1,689 research outputs found
Evaluation of Soil Test Phosphorus Extractants in Idaho Soils
Soil P testing is critical to ensure the accuracy of fertilizer recommendations and to optimize crop yield while minimizing negative environmental consequences. Olsen-P is the most commonly used soil P test for alkaline calcareous soils found in Idaho and the western United States. The Bray- 1 test is commonly used in the Pacific Northwest on neutral to acidic soils but underestimates P in alkaline calcareous soils. Mehlich-3 has been evaluated throughout various regions in the United States. Few data evaluating Mehlich-3 exist for soils in the western United States. Additionally, the comparatively newly developed HaneyâHaneyâHossnerâArnold (H3A) test, a component of the soil health tool, has not been widely evaluated on alkaline calcareous soils. Soil samples from the 0- to 30-cm depth were collected from agricultural fields throughout Idaho and analyzed with Bray-1, H3A, Mehlich-3, and Olsen-P extractants. The results indicate that Olsen-P was correlated with Mehlich-3, whereas Bray-1 and H3A were not correlated with Olsen-P. Both Bray-1 and H3A resulted in lower values of extractable P than the Olsen-P test, whereas Mehlich-3 resulted in greater values. A threshold point in CaCO3 (i.e., inorganic C) of 6.7 and 5.1 mg kg-1 for the Bray-1 and H3A was obtained, respectively, which indicated that inorganic C concentrations at or above these levels resulted in a reduction in extractable soil P. Thus Mehlich-3 could be evaluated for use in alkaline calcareous soils, whereas Bray-1 and H3A have notable issues that would limit their applicability
Gaps and Runs in Nest Cavity Occupancy: Cavity âDestroyersâ and âCleanersâ Affect Reuse by Secondary Cavity Nesting Vertebrates
Many animals require tree cavities for breeding and these sites may be reused by a diversity of secondary cavity nesters over a timespan of decades. It is unknown whether the reuse of holes changes their desirability as nest sites. We hypothesized that some species, âcavity destroyers,â degrade the quality of holes by filling them with coarse nest material or waste whereas excavating species, âcavity cleaners,â might prolong the use of a hole by removing debris or enlarging the hole. Using data gathered during 22 years from a field study in central British Colombia, we analyzed long-term patterns of cavity occupancy in relation to their sequential use by bird and mammal species, grouped by traits. Patterns of cavity occupancy were variable with 49% of 875 large-sized holes (excavated by northern flickers Colaptes auratus and pileated woodpeckers Dryocopus pileatus) and 19% of 652 smaller-sized holes incorporating runs of sequential use that lasted to 18 years. About 11% of large and 25% of small cavities also had gaps of 3â13 years between occupancies. Mammals, raptors and European starlings, consistent with the hypothesis, were cavity destroyers, occupying cavities as terminal users and before gaps more often than expected by chance. The pattern of occupancy by northern flickers was random in relation to gaps or prior use by other species. Although flickers did not target old holes to clean, neither did they avoid them. Small cavities that were renovated by flickers into larger cavities were reused at twice the rate after renovation. Runs of cavity occupancy that involved only cavity-destroying species were shorter than runs that involved periodic use by flickers, suggesting the woodpecker, through its cleaning and renovation, prolonged the use of such holes. Our study contributes insights on additional ecological factors, namely previous users, that can influence the use and availability of cavities over time.Fil: Wiebe, Karen L.. University of Saskatchewan; CanadĂĄFil: Cockle, Kristina Louise. University of British Columbia; CanadĂĄ. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - Nordeste. Instituto de BiologĂa Subtropical. Instituto de BiologĂa Subtropical - Nodo Puerto IguazĂș | Universidad Nacional de Misiones. Instituto de BiologĂa Subtropical. Instituto de BiologĂa Subtropical - Nodo Puerto IguazĂș; ArgentinaFil: Trzcinski, M. Kurtis. University of British Columbia; CanadĂĄFil: Edworthy, Amanda B.. University of British Columbia; CanadĂĄFil: Martin, Kathy. University of British Columbia; Canad
Fetal origins of malarial disease: cord blood cytokines as risk markers for pediatric severe malarial anemia.
BACKGROUND: Severe malarial anemia (SMA) remains a major cause of pediatric illness and mortality in Sub-Saharan Africa. Here we test the hypothesis that prenatal exposures, reflected by soluble inflammatory mediators in cord blood, can condition an individual's susceptibility to SMA. METHODS: In a Tanzanian birth cohort (n = 743), we measured cord blood concentrations of tumor necrosis factor (TNF), TNF receptors I and II (TNF-RI and TNF-RII), interleukin (IL)-1ÎČ, IL-4, IL-5, IL-6, IL-10, and interferon gamma (IFN-Îł). After adjusting for conventional covariates, we calculated the hazard ratios (HR) for time to first SMA event with log(e) cytokine concentrations dichotomized at the median, by quartile, and per standard deviation (SD) increase. RESULTS: Low levels of TNF, TNF-RI, IL-1ÎČ, and IL-5 and high levels of TNF-RII were associated statistically significantly and respectively with approximately 3-fold, 2-fold, 8-fold, 4-fold, and 3-fold increased risks of SMA (Hb < 50 g/L). TNF, TNF-RI, and IL-1ÎČ concentrations were inversely and log-linearly associated with SMA risk; the HR (95% confidence interval [CI]) per 1-SD increase were respectively 0.81 (.65, 1.02), 0.76 (.62, .92), and 0.50 (.40, .62). CONCLUSIONS: These data suggest that proinflammatory cytokine levels at birth are inversely associated with SMA risk and support the hypothesis that pediatric malarial disease has fetal origins
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Accelerated Oxygen Atom Transfer and CâH Bond Oxygenation by Remote Redox Changes in Fe_3Mn-Iodosobenzene Adducts
We report the synthesis, characterization, and reactivity of [Lfe_3(PhPz)_3OMn(^sPhIO)][OTf]_x (3: x=2; 4: x=3), where 4 is one of very few examples of iodosobenzeneâmetal adducts characterized by X-ray crystallography. Access to these rare heterometallic clusters enabled differentiation of the metal centers involved in oxygen atom transfer (Mn) or redox modulation (Fe). Specifically, ^(57)Fe Mössbauer and X-ray absorption spectroscopy provided unique insights into how changes in oxidation state (Fe^(III)_2Fe^(II)Mn^(II) vs. Fe^(III)_3Mn^(II)) influence oxygen atom transfer in tetranuclear Fe_3Mn clusters. In particular, a one-electron redox change at a distal metal site leads to a change in oxygen atom transfer reactivity by ca. two orders of magnitude
The Velocity Function of Galaxies
We present a galaxy circular velocity function, Psi(log v), derived from
existing luminosity functions and luminosity-velocity relations. Such a
velocity function is desirable for several reasons. First, it enables an
objective comparison of luminosity functions obtained in different bands and
for different galaxy morphologies, with a statistical correction for dust
extinction. In addition, the velocity function simplifies comparison of
observations with predictions from high-resolution cosmological N-body
simulations.
We derive velocity functions from five different data sets and find rough
agreement among them, but about a factor of 2 variation in amplitude. These
velocity functions are then compared with N-body simulations of a LCDM model
(corrected for baryonic infall) in order to demonstrate both the utility and
current limitations of this approach. The number density of dark matter halos
and the slope of the velocity function near v_*, the circular velocity
corresponding to an ~L_* spiral galaxy, are found to be comparable to that of
observed galaxies. The primary sources of uncertainty in construction of
Psi(log v) from observations and N-body simulations are discussed and
explanations are suggected to account for these discrepancies.Comment: Latex. 28 pages, 4 figures. Accepted by Ap
Natural stimulus responsive scaffolds/cells for bone tissue engineering : influence of lysozyme upon scaffold degradation and osteogenic differentiation of cultured marrow stromal cells induced by CaP coatings
This work proposes the use of nonporous, smart, and stimulus responsive chitosan-based scaffolds for bone
tissue engineering applications. The overall vision is to use biodegradable scaffolds based on chitosan and starch
that present properties that will be regulated by bone regeneration, with the capability of gradual in situ pore
formation. Biomimetic calcium phosphate (CaP) coatings were used as a strategy to incorporate lysozyme at the
surface of chitosan-based materials with the main objective of controlling and tailoring their degradation profile
as a function of immersion time. To confirm the concept, degradation tests with a lysozyme concentration similar
to that incorporated into CaP chitosan-based scaffolds were used to study the degradation of the scaffolds and
the formation of pores as a function of immersion time. Degradation studies with lysozyme (1.5 g=L) showed the
formation of pores, indicating an increase of porosity (*5â55% up to 21 days) resulting in porous threedimensional
structures with interconnected pores. Additional studies investigated the influence of a CaP
biomimetic coating on osteogenic differentiation of rat marrow stromal cells (MSCs) and showed enhanced
differentiation of rat MSCs seeded on the CaP-coated chitosan-based scaffolds with lysozyme incorporated.
At all culture times, CaP-coated chitosan-based scaffolds with incorporated lysozyme demonstrated greater
osteogenic differentiation of MSCs, bone matrix production, and mineralization as demonstrated by calcium
deposition measurements, compared with controls (uncoated scaffolds). The ability of these CaP-coated
chitosan-based scaffolds with incorporated lysozyme to create an interconnected pore network in situ coupled
with the demonstrated positive effect of these scaffolds upon osteogenic differentiation of MSCs and mineralized
matrix production illustrates the strong potential of these scaffolds for application in bone tissue engineering
strategies.The authors would like to acknowledge Dr. Serena Danti. This work was supported by the European NoE EX-PERTISSUES (NMP3-CT-2004-500283), the European STREP HIPPOCRATES (NMP3-CT-2003-505758), and the Portuguese Foundation for Science and Technology (FCT) through POCTI and/or FEDER programs. This work was also supported by a grant from the National Institutes of Health (NIH; R01 DE15164) (A. G. M.) and a Bioengineering Research Partnership with the Baylor College of Medicine through the National Institute of Biomedical Imaging and Bioengineering (NIH Grant 5 R01 EB005173-02). F. K. K. is supported by a training fellowship from the Keck Center Nanobiology Training Program of the Gulf Coast Consortia (NIH Grant 5 T90 DK070121-03)
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