadamard ones, for both full sampling (N2 for Gao-Boole patterns, 2N2 for Hadamard basis patterns) and undersampling cases in experiment. Effectively reducing the patterns numbers and sampling times without sacrificing imaging quality, our designed Gao-Boole patterns provide a superior option for structural patterns in SPI and help to steer SPI toward practical imaging application.

Near-infrared ITO-based photonic hypercrystals with large angle-insensitive bandgaps.

The angle-sensitive photonic bandgap (PBG) is one of the typical features of one-dimensional photonic crystals. Based on the phase-variation compensation effect between the dielectric and hyperbolic metamaterials (HMMs), angle-insensitive PBGs can be realized in photonic hypercrystals. However, since hypercrystals are usually constructed using metal components, these angle-insensitive PBGs are mostly limited to narrow bandwidths in visible range. Here, we replace metal with indium tin oxide (ITO) to construct HMMs in the near-infrared range. In these ITO-based HMMs, we experimentally demonstrate the negative refraction of light in transverse magnetic polarization. With this HMM component, we realize a photonic hypercrystal with an angle-insensitive PBG in the wavelength range of 1.15-2.02 µm. These ITO-based hypercrystals with large angle-insensitive PBGs can find applications in near-infrared reflectors or filters.

Experimental and Computational Studies of Palladium-Catalyzed Spirocyclization via a Narasaka-Heck/C(sp3 or sp2)-H Activation Cascade Reaction.

The first synthesis of highly strained spirocyclobutane-pyrrolines via a palladium-catalyzed tandem Narasaka-Heck/C(sp3 or sp2)-H activation reaction is reported here. The key step in this transformation is the activation of a δ-C-H bond via an in situ generated σ-alkyl-Pd(II) species to form a five-membered spiro-palladacycle intermediate. The concerted metalation-deprotonation (CMD) process, rate-determining step, and energy barrier of the entire reaction were explored by density functional theory (DFT) calculations. Moreover, a series of control experiments was conducted to probe the rate-determining step and reversibility of the C(sp3)-H activation step.

Value of Xpert MTB/RIF Using Bronchoalveolar Lavage Fluid for the Diagnosis of Pulmonary Tuberculosis: a Systematic Review and Meta-analysis.

The performance of Xpert MTB/RIF using bronchoalveolar lavage fluid (BAL) for the diagnosis of pulmonary tuberculosis (PTB) remains unclear. Therefore, a systematic review/meta-analysis was conducted. Studies published before 31 December 2019 were retrieved from the PubMed, Embase, and Web of Science databases using the keywords "pulmonary tuberculosis," "Xpert MTB/RIF," and "BAL." Two independent evaluators extracted the data and assessed the bias risk of the included studies. A random-effects model was used to calculate the overall sensitivity, specificity, positive and negative likelihood ratios (PLR and NLR, respectively), diagnostic odds ratio (DOR), and the area under the curve (AUC), as well as the respective 95% confidence intervals (CIs). Nineteen trials involving 3,019 participants met the inclusion criteria. Compared to the culture method, the pooled sensitivity, specificity, PLR, NLR, DOR, and the AUC with 95% CIs of Xpert MTB/RIF were 0.87 (0.84 to 0.90), 0.92 (0.91 to 0.93), 10.21 (5.78 to 18.02), 0.16 (0.12 to 0.22), 78.95 (38.59 to 161.53), and 0.9467 (0.9462 to 0.9472), respectively. Relative to the composite reference standard, the observed values were 0.69 (0.65 to 0.72), 0.98 (0.98 to 0.99), 37.50 (18.59 to 75.62), 0.30 (0.21 to 0.43), 171.98 (80.82 to 365.96), and 0.9691 (0.9683 to 0.9699), respectively. All subgroups, except children, showed high sensitivity and specificity. In conclusion, the use of Xpert MTB/RIF in the context of BAL samples has a high diagnostic performance for PTB (except for children) and may serve as an alternative rapid diagnostic tool.

Inverse computational ghost imaging for image encryption.

Computer-generated random patterns and bucket detection are two key characteristics of computational ghost imaging (GI), which offer it a potential application in optical encryption. Here, we propose an inverse computational GI scheme, in which bucket signals are firstly selected and then random patterns are calculated correspondingly. Different GI reconstruction algorithms are used to test the inverse computational GI, and the relationship between imaging quality and error ratio factor is discussed as well. Compared with computational GI, our inverse one not only has disguised bucket signals but also provides an opportunity to combine with other cryptographies, both of which enrich the GI-based encryption process and enhance the security simultaneously.

Quasiperiodic metamaterials empowered non-metallic broadband optical absorbers.

Realizing a polarization-insensitive broadband optical absorber plays a key role in the implementation of microstructure optoelectrical devices with on-demand functionalities. However, the challenge is that most of these devices involve the constituent metals, thus suffering from poor chemical and thermal stability and a complicated manufacturing process. In addition, the extreme contrast between the negative (metallic) and positive (dielectric) real parts of the constituent permittivities can cause additional problems in the design of structural devices. Based on these facts, this work proposes a design of planar broadband one-dimensional structure based on Fibonacci geometry. Experimental results show that the proposed planar structure exhibits high absorptivity behavior independent of polarization and angle in the wavelength range of 300-1000 nm. The absorptivity remains more than 80% when the incident angle is 60°. This proof-of-concept represents a new strategy for realizing non-metallic broadband optical absorbers with advantages of polarization-independence, low-cost, and wide-field-of-view and paves the way for light manipulation under harsh conditions.

Nonreciprocal Tamm plasmon absorber based on lossy epsilon-near-zero materials.

Contrary to conventional Tamm plasmon (TP) absorbers of which narrow absorptance peaks will shift toward short wavelengths (blueshift) as the incident angle increases for both transverse magnetic (TM) and transverse electric (TE) polarizations, here we theoretically and experimentally achieve nonreciprocal absorption in a planar photonic heterostructure composed of an isotropic epsilon-near-zero (ENZ) slab and a truncated photonic crystal for TM polarization. This exotic phenomenon results from the interplay between ENZ and material loss. And the boundary condition across the ENZ interface and the confinement effect provided by the TP can enhance the absorption in the ENZ slab greatly. As a result, a strong and nonreciprocal absorptance peak is observed experimentally with a maximum absorptance value of 93% in an angle range of 60∼70°. Moreover, this TP absorber shows strong angle-independence and polarization-dependence. As the characteristics above are not at a cost of extra nanopatterning, this structure is promising to offer a practical design in narrowband thermal emitter, highly sensitive biosensing, and nonreciprocal nonlinear optical devices.

Full-color photon-counting single-pixel imaging.

We propose and experimentally demonstrate a high-efficiency single-pixel imaging (SPI) scheme by integrating time-correlated single-photon counting (TCSPC) with time-division multiplexing to acquire full-color images at an extremely low light level. This SPI scheme uses a digital micromirror device to modulate a sequence of laser pulses with preset delays to achieve three-color structured illumination, then employs a photomultiplier tube into the TCSPC module to achieve photon-counting detection. By exploiting the time-resolved capabilities of TCSPC, we demodulate the spectrum-image-encoded signals, and then reconstruct high-quality full-color images in a single round of measurement. Based on this scheme, strategies such as single-step measurement, high-speed projection, and undersampling can further improve imaging efficiency.

Use of thiazide diuretics for the prevention of recurrent kidney calculi: a systematic review and meta-analysis.

BACKGROUND: Thiazide diuretics reduce the risk of recurrent kidney calculi in patients with kidney calculi or hypercalciuria. However, whether thiazide diuretics can definitely prevent recurrent kidney calculi remains unclear. We aimed to evaluate the effect and safety of thiazide diuretics on recurrent kidney calculi. METHODS: The PubMed, Cochrane Library, and EMBASE databases were systematically searched using the keywords thiazide diuretics and kidney calculi to identify randomized controlled trials (RCTs). The primary outcome was the incidence of recurrent kidney calculi, and the secondary outcome was the 24-h urinary calcium level. The pooled risk ratio (RR), risk difference (RD), standardized mean difference (SMD), and 95% confidence interval (CI) were calculated. The evidence quality was graded using the GRADE criteria, and recommendations for recurrent kidney calculus prevention using thiazide diuretics were reassessed. RESULTS: Eight RCTs involving 571 patients were included. The pooled RR for the incidence of kidney calculi in the thiazide diuretic groups was 0.44 (95% CI 0.33-0.58, P < 0.0001) compared to that in the placebo and untreated groups; the pooled RD was - 0.23 (95% CI - 0.30 to - 0.16, P < 0.0001). The pooled SMD for the 24-h urinary calcium level was - 18.59 (95% CI - 25.11 to - 12.08, P < 0.0001). The thiazide diuretic groups had a high incidence of adverse reactions and low tolerance. The evidence quality for decrease in kidney calculus incidence using thiazide diuretics was low, while that for the 24-h urinary calcium level decrease among those with recurrent kidney calculi was moderate, and that for the decrease in kidney calculus incidence using short-acting and long-acting thiazide diuretics was low. The overall strength of recommendation for prevention of recurrent renal calculi using thiazide diuretics was not recommended. The subgroup and sensitivity analysis findings were robust. CONCLUSIONS: Long-term use of thiazide diuretics reduces the incidence of recurrent renal calculi and 24-h urinary calcium level. However, the benefits are insufficient, and the evidence quality is low. Considering the adverse effects, poor patient compliance, and economic burden of long-term medication, their use in preventing recurrent kidney calculi is not recommended.

Computational ghost imaging with spatiotemporal encoding pseudo-random binary patterns.

Computational ghost imaging (CGI) can reconstruct the pixelated image of a target without lenses and image sensors. In almost all spatial CGI systems using various patterns reported in the past, people often only focus on the distribution of patterns in the spatial dimension but ignore the possibility of encoding in the time dimension or even the space-time dimension. Although the random illumination pattern in CGI always brings some inevitable background noise to the recovered image, it has considerable advantages in optical encryption, authentication, and watermarking technologies. In this paper, we focus on stimulating the potential of random lighting patterns in the space-time dimension for embedding large amounts of information. Inspired by binary CGI and second-order correlation operations, we design two novel generation schemes of pseudo-random patterns for information embedding that are suitable for different scenarios. Specifically, we embed a total of 10,000 ghost images (64 × 64 pixels) of the designed Hadamard-matrix-based data container patterns in the framework of CGI, and these ghost images can be quantitatively decoded to two 8-bit standard grayscale images, with a total data volume of 1, 280, 000 bits. Our scheme has good noise resistance and a low symbol error rate. One can design the number of lighting patterns and the information capacity of the design patterns according to the trade-off between accuracy and efficiency. Our scheme, therefore, paves the way for CGI using random lighting patterns to embed large amounts of information and provides new insights into CGI-based encryption, authentication, and watermarking technologies.

Three-Component Ruthenium-Catalyzed Direct Meta-Selective C-H Activation of Arenes: A New Approach to the Alkylarylation of Alkenes.

Multicomponent reactions are fundamentally different from two-component reactions, as multicomponent reactions can enable the efficient and step-economical construction of complex molecular scaffolds from simple precursors. Here, an unprecedented three-component direct C-H addition was achieved in the challenging meta-selective fashion. Fluoroalkyl halides and a wide range of alkenes, including vinylarenes, unactivated alkenes, and internal alkenes, were employed as the coupling partners of arenes in this strategy. The detailed mechanism presented is supported by kinetic isotope studies, radical clock experiments, and density functional theory calculations. Moreover, this strategy provided access to various fluoride-containing bioactive 1,1-diarylalkanes and other challenging synthetically potential products.

Integrated dual-channel sensing utilizing polarized dissimilation based on photonic spin-orbit interaction.

An integrated dual-channel sensing method utilizing polarized dissimilation is investigated with an appropriately designed plasmonic metasurface. By assembling two different kinds of nano-gold antennas to constitute a periodic array, the phase of diffraction fields contains both spin-dependent geometric phase and resonance-dependent dynamic phase components. Accurate control over the superposition of orthogonal spin components utilizing strong photonic spin-orbit interaction of metasurface leads to dissimilar response of different diffraction orders. The simulation shows that the linear polarization of ±1 diffraction orders rotate in the reverse direction (±19°) with the refractive index variation (1.3-1.5). The sensing method exhibits an extremely high signal-to-noise ratio and stability.

Dynamic contrast-enhanced MRI for the assessment of spinal tumor vascularity: correlation with angiography.

PURPOSE: To determine if dynamic contrast-enhanced MRI (DCE-MRI) could correlate well with invasive angiography in the characterization of spinal tumor vascularity. METHODS: Totally 40 patients with untreated spinal tumors underwent MRI before preoperative angiography and embolization. Tumors were assigned to hypervascular, moderate, or hypovascular groups based on angiographic appearance. Tumor vascularity was also evaluated with enhancement degree on standard MR and with DCE-MRI parameters via ROI analysis of enhanced tumor area. The Spearman correlation coefficient was calculated to determine the correlation between the degree of angiographic vascularity and enhancement on MRI and DCE-MRI parameters. ROC analysis was conducted to assess the appropriate cut-off value. RESULTS: There were 12 hypervascular, 12 moderate, and 16 hypovascular tumors, respectively. The Spearman correlation coefficient between DCE-MRI parameter and the degree of angiographic vascularity was 0.899 (RSlopemax), 0.847 (Slopemax), 0.697 (E max), 0.694 (ERmax), and -0.587 (TTP), respectively, which showed excellent-to-moderate relationships. The RSlopemax cut-off value of 1.325 provided the highest specificity of 100 % and sensitivity of 87.5 % in predicting hypovascular tumors and the value of 1.85 provided the highest sensitivity of 100 % and specificity of 96.4 % in characterizing hypervascular ones. CONCLUSIONS: DCE-MRI is an accurate technique for the assessment of spinal tumor vascularity, which may have a potential value in the decision-making of preoperative embolization.

PagWOX11/12a from hybrid poplar enhances drought tolerance by modulating reactive oxygen species.

WOX11/12 is a homeobox gene of WOX11 and WOX12 in Arabidopsis that plays important roles in crown root development and growth. It has been reported that WOX11/12 participates in adventitious root (AR) formation and different abiotic stress responses, but the downstream regulatory network of WOX11/12 in poplar remains to be further investigated. In this study, we found that PagWOX11/12a is strongly induced by PEG-simulated drought stress. PagWOX11/12a-overexpressing poplar plantlets showed lower oxidative damage levels, greater antioxidant enzyme activities and reactive oxygen species (ROS) scavenging capacity than non-transgenic poplar plants, whereas PagWOX11/12a dominant repression weakened root biomass accumulation and drought tolerance in poplar. RNA-seq analysis revealed that several differentially expressed genes (DEGs) regulated by PagWOX11/12a are involved in redox metabolism and drought stress response. We used RT-qPCR and yeast one-hybrid (Y1H) assays to validate the downstream target genes of PagWOX11/12a. These results provide new insights into the biological function and molecular regulatory mechanism of WOX11/12 in the abiotic resistance processes of poplar.

Air-Stable Self-Driven UV Photodetectors on Controllable Lead-Free CsCu2I3 Microwire Arrays.

The rapid evolution of the Internet of Things has engendered increased requirements for low-cost, self-powered UV photodetectors. Herein, high-performance self-driven UV photodetectors are fabricated by designing asymmetric metal-semiconductor-metal structures on the high-quality large-area CsCu2I3 microwire arrays. The asymmetrical depletion region doubles the photocurrent and response speed compared to the symmetric structure device, leading to a high responsivity of 233 mA/W to 355 nm radiation. Notably, at 0 V bias, the asymmetric device produces an open-circuit voltage of 356 mV and drives to a short-circuit current of 372 pA; meanwhile, the switch ratio (Iph/Idark) reaches up to 103, indicating its excellent potential for detecting weak light. Furthermore, the device maintains stable responses throughout 10000 UV-light switch cycles, with negligible degradation even after 90-day storage in air. Our work establishes that CsCu2I3 is a good candidate for self-powered UV detection and thoroughly demonstrates its potential as a passive device.

Properties of high-order ghost imaging with natural light.

We discuss theoretically the visibility and contrast-to-noise ratio (CNR) of high-order thermal ghost imaging with natural light. Five cases of an object beam and a reference beam with different polarized light are analyzed. Theoretical calculations show that a higher-order N can optimize the ghost imaging in both visibility and CNR in all five cases.

Metalens and microtaper spectrometers on a fingertip.

A multi-foci metalens and a leaky-mode microtaper provide innovative platforms to achieve high-resolution, wideband light spectra in millimeter-sized devices, thereby paving new ways for the commercialization of on-fingertip spectrometers.