DC Ratio Research Articles

Development and implementation of an automated four-terminal-pair Josephson impedance bridge

The four-terminal-pair impedance bridge using pulse-driven Josephson voltage standards at PTB has been fully automated. The same bridge configuration was employed to determine R:R and C:C ratios over the frequency range between 53 Hz to 50 kHz. Only minor changes are needed to cover this large frequency range: amplifiers to increase the sensitivity of the current detections for low frequencies and signal generators with higher resolution at high frequencies to reach 50 kHz. Furthermore, the bridge can be operated for quadrature R:(1/ωC) measurements. The combined standard uncertainties (k = 1) for the new bridge were evaluated for all operating frequencies. They reach 2 nF F−1 and 4 nΩ Ω−1 at 1233.15 Hz. At this frequency, the 10 nF:10 nF ratio matched the ratio of PTB’s bridge employing inductive voltage dividers within 1 nF F−1 ± 3 nF F−1 (k = 1). Over 45 days, the 10 nF:10 nF ratio deviated less than −2 nF F−1 ± 3 nF F−1 (k = 1). The 12.9 kΩ:10 kΩ ratio at 53 Hz differed −2 nΩ Ω−1 ± 5 nΩ Ω−1 (k = 1) from the DC ratio measured by the PTB’s cryogenic current comparator bridge. Using a 12.9 kΩ resistance standard and a graphene AC quantum Hall resistance, the 10 nF:10 nF ratios derived from quadrature measurements agreed with the PTB’s inductive voltage divider bridge better than 9 nF F−1 ± 13 nF F−1 (k = 1).

EMD-Based Noninvasive Blood Glucose Estimation from PPG Signals Using Machine Learning Algorithms

Effective management of diabetes requires accurate monitoring of blood glucose levels. Traditional invasive methods for such monitoring can be cumbersome and uncomfortable for patients. In this study, we introduce a noninvasive approach to estimate blood glucose levels using photoplethysmography (PPG) signals. We have focused on blood glucose prediction using wrist PPG signals and explored various PPG waveform-based features, including AC to DC ratio (AC/DC) and intrinsic mode function (IMF)-based features derived from empirical mode decomposition (EMD). To the best of our knowledge, no studies have been found using EMD-based features to estimate blood glucose levels noninvasively. Additionally, feature importance-based selection has also been used to further improve the accuracy of the proposed model. Among the four machine learning algorithms considered in this study, CatBoost consistently outperformed XGBoost, LightGBM, and random forest across a wide number of features. The best performing model, CatBoost, achieved Pearson’s r of 0.96, MSE 0.08, R2 score 0.92, and MAE 8.01 when considering the top 50 features selected from both PPG waveform-based features and IMF-based features. The p-values for all models were <0.001, indicating statistically significant correlations. Overall, this study provides valuable insights into the feasibility and effectiveness of noninvasive blood glucose monitoring using advanced machine learning techniques.

Closed-Form ZVS Boundaries for Three-Phase M-Level-to-N-Level DAB Converters With Different Winding Configurations

One of the essential characteristics of a three-phase dual-active-bridge (DAB) DC-DC converter is its inherent zero-voltage switching (ZVS) capability during the turn-on of the switches. This paper provides closed-form equations that identify the ZVS boundaries for an M-level-to-N-level DAB converter, where M and N can be any natural numbers. It is shown that the derived ZVS boundaries can be used for different converter topologies, including but not limited to: two-level full-bridge converter, three-level neutral-point-clamped converter, T-type converter, transition arm converter, modular multilevel converter, and controlled-transition-bridge converter. The effect of different winding configurations of the medium frequency transformer—YY, Y <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\Delta$</tex-math></inline-formula> , and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\Delta \Delta$</tex-math></inline-formula> —is also considered in the study. Additionally, easy-to-implement simplified ZVS boundaries are provided, and the effects of the different number of levels, transition times, and dead times on the ZVS operation are quantified. An important result shown is that the converters with the YY and the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\Delta \Delta$</tex-math></inline-formula> windings lose ZVS at partial loads as soon as the transition time increases from zero, whereas the ones with the Y <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\Delta$</tex-math></inline-formula> configuration retain ZVS at partial loads and DC ratios close to unity, without any advanced modulation techniques. The derived analytical models are validated with MATLAB simulations and experiments.

Pembrolizumab immunotherapy in advanced and recurrent/metastatic salivary gland carcinoma (R/M SGC): A systematic review and meta-analysis.

e18101 Background: Treatment options for advanced R/M SGC are a limited and with variable response rates due to their safety/toxicity profile and the heterogenous l histology. Recent clinical trials tested pembrolizumab (PMB), a PD-1 inhibitor, in diverse settings. Methods: We performed a systematic review and single arm meta-analysis of clinical trials of PMB monotherapy or combined therapy in advanced and R/M SGC. PubMed, Scopus, and Cochrane database were searched for clinical trials published up to January 31, 2023. Data were extracted from published reports and quality assessment was performed per Cochrane recommendations. The primary endpoints of interest were complete/partial response (CR,PR) and disease control (DC= SD or better response) per RECIST v1.1, at any period of the trial. Results: Out of 199 database results, 4 clinical trials and 180 patients were included, all were using some form of PMB therapy. Overall, PMB was associated with a CR,PR ratio of 5.6% (95% CI 0.01-0.10, I²=25%, p=0.262) and DC ratio of 58.4% (95% CI 0.50-0.66, I²=13%, p=0.326), somewhat similar to recent evidence of PD-1/CTLA-4 combined therapy (nivolumab + ipilimumab [CR,PR=6-16%) in ongoing phase II clinical trials or PD-1 monotherapy (nivolumab [CR,PR=6%; SD=50%] in a completed clinical trial. Other systemic therapies, in which the current guidelines are based, include TKI (lenvatinib + sorafenib PR=3-15%; SD=50-94%) for adenoid cystic carcinoma (ACC); NTRK (larotrectinib CR,PR=90%, entrectinib CR,PR=86%), HER2 (transtuzumab associations CR,PR=60-90%), and AR (leuprorelin + bicalutamide CR,PR=42%, enzalutamide PR=4-15%; SD=52%) in non-ACC; and cytotoxic chemotherapy associations CR,PR=16-34% in heterogeneous histology tumors. Conclusions: There are marked limitations to the applicability of these findings in clinical practice, therefore a cautionary approach to this data is recommended, given their overall low statistical power, heterogenous histology, and tolerability to adverse effects. New trials with better standardized outcomes and comparative arms for different therapy associations and populations will help clarify the effects PD-1 inhibitors in the treatment of advanced and R/M SGC. [Table: see text]

Analytical Approach to THD Formulation and Optimization in Sine-PWM-Based Single-Phase Multilevel Inverters With Variable DC Ratios

Asymmetric Multilevel Inverters (MLI) with Unequal Voltage Steps (UVS) are often combined with the Staircase Modulation (SCM) technique to improve both voltage and current THD - an approach known as Optimal Minimization of THD (OMTHD). This is usually achieved by varying both the Switching Angles (SA) and the DC source Ratios (DCR), to obtain the desired Modulation Index (MI) while THD is minimized. In this article, a novel Sine-PWM (SPWM) based OMTHD is considered as an alternative to SCM-based OMTHD. Because only the DCRs need to be optimized instead of both SAs and DCRs, the OMTHD process is simplified, while voltage THD, current THD, as well as power efficiency, are improved, especially for the medium-low MI range, compared to conventional SPWM. An analytical formulation of phase-voltage THD for UVS-based SPWM MLIs is derived and utilized for the novel SPWM-based OMTHD. Validation is carried out by theoretical analysis, digital simulations, and real-time C-HIL-based experiments.

Current-THD minimization in multilevel inverters with variable DC ratios utilizing a generic closed-form analytic formulation of line-voltage WTHD

This article presents a generic approach to load-current THD minimization in hard-switched Staircase Modulation (SCM) based three-phase (3ɸ) Multilevel Inverters (MLI) with either fixed or variable DC source Ratios (DCR). First, a computer-aided closed-form analytical formulation of Weighted THD (WTHD) applied directly to line-voltage waveforms is derived using Maple software and then verified against numerically-obtained results of previous works. The proposed symbolic analysis of Weighted Line-voltage THD (WLTHD) applies to 3ɸ-MLIs of any topology with Equal Voltage Steps (EVS) or Unequal Voltage Steps (UVS), and any number of voltage levels count (N), either odd or even. Such an analytical approach eliminates the risk of underestimation errors associated with numerical methods. The proposed closed-form WLTHD expression is then utilized for optimal minimization of current-THD in 3ɸ inductive loads with unconnected neutral. This is achieved by introducing a generic UVS-based Optimal Minimization of WLTHD (OMWLTHD), which calculates the optimum Phase Switching Angles (PSA) and the supply DC-Ratios (DCR), given any desired Modulation Index (MI), thus ensuring minimum current-THD across the entire linear MI range. The revealed OMWLTHD approach is fully validated by both digital simulations and controller plus hardware-in-loop (C-HIL) based experiments, using 7-, 8-, and even 13-level 3ɸ-MLIs of both EVS and UVS configurations. Furthermore, to reveal the impact of WLTHD minimization on actual load current-THD, the MLIs were loaded by a Resistive-Inductive-EMF (RLE) load, as well as a 3ɸ squirrel cage induction motor, thus representing a wide range of possible loads, such as motors and ac grids. The conclusive verification results have shown that in the case of 3-wire inductive loads with a power factor up to 0.95, the proposed UVS-based WLTHD optimization is more beneficial for current-THD minimization over other harmonic distortion quantifying parameters, as WLTHD presents the strongest correlation to actual load current THD when tested against any other parameter such as phase and line THD or WTHD. The revealed improvement in current THD was even more pronounced for UVS-based SCM compared to traditional EVS-based SCM. Additionally, MATLAB and Maple source files of the proposed WLTHD formulations and Excel-based pre-calculated optimum PSA and DCR sets for different values of N are provided as downloadable links to further enhance the contribution of the article.

A detailed study of Qdc of 3D micro air-core inductors for integrated power supplies: Power supply in package (PSiP) and power supply on chip (PSoC)

• A sensitivity analysis is carried out to understand the impact of various design parameters on the Q d c of 3D inductors. • The solenoid and the toroid inductors are implemented on a PCB of size 5 mm × 5 mm to demonstrate the research findings. • The design and analysis presented in this work help in the optimization of the performance of 3D inductors. This work presents the impact of design parameters such as the number of turns, pitch, height, conductor dimensions, etc., on the dc ratio of inductance to resistance ( L d c / R d c ) (also known as dc quality factor Q d c ) of 3D micro air-core inductors. We consider two well-known traditional inductors for the illustration: the toroid and the solenoid. We evaluate the performance of these inductors with respect to Q d c over a wide range of design parameters. To demonstrate our research findings, we have implemented the solenoid and toroid inductors on a PCB of size 5 mm × 5 mm.

High-Intensity Light-Emitting Diode and Reduced Curing Times—An In Vitro Study

Objective: To evaluate and compare the effect of high-intensity light-emitting diode (LED) light-curing unit at different curing times on the shear bond strength (SBS), surface enamel loss, and degree of polymerization of a light-cure and dual-cure adhesive system. Materials and Methods: One hundred and twenty extracted human premolar teeth were divided into 2 groups— group 1 (light cure) and group 2 (dual cure), depending on the adhesive system used. These groups were further subdivided into 3 subgroups with 20 teeth each, depending on the duration of curing. A high-intensity LED curing unit was used to bond metal brackets onto the teeth. The samples were tested on a universal testing machine to measure the SBS. The samples were then observed under a simple microscope and modified adhesive remnant index scores were assigned. The bracket bases were mapped with energy-dispersive X-ray spectrometry to evaluate the amount of enamel present. Cured adhesive was scraped and was subjected to Fourier-Transform Infrared Spectroscopy to assess the degree of cure (%DC). Results: An increase in curing durations increased mean SBS values, %DC, and calcium-phosphorous ratios (Ca:P). Similarly, these parameters were higher for dual-cure subgroups when compared to light-cure subgroups. Conclusion: High-intensity LEDs can be used successfully for bonding orthodontic brackets with reduced curing duration. These LEDs help to reduce chairside time and can minimize damage to enamel without compromising bond strength.

Influence of resin matrix on the rheology, translucency, and curing potential of experimental flowable composites for bulk-fill applications

ObjectiveTo propose monomer formulations that show an optimal degree of conversion as a function of depth for bulk-fill applications. MethodsFour resin blends were formulated with methacrylate-based monomers: BisGMA + TEGDMA (control); BisEMA + BisGMA + TEGDMA (BisEMA-based); UDMA + BisGMA + TEGDMA (UDMA-based) and BisEMA + UDMA + BisGMA + TEGDMA (BisEMA + UDMA-based). For each material, a photoinitiating system and silanized filler particles were added. The rheological analyses were performed with a rotational rheometer using the cone/plate geometry. CIELab coordinates were assessed over black and white backgrounds using a bench spectrophotometer (SP60, X-Rite) to calculate the translucency parameter (TP) for samples with 0.5, 4, and 6 mm thickness. The degree of CC conversion (DC) was determined by infrared spectroscopy (FTIR/ATR) at 0.05 mm (top), 4, and 6 mm depths (bottom), and the bottom-to-top ratio was considered. A broad spectrum–based LED was used for light activation. Analysis of variance and Tukey’s test (95%) were performed on the results. ResultsThe materials tested showed pseudoplastic and thixotropic behavior and a predominance of viscous effects over elastics. The control resin yielded the lowest viscosity for the entire shear rate investigated, followed by the BisEMA-based, BisEMA + UDMA-based, and UDMA-based group, which had the highest viscosity. The UDMA-based material showed the lowest TP as a function of thickness. Both the materials’ formulations and depths significantly influenced the DC. The UDMA-based group promoted the highest DC ​​on the top (71 ± 1%) and 4 mm depth (68 ± 1%) but exhibited lower bottom-to-top DC ratio. The BisEMA + UDMA-based material promoted the highest bottom-to-top DC ratio at 4 mm (99%) and 6 mm (97%). SignificanceThe resin matrix interferes in the rheological behavior, translucency parameter, and polymerization capacity as a function of depth. The material formulated with the addition of UDMA and BisEMA demonstrated the highest curing potential as a function of depth and can be useful for bulk-fill applications.

The effect of kangaroo care on modulate chronic stress response in preterm infants and mothers

To assess stress experienced during Neonatal Intensive Care Unit (NICU) stay, we analyzed fingernail Cortisol (CORT) and Dehydroepiandrosterone (DHEA) levels and ratios in mothers and preterm infants (PI); compared hormones levels/ratio (CORT and DHEA) in kangaroo care (KC) versus standard care (SC) groups and examined relationships between PI hormone levels total days spent in the NICU. Mothers and their infants were recruited in the NICU, included levels I-IV and kangaroo care unit, within one week of infant birth in hospitals in Brazil. At 3 months after birth, mothers provided 3-month growth clippings from all ten digits of their own and their infants’ fingernails. CORT and DHEA were measured using enzyme immunoassays (mothers) and high-performance-liquid-chromatography-with-mass-spectrometry (infants). Sample: n = 59 mothers (KC = 30/SC = 29) and 63 infants (KC = 32/SC = 31). Data were analyzed using non-parametric/parametric comparative statistics. NICU stay ranged from 3–103 days. For mothers in Kangaroo and Standard Care the CORT, DHEA levels and DHEA:CORT ratio (DC) ratio did not differ. Infants in KC had higher DHEA (p = 0.003) and a higher DC ratio (p = 0.011) than SC infants. Even though KC infants stayed in the NICU for a greater number of days than infants in SC, they had higher mean level of DHEA, and DC ratio, suggesting that KC played a role in promoting their stress regulatory capacities and may mitigate toxic effects of chronic hypercortisolemia. However, for mothers, KC did not reduce chronic stress compared to that in women in the SC condition. Further research warranted.

A Review and Comparison of Solid, Multi-Strands and Litz Style PCB Winding

At high frequency, AC resistance of a printed circuit board (PCB) winding becomes important and accounts for a large proportion of planar transformer losses. The winding is then influenced by both skin and proximity phenomenon, which makes the current distribution uneven resulting in an increased resistance. The study of improving AC resistance of a PCB winding has been tackled by many researchers. However, the lack of an overview and comparison among improvements has made it difficult to apply those methods to a specific winding. To overcome the above limitations, this paper investigates the pros and cons of three popular AC resistance optimizing methods: optimizing track width of a solid PCB winding, using multi-strands and using Litz style PCB winding. To verify the theoretical analysis, a total of 12 PCBs are simulated by finite element (FEM) and tested in the laboratory. Five criteria are analyzed, including skin resistance, proximity resistance, AC to DC ratio, total AC resistance and complexity are taken into consideration. The results of this study show that optimizing track width method has a significant improvement on AC resistance while the use of Litz PCB is effective for applications that need stable AC resistance in a wide frequency range. The use of parallel strands winding should be carefully considered as there is not significant benefit in both reducing the AC resistance and AC to DC ratio.

Optimizing AC Resistance of Solid PCB Winding

At high frequency, power losses of a winding due to eddy currents becomes significant. Moreover, the skin and proximity AC resistances are influenced by the width of printed circuit board (PCB) conductors and distance between the adjacent tracks which causes many difficulties to design windings with lowest AC resistances. To clarify this phenomenon, this paper focuses on modeling the influence of skin and proximity effects on AC resistance of planar PCB winding, thereby providing guidelines to reduce the winding AC resistance. An approximate electromagnetic calculation method is proposed and it shows that when the winding proximity AC to DC ratio ( F p r o x i m i t y ) is equal to 1 3 the AC on DC ratio caused by skin effect ( F s k i n ) , the winding is optimized and it has lowest AC resistance. 3-D finite element simulations of 3, 7 and 10-Turn windings, which are divided into 3 groups with the same footprint, are presented to investigate the lowest AC resistance when the track width varies from 3 mm to 5 mm and the frequency range is up to 700 kHz. In order to verify the theoretical analysis and simulation results, an experiment with 3 simulated groups, (9 prototypes in total) is built and has a very good fit with simulation results. Experimental results show that at the optimal width, the AC resistance of the windings can be reduced up to 16.5 % in the frequency range from 200 kHz to 700 kHz.

Triangular Omnidirectional Wheel Motion Control System

Omni-directional wheels are more flexible than traditional wheeled robots. Through three rounds of omni-directional wheel mobile platform modeling and kinematics analysis. The speed of the three wheels can be analyzed when the omni-moving platform moves in a certain direction. Then the CPU by the PID algorithm to calculate the connection of omni-directional wheel three dc motor need duty ratio, round so as to realize omnidirectional mobile platform of fast moving to any Angle. The experimental results show that the mobile platform can move rapidly in any direction.

Analytical Formulation and Minimization of Voltage THD in Staircase Modulated Multilevel Inverters With Variable DC Ratios

Staircase Modulation (SCM) is a commonly employed switching strategy in Multilevel Inverters (MLI) with a high number of voltage levels (N). The main challenges in SCM are adjusting the Modulation Index (MI) to the desired value while minimizing the Total Harmonic Distortion (THD). This is achieved by solving an objective function for its optimum variables. These variables are the Switching Angles (SA) in the case of an MLI with Equal DC voltage Supply (EDCS), or both the SAs and the DC voltage supply Ratios (DCR), in the case of an MLI with Unequal DC voltage Supply (UDCS). Such an approach, which is referred to as Optimum Minimization of THD (OMTHD), relies on the accuracy of the THD expression used for the objective function. This paper reveals generic analytical closed-form formulations of both Phase-voltage THD (PTHD) for single-phase (1φ) MLIs and Line-voltage THD (LTHD) for three-phase (3φ) MLIs. The revealed THD expressions apply to SCM based MLIs of any topology, with either EDCS or UDCS voltage source configurations, which may be fixed or varying, and arbitrary value of N (odd and even). Given an arbitrary N value, the proposed unified formulations can be used to generate symbolic N-level PTHD or LTHD expressions, which are analytical functions of the SA and (optionally) DCR variables. The proposed THD expressions were used to form a generic OMTHD problem and solve for optimum SA and DCR variables, ensuring PTHD or LTHD minimization, subject to a set of optional constraints, such as the target MI, tolerable Modulation Error (ME), and the Maximum DCR (MDCR). Outcomes of the proposed OMTHD algorithm were successfully verified by Controller + Hardware-in-Loop (C-HIL) based experiments and compared against results of previous works, raveling significant improvement in THD accuracy and MLI's performance. A downloadable supplemental file containing Maple and MATLAB functions of the proposed THD expressions, as well as pre-calculated sets of optimum SAs and DCRs tables for 13 different values of N (4 ≤ N ≤ 16), is provided for readers' convenience.

Autophagic induction modulates splenic plasmacytoid dendritic cell mediated immune response in cerebral malarial infection model

Splenic plasmacytoid dendritic cells (pDC) possess the capability to harbor live replicative Plasmodium parasite. Isolated splenic pDC from infected mice causes malaria when transferred to naïve mice. Incomplete autophagic degradation might cause poor antigen processing and poor immune response. Induction of autophagic flux by rapamycin treatment led to better prognosis by boosting pDC centered immune response against the pathogen. Splenic pDC from rapamycin-treated infected mice, caused less parasitemia in naïve mice. The downregulation of adhesion with unaltered phagocytic potential of the cells post autophagic induction restricted excessive parasite burden within them. Rapamycin-treated pDC played a better role in antigen presentation. They showed higher expression of co-stimulatory molecules CD80, CD86, DEC205, MHCI. Rapamycin-treated pDC induced CD28 expression on CD8+ T cells and suppressed FasL level. This cells also influenced differentiation of effector, memory T cell population. The increase in IL10: TNFα ratio, Treg: Th17 ratio and lowering of myeloid DC: plasmacytoid DC ratio was observed. It shifted the overaggressive inflammation mediated Th1 pathway that is reported to incur host damage, to a better well-balanced cytokine profile exhibiting Th2 pathway. Autophagic flux induction within pDC proved to be beneficial in combating malarial pathogenicity.

Sex-specific contribution of DHEA-cortisol ratio to prefrontal-hippocampal structural development, cognitive abilities and personality traits.

Although dehydroepiandrosterone (DHEA) may exert neuroprotective effects in the developing brain, prolonged or excessive elevations in cortisol may exert neurotoxic effects. The ratio between DHEA and cortisol (DC ratio) has been linked to internalising and externalising disorders, as well as cognitive performance, supporting the clinical relevance of this hormonal ratio during development. However, the brain mechanisms by which these effects may be mediated have not yet been identified. Furthermore, although there is evidence that the effects of cortisol in the central nervous system may be sexually dimorphic in humans, the opposite is true for DHEA, with human studies showing no sex-specific associations in cortical thickness, cortico-amygdalar or cortico-hippocampal structural covariance. Therefore, it remains unclear whether sex moderates the developmental associations between DC ratio, brain structure, cognition and behaviour. In the present study, we examined the associations between DC ratio, structural covariance of the hippocampus with whole-brain cortical thickness, and measures of personality, behaviour and cognition in a longitudinal sample of typically developing children, adolescents and young adults aged 6-22years (N=225 participants [F=128]; 355 scans [F=208]), using mixed effects models that accounted for both within- and between-subject variances. We found sex-specific interactions between DC ratio and anterior cingulate cortex-hippocampal structural covariance, with higher DC ratios being associated with a more negative covariance between these structures in girls, and a more positive covariance in boys. Furthermore, the negative prefrontal-hippocampal structural covariance found in girls was associated with higher verbal memory and mathematical ability, whereas the positive covariance found in boys was associated with lower cooperativeness and reward dependence personality traits. These findings support the notion that the ratio between DHEA and cortisol levels may contribute, at least in part, to the development of sex differences in cognitive abilities, as well as risk for internalising/externalising disorders, via an alteration in prefrontal-hippocampal structure during the transition from childhood to adulthood.

Role of DHEA and cortisol in prefrontal-amygdalar development and working memory

There is accumulating evidence that both dehydroepiandrosterone (DHEA) and cortisol play an important role in regulating physical maturation and brain development. High DHEA levels tend to be associated with neuroprotective and indirect anabolic effects, while high cortisol levels tend to be associated with catabolic and neurotoxic properties. Previous literature has linked the ratio between DHEA and cortisol levels (DC ratio) to disorders of attention, emotional regulation and conduct, but little is known as to the relationship between this ratio and brain development. Due to the extensive links between the amygdala and the cortex as well as the known amygdalar involvement in emotional regulation, we examined associations between DC ratio, structural covariance of the amygdala with whole-brain cortical thickness, and validated report-based measures of attention, working memory, internalizing and externalizing symptoms, in a longitudinal sample of typically developing children and adolescents 6–22 years of age. We found that DC ratio predicted covariance between amygdalar volume and the medial anterior cingulate cortex, particularly in the right hemisphere. DC ratio had a significant indirect effect on working memory through its impact on prefrontal-amygdalar covariance, with higher DC ratios associated with a prefrontal-amygdalar covariance pattern predictive of higher scores on a measure of working memory. Taken together, these findings support the notion, as suggested by animal and in vitro studies, that there are opposing effects of DHEA and cortisol on brain development in humans, and that these effects may especially target prefrontal-amygdalar development and working memory, in a lateralized fashion.

Soil Erosion as Affected by Freeze‐Thaw Regime and Initial Soil Moisture Content

Core Ideas Freeze‐thaw generally increased detachment capacity by an average of 36.5%. The impact of freeze‐thaw on soil erosion was affected by initial moisture content. Detachment capacity and rill erodibility was increased at 30 and 45% moisture. Soil erosion was reduced at 20% moisture content after 5 or 10 freeze‐thaw cycles. The effect of freeze‐thaw exponentially increased with the freeze‐thaw cycles. To quantify the effects of freeze‐thaw (F‐T) on rill erosion, scouring test using a tilting flume (5 m length, 0.4 m width) was conducted. Typical black soil in Northeast China was tested. Five F‐T cycles (FTCs; 0, 1, 3, 5 and 10), four gravimetric moisture contents (θg; 10, 20, 30 and 45%), and seven flow shear stresses (τ; evenly spaced from 1.90 to 14.59 Pa) were examined. The soil samples subjected to 0 FTC were termed as the unfrozen control group. The results showed that the F‐T processes increased soil detachment capacity (Dc) by an average of 36.5% across all experimental conditions together. The effects of F‐T on Dc varied with initial θg. To eliminate the consolidation impact induced by water spraying, the Dc ratio (RDc) between each F‐T group and the corresponding unfrozen control group was calculated. This ratio was found to exponentially increase with FTCs, with an R2 of 0.94. The rill erodibility (Kr) increased with FTCs only at initial θg of 30 and 45%. Soil critical shear stress (τc) of the experimental group was significantly higher relative to the unfrozen control group and reached its maximum after 10 FTCs at the initial θg of 20%. These findings help to understand the effects of FTCs on soil erosion and thereby to improve soil erosion models, e.g. modifying rill erodibility parameters.

OP15. ENHANCEMENT OF MYELOID DENDRITIC CELLS THROUGH MAPK P38 INHIBITION PROMOTES T CELL PROLIFERATION AND RESTORES ADAPTIVE IMMUNITY IN GBM PATIENTS

AbstractINTRODUCTION: Immunotherapy is an emerging backbone to oncology treatment in a number of cancers, mainly due to the advent of checkpoint blockade therapy. In Glioblastoma (GBM) immunotherapies such as peptide vaccines and laboratory generated monocyte-derived dendritic cells (moDC) are demonstrating promise in advanced stages of clinical trials. Recently however, a number of studies have highlighted the immune advantages circulating DC possess. We previously showed that the potential novel adoptive transfer of isolated circulating myeloid DC (MDC1) may be hampered in GBM patients due to reduced numbers of MDC1 and suppressed production of the key Th1-polarising cytokine IL-12. Importantly, IL-12 production by MDC1 was rescued and enhanced upon exposure to a MAPK p38 inhibitor (p38i). The increase in IL-12 with p38i was unique to MDC1s and in contrast to its effects on moDC. Here we tested the hypothesis that p38i enhances the capacity of MDC1 to promote T-cell proliferation. METHOD: Paramagnetic bead isolation kits were used to isolate circulating MDC1, CD4+ cells or peripheral blood lymphocytes (PBL) from mononuclear cells. A model of GBM:DC interaction was devised in which DC were co-cultured with tumour lysate (TL) from U87 (TL:DC ratio 50:1), or dexamethasone (Dex) 10-6M. The p38i, BIRB0796 1μM, was added to inhibit the MAPK pathway in MDC1s. The impact of GBM/Dex on DC function was determined in a mixed lymphocyte reaction (MLR) with PBL as responders. Further experiments, determined the impact of checkpoint inhibitors (Ipilimumab and Pembrolizumab) on the MLR. The MLR supernatants were analysed for IFN-γ and IL-10. RESULTS: Exposure to TL or Dex markedly inhibited the capacity of MDC1 to stimulate an MLR (p=0.001 and p<0.001 respectively). However, pre-treatment with p38i reversed this increasing proliferation above that of control cells (TL, p=0.001; DEX, p=0.021). Analysis of the supernatants of p38i-treated MDC1 stimulated PBL, showed a prominent increase in the Th1-cytokine IFN-γ. The addition of checkpoint inhibitors to TL or Dex treated MDC1 also restored T-cell proliferation. However, the greatest proliferation was observed with the combination of p38i MDC1s and checkpoint inhibitors. This combination was associated with further increases in IFN-γ secretion. CONCLUSION: MAPK p38 inhibited MDC1s stimulate an adaptive immune response greater than that of healthy MDC1s. Furthermore, this can reverse immunosuppression from Dex and TL on DCs, experienced by GBM patients. Interestingly, the combination of p38i MDC1 with checkpoint blockade inhibitors was most favourable at stimulating a lymphocyte response, postulating an advantageous immunotherapeutic strategy in patients.

Study the Performance of the AC/DC Resistors During Their DC and AC Measurements

Some of traceability chains for the AC resistance measurements are based on AC/DC resistors. In this paper, performance of two types of them with different values has been investigated for their optimum utilization. Tinsley and Cambridge AC/DC resistors have been measured as DC resistors using different measurement methods and as AC resistors at various frequencies. DC direct method using digital reference multimeter is more accurate for the resistance values 1, 10, 100 Ω, and 1 kΩ. For the values 10 and 100 kΩ; measurement results are very near by using the DC direct and ratio methods. At 100 kΩ; representation of the resistance as an equivalent series resistance is not suitable at frequencies above 10 kHz, while for 100 mΩ and 1 Ω; the equivalent parallel representation is not suitable above the same frequency. The uncertainty analysis is also studied for all the obtained results.