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Abstract This letter presents the design of a 13.56 MHz offset‐enhanced full‐wave active rectifier, tailored for wirelessly powered biomedical implants. The design incorporates digitally assisted, delay‐compensated active diodes and symmetrical bulk biasing in the rectifier core to enhance conduction time, thus improving the voltage conversion ratio (VCR) and power conversion efficiency (PCE). A delay improvement is achieved both in no‐load and high‐load conditions through an additional comparison path with an offset voltage that is higher than zero. The proposed rectifier is implemented and fabricated in a 180 nm CMOS technology with an area of 0.024 mm2. The rectifier, tested and measured with inductive links, offers a maximum VCR of 96.4% and a maximum PCE of 89%.

This paper presents a wireless power conversion system designed for biomedical implants, with integrated automatic resonance tuning. The automatic tuning mechanism improves power transfer efficiency (PTE) by finely tuning the resonant frequency of the power link and maximizing the rectified voltage. This adjustment ensures robust and reliable remote powering, even in the face of environmental changes and process variations, while also minimizing tissue exposure to power. On-chip switched array capacitors are connected in parallel with the resonant capacitor, and the system identifies the optimal switched capacitor combination for the highest rectified voltage by iterating over each of them. The proposed system is implemented and fabricated in standard 180nm CMOS technology, with a total area of 0.339 mm2, and its operation is verified. The measurement results demonstrate that this system provides tolerance up to mismatches equivalent to 75 pF capacitance variation in LC tank, ±15% LC variation in this design. The system offers a PTE enhancement from 9.1% to 30.2% in case of high LC variation, and the tuning control consumes 154.7 $\mu \text{W}$ of power during resonance tuning. Moreover, the power conversion chain delivers an optimized rectified voltage along with a regulated voltage of 1.8 V.

Abstract:In this paper, a tunable absorber structure based on a graphene hexagonal array in the terahertz range is investigated. The graphene hexagonal absorber is simulated by the finite element method. The effects of the geometry, graphene Fermi energy level and incident light angle, and light polarization on the absorptance of the structure are investigated. The results show that the absorptance spectrum of the proposed absorber is tuned from 6.1 THz to 9.1 THz when the Fermi energy increases from 0.4eV to 0.9eV. The absorptance peak shifts to lower and higher frequencies with increasing hexagonal side length and Fermi energy level, respectively. The absorption of the structure is over 90% in the incident light angle range from 0 to 80º for the TE polarization and in the range of 0-40º for the TM polarization. Also, results indicate that the absorption peaks shift to the lower energies with increasing the dielectric constant of the dielectric layer.

In this research, biosynthesis of Ag nanoparticle investigated using Urtica extract. Different parameter such as temperature, pH, time and concentration of Ag salt optimize for this goal. Synthesized nanoparticle characterized by Uv-vis, XRD and TEM methods. Results show Ag nanoparticle synthesized in the size of 10 nm. In continuous, Ag nanoparticle was used for preparation of modified carbon paste electrode. And its effect investigated on electron exchange system for K4[Fe(CN6)] as a standard system. The obtained result shows that synthesized nanoparticle can be improved electrical conductivity of electron exchange in electrochemical systems.

Abstract Background Although headache is a common complaint in younger individuals, it is one of the most common complaints among persons over the age of 50 and is a significant cause of morbidity. As there are differences in the causes and types of headache, the diagnosis and management of headache in older adults differ from that in younger individuals. Methods In this cross-sectional study, 570 patients ≥ 50 years were recruited at a university affiliated tertiary headache center between 2016 and 2019. Demographic data, headache characteristics, and comorbid medical conditions were recorded. The presence of depression was explored using the Beck Depression Inventory. The patients were evaluated using the STOP-BANG scale to determine the risk of obstructive sleep apnea. Results The mean age of the patients was 57.7 years. Seventy-three percent of the patients had primary headache disorders, with the most prevalent types being migraine, followed by tension-type headache. Secondary headaches were primarily the result of overuse of medication, cervical spine disease, and hypertension. Patients with medication-overuse headache were significantly more likely to suffer from hypothyroidism and gastrointestinal problems such as bleeding/ulcers. Irritable bowel syndrome was also more common in patients with medication-overuse headaches and migraines. The risk for obstructive sleep apnea was intermediate in 45.2% of the patients with hypertension-induced headache, but was lower in the majority of others. There was a high tendency for moderate-to-severe depression in the participants; however, the Beck Depression Inventory scores were significantly higher in medication-overuse headache patients. Conclusion Proper treatment of headache in middle-aged and older adults requires the recognition of secondary causes, comorbid diseases, and drug induced or medication overuse headaches. Special attention should be paid to depression and obstructive sleep apnea in such patients suffering from headache disorders.