Threshold in breast compression reduction for full-field digital mammography and digital breast tomosynthesis.

INTRODUCTION: Breast compression is essential in mammography to improve image quality and reduce radiation dose. However, it can cause discomfort or even pain in women which could discourage them from attending future mammography examinations. Therefore, this study aims to explore the maximum reduction in breast compression in full-field digital mammography (FFDM) and digital breast tomosynthesis (DBT) that is achievable without impacting on image quality and dose. METHODS: Ten compression force (CF) levels (20N-110N, with 10N intervals) were assessed on Siemens MAMMOMAT Inspiration with Nuclear Associates 18-228 phantom. Imaging was carried out in craniocaudal projection using Automatic Exposure Control at 28 kVp with a Tungsten/Rhodium anode/filter combination, and at 50° sweep angle for DBT. Using ImageJ software, image quality of the acquired mammograms and central tomosynthesis slices were examined based on mass conspicuity (MC) and microcalcification conspicuity (MicroC). Entrance skin dose (ESD) and mean glandular dose (MGD) were recorded from Digital Imaging and Communication in Medicine image header. Linear regression was performed to examine the relationship between CF with ESD, MGD, MC and MicroC. Differences in image quality and radiation dose were assessed with one-way analysis of variance and Kruskal-Wallis H test. RESULTS: Significant correlations were noted between CF with ESD and MicroC for FFDM and DBT, with DBT also demonstrating associations with MGD and MC. No significant differences were observed for ESD, MGD, MC and MicroC when CF was reduced to 40N and 80N in FFDM and DBT respectively. CONCLUSION: This study demonstrated that CF can be reduced as low as 40N and 80N in FFDM and DBT respectively, without significant impact on image quality and radiation dose. IMPLICATIONS FOR PRACTICE: Reduced mammographic compression may reduce discomfort or pain in women, which may improve attendance rate in breast screening programmes. Findings from this study will provide reference for future work examining breast compression in mammography.

Modeled energetics of bacterial communities in ancient subzero brines.

Cryopeg brines are isolated volumes of hypersaline water in subzero permafrost. The cryopeg system at Utqiagvik, Alaska, is estimated to date back to 40 ka BP or earlier, a remnant of a late Pleistocene Ocean. Surprisingly, the cryopeg brines contain high concentrations of organic carbon, including extracellular polysaccharides, and high densities of bacteria. How can these physiologically extreme, old, and geologically isolated systems support such an ecosystem? This study addresses this question by examining the energetics of the Utqiagvik cryopeg brine ecosystem. Using literature-derived assumptions and new measurements on archived borehole materials, we first estimated the quantity of organic carbon when the system formed. We then considered two bacterial growth trajectories to calculate the lower and upper bounds of the cell-specific metabolic rate of these communities. These bounds represent the first community estimates of metabolic rate in a subzero hypersaline environment. To assess the plausibility of the different growth trajectories, we developed a model of the organic carbon cycle and applied it to three borehole scenarios. We also used dissolved inorganic carbon and nitrogen measurements to independently estimate the metabolic rate. The model reconstructs the growth trajectory of the microbial community and predicts the present-day cell density and organic carbon content. Model input included measured rates of the in-situ enzymatic conversion of particulate to dissolved organic carbon under subzero brine conditions. A sensitivity analysis of model parameters was performed, revealing an interplay between growth rate, cell-specific metabolic rate, and extracellular enzyme activity. This approach allowed us to identify plausible growth trajectories consistent with the observed bacterial densities in the cryopeg brines. We found that the cell-specific metabolic rate in this system is relatively high compared to marine sediments. We attribute this finding to the need to invest energy in the production of extracellular enzymes, for generating bioavailable carbon from particulate organic carbon, and the production of extracellular polysaccharides for cryoprotection and osmoprotection. These results may be relevant to other isolated systems in the polar regions of Earth and to possible ice-bound brines on worlds such as Europa, Enceladus, and Mars.

The metabolic rate of the biosphere and its components.

We assessed the relationship between rates of biological energy utilization and the biomass sustained by that energy utilization, at both the organism and biosphere level. We compiled a dataset comprising >10,000 basal, field, and maximum metabolic rate measurements made on >2,900 individual species, and, in parallel, we quantified rates of energy utilization, on a biomass-normalized basis, by the global biosphere and by its major marine and terrestrial components. The organism-level data, which are dominated by animal species, have a geometric mean among basal metabolic rates of 0.012 W (g C)-1 and an overall range of more than six orders of magnitude. The biosphere as a whole uses energy at an average rate of 0.005 W (g C)-1 but exhibits a five order of magnitude range among its components, from 0.00002 W (g C)-1 for global marine subsurface sediments to 2.3 W (g C)-1 for global marine primary producers. While the average is set primarily by plants and microorganisms, and by the impact of humanity upon those populations, the extremes reflect systems populated almost exclusively by microbes. Mass-normalized energy utilization rates correlate strongly with rates of biomass carbon turnover. Based on our estimates of energy utilization rates in the biosphere, this correlation predicts global mean biomass carbon turnover rates of ~2.3 y-1 for terrestrial soil biota, ~8.5 y-1 for marine water column biota, and ~1.0 y-1 and ~0.01 y-1 for marine sediment biota in the 0 to 0.1 m and >0.1 m depth intervals, respectively.

Phosphate availability and implications for life on ocean worlds.

Several moons in the outer solar system host liquid water oceans. A key next step in assessing the habitability of these ocean worlds is to determine whether life's elemental and energy requirements are also met. Phosphorus is required by all known life and is often limited to biological productivity in Earth's oceans. This raises the possibility that its availability may limit the abundance or productivity of Earth-like life on ocean worlds. To address this potential problem, here we calculate the equilibrium dissolved phosphate concentrations associated with the reaction of water and rocks-a key driver of ocean chemical evolution-across a broad range of compositional inputs and reaction conditions. Equilibrium dissolved phosphate concentrations range from 10-11 to 10-1 mol/kg across the full range of carbonaceous chondrite compositions and reaction conditions considered, but are generally > 10-5 mol/kg for most plausible scenarios. Relative to the phosphate requirements and uptake kinetics of microorganisms in Earth's oceans, such concentrations would be sufficient to support initially rapid cell growth and construction of global ocean cell populations larger than those observed in Earth's deep oceans.

Corrigendum: Modeled energetics of bacterial communities in ancient subzero brines.

[This corrects the article DOI: 10.3389/fmicb.2023.1206641.].

Probing Internal Assumptions of the Revised Bloom's Taxonomy.

Bloom's taxonomy is a classification of learning objectives originally developed for general educational purposes. The taxonomy was revised to expand beyond cognitive processes and to include knowledge types as an orthogonal dimension. As Bloom's taxonomy is a tool widely used in biology education by researchers and instructors, it is important to examine the underlying assumptions embedded within how people may implicitly understand and use the taxonomy. In this paper, we empirically examine two major assumptions: the independence of the knowledge-type and cognitive-process dimensions and the use of action verbs as proxies for different cognitive processes. Contingency analysis on 940 assessment items revealed that the knowledge-type and cognitive-process dimensions are related and not independent. Subsequent correspondence analysis identified two principle axes in how the two dimensions are related, with three clusters of knowledge types and cognitive processes. Using the Shannon evenness index, we did not find a clear relationship between question prompt words (including action verbs) and cognitive processes in the assessment items. Based on these results, we suggest that both dimensions of the revised Bloom's taxonomy should be used and that question prompt words or action verbs alone are not sufficient in classifying the embedded learning objectives within assessment items.

Science Objectives for Flagship-Class Mission Concepts for the Search for Evidence of Life at Enceladus.

Cassini revealed that Saturn's Moon Enceladus hosts a subsurface ocean that meets the accepted criteria for habitability with bio-essential elements and compounds, liquid water, and energy sources available in the environment. Whether these conditions are sufficiently abundant and collocated to support life remains unknown and cannot be determined from Cassini data. However, thanks to the plume of oceanic material emanating from Enceladus' south pole, a new mission to Enceladus could search for evidence of life without having to descend through kilometers of ice. In this article, we outline the science motivations for such a successor to Cassini, choosing the primary science goal to be determining whether Enceladus is inhabited and assuming a resource level equivalent to NASA's Flagship-class missions. We selected a set of potential biosignature measurements that are complementary and orthogonal to build a robust case for any life detection result. This result would be further informed by quantifications of the habitability of the environment through geochemical and geophysical investigations into the ocean and ice shell crust. This study demonstrates that Enceladus' plume offers an unparalleled opportunity for in situ exploration of an Ocean World and that the planetary science and astrobiology community is well equipped to take full advantage of it in the coming decades.

Prevalence and Characterization of Quinolone Resistance in Campylobacter spp. Isolates in Chicken Livers from Retail Stores in Georgia, USA.

ABSTRACT: Campylobacter is a bacterial pathogen that causes human foodborne illnesses worldwide, and outbreaks have been associated with consumption of undercooked chicken livers. The objectives of this study were to compare two PCR assays of 250 Campylobacter isolates for identification to species, to assess antibiotic resistance of the isolates, and to analyze genetic diversity of the quinolone resistance determining regions (QRDRs) of the isolates. A double-blind design was used to identify the species of Campylobacter; 181 (72%) of the isolates were identified as Campylobacter jejuni, and 69 (28%) isolates were identified as Campylobacter coli by both PCR assays. A total of 93 (37.2%) isolates were resistant to at least one antibiotic. Among 88 C. jejuni isolates, 33 (18%) were resistant to nalidixic acid (NAL) and ciprofloxacin (CIP), 25 (14%) were resistant to tetracycline (TET), and 18 (10%) were resistant to NAL and TET. Two C. jejuni isolates were resistant to four of the tested antibiotics, and one isolate was resistant to five antibiotics. Two C. coli isolates were resistant to TET, and two were resistant to NAL, CIP, and TET. The amino acid sequences of the QRDRs for the isolates had eight point mutations and could be classified into 12 groups. Thirty-eight C. jejuni isolates resistant to NAL and CIP had a point mutation at residue 86 (substitution from threonine to isoleucine). However, six isolates without this substitution were resistant to NAL and/or CIP. Ten isolates with a point mutation at residue 86 were susceptible to NAL and CIP. This observation suggests that in addition to the substitution at residue 86 other mechanisms may confer resistance to quinolones. Further studies are needed to elucidate mechanisms for quinolone resistance in Campylobacter. The Campylobacter spp. isolated from chicken livers in this study were resistant to quinolones and other classes of antibiotics.

Microbial Communities in a Serpentinizing Aquifer Are Assembled through Strong Concurrent Dispersal Limitation and Selection.

In recent years, our appreciation of the extent of habitable environments in Earth's subsurface has greatly expanded, as has our understanding of the biodiversity contained within. Most studies have relied on single sampling points, rather than considering the long-term dynamics of subsurface environments and their microbial populations. One such habitat are aquifers associated with the aqueous alteration of ultramafic rocks through a process known as serpentinization. Ecological modeling performed on a multiyear time series of microbiology, hydrology, and geochemistry in an ultrabasic aquifer within the Coast Range Ophiolite reveals that community assembly is governed by undominated assembly (i.e., neither stochastic [random] nor deterministic [selective] processes alone govern assembly). Controls on community assembly were further assessed by characterizing aquifer hydrogeology and microbial community adaptations to the environment. These analyses show that low permeability rocks in the aquifer restrict the transmission of microbial populations between closely situated wells. Alpha and beta diversity measures and metagenomic and metatranscriptomic data from microbial communities indicate that high pH and low dissolved inorganic carbon levels impose strong environmental selection on microbial communities within individual wells. Here, we find that the interaction between strong selection imposed by extreme pH and enhanced ecological drift due to dispersal limitation imposed by slow fluid flow results in the undominated assembly signal observed throughout the site. Strong environmental selection paired with extremely low dispersal in the subsurface results in low diversity microbial communities that are well adapted to extreme pH conditions and subject to enhanced stochasticity introduced by ecological drift over time. IMPORTANCE Microbial communities existing under extreme or stressful conditions have long been thought to be structured primarily by deterministic processes. The application of macroecology theory and modeling to microbial communities in recent years has spurred assessment of assembly processes in microbial communities, revealing that both stochastic and deterministic processes are at play to different extents within natural environments. We show that low diversity microbial communities in a hard-rock serpentinizing aquifer are assembled under the influence of strong selective processes imposed by high pH and enhanced ecological drift that occurs as the result of dispersal limitation due to the slow movement of water in the low permeability aquifer. This study demonstrates the important roles that both selection and dispersal limitation play in terrestrial serpentinites, where extreme pH assembles a microbial metacommunity well adapted to alkaline conditions and dispersal limitation drives compositional differences in microbial community composition between local communities in the subsurface.

A dynamic microbial sulfur cycle in a serpentinizing continental ophiolite.

Serpentinization is the hydration and oxidation of ultramafic rock, which occurs as oceanic lithosphere is emplaced onto continental margins (ophiolites), and along the seafloor as faulting exposes this mantle-derived material to circulating hydrothermal fluids. This process leads to distinctive fluid chemistries as molecular hydrogen (H2 ) and hydroxyl ions (OH- ) are produced and reduced carbon compounds are mobilized. Serpentinizing ophiolites also serve as a vector to transport sulfur compounds from the seafloor onto the continents. We investigated hyperalkaline, sulfur-rich, brackish groundwater in a serpentinizing continental ophiolite to elucidate the role of sulfur compounds in fuelling in situ microbial activities. Here we illustrate that key sulfur-cycling taxa, including Dethiobacter, Desulfitispora and 'Desulforudis', persist throughout this extreme environment. Biologically catalysed redox reactions involving sulfate, sulfide and intermediate sulfur compounds are thermodynamically favourable in the groundwater, which indicates they may be vital to sustaining life in these characteristically oxidant- and energy-limited systems. Furthermore, metagenomic and metatranscriptomic analyses reveal a complex network involving sulfate reduction, sulfide oxidation and thiosulfate reactions. Our findings highlight the importance of the complete inorganic sulfur cycle in serpentinizing fluids and suggest sulfur biogeochemistry provides a key link between terrestrial serpentinizing ecosystems and their submarine heritage.

Probing the geological source and biological fate of hydrogen in Yellowstone hot springs.

Hydrogen (H2 ) is enriched in hot springs and can support microbial primary production. Using a series of geochemical proxies, a model to describe variable H2 concentrations in Yellowstone National Park (YNP) hot springs is presented. Interaction between water and crustal iron minerals yields H2 that partition into the vapour phase during decompressional boiling of ascending hydrothermal fluids. Variable vapour input leads to differences in H2 concentration among springs. Analysis of 50 metagenomes from a variety of YNP springs reveals that genes encoding oxidative hydrogenases are enriched in communities inhabiting springs sourced with vapour-phase gas. Three springs in the Smokejumper (SJ) area of YNP that are sourced with vapour-phase gas and with the most H2 in YNP were examined to determine the fate of H2 . SJ3 had the most H2 , the most 16S rRNA gene templates and the greatest abundance of culturable hydrogenotrophic and autotrophic cells of the three springs. Metagenomics and transcriptomics of SJ3 reveal a diverse community comprised of abundant populations expressing genes involved in H2 oxidation and carbon dioxide fixation. These observations suggest a link between geologic processes that generate and source H2 to hot springs and the distribution of organisms that use H2 to generate energy.

Alcohol Use and Drinking Motives Among Suddenly Bereaved College Students.

Objective: Thousands of Americans grieve the sudden death of a loved one each year. These sudden deaths may be the result of violent deaths, as in the cases of homicide, suicide, or fatal accidents, or may occur as the result of natural causes such as heart attacks or strokes. Sudden loss survivors often experience negative mental health outcomes such as depression, prolonged grief disorder, and posttraumatic stress disorder. Survivors may also misuse alcohol for varied reasons after these losses, which can put them at risk for alcohol-related consequences. Thus, the purpose of this study was to explore associations between psychological distress and alcohol-related outcomes among young adults with a history of sudden loss. Methods: A sample of 659 young adults completed a series of self-report measures assessing loss history, psychosocial distress, perceived alcohol-related problems, and drinking motives. Results: Results showed that survivors of sudden, violent losses reported higher rates of past 30-day alcohol use than those who had lost a loved one to a sudden, natural loss or those who reported no loss history. Although there were no statistically significant differences in drinking motives between violent or natural loss survivors, more severe depression symptoms among bereaved individuals were associated with drinking to cope and to conform. Participants experiencing prolonged grief symptoms were also more likely to report drinking to conform. Conclusions: Bereavement-related distress may influence drinking motives among young adults with a history of sudden loss.

Running Economy While Running in Shoes Categorized as Maximal Cushioning.

The purpose of the study was to determine if running economy was influenced by wearing maximal cushioning shoes vs. control (neutral cushioning) shoes. Participants (n=10, age=28.2±6.1yrs; mass=68.1±10.2 kg; height=170±6.1 cm) completed two experiments. Each experiment included running conditions wearing control and maximal cushioning shoes. In Experiment 1, participants ran on a treadmill at three speeds in each shoe condition (6 total conditions). The speeds were: 1) preferred speed, 2) preferred speed + 0.447 m·s-1, and 3) preferred speed - 0.447 m·s-1. In Experiment 2, participants ran on a treadmill at two inclines (0%, 6%) in each shoe condition (4 total conditions) at preferred speed. Experiments were conducted on separate days with Experiment 1 first. For all conditions, participants ran for 8-10 minutes while rate of oxygen consumption (VO2) was recorded. Average VO2 during steady state for each running condition was calculated. For Experiment 1, a 2 (shoe) × 3 (speed) repeated measures ANOVA (α=0.05) was used. For Experiment 2, a 2 (shoe) × 2 (incline) repeated measures ANOVA (α=0.05) was used. Rate of oxygen consumption was not influenced by the interaction of speed and shoe (p=0.108); VO2 was different between speeds (p<0.001), but not between shoes (p=0.071). Rate of oxygen consumption was not influenced by the interaction of incline and shoe (p=0.191); VO2 was greater for incline vs. level (p<0.001), but not different between shoes (p=0.095). It is concluded that a maximal cushioning running shoe did not influence running economy when compared to a control shoe (neutral cushioning running shoe).

Subsurface processes influence oxidant availability and chemoautotrophic hydrogen metabolism in Yellowstone hot springs.

The geochemistry of hot springs and the availability of oxidants capable of supporting microbial metabolisms are influenced by subsurface processes including the separation of hydrothermal fluids into vapor and liquid phases. Here, we characterized the influence of geochemical variation and oxidant availability on the abundance, composition, and activity of hydrogen (H2 )-dependent chemoautotrophs along the outflow channels of two-paired hot springs in Yellowstone National Park. The hydrothermal fluid at Roadside East (RSE; 82.4°C, pH 3.0) is acidic due to vapor-phase input while the fluid at Roadside West (RSW; 68.1°C, pH 7.0) is circumneutral due to liquid-phase input. Most chemotrophic communities exhibited net rates of H2 oxidation, consistent with H2 support of primary productivity, with one chemotrophic community exhibiting a net rate of H2 production. Abundant H2 -oxidizing chemoautotrophs were supported by reduction in oxygen, elemental sulfur, sulfate, and nitrate in RSW and oxygen and ferric iron in RSE; O2 utilizing hydrogenotrophs increased in abundance down both outflow channels. Sequencing of 16S rRNA transcripts or genes from native sediments and dilution series incubations, respectively, suggests that members of the archaeal orders Sulfolobales, Desulfurococcales, and Thermoproteales are likely responsible for H2 oxidation in RSE, whereas members of the bacterial order Thermoflexales and the archaeal order Thermoproteales are likely responsible for H2 oxidation in RSW. These observations suggest that subsurface processes strongly influence spring chemistry and oxidant availability, which in turn select for unique assemblages of H2 oxidizing microorganisms. Therefore, these data point to the role of oxidant availability in shaping the ecology and evolution of hydrogenotrophic organisms.

An Evaluation of Select Physical Activity Exercise Classes on Bone Metabolism.

Weight-bearing physical activity can optimize bone mass early in life and prevent the development of osteoporosis. However, less is known about the potential benefits of non-weight-bearing activities. The purpose of this study was to assess the efficacy of structured physical activity classes on bone metabolism. Twenty-eight premenopausal women, aged 18-35 years who were either enrolled in a yoga class (n=14) or cardio-kickboxing class (n=14) voluntarily consented to participate. Both classes were introductory classes meeting twice per week for 50 min per session for 12 weeks. Anteroposterior spine (L1-L4), hip (dual femur), and total body bone mineral density (BMD) was measured in both groups pre and post intervention using dual-energy X-ray absorptiometry (DXA). Pre and post blood samples were drawn for measurement of serum osteocalcin (OC) by enzyme-linked immunosorbent assay (ELISA) in each group. Baseline subject characteristics including age, height, weight, body fat percentage, and lean body mass did not differ between groups. BMD levels did not increase but were held stable over the course of the intervention. Yoga increased OC by 68% (P < 0.001) and cardio-kickboxing increased OC by 67% (P < 0.001) over the course of the 12-week classes. While 12 weeks of yoga and cardio-kickboxing were insufficient to induce BMD changes, OC levels reflect the bone formation process was initiated, but not yet complete. Increased OC levels suggest the selected physical activity classes provided enough of a stimulus to precipitate a future response of bone growth, assuming exercise training remains constant.

Comparison of Bioelectrical Impedance Analysis and Dual-Energy X-Ray Absorptiometry for Estimating Bone Mineral Content.

The purpose of this study was to validate single-frequency hand-to-foot bioelectrical impedance analysis (HFBIA) for estimating bone mineral content (BMC) using dual-energy X-ray absorptiometry as the criterion measure in healthy men and women aged 18-40 years. A total of 80 men and women participated in this study. BMC was estimated on the same day using HFBIA and dual-energy X-ray absorptiometry. The HFBIA device provided higher mean BMC values in men and the entire sample, but not in women. A smaller standard error of estimate was observed in women (0.20, corresponding to 8% of the mean reference BMC values) compared with men (0.39, corresponding to 12% of the mean reference BMC values) and the combined sample (0.31). HFBIA provided a smaller constant error and individual estimation error indicated by the 95% limits of agreement in women (-0.05 ± 0.39) compared with men (-0.16 ± 0.78) and the entire sample (-0.10 ± 0.63). In conclusion, although BMC values were found to be more accurate in women, HFBIA overestimated BMC compared with dual-energy X-ray absorptiometry, especially in individuals with lower values. Given these results, using HFBIA to measure BMC would be inappropriate for diagnostic purposes.