Co-condensation of mixed SiGe nanoclusters and impingement of SiGe nanoclusters on a Si substrate were applied using molecular dynamics (MD) simulation in this study to mimic the fast epitaxial growth of SiGe/Si heterostructures under mesoplasma chemical vapor deposition (CVD) conditions. The condensation dynamics and properties of the SiGe nanoclusters during the simulations were investigated first, and then the impingement of transient SiGe nanoclusters on both Si smooth and trench substrate surfaces under varying conditions was studied theoretically. The results show that the mixed nanoclusters as precursors demonstrate potential for enhancing epitaxial SiGe film growth at a high growth rate, owing to their loosely bound atomic structures and high mobility on the substrate surface. By varying cluster sizes and substrate temperatures, this study also reveals that smaller clusters and higher substrate temperatures contribute to faster structural ordering and smoother surface morphologies. Furthermore, the formed layers display a consistent SiGe composition, closely aligning with nominal values, and the cluster-assisted deposition method achieves the epitaxial bridging of heterostructures during cluster impingement, highlighting its additional distinctive characteristics. The implications of this work make it clear that the mechanism of fast alloyed epitaxial film growth by cluster-assisted mesoplasma CVD is critical for extending it as a versatile platform for synthesizing various epitaxial films.

In this paper, numerical simulations of single-jet impingement cooling and double-jet impingement cooling processes of heated L-shaped steel are carried out using the VOF model. The SIMPLEC pressure-velocity coupling algorithm and realizable k-ε model are used for the solution. The effects of jet position, water flow, and jet distance in the single-jet condition are analyzed in the simulations. The distributions of impact pressure, turbulence kinetic energy, and Nusselt number were obtained, as well as the variation of the peak values of these three factors with the jet position, water flow, and jet distance. The water flow rate is 3-11 L/min, and the jet distance is 5-25 cm. The effect of the distance between the two nozzles on the jet cooling uniformity under the dual jet condition was also analyzed. The distance between the two nozzles was 15-45 mm. The results showed that the variation of water flow rate had a greater effect on the ability of jet cooling compared with the jet position and jet distance, and the heat transfer efficiency also increased gradually with the increase of water flow, but the increased rate of heat transfer efficiency decreased gradually. When the flow rate increased from 3 to 11 L/min, the maximum instantaneous cooling rates at 1/4 of the thickness of the short side upper side, long side upper side, short side lower side, and long side lower side positions increased by 38.9%, 48.5%, 48.2%, and 32.9%, respectively. To ensure that the jet does not shift, the jet distance should be less than or equal to 10 cm. In the case of the double jet, the nozzle distance is 1.5 cm, and the cooling uniformity of the cooling area between the two nozzles is better. The peak Nusselt number in the cooling area of each part under the double jet cooling condition increased by 5%, 9.4%, 10.2%, and 13.3%, respectively, compared with the single jet.

UNASSIGNED: The aim was to evaluate the effects of different glenosphere eccentricities on impingement, range of motion (ROM), and muscle length during standard activities in reverse total shoulder arthroplasty (RSA).
UNASSIGNED: In this study, we utilized computational modeling techniques to create native shoulder and shoulder models undergoing RSA and simulate shoulder movements in all abduction-adduction, flexion-extension, and rotation. We tested a total of 36 different glenosphere configurations, which included three different inferior tilts (0°, +10°, +20°) and two different lateral offsets (0 mm and +4 mm), as well as six different glenosphere eccentricities (concentricity, inferior, posterior, anterior, anteroinferior, and posteroinferior). We evaluated the maximum impingement-free ROM, impingement sites, and muscle lengths.
UNASSIGNED: All glenosphere configurations exceeded 50% of native shoulder ROM in three planes and total global ROM. In abduction-adduction, there was no significant difference among the different glenosphere eccentricities (p > 0.05). In flexion-extension, the posteroinferior eccentricity had the maximum ROM among the different eccentricities, but no significant difference among the different glenosphere eccentricities (p > 0.05). In rotation, there was a significant difference overall, and anteroinferior eccentricity had a significant advantage over concentricity (p < 0.05). In total global ROM, anteroinferior eccentricity had a significant advantage over concentricity when lateral offset was 0 mm (p < 0.05). In all models of glenosphere eccentricities, only the elongation of the infraspinatus muscle was statistically significant (p < 0.05).
UNASSIGNED: Glenosphere eccentricity significantly influenced rotation, total global ROM, and the length of the subscapularis muscle. Among them, anteroinferior offset achieved the maximum ROM in abduction-adduction, rotation, and total global activities. Both anteroinferior and inferior glenoid eccentricity showed significant advantages over the concentricity in rotation and total global ROM.
UNASSIGNED: Basic Science Study; Computer Modeling.

Background: Dissociation of the polyethylene liner after reverse shoulder arthroplasty could cause shoulder dislocation that could not achieve closed reduction. The cause of liner dissociation is currently unclear. Method: Non-homogeneous model of the bone was constructed and dynamic finite element analysis was utilized to simulate the impingement of the polyethylene liner and scapula during humeral adduction. The stress distribution of the fixation claws, their degree of deformation (DOD), and the stress of the impingement sites in three initial humeral postures (neutral, 30° flexion, and 30° extension) were measured and analyzed. The influence of the liner material stiffness was also investigated. Result: The impingement stress on the liner and scapula was 100-200 MPa, and different humeral postures caused different locations of impingement points. The fixation claws\' maximum principal stress (MPS) results were below 5 MPa. In the connection area between some fixation claws and the liner, compressive stresses on the inside and tensile stresses on the outside were observed, which showed that the fixation claws were prone to deform toward the center direction. The maximum DOD results of three initial humeral postures (neutral, 30° flexion, and 30° extension) were 3.6%, 2.8%, and 3.5%, respectively. The maximum DOD results of neutral initial humeral posture were 0.51% and 11.4% when the elastic modulus of the liner was increased and decreased by a factor of 10, respectively. Conclusion: The humeral adduction impingement could lead to the deformation of the claw-shaped liner fixation structure, which might be one of the reasons for the liner dissociation. The increased stiffness of the liner material helped to reduce the deformation of the fixation structure.

BACKGROUND: Subacromial impingement of the rotator cuff caused by variations in acromial anatomy or altered glenohumeral kinematics leads to inflammation and degeneration of the rotator cuff, ultimately contributing to the development of tendinopathy. However, the underlying cellular and molecular changes in the impinged tendon remain poorly understood. Because the rat is an accepted model for rotator cuff studies, we have developed a rat model to study rotator cuff tendinopathy.
METHODS: Forty-four adult male Sprague-Dawley rats were allocated to one of 4 study groups: intact control group (group 1, n = 11); bilateral subacromial surgical clip placement to induce supraspinatus impingement for 2 weeks (group 2, n = 11), 4 weeks (group 3, n = 11), and 8 weeks (group 4, n = 11). Bilateral shoulder specimens were harvested for biomechanical testing, histology, and quantitative real-time polymerase chain reaction (qRT-PCR) analysis.
RESULTS: Radiography confirmed that all microvascular clips remained in stable position in the subacromial space. Gross inspection of supraspinatus tendon specimens in the impingement groups revealed changes in tendon morphology at the enthesis and midsubstance. Biomechanical evaluation demonstrated decreased supraspinatus tendon failure force and tissue stiffness at all time points compared with control tendons. Semiquantitative scoring of histologic specimens demonstrated significant, persistent tendinopathic changes over 8 weeks. qRT-PCR analysis of impinged tendon specimens demonstrated upregulation of gene expression for Col3 and Mmp14 in the impingement groups compared with control groups. In muscle samples, significant upregulation was seen in the expression of genes that are commonly associated with muscle atrophy (MuRF1 and Ube2b) and fatty infiltration (Fabp4, Pparg2, and Klf15).
CONCLUSIONS: This new rat subacromial impingement model creates cellular and molecular changes consistent with the development of rotator cuff tendinopathy. The results of this study may serve as a baseline for future investigation.

BACKGROUND: Lipped or elevated acetabular liners are to improve posterior stability and are widely used in hip arthroplasty. However, concerns of increasing impingement exist when using such liners and optimal orientation of the elevated rim remains unknown. We aimed to identify the impact of lipped liner on the range of motion (ROM) before impingement and propose its optimal orientation.
METHODS: An isochoric three-dimensional model of a general hip-replacement prosthesis was generated, and flex-extension, add-abduction and axial rotation were simulated on a computer. The maximum ROM of the hip was measured before the neck impinged on the liner. Different combinations of acetabular anteversion angles ranging from 5 to 30 degrees, and lipped liner orientations from posterior to anterior were tested.
RESULTS: When acetabular anteversion was 10 or 15 degrees, placing the lip of the liner in the posterosuperior of the acetabulum allowed satisfactory ROM in all directions. When acetabular anteversion was 20 degrees, extension and external rotation were restricted. Adjusting the lip to the superior restored satisfactory ROM. When acetabular anteversion was 25 degrees, only placing the lip into the anterosuperior could increase extension and external rotation to maintain satisfactory ROM.
CONCLUSIONS: This study showed that optimal lipped liner orientation should depend on acetabular anteversion. When acetabular anteversion was smaller than 20 degrees, placing lip in the posterior allowed an optimally ROM. When acetabular anteversion was greater than 20 degrees, adjusting lip to the anterior allowed a comprehensive larger ROM to avoid early impingement.

BACKGROUND: The present study aimed to use magnetic resonance (MR) to explore the dynamic changes of the ischiofemoral space (IFS) under the triaxial motion of the hip joint and verify the clinical test mechanism for ischiofemoral impingement (IFI).
METHODS: A prospective design was used to screen 37 patients with clinically confirmed IFI, which included a total of 67 lateral hips, and 39 healthy controls with a total of 69 lateral hips. A dynamic MR examination was performed in positions designed by a simulated IFI test (adduction, adduction with 30° external rotation, 30° internal rotation, supine with 30° flexion, and prone with 30° backward extension). The IFS (mm) and quadratus femoris space (QFS, mm) were measured in different positions. All the data were evaluated independently by three musculoskeletal radiologists. The differences between the two groups were compared using the two-tailed t-test.
RESULTS: The IFS and QFS in the case group were smaller than those in the control group. The IFS and QFS were significantly reduced in the prone with backward extension and adduction with external rotation positions of the hip. The correlation coefficients of the IFI test and long-stride walking (LSW) test were -0.621 and -0.715 for IFS and -0.653 and -0.696 for QFS, respectively.
CONCLUSIONS: In this study, the mechanism of the IFI-specific clinical examination (IFI and LSW tests) was verified by triaxial dynamic MR imaging of the hip joint, which provided a dynamic imaging basis for the clinical application of the IFI-specific impingement test. The IFI impingement test can be used as a specific clinical test for IFI screening.

BACKGROUND: The underlying cellular and molecular mechanisms involved in the development of tendinopathy due to subacromial supraspinatus tendon (SST) impingement and the response to subsequent removal of impingement remain unknown.
OBJECTIVE: To investigate the involvement of Indian hedgehog (IHH) signaling in the development of SST tendinopathy and the subsequent healing process after the relief of subacromial impingement in a novel mouse shoulder impingement model.
METHODS: Controlled laboratory study.
METHODS: A total of 48 male wild-type C57BL/6 mice were used in this study. Supraspinatus tendinopathy was induced by inserting a microsurgical clip into the subacromial space bilaterally. Eleven mice were sacrificed at 4 weeks after surgery to establish impingement baseline; 24 mice underwent clip removal at 4 weeks after surgery and then were euthanized at 2 or 4 weeks after clip removal. Thirteen mice without surgical intervention were utilized as the control group. All SSTs were evaluated with biomechanical testing; quantitative histomorphometry after staining with hematoxylin and eosin, Alcian blue, and picrosirius red; and immunohistochemical staining (factor VIII, IHH, Patched1 [PTCH1], and glioma-associated oncogene homolog 1 [GLI1]).
RESULTS: The mean failure force and stiffness in the 4-week impingement group decreased significantly compared with the control group (P < .001) and gradually increased at 2 and 4 weeks after clip removal. Histological analysis demonstrated increased cellularity and disorganized collagen fibers in the SST, with higher modified Bonar scores at 4 weeks, followed by gradual improvement after clip removal. The IHH-positive area and PTCH1- and GLI1-positive cell percentages significantly increased after 4 weeks of clip impingement (20.64% vs 2.06%, P < .001; 53.9% vs 28.03%, P = .016; and 30% vs 12.19%, P = .036, respectively) and continuously increased after clip removal.
CONCLUSIONS: The authors\' findings suggest that the hedgehog signaling pathway and its downstream signaling mediator and target GLI1 may play a role in the development and healing process of rotator cuff tendinopathy due to extrinsic rotator cuff impingement.
CONCLUSIONS: This study suggests the potential for the hedgehog pathway, together with its downstream targets, as candidates for further study as potential therapeutic targets in the treatment of supraspinatus tendinopathy.

The report of COVID-19 virus in municipal wastewater raises the question of whether viruses can become airborne during wastewater transport in sewer systems. The present work experimentally investigates a water jet impinging vertically onto a horizontal plate and the behaviours of the generated tiny droplets. Depending on whether the jet breaks into primary drops before the impingement, three regimes can be defined: non-splashing, jet-splashing and drop-splashing regimes. The splashing ratio, i.e., the portion of jet flow rate becoming splashing droplets, ranges from 1% to 70% in the drop-splashing regime, while it remains less than 2% in the jet-splashing regime. For the splashing droplets, their size and velocity distributions follow log-normal laws. Their diameters are mainly in the range from 0 to 0.3 of the impact jet or drop diameter with the median less than 0.1. Their velocities mostly range from 0 to 3.0 times of the impact velocity with the median around 1.0. The medians of both the dimensionless diameter and velocity of splashing droplets decrease with the impact Weber number. The ejection angles of splashing droplets obey a bell-shaped distribution with the maximum around 70° and the median ranging from 16° to 30°.

UNASSIGNED: Graft impingement is one of the main concerns in double-bundle anterior cruciate ligament reconstruction (DB-ACLR). Impingement between the anteromedial (AM) and posterolateral (PL) bundles has been postulated to cause graft deterioration or rerupture, but this has not been thoroughly investigated, and the interbundle impingement pressure (IIP) has not been well researched.
UNASSIGNED: To determine the IIP between the AM and PL bundles in the native anterior cruciate ligament (ACL) and in DB-ACLR with individualized and nonindividualized double-tunnel placement.
UNASSIGNED: Controlled laboratory study.
UNASSIGNED: A total of 30 fresh-frozen, nonpaired, human cadaveric knees were randomly divided into 3 groups of 10 knees: native intact ACL (NI group), DB-ACLR tunnel placement using the preserved remnant procedure (individualized reconstruction) (PR group), and DB-ACLR tunnel placement using the bony landmark procedure (nonindividualized reconstruction) (BL group). Pressure sensors were inserted between the AM and PL bundles. The knee was moved passively from full extension to full flexion, and the IIP between the 2 ACL bundles was measured every 15°. Similarly, the impingement pressure was measured between the ACL and intercondylar roof and between the ACL and posterior cruciate ligament (PCL).
UNASSIGNED: No significant differences were found in the maximum, mean, or minimum ACL-roof and ACL-PCL impingement pressures among the 3 groups. The IIP significantly increased when the knee joint was flexed >120° in all 3 groups (P < .001). Compared with the other 2 groups, the BL group had significantly higher maximum and mean IIP throughout the range of knee movement (P < .001) and from maximum extension to 120° of flexion (P < .001). The BL group also had significantly higher minimum IIP than the other 2 groups when knee flexion was >120° (P < .001). No significant differences were seen in maximum, minimum, or mean IIP between the NI and PR groups.
UNASSIGNED: The PR procedure (individualized DB-ACLR) was more consistent with the interbundle biomechanical conditions of the native ACL, whereas the BL procedure (nonindividualized DB-ACLR) had higher maximum and mean IIP. The IIP was higher than the ACL-intercondylar roof or ACL-PCL pressures, and it increased significantly when knee flexion was >120°.
UNASSIGNED: These data suggest that surgeons can perform individualized DB-ACLR using preserved remnants for tunnel placement as impingement-free DB-ACLR.