Hold Duration Research Articles

Analysis of utility of optical surface imaging system for patients who received radiotherapy with active breath control

Objective To analyze the precision and stability of optical surface imaging system for patients who received radiotherapy with active breath control. Methods Eighteen radiotherapy patients with lung metastasis were managed by active breath control (ABC). The difference error detected by optical surface imaging system and CBCT were defined as the precision of optical surface imaging system. The variation among the error of optical surface imaging positioning the value of correction of treatment position and the error detected by optical surface imaging again were defined as the stability of optical surface imaging system. Intrafractional errors were analyzed by optical surface imaging system through whole treatment process (including breath hold and free breath). Results The optical surface imaging system had precision (systematic (Σ) and random errors (σ)) of 1.78/3.42 mm 2.54/6.57 mm and 2.79/3.22 mm respectively and stability of2.12/2.54 mm 3.09/4.02 mm and 1.37/3.55 mm respectively in lateral-medial superior-inferior and anterior-posterior directions. The intrafractional errors (Σ and σ) were 0.42/0.85 mm 0.41/1.47 mm and 0.41/1.47 mm respectively for breath hold duration and 4.76/4.16 mm 6.54/7.78 mm and 3.13/5.92 mm for free breath duration in lateral-medial superior-inferior and anterior-posterior directions. Conclusions As an effective method for validate breath hold; Optical surface imaging system can improve the precision and safety of active breath control. However, the factors that affect the accuracy and stability of the optical surface imaging system in patients undergoing radiotherapy with ABC are not clear; it cannot replace the CBCT for positioning verification. Key words: Tomography, X-ray computed, three-dimensional; Active breath control; Systematic error; Setting error

Sweetpotato Transplant Holding Duration Effects on Plant Survival and Yield

Studies were conducted in North Carolina to determine the effect of holding durations (HDs) [0, 1, 3, 5, and 7 days before planting (DBP)] of ‘Covington’ sweetpotato (Ipomoea batatas) transplants on plant stand and storage root numbers and yield in production fields. In a second field study, the effect of preplant irrigation (PI) treatments (PI and nonirrigation) were evaluated along with the transplant HD on plant stand, storage root numbers, and yield. Transplants held for 7 DBP did not survive as well as the other treatments (lower plant stands) and had lower no. 1, marketable, and total storage root numbers and yields than other holding treatments. HD of 1 or 3 DBP resulted in higher plant stands, and no. 1, marketable, and total numbers of storage roots and yields than holding for 0, 5, or 7 DBP. This study affirms the importance of soil moisture at and shortly after planting for transplant survival and yield. Holding transplants for 1–3 DBP can improve stand establishment and yields when dry conditions occur either before or soon after planting. However, holding transplants for 7 DBP can result in reduced plant stands and yields when stress/dry conditions occur soon after planting.

Individualized tracking of self-directed motor learning in group-housed mice performing a skilled lever positioning task in the home cage.

Skilled forelimb function in mice is traditionally studied through behavioral paradigms that require extensive training by investigators and are limited by the number of trials individual animals are able to perform within a supervised session. We developed a skilled lever positioning task that mice can perform within their home cage. The task requires mice to use their forelimb to precisely hold a lever mounted on a rotary encoder within a rewarded position to dispense a water reward. A Raspberry Pi microcomputer is used to record lever position during trials and to control task parameters, thus making this low-footprint apparatus ideal for use within animal housing facilities. Custom Python software automatically increments task difficulty by requiring a longer hold duration, or a more accurate hold position, to dispense a reward. The performance of individual animals within group-housed mice is tracked through radio-frequency identification implants, and data stored on the microcomputer may be accessed remotely through an active internet connection. Mice continuously engage in the task for over 2.5 mo and perform ~500 trials/24 h. Mice required ~15,000 trials to learn to hold the lever within a 10° range for 1.5 s and were able to further refine movement accuracy by limiting their error to a 5° range within each trial. These results demonstrate the feasibility of autonomously training group-housed mice on a forelimb motor task. This paradigm may be used in the future to assess functional recovery after injury or cortical reorganization induced by self-directed motor learning. NEW & NOTEWORTHY We developed a low-cost system for fully autonomous training of group-housed mice on a forelimb motor task. We demonstrate the feasibility of tracking both end-point, as well as kinematic performance of individual mice, with each performing thousands of trials over 2.5 mo. The task is run and controlled by a Raspberry Pi microcomputer, which allows for cages to be monitored remotely through an active internet connection.

Improved post-processing strategy for MOLLI based tissue characterization allows application in patients with dyspnoe and impaired left ventricular function

Contrast and non-contrast MRI based characterization of myocardium by T1-mapping will be of paramount importance to obtain biomarkers, e.g. fibrosis, which determines the risk of heart failure patients.T1-mapping by the standard post-processing of the modified look-locker inversion recovery (MOLLI) lacks of accuracy when trying to reduce its duration, which on the other hand, is highly desirable in patients with heart failure. The recently suggested inversion group fitting (IGF) technique, which considers more parameters for fitting, has a superior accuracy for long T1 times despite a shorter duration. However, for short T1 values, the standard method has a superior precision. A conditional fitting routine is proposed which ideally takes advantage of both algorithms. Materials and methodsAll measurements were performed on a 1.5T clinical scanner (ACHIEVA, Philips Healthcare, The Netherlands) using a MOLLI 5(n)3(n)3 prototype with n(heart beats) being a variable waiting time between inversion experiments. Phantom experiments covered a broad range of T1 times, waiting times and heart rates. A saturation recovery experiment served as a gold standard for T1 measurement. All data were analyzed with the standard MOLLI, the IGF fit and the conditional fitting routine and the obtained T1 values were compared with the gold standard. In vivo measurements were performed in a healthy volunteer and a total of 34 patients with normal findings, dilative cardiomyopathy and amyloidosis. ResultsTheoretical analysis and phantom experiments provided a threshold value for an apparent IGF T1* determining processing with IGF post processing for values above, or switching to the standard technique for values below. This was validated in phantoms and patients measurements. A reduction of the waiting time to 1 instead of 3 heart beats between the inversion experiments showed reliable results. The acquisition time was reduced from 17 to 13 heart beats. The in vivo measurements showed ECV values between 25% (18–33%; SD 0.03) in the healthy, 30% (22–40%; SD 0.04) in patients with DCM and 45% (30–60%; SD 0.9) in patients with amyloidosis. ConclusionThe adopted post-processing algorithm determines long T1 values with high accuracy and short T1 values while maintaining a high precision. Based on reduction of waiting time, and independence of heart rate, it shortens breath hold duration and allows fast T1-mapping, which is frequently a prerequisite in patients with cardiac diseases.

Does fault strengthening in laboratory rock friction experiments really depend primarily upon time and not slip?

AbstractThe popular constitutive formulations of rate‐and‐state friction offer two end‐member views on whether friction evolves only with slip (Slip law) or with time even without slip (Aging law). While rate stepping experiments show support for the Slip law, laboratory‐observed frictional behavior near zero slip rates has traditionally been inferred as supporting Aging law style time‐dependent healing, in particular, from the slide‐hold‐slide experiments of Beeler et al. (1994). Using a combination of new analytical results and explicit numerical (Bayesian) inversion, we show instead that the slide‐hold‐slide data of Beeler et al. (1994) favor slip‐dependent state evolution during holds. We show that, while the stiffness‐independent rate of growth of peak stress (following reslides) with hold duration is a property shared by both the Aging and (under a more restricted set of parameter combinations) Slip laws, the observed stiffness dependence of the rate of stress relaxation during long holds is incompatible with the Aging law with constant rate‐state parameters. The Slip law consistently fits the evolution of the stress minima at the end of the holds well, whether fitting jointly with peak stresses or otherwise. But neither the Aging nor Slip laws fit all the data well when a − b is constrained to values derived from prior velocity steps. We also attempted to fit the evolution of stress peaks and minima with the Kato‐Tullis hybrid law and the shear stress‐dependent Nagata law, both of which, even with the freedom of an extra parameter, generally reproduced the best Slip law fits to the data.

SLM-processed Sc- and Zr- modified Al-Mg alloy: Mechanical properties and microstructural effects of heat treatment

Traditionally 4xxx casting alloys are used for the additive manufacturing of structurally optimised lightweight parts in space, aerospace and automotive. However, for such applications there is a need for hardenable high-strength Al-alloys exceeding the properties of the 4xxx alloys family. The study analyses the hardness response of different heat treatment temperatures and hold durations applied to a Sc- and Zr-modified Al-Mg (5xxx-) alloy (Scalmalloy®) processed by Selective Laser Melting, and compares the mechanical properties and microstructure in the as-processed and annealed condition, and these properties are clearly related to the very fine grained microstructure. The results show that the static mechanical properties are exceptionally good with Rm-values exceeding 500MPa along with almost no build-orientation related anisotropic effects, and a high ductility even in the heat treated condition. These properties are clearly related to the very fine grained material, along with the good hardenability of the alloy. The stress-strain curves show the typical Portevin-Le-Chatelier (PLC) effect as known for other 5xxx alloys. Due to significant grain boundary pinning by different particles the very fine-grained bi-modal microstructure originating from the SLM-process can be maintained even in the heat treated condition, and only a HIP treatment leads to local grain growth only in coarser grained regions.

Chest-MRI under pulsatile flow ventilation: A new promising technique.

ObjectivesMagnetic resonance imaging (MRI) of the chest has long suffered from its sensitivity to respiratory and cardiac motion with an intrinsically low signal to noise ratio and a limited spatial resolution. The purpose of this study was to perform chest MRI under an adapted non invasive pulsatile flow ventilation system (high frequency percussive ventilation, HFPV®) allowing breath hold durations 10 to 15 times longer than other existing systems.MethodsOne volunteer and one patient known for a thymic lesion underwent a chest MRI under ventilation percussion technique (VP-MR). Routinely used sequences were performed with and without the device during three sets of apnoea on inspiration.ResultsVP-MR was well tolerated in both cases. The mean duration of the thoracic stabilization was 10.5 min (range 8.5–12) and 5.8 min (range 5–6.2) for Volunteer 1 and Patient 1, respectively. An overall increased image quality was seen under VP-MR with a better delineation of the mediastinal lesion for Patient 1. Nodules discovered in Volunteer 1 were confirmed with low dose CT.ConclusionVP-MR was feasible and increased spatial resolution of chest MRI by allowing acquisition at full inspiration during thoracic stabilization approaching prolonged apnoea. This new technique could be of benefit to numerous thoracic disorders.

Optimizing Process Parameters for Aluminum-Silicon High Pressure Die Cast Powertrains

Abstract Aluminum components with refined microstructures produced by high pressure die casting enable manufacturers to gain energy savings via shorter production cycles—if casting and tempering parameters are optimized. This article reports on research results indicating it is possible to increase hardness of hypereutectic Al-Si alloys by optimizing the water quenching rate and duration of room temperature hold, and producing castings with finer microstructures.

Long term creep-fatigue interaction studies on India-specific reduced activation ferritic-martensitic (IN-RAFM) steel

Deterioration in fatigue life occurs due to introduction of hold in peak tensile or peak compressive or in both peak tensile and compressive strains in a triangular waveform. The hold period of a creep fatigue interaction (CFI) cycle denote the uninterrupted service period during which creep damage is predominant. CFI experiments comprising of long hold periods are relatively scarce but are indispensable for the understanding of long term materials behavior under CFI. Keeping this in view, CFI experiments have been performed at 823K on a commercial heat of reduced activation ferritic-martensitic (RAFM) steel using different directions of hold (tensile hold alone, compressive hold alone and simultaneous tensile and compressive holds) for different durations and by employing two strain amplitudes, ±0.25% and ±0.6%. The extent of deterioration in fatigue life in IN-RAFM steel is found to be dependent upon the direction of application of hold. Factors such as oxidation, plastic strain accumulation, mean stresses and stress relaxation during the application of the hold played a significant role in affecting CFI life of RAFM steel. The importance of stress relaxation (SR) in assessing fatigue damage under CFI has been described. A universal relationship between CFI life and SR has been arrived at and which is found to be independent of the type of the waveform, strain amplitude or the duration of hold. Though the relationship between stress relaxation and fatigue life is non-linear, the log–log plot between SR and CFI life value depict an inverse linear relationship. The sum of least squares of the offset from the linear fit, R2 is 0.93 which is a reasonably good approximation. The log–log plot of SR versus CFI life denotes the creep-fatigue interaction line and can be used to predict CFI life for a given amount of SR occurring in the material. The proposed relationship is applicable only for long duration CFI experiments and depicts microstructural creep-fatigue interaction in true sense. Test conditions that do not prominently show the effects of creep-fatigue interaction, do not fall on the CFI interaction line.

Process Parameter Optimization for Hot Embossing Uniformly Textured UHMWPE Surfaces for Orthopedic Bearings

To improve wear properties and reduce friction in orthopedic bearings, UHMWPE surface texturing is a proposed approach to retain fluid, reduce stress in the polymer and promote lubrication in the joint. The objective of this study was to establish a preliminary procedure to texture UHMWPE specimens using a custom die in a hot embosser. Four parameters were varied in subsequent stages: hold pressure, chamber temperature, hold duration and specimen cooling. Each stage was based upon the successful results of the previous stage. A dimple diameter of 96% of the desired diameter was achieved. These parameters will be used to commence a formal procedure to optimize the process using a formal DOE method.

TracMouse: A computer aided movement analysis script for the mouse inverted horizontal grid test.

In rodents, detection and quantification of motor impairments is difficult. The traction test (inverted grid with mice clinging to the underside) currently has no objective rating system. We here developed and validated the semi-automatic MATLAB script TracMouse for unbiased detection of video-recorded movement patterns. High precision videos were analyzed by: (i) principal identification of anatomical paw details frame-by-frame by an experimentally blinded rater; (ii) automatic retrieval of proxies by TracMouse for individual paws. The basic states of Hold and Step were discriminated as duration and frequency, and these principle parameters were converted into static and dynamic endpoints and their discriminating power assessed in a dopaminergic lesion model. Relative to hind paws, forepaws performed ~4 times more steps, they were ~20% longer, and Hold duration was ~5 times shorter in normal C57Bl/6 mice. Thus, forepaw steps were classified as exploratory, hind paw movement as locomotive. Multiple novel features pertaining to paw sequence, step lengths and exploratory touches were accessible through TracMouse and revealed subtle Parkinsonian phenotypes. Novel proxies using TracMouse revealed previously unidentified features of movement and may aid the understanding of (i) brain circuits related to motor planning and execution, and (ii) phenotype detection in experimental models of movement disorders.

Thermoluminescence measurements of trap depth in alkali feldspars extracted from bedrock samples

Various measurements of thermal trap depth are evaluated for K-feldspar grains extracted from a bedrock sample. The initial rise method and the various heating rates method yield consistent results for both the natural signal (E = 1.23 and 1.16 eV, respectively) and for a regenerative dose of 64 Gy (0.83 and 0.78 eV). For the fractional glow curve, apparent E-values range from 0.39 eV to a plateau around 1.50 eV. The highest values for the natural and regenerative signals are obtained using the newly-developed post-isothermal TL (pI-TL) method wherein the isothermal loss curves (gotten by subtracting TL curves obtained after different preheat durations) are fitted in the initial rise region on an Arrhenius plot. For a dose of 12.8 Gy, this method measures apparent E-values ranging from 0.73 eV to a plateau near 1.84 ± 0.06 eV. We repeat this analysis on three additional feldspar samples (two perthites and a high albite) to get a mean value of E = 1.86 ± 0.03 eV. The same analysis of natural aliquots of the K-feldspar sample yields similar results, with the two highest E-values at 1.81 and 1.86 eV. The kinetic order does not systematically vary with isothermal holding temperature or duration but remains relatively constant at 1.6 ± 0.3 (regenerative dose) and 1.5 ± 0.5 (natural dose). The apparent frequency factor, measured assuming a single E-value of 1.86 eV, decreases systematically (∼1023−1012s−1) with hold temperature and duration, a result which is consistent with a thermally-activated, distance-dependent tunneling model for feldspar thermoluminescence (i.e., a single trap depth and a continuum of apparent frequency factors). Frequency factor values measured following identical isothermal treatments are comparable between the natural and regenerative post-isothermal TL curves. By contrast, if different E-values are assumed, the apparent frequency factor values appear stochastic. Finally, it is speculated that the plateau of pI-TL E-values may be interpreted as the thermal depth of the main dosimetric trap measured with IRSL protocols.

Distress intolerance during smoking cessation treatment

Distress intolerance is a key vulnerability factor implicated in the maintenance and relapse of cigarette smoking. Yet, past work has not examined changes in these processes during smoking cessation treatment or their relation to smoking cessation outcomes. The aim of the present study was to examine the effect of two smoking cessation interventions on changes in self-report and behavioral distress intolerance indices during treatment, and whether these changes are associated with smoking cessation outcomes. Treatment-seeking smokers (N = 384) were randomly assigned to one of two 4-session smoking cessation treatment programs: Standard Cessation Program (SCP) or Smoking Treatment and Anxiety Management Program (STAMP). Quit dates were scheduled to coincide with the final treatment session. Physical domains of distress intolerance were assessed at baseline and at each weekly session, via the Discomfort Intolerance Scale (DIS; higher scores indicate more intolerance for discomfort) and Breath Holding Duration Task (shorter durations indicate more intolerance for respiratory distress). The STAMP condition produced a greater rate of reduction in DIS scores than did the SCP condition. Changes in DIS scores during treatment mediated the effect of STAMP treatment on 7-day point prevalence abstinence at Month 3 post-quit attempt. There were no treatment conditions differences in changes in Breath-Holding duration. Data suggest self-reported distress intolerance is malleable in the context of stress sensitivity reduction treatment, but not standard smoking cessation treatment, and such reductions may result in promotion of smoking abstinence.

Electrocatalytic Reduction of Selenate on Gold Electrodes in the Presence of Copper (II)

Reduction of aqueous selenate (SeO4 2-) to lower oxidation states of selenium is typically a very slow reaction, but important to the detection and removal of soluble selenium from wastewater. Electrocatalytic reduction of selenate has not been exhaustively explored; only a few electrocatalytic methods for reducing selenate have been reported to date [1-6]. Commercially available selenate is often contaminated with selenite (SeO3 2-), a species that can be readily reduced to yield elemental selenium or selenides. No selenate reduction studies to date acknowledge the presence of this impurity. Furthermore, not all these studies unambiguously show that selenate itself is reduced, as opposed to these traces of selenite. Previous literature claims that gold electrodes are capable of reducing selenate at electrode potentials below 0.6 V vs SHE [1], forming a selenium deposit that strips anodically above 0.9 V vs SHE. Cyclic voltammetry experiments in this work reproduced the reported redox features, shown in Fig. 1 as peak A and B, respectively. However, when selenite was removed from selenate solutions with a titania adsorbent, no redox activity is seen on gold electrodes. It can be concluded that the previous report [1] was in fact measuring currents associated with trace selenite reduction. Selenate undergoes specific adsorption on gold and no other reaction. Peak C in Fig. 1 can be attributed to specific adsorption of selenate. Figure 1: Cyclic voltammetry at 0.2 V/s on Au wire electrode with 1mM of selenate in 0.1 M HClO4. Two purities of selenate were used. The first was selenate decahydrate purchased from Alfa Aesar at a purity of 99.9%, used as received. The other sample of selenate was the same, but was exposed to a titania adsorbent in order to remove traces of selenite. A cyclic voltammogram is also shown after selenite addition. We have found that the chemical inertness of selenate can be overcome by addition of copper (II) salts. Copper (II) can be reduced to an adlayer of underpotential deposited copper on gold electrodes between 0.64 and 0.24 V SHE. Once formed, we have found that this adlayer induces slow reduction of selenate, yielding a thin copper selenide film. The mechanism for CuxSe formation was investigated using potentiostatic deposition, followed by linear sweep stripping voltammetry. This technique allows determination of Cu and Se stripping charges separately, observed in Fig. 2 as peak D and E, respectively. At lower electrode potentials (< 0.24 V vs SHE), where copper (II) is reduced to bulk copper metal, selenate both accelerates Cu deposition and is reduced. Selenium co-deposits with bulk copper formed in selenate / copper (II) solutions. In this regime, selenate reduction is much faster than reduction by UPD copper. Figure 2: Linear sweep stripping voltammograms at 0.1 V/s after potential holds at 0.325 V on a Au electrode. Solution was 0.1 M HClO4 with 5 mM Cu(ClO4)2 and 1 mM Na2SeO4(titania purified). Potential hold duration for each curve is indicated in the legend.

Influence of Spray-Solution Temperature and Holding Duration on Weed Control with Premixed Glyphosate and Dicamba Formulation

Water is the primary carrier for herbicide application, and carrier-water–related factors can influence herbicide performance. In a greenhouse study, premixed formulation of glyphosate plus dicamba was mixed in deionized (DI) water at 5, 18, 31, 44, or 57 C and applied immediately. In a companion study, glyphosate and dicamba formulation was mixed in DI water at temperatures of 5, 22, 39, or 56 C and sprayed after the herbicide solution was left at the respective temperatures for 0, 6, or 24 h. In both studies, glyphosate plus dicamba was applied at 0.275 plus 0.137 kg ae ha−1(low rate), and 0.55 plus 0.275 kg ha−1(high rate), respectively, to giant ragweed, horseweed, Palmer amaranth, and pitted morningglory. Glyphosate plus dicamba applied at a low rate with solution temperature of 31 C provided 14% and 26% greater control of giant ragweed and pitted morningglory, respectively, compared to application at solution temperature of 5 C. At both rates of glyphosate and dicamba formulation, giant ragweed and pitted morningglory control was 15% or greater at solution temperature of 44 C compared to 5 C. Weed control was not affected with premixture of glyphosate and dicamba applied ≤ 24 h after mixing herbicide. When considering solution temperature, glyphosate and dicamba applied at low rate provided 13 and 6% greater control of Palmer amaranth and pitted morningglory, respectively, with solution temperature of 22 C compared to 5 C. Similarly, giant ragweed control was 8% greater with solution temperature of 39 C compared to 5 C. Glyphosate and dicamba applied at high rate provided 8% greater control of giant ragweed at solution temperature of 22 or 39 C compared to 5 C. Therefore, activity of premixed glyphosate and dicamba could be reduced with spray solution at lower temperature; however, the result is dependent on weed species.

Apnea-like suppression of respiratory motion: First evaluation in radiotherapy

Background and purposeCompensation for respiratory motion is needed while administering radiotherapy (RT) to tumors that are moving with respiration to reduce the amount of irradiated normal tissues and potentially decrease radiation-induced collateral damages. The purpose of this study was to test a new ventilation system designed to induce apnea-like suppression of respiratory motion and allow long enough breath hold durations to deliver complex RT. Material and methodsThe High Frequency Percussive Ventilation system was initially tested in a series of 10 volunteers and found to be well tolerated, allowing a median breath hold duration of 11.6min (range 3.9–16.5min). An evaluation of this system was subsequently performed in 4 patients eligible for adjuvant breast 3D conformal RT, for lung stereotactic body RT (SBRT), lung volumetric modulated arc therapy (VMAT), and VMAT for palliative pleural metastases. ResultsWhen compared to free breathing (FB) and maximal inspiration (MI) gating, this Percussion Assisted RT (PART) offered favorable dose distribution profiles in 3 out of the 4 patients tested. PART was applied in these 3 patients with good tolerance, without breaks during the “beam on time period” throughout the overall courses of RT. The mean duration of the apnea-like breath hold that was necessary for delivering all the RT fractions was 7.61min (SD=2.3). ConclusionsThis first clinical implementation of PART was found to be feasible, tolerable and offers new opportunities in the field of RT for suppressing respiratory motion.

Low cycle fatigue and creep–fatigue interaction behaviour of 2.25Cr1MoV steel at elevated temperature

This study reports the fatigue behaviour of 2.25Cr1MoV steel under low cycle fatigue (LCF) loading and creep-fatigue interaction (CFI) loading at 355, 455 and 555 °C. Various hold durations up to 600 s were introduced in the CFI tests at the peak/valley strain under strain or stress control. In LCF tests, the steel exhibited remarkable strengthening at 455 °C, which can be ascribed to the effect of dynamic strain aging. In CFI tests, tensile holds were found more damaging than compressive holds but considerably less harmful than the combined tensile-compressive holds. A modified plastic strain energy approach based on the damage mechanisms was proposed to predict fatigue life under LCF and CFI conditions. The predictions obtained compared very favourably with the experimental results.

Characterization of operating parameters for XMuLV inactivation by low pH treatment.

To ensure the viral safety of protein therapeutics made in mammalian cells, purification processes include dedicated viral clearance steps to remove or inactivate adventitious and endogenous viruses. One such dedicated step is low pH treatment, a robust and effective method commonly used in monoclonal antibody production to inactivate enveloped viruses. To characterize the operating space for low pH viral inactivation, we performed a statistically designed experiment evaluating the effect of pH, temperature, hold duration, acid type, and buffer concentration on inactivation of the retrovirus model, XMuLV. An additional single factor experiment was performed to study the effect of protein concentration. These data were used to generate predictive models of inactivation at each time point studied, which can be used to identify conditions for robust and effective XMuLV inactivation. At pH 3.6, XMuLV inactivation was rapid, robust, and relatively unaffected by the other factors studied, providing support for this as a generic viral inactivation condition for products that can tolerate this low pH. At pH 3.7 and 3.8, other factors besides pH affected XMuLV inactivation. By understanding the impact of each factor on inactivation, the factors can be manipulated within the operating space to ensure effective inactivation while achieving desired product quality goals.

Creep–fatigue interaction behavior of 316LN austenitic stainless steel with varying nitrogen content

Creep–fatigue interaction (CFI) behavior of 316LN stainless steel with varying nitrogen content (0.07, 0.14 and 0.22wt.%) is investigated at temperature of 873K under strain-controlled fatigue tests with a tensile-hold period of 1, 13.3 and 30min. Dynamic strain aging, thermal-recovery and/or dislocation–precipitate interactions are found to strongly control CFI deformation. At all the nitrogen contents in 316LN SS, the amount of stress relaxation and the associated relaxation strain rate decreased with increase in hold duration. Irrespective of the hold period, wavy-slip dislocation structures (cells, tangles, walls) are noticed at 0.07wt.% N, whereas dislocation structures such as planar slip bands impinging on grain boundary are noticed, in addition, at nitrogen contents above 0.07wt.%. Nitrogen content played a dual-role in influencing the CFI life. At 1-min hold where the failure is by transgranular plus intergranular fracture, increase in nitrogen from 0.07 to 0.14wt.% caused an improvement in CFI life. On the other hand, CFI life decreased with increasing nitrogen content at 13.3 and 30-min hold durations that induced significant intergranular damage. Intergranular damage is evidenced in the form of triple point cracks and interconnected networks of grain boundary decohesion.

Understanding low cycle fatigue and creep–fatigue interaction behavior of 316 L(N) stainless steel weld joint

The aim of this work is to study the time dependent effects on the low cycle fatigue (LCF) behavior of 316 L(N) stainless steel weld joint. Influence of strain rate, temperature, strain range, hold time and hold duration on fatigue life is evaluated. Occurrence of dynamic strain aging, creep damage, overall distribution of damage across the weld joint and the role of microstructure on the failure mode and failure location of the weld joint is discussed as a function of test parameters.