Multiband Terahertz Metamaterial Absorber Based on Multipolar Plasmonic Resonances

Terahertz metamaterial absorbers (MMA) have found wide scope of research prospective, remarkably in the development of multiband absorbers. Considerable applications are established using these multiband absorbers in THz imaging, wireless communication and bolometric detectors. The MMA was built on a GaAs substrate of 30 µm thickness and the hexagonal metallic pattern was etched out on a gold layer of 0.4 µm thickness on the top surface. The underlying ground layer is metallic backed. This design realizes the multiband (9-bands) of absorption in the spectral region from 0.56 to 0.92 THz. The multiband absorption mechanism of the absorber was examined by electric field dispersion analysis and impedance matching concept. From the established results, the absorber exhibits nine bands within a narrow frequency range and secures promising applications in hyperspectral imaging, clinical sensing and detection.

     

Buoyant Density and Satellite Composition of DNA of Mouse Heterochromatin

Ten per cent of mouse DNA occurs as a satellite band with a buoyant density lighter than that of the main band¹. This satellite contains highly repetitious DNA^2,3. It has been shown that the amount of satellite is markedly increased in DNA isolated from the heterochromatin fraction of mouse nuclei⁴. Furthermore, in situ hybridization studies have shown that satellite DNA is localized to the pericentromeric heterochromatin of all the mouse chromosomes except the Y^5,6. These observations demonstrate an intimate association between mouse satellite DNA and heterochromatin and they raise the question: is all the DNA from mouse heterochromatin composed of satellite DNA or is a significant portion composed of non-satellite DNA?     

A Newfangled Terahertz Absorber Tuned Temper by Temperature Field Doped by the Liquid Metal

In this article, a terahertz absorber tuned by temperature field with a newfangled structure is presented, which comprises the mercury resonators. In this scheme, temperature (T) build-up will lead the mercury stored in the bottom slot to expand through the columniform hole and be full of the upper central cross container, which can transform the absorption bands of such an absorber. The simulated results manifest that when T is increased from 0 to 25 °C, the dual-frequency absorption points (2.59 THz, 3.03 THz) and a narrow absorption region over 90% (6.54–7.10 THz), whose relative bandwidth (RB) is 7.9%, will be tailored to a single-frequency point absorption (3.12 THz) and a broadband absorption area (6.00–7.21 THz, and RB = 18.3%). For figuring out the property of the absorber mentioned above, the impacts of incident and polarization angles along with some relevant parameters of the structure on the absorption property are investigated. In addition, for plainly expounding the physical mechanism of absorption, the distributions of the surface current diagrams of the presented absorber are calculated, as well as the electric field diagrams, the magnetic field diagrams, the power loss density diagrams, and the power flow density diagrams. The proffered scheme in this article may offer a novel idea for realizing the reconfigurable absorbers.

     

Identification and characterization of the pathogenic effect of a Vibrio parahaemolyticus-related bacterium isolated from clam Meretrix meretrix with mass mortality

A mass mortality of clam, Meretrix meretrix, occurred in Jiangsu Province of China in the late September of 2007. Of the isolates obtained from the diseased clams, MM21 had the strongest virulence to the clam in the virulence test, with a LD50 value of ∼6 × 10⁶ CFU ml⁻¹. MM21 was identified as Vibrio parahaemolyticus by the VITEK 2 Compact system and 16S rDNA sequencing. Detection of virulence-associated genes by PCR indicated that MM21 was positive for toxR and tlh, and negative for tdh. Compared with control group, histiocytes from MM21-infected clams displayed a variety of cytopathological changes by transmission electron microscopy examination, which included increased lipid droplets in hepatocytes, deposition of granules in the mantle, excessive secretion in the gill. The results of our study suggested that MM21 may have been an etiological element in the mass mortalities of hard clam (M. meretrix) in Jiangsu Province of China in 2007.     

Nuclear replication activities during imbibition of abscisic acid- and gibberellin-deficient tomato (Lycopersicon esculentum Mill.) seeds

The role of cis-abscisic acid (ABA) and gibberellins (GAs) in the induction of cell-cycle activities has been studied during imbibition and subsequent germination of tomato seeds. Using flow cytometry, nuclear replication activity was investigated in embryo root tips isolated from seeds of the ABA-deficient mutant sit ^w , the GA-deficient mutant gib-1, and the wild-type (MM) tomato (Lycopersicon esculentum Mill. cv. Moneymaker) upon imbibition in water, 10 μM GA₄₊₇, 5 μM ABA or 5 μM ABA+10 μM GA₄₊₇. The nuclei of fully matured dry MM, sit ^w and gib-1 seeds predominantly showed 2C DNA signals, indicating that the cell-cycle activity of most root-tip cells had been arrested at the G₁ phase of nuclear division. However, ABA-deficient sit ^w seeds contained a significantly higher amount of G₂ cells (4C DNA) compared with the other genotypes, suggesting that, during maturation, cell-cycle activity in sit ^w seeds is less efficiently arrested in G₁. Upon imbibition in water, an induction of the 4C signal, indicating nuclear replication, was observed in the root tip cells of both MM and sit ^w embroys. The augmentation in the 4C signal occurred before visible germination. Gib-1 seeds did not show cell-cycle activity and did not germinate in water. Upon imbibition in GA₄₊₇, both cell-cycle activity and subsequent germination were enhanced in MM and sit ^w seeds, and were induced in gib-1. In ABA, the germination of MM and sit ^w seeds was inhibited while nuclear replication of these seeds was not affected. It is concluded that GA influences germination by acting upon processes that precede cell-cycle activation, while ABA affects growth by acting upon processes that follow cell-cycle activation.     

The role of key genes and pathways involved in the tumorigenesis of Malignant Mesothelioma

Malignant Mesothelioma (MM) is a very aggressive cancer with low survival rates and often diagnosed at an advanced stage. Several players have been implicated in the development of this cancer, such as asbestos, erionite and the simian virus 40 (SV40). Here, we have reviewed the involvement of erionite, SV40, as well as, the role of several genes (p16^INK4a, p14^ARF, NF2, LATS2, SAV, CTNNB1 and among others), the pathways (RAS, PI3K, Wnt, BCL and Hippo), and their respective roles in the development of MM.     

Theoretical studies on the crystal structure, thermodynamic properties, detonation performance and thermal stability of cage-tetranitrotetraazabicyclooctane as a novel high energy density compound

The B3LYP/6-31G (d) method of density functional theory (DFT) was used to study molecular geometry, electronic structure, infrared spectrum (IR) and thermodynamic properties. The heat of formation (HOF) and calculated density were estimated to evaluate the detonation properties using Kamlet–Jacobs equations. Thermal stability of 3,5,7,10,12,14,15,16-octanitro- 3,5,7,10,12,14,15,16-octaaza-heptacyclo[7.5.1.1^2,8.0^1,11.0^2,6.0^4,13.0^6,11]hexadecane (cage-tetranitrotetraazabicyclooctane) was investigated by calculating the bond dissociation energy (BDE) at unrestricted B3LYP/6-31G (d) level. The calculated results show that the N–NO₂ bond is a trigger bond during thermolysis initiation process. The crystal structure obtained by molecular mechanics (MM) methods belongs to Pna2₁ space group, with cell parameters a?=?12.840 Å, b?=?9.129 Å, c?=?14.346 Å, Z?=?6 and ρ?=?2.292 g·cm^?3. Both the detonation velocity of 9.96 km·s^?1 and the detonation pressure of 47.47 GPa are better than those of CL-20. According to the quantitative standard of energetics and stability, as a high energy density compound (HEDC), cage-tetranitrotetraazabicyclooctane essentially satisfies this requirement.     

Effects of H₂O₂ on electrical membrane properties of skeletal myotubes

Reactive oxygen species (ROS), normally generated in skeletal muscles, could control excitability of muscle fibers through redox modulation of membrane ion channels. However, the mechanisms of ROS action remain largely unknown. To investigate the action of ROS on electrical properties of muscle cells, patch-clamp recordings were performed after application of hydrogen peroxide (H₂O₂) to skeletal myotubes. H₂O₂ facilitated sodium spikes after a hyperpolarizing current pulse, by decreasing the latency for spike initiation. Importantly, the antioxidant N-acetylcysteine induced the opposite effect, suggesting the redox control of muscle excitability. The effect of H₂O₂ was abolished in the presence of catalase. The kinetics of sodium channels were not affected by H₂O₂. However, the fast inward rectifier K⁺ (K_IR) currents, activated by hyperpolarization, were reduced by H₂O₂, similar to the action of the potassium channel blockers Ba²⁺ and Cs⁺. The block of the outward tail current contributing to K_IR deactivation can explain the shorter latency for spike initiation. We propose that the K_IR current is an important target for ROS action in myotubes. Our data would thus suggest that ROS are involved in the control of the excitability of myotubes and, possibly, in the oscillatory behavior critical for the plasticity of developing muscle cells.     

Tunable and Multichannel Terahertz Perfect Absorber Due to Tamm Plasmons with Topological Insulators

In this paper, Tamm plasmons with topological insulators in a composite structure consisting of Bi₂Se₃, spacer layer, and one-dimensional photonic crystal (1DPC) have been demonstrated theoretically. The perfect absorption has been realized in the terahertz regime because of the optical Tamm states (OTSs) excited at the interface between Bi₂Se₃ and 1DPC. The perfect absorption can be realized for both TE and TM waves, and it is noted that the perfect absorption can be obtained at any incident angle by simultaneously changing the wavelength of incident light for TE-polarizations. Moreover, the perfect absorption can be realized at different wavelengths with the change of the chemical potential and the thickness of Bi₂Se₃. The thickness and the dielectric constant of the spacer layer will also play a vital role in the performance of the perfect absorber. Especially, the multichannel perfect absorption phenomenon can be achieved by choosing the appropriate thickness of the spacer layer. This tunable and multichannel terahertz perfect absorber has great application potential in the solar energy, photodetection, and THz biosensor.

     

An Ultra-Wideband Terahertz Metamaterial Absorber Utilizing Sinusoidal-Patterned Dielectric Loaded Graphene

In this paper, a non-structured graphene sheet loaded with a sinusoidal-patterned dielectric is introduced as an ultra-wideband metamaterial absorber in terahertz regime. Regardless of conventional structures with multilayered-graphene, a single layer sheet of non-structured graphene is used whereas the proposed structure benefits from dielectric width modulation and cavity method in order to excite continuous graphene plasmon resonances. The structure comprises four layers that two Fabry-Perot cavity mirrors are constructed by upper sinusoidal-patterned dielectric and a gold film. Full wave simulation results demonstrate that a broadband over 90% absorption with absolute bandwidth of 6.58 THz and central frequency of 3.97 THz is achieved under normal TE/TM incident plane wave. The designed structure yields 166% relative bandwidth. According to the symmetric configuration, the absorption spectra of mentioned polarizations are thoroughly close to each other resulting to a polarization insensitive structure. The stability of bandwidth and absorbance of the structure versus angle of incidence, θ, up to 35°/65° for TM/TE polarizations, respectively, and azimuth angle, φ, shows an interesting capability for utilization as detectors and sensors. The simple geometry of utilized graphene layer results in easy fabrication. The designed structure has wideband absorption in THz regime. Moreover, it is more compact than conventional broadband THz absorbers.

     

Quantifying the Mechanical Properties of the Endothelial Glycocalyx with Atomic Force Microscopy

Our understanding of the interaction of leukocytes and the vessel wall during leukocyte capture is limited by an incomplete understanding of the mechanical properties of the endothelial surface layer. It is known that adhesion molecules on leukocytes are distributed non-uniformly relative to surface topography ³, that topography limits adhesive bond formation with other surfaces ⁹, and that physiological contact forces (≈ 5.0 − 10.0 pN per microvillus) can compress the microvilli to as little as a third of their resting length, increasing the accessibility of molecules to the opposing surface ^{3, 7}. We consider the endothelium as a two-layered structure, the relatively rigid cell body, plus the glycocalyx, a soft protective sugar coating on the luminal surface ⁶. It has been shown that the glycocalyx can act as a barrier to reduce adhesion of leukocytes to the endothelial surface ⁴. In this report we begin to address the deformability of endothelial surfaces to understand how the endothelial mechanical stiffness might affect bond formation. Endothelial cells grown in static culture do not express a robust glycocalyx, but cells grown under physiological flow conditions begin to approximate the glycocalyx observed in vivo ². The modulus of the endothelial cell body has been measured using atomic force microscopy (AFM) to be approximately 5 to 20 kPa ⁵. The thickness and structure of the glycocalyx have been studied using electron microscopy ⁸, and the modulus of the glycocalyx has been approximated using indirect methods, but to our knowledge, there have been no published reports of a direct measurement of the glycocalyx modulus in living cells. In this study, we present indentation experiments made with a novel AFM probe on cells that have been cultured in conditions to maximize their glycocalyx expression to make direct measurements of the modulus and thickness of the endothelial glycocalyx.     

A Tunable Perfect THz Metamaterial Absorber with Three Absorption Peaks Based on Nonstructured Graphene

In this paper, a graphene-based tunable multi-band terahertz absorber is proposed and numerically investigated. The proposed absorber can achieve perfect absorption within both sharp and ultra-broadband absorption spectra. This wide range of absorption is gathered through a unique combination of periodically cross- and square-shaped dielectrics sandwiched between two graphene sheets; the latter enables it to offer more absorption in comparison with the traditional single-layer graphene structures. The aforementioned top layer is mounted on a gold plate separated by a Topas layer with zero volume loss. Furthermore, in our proposed approach, we investigated the possibility of changing the shapes and sizes of the dielectric layers instead of the geometry of the graphene layers to alleviate the edge effects and manufacturing complications. In numerical simulations, parameters, such as graphene Fermi energy and the dimensions of the proposed dielectric layout, have been optimally tuned to reach perfect absorption. We have verified that the performance of our dielectric layout called fishnet, with two widely investigated dielectric layouts in the literature (namely, cross-shaped and frame-and-square). Our results demonstrate two absorption bands with near-unity absorbance at frequencies of 1.6–2.3 and 4.2–4.9 THz, with absorption efficiency of 98% in 1.96 and 4.62 THz, respectively. Moreover, a broadband absorption in the 7.77–9.78 THz is observed with an absorption efficiency of 99.6% that was attained in 8.44–9.11 THz. Finally, the versatility provided by the tunability of three operation bands of the absorber makes it a great candidate for integration into terahertz optoelectronic devices.

     

Cytoarchitectonic subdivisions in the subtectal midbrain of the lizard Gallotia galloti

Contemporary study of molecular patterning in the vertebrate midbrain is handicapped by the lack of a complete topological map of the diverse neuronal complexes differentiated in this domain. The relatively less deformed reptilian midbrain was chosen for resolving this fundamental issue in a way that can be extrapolated to other tetrapods. The organization of midbrain centers was mapped topologically in terms of longitudinal columns and cellular strata on transverse, Nissl-stained sections in the lizard Gallotia galloti. Four columns extend along the whole length of the midbrain. In dorsoventral order: 1) the dorsal band contains the optic tectum, surrounded by three ventricularly prominent subdivisions, named griseum tectale, intermediate area and torus semicircularis, in rostrocaudal order; 2) a subjacent region is named here the lateral band, which forms the ventral margin of the alar plate and also shows three rostrocaudal divisions; 3) the basal band forms the basal plate or tegmentum proper; it appears subdivided into medial and lateral parts: the medial part contains the oculomotor and accessory efferent neurons and the medial basal part of the reticular formation, which includes the red nucleus rostrally; the lateral part contains the lateral basal reticular formation, and includes the substantia nigra caudally; 4) the median band contains the ventral tegmental area, representing the mesencephalic floor plate. The alar regions (dorsal and lateral) show an overall cellular stratification into periventricular, central and superficial strata, with characteristic cytoarchitecture for each part. The lateral band contains two well developed superficial nuclei, one of which is commonly misidentified as an isthmic formation. The basal longitudinal subdivisions are simpler and basically consist of periventricular and central strata.     

A Direct Comparison between Circadian and Noncircadian Rhythms in Neurospora crassa

A method has been devised for observing both circadian and noncircadian rhythms in a single wild type strain of Neurospora crassa. This method allows a direct comparison of the properties of the two types of rhythm. The circadian rhythm of conidiation always entrains to a light-dark cycle, damps out in constant light, and has a temperature-compensated period length. The noncircadian rhythm of hyphal branching, expressed by the same strain under different environmental conditions, does not entrain to a light-dark cycle, persists in constant light, and its period length is temperature-dependent. These results suggest that the two rhythms have different underlying mechanisms and demonstrate that the differences in the rhythms previously observed in different strains (patch, band, and clock) are not due to genetic differences between these strains but rather are inherent properties of the rhythms themselves.     

Staked Graphene for Tunable Terahertz Absorber with Customized Bandwidth

Terahertz (THz) absorber with dynamically tunable bandwidth possesses huge application value in the fields of switches, sensors, and THz detection. However, the perfect absorbers based on photonic crystals and metamaterials are not intelligent enough to capture the electromagnetic wave in a tunable way. In this paper, we utilized only patterned graphene to tune the absorption positions and the bandwidth in the terahertz regime. More distinguished than some dynamic absorbers proposed before, the performances with peak frequency relative tuning range of 68 % and nearly unity absorbance are obtained by a single cross-shaped graphene layer. Additionally, the working bandwidth can be broadened with stacked structured graphene. The almost perfect absorption shifted from 2.36～3.2 to 3.26～3.99 THz continuously via changing the chemical potential of graphene.     

The Osteoblastogenesis Potential of Adipose Mesenchymal Stem Cells in Myeloma Patients Who Had Received Intensive Therapy

Multiple myeloma (MM) is characterized by advanced osteolytic lesions resulting from the activation of osteoclasts (OCs) and inhibition of osteoblasts (OBs). OBs are derived from mesenchymal stem cells (MSCs) from the bone marrow (BM), however the pool and function of BMMSCs in MM patients (MM-BMMSCs) are reduced by myeloma cells (MCs) and cytokines secreted from MCs and related anti-MM treatment. Such reduction in MM-BMMSCs currently cannot be restored by any means. Recently, genetic aberrations of MM-BMMSCs have been noted, which further impaired their differentiation toward OBs. We hypothesize that the MSCs derived from adipose tissue (ADMSCs) can be used as alternative MSC sources to enhance the pool and function of OBs. Therefore, the purpose of this study was to compare the osteogenesis ability of paired ADMSCs and BMMSCs in MM patients who had completed intensive therapy. Fifteen MM patients who had received bortezomib-based induction and autologous transplantation were enrolled. At the third month after the transplant, the paired ADMSCs and BMMSCs were obtained and cultured. Compared with the BMMSCs, the ADMSCs exhibited a significantly higher expansion capacity (100% vs 13%, respectively; P = .001) and shorter doubling time (28 hours vs 115 hours, respectively; P = .019). After inducing osteogenic differentiation, although the ALP activity did not differ between the ADMSCs and BMMSCs (0.78 U/µg vs 0.74±0.14 U/µg, respectively; P = .834), the ADMSCs still exhibited higher calcium mineralization, which was determined using Alizarin red S (1029 nmole vs 341 nmole, respectively; P = .001) and von Kossa staining (2.6 E+05 µm² vs 5 E+04 µm², respectively; P = .042), than the BMMSCs did. Our results suggested that ADMSCs are a feasible MSC source for enhancing the pool and function of OBs in MM patients who have received intensive therapy.     

The Right Tool for the Job: Detection of Soil-Transmitted Helminths in Areas Co-endemic for Other Helminths

Background

Due to the recent increased use of the McMaster (MM) fecal egg counting method for assessing benzimidazole drug efficacy for treating soil-transmitted helminth (STH) infections, the aim of the current study was to determine the operational value of including the MM method alongside the Kato-Katz (KK) fecal thick smear to increase the diagnostic sensitivity when STHs are co-endemic with trematode helminths (e.g., Schistosoma mansoni).

Methods

A cross-sectional study was conducted in school-aged children aged 4-18 years in the northeastern region of the State of Minas Gerais (Brazil), where Necator americanus, Ascaris lumbricoides, Trichuris trichiura, and S. mansoni are co-endemic. One fecal sample from each participant was collected and transported to the field laboratory for analysis. Coprological diagnosis was performed on each fecal sample by three different methods: Formalin-Ether Sedimentation (FES), KK and the MM technique. The diagnostic sensitivity and negative predictive value (NPV) of each technique was calculated using the combination of all three techniques as the composite standard. In order to determine the agreement between the three techniques Fleiss´ kappa was used. Both the Cure Rate (CR) and the Fecal Egg Count Reduction (FECR) were calculated using the two quantification techniques (i.e., the MM and KK).

Results

Fecal samples from 1260 children were analyzed. The KK had higher diagnostic sensitivity than the MM for the detection of both A. lumbricoides (KK 97.3%, MM 69.5%) and hookworm (KK 95.1%, MM 80.8%). The CR of a single dose of mebendazole varied significantly between the KK and MM for both A. lumbricoides (p = 0.016) and hookworm (p = 0.000), with lower rates obtained with the KK. On the other hand, the FECR was very similar between both techniques for both A. lumbricoides and hookworm.

Conclusion

The MM did not add any diagnostic value over the KK in areas where both STHs and trematodes were co-endemic. The lower sensitivity of the MM would have an important impact on the administration of selective school-based treatment in this area since if only the MM were used, 36 (13.9%) children diagnosed with A. lumbricoides would have gone untreated.     

Tunable Salisbury Screen Absorber Using Square Lattice of Plasmonic Nanodisk

We propose a novel polarization independent Salisbury screen absorber to provide tunable resonant absorption at terahertz (THz) frequencies. The Salisbury screen absorber is designed by using a planar array of thin gold nanodisks arranged in a square lattice. Certain configurations of Salisbury screen have multiple distinctive absorption bands that support near-unity/FWHM absorption bandwidth reaching 36 THz/169 THz, respectively. Moreover, the absorption bandwidth depends upon the optical thickness of the dielectric spacer between the metasurface and the metallic ground plane. The proposed tunable Salisbury screen absorber can find practical applications in photonic detection, imaging, sensing, and solar cells at optical frequencies.