The essence of fertilization: oocyte meets sperm

The problem of reduced fertility in high yielding dairy cattle is a very complicated one, and the relationship between various measures of fertility and level of milk production remains controversial. In this brief review the essence of the problem is considered: what is the oocyte's and the sperm's contribution, and what is the importance of the resulting embryo in the declining fertility of the Holstein Friesian cow

A modular multilevel based high-voltage pulse generator for water disinfection applications

The role of irreversible electroporation using pulsed electric field (PEF) is to generate high voltage (HV) pulses with a predefined magnitude and duration. These HV pulses are applied to the treatment chamber until decontamination of the sample is completed. In this paper, a new topology for HV rectangular pulse generation for water disinfection applications is introduced. The proposed topology has four arms comprised of series connected half H-bridge modular multilevel converter cells. The rectangular pulse characteristics can be controlled via a software controller without any physical changes in power topology. The converter is capable of generating both bipolar and monopolar HV pulses with micro-second pulse durations at a high frequency rate with different characteristics. Hence, the proposed topology provides flexibility by software control, along with hardware modularity, scalability, and redundancy. Moreover, a cell's capacitance is relatively small which drastically reduces the converter footprint. The adopted charging and discharging process of the cell capacitors in this topology eliminate the need of any voltage measurements or complex control for cell-capacitors voltage balance. Consequently, continuity of converter operation is assured under cell malfunction. In this paper, analysis and cell-capacitor sizing of the proposed topology are detailed. Converter operation is verified using MATLAB/Simulink simulation and scaled experimentation

Synthesis and characterization of new imidazolidineiminothione and bis-imidazolidineiminothione derivatives as potential antimicrobial agents

A series of new imidazolidineiminothiones (2-4) and bis-imidazolidineiminothiones (5) were synthesized through the cycloaddition reaction of N-arylcyanothioformamides (1) with some electrophilic reagents. Structure of imidazolidineiminothione derivatives were established based on spectroscopic IR, 1H NMR, 13C NMR, MS and elemental analyses data. These compounds were screened for their antibacterial and antifungal activities. Among the synthesized compounds, imidazolidineiminothione derivative 3a showed about 25% less potent effect than Ampicillin against S. epidermidis and B. subtilis (MIC, 0.49 μg/mL) and about 50 % less potent effect than Amphotericin B against A. clavatus and G. Candidum. Bis-imidazolidineiminothione derivative 5a was equipotent to the Gentamycin in inhibiting the growth of N. gonorrhoeae (MIC, 0.49 μg/mL), and displayed 50% less active than Amphotericin B against A. clavatus

DDPG Performance in THz Communications over Cascaded RISs: A Machine Learning Solution to the Over-Determined System

THz technology is considered a key element in 6G wireless communication because it provides ultra-high bandwidths, considerable capacities, and significant gains. However, wireless systems operating at high frequencies are faced with uncertainty and highly dynamic channels. Reflecting intelligent surfaces (RISs) can increase the range of the THz communication links and boost the rate at the receiver. In contrast to the existing literature, we investigate the scenario of multiple access multi-hop (cascaded) RISs uplink THz networks in a correlated channel environment. We show that our inspected cascaded RIS system is over-determined and that the rate maximization optimization problem is non-convex. To this end, we derive a closed-form expression of the received power and derive an analytical solution based on pseudo-inverse to obtain optimum RISs' phase shifts that maximize the received signal power and hence increase the rate. In addition, we utilize deep reinforcement learning (DRL), which is capable of solving non-convex optimization problems, to obtain the optimum cascaded RISs' phase shifts at the receiver taking into account the situation of the spatially correlated channels. Simulation results demonstrate that the DRL algorithm achieves higher rates than the mathematical sub-optimal method and the case of randomized phases

Quasi two-level PWM operation of a nine-arm modular multilevel converter for six-phase medium-voltage motor drives

This paper proposes a hybrid converter for medium-voltage six-phase machine drive systems that mixes the operation of a traditional two-level voltage-source inverter and the modular multilevel converter (MMC) to enable operation over a wide frequency range. Topologically, the proposed converter consists of nine arms resembling two sets of three-phase MMCs with three common arms, yielding a nine-arm MMC with a 25% reduction in the number of employed arms compared to a traditional dual three-phase MMC. The multilevel property of a standard MMC is emulated in the proposed converter, however on a two-level basis, resulting in a stepped two-level output voltage waveform. The proposed converter has a reduced footprint with advantages of small voltage steps, modular structure, and ease of scalability. Further, it is able to drive high-power six-phase machines within low operating frequencies at the rated torque. The operating principle of the converter is elaborated, and its modulation scheme is discussed. The features of the proposed converter are verified through simulations and experimentally

A modular multilevel voltage-boosting Marx pulse-waveform generator for electroporation applications

In order to overcome the limitations of the existing classical and solid-state Marx pulse generators, this paper proposes a new modular multilevel voltage-boosting Marx pulse generator (BMPG). The proposed BMPG has hardware features that allow modularity, redundancy, and scalability as well as operational features that alleviate the need of series-connected switches and allows generation of a wide range of pulse waveforms. In the BMPG, a controllable, low-voltage input boost converter supplies, via directing/blocking (D/B) diodes, two arms of a series modular multilevel converter half-bridge sub-modules (HB-SMs). At start up, all the arm's SM capacitors are resonantly charged in parallel from 0 V, simultaneously via directing diodes, to a voltage in excess of the source voltage. After the first pulse delivery, the energy of the SM capacitors decreases due to the generated pulse. Then, for continuous operation without fully discharging the SM capacitors or having a large voltage droop as in the available Marx generators, the SM capacitors are continuously recharged in parallel, to the desired boosted voltage level. Because all SMs are parallelly connected, the boost converter duty ratio is controlled by a single voltage measurement at the output terminals of the boost converter. Due to the proposed SMs structure and the utilization of D/B diodes, each SM capacitor is effectively controlled individually without requiring a voltage sensor across each SM capacitor. Generation of the commonly used pulse waveforms in electroporation applications is possible, while assuring balanced capacitors, hence SM voltages. The proposed BMPG has several topological variations such as utilizing a buck-boost converter at the input stage and replacing the HB-SM with full-bridge SMs. The proposed BMPG topology is assessed by simulation and scaled-down proof-of-concept experimentation to explore its viability for electroporation applications

The association between thyroid function and nutritional status in patients with end-stage renal disease on hemodialysis

Introduction: Malnutrition is common in patients with End-Stage Renal Disease (ESRD) on hemodialysis (HD) which significantly affects their quality of life. ESRD is associated with thyroid dysfunction which may affect morbidity and mortality. Changes in thyroid function in this population could be a marker of malnutrition. Our aim was the assessment of the nutritional status of patients with ESRD on HD and its association with thyroid function. Methods: A cross-sectional study was conducted on 84 patients with ESRD on HD. Nutritional status was assessed by anthropometric measurements and Subjective Global Assessment (SGA) Score. Serum FT3, FT4, and TSH concentrations were determined. CBC, kidney function tests, serum albumin, serum iron, total iron-binding capacity, serum cholesterol, and CRP were measured. Patients’ comorbidity status was determined using the Charlson Comorbidity Index (CCI). Results: The mean SGA score for studied patients was 13.73 ± 4.4, mean values of thyroid functions were: TSH 2.99 ± 2.93uIU/ml; FT4 1.08 ± 0.21 ng/dl and FT3 2.55 ± 0.52 pg/ml. According to SGA score, 26.2% of patients had normal nutritional status, 69% had mild to moderate malnutrition and 4.8% had severe malnutrition. SGA had significant negative correlation with FT3, while there was no significant correlation between it and FT4 or TSH. Serum FT3 concentration inversely correlated with age (r = −0.25, P= 0.02), CCI (r = −0.48, P= 0.0001), CRP (r = −0.46, P= 0.0001), and SGA (r = −0.49, P= 0.0001), and positively correlated with serum albumin (r = 0.47, P= 0.0001). In multivariate regression analysis, SGA was independently associated with FT3 (β, −1.36; 95% confidence interval, −2.5 to −0.2, P= 0.02) Conclusions: Malnutrition is prevalent among patients with ESRD on HD. FT3 is a marker of malnutrition and could be used as an accessible and reproducible periodical method to detect such states

A modular multilevel converter with integrated shared capacitor sub-module for MV motor drives incorporating symmetrical six-phase machines

This paper proposes a new modular multilevel converter (MMC) configuration as a medium-voltage drive for variable-speed applications incorporating symmetrical six-phase machines. The proposed topology employs six MMC phase-legs feeding two isolated groups of three-phase machine windings, each with 60° spatial phase-displacement. A novel concept of sharing one capacitor between each pair of adjacent-arm submodules (SMs) of MMC phase-legs, while feeding machine windings in a spatial phase-opposition, is realized through a new integrated SM arrangement. The integrated SM allows the shared capacitor to absorb and release the same energy amount in a consecutive switching scheme, where the capacitor is experiencing both charging and discharging arm currents, one after another. This results in a limited voltage variation across the SM shared capacitor, independent of the operating frequency. Also, the proposed approach allows the MMC to utilize half the number of the SM capacitors, compared to a traditional MMC topology, while further diminishes the SM capacitance requirement, reducing the volume of the MMC system and its stored energy. The proposed configuration can efficiently operate at near zero frequency, therefore a machine speed-range from zero speed to the rated speed is possible under rated torque operating condition. The proposed MMC topology is elucidated in detail, and its effective performance is verified using simulation

A modular multilevel converter with ripple-power decoupling channels for three-phase MV adjustable-speed drives

This paper presents a drive system based on a modular multilevel converter (MMC) with high-frequency magnetic channels between adjacent-arm submodules (SMs), suitable for medium-voltage, high-power three-phase variable-speed machines. The configuration employs chains of dual half-bridge (DHB) modules linking adjacent SMs of three-phase symmetrical arms. The DHB modules are operating as power channels enabling energy exchange to restore the power imbalance among the SM capacitors. This allows arms' ripple-powers to be entirely decoupled through bidirectional power transfer between adjacent-arm SMs, resulting in a near ripple-free SM capacitor voltage profile. Therefore, the MMC common problem of wide voltage fluctuation across SM capacitors is comprehensively solved, independent of the operating frequency. Additionally, a significant reduction in the sizing requirement of SM capacitance is achieved. The configuration is able to drive multi-megawatt machines from standstill to the rated speed at the rated torque operating condition. The operating principle of the proposed MMC configuration is explained and necessary mathematical analysis is derived. Features and viability of the proposed drive system are verified through simulation and experimentation