Debris flow chronology and analysis of controls on debris flow occurrence in the Upper Colorado River valley, Rocky Mountain National Park, CO, A

2012 Fall.Includes bibliographical references.The role of debris flows along the Upper Colorado River was recently highlighted when the Grand Ditch, a 19th-century water-conveyance ditch, overtopped from snowmelt in 2003 and triggered a large debris flow along Lulu Creek, a tributary of the Colorado. Historical aerial photographs indicate that at least two other debris flows have been triggered from the Grand Ditch over the last century. This study examines the natural regime of debris flows in the Colorado River headwaters to assess whether the Grand Ditch has increased magnitude and frequency of debris flow occurrence on the west side of the Colorado River valley. Ten distinct sites of debris flow deposition were mapped using aerial photographs and field exploration, dated from tree cores and tree scars, and analyzed for magnitude using field-estimated volumes of deposition. Six of these ten depositional sites are on the west side of the valley, and several of them have evidence of multiple debris flows. Forty scarred survivor trees and 38 cores from even-aged stands were dated, with corresponding dates of debris flow occurrence ranging from 1923 to 2003. At least 19 debris flows have occurred in this catchment over the last century, but only those at the across-from-Specimen Creek, Lady Creek, Lulu Creek, and Little Yellow sites appear to have been large enough to affect the Colorado River. There is not a substantial difference in the frequency of total debris flows catalogued at the ten sites of deposition between the east (8) and west (11) sides of the Colorado River valley over the last century, but three of the four largest debris flows originated on the west side of the valley in association with the Grand Ditch, while the fourth is on a steep hillslope of hydrothermally altered rock on the east side of the valley. Although ability to interpret the debris flow record is limited by frequent disturbance and burial of older deposits, and estimates of magnitude have high uncertainty, these data suggest that the Grand Ditch has altered the natural regime of debris flow activity in the Colorado River headwaters by increasing the frequency of debris flows large enough to reach the Colorado River. Likelihood of debris flow occurrence is augmented by steep slopes and hydrothermally altered rock, which are both common in the vicinity of the Grand Ditch. This study demonstrates the applicability of dendrochronology for dating geomorphic events in Rocky Mountain National Park and provides context for restoration following debris flows

An increase in N-Ras expression is associated with development of hormone refractory prostate cancer in a subset of patients

Protein expression of H, K and N-Ras was assessed in hormone sensitive and hormone refractory prostate tumour pairs from 61 patients by immunohistochemistry. Expression of H-Ras and K- Ras was not associated with any known clinical parameters. In contrast an increase in N-Ras membrane expression in the transition from hormone sensitive to hormone refractory prostate cancer was associated with shorter time to relapse (p=0.01) and shorter disease specific survival (p=0.008). In addition, patients with an increase in N-Ras membrane expression had lower levels of PSA at relapse (p=0.02) and expression correlated with phosphorylated MAP kinase (p=0.010) and proliferation index (Ki67, p=0.02). These results suggest that in a subgroup patients N-Ras expression is associated with development of hormone refractory prostate cancer via activation of the MAP kinase cascade

Automated Fiber Placement Defect Identity Cards: Cause, Anticipation, Existence, Significance, and Progression

Automated Fiber Placement (AFP), a major composite manufacturing process, can result in many defects during the layup process that often require manual corrective action to produce a part with acceptable quality. These defects are the main limitation of the technology and can be hard to categorize or define in many situations. This paper provides a thorough definition and classification of all AFP defects. This effort constitutes a comprehensive and extensive library relevant to AFP defects. The defects selected and defined in this work are based on understanding and experience from the manufacture and research of advanced composite structure. Proper classification of these defects required an in-depth literature review and consideration of various viewpoints ranging from designers, manufacturers, analysts, and inspection professionals. Collectively, these sources were utilized to develop the most accurate view of each of the individual defect types. The results are presented as identity cards for each defect type, intended to provide researchers and the manufacturing industry a clear understanding of the (1) cause, (2) anticipation, (3) existence, (4) significance, and (5) progression of the defined AFP defects. The link between AFP defects and process planning, layup strategies, and machining was also investigated. Categorization of all important automated fiber placement defects is presented

Innovation in wastewater near-source tracking for rapid identification of COVID-19 in schools [Comment]

COVID-19 is one of the biggest global public health challenges of the century with almost 42 million cases and more than a million deaths to date. Until a COVID-19 vaccine or effective pharmaceutical intervention is developed, alternative tools for the rapid identification, containment, and mitigation of the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are of paramount importance for managing community transmission. Within this context, school closure has been one of the strategies implemented to reduce spread at local and national levels. [...

Characterization of Prepreg Tack for Composite Manufacturing by Automated Fiber Placement

Automated fiber placement (AFP) has become the industry standard for large-scale production of carbon fiber reinforced plastics (CFRP) to improve rate and reduce defects associated with manual layup. Still, defects generated during AFP processes require manual, painstaking inspection by technicians and rework of the part when substantial defects are found. Prepreg (carbon fiber infused with uncured epoxy resin) tack is one of the primary factors that influences the generation of defects that arise during auto-mated fiber placement (AFP). Tack, as it relates to AFP processes and defect formation, can be understood as a combination of two stages, cohesion and decohesion. During the cohesion phase, two pieces of prepreg are brought into contact under elevated temperature and pressure. Compaction of the resin within the contact area will result in a degree of intimate contact, I, between the mating prepreg surfaces. Defect formation, as a result of decohesion between prepreg surfaces, occurs after the cohesion phase and arises due to stress from events such as fiber placement over an existing defect, on a contoured path, etc. (Figure 1). Tack strength resists the displacement of prepreg on a surface due to stresses developed during deposition

Resin infusion of layered metal/composite hybrid and resulting metal/composite hybrid laminate

A method of fabricating a metal/composite hybrid laminate is provided. One or more layered arrangements are stacked on a solid base to form a layered structure. Each layered arrangement is defined by a fibrous material and a perforated metal sheet. A resin in its liquid state is introduced along a portion of the layered structure while a differential pressure is applied across the laminate structure until the resin permeates the fibrous material of each layered arrangement and fills perforations in each perforated metal sheet. The resin is cured thereby yielding a metal/composite hybrid laminate

Materials for Heated Head Automated Thermoplastic Tape Placement

NASA Langley Research Center (LaRC) is currently pursuing multiple paths to develop out of autoclave (OOA) polymeric composite materials and processes. Polymeric composite materials development includes the synthesis of new and/or modified thermosetting and thermoplastic matrix resins designed for specific OOA processes. OOA processes currently under investigation include vacuum bag only (VBO) prepreg/composite fabrication, resin transfer molding (RTM), vacuum assisted resin transfer molding (VARTM) and heated head automated thermoplastic tape placement (HHATP). This paper will discuss the NASA Langley HHATP facility and capabilities and recent work on characterizing thermoplastic tape quality and requirements for quality part production. Samples of three distinct versions of APC-2 (AS4/PEEK) thermoplastic dry tape were obtained from two materials vendors, TENCATE, Inc. and CYTEC Engineered Materials** (standard grade and an experimental batch). Random specimens were taken from each of these samples and subjected to photo-microscopy and surface profilometry. The CYTEC standard grade of APC-2 tape had the most voids and splits and the highest surface roughness and/or waviness. Since the APC-2 tape is composed of a thermoplastic matrix, it offers the flexibility of reprocessing to improve quality, and thereby improve final quality of HHATP laminates. Discussions will also include potential research areas and future work that is required to advance the state of the art in the HHATP process for composite fabrication

Experimental Calibration of a Numerical Model of Prepreg Tack for Predicting AFP Process Related Defects

Wrinkles, puckers, and fiber bridging are among the major defects encountered in the Automated Fiber Placement (AFP) process, and are all different manifestations of fiber misalignment. The main driver for these defects are the residual stresses introduced in the tow during the deposition stage by the AFP head. In contrast, the tack between the deposited tape and the substrate is the resisting force against the formation of such defects. Tack may be defined as the ability of a material to form a bond immediately on contact with another surface. Tack is a very complex phenomenon that is influenced by a variety of process parameters including temperature, head pressure and speed, as well as degree of cure, moisture content, and surface roughness A physics-based modeling framework for simulation of tack was developed in this study that allows for prediction of tack response. The developed tack model is incorporated in the AFP placement modelling framework developed to simulate AFP defects

Decreased Pulmonary Function Measured in Children Exposed to High Environmental Relative Moldiness Index Homes

Background: Exposures to water-damaged homes/buildings has been linked to deficits in respiratory health. However, accurately quantifying this linkage has been difficult because of the methods used to assess water damage and respiratory health. Purpose: The goal of this analysis was to determine the correlation between the water-damage, as defined by the Environmental Relative Moldiness Index (ERMI) value in an asthmatic child’s home, and the child’s pulmonary function measured by spirometry, “forced expiratory volume in one second, percent predicted” or FEV1%. Methods: This analysis utilized data obtained from the “Heads-off Environmental Asthma in Louisiana” (HEAL) study. The children (n= 109), 6 to 12 years of age, who had completed at least one spirometry evaluation and a dust sample collected for ERMI analysis from the home at approximately the same time as the spirometry testing, were included in the analysis. Statistical evaluation of the correlation between ERMI values and FEV1% was performed using the Spearman’s Rank Correlation analysis. The relationship between ERMI values and FEV1% was performed using B-spline regression. Results: The average ERMI value in the HEAL study homes was 7.3. For homes with ERMI values between 2.5 and 15, there was a significant inverse correlation with the child’s lung function or FEV1% measurement (Spearman’s rho -0.23; p= 0.03), i.e. as the ERMI value increased, the FEV1% value decreased. Conclusions: Measures of water-damage (the ERMI) and clinical assessments of lung function (FEV1%) provided a quantitative assessment of the impact of water-damaged home exposures on children’s respiratory health