A new design approach for dual-band power amplifiers based on dual-band HCC and bandpass filter

This paper introduces a novel design approach based on the dual-band harmonic control circuit and bandpass filter for dual-band power amplifiers. The circuit schematic of the proposed approach is constructed using four resonators and RFC inductors. The first two resonators are dedicated to controlling the second harmonics, while the third and fourth resonators serve as a harmonic blocker, allowing only the main signals to pass through to the load. Subsequently, all components are replaced by circuits based on microstrip elements, forming the proposed OMN. This OMN includes a novel wideband bias circuit, elliptically coupled resonators, and a new dual-band bandpass filter. To ensure compatibility with the transistor, a compensator line has been integrated. As a result, a dual-band power amplifier has been fabricated and measured at two operating frequencies, 2.1 GHz and 2.91 GHz. The measured values for drain efficiency, output power, and power gain at 2.1 GHz are 75.98%, 37.5 dBm, and 12.5 dB, respectively. Similarly, at 2.91 GHz, these values are 75.73%, 37.24 dBm, and 12.24 dB, respectively.

High Transmission All-Optical Combinational Logic Circuits Based on a Nanoring Multi-Structure at 1.31 µm

The main purpose of this study is to design combinational logic gates based on a novel configuration of insulator-metal-insulator (IMI) nanoring plasmonic waveguides. Plasmonic logic gates are half adder, full adder, half subtractor, full subtractor, and one-bit comparator and are realized in one structure. The performance of the logic circuits is based on constructive and destructive interferences between the input and control signals. The transmission threshold value is assumed to be 0.35 at the resonance wavelength of 1.310 μm. The transmission spectrum, contrast loss (CL), insertion loss (IL), modulation depth (MD), and contrast ratio (CR) are calculated in order to evaluate the structure's performance. The maximum transmission of the proposed structure is 232% for full a adder logic gate, and MD exceeds 90% in all plasmonic combinational logic circuits. The suggested design plays a key role in the photonic circuits and nanocircuits for all-optical systems and optical communication systems. The combinational logic gates are analyzed and simulated using the finite element method (FEM).

Design of dual-band power amplifier using bandstop filter and dual-mode bias circuit for multistandard transceiver systems

This paper presents a dual-band power amplifier (PA) using a meandered line bandstop filter (BSF). An important challenge addressed in this design is to achieve proper isolation between the operational bands of the amplifier. The proposed BSF provides isolation and efficiency, effectively separating the output power and power gain between the two operational bands. Additionally, a dual-mode bias circuit is designed to serve as an inductor choke and control the second harmonics for both operating frequencies simultaneously. Two dual-band PAs, utilizing LDMOS and GaN HEMT transistors, have been designed using the proposed output matching circuit, which incorporates the BSF, bias circuit, and compensation circuit. The results obtained from both PAs, employing different transistors, are identical. Based on the presented concepts, a dual-band PA with an LDMOS transistor has been fabricated and measured. The measurements reveal an efficiency of 79.23%, an output power of 39.85 dBm, and a power gain of 14.85 dB at a frequency of 0.7 GHz. Similarly, at a frequency of 1.9 GHz, the efficiency is 77.24%, the output power is 38.22 dBm, and the power gain is 13.22 dB.

Investigation of temperature variations on a Class-E inverter and proposing a compensation circuit to prevent harmful effects on biomedical implants

In this paper, a Class-E inverter and a thermal compensation circuit for wireless power transmission in biomedical implants are designed, simulated, and fabricated. In the analysis of the Class-E inverter, the voltage-dependent non-linearities of C_ds, C_gd, and R_ON as well as temperature-dependent non-linearity of R_ON of the transistor are considered simultaneously. Close agreement of theoretical, simulated and experimental results confirmed the validity of the proposed approach in taking into account these nonlinear effects. The paper investigated the effect of temperature variations on the characteristics of the inverter. Since both the output power and efficiency decrease with increasing temperature, a compensation circuit is proposed to keep them constant within a wide temperature range to enable its application as a reliable power source for medical implants in harsh environments. Simulations were performed and the results confirmed that the compensator enables significant improvements by maintaining the power and efficiency almost constant (8.46 ± 0.14 W and 90.4 ± 0.2%) within the temperature range of - 60 to 100 °C. Measurements performed at 25 °C and 80 °C with and without the compensation circuit were in good agreement with the theoretical and simulation results. The obtained measured output power and efficiency at 25 °C are equal to 7.42 W and 89.9%.

Low Cost Digital Implementation of Hybrid FitzHugh Nagumo-Morris Lecar Neuron Model Considering Electromagnetic Flux Coupling

Digital realization of neuron models, especially implementation on a field programmable gate array (FPGA), is one of the key objectives of neuromorphic research, because the effective hardware realization of the biological neural networks plays a crucial role in implementing the behaviors of the brain for future applications. In this paper, a hybrid FitzHugh Nagumo-Morris Lecar (FNML) neuron model with electromagnetic flux coupling is considered, and two multiplierless piecewise linear (PWL) models, which have similar behaviors to the biological neuron, are presented. A comparison between digital implementation results of the original FNML and PWL models illustrates that, the PWL1 model provides a 65% speed-up with an overall saving (in FPGA resources) of 66.2%, and the PWL2 model yields a 71% speed-up with an overall saving of 78.2%.

Optical biosensors using plasmonic and photonic crystal band-gap structures for the detection of basal cell cancer

One of the most interesting topics in bio-optics is measuring the refractive index of tissues. Accordingly, two novel optical biosensor configurations for cancer cell detections have been proposed in this paper. These structures are composed of one-dimensional photonic crystal (PC) lattices coupled to two metal-insulator-metal (MIM) plasmonic waveguides. Also, the tapering method is used to improve the matching between the MIM plasmonic waveguides and PC structure in the second proposed topology. The PC lattices at the central part of the structures generate photonic bandgaps (PBGs) with sharp edges in the transmission spectra of the biosensors. These sharp edges are suitable candidates for sensing applications. On the other hand, the long distance between two PBG edges causes that when the low PBG edge is used for sensing mechanism, it does not have an overlapping with the high PBG edge by changing the refractive index of the analyte. Therefore, the proposed biosensors can be used for a wide wavelength range. The maximum obtained sensitivities and FOM values of the designed biosensors are equal to 718.6, 714.3 nm/RIU, and 156.217, 60.1 RIU^-1, respectively. The metal and insulator materials which are used in the designed structures are silver, air, and GaAs, respectively. The finite-difference time-domain (FDTD) method is used for the numerical investigation of the proposed structures. Furthermore, the initial structure of the proposed biosensors is analyzed using the transmission line method to verify the FDTD simulations. The attractive and simple topologies of the proposed biosensors and their high sensitivities make them suitable candidates for biosensing applications.

Toxin typing of Clostridium perfringens Associated with Enterotoxaemia in Sheep in Fars Province

Clostridium perfringens is implicated in the etiology of some diseases including fatal enterotoxaemia. Determining dominant toxin types of this microorganism can be helpful in epidemiologic surveys and the formulation of more proper vaccines. To understand the pathogenicity of this bacterium, it seems necessary to describe the toxin and virulence genes content of strains involved in enterotoxaemia and other associated diseases. The current study aimed to isolate and type the toxins of C. perfringens in sheep with suspected enterotoxaemia in Fars province by culture-PCR and ELISA methods and to compare them to isolates of a healthy group. Samples of intestinal contents were collected from enterotoxaemia cases and a healthy group of sheep. The presence of alpha, beta, and epsilon toxins were evaluated by ELISA method. After culture and isolation of C. perfringens, toxin typing and screening of isolates for the presence of beta-2 and enterotoxin were performed by PCR method. C. perfringens was isolated from 102 of 167 suspected enterotoxaemia cases of sheep and from 22 of 50 healthy sheep. The PCR results showed that type A was the most prevalent toxin type in both groups, but according to ELISA type D was the dominant toxin type in the clinical group. The enterotoxin gene was detected in 10% of all isolates from healthy and suspected group isolates of types A and D. The beta-2 gene was identified in 35% and 63.6% of enterotoxaemia-associated isolates and isolates not associated with disease, respectively. In conclusion, Type D of C. perfringens was the dominant causative organism of fatal enterotoxaemia in sheep in Fars province.

A Digital Realization of Astrocyte and Neural Glial Interactions

The implementation of biological neural networks is a key objective of the neuromorphic research field. Astrocytes are the largest cell population in the brain. With the discovery of calcium wave propagation through astrocyte networks, now it is more evident that neuronal networks alone may not explain functionality of the strongest natural computer, the brain. Models of cortical function must now account for astrocyte activities as well as their relationships with neurons in encoding and manipulation of sensory information. From an engineering viewpoint, astrocytes provide feedback to both presynaptic and postsynaptic neurons to regulate their signaling behaviors. This paper presents a modified neural glial interaction model that allows a convenient digital implementation. This model can reproduce relevant biological astrocyte behaviors, which provide appropriate feedback control in regulating neuronal activities in the central nervous system (CNS). Accordingly, we investigate the feasibility of a digital implementation for a single astrocyte constructed by connecting a two coupled FitzHugh Nagumo (FHN) neuron model to an implementation of the proposed astrocyte model using neuron-astrocyte interactions. Hardware synthesis, physical implementation on FPGA, and theoretical analysis confirm that the proposed neuron astrocyte model, with significantly low hardware cost, can mimic biological behavior such as the regulation of postsynaptic neuron activity and the synaptic transmission mechanisms.

Prevalence and distribution of the stx, stx genes in Shiga toxin producing E. coli (STEC) isolates from cattle

BACKGROUND AND OBJECTIVES

Shiga toxin-producing Escherichia coli (STEC) strains are human pathogens linked to hemorrhagic colitis and hemolytic uremic syndrome. Shiga toxins (Stx1 and Stx2) are the major virulence factors of these strains. The aim of this work was to study the prevalence and distribution of stx(1) and stx(2) gene in E. coli O157:H7 and non-O157:H7 strains isolated from cattle in Shiraz, Iran.

MATERIALS AND METHODS

Four hundred and twenty samples consisted of recto-anal mucosal swabs were collected from cattle. They were checked for the presence of the stx1 and stx2 gene using multiplex-PCR every 1 week over a 1-year period (2007-2008).

RESULTS

A total of 146 strains carrying the stx1 and stx2 gene were isolated from 51 (12.14%) cattle. Overall, 15 (3.57%) were identified as O157:H7 and 131 (31.19%) revealed to be non-O157:H7. Both stx2 and stx1 genes were detected in 51 (34.93%) STEC isolates. Genotypes stx1 and stx2 were detected in 15 (10.27%) and 78 (53.42%) respectively. Seasonal distribution of stx genes revealed high percentage of positive animals in warm seasons. The gene sequence similarity ranged from 94 to 100%.

CONCLUSION

Frequency of stx1 and stx2 in animals and its relation to human disease is not well understood in Iran. The high prevalence of STEC in cattle seems to parallel that which is usually observed in warm seasons and it also parallels occurrence of human STEC. The higher prevalence of the stx2 gene than stx1 in strain populations isolated from cattle indicates a risk alert of E. coli O157:H7 being shed by cattle in these populations. Appropriate measures are now needed to prevent the spread of this life-threatening foodborne disease in our country.

[Nutritional condition, food consumption and nutritional intake in students in Saudi Arabia. II. Food consumption and nutritional intake]

In field surveys in 13 schools in different regions of Saudi-Arabia, energy expenditure, food consumption, and nutrient intake were studied. Cereal products, especially bread, have the greatest significance in nutrition. Many students do not eat other foodstuffs regularly. A certain dependency of food consumption from the region was found in regard to the schools. The frequency of foodstuffs was generally low, but lowest in remote villages. In some age groups, the sufficient energy intake leaves much to be desired, 70 % do not reach recommended dietary allowances of animal protein and 100 % in fat. Intake of carbohydrates was too high, while intake of linoleic acid, minerals and vitamins is too low of nearly all test persons. To secure regularly a sufficient intake of essential nutrients, a school lunch program for the Saudi-Arabian boys is to be recommended.

[Nutritional status, food consumption and food supply of studies in Saudi Aribia. I. Anthropometric data]

A field study about the nutritional status was made in school classes with boys 6 to 19 years old in different regions of Saudi-Arabia. It is reported about 341 pupils in regard to weight, height, skinfold-thickness, circumferences and other body-size measurements. In comparison with anthropometric measurements of comparable surveys in other countries, the Saudi-Arabian school boys were found to be smaller and leaner than boys from the USA, Europe, other Arabian countries and well-to-do Indian boys.