Preparation of MIL-88(Fe)@Fe2O3@FeSiCr double core-shell-structural composites and their wave-absorbing properties.

To tackle the aggravating electromagnetic wave (EMW) pollution issues, high-efficiency EMW absorption materials are being urgently explored. The FeSiCr soft magnetic alloy is one of the more widely used and well-received iron-based soft magnetic alloy materials with high permeability; however, the development of high-performance FeSiCr alloy wave-absorbing materials is still a major challenge. In this study, double core-shell-structured composites of MIL-88(Fe)@Fe2O3@FeSiCr were successfully prepared by the oxidative heat treatment of the flaky FeSiCr obtained after ball milling and then in situ composited with MIL-88(Fe). The heterogeneous interfacial composition and microstructure were regulated to balance the microwave-loss capability and impedance matching of the material, and an enhancement of the composite absorbing performance was achieved. The composite material had a reflection-loss minimization (RLmin) of -72.65 dB, corresponding to a frequency of 6.61 GHz, with an absorbing coating thickness of 2.97 mm and an effective absorbing bandwidth (RL ≤ -10 dB) of 2.38 GHz (5.42-7.80 GHz). The results of this study provide useful ideas for wave-absorbing materials by applying high permeability soft magnetic alloy micropowders.

Giant exchange bias field above room temperature in perovskite YbCr1-xFexO3 (x = 0.6-0.9).

Temperature-induced exchange bias is observed in perovskite YbCr1-xFexO3 (x = 0.6-0.9) compounds. This is ascribed to the ferromagnetic (FM) coupling between Fe3+/Cr3+ ions and Yb3+ ions. During demagnetization, the Yb3+ ions will show a tendency to rotate with the direction of the applied magnetic field. However, the antiferromagnetic coupling of Fe3+/Cr3+ ions has a pinning effect, hindering their rotation, and thus producing an exchange bias effect. With increasing Fe3+ ion content, the magnetization and exchange bias field gradually become larger. When x = 0.8 and 0.9, the exchange bias field reaches up to -9.7 kOe and -13.6 kOe at 300 K, respectively. This giant room temperature exchange bias field will be more conducive for practical applications in magnetoelectronic devices.

Histological and ultrastructural studies of female reproductive vasculature of one humped camel in relation to possible thermoregulation and ovarian hormones.

The study was designed to explore anatomical and histological vasculature changes in the female genital system of camel and serological aspects that might be responsible to maintain thermoregulation. Twenty-four adult female camels were sampled during breeding (November-April) and non-breeding (May-October) season. Blood was collected for estrogen, progesterone and cortisol level estimation. Genital organs were sampled and described after slaughtering. Samples were taken from the ovarian artery (OA), vein (OV) and arterio-venous complex (AVC), for light and scanning electron microscopy. Sections were stained with Hematoxylin and Eosin. (H&E), Masson's trichrome, Weigert's elastic and toluidine blue. Temperature and relative humidity were used to calculate stress indicator. Stress indicator was higher in non-breeding season (NBS). Anatomical and histological vasculature (OA, OV, AVC) dynamics were significantly higher in breeding season (BS) especially diameter of left OA. Parameters of OA were positively associated with estrogen level. Collagen, elastic, smooth muscles and mast cells were recorded least in BS compared to NBS. Unique venous structure, intra-mural venules (IMV), was discovered in tunica intima of OA, seen positively and negatively associated with estrogen and cortisol level in BS, respectively. Scanned electron-micrograph exhibited penetration and wrapping of OA by small thinned-walled venules that may form IMV. The AVC was too tightly packed to differentiate due to the collapse of the wall. Hormonal, seasonal, stress indicator and vascular dynamic of female genital system are interlinked and IMV in association with OA and OV may be proposed as the site of counter-current exchange in female reproductive system of the camel.

Optimized Microstructure and Improved Magnetic Properties of Pr-Dy-Al-Ga Diffused Sintered Nd-Fe-B Magnets.

The grain boundary diffusion process (GBDP) has become an important technique in improving the coercivity and thermal stability of Dy-free sintered Nd-Fe-B magnets. The influence of Dy70Al10Ga20 and (Pr75Dy25)70Al10Ga20 alloys by the GBDP on sintered Nd-Fe-B magnets are investigated in this paper. After diffusing Dy70Al10Ga20 and (Pr75Dy25)70Al10Ga20 alloys, the coercivity (Hcj) of the magnets increased from 13.58 kOe to 20.10 kOe and 18.11 kOe, respectively. Meanwhile, the remanence of the magnets decreased slightly. The thermal stability of the diffused magnets was improved by the GBDP. The microstructure shows continuous Rare-earth-rich (RE-rich) grain boundary phases and (Dy, Pr/Nd)2Fe14B core-shell structures which contribute to improving the coercivity. Moreover, the Dy concentration on the surface of the (Pr75Dy25)70Al10Ga20 diffused magnets decreased with the Pr substitution for the Dy element. The openness of the recoil loops for the (Pr75Dy25)70Al10Ga20 diffused magnets is smaller than that of the original magnets and Dy70Al10Ga20 diffused magnets. The results show that the (Pr75Dy25)70Al10Ga20 alloys can effectively optimize the microstructure and improve the magnetic properties and thermal stability of the sintered Nd-Fe-B magnets.

Design of a Compact Dual-Band MIMO Antenna System with High-Diversity Gain Performance in Both Frequency Bands.

A compact four-element dual-band multiple-input and multiple-output (MIMO) antenna system is proposed to achieve high isolation and low channel capacity loss. The MIMO antenna was designed and optimized to cover the dual-frequency bands; the first frequency band is a wide band, and it covers the frequency range of 1550-2650 MHz, while the other frequency band covers the 3350-3650 MHz range. The measured wide-band impedance bandwidths of 1.1 GHz and 300 MHz were achieved in the lower and upper frequency bands, respectively. The proposed structure consists of four novel antenna elements, along with a plus-sign-shaped ground structure on an FR4 substrate. The overall electrical size of the whole dual-band MIMO antenna system is 0.3λ(W) × 0.3λ(L) × 0.008λ(H) for the lower frequency band. It achieved greater than 10 and 19 dB isolation in the lower and upper frequency bands, respectively. The antenna system accomplished an envelope correlation coefficient of |ρ|≤0.08 in the lower frequency band, while it achieved |ρ|≤0.02 in the higher frequency band. The computed channel capacity loss remained less than almost 0.4 bits/s/Hz in both frequency bands. Therefore, it achieved good performance in both frequency bands, with the additional advantage of a compact size. The proposed MIMO antenna is suitable for compact handheld devices and smartphones used for GSM (Global System for Mobiles), UMTS (Universal Mobile Telecommunications Service), WCDMA (Wideband Code Division Multiple Access), LTE (Long Term Evolution), 5G sub-6 GHz, PCS (Personal Communications Service), and WLAN (wireless local area network) applications.

An Online-Offline Certificateless Signature Scheme for Internet of Health Things.

The Internet of Health Things (IoHT) is an extended breed of the Internet of Things (IoT), which plays an important role in the remote sharing of data from various physical processes such as patient monitoring, treatment progress, observation, and consultation. The key benefit of the IoHT platform is the ease of time-independent interaction from geographically distant locations by offering preventive or proactive healthcare services at a lower cost. The communication, integration, computation, and interoperability in IoHT are provided by various low-power biomedical sensors equipped with limited computational capabilities. Therefore, conventional cryptographic solutions are not feasible for the majority of IoHT applications. In addition, executing computing-intensive tasks will lead to a slow response time that can deteriorate the performance of IoHT. We strive to resolve such a deficiency, and thus a new scheme has been proposed in this article, called an online-offline signature scheme in certificateless settings. The scheme divides the signing part into two phases, i.e., online and offline. In the absence of a message, the offline phase performs computationally intensive tasks, while lighter computations are executed in the online phase when there is a message. Security analyses and comparisons with the respective existing schemes are carried out to show the feasibility of the proposed scheme. The results obtained authenticate that the proposed scheme offers enhanced security with lower computational and communication costs.

Detection of West Nile virus lineage 1 sequences in blood donors, Punjab Province, Pakistan.

OBJECTIVES: This study was performed to determine the presence of West Nile virus (WNV) in mosquito specimens and human blood donors in Pakistan. METHODS: A total of 4150 mosquito specimens were collected using CO2-baited traps from five selected districts of Punjab Province, Pakistan. The mosquitoes were taxonomically identified using standard morphological keys, resulting in 166 pools. In addition, 1070 serum samples were collected from human blood donors. RNA was extracted from mosquito and human samples and screened for WNV using a reverse transcriptase PCR (RT-PCR). RESULTS: None of the mosquito pools tested positive for WNV, whereas three samples from asymptomatic humans tested positive. To determine the WNV strains, partial sequences were compared against a global representation of 23 WNV sequences. The study strains were determined to come from WNV lineage 1. CONCLUSIONS: This study is novel in reporting the circulation of lineage 1 WNV in Pakistan. Given its ability to transmit from human to human via blood transfusion, this highlights the urgent need for nationwide surveillance to assess the distribution and impact of WNV in Pakistan. Determining the source of human infection will require more extensive mosquito sampling.

Hybrid Surface Plasmon Polariton Wave Generation and Modulation by Chiral-Graphene-Metal (CGM) Structure.

Theoretical investigations are carried out to study hybrid SPP wave propagation along the Chiral-Graphene-Metal (CGM) interface. The Kubo formulism is used for the physical modeling of single-layer graphene and the impedance boundary conditions approach is applied at the CGM interface to compute the dispersion relationship for hybrid SPP waves. It is demonstrated that the chirality (ξ) and chemical potential (µc) parameters can be used to modulate the resonance surface plasmon frequencies of the upper and lower propagating modes. Furthermore, the propagation bandgap between the upper and the lower modes can be tuned by changing the chirality parameter. The effect of the chemical potential (µc)and the relaxation time (τ) on the normalized propagation constant, propagation length, and the effective refractive index is studied. The present work may have potential applications in optical and chiral sensing in the terahertz frequency range.