Amplitude Of Fluctuations Research Articles

Altered spontaneous brain activity in children with deprivation amblyopia: a resting-state functional magnetic resonance imaging study

BackgroundTo investigate the alterations in spontaneous brain activity and the similarities and differences between monocular deprivation amblyopia and binocular deprivation amblyopia.MethodsTwenty children with binocular deprivation amblyopia, 26 children with monocular deprivation amblyopia and 20 healthy controls underwent resting-state functional magnetic resonance imaging. The evaluation of altered spontaneous brain activity was conducted using fractional amplitude of low-frequency fluctuations (fALFF). One-way analysis of variance was employed to analyze fALFF values among the three groups. Additionally, the relationship between fALFF values and best corrected visual acuity (BCVA) was analyzed via correlation analysis.ResultsCompared to healthy controls, children with binocular deprivation amblyopia presented increased fALFF values in the left medial superior frontal gyrus, left middle frontal gyrus, left anterior cingulate cortex, left postcentral gyrus and bilateral precentral gyrus, and decreased fALFF values in the right fusiform gyrus. Compared to healthy controls, children with monocular deprivation amblyopia presented increased fALFF values in the right lingual gyrus, right superior frontal gyrus, right middle frontal gyrus, left superior temporal gyrus, triangular part of the left inferior frontal gyrus and bilateral middle temporal gyrus, and decreased fALFF values in the right precuneus. Compared with monocular deprivation amblyopia, fALFF values of binocular deprivation amblyopia were decreased in the triangular part of the left inferior frontal gyrus, right lingual gyrus and right cuneus, and increased in the left precentral gyrus and left postcentral gyrus. No significant correlations were found between the fALFF values of identified regions and the BCVA of amblyopic eyes for either type of amblyopia.ConclusionsChildren with deprivation amblyopia presented alterations in spontaneous activity in multiple brain regions, and these alterations differed between monocular amblyopia and binocular amblyopia. These abnormal spontaneous activities may reflect dysfunctions and compensation related to amblyopia.

АЛГОРИТМ ИССЛЕДОВАНИЯ ДИНАМИЧЕСКИХ ПРОЦЕССОВ В ТЕХНОЛОГИЧЕСКОМ ОБОРУДОВАНИИ НА ГАЗОСТАТИЧЕСКИХ ПОДШИПНИКАХ

Study purpose is to develop a generalized algorithm for studying dynamic processes during the operation of spindles and other equipment with gasostatic bearings using machine-building CAD tools. The following tasks are solved: analyzing dynamic processes during the operation of equipment, selecting software for studying stiffness and bearing capacity, and then studying vibrations of an unbalanced rotor with gasostatic bearings, performing computer calculating experiments (CCE) in accordance with the developed methodology, presenting the results graphically and analyzing them. Research method include computer calculating experiments in CAE-programs of machine-building CAD. The novelty of the work is in the developed generalized algorithm for studying dynamic processes by conducting computer calculating experiments based on a three-dimensional computational model; in the obtained functional dependencies for the pressure of a gas lubricant and the amplitudes of temperature fluctuations on various parameters and conditions. There are study results of the pressure distribution of air lubrication in conical gasostatic bearings of a high-speed spindle under varying external loads, as well as the amplitude of transverse vibrations of an unbalanced rotor during accelerating and passing three critical rotational speeds at which the phenomenon of resonance occurs. Conclusions: the developed algorithm of computer calculating experiments based on a three-dimensional computational model allows studying accurately the dynamic processes that occur during the operation of spindles using machine-building CAD systems; the presented algorithm is universal, therefore, it can be used to study physical processes during the operation of equipment for various purposes; the use of this algorithm allows obtaining the results necessary to make new technical facilities without conducting numerous field tests, which significantly reduces the time and cost of research and development work.

Differentiation between multiple sclerosis and neuromyelitis optic spectrum disorders with multilevel fMRI features: A machine learning analysis

The conventional statistical approach for analyzing resting state functional MRI (rs-fMRI) data struggles to accurately distinguish between patients with multiple sclerosis (MS) and those with neuromyelitis optic spectrum disorders (NMOSD), highlighting the need for improved diagnostic efficacy. In this study, multilevel functional metrics including resting state functional connectivity, amplitude of low frequency fluctuation (ALFF), and regional homogeneity (ReHo) were calculated and extracted from 116 regions of interest in the anatomical automatic labeling atlas. Subsequently, classifiers were developed using different combinations of these selected features to distinguish between MS and NMOSD. Compared to models based on individual MRI features, support vector machine (SVM) and logistic regression (LR) models that integrated multilevel functional features such as RSFC, ALFF, and ReHo demonstrated the highest levels of performance on the testing cohorts (SVM, AUC = 0.857; LR, AUC = 0.929). Adding structural features of gray matter volume (GMV) data did not notably improve the classification performance of the machine learning models using multilevel rs-fMRI features. Notably, similar trends were observed across different brain templates, with models based on RSFC, ALFF, and ReHo yielding optimal performance. These findings suggest that utilizing multilevel fMRI features can effectively differentiate between MS and NMOSD patients.

Altered amplitude of low-frequency fluctuation and functional connectivity in patients with acute unilateral vestibulopathy: a resting-state fMRI study

ObjectiveTo investigate changes of brain functional activity in patients with acute unilateral vestibulopathy (AUVP) using functional magnetic resonance imaging (fMRI).MethodsWe studied 32 AUVP patients and 30 healthy controls (HC) who received resting-state fMRI scanning. Methods of voxel-based amplitude of low-frequency fluctuation (ALFF) and seed-based functional connectivity (FC) were adopted to compare the difference in brain function between the two groups. In addition, we evaluated the associations between abnormal neuroimaging results and clinical data in AUVP patients.ResultsCompared with HC, patients with AUVP showed lower ALFF in brain regions of bilateral insular, right precentral gyrus, left inferior frontal gyrus and right middle frontal gyrus, as well as higher ALFF in left cerebellar anterior lobe. Using these abnormal brain areas as seeds, we observed decreased FC between left insular and left precuneus in AUVP patients. Furthermore, AUVP patients showed increased FC between left insular and left supplementary motor area. Results of correlation analysis indicated that ALFF value (z-value) in left insular was negatively correlated with the canal paresis value (p = 0.005, r = −0.483), and the FC (z-value) between left insular and left precuneus was negatively correlated with dizziness handicap inventory score (p = 0.012, r = −0.438) in patients with AUVP.ConclusionPatients with AUVP during acute period showed altered functional activity and connectivity in brain regions mainly involved in motor control and vestibular information processing. These changes in brain functional activity and connectivity were potentially attributed to decreased vestibular input resulting from unilateral peripheral vestibular impairment.

Transonic Turbulence and Density Fluctuations in the Near-Sun Solar Wind

Abstract We use in situ measurements from the first 19 encounters of Parker Solar Probe and the most recent five encounters of Solar Orbiter to study the evolution of the turbulent sonic Mach number M t (the ratio of the amplitude of velocity fluctuations to the sound speed) with radial distance and its relationship to density fluctuations. We focus on the near-Sun region with radial distances ranging from about 11 to 80 R ⊙. Our results show that (1) the turbulent sonic Mach number M t gradually moves toward larger values as it approaches the Sun, until at least 11 R ⊙, where M t is much larger than the previously observed value of 0.1 at and above 0.3 au; (2) transonic turbulence with M t ∼ 1 is observed in situ for the first time and is found mostly near the Alfvén critical surface; (3) Alfvén Mach number of the bulk flow M A shows a strong correlation with the plasma beta, indicating that most of the observed sub-Alfvénic intervals correspond to a low-beta plasma; (4) the scaling relation between density fluctuations and M t gradually changes from a linear scaling at larger radial distances to a quadratic scaling at smaller radial distances; and (5) transonic turbulence is more compressible than subsonic turbulence, with enhanced density fluctuations and slightly flatter spectra than subsonic turbulence. A systematic understanding of compressible turbulence near the Sun is necessary for future solar wind modeling efforts.

The Temporal and Spatial Evolution of Flow Heterogeneity During Water Flooding for an Artificial Core Plate Model

In the process of reservoir water flooding development, the characteristics of underground seepage field have changed, resulting in increasingly complex oil–water distribution. The original understanding of reservoir physical property parameters based on the initial stage of development is insufficient to guide reservoir development efforts in the extra-high water cut stage. To deeply investigate the spatio-temporal evolution of heterogeneity in the internal seepage field of layered reservoirs during water flooding development, water–oil displacement experimental simulations were conducted based on layered, normally graded models. By combining CT scanning technology and two-phase seepage theory, the variation patterns of heterogeneity in the seepage field of medium-to-high permeability, normally graded reservoirs were analyzed. The results indicate that the effectiveness of water flooding development is doubly constrained by differences in oil–water seepage capacities and the heterogeneity of the seepage field. During the development process, both the reservoir’s flow capacity and the heterogeneity of the seepage field are in a state of continuous change. Influenced by the extra resistance brought about by multiphase flow, the reservoir’s flow capacity drops to 41.6% of the absolute permeability in the extra-high water cut stage. Based on differences in the variation amplitudes of oil–water-phase permeabilities, changes in the heterogeneity of the internal seepage field of the reservoir can be broadly divided into periods of drastic change and relative stability. During the drastic change stage, the fluctuation amplitude of the water-phase permeability variation coefficient is 114.5 times that of the relative stable phase, while the fluctuation amplitude of the oil-phase permeability variation coefficient is 5.2 times that of the stable stage. This study reveals the dynamic changes in reservoir seepage characteristics during the water injection process, providing guidance for water injection development in layered reservoirs.

Distinction in the function and microstructure of white matter between major depressive disorder and generalized anxiety disorder.

Major depressive disorder (MDD) and generalized anxiety disorder (GAD) are two of the leading causes of impairment to human mental health. These two psychiatric disorders overlap in many symptoms and neurobiological features thus difficult to distinguish in some cases. We enrolled 102 participants, comprising 40 patients with MDD, 32 patients with GAD and 30 matched healthy controls (HCs), to undergo multimodal magnetic resonance imaging (MRI) scans. We identified 18 major white matter (WM) tracts with automated fiber quantification (AFQ) method, to evaluated microstructure with fractional anisotropy (FA) and function with amplitude of low-frequency fluctuation (ALFF). An analysis of variance (ANOVA) was employed to identify differences among groups. We further explored the correlations of FA and ALFF features with clinical symptoms. We identified the white matter microstructure and function of 89 participants. ANOVA and post-hoc analysis revealed that GAD group exhibited significantly higher FA of right anterior thalamic radiation (ATR) than in MDD and HC groups. Additionally, MDD group exhibited significantly decreased ALFF in forceps major (FMA), forceps minor (FMI), bilateral corticospinal tracts (CST) and left inferior fronto-occipital fasciculus (IFOF) compared to both GAD and HC group. ALFF of right CST was significantly negatively correlated to HAMA and a moderate effect size and marginal significance was found between FA of the right ATR and HAMA in GAD group. This study used cross-sectional data and sample size was small. Tracking microstructure and function of WM with AFQ method has the potential to distinguish different psychiatric diseases.

Study on the effectiveness and safety of artificial intermittent infusion hemodiafiltration in MHD patients with intradialytic hypotension.

To evaluate the effectiveness and safety of artificial intermittent infusion hemodiafiltration (I-HDF) in maintenance hemodialysis (MHD) patients with intradialytic hypotension (IDH), and to determine the optimal infusion dosage. This single-center, prospective, self-controlled study included 30 MHD patients with IDH, treated from December 2022 to July 2023. Patients underwent three sessions of I-HDF as treatment group and conventional hemodialysis as control group. Comparisons were made between the two groups regarding changes in blood pressure, hypotension symptoms, changes in body water content, and achievement of infusion doses. 1. The fluctuation amplitude of SBP in the treatment group was 18.96 ± 10.400, while in the control group it was 27.4 ± 11.796. There was a significant difference between the two groups (p < 0.05). 2. During 90 sessions of dialysis, 39 interventions were needed in the treatment group, compared to 59 interventions in the control group. The treatment group required fewer interventions, with a significant difference (p < 0.05). 3. No hypotension symptoms occurred in the treatment group, whereas six cases were observed in the control group, which was significantly higher (p < 0.05). 4. One patient in the 250 ml infusion group experienced chest tightness. Among the three infusion groups, the 250 ml group had the greatest fluctuation in DBP, with a significant difference (p < 0.05). 5. Among the three infusion volumes groups, there was a significant difference between the theoretical and actual infusion volumes in the 150 and 200 ml groups (p < 0.05). The artificial I-HDF mode effectively improves the occurrence of IDH. An infusion dose of 150-200 ml is deemed appropriate.

Aberrant regional neural fluctuations and functional connectivity in insomnia comorbid depression revealed by resting-state functional magnetic resonance imaging.

Insomnia is a common mental illness seriously affecting people lives, that might progress to major depression. However, the neural mechanism of patients with CID comorbid MDD remain unclear. Combining fractional amplitude of low-frequency fluctuation (fALFF) and seed-based functional connectivity (FC), this study investigated abnormality in local and long-range neural activity of patients with CID comorbid MDD. Here, we acquired resting-state blood oxygenation level dependent (BOLD) data from 57 patients with CID comorbid MDD and 57 healthy controls (HC). Compared with the controls, patients with CID comorbid MDD exhibited abnormal functional activity in posterior cerebral cortex related to the visual cortex, including the middle occipital gyrus (MOG), the cuneus and the lingual gyrus, specifically, lower fALFF values in the right MOG, left cuneus, and right postcentral gyrus, increased FC between the right MOG and the left cerebellum, and decreased FC between the right MOG and the right lingual gyrus. Neuropsychological correlation analysis revealed that the decreased fALFF in the right MOG was negatively correlated with all the neuropsychological scores of insomnia and depression, reflecting common relationships with symptoms of CID and MDD. While the decreased fALFF of the left cuneus was distinctly correlated with the scores of depression related scales. The decreased FC between the right MOG and the right lingual gyrus was distinctly correlated with the scores of insomnia related scales. This study not only widened neuroimaging evidence that associated with insomnia and depressive symptoms of patients with CID comorbid MDD, but also provided new potential targets for clinical treatment.

A preliminary study of fMRI and the relationship with depression and anxiety in Meniere's patients

PurposeTo examine alterations in Blood Oxygen Level-Dependent (BOLD) resting-state functional magnetic resonance imaging (rs-fMRI) signals, utilizing regional homogeneity (ReHo) and fractional amplitude of low-frequency fluctuation (fALFF) metrics, within activated brain regions. Additionally, this study aims to explore the relationship between these neural changes and clinical characteristics, as well as emotional states, in patients diagnosed with unilateral Meniere's disease (MD). MethodThe study included 24 patients diagnosed with left Meniere's disease (L-MD), 25 patients diagnosed with right Meniere's disease (R-MD), and 23 healthy control subjects. Resting-state blood‑oxygen-level-dependent functional magnetic resonance imaging (rest-BOLD-fMRI) data were preprocessed. A two-sample t-test was employed to compare the regional homogeneity (ReHo) and fractional amplitude of low-frequency fluctuation (fALFF) between the patient groups and the control group. Brain regions exhibiting significant differences were further analyzed for correlations with disease duration, vertigo severity, vertigo duration, hearing loss grade, and levels of anxiety and depression. ResultsIn patients with L-MD, fALFF values were significantly decreased in the right cerebellar hemisphere, middle occipital gyrus, among other regions. In patients with right-sided Ménière's disease (R-MD), fractional amplitude of low-frequency fluctuation (fALFF) values were elevated in the right middle inferior temporal gyrus and fusiform gyrus. Regional homogeneity (ReHo) values exhibited both increases and decreases in the temporal gyrus, parahippocampal gyrus, occipital gyrus, superior marginal gyrus, anterior central gyrus, and fusiform gyrus. In studies examining relational aspects, the parahippocampal gyrus, inferior temporal gyrus, middle occipital gyrus, superior middle occipital gyrus, superior marginal gyrus, and occipital gyrus demonstrated positive or negative correlations with clinical characteristics and emotional states. ConclusionsPatients with unilateral Meniere's disease (MD) exhibited both increased and decreased activation in various brain regions when compared to control subjects. A correlation was identified between these neural activation patterns and clinical characteristics, as well as emotional state, which holds significant implications for clinical treatment, prognosis, and rehabilitation strategies for MD patients.

Cerebellar activity and functional connectivity in subacute subcortical aphasia: Association with language recovery

Loss of language function (aphasia) is a common complication after stroke, and post-stroke recovery remains highly unpredictable due to the absence of reliable neurobiomarkers. Growing evidence points to involvement of the cerebellum in language processing; however, it is unclear if abnormal cerebellar activity and altered functional connectivity (FC) to language-related regions of cerebral cortex are underlying neural mechanisms for subcortical aphasia. In this longitudinal observational study, we used resting-state functional magnetic resonance imaging to examine potential abnormalities in spontaneous cerebellar activity and resting-state (rs)FC with language networks among post-stroke patients with subacute subcortical aphasia (n = 19) compared to healthy controls (HCs, n = 18).In addition, correlations between rsFC variables and language performance metrics were examined at post-stroke baseline and at follow-up. Compared to HCs, patients with subacute subcortical aphasia exhibited significantly reduced fractional amplitude of low frequency fluctuations, a measure of spontaneous activity, in the right cerebellar Crus II (rCrus II) region and reduced rsFC between rCrus II and left inferior frontal gyrus (LIFG), left angular gyrus (LAG), and left middle temporal gyrus (LMTG). Both rCrus II–LAG and rCrus II–LMTG rsFC values were positively correlated with Aphasia Battery of Chinese scores at baseline. Baseline rCrus II–LIFG rsFC was also positively correlated with spontaneous speech and naming scores at follow-up. A stronger baseline rCrus II–LIFG rsFC predicted superior recovery of language function post-stroke. We conclude that the right cerebellum may be an effective therapeutic target for subcortical aphasia.

Effects of the inlet gas volume fraction on the structural dynamic characteristics of gas‒liquid multiphase pumps

The inlet gas volume fraction (IGVF) has a significant impact on the performance of the gas‒liquid multiphase pump. To explore the effects of different IGVFs on the performance of gas–liquid multiphase pump, it is taken as the research object and the deformation and stress of the impeller and pump shaft under pure water and different IGVFs are obtained. The results show that the maximum deformation of the impeller occurs at the blade trailing edge. The maximum deformation of the impeller under 20%, 30% IGVF is reduced by 9.97% and 16.79% compared to 10% IGVF, respectively. The maximum deformation of the pump shaft is decreased by 0.15% and 0.26%, respectively. The stress of the impeller at the connection between the blade trailing edge and the hub is the largest. The maximum stress of the impeller at 20% and 30% IGVF is reduced by 310 Pa and 600 Pa compared to 10% IGVF, respectively. The radial force and the axis trace are uniformly under pure water and are chaotic under different IGVFs. Under pure water condition, the maximum deformation and stress fluctuation on the impeller and shaft is smaller than that under different IGVFs. The amplitude of maximum deformation fluctuation on the impeller and shaft becomes smaller with the increasing IGVF.

Subcomponent analysis of the directional sensitivity of dynamic cerebral autoregulation.

The origin of the directional sensitivity (DS) of dynamic cerebral autoregulation (dCA) is not known. In 140 healthy participants (67 male, 27.5 ± 6.1 yr old), middle cerebral artery velocity (MCAv, transcranial Doppler), arterial blood pressure (ABP, Finometer), and end-tidal CO2 (EtCO2, capnography) were recorded at rest. Critical closing pressure (CrCP) and resistance-area product (RAP) were obtained for each cardiac cycle, as well as mean MCAv and ABP (MAP). The integrated positive and negative derivatives of MAP (MAP+D and MAP-D, respectively) were used as simultaneous inputs to an autoregressive moving average model to generate two distinct MCAv step responses. Similar models allowed the estimation of corresponding MAP-CrCP and MAP-RAP responses to step changes in MAP+D and MAP-D. The strength of DS (ΔDS) was expressed by the difference in mean values of the step responses for the time interval 12-18 s. ΔDS was significant for MCAv (8.5 ± 46.9% vs. 26.7 ± 42.0%, P < 0.001) and RAP (-93.9 ± 48.1 vs. -74.5 ± 43.0%, P < 0.001), respectively, for MAP+D and MAP-D inputs, but not for CrCP (2.2 ± 48.1% vs. 0.72 ± 42.9%, P = 0.76). Compared with males, female participants had higher MCAv (63.9 ± 15.6 cm/s vs. 55.4 ± 12.9 cm/s, P < 0.001) but lower EtCO2 (P < 0.001) and RAP (P = 0.015). Sex did not influence ΔDS for any of the three-step responses. The presence of directional sensitivity in the RAP, but not in the CrCP transfer function, suggests that the origin could be solely myogenic, without metabolic involvement.NEW & NOTEWORTHY The directional sensitivity of the cerebral blood velocity response to a sudden change in mean arterial blood pressure (MAP) is mediated by the resistance-area product, without involvement from the cerebral critical closing pressure. The reduced amplitude of MAP spontaneous fluctuations at rest suggests that it is less likely that directional sensitivity has origins in the sympathetic control of cerebral blood vessels, thus generating the need to consider other alternatives.

Neural correlates of basketball proficiency: An MRI study across skill levels.

Basketball is an attractive sport required both cooperative and antagonistic motor skills. However, the neural mechanism of basketball proficiency remains unclear. This study aimed to examine the brain functional and structural substrates underlying varying levels of basketball capacity. Twenty advanced basketball athletes (AB), 20 intermediate basketball athletes (IB) and 20 age-matched non-athlete individuals without basketball experience (NI) participated in this study and underwent T1-weighted MRI and resting-state fMRI scanning. Voxel-mirrored homotopic connectivity (VMHC), amplitude of low frequency fluctuations (ALFF), and gray matter (GM) density were calculated and compared among the three groups. The VMHC in the bilateral postcentral gyrus, middle temporal gyrus, and superior temporal gyrus, as well as the GM density in the right precentral gyrus, exhibited a hierarchical structure of AB>IB>NI. Compared with NI group, AB and IB groups showed strengthened VMHC in supplementary motor area, paracentral lobule and superior frontal gyrus. Additionally, the ALFF of left middle occipital gyrus and right hippocampal and the GM density of left medial superior frontal gyrus exhibited differences in AB-IB and AB-NI comparisons. By conducting the cross-sectional comparison, this study firstly identifies the varying levels of basketball proficiency related brain resting-state functional and structural plasticity. Especially, the regions associated with motor perception and control, including bilateral postcentral gyrus, middle and superior temporal gyrus and right precentral gyrus, are involved in the key neural mechanisms of basketball proficiency. Future longitudinal studies are necessary to further validate these findings.

Study on the One-year Accuracy of Pulsar Time-scale

Abstract Determining accurate pulsar timing model parameters is essential for establishing TT(PT), a realization of Terrestrial Time(TT) based on a pulsar time-scale(PT). This study discusses the impact of different data spans on the accuracy of pulsar timing model parameters when determining pulsar timing model parameters. Using observations of PSR J0437-4715, J1909-3744, J1713+0747, and J1744-1134 from the second data release of the International Pulsar Timing Array (IPTA II, Version A), we compare the accuracy of the timing model parameters determined by these observations with different data spans. The results show for PSR J0437-4715, J1713+0747, and J1909-3744, the amplitude fluctuations of rotational frequency remain within $10^{-15}$, $10^{-14}$, and $10^{-14}$ Hz, respectively, when the data spans for determining pulsar timing model parameters exceed 13, 14, and 6 years. Additionally, the one-year accuracy of TT(PT) is crucial for its application in timekeeping. By comparing the frequency deviations of TT(PT) relative to TT(BIPM) under both ideal ($k_{r}$) and actual ($k_{p}$) conditions across different data spans, we find that when the data span reaches the duration above, the accuracy of TT(PT) surpasses that of TT(TAI) under ideal conditions, slightly inferior under actual conditions. This suggests with improved observational technologies, the accuracy of TT(PT) can be further enhanced.

Turbulence scale and strength analysis in the roughness and inertial sublayers over urban areas: A wind tunnel study

The dissimilarity of dynamics and turbulence structures between the roughness and inertial sublayers (RSL, ISL) over roughness elements show that ISL turbulence is much more homogeneous. Conventional logarithmic law of the wall is merely applicable for the RSL mean-wind-speed profiles. To characterize the turbulence scales and elucidate the mechanism, the flows in the atmospheric surface layer (ASL) over real urban morphology are measured in wind tunnel experiments fabricated by 3D-printing, reduced-scale model of downtown Kowloon Peninsula, Hong Kong. Elevated dispersive stress at urban canopy signifies the influence from individual buildings and inhomogeneous RSL flows. A positive momentum contribution appears in the low-frequency regime. The large-scale turbulence in RSL thus enhances the mixing and transport, resulting in inhomogeneous flows. The contribution from ejection Q2 and sweep Q4 increases and decreases, respectively, with increasing RSL motion strength. The conventional −5/3 law is observed by empirical mode decomposition (EMD) and the largest amplitude fluctuation occurs more often when the turbulence length scale is comparable to the turbulent boundary layer (TBL) thickness. The single-point amplitude modulation (AM) shows that the large- and small-scale turbulence correlates tightly at the bottom of RSL. Besides, the joint probability density function (JPDF) illustrates that accelerating large scales often occur with decelerating small scales, and they are intensified with increasing wall-normal distance. As a result, large-scale turbulence influences substantially the flow structures over urban areas and the small-scale turbulence (even) in RSLs in the vicinity of building obstacles.

Experimental investigation on swirling annular liquid film breakup characteristics of prefilming airblast atomizer

In order to further improve the understanding of the liquid film breakup characteristics of prefilming airblast atomizer, the effects of key operating parameters and structural parameters (swirl intensity, diameter and number of injection holes on pilot stage, length of pre-film lip and sleeve angle) on the liquid film pattern of prefilming airblast atomizer were investigated using the high-speed shadow method and the Otsu’s method. The mechanism of liquid film breakage was analyzed, the results show that, with the increase of fuel injection pressure, the spray morphology experiences “columnar-shaped”, “tulip-shaped” and “fully cone-shaped”. Meanwhile, the main fluctuation frequency of liquid film varies from 100.5 Hz in the “columnar-shaped” and “tulip-shaped” to 25.12 Hz in the “fully cone-shaped”. With increasing relative pressure drops of swirler, the film breakup length and film fluctuation frequency decrease, while the film fluctuation amplitude increases. An increase in inner-stage swirl intensities will lead to a reduction in the film breakup distance, while an increase in outer-stage swirl intensities will mainly lead to a larger spray angle. The increase of the diameter and number of injection holes and the length of pre-film lip leads to the rise of the liquid film breakup length, while the decrease of sleeve angle mainly leads to the rise of spray angle, which makes the liquid film more easily broken.

Design and Control Method of a Coupled Loading–Damping Mechanism of Cable‐Detecting Robots for Large Bridges

ABSTRACTThe climbing stability of cable‐detecting robots holds important significance for bridge detection. To improve the climbing stability of robots under cable vibration, a loading mechanism coupling variable stiffness and damping and a control method were proposed for robots. At first, aiming at the slip of cable‐detecting robots during climbing, the influences of cable vibration on the climbing stability of the robot and the damping mechanism of the variable‐stiffness and variable‐damping mechanism were assessed. Then, a new coupled loading mechanism was designed, and a mechanical model was established. The damping and stiffness were adjusted according to cable vibration, thus automatically adjusting the loading force of the robot. Afterwards, a fuzzy proportional–integral–derivative (PID) control strategy was devised and PID parameters were adjusted in accordance with cable vibration, thereby dynamically adjusting the clamping force of the coupled loading mechanism. Finally, a laboratory vibration test platform was established to conduct experiments on the output force of the coupled loading mechanism and on the robot climbing under vibration. Experimental results show that the maximum fluctuation amplitude of the climbing speed of the proposed robot decreases to 0.018 m/s, and the speed stability improves by 78.9% at the cable‐vibration frequency of 10 Hz and amplitude of 4 mm, when compared with the original common helical‐spring loading mechanism.

Impact of Spinal Manipulative Therapy on Brain Function and Pain Alleviation in Lumbar Disc Herniation: A Resting-State fMRI Study.

To elucidate how spinal manipulative therapy (SMT) exerts its analgesic effects through regulating brain function in lumbar disc herniation (LDH) patients by utilizing resting-state functional magnetic resonance imaging (rs-fMRI). From September 2021 to September 2023, we enrolled LDH patients (LDH group, n=31) and age- and sex-matched healthy controls (HCs, n=28). LDH group underwent rs-fMRI at 2 distinct time points (TPs): prior to the initiation of SMT (TP1) and subsequent to the completion of the SMT sessions (TP2). SMT was administered once every other day for 30 min per session, totally 14 treatment sessions over a span of 4 weeks. HCs did not receive SMT treatment and underwent only one fMRI scan. Additionally, participants in LDH group completed clinical questionnaires on pain using the Visual Analog Scale (VAS) and the Japanese Orthopedic Association (JOA) score, whereas HCs did not undergo clinical scale assessments. The effects on the brain were jointly characterized using the amplitude of low-frequency fluctuations (ALFF) and regional homogeneity (ReHo). Correlation analyses were conducted between specific brain regions and clinical scales. Following SMT treatment, pain symptoms in LDH patients were notably alleviated and accompanied by evident activation of effects in the brain. In comparison to TP1, TP2 exhibited the most significant increase in ALFF values for Temporal_Sup_R and the most notable decrease in ALFF values for Paracentral_Lobule_L (voxelwise P<0.005; clusters >30; FDR correction). Additionally, the most substantial enhancement in ReHo values was observed for the Cuneus_R, while the most prominent reduction was noted for the Olfactory_R (voxelwise P<0.005; clusters >30; FDR correction). Moreover, a comparative analysis revealed that, in contrast to HCs, LDH patients at TP1 exhibited the most significant increase in ALFF values for Temporal_Pole_Sup_L and the most notable decrease in ALFF values for Frontal_Mid_L (voxelwise P<0.005; clusters >30; FDR correction). Furthermore, the most significant enhancement in ReHo values was observed for Postcentral_L, while the most prominent reduction was identified for ParaHippocampal_L (voxelwise P<0.005; clusters >30; FDR correction). Notably, correlation analysis with clinical scales revealed a robust positive correlation between the Cuneus_R score and the rate of change in the VAS score (r=0.9333, P<0.0001). Long-term chronic lower back pain in patients with LDH manifests significant activation of the "AUN-DMN-S1-SAN" neural circuitry. The visual network, represented by the Cuneus_R, is highly likely to be a key brain network in which the analgesic efficacy of SMT becomes effective in treating LDH patients. (Trial registration No. NCT06277739).

Effect of carotid artery stenting on cognitive function in patients with asymptomatic carotid artery stenosis, a multimodal magnetic resonance study.

More and more evidence suggesting that internal carotid artery stenosis is not only a risk factor for ischemic stroke but also for cognitive impairments. Hypoperfusion and silent micro emboli have been reported as the pathophysiological mechanisms causing cognitive impairment. The effect of carotid artery stenting (CAS) on cognitive function varied from study to study. This study aims to explore the effect of CAS on cognition and exam the changes in cerebral perfusion and brain connectivity with pulsed arterial spin labeling (pASL) and resting-state functional MRI (R-fMRI). We conducted a controlled trial to assess alterations in cognitive performance among patients with "asymptomatic" carotid artery stenosis prior to and 3 months post-CAS intervention. Cognitive function including the Montreal Cognitive Assessment (MoCA) Beijing Version, the Minimum Mental State Examination (MMSE), the Digit Symbol Test, the Rey Auditory Verbal Learning Test (RAVLT), and the Verbal Memory Test. pASL perfusion MRI and R-fMRI were also performed prior to and 3 months post-CAS intervention. 13 patients completed all the follow-up. We observed increased perfusion in the right parietal lobe and right occipital lobe, increased amplitude of low-frequency fluctuation (ALFF) in the right precentral gyrus, increased connectivity to the posterior cingulate cortex (PCC) in the right frontal gyrus and right precuneus, and increased voxel-wise mirrored homotopic connectivity (VMHC) in the right precuneus 3 months after CAS when compared with prior to CAS. Cognitive test results showed significant improvement in the scores on the MMSE, the Verbal Memory test, and the delayed recall. CAS can partly improve the cognitive function in patients with "asymptomatic" carotid artery stenosis, and the improvement may be attributable to the increased perfusion in the right parietal lobe and right occipital lobe, increased ALFF in the right precentral gyrus, increased connectivity to the PCC in the right frontal gyrus and right precuneus, and increased VMHC in the right precuneus.