Maximal Induction Research Articles

Hall probe calibration in high-precision magnetic field mapping system of superconducting cyclotron

Abstract Introduction Superconducting cyclotron can generate high-energy proton beams and are mainly used for radiation therapy of tumors and cancers. In the superconducting cyclotron SC200, the maximum magnetic induction intensity can typically reach up to 4.6 T, and the magnetic field accuracy is 1e-4. Hall probes are commonly used tools for measuring high-intensity magnetic fields. Objective Through comprehensive consideration, this study selects the SENIS Low-Noise Teslameter 3MH5 and Hall probe C to measure the magnetic field. When the magnetic field exceeds the range of 2 T, the measurement accuracy of the Hall probe is less than 1e-4, and the Hall probe needs to be calibrated to improve its measurement accuracy. Methods The Hall probes are calibrated using Swiss METROLAB PT2025 nuclear magnetic resonance (NMR) Tesla instrument and 1062 probe. Based on the calibration principle, a calibration system platform was built, test data were collected, and calibration curves were obtained. At the same time, the calibration data were analyzed through cross-validation experiments using the cubic polynomial fitting method. Results The results indicate that the test deviation range is from −0.1 g to 0.1 g, and the measurement accuracy can reach 1e-4. Conclusion In summary, the Hall probe can accurately measure the magnetic field distribution of the superconducting cyclotron. It can provide accurate and important data for the calculation and analysis of particle beam dynamics.

CAMP driven UCP1 induction in human adipocytes requires ATGL-catalyzed lipolysis

ObjectiveThe uncoupling protein 1 (UCP1) is induced in brown or “beige” adipocytes through catecholamine-induced cAMP signaling, which activates diverse transcription factors. UCP1 expression can also be enhanced by PPARγ agonists such as rosiglitazone (Rsg). However, it is unclear whether this upregulation results from de-novo differentiation of beige adipocytes from progenitor cells, or from the induction of UCP1 in pre-existing adipocytes. To explore this, we employed human adipocytes differentiated from progenitor cells and examined their acute response to Rsg, to the adenylate-cyclase activator forskolin (Fsk), or to both simultaneously. MethodsAdipocytes generated from primary human progenitor cells were differentiated without exposure to PPARγ agonists, and treated for 3, 6 or 78 h to Fsk, to Rsg, or to both simultaneously. Bulk RNASeq, RNAScope, RT-PCR, CRISPR-Cas9 mediated knockout, oxygen consumption and western blotting were used to assess cellular responses. ResultsUCP1 mRNA expression was induced within 3 h of exposure to either Rsg or Fsk, indicating that Rsg’s effect is independent on additional adipocyte differentiation. Although Rsg and Fsk induced distinct overall transcriptional responses, both induced genes associated with calcium metabolism, lipid droplet assembly, and mitochondrial remodeling, denoting core features of human adipocyte beiging. Unexpectedly, we found that Fsk-induced UCP1 expression was reduced by approximately 80% following CRISPR-Cas9-mediated knockout of PNPLA2, the gene encoding the triglyceride lipase ATGL. As anticipated, ATGL knockout suppressed lipolysis; however, the associated suppression of UCP1 induction indicates that maximal cAMP-mediated UCP1 induction requires products of ATGL-catalyzed lipolysis. Supporting this, we observed that the reduction in Fsk-stimulated UCP1 induction caused by ATGL knockout was reversed by Rsg, implying that the role of lipolysis in this process is to generate natural PPARγ agonists. ConclusionsUCP1 transcription is known to be stimulated by transcription factors activated downstream of cAMP-dependent protein kinases. Here we demonstrate that UCP1 transcription can also be acutely induced through PPARγ-activation. Moreover, both pathways are activated in human adipocytes in response to cAMP, synergistically inducing UCP1 expression. The stimulation of PPARγ in response to cAMP may result from the production of natural PPARγ activating ligands through ATGL-mediated lipolysis.

Study on the influence mechanism of electromagnetic field on multifield coupling during the laser cladding Fe60 process

During laser cladding, microdefects such as pores, cracks, and segregation inevitably occur. Practical experience has shown that applying an electromagnetic field is an effective method for eliminating these microdefects during the cladding process. In the study, a multifield coupling three-dimensional numerical model was established for the electromagnetic field-assisted laser cladding Fe60 process. The instantaneous evolution law in the temperature field, flow field, and stress field under the influence of a magnetic field and without magnetic influence was calculated and revealed. At the same time, the two were compared and analyzed, focusing on the influence of an external electromagnetic field on the flow of molten pool Marangoni and its action mechanism. The results show that under the electromagnetic conditions applied in the study, the maximum magnetic induction intensity and the maximum Lorentz force density in the molten pool reach 0.13 T and 6.84 × 103 N/m3. Under the influence of magnetic force, the “double vortex” flow of Marangoni convection is asymmetrically distributed in the center of the molten pool. The fluid flow line has irregular flow and the circulation area generated at the front of the molten pool is larger in the corresponding scanning direction. Under the magnetic field influence, the overall flow velocity of the molten pool obviously increases, and the maximum flow velocity of the molten pool reaches 0.28 m/s. The study lays a significant theoretical foundation for revealing the mechanism of laser cladding assisted by a magnetic field.

High Quality Factor Miniaturized CMOS Transmission Lines Using Cascaded T-Networks for 60 GHz Millimeter Wave Applications

This work presents an on-chip 60 GHz lumped element transmission line (TL) using cascaded T-networks with a high Quality factor. Each T-network consists of a series inductance with a shunt capacitance at its center. We have derived the design equations for this TL configuration and proved that a TL whose electrical length ≥ 60° achieves additional miniaturization when implemented with three or more cascaded T-networks. The inductance is implemented using a straight wire model with no ground below it, while the capacitance is implemented using a parallel plate model with a grounding pedestal. Both configurations guarantee maximum inductance per unit length and capacitance per unit area to further improve the miniaturization level. A quarter wavelength TL with three cascaded T-networks is fabricated as proof of concept. The measured and simulated results of the fabricated TL have good agreement, and the measured quality factor is 17 at 60 GHz.

Customizable Induction Heating Profiles: from Tailored Colloidally Stable Nanoparticles Toward Multi‐Stage Heatable Supraparticles

AbstractMagnetic nanoparticles (NPs) are efficient heat mediators in induction heating. Originally explored for hyperthermia, their applications have broadened to industrial processes where temperature control is crucial. By adjusting the NP composition or morphology, magnetic characteristics such as Curie temperatures can be tailored, allowing control over maximum heating thresholds. These NPs are, however, usually designed for maximum heating rates at specific magnetic fields. In this work, the synthesis is presented for colloidally stable Co and ZnCo ferrite NPs with customizable maximum heating temperatures, and their combination within micron‐scaled supraparticles (SPs). Maximum induction heating temperatures of ZnCo ferrite NPs are tuned between 150 and 220 °C, while customization of Co ferrite species yields temperatures between 200 and 350 °C. These distinct magnetic properties are exploited in the selective multi‐stage heating of SPs consisting of both species. Here, ZnCo ferrite components heat up to a first temperature plateau at low alternating magnetic fields (AMF), while Co ferrite NPs reach higher temperatures at increased AMF. The precise control of induction heating thresholds through the adaptability of NPs offers a high degree of customizability which makes induction heating particularly attractive for applications requiring sequential or spatial heating, such as catalysis or debonding on demand.

Accurate design, simulation and implementation of AC/DC inductors for power electronic converters

AbstractThis article proposes a holistic and improved methodology for the inductors' design in power electronic circuits operating at high frequencies. This methodology includes an analytical design, a finite element modeling of the electromagnetic behavior with JMAG software, a simulation analysis in a Simulink environment, and experimental verification of the effectiveness of inductor design in a laboratory‐scale step‐up boost power converter prototype. The holistic approach allowed us to achieve all target specifications such as maximum power (300 W), minimum voltage (60 V), inductance (1.77 mH), and maximum current ripple (1 A). It guarantees the losses' minimization in core and copper (21.47 W), and marginal errors below 4% between the analytical, simulated, and experimental values.

Electromagnetic simulation and electromagnetic safety characteristics analysis of implantable medical devices in wireless charging processes

In recent years, wireless charging technology for electric vehicles has received increasing attention. Existing research has been limited to the safety of specific body parts in the electromagnetic environment of wireless charging for electric vehicles, with insufficient consideration for the overall human body and the electromagnetic safety of implanted medical devices. In order to assess its safety in the electromagnetic environment more comprehensively, a three-dimensional electromagnetic simulation software based on the finite element method is used to construct models of the human body and implanted medical devices in the electromagnetic environment of wireless charging for electric vehicles. The study aims to investigate the impact of this electromagnetic environment on the human body and implanted medical devices. The results indicate that, except for the maximum magnetic induction of 0.47 μT at the ankle, which exceeds the limit, the magnetic induction intensity and electric field strength in important tissue areas, especially the upper trunk of the human body, are both below the safety limits specified by the International Commission on Non-Ionizing Radiation Protection (ICNIRP) guidelines. For implanted cardiac pacemakers, the effective and peak magnetic field strengths are 13.7 A/m and 19.4 A/m, respectively, when the coil input power is 22 kW, meeting the relevant magnetic field strength requirements. The maximum temperature rise of the pacemaker is 3.2 × 10-3∘C, and there are no significant changes in the temperature of the major organs in the human body after the implantation of the pacemaker. The thermal effects of electromagnetic waves on the temperature rise caused by implanted cardiac pacemakers have minimal impact on the human body.

PPARγ activation by lipolysis-generated ligands is required for cAMP dependent UCP1 induction in human thermogenic adipocytes.

The uncoupling protein 1 (UCP1) is induced in brown or "beige" adipocytes through catecholamine-induced cAMP signaling, which activates diverse transcription factors. UCP1 expression can also be enhanced by PPARγ agonists such as rosiglitazone (Rsg). However, it is unclear whether this upregulation results from de-novo differentiation of beige adipocytes from progenitor cells, or from the induction of UCP1 in pre-existing adipocytes. To explore this, we employed human adipocytes differentiated from progenitor cells and examined their acute response to Rsg, to the adenylate-cyclase activator forskolin (Fsk), or to both simultaneously. Adipocytes generated from primary human progenitor cells were differentiated without exposure to PPARγ agonists, and treated for 3, 6 or 78 hours to Fsk, to Rsg, or to both simultaneously. Bulk RNASeq, RNAScope, RT-PCR, CRISPR-Cas9 mediated knockout, oxygen consumption and western blotting were used to assess cellular responses. UCP1 mRNA expression was induced within 3 hours of exposure to either Rsg or Fsk, indicating that Rsg's effect is independent on additional adipocyte differentiation. Although Rsg and Fsk induced distinct overall transcriptional responses, both induced genes associated with calcium metabolism, lipid droplet assembly, and mitochondrial remodeling, denoting core features of human adipocyte beiging. Unexpectedly, we found that Fsk-induced UCP1 expression was reduced by approximately 80% following CRISPR-Cas9-mediated knockout of PNPLA2 , the gene encoding the triglyceride lipase ATGL. As anticipated, ATGL knockout suppressed lipolysis; however, the associated suppression of UCP1 induction indicates that maximal cAMP-mediated UCP1 induction requires products of ATGL-catalyzed lipolysis. Supporting this, we observed that the reduction in Fsk-stimulated UCP1 induction caused by ATGL knockout was reversed by Rsg, implying that the role of lipolysis in this process is to generate natural PPARγ agonists. UCP1 transcription is known to be stimulated by transcription factors activated downstream of cAMP-dependent protein kinases. Here we demonstrate that UCP1 transcription can also be acutely induced through PPARγ-activation. Moreover, both pathways are activated in human adipocytes in response to cAMP, synergistically inducing UCP1 expression. The stimulation of PPARγ in response to cAMP occurs as a result of the production of natural PPARγ activating ligands through ATGL-mediated lipolysis.

Thermally-assisted magnetization of magnetic composites for enhanced micro actuator performance: a low-cost approach using permanent magnets

A micro actuator based on magnetic composite materials can control its deformation and movement through varying magnetic fields, showcasing significant applications in fields such as soft robotics and biomedicine. However, existing magnetic composite materials still require complex magnetization processes involving sophisticated equipment and demanding external magnetic fields. This paper proposed a low-cost, thermally-assisted magnetization process based on permanent magnets. It was observed that the maximum magnetic induction intensity on the surface of magnetic composites is linearly correlated with the heating temperature. Additionally, magnetically treated materials at elevated temperatures can achieve traditional high-field magnetization effects at lower field strengths. Specifically, we synthesized a magnetic composite with 50%wt NdFeB@PDMS and investigated the conditions of the thermally-assisted magnetization process based on permanent magnets, along with mechanical and magnetic performance characterization methods. Experimental results indicate that below 200 °C, the tensile strength and elastic modulus of the base material increase with rising temperatures, demonstrating a trend of high-temperature hardening. However, when the temperature exceeds 200 °C, the elevated temperature leads to the decomposition of the base material, resulting in a rapid decrease in the tensile strength and elastic modulus of the magnetic composite. Furthermore, high temperatures can disrupt the magnetic domains of the magnetic material, reducing its coercive force and making it more susceptible to external magnetic fields and heat, thereby compromising the stability of the magnetic material. These findings provide new insights into the development of more stable and controllable magnetic composite materials.

Luteolin Inhibits Indoxyl Sulfate-Induced ICAM-1 and MCP-1 Expression by Inducing HO-1 Expression in EA.hy926 Human Endothelial Cells.

In patients with chronic kidney disease, the uremic toxin indoxyl sulfate (IS) accelerates kidney damage and the progression of cardiovascular disease. IS may contribute to vascular diseases by inducing inflammation in endothelial cells. Luteolin has documented antioxidant and anti-inflammatory properties. This study aimed to investigate the effect of luteolin on IS-mediated reactive oxygen species (ROS) production and intercellular adhesion molecule (ICAM-1) and monocyte chemoattractant protein (MCP-1) expression in EA.hy926 cells and the possible mechanisms involved. IS significantly induced ROS production (by 6.03-fold, p < 0.05), ICAM-1 (by 2.19-fold, p < 0.05) and MCP-1 protein expression (by 2.18-fold, p < 0.05), and HL-60 cell adhesion (by 31%, p < 0.05), whereas, luteolin significantly decreased IS-induced ROS production, ICAM-1 and MCP-1 protein expression, and HL-60 cell adhesion. Moreover, luteolin attenuated IS-induced nuclear accumulation of p65 and c-jun. Luteolin dose-dependently increased heme oxygenase-1 (HO-1) expression and the maximum fold induction of HO-1 by luteolin was 3.68-fold (p < 0.05), whereas, HO-1 knockdown abolished the suppression of ICAM-1 and MCP-1 expression by luteolin. Luteolin may protect against IS-induced vessel damage by inducing HO-1 expression in vascular endothelial cells, which suppresses nuclear factor kappa B (NF-κB) and activator protein 1 (AP-1) mediated ICAM-1 and MCP-1 expression.

Structural Optimization of a Giant Magnetostrictive Actuator Based on BP-NSGA-II Algorithm

This study introduces an integrated structural optimization design method based on a BP neural network and NSGA-II multi-objective genetic algorithm. Initially, a two-dimensional axisymmetric finite element model of the Giant Magnetostrictive Actuator (GMA) was established, and the coupling simulation of the electromagnetic field, structural field, and temperature field was conducted to obtain the GMA’s performance parameters. Subsequently, the structural parameters of the GMA magnetic circuit, including the magnetic conducting ring, magnetic conducting sidewall, magnetic conducting body, and coil, were used as inputs, and the axial magnetic induction intensity, uniformity of axial magnetic induction intensity, and coil loss on the Giant Magnetostrictive Material (GMM) rod were used as outputs to establish a back propagation (BP) neural network model. This model delineated the nonlinear relationship between structural parameters and performance parameters. Then, the BP-NSGA-II algorithm was applied to perform multi-objective optimization on the actuator’s structural parameters, resulting in a set of Pareto optimal non-dominated solutions, from which a set of optimal solutions was obtained using the entropy weight method. Finally, simulation analysis of this optimal solution was conducted, indicating that under a 5 A power supply excitation, the maximum axial magnetic induction intensity on the optimized GMM rod increased from 0.87 T to 1.12 T; the uniformity of axial magnetic induction intensity improved from 93.1% to 96.5%; and the coil loss decreased from 7.79 × 104 W/m3 to 4.97 × 104 W/m3. Based on the optimization results, a prototype actuator was produced, and the test results of the prototype’s output characteristics proved the feasibility of this optimization design method.

A new magneto-plastic coupling model for residual stress description in ferromagnetic materials

The paper addresses the topic of residual stress in magnetic behaviour of the ferromagnetic materials. Carbon steel parts are submitted to several stress loads and the magnetic behaviour is collected at several operating points. After stress load, the hysteresis data are measured and illustrate a complex behaviour in hysteresis morphology where a big belly is observed near coercive field and a short neck in maximum induction zone. In order to describe the B-H curves, a modified Arctangent model is proposed. A comparison between experiments and model signals show a very good accuracy.

Characteristics of electromagnetic radiation of the veterinary physiotherapy device UMI-05-V

We studied some physical characteristics of the veterinary physiotherapeutic device UMI-V-05. The magnetic induction at different power levels was determined using TPU 02 militeslameter. The magnetic induction was measured for each power value. The probe of the milliteslameter was placed directly on the working surface, in the center of the inductor. It was found that the minimum magnetic induction of the device is 350±6.0 mTl, and the maximum is 1058±10.0 mTl. During the device operation, the heating of the inductor was determined using a thermal imager and a stopwatch. During the recommended time range (10 minutes), the inductor temperature did not exceed 46 °C. Determination of the pulse radiation frequency depending on the magnetic induction value was carried out using a stopwatch. At each working power the number of pulses per minute was counted and the number of pulses per second was calculated (frequency determination). It was revealed that UMI-V-05 is a low-frequency source of pulsed magnetic radiation with the maximum frequency of 1.3 Hz at the minimum magnetic induction of 350±6.0 mTl and the minimum frequency of 0.1 Hz at the maximum magnetic induction of 1058±10.0 mTl. Using a ruler and a TPU 02 milliteslameter, the degree of magnetic pulse attenuation depending on the distance to the working surface of UMI-V-05 was determined, it was fixed that the value of magnetic induction varies inversely proportional to the distance from the inductor. The penetration ability of the electromagnetic pulse through different media: biological and non-biological using TPU 02 militeslameter was studied. Biological tissues (muscle, bone) and some nonbiological media (paper, glass, wood, polyethylene, water) do not affect the passage of the electromagnetic pulse, while steel significantly reduces the passage of the pulse.

ESTABLISHMENT OF AN EFFICIENT MICROPROPAGATION PROTOCOLS FOR THREE KENAF (HIBISCUS CANNABINUS L.) CULTIVARS

This study was aimed to establish an efficient micropropagation protocol for three popular kenaf (Hibiscus cannabinus L.) cultivars (V36, HF992 and KB6) using different types of plant growth regulators (PGR’s) on Murashige and Skoog medium (MS). The shoot tip, cotyledon and hypocotyl isolated from 2 weeks old seedlings were used as explants. MS medium fortified with different types and concentrations of cytokinins and auxin were evaluated for establishment callus formation, shoot multiplication and rooting. Among different PGR’s used, 5.0 mg/l 2iP + 0.1 mg/l NAA was the best concentration for direct shoot regeneration from cotyledon with shooting percentage of 55% in HF992 cultivar. In multiple shoot induction experiment, 1.0 mg/l TDZ + 0.1 mg/l NAA mg/l concentration has induced the highest (10.4) shoots/explant. Moreover, indirect shoot regeneration was established from callus which was induced from cotyledon, maximum callus induction percentage (88.75%) was recorded on 0.5 mg/l TDZ and 1.0 mg/l NAA in V36 variety. While, for shoot elongation and rooting, MS media half strength supplemented with 1.0 mg/l kinetin + 1.0 mg/l IBA was found to be an optimum concentration.

Development of stability charts for double salience reluctance machine modeled using hill’s equation

The paper presents a novel algorithm for the development of stability charts. The second-order differential homogeneous equation describing a double salient reluctance machine with a capacitance connected to its stator winding is transformed into hill’s equation. The circuit components are the stator coil time-varying inductance of a double salient reluctance machine, capacitance and resistance. All these are modeled by hill’s equation. The double salient reluctance machine acts as an energy conversion system. The maximum and minimum inductance of the energy conversion system is measured in laboratory by inductance, capacitance, and resistance (LCR) meter. These values help to determine the inductance modulation index. The inductance modulation indetx, the characteristic constant and the characteristic parameter obtained from modeling equations are used in the MATLAB/Simulink model. The MATLAB/Simulink simulations generate stable and unstable oscillations to form stability charts. The proposed stability charts are in good agreement with the Ince-Stritt stability chart, which is widely applied in physics, mechanics and in electrical engineering, especially where the state of stability of a system or an electric oscillatory circuit is to be determined.

IN VITRO CALLUS INDUCTION AND REGENERATION OF ORYZA SATIVA L. VAR. MTU1075 (PUSHYAMI)

In vitro inducement of callus and plant regeneration capacity were investigated using mature embryos of the Indian rice (Oryza sativa L.) variety MTU1075. The investigation was conducted using callus induction media (Murashige and Skoog, 1962) with varying concentrations of 2, 4-D, namely 1.0, 1.5, 2.0, 2.5, 3.0, and 3.5mg/l. It shows the maximum degree of callus induction at 2 mg/l 2,4-D. The maximum callus induction rate was 86%. Plant regeneration efficacy of in vitro generated plantlets was studied then successfully transferred into soil conditions.

Scanning electron microscopic and morphological studies on in-vitro derived callus of low-chill peach (Prunus persica L. Batsch)

In this investigation the effect of collection seasons of explants (winter, spring and summer), type of explants (leaf disc and intermodal segments) and length of explants (0.5, 1.0 and 1.5 cm) for callusing in low-chill peach were standardized. The maximum callus induction (97.78%) in the low-chill peach was obtained from the intermodal segments of 0.5 cm in length used as an explant collected during spring season. The structural changes on the surface of the callus (5–7 weeks old yellowish green compact callus) during the progress of somatic embryogenesis of low-chill peach from the both intermodal segment as well as leaf disc derived callus were also examined with the use of scanning electron microscope (SEM). The SEM studies indicated that callus derived from internodal segment explant had the highest frequency of somatic embryos than callus from leaf discs. The SEM investigation, also demonstrated the sequential events/steps leading to low-chill peach somatic embryogenesis which was originating from somatic embryo mother cells through one unicellular pathway. Two types of calli were morphologically distinguished in both leaf disc and intermodal segment generated callus and these were the compact, well organized yellowish green embryogenic callus, containing large number of small, rich cytoplasmic, starch containing meristematic cells and soft and unorganized non-embryogenic callus containing sparsely cytoplasmic, vacuolated, and large cells devoid of metabolic reserves. The present SEM studies clearly demonstrated that somatic cells from peach explants generated callus could develop into fully differentiated somatic embryos through the characteristic embryological patterns of differentiation.

Electromagnetic field simulation modeling method and distribution characteristics of electric vehicle wireless charging system

In recent years, wireless charging technology for electric vehicles has gained significant attention. To accurately analyze the distribution characteristics of the electromagnetic field during the wireless charging process of electric vehicles, a finite element-based electromagnetic analysis method was employed. Applied in the commercial simulation software, the electromagnetic environment of the resonant coil and electric vehicle model was simulated under high-power charging conditions, resulting in an overall electromagnetic field distribution for the electric vehicle. The results indicated that within the coil region, the magnetic induction intensity in the central area of the coil was zero, and it increased as the distance from the center of the coil grew. Outside the coil region, the magnetic induction intensity gradually decreased. The electric field intensity of the resonant coil was maximum in the central area of the coil, and it weakened as the distance from the center of the coil increased. When a magnetic shielding resonant coil was used, the electromagnetic field was confined between the shielding materials, and the magnetic field rapidly attenuated on both sides of the magnetic shield. The electromagnetic field energy of the electric vehicle body was mainly concentrated at the bottom of the vehicle near the coil. When the coil was located in the front of the car body, the maximum electric field intensity distribution in the car body was 8.50 V/m, and the maximum magnetic induction intensity was 0.024 μT. When the coil was located in the middle of the car body, the maximum electric field intensity was 2.31 V/m, the maximum magnetic induction intensity was 0.019 μT. As the distance from the coil position increased, the energy weakened.

The Role of 24-hydroxylase in Homeostatic Regulation of 1,25-dihydroxyvitamin D

Background. Because of the importance of vitamin D (VitD) in calcium balance and bone health, the body has evolved effective homeostatic mechanisms to maintain 1,25-dihydroxyvitamin D [1,25(OH)2D] — the biologically active form — in a narrow physiological range. Objective and hypothesis. We developed a mathematical model to investigate homeostatic mechanisms regulating VitD metabolism with the objective of elucidating regulatory mechanisms maintaining levels of 1,25(OH)2D within a narrow physiological range despite wide variation in availability of VitD. Methods. We studied 11 otherwise healthy VitD deficient [25(OH)D&lt;20 ng/mL] participants before and after VitD3 supplementation (50,000 IU once or twice a week depending on BMI for 4-6 weeks). We measured 25(OH)D, 1,25(OH)2D, 24,25(OH)2D, PTH, and FGF23. We used a 2-tailed paired Student’s t-test to analyze our data; p=0.05 was selected as the criterion for statistical significance. This represents a secondary analysis of a previously published clinical trial [Shahidzadeh Yazdi et al. (2023) J Clin Endocrinol Metab, doi: 10.1210/clinem/dgad554]. Results. VitD3 supplements induced a significant 2.7-fold increase (p=0.0006) in mean 25(OH)D and a 4.3-fold increase (p=0.0002) in 24,25(OH)2D, but did not change 1,25(OH)2D, PTH, or FGF23. Our model showed that 24-hydroxylase activity was regulated over a 10-fold range — with maximal induction for 25(OH)D&gt;50 ng/mL and maximal suppression for 25(OH)D&lt;10-20 ng/mL). Because 24-hydroxylase catalyzes metabolic clearance of 1,25(OH)2D, high levels protect against VitD toxicity and low levels preserve 1,25(OH)2D when VitD is scarce. Thus, suppression of 24-hydroxylase activity is a homeostatic mechanism reflecting the body’s perception of VitD deficiency. Accordingly, measurements of 24,25(OH)2D levels can contribute to assessment of VitD status. However, measurements of total levels of all VitD metabolites [including 24,25(OH)2D] are confounded by the ~3-fold inter-individual variation in VitD binding protein (VDBP) levels. Fortunately, the ratio of 1,25(OH)2D /24,25(OH)2D is independent of VDBP levels. Our analysis suggests that this ratio provides a superior assessment of VitD status compared to the current recommendation to measure total 25(OH)D. For example, 24-hydroxylase activity is highly correlated with 1,25(OH)2D /24,25(OH)2D (ρ2=0.91) but less well correlated with 25(OH)D (ρ2=0.91). Conclusions. The body has two defense mechanisms to protect against VitD deficiency. The first line of defense is suppression of 24-hydroxylase, which is triggered by mild-moderate VitD deficiency and preserves VitD from degradation. However, at times of severe VitD deficiency, the first line of defense may be insuffcient to maintain 1,25(OH)2D in a physiological range. Therefore, the body triggers a second line of defense — secondary hyperparathyroidism, which in turn upregulates 1-hydroxylation and increases production of 1,25(OH)2D. By better understanding the physiology of homeostatic regulation of VitD metabolism, physicians can advance the state-of-the-art in diagnosing and treating VitD deficiency. Funding: R01DK118942; T32DK098107. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Improving the performance of room temperature rotary magnetic refrigerators via magnet shape optimization

A magnetic structure intended for use in a room-temperature rotary active magnetic regenerator (AMR) is presented, under construction at the University of Genoa. Given the overall size of the regenerator and the thickness of the gap, the magnet design is optimized to produce the highest possible magnetic field difference between two adjacent regions. Magnet shape optimization is obtained by introducing a geometry with four degrees of freedom corresponding to the position of the edges of each magnet, plus the remanence angle. This approach serves two main purposes: the primary is to increase the magnetic induction and, to follow, some effort is made to minimize the volume and weight of the expensive NdFeB magnets, while preserving the cooling performance. So, a balance between these two goals must be achieved. After a rough preliminary sizing, a parametric investigation is performed toward these targets and some shapes are presented. The magnetic flux density in the gap, and other consolidated and novel performance indices, are evaluated and compared to those found in the literature for similar devices. The final design achieves, in the air gap, a maximum induction value of 1.045 T, and an average flux density of 0.83 T in a volume per unit length of 0.00268 m3/m in the high induction region. This is accomplished by using 0.00606 m3/m of magnetic material (N50, NdFeB). The magnet designs presented here exhibit a well-balanced performance (in terms of greater cooling for the same magnet weight) compared to earlier designs for similar AMR devices.