Hemophilic arthropathy of the foot and ankle

The major deformities in hemophilic arthropathy of the foot and ankle fall into the three groups of equinus, varus, and cavus. These pathologic positions develop through a repetitive pattern of intra-articular and intramuscular bleeding within the area of the distal calf, foot, and ankle. Appropriate infusion therapy with factor VIII concentrate and factor IX concentrate plus splinting, bracing, and logical rehabilitative maneuvers can delay or prevent the advent of permanent deformity. The actual articular damage seems to be directly related to the release of digestive enzymes from leukocytes, synovial cells, and other blood products. These pathologic mechanisms appear to be similar to those recently described in explaining joint destruction in rheumatoid and degenerative arthritis. The indication for certain reconstructive orthopedic procedures in these situations are given and case examples provided. Total joint replacement in the area of the foot and ankle in hemophilia has been considered for certain patients by the authors but not attempted as yet.     

Statistical investigation of die wear in metal extrusion processes

The aim of this paper is the statistical process control analysis of the tool wear evolution during metal extrusion process for better understanding the principal causes that generate the variability of such a complex phenomenon. The wear prediction is carried out using finite element simulation including the Archard wear model. The tool wear modeling is presented briefly as well as the response surface methodology. The study is based on the application of the central composites designs and allows for the analysis of the response (wear) sensitivity of the tool. The statistical investigation of the process makes it possible to study the influence of each process parameter on the response sensitivity.     

Orchestrating the emergence of conceptual learning: a case study in a geometry class

This paper is about orchestrating the emergence of conceptual learning in a collaborative setting. We elaborate on the idea of critical moments in group learning, events which may lead to a particular development at the epistemic level regarding the shared object. We conjecture that teachers’ identification of critical moments may help them guide students to the emergence of conceptual learning. The complexity of small group settings in classrooms prevents teachers from noticing these critical moments, though. Here we present an environment, SAGLET (System for Advancing Group Learning in Educational Technologies), based on the VMT (Virtual Math Teams) environment (Stahl 2009), which allows teachers to observe multiple groups engaging in problem-solving in geometry. SAGLET capitalizes on machine learning techniques to inform teachers about on-line critical moments by sending them alerts, so that they can then decide whether (and how) to use the alerts in guiding their students. One teacher in an elementary school used SAGLET to help multiple groups of students solve difficult problems in geometry. We observed how the teacher mediated two cohorts of multiple groups at two different times in a mathematics classroom. We show that in both cases the teacher could detect the needs of the groups (partly thanks to the alerts) and could provide adaptive guidance for all the groups.     

Phase formation between La(Sr)Ga(Mg)O3 and Ce(La)O2 for solid oxide fuel cell applications

In strontium- and magnesium-doped LaGaO₃ (LSGM) electrolyte-based solid oxide fuel cells (SOFC), lanthanum-doped CeO₂ (LDC) is usually used as buffer layer material to prevent reactions between LSGM electrolyte and NiO-based anode. In literature, based on results for one particular LSGM composition, a fixed buffer layer composition of 40% La-doped ceria (LDC40) has been used even with electrolytes of different LSGM compositions. In this study, we report the results of a comprehensive study of phase formations between various LSGM and LDC compositions. Our results show that only one LSGM/LDC combination results in no additional phases. For the other combinations, at least one and often two additional phases, LaSrGaO₄ and LaSrGa₃O₇, result. Because LaSrGa₃O₇ has much lower conductivity, it is necessary to select combinations that avoid this phase. We propose that the combination that results in no additional phase should be considered favorably for SOFCs. For other LSGM compositions, LDC50 should be used as a buffer layer instead of LDC40 as is presently done in SOFC studies. Alternately, if LDC40 is preferred for buffer layer, then lower Sr content LSGM compositions should be used as electrolytes. These combinations are likely to lead to better long-term SOFC performance.     

Minimal Design Augmentation Schemes to Resolve Complex Aliasing in Industrial Experiments

Highly fractionated designs are often used for screening purposes in order to reduce the number of runs. In fractionary-designed experiments, the factor effects are confounded with interactions that are potentially active. Estimating separately the confounded effects is sometimes difficult and the results may be inconclusive as to which effect is real. Foldover designs are usually used to resolve such ambiguities. In this article, a method based on overlapping designs that enables one to separate the confounded effects in a smaller amount of runs is proposed. We illustrate this with an application.     

A single center,open‐label,randomized, parallel group study assessing the relationship between asymptomatic bacteriuria and inflammation in maintenance hemodialysis patients

Introduction: The significance of asymptomatic bacteriuria in maintenance hemodialysis (MHD) patients remains controversial. We hypothesized that the presence of asymptomatic bacteriuria as a sole clinical manifestation of urinary tract infection (UTI) in asymptomatic MHD patient may contribute to the chronic inflammatory response. Our aim was to explore the relationship between asymptomatic bacteriuria and elevated levels of inflammatory markers in MHD patients. Methods: A randomized open‐label single center study of 114 MHD patients was conducted. Forty‐six patients presented negative urine culture and 41 subjects were excluded due to different reasons. The remaining 27 patients (mean age of 71.5 ± 12.2 years, 63% men), fulfilling the criteria for having asymptomatic bacteriuria, were randomly assigned to either the treatment group (13 patients) or the observational group (14 subjects). The treatment group received 7 days of antibiotic treatment given according to bacteriogram sensitivity. After 3 months of follow‐up all measurements of the study were repeated. The primary end point was change in inflammatory biomarkers from baseline by the end of the study. Findings: There were no statistically significant differences in white blood cell changes (P = 0.27), ferritin (P = 0.09), C‐reactive protein (P = 0.90), and interleukin‐6 (P = 0.14) levels between the groups from baseline to the end of study or at the end of the study. Analyzing cross‐sectional data, asymptomatic bacteriuria was found to not be a predictor of higher levels of inflammatory parameters at baseline. Discussion: Asymptomatic bacteriuria is not a modifiable risk factor for chronic inflammation in the MHD population.     

Structural (in)stability and spontaneous cracking of Li-La-zirconate cubic garnet upon exposure to ambient atmosphere

Among the Li-ion conducting inorganic materials, lithium lanthanum zirconate (LLZO) is believed to possess good chemical stability against Li metal and hence considered to be a promising solid electrolyte for Li-ion batteries. However, systematic sets of studies conducted here at regular intervals during storage of Al-doped LLZO (cubic garnet) sintered pellets in ambient atmosphere have raised serious concerns over their structural/mechanical stability/integrity upon exposure to air. Spontaneous cracking/disintegration/pulverization of LLZO pellets takes place after about three weeks of exposure, primarily due to formation of La₂Zr₂O₇ in the LLZO bulk; as found to be thermodynamically feasible at room temperature upon reaction with CO₂/moisture. Steep increase in La₂Zr₂O₇ content coincides with the spontaneous cracking/disintegration. Estimation suggests that internal stresses associated with the formation of La₂Zr₂O₇ from LLZO can be high enough to cause spontaneous fracture. This mandates the development/fabrication/usage of solid-state cells using LLZO under stringent controls against exposure to atmospheric species.     

Atmospheric modulation transfer function in the infrared

In high-resolution ultranarrow field-of-view thermal imagers, image quality over relatively long path lengths is typically limited by atmospheric degradation, especially atmospheric blur. We report our results and analyses of infrared images from two sites, Fort A. P. Hill and Aberdeen Proving Ground. The images are influenced by the various atmospheric phenomena: scattering, absorption, and turbulence. A series of experiments with high-resolution equipment in both the 3-5- and 8-13-microm regions at the two locations indicate that, as in the visible, image quality is limited much more by atmosphere than by the instrumentation for ranges even of the order of only a few kilometers. For paths close to the ground, turbulence is more dominant, whereas for paths involving higher average elevation, aerosol modulation transfer function (MTF) is dominant. As wavelength increases, turbulence MTF also increases, thus permitting aerosol MTF to become more dominant. A critical role in aerosol MTF in the thermal infrared is attributed to absorption, which noticeably decreases atmospheric transmission much more than in the visible, thereby reducing high-spatial-frequency aerosol MTF. These measurements indicate that atmospheric MTF should be a basic component in imaging system design and analysis even in the infrared, especially as higher-resolution hardware becomes available.