7,628 research outputs found
A non-LTE spectral analysis of the 3He and 4He isotopes in the HgMn star kappa Cancri
We present a pilot study on non-local thermodynamic equilibrium (NLTE)
line-formation computations for the isotopes 3He and 4He in the
mercury-manganese star kappa Cancri. The impact of NLTE effects on the
determination of isotopic abundances and the vertical stratification of helium
in the atmosphere is investigated. Modern NLTE line-formation computations were
employed to analyse a high-resolution and high signal-to-noise ratio
ESO-VLT/UVES spectrum of kap Cnc. The atmospheric parameters were determined
from fitting the hydrogen Balmer lines and the spectral energy distribution.
Multiple HeI lines were investigated, including HeI 4921A and 6678A, which show
the widest isotopic splits. Half of the observed HeI lines in the spectrum of
kap Cnc show significant NLTE strengthening, the effects are strongest in the
red lines HeI 5875A and HeI 6678A. NLTE abundances from individual HeI lines
are up to a factor of about 3 lower than LTE values. Helium is found to be
stratified in the atmosphere of kap Cnc. While the LTE analysis indicates a
step-like profile of the helium abundance, a gradual decrease with height is
indicated by the NLTE analysis. A 3He/4He ratio of about 0.25-0.30 is found.
With the available data it cannot be decided whether the two isotopes follow
the same stratification profile, or not. This work implies that NLTE effects
may be ubiquitous in the atmospheres of HgMn stars and may have a significant
impact on abundance determinations and the interpretation of the vertical
abundance stratification of elements.Comment: 7 pages, 9 figure
La Influencia de los Principia de Newton en el pensamiento cientÃficomatemático de José Celestino Mutis, como base para el desarrollo de la Ciencia Nacional
En la historia de la ciencia es notable la influencia de los logros matemáticos de los
siglos XVII y XVIII. En particular, se destaca la obra Philosophiae Naturalis
Principia Mathematica de Newton, por lo que se presentará un análisis a la
traducción inédita realizada por José Celestino Mutis. Este último introdujo avances
cientÃficos en la América Colonial con su primera cátedra de matemáticas y asesoró
las reformas curriculares adelantadas por el Virrey Caballero y Góngora, Eloy
Valenzuela y el fiscal Moreno y Escandón. Con este trabajo también se pretende
mostrar la labor cientÃfica que desarrollaban algunos intelectuales criollos y su
relación con la ilustración europea. Con lo anterior se reforzará la idea de que el
desarrollo de la ciencia y las matemáticas en Colombia presupone un proceso
histórico, cuya base, sobre la cual se erige la naciente educación cientÃfica
neogranadina es bajo el aporte newtoniano
Legal Uncertainty and Land Disputes in the Peri-Urban Areas of Mozambique: Land Markets in Transition
The Government of Mozambique is considering legal changes in its land law and administration of state leasehold property-an enormous challenge given its past socialist history and the uncertainties created by its current transition to a private market economy. The present research sought to identify dispute causes and de facto processes of dispute resolution as one basis for gauging inadequacies in the current law and system of state land administration.Land Economics/Use,
Aquatic polymers can drive pathogen transmission in coastal ecosystems.
Gelatinous polymers including extracellular polymeric substances (EPSs) are fundamental to biophysical processes in aquatic habitats, including mediating aggregation processes and functioning as the matrix of biofilms. Yet insight into the impact of these sticky molecules on the environmental transmission of pathogens in the ocean is limited. We used the zoonotic parasite Toxoplasma gondii as a model to evaluate polymer-mediated mechanisms that promote transmission of terrestrially derived pathogens to marine fauna and humans. We show that transparent exopolymer particles, a particulate form of EPS, enhance T. gondii association with marine aggregates, material consumed by organisms otherwise unable to access micrometre-sized particles. Adhesion to EPS biofilms on macroalgae also captures T. gondii from the water, enabling uptake of pathogens by invertebrates that feed on kelp surfaces. We demonstrate the acquisition, concentration and retention of T. gondii by kelp-grazing snails, which can transmit T. gondii to threatened California sea otters. Results highlight novel mechanisms whereby aquatic polymers facilitate incorporation of pathogens into food webs via association with particle aggregates and biofilms. Identifying the critical role of invisible polymers in transmission of pathogens in the ocean represents a fundamental advance in understanding and mitigating the health impacts of coastal habitat pollution with contaminated runoff
Sex differences and correlates of poor glycaemic control in type 2 diabetes: a cross-sectional study in Brazil and Venezuela.
OBJECTIVE: Examine whether glycaemic control varies according to sex and whether the latter plays a role in modifying factors associated with inadequate glycaemic control in patients with type 2 diabetes (T2D) in Brazil and Venezuela. DESIGN, SETTING AND PARTICIPANTS: This was a cross-sectional, nationwide survey conducted in Brazil and Venezuela from February 2006 to June 2007 to obtain information about glycaemic control and its determinants in patients with diabetes mellitus attending outpatient clinics. MAIN OUTCOME MEASURES: Haemoglobin A1c (HbA1c) level was measured by liquid chromatography, and patients with HbA1c ≥7.0% (53 mmol/mol) were considered to have inadequate glycaemic control. The association of selected variables with glycaemic control was analysed by multivariate linear regression, using HbA1c as the dependent variable. RESULTS: A total of 9418 patients with T2D were enrolled in Brazil (n=5692) and in Venezuela (n=3726). They included 6214 (66%) women and 3204 (34%) men. On average, HbA1c levels in women were 0.13 (95% CI 0.03 to 0.24; p=0.015) higher than in men, after adjusting for age, marital status, education, race, country, body mass index, duration of disease, complications, type of healthcare, adherence to diet, adherence to treatment and previous measurement of HbA1c. Sex modified the effect of some factors associated with glycaemic control in patients with T2D in our study, but had no noteworthy effect in others. CONCLUSIONS: Women with T2D had worse glycaemic control than men. Possible causes for poorer glycaemic control in women compared with men include differences in glucose homeostasis, treatment response and psychological factors. In addition, sex modified factors associated with glycaemic control, suggesting the need to develop specific treatment guidelines for men and women
Kreativitas Masyarakat Kota Malang dalam Membentuk Identitas Kota
Identitas suatu kota tidak hanya dibentuk melalui warisan budaya atau peninggalan sejarah. Secara tidak langsung, perilaku masyarakat juga dapat mencerminkan identitas kota mereka, termasuk melihat hubungan masyarakat dengan lingkungan sekitarnya. Lingkungan yang kumuh memberikan image yang negatif bagi suatu kota. Kreativitas masyarakat kota Malang dalam memperbaiki pemukiman kumuh yang ada di kawasan sungai Brantas, ternyata memberikan dampak positif tidak hanya bagi masyarakatnya namun juga bagi kota tersebut. Oleh karena itu, penelitian ini dilakukan dengan tujuan untuk mengidentifikasi identitas kota Malang yang terbentuk melalui kreativitas masyarakatnya
The Influence of Neural Networks on Hydropower Plant Management in Agriculture: Addressing Challenges and Exploring Untapped Opportunities
Hydropower plants are crucial for stable renewable energy and serve as vital
water sources for sustainable agriculture. However, it is essential to assess
the current water management practices associated with hydropower plant
management software. A key concern is the potential conflict between
electricity generation and agricultural water needs. Prioritising water for
electricity generation can reduce irrigation availability in agriculture during
crucial periods like droughts, impacting crop yields and regional food
security. Coordination between electricity and agricultural water allocation is
necessary to ensure optimal and environmentally sound practices. Neural
networks have become valuable tools for hydropower plant management, but their
black-box nature raises concerns about transparency in decision making.
Additionally, current approaches often do not take advantage of their potential
to create a system that effectively balances water allocation.
This work is a call for attention and highlights the potential risks of
deploying neural network-based hydropower plant management software without
proper scrutiny and control. To address these concerns, we propose the adoption
of the Agriculture Conscious Hydropower Plant Management framework, aiming to
maximise electricity production while prioritising stable irrigation for
agriculture. We also advocate reevaluating government-imposed minimum water
guidelines for irrigation to ensure flexibility and effective water allocation.
Additionally, we suggest a set of regulatory measures to promote model
transparency and robustness, certifying software that makes conscious and
intelligent water allocation decisions, ultimately safeguarding agriculture
from undue strain during droughts
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