434 research outputs found
Trends in Real Food Prices in Six Sub-Saharan African Countries
Demand and Price Analysis, Downloads July 2008-July 2009: 12,
Analysis of the Brinkman-Forchheimer equations with slip boundary conditions
In this work, we study the Brinkman-Forchheimer equations driven under slip
boundary conditions of friction type. We prove the existence and uniqueness of
weak solutions by means of regularization combined with the Faedo-Galerkin
approach. Next we discuss the continuity of the solution with respect to
Brinkman's and Forchheimer's coefficients. Finally, we show that the weak
solution of the corresponding stationary problem is stable
Sun's retrograde motion and violation of even-odd cycle rule in sunspot activity
The sum of sunspots number over an odd numbered 11 yr sunspot cycle exceeds
that of its preceding even numbered cycle, and it is well known as Gnevyshev
and Ohl rule (or G--O rule) after the names of the authors who discovered it in
1948. The G--O rule can be used to predict the sum of sunspot numbers of a
forthcoming odd cycle from that of its preceding even cycle. But this is not
always possible because occasionally the G--O rule is violated. So far no
plausible reason is known either for the G--O rule or the violation of this
rule. Here we showed the epochs of the violation of the G--O rule are close to
the epochs of the Sun's retrograde orbital motion about the centre of mass of
the solar system (i.e., the epochs at which the orbital angular momentum of the
Sun is weakly negative). Using this result easy to predict the epochs of
violation of the G--O rule well in advance. We also showed that the solar
equatorial rotation rate determined from sunspot group data during the period
1879--2004 is correlated/anti-correlated to the Sun's orbital torque during
before/after 1945. We have found the existence of a statistically significant
17 yr periodicity in the solar equatorial rotation rate. The
implications of these findings for understanding the mechanism behind the solar
cycle and the solar-terrestrial relationship are discussed.Comment: 13 pages, 4 figures, accepted by MNRA
Lead Levels and Ischemic Heart Disease in a Prospective Study of Middle-Aged and Elderly Men: the VA Normative Aging Study
Background: Lead exposure has been associated with higher blood pressure, hypertension, electrocardiogram abnormalities, and increased mortality from circulatory causes.Objective We assessed the association between bone lead—a more accurate biomarker of chronic lead exposure than blood lead—and risk for future ischemic heart disease (IHD). Methods: In a prospective cohort study (VA Normative Aging Study), 837 men who underwent blood or bone lead measurements at baseline were followed-up for an ischemic heart disease event between 1 September 1991 and 31 December 2001. IHD was defined as either a diagnosis of myocardial infarction or angina pectoris that was confirmed by a cardiologist. Events of fatal myocardial infarction were assessed from death certificates. Results: An IHD event occurred in 83 cases (70 nonfatal and 13 fatal). The mean blood, tibia, and patella lead levels were higher in IHD cases than in noncases. In multivariate Cox-proportional hazards models, one standard deviation increase in blood lead level was associated with a 1.27 (95% confidence interval, 1.01–1.59) fold greater risk for ischemic heart disease. Similarly, a one standard deviation increase in patella and tibia lead levels was associated with greater risk for IHD (hazard ratio for patella lead = 1.29; 95% confidence interval, 1.02–1.62). Conclusions: Men with increased blood and bone lead levels were at increased risk for future IHD. Although the pathogenesis of IHD is multifactorial, lead exposure may be one of the risk factors
The Benefits and Harms of Transmitting Into Space
Deliberate and unintentional radio transmissions from Earth propagate into
space. These transmissions could be detected by extraterrestrial watchers over
interstellar distances. Here, we analyze the harms and benefits of deliberate
and unintentional transmissions relevant to Earth and humanity. Comparing the
magnitude of deliberate radio broadcasts intended for messaging to
extraterrestrial intelligence (METI) with the background radio spectrum of
Earth, we find that METI attempts to date have much lower detectability than
emissions from current radio communication technologies on Earth. METI
broadcasts are usually transient and several orders of magnitude less powerful
than other terrestrial sources such as astronomical and military radars, which
provide the strongest detectable signals. The benefits of radio communication
on Earth likely outweigh the potential harms of detection by extraterrestrial
watchers; however, the uncertainty regarding the outcome of contact with
extraterrestrial beings creates difficulty in assessing whether or not to
engage in long-term and large-scale METI.Comment: Published in Space Polic
Association between 24-Hour Urinary Cadmium and Pulmonary Function among Community-Exposed Men: The VA Normative Aging Study
Background: High levels of cadmium exposure are known to cause emphysema in occupationally exposed workers, but little has been reported to date on the association between chronic environmental cadmium exposure and pulmonary function. Objective: In this study we examined the association between pulmonary function and cadmium body burden in a subcohort of the Normative Aging Study, a community-based study of aging. Methods: We examined 96 men who had cadmium measured in single 24-hr urinary specimens collected in 1994–1995 and who had one to three tests of pulmonary function between 1994 and 2002 (a total of 222 observations). We used mixed-effect models to predict pulmonary function based on individual 24-hr urinary cadmium output, adjusted for age, height, time elapsed from the baseline, and smoking status. We assessed effect modification by smoking status. Results: Among all subjects, a single log-unit increase in baseline urinary cadmium was inversely associated with forced expiratory volume in 1 sec (FEV1) percent predicted [β = −7.56%; 95% confidence interval (CI) −13.59% to −1.53%]; forced vital capacity (FVC) percent predicted (β = −2.70%; 95% CI −7.39% to 1.99%), and FEV1/FVC ratio (β = −4.13%; 95% CI −7.61% to −0.66%). In models including an interaction between urinary cadmium and smoking status, there was a graded, statistically significant reduction in FEV1/FVC ratio across smoking status in association with urinary cadmium. Conclusions: This study suggests that chronic cadmium exposure is associated with reduced pulmonary function, and cigarette smoking modifies this association. These results should be interpreted with caution because the sample size is small, and further studies are needed to confirm our findings
Nematode-based indices in soil ecology: Application, utility, and future directions
14 Pág.The health and functioning of soil ecosystems are the foundation of sustainable food production and land management. Of key importance in achieving sustainability, is the frequent measurement of soil health, and indices based on the community structure of nematodes are amongst the most widely used toolsets by soil ecologists. Thirty years after the development of the Maturity Index, we aimed to evaluate the application, utility, and future directions of nematode-based indices (NBIs). This review focused on NBIs that are calculated using the coloniser-persister classification of nematodes. Data from 672 empirical studies in terrestrial environments revealed that the NBIs presented a dissimilar usage trend. The Channel Index and Metabolic Footprints showed the strongest increase in application rates over time, thus indicating a greater interest in studying decomposition pathways and ecosystem functioning, respectively. Furthermore, nematode-based indices were mostly applied in agricultural systems associated with herbaceous crops and in studies investigating, for example, soil nutrient enrichment following manure and/or inorganic fertilizer application. We further provide a framework for selecting a focus-orientated subset of NBIs for testing hypotheses based on the underlying ecological mechanisms. Also, we highlight important considerations, including the unexpected behaviour of some nematode taxa, in the interpretation of NBIs. The improvement of NBIs relies on advancing our understanding of the autecology of nematodes. Finally, we deliver insight into the further development of NBIs considering recent methodological advancements. We highlight that NBIs have been and might become increasingly important in providing valuable information on soil ecosystem health and functioning, especially considering the urgent need for more sustainable land use.The contribution of JHS was funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) — :— Project no. 420414676: “The self-regulatory potential of agro-ecosystems: Using
nematodes as indicators for legume disease suppressive soils”.Peer reviewe
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