Decreasing Sample Size Research Articles

Implementation of Mobile Health Technologies in Clinical Trials of Movement Disorders: Underutilized Potential.

Mobile health technologies (mHealth) are patient-worn or portable devices aimed at increasing the granularity and relevance of clinical measurements. The implementation of mHealth has the potential to decrease sample size, duration, and cost of clinical trials. We performed a review of the ClinicalTrials.gov database using a standardized approach to identify adoption in and usefulness of mHealth in movement disorders interventional clinical trials. Trial phase, geographical area, availability of data captured, constructs of interest, and outcome priority were collected. Eligible trials underwent quality appraisal using an ad hoc 5-point checklist to assess mHealth feasibility, acceptability, correlation with patient-centered outcome measures, and clinical meaningfulness. A total of 29% (n = 54/184) registered trials were using mHealth, mainly in Parkinson's disease and essential tremor (59.3% and 27.8%). In most cases, mHealth were used in phase 2 trials (83.3%) as secondary outcome measures (59.3%). Only five phase 3 trials, representing 9.3% of the total, used mHealth (1 as primary outcome measure, 3 as secondary, and 1 as tertiary). Only 3.7% (n = 2/54) of all trials used mHealth for measuring both motor and non-motor symptoms, and 23.1% (n = 12/52) used mHealth for unsupervised, ecologic outcomes. Our findings suggest that mHealth remain underutilized and largely relegated to phase 2 trials for secondary or tertiary outcome measures. Efforts toward greater alignment of mHealth with patient-centered outcomes and development of a universal, common-language platform to synchronize data from one or more devices will assist future efforts toward the integration of mHealth into clinical trials.

Size effect in cyclic torsion of micron-scale polycrystalline copper wires

Cyclic torsion of micron-scale polycrystalline copper wires was experimentally studied. It was found that cyclic hardening is more pronounced with larger strain amplitude under symmetric cyclic straining. The mean stress relaxation is accelerated with larger initial strain and smaller strain amplitude under asymmetric cyclic straining. Meanwhile, both sample size and grain size effects were observed. That is the mean stress relaxation increases with decreasing sample size and grain size. The grain size effect is caused by an elevated internal stress in wire with smaller grain size. The observed sample size effect is attributed to the internal stress induced by geometrically necessary dislocations.

Assessing the reliability of virtual reconstruction of mandibles

Mandibular morphological variation is often used to examine various aspects of human palaeobiology. However, fossil and archeological skeletal remains are often fragmented/distorted and so are frequently excluded from studies. This leads to decreased sample sizes and, potentially, to biased results. Thus, it is of interest to restore the original anatomy of incomplete/distorted specimens. Thin plate splines (TPS), commonly used in Geometric Morphometrics (GM), offer the prospect of reconstruction of missing parts and particularly of interest here, missing landmarks. Here, the reliability of TPS based mandibular reconstruction is tested. To that end missing landmarks were simulated in originally complete hemimandibles. TPS was then used to restore the location of simulated missing data and the predicted landmarks were compared to the original ones. Results show that error varies according to the number and location of estimated landmarks. Notwithstanding, estimation error is usually considerably smaller than the morphological differences between individuals from the same species. TPS based reconstruction allows fragmentary mandibles to be used in studies of whole mandibular variation, provided the above mentioned caveats are considered.

Towards ultraefficient nanoscale straintronic microwave devices

We investigate the ultrafast magnetization dynamics of individual nanomagnets resonantly excited by surface acoustic waves (SAWs) generated nonlocally by nonmagnetic phononic gratings. Using a time-resolved magneto-optic Kerr effect microscope, we report the dependence of the magnetoelastic resonance on SAW wavelength and nanomagnet size. Our measurements show that the precession amplitude of single nanomagnets increases monotonically and nonlinearly with decreasing sample size. In addition, for nanomagnets below a critical size we find that the oscillation amplitude increases with SAW frequency. Field-swept measurements of the magnetization dynamics reveal that the damping of the magnetoelastic resonance also decreases with the size of the magnet, ultimately reaching a minimum value determined by the Gilbert damping. This work shows that acoustically driven spin dynamics possess favorable scaling characteristics, which supports the notion that efficient, high-frequency (10--100 GHz) nanoscale straintronic devices limited only by $\ensuremath{\alpha}$ are feasible.

Dating of rockfall damage in trees yields insights into meteorological triggers of process activity in the French Alps

Rockfall release is a rather unpredictable process. As a result, the occurrence of rockfall often threatens humans and (infra)structures. The assessment of potential drivers of rockfall activity therefore remains a major challenge, even if the relative influence of rainfall, snowmelt, or freeze–thaw cycles has long been identified in short‐term monitoring projects. In the absence of longer‐term assessments of rockfall triggers and possible changes thereof, our knowledge of rockfall dynamics remains still lacunary as a result of the persisting scarcity of exhaustive and precise rockfall databases. Over the last decades, several studies have employed growth disturbances (GDs) in tree‐ring series to reconstruct rockfall activity. Paradoxically, these series were only rarely compared to meteorological records. In this study, we capitalize on the homogeneity of a centennial‐old reforestation plot to develop two reconstructions – R1 including only growth suppressions, and R2 based on injuries – with limited biases related to decreasing sample size and changes in exposed diameters back in time. By doing so, our study also and quite clearly highlights the large potential that protection forests have in terms of yielding reliable, multidecadal rockfall reconstructions. From a methodological perspective, we find no synchronicity between R1 and R2, as well as an absence of meteorological controls on rockfall processes in R1. This observation pleads for a careful selection of GDs in future reconstructions. In terms of process dynamics, we demonstrate that summer intense rainfall events (>10 mm day−1) are the main drivers for rockfall activity at our study site. Despite the stringency of our detection procedure, correlations between rockfall activity and meteorological variables remain comparable to those reported in previous studies, as a result of the complexity and multiplicity of triggering factors. We therefore call for a more systematic coupling of tree‐ring analysis with rockfall and microclimatic monitoring in future studies. © 2020 John Wiley & Sons, Ltd.

Effect of Sample Size on Common Item Equating Using the Dichotomous Rasch Model

ABSTRACTThis study addresses equating issues with varying sample sizes using the Rasch model by examining how sample size affects the stability of item calibrations and person ability estimates. A resampling design was used to create 9 sample size conditions (200, 100, 50, 45, 40, 35, 30, 25, and 20), each replicated 10 times. Items were recalibrated using each of these 90 samples. The deviation of these calibrations from the full sample (N = 9,678) calibrations were then computed. The ability estimates for all 9,678 examinees were then recomputed 90 times using the item calibrations from each of the 90 different samples. The deviation of 90 sets of ability estimates from the original set of ability estimates was computed. This study found that less precision and item calibration instability occur with smaller sample sizes; however, the decreasing sample size has minimal effect on the person ability estimates.

Transforming a Face-to-Face Legacy Intervention to a Web-Based Legacy Intervention for Children With Advanced Cancer.

Research is needed to examine new and innovative web-based intervention delivery methods that are feasible, cost-effective, and acceptable to children and their families to increase access to palliative care services in the home and community. Our previous work included the development of a legacy intervention using face-to-face digital storytelling for children with cancer that showed feasibility and strong promise to improve child outcomes. However, face-to-face intervention delivery techniques limited our recruitment, thus decreasing sample size and potential access to broader populations. Here we present the systematic steps of the development of a web-based legacy intervention for children (7-17 years of age) with relapsed or refractory cancer and their parent caregivers. Counts and frequencies for parent (n = 81) reports on satisfaction surveys are presented and parent suggestions for future work. Results suggest the web-based legacy intervention is feasible and acceptable, with parent-perceived beneficial outcomes for the child, parent, and family. Results provide a foundation for web-based intervention development in palliative care and the implementation of a theoretically grounded intervention to reduce suffering of seriously ill children and their family members, thereby advancing the science of symptom management in vulnerable palliative care populations.

Next Generation Sequence Minimal Residual Disease (NGS-MRD) Predicts Outstanding Event Free Survival (EFS) Regardless of Hematopoietic Cell Transplantation (HCT) Preparative Approach or Graft Alpha/Beta Depletion in Children with Acute Lymphoblastic Leukemia (ALL)

MRD detected by flow cytometry (FC) or PCR has been associated with key outcomes after HCT for ALL. In a prospective multicenter trial (NCT02646839; Pediatric Blood and Marrow Transplant Consortium [PBMTC] ONC1401), we performed a planned sub-study of NGS-MRD to predict outcomes pre- and post-HCT for ALL patients (n=57, median follow-up 523 [range 58-1198] days post-HCT). In addition, we performed analyses of relevant clinical factors to assess their relationship to EFS. The larger trial studying the role of KIR favorable haploidentical vs. other transplantation approaches for children diagnosed with ALL, acute myeloid leukemia and myelodysplastic syndrome will be reported separately. We evaluated baseline blast samples from 74 patients for dominant BCR/TCR rearrangements and to follow MRD by NGS. Dominant rearrangements were identified in 100% of B-ALL patients, 96.8% (61/63) in BCR and 3.2% in TCR gamma. For T-ALL patients, rearrangements were identified in 62.7% (7/11), with the remaining 37.3% being polyclonal. Patients proceeded to HCT only if they were in morphological remission. Pre-HCT NGS-MRD from bone marrow (BM) was highly predictive of EFS (n=29 P=0.027, Figure 1) and although NGS-MRD from peripheral blood (PB) did not reach statistical significance due to decreased sample size (n=27, P=0.17, Figure 2), it trended similarly. In BM NGS-MRD negative patients, relapse was exceptionally low with all events due to transplant related mortality (TRM). There did not appear to be a benefit of acute graft-vs-host-disease (aGVHD) in NGS-MRD- patients (Figure 3) or chronic (c)GVHD, but sample size was a limitation. Pre-HCT, 10% of the BM samples were MRD+ by FC, but 35% were MRD+ by NGS. Direct comparison of NGS-MRD in BM and PB with FC MRD pre- and post-HCT showed improvements positive and negative predictive power (data not shown). Alpha/beta depleted haploidentical grafts had similar outcomes to other stem cell sources (Figure 4) with decreased incidence of GVHD [aGVHD > grade 2: n=1 (3.3%) and extensive cGVHD: n=1(3.3%)]. TBI (total body irradiation) based myeloablative conditioning (TBI/TT [Thiotepa]/CY [Cyclophosphamide], TBI/CY, or TBI/VP16; ± anti-thymocyte globulin [ATG]) and non-TBI reduced toxicity (Flu [Fludarabine]/Mel [Melphalan]/TT; ± ATG) had identical EFS (P= 0.31). TRM was very low 8.7%(n=5) in this population (n=57)) and rescue of relapse was high for the duration of follow up to date, resulting in similar OS for MRD- vs. MRD+ patients (P= 0.15), likely due to rescue with cell/immunotherapy. We next examined the interaction of obesity, using body mass index (BMI) based on height/weight pre-HCT, in the context of NGS-MRD on EFS. The BMI score was converted to a percentile through population norms for age and gender and defined thresholds published by the Centers for Disease Control and prevention (CDC). Lean patients (< 85th percentile [%]) overall had better survival than the overweight (OW)/obese (85-94%/≥95%) (Figure 5: P=0.016). But among the lean patients, NGS-MRD still had an effect, with NGS-MRD+ patients had poorer EFS. Same was observed with the OW/obese group, where being NGS MRD+ adds further reduction in survival. Overweight/Obese patients who were pre-HCT MRD- had survival closer to the lean/MRD+ patients. We observed decreased EFS by weight category and NGS-MRD (Figure 6: P= 0.02). In conclusion, NGS-MRD was highly predictive for EFS regardless of HCT preparative approach or graft Alpha/Beta Depletion. NGS improved predictive power for MRD positivity compared to FC. NGS was able identify rearrangements suitable for MRD tracking in all B-ALL and in most of T-ALL samples. In BM NGS-MRD negative patients, relapse was exceptionally low. There did not appear to be a benefit of aGVHD or cGVHD in NGS-MRD- patients. Alpha/beta depleted haploidentical grafts had similar outcomes to other stem cell sources with decreased incidence of severe GVHD. We observed decreased EFS by weight category and NGS-MRD. Lean patients had better survival, after HCT, than OW/Obese patients. But among the lean patients, NGS-MRD+ patients had poorer EFS. Disclosures Abdel-Azim: Adaptive: Research Funding. Dvorak:Jazz Pharmaceuticals: Consultancy; Alexion Inc: Consultancy. Bunin:PRA Health Sciences: Other: Immediate family member employed. Walters:Editas Medicine: Consultancy; TruCode: Consultancy; AllCells, Inc: Consultancy. Cairo:Jazz Pharmaceuticals: Other: Advisory Board, Research Funding, Speakers Bureau; Miltenyi: Other: MTA; Osuka: Research Funding. Kitko:Novartis: Consultancy, Honoraria; Mallinckrodt: Honoraria. Jacob:Adaptive Biotechnologies: Employment, Other: shareholder. Wing:Miltenyi Biotec: Employment. Pulsipher:Medac: Honoraria; Miltenyi: Research Funding; Bellicum: Consultancy; Amgen: Other: Lecture; CSL Behring: Membership on an entity's Board of Directors or advisory committees; Adaptive: Membership on an entity's Board of Directors or advisory committees, Research Funding; Jazz: Other: Education for employees; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau.

On the size and orientation effect in additive manufactured Ti-6Al-4V

In this work, the influence of the specimen size and orientation on the strength and ductility of additive manufactured Ti-6Al-4V is analysed and rationalised in a complete framework. First, the mechanical properties are addressed – as a function of surface-type, orientation, and size. Our results show systematic strengthening and a drastic drop in ductility as the material section is reduced. These changes are rationalised and linked to changes in microstructure, chemistry, and surface quality. Strengthening is due to combined changes in α-lath thickness, oxygen enrichment, and prior-β grain size. The microstructural changes are due to the differences in the ratio between contouring and hatching laser strategies as the sample size decreases. Changes in the chemical composition is due to an increase in the surface-to-volume ratio as the sample size decreases. Lost of ductility is due to poor surface quality – smaller sections show rougher surfaces – and grain orientations. Finally, these findings are used to develop a set of conceptual design maps of strength and ductility as a function of the component type, thickness, and orientation.

Accuracy of Estimating Soil Properties with Mid‐Infrared Spectroscopy: Implications of Different Chemometric Approaches and Software Packages Related to Calibration Sample Size

Core Ideas Selection of spectral regions was included in MIR predictions of soil properties. The R software outperformed a commercial chemometric software. SVMR and model averaging performed better than PLSR and artificial neural networks. With decreasing calibration sample size, the usefulness of SVMR over PLSR decreased. MIRS studies may focus more on representativeness, sample sizes, and variabilities. Different algorithms exist in various software programs for the estimation of soil properties using mid‐infrared (MIR) spectroscopy, with recommendations varying between different studies regarding which algorithm should be used. Objectives were to compare the performance of the commercial OPUS Quant 2 software, which uses partial least squares regression (PLSR) and a selection of spectral ranges, with the R software and to study the accuracy of different algorithms as a function of the information provided in the calibration. Contents of soil organic carbon (SOC), nitrogen, and texture for surface soils of an arable field were determined, and MIR were spectra recorded. Partial least squares regression used with either software was useful (ratio of performance to interquartile distance in the validation sample [RPIQV] >1.89) for an estimation of SOC, clay, and N contents but not for sand and silt. The wavenumber region selection concept used in OPUS was also implemented in R, and it proved useful for SOC (all algorithms) and total nitrogen (artificial neural networks, support vector machine regression [SVMR]) in the validation. Support vector machine regression generally slightly outperformed the other approaches and resulted in a successful estimation of sand content. The usefulness of SVMR over PLSR generally decreased with decreasing sample size used for the calibration (thus decreasing the information provided), and PLSR partly outperformed SVMR in the validation. Overall, this study indicates that there is no general superiority of a chemometric algorithm over PLSR independent of the information provided in the calibration sample.

Unbiased Recursive Partitioning to Stratify Patients with Acute Traumatic Spinal Cord Injuries: External Validity in an Observational Cohort Study.

Clinical trials of novel therapies for acute spinal cord injury (SCI) are challenging because variability in spontaneous neurologic recovery can make discerning actual treatment effects difficult. Unbiased Recursive Partitioning regression with Conditional Inference Trees (URP-CTREE) is a novel approach developed through analyses of a large European SCI database (European Multicenter Study about Spinal Cord Injury). URP-CTREE uses early neurologic impairment to predict achieved motor recovery, with potential to optimize clinical trial design by optimizing patient stratification and decreasing sample sizes. We performed external validation to determine how well a previously reported URP-CTREE model stratified patients into distinct homogeneous subgroups and predicted subsequent neurologic recovery in an independent cohort. We included patients with acute cervical SCI level C4–C6 from a prospective registry at a quaternary care center from 2004–2018 (n = 101) and applied the URP-CTREE model and evaluated Upper Extremity Motor Score (UEMS) recovery, considered correctly predicted when final UEMS scores were within a pre-specified threshold of 9 points from median; sensitivity analyses evaluated the effect of timing of baseline neurological examination. We included 101 patients, whose mean times from injury baseline and follow-up examinations were 6.1 days (standard deviation [SD] 17) and 235.0 days (SD 71), respectively. Median UEMS recovery was 7 points (interquartile range 2–12). One of the predictor variables was not statistically significant in our sample; one group did not fit progressively improving UEMS scores, and three of five groups had medians that were not significantly different from adjacent groups. Overall accuracy was 75%, but varied from 82% among participants whose examinations occurred at <12 h, to 64% at 12–24 h, and 58% at >24 h. A previous URP-CTREE model had limited ability to stratify an independent into homogeneous subgroups. Overall accuracy was promising, but may be sensitive to timing of baseline neurological examinations. Further evaluation of external validity in incomplete injuries, influence of timing of baseline examinations, and investigation of additional stratification strategies is warranted.

Unique Structural/Stereo-Isomer and Isobar Analysis of Novel Fentanyl Analogues in Postmortem and DUID Whole Blood by UHPLC-MS-MS.

The presented analytical method enabled the Toxicology Department at the Cuyahoga County Medical Examiner's Office to identify 26 and quantitatively report 24 compounds in 500μL of whole blood, including fentanyl analogues (fentalogues) such as methoxyacetyl fentanyl (MeOAF) and cyclopropyl fentanyl (CPF). This second-generation method (FG2) was developed with the objective to improve the existing analysis (FG1) by decreasing sample size, lowering limits of detection (LOD) and lower limit of quantitation, minimizing ion suppression and resolving chromatographic interferences. Interferences may occur in the analysis of fentanyl, MeOAF, CPF, 3-methylfentanyl (3MF), butyryl fentanyl and isobutyryl fentanyl due to isobars and structural or geometric isomerism with another analogue or metabolite. The isomeric and isobaric fentalogues were grouped into three sets. The LOD established for Set 1 [MeOAF, para-methoxyacetyl fentanyl, para-fluoro acryl fentanyl (isobar), fentanyl carbamate], 2-furanyl fentanyl, Set 2 [CPF, (E)-crotonyl fentanyl] and carfentanil was 0.0125ng/mL. The LOD established for N-methyl norfentanyl, norfentanyl, norcarfentanil, despropionyl fentanyl (4-ANPP), acetyl fentanyl, β-hydroxy fentanyl, benzyl fentanyl, acryl fentanyl, alfentanil, fentanyl, para-fluoro fentanyl, Set 3 [(±)-trans-3MF, (±)-cis-3MF, isobutyryl and butyryl fentanyl], para-fluoroisobutyryl fentanyl, sufentanil, phenyl fentanyl and cyclopentenyl fentanyl was 0.0625ng/mL. Seven-point linear calibration curves were established between 0.025 and 4.0ng/mL for the 8 analytes with the lower LOD and 0.125 and 20ng/mL for the 18 analytes with the higher LOD. 4-ANPP and cyclopentenyl fentanyl met qualitative reporting criteria only. The results for five postmortem and two driving under the influence of drugs authentic case samples are presented. To the authors' knowledge, FG2 is the first published method that achieved baseline resolution of the nine structural/stereo isomers and one isobar by ultra-high performance liquid chromatography-MS-MS and provided quantitative validation data for nine compounds. FG2 may be used as the new baseline for future isomers that need to be chromatographically separated.

Non-connected pores of the Longmaxi shale in southern Sichuan Basin of China

Abstract The characteristics of non-connected pores of four Longmaxi shale samples from the southern Sichuan Basin of China were investigated from the studies of pore size distribution (PSD), pore volumes, pore types using helium pycnometry [gas injection porosimetry (GIP) and GRI (Gas Research Institute) method], nuclear magnetic resonance (NMR), nuclear magnetic resonance cryoporometry (NMRc), and spontaneous water and oil imbibition experiments. GRI porosity on particle sizes less than 5 mm sample and a 2 MPa helium injection pressure provides information on the total porosity, including both non-connected and connected pores. GIP porosity using core plugs only measures connected pores which extend to the surface of the sample accessible by helium. So the difference between GRI and GIP porosities is used to estimate the volumes of non-connected pores. And the volumes of non-connected pores accounts for 17.5%–40.3% of the total pore volume. For NMRc test results, total pore volume increases with sample size decrease, and the great difference of pore volume with a pore diameter range from 5 nm to 31 nm between small cylinder sample and 0.15–0.075 mm crushed sample is caused by non-connected pores opened. With a decrease of length for cubic samples, the increase in volume and rate of oil imbibition is greater than that of water imbibition, indicating that the non-connected pores are considered to be mainly oil-wet. In addition, the percentage of non-connected pores has a good correlation with TOC (total organic carbon) content. Therefore, this evidence implies that non-connected pores are mainly within the organic matter. NMR tests at different drying temperatures and a NMRc experiment provide a quantitative classification of the shale pore system which indicates that the exploitable pore diameters are larger than 4.25 nm. So non-connected pores with a diameter of 5–31 nm could be effectively exploited if connected by fracturing. The more the non-connected pores are opened, the better the pore connectivity of shale reservoir will be, with a less possibility of water blocking. In the process of shale gas development, attention should be paid to the interaction between fracturing fluid and rock components in order to release more non-connected pores. Therefore, to increase shale gas extraction efficiency, more effort should be directed towards identifying natural, and creating induced, porosity.

A new method and insights for estimating phenological events from herbarium specimens.

Premise of the StudyA novel method of estimating phenology of herbarium specimens was developed to facilitate more precise determination of plant phenological responses to explanatory variables (e.g., climate).Methods and ResultsSimulated specimen data sets were used to compare the precision of phenological models using the new method and two common, alternative methods (flower presence/absence and ≥50% flowers present). The new “estimated phenophase” method was more precise and extracted a greater number of significant species‐level relationships; however, this method only slightly outperformed the simple “binary” (e.g., flowers present/absent) method.ConclusionsThe new method enables estimation of phenological trends with greater precision. However, when time and resources are limited, a presence/absence method may offer comparable results at lower cost. Using a more restrictive approach, such as only including specimens in a certain phenophase, is not advised given the detrimental effect of decreased sample size on resulting models.

Strengthening to softening transition in lath martensite

Size induced strengthening, i.e. increase in strength with decreasing sample size, has been reported for a variety of single crystal body centered cubic (bcc) materials. However, studies on bcc lath martensite are very limited, in part due to its complex microstructure and the difficulty of small-scale experimentation. In this work, we demonstrate for the first time a size induced strengthening followed by a softening in bcc lath martensite pillars by reducing pillar diameter from 8 µm to 250 nm. These martensitic pillars are tested under uniaxial compression conducted in-situ inside of a scanning electron microscope. High-resolution microstructural characterization by transmission electron microscopy is used for post-mortem examination of the compressed pillars in order to study the deformation mechanisms governing their plasticity. We find that the size-induced strengthening during compression can be rationalized in terms of the competition between dislocation slip and boundary sliding, while softening at the finest scales is attributed to the boundary sliding mechanisms. Our work provides direct observations of block/lath boundaries behavior during compression as well as new insights into the deformation mechanisms in lath martensite.

The strain hardening of micro-sized face-centered-cubic single crystal metals: A crystal plasticity study

Recent experimental and theoretical studies indicate the “external geometry” and “internal structure” are the controlling factors to characterize the size-dependent plastic flow for micro-sized single crystal metals. i.e., increasing yield strength with decreasing sample size. This paper aims to investigate the strain hardening behavior for micro-sized face-centered-cubic (FCC) metals by employing crystal plasticity approach. The size-dependent dislocation density evolution law incorporates the dimensional parameters of internal structure and external geometry in order to consider the dislocation surface annihilation and dislocation source controlled plastic mechanisms. The current shear yield strength for micro-sized FCC metals is formulated by introducing the dislocation source length in classical anisotropic hardening model of Franciosi type. Combined with the above two aspects, crystal plasticity finite element method is developed to examine the strain hardening behavior of single crystal micro-sized metals during uniaxial compression. The validity of the new theoretical formulation and modeling approach is checked by comparing the simulation results with the experimental results available in literatures. The simulation results indicate that the micro-sized FCC metals have significant size effect. Further studies are performed to evaluate the influences of the initial dislocation density and the number of dislocation sources on strain hardening behavior of micro-sized FCC metals.

Characterization of the thermal properties of millimeter-sized insulating materials

The work deals with the thermal characterization of low conductivity millimeter-sized samples. Regarding the increasing of the technical problems when the sample sizes decrease and become millimetric, an analytical solution obtained from the fin model and adapted from previous work is developed to estimate the thermal diffusivity and a modified Biot number by least-squares method. Then separated calorimetric and density measurements enable the calculation of the thermal conductivity. During experiment, the sample is heated from one side for a few seconds. An infrared thermography is used to measure the temperature field of the sample surface. At first, the method is tested with polycarbonate and balsa samples, which thermal properties are well-known. Then, the thermal diffusivity and conductivity of the hemp shiv are estimated, which values are of the same order of magnitude as those encountered in the literature for cellulosic materials of same density. If the estimation of the thermal diffusivity of the samples is in good agreement with a low uncertainty, the uncertainty on the thermal conductivity is about 10% due to the difficulty to consider the heat exchange coefficient when the tested material becomes a better insulator. Nevertheless, this method seems relevant to characterize millimeter samples of low thermal conductivity.

A highly sensitive co-resonant cantilever sensor for materials research: Application to nanomaterial characterization

Abstract

Investigating the genetic diversity and differentiation patterns in the Penstemon scariosus species complex under different sample sizes using AFLPs and SSRs

Habitat fragmentation due to anthropogenic activities is the major cause of biodiversity loss. Endemic and narrowly distributed species are the most susceptible to habitat degradation. Penstemon scariosus is one of many species whose natural habitat is vulnerable to industrialization. All varieties of P. scariosus (P. scariosus var. albifluvis, P. scariosus var. cyanomontanus, P. scariosus var. garrettii, P. scariosus var. scariosus) have small distribution ranges, but only P. scariosus var. albifluvis is being considered for listing under the Endangered Species Act. We used eight microsatellites or simple sequence repeats (SSRs) loci and two amplified fragment length polymorphism (AFLP) primer combinations to investigate the population genetic structure and diversity of P. scariosus varieties. Moreover, we compared the utility of the two marker systems in conservation genetics and estimated an appropriate sample size in population genetic studies. Genetic differentiation among populations based on Fst ranged from low to moderate (Fst = 0.056–0.157) and from moderate to high when estimated with Des (Des = 0.15–0.32). Also, AMOVA analysis shows that most of the genetic variation is within populations. Inbreeding coefficients (Fis) were high in all varieties (0.20–0.56). The Bayesian analysis, STRUCTURE, identified three clusters from SSR data and four clusters from AFLPs. Clusters were not consistent between marker systems and did not represent the current taxonomy. MEMGENE revealed that a high proportion of the genetic variation is due to geographic distance (R2 = 0.38, P = 0.001). Comparing the genetic measurements from AFLPs and SSRs, we found that AFLP results were more accurate than SSR results across sample size when populations were larger than 25 individuals. As sample size decreases, the estimates become less stable in both AFLP and SSR datasets. Finally, this study provides insight into the population genetic structure of these varieties, which could be used in conservation efforts.

Harmonised method for impact resistance requirements of E-glass fibre/unsaturated polyester resin composite railway car bodies

This paper shows for the first time an approach to harmonise and unify various railway standards into a single method for small object strike against rail vehicles. Emerging composite materials applications for structural parts of railway vehicles highlight the need for assessment of impact response. The objective of this work is to provide a practical and cost-effective approach for rail vehicle car bodies affected by object strikes such as flying ballast, which is a concern and restricting phenomenon for high speed rail operation. A static destructive test method combined with numerical models has been developed. High velocity impact (HVI) simulations are performed with E-glass/polyester laminates based on experiments and similarities between the two cases are highlighted. Validated numerical models are used to simulate three railway standards that are relevant to object strike in order to unify them into the proposed single method. The analysis of the energy transfer characteristics, contact forces, and impact velocity change of the projectile showed that the proposed method can be used alone instead of various existing standards, providing a significant decrease in sample size as well as avoiding the costly high-velocity impact experiments, hence resulting in substantial cost savings.