Search Results (8)

Background: Endovascular treatment of lower-extremity peripheral disease (PAD) is associated with higher complication rates and suboptimal outcomes in women. Atherectomy has shown favourable outcomes in calcified lesions, minimising the incidence of stent placement caused by recoil or flow-limiting dissection. To date, there are no published mid-term outcomes evaluating the performance of atherectomy differentiated by sex. This study aims to evaluate sex-specific outcomes and prognostic factors affecting the results of atherectomy-assisted endovascular treatment in severe PAD. Methods: A retrospective analysis was conducted at a single centre in Germany, initiated by physicians and not sponsored by industry, on patients presenting with Rutherford categories ranging from III to V and featuring de novo occlusive or stenotic lesions of the superficial femoral (SFA) and/or popliteal arteries. The intervention involved rotational atherectomy-assisted angioplasty utilising the Jetstream (Boston, US^®) device. The point of interest of this study was postinterventional clinical improvement as well as mid-term outcomes, including primary patency, over a targeted 2-year follow-up period. Statistical analysis utilised Cox regression (survival analysis) to calculate hazard ratios according to sex category. Comparative survival analysis was performed using the log-rank test and visually represented through Kaplan–Meier curves. Risk factors associated with absence of clinical improvement were examined across both sex groups utilising the chi-square or Fisher exact test, as appropriate. Results: A total of 98 patients (103 limbs) were initially included, with >75% having moderate-to-severe lesion calcification (>50%). A total of 84 patients (97 limbs, 62 male and 35 female) proceeded to a 2-year follow-up (mean 16.4 months for males and 16.1 for females) after a successful index procedure. Age distribution, Rutherford class, diabetes, chronic kidney disease (CKD), target vessel, lesion type, and length were balanced among both groups. Similar primary patency rates, of 89% among female and 91% among male limbs, were observed (p = 0.471). Female patients exhibited a lower rate of clinical improvement based on the Rutherford scale in comparison to males (80.6% vs. 94.5%, p = 0.048). CDK was the only significant prognostic factor across pooled data (odds ratio for CKD: 15.15, p < 0.001). Conclusions: Rotational atherectomy showed comparably high rates of mid-term primary patency, with low rates of bailout stent placement. These findings highlight the beneficial use of atherectomy in female patients who are per se at risk for higher rates of complications during and after endovascular interventions. Full article

An experimental testing system for the two-dimensional (2D) fuze overload loading process was designed to address the loading issues of recoil overload and centrifugal overload in fuze safety and arming (S&A) device. By incorporating centrifuge rotation energy storage, impact acceleration simulation, and equivalent centrifugal rotation simulation, a block equipped with a fuze S&A device accelerated instantly upon having impact from a centrifuge-driven impact hammer, simulating recoil overload loading. The impact hammer was retracted instantaneously by adopting an electromagnetic brake, which resulted in the centrifugal rotation of the block around its track, to simulate the centrifugal overload loading. The dynamic equations of the experimental testing system and the equations of impact hammer motions were established, whereby the rotation speed of the centrifuge and the braking force of the electromagnetic brake were calculated and selected. A dynamic model of the collision between the impact hammer and block was established using ANSYS/LS-DYNA software for simulation analysis. The acceleration curves of the recoil overload and centrifugal overload with variations in the centrifuge speed, cushion material, and buffer thickness were obtained, which verified the feasibility of the proposed loading simulation method. Two-dimensional overload loading simulation tests were performed using the developed experimental testing system, and the acceleration curves of the recoil overload and centrifugal overload were measured. The test results indicated that the proposed system can accomplish 2D overload loading simulations for a recoil overload of several 10,000× g and centrifugal overload of several 1000× g. Full article

The temporal and spatial evolution of shear banding during startup and steady-state shear flow was studied for solutions of entangled, linear, monodisperse polyethylene ${\mathrm{C}}_{3000}{\mathrm{H}}_{6002}$ dissolved in hexadecane and benzene solvents. A high-fidelity coarse-grained dissipative particle dynamics method was developed and evaluated based on previous NEMD simulations of similar solutions. The polymeric contribution to shear stress exhibited a monotonically increasing flow curve with a broad stress plateau at intermediate shear rates. For startup shear flow, transient shear banding was observed at applied shear rates within the steady-state shear stress plateau. Shear bands were generated at strain values where the first normal stress difference exhibited a maximum, with lifetimes persisting for up to several hundred strain units. During the lifetime of the shear bands, an inhomogeneous concentration distribution was evident within the system, with higher polymer concentration in the slow bands at low effective shear rate; i.e., $\dot{\gamma }<{\tau }_R^{-1}$, and vice versa at high shear rate. At low values of applied shear rate, a reverse flow phenomenon was observed in the hexadecane solution, which resulted from elastic recoil of the molecules within the slow band. In all cases, the shear bands dissipated at high strains and the system attained steady-state behavior, with a uniform, linear velocity profile across the simulation cell and a homogeneous concentration. Full article

The reverse magnetization behavior for bulk composite alloys containing Mn-Al-C and α-Fe nanoparticles (NPs) has been investigated by hysteresis loops, recoil, and first-order reversal curves (FORC) analysis. The effect of adding different percentages of α-Fe (5, 10, 15, and 20 wt. %) on the magnetic properties and demagnetization behavior of Mn-Al-C nanostructured bulk magnets was investigated. The fabricated nanocomposites were characterized by XRD and VSM for structural analysis and magnetic behavior investigations, respectively. The demagnetization curve of the sample Mn-Al-C-5wt. % α-Fe showed a single hard magnetic behavior and showed the highest increase in remanence magnetization compared to the sample without α-Fe, and therefore this combination was selected as the optimal composition for FORC analysis. Magnetic properties for Mn-Al-C-5 wt. % α-Fe nanocomposite were obtained as M_s = 75 emu/g, M_r = 46 emu/g, H_c = 3.3 kOe, and (BH)_max = 1.6 MGOe, indicating a much higher (BH)_max than the sample with no α-Fe. FORC analysis was performed to identify exchange coupling for the Mn-Al-C-0.05α-Fe nanocomposite sample. The results of this analysis showed the presence of two soft and hard ferromagnetic components. Further, it showed that the reverse magnetization process in the composite sample containing 5 wt. % α-Fe is the domain rotation model. Full article

The clearance between the main roller and the cylinder cam has an important impact on the operational status of the bolt. In order to achieve the clearance and recoil of the cylinder cam mechanism, a bolt model was built and studied. The leading dynamic roller group and the dynamic bolt were analyzed. Positive stress and friction force change quickly on the high-speed leading roller group, influencing multiple aspects. When the main roller suddenly rotates or reverses in several short intervals, the assembling clearance and the massive friction force between the main roller and the cam curve slot are the main wear factors in theoretical analysis and test experiments. The leading roller group, the pure rolling criterion of the cylindrical cam mechanism of the automaton, is derived in this paper. Moreover, a new fault diagnosis method is developed, based on the Variational Box Dimension Kernel Fuzzy Mean Clustering Algorithm (VK) algorithm, which combines the variational mode decomposition and fractal box-counting dimension (VMD-FBCD) and the fuzzy clustering algorithms with a kernelized Mahalanobis distance (KMD-FC). With the simulation validation from 2810 samples, diagnosis using the VK algorithm is found to have a higher accuracy rate and slightly lower fallacy rate and to be faster than other diagnostic methods of similar studies. The results in terms of the recoil cylinder cam mechanism’s multi-body dynamic analysis and high-speed fault identification also have significance as a reference for solving similar problems. Full article

The drop tests of a twin tandem landing gear with different filling parameters are carried out in two different landing attitudes (level and tail-down). The overload coefficient and power absorption efficiency are obtained. Curves of dynamic oscillation and pressure change for the pitch damper are obtained. The results show that twin tandem landing gear has a good ability to absorb the work of landing impact. Under landing weight, the vertical overload coefficients during level landing and tail-down landing are 1.14 and 1.07, respectively, when the corresponding efficiencies of its buffer system are 80.9% and 83.3%. During tail-down landing, the work absorbed by the pitch damper accounts for only 14.9% of the maximum pitching kinetic energy of the trolley. When the orifice diameter of the pitch damper keeps the same, its peak axial load does not change significantly with the change of its initial pressure. When the initial pressure of the pitch damper keeps the same, the decrease of its orifice diameter is beneficial to the vibration attenuation of the trolley. The smaller recoil channel may lead to a significant increase in the peak pressure of the pitch damper, which should be a consideration in its design. Full article

Trabecular meshwork (TM) motion abnormality is the leading cause of glaucoma. With technique limitations, how TM moves is still an enigma. This study describes a new laboratory platform to investigate TM motion responses to ocular transients in ex vivo eyes. The anterior segments of human cadaver and primate eyes were mounted in a perfusion system fitting. Perfusion needles were placed to establish mean baseline pressure. A perfusion pump was connected to the posterior chamber and generated an immediate transient pressure elevation. A phase-sensitive optical coherent tomography system imaged and quantified the TM motion. The peak-to-peak TM displacements (ppTMD) were determined, a tissue relaxation curve derived, and a time constant obtained. This study showed that the ppTMD increased with a rise in the pulse amplitude. The ppTMD was highest for the lowest mean pressure of 16 mmHg and decreased with mean pressure increase. The pulse frequency did not significantly change ppTMD. With a fixed pulse amplitude, an increase in mean pressure significantly reduced the time constant of recoil from maximum distension. Our research platform permitted quantitation of TM motion responses to designed pulse transients. Our findings may improve the interpretation of new TM motion measurements in clinic, aiding in understanding mechanisms and management. Full article

Purpose: In this study, the required dose rates for optimal treatment of tumoral tissues when using proton therapy in the treatment of defective tumours seen in mandibles has been calculated. We aimed to protect the surrounding soft and hard tissues from unnecessary radiation as well as to prevent complications of radiation. Bragg curves of therapeutic energized protons for two different mandible (molar and premolar) plate phantoms were computed and compared with similar calculations in the literature. The results were found to be within acceptable deviation values. Methods: In this study, mandibular tooth plate phantoms were modelled for the molar and premolar areas and then a Monte Carlo simulation was used to calculate the Bragg curve, lateral straggle/range and recoil values of protons remaining in the therapeutic energy ranges. The mass and atomic densities of all the jawbone layers were selected and the effect of layer type and thickness on the Bragg curve, lateral straggle/range and the recoil were investigated. As protons move through different layers of density, lateral straggle and increases in the range were observed. A range of energies was used for the treatment of tumours at different depths in the mandible phantom. Results: Simulations revealed that as the cortical bone thickness increased, Bragg peak position decreased between 0.47–3.3%. An increase in the number of layers results in a decrease in the Bragg peak position. Finally, as the proton energy increased, the amplitude of the second peak and its effect on Bragg peak position decreased. Conclusion: These findings should guide the selection of appropriate energy levels in the treatment of tumour structures without damaging surrounding tissues. Full article