Resistance Peak Research Articles

Comparison of Ocular Blood Flow in Glaucomatous Eyes and Nonglaucomatous Eyes at a Tertiary Hospital in South India: A Prospective Case-control Study.

To compare the ocular blood flow in glaucomatous eyes and normal healthy eyes. This study compares open-angle glaucoma patients to healthy adults by measuring various parameters in the ophthalmic artery (OA), central retinal artery (CRA), and short posterior ciliary artery (SPCA). A total of 50 glaucomatous eyes and 50 normal eyes were included in a prospective case-control study over 1 year. The color Doppler imaging (CDI) was conducted using a noninvasive linear multifrequency probe with a frequency range of 5-9 MHz. OA, CRA, and SPCA were measured for peak systolic velocity (PSV), end-diastolic volume (EDV), pulsatility index (PI), and resistivity index (RI). When compared with controls, PSV was decreased in all three vessels, with the results being remarkable only in CRA. The EDV also showed a remarkable decrease in all three vessels. Additionally, all three vessels showed significant increases in PI and RI except OA, p-value < 0.05. Blood velocity is decreased, and resistive indices are increased in glaucomatous eyes compared with normal eyes. Variations in ocular blood flow could be a cause or consequence of glaucomatous optic neuropathy and are an important predictor of disease progression. Murugesan MAD, Venkat P, Basetti B. Comparison of Ocular Blood Flow in Glaucomatous Eyes and Nonglaucomatous Eyes at a Tertiary Hospital in South India: A Prospective Case-control Study. J Curr Glaucoma Pract 2024;18(2):45-50.

Interplay between superconducting fluctuations and weak localization in disordered TiN thin films.

The interplay between superconducting fluctuations (SFs) and weak localization (WL) has been probed by temperature dependent resistance [R(T)] and magnetoresistance (MR) measurements in two-dimensional disordered superconducting TiN thin films. Within a narrow range of temperature above transition temperature (Tc), the coexistence of SF-mediated positive MR and WL-led negative MR in different ranges of magnetic fields and a crossover from positive MR to negative MR with an increase in temperature are reported herein. The crossover temperature coincides with a characteristic temperature (Tmax) at which a resistance peak appears in the zero-field R(T). The resistance peak and associated magnetoresistance anomalies are addressed using quantum corrections to conductivity (QCC) theory. We show that WL can be accounted for the observed negative MR. By introducing individual coefficients to both SFs and WL contributions, the dominance of one over the other is monitored with respect to temperature. It is observed that just above Tc, SFs dominate; with an increase in temperature, the contributions from both become comparable; and finally, at Tmax, WL takes over completely. The presented approach may be adopted to compare various quantum contributions in two-dimensional superconductors, particularly in the regime where both SFs and WL are pronounced.

Granularity mediated multiple reentrances with negative magnetoresistance in disordered TiN thin films

Granular superconductors are the common examples of experimentally accessible model systems which can be used to explore various fascinating quantum phenomena that are fundamentally important and technologically relevant. One such phenomenon is the occurrence of reentrant resistive states in granular superconductors. Here, we report the observation of multiple reentrant resistive states for a disordered TiN thin film in its temperature and magnetic field dependent resistance measurements, R(T) and R(B), respectively. At each of the peak-temperatures corresponding to the zero-field R(T), a resistance peak appears in the R(B) around zero field which leads to a negative magnetoresistance (MR) region in its surrounding. These low-field negative MR regions appear for both perpendicular and parallel field directions with relatively higher amplitude and larger width for the parallel field. By adopting a granularity-based model, we show that the superconducting fluctuations in granular superconductors may lead to the observed reentrant states and the corresponding negative MR. Here, we propose that the reduction in the density of states in the fermionic channel due to the formation of Cooper pairs leads to the reentrant resistive state and the competition between the conduction processes in the single particle and Cooper channels result into the multiple resistive reentrances.

Advanced process characterization and machine learning-based correlations between interdiffusion layer and expulsion in spot welding

Over the past decades, substantial endeavors have been dedicated to unraveling the intricacies inherent to Resistance Spot Welding (RSW). However, a comprehensive and consensual understanding of the RSW process physics is still lacking, including the exact number of physical phases behind the RSW process. For example, a widely accepted model indicates that metal only starts melting after the peak of dynamic resistance, while the latest research on welding uncoated materials challenges this by suggesting that melting begins around the resistance peak. Furthermore, most of existing physical models only consider welding materials without coatings in a controlled lab setting, whereas coated sheet metal is the norm in real production. Addressing these challenges, this paper introduces an enhanced model for RSW that considers the melting phase of the coating's InterDiffusion Layer (IDL) in Press Hardening Steels (PHS). This phase is believed to influence both welding quality and the occurrence of expulsions. Additionally, the timing at which each phase starts has been determined by analyzing real-time, multi-variable sensing data from various welding scenarios, and a signal processing technique has been devised to automatically identify when these phases begin. Leveraging this refined process understanding and characterization, meaningful explainable features are extracted, and a data-driven multilayer perceptron model is constructed for 1) predicting IDL thickness and 2) detecting expulsions upon predicted IDL thickness. The experimental results validate that the proposed IDL-inclusive model advances existing physical models for RSW and the IDL prediction improves the RSW defect detection and process monitoring.

Underwater electrical explosion of metallic wire and tube: A comparison study

With an initial energy storage of approximately 53.5 kJ, experiments on underwater electrical explosions of metallic wire and thin-wall tube were conducted. Two sets of controlled experiments were designed, and the wire and tube for each set were of the same length, cross-sectional area, and material. Load voltage, circuit current, and shock wave pressure were measured and analyzed, and electric power, energy deposition, and energy deposition rate were also calculated and investigated. Experimental results indicated that the underwater electrical tube explosion (UETE) always has higher and earlier local resistance peak, voltage peak, and electric power peak, as well as faster phase transition and ionization process than the underwater electrical wire explosion (UEWE). In addition, the energy deposition rate from the beginning of discharge or the decrease in current to the voltage peak is significantly increased when replacing a wire with a tube. For the shock-wave characteristics, the peak pressure, energy density, and impulse of the shock wave generated by UETE are greater than that generated by UEWE. The peak pressure at ∼33 cm increased from 21.1 to 24.5 MPa in the first set and from 18.1 to 21.7 MPa in the second when a tube was used instead of a wire. These experimental results help us understand the physical process of UETE and provide an alternative methodology for load design in industrial applications.

Large anomalous Hall effect and negative magnetoresistance in half-topological semimetals

Proposed mechanisms for large intrinsic anomalous Hall effect (AHE) in magnetic topological semimetals include diverging Berry curvatures of Weyl nodes, anticrossing nodal rings or points of non-trivial bands. Here we demonstrate that a half-topological semimetal (HTS) state near a topological critical point can provide an alternative mechanism for a large AHE via systematic studies on an antiferromagnetic (AFM) half-Heusler compound TbPdBi. We not only observe a large AHE with tanΘH ≈ 2 in its field-driven ferromagnetic (FM) phase, but also find a distinct Hall resistivity peak in its canted AFM phase. Moreover, we observe a large negative magnetoresistance with a value of ~98%. Our in-depth theoretical modelling indicates that these exotic transport properties originate from the HTS state which exhibits Berry curvature cancellation between the trivial spin-up and nontrivial spin-down bands. Our study offers alternative strategies for improved materials design for spintronics and other applications.

Ventilator hyperinflation associated with flow bias optimization in the bronchial hygiene of mechanically ventilated patients

Background: Ventilation configurations are of great clinical importance for adequate outcomes in mechanically ventilated patients, and they may even be used as specific physical therapy techniques.Objectives: To compare the effectiveness of lung hyperinflation through mechanical ventilation (HMV) with HMV plus flow bias optimization regarding respiratory mechanics, hemodynamics, and volume of secretion.Methods: Patients mechanically ventilated > 24 h were included in this randomized crossover clinical trial. The following techniques were applied: HMV alone (control group) and HMV plus flow bias optimization (intervention group).Results: The 20 included patients underwent both techniques, totaling 40 collections. A total of 52 % were women, the mean age was 60.8 (SD, 15.7) years, and the mean mechanical ventilation time was 4.3 (SD, 3.0) days. The main cause of mechanical ventilation was sepsis (44 %). Expiratory flow bias in optimized HMV was higher. than conventional HMV (p < 0.001). The volume of tracheal secretions collected was higher during optimized than conventional HMV. (p = 0.012). Significant differences in peak flow occurred at the beginning of the technique and a there was a significant decrease in respiratory system resistance immediately and 30 min after applying the technique in the intervention group.Conclusions: The volume of tracheal secretions collected was higher during optimized HMV, and, HMV with flow bias optimization resulted in lower respiratory system resistance and flow peaks and produced expiratory flow bias.

Ferroelectric-driven disorder inducing transition of bosonic insulator–superconductor in TiN/Hf0.5Zr0.5O2 heterojunction

Unique quantum states induced by disorders can be characterized by quantum phase transitions in many-body systems. In this study, we experimentally observed a sharp resistance peak near the superconducting transition in superconductor/ferroelectric TiN/Hf0.5Zr0.5O2 heterostructures. The peak is attributed to the disorder introduced by ferroelectric fluctuations within the empirical model of metal–boson insulator–superconductor transitions. By modulating the quantum phase transitions in superconductivity and competing with the disorder through ferroelectric polarization, we provide a versatile platform for investigating the influence of ferroelectric materials on superconducting states.

The effects of 12 weeks of high-intensity interval training and moderate-intensity continuous training on FGF21, irisin, and myostatin in men with type 2 diabetes mellitus

This study investigated the influence of a 12-week high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) on irisin, fibroblast growth factor 21 (FGF21), and myostatin (MSTN) among men with type 2 diabetes mellitus (T2DM). Forty-five adult men with T2DM were randomly selected and assigned to receive and perform HIIT (4 × 4 min at 85–95% HRmax with three min of active rest at 50–60% HRmax in between) and MICT (walking/running continuously for 47 min at 60–70% HRmax) three sessions per week for 12 weeks, or to act as a non-exercise control (CON) group. The subjects’ blood samples were collected at baseline and 48 hours after the last intervention session. Our research revealed that both interventions resulted in similar decreases in FGF21 and MSTN when compared to the CON (p < .01). However, only the HIIT group showed a significant increase in irisin (p < .01) compared to the CON. Further, improvements in insulin resistance, body composition, and VO2 peak were noted in both intervention groups compared with those of the CON group (p < .01). It seems that while either aerobic exercise strategy could be seen as a therapy for men with T2DM, HIIT had a more advantageous effect on the irisin response.

Design of a perovskite oxide cathode for a protonic ceramic fuel cell

High catalytic activity, low-cost and stable cathode in a temperature range 550–700 °C is essential for the development of protonic ceramic fuel cells (PCFCs). Doping nickel into perovskite La0.5Sr0.5MnO3-δ(LSM) is designed as a cobalt-free cathode based on theoretical calculations and experiments. La0.5Sr0.5Mn0.9Ni0.1O3-δ (LSMNi) as cathode shows higher proton conductivity and ORR activity than the undoped LSM. The PCFCs with LSMNi exhibit low polarization resistance and high peak power density 1.1 W cm−2 at 700 °C. The density functional theory simulations indicate that doping with nickel decreases the oxygen vacancy formation energy and promotes the formation of hydroxide defects. The decrease in proton transfer energy barriers and hydration energy improves the proton conductivity. The improved performance is attributed to fast proton transfer and rapid kinetics of oxygen reduction on the surface of LSMNi. This work provides a novel approach to design cobalt-free cathode for a protonic ceramic fuel cell.

The resistance of a trans-critically accelerating ship in shallow water

ABSTRACT The acceleration resistance of a vessel advancing in shallow water is investigated. Four acceleration intensities and two water depths are modelled using the CFD and potential flow methods. The results show a pronounced peak in resistance exists near the critical depth Froude number, but its location and magnitude are sensitive to the acceleration intensity and water depth. Excellent agreement between the results obtained from the CFD and potential flow methods is found in the low and high depth Froude number ranges regardless of water depth or acceleration, indicating that linear and unsteady methods can provide robust results at a low cost in those ranges. The magnitude of the resistance peak and its position are sensitive to nonlinear effects, evidenced by slight disagreements between the two adopted methodologies. The variation in the results produced by the two solvers is found to be sensitive to the parameters investigated.

Evaluation of changes in thyroid volume and selected parameters on Doppler ultrasound examination in radically irradiated patients with primary cancers of the head and neck region – preliminary report

Introduction: Implementation of even the most advanced radiotherapy techniques is still associated with a risk of damaging healthy tissues and organs by ionizing radiation. Structural and functional abnormalities of the thyroid gland have been reported in patients after radiotherapy administered for head and neck cancers (HNC). Aim: Ultrasound evaluation of changes in thyroid volume, characteristics of blood flow in the right inferior thyroid artery (ITA) and vascular invasion (VI) of the thyroid gland in patients radically irradiated due to primary HNC. Material and methods: The study group consisted of 20 patients who underwent ultrasound examinations at three time points: prior to commencing radiotherapy (I), in the first week after completion of radiotherapy (II) and after another 3–6 months (III). Results: The mean radiation dose absorbed by the thyroid gland was 54.95 6.95 Gy. The mean thyroid volume measured at the first time point was 17.14 (13.74–23.43) cm3 and this result turned out to be higher as compared to measurements obtained in the second and third examinations: 15.92 (12.51–20.35) cm3 with p&lt;0.001; 15.01 (11.16–18.92) cm3 with p&lt;0.001, respectively. Thyroid volume from the second examination was also greater than in the third examination (p&lt;0.001). Evaluation conducted at time point II showed an increase in the following vascular flow parameters: peak systolic velocity (PSV), pulsatility index (PI) and resistivity index (RI) measured in the ITA, as well as an increase in thyroid VI in comparison to results from time point I. Furthermore, a decrease of the above-mentioned values was observed at time point III as compared to time point II. However, the ultrasound vascular characteristics measured in the ITA and VI of the thyroid gland were still higher on examination III when compared to the initial values. Conclusions: We have observed that radiotherapy leads to a decrease in thyroid volume, which is found to be progressing for at least 3–6 months after treatment completion. Post-radiotherapy changes in vascular parameters of the ITA and VI value measured on Doppler ultrasound partially resolve within 3–6 months after the end of radiation treatment.

Shallow waters resistance of an accelerating ship

This paper investigates the acceleration resistance of a vessel in shallow waters using potential flow and CFD methods. Results indicated a pronounced resistance peak near the critical depth Froude number. The peak’s location and magnitude were sensitive to acceleration intensity and water depth. Excellent agreement between potential flow and CFD methods was found in low and high depth Froude number ranges, suggesting their effectiveness and cost-efficiency. However, non-linear effects affected the resistance peak’s magnitude and position, leading to slight disagreements between the methods. The solvers’ variation was observed to be sensitive to the investigated parameters.

Quantum magneto-transport properties of monolayers MoSi2N4, WSi2N4, and MoSi2As4

We study the transport properties of monolayers MoSi2N4, WSi2N4, and MoSi2As4 in a perpendicular magnetic field. The Landau level (LL) band structures including spin and exchange field effects are derived and discussed using a low-energy effective model. We show that the LLs band structures of these materials are similar to those of phosphorene and transition-metal dichalcogenides rather than graphene or silicene. The combination of strong spin–orbit coupling and exchange fields reduces the degradation of the LLs, leading to new plateaus in the Hall conductivity and Hall resistivity and new peaks in the longitudinal conductivity and longitudinal resistivity. The effect of the exchange field, carrier density, and LLs band structure on the conductivities and resistivities have been investigated. At high temperatures, the steps in Hall conductivity and resistivity plateaus disappear and reduce to their corresponding classical forms.

Exchange Coupling Effects on the Magnetotransport Properties of Ni-Nanoparticle-Decorated Graphene

We characterize the effect of ferromagnetic nickel nanoparticles (size ∼6 nm) on the magnetotransport properties of chemical-vapor-deposited (CVD) graphene. The nanoparticles were formed by thermal annealing of a thin Ni film evaporated on top of a graphene ribbon. The magnetoresistance was measured while sweeping the magnetic field at different temperatures, and compared against measurements performed on pristine graphene. Our results show that, in the presence of Ni nanoparticles, the usually observed zero-field peak of resistivity produced by weak localization is widely suppressed (by a factor of ∼3), most likely due to the reduction of the dephasing time as a consequence of the increase in magnetic scattering. On the other hand, the high-field magnetoresistance is amplified by the contribution of a large effective interaction field. The results are discussed in terms of a local exchange coupling, J∼6 meV, between the graphene π electrons and the 3d magnetic moment of nickel. Interestingly, this magnetic coupling does not affect the intrinsic transport parameters of graphene, such as the mobility and transport scattering rate, which remain the same with and without Ni nanoparticles, indicating that the changes in the magnetotransport properties have a purely magnetic origin.

Role of Multiparametric Ultrasound in Evaluating Hepatic Acute Graft-versus-Host Disease: An Animal Study.

Hepatic acute graft-versus-host disease (aGVHD) is a serious complication of allogeneic hematopoietic stem cell transplantation (allo-HSCT) and is one of the leading causes of early non-recurrent death. The current diagnosis is based mainly based on clinical diagnosis, and there is a lack of non-invasive quantitative diagnosis methods. We propose a multiparametric ultrasound (MPUS) imaging method and explore its effectiveness in evaluating hepatic aGVHD. In this study, 48 female Wistar rats were used as receptors and 12 male Fischer 344 rats were used as donors for allo-HSCT to establish aGVHD models. After transplantation, 8 rats were randomly selected for ultrasonic examination weekly, including color Doppler ultrasound, contrast-enhanced ultrasound (CEUS) and shear wave dispersion (SWD) imaging. The values of nine ultrasonic parameters were obtained. Hepatic aGVHD was subsequently diagnosed by histopathological analysis. A classification model for predicting hepatic aGVHD was established using principal component analysis and support vector machines. According to the pathological results, the transplanted rats were categorized into the hepatic aGVHD and non-GVHD (nGVHD) groups. All parameters obtained by MPUS differed statistically between the two groups. The first three contributing percentages of principal component analysis results were resistivity index, peak intensity and shear wave dispersion slope, respectively. The accuracy of classifying aGVHD and nGVHD using support vector machines reached 100%. The accuracy of the multiparameter classifier was significantly higher than that of the single parameter. The MPUS imaging method has proven to be useful in detecting hepatic aGVHD.

Gate-Tunable Multiband Transport in ZrTe5 Thin Devices.

Interest in ZrTe5 has been reinvigorated in recent years owing to its potential for hosting versatile topological electronic states and intriguing experimental discoveries. However, the mechanism of many of its unusual transport behaviors remains controversial: for example, the characteristic peak in the temperature-dependent resistivity and the anomalous Hall effect. Here, through employing a clean dry-transfer fabrication method in an inert environment, we successfully obtain high-quality ZrTe5 thin devices that exhibit clear dual-gate tunability and ambipolar field effects. Such devices allow us to systematically study the resistance peak as well as the Hall effect at various doping densities and temperatures, revealing the contribution from electron-hole asymmetry and multiple-carrier transport. By comparing with theoretical calculations, we suggest a simplified semiclassical two-band model to explain the experimental observations. Our work helps to resolve the longstanding puzzles on ZrTe5 and could potentially pave the way for realizing novel topological states in the two-dimensional limit.

Prevalence and Antibiotic Resistance Pattern of Streptococcus, Staphylococcus, Neisseria meningitidis and Enterobacteriaceae in Two Reference Hospitals of Yaoundé: An Overview before and during COVID-19 Pandemic Era.

The COVID-19 pandemic led to tremendously use of antimicrobial due to the lack of proper treatment strategies, raising concerns about emergence of antimicrobial resistance (AMR). This study aimed at determining the prevalence and antibiotic resistance pattern of selected bacteria isolates in 02 referral health facilities in Yaoundé before and during the COVID-19 pandemic era. We conducted a retrospective study over a period of 03 years (from 1 January 2019 to 31 December 2021) in the bacteriology units of the Central and General Hospitals of Yaoundé, Cameroon. Data on bacteria genera (Streptococcus, Staphylococcus, Neisseria meningitidis and Enterobacteriaceae) as well as their corresponding specifics antibiotics: Cefixime, azythromycin and erythromycin were obtained from laboratory records. The global resistance rate of bacteria as well as their correlation with antibiotics according to COVID-19 pandemic era was determined and compared. For p < 0.05, the difference was statistically significant. In all, 426 bacterial strains were included. It appeared that the highest number of bacteria isolates and lowest rate of bacterial resistance were recorded during the pre-COVID-19 period in 2019 (160 isolates vs. 58.8% resistance rate). Conversely, lower bacteria strains but greater resistance burden were recorded during the pandemic era (2020 and 2021) with the lowest bacteria amount and peak of bacteria resistance registered in 2020, the year of COVID-19 onset (120 isolates vs. 70% resistance in 2020 and 146 isolates vs. 58.9% resistance in 2021). In contrast to almost all others groups of bacteria where the resistance burden was quite constant or decreasing over years, the Enterobacteriaceae exhibited greater resistance rate during the pandemic period [60% (48/80) in 2019 to 86.9% (60/69) in 2020 and 64.5% (61/95) in 2021)]. Concerning antibiotics, unlike erythromycin, azythromycin related resitance increased during the pandemic period and the resistance to Cefixim tends to decrease the year of the pandemic onset (2020) and re-increase one year therafter. A significant association was found between resistant Enterobacteriaceae strains and cefixime (R = 0.7; p = 0.0001) and also, between resistant Staphylococcus strains and erythromycin (R = 0.8; p = 0.0001). These retrospective data showed a herogeneous MDR bacteria rate and antibiotic resistance pattern over time before and during the COVID-19 pandemic era suggesting that antimicrobial resistance needs to be more closely monitored.

Early effects of inactivated (CoronaVac) SARS-CoV-2 vaccine on retrobulbar vascular blood flow and retinal vascular density

AimsWe aimed to investigate the early effects of inactivated SARS-CoV-2 vaccine on retrobulbar vascular blood flow and retinal vascular density in healthy subjects. MethodsThirty-four eyes of 34 healthy volunteers who received the CoronaVac (Sinovac Life Sciences, China) were included in this prospective study. Resistive index (RI), pulsatility index (PI) and peak systolic velocity (PSV) of the ophthalmic artery (OA), central retinal artery (CRA), and the temporal and nasal posterior ciliary arteries (PCA) were evaluated with color Doppler ultrasonography (CDUS) before vaccination, at the 2nd and 4th weeks after vaccination. Superficial capillary plexus (SCP) and deep capillary plexus (DCP) vessel density (VD), foveal avascular zone (FAZ), and choriocapillaris blood flow (CCF) measurements were made using optical coherence tomography angiography (OCTA). ResultsWhen compared to the pre-vaccination values, there was no significant change in OA-PSV, temporal-nasal PCA-PSV, CRA-EDV, temporal-nasal PCA-EDV at 2nd and 4th weeks after vaccination. However statistically significant reductions were found in the OA-RI, OA-PI, CRA-RI, CRA-PI, temporal-nasal PCA-RI, temporal-nasal PCA-PI values, CRA-PSV at post-vaccination 2nd week (p<0.05 for all). While there was sustained reduction in OA-RI, OA-PI, CRA-PSV, and nasal PCA-RI values at 4th week after vaccination, the change in CRA-RI, CRA-PI, temporal PCA-RI, temporal-nasal PCA-PI values were not significant compared to pre-vaccination values. There was no statistically significant difference in the SCP-VD, DCP-VD, FAZ and CCF measurements. ConclusionsOur findings demonstrating that CoronaVac vaccine did not affect retinal vascular density in the early period, but it caused alterations in the retrobulbar blood flow.

Epitaxial growth of trilayer graphene moiré superlattice

The graphene-based moiré superlattice has been demonstrated as an exciting system for investigating strong correlation phenomenon. However, the fabrication of such moiré superlattice mainly relies on transfer technology. Here, we report the epitaxial growth of trilayer graphene (TLG) moiré superlattice on hexagonal boron nitride (hBN) by a remote plasma-enhanced chemical vapor deposition method. The as-grown TLG/hBN shows a uniform moiré pattern with a period of ∼ 15 nm by atomic force microscopy (AFM) imaging, which agrees with the lattice mismatch between graphene and hBN. By fabricating the device with both top and bottom gates, we observed a gate-tunable bandgap at charge neutral point (CNP) and displacement field tunable satellite resistance peaks at half and full fillings. The resistance peak at half-filling indicates a strong electron–electron correlation in our grown TLG/hBN superlattice. In addition, we observed quantum Hall states at Landau level filling factors ν = 6, 10, 14, …, indicating that our grown trilayer graphene has the ABC stacking order. Our work suggests that epitaxy provides an easy way to fabricate stable and reproducible two-dimensional strongly correlated electronic materials.