Small Initial Size Research Articles

Increasing temperature threatens post‐fire auto‐successional dynamics of a Mediterranean obligate seeder

Abstract Reproductive traits influence plant auto‐successional dynamics in post‐fire regeneration. Obligate seeding species rely on their seedbank and on the climatic conditions following the fire to ensure a successful recovery, defining the window of opportunity for seedling emergence. In the Mediterranean basin, emergence opportunities generally begin with autumnal rains. However, climate change‐induced increases in temperature and drought could jeopardise the regeneration capacity of seeding species by causing temporal shifts in emergence opportunities or by modifying wildfire seasonality. This study aimed to explore the impact of experimentally induced climate change on regeneration dynamics of Aleppo pine (Pinus halepensis), a serotinous Mediterranean obligate seeder. In March 2021, we set up an 18‐month climate change simulation experiment with 15 open‐top chambers (OTC), each paired with a control subplot (CON) on top of Aleppo pines that were naturally regenerating after a stand‐replacing wildfire in SW Catalonia (June 2019). We tagged 178 young Aleppo pine recruits in OTC and CON subplots (98 and 81 respectively), classified according to their initial size, to periodically measure height growth and survival throughout the experiment duration. Furthermore, Aleppo pine seeds were seasonally sown (7900 total seeds) in 10 subplot pairs between May 2021 and April 2022, to monthly monitor temporal patterns of seedling emergence and survival. We found that OTCs reduced overall emergence rates and caused the loss of the autumnal window of opportunity for the emergence of Aleppo pine seedlings. Furthermore, seedlings which emerged within OTCs faced higher mortality rates in all seasons, with only 1% of seedlings surviving compared with 21.1% of seedlings in control plots. The OTC‐induced conditions were also detrimental to the survival of recruited seedlings, especially those with a smaller initial size, although no significant effects of temperature increase were found on growth. Synthesis. Climate change is likely to interfere with the post‐fire regeneration dynamics of obligate seeders by shortening the temporal window of opportunities for emergence and by enhancing the bottleneck effects throughout the recruitment process in the early phases of pine demographic recovery. Altogether, it could threaten post‐fire regeneration by increasing the hazard of a demographic collapse of Aleppo pine.

A Real-World Longitudinal Study in Non-Functioning Pituitary Incidentalomas: A PRECES Micro-Adenomas Sub-Analysis.

Background. Incidentalomas have an increasing incidence all over the world due to a larger access to imaging assessments, and endocrine incidentalomas make no exception in this matter, including pituitary incidentalomas (PIs). Objective. Our objective was to analyse the dynamic changes amid a second computed tomography (CT) scan after adult patients were initially confirmed with a PI (non-functioning micro-adenoma). Methods. This was a multi-centric, longitudinal, retrospective study in adults (aged between 20 and 70 y) amid real-world data collection. We excluded patients who experienced baseline pituitary hormonal excess or deficiency or those with tumours larger than 1 cm. Results. A total of 117 adults were included (94.02% females) with a mean age of 43.86 ± 11.99 years, followed between 6 and 156 months with a median (M) of 40 months (Q1 Q3: 13.50, 72.00). At the time of PI diagnosis, the transverse diameter had a mean value of 0.53 ± 0.16 cm, the longitudinal mean diameter was 0.41 ± 0.13 cm, and the largest diameter was 0.55 ± 0.16 cm. No PI became functioning during follow-up, neither associated hypopituitarism nor increased >1 cm diameter. A total of 46/117 (39.32%) patients had a larger diameter during follow-up (increase group = IG) versus a non-increase group (non-IG; N = 71, 60.68%) that included the subjects with stationary or decreased diameters. IG had lower initial transverse, longitudinal, and largest diameter versus non-IG: 0.45 ± 0.12 versus 0.57 ± 0.17 (p < 0.0001), 0.36 ± 0.11 versus 0.43 ± 0.13 (p = 0.004), respectively, 0.46 ± 0.12 versus 0.6 ± 0.16 (p < 0.0001). IG versus non-IG had a larger period of surveillance: M (Q1, Q3) of 48 (24, 84) versus 32.5 (12, 72) months (p = 0.045) and showed similar age, pituitary hormone profile, and tumour lateralisation at baseline and displayed a median diameter change of +0.14 cm versus -0.03 cm (p < 0.0001). To conclude, a rather high percent of patients might experience PI diameter increase during a longer period of follow-up, including those with a smaller initial size, while the age at diagnosis does not predict the tumour growth. This might help practitioners with further long-term surveillance protocols.

Genetic diversities in wild and cultivated populations of the two closely-related medical plants species, Tripterygium Wilfordii and T. Hypoglaucum (Celastraceae)

BackgroundThe sustainable supply of medicinal plants is important, and cultivating and domesticating them has been suggested as an optimal strategy. However, this can lead to a loss of genetic diversity. Tripterygium wilfordii Hook. f. is a medicinal plant commonly used in traditional Chinese medicine, but its wild populations are dwindling due to excessive harvesting. To protect the species and meet the increasing demand, it is urgent to cultivate it on a large scale. However, distinguishing between T. wilfordii and T. hypoglaucum, two similar species with different medicinal properties, is challenging. Therefore, it is crucial to understand the genetic diversity and population structure of these species for their sustainable utilization.ResultsIn this study, we investigated the genetic diversity and population structure of the two traditional medicinal semiwoody vines plant species, Tripterygium wilfordii and T. hypoglaucum, including wild and cultivated populations using chloroplast DNA (cpDNA) sequences and microsatellite loci. Our results indicated that the two species maintain a high level of genetic divergence, indicating possible genetic bases for the different contents of bioactive compounds of the two species. T. wilfordii showed lower genetic diversity and less subdivided population structures of both markers than T. hypoglaucum. The potential factors in shaping these interesting differences might be differentiated pollen-to-seed migration rates, interbreeding, and history of population divergence. Analyses of cpDNA and microsatellite loci supported that the two species are genetically distinct entities. In addition, a significant reduction of genetic diversity was observed for cultivated populations of the two species, which mainly resulted from the small initial population size and propagated vegetative practice during their cultivation.ConclusionOur findings indicate significant genetic divergence between T. wilfordii and T. hypoglaucum. The genetic diversity and population structure analyses provide important insights into the sustainable cultivation and utilization of these medicinal plants. Accurate identification and conservation efforts are necessary for both species to ensure the safety and effectiveness of crude drug use. Our study also highlighted the importance of combined analyses of different DNA markers in addressing population genetics of medicinal plants because of the contrasts of inheritance and rates of gene flow. Large-scale cultivation programs should consider preserving genetic diversity to enhance the long-term sustainability of T. wilfordii and T. hypoglaucum. Our study proposed that some populations showed higher genetic diversity and distinctness, which can be considered with priority for conservation and as the sources for future breeding and genetic improvement.

Evaluation of Lifetime Predictions for Future Hydrogen Pipelines by Different Fracture Mechanics‐Based Design Codes

The realization of a hydrogen transport network requires the requalification of existing high‐pressure natural gas pipelines and the design and construction of new hydrogen pipelines. Therefore, appropriate design codes are needed, which consider the detrimental effects of gaseous hydrogen on the mechanical properties and ensure a robust, but not too conservative, lifetime concept. For the assessment of hydrogen pipelines, the ASME B31.12 is understood as a benchmark standard. Recently, the technical rule DVGW G 464 (2023) was published in Germany. Both standards consider a fracture mechanics‐based concept, where the pipeline design lifetime is assessed by the hydrogen‐assisted fatigue crack growth of a pre‐existing defect until a defined lifetime criterion is reached. This article compares both concepts within a use case study, where influencing factors on the lifetime predictions are identified and discussed. Relatively similar results are obtained for typical loading scenarios, whereby the ASME B31.12 predicts more allowable cycles compared to the DVGW G 464 mostly arising from a different assumed crack length. To reduce the conservatism, the focus in the design and assessment of hydrogen pipelines should be placed on a detectable small initial crack size and the measurement of material‐specific crack growth curves resulting in pronounced lifetime enhancements.

Volumetric reduction in large cystic jaw lesions postoperative enucleation: a longitudinal clinical study

BackgroundEnucleation, a surgical procedure, is commonly used to treat large jaw cysts, unicystic ameloblastomas and keratocysts. However, it remains unclear to what extent the jaw bone regenerates after enucleation. We aimed to evaluate the percentage and the survival analysis of jaw bone regeneration, in terms of cavity volume residual (CVR), in patients who underwent enucleation of large jaw cysts, unicystic ameloblastomas and keratocysts.MethodsWe collected data longitudinally from 75 patients who underwent jaw cystic lesions enucleation at the Stomatological Hospital of Xi’an Jiaotong University, between January 2015 and June 2021. All patients had both preoperative and postoperative cone-beam computed tomography (CBCT) imaging data. CBCT images were analyzed using Image J. Changes in the CVR were assessed at various follow-up time points, and the Kaplan-Meier method was utilized to evaluate the CVR over time.ResultsThe patients had a mean age of 31.7 years (range: 5.5–72 years) with 58.66% of them being male. The postoperative CVR was 32.20% at three months, 21.10% at six months, 15.90% at 12 months, and 5.60% at 24 months. The percentage of CVR during follow-up periods for the initial size Quartile (Q)1 (212.54-1569.60 mm3) was substantially lower than those of Q2 and Q3 at and after seven months of follow-up and became statistically significant at the 12-month mark.ConclusionThis study demonstrates that spontaneous bone regeneration can occur after enucleation of large jaw cysts, unicystic ameloblastomas and keratocysts, even without the use of filler materials. The initial size of the lesion had a significant impact on the outcome of cystic lesion enucleation over time. To minimize the risks associated with radiation exposure and expenses, we recommend reducing the frequency of CT imaging follow-ups for patients with small initial cavity sizes (ranging from 212.54 to 1569.60 mm3).

Race to the canopy: the development of tree size hierarchies following a partial disturbance in a boreal old-growth forest

In boreal old-growth forests, advance regeneration typically attains canopy dominance through growth release events following partial disturbances. We sampled competing Picea mariana (Mill.) and Abies balsamea (L.) in disturbed old-growth stands in Quebec, Canada, to understand the intra- and interspecific size hierarchy development. We reconstructed tree size development and examined the role of initial size difference, time between germination and a disturbance, and the strength of response to the disturbance in determining tree size hierarchies. Trees that regenerated first generally dominated their intraspecific competitors also following a disturbance event. However, prolonged time between germination and disturbance resulted in a less deterministic outcome. Tree size difference prior to disturbance also influenced the development of size hierarchies. In interspecific competition between individuals of the same diameter, A. balsamea had a 61% probability of gaining dominance over P. mariana, the probability being 50% if P. mariana was 5 mm larger than A. balsamea. Dominant trees generally had the strongest response to the disturbance, reinforcing the existing size hierarchies. The largest trees typically gain dominance after a partial disturbance. However, interspecific competition is less predictable than intraspecific competition, small initial size difference, and prolonged time in suppression potentially changing tree size hierarchies.

Postpartum Juvenile Granulosa Cell Tumor: A Case Report

Granulosa Cell Tumors (GCTs) are extremely rare, sex cord-stromal tumors constituting only 1% to 2% of all ovarian malignancies. On the basis of age of onset and pathohistological characteristics, these tumors are subdivided into two distinct forms, the adult type (AGCT) and the juvenile type (JGCT), representing 95% and 5% of the tumors, respectively. Compared to the adult type, which is more common in the fifth decade, JGCT is rarely seen and the majority (90%) is reported in prepubertal individuals or those aged less than 30 years. We report an interesting case of a 24-years old woman with enormous ovarian juvenile granulosa cell tumor of the right ovary. Considering all the anamnestic data and ultrasound reports before and during the first pregnancy, where there has been no evidence for the presence of any tumor, we came to conclusion that the tumor grew rapidly during the first year since delivery. Maybe the tumor was present during the pregnancy or even before, but most probably it was not noticed because it small initial size or it was masked by the growing uterus at ultrasound. The first data for the tumor existence is 3 months before the surgical treatment.

Numerical Simulation of the Microscopic Plugging Mechanism and Particle Flow Process of the Microsphere System.

The microsphere system has small initial particle size, excellent swelling performance, simple manufacturing process, and strong plugging ability. It has great application potential in the field of plugging and profile control of deep reservoirs. Microspheres can effectively plug the pores of fractured cores, inhibit the rapid breakthrough process, and improve the sweep efficiency of the injected fluids. However, the microscopic plugging mechanism of microspheres on fractured cores is still unclear. In this study, the distribution of microspheres after plugging was observed through specially prepared core models. Furthermore, the microscopic plugging mechanism of microspheres in fractured reservoir cores was clarified, including direct microsphere plugging, cluster bridging plugging, adhesion plugging, extrusion-deformation plugging, and extrusion-crushing plugging. Then, particle flow simulation software was used to establish the fluid-solid coupling model of microsphere plugging, and then, the numerical simulation of the plugging process was realized by Python module programming. Through this study, the plugging effect of microspheres under different fracture opening conditions was clarified. Moreover, the effects of injection pressure difference, fracture width, and particle size ratio on the fluid-solid structures of microsphere plugging were analyzed. The results show that the smaller the particle size ratio, the greater the injection pressure difference, the fracture width, and the reduction magnitudes in fracture porosity and core permeability and the higher the plugging rate. The numerical simulation results well support the microsphere plugging mechanism obtained by experiments. The results of this study can provide theoretical and technical support for the development of deep profile control and flooding and enhanced oil recovery technology of the polymer microsphere dispersion system in fractured low-permeability reservoirs.

Stretching your data with taffy filters

AbstractPopular approximate membership query structures such as Bloom filters and cuckoo filters are widely used in databases, security, and networking. These structures represent sets approximately, and support at least two operations—insert and lookup; lookup always returns true on elements in the structure; it also returns true with some probability on elements not in the structure. These latter elements are called false positives. Compensatory for these false positives, filters can be much smaller than hash tables that represent the same set. However, unlike hash tables, cuckoo filters, and Bloom filters must be initialized with the intended number of maximum entries, and cannot grow larger—inserts beyond this number fail or significantly increase the false positive probability. This article presents designs and implementations of filters than can grow without inserts failing and without meaningfully increasing the false positive probability, even if the filters are created with a small initial size. The resulting code is available on GitHub under a permissive open source license.

Contribution of the proximal and distal gastric phases to the breakdown of cooked starch-rich solid foods during static in vitro gastric digestion

In vitro gastric digestion studies commonly focus on the acidic environment of the stomach (the distal phase), neglecting that the contact time between food and salivary amylase can be extended during bolus’ temporary storage in the proximal stomach (the proximal phase). Consequently, the role of the proximal phase of gastric digestion on the breakdown of solid starch-based foods is not well understood. This study aimed to address this question using a static in vitro digestion approach. Cooked starch-rich foods of different physical structures (wheat couscous, wheat pasta, rice couscous, rice noodle, and rice grain) were subjected to 30 s oral phase digestion, followed by prolonged incubation of the oral phase mixture (pH 7) for up to 30 min representing different proximal phase digestion times. Each proximal phase sample was sequentially incubated in excess simulated gastric fluid (distal phase, pH 2) for up to an additional 180 min. The proximal phase aided solid food breakdown through starch hydrolysis that caused leaching of particles <2 mm. The distal phase led to softening of food particles, but the softening process was not enhanced with longer proximal phase. In foods with smaller initial size (couscous and rice couscous), a proximal phase of 15 min or longer followed by 180-min distal phase increased starch hydrolysis in the liquid and suspended solid fractions of the digesta, indicating the influence of food structure on acid hydrolysis during in vitro gastric digestion.

Gas holdup at dynamic equilibrium region of a bubble column: Effect of bubble generator performance

Gas holdup along with the superficial gas velocity was systematically investigated in a lab-scale bubble column. The experiments were conducted in a bubble column with a height of 6 m at superficial gas velocity of 0.01–0.13 m/s. Experimental results show that dynamic equilibrium region was achieved at a distance of 2800 mm above the bubble generator. Small initial bubble size will lead to higher gas holdup and slump trend. To overcome the trade-off between sufficient gas holdup and slump trend, a reasonable gas holdup without slump can be obtained by controlling the liquid mass flow in the nozzle. Based on previous empirical correlations and experiment data, a semi empirical correlation of gas holdup was established consider the flow regime transition and bubble generator performance. The semi empirical correlation in this work gives a fairly accurate prediction while several empirical coefficients were used.

On the Two Types of Tropical Cyclone Eye Formation: Clearing Formation and Banding Formation

Abstract Two types of eye formation are proposed: “clearing formation (CF)” and “banding formation (BF)”. The objectives are to identify the tropical cyclone (TC) characteristics associated with these two types of eye formation and to clarify how the environment, pattern of synoptic systems and TC structure during initial and development stages affect the eye formation. The satellite imagery and best-track data are used to classify and analyze the TCs named in the western North Pacific from 2007 to 2020. The results show that TCs with CF have significantly higher intensity and intensification rate during the period of the first eye presence, smaller size after genesis and prior to eye formation, smaller eye size when the eye forms and a more westward track. It is noted that CF and BF TCs tend to occur in autumn and summer, respectively. Meanwhile, the composite results using reanalysis data show that the CF TCs are generally characterized by easterly-wave features with a dryer environment, smaller initial size and larger radial gradient of vorticity, while the BF TCs feature a monsoon-depression structure with a wetter environment, larger initial size and flatter vorticity profile. A conceptual hypothesis is thus proposed, as compared to BF TCs, the smaller size and weaker outer wind in CF storms associated with the easterly-wave disturbance are facilitated by inactive outer convection, leading to larger radial gradient of inertial stability. The low-level inflow can penetrate inward close to the center, resulting in more diabatic heating inside the radius of maximum wind with much higher heating efficiency, and also a higher intensification rate.

Study of the effect of ultra-low arsenic flux on the formation of In(As)/GaAs nanostructures by droplet epitaxy

In this paper, we present the results of studying the influence of arsenic pressure in the range of ultra-low values (10-7-10-6 Pa) on the processes of modification of In/GaAs(001) droplets with various initial sizes obtained by droplet epitaxy. We experimentally demonstrate that exposure of droplets to the ultralow arsenic flux makes it possible to reduce the droplet size to subcritical sizes while maintaining the initially specified surface density. The exposure of droplet nanostructures in the arsenic flux can be accompanied only by a decrease in their size, which is more typical for droplets obtained at large amounts of indium deposited material. For droplets with a smaller initial size, the formation of rings along the perimeter of the initial droplets and holes inside the rings is typical along with the droplet reduction. We also reveal that the dependence of the relative volume of droplets subjected to diffusion decay in the arsenic flux becomes more significant with a decrease in their initial size. Keywords: droplet epitaxy, nanostructures, In(As)/GaAs, arsenic flux.

Исследование влияния ультрамалого потока мышьяка на процессы формирования наноструктур In(As)/GaAs методом капельной эпитаксии

In this paper, we present the results of studying the influence of arsenic pressure in the range of ultra-low values (10^-7-10^-6 Pa) on the processes of modification of In/GaAs(001) droplets with various initial sizes obtained by droplet epitaxy. We experimentally demonstrate that exposure of droplets to the ultralow arsenic flux makes it possible to reduce the droplet size to subcritical sizes while maintaining the initially specified surface density. The exposure of droplet nanostructures in the arsenic flux can be accompanied only by a decrease in their size, which is more typical for droplets obtained at large amounts of indium deposited material. For droplets with a smaller initial size, the formation of rings along the perimeter of the initial droplets and holes inside the rings is typical along with the droplet reduction. We also reveal that the dependence of the relative volume of droplets subjected to diffusion decay in the arsenic flux becomes more significant with a decrease in their initial size.

Numerical study of asymmetric breakup behavior of bubbles in Y-shaped branching microchannels

Microfluidic technology based on microchannel two-phase flow has been widely used. The precise control of the bubble or droplet size in the channel plays a crucial role in designing the microfluidic systems. In this work, the bubble breakup behavior in Y-shaped microchannel is reconstructed based on the volume of fluid method (VOF), and the effects of bubble dimensionless size (1.2–2.7), outlet flow ratio (1–4) and main channel Reynolds number (100–600) on the bubble breakup behavior are systematically investigated. The bubble asymmetric breakup process is found to be divided into three stages: extension stage, squeeze stage, and rapid pinch-off stage. In the case of small initial bubble size or relatively high outlet flow rate, the bubble does not break, but only experiences the extension stage and the squeezing stage. Four flow patterns of bubble breakup are further revealed for the bubbles with different sizes and outlet flow ratios: tunnel-tunnel breakup, obstruction-obstruction breakup, tunnel-obstruction breakup, and non-breakup. With the increase of outlet flow ratio, the breakup process of the bubble gradually becomes asymmetrical, and the flow pattern shifts along the tunnel-tunnel breakup and the obstruction-obstruction breakup, gradually turns toward the tunnel-obstruction breakup and non-breakup. On this basis, the critical flow ratio of bubble breakup and the variation of daughter bubble volume ratio with outlet flow ratio are obtained for different Reynolds numbers and initial bubble sizes, and the corresponding criterion correlation equation is refined, which can provide theoretical guidance for accurately regulating the daughter bubble size after breakup.

Experimental investigation on effective thermal conductivity of powder-packed assembly gaps in heat pipe cooled reactor core

The heat pipe cooled reactor utilizes monolithic solid core inserted with fuel rods and heat pipes. There exist assembly gaps between fuel rods, heat pipes and the solid block to avoid contact stress resulted from heterogeneous thermal expansion. In order to reduce the additional thermal resistance caused by assembly gaps, thermal conductive powders can be filled into the gaps. For the sake of evaluation on the effects of powder packed gaps on the reactor safety margin of heat pipe cooled reactor, the effective thermal conductivity of stainless-steel powder packed beds with different particle sizes was measured using the one-dimensional steady-state hollow-cylinder method in both air and helium atmosphere under the heating temperature of 800–1000 K and the pressure of 1 bar. The Zehner-Schlünder model was calibrated by adjusting the particle deformation parameter and the flattened surface fraction based on the experimental data in air. The comparison of prediction results by the adjusted Zehner-Schlünder model with experimental results in helium and relevant experimental data from previous literature shows the relatively error within ± 20%. Finally, the performance of powder packed gaps on increasing the reactor safety margin was evaluated by analyzing the different heat transfer modes and initial assembly-gap sizes. Results show that the performance improves with the increase of initial assembly-gap size and the fuel temperature decreases by 19.19 K compared to the helium-filled gap even with a small initial assembly-gap size of 0.2 mm.

Effectiveness and nonlinear characterization of vibro-impact energy harvesting absorbers in controlling base-excited systems

In this study, model derivations are carried out of a dynamical system under base excitations with a piezoelectric energy harvesting absorber as the tuned-mass-damper. Additionally, amplitude stoppers are included to the absorber in order to create a broadband resonant response, increasing the window of operational use for energy harvesting and system’s control. This study is unique in the fact that the energy harvester is coupled to the source of its excitation. A nonlinear reduced-order model is developed using Euler–Lagrange principle and the Galerkin method to accurately estimate the energy harvesting absorber’s displacement, harvested power, and the oscillating response of the primary structure. The nonlinear interaction of the energy harvesting absorber and the amplitude stoppers are the focus of this study, where an in-depth investigation of bifurcation points of the primary structure and energy harvesting absorber responses is performed. Due to a transfer of energy between the primary structure and the absorber, it is shown that a soft stopper with stiffness has great control of the primary structure with 60% of the uncontrolled amplitude being reduced, as well as an increase of the harvested energy. Medium stoppers with small initial gaps size and hard stoppers do not control the primary structure and show a decrease in the energy harvesting capabilities due to the activation of the nonlinear contact-impact interactions. These stoppers also generate aperiodic regions due to the possible presence of grazing bifurcations.

Grain size dependent microstructure and texture evolution during dynamic deformation of nanocrystalline face-centered cubic materials

Evolution of microstructure and texture in nanocrystalline (nc) face-centered cubic materials subjected to high-strain-rate compression are investigated. Three nc materials, differing in grain size or stacking fault energy, namely, 27 nm Ni, 70 nm Ni, and a 27 nm NiCo alloy are deformed under high strain rates (8000–23000 s−1) using the split-Hopkinson pressure bar technique. The transmission Kikuchi diffraction technique and discrete-crystal plasticity finite element (D-CPFE) simulations are used to evaluate structural evolution. Experimental results show that grain growth and grain refinement occurred in samples with small and large initial grain sizes, respectively, while all deformed materials evolve to a (110) texture. The D-CPFE simulations, built for grain-size dependent nc deformation with no fitting parameters, reveal that partial dislocation slip caused faster texture evolution than full dislocation slip. Comparison between experimental and simulation results suggests that the (110) texture is mainly generated by combined full and partial dislocation slip in the 27 nm and 70 nm Ni samples, and by partial dislocation slip alone in the NiCo alloy. Deformation twinning made almost no contributions to the observed texture evolution. Grain-boundary-mediated deformation facilitates grain coarsening, while partial dislocation activities help to promote dynamic stabilization and further refinement of the nano-grains. The highly coupled evolution of microstructure and texture during dynamic deformation is controlled by a synergy of grain size and strain rate effects.

MCF Tree-Based Clustering Method for Very Large Mixed-Type Data Set

Several clustering methods have been proposed for analyzing numerous mixed-type data sets composed of numeric and categorical attributes. However, existing clustering methods are not suitable for clustering very large mixed-type data sets because they require a high computational cost or a large memory size. We propose a novel clustering method for very large data sets using a mixed-type clustering feature (MCF) vector with summary information about a cluster. The MCF vector consists of the CF vector and a histogram to summarize the mixed-type values. Based on the MCF vector, we propose an MCF tree, along with a distance measure between the MCF vectors representing two clusters. Unlike previous studies that summarize a data set based on a fixed memory size, we estimate a small initial memory size of the data set for building the tree. Then, the memory size is adaptively increased to estimate a more accurate threshold by reflecting the size reduction in the re-built tree. Our theoretical analysis demonstrates the efficiency of the proposed approach. Experimental results on very large synthetic and real data sets demonstrate that the proposed approach clusters the data sets significantly faster than existing clustering methods while maintaining similar or better clustering accuracy.

Hearing aid use and cognition in older adults: Can we delay decline or even improve cognitive function?

AbstractBackgroundHearing loss is associated with accelerated cognitive decline in older adults, and has been identified as a modifiable risk factor for dementia. Although hearing aids are a successful treatment for hearing loss, it is unknown whether hearing aid use can delay the onset of cognitive decline or improve cognitive function in older adults with hearing loss. This prospective longitudinal study is investigating the effect of hearing aid use on cognitive decline and addresses many of the methodological limitations of previous studies.MethodPatients are recruited from the University of Melbourne Academic Hearing Aids Audiology Clinic and assessed before and every 18 months after hearing aid fitting. When numbers are sufficient, results will be compared with those of a control group of approximately 400 participants of a cohort study of ageing in older adults. Assessments include cognitive function (visually presented computerised assessment battery), hearing, speech perception, quality of life, activity, diet, loneliness and isolation, anxiety, depression, medical health and genetic risk.ResultAt baseline, multiple linear regression for 98 participants (62‐82 years), controlling for age, gender, cardiovascular conditions, education, and working/retired, with mean better ear PTA 31dB showed hearing loss and age predicted significantly poorer executive function, while tertiary education predicted significantly better executive function and visual learning. At 18‐month follow up, results for a subset of participants showed significant improvements in speech perception, listening disability and quality of life. Group mean scores across the cognitive assessment battery showed no significant decline and executive function was significantly improved. There was either clinically significant improvement or stability for executive function for over 97% of the subset, and for females for working memory, visual learning and visual attention, despite significantly greater hearing loss over this period.ConclusionDespite a small initial sample size, hearing loss, age and education significantly predicted baseline cognitive function. At 18‐month follow up, the majority of participants had either remained stable or demonstrated a meaningful clinical improvement in cognitive function, with significant group mean improvements for executive function and working memory. Treatment of hearing loss with hearing aids may delay cognitive decline. These are initial results, and further follow up is required.