Microstructure and Mechanical Properties of High-Strength AA6011 Aluminum Alloy Welding with Novel 4xxx Filler Metals.

Welding high-strength 6xxx aluminum alloys using a commercial ER4043 filler often results in inferior joint strength. This study investigated the effects of newly developed Al-Si-Mg filler metals with varying Mg (0.6-1.4 wt.%) and Mn (0.25-0.5 wt.%) contents on the microstructure evolution and mechanical performance of high-strength AA6011-T6 plates using gas metal arc welding. Two commercial fillers, ER4043 and ER4943, were used as references for comparison. The results revealed that increasing the Mg and Mn contents in the novel fillers resulted in sufficiently high alloying elements in the fusion zone (FZ), leading to higher microhardness. Under as-welded conditions, the weakest region of the joint was the heat-affected zone (HAZ). The joint strength was almost independent of the filler type and was controlled by the HAZ strength, measuring a UTS of 230 and 241 MPa for ER4043 and the other joints, respectively. The higher Mg contents in the novel fillers promoted the precipitation of a large volume fraction of fine ß″-MgSi in the FZ during post-weld heat treatment (PWHT), resulting in superior strength and higher welding efficiency relative to the reference fillers. The optimal Mg content of the novel fillers was 0.6 wt.%. Increasing the Mn content of the filler metal had an insignificant effect. The FMg0.6 filler with 0.6% Mg achieved the best combination of strength (UTS of 410 MPa) and elongation (6.7%) as well as the highest welding efficiency (94%) after PWHT, among all of the fillers studied. However, the newly developed fillers adversely affected the impact toughness of the joints.

Evolution of Sleep Complaints in Myotonic Dystrophy Type 1: A 9-Year Longitudinal Study.

The objective was to characterize the progression of sleep complaints in 115 dystrophy type 1 (DM1) patients who filled out a sleep questionnaire twice at a 9-year interval. Daytime napping (22.1% vs. 34.5%, p < 0.05), early awakenings (11.4% vs 21.1%, p < 0.05), nonrestorative sleep (39.5% vs 51.8%, p < 0.05), stimulant use (7.0% vs 19.3%, p < 0.01), breathing cessation (10.7% vs 23.2%, p < 0.01), and nighttime urination (42.5% vs 54.9%, p < 0.05) increased between Time 1 and Time 2. Sleep-related complaints are prominent and augment rapidly in DM1 patients. Physicians need to better identify and treat them to help alleviate the burden they impose on patients and their caregivers.

Évolution des troubles du sommeil dans la dystrophie myotonique de type 1 : une étude longitudinale de 9 ans.L'objectif était de caractériser l'évolution des plaintes liées au sommeil chez 115 patients atteints de dystrophie myotonique de type 1 (DM1) ayant rempli un questionnaire sur le sommeil à deux reprises à 9 ans d'intervalle. La prévalence des siestes (22,1 % vs 34,5 %, p < 0,05), des réveils matinaux précoces (11,4 % vs 21,1 %, p < 0,05), du sommeil non réparateur (39,5 % vs 51,8 %, p < 0,05), de la consommation de stimulants (7,0 % vs 19,3 %, p < 0,01), des arrêts respiratoires (10,7 % vs 23,2 %, p < 0,01) et des mictions nocturnes (42,5 % vs 54,9 %, p < 0,05) a augmenté entre le temps 1 et le temps 2. Les plaintes liées au sommeil sont fréquentes et augmentent rapidement dans la DM1. Les médecins doivent mieux les identifier et les traiter pour aider à alléger le fardeau qu'ils imposent aux patients et à leurs aidants.

Welding of AA6061-T6 Sheets Using High-Strength 4xxx Fillers: Effect of Mg on Mechanical and Fatigue Properties.

Al-Si-Mg 4xxx filler metals are widely used in aluminum welding owing to their excellent weldability and capability for strength enhancement by heat treatment. However, weld joints with commercial Al-Si ER4043 fillers often exhibit poor strength and fatigue properties. In this study, two novel fillers were designed and prepared by increasing the Mg content in 4xxx filler metals, and the effects of Mg on the mechanical and fatigue properties were studied under as-welded and post-weld heat-treated (PWHT) conditions. AA6061-T6 sheets were used as the base metal and welded by gas metal arc welding. The welding defects were analyzed using X-ray radiography and optical microscopy, and the precipitates in the fusion zones were studied using transmission electron microscopy. The mechanical properties were evaluated using the microhardness, tensile, and fatigue tests. Compared to the reference ER4043 filler, the fillers with increased Mg content produced weld joints with higher microhardness and tensile strength. Joints made with fillers with high Mg contents (0.6-1.4 wt.%) displayed higher fatigue strengths and longer fatigue lives than joints made with the reference filler in both the as-welded and PWHT states. Of the joints studied, joints with the 1.4 wt.% Mg filler exhibited the highest fatigue strength and best fatigue life. The improved mechanical strength and fatigue properties of the aluminum joints were attributed to the enhanced solid-solution strengthening by solute Mg in the as-welded condition and the increased precipitation strengthening by ß″ precipitates in the PWHT condition.

The Use of UAS to Release the Egg Parasitoid Trichogramma spp. (Hymenoptera: Trichogrammatidae) Against an Agricultural and a Forest Pest in Canada.

The egg parasitoid Trichogramma spp. (Hymenoptera: Trichogrammatidae) is a widely used biocontrol agent against lepidopteran pests. Historically, Trichogramma were deployed either by plane or by using cardboard cards on which parasitized eggs are glued and manually installed at sites. Plane deployment is costly and card installation is time consuming, but the use of Trichogramma has been shown to be efficient against several pests. In 2016 and 2017, a research project investigated the potential use of unmanned aerial system for distributing Trichogramma as biocontrol agents against two major pests: an agricultural pest of maize, the European corn borer, Ostrinia nubilalis (Hübner) (Lepidoptera: Crambidae), and a forest pest, the eastern spruce budworm, Choristoneura fumiferana (Clemens) (Lepidoptera: Tortricidae). Exposure duration of parasitized eggs to field conditions (temperature, predation, etc.) in maize fields influenced the Trichogramma's emergence rate, suggesting that timing of parasitoid releases with their emergence is essential. Although parasitism of naturally occurring eggs in maize fields could not be compared due to the low density of the European corn borer, parasitism of sentinel eggs by Trichogramma was more prominent in plots with unmanned aircraft systems (UAS)-releases compared to control plots. For spruce budworm, treatment with Trichogramma increased egg parasitism and there was no difference between the deployment by UAS and by Trichocards. We discuss these results in the context of pest biology and management. We also discuss the advantages and shortcomings of both methods and offer insights into where future work might go to further leverage the use of UAS in managing these important pests.

One-Year Lifestyle Intervention, Muscle Lipids, and Cardiometabolic Risk.

PURPOSE: Low-attenuation muscle (LAM) area at mid-thigh, a computed tomography (CT)-derived index of intramuscular lipids, is associated with insulin resistance, obesity, and type 2 diabetes. The present study aimed at testing the hypothesis that changes in LAM area in trunk muscles from a single abdominal scan could provide relevant information to evaluate the effects of a lifestyle intervention without the use of a mid-thigh CT scan. METHODS: Cardiometabolic risk variables, including waist circumference, lipoprotein-lipid profile, glucose tolerance, and cardiorespiratory fitness, were assessed in a sample of 102 dyslipidemic viscerally obese men at baseline and after a 1-yr lifestyle intervention. Abdominal (L4-L5) and mid-thigh CT scans were performed and abdominal muscles classified as psoas and core muscles. Scans were segmented to calculate muscle areas, LAM areas, and mean attenuation values. RESULTS: All muscle groups showed a decrease in LAM areas (P < 0.0001) in response to the lifestyle intervention. Changes in LAM areas were significantly associated with changes in triglycerides, high-density lipoprotein (HDL) cholesterol, cholesterol/HDL cholesterol ratio and log triglycerides/HDL cholesterol ratio (mid-thigh, 0.20 ≤ |r| ≤ 0.29; psoas, 0.28 ≤ |r| ≤ 0.38; core, 0.29 ≤ |r| ≤ 0.34, P < 0.05). Changes in core LAM area were significantly associated with changes in 2-h glucose levels, glucose area measured during the oral glucose tolerance test and homeostasis model assessment of insulin resistance (0.21 ≤ r ≤ 0.34, P < 0.05). Stepwise regression analyses showed that changes in LAM psoas area were associated with changes in HDL cholesterol and the cholesterol/HDL cholesterol ratio independently from changes in visceral adiposity. CONCLUSIONS: Changes in trunk LAM areas are useful indices of changes in mid-thigh LAM area observed with a 1-yr lifestyle intervention. Thus, an additional mid-thigh scan is not necessary to evaluate muscle lipid content by CT when an abdominal CT scan is available.

Trunk muscle quality assessed by computed tomography: Association with adiposity indices and glucose tolerance in men.

BACKGROUND/OBJECTIVES: Thigh muscle attenuation measured by computed tomography (CT) has been shown to be a reliable and useful index of skeletal muscle fat infiltration. Thigh muscle fat content assessed by CT has been linked to obesity and type 2 diabetes and is a correlate of insulin resistance in sedentary individuals. However, as measurement of mid-thigh fat content requires the assessment of another region of interest beyond the usual abdominal scan required to measure levels of visceral and subcutaneous abdominal adipose tissue, this study aimed at testing the hypothesis that skeletal muscle fat measured from a single abdominal scan (L4-L5) would also provide information relevant to the estimation of muscle fat infiltration as it relates to cardiometabolic risk. METHODS: Abdominal (L4-L5) and mid-thigh CT scans were performed in a sample of 221 sedentary men covering a wide range of adiposity values. Trunk muscles on the L4-L5 scan were classified into 2 groups: 1) psoas and 2) core muscles. The two scans were segmented to calculate muscle areas, mean attenuation values as well as low-attenuation muscle (LAM) areas, the latter being considered as an index of skeletal muscle fat infiltration. Body mass index (BMI), body composition and waist circumference were assessed and a 75 g oral glucose tolerance test (OGTT) was performed. RESULTS: Mid-thigh, psoas and core LAM areas were all significantly associated with body composition indices (0.46 ≤ r ≤ 0.71, p < 0.0001) whereas trunk muscle indices were more strongly associated with visceral adiposity and waist circumference (0.54 ≤ r ≤ 0.79, p < 0.0001) than were mid-thigh muscle variables (0.44 ≤ r ≤ 0.62, p < 0.0001). Mid-thigh LAM area as well as psoas and core LAM areas were significantly associated with fasting glucose, 2-h plasma glucose levels, the glucose area under the curve and with the HOMA-IR index (mid-thigh LAM area: 0.18 ≤ r ≤ 0.25, p < 0.01; psoas LAM area: 0.27 ≤ r ≤ 0.33, p < 0.0001; core LAM area: 0.24 ≤ r ≤ 0.34, p < 0.01). Multivariable stepwise regression analyses revealed that the associations between trunk muscle indices and glucose tolerance/insulin resistance were no longer significant after controlling for visceral adiposity measured at L4-L5. CONCLUSION: Our results suggest that CT-imaging derived indices of trunk muscle quality are related to glucose tolerance and visceral adiposity. However, the relationship between skeletal muscle fat and insulin resistance appears to be largely mediated by the concomitant variation in visceral adiposity. Finally, our results suggest that a single CT scan performed at L4-L5 is adequate to assess skeletal muscle fat content related to cardiometabolic risk.