Hold Time Research Articles

Pediatric Ethics Consults for Caregivers: Anybody Home?

Pediatric Ethics Consults for Caregivers: Anybody Home?

Direct quantification of PAHs and nitro-PAHs in atmospheric PM by thermal desorption gas chromatography with electron ionization mass spectroscopic detection

In this work, we developed and optimized a method for the analysis of PAHs and nitro-PAHs in atmospheric particulate matter (PM) samples by using thermal desorption gas chromatography coupled with electron ionization single quadrupole mass spectrometry (TD-GC-(EI)-MS). The method uses thermal desorption from a PM on a filter sample as means of sample introduction to a column and obviates the need for complex extraction procedures, which are time-consuming and require environmentally unfriendly solvents. Moreover, the possibility of systematic errors is minimized and a significantly smaller amount of sample is required compared to traditional techniques requiring a pre-extraction step (approx. 10-times). Thirteen PAHs and three nitro-PAHs were used during method development. Although Tenax cartridges are typically used to capture volatile pollutants from the air, we found that glass-wool liner is the most suitable trap for the examined analytes after desorption from a quartz filter. Among the various instrument parameters which were tested and optimized, TD desorption flow and hold time, and temperature of the cooled injection system (CIS) proved to be most critical. We also found out that the matrix effect is especially pronounced in the case of high PM loadings, which should be kept in mind when planning the analysis. After the optimization, standard reference materials (ERM-CZ100 and NIST 1648a) were used for partial method validation and finally, real PM10 and PM2.5 samples from two Slovenian cities were successfully analyzed.

Investigation on the creep-fatigue crack growth behavior of 316H welded joints in sodium-cooled fast reactors

The failure analysis of 316H steel welded joints in sodium-cooled fast reactors at 550 °C under creep-fatigue load with different hold times has been systematically investigated through this work. For the first time, the reason for the difference of cracking failure mechanism between base metal and weld metal was illustrated from the perspective of microstructure evolution. Under various hold times, different damage mechanisms led the fracture surfaces of the samples to exhibit different degrees of tunneling. Meanwhile, due to the existence of a δ-ferrite network in the weld metal, the cracks were deflected, resulting in higher resistance to crack propagation and a more tortuous crack propagation path than those in the base metal. In addition, the nucleation and growth of voids at the grain boundaries were the primary reasons that base material exhibited intergranular crack propagation, and the evolution of ferrite in the weld was a critical reason for the formation of intergranular pores in the welded metal.

Thermal Preprocessing of Rapidly Solidified Al 6061 Feedstock for Tunable Cold Spray Additive Manufacturing

In this work, the influence of thermal pre-processing upon the microstructure and hardness of Al 6061 feedstock powder is considered through the lens of cold spray processing and additive manufacturing. Since solid-state cold spray processes refine and retain microstructural constituents following impact-driven and high-strain rate severe plastic deformation and bonding, thermal pre-processing enables application-driven tuning of the resultant consolidation achieved via microstructural and, therefore, mechanical manipulation of the feedstock prior to use. Microstructural analysis was achieved via X-ray diffraction, scanning electron microscopy, transmission electron microscopy, electron backscatter diffraction, energy dispersive spectroscopy, and differential thermal calorimetry. On the other hand, nanoindentation testing and analysis were relied upon to quantify pre-processing effects and microstructural evolution influences on the resultant hardness as a function of time at 540 °C. In the case of the as-atomized powder, β-Mg2Si-, Al-Fe-, and Mg-Si-type phases were observed along polycrystalline grain boundaries. Furthermore, after a 60 min hold time at 540 °C, Al-Fe-Si-Cr-Mn- and Mg-Si-type intermetallic phases were also observed along grain boundaries. Furthermore, the as-atomized hardness at 250 nm of indentation depth was 1.26 GPa and continuously decreased as a function of hold time until reaching 0.88 GPa after 240 min at 540 °C. Finally, contextualization of the observations with tuning cold spray additive manufacturing part performance via powder pre-processing is presented for through-process and application-minded design.

Factors determining the flow erosion/part deformation of film insert molded thermoplastic products

Abstract Flow erosion and part deformation are unsolved molding problems that restrict the overall success of film insert molding. This work investigated, both experimentally and numerically, the factors that affect flow erosion and part deformation in film inset molded products. Three plate-with-thickness-variation geometries, namely flat, thin-to-thick, and thick-to thin, were molded for the products. Polystyrene films and polyethylene terephthalate (PET) resins were employed in the experiments. It was found that the thin-to-thick specimens exhibited the most severe flow erosion. Increasing the injection pressure or melt temperature worsened flow erosion. Meanwhile, for the processing parameters adopted in the experiments, part deformation generally increased with melt temperature and hold time, while it decreased with injection pressure and hold pressure. Additionally, a numerical software (Moldex® 3-D) was employed to simulate the temperature and shear stress distributions in molded products. The calculated results suggested that part deformation in insert molded products results mainly from the non-uniform temperature profile during the cooling stage, owing to the product configuration and the insert film, while flow erosion is induced by the high shear stress of the polymer melt in the filling stage.

Preliminary Reproducibility Evaluation of a Phage Susceptibility Testing Method Using a Collection of Escherichia coli and Staphylococcus aureus Phages.

Increasing antimicrobial resistance combined with a lagging pipeline of novel antimicrobial compounds have resulted in a resurgence of interest in phage therapy. To select optimal phage or phage combinations for patients for whom phage therapy is considered, assessment of activity of a panel of phages against the patients' bacterial isolate(s) should ideally be performed. Classical phage susceptibility testing methods (i.e., agar overlay) may be laborious, with expertise outside of normal training and competency of medical laboratory science staff needed. Adaptive Phage Therapeutics™ leveraged a commercially available phenotyping system (Biolog OmniLog®) to generate the PhageBank Susceptibility Test™, which uses a custom data analysis pipeline (PhageSelect™) to measure the delay in reaching log-phase metabolic activity ("hold time") when a given isolate is challenged with a specific phage. The goal of this study was to preliminarily assess reproducibility of this approach by testing 2 bacterial species at 2 sites, APT and an academic site. Nineteen Escherichia coli phages were tested against 18 bacterial isolates, and 21 Staphylococcus aureus phages, against 11 bacterial isolates. Result comparisons were statistically excellent for E. coli (κ = 0.7990) and good/fair for S. aureus (κ = 0.6360). The described method provides good/fair to excellent statistical reproducibility for assessment of phage susceptibility of 2 commonly encountered bacterial species.

Direct thermal desorption-gas chromatography-tandem mass spectrometry versus microwave assisted extraction and GC-MS for the simultaneous analysis of polyaromatic hydrocarbons (PAHs, PCBs) from sediments

Polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) are regulated contaminants usually investigated in sediments. Conventional approaches often use GC-MS to analyse them with a preliminary extraction step which can be solvent- and time-consuming. Here two extraction methodologies were optimized using experimental designs, and compared: microwave assisted extraction (MAE) and thermal desorption (TD); the latter was rarely used for sediments analyses. Several factors that may influence extraction recoveries were studied including matrix parameters (mass, organic matter (OM) content) and processing parameters. A definitive screening design DSD was performed to screen the 6 most influencing factors and model the extraction recoveries using TD. Whatever the OM content, a minimum sediment mass (5 mg) was better for an optimal extraction, with a minimum temperature rate (15 °C min−1), a maximum final temperature (350 °C) associated with a minimum hold time (5 min), and a maximum vent flow (150 mL min−1) between the TD unit and the cryogenic trap. Thereafter matrix effects were evaluated using standard addition, and quality assurance and control were implemented for comparing MAE and TD. TD-GC-MS/MS sensitivity was higher than MAE-GC-MS with detection limits in the range 5–1160 pg and 20–125 pg for PAHs and PCBs, respectively. When considering the appropriate strategy for quantification, TD was also reliable for sediments analysis. Although MAE was less sensitive to matrix effects, TD could significantly improve the analytical process, due to direct coupling with GC-MS/MS and complete automation. Moreover, TD offered possible higher spatial resolution than MAE, particularly for sediment cores analysis, due to the 1000-times lower sample size. At last, TD-GC-MS/MS appeared as a greener analytical procedure.

Universal Correlation between the Roughness Factor and PEMFC Performance Losses in Voltage Cycling Based Accelerated Stress Tests

During operational lifetime, proton exchange membrane fuel cells (PEMFCs) suffer from high performance losses. For the year 2025, the U.S. Department of Energy (DoE) set the durability target for PEMFC light-duty transportation applications at 5,000 hours.1 To meet the automotive target, different aging protocols were established in order to simulate load cycle variations.2 It is well known that load or voltage cycling induces substantial catalyst degradation due to an increasing loss of electrochemically active surface area (ECSA), which is known to be a main driver for the resulting performance penalties.3 Thus, an increasing interest exists in developing accelerated stress test (AST) protocols that can sufficiently describe the degradation of the different components of a membrane electrode assembly (MEA) during automotive application using shorter measurement times.In this study, we report on a strategy to predict the performance degradation of an MEA, making use of a strongly accelerated voltage cycling based ASTs. For this, voltage cycling based ASTs were performed using 5 cm2 MEAs with a 0.1 mgPt cmMEA -2 loaded Pt/C catalyst (TEC10V20E, Tanaka) for both cathode and anode. Voltage cycling was done under H2/N2 (200/75 nccm) at 80 °C, 95% RH, and ambient pressure using square wave profiles with a constant lower potential limit (LPL) of 0.6 V and different upper potential limits (UPLs) of 0.85, 0.95, and 1.0 V, with LPL/UPL hold times of 1, 2, or 8 s. Full characterization of the MEA at beginning-of-life and after each set of voltage cycling intervals was performed by: i) measuring H2/O2 and H2/air polarization curves; ii) determining the ECSA by cyclic voltammetry and CO stripping; iii) conducting limiting current measurement to calculate the O2 transport resistance (R O2 total); and, iv) conducting electrochemical impedance spectroscopy (EIS) measurements under blocking conditions to quantify the proton conduction resistance in the cathode catalyst layer (R H+ cath).When the ECSA loss ranges between ≈20-85%, it was found that the ECSA decreases approximately linearly when plotted against the logarithm of the number of cycles (see fig. 1), exhibiting higher slopes for procedures with higher UPLs and longer hold times, in agreement with the results from previous studies.3, 4 In addition, a direct and AST protocol independent correlation between the loss in total available surface area, i.e., the roughness factor (rf ≡ ECSA × Pt-loading), and the individual loss contributions in H2/air performance curves, namely kinetic (mass/specific activity for the oxygen reduction reaction (ORR)) and O2 transport resistance contributions, was shown. This is due to the fact, that these individual voltage losses are not only highly affected by the cathode rf,3, 5 but that the Pt dissolution/redeposition mechanism seems to be identical for all of the here investigated voltage cycling ASTs, despite the largely varying UPLs and hold times. As a result, a universal correlation between the H2/air performance losses and the rf deterioration was found throughout all ASTs. The important corollary of this finding is that the data from quickly degrading voltage cycling ASTs (i.e., with high UPL) can be used to project the H2/air performance losses when cycling under less degrading conditions.

Development and comparison of field assisted sintering techniques to densify CeO2 ceramics

Cerium dioxide (CeO2) was densified by conventional and field assisted sintering techniques in order to examine the effect of a range of sintering parameters on the resultant pellet microstructure, namely: temperature, hold time, atmosphere, electric field strength and polarity. CS at 1400 °C for 2 h in static air atmospheres provided the highest densities and grain sizes compared with an argon atmosphere, due to the retention of near stoichiometry maintaining sintering kinetics. SPS produced dense ceramics at similar sintering temperatures (1300 °C), but with greatly reduced sintering hold (5 min) and cycle times. However, microstructural inhomogeneity arose from the direct current polarity which led to oxygen ion diffusion toward the positive electrode. FS was performed with an alternating current electric field and produces samples of comparable density at sintering temperatures of ~1100 °C for a hold time of around 1 h with no inhomogeneity due to the alternating current employed.

A call to action for anticoagulation stewardship

A call to action for anticoagulation stewardship

Optimization of the Spark Plasma Sintering Process for High-Volume Fraction Tungsten Carbide/Al 2025 Composites

With an orthogonal experimental design, Spark plasma sintering method was used to create tungsten carbide with Al 2025 composites. Pressure, temperature, and hold time all had an influence on the mechanical characteristics of the composites. Pressure had the greatest effect on density and bending strength, followed by temperature and holding duration. After five minutes of sintering at 556°C under 40 MPa, a 50% tungsten carbide/Al 2025 composite material was produced, resulting in a density of 997.7 percent and a spectacular bending strength of 766.65 MPa. This study revealed the ability of high-volume fraction mixes to support huge loads.

Optimization of Ultrasonic Welding Process Parameters to Enhance Weld Strength of 3C Power Cases Using a Design of Experiments Approach.

Ultrasonic welding (UW) is a joining of plastics through the use of heat generated from high-frequency mechanical motion, which is known as an efficient process in many applications, such as textile, packaging, or automotive. UW of thermoplastics has been widely employed in industry since no polymer degradations are found after UW. However, the trial-and-error approach is frequently used to study optimum UW process parameters for new 3C plastic power cases in current industry, resulting in random efforts, wasted time, or energy consumption. In this study, Taguchi methods are used to study optimum UW process parameters for obtaining high weld strength of a plastic power case. The most important control factor influencing the weld strength is amplitude, followed by weld pressure, hold time, and trigger position. The optimum UW process parameters are amplitude of 43.4 µm, weld pressure of 115 kPa, hold time of 0.4 s, and trigger position of 69.95 mm. Finally, the confirmation experiments are performed to verify the optimum process parameters obtained in this study.

Modelling of the transition from mode I to crystallographic crack growth in a single crystal gas turbine blade alloy under service-like loading conditions

In fatigue life prediction of single crystal gas turbine blades, the risk of rapid crystallographic crack growth along the close-packed planes poses a large uncertainty. A criterion is proposed to predict the transition from mode I to crystallographic crack growth, which is necessary for reliable prediction of the number of cycles from crack initiation to the onset of crystallographic crack growth. The proposed criterion is calibrated against tests performed under a wide range of conditions representative for a gas turbine blade, including isothermal fatigue crack growth tests and thermomechanical fatigue crack growth tests, some including hold times and pre-test aging.

Stress-Controlled Creep–Fatigue of an Advanced Austenitic Stainless Steel at Elevated Temperatures

Creep–fatigue interaction occurs in many structural components of high-temperature systems operating under cyclic and steady-state service conditions, such as in nuclear power plants, aerospace, naval, and other industrial applications. Thus, understanding micromechanisms governing high-temperature creep–fatigue behavior is essential for safety and design considerations. In this work, stress-controlled creep–fatigue tests of advanced austenitic stainless steel (Alloy 709) were performed at a 400 MPa stress range and 750 °C with tensile hold times of 0, 60, 600, 1800, and 3600 s, followed by microstructural examinations. The creep–fatigue lifetime of the Alloy 709 was found to decrease with increasing hold time until reaching a saturation level where the number of cycles to failure did not exhibit a significant decrease. Softening behavior was observed at the beginning of the test, possibly due to the recovery of entangled dislocations and de-twining. In addition, hysteresis loops showed ratcheting behavior, although the mean stress was zero during creep–fatigue cycling, which was attributed to activity of partial dislocations. Microstructural examination of the fracture surfaces showed that fatigue failure dominated at small hold times where the cracks initiated at the surface of the sample. Larger creep cracks were found for longer hold times with a lower probability of dimpled cavities, indicating the dominance of creep deformation. The results were compared with other commonly used stainless steels, and plausible reasons for the observed responses were described.

Influence of thermal aging modes on mechanical properties of steel welded joint 03N18K9M5T

The article presents results of research of the influence of the modes of thermal aging, namely temperature of aging and hold time, on mechanical properties of a weld joint from maraging steel 03H18K9M5T. Aging curves were constructed, that is, the hardness of the metal under study versus the holding time at certain temperatures. Based on the results obtained, an optimal thermal aging regime was proposed for all areas of the welded joint, after which the welded joints were heat-treated by aging in optimal conditions. Hardness distributions were built over the section of the welded joint of martensitic-aging steel samples. Metallographic studies were carried out on the weld microspheres.

A Soft Error Detection and Recovery Flip-Flop for Aggressive Designs With High-Performance

Soft errors induced by Single Event Transient (SET) or Single Event Upset (SEU) are a great threat to integrated circuits. To reduce the error rate and improve the reliability of the circuits, we proposed a radiation hardened flip-flop in this paper, namely, Soft Error Detection and Recovery flip-flop (SEDR-FF). Error detection is based on delayed sampling and redundant storage by a redundant latch. A pulsed clock is adopted to control the redundant latch to reduce the hold time constraint of the latch. To generate the pulsed clock, two efficient delay elements are presented in this paper. Error recovery is accomplished by reloading the previous data stored in a history latch. Transistor-level simulations and timing-annotated gate-level simulations under 65 nm technology show that the proposed flip-flop can efficiently detect and correct the soft errors caused by SET or SEU. It has low overhead of setup time, and is suitable for high-performance designs. In addition, compared with other radiation hardened cells, the proposed flip-flop has moderate power and area overhead, and has lower area cost for fixing hold time violations in circuits designs.

Improved process intermediate stability through the identification and elimination of reactive glycation residues – a monoclonal antibody case study

ABSTRACT The manufacturing of therapeutic biologics can result in a heterogeneous population of charge variants, encompassing many quality attributes which could impact activity and pharmacokinetics. Monitoring the relative abundance of these charge variants to demonstrate process consistency is an expectation of regulatory agencies. Control of the relative abundance of charge variants is also necessary to ensure product comparability across the product lifecycle. We have observed a significant shift in the relative abundance of charged species, as measured by capillary isoelectric focusing, during clarified cell culture fluid holds for several monoclonal antibodies. This lack of stability requires that the hold time for this process intermediate be significantly curtailed, eliminating manufacturing flexibility. We have identified the cause of this shift in relative abundance of charged species as changes in glycation levels, focused predominantly on three conserved, solvent accessible, lysine residues. Mutants of a model protein were generated that show increased charge state stability can be gained by eliminating these reactive lysines. Further, characterization studies were conducted on these mutants to determine the impact to biological activity and stability of the molecule, with no detrimental effects observed. Incorporating this knowledge into the assessments of candidate drugs could allow for the selection of molecules less susceptible to this product degradation pathway, allowing for greater manufacturing flexibility. This process of identifying and removing reactive lysine residues could be useful in the design of drug candidates with improved charge state stability, across a range of modalities.

Implementation of rapid microwave sintering using a 24GHz gyrotron system.

Rapid microwave sintering of different oxide ceramics with heating rates up to 300 °C/min and zero hold time has been implemented using a 24GHz gyrotron-based system for high-temperature processing of materials. The design of the system, principle of operation, and process control are described. Particular attention is given to the design of thermal insulation assemblies and the implementation of temperature measurement in an environment with intense electromagnetic fields. A description of an optical system for dilatometry and temperature measurement is presented. The interrelation between the automatically regulated output power of the gyrotron and the microwave power absorbed volumetrically in the sample is analyzed on the basis of energy balance considerations. The analysis is illustrated by considering examples of rapid sintering processes with ZnO-based and BaTiO3 ceramic samples making use of direct and susceptor-assisted microwave heating. It is demonstrated that an increase in the volumetrically absorbed power leads to the development of a controlled thermal instability, which results in a lower temperature of the densification onset.

The Lumbopelvic-Hip Complex Contribution During Lower Extremity Screening Tests in Elite Figure Skaters.

Figure skating requires power and stability for takeoff and landing from multirotational jumps and various on-ice skills. Repetitive forces may cause overuse injuries distally, making lumbopelvic-hip endurance, strength, and neuromuscular control imperative. To compare lumbopelvic-hip endurance and neuromuscular control in elite figure skaters between sexes and landing and nonlanding limbs using common screening tests. Cross-sectional study. US Olympic and Paralympic Training Center. Forty elite figure skaters (20 women, 20 men; age = 23.2 ± 4.3 years) performed the Y-balance test, single-legged squat (SLS), single-legged squat jump (SLSJ), and unilateral hip-bridge endurance test (40 right [R] landing limbs, length = 169.1 ± 12.2 cm). Normalized reach difference (% of leg length) and composite scores [(anterior + posteromedial + posterolateral)/(limb length × 3) × 100] were calculated for the Y-balance test. Skaters held the unilateral hip bridge until failure with a maximum allotted time of 120 seconds. They performed 5 SLSs and 5 SLSJs while barefoot with the contralateral limb held behind them to mimic a landing position. Both tests were scored by the number of times the patella moved medially to the first ray (medial knee displacement [MKD]). Multivariate analyses of variance with post hoc independent t tests were conducted between sexes and groups. Paired t tests were used to analyze limb differences. Women had a larger composite Y-balance score (R = 10.8% of leg length, P = .002; left = 10.5%, P = .001) and hip-bridge hold time (R = 26.4 seconds, P = .004; left = 28.2 seconds, P = .002) for both limbs compared with men. Men held the hip-bridge longer on their landing limb. Six skaters performed worse on their nonlanding limb during the SLS, and 11 skaters had no MKD with either the SLS or SLSJ. Women performed better on the Y-balance and unilateral hip bridge tests. Increased MKD for some skaters during the SLS and SLSJ may have indicated hip-abductor weakness. Understanding the proximal lumbopelvic-hip variables during takeoff and landing may elucidate contributing factors to distal overuse injuries.

Weaving method-based capacitive yarn touch sensor fabricated of Cu/PET filament composite yarn

In this study, we fabricated a textile-based touch sensor for use in smart clothing. Conductive yarns were fabricated in a sheath-core structure using PET and Cu filaments. E-textile touch sensors were woven using cotton yarns and Cu/PET filament composite conductive yarns, which were woven by varying the composition ratios (8:4, 12:7, and 16:9) of the conductive yarn used as warp and weft. The sensitivity of the e-textile touch sensors was evaluated by measuring their impedance under a load. We observed the highest sensitivity at an 8:4 ratio, owing to the largest change in impedance. Additionally, the sensitivity to touch speed, touch hold time, and touch intensity was measured considering the user’s touch motion. It was confirmed that the user’s touch motion affects the sensitivity of the e-textile touch sensor. This new e-textile touch sensor is expected to be useful in the field of wearable devices because it can be applied to various fabrics. HIGHLIGHTS Fiber only touch sensors were successfully manufactured. Touch performance was analyzed using a self-programmed program. Correlation of sensitivity with electrode composition and touch motion was analyzed.