Leaf-cutting ants are the most important pests in several cropping systems in the Neotropics. Granulated baits containing active ingredients, considered hazardous by the Stockholm Convention, are the ...usual method to control these ants. Isocycloseram is a new insecticide molecule with high safety margin for mammals, but without registration for the ants in general. Thus, this study investigated the effectiveness of granulated baits with isocycloseram in leaf-cutting ants control under laboratory and field conditions. Initially, the mortality of Atta sexdens workers, fed with dehydrated citrus pulp paste containing different concentrations of isocycloseram was evaluated in the laboratory for 21 days, for toxicological classification. Subsequently, the loading, devolution, and incorporation of baits with different concentrations of isocycloseram and the mortality of A. sexdens colonies were evaluated in the laboratory. After that, the percentages of loading and devolution of baits, foraging activity, and colony mortality treated with 0.05, 0.1, 0.2, and 0.3% of isocycloseram were evaluated for the species A. sexdens, A. laevigata, and Acromyrmex lundii in field conditions. All concentrations of isocycloseram killed more than 15% of ants in 24 h and more than 90% in 21 days in the laboratory, being classified as a fast-acting and highly effective active ingredient. Baits with 0.001 to 0.03% of isocycloseram were highly loaded and exhibited low rate of devolution. The mortality of A. sexdens colony was higher at concentrations between 0.075 and 0.3%, in the laboratory. Baits containing isocycloseram at concentrations of 0.2 and 0.3% were highly loaded, presented low devolution rates, and were highly efficient in controlling A. sexdens, A. laevigata, and A. lundii in the field, at dosages of 6, 10, and 12 g/m² of nest. This is the first report of the use of isocycloseram against leaf-cutting ants, contributing to the development of efficient and toxicologically safer ant baits.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
In this paper, we study the tidal stripping process for satellite galaxies orbiting around a massive host galaxy, and focus on its dependence on the morphology of both satellite and host galaxy. For ...this purpose, we use three different morphologies for the satellites: pure disc, pure bulge and a mixture bulge+disc. Two morphologies are used for the host galaxies: bulge+disc and pure bulge. We find that while the spheroidal stellar component experiences a constant power law like mass removal, the disc is exposed to an exponential mass-loss when the tidal radius of the satellite is of the same order of the disc scalelength. This dramatic mass-loss is able to completely remove the stellar component on time-scale of 100 Myr. As a consequence two satellites with the same stellar and dark matter masses, on the same orbit could either retain considerable fraction of their stellar mass after 10 Gyr or being completely destroyed, depending on their initial stellar morphology. We find that there are two characteristic time-scales describing the beginning and the end of the disc removal, whose values are related to the size of the disc. This result can be easily incorporated in semi-analytical models. We also find that the host morphology and the orbital parameters also have an effect on determining the mass removal, but they are of secondary importance with respect to satellite morphology. We conclude that satellite morphology has a very strong effect on the efficiency of stellar stripping and should be taken into account in modelling galaxy formation and evolution.
ABSTRACT Recently it has been shown that a large fraction of the dwarf satellite galaxies orbiting the Andromeda galaxy are surprisingly aligned in a thin, extended, and kinematically coherent planar ...structure. The presence of such a structure seems to challenge the current Cold Dark Matter paradigm of structure formation, which predicts a more uniform distribution of satellites around central objects. We show that it is possible to obtain a thin, extended, rotating plane of satellites resembling the one in Andromeda in cosmological collisionless simulations based on the Cold Dark Matter model. Our new high-resolution simulations show a correlation between the formation time of the dark matter halo and the thickness of the plane of satellites. Our simulations have a high incidence of satellite planes as thin, extended, and as rich as the one in Andromeda and with a very coherent kinematic structure when we select high concentration/early forming halos. By tracking the formation of the satellites in the plane we show that they have mainly been accreted onto the main object along thin dark matter filaments at high redshift. Our results show that the presence of a thin, extended, rotating plane of satellites is not a challenge for the Cold Dark Matter paradigm, but actually supports one of the predictions of this paradigm related to the presence of filaments of dark matter around galaxies at high redshift.
NIHAO VI. The hidden discs of simulated galaxies Obreja, Aura; Stinson, Gregory S; Dutton, Aaron A ...
Monthly notices of the Royal Astronomical Society,
06/2016, Letnik:
459, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Detailed studies of galaxy formation require clear definitions of the structural components of galaxies. Precisely defined components also enable better comparisons between observations and ...simulations. We use a subsample of 18 cosmological zoom-in simulations from the Numerical Investigation of a Hundred Astrophysical Objects (NIHAO) project to derive a robust method for defining stellar kinematic discs in galaxies. Our method uses Gaussian Mixture Models in a 3D space of dynamical variables. The NIHAO galaxies have the right stellar mass for their halo mass, and their angular momenta and Sérsic indices match observations. While the photometric disc-to-total ratios are close to 1 for all the simulated galaxies, the kinematic ratios are around ∼0.5. Thus, exponential structure does not imply a cold kinematic disc. Above M
* ∼ 109.5 M⊙, the decomposition leads to thin discs and spheroids that have clearly different properties, in terms of angular momentum, rotational support, ellipticity, Fe/H and O/Fe. At M
* ≲ 109.5 M⊙, the decomposition selects discs and spheroids with less distinct properties. At these low masses, both the discs and spheroids have exponential profiles with high minor-to-major axes ratios, i.e. thickened discs.
The nature of dark matter is still unknown and one of the most fundamental scientific mysteries. Although successfully describing large scales, the standard cold dark matter model (CDM) exhibits ...possible shortcomings on galactic and sub-galactic scales. It is exactly at these highly non-linear scales where strong astrophysical constraints can be set on the nature of the dark matter particle. While observations of the Lyman- alpha forest probe the matter power spectrum in the mildly non-linear regime, satellite galaxies of the Milky Way provide an excellent laboratory as a test of the underlying cosmology on much smaller scales. Here we present results from a set of high resolution simulations of a Milky Way sized dark matter halo in eight distinct cosmologies: CDM, warm dark matter (WDM) with a particle mass of 2 keV and six different cold plus warm dark matter (C+WDM) models, varying the fraction, f sub(wdm) and the mass, m sub(wdm), of the warm component. We used three different observational tests based on Milky Way satellite observations: the total satellite abundance, their radial distribution and their mass profile. We show that the requirement of simultaneously satisfying all three constraints sets very strong limits on the nature of dark matter. This shows the power of a multi-dimensional small scale approach in ruling out models which would be still allowed by large scale observations.
Duodenal-jejunal bypass liner (DJBL) is an endoscopic device that may mimic small bowel mechanisms of Roux-en-Y gastric bypass (RYGB). Previous studies have demonstrated the efficacy of DJBL at ...inducing weight loss. We assessed the effect of DJBL on glycemic control in patients with type 2 diabetes (T2D) with obesity.
Data sources included MEDLINE, EMBASE, and Web of Science through 1 July 2017. Included were published studies that assessed DJBL outcomes in obese T2D patients.
Primary outcomes were change in HbA
and HOMA of insulin resistance (HOMA-IR). Secondary outcomes were change in weight and gut hormones glucose-dependent insulinotropic peptide (GIP), glucagon-like peptide 1 (GLP-1), peptide YY (PYY), and ghrelin. Seventeen studies were included. At explant, HbA
decreased by 1.3% 95% CI 1.0, 1.6 and HOMA-IR decreased by 4.6 2.9, 6.3. Compared with control subjects, DJBL subjects had greater HbA
reduction by 0.9% 0.5, 1.3. Six months after explant, HbA
remained lower than baseline by 0.9% 0.6, 1.2. At explant, patients lost 11.3 kg 10.3, 12.2, corresponding to a BMI reduction of 4.1 kg/m
3.4, 4.9, total weight loss of 18.9% 7.2, 30.6, and excess weight loss of 36.9% 29.2, 44.6. The amount of weight loss remained significant at 1 year postexplantation. After DJBL, GIP decreased, whereas GLP-1, PYY, and ghrelin increased.
DJBL improves glycemic control and insulin resistance in T2D patients with obesity. DJBL also appears to induce significant weight loss in this population. Additionally, changes in gut hormones suggest mechanisms similar to RYGB. Study limitations included heterogeneity among studies.
ABSTRACT
We introduce algorithms for black hole physics, i.e. black hole formation, accretion, and feedback, into the Numerical Investigation of a Hundred Astrophysical Objects (NIHAO) project of ...galaxy simulations. This enables us to study high mass, elliptical galaxies, where feedback from the central black hole is generally thought to have a significant effect on their evolution. We furthermore extend the NIHAO suite by 45 simulations that encompass z = 0 halo masses from 1 × 1012 to $4 \times 10^{13}\, \mathrm{M}_{\odot }$, and resimulate five galaxies from the original NIHAO sample with black hole physics, which have z = 0 halo masses from 8 × 1011 to $3 \times 10^{12}\, \mathrm{M}_{\odot }$. Now NIHAO contains 144 different galaxies and thus has the largest sample of zoom-in simulations of galaxies, spanning z = 0 halo masses from 9 × 108 to $4 \times 10^{13}\, \mathrm{M}_{\odot }$. In this paper we focus on testing the algorithms and calibrating their free parameters against the stellar mass versus halo mass relation and the black hole mass versus stellar mass relation. We also investigate the scatter of these relations, which we find is a decreasing function with time and thus in agreement with observations. For our fiducial choice of parameters we successfully quench star formation in objects above a z = 0 halo mass of $10^{12}\, \mathrm{M}_{\odot }$, thus transforming them into red and dead galaxies.
Deoxy sugars represent an important class of carbohydrates, present in a large number of biomolecules involved in multiple biological processes. In various antibiotics, antimicrobials, and ...therapeutic agents the presence of deoxygenated units has been recognized as responsible for biological roles, such as adhesion or great affinity to receptors, or improved efficacy. The characterization of glycosidases and glycosyltranferases requires substrates, inhibitors and analogous compounds. Deoxygenated sugars are useful for carrying out specific studies for these enzymes. Deoxy sugars, analogs of natural substrates, may behave as substrates or inhibitors, or may not interact with the enzyme. They are also important for glycodiversification studies of bioactive natural products and glycobiological processes, which could contribute to discovering new therapeutic agents with greater efficacy by modification or replacement of sugar units. Deoxygenation of carbohydrates is, thus, of great interest and numerous efforts have been dedicated to the development of methods for the reduction of sugar hydroxyl groups. Given that carbohydrates are the most important renewable chemicals and are more oxidized than fossil raw materials, it is also important to have methods to selectively remove oxygen from certain atoms of these renewable raw materials. The different methods for removal of OH groups of carbohydrates and representative or recent applications of them are presented in this chapter. Glycosidic bonds in general, and 2-deoxy glycosidic linkages, are included. It is not the scope of this survey to cover all reports for each specific technique.
The methods for the synthesis of deoxy sugars, involving deoxygenation and glycosidation, give access to useful molecules for multiple purposes.
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