Investigation of Alkali‐Ion (Li,Na, and K) Intercalation in KxVPO4F (x ∼ 0) Cathode

This work compares the intercalation of K, Na, and Li in K_xVPO₄F (x ～ 0). The K_xVPO₄F (x ～ 0) cathode delivers reversible capacities of ≈90–100 mAh g^?1 in K, Na, and Li cells, at an average voltage of ≈4.33 V for K, ≈3.98 V for Na, and ≈3.96 V for Li. This is so far the highest average voltage known for a K‐intercalation cathode. The lower voltage of Li insertion compared to Na is attributable to undercoordinated Li ions in the K_xVPO₄F (x ～ 0) framework. While the material shows high rate capability for all the alkali ions, Li migration in K_xVPO₄F (x ～ 0) is more difficult than with Na and K. This work suggests that a large cavity is not always good for insertion of alkali ions and cathode materials need to be suitably tailored to each intercalating ion species.     

One-Step Chemical Synthesis of Native Met1-Linked Poly-Ubiquitin Chains

The enzyme-mediated construction of poly-ubiquitin (Ub) chains on target proteins leads to a variety of cellular responses and is involved in processes ranging from protein degradation to cell cycle control and immune responses. This complex post-translational modification system is under intense investigation, but generation of specific Ub chains and tools made thereof is not always trivial. We discovered that native methionine-1-linked polymeric ubiquitin chains can be constructed in a single chemical reaction. We validate correct folding and regioselective attachment of such chains using linkage specific proteases and further demonstrate that these poly-Ub chains can be converted into thioesters by the activating E1-enzyme. Subsequent ligation reactions using these in situ prepared thioesters leads to poly-ubiquitinated peptides.     

Clinical audit: Development of the criteria of good practices

Clinical audit is a systematic review of the procedures in order to improve the quality and the outcome of patient care, whereby the procedures are examined against agreed standards for good medical RADIOLOGICAL procedures. The criteria of good procedures (i.e. the good practice) are thus the cornerstones for development of clinical audits: these should be the basis of assessments regardless of the type of the audit--external, internal, comprehensive or partial. A lot of criteria for good practices are available through the recommendations and publications by international and national professional societies and other relevant organisations. For practical use in clinical audits, the criteria need to be compiled, sorted out and agreed on for the particular aims of an audit (comprehensive or partial, external or internal). The national professional and scientific societies can provide valuable contribution to this development. For examination--or treatment-specific criteria--preliminary consensus needs to be obtained with the help of clinical experts, while clinical audits can be useful as a benchmarking tool to improve the criteria.     

Intramedullary versus extramedullary fixation of subtrochanteric fractures. A biomechanical study

We compared two different subtrochanteric fracture fixation techniques, an intramedullary hip screw system (IMHS) and an extramedullary, dual sliding screw-plate system (MSP), to determine relative fixation stability. 6 matched pairs of osteosynthesized osteopenic cadaver femurs were axially loaded to 1000 N with concurrent, simulated abductor forces of 0%, 50%, or 86% of the applied head force. The initial loading sequence was made with uniaxial dynamization--the lag screw of the MSP locked and distal locking of the IMHS nail. Femoral head displacement and medial femoral strain were measured for intact femur controls, after fixation of a 2-part reverse oblique subtrochanteric fracture and finally a 3-part reverse oblique subtrochanteric fracture with a lateral wedge defect. The samples were then loaded at 750 N for 10(4) cycles with both devices uniaxially locked, followed by 10(4) cycles with both devices fully biaxially dynamized (unlocked). For the 2-part subtrochanteric fracture pattern, both devices exhibited similar inferior displacements of the femoral head (average 2.0 mm) and medial femoral strain (approximately 70% of intact). Increasing abductor forces decreased medial compressive strain but did not significantly affect head displacement. For the 3-part fracture model, the MSP demonstrated significantly less inferior displacement of the head (1.6 mm vs. 2.1 mm) and both devices demonstrated significantly decreased medial strain. After cycling, head displacement increased approximately 50% in both devices and medial strain increased slightly. After unlocking and cycling, the MSP group showed significant lateral displacement of the proximal fragment. The IMHS and MSP devices provide similar stability for fixation of 2-part and 3-part reverse oblique subtrochanteric fractures. In a biaxially dynamized, 3-part reverse oblique fracture, displacement of the proximal fragment can occur with the MSP.     

Structural Basis for Metastability in Amorphous Calcium Barium Carbonate (ACBC)

Metastable amorphous precursors are emerging as valuable intermediates for the synthesis of materials with compositions and structures far from equilibrium. Recently, it was found that amorphous calcium barium carbonate (ACBC) can be converted into highly barium‐substituted “balcite,” a metastable high temperature modification of calcite with exceptional hardness. A systematic analysis ACBC (Ca_1‐xBa_xCO₃·1.2H₂O) in the range from x = 0–0.5 is presented. Combining techniques that independently probe the local environment from the perspective of calcium, barium, and carbonate ions, with total X‐ray scattering and a new molecular dynamics/density functional theory simulations approach, provides a holistic picture of ACBC structure as a function of composition. With increasing barium content, ACBC becomes more ordered at short and medium range, and increasingly similar to crystalline balcite, without developing long‐range order. This is not accompanied by a change in the water content and does not carry a significant energy penalty, but is associated with differences in cation coordination resulting from changing carbonate anion orientation. Therefore, the local order imprinted in ACBC may increasingly lower the kinetic barrier to subsequent transformations as it becomes more pronounced. This pathway offers clues to the design of metastable materials by tuning coordination numbers in the amorphous solid state.     

Investigation of Potassium Storage in Layered P3‐Type K0.5MnO2 Cathode

Novel and low‐cost batteries are of considerable interest for application in large‐scale energy storage systems, for which the cost per cycle becomes critical. Here, this study proposes K_0.5MnO₂ as a potential cathode material for K‐ion batteries as an alternative to Li technology. K_0.5MnO₂ has a P3‐type layered structure and delivers a reversible specific capacity of ≈100 mAh g^?1 with good capacity retention. In situ X‐ray diffraction analysis reveals that the material undergoes a reversible phase transition upon K extraction and insertion. In addition, first‐principles calculations indicate that this phase transition is driven by the relative phase stability of different oxygen stackings with respect to the K content.     

Prediction of ordered superstructure phase equilibria

The approach to phase diagram calculations has changed drastically within the last few years. Previously, mean-field models (regular solution, Bragg-Williams, concentration waves) were used almost exclusively. These models rely on two very poor approximations: supe5rposition of ’point’ probabilities for pair probabilities and an ideal solution model for the configurational entropy. Today, effective cluster interactions can be calculated from first-principles electronic structure methods: the superposition approximation is avoided, and cluster formulations for the entropy are available. As will be shown by recently computed examples, such cluster methods predict first-priciples phase diagrams that are often in excellent agreement with those determined empirically. The pater was presented at the International Phase Diagram Prediction Symposium sponsored by the ASM/MSD Thermodynamics and Phase Equilibria Committee at Materials Week, October 21-23,1991, in Cincinnati, OH. The symposium was organized by John Morral, University on Connecticut, and Philip Nash, Illinois Institute of Technology.     

The first-principles calculation of phase stability and thermodynamic properties

A well-defined formalism exists to predict macroscopic thermodynamic information from a series of quantum mechanical energy calculations. The availability of accurate implementations of density functional theory and the practice of using better parameterized cluster expansions is leading to practical phase diagram predictions on relatively complicated systems. Some progress is being made to include entropic contributions beyond those due to configurational disorder.     

Computation of alloy phase diagrams at low temperatures

Standard statistical-mechanics techniques for alloy-Ising models such as Monte Carlo simulations or the cluster variation method usually present numerical problems at low temperatures or for highly stoichiometric compounds. Under these conditions, their application to complex alloy Hamiltonians, with extended pair and multi-site interactions, is non trivial and can be very computer-time demanding. In this work, we investigate the application of a low-temperature expansion of the thermodynamic potentials for Hamiltonians with many pair and multi-site interactions. In this way, analytic expressions can be obtained for the free energies from which temperature-composition phase diagrams for any alloy can easily be computed regardless of the complexity of the Ising energy expression. It is demonstrated that with only a few terms in the expansion, the low-temperature expansion is accurate up to temperatures where Monte Carlo simulations or cluster variation calculations are practical. Consequently, these three methods can be used as complimentary techniques to compute a single phase diagram. Furthermore, we also show that the coefficients of the low-temperature expansion can be computed from the same information used to build the cluster variational free energy, thereby making the low-temperature expansion very simple to use. We illustrate the application of this new approach by computing the fcc Pd-rich phase diagram of the Pd-V alloy.