Meniscus Surface Research Articles

Ультразвуковые предикторы прогрессирования рентгенологически нулевой стадии остеоартроза в рентгенопозитивную 1 стадию

The purpose of the study is to estimate of probable predictors for the probable predictors of
 knee joint osteoarthritis progression in X-ray negative stage based on ultrasound examination.
 The sixty five patients with X-ray negative gonarthritis were selected into the study. Both X-ray and ultrasound
 examinations were performed for each of the patients (before the study and since one year). The authors
 determined degeneration of the medial meniscus and articular surfaces roughness had the most degree of sensitivity
 (91%), and cartilage thickness of medial joint parts (86%). The degenerative changes of the posterior cruciate
 ligament had the lowest sensitivity (42%), and degeneration in the lateral meniscus (47%). During the regression
 analysis only two quality indicator such as cartilage thickness of the medial parts, and articular surfaces
 brought significant contribution to the risk prediction of the osteoarthritis progression (odds ratio=22.7 and 71.4;
 p=0.018 and 0.002, respectively). The degeneration in the anterior cruciate ligament was not significant for the
 model (odds ratio= 26,3; p=0.05).

The meniscal insertion of the knee anterolateral ligament.

The aim of this study is to characterize in detail the meniscal insertion of the anterolateral ligament (ALL) of the knee, establishing parameters regarding the circumference of the lateral meniscus and the popliteal muscle tendon (PMT) groove in addition to its histological analysis. A total of 33 knees of cadavers were dissected. The ALL and the lateral meniscus were removed en bloc. After removal of the anatomical specimen, the meniscus circumference, the ALL insertion points on the external surface of the lateral meniscus, and the PMT groove were measured. Eight menisci were subjected to histological analysis. The ALL was found in all dissections performed. The ALL insertion occurred macroscopically in the transition between the anterior horn and the lateral meniscus body, specifically beginning at 36.0% and ending at 41.9% of the meniscal circumference, occupying a mean area of 5.6 mm. The distance between the end of the ALL meniscal insertion and the beginning of the PMT groove averaged 12.9 mm. In the histological evaluation, in longitudinal sections, we observed dense collagen fibers of the ligament inserting on the external surface of the meniscus. It is possible to observe a spreading of collagen fibers at the moment of meniscal insertion. The ALL meniscal insertion was found in all dissected specimens, beginning with approximately 36% of the meniscal outer diameter, 12.9 mm anterior to the beginning of the PMT groove. The histological analysis confirmed the presence of true ligamentous tissue in the dissected specimens.

Mesure des allogreffes méniscales par microtomographies radiographiques

BackgroundX-ray microcomputed tomography (XMT) is a technique widely used to image hard and soft tissues. Meniscal allografts as collagen structures can be imaged and analyzed using XMT. The aim of this study was to present an XMT scanning protocol that can be used to obtain the 3D geometry of menisci. It was further applied to compare two methods of meniscal allograft measurement: traditional (based on manual measurement) and novel (based on digital measurement of 3D models of menisci obtained with use of XMT scanner). HypothesisThe XMT-based menisci measurement is a reliable method for assessing the geometry of a meniscal allograft by measuring the basic meniscal dimensions known from traditional protocol. Materials and methodsThirteen dissected menisci were measured according to the same principles traditionally applied in a tissue bank. Next, the same specimens were scanned by a laboratory scanner in the XMT lab. The images were processed to obtain a 3D mesh. Three-dimensional models of allograft geometry were then measured using a novel protocol enhanced by computer software. Then, both measurements were compared using statistical tests. ResultsThe results showed significant differences (P<0.05) between the lengths of the medial and lateral menisci measured in the tissue bank and the XMT Lab. Also, medial meniscal widths were significantly different (P<0.05). DiscussionDifferences in meniscal lengths may result from difficulties in dissected meniscus measurements in tissue banks, and may be related to the elastic structure of the dissected meniscus. Errors may also be caused by the lack of highlighted landmarks on the meniscal surface in this study. ConclusionThe XMT may be a good technique for assessing meniscal dimensions without actually touching the specimen. Level of evidenceLevel IV.

Meniscal and Articular Cartilage Predictors of Clinical Outcome following Revision ACL Reconstruction

Objectives:Revision ACL reconstruction has been documented to have worse outcomes compared with primary ACL reconstructions. The reasons why remain unknown. The purpose of this study was to determine if both the prevalence and/or degree of meniscal and chondral damage noted at the time of ACL revision reconstruction predicts activity level, sports function, and OA symptoms at two year follow-up.Methods:Revision ACL reconstruction patients were identified and prospectively enrolled between 2006 and 2011. Data collected included baseline demographics, surgical technique and pathology, and a series of validated patient reported outcome instruments (IKDC, KOOS, WOMAC, and Marx activity rating score). Patients were followed up for 2 years, and asked to complete the identical set of outcome instruments. Regression analysis was used to control for age, gender, BMI, smoking status, activity level, baseline outcome scores, revision number, time since last ACLR, previous and current meniscal and articular cartilage pathology, in order to assess the meniscal and AC pathology risk factors for clinical outcomes 2 years after revision ACL reconstruction.Results:1205 patients met the inclusion criteria and were successfully enrolled. 697 (58%) were males, with a median cohort age of 26 years. The median time since their last ACL reconstruction was 3.4 years. Surgeons noted previous pathology in the medial meniscus (39%), lateral meniscus (20%), and articular surfaces (12%) at the time of revision surgery. Surgeons reported current pathology in the medial meniscus (45%), lateral meniscus (37%), MFC (43%), LFC (29%), MTP (11%), LTP (17%), patella (30%), and trochlea (20%). At 2 years, follow-up was obtained on 82% (989/1205). Previous meniscal pathology (both medial and lateral), as well as current AC pathology (in the MFC, LFC, MTP, LTP, and trochlea) were found to be significant drivers of poorer outcomes at 2 years (Table 1). The most consistent cartilage-related factors driving outcome in revision patients were previous lateral meniscus pathology and current trochlea AC pathology. Having a previous excision on the lateral meniscus resulted in significantly poorer outcomes on the IKDC (odds ratio=1.69; 95% CI=1.16-2.44; p=0.005), all KOOS subscales (OR range=1.54-2.08; 95% CI=1.04-3.03; p<0.029), and all WOMAC subscales (OR=1.56; 95% CI=1.06-2.27; p=0.02). Having a current Grade 3-4 AC chondrosis of the trochlea resulted in significantly poorer outcomes in the IKDC (OR=1.89; 95% CI=1.25-2.94; p-0.003), 4 of 5 KOOS subscales (OR range = 1.64-2.70; 95% CI=1.09-4.17; p<0.02), and 2 of 3 WOMAC subscales (OR range = 1.61-2.70; 95% CI=1.04-4.17; p<0.03). Lower baseline outcome scores, lower baseline activity level, and shorter time since the patient’s last ACL reconstruction all significantly increased the odds of reporting poorer clinical outcomes at 2 years. Meniscal and AC pathology was not found to be a significant risk factor for 2 year activity levels. Interestingly, previous AC pathology and current meniscal pathology were not found to be significant risk factors for 2 year outcomes in this revision cohort.Conclusion:Having a previous meniscal excision, as well as grade 3-4 chondral damage noted at the time of ACL revision reconstruction results in decreased sports outcome scores and worse WOMAC scores at two years following revision surgery. However, incidence of meniscal and AC pathology was not found to be a predictor of a patient’s activity level at 2 years.

Biomechanical properties of murine meniscus surface via AFM-based nanoindentation

This study aimed to quantify the biomechanical properties of murine meniscus surface. Atomic force microscopy (AFM)-based nanoindentation was performed on the central region, proximal side of menisci from 6- to 24-week old male C57BL/6 mice using microspherical tips (Rtip≈5µm) in PBS. A unique, linear correlation between indentation depth, D, and response force, F, was found on menisci from all age groups. This non-Hertzian behavior is likely due to the dominance of tensile resistance by the collagen fibril bundles on meniscus surface that are mostly aligned along the circumferential direction. The indentation resistance was calculated as both the effective modulus, Eind, via the isotropic Hertz model, and the effective stiffness, Sind = dF/dD. Values of Sind and Eind were found to depend on indentation rate, suggesting the existence of poro-viscoelasticity. These values do not significantly vary with anatomical sites, lateral versus medial compartments, or mouse age. In addition, Eind of meniscus surface (e.g., 6.1±0.8MPa for 12 weeks of age, mean±SEM, n=13) was found to be significantly higher than those of meniscus surfaces in other species, and of murine articular cartilage surface (1.4±0.1MPa, n=6). In summary, these results provided the first direct mechanical knowledge of murine knee meniscus tissues. We expect this understanding to serve as a mechanics-based benchmark for further probing the developmental biology and osteoarthritis symptoms of meniscus in various murine models.

X-ray microtomography-based measurements of meniscal allografts

BackgroundX-ray microcomputed tomography (XMT) is a technique widely used to image hard and soft tissues. Meniscal allografts as collagen structures can be imaged and analyzed using XMT. The aim of this study was to present an XMT scanning protocol that can be used to obtain the 3D geometry of menisci. It was further applied to compare two methods of meniscal allograft measurement: traditional (based on manual measurement) and novel (based on digital measurement of 3D models of menisci obtained with use of XMT scanner). HypothesisThe XMT-based menisci measurement is a reliable method for assessing the geometry of a meniscal allograft by measuring the basic meniscal dimensions known from traditional protocol. Materials and methodsThirteen dissected menisci were measured according the same principles traditionally applied in a tissue bank. Next, the same specimens were scanned by a laboratory scanner in the XMT Lab. The images were processed to obtain a 3D mesh. 3D models of allograft geometry were then measured using a novel protocol enhanced by computer software. Then, both measurements were compared using statistical tests. ResultsThe results showed significant differences (P<0.05) between the lengths of the medial and lateral menisci measured in the tissue bank and the XMT Lab. Also, medial meniscal widths were significantly different (P<0.05). DiscussionDifferences in meniscal lengths may result from difficulties in dissected meniscus measurements in tissue banks, and may be related to the elastic structure of the dissected meniscus. Errors may also be caused by the lack of highlighted landmarks on the meniscal surface in this study. ConclusionThe XMT may be a good technique for assessing meniscal dimensions without actually touching the specimen. Level of evidenceLevel IV.

Osteochondral defect repair using a polyvinyl alcohol-polyacrylic acid (PVA-PAAc) hydrogel

Poly(vinyl alcohol) (PVA) hydrogels can be candidates for articular cartilage repair due to their high water content. We synthesized a PVA-poly(acrylic acid) (PAAc) hydrogel formulation and determined its ability to function as a treatment option for condylar osteochondral (OC) defects in a New Zealand white rabbit (NZWR) model for 12 weeks and 24 weeks. In addition to hydrogel OC implants, tensile bar-shaped hydrogels were also implanted subcutaneously to evaluate changes in mechanical properties as a function of in vivo duration. There were no statistically significant differences (p > 0.05) in the water content measured in the OC hydrogel implant that was harvested after 12 weeks and 24 weeks, and non-implanted controls. There were no statistically significant differences (p > 0.05) in the break stress, strain at break or modulus of the tensile bars either between groups. Histological analysis of the OC defect, synovial capsule and fibrous tissue around the tensile bars determined hydrogel biocompatibility. Twelve-week hydrogels were found to be in situ flush with the articular cartilage; meniscal tissue demonstrated an intact surface. Twenty-four week hydrogels protruded from the defect site due to lack of integration with subchondral tissue, causing fibrillation to the meniscal surface. Condylar micro-CT scans ruled out osteolysis and bone cysts of the subchondral bone, and no PVA-PAAc hydrogel contents were found in the synovial fluid. The PVA-PAAc hydrogel was determined to be fully biocompatible, maintained its properties over time, and performed well at the 12 week time point. Physical fixation of the PVA-PAAc hydrogel to the subchondral bone is required to ensure long-term performance of hydrogel plugs for OC defect repair.

Effect of disjoining pressure (Π) on multi-scale modeling for evaporative liquid metal (Na) capillary

This work presents a new multiscale model of an evaporating liquid metal capillary meniscus under nonequilibrium evaporation sustaining a nonisothermal interface. The primary investigation is elaborated on to examine the critical role of the disjoining pressure, which consists of both the traditional van der Waals component and a new electronic pressure component, for the case of liquid metals. The fully extended dispersion force is modeled along with an electronic disjoining pressure component that is unique to liquid metals attributing to their abundant free electrons. For liquid sodium (Na), as a favorable coolant for high temperature two-phase devices, the extended meniscus thin film model (sub-microscale) is coupled to a CFD model of the evaporating bulk meniscus (sub-millimeter scale). Two extreme cases are compared, i.e. with or without incorporation of the electronic disjoining pressure component. It is shown that the existence of electronic component of the disjoining pressure leads towards larger total capillary meniscus surface areas and larger net evaporative mass flow rates. Furthermore, the net evaporative mass flux in the bulk meniscus region is needed to be accounted for to obtain a true picture of the total capillary evaporation transport.

Influence of partial meniscectomy on attachment forces, superficial strain and contact mechanics in porcine knee joints

Numerous studies investigated the reasons for premature osteoarthritis due to partial meniscectomy (PM). However, the influence of meniscectomy on attachment forces and superficial strain of the tibial meniscus is unclear. It is hypothesised that these parameters depend on the degree of PM. Six porcine medial menisci were placed in a custom made apparatus, and each meniscal attachment was connected to a force sensor. After printing markers onto the tibial meniscal surfaces, the menisci were positioned on a glass plate enabling optical superficial strain measurement. Additionally, contact area and pressure were investigated. Each meniscus was axially loaded up to 650 N using its respective femoral condyle. Testing was conducted intact and after 50 and 75% PM of the posterior horn and extending 75% PM to the anterior horn. With increasing meniscectomy, the attachment forces decreased anteriorly by up to 17% (n.s.) and posteriorly by up to 55% (p = 0.003). The circumferential strain in the peripheral meniscal zones was not affected by the meniscectomy, while in some meniscal zones the radial strain changed from compression to tension. Contact area decreased by up to 23% (p = 0.01), resulting in an increase in 40% (p = 0.02) for the maximum contact pressure. Partial meniscectomy significantly alters the loading situation of the meniscus and its attachments. Specifically, the attachment forces decreased with increasing amount of meniscal tissue loss, which reflects the impaired ability of the meniscus to transform axial joint load into meniscal hoop stress.

Younger Patients Are at Increased Risk for Graft Rupture and Contralateral Injury After Anterior Cruciate Ligament Reconstruction

Background: Graft rupture of the same knee or injury to the anterior cruciate ligament (ACL) in the contralateral knee is a devastating outcome after ACL reconstruction surgery. While a number of factors have been identified as potentially increasing the risk of subsequent ACL injury, the literature is far from definitive. Purpose: To determine the rates of graft rupture and contralateral ACL injury in a large cohort and to investigate patient characteristics that may be associated with these. Study Design: Case-control study; Level of evidence, 3. Methods: A consecutive cohort of 750 patients who had undergone primary ACL reconstruction surgery with a minimum 3-year follow-up were questioned about the incidence of ACL graft rupture, contralateral ACL injury, family history of ACL injury, and current activity level. Patient databases provided details for age, sex, original injury mechanism, meniscus or articular surface injury, and graft diameter. Results: Responses were received from 561 patients (75%) at a mean ± SD follow-up time of 4.8 ± 1.1 years. Anterior cruciate ligament graft ruptures occurred in 25 patients (4.5%), and contralateral ACL injuries occurred in 42 patients (7.5%). The highest incidence of further ACL injury occurred in patients younger than 20 years at the time of surgery. In this group, 29% sustained a subsequent ACL injury to either knee. The odds for sustaining an ACL graft rupture or contralateral injury increased 6- and 3-fold, respectively, for patients younger than 20 years. Returning to cutting/pivoting sports increased the odds of graft rupture by a factor of 3.9 and contralateral rupture by a factor of 5. A positive family history doubled the odds for both graft rupture and contralateral ACL injury. Conclusion: Patients younger than 20 years who undergo ACL reconstruction are at significantly increased risk for both graft rupture and contralateral ACL injury. Whether age per se is a risk factor or age represents a proxy for other factors remains to be determined.

Enhanced boundary lubrication properties of engineered menisci by lubricin localization with insulin-like growth factor I treatment

In this study we analyzed the effects of IGF-I on the boundary lubricating ability of engineered meniscal tissue using a high density collagen gel seeded with meniscal fibrochondrocytes. Biochemical, histological, immunohistochemical, and tribological analyses were carried out to determine a construct's ability to functionally localize lubricin. Our study revealed that supplementation with IGF-I enhanced both the proliferation of cells within the construct as well as enhanced the anabolic activity of the seeded cells. Growth factor supplementation also facilitated the localization of ECM constituents (i.e. fibronectin and type II collagen) near the tissue surface that are important for the localization of lubricin, a boundary lubricant. Consequently, we found localized lubricin in the constructs supplemented with IGF-I. Tribologically, we demonstrated that lubricin serves as a boundary lubricant adsorbed to native meniscal surfaces. Lubricin removal from the native meniscus surface increased boundary friction coefficient by 40%. For the engineered constructs, the lubricin localization facilitated by growth factor supplementation also reduced friction coefficient by a similar margin, but similar results were not evident in control constructs. This study demonstrates that the use of growth factors in meniscal tissue engineering can enhance tribological properties by facilitating the localization of boundary lubricants at the surface of engineered tissue.

Shape and volume of liquid meniscus at the surface of a specimen

The change in the liquid meniscus at the surface of a specimen (rectangular or cylindrical) being lifted from water and immersed into it is considered. An equation for the meniscus surface is given, and the boundary conditions of its existence are determined. The solution of this equation describes the shape of the meniscus at all stages of its displacement from the vertical surface of a specimen to its upper and lower planes. The solution agrees with the data of observations. Dependences of the profile area and volume of a meniscus on its height have been obtained. The relationship between the meniscus parameters at the instant of its collapse and the contact angle is given. The meniscus parameters for a standard cylindrical specimen have been estimated. A typical curve of the change in the meniscus weight depending on its height is given. It can be employed for assessing the contact angle on a rough surface of a specimen.

Joint TGF-β Type II Receptor-Expressing Cells: Ontogeny and Characterization as Joint Progenitors

TGF-β type II receptor (Tgfbr2) signaling plays an essential role in joint-element development. The Tgfbr2(PRX-1KO) mouse, in which the Tgfbr2 is conditionally inactivated in developing limbs, lacks interphalangeal joints and tendons. In this study, we used the Tgfbr2-β-Gal-GFP-BAC mouse as a LacZ/green fluorescent protein (GFP)-based read-out to determine: the spatial and temporally regulated expression pattern of Tgfbr2-expressing cells within joint elements; their expression profile; and their slow-cycling labeling with bromodeoxyuridine (BrdU). Tgfbr2-β-Gal activity was first detected at embryonic day (E) 13.5 within the interphalangeal joint interzone. By E16.5, and throughout adulthood, Tgfbr2-expressing cells clustered in a contiguous niche that comprises the groove of Ranvier and the synovio-entheseal complex including part of the perichondrium, the synovium, the articular cartilage superficial layer, and the tendon's entheses. Tgfbr2-expressing cells were found in the synovio-entheseal complex niche with similar temporal pattern in the knee, where they were also detected in meniscal surface, ligaments, and the synovial lining of the infrapatellar fat pad. Tgfbr2-β-Gal-positive cells were positive for phospho-Smad2, signifying that the Tgfbr2 reporter was accurate. Developmental-stage studies showed that Tgfbr2 expression was in synchrony with expression of joint-morphogenic genes such as Noggin, GDF5, Notch1, and Jagged1. Prenatal and postnatal BrdU-incorporation studies showed that within this synovio-entheseal-articular-cartilage niche most of the Tgfbr2-expressing cells labeled as slow-proliferating cells, namely, stem/progenitor cells. Tgfbr2-positive cells, isolated from embryonic limb mesenchyme, expressed joint progenitor markers in a time- and TGF-β-dependent manner. Our studies provide evidence that joint Tgfbr2-expressing cells have anatomical, ontogenic, slow-cycling trait and in-vivo and ex-vivo expression profiles of progenitor joint cells.

Reverse roll-coating flow: a computational investigation towards high-speed defect free coating

A finite element Taylor–Galerkin pressure-correction algorithm is employed to simulate a high-speed defect-free roll-coating flow, which substantiates a coating process with a free meniscus surface. Findings are applicable across a wide range of coating sectors in optimisation of coating performance, which targets adaptive and intelligent process control. Industrially, there is a major drive towards using new material products and raising coating line-speeds, to address increased efficiency and productivity. This study has sought to attack these issues by developing an effective predictive toolset for high-speed defect-free coatings. Here, time-stepping/finite element methods are deployed to model this free-surface problem that involves the transfer of a coating fluid from a roller to a substrate (of prescribed wet-film thickness). This procedure is used in conjunction with a set of constitutive equations capable of describing the relevant fluid-film rheology in appropriate detail. Quantities of pressure, lift and drag have been calculated streamwise across the flow domain, and streamline patterns reveal a large recirculating vortex around the meniscus region. Such pressure distributions across the domain display a positive peak which decreases as nip-gap size increases. Further analysis has been conducted, mimicking the presence of a wetting line, whilst varying boundary conditions at the nip. Observation has shown that such inclusion would serve as a relief mechanism to the positive peak pressures generated around the nip zone. Here, through an elasto-hydrodynamic formulation, the elastic deformation of a rubber roll cover (elastomer) has also been introduced, which offers fresh insight into the process with respect to nip-flow behaviour, and allows for the analysis of both positive and negative nip-gaps.

Indentation properties and glycosaminoglycan content of human menisci in the deep zone

Menisci are two crescent shaped fibrocartilaginous structures that provide fundamental load distribution and support within the knee joint. Their unique shape transmits axial stresses (i.e. “body force”) into hoop or radial stresses. The menisci are primarily an inhomogeneous aggregate of glycosaminoglycans (GAGs) supporting bulk compression and type I collagen fibrils sustaining tension. It has been shown that the superficial meniscal layers are functionally homogeneous throughout the three distinct regions (anterior, central and posterior) using a 300μm diameter spherical indenter tip, but the deep zone of the meniscus has yet to be mechanically characterized at this scale. Furthermore, the distribution and content of GAG throughout the human meniscal cross-section have not been examined. This study investigated the mechanical properties, via indentation, of the human deep zone meniscus among three regions of the lateral and medial menisci. The distribution of GAGs through the cross-section was also documented. Results for the deep zone of the meniscus showed the medial posterior region to have a significantly greater instantaneous elastic modulus than the central region. No significant differences in the equilibrium modulus were seen when comparing regions or the hemijoint. Histological results revealed that GAGs are not present until at least ∼600μm from the meniscal surface. Understanding the role and distribution of GAG within the human meniscus in conjunction with the material properties of the meniscus will aid in the design of tissue engineered meniscal replacements.

Clinico-radiological correlation in the diagnosis of ligament and meniscus injuries at knee joint: A prospective study

Purpose: The purpose of this study was to determine the MRI appearances and various patterns of ligament and meniscus tears in knee joint injuries and to correlate the clinical findings with MRI findings. Materials and Methods: Our study included 50 patients, who were referred to radiology department for MRI of knee joint following injury. Prior to MRI, a detailed clinical and local examination was done in all the subjects. MRI was carried out on MAGNETOM Avanto 18 Channel 1.5 Tesla Machine by Siemens India Ltd and the standard protocol consisted of PD(TE 45 TR 2800), T2W(TE 73 TR 5090), fat suppressed T2W(TE 26 TR 5000) spin echo sequences in axial, sagittal and coronal planes. The MRI findings were compared with arthroscopic findings in 30 subjects and in rest of the subjects characteristic MRI features were considered diagnostic. Results: Diagnostic accuracy of clinical examination (83%) was relatively low as compared to MR examination (88%) in our study. The percentage correlation between clinical and MRI findings regarding presence or absence of ligament/meniscus tear was highest in case of PCL tears (94%). Amongst ligament injuries, complete tear of ACL alone was the most common injury (53%) and ACL injury was most commonly associated with MM injury (16%), intrasubstance tears were more common than attachment site tears. Conclusions: MR is unique in its ability to evaluate the architecture as well as the surface of ligaments and menisci. MRI is more sensitive than clinical examination in diagnosing ligament and meniscus injuries.

Numerical Simulation of Fluid Flow in a Round Bloom Mold with In-Mold Rotary Electromagnetic Stirring

In this article, an electromagnetic field simulation and a flow analysis model are performed to describe the three-dimensional electromagnetic field distribution and the electromagnetically driven flow characteristics in a round-bloom mold with a low-frequency in-mold rotary electromagnetic stirrer. The interaction between the induced flow and the inertial impinging jet from a straight-through submerged entry nozzle (SEN) of the caster is considered. The effects of stirrer current and frequency on the electromagnetic field and the flow in the round-bloom mold are investigated, and a strategy to optimize the stirring parameters is proposed. The results show that the distributions of magnetic flux density and electromagnetic force magnitude are nonuniform in a three-dimensional electromagnetic stirring (EMS) configuration. There exists a significant axial induced component of electromagnetic force. The flow in the in-mold EMS system is characterized by a dominant swirling movement at the transverse sections, coupled with the recirculating flows in the axial direction. An upper recirculation zone and a lower recirculation zone with the reverse melt flowing are found near the strand wall at the axial location close to the middle of the stirrer, and another recirculation zone is formed due to the interference of the induced flow with the jet from SEN. The meniscus surface has a swirl flow, and the meniscus level rises near the bloom strand wall and sinks around the SEN wall. All of these flow features are closely associated with metallurgical performances of the in-mold rotary stirrer. With the increase of stirring current and the decrease of frequency, the magnetic flux magnitude increases. There is an optimum frequency to obtain a peak of electromagnetic force magnitude and maximum tangential velocity. For a mold rotary EMS system, to determine the optimum stirring intensity, it is necessary to make a compromise between a larger tangential velocity and a relatively quiescent meniscus surface.

Capillary filling dynamics of water in nanopores

We portray a universal description of dynamic slip-stick behavior of water flowing through nanoscale pores. Based on fundamental molecular transport considerations, we derive a generalized constitutive model for describing resistive forces acting on the water column in a capillary that is being dynamically filled, as a combined function of the meniscus height, surface wettability, and roughness. This effectively acts like a unique signature of nanopore imbibition characteristics of water, which, when substituted in a simple one-dimensional force balance model agrees quantitatively with results from molecular dynamics simulations for a general class of problems, without necessitating the employment of any artificially tunable fitting parameters.

Evaluation of lower tear meniscus shape with OCT

AbstractPurpose When measuring the tear meniscus radius and calculating tear volume, the anterior radius of the meniscus is assumed to be spherical. This study aimed to define the shape of the meniscus more precisely using high‐resolution optical coherence tomography (OCT).Methods Images of the lower tear meniscus of 30 normal subjects (8M, 22F; mean age 27.5±9.6yrs), recruited from the patient pool of Höhere Fachschule für Augenoptik, Cologne, Germany, were taken using the Zeiss Cirrus HD OCT. Applying ImageJ software, the tear meniscus height (TMH) was measured and the xy‐coordinates of 12 marked points on the anterior tear meniscus curve were determined. With these coordinates a graph was plotted and the best fitting trend‐line (defining TM curvature) was calculated. Furthermore, the distance between the edge of the lower eyelid and the vertex of the curve (TMH‐V) was calculated and compared to the half TMH (TMH‐H).Results Mean TMH was 0.24 SD±0.06mm. The mean fitting trend‐line appeared to be a quadratic equation (R‐squared range from 0.908 to 0.996). TMH‐V (0.12±0.04mm) and TMH‐H (0.12±0.03mm) were significantly correlated (r=0.62; p&lt;0.001). The 95% LoA showed that the TMH‐V could be expected to be up to ‐0.07 mm below and 0.07 mm above the TMH‐H.Conclusion With high‐resolution OCT the anterior surface of tear meniscus was found to have a parabolic shape, which will help to calculate tear volume more precisely. To know the position of the parabolas vertices is useful when explaining the position of light reflexes from the tear meniscus particularly in reflective meniscometry.

Nanoindentation of human meniscal surfaces

Menisci are crescent shaped fibrocartilaginous structures which support load distribution of the knee. The menisci are specifically designed to fit the contour of the femoral condyles, aiding to disperse the stresses on the tibial plateau and in turn safeguarding the underlying articular cartilage. The importance of the meniscal superficial layer has not been fully revealed and it is suspected that this layer plays a pivotal role for meniscal function. In this study, both femoral (proximal) and tibial (distal) contacting meniscal surfaces were mechanically examined on the nano-level among three distinct regions (anterior, central and posterior) of the lateral and medial menisci. Nanoindentation testing showed no significant differences among regions, surfaces or anatomical locations, possibly elucidating on the homogeneity of the meniscal superficial zone structure (Einstantaneous: 3.17–4.12MPa, Esteady-state: 1.47–1.69MPa). Nanomechanical moduli values were approximately an order of magnitude greater than micro-scale testing derived moduli values. These findings validate the structural homogeneity of the meniscal superficial zone, showing that material properties are statistically similar regardless of meniscal surface and region. Understanding the mechanical behavior of meniscal surfaces is imperative to properly design an effective meniscal replacement.