Optimal parameter selection for the THz-CCS system based on an incoherent light source.

Terahertz cross correlation spectroscopy (THz-CCS) systems using broadband incoherent light as the pumping source have received increasing attention from researchers in recent years. However, a comprehensive and in-depth understanding of THz-CCS is still needed to obtain a detailed optimization scheme. Here we systematically investigate the influences of the detection parameters, light propagation process, and pump source on the CCS signals.

Composition, Release, and Transformation of Earthworm Tissue-Bound Residues of Tetrabromobisphenol A in Soil.

Earthworms accumulate organic pollutants to form earthworm tissue-bound residues (EBRs); however, the composition and fate of EBRs in soil remain largely unknown. Here, we investigated the fate of tetrabromobisphenol A (TBBPA)-derived EBRs in soil for 250 days using a C-radioactive isotope tracer and the geophagous earthworm . The EBRs of TBBPA in soil were rapidly transformed into nonextractable residues (NERs), mainly in the form of sequestered and ester-linked residues.

Active terahertz beam steering based on mechanical deformation of liquid crystal elastomer metasurface.

Active metasurfaces are emerging as the core of next-generation optical devices with their tunable optical responses and flat-compact topography. Especially for the terahertz band, active metasurfaces have been developed as fascinating devices for optical chopping and compressive sensing imaging. However, performance regulation by changing the dielectric parameters of the integrated functional materials exhibits severe limitations and parasitic losses.

Terahertz metasurface with multiple BICs/QBICs based on a split ring resonator.

Bound state in the continuum (BIC) refers to the trapped state in the radiation continuum of a system. In the terahertz band, BIC provides a unique and feasible method to design devices with ultra-high quality factor (Q factor) and to achieve intense terahertz-matter interaction, which is of great value to terahertz science and technology. Here, multiple BICs protected by the resonance symmetry in the terahertz metasurface consisting of metallic split ring resonators (SRR) is demonstrated.

Water dynamics in the hydration shell of hyper-branched poly-ethylenimine.

We performed THz and GHz dielectric relaxation spectroscopy to investigate the reorientational dynamics of water molecules in the hydration shell of amphiphilic hyper-branched poly-ethylenimine (HPEI). Four Debye equations were employed to describe four types of water in the hydration shell, including bulk-like water, under-coordinated water, slow water (water molecules hydrating the hydrophobic groups and water molecules accepting hydrogen bonds from the NH groups) and super slow water (water molecules donating hydrogen bonds to and accepting hydrogen bonds from NH groups). The time scales of undercoordinated and bulk-like water show a slight decline from 0.

Does more stringencies in government policies during pandemic impact stock returns? Fresh evidence from GREF countries, a new emerging green bloc.

In this paper, we investigate the impact of the government economic policies in addition to the more stringent Covid-19 policies on stock index returns of GREF countries, that is, a new economic bloc of 5 countries (Pakistan, Iran, Turkey, Russia, and China) to foster for sustainable development of the region. Using the Panel, ARDL model and data for index returns and economic and Covid-19 control policies for the period March 1, 2020-June 30, 2021, results show that Income support, workplace closure, stringency index, and cancellation of public events have a significant positive impact on the stock index returns over the long run. In contrast, school closure, restriction on public gatherings, and international travel control policies negatively impact stock returns.

Negative refraction in twisted hyperbolic metasurfaces.

Hyperbolic metasurfaces with unique dispersion properties can manipulate light-matter interactions according to the demands. However, due to their inherent physical properties, topological transitions (flat bands) exist only in the orthogonal directions, which greatly limit their application. Here, we unveil rich dispersion engineering and topological transitions in hyperbolic metasurfaces.

Topological edge state bandwidth tuned by multiple parameters in two-dimensional terahertz photonic crystals with metallic cross structures.

Originating from the study of topological photonic crystals (TPCs), analogues of the quantum spin Hall effect have been used as a potential way to control the propagation of electromagnetic waves. Due to the topological robustness of the spin TPCs, the edge states along the interface between the trivial and topological areas are topologically protected and not reflected from structural defects and disorders. Here, on the basis of the time-spatial reversal symmetry and topological defect theory, we demonstrate broadening of the edge state bandwidth in spin TPCs made of regular metallic cross structures by simultaneously deforming the hexagonal honeycomb lattice and adjusting the rotation angle.

Asymmetric transmission of linearly polarized waves based on Mie resonance in all-dielectric terahertz metamaterials.

Interest in asymmetric transmission (AT) at terahertz frequencies has increased dramatically in recent years. We present an all-silicon metamaterial to achieve the AT effect for linearly polarized electromagnetic waves in the terahertz regime. The metamaterial is constructed by rectangular silicon pillars and a thick silicon substrate.

All-dielectric nanograting for increasing terahertz radiation power of photoconductive antennas.

Photoconductive antenna (PCA) is a widely used terahertz (THz) radiation source, but its low radiated power limits the signal-to-noise ratio and bandwidth in THz imaging and spectroscopy applications. Here, we achieved significant PCA power enhancement through etching nanograting directly on the surface of the PCA substrate. The integrated nanograting not only maximizes the generation of photocarriers, but also benefits the bias electric field loaded on the photocarriers.

Bioaccumulation, physiological distribution, and biotransformation of tetrabromobisphenol a (TBBPA) in the geophagous earthworm Metaphire guillelmi - hint for detoxification strategy.

The mechanisms underlying the bioaccumulation and detoxification of tetrabromobisphenol A (TBBPA) by terrestrial invertebrates are poorly understood. We used uniformly ring-C-labelled TBBPA to investigate the bioaccumulation kinetics, metabolites distribution, and subsequent detoxification strategy of TBBPA in the geophagous earthworm Metaphire guillelmi in soil. The modeling of bioaccumulation kinetics showed a higher biota-soil-accumulation-factor of total C than that of the parent compound TBBPA, indicating that most of the ingested TBBPA was transformed into metabolites or sequestered as bound residues in the earthworms.

Ultra-broadband microwave metamaterial absorber with tetramethylurea inclusion.

The absorption region of a water-based absorber was expanded by introducing tetramethylurea (TMU) into the inclusion, whose dielectric properties are tunable through the concentration of TMU. The dielectric spectroscopy of a TMU/water mixture was deconstructed using a Debye model. We designed a four-layer ultra-broadband microwave absorber with a supernatant micro-structure.

Water Dynamics in the Hydration Shell of Amphiphilic Macromolecules.

In the present work, the dynamics of water in the hydration shell of amphiphilic hyperbranched polyglycerol (HPG) molecules was investigated using THz and GHz dielectric relaxation spectroscopies. Different from the typical small amphiphilic molecules, the HPG macromolecule provides a rather dispersionless background and allows the direct observation of four types of water molecules in the hydration shell, including bulk-like water, undercoordinated water, slow water (water molecule hydrating hydrophobic groups and water molecule accepting hydrogen bond from OH hydroxyl groups), and super slow water that are strongly hydrogen-bonded to ether groups. For bulk-like water and undercoordinated water, the time constant remains invariant with HPG concentration, while the time constant of slow water molecules increases from 15 to 24 ps with increase of HPG concentration.

Polarization-dependent electromagnetic responses in an A-shape metasurface.

We numerically and experimentally demonstrate polarization-dependent terahertz responses in a proposed metasurface of A-shape resonators. With the horizontal polarization incidence, the observed transmission window is formed by two resonance dips, corresponding to the inductive-capacitive resonance at the lower frequency and the high-order antisymmetric resonance at a higher frequency, respectively. When the incident wave is perpendicularly polarized, the transmission window arises from the plasmon-induced transparency spectral response.

Tailoring the plasmon-induced transparency resonances in terahertz metamaterials.

We experimentally demonstrate that a coupled metamaterial composed of sub-wavelength split-ring-resonators (SRRs) and closed-ring-resonators (CRRs) can tailor the plasmon-induced-transparency (PIT) resonances when the external electric field is parallel to the gaps of SRRs. Rotating or moving SRRs in vertical direction plays a critical role in the EIT functionality, while an excellent robust performance can be acquired via moving SRRs in the horizontal direction. Based on the results, a polarization-independent and polarization-dependent planar metamaterial are designed, fabricated and measured.

Transmission and plasmonic resonances on quasicrystal metasurfaces.

The control of light-matter interaction in metasurfaces offers an unexplored potential for the excitation and manipulation of light. Here, we combine experimental terahertz time-domain spectroscopy and near-field scanning terahertz microscopy to demonstrate the role of reciprocal vectors in the transmission and plasmonic resonances of quasicrystal metasurfaces. An investigation of two-dimensional metasurface structures with different rotationally symmetric quasicrystal arrangements demonstrates that the transmission minima resulting from Wood's anomaly are directly related to the surface plasmon resonances.

Multi-wavelength lenses for terahertz surface wave.

Metasurface-based surface wave (SW) devices working at multi-wavelength has been continuously arousing enormous curiosity recently, especially in the terahertz community. In this work, we propose a multi-layer metasurface structure composed of metallic slit pairs to build terahertz SW devices. The slit pair has a narrow bandwidth and its response frequency can be altered by its geometric parameter, thereby suppressing the frequency crosstalk and reducing the difficulty of design.

Ultrathin metasurface-based carpet cloak for terahertz wave.

Ultrathin metasurfaces with local phase compensation deliver new schemes to cloaking devices. Here, a large-scale carpet cloak consisting of an ultrathin metasurface is demonstrated numerically and experimentally in the terahertz regime. The proposed carpet cloak is designed based on discontinuous-phase metallic resonators fabricated on a polyimide substrate, offering a wide range of reflection phase variations and an excellent wavefront manipulation along the edges of the bump.

Terahertz surface plasmon polariton waveguiding with periodic metallic cylinders.

We demonstrated a structure with periodic cylinders arranged bilaterally and a thin dielectric layer covered inside that supports bound modes of surface plasmon polaritons at terahertz frequencies. This structure can confine the surface plasmon polaritons in the lateral direction, and at the same time reduce the field expansion into space. We examined and explored the characteristics of several different structures using scanning near-field terahertz microscopy.

Full-State Controls of Terahertz Waves Using Tensor Coding Metasurfaces.

Coding metasurfaces allow us to study metamaterials from a fully digital perspective, enabling many exotic functionalities, such as anomalous reflections, broadband diffusions, and polarization conversion. Here, we propose a tensor coding metasurface at terahertz (THz) frequency that could take full-state controls of an electromagnetic wave in terms of its polarization state, phase and amplitude distributions, and wave-vector mode. Owing to the off-diagonal elements that dominant in the reflection matrix, each coding particle could reflect the normally incident wave to its cross-polarization with controllable phases, resulting in different coding digits.

Fate and O-methylating detoxification of Tetrabromobisphenol A (TBBPA) in two earthworms (Metaphire guillelmi and Eisenia fetida).

Tetrabromobisphenol A (TBBPA) is the world's most widely used brominated flame retardant but there is growing concern about its fate and toxicity in terrestrial organisms. In this study, two ecologically different earthworms, Metaphire guillelmi and Eisenia fetida, were exposed to soil spiked with C-labeled TBBPA for 21 days. M.

Near-field surface plasmons on quasicrystal metasurfaces.

Excitation and manipulation of surface plasmons (SPs) are essential in developing cutting-edge plasmonic devices for medical diagnostics, biochemical spectroscopy and communications. The most common approach involves designing an array of periodic slits or grating apertures that enables coupling of the incident light to the SP modes. In recent years, plasmonic resonances, including extraordinary optical transmission through periodic arrays, quasicrystals and random aperture arrays, have been investigated in the free space.

Effects of the earthworm Metaphire guillelmi on the mineralization, metabolism, and bound-residue formation of tetrabromobisphenol A (TBBPA) in soil.

Tetrabromobisphenol A (TBBPA) is one of the most widely used brominated flame retardants worldwide. The degradation and fate of this organic pollutant of soils is of great concern and can be strongly affected by geophagous earthworms through ingestion and burrowing activities. Using C-tracers, we studied the effects of the geophagous earthworm Metaphire guillelmi on the mineralization, metabolism, and bound-residue formation of TBBPA in a typical Chinese rice paddy soil during 30days of incubation in the laboratory.

Habitat fragmentation influences gene structure and gene differentiation among the Loxoblemmus aomoriensis populations in the Thousand Island Lake.

Thousand Island Lake (TIL) is a fragmented landscape consisting of more than 1000 land-bridge islands isolated during reservoir formation. To evaluate the effects of fragmentation and island attributes on insect populations, we examined the genetic structure of Loxoblemmus aomoriensis, a species of cricket widely distributed in TIL, and compared genetic diversity between islands samples. Population genetic analyses was conducted based on mitochondrial DNA haplotype frequencies of 10 sample islands.