Following the characterization of the new amphibole species fluoro-leakeite, ideally ANa BNa2 C(Mg2Al2Li) TSi8 O22 WF2, at Norra Karr (Sweden), so far considered the type locality of eckermannite, ...re-examination of the holotype material of eckermannite deposited at the Museum of Natural History in London (BM 1949.151) and of the original sample analyzed by Tornebohm (1906) confirmed that they both are actually fluoro-leakeite. A survey of literature data showed that the only analysis reported for eckermannite is that of sample AMNH 108401 from the Jade Mine Tract, Myanmar. Complete characterization of that sample has led to the approval of a new holotype for eckermannite (IMA-CNMNC 2013-136), ideally ANa BNa2 C(Mg4Al) TSi8 O22 W(OH)2, which is described in this work.Holotype eckermannite from Myanmar has the empirical unit formula A(Na0.87K0.06)Σ=0.93 B(Na1.89Ca0.11)Σ=2.00 C(Mg3.87Fe2+ 0.09Mn0.01Fe3+ 0.38Al0.62)Σ=4.97 TSi8.00 O22 W(F0.03OH1.97)Σ=2.00. It is monoclinic, C2/m, with a = 9.8087(7), b = 17.8448(13), c = 5.2905(4) A, β = 103.660(1), V = 899.8(1) A3; Z = 2, Dcalc = 3.02 g/cm3. Optics: biaxial (-); α = 1.605, β = 1.630, γ = 1.634 all ±0.002 (λ = 590 nm). The 10 strongest reflections in the X-ray powder pattern d values (in A), I, (hkl) are: 2.702, 100, (331) (151); 3.395, 59, (131); 3.128, 56, (310); 2.525, 56, (202); 8.407, 42, (110); 2.574, 36, (061) (002); 3.257, 34, (240); 2.161, 33, (261); 2.966, 33, (060); 4.460, 30, (040).The reason for the rarity of eckermannite compositions are examined and discussed based on considerations on the short-range order of A cations and W anions.
Three synthetic Ca-rich clinopyroxenes on the hedenbergite-ferrosilite join, with compositions (Hd50Fs50), (Hd60Fs40), and (Hd70Fs30), were investigated by single-crystal X-ray diffraction and ...Mossbauer spectroscopy at room temperature. For all samples, there is no evidence for the presence of phases with symmetry other than C2/c. Structure refinement, using a split-atom model, shows the existence of two different local configurations in the M2 cavity, a hedenbergite-like arrangement and a C2/c clinoferrosilite-like arrangement that are centered by Ca and Fe2+, respectively. The Mossbauer spectra were analyzed by a quadrupole splitting distribution (QSD) method, and the hyperfine parameters of the QSD fit indicate the presence of Fe2+ in three local environments that are similar to those of Fe2+ at the M1 site in hedenbergite, and the M1 and M2 sites in C2/c clinoferrosilite, in agreement with the structure-refinement results. Our results are consistent with the calculated phase diagram for hedenbergite-ferrosilite, where a miscibility gap and a two-phase field of metastable hedenbergite and metastable pigeonite occur at low temperature. The coexistence of a hedenbergite-like configuration around Ca and a C2/c clinoferrosilite-like configuration around Fe can be considered as a precursor for pyroxene exsolution at low temperature. Our results support previous structure-refinement work on Ca-rich clinopyroxenes along the diopside-enstatite join, and provide a new insight in the interpretation of Mossbauer spectra of Ca-rich C2/c clinopyroxenes.
The purpose of this study is to determine if arthroscopic shavers can effectively collect and process connective tissue progenitor (CTP) cells from subacromial bursal tissue for utilization in ...rotator cuff repair augmentation. Subacromial bursal tissue was collected and processed using two arthroscopic shavers, Shaver A and Shaver B, in 10 patients undergoing arthroscopic rotator cuff repair. Each shaver was used in a random order for the same patient. Tissue samples underwent testing for cellular proliferation, cellular concentration, number of colony-forming units (CFU), live/dead assay, fluorescence-activated cells sorting (FACS) analysis, cytokine analysis, and growth factor analysis. Shaver A produced more CFUs compared to Shaver B (210.3 vs. 125.9; p < 0.001). At 3 weeks, cells collected via Shaver A had greater cellular proliferation (0.35 vs. 0.51; p < 0.001) as well as more viable cells (214,773 vs. 132,356 cells/gram; p < 0.001). Tissue collected with Shaver B had greater amounts of the cytokines MMP-1 (3741 vs. 5500 pg/mL; p < 0.001), MMP-3 (1131 vs. 1871 pg/mL; p < 0.001), and MMP-13 (179 vs. 401 pg/mL; p < 0.001), while those collected with Shaver A had greater vascular endothelial growth factor (VEGF) (47.8 vs. 9.0 pg/mL; p < 0.05). Arthroscopic shavers are capable of harvesting and processing CTP cells from subacromial bursal tissue. Different shavers may produce different yields of viable CTP cells.
The purpose of this study was to investigate proteomic alteration that occurs to whole blood when converted to activated serum (AS) using an autologous thrombin system. This study further sought to ...evaluate the functional in vitro effect of AS on tenocytes, chondrocytes, subacromial bursal cells, and osteoblasts. The peptide/protein composition of AS was analyzed by liquid chromatography−mass spectrophotometry (LC-MS). The cell lines were treated with AS, and cellular proliferation was quantified 48 h after treatment. Platelet-derived growth factor (PDGF), insulin-like growth factor 1 (IGF-1), vascular endothelial growth factor (VEGF), interleukin-1 beta (IL-1β), and interleukin-1 receptor antagonist (IL-1Ra) were quantified utilizing enzyme-linked immunosorbent assays (ELISAs). LC-MS identified 357 proteins across the AS and whole blood. Fifty-four of the proteins identified had significant differences between the relative protein abundance of the AS samples compared to whole blood. Treatment with AS in all cell lines significantly increased proliferation compared to control cells at 48 h. Increased PDGF, VEGF, and IGF-1 in all cell lines exposed to AS compared to the control (p < 0.05) were observed. These findings suggest that treatment with AS increases in vitro cellular proliferation and the release of growth factors that may play a role in tissue repair.
Since their introduction in 1929, Pauling's five rules have been used by scientists from many disciplines to rationalize and predict stable arrangements of atoms and coordination polyhedra in ...crystalline solids; amorphous materials such as silicate glasses and melts; nanomaterials, poorly crystalline solids; aqueous cation and anion complexes; and sorption complexes at mineral-aqueous solution interfaces. The predictive power of these simple yet powerful rules was challenged recently by George et al. (2020), who performed a statistical analysis of the performance of Pauling's five rules for about 5000 oxide crystal structures. They concluded that only 13% of the oxides satisfy the last four rules simultaneously and that the second rule has the most exceptions. They also found that Pauling's first rule is satisfied for only 66% of the coordination environments tested and concluded that no simple rule linking ionic radius to coordination environment will be predictive due to the variable quality of univalent radii. We address these concerns and discuss quantum mechanical calculations that complement Pauling's rules, particularly his first (radius sum and radius ratio rule) and second (electrostatic valence rule) rules. We also present a more realistic view of the bonded radii of atoms, derived by determining the local minimum in the electron density distribution measured along trajectories between bonded atoms known as bond paths, i.e., the bond critical point (rc). Electron density at the bond critical point is a quantum mechanical observable that correlates well with Pauling bond strength. Moreover, a metal atom in a polyhedron has as many bonded radii as it has bonded interactions, resulting in metal and O atoms that may not be spherical. O atoms, for example, are not spherical in many oxide-based crystal structures. Instead, the electron density of a bonded oxygen is often highly distorted or polarized, with its bonded radius decreasing systematically from ∼1.38 Å when bonded to highly electropositive atoms like sodium to 0.64 Å when bonded to highly electronegative atoms like nitrogen. Bonded radii determined for metal atoms match the Shannon (1976) radii for more electropositive atoms, but the match decreases systematically as the electronegativities of the M atoms increase. As a result, significant departures from the radius ratio rule in the analysis by George et al. (2020) is not surprising. We offer a modified, more fundamental version of Pauling's first rule and demonstrate that the second rule has a one-to-one connection between the electron density accumulated between the bonded atoms at the bond critical point and the Pauling bond strength of the bonded interaction. Pauling's second rule implicitly assumes that bond strength is invariant with bond length for a given pair of bonded atoms. Many studies have since shown that this is not the case, and Brown and Shannon (1973) developed an equation and a set of parameters to describe the relation between bond length and bond strength, now redefined as bond valence to avoid confusion with Pauling bond-strength. Brown (1980) used the valence-sum rule, together with the path rule and the valence-matching principle, as the three axioms of bond-valence theory (BVT), a powerful method for understanding many otherwise elusive aspects of crystals and also their participation in dynamic processes. We show how a priori bond-valence calculations can predict unstrained bond-lengths and how bond-valence mapping can locate low-Z atoms in a crystal structure (e.g., Li) or examine possible diffusion pathways for atoms through crystal structures. In addition, we briefly discuss Pauling's third, fourth, and fifth rules, the first two of which concern the sharing of polyhedron elements (edges and faces) and the common instability associated with structures in which a polyhedron shares an edge or face with another polyhedron and contains high-valence cations. The olivine α-(MgxFe1-x)2SiO4 crystal structure is used to illustrate the distortions from hexagonal close-packing of O atoms caused by metal-metal repulsion across shared polyhedron edges. We conclude by discussing several applications of BVT to Earth materials, including the use of BVT to: (1) locate H+ ions in crystal structures, including the location of protons in the crystal structures of nominally anhydrous minerals in Earth's mantle; (2) determine how strongly bonded (usually anionic) structural units interact with weakly bonded (usually cationic) interstitial complexes in complex uranyl-oxide and uranyl-oxysalt minerals using the valence-matching principle; (3) calculate Lewis acid strengths of cations and Lewis base strengths of anions; (4) determine how (H2O) groups can function as bond-valence transformers by dividing one bond into two bonds of half the bond valence; (5) help characterize products of sorption reactions of aqueous cations (e.g., Co2+ and Pb2+) and oxyanions e.g., selenate (Se6+O4)2- and selenite (Se4+O3)2- at mineral-aqueous solution interfaces and the important role of protons in these reactions; and (6) help characterize the local coordination environments of highly charged cations (e.g., Zr4+, Ti4+, U4+, U5+, and U6+) in silicate glasses and melts.
A Substantial Clinical Benefit (SCB) value is the amount of change in a patient-reported outcome measure required for a patient to feel they significantly improved from an intervention. Previously ...published SCB values are often cited by researchers when publishing outcomes data. Where these SCB values are set can have a large impact on the conclusions drawn from a study citing them. As such, the goal of this study was to determine the generalizability of SCB values for a procedure when stratified by time from surgery and geographic region.
A nationwide outcomes database was utilized to obtain preoperative, one-year, and two-year postoperative outcome measurements for patients who underwent anatomic total shoulder arthroplasty (TSA) or reverse TSA. The data were divided into three geographic regions: the South, the Midwest, and the West. An East region was not included due to its limited number of patients. SCB values were calculated for four outcomes measures: Single Assessment Numeric Evaluation score, American Shoulder Elbow Surgeons score, Visual Analog Scale, and Western Ontario Osteoarthritis of the Shoulder score. SCB values were calculated for each region, for each procedure, and at both one and two years postoperatively. To determine the variability of potential SCBs within each region, simulated datasets were created to determine a distribution of possible calculated SCBs.
A total of 380 anatomic TSA patients and 543 reverse TSA patients were included for analysis. There was a high degree of variability of SCB values when stratified by procedure, time, and region. While some simulated datasets did produce homogenous SCB distributions among regions, some outcome measures demonstrated a large heterogeneity in distribution among regions, with concomitant large distributions of values within individual regions.
There is notable heterogeneity of SCB values when stratified by region or time. The current method of citing previously published SCB values for determining the efficacy of an intervention may be inappropriate. It is likely that this variability holds true in other areas of orthopedics.
Intra-articular distal humerus fractures frequently require olecranon osteotomies for adequate exposure, but fixation of olecranon osteotomies is associated with high rates of hardware-related ...complications requiring subsequent reoperation for removal. Intramedullary screw fixation is an attractive option to attempt to minimize hardware prominence. The purpose of this biomechanical study is to directly compare intramedullary screw fixation (IMSF) with plate fixation (PF) of chevron olecranon osteotomies. It was hypothesized that PF would be biomechanically superior to IMSF.
Chevron olecranon osteotomies of 12 matched pairs of fresh-frozen human cadaveric elbows were repaired with either precontoured proximal ulna locking plates or cannulated screws with a washer. Displacement and amplitude of displacement at the dorsal and medial aspects of the osteotomies under cyclic loading conditions were measured. Finally, the specimens were loaded to failure.
The IMSF group had significantly greater medial displacement (P = .034) and dorsal amplitude (P = .029) than the PF group. Medial displacement was negatively correlated with bone mineral density in the IMSF group (r = −0.66, P = .035) but not in the PF group (r = .160, P = .64). Mean load to failure between groups, however, was not statistically significant (P = .183).
While there was no statistically significant difference in the load to failure between the two groups, IMSF repair resulted in significantly greater displacement of the medial osteotomy site during cyclic loading and greater amplitude of displacement dorsally with loading force. Decreased bone mineral density was associated with an increased displacement of the medial repair site. These results suggest that IMSF of olecranon osteotomies may result in increased fracture site displacement when compared to PF; this displacement may be greater in patients with poor bone quality.
Category:
Ankle; Basic Sciences/Biologics; Other
Introduction/Purpose:
The purpose of this study was to evaluate the presence of connective tissue progenitor cells within the retrocalcaneal bursa. ...The study evaluation included an assessment of the viability of connective tissue progenitor cells, their proliferative potential, and their ability to differentiate into osteoblasts, adipocytes, and chondrocytes.
Methods:
The retrocalcaneal bursa samples were excised from 10 patients (age: 51.5 +- 10.8 years) undergoing Achilles surgery in which the retrocalcaneal bursa is routinely excised. Bursal tissue was processed by digesting cells with collagenase and obtaining nucleated cell counts and cellular concentrations. The cells were cultured, and differentiated into osteoblasts, adipocytes, and chondrocytes. Analysis of bursal derived cells consisted of fluorescent activated cell sorting (FACS) analysis, cellular proliferation and viability assay, and analysis of differentiation into osteoblasts, adipocytes, and chondrocytes. The CTP differentiation was confirmed using histology staining to qualitatively express differentiation, and qPCR to quantify gene expression.
Results:
Cell migration at 3 weeks on average was found to be 3.84x107 nucleated cells/gram of tissue and nucleated cellular concentration on average was found to be 6.28x105 cells/mL of suspension. The proliferation data showed high levels of proliferation on average of 1.72 +-0.58. The FACS analysis showed a high percentage of positive surface markers for CTPs measuring greater than 96% (CD105, CD90, CD73) and measuring < 1.1% for negative surface markers (CD45 and CD31). Differentiation into osteoblasts, adipocytes, and chondrocytes were stained appropriately displaying differentiation.
Conclusion:
The retrocalcaneal bursa is a novel source of connective tissue progenitor cells. This is the first study to our knowledge analyzing the retrocalcaneal bursa as a novel source for CTPs, making it a potential augment to expedite the healing process of the Achilles tendon. Overall, it is unclear what the role of the CTPs within the bursa is, however, they may help to reduce the extensive healing time for the Achilles tendon thereby returning patients with Achilles tendon pathology back to functional status more promptly.
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