bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of moisture content and heating condition on pyrolysis and combustion properties of structural fuels
Authors: Hedayati Faraz , Yang Wenxu , Zhou Aixi
Published: April 2018

The objective of this research was to measure the pyrolysis and combustion properties of selected structural fuels as a function of fuel moisture content (MC) levels under various external heating conditions. The pyrolysis properties were measured by using the thermogravimetric analysis technique at 3 MC levels (5%, 10%, and 15%) and 3 heating rates (5, 15, and 25K/min.). The combustion properties were measured by using a cone calorimeter at the same MC levels and 3 heat flux levels (20, 30, and 50 kW/m2). In addition, density and thermal conductivity as a function of MC levels were also measured. Statistical analysis was performed over the experimental data by using a 95% confidence interval. Most materials had significant increase in density when the MC levels increased, while the increase was more significant for natural woods than engineered woods. No statistically significant changes in thermal conductivity were observed for most materials. The pyrolysis properties were affected by both the MC and heating rate levels. Both MC and heat flux levels affected the combustion properties.
Prognostic value of chromosomal imbalances, gene mutations, and BAP1 expression in uveal melanoma
Authors: Patrone Serena , Maric Irena , Rutigliani Mariangela , Lanza Francesco , Puntoni Matteo , Banelli Barbara , Rancati Silvia , Angelini Giovanna , Amaro Adriana , Ligorio Paolo , Defferrari Carlotta , Castagnetta Mauro , Bandelloni Roberto , Mosci Carlo , DeCensi Andrea , Romani Massimo , Pfeffer Ulrich , Viaggi Silvia , Coviello Domenico A.
Published: April 2018

Uveal melanoma (UM) exhibits recurring chromosomal abnormalities and gene driver mutations, which are related to tumor evolution/progression. Almost half of the patients with UM develop distant metastases, predominantly to the liver, and so far there are no effective adjuvant therapies. An accurate UM genetic profile could assess the individual patient's metastatic risk, and provide the basis to determine an individualized targeted therapeutic strategy for each UM patient. To investigate the presence of specific chromosomal and gene alterations, BAP1 protein expression, and their relationship with distant progression free survival (DPFS), we analyzed tumor samples from 63 UM patients (40 men and 23 women, with a median age of 64 years), who underwent eye enucleation by a single cancer ophthalmologist from December 2005 to June 2016. UM samples were screened for the presence of losses/gains in chromosomes 1p, 3, 6p, and 8q, and for mutations in GNAQ, GNA11, BAP1, SF3B1, and EIF1AX. BAP1 protein expression was detected by immunohistochemistry (IHC). Multivariate analysis showed that the presence of monosomy 3, 8q gain, and loss of BAP1 protein were significantly associated to DPFS, while BAP1 gene mutation was not, mainly due to the presence of metastatic UM cases with negative BAP1 IHC and no BAP1 mutation detected by Sanger sequencing. Loss of BAP1 protein expression and monosomy 3 represent the strongest predictors of metastases, and may have important implications for implementation of patient surveillance, properly designed clinical trials enrollment, and adjuvant therapy.
Is externalizing psychopathology a robust risk factor for suicidal thoughts and behaviors? A meta‐analysis of longitudinal studies
Authors: Witte Tracy K. , Gauthier Jami M. , Huang Xieyining , Ribeiro Jessica D. , Franklin Joseph C.
Published: April 2018

Objective

Our primary objective was to determine the potency of externalizing psychopathology as a risk factor for suicidal thoughts and behaviors (STBs).

Method

We conducted a random effects meta‐analysis of 174 prospective studies (839 unique statistical tests) examining externalizing psychopathology and suicidal thoughts and behaviors (STBs) published prior to December 8, 2017. The weighted mean odds ratios for the overall relationship between externalizing psychopathology and STBs were below 2.00 in magnitude, and all risk factor subcategories were also fairly modest predictors of STBs. Taking publication bias into account reduced the magnitude of these associations, particularly for death. Although externalizing psychopathology modestly predicts STBs, this may be due to design limitations of existing studies. Future research should employ shorter follow‐up periods, consider risk factors in combination, and focus on forms of externalizing psychopathology that have not been studied extensively.

Results

The weighted mean odds ratios for the overall relationship between externalizing psychopathology and STBs were below 2.00 in magnitude, and all risk factor subcategories were also fairly modest predictors of STBs. Taking publication bias into account reduced the magnitude of these associations, particularly for death. Additionally, our results were mostly consistent regardless of sample age, sample severity, follow‐up length, and predictor scale.

Conclusions

Although externalizing psychopathology modestly predicts STBs, this may be due to design limitations of existing studies. Future research should employ shorter follow‐up periods, consider risk factors in combination, and focus on forms of externalizing psychopathology that have not been studied extensively.
Specificity and affinity of neuraminic acid exhibited by canine rotavirus strain K9 carbohydrate‐binding domain (VP8*)
Authors: Mishra Rahul , Yu Xing , Kishor Chandan , Holloway Gavan , Lau Kam , von Itzstein Mark , Coulson Barbara S. , Blanchard Helen
Published: April 2018

The outer capsid spike protein VP4 of rotaviruses is a major determinant of infectivity and serotype specificity. Proteolytic cleavage of VP4 into 2 domains, VP8* and VP5*, enhances rotaviral infectivity. Interactions between the VP4 carbohydrate‐binding domain (VP8*) and cell surface glycoconjugates facilitate initial virus‐cell attachment and subsequent cell entry. Our saturation transfer difference nuclear magnetic resonance (STD NMR) and isothermal titration calorimetry (ITC) studies demonstrated that VP8*64‐224 of canine rotavirus strain K9 interacts with N‐acetylneuraminic and N‐glycolylneuraminic acid derivatives, exhibiting comparable binding epitopes to VP8* from other neuraminidase‐sensitive animal rotaviruses from pigs (CRW‐8), cattle (bovine Nebraska calf diarrhoea virus, NCDV), and Rhesus monkeys (Simian rhesus rotavirus, RRV). Importantly, evidence was obtained for a preference by K9 rotavirus for the N‐glycolyl‐ over the N‐acetylneuraminic acid derivative. This indicates that a VP4 serotype 5A rotavirus (such as K9) can exhibit a neuraminic acid receptor preference that differs from that of a serotype 5B rotavirus (such as RRV) and the receptor preference of rotaviruses can vary within a particular VP4 genotype.
Imidazo[1,2‐c]pyrimidin‐5(6H)‐one as a novel core of cyclin‐dependent kinase 2 inhibitors: Synthesis, activity measurement, docking, and quantum mechanical scoring
Authors: Ajani Haresh , Jansa Josef , Köprülüoğlu Cemal , Hobza Pavel , Kryštof Vladimír , Lyčka Antonín , Lepsik Martin
Published: April 2018

We report on the synthesis, activity testing, docking, and quantum mechanical scoring of novel imidazo[1,2‐c]pyrimidin‐5(6H)‐one scaffold for cyclin‐dependent kinase 2 (CDK2) inhibition. A series of 26 compounds substituted with aromatic moieties at position 8 has been tested in in vitro enzyme assays and shown to inhibit CDK2. 2D structure‐activity relationships have ascertained that small substituents at position 8 (up to the size of naphtyl or methoxyphenyl) generally lead to single‐digit micromolar IC50 values, whereas bigger substituents (substituted biphenyls) decreased the compounds' activities. The binding modes of the compounds obtained using Glide docking have exhibited up to 2 hinge‐region hydrogen bonds to CDK2 and differed in the orientation of the inhibitor core and the placement of the 8‐substituents. Semiempirical quantum mechanics‐based scoring identified probable favourable binding modes, which will serve for future structure‐based design and synthetic optimization of substituents of the heterocyclic core. In summary, we have identified a novel core for CDK2 inhibition and will explore it further to increase the potencies of the compounds and also monitor selectivities against other protein kinases.
Raman spectroscopy probing of redox states and mechanism of flavin coenzyme
Authors: Silwal Achut P. , Lu H. Peter
Published: April 2018

Redox states of flavin mononucleotide (FMN) play important and regulating roles in living systems. To understand the involvement and contribution of FMN coenzyme in different biological processes, probing and characterizing of the associated FMN redox states using powerful experimental approaches are fundamental and crucial. In this study, we have generated a number of typical FMN redox states in Britton–Robinson buffer at different pH environments by applying electric potentials. The electric potential and pH‐dependent events of protonation, deprotonation, and electron transfer process of FMN are probed and characterized by surface‐enhanced Raman spectroscopy (SERS) or resonance SERS (SERRS) using silica coated silver nanoparticles (AgNP@SiO2) as SERS substrate. In addition to experimental SERS analysis, we, using density functional theory, computationally calculated Raman spectra to identify the spectral signatures of the FMN redox‐state sensitive Raman modes. Here, we have specifically probed, analyzed, and characterized signature Raman modes of different redox states of FMN coenzyme including FMNH2•+ (1508‐1510 cm−1), FMNH2 (1512‐1514 cm−1), FMN2−• (1498 cm−1), and FMN3− (1492 cm−1) and proposed the redox reaction schemes of FMN in different experimental conditions.
Boronate affinity monolithic column incorporated with graphene oxide for the in‐tube solid‐phase microextraction of glycoproteins
Authors: Wang Rong , Chen Zilin
Published: April 2018

A poly(vinylphenylboronic acid–ethylene glycol dimethacrylate) monolithic material incorporated with graphene oxide was synthesized inside a poly(ether ether ketone) tube. This tube with boronate affinity monolith was coupled with a high‐performance liquid chromatography system through a six‐port valve to construct an online solid‐phase microextraction with high‐performance liquid chromatography system. The performance of this solid‐phase microextraction with high‐performance liquid chromatography system was demonstrated by standard glycoprotein in aqueous samples, namely, horseradish peroxidase. Some parameters that affect the extraction performance were investigated, including sampling rate, pH of sample solution, and sampling volume. Under the optimized conditions, the developed method showed high extraction efficiency toward horseradish peroxidase. The addition of graphene oxide greatly increased the extraction efficiency of boronate affinity monolith for horseradish peroxidase. The limit of detection of the proposed method was as low as 0.01 μg/mL by using ultraviolet detection. The recognition specificity was also evaluated by analyzing the mixture of bovine serum albumin (nonglycoprotein) and horseradish peroxidase. The results showed that this material could selectively extract horseradish peroxidase from the mixture, indicating its good specificity toward glycoproteins. The proposed method was further applied for analyzing rat plasma samples spiked with horseradish peroxidase. Good recovery and repeatability were obtained.
Enhancing tailings revegetation using shallow cover systems in arid environments: Hydrogeochemical, nutritional, and ecophysiological constraints
Authors: Robson Thomas , Golos Peter J. , Stevens Jason , Reid Nathan
Published: April 2018

Mineral tailings impoundments represent a rapidly growing land area requiring revegetation and a major challenge to restoring biodiversity in postmined environments. Topsoil covers are essential for revegetation, to mitigate the physical and hydrogeochemical obstacles presented by tailings. However, mines in arid and semiarid regions are often large scale and geographically isolated from resources and suffer a scarcity of suitable topsoil, stimulating interest in cost‐effective shallow cover systems incorporating minimal volumes of local material. Using a mine in arid Western Australia as a case‐study, we address challenges pertinent to using 200‐mm‐deep sandy topsoil directly overlying mildly reactive, circum‐neutral copper ore tailings. We combined detailed hydrogeochemical, ecophysiological, and nutritional data from a year‐long glasshouse experiment, to evaluate responses of native species to the model system. The model system enhanced emergence, growth, and root development by providing a physical and hydrogeochemical buffer, increasing the volume of profile with conditions favourable to water and nutrient acquisition. Plants scarcely utilised saline water from the underlying tailings, limiting growth between irrigation events, although the tailings did support minimal functional activity over timescales in the order of weeks. We identified relatively high tailings pore‐water salinity, the limited volume of geochemically benign topsoil providing storage release of uncontaminated meteoric water, and the geochemically evolving nature of the tailings cover system, as key challenges to overcome. The findings encourage further studies incorporating optimised designs and demonstrate the benefits of combining detailed, temporally resolved hydrogeochemical and ecophysiological data to adequately capture the plant–water relations existing within candidate cover systems.
Divergence, convergence, and path dependency of paraglacial adjustment of alpine lateral moraine slopes
Authors: Draebing Daniel , Eichel Jana
Published: April 2018

Lateral moraines represent important sediment storages and are one of the most dynamic areas within glacier forelands. Following glacier retreat, lateral moraine slopes adjust as their material is reworked by paraglacial processes. Previous research focused primarily on the role of gullying, however, path‐dependent slope adjustment and divergent adjustment of lateral moraine slopes are poorly understood. We report data from geomorphic and vegetation mapping, electrical resistivity tomography, soil moisture measurements, and soil texture analysis acquired in the Turtmann glacier foreland in the Swiss Alps where periglacial processes are abundant. We demonstrate that paraglacial slope adjustment shows divergent, convergent, and path‐dependent behaviour. Steep proximal moraine slopes are first eroded by gullying processes. When moraine slopes reach a threshold angle of 30°, the importance of solifluction increases, and solifluction processes subsequently rework debris flow deposits. In contrast, more gently inclined distal slopes are below the threshold angle immediately following glacier retreat and biogeomorphic feedbacks result in an earlier onset of solifluction processes. We identified two different types of turf‐banked solifluction lobes based on their temporal development and genesis. Lobe Type 1 develops on distal moraine slopes and reworks glacial till, whereas Lobe Type 2 evolves from debris flow deposits at the footslopes of the lateral moraines. Both lobe types can only be differentiated using actual shape. Overprinting by subsequent geomorphic processes can result in equifinal and convergent forms such as solifluction sheets from the Last Glaciation. Our study provides an actualistic example of how paraglacial solifluction in 90 to 150 years rapidly reworks glacial sediments.
Zwitterionic Polymer Design that Inhibits Aggregation and Facilitates Insulin Refolding: Mechanistic Insights and Importance of Hydrophobicity
Authors: Rajan Robin , Suzuki Yu , Matsumura Kazuaki
Published: April 2018

The synthesis of a zwitterionic polymer, poly‐sulfobetaine (poly‐SPB), which shows remarkable efficiency in the suppression of insulin aggregation is described. Hydrophobic modification of the polymer results in almost complete inhibition at very low polymer concentrations. Further studies reveal that these polymers facilitate the complete retention of insulin's secondary structure, which is otherwise lost after incubation. Refolding studies show that addition of polymers to preaggregated insulin sample leads to the refolding of denatured insulin, indicating their potential to facilitate the refolding of the denatured proteins. In addition, 2D NMR studies show that the presence of hydrophobic poly‐SPB alters the hydrophobic environment of insulin, which may suppress hydrophobic interactions that lead to aggregation. These results indicate the enormous potential of these polymers for suppressing insulin aggregation and provide significant insight into the complex mechanism of insulin protection by zwitterionic polymers.
Synergistic Effects of Beta Tri‐Calcium Phosphate and Porcine‐Derived Decellularized Bone Extracellular Matrix in 3D‐Printed Polycaprolactone Scaffold on Bone Regeneration
Authors: Kim Jun‐Young , Ahn Geunseon , Kim Changhwan , Lee Jeong‐Seok , Lee In‐Gyu , An Sang‐Hyun , Yun Won‐Soo , Kim Shin‐Yoon , Shim Jin‐Hyung
Published: April 2018

Bone‐derived extracellular matrix (ECM) is widely used in studies on bone regeneration because of its ability to provide a microenvironment of native bone tissue. However, a hydrogel, which is a main type of ECM application, is limited to use for bone graft substitutes due to relative lack of mechanical properties. The present study aims to fabricate a scaffold for guiding effective bone regeneration. A polycaprolactone (PCL)/beta‐tricalcium phosphate (β‐TCP)/bone decellularized extracellular matrix (dECM) scaffold capable of providing physical and physiological environment are fabricated using 3D printing technology and decoration method. PCL/β‐TCP/bone dECM scaffolds exhibit excellent cell seeding efficiency, proliferation, and early and late osteogenic differentiation capacity in vitro. In addition, outstanding results of bone regeneration are observed in PCL/β‐TCP/bone dECM scaffold group in the rabbit calvarial defect model in vivo. These results indicate that PCL/β‐TCP/bone dECM scaffolds have an outstanding potential as bone graft substitutes for effective bone regeneration.
Hybrid Nanoparticle–Polymer Brush Composites for Detection of Low‐Level Radiostrontium in Water
Authors: Bliznyuk Valery N. , Seliman Ayman F. , Husson Scott M. , Lvov Yuri M. , DeVol Timothy A.
Published: April 2018

Combining extraction and scintillation properties within the same material is a relatively new approach in development of sensors for detection of radioactive elements. Structural organization of such materials at a nanoscale typically offers higher efficiency of detection and shorter response time. In this contribution, several new protocols are discussed for fabrication of stable extractive scintillating systems based on commercial Superlig 620 (SL) material with high affinity to radiostrontium. Application of hybrid organic–inorganic beads with SL particles used as core and halloysite clay nanotubes (HNT) modified with a polyvinyltoluene (PVT) brush as a permeable shell combines high‐performance extracting properties of the SL material with efficient light emission properties of the polymer scintillator. The developed SL–HNT–PVT hybrid extractive scintillating material allows real‐time detection of low‐level concentrations of radiostrontium in water. Moreover, the suggested approach is not limited to detection of Sr but can find broader application in development of chemical, biological, or radioluminescent sensors and multifunctional materials.
Water‐Resistant and Haze‐Tunable Transparent Cellulose Nanopaper for Patterned Electroluminescence Devices
Authors: Yu Ziya , Xu Zhilong , Qiao Ke , Zhang Liangmiao , Chen Zhang , Yang Xiao , Ji Aiyan , Wu Min , Gao Yanfeng
Published: April 2018

A water‐resistant cellulose nanopaper with thermal stability (290 °C is decomposition temperature) and higher fracture strength (127 MPa maximum) than polyethylene terephthalate film is demonstrated. The extraordinary swelling ability of dimethyl sulfoxide for cellulose is used to decrease the size of cellulose fibers. A highly transparent (93% at a wavelength of 550 nm for a 100 µm thick nanopaper) and haze‐tunable (from 5.5% to 41.5% at a wavelength of 600 nm) nanopaper is obtained. Additionally, the water‐resistant cellulose nanopaper is further used as a flexible transparent substrate for patterned electroluminescence devices, revealing that this cellulose nanopaper holds great promise for electronic devices.
Theory on Capillary Filling of Polymer Melts in Nanopores
Authors: Yao Yang , Butt Hans‐Jürgen , Floudas George , Zhou Jiajia , Doi Masao
Published: April 2018

A unified theory for the imbibition dynamics of entangled polymer melting into nanopores is presented. Experiments demonstrate the validity oft1/2dependence but contradict the predictions of the classical Lucas–Washburn equation because of the prefactor. A reversal in dynamics of capillary filling is reported with increasing polymer molecular weight. Polymer imbibition under nanometer confinement can be discussed by two mechanisms: one is the standard hydrodynamic flow, resulting in a parabolic flow profile. When the inner wall has a strong attraction to the polymer, a layer of immobile chains is created, resulting in an increase of the effective viscosity and to slower imbibition. The other is the reptation model proposed by Johner et al., leading to a plug flow profile and to the reduction in the effective viscosity (faster imbibition). The reversal in dynamics of polymer imbibition can be explained by the competition between these two mechanisms.
Twisted Linker Effect on Naphthalene Diimide‐Based Dimer Electron Acceptors for Non‐fullerene Organic Solar Cells
Authors: Oh Jae Taek , Ha Yeon Hee , Kwon Soon‐Ki , Song Seyeong , Kim Jin Young , Kim Yun‐Hi , Choi Hyosung
Published: April 2018

Naphthalene diimide (NDI) dimers, NDI–Ph–NDI with a phenyl linker and NDI–Xy–NDI with a xylene linker, are designed and synthesized. The influence of the xylene and phenyl linkers on optical properties, electrochemical properties, morphology, and device performance is systematically investigated. Non‐fullerene organic solar cells (OSCs) with NDI–Ph–NDI show poor device efficiency due to aggregation of polymer chains and/or NDI dimers caused by the highly planar structure of NDI–Ph–NDI. Although NDI–Xy–NDI is a non‐planar structure, uniform surface morphology and weak bimolecular recombination lead to high power conversion efficiencies of 3.11%, which is the highest value in non‐fullerene OSCs with NDI small molecules.
Scaling Behavior of Nafion with Different Model Parameterizations in Dissipative Particle Dynamics Simulations
Authors: Liu Hongjun , Cavaliere Sara , Jones Deborah J. , Rozière Jacques , Paddison Stephen J.
Published: April 2018

The scaling behavior of the conformation and dynamics of mesoscopic models of a polymer melt, Nafion, and hydrated Nafion are investigated with dissipative particle dynamics (DPD) simulations. The scaling behavior of all studied systems generally follows the Rouse theory. For the polymer melt and dry Nafion, increase in chain stiffness slightly shrinks the polymer and leads to slower dynamics with longer polymer relaxation time. The addition of a stiff constraint to five different DPD parameterizations of hydrated Nafion expands the chain conformation, while the repulsion parameter effect on size is secondary. In contrast, softer repulsion predominately dictates faster dynamics of both the polymer and water, and stiffer chains also lead to improved water diffusion to a much lesser extent. Sufficiently long Nafion chains are required to realistically represent the relatively immobile Nafion framework and mobile proton conducting water domain. Direct quantitative cluster size analysis is advocated to characterize the water channel connectivity.
Metabolomics‐Based Dietary Biomarkers in Nutritional Epidemiology—Current Status and Future Opportunities
Authors: Brennan Lorraine , Hu Frank B.
Published: April 2018

The application of metabolomics in nutrition epidemiology holds great promise and there is a high expectation that it will play a leading role in deciphering the interactions between diet and health. However, while significant progress has been made in the identification of putative biomarkers, more work is needed to address the use of the biomarkers in dietary assessment. The aim of this review is to critically evaluate progress in these areas and to identify challenges that need to be addressed going forward. The notable applications of dietary biomarkers in nutritional epidemiology include 1) determination of food intake based on biomarkers levels and calibration equations from feeding studies, 2) classification of individuals into dietary patterns based on the urinary metabolic profile, and 3) application of metabolome wide–association studies. Further work is needed to address some specific challenges to enable biomarkers to reach their full potential.
Electronic circuit design for RF energy harvesting using 28 nm FD‐SOI technology
Authors: Awad M. , Benech P. , Duchamp J. M.
Published: April 2018

In this article, a voltage doubler circuit designed using 28 nm FD‐SOI technology has been studied for electromagnetic energy harvesting. NLVT transistor type is chosen and used as a diode for the realization of a Dickson voltage doubler circuit. Moreover, the impact of back gate polarization on circuit performance has been analyzed. The optimization of the circuit along with the measurement results has been presented (1.19 V for 1 stage at −26.3 dBm @ 2.45 GHz).
Microwave imaging of a conducting cylinder buried in a lossless half space by modified fireworks algorithm
Authors: Lee Kun‐Chou
Published: April 2018

In this article, the microwave imaging of a conducting cylinder buried in a lossless half space is given by the modified fireworks algorithm. The interface scattering effects are treated by the half‐space Green's function. The target shape is represented by a Fourier series with finite terms. Image reconstruction is first transformed into an optimization problem. The variables are Fourier series coefficients of the target shape. The objective function is defined by comparing scattered electric fields from the guessed and true shapes, respectively. The transformed optimization problem is then solved by the modified fireworks algorithm. Numerical results show that the proposed image reconstruction scheme is accurate, converges well, and can tolerate multiple scattering effects.
Model analysis of coupled‐mode leaky‐wave antenna for forward and backward frequency scanning
Authors: Kandwal Abhishek , Zhang Qingfeng , Das R. , Tang Xiaolan , Louis L.W.
Published: April 2018

This article proposes model analysis of a microstrip leaky‐wave antenna for forward and backward scanning. Mode coupling and dual scan concept is introduced in this article with an inverted V‐section leaky‐wave antenna. The proposed design concept has been implemented on microstrip planar structure. An inverted V‐section has been therefore implemented which resulted in frequency scanning in forward and backward directions in the right‐hand (RH) region. The phenomenon has been observed within same frequency bandwidth of leaky‐wave region which is normally difficult to see in conventional leaky‐wave antennas. The article has also provided a circuit model analysis and design implementation explained by mode coupling theory. The proposed dual scanning leaky‐wave antenna (DSLWA) design is providing a wide impedance bandwidth in the Ku‐band and K‐band with high gain, reduced side lobe levels and high radiation efficiency.
Multistub multimode resonating structure for microwave multiband band‐pass filtering applications
Authors: Pandit Nidhi , Pathak Nagendra Prasad
Published: April 2018

This article proposes a design, analysis, and characterization of multistub resonator with its multimode characteristics for band‐pass filtering applications. First, the principle of resonating structure is explained with related mathematical explanations. Next, the proposed multimode structure is introduced with simple technique to analyze resonating frequency behavior by related mathematics. Through mathematical analysis, it has been presented that the number of resonating frequency and their position can be individually controlled by structural parameter. As a result, the proposed resonating structure can be utilized to design different microstrip band‐pass filters (BPFs). For validating the concept, an ultra wide band (UWB) BPF with −3 dB impedance bandwidth of 4.6 GHz (1.9–6.5 GHz) and a dual band BPF with −3 dB impedance bandwidth of approximately 1.5 GHz (2.7–4.3 GHz) for the first band and around 2.1 GHz (6.2–8.3 GHz) for the second band; have been implemented on Neltec substrate with dielectric constant 3.38, thickness 1.52 mm, and loss tangent 0.0016 and characterized on Keysight vector network analyzer N9918A. All the measured and simulated results are in good agreement with each other.
A butterfly‐based direct solver using hierarchical LU factorization for Poggio‐Miller‐Chang‐Harrington‐Wu‐Tsai equations
Authors: Guo Han , Liu Yang , Hu Jun , Michielssen Eric
Published: April 2018

A butterfly‐based hierarchical LU factorization scheme for solving the PMCHWT equations for analyzing scattering from homogenous dielectric objects is presented. The proposed solver judiciously re‐orders the discretized integral operator and butterfly‐compresses blocks in the operator and its LU factors. The observed memory and CPU complexities scale as O(N log2 N) and O(N1.5 log N), respectively. The proposed solver is applied to the analyses of scattering several large‐scale dielectric objects.
A 40‐GHz hybrid class‐AB/class‐BCMOSVCO with a current‐combining transformer
Authors: Oh Juntaek , Jang Jingyu , Hong Songcheol
Published: April 2018

A 40‐GHz hybrid class‐AB/class‐B CMOS VCO with a current‐combining transformer (CCT) using a 65‐nm RF CMOS process is presented. The hybrid class‐AB/class‐B configuration is adapted to two cross‐coupled pairs to lower the power consumption while maintaining the phase noise performance. As a simple coupling network between two cross‐coupled pairs with different bias conditions, the CCT performs the roles of a high Q‐factor resonator, a large impedance transformer, and a buffer without additional circuitry. The VCO operates at 38.15–40 GHz with power consumption in the range of 11–13 mW. The measured phase noise at a 1‐MHz offset from the 40 GHz carrier is −117.1 dBc/Hz with a 1.0 V supply voltage. The proposed power oscillator achieves an FOMT value of −191.3 dBc/Hz.
A 55‐W high efficiency unbalanced three‐stage Doherty power amplifiers for various output power back‐offs
Authors: Kim Ji‐Yeon , Kang Yunho , Kim Jong‐Heon
Published: April 2018

High efficiency unbalanced three‐stage Doherty power amplifiers (DPA) for input signals with various peak to average power ratios (PAPR) are presented. The amplifier uses three GaN devices of equal size. The output power back‐off (OPBO) at the efficiency peak of the amplifier can be extended and reduced according to the input signals with various PAPR. This is achieved by adjusting the impedances of the λ/4 impedance transformers at the individual amplifier output stages in the three‐stage DPA without the use of additional circuitries and by changing the impedance matching circuit at the input stages of the amplifiers. The current of the individual amplifiers in the three‐stage DPA is calculated according to the PAPR of the input signals. The impedances of the λ/4 impedance transformers are determined by the current ratio for the main, first peaking, and second peaking amplifiers and are implemented by microstrip lines. 55 W unbalanced three‐stage DPAs for extended and reduced OPBO are designed and fabricated to be operated at the frequency of 1810 MHz.
Gain enhancement of a printed leaf shaped UWB antenna using dual FSS layers and experimental study for ground coupling GPR applications
Authors: Kundu Surajit , Chatterjee Ayan , Jana Sanjay Kumar , Parui Susanta Kumar
Published: April 2018

A printed leaf shaped compact (40 mm × 30 mm × 0.8 mm) UWB antenna added with dual frequency selective surfaces (FSS) of dimension 44 mm × 44 mm × 1.6 mm is proposed. The FSS layers having 4 × 4 array in each can provide maximum gain of 8.7 dBi and gain enhancement by 2–4.5 dBi in the antenna bandwidth of 3–14.64 GHz. The proposed design also ensures maximum radiation in the broadside direction with average radiation efficiency of 85%. The antenna bandwidth and group delay responses were measured in close proximity of soil test bed for varying test bed thicknesses. Relative bandwidth of more than 114% with non‐varying group delay response ensure the ability of proposed antenna to work for ground coupling ground penetrating radar applications.
A high frequency ratio quadri‐band frequency independently tunable antenna with spurious‐mode suppression
Authors: Li Peng Kai , You Chang Jiang , Yu Hong Fang , Cheng Yu Jian , Yang Yuan Wang , Deng Jian Hua
Published: April 2018

A quadri‐band frequency independently tunable patch antenna with high frequency ratio is proposed in this article. It is realized by nesting two rectangular patches and two U‐shaped patches together separated with gaps. Each patch is resonating at one band. U‐shaped patches are utilized to suppress the spurious‐mode resonances when designing antenna with high frequency ratio. Two parallel varactors are embedded on each patch to tune its resonant frequency. Measured results demonstrate the quadri‐band antenna has tunable ranges of 0.75–0.97, 1.87–2.11, 2.37–2.63, and 3.36–3.72 GHz, respectively, with a high frequency ratio of 5, low spurious‐mode resonances, comparatively high gains of 2–8 dBi and efficiencies of 30–80%.
Design of optical leaky wave antenna with circular and diamond Si perturbations for enhancing its performance
Authors: Shah Karan H. , Sonagara Japit S. , Patel Shobhit K. , Argyropoulos Christos
Published: April 2018

In this manuscript a design of silicon on insulator (SOI)‐based dielectric (silicon nitride) Optical Leaky Wave Antenna loaded with periodic circular and diamond shape semiconductor (Si) perturbation is proposed. This optical antenna is excited at one end of dielectric waveguide. The proposed design is also compared with the existing design and the results are obtained which shows that proposed design is more efficient than the existing one. The design results in form of transmission coefficient and reflection coefficient are compared. The efficiency is increased by introducing circular and diamond shape perturbation in the waveguide. The designed Optical Leaky Wave Antenna will be applicable in optical switching and optical imaging.
Investigation on the surface flashover of high gain SI‐GaAs PCSS
Authors: Ji Weili , Shi Wei , Ma Cheng , Cao Juncheng
Published: April 2018

The GaAs photoconductive semiconductor switch (PCSS) is generally recognized currently as a leading power electronic device for its unique advantages. A major limitation of PCSS has been its surprisingly low voltage threshold for the surface flashover found when PCSS works at the high gain mode. In this paper, the surface flashover of high gain PCSS is studied by experiments. We propose that the non‐uniform distribution of the surface field that resulted from the photo‐activated charge domain (PACD) and the gas desorption is the key cause of such reducing of the SF field. SF6 ambient dielectric is efficient in increasing the surface field, and the experiment results show that the PCSS we developed could resist a voltage as high as 20 kV/cm when the ambient dielectric is 3 atmospheric SF6. This conclusion has the practical application of significance to improve the performance of the high gain PCSS, which is severely limited by the premature breakdown effects.
Slot‐loaded patches with a switching mechanism to extend the scanning range of a phased array subject to scan blindness
Authors: Ayissi Manga Aurélien , Gillard Raphaël , Loison Renaud , Le Roy‐Naneix Isabelle , Renard Christian
Published: April 2018

This article presents a novel solution to extend the scanning range of a cavity‐backed stacked‐patch phased array whose performances are limited by scan blindness. Two main aspects are investigated. The first section is a thorough description of the scan blindness mechanism and the associated mutual coupling scheme occurring in the reported array. The second section introduces a revised array topology that allows extending the scanning range up to the blind angle. The article focuses on the proof of concept of the proposed solution, which is based on the switching between two operating modes of the structure, each one covering a part of a globally wider scanning range. In the present case, the scanning capability of the array has been extended by 10° in the scanning plane of interest. Besides, the restored impedance matching allows for a 2 dBi gain improvement at the scan blindness angle.
Accurate time difference of arrival estimation for HF radio broadcast signals
Authors: Jain Ankit , Pagani Pascal , Fleury Rolland , Ney Michel M. , Pajusco Patrice
Published: April 2018

Geolocation of high frequency (HF) transmitters at distances in the order of 2000 km is possible by exploiting the time difference of arrival (TDoA) among multiple distributed single antenna receivers. HF radio signals propagate via skywaves between the Earth‐Ionosphere medium and the signals are received through non‐line‐of‐sight mode. This experimental study demonstrates that it is possible to evaluate the TDoA between two receivers for a HF radio broadcast signal propagating through the ionospheric channel. The HF propagation path geometry for one hop propagation mode is explained. Simulations are performed using this model to evaluate the theoretical TDoA between the signals received at two synchronized receivers. In the second step, two remotely controllable receivers built to capture distinct HF signals are deployed in two cities in France. Radio broadcast signals from different HF transmitters across Europe are captured simultaneously on the two synchronized receivers. The TDoA is obtained by cross‐correlating the captured signals from the receivers. The TDoA obtained by experimental and simulation methods are compared for different radio propagation paths and results show some very good agreement.
Circularly polarized monopole hook antenna for ISM‐band systems
Authors: Donelli M. , Robol F.
Published: April 2018

In this letter, a circular polarized monopole hook antenna for ISM‐band applications is proposed. The antenna is printed on dielectric substrate and is fed by a 50 microstrip line. The antenna demonstrated good radiation properties, a wideband return loss, and a very good axial ratio. The influence of geometrical antenna parameters and in particular the hook angle which affect the antenna polarization are investigated and optimized. The obtained experimental results are in good agreement with the simulations.
Novel microstrip quadruplexer with wide stopband for WiMAX applications
Authors: Rezaei Abbas , Noori Leila
Published: April 2018

This work introduces a planar harmonic suppresser microstrip four‐channel multiplexer based on an originally novel geometrical structure. It consists of coupled lines connected to engraved semicircular cells. The realized quadruplexer operates at 3.211, 3.276, 3.38, and 3.491 GHz for IEEE 802.16 WiMAX. Wide stopbands above all passbands are obtained up to about 20 GHz so that fifth harmonics are attenuated properly. The semicircular structures provide quite close channels, which make it appropriate for FDD scheme. Compared to the previous reported quadruplexer, the common port return loss is decreased significantly, where improving the common port impedance matching for very close passbands is an important challenge. To minimize the circuit size, a new matching network consisting of coupled line and step impedance cell is embedded. To verify the designing methodology, the proposed multiplexer is fabricated and measured, where the simulated and measured results are in a good agreement.
Triple‐band hybrid antenna with integral isolation mechanism for MIMO applications
Authors: Das Gourab , Sharma Anand , Gangwar Ravi Kumar
Published: April 2018

This research article explains the designing of triband multiple input multiple output (MIMO) hybrid radiator for diversified wireless applications. It comprises of two symmetrically placed hybrid radiators. These hybrid radiators are placed on a FR4 substrate with protruded ground plane to provide maximum isolation
and improved diversity performance. Hybrid radiator consists of two C‐shaped printed lines and cylindrical dielectric resonator (CDR). A dual C‐shaped printed line behaves as a magnetic dipole and produces two different radiating modes in CDRA, that is, HE11δ and TE01δ mode. For confirming the simulated results, the prototype has been constructed and examined. Good agreement has been establish between simulated and experimental results. The proposed radiator is working over three frequency bands, that is, 1.86–2.60, 3.3–3.64, and 4.42–6.75 GHz. Different MIMO diversity performance parameters (ECC, DG, MEG, and CCL) are also examined and found to be in acceptable limit.
A compact open complementary split ring resonator inspired triband reconfigurable coplanar waveguide fed antenna
Authors: Rasool Maryam , Farooq Rabiya , Rashid Muhammad Hashir , Zafar Abdullah , Afzal Hira , Alimgeer Khurram Saleem , Ijaz Bilal , Iftikhar Adnan
Published: April 2018

This paper presents the implementation of open complimentary split ring resonator (OCSRR) structure in small rectangular radiating elements to achieve triple band and dual band reconfigurability using PIN diode. The proposed design is a coplanar waveguide fed structure and consists of three small radiating elements, whereas two OCSRR structures are coupled with the two‐radiating elements. The third radiating element embedded with OCSRR is connected using a PIN diode. Under DC biasing conditions the whole design resonates at three frequencies, that is,
,
, and
, whereas the proposed design switches to dual band operation at
and
in the diode ‘OFF’ state. The proposed structure is designed and fabricated on a single sided ungrounded FR
substrate. Overall, a good agreement between simulated and measured results is observed. It is also observed that the radiation patterns of the proposed antenna are the same with gains of
,
, and
at
, and
in the PIN diode ‘ON’ state, respectively, whereas in the diode ‘OFF’ state, at
the gain is
and at
the gain is
.
A reconfigurable miniaturized planar inverted‐F antenna with integrated BaSrTiO3 capacitor
Authors: Haskou Abdullah , Sharaiha Ala , Collardey Sylvain , Borderon Caroline , Ginestar Stéphane , Renoud Raphaël , Gundel Hartmut W.
Published: April 2018

In this letter, a wide‐tuning range planar inverted‐F antenna (PIFA) of 17 × 10 mm2 dimension printed on a Rogers duroid RT5880 substrate is presented. The printed circuit board (PCB) dimensions are 1 × 60 mm2. First, the antenna is simulated with a localized capacitor and the effect of the capacitor losses on the antenna efficiency is studied. Then, the antenna is simulated with an integrated BaSrTiO3 (BST) tunable capacitor. The obtained results are in very good agreement with those obtained with localized elements. Finally, the BST thin film capacitor is fabricated and mounted on the antenna. The experimental results show a capacitor tunability of 56.7% at a bias voltage of 35 V, leading to an antenna agility of 42.2%.
VHF suspended plate transmitter antenna design for DVB‐T and DAB‐T
Authors: Ali Abdul , Ciydem Mehmet , Altintas Ayhan , Koc Sencer
Published: April 2018

This paper presents the design of stacked suspended plate transmitter antenna for digital video and audio broadcasting. Contrary to conventional dipole structures, we have designed the antenna in VHF band (174–254 MHz) with two plates for wideband matching and design flexibility. Radiating primary plate has been excited by novel wideband modified inverted L‐type probe. Parasitic secondary plate, and vertical wall between primary plate, and ground plane have been used for further matching and beamwidth adjustment. A bandwidth of 42% and gain of 8.5 dBi is obtained at center frequency. Together with equivalent lumped element circuit model of designed antenna and experimental results for S11, gain, and radiation pattern are presented. To the best of authors knowledge this is the first stacked suspended plate antenna achieving a record bandwidth of 42% in VHF band.
Detection of different concentrated salt and sugar solution based on dielectric properties using microstrip technology
Authors: Rahman M. N. , Islam M. T. , Samsuzzaman M.
Published: April 2018

This article presents a microwave system to detect salt and sugar content in water using microstrip technology. The presented technology consists of a microstrip patch antenna which involves a tuning fork‐shaped patch and slotted partial ground plane. The antenna is printed on Rogers RT/duroid 5880 material with a thickness of 1.57 mm. The antenna has a compact physical size of 24 mm × 18 mm. Being used as a sensor the microstrip antenna detect the salt and sugar in water in terms of the reflection coefficient. The percentage of salt and sugar in water changes the dielectric properties which also change the reflection coefficients. In the practical experiments, the reflection coefficient decreases with the increment of the percentage of salt and sugar in water.
Design of a compact dual‐band monopole antenna using a top‐loaded octagon patch and perforated shorting pin
Authors: Park Jae Sung , Choi Hak Keun
Published: April 2018

In this article, an antenna operated in the dual band (824‐894 and 1750–2800 MHz) is proposed, and its performance is verified. The proposed antenna is structured with a monopole antenna of a reversed crossing trapezoidal type, over which a top‐loaded octagon patch is added; moreover, a perforated shorting pin is appended to the center of the reversed crossing trapezoidal monopole antenna. The performance is verified while changing the width at the connector between the top‐loaded octagon patch and reversed crossing trapezoidal monopole antenna and the width of the inverted‐L slit width after inserting it between the reversed crossing trapezoidal monopole antenna and the top‐loaded octagon patch. The monopole antenna of the crossed reversed crossing trapezoidal type has a broadband characteristic at the 1750‐ to 2800‐MHz band and can be run even in the 824‐ to 894‐MHz band by adding the top‐loaded octagon patch and perforated shorting pin. The antenna proposed in this study is a low‐profile antenna with a height of ∼λ/7 in the 824‐ to 894‐MHz (center frequency: 859 MHz) band, and it satisfies a return loss below −14 dB. The band characteristic at 1750–2800 MHz satisfies a return loss below −14 dB, even if the structure for the 824‐ to 894‐MHz band is added. The antenna gain is revealed as ∼−1 to 1 dBi in the 824‐ to 894‐MHz band.