12,179 research outputs found
The water problem in Iowa
Water deficiencies throughout Iowa and other Midwest states the past 3 years have re-emphasized the importance of water to our farms and cities. Cities have had to resort to more costly means of procuring adequate water for their citizens. Farmers have been digging deeper wells, constructing ponds and hauling water to meet their domestic and livestock needs. Many farmers have started to use or have contemplated using water from streams and wells to irrigate their crops. Industries are becoming increasingly concerned with the availability of water as a major factor in locating and expanding plants.
Experience during the last 3 years has demonstrated that water problems are aggravated periodically by rainfall deficiencies. However, these periodic aggravations emphasize but do not explain the basic water problem before us. In the main our water problems result from greatly increased demands upon available water supplies. These increasing demands stem from two factors: (1) a growing population and (2) an increasing per capita consumption. These two elements of the increasing demand for water show no indication of relaxing their rates of increase
Continuity equation and local gauge invariance for the N3LO nuclear Energy Density Functionals
Background: The next-to-next-to-next-to-leading order (N3LO) nuclear energy
density functional extends the standard Skyrme functional with new terms
depending on higher-order derivatives of densities, introduced to gain better
precision in the nuclear many-body calculations. A thorough study of the
transformation properties of the functional with respect to different
symmetries is required, as a step preliminary to the adjustment of the coupling
constants. Purpose: Determine to which extent the presence of higher-order
derivatives in the functional can be compatible with the continuity equation.
In particular, to study the relations between the validity of the continuity
equation and invariance of the functional under gauge transformations. Methods:
Derive conditions for the validity of the continuity equation in the framework
of time-dependent density functional theory. The conditions apply separately to
the four spin-isospin channels of the one-body density matrix. Results: We
obtained four sets of constraints on the coupling constants of the N3LO energy
density functional that guarantee the validity of the continuity equation in
all spin-isospin channels. In particular, for the scalar-isoscalar channel, the
constraints are the same as those resulting from imposing the standard U(1)
local-gauge-invariance conditions. Conclusions: Validity of the continuity
equation in the four spin-isospin channels is equivalent to the local-gauge
invariance of the energy density functional. For vector and isovector channels,
such validity requires the invariance of the functional under local rotations
in the spin and isospin spaces.Comment: 12 Latex pages, submitted to Physical Review
The Non-thermal Radio Jet Toward the NGC 2264 Star Formation Region
We report sensitive VLA 3.6 cm radio observations toward the head of the Cone
nebula in NGC 2264, made in 2006. The purpose of these observations was to
study a non-thermal radio jet recently discovered, that appears to emanate from
the head of the Cone nebula. The jet is highly polarized, with well-defined
knots, and one-sided. The comparison of our images with 1995 archive data
indicates no evidence of proper motions nor polarization changes. We find
reliable flux density variations in only one knot, which we tentatively
identify as the core of a quasar or radio galaxy. An extragalactic location
seems to be the best explanation for this jet.Comment: 12 pages, 5 figure
The Whole Heliosphere Interval in the Context of a Long and Structured Solar Minimum: An Overview from Sun to Earth
Throughout months of extremely low solar activity during the recent extended solar-cycle minimum, structural evolution continued to be observed from the Sun through the solar wind and to the Earth. In 2008, the presence of long-lived and large low-latitude coronal holes meant that geospace was periodically impacted by high-speed streams, even though solar irradiance, activity, and interplanetary magnetic fields had reached levels as low as, or lower than, observed in past minima. This time period, which includes the first Whole Heliosphere Interval (WHI 1: Carrington Rotation (CR) 2068), illustrates the effects of fast solar-wind streams on the Earth in an otherwise quiet heliosphere. By the end of 2008, sunspots and solar irradiance had reached their lowest levels for this minimum (e.g., WHI 2: CR 2078), and continued solar magnetic-flux evolution had led to a flattening of the heliospheric current sheet and the decay of the low-latitude coronal holes and associated Earth-intersecting high-speed solar-wind streams. As the new solar cycle slowly began, solar-wind and geospace observables stayed low or continued to decline, reaching very low levels by June – July 2009. At this point (e.g., WHI 3: CR 2085) the Sun–Earth system, taken as a whole, was at its quietest. In this article we present an overview of observations that span the period 2008 – 2009, with highlighted discussion of CRs 2068, 2078, and 2085. We show side-by-side observables from the Sun’s interior through its surface and atmosphere, through the solar wind and heliosphere and to the Earth’s space environment and upper atmosphere, and reference detailed studies of these various regimes within this topical issue and elsewhere
Singular continuous spectra in a pseudo-integrable billiard
The pseudo-integrable barrier billiard invented by Hannay and McCraw [J.
Phys. A 23, 887 (1990)] -- rectangular billiard with line-segment barrier
placed on a symmetry axis -- is generalized. It is proven that the flow on
invariant surfaces of genus two exhibits a singular continuous spectral
component.Comment: 4 pages, 2 figure
Severe hyperkalaemia: demographics and outcome
Background. Few studies have evaluated the prevalence of severe hyperkalaemia in unselected
patient populations.We identified all episodes of severe hyperkalaemia occurring in 1 year, and described
patient demographics, clinical response and outcome. We also assessed junior doctor
knowledge of its causes and significance.
Materials and methods. A retrospective interrogation of the database of the regional biochemical
laboratory identified all episodes of severe hyperkalaemia (K ≥ 6.5 mmol/L) occurring in 2011. The
understanding of trainee doctors of the importance, causes and treatment of severe hyperkalaemia
was assessed by structured questionnaire.
Results. Severe hyperkalaemia was recorded in 433 samples (365 patients) giving a prevalence of
0.11%. Thirty-six per cent of episodes occurred in patients under the care of a nephrologist, who
were significantly younger than those not under the care of a nephrologist. In the nephrology
cohort, 86% occurred in patients with chronic kidney disease (CKD), the majority of which had CKD
Stage 5. In the non-nephrology cohort, only 65% occurred in the context of CKD, which was
equally distributed between Stages 3 and 5 CKD. In both patient groups, roughly 50% of episodes
occurred in association with acute kidney injury (AKI). Acute mortality (death within 48 h of documented
severe hyperkalaemia) was higher in the non-nephrology compared with the nephrology
cohort. Time to repeat serum potassium was influenced by the clinical setting with shorter time to
repeat for acute care compared with ward settings. Assessment of trainee doctor’s knowledge
suggested significant deficiencies in relation to severe hyperkalaemia.
Conclusions. The prevalence of severe hyperkalaemia was low and occurred predominantly in the
context of CKD and/or AKI. The majority of episodes occurred in patients not under the care of a
nephrologist. Variability in time to repeat serum potassium levels suggested deficiencies in care,
and assessment of trainee doctor’s knowledge suggests the need for further educational initiatives
to highlight its importance
Long-term and recent trends in hypertension awareness, treatment and control in twelve high-income countries: an analysis of 123 nationally representative surveys
Background: Antihypertensive medicines are effective in reducing adverse cardiovascular events. Our aim was to compare hypertension awareness, treatment and control, and how they have changed over time, in high-income countries.
Methods: We used data on 526,336 participants aged 40-79 years in 123 national health examination surveys from 1976 to 2017 in twelve high-income countries: Australia, Canada, Finland, Germany, Ireland, Italy, Japan, New Zealand, South Korea, Spain, the UK, and the USA. We calculated the percent of participants with hypertension – defined as systolic blood pressure ≥140 mmHg or diastolic blood pressure ≥90 mmHg or being on pharmacological treatment for hypertension – who were aware of their condition, who were treated, and whose hypertension was controlled (i.e. lower than 140/90 mmHg).
Findings: Canada, South Korea, Australia and the UK have the lowest prevalence of hypertension, and Finland the highest. In the 1980s and early 1990s, treatment rates were at most 40% and control rates were below 25% in most countries and age-sex groups. Over time, hypertension awareness and treatment increased and control rate improved in all twelve countries, with South Korea and Germany experiencing the largest improvements. Most of the increase occurred in the 1990s and early-mid 2000s, having plateaued since in most countries. Canada, Germany, South Korea and the USA have the highest rates of awareness, treatment and control, while Finland, Ireland, Japan and Spain the lowest. Even in the best performing countries, treatment coverage was at most 80% and control rates were below 70%.
Interpretation: Hypertension awareness, treatment and control have improved substantially in high-income countries since the 1980s and 1990s. However, control rates have plateaued in the past decade, at levels lower than those in high-quality hypertension programmes. There is substantial variation across countries in the rates of hypertension diagnosis, treatment an
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