Size Mismatch Research Articles

Static stability of novel uncemented elbow hemiarthroplasty stabilized with ligament reconstruction

The purpose of this study was to create a model to simulate treatment of unreconstructable distal humerus fractures with hemiarthroplasty. Stability was restored with a new plate-system that simultaneously tensions medial and lateral collateral ligament grafts. Static varus and valgus elbow stability was tested in 11 cadaver elbows with intact ligaments and capsule at five flexion angles (0, 30, 60, 90, 120 degrees). The elbows were then destabilized via release of all ligaments and capsular attachments. The distal humerus articular cartilage was excised and replaced with an uncemented hemiarthroplasty. Ligament reconstruction was subsequently performed, and elbow stability was measured and compared to the native state. Dimensions of the hemiarthroplasty component were compared to native elbow dimensions to assess and quantify any existing relationship to elbow stability. A hemiarthroplasty was implanted in all specimens. A size mismatch occurred between the distal humerus trochlea and the olecranon fossa in all specimens and averaged 6.3 mm. Following ligament reconstruction, specimens reproduced the flexion angle-dependent stability of native elbows to both varus and valgus stress. On the medial side, elbow joint stability in mid-flexion was approximately 7% tighter after hemiarthroplasty. Laterally, the elbow was approximately 15% tighter after hemiarthroplasty and demonstrated peak stability in full flexion. The three assessed hemiarthroplasty components and bony dimensions did not exhibit any relationship between implant-bone mismatch and elbow stability after ligamentous reconstruction. Cadaveric elbow specimens underwent uncemented hemiarthroplasty with soft tissue stabilization with a novel technique for ligament reconstruction. Following hemiarthroplasty and ligament reconstruction, these specimens maintained secure fixation between ligament and bone. Static stability was maintained at varying degrees of elbow flexion regardless of variable mismatch between the hemiarthroplasty component and the native olecranon fossa.

Roles and practice of living-related lobar lung transplantation.

Living-donor lobar lung transplantation (LDLLT) was first performed in the USA and thereafter it was introduced in Japan in 1998 as an alternative modality to brain-dead donor lung transplantation (BDLT). Although the LDLLT procedure was employed for rapidly deteriorating patients who were hospitalized and mechanically ventilated at the time of transplantation, LDLLT demonstrated better or comparable post-transplant outcomes in comparison to BDLT. Less injured lobar grafts and a significantly shorter graft ischemic time possibly contributed to a significantly lower incidence of severe primary graft dysfunction (PGD) after LDLLT in comparison to BDLT. In standard LDLLT, patients obtained lobar grafts from two different donors, and thus most patients developed chronic lung allograft dysfunction (CLAD) only in the unilateral lung graft. This indicates that the contralateral unaffected lung graft could reserve lung function after the unilateral development of CLAD. In our transplant program, the incidence of CLAD per donor in LDLLT (14.4%) was also significantly lower in comparison to BDLT (24.7%). The 1-, 5- and 10-year survival rates after LDLLT were 90.9%, 75.5% and 57.2%, respectively, which were equivalent to those after BDLT (92.9%, 73.4% and 62.2%). The inherent surgical risk to the living donors should always be considered. In our experience, living-donor surgery was associated with a complication rate of 12.7%, and importantly, all living donors finally returned to their previous social lives. Precise functional and anatomical size matching between donor lobar graft and recipient could provide a favorable pulmonary function after LDLLT. We recently established multimodal surgical approaches, such as native upper lobe-sparing, right-to-left horizontally rotated, segmental, and single-lobe transplantation, in order to resolve the issue of size mismatch between the donor lobar graft and the recipient.

Potential Application of Orofacial MSCs in Tissue Engineering Nerve Guidance for Peripheral Nerve Injury Repair.

Injury to the peripheral nerve causes potential loss of sensory and motor functions, and peripheral nerve repair (PNR) remains a challenging endeavor. The current clinical methods of nerve repair, such as direct suture, autografts, and acellular nerve grafts (ANGs), exhibit their respective disadvantages like nerve tension, donor site morbidity, size mismatch, and immunogenicity. Even though commercially available nerve guidance conduits (NGCs) have demonstrated some clinical successes, the overall clinical outcome is still suboptimal, especially for nerve injuries with a large gap (≥ 3cm) due to the lack of biologics. In the last two decades, the combination of advanced tissue engineering technologies, stem cell biology, and biomaterial science has significantly advanced the generation of a new generation of NGCs incorporated with biological factors or supportive cells, including mesenchymal stem cells (MSCs), which hold great promise to enhance peripheral nerve repair/regeneration (PNR). Orofacial MSCs are emerging as a unique source of MSCs for PNR due to their neural crest-origin and easy accessibility. In this narrative review, we have provided an update on the pathophysiology of peripheral nerve injury and the properties and biological functions of orofacial MSCs. Then we have highlighted the application of orofacial MSCs in tissue engineering nerve guidance for PNR in various preclinical models and the potential challenges and future directions in this field.

When is size mismatch good? The anomalous behaviour of scandium in titanate-based proton conductors

When is size mismatch good? The anomalous behaviour of scandium in titanate-based proton conductors

Synthesis of a novel graphene oxide/belite cement composite and its effects on flexural strength and interfacial transition zone of ordinary portland cement mortars

In order to address the size mismatch between nanoscale graphene oxide and micron-scale ordinary portland cement (OPC), a novel graphene oxide/belite cement (GO/BC) composite hydrated for different periods was synthesized and applied to OPC-based mortar specimens. The morphology, surface area and pore size distributions of hydrated GO/BC composites were characterized. Thermogravimetric analyses and X-ray photoelectron spectroscopy (XPS) test were carried out to investigate the relative amount of different phase assemblages in the composite and possible chemical interactions between graphene oxide and belite cement, respectively. Moreover, the effects of GO/BC composite addition on the flexural strength, the porosity and thickness of ITZ in the OPC-based mortars were examined. Experimental results showed that the GO/BC composite after 14 and 21 days of curing exhibited some flower-like hydration products with ‘petals’ sizing around several microns and a large surface area. The hydrated GO/BC composite after 14 and 28 days, for 14-day in particular, is more effective in elevating the flexural strength and densifying the ITZ region of OPC-based binders, compared to the graphene oxide or belite cement alone. Thus, hydrated GO/BC composites could be served as a better nucleation seed for promoting the hydration of OPC due probably to their greater surface area, suitable sizes and chemical interactions between graphene oxide and belite cement.

Layer control of Sr1.8Bi0.2Nan-3NbnO3n+1 (n = 3–5) perovskite nanosheets: dielectric to ferroelectric transition of film deposited by Langmuir Blodgett method

Solution-based processable high-k 2-dimensional (2D) ferroelectrics have attracted significant interest for use in next-generation nanoelectronics. Although few studies on potential 2D ferroelectric nanosheets in local areas have been conducted, reports on the thin-film characteristics applicable to the device are insufficient. In this study, we successfully synthesize high-k 2D Sr1.8Bi0.2Nan-3NbnO3n+1 (octahedral units, n = 3–5) nanosheets by the engineering of the n of NbO6 octahedral layers with A-site modification, and realized ferroelectric characteristics in ultrathin films (below 10 nm). The nanosheets are synthesized by a solution-based cation exchange process and deposited using the Langmuir-Blodgett (LB) method. As increasing the NbO6 octahedral layer, the thickness of the nanosheets increased and the band gaps are tuned to 3.80 eV (n = 3), 3.76 eV (n = 4), and 3.70 eV (n = 5). In addition, the dielectric permittivity of the 5-layer stacked nanofilm increase to 26 (n = 3), 33 (n = 4), and 62 (n = 5). In particular, the increased perovskite layer exhibits large distortions due to the size mismatch of Sr/Bi/Na ions at the A-site and promotes local ferroelectric instability due to its spontaneous polarization along the c-axis caused by an odd n number. We investigate the stable ferroelectricity in Pt/ 5-layer Sr1.8Bi0.2Na2Nb5O16 / Nb:STO capacitor by polarization-electric field (P-E) hysteresis; the coercive electric field (Ec) was 338 kV cm−1 and the remnant polarization (Pr) 2.36 μC cm−2. The ferroelectric properties of ultrathin 2D materials could drive interesting innovations in next-generation electronics.

Size-mismatched transplantation from large donors to small recipients is associated with pancreas graft thrombosis: A retrospective national observational study.

Donor-recipient (D/R) size mismatch has been evaluated for a number of organs but not for pancreas transplantation. We retrospectively evaluated 438 patients who had undergone pancreas transplantation. The D/R body surface area (BSA) ratio was calculated, and the relationship between the ratio and graft prognosis was evaluated. We divided the patients into two groups and evaluated graft survival. The incidence of pancreas graft thrombosis resulting in graft failure within 14days and 1-year graft survival were compared using Kaplan-Meier curves, and the prognostic factors associated with graft thrombosis were identified by univariate and multivariate analyses. The mean/median donor and recipient BSAs were 1.63m2 /1.65m2 , and 1.57m2 /1.55m2 , respectively; the mean and median D/R BSAs were both 1.05. The receiver operating characteristic curve cutoff for the D/R BSA ratio was 1.09, and significant differences were identified between patients with ratios of ≥1.09 (high group) versus <1.09 (low group). The incidence of graft thrombosis resulting in pancreas graft failure within 14days was significantly higher in the high group than in the low group (p<.01). One-year overall and death-censored pancreas graft survival were significantly higher in the low group than in the high group (p<.01). Multivariate analysis identified recipient height, donor BSA, and donor hemoglobin A1c as significant independent factors for graft thrombosis. Cubic spline curve analysis indicated an increased risk of graft thrombosis with increasing D/R BSA ratio. D/R size mismatch is associated with graft thrombosis after pancreas transplantation.

Effects of atomic size mismatch on glass transition decoupling in high-entropy metallic glasses

The calorimetric and dynamical glass transitions are uncoupled in high entropy metallic glasses (HEMGs). That is, the thermal glass-transition or vitrification temperature (Tg) and α-relaxation temperature (Tα) are uncorrelated as a function of alloy stoichiometry. The underlying mechanism that gives rise to this is not understood, nor is the connection to atomic structure. Here, molecular dynamic (MD) simulations of different HEMG model systems are performed to investigate the glass transition behavior. In addition to the high configurational entropy of mixing (for an ideal solution), we show that the effect of mismatch entropy plays a critical role in decoupling vitrification kinetics/α-relaxation in HEMGs. Microscopically, the atomic size difference contributes significantly to the sluggishness of long-range diffusion and decreased dynamic heterogeneities. This gives rise to a depressed structural α-relaxation. More importantly, we find that HEMGs with the decoupling vitrification kinetics/α-relaxation can show unique mechanical performance, such as better radiation tolerance and higher resistance to shear banding. Our results provide insights into the high entropy effect of glassy metallic materials, and suggest a means for tuning properties of HEMGs.

Pig-to-human heart xenotransplantation in two recently deceased human recipients.

Genetically modified xenografts are one of the most promising solutions to the discrepancy between the numbers of available human organs for transplantation and potential recipients. To date, a porcine heart has been implanted into only one human recipient. Here, using 10-gene-edited pigs, we transplanted porcine hearts into two brain-dead human recipients and monitored xenograft function, hemodynamics and systemic responses over the course of 66 hours. Although both xenografts demonstrated excellent cardiac function immediately after transplantation and continued to function for the duration of the study, cardiac function declined postoperatively in one case, attributed to a size mismatch between the donor pig and the recipient. For both hearts, we confirmed transgene expression and found no evidence of cellular or antibody-mediated rejection, as assessed using histology, flow cytometry and a cytotoxic crossmatch assay. Moreover, we found no evidence of zoonotic transmission from the donor pigs to the human recipients. While substantial additional work will be needed to advance this technology to human trials, these results indicate that pig-to-human heart xenotransplantation can be performed successfully without hyperacute rejection or zoonosis.

Effects of Quantum and Dielectric Confinement on the Emission of Cs‐Pb‐Br Composites

AbstractThe halide perovskite CsPbBr3 belongs to the Cs‐Pb‐Br material system, which features two additional thermodynamically stable ternary phases, Cs4PbBr6 and CsPb2Br5. The coexistence of these phases and their reportedly similar photoluminescence (PL) have resulted in a debate on the nature of the emission in these systems. Herein, optical and microscopic characterizations are combined with an effective mass, correlated electron–hole model of excitons in confined systems, to investigate the emission properties of the ternary phases in the Cs‐Pb‐Br system. It is found that all Cs‐Pb‐Br phases exhibit green emission and the non‐perovskite phases exhibit PL quantum yields orders of magnitude larger than CsPbBr3. In particular, blue‐ and red‐shifted emission for the Cs‐ and Pb‐rich phases, respectively, are measured, stemming from embedded CsPbBr3 nanocrystals (NCs). This model reveals that the difference in emission shift is caused by the combined effects of NC size and different band mismatch. Furthermore, the importance of including the dielectric mismatch in the calculation of the emission energy for Cs‐Pb‐Br composites is demonstrated. The results explain the reportedly limited blue shift in CsPbBr3@Cs4PbBr6 composites and rationalize some of its differences with CsPb2Br5.

Elastic modelling of lattice distortions in concentrated random alloys

Lattice distortions, i.e. small atomic displacements away from the average lattice, are linked to a number of functional and mechanical properties of concentrated metallic alloys, particularly their yield strength. Here we develop an elastic model of lattice distortions where every atom is modeled as an Eshelby inclusion in a homogeneous elastic matrix. Local environment effects are included by considering fluctuating anisotropic eigenstrain tensors associated to the inclusions. The model is tested on several concentrated alloys, face-centered cubic (FCC) AlMg and FeNiCr alloys, as well as a fictitious body-centered cubic (BCC) binary alloy to study systematically and independently the effects of a size and an elastic modulus mismatch between the constituents. The elastic model predicts lattice distortions well when the size and elastic modulus mismatches are typically less than 5% and 25%, respectively. Interestingly, we find that when the size mismatch is small, as in FeNiCr alloys, the lattice distortion is dominated by the fluctuations of the dilatational eigenstrains rather than their average value as often assumed in elastic models of concentrated alloys. Moreover, models usually assume homogeneous elastic constants, while the limit obtained here of 25% is often exceeded in concentrated alloys, particularly with a BCC structure.

Amorphous/crystalline Zn60Zr40 alloys lattice structures with improved mechanical properties fabricated by mechanical alloying and selective laser melting

ABSTRACT In the present study, mechanical alloying (MA) was employed for synthesising non-equilibrium Zn60Zr40 amorphous powders, and then consolidated into amorphous/crystalline Zn60Zr40 alloys using selective laser melting (SLM). The results showed that the MA process destabilised the atomic periodicity of Zn and Zr powders and induced crystalline-to-amorphous transformation due to atomic size mismatch and negative heat of mixing. Moreover, the amorphisation trend of as-milled powders was intensified with increasing milling time and attained almost fully amorphous structure after 30 h of milling. During SLM, the ultra-high cooling rate restricted the long-range atomic diffusion of the amorphous powders and enabled successful survival of amorphous phase, leading to amorphous/crystalline Zn60Zr40 alloys. The alloys exhibited a maximum compressive yield strength and microhardness of 160.9 ± 9.1 MPa and 3.73 ± 0.8 GPa, respectively. These findings demonstrated that the developed MA-SLM process might be a promising strategy for the preparation of amorphous/crystalline alloys with superior properties.

Structural and spin-glass properties of single crystal J eff = ½ pyrochlore antiferromagnet NaCdCo2F7: correlating T f with magnetic-bond-disorder

Weak bond disorder disrupts the expected spin-liquid ground-state of the ideal S = 1/2 Heisenberg pyrochlore antiferromagnet. Here we introduce a single crystal study of the structural and magnetic properties of the bond-disordered pyrochlore NaCdCo2F7. The magnetic susceptibility appears isotropic, with a large negative Curie-Weiss temperature (θCW = −108(1) K), however no magnetic order is observed on cooling until a spin-glass transition at T f = 4.0 K. AC-susceptibility measurements show a frequency-dependent shift of the associated cusp in χ’ at T f, that can be fitted well by the empirical Vogel-Fulcher law. The magnetic moment of μ eff = 5.4(1) μ B/Co2+ indicates a significant orbital contribution and heat capacity measurements show that down to 1.8 K, well below T f, only S mag ∼ Rln(2) of the magnetic entropy is recovered, suggestive of residual continued dynamics. Structural and magnetism comparisons are made with the other known members of the NaA’’Co2F7 family (A″ = Ca2+, Sr2+), confirming the expected relationship between spin-glass freezing temperature, and extent of magnetic bond disorder brought about by the size mismatch between A-site ions.

Study on mechanical alloying behavior and thermal stability of HfMoNbTaTi refractory high-entropy alloy

The present study prepared HfMoNbTaTi refractory high-entropy alloy powders with uniform distribution of components by mechanical alloying (MA). Six scenarios were designed to investigate the effects of rotational speed, milling duration, ball-to-powder weight ratio (BPR), and process control agent (PCA) on the alloy powder to achieve complete alloying, controlled morphology, and refined grain size. Results showed that the alloying efficiency and lattice strain increased significantly while the grain size decreased with increased rotational speed and BPR. In addition, the content of impurity elements (e.g., C, O, and Fe) also increased. Stearic acid added as PCA effectively prevented cold-welding and refined the particle/grain size but led to the appearance of unknown carbides. Excellent thermal stability was provided by the mechanically alloyed powders when annealed below 1000 °C. In contrast, the single body centered cubic (BCC) solid solution structure decomposed at 1200 °C annealing, and the decomposition temperature range was 942.5 °C–1041.2 °C based on the DSC curve. Finally, the dissolution pattern of components, the size mismatches effect, impact energy, and the optimal range of mechanical alloying process parameters were discussed in detail.

Addressing extreme size mismatch in pediatric intestinal transplantation: Outcomes of intestinal length reduction.

Bench liver reduction, with or without intestinal length reduction (LR) (coupled with delayed closure and abdominal wall prostheses), has been a strategy adopted by our program for small children due to the limited availability of size-matched donors. This report describes the short, medium, and long-term outcomes of this graft reduction strategy. A single-center, retrospective analysis of children that underwent intestinal transplantation (April 1993 to December 2020) was performed. Patients were grouped according to whether they received an intestinal graft of full length (FL) or following LR. Overall, 105 intestinal transplants were performed. The LR group (n = 10) was younger (14.5 months vs. 40.0 months, p = .012) and smaller (8.7 kg vs. 13.0 kg, p = .032) compared to the FL group (n = 95). Similar abdominal closure rates were achieved after LR, without any increase in abdominal compartment syndrome (1/10 vs. 7/95, p = .806). The 90-day graft and patient survival were similar (9/10, 90% vs. 83/95, 86%; p = .810). Medium and long-term graft survival at 1 year (8/10, 80% vs. 65/90, 71%; p = .599), and 5 years (5/10, 50% vs. 42/84, 50%; p = 1.00) was similar. LR of intestinal grafts appears to be a safe strategy for infants and small children requiring intestinal transplantation. This technique should be considered in the situation of significant size mismatch of intestine containing grafts.

Regulating phase ratio of β/α and static recrystallization of Ti-5Al-5Mo-5Cr-3Nb-2Zr with high plasticity alloyed by vanadium

To research the recrystallization mechanism without deformation of the α phase and control the phase ratio of β/α, Ti-5Al-5Mo-5Cr-3Nb-2Zr alloys with different vanadium contents were melted. The results indicate that with increasing vanadium content, the content and aspect ratio of the primary α (αp) and secondary α (αs) phases decrease, and the ratio of the β phase increases from 7% to 88%. The degree of recrystallization of αp and grain boundary α (αGB) phases increases, and their morphology changes from lath to equiaxed. The mechanism of static recrystallization is that the enrichment of V aggravates the local lattice strain and leads to the migration of the α phase interface. The V element aggravates the atomic size mismatch and the local lattice strain and reduces the β transition temperature of the enrichment region. The strength in the Ti-0 V alloy is the highest at ∼1056 MPa and then decreases. The Ti-2 V alloy had the highest toughness of ∼68.4 MPa·m1/2. The elongation of the Ti-6 V alloy is the highest at ∼16.1% due to the increase of β phase content and α phase recrystallization, which is ∼1.8 and ∼ 1.7 times that of the Ti-0 V and Ti-8 V alloys, respectively. The equiaxed αp phase and αs phase lead to shortening of the crack deflection path, and crack propagation is easier due to the increase of β phase content, which causes the crack propagation path to change from tortuous to straight.

Entropic stabilization and descriptors of structural transformation in high entropy alloys

With first-principles theoretical analysis of the local structure using Bond-Orientational Order parameters and Voronoi partitioning, we establish (a) HCP→BCC structural transformation in high-entropy alloys (HEAs) Nbx(HfZrTi)y at 16% Nb-concentration, and (b) that the internal lattice distortions (ILDs) peak at the transition. We demonstrate that the relative stability of HCP and BCC structures is driven by energetics, while the overall stability is achieved with contribution from the vibrational entropy that exceeds the configurational entropy of mixing. We show that along with atomic size mismatch, low average number (<5) of valence electrons and disparity in the crystal structures of constituent elements are responsible for larger ILDs in Nbx(HfZrTi)y than in HEAs like NbaMobWcTad.

Biliary complications after liver transplantation: A computed tomography and magnetic resonance imaging pictorial review.

Biliary complications are the most common complications after liver transplantation. Computed tomography (CT) and magnetic resonance imaging (MRI) are cornerstones for timely diagnosis of biliary complications after liver transplantation. The diagnosis of these complications by CT and MRI requires expertise, mainly with respect to identifying subtle early signs to avoid missed or incorrect diagnoses. For example, biliary strictures may be misdiagnosed on MRI due to size mismatch of the common ducts of the donor and recipient, postoperative edema, pneumobilia, or susceptibility artifacts caused by surgical clips. Proper and prompt diagnosis of biliary complications after transplantation allows the timely initiation of appropriate management. The aim of this pictorial review is to illustrate various CT and MRI findings related to biliary complications after liver transplantation, based on time of presentation after surgery and frequency of occurrence.

Characteristics of betatron radiation in AWAKE Run 2 experiment

The oscillating relativistic electrons in the accelerating/focusing wakefields of plasma accelerators emit electromagnetic radiation known as betatron radiation (BR). The proton-driven plasma wakefield acceleration has been demonstrated in the Advanced Wakefield Experiment (AWAKE) at CERN; however, its accompanying radiation emission is less explored compared with those in the laser- and electron beam-driven plasma accelerators. In this paper, a detailed simulation study of BR in the AWAKE is presented. Considering the new set-up of the AWAKE Run 2 (2021–), the radiation emission from both the witness electron beam and the seeding electron beam is investigated using particle-in-cell simulations. The influence of radial size mismatch and misaligned off-axis injection on the witness beam dynamics, as well as the spectral features of the relevant BR are studied. These non-ideal electron injections are likely to occur in experiment. The proton self-modulation stage is also investigated with a close look at the seeding electron beam dynamics and its BR. As a footprint of the emitting particles, BR can provide valuable information about the beam dynamics. Some practical challenges to implement the betatron diagnostic in the AWAKE Run 2 experiment are also addressed.

A NOVEL TECHNIQUE FOR MANAGEMENT OF A CRITICALLY-SIZED BONE DEFECT IN THE OPEN PROXIMAL TIBIAL FRACTURE: EMPLOYING THE CAPANNA TECHNIQUE IN TRAUMA

A NOVEL TECHNIQUE FOR MANAGEMENT OF A CRITICALLY-SIZED BONE DEFECT IN THE OPEN PROXIMAL TIBIAL FRACTURE: EMPLOYING THE CAPANNA TECHNIQUE IN TRAUMA