Fatigue Behavior of Welded Connections Enhanced with UIT and Bolting

A common problem in bridges employing welded steel girders is development of fatigue cracks at the ends of girder coverplates. Fatigue cracks tend to form at the toes of the transverse welds connecting a coverplate to a girder flange since this detail has a region of very high stress concentration. Because many aging bridges employ these fatigue-prone, AASHTO fatigue Category E or E' details, a means to effectively enhance the fatigue lives of these details is being sought. A research project funded by the Kansas Department of Transportation was undertaken at the University of Kansas to investigate the fatigue life enhancement afforded by two retrofit methods. One retrofit method was similar to a method described in the AASTHO Bridge Design Specification (AASHTO 2004) and involved pretensioned bolts being added to the ends of coverplates near the transverse welds. Unlike the AASHTO bolting procedure, the modified bolting procedure studied during this project utilized coverplates having transverse fillet welds that were left in the as-fabricated state. The other retrofit method was the use of a proprietary needle peening procedure called Ultrasonic Impact Treatment (UIT). Results of the research project showed that UIT was highly effective at enhancing the fatigue lives of coverplate end details while the bolting procedure was ineffective. Weld treatment with UIT resulted in an improvement in fatigue life over control specimens by a factor of 25. This translated in an improvement from an AASTHO fatigue Category E detail rating to and AASHTO fatigue Category A detail rating. The modified coverplate bolting procedure tested during this project had either no effect on fatigue life or, in some cases, had a detrimental effect on fatigue life. The coverplate bolting procedure included in the AASHTO specification allows a coverplate end detail to achieve a fatigue Category B resistance when bolted rather than transversely welded. 11 Therefore, the modified bolting procedure tested during this project was much less effective at enhancing fatigue life than either the AASHTO bolting procedure or UIT

Post Retrofit Analysis of the Tuttle Creek Bridge Br. No. 16-81-2.24

The Tuttle Creek Bridge was built in 1962. Like many older welded steel bridges, it has developed fatigue cracks. The majority of cracks were forming in the upper web-gap region. In addition, fatigue cracking was occurring along gusset plates in the structure. A retrofit was performed in 1986 to prevent further fatigue cracking. Unfortunately, the cracks propagated after the retrofit. Therefore, finite element models were created at the University of Kansas to investigate the continued fatigue cracking. The models supplied a more effective retrofit procedure that included attaching the connection stiffener to the upper flange of the girder. Two tests were planned to determine the effectiveness of the retrofit. The first field test occurred before the repair was started. Its purpose was to provide stress values in key areas for comparison after the repair. In addition, the pre-retrofit test provided information for future finite element models. In 2005, the second retrofit was completed. The purpose of this report is to present results of the post-retrofit test with data from the pre-retrofit test. Comparisons of stresses for each key area are included in the report. Details of the Tuttle Creek Bridge and testing procedure are provided. In addition, minor changes from the previous test are described

Field Instrumentation and Analysis of the Tuttle Creek Bridge

Fatigue cracking has been an extensive problem for many steel bridges designed prior to the identification of fatigue-prone details. Distortion in bridges coupled with stress concentrations within bridge components can eventually lead to crack initiation. The Tuttle Creek Bridge, built in 1962, has developed fatigue cracks like many older steel bridges. The structure is a 5,350 ft. long, plate-girder bridge with two girders supporting a non-composite concrete deck. The majority of the cracks on the bridge are found in the upper web-gap region, which lies between the vertical connection stiffener and the upper flange. Cracks also have occurred in the transverse welds attaching the lateral gusset plates to the lower flange. Both these crack types are believed to be caused by differential deflection of the two girders. In 1986, the bridge was retrofitted to prevent further cracking. Cracking, however, continued after the 1986 retrofit. In 2000, the Kansas Department of Transportation retained the services of the University of Kansas to investigate the fatigue cracking. Finite element models were created to estimate the stresses in the upper web-gap regions in order to determine a proper repair plan. The recommended repair scheme was to positively attach the connection stiffener to the upper flange, which was also successfully performed in similar web-gap repairs. The University of Kansas also was retained to perform two load tests on the bridge to investigate the effectiveness of the repair. The first load test, which this report entails, examined the stresses within the fatigued regions prior to retrofit. A second test will be conducted after the repairs have been performed. Measurements taken during both tests will be compared to determine the fatigue improvement within the structure. Also, information gathered during the first test will also provide insight to improving the finite element models. This report includes information about the Tuttle Creek Bridge and a summary of its structural deficiencies. Details of the gage installation and load testing are provided. Stresses induced by the truck loadings are presented in addition to the inferences from the measurements taken

English Language Teaching Approaches: A Comparison of the Grammar-translation, Audiolingual, Communicative, and Natural Approaches

This work compares four of the most widely used teaching approaches in foreign language contexts; Grammar-Translation, Audiolingual, Communicative, and Natural Approaches. For the comparison, seven features were considered; supporting theories, creation purpose, materials and techniques used, and the roles of teachers, students, and students´ mother tongue in the teaching-learning process. A checklist was created to provide a visual representation of the characterization of the features compared in each approach. Several texts and articles were reviewed to be accurate in the characterization of the information. The results show that the characteristics of each approach were determined for the epoch in which they were proposed and promoted. Some characteristics such as the use of books overlapped all approaches compared in this work; others were unique to certain approaches, supporting theories, for instance; and, others were common in two or three approaches, as in the case of the use of conversations and the role of learners as active learners, to cite some examples

New Insights into Acylhydrazones E/Z isomerization: An Experimental and Theoretical Approach.

Publicación en Open Acces. https://www.mdpi.com/1422-0067/24/19/14739A family of acylhydrazones have been prepared and characterized with the aim of investigating their potential as information storage systems. Their well stablished synthetic methodologies allowed the preparation of seven chemically stable acylhydrazones in excellent yields, that have been photophysically and photochemically characterized. In addition, DFT and TD-DFT calcula-tions have been performed to gain more insights into the structural, energetics and photophysi-cal properties of the E/Z isomers. Our results reveal that the E,Z configurational isomerization upon irradiation is highly dependent on the stabilization of the E or Z isomer due to the for-mation of intramolecular H bonds and electronic/steric effects intrinsically related to their structures. In addition, Raman spectroscopy is also used to confirm molecular structural changes after the formation of hydrogen bonds in the isomersThis research at the University of Málaga was funded by the Junta de Andalucı́a (FQM-159 and FQM-017) projects, Ministerio de Ciencia y Educación (PID2019-110305GB-I00 and PID2019-104293GB-I00). and “Plan Propio Universidad de Málaga” (UMA-Andalucía-TECH)

The Dynamics of the Pulmonary Microbiome During Mechanical Ventilation in the Intensive Care Unit and the Association with Occurrence of Pneumonia

RATIONALE: Ventilator-associated pneumonia (VAP) is the most common nosocomial infections in patients admitted to the ICU. The adapted island model predicts several changes in the respiratory microbiome during intubation and mechanical ventilation. OBJECTIVES: We hypothesised that mechanical ventilation and antibiotic administration decrease the diversity of the respiratory microbiome and that these changes are more profound in patients who develop VAP. METHODS: Intubated and mechanically ventilated ICU-patients were included. Tracheal aspirates were obtained three times a week. 16S rRNA gene sequencing with the Roche 454 platform was used to measure the composition of the respiratory microbiome. Associations were tested with linear mixed model analysis and principal coordinate analysis. MEASUREMENTS AND MAIN RESULTS: 111 tracheal aspirates were obtained from 35 patients; 11 had VAP, 18 did not have VAP. Six additional patients developed pneumonia within the first 48 hours after intubation. Duration of mechanical ventilation was associated with a decrease in α diversity (Shannon index; fixed-effect regression coefficient (β): -0.03 (95% CI -0.05 to -0.005)), but the administration of antibiotic therapy was not (fixed-effect β: 0.06; 95% CI -0.17 to 0.30). There was a significant difference in change of β diversity between patients who developed VAP and control patients for Bray-Curtis distances (p=0.03) and for Manhattan distances (p=0.04). Burkholderia, Bacillales and, to a lesser extent, Pseudomonadales positively correlated with the change in β diversity. CONCLUSION: Mechanical ventilation, but not antibiotic administration, was associated with changes in the respiratory microbiome. Dysbiosis of microbial communities in the respiratory tract was most profound in patients who developed VAP.info:eu-repo/semantics/publishedVersio

Visualisation of water droplets during the operation of PEM fuel cells

A transparent proton exchange membrane fuel cell (PEMFC) has been designed to enable visualisation of water droplets during its operation. Images of the formation of droplets on the surface of the gas diffusion layer (GDL) on its cathode side, which result in water accumulation and blockage to the airflow channels, were recorded using a CCD camera. Measurement of the cell current and droplet characterisation have been carried out simultaneously and the effect of the airflow and external resistive load has been quantified. The droplet images show that water accumulation occurs first in the middle channels of a serpentine reactant-flow fuel cell design and that no droplets are formed at the bends of the flow channels. Water blockage to the airflow path was caused by the overlapping of two land-touching droplets developing on each side of the channel. Flooding was found to be more susceptible to the airflow than the other test operating conditions

Genome-wide association reveals host-specific genomic traits in Escherichia coli

Background Escherichia coli is an opportunistic pathogen which colonizes various host species. However, to what extent genetic lineages of E. coli are adapted or restricted to specific hosts and the genomic determinants of such adaptation or restriction is poorly understood. Results We randomly sampled E. coli isolates from four countries (Germany, UK, Spain, and Vietnam), obtained from five host species (human, pig, cattle, chicken, and wild boar) over 16 years, from both healthy and diseased hosts, to construct a collection of 1198 whole-genome sequenced E. coli isolates. We identified associations between specific E. coli lineages and the host from which they were isolated. A genome-wide association study (GWAS) identified several E. coli genes that were associated with human, cattle, or chicken hosts, whereas no genes associated with the pig host could be found. In silico characterization of nine contiguous genes (collectively designated as nan-9) associated with the human host indicated that these genes are involved in the metabolism of sialic acids (Sia). In contrast, the previously described sialic acid regulon known as sialoregulon (i.e. nanRATEK-yhcH, nanXY, and nanCMS) was not associated with any host species. In vitro growth experiments with a Δnan-9 E. coli mutant strain, using the sialic acids 5-N-acetylneuraminic acid (Neu5Ac) and N-glycolylneuraminic acid (Neu5Gc) as sole carbon source, showed impaired growth behaviour compared to the wild-type. Conclusions This study provides an extensive analysis of genetic determinants which may contribute to host specificity in E. coli. Our findings should inform risk analysis and epidemiological monitoring of (antimicrobial resistant) E. coli

Caracterización clínica y neurofisiológica del síndrome de Guillain-Barré en el Hospital Escuela

Background and Objective. In Honduras, between 1989 and 1999, a study aiming to calculate the incidence of Guillain-Barré syndrome and flaccid paralysis in a pediatric population was developed in the Materno-Infantil Hospital. High compared to other studies, the ratio found at the time was 1.37/100.000 cases of Guillain-Barré syndrome per year and 1.89/100.000 cases of flaccid paralysis per year. The objective of this study was to determine the clinical and neurophysiological subtypes found in patients with Guillain-Barré syndrome in a Honduran pediatric and adult population, compared to a healthy control group. Materials and Methods A transversal analytical study with consecutive patients following the criteria from Asbury at el was developed. The 29 patients, who were between the ages of 2 and 55 years, attended the Hospital Escuela and Materno Infantil during February 1, 2007, through August 2008. A clinical and neurophysiological evaluation was performed to the patients and the 58 healthy individuals. Motor function was assessed to the median, ulnar, peroneal, and tibial nerves, as well as the late F-wave response and the H reflex. The sensitive function of the median, ulnar, and sural nerves was evaluated following the technique described by Parano E, Uncini A. et al (9). Results The demyelinating forms presented in 19 patients (65%); the axonal forms in 10 (35%). The former had greater severity and generated more incapacity, 9 of them requiring attention in the Intensive Care Unit resulting in more bed days, compared to the demyelinating forms (p=0,003). Conclusions Similar to studies held at Northern China and Japan, a high incidence of the axonal forms of Guillain-Barré syndrome was found, presenting a greater severity and more bed days compared to the demyelinating forms. Key Words: Guillain-Barré Syndrome; demyelinating; axonal; electrophysiological; electromyography; palsy. DOI: http://dx.doi.org/10.5377/rct.v0i5.520 Revista Ciencia y Tecnología, No. 5, Segunda época, Diciembre 2009: 66-86En Honduras se realizó entre 1989-1999 un estudio que valoró la incidencia de Guillain-Barré y parálisis flácida en una población pediátrica, en el hospital Materno Infantil obteniendo valores de 1.37/100,000 casos por año para Síndrome de Guillain-Barrè; por otro lado de 1.89/100,000 habitantes por año de parálisis flácida a nivel nacional y hospitalaria. La incidencia fue considerada alta en comparación con otros estudios. El objetivo del presente estudio fue investigar los subtipos clínicos y neurofisiológicos de pacientes con SGB en una población hondureña pediátrica y adulta en Honduras comparado con un grupo control sano. Materiales y Métodos Este es un estudio transversal, analítico con pacientes consecutivos siguiendo los criterios de Asbury et al., en pacientes de 2 a 55 años de edad en el Hospital Escuela y Materno Infantil en el período de 1 febrero 2007 a Agosto 2008, se estudiaron 29 pacientes y 58 controles sanos. Se les realizó la evaluación clínica y neurofisiológica. Se estudiaron los nervios motores Mediano, Ulnar, Peroneo, Tibial y las respuestas tardías onda F y reflejo H; los nervios sensitivos Mediano, Ulnar y Sural con la técnica descrita por Parano E, Uncini A. et al (9). Resultados Las formas desmielinizantes se presentaron en 19 (65%) pacientes y las formas axonales en 10 (35%) de los casos. Estas últimas tuvieron la mayor severidad y discapacidad, así mismo 9 (90%) de los casos requirieron asistencia en una Unidad de Cuidados Intensivos, y un significativo mayor número de días de hospitalización en relación a las formas desmielinizantes p=0.003. Conclusiones Se encontró una alta incidencia de formas axonales del SGB, similar a los datos obtenidos en estudios realizados en el Norte de China y Japón. Presentando una mayor severidad, discapacidad y un incremento de los días de hospitalización en relación a las formas desmielinizantes. Palabras Clave: Guillain-Barré; desmielinizante; axonal; electrofisiológico; electromiografía; parálisis DOI: http://dx.doi.org/10.5377/rct.v0i5.520 Revista Ciencia y Tecnología, No. 5, Segunda época, Diciembre 2009: 66-8