The influence of crop density on the remobilization of dry matter and nitrogen from vegetative plant parts to the developing grain, was investigated in the durum wheat (
Triticum durum Desf.) ...varieties Creso, Simeto and Svevo cultivated in the field at three seeding rates, 200, 250 and 400
seeds
m
−2. Variety
×
seeding rate interaction was unsignificant for all recorded characters. Grain yield declined in the order Svevo
>
Simeto
>
Creso. Yield differences mainly depended on the different number of kernels per unit land and, secondly, on mean kernel weight. Spike components differed among varieties: Svevo and Simeto showed more kernels per spikelet and Creso more spikelets per spike. Grain yield was highest with 400
seeds
m
−2 primarily due to the higher number of spikes per unit area, and secondly, to the higher mean kernel weight. Post-heading dry matter accumulation was highest in Svevo and lowest in Creso, but varieties showed a reverse order for dry matter remobilization and contribution of dry matter remobilization to grain yield. The increase of seeding rate increased both the post-heading dry matter accumulation and the dry matter remobilization from vegetative plant parts to grain. Nitrogen uptake of the whole crop and N content of grain was higher in Simeto and Svevo than in Creso. The N concentration of grain did not vary among varieties, but Svevo showed a markedly lower N concentration and N content of culms at maturity, which may be consequence of the high N remobilization efficiency performed by this variety. The N uptake by the crop was highest with 400
seeds
m
−2, but the N concentration of culms, leaves and even grain was slightly lower than with the lower seed rates. The post-heading N accumulation was by far higher in Simeto and Svevo than in Creso, whereas remobilization was highest in Svevo and lowest in Simeto. The percentage contribution of N remobilization to grain N was by far higher in Creso than in the other two varieties. Post-heading N accumulation and N remobilization were highest with the highest plant density, but the contribution of N remobilization to N grain content did not differ between seeding rates.
Insect societies require an effective communication system to coordinate members' activities. Although eusocial species primarily use chemical communication to convey information to conspecifics, ...there is increasing evidence suggesting that vibroacoustic communication plays a significant role in the behavioural contexts of colony life. In this study, we sought to determine whether stridulation can convey information in ant societies. We tested three main hypotheses using the Mediterranean ant Crematogaster scutellaris: (i) stridulation informs about the emitter'caste; (ii) workers can modulate stridulation based on specific needs, such as communicating the profitability of a food resource, or (iii) behavioural contexts. We recorded the stridulations of individuals from the three castes, restrained on a substrate, and the signals emitted by foragers workers feeding on honey drops of various sizes. Signals emitted by workers and sexuates were quantitatively and qualitatively distinct as was stridulation emitted by workers on different honey drops. Comparing across the experimental setups, we demonstrated that signals emitted in different contexts (restraining vs feeding) differed in emission patterns as well as certain parameters (dominant frequency, amplitude, duration of chirp). Our findings suggest that vibrational signaling represents a flexible communication channel paralleling the well-known chemical communication system.
One of the main tasks a freshly mated ant queen has to face is to find a safe and suitable nest site to start a new colony. Colony foundation by associated queens, also known as pleometrosis, has ...been described for several ant species and, under specific selective pressures, represents an alternative to independent colony foundation. Despite most newly mated queens of the common Mediterranean acrobat ant
Crematogaster scutellaris
generally adopting independent colony foundation inside tree trunks, both field and laboratory studies have demonstrated that the formation of pleometrotic groups may occur, particularly inside lignified aphid galls on poplar or oak trees. These associations typically end with the survival of only one queen after the foundation phase, and the benefits they may provide remain unclear. In this study, we investigated how queen density and different nest availability may promote the formation of pleometrotic associations in
C. scutellaris
. We found that occupied nests are not actively sought after by queens, as hypothesised in previous studies, but might be accepted when they are the only safe refugia available. Moreover, the tendency to form groups increases as queen density increases, and nest availability is a limiting factor. Finally, we found no evidence that the size of the queen affects whether to join an already occupied nest.
The Pixel Chamber project purpose is the production of the first solid state active target capable of performing continuous, high-resolution (O(μm)) 3D tracking. The aim is to create a bubble ...chamber-like high-granularity stack of hundreds of very thin monolithic active pixel sensors (MAPS) glued together. In this paper, the R&D to develop the first prototypes with ALPIDE sensors, designed for the ALICE experiment at the CERN LHC, will be presented. Tracking and vertexing algorithms were developed to reconstruct tracks and vertices inside Pixel Chamber. They were tested on Monte Carlo simulations which show that it is possible to obtain a high efficiency for the reconstruction of hadronic tracks, and for the primary and secondary vertices inside the detector. The tracking algorithm has been tested on test beam data to reconstruct long tracks produced in a single ALPIDE sensor parallel to a beam. Results show that it is possible to obtain very good performances in long track reconstruction on a single ALPIDE. Among the possible applications, Pixel Chamber used as an active target, has the potential to allow precision measurements of charm and beauty production. Even more interesting are possible medical and astrophysical applications. The usage of the Pixel Chamber as scatterer detector in Compton Cameras would reduce by orders of magnitude the numbers of gammas required for performing a precise source imaging, both for in vivo monitoring during hadron therapy and for astrophysics measurements.
The effects of intercropping on dry weight (DW) of herbage and nitrogen (N) nutrition of plants of two winter cereals, barley and wheat, and two legumes, white lupin and common vetch, were ...investigated, and above- and below-ground competition were separated in a fully factorial additive design. Intercropping increased DW compared with the sole species and the increase was higher for the cereals and lupin than for cereals and vetch intercropping systems. Above-ground competition for light reduced DW of cereals and lupin while it did not influence the DW of vetch. Processes involved in below-ground competition increased shoot growth of cereals and reduced shoot growth of legumes. N nutrition of cereals was enhanced by below-ground competition with legumes and N nutrition of vetch was enhanced by above-ground competition with cereals. Cereals had a higher competitive ability than legumes as a result of their below-ground competitive ability. The interaction between above- and below-competition is not predictable: negative, positive and no interaction (additivity) between different types of competition were found. In low-input intercropping systems, when a N-fixing species is present, the mixture of the roots of components is important for the utilization of the soil resources and, when a climbing species is also present, the mixture of shoots can result in an increased utilization of light.
We report on a precision measurement of low-mass muon pairs in 158 AGeV indium-indium collisions at the CERN SPS. A significant excess of pairs is observed above the yield expected from neutral meson ...decays. The unprecedented sample size of 360,000 dimuons and the good mass resolution of about 2% allow us to isolate the excess by subtraction of the decay sources. The shape of the resulting mass spectrum is consistent with a dominant contribution from pi+pi- -->rho -->mu+mu- annihilation. The associated space-time averaged spectral function shows a strong broadening, but essentially no shift in mass. This may rule out theoretical models linking hadron masses directly to the chiral condensate.
The Formica rufa group comprises several ant species which are collectively referred to as “red wood ants” (hereafter RWA). These species have key roles in forest ecosystems, where they are ...ecologically dominant and greatly influence the dynamics of the habitat they colonise. Various studies have shown how their trophic activity may affect other organisms, which include both other invertebrates and plants. We can therefore hypothesize that their presence could affect the taxonomic and functional composition of epiphytes, despite clear information on such an effect is lacking. This study aimed to fill this research gap by evaluating whether the presence of red wood ants could affect the structure and composition of lichen communities. We selected two sites on the Apennine Mountains in Italy, where the red wood ant F. paralugubris was introduced from the Alps more than 50 years ago. In each site, lichen assemblages on Abies alba trees located within the colonised areas were compared to those from nearby, non-occupied areas. The results allowed for the identification of significant effects of F. paralugubris on the structure of lichen communities. Although there was no detectable impact on lichen species richness, a significant difference in their community composition between colonised and control sites was detected. Furthermore, ant presence seemed to be associated with specific lichen functional traits such as asexual reproduction. We argue that RWA could affect the lichen community either directly, e.g., by actively dispersing the species capable of asexual reproduction through their movements on trees (ant-mediated dispersion), or indirectly through herbivore exclusion. Finally, we also observed differences in β-diversity among the colonised and non-colonised sites.
During the second half of the XIX century, several species of red wood ants (
Formica rufa
group) were used as biological control agents and introduced to the Italian Apennine mountains where they ...were formerly absent. Among these,
Formica lugubris
was the most widely introduced alien species. In 1996, however, a taxonomic revision defined two sibling species,
F. lugubris
and
F. paralugubris
, each with distinct ecological and behavioural characteristics that differently affect their spatial distribution. The first one can be both monodomous and polydomous with a low number of interlinked nests, and it is obliged to mate by nuptial flight. Conversely,
F. paralugubris
is usually unicolonial, with a considerable portion of intranest mates. Discrimination between the two species using morphological characters is possible but requires considerable taxonomic expertise. Restriction analysis, whereby presence/absence of a BamHI site in the mitochondrial DNA COI gene results in different restriction profiles, provides an alternative efficient method to unambiguously distinguish
F. lugubris
from
F. paralugubris
. We applied this method to identify ant species introduced to several locations in the Campigna Forest of the Foreste Casentinesi, Monte Falterona and Campigna National Park, one of the Italian locations mostly affected by alien ant introductions. This area has considerable ecological relevance. Given the potential impact of ants on native arthropod communities, it is of the most importance to identify which species has been introduced. Contrary to previous assumptions, results of our analysis clearly show that only
F. paralugubris
is present in the National park.
NA60 results on thermal dimuons Arnaldi, R.; Banicz, K.; Borer, K. ...
European physical journal. C, Particles and fields (Print),
06/2009, Letnik:
61, Številka:
4
Journal Article, Conference Proceeding
Recenzirano
Odprti dostop
The NA60 experiment at the CERN SPS has measured muon pairs with unprecedented precision in 158
A
GeV In–In collisions. A strong excess of pairs above the known sources is observed in the whole ...mass region 0.2<
M
<2.6 GeV. The mass spectrum for
M
<1 GeV is consistent with a dominant contribution from
π
+
π
−
→
ρ
→
μ
+
μ
−
annihilation. The associated
ρ
spectral function shows a strong broadening, but essentially no shift in mass. For
M
>1 GeV, the excess is found to be prompt, not due to enhanced charm production, with pronounced differences to Drell–Yan pairs. The slope parameter
T
eff
associated with the transverse momentum spectra rises with mass up to the
ρ
, followed by a sudden decline above. The rise for
M
<1 GeV is consistent with radial flow of a hadronic emission source. The seeming absence of significant flow for
M
>1 GeV and its relation to parton–hadron duality is discussed in detail, suggesting a dominantly partonic emission source in this region. A comparison of the data to the present status of theoretical modeling is also contained. The accumulated empirical evidence, including also a Planck-like shape of the mass spectra at low
p
T
and the lack of polarization, is consistent with a global interpretation of the excess dimuons as thermal radiation. We conclude with first results on
ω
in-medium effects.
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