Injection Level Research Articles

Experimental Observations of Heat-Assisted Boycott Effect in Trapezoidal Enclosures

The present study examined the influence of controlled heat injection on the sedimentation of fine particles in a trapezoidal container, aiming to explore the combined effects of the Boycott effect and convection induced by heating. The experimental design incorporates varying initial particle concentrations (1500 ppm and 3000 ppm) and heat injection levels (0 W, 4.5 W, and 9 W imposed power) to analyze sedimentation dynamics, focusing on concentration distribution patterns and clear water production. The findings reveal complex interactions between heat injection and particle concentration. At 1500 ppm, heat injection shows minimal impact on sedimentation due to particle resuspension. However, at 3000 ppm, particularly with a 9 W heat injection, the sedimentation performance improves significantly during the early stages of the process, achieving an average sedimentation rate approximately 40 % higher than without heat injection and an average clear water generation rate nearly four times greater. These clear water generation rates were determined considering water with particle concentrations below 20 % of the initial concentration (300 ppm for 1500 ppm and 600 ppm for 3000 ppm). A further analysis of the column and row data reveals stratification patterns influenced by heat injection, characterized by distinct horizontal and vertical layers. Additionally, the results suggest that wall temperature distributions are largely unaffected by the initial particle concentration, while clear water production and sedimentation efficiency are highly dependent on heat levels and initial particle density. These results highlight the potential of heat-enhanced sedimentation to improve separation processes in industrial systems. Specifically, they provide valuable insights for optimizing the design and efficiency of lamella settlers, commonly used in water treatment and other particulate separation applications. Future studies will explore the combined use of coagulants and flocculants and the application of these findings to real mixtures, such as mine water or wastewater, to further validate and expand their industrial applicability.

Comparison of patient radiation exposure and procedure time between CT-fluoroscopy and spiral CT for lumbar epidural steroid injections.

To compare patient radiation exposure and procedure time for lumbar epidural steroid injections (ESIs) performed under CT-fluoroscopy (CTF) vs spiral CT-guidance. A retrospective cohort study of 767 consecutive lumbar ESIs performed between 2015-2023 using CTF vs spiral CT-guidance was conducted. Patient characteristics (age, sex, weight), procedural characteristics (injection level, type of ESI, trainee participation), and outcomes (patient radiation exposure, procedure time, pain relief, complications) were compared. Student's t and chi-squared tests were performed for statistical analysis. There were 240 CTF and 527 spiral CT-guided lumbar ESIs. There were no significant differences in patient demographics between groups. Radiation exposure for the CTF group was 37.2 ± 50.5mGy cm, compared to 251.1 ± 178.6mGy cm in the spiral CT group (p < 0.001). Procedure times were shorter in the CTF group (20.1 ± 6.1 vs 29.6 ± 12.9min, p < 0.001). There was no significant difference in immediate post-procedure pain reduction in CTF vs spiral CT groups (p = 0.12). There were no intrathecal puncture complications in the CTF group and four in the spiral CT group. Subgroup analysis of attending-only and trainee-performed lumbar ESIs comparing CTF vs spiral-CT groups showed similar results as the primary analysis, with significant reductions in patient radiation (attending: 31.6 ± 40.7 vs 144.4 ± 97.4mGy cm; trainee: 40.7 ± 55.5 vs 264.5 ± 182.0mGy cm; both p < 0.001) and procedural time (attending: 18.3 ± 4.2 vs 24.4 ± 7.4min; trainee: 21.2 ± 6.8 vs 30.2 ± 12.4; both p < 0.001). Image-guided lumbar ESIs using CTF were associated with less patient radiation exposure and shorter procedure times without differences in pain relief when compared with spiral CT technique in our practice.

The anesthetic and recovery profiles of low-dose hypobaric mepivacaine and bupivacaine for spinal anesthesia in total hip and knee arthroplasty: a prospective observational study.

Same-day mobilization and early hospital discharge is increasingly emphasized following hip and knee arthroplasty. One challenge of spinal anesthesia in this setting is achieving adequate block height while avoiding excessively large local anesthetic doses and prolonged motor and sensory blockade. Using a hypobaric local anesthetic solution is one potential strategy, as its intrathecal distribution can be reliably manipulated by patient positioning to achieve adequate block height independent of dose. We conducted a prospective observational study to determine the clinical characteristics of spinal anesthesia with low-dose hypobaric mepivacaine and bupivacaine in patients undergoing hip and knee arthroplasty. Thirty patients scheduled for same-day discharge received 51mg of hypobaric 1.5% mepivacaine and 30 patients scheduled for inpatient stay received 10mg of hypobaric 0.33% bupivacaine. The mean (standard deviation) time to achieve sensory blockade at or above L1 and T10 in the operative limb was 5.7 (1.8) and 7.3 (3.3) min with mepivacaine and 6.2 (2.6) and 8.1 (4.8) min with bupivacaine, respectively. Anesthesia was adequate for surgical commencement in all patients regardless of spinal injection level. Four patients required anesthetic supplementation for surgical completion. Sensory block duration at or above T10 and L1 in the operative limb was 97 (27) and 115 (37) min with mepivacaine and 127 (32) and 161 (34) min with bupivacaine, respectively. Motor function returned by 145 (37) and 217 (43) min in mepivacaine and bupivacaine groups, respectively. The anesthetic profiles of low-dosehypobaric mepivacaine and bupivacaine were favorable for fast-track hip and knee arthroplasty with short and predictable operating times.

Influence of Material Composition and Wafer Thickness on the Performances of Electron Irradiated Gallium‐Doped Silicon Heterojunction Solar Cells

Past studies have underlined the importance of silicon material composition for optimum space solar cells performances. However, the maturity and performances of silicon cells have evolved over the last decades. Due to the increasing space photovoltaic power demand, it becomes crucial to assess modern silicon radiation hardness. Herein, the influence of material composition (resistivity and interstitial oxygen, gallium, and thermal donor concentrations) of modern gallium‐doped silicon wafers on their electronic properties after electron irradiation is investigated. Results demonstrate stable majority carrier concentrations and mobilities within the doping ranges and fluences investigated. Regarding the post‐irradiation carrier recombinations, the higher the resistivity the higher the carrier lifetime is at low injection level. Similarly, the electron diffusion length is six times higher for the 60 Ω.cm samples compared to the 0.9 Ω.cm ones. The Shockley–Read–Hall recombination signature of a vacancy‐related defect (reported in boron‐doped silicon) reproduces well this trend. Then, complete heterojunction solar cells are processed from these materials. While highest resistivity samples feature better carrier lifetimes after irradiation, the best conversion efficiencies are obtained for intermediate resistivity samples (15 Ω.cm). It is shown that it is essentially due to the positive effect of higher majority carrier concentration on the open‐circuit voltage.

Effect of second iron injection on growth performance, hematological parameters, and fecal microbiome of piglets fed different dietary iron levels.

This experiment was conducted to evaluate the effects of a second iron injection for suckling pigs fed diets with different dietary iron levels in the nursery period on growth performance, hematological parameters, serum and liver trace mineral content, fecal score, microbiome, and metabolites. A total of 70 newborn pigs from 7 litters were assigned to either one or two iron injections within litter and received the first i.m. iron injection (200mg) at 2-3 d of age. Pigs assigned to the second injection treatment received an additional iron injection 5 d after the first injection. At weaning (d 27-30 of age), pigs within iron injection treatments were divided into 2 nursery diet treatments for a 27-d growth period. Treatments were: 1) no additional iron injection + nursery diets with 100ppm iron (NC), 2) second i.m. iron injection (200mg) + NC diets, 3) no additional iron injection + nursery diets with 200ppm iron (PC), and 4) second i.m. iron injection (200mg) + PC diets. The second iron injection increased liver iron content at weaning (P = 0.08, tendency), and serum iron, hemoglobin, and hematocrit levels until d 13 postweaning (P < 0.05). In the nursery period, pigs receiving the second iron injection had a greater final body weight (P = 0.08, tendency), overall growth rate (P = 0.08, tendency) and feed intake (P < 0.05), and lower fecal score (P < 0.05) indicating firmer feces compared to those receiving one iron injection. There was no major effect of dietary iron level or interaction with the iron injection treatment in any measurements except that the pigs fed the PC diets had greater hemoglobin and hematocrit levels (P < 0.05) at d 27 postweaning and a lower fecal score (P = 0.08, tendency) in the late nursery period than those fed the NC diets. The second iron injection reduced fecal bacterial alpha-diversity based on Faith's phylogenetic diversity at weaning (P < 0.05), while the second iron injection and dietary iron levels resulted in dissimilarity in the fecal bacterial community based on Unweighted Unifrac analysis (P < 0.05; at weaning by iron injection and d 27 postweaning by dietary iron level). In conclusion, the second iron injection for suckling pigs improved postweaning growth performance and hemoglobin levels and affected the fecal microbiome, whereas an additional 100ppm of dietary iron supplementation increased hemoglobin levels and altered the fecal microbiome in the late nursery period but did not affect postweaning growth.

Implied J-V Curves Recorded at Elevated Temperatures Using Light Controlled Heating

The carrier lifetime characterization of solar cells is typically performed at room temperature, although the operational temperature of a solar panels can reach 60 °C. We realized a setup for laser controlled photoconductance decay (PCD) measurement at elevated temperatures induced by light. We investigated precursor p-PERC cells from multiple parts of the same ingot using this technique. From the injection level dependent carrier lifetime results the implied current-voltage characteristics are evaluated as well. We observed a relatively small but noticeable increase of the carrier lifetime up to 30% with increasing the temperature from 30°C to 60°C in all samples. Saturation current values obtained using the Kane-Swanson method indicate, that not only the bulk lifetime improves but the surface recombination rate weakens. Temperature coefficient values of the implied cell efficiency are around -0.35 rel%/°C and slightly below which agrees with typical results of electrical tests. However, due to the minor increase of the carrier lifetime, this is still a bit above the value one can obtain theoretically considering purely the known decrease of the open circuit voltage caused by the increased intrinsic charge carrier concentration at higher temperatures.

Anatomical assessments of injectate spread stratified by the volume of the intertransverse process block at the T2 level

BackgroundThis cadaveric study aimed to analyze injectate spread to target nerves during a single-injection, ultrasound-guided intertransverse process block.MethodsAn ultrasound-guided intertransverse process block with three different injectate volumes was administered to...

Compact Modeling of Base Current High Injection Effect in SiGe HBTs

In bipolar transistor compact modeling, the forward mode base current typically consists of three components: space-charge recombination, back injection into the emitter, and neutral-base-recombination (NBR). At medium and high base-emitter voltages (VBE), the emitter back injection and NBR components dominate, and both increase exponentially with VBE. Deviation from the ideal behavior occurs at high VBE due to parasitic base and emitter resistance or self-heating.However, in many SiGe HBTs, standard compact models fail to capture experimentally observed IB-VBE characteristics, where the base current (IB) exhibits a high injection behavior that is more evident at lower collector-base voltages (VCB), as shown in Fig. 1. The simulation is done with Mextram 505.2 with resistance and self-heating parameters already calibrated. At a relatively low VBE of 0.72 V, the measured IB starts to bend downward compared to its typical behavior shown by the model, causing the increase of beta with VBE from 0.72 to 0.82 V. Parameter optimization cannot possibly fit silicon data and a new base current model is called for.Similar behavior has been observed by other groups and attributed to carbon-induced NBR [1]-[3]. Interestingly, the onset of this IB high injection occurs at a lower VBE than the onset of collector current (IC) high injection, which is typically due to Kirk's effect or quasi-saturation effect. Such IB high injection behavior also exhibits a complex VCB dependence. The change of IB-VBE slope is less visible at higher VCB due to self-heating, which increases IB.We present a recently developed compact model of base current that models this high-injection effect. The foundation of the high-injection effect model is an analytical expression of the neutral base recombination rate applicable to all injection levels derived from SiGe HBT NBR physics. Based on experimental data measured on devices with different geometries, we model both the area component and peripheral component with separate temperature coefficients. The area component is subject to neutral base width modulation modeled by the same parameters used for the Early effect. A quasi-saturation-induced component is included to model the NBR after the electrical neutral base pushes out at high current densities. The quasi-saturation component has its dedicated parameters to account for the NBR at the SiGe-base/Si-substrate epitaxial growth interface discussed in [4] and [5]. This component comes into play at higher VBE.Fig. 2 demonstrates the new model's capability in capturing the measured IB high injection behavior and its complex VCB dependence, as well as the much-improved fitting of the beta vs. VBE characteristics. The inclusion of the NBR high-injection effect in the base current model enables more accurate modeling of SiGe HBTs. The model has been implemented in Mextram 505.3 and later versions [6].

Theoretical study of the solution of the diffusion equation under effect of the magnetic field on the silicon solar cell

PurposeThe purpose of this study is to investigate the behavior of a silicon solar cell when subjected to a magnetic field. Specifically, the study aims to understand how the presence of the magnetic field influences the distribution of excess minority carriers within the base region of the solar cell. By solving the one-dimensional continuity equation under these conditions, the study seeks to elucidate the transient dynamics of carrier generation, recombination and transport processes. This research contributes to the broader understanding of how external magnetic fields can impact the performance and efficiency of silicon solar cells, potentially informing future optimizations or applications in photovoltaic technology.Design/methodology/approachThe solar cell is assumed to be uniformly illuminated, which simplifies the analysis of carrier generation to a function of depth (x). The emitter and space charge region contributions are considered while neglecting the diffusion region. The injection level remains constant throughout the analysis, focusing specifically on the base thickness region, H = 200 µm.FindingsThe findings of this study reveal significant insights into the behavior of a silicon solar cell under the influence of a magnetic field. Key findings include Impact on carrier distribution: the magnetic field affects the distribution of excess minority carriers within the base region of the solar cell. This distribution is crucial for understanding the efficiency of carrier collection and overall cell performance. Transient dynamics: the transient behavior of carrier generation, recombination and transport processes in the base region is influenced by the magnetic field. This understanding helps in predicting the response time and effectiveness of the solar cell under varying magnetic field strengths. Optimization potential: insights gained from this study suggest potential strategies for optimizing the design and operation of silicon solar cells to enhance their performance in environments where magnetic fields are present. Theoretical framework: the study provides a theoretical framework based on the one-dimensional continuity equation, offering a systematic approach to analyzing and predicting the behavior of solar cells under magnetic field conditions. These findings contribute to advancing the understanding of how external factors such as magnetic fields can impact the operation and efficiency of silicon solar cells, thereby guiding future research and development efforts in photovoltaic technology.Originality/valueThe originality and value of this study lie in its contribution to advancing the understanding of how magnetic fields influence silicon solar cell performance, providing both theoretical insights and potential practical applications in diverse technological contexts.

Synchronization Between Kerr Cavity Solitons and Broad Laser Pulse Injection

The synchronization of a soliton frequency comb in a Kerr cavity with pulsed laser injection is studied numerically. The neutral delay differential equation is used to model the light dynamics in the cavity. This model allows for the investigation of both cases where the pulse repetition period is close to the cavity round-trip time and where the repetition period of the injection pulses is close to a rational fraction M/N of the round-trip time. It is demonstrated that solitons can exist in this latter case, provided that the injection pulses are of a higher amplitude, which is directly proportional to the number M. Furthermore, it is shown that the synchronization range of the solitons is also proportional to the number M. The solitons excited by pulses with a period slightly different from the M:N-resonance can be destabilized by the Andronov–Hopf bifurcation, which occurs when the injection level at the soliton position decreases to M times the injection amplitude corresponding to the saddle-node bifurcation in a model equation with uniform injection.

Dynamics of Photoinduced Charge Carriers in Metal-Halide Perovskites.

The measurement and description of the charge-carrier lifetime (τc) is crucial for the wide-ranging applications of lead-halide perovskites. We present time-resolved microwave-detected photoconductivity decay (TRMCD) measurements and a detailed analysis of the possible recombination mechanisms including trap-assisted, radiative, and Auger recombination. We prove that performing injection-dependent measurement is crucial in identifying the recombination mechanism. We present temperature and injection level dependent measurements in CsPbBr3, which is the most common inorganic lead-halide perovskite. In this material, we observe the dominance of charge-carrier trapping, which results in ultra-long charge-carrier lifetimes. Although charge trapping can limit the effectiveness of materials in photovoltaic applications, it also offers significant advantages for various alternative uses, including delayed and persistent photodetection, charge-trap memory, afterglow light-emitting diodes, quantum information storage, and photocatalytic activity.

Carrier density dynamics and frequency shift in optically injected VCSELs

We theoretically and systematically study the dynamics of carrier density in optically injected VCSELs and correlate it to the observed frequency shift outside the locking region. We also show the dependence of carrier dynamics on all major parameters including frequency detuning, injection level and the linewidth enhancement factor (LEF).

Interfacial Exciton-Polaron Quenching in Organic Light-Emitting Diodes

In organic light-emitting diodes (OLEDs), understanding the efficiency loss mechanism known as exciton-polaron quenching (EPQ) has been a longstanding challenge. Traditionally, EPQ was believed to occur mainly the bulk of the OLED emission layer (EML) due to the coexistence of polarons and excitons, limiting our understanding of its full impact. Here, we report a previously overlooked phenomenon termed “interfacial EPQ (Inf. EPQ),” which occurs at the heterointerface between the EML and the adjacent charge transport layer (CTL). We observe the transfer of EML excitons to CTL polarons across this interface, spanning distances of up to 4 nm. Notably, Inf. EPQ exceeds EPQ within the EML bulk, even in devices with a interfacial energy barrier (&gt;0.2 eV). We propose a methodology that enables independent probing of Inf. EPQ, systematic validation of its essential parameters, and the identification of Dexter energy transfer as its governing mechanism. Importantly, our findings highlight Inf. EPQ as a phenomenon across devices with various luminescent mechanisms, wavelengths, and injection levels. By effectively addressing Inf. EPQ, we achieve efficiency enhancements in red, green, and blue phosphorescent OLEDs, by 70%±8%, 47%±5%, and 66%±6%, respectively. Our work advances the physical understanding of exciton and polaron dynamics at organic heterointerfaces, providing applicable solutions to Inf. EPQ-related issues in practical devices. Published by the American Physical Society 2024

Endotoxin Detection in Magnetic Resonance Imaging Contrast Agent Using Optimising Chromogenic Limulus Amebocyte Lysate Assay.

Endotoxin contamination in magnetic resonance imaging (MRI) contrast agents can pose a risk to patient safety causing immune reactions. Strict endotoxin limits are enforced for implants and catheters inserted into the body, but there are not clear rules for MRI contrast agents. Here, we investigated the efficacy of chromogenic LAL assay test for screening endotoxin activity in MRI contrast media manufactured in Malaysia. The powdered agent was dissolved in water for injection and endotoxin levels were measured. The coefficient of efficiency value for the standard curve, exhibiting r 2 ≥ 0.98, along with the absence of interfering substances and endotoxin activity below the regulatory threshold of 0.5 EU/mL, support the conclusion that the agent is unlikely to be pyrogenic or induce pyrogenic effect.

Time of day-dependent alterations of ferroptosis in LPS-induced myocardial injury via Bmal-1/AKT/ Nrf2 in rat and H9c2 cell

BackgroundOne of the most prevalent causes of death in sepsis is sepsis-induced cardiomyopathy (SICM). Circadian disruption is involved in the progress of sepsis. However, the molecular mechanism remains unclear. MethodsHere, we built LPS-induced SICM in-vivo and in-vitro models. LPS was administrated at the particular Zeitgeber times (ZT), ZT4-ZT10-ZT16-ZT22 and ZT10-ZT22 in vivo and vitro experiments, respectively. ResultsIn vivo experiment, injection of LPS at ZT10 induced higher infiltration of inflammatory cells and content of intracellular Fe2+, and lower level of Glutathione peroxidase 4 (GPX4) and cardiac function than other ZTs (P < 0.05), which indicated that myocardial ferroptosis in septic rat presented a time of day-dependent manner. Bmal-1 protein and mRNA levels of injection of LPS at ZT10 were lower than those at other three ZTs (P < 0.05). The ratios of pAKT/AKT at ZT4 and ZT10 LPS injection were lower than those at ZT16 and ZT22 (P < 0.05). Nrf2 protein levels at ZT10 LPS injection were lower than those at other three ZTs (P < 0.05). These results indicated that the circadian of Bmal-1 and its downstream AKT/Nrf2 pathway in rat heart were inhibited under SICM condition. Consistent with in-vivo experiment, we found LPS could significantly reduce the expressions of Bmal-1 protein and mRNA in H9c2 cell. Up-regulation of Bmal-1 could reduce the cell death, oxidative stress, ferroptosis and activation of AKT/Nrf2 pathway at both ZT10 and ZT22 LPS administration. Conversely, its down-regulation presented opposite effects. AKT siRNA could weaken the effect of Bmal-1 pcDNA. ConclusionFerroptosis presented the time of day-dependent manners via Bmal-1/AKT/Nrf2 in vivo and vitro models of SICM.

EHD Instabilities in Two Layers of Insulating and Conducting Immiscible Liquids Subjected to Unipolar Charge Injection

In this paper, the instability of two layers of insulating and conducting immiscible liquids separated by a deformable interface and subjected to unipolar injection is examined. Taking into account the slight deformation of the interface between the two liquids, a system of equations and boundary conditions is derived at marginal state. Non zero numerical solutions for both layers exist only for eigenvalues of the instability parameter T, which depends on the following parameters: injection level C, Bond number Bo, a new non-dimensional parameter P proportional to interfacial tension and the ratio of the layers’ thickness and of liquids viscosity. The variations in the instability criterion Tc, corresponding to the smallest eigenvalue, are examined in detail as a function of the main characteristic parameters C, P and the Bond number. We find that for some values of P, two instability mechanisms convective and interfacial ones can take place. When the strength of interfacial tension or the liquid thickness ratio is very low, the critical number tends to a value corresponding to interfacial instability. The influence of injection-induced convection in the insulating layer and the effect of interfacial deformation on interfacial instability are also discussed.

Inhibition of Calcineurin with FK506 Reduces Tau Levels and Attenuates Synaptic Impairment Driven by Tau Oligomers in the Hippocampus of Male Mouse Models.

Alzheimer's disease (AD) is the most common age-associated neurodegenerative disorder, characterized by progressive cognitive decline, memory impairment, and structural brain changes, primarily involving Aβ plaques and neurofibrillary tangles of hyperphosphorylated tau protein. Recent research highlights the significance of smaller Aβ and Tau oligomeric aggregates (AβO and TauO, respectively) in synaptic dysfunction and disease progression. Calcineurin (CaN), a key calcium/calmodulin-dependent player in regulating synaptic function in the central nervous system (CNS) is implicated in mediating detrimental effects of AβO on synapses and memory function in AD. This study aims to investigate the specific impact of CaN on both exogenous and endogenous TauO through the acute and chronic inhibition of CaN. We previously demonstrated the protective effect against AD of the immunosuppressant CaN inhibitor, FK506, but its influence on TauO remains unclear. In this study, we explored the short-term effects of acute CaN inhibition on TauO phosphorylation and TauO-induced memory deficits and synaptic dysfunction. Mice received FK506 post-TauO intracerebroventricular injection and TauO levels and phosphorylation were assessed, examining their impact on CaN and GSK-3β. The study investigated FK506 preventive/reversal effects on TauO-induced clustering of CaN and GSK-3β. Memory and synaptic function in TauO-injected mice were evaluated with/without FK506. Chronic FK506 treatment in 3xTgAD mice explored its influence on CaN, Aβ, and Tau levels. This study underscores the significant influence of CaN inhibition on TauO and associated AD pathology, suggesting therapeutic potential in targeting CaN for addressing various aspects of AD onset and progression. These findings provide valuable insights for potential interventions in AD, emphasizing the need for further exploration of CaN-targeted strategies.

Investigation of BPD Faulting under Extreme Carrier Injection in Room vs High Temperature Implanted 3.3kV SiC MOSFETs

Implantation process for high Al dose p+ contact layers in SiC MOSFETs can generate new basal plane dislocations (BPDs). Such BPD faulting under high carrier injection was investigated in SiC MOSFET layers designed for 3.3kV operation with either room temperature (RT) or high temperature (HT) implantations performed for their high dose p+ contact layer. For excess carrier injection levels of ~1x1018 cm-3 implant induced BPDs faulted from the termination regions of the MOSFETs in the case of RT samples, while the HT samples show no BPD faulting because there were no implant-induced BPDs. However, in the active region of the device no BPDs faulted for both the RT as well as HT samples even at a higher carrier injection of ~1x1019 cm-3. Technology computer-aided design (TCAD) simulations show that the lower doped p-well region below the p+ contact in the active area of the device prevents the minority electron density in the p+ contact layer to below 10x the hole density, which limits BPD faulting even when they are present in that layer as in the case of RT implanted samples.

Short-term voltage stability analysis in power systems: A voltage solvability indicator

This paper presents an analytical study for short-term voltage stability based on a novel indicator. First, it is shown that the reduced Jacobian matrix of network equations can be transformed to obtain an approximately symmetric matrix which is usually positive definite when the system under study is stable. The minimum eigenvalue of the matrix is suggested as a short-term Voltage Solvability Indicator (VSI). Then, properties of the reduced conductive matrix and susceptance matrix which have significant impacts on VSI are examined. The focus of the study is power systems with multiple constant power injections, while VSI can also be applied to analyze the impact of generic power system models. It is shown that as the penetration level of constant power injections increases, VSI decreases and the system becomes more vulnerable to voltage collapse. Finally, the relationship between the eigenvalues of the reduced Jacobian matrix and the structure-preserving Jacobian matrix is established. As a result, the suggested VSI can be efficiently computed by exploring the sparsity of structure-preserving Jacobian matrix of network equations. Case studies of several test systems including a simplified 575-machine 8117-bus East China power system are reported, demonstrating the effectiveness and practicability of the proposed method.

Synergistic effect of independent risk factors for post-endoscopic retrograde cholangiopancreatography pancreatitis: a multicenter retrospective study in Japan.

This study aimed to examine the synergistic effect of independent risk factors on post-endoscopic retrograde cholangiopancreatography (ERCP) pancreatitis (PEP). This multicenter retrospective study included 1,273 patients with native papillae who underwent ERCP for bile duct stones in Japan. Independent PEP risk factors were identified using univariate and multivariate analyses. Significant risk factors for PEP in the multivariate analysis were included in the final analysis to examine the synergistic effect of independent risk factors for PEP. PEP occurred in 45 of 1,273 patients (3.5%). Three factors including difficult cannulation ≥10 minutes, pancreatic injection, and normal serum bilirubin level were included in the final analysis. The incidences of PEP in patients with zero, one, two, and three factors were 0.5% (2/388), 1.9% (9/465), 6.0% (17/285), and 12.6% (17/135), respectively. With increasing risk factors for PEP, the incidence of PEP significantly increased (1 factor vs. 2 factors, p=0.006; 2 factors vs. 3 factors, p=0.033). As the number of risk factors for PEP increases, the risk of PEP may not be additive; however, it may multiply. Thus, aggressive prophylaxis for PEP is strongly recommended in patients with multiple risk factors.