Flowering Dates of Viola sororia Willd. and V. pensylvanica Michx. at Different Latitudes

The response to daylength has been shown to be significant in the initiation of flowering in many species of vascular plants. Herbarium specimens of Viola sororia Willd. and V. pensylvanica Michx. from a wide range of latitudes were examined to ascertain correlation between dates of flowering and length of day. Two observations were made: the higher the latitude, the later flowering occurred in the spring; and the higher the latitude the greater the daylength at the time of open flowering. It is suggested that these north-south clines represent a genetic response arrived at through natural selection. Further studies arc proposed to test this hypothesis

Blood pressure vs altitude in hypertensive and non-hypertensive himalayan trekkers

Introduction: Determine blood pressure (BP) response to changes in altitude in Himalayan trekkers with and without hypertension (HTN). Methods: BP was measured in Lukla (2800m), Namche (3400m), and either Pheriche or Dingboche (4400m) on ascent and descent. Hypertensive subjects were defined by self-reported diagnosis of HTN. Results: Trekkers had HTN (H, n=60) or no HTN (NH, n=604). Of those with HTN, 50 (83%) took one or more BP medications including ACEIs/ARBs (n=35, 48%), Ca++ channel blockers (n=15, 22%), beta-blockers (n=9, 13%), thiazide diuretics (n=7, 10%), and others (n=5, 7%). At 2800m, systolic BP (SBP) and diastolic BP (DBP) were greater in the H group than in the NH group [mean SBP= 151mmHg (95% CI 145.4-155.7) vs 127mmHg (95% CI 125.5 128.0); mean DBP=88mmHg (95% CI 85.1-91.7) vs 80mmHg (95% CI 79.3-80.8)] and remained higher at both 3400m [mean SBP=150mmHg (95% CI 143.7-156.9) vs 127mmHg (95% CI 125.8-128.5); mean DBP=88mmHg (95% CI 84.3-90.8) vs 82mmHg (95% CI 80.7-82.5)] and 4400m [mean SBP=144mmHg (95% CI 136.7-151.7) vs 128mmHg (95% CI 126.4-129.5); mean DBP=87mmHg (95% CI 83.2-91.7) vs 82mmHg (95% CI 81.3-83.2)]. Between 2800m and 3400m, BP increased in 37% of trekkers, decreased in 25%, and did not change in 38%; from 3400m to 4400m, BP increased in 35% of trekkers, decreased in 26%, and did not change in 40%. Prevalence of severe hypertension (BP\u3e180/120mmHg) was similar across altitudes but higher in the H group (9%; 10%; 8% vs 0.7%; 0.6%, 0.3%) at 2800m, 3400m, and 4400m, respectively. No subjects reported symptoms of hypertensive emergency (chest pain, stroke, etc.). Conclusion: Blood pressure response to altitude is variable. High prevalence of severe hypertension in hypertensive trekkers warrants further study regarding BP control at high altitude

Dynamics, stratospheric ozone, and climate change

Dynamics affects the distribution and abundance of stratospheric ozone directly through transport of ozone itself and indirectly through its effect on ozone chemistry via temperature and transport of other chemical species. Dynamical processes must be considered in order to understand past ozone changes, especially in the northern hemisphere where there appears to be significant low-frequency variability which can look “trend-like” on decadal time scales. A major challenge is to quantify the predictable, or deterministic, component of past ozone changes. Over the coming century, changes in climate will affect the expected recovery of ozone. For policy reasons it is important to be able to distinguish and separately attribute the effects of ozone-depleting substances and greenhouse gases on both ozone and climate. While the radiative-chemical effects can be relatively easily identified, this is not so evident for dynamics — yet dynamical changes (e.g., changes in the Brewer-Dobson circulation) could have a first-order effect on ozone over particular regions. Understanding the predictability and robustness of such dynamical changes represents another major challenge. Chemistry-climate models have recently emerged as useful tools for addressing these questions, as they provide a self-consistent representation of dynamical aspects of climate and their coupling to ozone chemistry. We can expect such models to play an increasingly central role in the study of ozone and climate in the future, analogous to the central role of global climate models in the study of tropospheric climate change

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

Reverse osmosis desalination with osmotic polyelectrolyte intermediate

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