Evolution of competitive ability for essential resources

Competition for limiting resources is among the most fundamental ecological interactions and has long been considered a key driver of species coexistence and biodiversity. Species’ minimum resource requirements, their R*, are key traits that link individual physiological demands to the outcome of competition. However, a major question remains unanswered -- to what extent are species’ competitive traits able to evolve in response to resource limitation? To address this knowledge gap, we performed an evolution experiment in which we exposed Chlamydomonas reinhardtii for approximately 285 generations to seven environments in chemostats which differed in resource supply ratios (including nitrogen, phosphorus and light limitation) and salt stress. We then grew the ancestors and descendants in common garden experiments and quantified their competitive abilities for essential resources. We investigated constraints on trait evolution by testing whether changes in resource requirements for different resources were correlated. Competitive abilities for phosphorus improved in all populations, while competitive abilities for nitrogen and light increased in some populations and decreased in others. In contrast to the common assumption that there are trade-offs between competitive abilities for different resources, we found that improvements in competitive ability for a resource came at no detectable cost. Instead, improvements in competitive ability for multiple resources were either positively correlated or not significantly correlated. Using resource competition theory, we then demonstrated that rapid adaptation in competitive traits altered the predicted outcomes of competition. These results highlight the need to incorporate contemporary evolutionary change into predictions of competitive community dynamics over environmental gradients

Does 24-48 or 48-96 Promote Better REM Sleep Within Firefighters?

A firefighter’s work schedule can be very demanding regardless if they work 24 hours followed by a 48-hour time off schedule or a 48-hour on followed by a 96-hour time off. Rapid Eye Movement (REM) sleep could be the deciding factor of how well a firefighter can perform following a certain work schedule. REM sleep is associated with the mental activity of dreaming; an individual averages 20-25% REM sleep of their total sleep time (Carskadon & Dement, 2005). REM is important for recovery because it can impact cognitive functions such as impulse control and decision making (Brunet, et al, 2020). This study examined the influence shift type had on REM sleep after a day of rest within 24-48, compared to a rest day within a 48-96 work schedule. PURPOSE: The study was designed to measure REM sleep on the 24-48 and 48-96 shift schedules and determine which shift type had a more optimal level of REM sleep. METHODS: 54 firefighters participated and were split into two cohorts depending on the department\u27s work schedule: 24-48 (n = 28) and 48-96 (n = 26). Data was collected through the use of WHOOP® (WHOOP, Inc.) wrist bands, which measures heart rate, HRV, strain, and sleep. A two-way ANOVA was utilized to determine the differences in shift type (24-48, 48-96) and day type, On Day 1 (OD1), On Day 2 (OD2), Rest Day 1 (RD1), Rest Day 2 (RD2), and Rest Day 3 (RD3). RESULTS: Participants exhibited 24.7 ± 9.2% of REM sleep. There was a significant difference between 24-48 OD1 REM (1.56 ± 0.66,) and 48-96 OD1 REM (1.31 ± 0.63) (p \u3c 0.001). Another significant difference existed between 48-96 RD1 REM (1.44 ± 0.71) and 48-96 RD2 REM (1.66 ± 0.78) (p = 0.004) as well as 48-96 RD3 REM (1.66 ± 0.68) (p = 0.007). No further significances were found when comparing shift days and rest days between the shift types. CONCLUSION: Therefore, shift type may have little effect on the amount of REM sleep a firefighter gets on a daily basis. Within the 48-96 shift type, significant differences in REM sleep amount do exist, indicating that recovery improves from the first and second rest day, with no further improvements after that

Pulsar Timing and its Application for Navigation and Gravitational Wave Detection

Pulsars are natural cosmic clocks. On long timescales they rival the precision of terrestrial atomic clocks. Using a technique called pulsar timing, the exact measurement of pulse arrival times allows a number of applications, ranging from testing theories of gravity to detecting gravitational waves. Also an external reference system suitable for autonomous space navigation can be defined by pulsars, using them as natural navigation beacons, not unlike the use of GPS satellites for navigation on Earth. By comparing pulse arrival times measured on-board a spacecraft with predicted pulse arrivals at a reference location (e.g. the solar system barycenter), the spacecraft position can be determined autonomously and with high accuracy everywhere in the solar system and beyond. We describe the unique properties of pulsars that suggest that such a navigation system will certainly have its application in future astronautics. We also describe the on-going experiments to use the clock-like nature of pulsars to "construct" a galactic-sized gravitational wave detector for low-frequency (f_GW ~1E-9 - 1E-7 Hz) gravitational waves. We present the current status and provide an outlook for the future.Comment: 30 pages, 9 figures. To appear in Vol 63: High Performance Clocks, Springer Space Science Review

The metabolic regimes of 356 rivers in the United States

A national-scale quantification of metabolic energy flow in streams and rivers can improve understanding of the temporal dynamics of in-stream activity, links between energy cycling and ecosystem services, and the effects of human activities on aquatic metabolism. The two dominant terms in aquatic metabolism, gross primary production (GPP) and aerobic respiration (ER), have recently become practical to estimate for many sites due to improved modeling approaches and the availability of requisite model inputs in public datasets. We assembled inputs from the U.S. Geological Survey and National Aeronautics and Space Administration for October 2007 to January 2017. We then ran models to estimate daily GPP, ER, and the gas exchange rate coefficient for 356 streams and rivers across the continental United States. We also gathered potential explanatory variables and spatial information for cross-referencing this dataset with other datasets of watershed characteristics. This dataset offers a first national assessment of many-day time series of metabolic rates for up to 9 years per site, with a total of 490,907 site-days of estimates.We thank Jill Baron and the USGS Powell Center for financial support for this collaborative effort (Powell Center Working Group title: "Continental-scale overview of stream primary productivity, its links to water quality, and consequences for aquatic carbon biogeochemistry"). Additional financial support came from the USGS NAWQA program and Office of Water Information. NSF grants DEB-1146283 and EF1442501 partially supported ROH. A post-doctoral grant from the Basque Government partially supported MA. NAG was supported by the U.S. Department of Energy's Office of Science, Biological and Environmental Research. Oak Ridge National Laboratory is managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725. Leah Colasuonno provided expert logistical support of our working group meetings. The developers of USGS ScienceBase were very helpful both in hosting this dataset and in responding to our requests. Randy Hunt and Mike Fienen of the USGS Wisconsin Modeling Center graciously provided access to their HTCondor cluster. Mike Vlah provided detailed and insightful reviews of the data and metadata

Angiographic correlations of patients with small vessel disease diagnosed by adenosine-stress cardiac magnetic resonance imaging

Cardiac magnetic resonance imaging (CMR) with adenosine-stress myocardial perfusion is gaining importance for the detection and quantification of coronary artery disease (CAD). However, there is little knowledge about patients with CMR-detected ischemia, but having no relevant stenosis as seen on coronary angiography (CA). The aims of our study were to characterize these patients by CMR and CA and evaluate correlations and potential reasons for the ischemic findings. 73 patients with an indication for CA were first scanned on a 1.5T whole-body CMR-scanner including adenosine-stress first-pass perfusion. The images were analyzed by two independent investigators for myocardial perfusion which was classified as subendocardial ischemia (n = 22), no perfusion deficit (n = 27, control 1), or more than subendocardial ischemia (n = 24, control 2). All patients underwent CA, and a highly significant correlation between the classification of CMR perfusion deficit and the degree of coronary luminal narrowing was found. For quantification of coronary blood flow, corrected Thrombolysis in Myocardial Infarction (TIMI) frame count (TFC) was evaluated for the left anterior descending (LAD), circumflex (LCX) and right coronary artery (RCA). The main result was that corrected TFC in all coronaries was significantly increased in study patients compared to both control 1 and to control 2 patients. Study patients had hypertension or diabetes more often than control 1 patients. In conclusion, patients with CMR detected subendocardial ischemia have prolonged coronary blood flow. In connection with normal resting flow values in CAD, this supports the hypothesis of underlying coronary microvascular impairment. CMR stress perfusion differentiates non-invasively between this entity and relevant CAD

Low Concentrations of Silver Nanoparticles in Biosolids Cause Adverse Ecosystem Responses under Realistic Field Scenario

A large fraction of engineered nanomaterials in consumer and commercial products will reach natural ecosystems. To date, research on the biological impacts of environmental nanomaterial exposures has largely focused on high-concentration exposures in mechanistic lab studies with single strains of model organisms. These results are difficult to extrapolate to ecosystems, where exposures will likely be at low-concentrations and which are inhabited by a diversity of organisms. Here we show adverse responses of plants and microorganisms in a replicated long-term terrestrial mesocosm field experiment following a single low dose of silver nanoparticles (0.14 mg Ag kg−1 soil) applied via a likely route of exposure, sewage biosolid application. While total aboveground plant biomass did not differ between treatments receiving biosolids, one plant species, Microstegium vimeneum, had 32 % less biomass in the Slurry+AgNP treatment relative to the Slurry only treatment. Microorganisms were also affected by AgNP treatment, which gave a significantly different community composition of bacteria in the Slurry+AgNPs as opposed to the Slurry treatment one day after addition as analyzed by T-RFLP analysis of 16S-rRNA genes. After eight days, N2O flux was 4.5 fold higher in the Slurry+AgNPs treatment than the Slurry treatment. After fifty days, community composition and N2O flux of the Slurry+AgNPs treatment converged with the Slurry. However, the soil microbial extracellular enzymes leucine amino peptidase and phosphatase had 52 and 27% lower activities, respectively, while microbial biomass was 35% lower than the Slurry. We also show that the magnitude of these responses was in all cases as large as or larger than the positive control, AgNO3, added at 4-fold the Ag concentration of the silver nanoparticles

Design of pure heterodinuclear lanthanoid cryptate complexes

Heterolanthanide complexes are difficult to synthesize owing to the similar chemistry of the lanthanide ions. Consequently, very few purely heterolanthanide complexes have been synthesized. This is despite the fact that such complexes hold interesting optical and magnetic properties. To fine-tune these properties, it is important that one can choose complexes with any given combination of lanthanides. Herein we report a synthetic procedure which yields pure heterodinuclear lanthanide cryptates LnLn*LX(3) (X = NO(3)(−) or OTf(−)) based on the cryptand H(3)L = N[(CH(2))(2)N[double bond, length as m-dash]CH–R–CH[double bond, length as m-dash]N–(CH(2))(2)](3)N (R = m-C(6)H(2)OH-2-Me-5). In the synthesis the choice of counter ion and solvent proves crucial in controlling the Ln–Ln* composition. Choosing the optimal solvent and counter ion afford pure heterodinuclear complexes with any given combination of Gd(iii)–Lu(iii) including Y(iii). To demonstrate the versatility of the synthesis all dinuclear combinations of Y(iii), Gd(iii), Yb(iii) and Lu(iii) were synthesized resulting in 10 novel complexes of the form LnLn*L(OTf)(3) with LnLn* = YbGd 1, YbY 2, YbLu 3, YbYb 4, LuGd 5, LuY 6, LuLu 7, YGd 8, YY 9 and GdGd 10. Through the use of (1)H, (13)C NMR and mass spectrometry the heterodinuclear nature of YbGd, YbY, YbLu, LuGd, LuY and YGd was confirmed. Crystal structures of LnLn*L(NO(3))(3) reveal short Ln–Ln distances of ∼3.5 Å. Using SQUID magnetometry the exchange coupling between the lanthanide ions was found to be anti-ferromagnetic for GdGd and YbYb while ferromagnetic for YbGd

Impaired Ca2+-handling in HIF-1α+/− mice as a consequence of pressure overload

The hypoxia-inducible factor (HIF)-1 is critically involved in the cellular adaptation to a decrease in oxygen availability. The influence of HIF-1α for the development of cardiac hypertrophy and cardiac function that occurs in response to sustained pressure overload has been mainly attributed to a challenged cardiac angiogenesis and cardiac hypertrophy up to now. Hif-1α+/+ and Hif-1α+/− mice were studied regarding left ventricular hypertrophy and cardiac function after being subjected to transverse aortic constriction (TAC). After TAC, both Hif-1α+/+ and Hif-1α+/− mice developed left ventricular hypertrophy with increased posterior wall thickness, septum thickness and increased left ventricular weight to a similar extent. No significant difference in cardiac vessel density was observed between Hif-1α+/+ and Hif-1α+/− mice. However, only the Hif-1α+/− mice developed severe heart failure as revealed by a significantly reduced fractional shortening mostly due to increased end-systolic left ventricular diameter. On the single cell level this correlated with reduced myocyte shortenings, decreased intracellular Ca2+-transients and SR-Ca2+ content in myocytes of Hif-1a+/− mice. Thus, HIF-1α can be critically involved in the preservation of cardiac function after chronic pressure overload without affecting cardiac hypertrophy. This effect is mediated via HIF-dependent modulation of cardiac calcium handling and contractility