Zirconia Phase Transformation,Metal Transfer,and Surface Roughness in Retrieved Ceramic Composite Femoral Heads in Total Hip Arthroplasty

Ceramic femoral heads have had promising results as a bearing surface in total hip arthroplasty. Our objective was to evaluate a series of retrieved alumina-zirconia composite ceramic femoral heads for evidence of the tetragonal to monoclinic zirconia phase transformation, metal transfer and articular surface roughness. Raman spectra showed evidence of the zirconia phase transformation in all retrieved specimens, with distinct monoclinic peaks at 183, 335, 383, and 479 cm^− 1. All components displayed metal transfer. An increase in the zirconia phase transformation was seen with increasing time in vivo. No correlation between extent of zirconia phase transformation and the surface roughness was found. These short-term results suggest that the use of an alumina-zirconia composite ceramic is a viable option for femoral heads in THA.     

基于全寿命周期的医院改建工程质量管理研究

文章以工程全寿命周期理念为基础,分析了医院工程改建的必要性和质量影响因素,以期指导改造工程中各参与方实施质量管理,以降低医院改造工程质量事故发生的概率。     

Soft spots and their structural signature in a metallic glass

In a 3D model mimicking realistic Cu₆₄Zr₃₆ metallic glass, we uncovered a direct link between the quasi-localized low-frequency vibrational modes and the local atomic packing structure. We also demonstrate that quasi-localized soft modes correlate strongly with fertile sites for shear transformations: geometrically unfavored motifs constitute the most flexible local environments that encourage soft modes and high propensity for shear transformations, whereas local configurations preferred in this alloy, i.e., the full icosahedra (around Cu) and Z16 Kasper polyhedra (around Zr), contribute the least.Metallic glasses (MGs) have an inherently inhomogeneous internal structure, with a wide spectrum of atomic-packing heterogeneities (1–4). As a result, an a priori identification of structural defects that carry atomic rearrangements (strains) under imposed stimuli such as temperature and externally applied stresses has always been a major challenge (3–6). In several quasi-2D or 3D models of amorphous solids (such as jammed packings of soft spheres interacting via repulsive potentials or colloidal particles), low-frequency vibrational normal modes have been characterized, and it has recently been demonstrated that some of these modes are quasi-localized (7–14). A population of “soft spots” has been identified among them in terms of their low-energy barriers for local rearrangements (13, 14), correlating also with properties in supercooled liquids such as dynamic heterogeneity (15–17). However, it is not certain where the soft spots are in realistic MGs (18), in terms of an explicit correlation with local atomic packing and topological arrangements (18–20). In particular, there is a pressing need to determine whether it is possible to identify shear transformation zones, i.e., the local defects that carry inelastic deformation (21, 22). Accomplishing this would permit the characterization of MG microstructure in a way that directly ties atomic configuration with mechanical response beyond the elastic regime. We will show here that there is indeed a correlation between soft modes and atoms that undergo shear transformations, and both have their structural signature in specific atomic packing environments defined in terms of coordination polyhedra (3).Fig. 1 displays the vibrational density of states (V-DOS), D(ω), calculated from the eigen-frequencies obtained by normal mode analysis of the Cu₆₄Zr₃₆MG prepared with a cooling rate of 10⁹ K/s (Methods). The main peak stays around 14 meV and becomes only slightly narrower (or wider) when the cooling rate used to prepare the MG is slower (or faster), as seen in Fig. S1; the glasses cooled at slower rates exhibit fewer low-frequency (or low-energy) vibrational modes. The blue portion in Fig. 1 indicates the 1% lowest-frequency normal modes, which will be summed over in our calculations of the participation fraction, P_i, in soft modes (Methods). Those low-frequency vibrational modes are confirmed to be quasi-localized, similar to previous work on 2D models (15), as they involve a compact group of atoms on the basis of the amplitude distribution of their corresponding eigenvectors (also see the contour maps in Fig. 4).Open in a separate windowFig. 1.V-DOS of the inherent structure for Cu₆₄Zr₃₆ MG produced with the cooling rate of 10⁹ K/s. The blue portion indicates the 1% lowest frequency normal modes that were summed over to calculate the participation fraction (in soft modes) of atoms.Open in a separate windowFig. 4.Contoured maps showing the spatial distribution of participation fraction P_i (see sidebar) for Cu and Zr atoms in the Cu₆₄Zr₃₆ metallic glass with the cooling rate of 10⁹ K/s. The four sampled representative thin slabs (A–D) each has a thickness of 2.5 Å. White spots superimposed in the maps mark the locations of atoms that have experienced clear shear transformations (Methods) under AQS to a strain of 5%.We first demonstrate that certain types of coordination polyhedra, specifically those geometrically unfavored motifs (GUMs), contribute preferentially to the quasi-localized soft modes identified above, whereas the geometrically preferable clusters at this alloy composition represent the short-range order that participate the least. To establish the connection between the low-frequency modes and atomic packing structure, we analyze the latter first from the perspective of Cu-centered coordination polyhedra (23), in terms of the P_i of Cu atoms that are in the center of different types of polyhedra. In Fig. 2A, from left to right, each solid bar represents a bin that contains 10% of all of the Cu atoms, in ascending order from the lowest to the highest P_i. In addition, the 1% Cu atoms with the lowest P_i and the top 1% with the highest P_i are displayed on either end, each with a separate bar. The Cu atoms in full icosahedra (with Voronoi index <0, 0, 12, 0>) dominate the lowest P_i, which is consistent with the notion that full icosahedra are the short-range order most energetically and geometrically comfortable and hence least likely to participate in soft spots at this MG composition (23). Specifically, ∼98% of the Cu atoms with the 1% lowest participation fraction are enclosed in <0, 0, 12, 0>, which is much greater than the average value that ∼40% of Cu atoms center full icosahedra in this MG sample (23). In stark contrast, the local configurations on the other end of the coordination polyhedra spectrum, i.e., the GUMs (see examples below) that deviate considerably from the coordination number (CN) = 12 full icosahedra and their close cousins (Fig. 2), are not found at all among the atoms with the lowest 1% participation fraction. For the 1% of Cu atoms with the highest participation fraction, GUMs account for as high as 63%, whereas the share of full icosahedra is as low as only 1.1%. This observation clearly indicates that atoms involved with soft spots in low-frequency normal modes (i.e., soft modes) are those with the most unfavorable local coordination polyhedra.Open in a separate windowFig. 2.Atoms at the center of different types of (A) Cu-centered and (B) Zr-centered coordination polyhedra contribute differently to low-frequency normal modes. Each solid bar contains 10% of all of the Cu (or Zr) atoms; from left to right, the bins are ordered from the lowest to the highest participation fraction. Two additional bars describe the makeup of atoms contributing to the lowest 1% participation fraction and the highest 1% participation fraction, respectively. The latter is seen to be dominated by Cu (or Zr) atoms in GUMs.We also examined the dependence on local environments for Zr atoms. A plot analogous to Fig. 2A, this time for Zr-centered coordination polyhedra, is shown in Fig. 2B. From left to right, each solid bar represents a bin that contains 10% of all of the Zr atoms, in ascending order from the lowest to the highest P_i. In addition, the 1% Zr atoms with the lowest P_i and the top 1% with the highest P_i are displayed on either end, each with a separate bar. The most favorable Zr-centered Kasper polyhedra in this MG are of the Z16 type (<0, 0, 12, 4>) (23). Interestingly, for the Zr atoms with the 1% lowest participation fraction, ∼75% of them are enclosed in <0, 0, 12, 4>, which is much greater than the sample average of ∼17% in this MG (23). In contrast, GUMs that deviate considerably from the CN = 16 Kasper polyhedra and their close cousins (Fig. 2) only constitute ∼5%. Conversely, for the 1% of Zr atoms with the highest participation fraction, GUMs account for as high as 76%, whereas the share of Z16 clusters is as low as 1.6%.We now illustrate the GUMs, i.e., the typical types of coordination polyhedra that are strongly correlated with the soft modes. Fig. 3 A and B illustrates the local environments of the top five Cu atoms and Zr atoms, respectively, i.e., those with the highest participation fractions. For these five Cu-centered GUMs, the coordination polyhedra have Voronoi indices of <0, 0, 12, 2>, <0, 4, 4, 4>, <0, 6, 0, 6>, <0, 4, 4, 3>, and <0, 3, 6, 2>. For the five Zr GUMs, they are <1, 3, 4, 4>, <1, 2, 6, 5>, <0, 2, 9, 4>, <0, 3, 7, 4>, and <0, 4, 5, 6>. Clearly, they are among the polyhedra that deviate most significantly from the geometrically preferable Frank-Kasper polyhedra <0, 0, 12, 0> (for Cu) and <0, 0, 12, 4> (for Zr). Specifically, they are non-Kasper polyhedra and contain an increased density of extrinsic (e.g., fourfold) disclinations (3) at the favored CN, or clusters (including Kasper polyhedra) with unfavorable (too large or too small) CNs. In fact, those Zr-centered GUMs even contain sevenfold bonds, e.g., <1, 3, 4, 4> is actually <1, 3, 4, 4, 1> (except for these Zr-centered GUMs, the fifth digit is zero in the Voronoi indices for all the other coordination polyhedra in this work). From the perspective of either constituent element, Cu or Zr, these are the most geometrically unfavored clusters at the given alloy composition and atomic size ratio. According to ref. 24, transverse vibrational modes associated with defective (more disordered) soft structures could also be an origin of the boson peak [the excess rise in the D(ω) at low-frequency vibrational modes].Open in a separate windowFig. 3.Configurations of five different (A) Cu-centered and (B) Zr-centered polyhedra, in which the center atoms are the top five atoms with the highest participation fractions for each constituent species. These are representatives of GUMs in this MG. Orange spheres are for Cu atoms and silver ones for Zr atoms.The next task at hand is to correlate the relaxation events with vibrational modes. In a 2D sheared model glass, Manning et al. (14) recently associated low-frequency vibrational modes with soft spots where particle rearrangements are initiated. Here we use a similar analysis on our 3D realistic Cu₆₄Zr₃₆ glass. The contoured maps of participation fraction P_i for all of the (Cu and Zr) atoms inside four representative slabs, each with a thickness of 2.5 Å (roughly the average atomic spacing), are plotted in Fig. 4 A–D. We notice that the P_i distributions are heterogeneous: atoms that participated the most in soft modes tend to aggregate together, with a typical correlation length of ∼1 nm. For a direct comparison, the local atomic rearrangements in sheared Cu₆₄Zr₃₆ MG [under athermal quasi-static shear (AQS) to a global shear strain γ = 5%, well before global yielding/flow of the entire sample at γ ∼ 12%] are superimposed in Fig. 4 A–D, where white spheres represent the (Cu or Zr) atoms that have experienced the most obvious shear transformations (indicated by their large and simultaneous jumps of Dmin2 that are clearly above other atoms; Methods, Fig. S2, and SI Text). The distribution of these atoms is also inhomogeneous and, interestingly, almost always overlaps with the regions with high P_i. This observation is consistent with the correlation between quasi-localized low-frequency modes and low energy barriers (13). Fig. 5 displays the locations of all such Cu and Zr atoms in the simulation model, which are about 2% of the total number of atoms in the box. Two features are highly noteworthy. First, they cluster into patches (only 6 atoms are exceptions, being isolated in a group of <3 atoms), each comprising 10–40 atoms (Cu in orange and Zr in gray color). Second, the atoms in each cluster record a simultaneous jump in Dmin2. Taken together, the spatial and temporal correlations clearly indicate that these are the clusters of atoms that each has been through a well-defined shear transformation. The several representative cases in Fig. 4 (and Fig. S3) give a visual illustration of the correlation that, under imposed deformation, the most obvious shear transformations have a strong tendency to arise from the collection of atoms involved in soft modes. Each group (cluster) of the activated atoms in Fig. 5 centers a shear transformation zone.Open in a separate windowFig. 5.Cluster of atoms that have undergone obvious shear transformations (Methods) (24) in Cu₆₄Zr₃₆ MG sheared to γ = 5%. Atoms in each cluster are activated at the same time, as indicated by their simultaneous jump in ΔDmin2 at the same shear strain γ. Two such shear transformation zones are circled, with the Inset displaying the overlapping ΔDmin2 jumps of the atoms involved in each cluster.Note here that not all of the regions with the highest participation fraction P_i would undergo shear transformation for a particular loading condition, as seen in Fig. 4 and Fig. S3. One should keep in mind that such a local structure–property correlation in an amorphous system is expected to be statistical (better perceived in Fig. 6), rather than deterministic with a one-to-one correspondence (12, 14). The soft spots are only candidates for potential shear transformation zones. The ones actually activated are not necessarily the softest, and would be determined by the loading direction and local stress field interacting with the anisotropy of the soft spots. The statistical correlation is obvious for the entire range of imposed γ, from 2% to 10%. The contour maps similar to those in Fig. 4 for γ = 10% (before global yielding) are shown in Fig. S3. As another way to see this correlation, we present in Fig. 6 a plot correlating the average participation fraction with Dmin2 (with respect to the undeformed configuration) for γ from 2% to 10%. Each data point is an average for 5% of all of the atoms inside a bin (each bin contains atoms grouped in ascending participation fraction). Obviously, the atoms with higher participation in soft mode contribute more to the nonaffine deformation and therefore shear transformations. This trend persists throughout the entire range of strains we studied and is therefore statistically valid for all the atoms in the metallic glass.Open in a separate windowFig. 6.Correlation between the average Dmin2 (with reference to undeformed configuration) with participation fraction P_i for all of the (Cu and Zr) atoms in the Cu₆₄Zr₃₆ MG deformed to different γ levels (2–10%). Each data point is the average for 5% of all of the atoms, sorted in the order of increasing P_i.In conclusion, we identified soft spots in an MG. They are soft in the sense that the atoms (Cu and Zr in our case) in those local environments participate preferentially in soft vibrational modes and at the same time they have the highest propensity to undergo shear transformations. These two aspects are found to be strongly correlated: shear transformations in an MG preferentially occur at localized soft modes. In the language of the potential energy landscape, we established a correlation between the curvature at the bottom of the basin (stiffness) with the barrier for transitions between basins (energy barrier against reconfiguration). Importantly, we showed that both have a common signature in the local atomic packing environments: the GUMs are the local configurations most prone to instability. The GUMs, as the most disordered atomic arrangements, hence tend to constitute or center the “liquid-like regions” often hypothesized in the literature (4, 5, 25). They tend to be soft and fertile for shear transformations. Such a correlation, albeit statistical (not all soft modes or GUMs would be activated to undergo shear transformations for a given stress state/magnitude and loading duration), is very useful and important as a step forward in establishing a concrete structure–property relationship for MGs, i.e., a direct connection between short-range order and vibrational soft modes, as well as stress-induced atomic rearrangements. The spatial distribution of nanometer-scale patches observed in Fig. 4 and Fig. S3 (a 3D view from outside the MD box is in Fig. S4), in terms of property (soft spots) and corresponding structure (GUMs), may also help explain the origin of the heterogeneity in local elastic modulus and local viscoelasticity recently mapped out in experiments (26–28).     

Malignant transformation of rectal endometriosis: Preoperative diagnosis by endorectal ultrasound guided biopsy

The prevalence of malignant transformation of endometriotic lesions is estimated between 0.3% and 1%. Malignant transformations of endometriosis occur in the colorectum is rarer, accounting for 0.25%. Because the malignant transformation of colorectal endometriosis rarely involves mucosa, it is difficult to obtain abnormal tissue by routine endoscopic biopsy. In this case, we evaluated a patient with a rectal mass by endorectal ultrasound (ERUS) and performed endorectal ultrasound-guided biopsy (EGB). Malignant transformations of endometriosis were confirmed by histological result. For patients with rectal tumors but with negative findings on colonoscopy and biopsy, ERUS and EGB contribute to preoperative diagnosis.     

骨髓增生异常综合征患者的asxli基因变异分析

目的探讨骨髓增生异常综合征(myelodysplastic syndromes,MDS)患者ASXL1基因变异的发生情况及其与其他基因变异和部分临床参数之间的相关性。方法采用PCR扩增产物直接测序法检测149例MDS患者ASXU、U2AF1、SF3B1、DNMT3A、TET2、IDH1/2、NPM1、FLT3-ITD.C-KIT等基因的变异情况。结果在149例患者中,ASXU基因变异的检出率为24.8%(37/149),变异率>5%的基因分别是U2AF1(22.8%)、TET2(11.4%)、DNMT3A(9.4%)、NPM1(8.1%).SF3B1(6.0%)。ASXL1变异最常见的共存变异基因为U2AF1(27.0%,10/37)及TET2(18.9%,7/37)。ASXL1变异组与野生组患者在中位年龄、MDS亚型、染色体核型、外周白细胞、血红蛋白、血小板水平及骨髓原始细胞计数等方面的差异均无统计学意义(P>0.05)o对29例ASXL1变异患者进行了有效的随访,其中11例进展为急性髓系白血病(acute myeloid leukemia,AML),白血病转化率为37.9%。在92例野生型患者中,13例进展为AML,白血病转化率为14.1%。ASXL1变异组白血病转化率明显高于野生组,差异有统计学意义(PV 0.01)。结论ASXL1变异在MDS中有较高的发生率,并常与U2AF1及TET2基因变异共存,伴有该变异的患者具有更高的白血病转化率。     

Characterization of cathepsin X in colorectal cancer development and progression

The lysosomal cysteine carboxypeptidase cathepsin X (CTSX), localized predominantly in immune cells, has been associated with the development and progression of cancer. To determine its specific role in colorectal carcinoma (CRC), we analyzed CTSX expression in non-malignant mucosa and carcinoma of 177 patients as well as in 111 adenomas and related it with clinicopathological parameters. Further, the role of CTSX in the adhesion and invasion of the colon carcinoma cell lines HT-29 and HCT116 was investigated in an in vitro culture cell system with fibroblasts and monocytes, reflecting the situation at the tumor invasion front.Epithelial CTSX expression significantly increased from normal mucosa to adenoma and carcinoma, with highest expression levels in high grade intraepithelial neoplasia and in early tumor stages. Loss of CTSX occurred with tumor progression, and correlated with advanced local invasion, lymph node and distal metastasis, lymphatic vessel and vein invasion, tumor cell budding and poorer overall survival of patients with CRC. The subcellular distribution of CTSX changed from vesicular paranuclear expression in the tumor center to submembranous expression in cells of the invasion front. Peritumoral macrophages showed highest expression of CTSX. In vitro assays identified CTSX as relevant factor for cell–cell adhesion and tumor cell anchorage to fibroblasts and basal membrane components, whereas inhibition of CTSX caused increased invasiveness of colon carcinoma cells in mono- and co-culture. In conclusion, CTSX is involved in early tumorigenesis and in the stabilization of tumor cell formation in CRC. The results suggest that loss of CTSX may be needed for tumor cell detachment, local invasion and tumor progression. In addition, CTSX in tumor-associated macrophages indicates a role for CTSX in the anti-tumor immune response.     

Poikilodermatous mycosis fungoides with CD30‐positive large cell transformation successfully treated by brentuximab vedotin

We present a patient with a 33‐year history of poikilodermatous mycosis fungoides (MF) who subsequently developed CD30‐positive large cell transformation. After 6 years of conventional MF treatment, side effects of therapy and/or concomitant diseases prevented the previously applied treatment modalities. The CD30‐directed antibody‐cytotoxic drug conjugate (brentuximab vedotin) was introduced and followed by quick and excellent therapeutic response.