bluuebunny/crossref_metadata_2025 huggingface dataset:
Assessment of Radiation Dose in Nuclear Medicine Controlled Areas: Hot Lab, Injection and Isolated Rooms
Authors: Bidemi I. Akinlade , Sherif O. Kelani
Published: December 2019

Introduction: Observing radiation protection and safety culture in radiation practices reduce radiation exposure and the probability of radiation risk to workers, patients and the general public. This study assesses the radiation protection and safety practice at the pioneer Nuclear Medicine Centre in Nigeria, University College Hospital (UCH), Ibadan. This assessment involves measurements of dose rate and surface contamination in the hot laboratory, injection and patient’s isolated rooms and compares their values with international recommended limits.

Materials and Methods: Measurements of radiation doses and surface contamination in the controlled areas were carried out using three different high-sensitive and calibrated radiation detectors namely Ultra Radiac (model MRAD 1010), Ludlum (model 2241-3/44-9) and Redeye (model PRD).

Results: The dose rate values in the controlled areas monitored ranged from 0.103 to 0.430 µGy/h while the effective doses calculated from these values ranged from 0.2 to 0.86 mSv per annum. This is far less than the recommended dose limit of 20 mSv per annum for radiation worker, who usually worked in these areas. Also, the surface contamination values obtained in these areas ranged from 0.060 to 2.867 Bq/cm2, which is similarly less than the recommended limit of 10 Bq/cm2.

Conclusion: These results showed that the centre has a wide range of compliance with radiation safety practice according to the acceptable standards guided by the Nigerian Nuclear Regulatory Authority and International regulations.
Sinonasal Melanoma: A Rare Cause of Severe Nasal Bleeding
Authors: Derkyi-Kwarteng Leonard , P. Akakpo Kafui , A. Brown Ato , N. Derkyi-Kwarteng Abigail , Gustav Imbeah Emmanuel
Published: December 2019

Mucosal melanoma is an aggressive but very rare tumour that can occur within the nasal and paranasal sinuses. It accounts for less than 1.0% of all melanomas and 4.0% of all sinonasal tumours. We present a 48-year-old with a stage IVA nasal melanocytic melanoma who had surgery as primary treatment option.
Productivity of Cotton as Affected by Tillage Practices, Fertilizer Rates and Intercropping Systems in the Guinea Savannah Agroecology, Ghana
Authors: Ghanney Philip , Xorse Kugbe Joseph , Kongyeli Badii Benjamin , Asomning Odoom Daniel
Published: December 2019

Extensive areas of bare, compacted, and nutrient-poor soils hinder crop production in the Guinea Savannah Agro-ecological zone of Ghana. Resolving this challenge can be effected by developing sustainable land management strategies that can adequately improve soil nutrient status and enhance crop yield. Field studies were conducted to evaluate the productivity of cotton as affected by tillage practices, fertilizer rates and intercropping systems in the Guinea Savanna agroecology of Ghana, during the 2016 and 2017 cropping seasons. Treatments consisted of 2 tillage practices (ploughing and direct seeding [sole cotton]), 2 fertilizer application rates (54-30-30 kg/ha NPK and 0-0-0 kg/ha NPK) and 3 intercropping systems (sole cotton, cowpea intercrop and soybean intercrop) which were laid in split-split plot design with three replications. The tillage practices, fertilizer rates and the intercropping systems were respectively allocated as the main plot, sub-plot and sub-sub plot treatment respectively. Unlike the three-way interaction effect which did not significantly influence variation in growth, yield and yield components of cotton, the two-way interaction  and the single factors were however influential. The combined impact of the NPK fertilizer application rate at 54-30-30 kg/ha and ploughing resulted in higher seed yield of cotton. Comparatively, seed yield of cotton was 35.78% higher when 54-30-30 kg/ha fertilizer rate (1.29 t/ha) was applied compared with 0-0-0 kg/ha fertilizer rate (0.61 t/ha). It is however recommended that resource-poor farmers in the Guinea Savannah agro-ecological zone of Ghana adopt to the use of 54-30-30 kg/ha fertilizer rate and ploughing for cotton seed yield maximization.
Comparisons of Four Methods for Thinning Eucalyptus Hybrid Coppice Shoots in Brazil
Authors: Cesar Fiedler Nilton , Pinheiro Cabral Ricardo , Ribeiro de Mendonça Adriano , Pintor Canzian Weslen , Henrique Cordeiro Ramalho Antonio , Ransolin Soranso Denise
Published: December 2019

Both manual and semi-mechanized systems are used for operations involved in coppice remodeling. Thus, there is a paradigm about the higher yield of semi-mechanized operations compared to manual operations. However, the small volume of research on this subject does not present data which is capable of confirming this hypothesis. Thus, the present study aimed to perform a technical analysis of costs, quality and productivity of different methods for conducting regrowth in Eucalyptus grandis x Eucalyptus urophylla hybrid plantations under coppice regeneration in areas of forest fostering. The experiment was conducted under a completely randomized design with four treatments (sprouting methods) and four replications in plots of 360m² each. The methods used were: brushcutter, sickle, machete and hand digger. An F-test (p <0.05) was performed to verify the differentiation between treatments for a given characteristic after verifying the normal distribution of data and homogeneity of variances. The means were compared by analysis of variance at the 5% significance level to analyze if there was significant difference between the operating times in the analyzed methods. An estimate of the costs per hectare was subsequently obtained in each offspring method and the quality of the operation was evaluated by observing the frequency of damage to the remaining trunk. The mean operation time of the methods did not differ significantly (p> 0.05). The brushcutter presented the highest cost per hectare (US$ 40,06/ha-1) and the excavator presented the lowest (US$ 18,65/ha-1). Spreading with the brushcutter presented the lowest percentage of mechanical damage (6.88%) and the sickle obtained the highest (20.63%). It was concluded that the operation with brushcutter was the method that provided the highest productivity, but has the highest operational cost, making the method with brushcutter, advantageous for its low cost, associated with a satisfactory productivity.
Effect of Variety and Seedling Number on the Growth and Yield of Boro Rice in Bangladesh
Authors: Chowhan Sushan , Imdadul Hoque Md. , Rani Ghosh Shampa , Islam Majharul , Babul Akter Md.
Published: December 2019

Rice is the most important human food crop in the world. In Bangladesh rice is cultivated throughout the year as Aus, Aman and Boro. Among them boro rice is generally cultivated in November to March. More than half of the total production (55.5%) is obtained in this season. Generally, farmers use more than the recommended number of seedlings during transplanting. The number of seedlings plays a vital role in the growth, development and yield of rice. The aim of this experiment was to determine the number of seedling(s) during transplanting for boro rice varieties for higher growth and yield. This investigation was carried out at the research field of BINA sub-station under Khagrachari sadar upazila in Bangladesh during December 2017 to May 2018. The experiment tested three seedling numbers; S1 (Single), S2 (double), S3 (triple) and four varieties V1 (BRRI dhan-28), V2 (Binadhan-14), V3 (Heera-1), V4 (Shakti-2) in a factorial RCB design with three replications. Results revealed that significantly highest plant height was obtained with treatment S1´V3 (110.30 cm) and S3´V4 (109.4 cm) while the maximum number of tillers/hill from S3´V1 (16.93) and S2´V1 (16.07). In terms of production, treatment combination S3´V4 gave the highest grain (10.40 t/ha), straw (10.40 t/ha) and biological yield (10.40 t/ha). Harvest index was the highest in treatment S1´V4 (59.48). From the above findings it was observed that single seedling performed better than two and three seedlings per hill in terms of getting optimum yield of boro rice varieties. Hence, the rice growing farmers should avoid the use of extra seedlings during transplanting to save labor, time and money.
Investigation of P2O5% and Fe2O3% Geostatistically within Abu Tartour Phosphate Deposit, Western Desert, Egypt
Authors: Farag H. A. , Gouda M. A. , Yassin M. A.
Published: December 2019

Geostatistical techniques play an important role to study the mineralization behavior within the ore deposits. When preparing the phosphate deposits for marketing, we try to minimize the iron content due to the harmful effect of this element on the physical and mechanical properties of superphosphate and phosphoric acid. One of the biggest problems in Abu Tartour phosphate deposits, Western Desert, Egypt is the high iron content within apatite grains. The received data are analyzed statistically to show the distribution of P2O5% and Fe2O3% at Abu Tartour area. Also, experimental variograms have been constructed for P2O5% and Fe2O3% of phosphate deposits through the studied area to reflect different variogram models. After fitting the variogram to suitable variogram model, kriged models are established for each variable.
World War II Holds the Key to Understanding Global Warming and the Challenges Facing Science and Society
Authors: Herndon J. Marvin
Published: December 2019

At about the same time that Russian President declared that “We are really witnessing global warming, the reasons, however, remain obscure....”, I published the first of six scientific articles disclosing the evidence and basis for understanding that particulate pollution, not anthropogenic greenhouse gases, is the main cause of global warming. The global warming that occurred during World War II, but which quickly subsided after hostilities ceased, was key to that understanding. The disquieting parallel of scientific behaviour during World War II and at present is key to understanding the challenges humanity faces today concerning science and society.
Application of Electrical Resistivity and Hydrochemistry Methods for Mapping Groundwater Contamination around Okun Ilashe Island Area, Lagos State, Southwestern Nigeria
Authors: Alabi T. O. , Ilugbo S. O. , Akinmoye O. E. , Ibitomi M. A. , Aigbedion I. , Adeleke K. A. , Ajanaku B. S.
Published: December 2019

An application of Electrical Resistivity and hydrochemistry investigation involving Vertical Electrical Sounding (VES) and water quality analysis was conducted around Okun Ilashe Island area of Lagos state, southwestern Nigeria where there have been reported cases of groundwater contamination. The hydrochemical analysis was performed on five water samples in the area; two from boreholes and others from hand dug wells. Present study investigation showed that the groundwater had been contaminated by hydrocarbon arising from pipeline leakages in the studied area. The hydrocarbon contaminated plumes are specially characterized by relatively high resistivity values (> 800 Ω-m) and were delineated to a depth of about 12 m. Hydrochemical results showed that three of the sampled water have higher total dissolved solids (TDS) (>400 ppm) in compared to the remaining water samples. The major ions identified includes Na+, K+, Cl, Mg2+, Ca2+ and NO3-. Total Dissolved Solid (TDS) and Electrical Conductivity (EC) showed values not in agreement with WHO standards values. Ten (10) Vertical Electrical Sounding (VES) stations were occupied along four traverse lines trending E-W direction. The vertical electrical sounding results indicate maximum of four subsurface layers; Top soil, hydrocarbon contaminated sand, clay/clayey sand and sand/sandy clay. The contaminant plume has migrated to a significant depth of 12 m thus posing an inherent danger to the inhabitant of the area.
Ethnobotanical and Pharmacological Importance of Western Himalayan Fir Abies pindrow (Royle ex D. Don) Royle: A Review
Authors: Sinha Dwaipayan
Published: December 2019

Aims: Abies pindrow (Royle ex D. Don) Royle., colloquially known as the Western Himalayan fir, is a conifer that grows along the Himalayan mountains from Afghanistan to Nepal. The plant is extensively used by locals for the treatments of various ailments. Thus based on the available reports about its importance in traditional system of medicine, an attempt has been made to review this species in context of its medicinal and pharmaceutical importance.

Study Design: The review article has been designed based on literature survey. The article is grossly divided into four broad phases consisting of compiled information of Abies pindrow: (1) Ethnobotanical information (2) Chemical Constituents (3) Pharmacological activities (4) Discussion mainly highlighting the mode of action of the bioactive compounds in relation to its pharmacological activity.

Methodology: Extensive literature search have been performed in the web using PubMed, PubMed Central, google scholar as search platform. Efforts have also been taken to compile information from research papers and review articles not more than 10 years old. Information from old literatures were preferably avoided unless found to be very relevant to the subject.

Results: The literature survey revealed that the plant has been used to treat cough and cold, diabetes, cataract and bladder diseases. The plant is also considered to be carminative, astringent, antispasmodic, diuretic, tonic and anti-inflammatory. The plant is also rich in terpenes and terpene alcohols. Testing for antidiabetic, neuroprotective, anticataract and antixiolytic activities have been promising and the bioactive constituents and efforts are made to interpret the possible mechanism of action of bioactive compounds in bringing about the pharmacological activities.

Conclusion: It is concluded that the plant can be explored and bioprospected for an affordable source of drug and nutraceutical for better management of health related issues of people of Indian subcontinent.
Sonochemistry (Applications of Ultrasound in Chemical Synthesis and Reactions): A Review Part III
Authors: Mohamed Menshawy A.
Published: December 2019

As the need for friendly environment increasing the need for Sonochemistry increasing. Sonochemistry has become an important field of research for organic synthesis of diverse types of reactions, that decrease environmental hazardous and increase the yield of those reactions. The aim is to continue reviewing applications of ultrasound in chemical synthesis and reactions as reported in part I [1] and part II [2]. In this article I am trying to illustrate green sonochemical approaches for organic synthesis as one of the applications of ultrasound that minimize or eliminate the use and generation of hazardous substances and reduce environmental pollution.
Adverse Obstetric Outcomes in Pregnancies With Major Fetal Congenital Heart Defects
Authors: Hedermann Gitte , Hedley Paula L. , Gadsbøll Kasper , Thagaard Ida N. , Krebs Lone , Karlsen Mona Aarenstrup , Vedel Cathrine , Rode Line , Christiansen Michael , Ekelund Charlotte K.
Published: December 2024

Importance

Understanding the risk profile of obstetric complications in pregnancies with fetal major congenital heart defects (MCHDs) is crucial for obstetric counseling and care.

Objective

To investigate the risk of placenta-related adverse obstetric outcomes in pregnancies complicated by fetal MCHDs.

Design, Setting, and Participants

This cohort study retrieved data from June 1, 2008, to June 1, 2018, from the Danish Fetal Medicine Database, which includes comprehensive data on more than 95% of all pregnancies in Denmark since the database was instituted in 2008. All singleton pregnancies that resulted in a live-born child after 24 weeks’ gestation without chromosomal aberrations were included. A systematic search of the literature was performed in PubMed, Embase, and the Cochrane Library from inception to June 1, 2024, to compile existing knowledge and data on adverse obstetric outcomes among MCHD subtypes.

Exposure

Fetal MCHDs including 1 of 11 subtypes.

Main Outcomes and Measures

The primary outcome was a composite adverse obstetric outcome defined as preeclampsia, preterm birth, fetal growth restriction, or placental abruption. Secondary outcomes consisted of each adverse obstetric event. Adjusted odds ratios (AORs) were computed using generalized estimating equations adjusted for maternal body mass index, age, smoking, and year of delivery. Meta-analyses were conducted using random-effects models to pool effect sizes for each MCHD subtype and adverse obstetric outcome.

Results

A total of 534 170 pregnancies were included in the Danish cohort, including 745 with isolated fetal MCHDs (median [IQR] maternal age, 29.0 [26.0-33.0] years) and 533 425 without MCHDs (median [IQR] maternal age, 30.0 [26.0-33.0] years). Pregnancies with fetal MCHDs exhibited a higher rate of adverse obstetric outcomes at 22.8% compared with 9.0% in pregnancies without fetal MCHDs (AOR, 2.96; 95% CI, 2.49-3.53). Preeclampsia (AOR, 1.83; 95% CI, 1.33-2.51), preterm birth at less than 37 weeks (AOR, 3.84; 95% CI, 3.15-4.71), and fetal growth restriction (AOR, 3.25; 95% CI, 2.42-4.38) occurred significantly more frequently in pregnancies with MCHDs. Except for fetal transposition of the great arteries (AOR, 1.19; 95% CI, 0.66-2.15), all MCHD subtypes carried a greater risk of adverse obstetric outcomes. The meta-analysis included 10 additional studies that supported these results.

Conclusions and Relevance

These findings suggest that nearly 1 in 4 women expecting a child with an MCHD, except transposition of the great arteries, may be at high risk of adverse obstetric outcomes.
The CMS Sickle Cell Gene Therapy Access Model
Authors: Ballreich Jeromie , Odouard Ilina C. , Socal Mariana P.
Published: December 2024

This Viewpoint explores and provides policy recommendations for the Cell and Gene Therapy Access Model recently launched by the US Centers for Medicare & Medicaid Services (CMS), which aims to increase access to Medicaid recipiencts with rare and severe diseases.
Antenna Feeds
Authors: Bird Trevor S.
Published: December 2024

The term “antenna feeds” describe many types of antennas in common use today. Feeds are a means of supplying energy to (or receiving energy from) a secondary antenna, such as a reflector, lens, reflectarray, or beam waveguide, via a transmission line or waveguide. Everyday applications of antennas with feeds include satellite communications, radar, radio telescopes, deep‐space probes, and terrestrial microwave and millimeter‐wave radiolinks.

After a brief historical introduction, the basic characteristics of antenna feeds are explained. Specific feed types are then described under four main headings, namely, aperture, linear, traveling‐wave, and compound antennas. The approach adopted combines a short description of physical attributes with an outline of possible applications.

The class of aperture antennas is the most extensive, and details are given of various circular and rectangular waveguides and horns, self‐supporting feeds, and microstrip patches in feed applications. Linear antenna feeds include the Yagi–Uda, log‐periodic, and zigzag arrays. These are reviewed, and the properties of importance are highlighted. Under the heading of traveling‐wave antennas, the antennas discussed include dielectric rods, profiled slots, Vivaldi antennas, and linefeed antennas for cylindrical and spherical reflectors. Finally, the antennas covered in the compound feeds category are arrays, beam waveguides, splash plates, and dichroic reflectors.

Antenna feeds are linked intrinsically with feed systems, and some examples given are diplexers, beamforming networks, and comparator networks for monopulse tracking.

The article concludes with an outline of modern design methods of importance of feed antennas and some predictions of possible future developments.
Numerical Analysis for Planar High‐Frequency Circuits
Authors: Rautio James C.
Published: December 2024

Numerical electromagnetics entered mainstream high‐frequency and microwave design starting about 1990. Today, with much faster computers and more powerful algorithms and design flows, numerical electromagnetics is now considered a required part of nearly all high‐frequency design. This chapter discusses the impact of numerical electromagnetics on design of planar circuits at high frequency, including silicon and gallium arsenide‐integrated radiofrequency‐integrated circuits (RFICs), and low‐temperature‐cofired ceramic (LTCC) circuits.
Mode‐Matching Methods
Authors: Arndt Fritz
Published: December 2024

The article presents an overview of the state of the art of mode‐matching (MM) methods applied for the rigorous, fast CAD and optimization of waveguide components and describes some recent advances. The great technical importance of the MM technique is its extremely high computational efficiency, achieving complete full‐wave analyses of typical waveguide components orders of magnitude faster than electromagnetics (EM)‐based methods applying space discretization techniques. Hence, the MM technique allows advantageously the direct EM‐based optimization of waveguides components toward given specifications within shortest response times. Hybrid combinations with other EM methods, such as the finite‐element (FE) method and method of moments (MoM), provide extended flexibility. Typical application examples will illustrate the versatility of the MM methods.
Spice
Authors: Cheng Chung‐Kuan , Ho Chia‐Tung , Holtz Chester
Published: December 2024

SPICE (Simulation Program with Integrated Circuit Emphasis) is a program for electronic circuit design simulation and is one of the most successful academic products. Integrated circuit (IC) designers often use SPICE to check functionality, integrity, and power integrity before physical implementation (i.e., layout design) and tape‐out. Using SPICE to verify IC designs is essential for circuit validation due to the high cost of photolithographic masks and other manufacturing processes. The input to SPICE is a design “netlist,” which is composed of electronic components, such as resistance, transistor, capacitance, and sources. After the SPICE simulation, users can inspect the signal waveform or perform measurements virtually on the probing nodes in the netlist. Nowadays, there are open‐source and commercial SPICE programs for designers or researchers to incorporate SPICE into their projects. Active electronic components are usually described in the device model to reflect the current and voltage behaviors. According to user requirements, SPICE is capable of performing several types of analysis (e.g., DC, AC, transient, and DC sweep) and provides a bridge between time and frequency domain. Facing future challenges, many emerging methods and algorithms have been proposed to address the growing complexity of circuit designs and performance bottlenecks. Additionally, as technology evolves, SPICE continues to add device models to accurately capture the electronic component behavior in advanced technology nodes, such as the TSMC Interface and the Open Model Interface models.
Gyrotrons
Authors: Ives Robert L.
Published: December 2024

The gyrotron is a vacuum tube capable of delivering high levels of radio‐frequency (RF) power at frequencies from several gigahertz to more than 500 GHz, which covers the microwave and millimeter‐wave band. Because of the structure of the RF fields in the cavity, the magnitude of the electric fields and the RF losses in the cavity walls are much lower in gyrotrons than in most microwave and millimeter‐wave vacuum tubes. As the RF frequency increases, it is not necessary to reduce the size of the cavity and output waveguide. For these reasons, the gyrotron is the principal RF device for delivering high levels of RF power at frequencies between 30 and 500 GHz.
Resonant Tunneling Diodes
Authors: Maezawa Koichi
Published: December 2024

Resonant tunneling diodes (RTDs) exploit the quantum tunneling effect emerging in nanometer‐scale thin semiconductor heterostructures. The RTDs feature strong nonlinear current–voltage characteristics exhibiting negative differential resistance and also extremely high operation frequency. These features make the RTDs extremely useful for nonlinear microwave/millimeter‐wave circuits as well as high‐speed digital circuits. The features of RTDs and their applications to high‐frequency circuits are discussed.
Permittivity and Measurements
Authors: Komarov Vyacheslav V. , Wang Shaojin , Tang Juming
Published: December 2024

This article provides an overview of the dielectric properties of food, agricultural products, biological tissues, resins, plastics, ceramics, soils, and wood at radio and microwave frequencies. The influence of three main factors, namely, microwave frequency, temperature, and material moisture contents, on complex dielectric properties of lossy materials is analyzed. The most popular measurement techniques, such as the open‐ended coaxial probe method, transmission line method, and perturbation method, are described. Relevant dielectric property data are provided in tables and figures.
Phase Noise and Measurements
Authors: Chang Heng‐Chia
Published: December 2024

The phase of the electric signals or electromagnetic fields from the circuits and devices is often modulated or demodulated with important information in modern communication systems. However, there are always some random fluctuations in the phase of the signals caused by thermal noise (thermal motion of the carriers), or shot noise (discrete properties of the electric current sources), or several other mechanisms inside the devices, circuits, wired or wireless medium. The term phase noise is used for describing such short‐term random fluctuations of the signals. In this chapter the author especially describes the phase noise in the oscillators, because most of the phase noise sources in the communication systems come from the oscillators. The author explains the oscillator phase noise by theory, describes several techniques to improve phase noise, and illustrates several popular measurement techniques. The author concludes this chapter with some references for the interested readers to study by themselves the phase noise and the related measurement techniques further.
Radio‐Frequency‐Integrated Circuits
Authors: Chongcheawchamnan M. , Karacaoglu U. , Amsdon T. J. , Robertson I. D.
Published: December 2024

This chapter gives an overview of the technology and design of radiofrequency (RF)‐integrated circuits in silicon technology. These circuits have transformed the field of wireless communications, forming the heart of sophisticated multiple‐input, multiple‐output RF transceivers for use in cellular handsets. The technology is now starting to transform new fields in the millimeter‐wave frequency range, enabling it to be used for new consumer applications such as radars for autonomous cars. The chapter describes the key active device technologies and passive components before going on to describe the state of the art in circuit design techniques. There are separate sections dedicated to the design of amplifiers, oscillators, mixers and modulators, and integrated transceivers. A final section gives an introduction to the importance of taking the packaging into account at the chip design and layout stage, as well as describing the rapidly emerging field of RF system‐in‐package technology, where sophisticated millimeter‐wave antenna arrays can be integrated with active circuits. The chapter includes 180 references to research papers describing advanced techniques developed in both industry and academia.
Variable‐Frequency Oscillators
Authors: Gutierrez Germán
Published: December 2024

Oscillators are abundant around us. Most oscillators are of two basic kinds: sinusoidal and relaxation. This chapter covers the main topologies for all popular oscillators and the ways to make their frequency of oscillation variable. The description is independent of frequency and can be applied from very‐low‐frequency to microwave oscillators. Mechanical examples give a very simple explanation for the mechanism of oscillators and the concept of resonance.

An
oscillator
is defined as anything that swings back and forth like a pendulum (vibrates) or travels back and forth between two points. An
electronic oscillator
is a device used for producing alternating current (e.g., a radio frequency or audio frequency generator).
Frequency
is the number of times that a periodic function repeats the same sequence of values during a unit of time or the number of complete oscillations of a wave per second.

Oscillators are abundant all around us: light, sound, the rotation of the Earth, electric AC power, heartbeats, musical instruments, motors, microprocessor clocks, etc. Some of these oscillatory systems have variable frequencies, and some have fixed frequency. We will first describe all the different types of electronic oscillators to appreciate what determines their operating frequency and how it can be varied.
Voltage‐to‐Frequency Converters
Authors: Vidal‐Verdú Fernando , Navas‐González Rafael , Delgado‐Restituto Manuel , Rodríguez‐Vázquez Angel
Published: December 2024

Voltage‐to‐frequency converters (VFCs) typically employ relaxation oscillators to generate an output signal whose frequency depends linearly on an input voltage. VFCs are data converters; that is, they are designed to codify the input voltage by means of the output frequency. Hence, they have strong requirements regarding linearity, dynamic range, and stability. On the other hand, compared to other converters, they have the advantage of low cost, particularly for large resolutions; 13‐bit resolution is typical, and more than 20 bits are feasible. However, in such a case, several milliseconds may be necessary to complete the conversion—the smaller the resolution, the shorter the conversion time.

The serial frequency modulated output provided by VFCs is particularly well suited for telemetry, to send the outcome of a measurement by wire, radio, or fiber optic links. After the frequency‐modulated signal is received, it can be easily codified into a digital word, or converted back into a voltage by a frequency‐to‐voltage converter (FVC). This type of output simplifies galvanic isolation through the use of either an optocoupler or a magnetic coupler.

This chapter deals first with the concepts behind voltage‐to‐frequency conversion and then describes the main types of VFCs on the market, their limitations, and main applications. FVCs are also briefly described in the chapter.
RF Biometrics
Authors: Pizzillo Thomas J.
Published: December 2024

This report is a concise summary of research on radio frequency (RF) biometrics published in the open literature and informed by my own research as the Principal Investigator of the United States Army Research Laboratory's RF Biometrics program between 2007 and 2012. I provide a functional definition of RF Biometrics and define a concept of operations to provide context for the cited research. I explore the origins and evolution of RF Biometrics particularly in the context of security and defense applications, and provide a brief assessment of the current and future trends for RF Biometrics.
Antenna Booster Technology
Authors: Anguera Jaume , Andújar Aurora
Published: December 2024

Small and multiband antennas are always playing a predominant role in wireless communications to provide range, connectivity, and ensure battery life. In this regard, antenna booster technology features small size (∼
λ
/30), multiband, and multi‐radio behavior and at the same time easy to be embedded into a wireless device due to its chip‐like nature. The design of antenna systems radically differs from those based on conventional antenna design relying on shaping the geometry of the antenna to determine the frequencies of operation. On the contrary, with the antenna booster technology approach, the frequencies of operation are determined by the designer thanks to the combination of an antenna booster and a matching network. By doing so, all the complexity in the antenna part is removed and most of the intelligence is translated into the matching network. This enables making an antenna booster 10 times smaller than other antennas while flexibly adapting to any wireless protocol and device. Besides, reconfigurability can be combined with the matching network increasing the flexibility to adapt to any frequency band. Antenna booster technology is finding its applications in the design of wireless devices needing operation in the frequency range from 0.4 to 10 GHz.
The Use of Photonics for Analog RF Applications
Authors: Devgan Preetpaul S.
Published: December 2024

This chapter reviews the use of photonics for RF and microwave applications. As the need for more bandwidth increases, higher frequencies are being accessed. Photonics provides advantages over electronics at operating frequencies in the microwave and millimeter wave bands. This chapter provides examples of applications where photonics can be used. These applications include radio over fiber links, low phase noise clock signals, clock synchronization and simultaneous transmission and reception of RF signals. Photonics can address these applications and many more future use cases.
Collaborative Spectrum Sharing
Authors: Pham Quan , Shea John M. , Wong Tan F.
Published: December 2024

Explosion of the multitude of current and future wireless services has motivated the search for more efficient ways to allocate spectrum than fixed channel allocations enforced by regulatory agencies. In particular, dynamic spectrum‐sharing techniques allow spectrum to be assigned or selected for use based on the users and demand in a given geographic region. In this chapter, we consider collaborative spectrum sharing (CSS), in which users or networks share information about their spectrum needs and usage to facilitate efficient use of spectrum resources. We provide an ontology of CSS approaches and give an overview of previous CSS research. Then, we provide a more in‐depth discussion of the roles of CSS in two different example systems. The first is the Citizen Broadband Radio Service (CBRS), which is a system established by the Federal Communications Commission (FCC) in the United States, and which uses a centralized, hierarchical approach to CSS. The second is the Spectrum Collaboration Challenge (SC2), which was a competition run by the Defense Advanced Research Projects Agency (DARPA) in the United States to develop intelligent radios systems for CSS. In contrast to CBRS, the SC2 enforces a distributed, unified approach to CSS. The chapter concludes with a brief discussion of the progress and challenges in implementing CSS.
Full‐Duplex Communications Antennas
Authors: Smida Besma , Khaledian Seiran , Farzami Farhad , Atiqul Islam Md , Erricolo Danilo
Published: December 2024

Single‐antenna in‐band full‐duplex communication technology has the potential to substantially increase spectral efficiency. However, the implementation of full‐duplex systems is constrained by the cancellation of self‐interference (SI). This chapter provides an overview of all methodologies used to maintain a low level of SI in real‐time. First, a new analog SI cancellation technique is proposed. A radiofrequency (RF) circulator is used to separate transmitted (Tx) and received (Rx) signals. Instead of estimating the SI signals and subtracting them from the Rx signals, the inherent secondary SI signals at the circulator, reflected by the antenna, is used to cancel the primary SI signals leaked from the Tx port to the Rx port. The frequency response of the secondary SI signals is modified through a reconfigurable impedance mismatched terminal (IMT) circuit, which consists of two varactor diodes at the antenna port. The IMT adjustability makes it robust to antenna input impedance variations and fabrication errors.

Second, a comprehensive residual SI model based on a direct‐conversion transceiver structure considering nonlinearities of all the transceiver radio frequency components, in‐phase/quadrature (IQ) imbalances, phase noise effect, and receiver noise figure is offered. A more appropriate digital SI cancellation approach considering receiver chain RF and baseband (BB) nonlinearities is proposed to validate this model.

Finally, a prototype of the proposed technique at 2.45 GHz is analyzed and fabricated. An analog cancellation exceeding 40 dB over 65 MHz of bandwidth is achieved. The performance of the digital cancellation strategy is investigated and it achieves 20 dB more cancellation compared to existing methods.
Long‐Cycle Stable Zn2+ Storage in 2D Conductive Metal–Organic Frameworks via Exclusive Ligand Redox Mechanism
Authors: Liu Shuai , Kong Fantao , Chen Xiaofang , Song Erhong , Huang Aisheng
Published: December 2024

2D conductive metal–organic frameworks (2D c‐MOFs) have emerged as novel cathode materials in the development of rechargeable aqueous zinc‐ion batteries (ZIBs) because of its integrated multiple redox‐active moieties. However, the redox of the metal nodes usually leads to the collapse of the c‐MOF structure during Zn2+ insertion/extraction process, thereby curtailing its cycling lifespan. Herein, a triphenylene‐catecholate‐based 2D c‐MOF (Zn‐HHTP) is fabricated by chelating the inactive Zn nodes, endowing the structural stability during charge and discharge processes only through ligand redox. The 1D open channel of Zn‐HHTP facilitates rapid insertion and extraction of zinc ions, thus enabling stable working of ZIBs at high rates. Impressively, Zn‐HHTP as cathode in ZIBs exhibits an ultra‐long cycling stability with capacity retention of 86.6% after 4000 cycles at the current density of 4 A g−1, exceeding the other MOF‐based cathodes ever reported. Density functional theory (DFT) calculations combined with ex situ X‐ray photo‐electron spectroscopy (XPS) further elucidate the redox mechanism between catechol and benzene ring of HHTP during the successive insertion/extraction of Zn2+, due to their comparatively negative electrostatic potentials. This work provides a new strategy to prolong the cycling capability of ZIBs by utilizing the highly active non‐metallic redox moieties in 2D c‐MOFs.
Constructing RuNi‐MoO2 Heterojunction with Optimal Built‐In Electrical Field for Efficient Hydrogen Production in Anion Exchange Membrane Water Electrolyzer
Authors: Guo Peng , Zhang Pengan , Cao Shoufu , Huang Wenjing , Lu Xiaoqing , Zhang Bo , Chen Weizhe , Zhang Youzi , Wang Yijin , Zou Ruiqing , Li Xuanhua
Published: December 2024

Water electrolysis in alkaline media, demonstrating robust facility and cheap electrolyzer construction, are regarded as a promising strategy for industrial green hydrogen generation. Exploring effective alkaline hydrogen evolution electrocatalysts is remained an obstacle to date, which requires additional effort to obtain active hydrogen by water dissociation and promote the following unfavorable hydrogen coupling for further H2 release. Herein, the MoO2 supported RuNi nanoparticle (RuNi‐MoO2) is constructed as an efficient electrocatalyst for hydrogen evolution. Experimental and theoretical analysis demonstrate that the optimized built‐in electric field at the interface between MoO2 and RuNi alloy simultaneously accelerates the water dissociation kinetics and hydrogen spillover. It attains the current densities of 10 and 100 mA cm−2 at ultralow potential of −0.019 and −0.086 V versus RHE, respectively, along with rapid water cleavage kinetics, which even surpasses the commercial Pt/C. The constructing anion exchange membrane water electrolyzer adopting the RuNi‐MoO2 as a cathode electrocatalyst attains an industrial current density of 1 A cm−2 at a low voltage of 1.71 V and steadily operates over 1000 h with a large current density over 1 A cm−2.
Self‐Actuated Clot‐Piercing Nanoassembly Enabling Adaptable Drug Activation and Synergistic Thrombus Ablation
Authors: Zhang Hongyuan , Zhang Sen , Liu Shuwei , Fang Mingzhu , Wang Yuequan , Zhang Shenwu , Sun Jin , He Zhonggui , Luo Cong
Published: December 2024

Clinical thrombus therapy continues to be challenged by unsatisfactory antithrombotic outcomes and high bleeding risk. Rational design of prodrugs for thrombolytic agents is expected to ameliorate this situation. Nevertheless, a significant obstacle is the inadequate penetration of prodrugs and prodrug‐engineered nanomedicines, which hampers their effective interaction with the excessive stimuli produced in thrombi, resulting in suboptimal drug activation. Herein, a clot‐piercing nanoassembly is reported to facilitate photothermal clot penetration, adaptable drug activation, anti‐inflammatory action, and synergetic antithrombotic therapy, the nanoassembly is molecularly co‐assembled using a photothermal photosensitizer and a reactive oxygen species (ROS)‐sensitive antiplatelet dimeric prodrug. The nanoassembly demonstrates multiple advantages, including facile fabrication, high drug co‐loading capacity, long circulation time in the blood, thrombus‐targeting accumulation, photothermal‐potentiated clot‐piercing deep penetration, on‐demand prodrug activation in response to high H2O2 concentrations inside the clots, and anti‐inflammatory/antiplatelet synergy. These advantages result in significantly enhanced antithrombotic efficacy in vivo with favorable safety. This study presents a new paradigm for the development of prodrug‐driven antithrombotic nanomedicines.
Medium‐Entropy Engineering of Magnetism in Layered Antiferromagnet CuxNi2(1‐x)CrxP2S6
Authors: Upreti Dinesh , Basnet Rabindra , Sharma M. M. , Chhetri Santosh Karki , Acharya Gokul , Nabi Md Rafique Un , Sakon Josh , Benamara Mourad , Mortazavi Mansour , Hu Jin
Published: December 2024

Antiferromagnetic van der Waals‐type M2P2X6 compounds provide a versatile material platform for studying 2D magnetism and relevant phenomena. Establishing ferromagnetism in 2D materials is technologically valuable. Though magnetism is generally tunable via a chemical way, it is challenging to induce ferromagnetism with isovalent chalcogen and bimetallic substitutions in M2P2X6. Here, we report co‐substitution of Cu1+ and Cr3+ for Ni2+ in Ni2P2S6, creating CuxNi2(1‐x)CrxP2S6 medium‐entropy alloys spanning a full substitution range (x = 0 to 1). Such substitution strategy leads to a unique evolution in crystal structure and magnetic phases that are distinct from traditional isovalent bimetallic doping, with Cu and Cr co‐substitution enhancing ferromagnetic correlations and generating a weak ferromagnetic phase in intermediate compositions. This aliovalent substitution strategy offers a universal approach for tuning layered magnetism in antiferromagnetic systems, which along with the potential for light‐matter interaction and high‐temperature ferroelectricity, can enable multifunctional device applications.
Looking Back the Nonlinear Optical Crystals in a Functionalized Unit's Perspective
Authors: Mutailipu Miriding , Li Junjie , Pan Shilie
Published: December 2024

Nonlinear optics, signifying a revolutionary paradigm change within the realm of optics, has ushered in a transformative era by employing the nonlinear optical crystals to manipulate and harness the laser power for at least six decades. The most exciting aspects of nonlinear optical (NLO)crystal is the repercussions of bonding over extended functionalized units to external force and how slight alterations at the atomic scale can result in huge changes in the macroscopic properties. However, to date, precisely controlling the functionalized unit and its potential to induce directed property is, yet, not fully realized. Here, the NLO crystals are explored and prospected from the viewpoint of a functionalized unit, with an emphasis on the application of functionalized units in material design to control and regulate key optical properties and start regulating their functions. An introduction of anionic group theory is started here, which considers the functional unit to be primary, then turns to a discussion of functionalized unit modification through emerging design strategies and how this facilitates the design of new NLO materials. Additional breakthroughs in rational design strategy to fully functionalize the groups are covered, including integration, preferential arrangement induction, microcosmic performance maximization for functionalized units as well as the supports of these for new materials discovery with a theoretical method.   Beyond the gratifying achievements made, some future perspectives to move NLO crystals a step forward are finally provided.
A Nattokinase‐Loaded Nanozyme for Alleviating Acute Myocardial Infarction via Thrombolysis and Antioxidation
Authors: Shi Yingchao , Liu Chuanfen , Gui Yuesheng , Guo Yike , Zhang Yuanhao , Pan Jiangpeng , Tang Hao , Gao Chuanyu , Xing Junyue , Han Yu , Jiang Wei
Published: December 2024

Acute myocardial infarction (MI) induced by thrombus formation is a prevalent cardiovascular disorder, and thrombolytic therapy continues to be a principal treatment modality. Prior research indicates a substantial association among MI, thrombosis, and the activation of oxidative stress pathways. The effectiveness of current thrombolytic drugs is relatively constrained, and the need for innovative and versatile thrombolytic medications remains critical. Nattokinase (NK) is a naturally‐occurring enzyme known for its thrombolytic characteristics. Nonetheless, nattokinase's limited stability and susceptibility to inactivation in biological systems have impeded its clinical utility. This study designs a manganese oxide nanozyme (MnOx) loaded with NK (MnOx@NK), which exhibits both antioxidant and thrombolytic function. The administration of MnOx@NK through tail vein injection significantly restores vascular function and further reduces myocardial injury in a mouse model of myocardial infarction, demonstrating a pronounced protective effect against oxidative stress. These findings indicate that nattokinase‐loaded nanozymes can be a promising approach for treating acute myocardial infarction, providing a new strategy for clinical application.
Large Area Near‐Field Thermophotovoltaics for Low Temperature Applications
Authors: Selvidge Jennifer , France Ryan M. , Goldsmith John , Solanki Parth , Steiner Myles A. , Tervo Eric J.
Published: December 2024

Thermophotovoltaics, devices that convert thermal infrared photons to electricity, offer a key pathway for a variety of critical renewable energy technologies including thermal energy storage, waste heat recovery, and direct solar‐thermal power generation. However, conventional far‐field devices struggle to generate reasonable powers at lower temperatures. Near‐field thermophotovoltaics provide a pathway to substantially higher powers by leveraging photon tunneling effects. Here a large area near‐field thermophotovoltaic device is presented, created with an epitaxial co‐fabrication approach, that consists of a self‐supported 0.28 cm2 emitter‐cell pair with a 150 nm gap. The device generates 1.22 mW at 460 °C, a 25‐fold increase over the same cell measured in a far‐field configuration. Furthermore, the near‐field device demonstrates short circuit current densities greater than the far‐field photocurrent limit at all the temperatures tested, confirming the role of photon tunneling effects in the performance enhancement. Modeling suggests several practical directions for cell improvements and further increases in power density. These results highlight the promise of near‐field thermophotovoltaics, especially for low temperature applications.