Cross-sectional Area Ratio Research Articles

Age-Related Association Between Unilateral Single-Channel and Double-Channel Surgery and Postoperative Multifidus Muscle Atrophy and Fat Infiltration.

Unilateral biportal endoscopic laminotomy (UBE) and percutaneous endoscopic laminotomy (PEL) are minimally invasive spinal surgery (MISS) techniques used for unilateral and dual-channel endoscopic laminectomy. However, limited research has been conducted on lumbosacral multifidus muscle injuries in elderly individuals undergoing MISS for lumbar spinal canal stenosis. The objective of this study was to investigate the impact of single-channel and double-channel MISS on the multifidus muscle in elderly patients. A total of 107 patients who underwent MISS were stratified into two cohorts: group A (<65 years) and group B (≥65 years). Preoperative imaging data, including magnetic resonance imaging, were gathered to classify the degree of stenosis based on the nerve root compression. The extent of multifidus muscle atrophy and fat infiltration was assessed by calculating the fat-free cross-sectional area (FCSA)/cross-sectional area (CSA) ratio before and after surgery through measurements of CSA and FCSA. Total cross-sectional area/FCSA were calculated using MRI cross-sectional T2WI. The degree of atrophy and fat infiltration did not change between procedures in group A (P>.05), but changed significantly in group B (P<.05). Unilateral single-channel and double-channel surgery had no significant effect on the degree of multifidus muscle atrophy and fat infiltration in patients younger than 65 years. However, in patients 65 years and older, the degree of multifidus muscle atrophy and fat infiltration significantly increased with the increasing incidence of lateral recess stenosis, which was positively correlated with the duration of surgery. [Orthopedics. 202x;4x(x):xx-xx.].

Combination of Different Sectional Elastography Techniques with Age to Optimize the Downgrading of Breast BI-RAIDS Class 4a Nodules.

This study aims to optimize the downgrading of BI-RADS class 4a nodules by combining various sectional elastography techniques with age. We performed conventional ultrasonography, strain elastography (SE), and shear wave elastography (SWE) on patients. Quantitative parameters recorded included age, cross-sectional and longitudinal area ratios (C-EI/B, L-EI/B), strain rate ratios (C-SR, L-SR), overall average elastic modulus values (C-Emean1, L-Emean1), five-point average elastic modulus values (C-Emean2, L-Emean2), and maximum elastic modulus values (C-Emax, L-Emax). Histopathological evaluations showed that out of 230 lesions, 45 were malignant, and 185 were benign. The sensitivity and specificity of conventional ultrasonography were 100% and 0%, respectively. In contrast, SE and SWE exhibited higher specificity but lower sensitivity. Crosssectional parameters (C-EI/B, C-SR, C-Emean1, C-Emean2, and C-Emax) outperformed their longitudinal counterparts, with C-SR and C-Emax showing the highest specificity (72.43% and 73.51%) and satisfactory sensitivity (80.00% and 88.89%). Combining age with C-SR and C-Emax significantly improved diagnostic efficiency, achieving a sensitivity of 97.78% and a specificity of 77.30%. Integrating age with C-SR and C-Emax effectively reduces unnecessary biopsies for most BI-RADS 4a benign lesions while maintaining a very low misdiagnosis rate.

A diffusion model of explosion gas under airflow diversion during ventilation of a bifurcated tunnel

In this paper, the bifurcation tunnel in the Yue Long Men Tunnel (Chengdu-Lanzhou Railway, Sichuan Province, China) is used as the research object. Based on the field monitoring data, CFD is used to simulate the explosive gas diffusion process of explosive airflow during the bifurcation tunnel ventilation diversion process, and the effects of different bifurcation angles θ and cross-sectional area ratios s on the diversion flow field are compared. The results show that: (1) Under the control of a single factor, θ and s affect the flow field characteristics after shunt by changing the position of the eddy current in the main tunnel. Varying the bifurcation angle and cross-sectional area ratio increases the ventilation efficiency by up to 9.1% and 14.9%, respectively. (2) The locations of vortices are influenced by θ and s to different extents, and the more forward the locations of vortices in the bifurcated structure, the weaker the influences on explosive gas diffusion in the rear space; (3) Some airflows deflect after diversion and their velocity is influenced by s. An appropriate decrease of s is conducive to the discharge of explosive gas from the transverse tunnel. The research content can provide a basis for tunnel blasting and excavation ventilation schemes.

Investigation on dynamic response of thin spherical shells impacted by flat-nose projectile based on a novel damage model

Thin-shell structures are widely used in various engineering applications. It is essential to investigate the impact resistance of thin-shell structures, to provide theoretical support for engineering applications. Numerous impact tests have been conducted on thin spherical shells using ballistic guns. The effects of the impact velocity and shell thickness on the deformation and fracture of thin spherical shells are summarized. Moreover, a novel damage model based on statistic damage mechanics is proposed to better predict dynamic responses of thin shells impacted by projectiles. Considering that fracture surfaces are formed by void evolution and are affected by the stress states, the damage level is defined as the ratio of the statistical cross-sectional area of the voids to the cross-sectional area of the representative elements. Utilizing statistical methods, the incorporation of continuous void nucleation, ellipsoidal void growth, and the acceleration of dynamic void evolution are introduced into the novel damage model. Subsequently, numerical investigations of the dynamic response of spherical shells under impact are conducted based on the proposed damage model. The numerical results are consistent with the experimental results in terms of the depression deformations and strain signals. The effects of shell thickness and double-layer structures on the dynamic response of spherical shells are investigated via numerical simulations considering the novel damage model in detail. The results demonstrate that the proposed model can accurately predict the dynamic response of spherical shells impacted by flat-nose projectiles, thus serving as a valuable reference for engineering design.

EFFECT OF EXTREMELY LOW-FREQUENCY ELECTROMAGNETIC FIELDS ON PROMOTING MYOGENESIS IN THE EARLY PROCESS OF DENERVATED MUSCLEATROPHY

Objective: To investigate the effects of extremely low-frequency electromagnetic fields (ELF-EMF) on myogenesis during the early stage of denervated muscle atrophy in Sprague-Dawley (SD) rats. Methods: a total of 36 female SD rats were fed in cages and divided into three groups: the normal control group, the muscle atrophy group and the 10[Formula: see text]Hz/1.5[Formula: see text]mT magnetic field group. The rats in the 10[Formula: see text]Hz/1.5[Formula: see text]mT magnetic field group received a magnetic field intervention for 2[Formula: see text]h per day. The posterior muscle groups of the lower limbs of rats were sampled on the first, second, third and fourth weeks for evaluating the underlying changes. The harvested tissues were stained with hematoxylin–eosin (HE) dye to observe the morphology of the muscle atrophy and to measure the muscle fiber cross-sectional area ratio. A reverse transcription polymerase chain reaction was used to detect the expression of Myf5 mRNA in each group. The myogenesis-related proteins in the harvested muscle tissue were detected by western blot assay. Results: (1) HE staining showed that with the extension of denervation time, the structural disorder of muscle fibers was aggravated, and in the second week of the denervated muscle atrophy, muscle fiber cross-sectional area tended to increase in the 10[Formula: see text]Hz/1.5[Formula: see text]mT magnetic field group. Overall muscle atrophy was inevitable. (2) Results of RT-PCR showed that the expression of Myf5 mRNA in the 10[Formula: see text]Hz/1.5[Formula: see text]mT magnetic field group was significantly high in the second week of denervation, and the difference was statistically significant compared with the muscle atrophy group (*[Formula: see text]). (3) Western blot analysis showed that the expression of MYF5 proteins in the 10[Formula: see text]Hz/1.5[Formula: see text]mT magnetic field group was significantly higher than that in the muscle atrophy group (**[Formula: see text]) in the second week of denervation. Further, the expression of MYOG protein in the 10[Formula: see text]Hz/1.5[Formula: see text]mT magnetic field group was significantly higher than that in the muscle atrophy group (****[Formula: see text]). Conclusions: 10[Formula: see text]Hz/1.5[Formula: see text]mT ELF-EMF can significantly promote myogenesis during early denervated muscle atrophy in SD rats.

Simulating carbon dioxide diffusion during airflow merging in Y-shaped bifurcated tunnels after blasting operations

This research aims to evaluate the dilution and discharge effects of noxious gas produced by the drilling and blasting method under the merging of airflows during the ventilation of Y-shaped bifurcated tunnels. A finite volume model was utilized to simulate the overall diffusion process of explosion and noxious gas in the tunnel after blasting, taking into account various parameters of bifurcated structures. The flow field characteristics and the temporal and spatial evolution of the CO concentration field was analyzed under parameters including the bifurcating angle θ and cross-sectional area ratio F, as well as air supply ratio Q. The results show that the CO concentration decreases in a negative exponential manner with the ventilation time and it reaches the concentration limit within 480–610 s. By comparing conditions under different bifurcating angles θ of the main transverse tunnel, the dilution effect of CO is optimal when θ is 90° and the CO concentration reaches the safety threshold after ventilation for 489 s. Considering the influence of the cross-sectional area ratio (F) of the main transverse tunnel, the CO concentration reduces most rapidly when F is 0.7 and it reaches the safety threshold after ventilation for 476 s. Upon estimating the influence of the air supply ratio (Q) on the CO diffusion process, it is found that Q of 0.4 is most conducive to the dilution and discharge of CO and the CO concentration reaches the safety threshold after ventilation for 485 s. The results provide technical and theoretical support for the ventilation and smoke discharge during the construction of a Y-shaped bifurcated tunnel.

Three-Dimensional Finite Element Modeling of the Singer’s Formant Cluster Optimization by Epilaryngeal Narrowing With and Without Velopharyngeal Opening

This study aimed to find the optimal geometrical configuration of the vocal tract to increase the total acoustic energy output of human voice in the frequency interval 2-3.5 kHz “singer’s formant cluster”, (SFC) for vowels [a:] and [i:] considering epilaryngeal changes and the velopharyngeal opening (VPO). The study applied 3D volume models of the vocal and nasal tract based on computer tomography (CT) images of a female speaker. The epilaryngeal narrowing (EN) increased the total sound pressure level (SPL) and SPL of the SFC by diminishing the frequency difference between acoustic resonances F3 and F4 for [a:] and between F2 and F3 for [i:]. The effect reached its maximum at the low pharynx/epilarynx cross-sectional area ratio 11.4:1 for [a:] and 25:1 for [i:]. The acoustic results obtained with the model optimization are in good agreement with the results of an internationally recognized operatic alto singer. With the EN and the VPO, the vocal tract input reactance was positive over the entire fo singing range (ca. 75-1500 Hz). The VPO increased the strength of the SFC and diminished the SPL of F1 for both vowels, but with EN the SPL decrease was compensated. The effect of EN is not linear and depends on the vowel. Both the EN and the VPO alone and together can support (singing) voice production.

Experimental evaluation of the influence of the diffuser inlet to nozzle exit cross sectional area ratio on pressure oscillation in a high-altitude test facility

The ratio of diffuser inlet to nozzle exit area (Ad/Ae) is one of the most important parameters in designing and evaluating the performance of a high-altitude test facility (HATF). Typically, at motor pressures near start or operating pressure of the diffuser, the vacuum chamber pressure oscillates at a high Ad/Ae, which may be dangerous for the HATF. In the present study, the effect of the Ad/Ae on the starting and breakdown performance of a second throat exhaust diffuser (STED) has been investigated experimentally using a HATF supplied by high-pressure cold air apparatus. Upon examining the overall performance of the diffuser, it is observed that with an increase in Ad/Ae, the oblique sealing shock wave at the diffuser inlet undergoes significant changes in location and strength. This leads to a further reduction of the flow total pressure and a stronger separation of the flow along the diffuser. Consequently, flow instability arises during starting or breakdown phases near the STED starting or operating pressure. By frequency analysis, it is observed that as Ad/Ae increases, the number of oscillatory modes of the vacuum chamber pressure increases and the dominant frequency of the oscillations in these transient situations becomes larger. Additionally, there is a significant decrease in nozzle pressure related to the onset of pressure oscillations. Furthermore, with an increase in Ad/Ae from 1.27 to 7.81, the minimum starting pressure and breakdown pressure of STED increase by 20.33% and 28.47%, respectively. Also, the hysteresis range in performance of STED vanishes at high Ad/Ae values.

Hounsfield units of vertebrae as a predictor of cervical deep paraspinal muscles atrophy and neck pain in degenerative cervical myelopathy.

This study investigated the correlation between Hounsfield units (HU) of the cervical vertebrae and atrophy of the cervical deep paraspinal muscles, namely the multifidus and semispinalis cervicis (SCer), in patients diagnosed with degenerative cervical myelopathy (DCM). The authors retrospectively analyzed data from 136 patients aged 50-79 years (81 males and 55 females) who underwent surgical intervention for DCM. HU measurements of the cancellous bone in the C4 vertebra were acquired through standardized techniques. The authors evaluated fatty infiltration (FI); analyzed functional and vertebral cross-sectional area (CSA) of the multifidus and SCer at the C4-5, C5-6, and C6-7 levels; and analyzed the presence of Modic changes (MCs) and the incidence of axial neck pain. Patients were categorized into group A (n = 56) with mean ± SD HU of 293.3 ± 15.6 and group B (n = 80) with mean ± SD HU of 389.5 ± 10.6. Both groups demonstrated significant improvements in postoperative clinical outcomes (p < 0.05); however, no statistically significant difference was observed (p > 0.05). Significant disparities in HU measurements and visual analog scale (VAS) scores for neck pain were observed between the groups (p < 0.05). The highest VAS score correlated with MCs-1 type (i.e., low signal on T1-weighted images and high signal on T2-weighted images). The functional CSA to vertebral CSA ratios of the multifidus and SCer in group A were markedly reduced compared to those of group B (p < 0.05). No significant difference was noted in functional CSA asymmetry between the groups for both muscles (p > 0.05). Lower HU measurements directly correlated with increased FI in the multifidus (p = 0.002) and SCer (p = 0.035). Furthermore, a strong positive association was found between the functional CSA to vertebral CSA ratio of the multifidus and HU values (p = 0.003), whereas HU measurements and VAS scores exhibited a negative correlation (p = 0.020). Among those patients older than 50 years with DCM, those with decreased HU values demonstrated elevated FI levels in the multifidus and SCer muscles. Moreover, these patients presented with pronounced muscle atrophy, which correlated with axial neck pain. A significant relationship was also identified between MCs and diminished HU values.

Sparse modeling of dominant factors affecting porosity formation in laser powder bed fusion of aluminum alloy

The dominant factors affecting porosity formation in laser powder bed fusion (PBF-LB/M) of an aluminum alloy were investigated through sparse modeling with the cross-sectional pore area ratio as the target variable and the process parameters of PBF-LB/M and the melting and solidification conditions of the alloy as the explanatory variables. A combination of a few explanatory variables that did not significantly increase the mean squared error for the relationship between the measured pore area ratios and the ratios estimated via the regression equations was found through lasso regression and backward elimination, which indicated that the energy density (one of the process parameters) and melt-pool depth (one of the melting conditions) were the dominant factors affecting the pore area ratio. The obtained regression coefficients for the energy density and melt-pool depth were negative and positive, respectively. In addition, the relationship between the energy density and melt-pool depth was curvilinear. These results suggest not only that the pore area ratio increases with the energy density and melt-pool depth but also that it decreases with an increase in the energy density or a decrease in the change rate of the pool depth under the range of the slow increase in the pool depth with an increase in the energy density.

The Cross-Sectional Area Ratio of Right-to-Left Portal Vein Predicts the Effect of Preoperative Right Portal Vein Embolization.

Background and Objectives: Preoperative right portal vein embolization (RPVE) is often attempted before right hepatectomy for liver tumors to increase the future remnant liver volume (FRLV). Although many factors affecting FRLV have been discussed, few studies have focused on the ratio of the cross-sectional area of the right portal vein to that of the left portal vein (RPVA/LPVA). The aim of the present study was to evaluate the effect of RPVA/LPVA on predicting FRLV increase after RPVE. Materials and Methods: The data of 65 patients who had undergone RPVE to increase FRLV between 2004 and 2021 were investigated retrospectively. Using computed tomography scans, we measured the total liver volume (TLV), FRLV, the proportion of FRLV relative to TLV (FRLV%), the increase in FRLV% (ΔFRLV%), and RPVA/LPVA twice, immediately before and 2-3 weeks after RPVE; we analyzed the correlations among those variables, and determined prognostic factors for sufficient ΔFRLV%. Results: Fifty-four patients underwent hepatectomy. Based on the cut-off value of RPVA/LPVA, the patients were divided into low (RPVA/LPVA ≤ 1.20, N = 30) and high groups (RPVA/LPVA > 1.20, N = 35). The ΔFRLV% was significantly greater in the high group than in the low group (9.52% and 15.34%, respectively, p < 0.001). In a multivariable analysis, RPVA/LPVA (HR = 20.368, p < 0.001) was the most significant prognostic factor for sufficient ΔFRLV%. Conclusions: RPVE was more effective in patients with higher RPVA/LPVA, which is an easily accessible predictive factor for sufficient ΔFRLV%.

Percutaneous Screw Distraction for Anatomic Restoration: Case Series.

Percutaneous pedicle screw fixation with distraction reduces morbidity after traumatic thoracolumbar burst fractures; however, there are substantial limitations, particularly for correction of kyphosis. The use of fixed-angle screws may offer improved anatomic restoration, facilitating greater postdistraction vertebral height restoration and spinal canal fragment reduction. We examined the radiographic results of distraction across fixed-angle screws immediately after surgery and in long-term follow-up. Demographic and clinical characteristics were captured for patients with traumatic thoracolumbar fractures undergoing percutaneous pedicle screw fixation by a single surgeon. Radiographic measurements were collected at predistraction, postdistraction, and long-term follow-up time points. Paired t-tests, Student's t-tests, Mann-Whitney U tests, and χ2 tests were used to assess data where appropriate. The case series included 22 patients (77.3% male; mean age 42.0 ± 18.4 years). Hounsfield density consistent with osteopenia was seen in 13.6% of patients at the time of injury. Sporting injuries and motor vehicle accidents were common (both 31.8%). Most injuries occurred at L1 (45.5%). Upon long-term follow-up, the mean injured-level predistraction cross-sectional area improved from 2.1 to 2.9 cm2 (P < .01). Compared with the superadjacent level, the injured-level cross-sectional canal area improved by 28.6% (P < .01). Vertebral body index also improved significantly (18.8° mean change, P < .01). The mean bisegmental Cobb angle improved by 6.2° (P = .01), and injured vertebral body compression decreased by 22.4% (P < .01). Significant improvement in correction was achieved with experience, with final technique yielding superior cross-sectional area (P = .04) and compression ratios (P = .03). Distraction across fixed-angle percutaneous screw instrumentation systems stabilizes traumatic thoracolumbar burst fractures, corrects deformity, and decompresses the spinal canal. Further comparative research is necessary to demonstrate whether outcomes are different between percutaneous instrumentation vs open fusion for thoracolumbar trauma.

Mitigation of Erosion Wear Produced by Fly-Ash Slurry on 90&lt;sup&gt;0&lt;/sup&gt; Elbow by Changing the Cross-Section Shape and Area Ratio

The predominant method of transporting fly ash involves conveying it in slurry form through pipelines within diverse industrial facilities. The key elements of slurry conveyance encompass bends, pumps, and valves. These components of the pipeline endure significant erosion and wear due to the impact of discrete particles. In this investigation, the study assessed the wear induced by slurry erosion in conventional 900 pipe bend and 900 square section elbows of different area ratios using ANSYS Fluent. The discrete phase model was used to estimate the slurry erosion wear for the fly ash-water suspension. From the investigation, the outcomes from the standard k-turbulence model were discovered to be in agreement with the experimental data. This study also looked at a number of other influencing factors, such as the solid concentration and velocity. The analysis reveals that the average erosion wear is lower in the square cross-section elbow compared to the standard elbow. Furthermore, the erosion wear is observed to decrease further with an increase in the cross-sectional area of the square section elbow.

Biological variation in cervical spinal cord MRI morphometry in healthy individuals and people with multiple sclerosis.

Conclusions from prior literature regarding the impact of sex, age, and height on spinal cord (SC) MRI morphometrics are conflicting, while the effect of body weight on SC morphometrics has been found to be nonsignificant. The purpose of this case-control study is to assess the associations between cervical SC MRI morphometric parameters and age, sex, height, and weight to establish their potential role as confounding variables in a clinical study of people with multiple sclerosis (MS) compared to a cohort of healthy volunteers. Sixty-nine healthy volunteers and 31 people with MS underwent cervical SC MRI at 3 Tesla field strength. Images were centered at the C3/C4 intervertebral disc and processed using Spinal Cord Toolbox v.4.0.2. Mixed-effects linear regression models were used to evaluate the effects of biological variables and disease status on morphometric parameters. Sex, age, and height had significant effects on cord and gray matter (GM) cross-sectional area (CSA) as well as the GM:cord CSA ratio. There were no significant effects of body weight on morphometric parameters. The effect of MS disease duration on cord CSA in the C4 level was significant when controlling for all other variables. Studies of disease-related changes in SC morphometry should control for sex, age, and height to account for physiological variation.

Diagnostic efficiency of conventional ultrasound, shear wave elastography, and superb microvascular imaging in evaluating ulnar neuropathy at the elbow.

The current diagnosis of ulnar neuropathy at the elbow (UNE) relies mainly on the clinical presentation and nerve electrodiagnostic (EDX) testing, which can be uncomfortable and yield false negatives. The aim of this study was to investigate the diagnostic value of conventional ultrasound, shear wave elastography (SWE), and superb microvascular imaging (SMI) in diagnosing UNE. We enrolled 40 patients (48 elbows) with UNE and 48 healthy volunteers (48 elbows). The patients were categorized as having mild, moderate or severe UNE based on the findings of EDX testing. The cross-sectional area (CSA) was measured using conventional ultrasound. Ulnar nerve (UN) shear wave velocity (SWV) and SMI were performed in a longitudinal plane. Based on the EDX findings, UNE severity was graded as mild in 4, moderate in 10, and severe in 34. The patient group showed increased ulnar nerve CSA and stiffness at the site of maximal enlargement (CSA mean at the site of max enlargement [CSAmax] and SWV mean at the site of max enlargement [SWVmax]), ulnar nerve CSA ratio, and stiffness ratio (elbow-to-upper arm), compared with the control group (p < .001). Furthermore, the severe UNE group showed higher ulnar nerve CSAmax and SWVmax compared with the mild and moderate UNE groups (p < .001). The cutoff values for diagnosis of UNE were 9.5 mm2 for CSAmax, 3.06 m/s for SWVmax, 2.00 for CSA ratio, 1.36 for stiffness ratio, and grade 1 for SMI. Our findings suggest that SWE and SMI are valuable diagnostic tools for the diagnosis and assessment of severity of UNE.

Low-frequency sound attenuation by coiled-up meta-liner with nonuniform cross sections under grazing flow

We report a kind of coiled-up meta-liners with nonuniform cross sections (CMNC), which can efficiently attenuate low-frequency sound waves under grazing flow with a deep subwavelength thickness (e.g., ∼λ/17 at 500 Hz). At a grazing flow Mach number of 0.26, the average transmission loss of the meta-liner is 12.6 dB at 500–1000 Hz, which is twice as much as that of a double-degree-of-freedom acoustic liner of the same size. Physically, the nonuniform cross-sectional distribution and significant cross-sectional area ratio enhances vortex shedding, thus resulting in severe acoustic energy dissipation. The excellent low-frequency acoustic attenuation performance of CMNC is investigated thoroughly with experimental, theoretical, and numerical methods. This work provides an avenue for low-frequency noise reduction in grazing flow scenarios (e.g., in a high bypass ratio turbofan engine).

Low Temperature (Down to 6 K) and Quantum Transport Characteristics of Stacked Nanosheet Transistors with a High-K/Metal Gate-Last Process.

Silicon qubits based on specific SOI FinFETs and nanowire (NW) transistors have demonstrated promising quantum properties and the potential application of advanced Si CMOS devices for future quantum computing. In this paper, for the first time, the quantum transport characteristics for the next-generation transistor structure of a stack nanosheet (NS) FET and the innovative structure of a fishbone FET are explored. Clear structures are observed by TEM, and their low-temperature characteristics are also measured down to 6 K. Consistent with theoretical predictions, greatly enhanced switching behavior characterized by the reduction of off-state leakage current by one order of magnitude at 6 K and a linear decrease in the threshold voltage with decreasing temperature is observed. A quantum ballistic transport, particularly notable at shorter gate lengths and lower temperatures, is also observed, as well as an additional bias of about 1.3 mV at zero bias due to the asymmetric barrier. Additionally, fishbone FETs, produced by the incomplete nanosheet release in NSFETs, exhibit similar electrical characteristics but with degraded quantum transport due to additional SiGe channels. These can be improved by adjusting the ratio of the channel cross-sectional areas to match the dielectric constants.

A network model for can-annular combustors using a multidimensional transfer matrix based on the mode matching method

Heavy-duty land-based gas turbines with can-annular combustors typically exhibit a set of thermoacoustic modes with similar frequencies, due to their rotational symmetry and the weak coupling between neighbouring cans. The Bloch boundary condition is often used to simplify these combustors. Because the widely used (quasi-)one-dimensional model cannot naturally consider high-order modal components in the three-dimensional acoustic field, it is valid only when the frequency is sufficiently low and the length of the can-to-can interaction gap is sufficiently short. In this paper, we present a theoretical model using the mode-matching method to consider high-order modal components. A reflection coefficient matrix is used to accurately describe the acoustic characteristics of the gap area. This reflection coefficient matrix is found to depend on the nondimensional cross-sectional area ratio, the Helmholtz number based on the length of the gap area, and the Bloch number. To facilitate a full low-order network modelling of the high-frequency thermoacoustic modes in can-annular combustors, a flame transfer matrix is also used to describe the modal coupling effect across the flame. Based on this model, the thermoacoustic problem of a four-flame can-annular combustor is studied as an example. It is shown that the frequency and growth rate of the thermoacoustic modes can be predicted accurately using the reflection coefficient matrix and flame transfer matrix. The effects of high-order modal components across the flame and in the gap areas are studied separately. The results show that the model containing both of the two coupling effects has the widest range of validity. These couplings can be ignored if only low-frequency plane acoustic waves are considered but need to be carefully considered for higher frequency modes. Moreover, when multiple flames are considered, asymmetric flame distributions are found to more easily lead to modal coupling compared to symmetric flame distributions. All results are validated by comparing with the numerical solutions of the full two-dimensional Helmholtz equation using the finite element method.

Is the Tendon-to-Groove Ratio Associated with Elevated Risk for LHB Tendon Disorders?-A New Approach of Preoperative MR-Graphic Analysis for Targeted Diagnosis of Tendinopathy of the Long Head of Biceps.

Background: Pathologies of the long head of the biceps (LHB) tendon are a common cause of anterior shoulder pain. While the influence of the anatomical morphology of the intertubercular groove (ITG) on the development of LHB tendon instability has been investigated with ambiguous results, the relationship of the LHB to ITG anatomy has not yet been considered in this context. The objective of this study was to reliably extract the tendon-to-groove ratio from MRI scans of symptomatic patients and examine its potential influence on the occurrence of certain causes for LHB-associated symptoms. Methods: In this retrospective study, preoperative MRI scans of 35 patients (mean age of 46 ± 14 years) presenting with anterior shoulder pain and clinical indications of LHB tendinopathy were analyzed in transversal planes. Long and short diameters of the LHB tendon and ITG were measured, cross-sectional areas of the LHB tendon and ITG were calculated from these measurements, and the ratio of cross-sectional areas (LHB/ITG) was introduced. All measurements were repeated independently by three investigators and inter-rater reliability was assessed using intraclass correlation coefficient (ICC). Thereafter, tendon-to-groove ratios were compared in patients with and without intraoperative signs of LHB tendon instability. Results: All patients exhibited intraoperative signs of LHB tendinitis, with additional findings including pulley lesions and SLAP lesions. Analysis revealed variations in the dimensions of the LHB tendon and ITG cross sections, with the tendon-to-groove ratio decreasing from 37% at the pulley to 31% at the deepest point of the sulcus. Very good inter-rater reliability was observed for all measurements. The tendon-to-groove ratio did not significantly differ (p > 0.05) in patients with or without pulley lesions or SLAP lesions. Conclusions: Our study introduced the novel parameter of the tendon-to-groove ratio of cross-sectional areas as a reproducible parameter for the description of local anatomy in the field of targeted diagnosis of LHB tendon disorders. While our findings do not yet support the predictive value of the tendon-to-groove ratio, they underscore the importance of further research with larger cohorts and control groups to validate these observations.

125 Effects of Saccharmyces yeast postbiotics on nursey pig muscle fiber cross-sectional area and oxidative capacity

Abstract This study aimed to determine effects of dietary supplementation of Saccharomyces yeast postbiotics (celluTEIN, Puretein Bioscience, LLC, Minneapolis, MN) on nursery pig muscle fiber cross-sectional area (CSA), isoform, and succinate dehydrogenase (SDH) staining intensity. Newly weaned pigs [n = 32; 16 barrows and 16 gilts; 21 d of age, body weight (BW) 6.05 ± 0.24 kg] were stratified by BW within sex, placed in individual pens, and randomly assigned to one of two dietary treatments within each two-pig strata. Dietary treatments included pigs supplemented 0 (CON; n = 16) or 175 g/ton (CT; n = 16) of celluTEIN to their standard three-phase nursery ration. Pigs were harvested at d 35 of feeding and the longissimus lumborum muscle was collected for mean SDH staining intensity and immunohistochemistry analyses. Data were analyzed as a completely randomized design with pig as the experimental unit and treatment as the fixed effect. Statistical significance was determined at P ≤ 0.05. There were no treatment effects on type I and type IIB muscle fiber CSA (P &amp;gt; 0.14), but CT pigs had greater type IIA and type IIX muscle fiber CSA compared with CON (P &amp;lt; 0.05). When not analyzed by fiber isoform, pigs fed CT had a greater (P = 0.02) average muscle fiber CSA than CON pigs. There were no treatment effects on muscle fiber type percentage or SDH intensity of all fiber types (P ≥ 0.23); however, when calculated as a muscle fiber CSA ratio, CT type IIA fibers had a smaller ratio (darker staining/µm2) than CON type IIA fibers (P = 0.05). There were no treatment effects for type I, IIX, and IIB ratios (P &amp;gt; 0.21). In conclusion, supplementing Saccharomyces yeast postbiotics during the nursery period increased muscle fiber hypertrophy and type IIA fiber oxidative capacity.