This Letter reports a technique for the imaging of acoustic nonlinearity. By contrasting the energy of the diffuse field produced through the focusing of an ultrasonic array by delayed parallel ...element transmission with that produced by postprocessing of sequential transmission data, acoustic nonlinearity local to the focal point is measured. Spatially isolated wave distortion is inferred without requiring interrogation of the wave at the inspection point, thereby allowing nonlinear imaging through depth.
The Evolution of Cooperation Sachs, Joel L.; Mueller, Ulrich G.; Wilcox, Thomas P. ...
The Quarterly Review of Biology,
06/2004, Letnik:
79, Številka:
2
Book Review, Journal Article
Recenzirano
Darwin recognized that natural selection could not favor a trait in one species solely for the benefit of another species. The modern, selfish‐gene view of the world suggests that cooperation between ...individuals, whether of the same species or different species, should be especially vulnerable to the evolution of noncooperators. Yet, cooperation is prevalent in nature both within and between species. What special circumstances or mechanisms thus favor cooperation? Currently, evolutionary biology offers a set of disparate explanations, and a general framework for this breadth of models has not emerged. Here, we offer a tripartite structure that links previously disconnected views of cooperation. We distinguish three general models by which cooperation can evolve and be maintained: (i)directed reciprocation—cooperation with individuals who give in return; (ii)shared genes—cooperation with relatives (e.g., kin selection); and (iii)byproduct benefits—cooperation as an incidental consequence of selfish action. Each general model is further subdivided. Several renowned examples of cooperation that have lacked explanation until recently—plant‐rhizobium symbioses and bacteria‐squid light organs—fit squarely within this framework. Natural systems of cooperation often involve more than one model, and a fruitful direction for future research is to understand how these models interact to maintain cooperation in the long term.
Ecological and hydrological processes can interact strongly in landscapes, yet these processes are often studied separately. One particularly important interaction between these processes in patchy ...semiarid lands is how vegetation patches serve to obstruct runoff and then how this retained water increases patch growth that, in turn, provides feedbacks to the system. Such ecohydrological interactions have been mostly demonstrated for semiarid landscapes with distinctly banded vegetation patterns. In this paper, we use data from our studies and from the literature to evaluate how strongly four ecohydrological interactions apply across other patchy semiarid vegetations, and how these interactions are affected by disturbances. We specifically address four questions concerning ecohydrological interactions: (1) if vegetation patches obstruct runoff flows during rainfall events, how much more soil water is stored in these patches compared to open interpatch areas; (2) if inputs of water are higher in patches, how much stronger is the pulse of plant growth compared to interpatches; (3) if more soil water in patches promotes greater biological activity by organisms such as earthworms that create macropores, how much does this improve soil infiltrability; and (4) if vegetation patches are damaged on a hillslope, how much does this increase runoff and erosion and decrease biomass production? We used the trigger-transfer-reserve-pulse framework developed for Australian semiarid woodlands to put these four questions into a landscape context. For a variety of patchy semiarid vegetation types in Australia, Europe, and North America, we found that patches significantly stored more soil water, produced more growth and had better infiltrability than interpatches, and that runoff and erosion can markedly increase on disturbed hillslopes. However, these differences varied greatly and appeared to depend on factors such as the intensity and amount of input events (rainstorms) and type of topography, soils, and vegetation. Experimental and modeling studies are needed to better quantify how these factors specifically affect ecohydrological interactions. Our current findings do support the conclusion that vegetation patches and runoff-erosion processes do strongly interact in many semiarid landscapes across the globe, not just banded landscapes.
Ultrasonic nondestructive evaluation is used for detection, characterization, and sizing of defects. The accurate sizing of defects that are of similar or less size than the ultrasonic wavelength is ...of particular importance in assessing structural integrity. In this paper, we demonstrate how measurement of the scattering coefficient matrix of a cracklike defect can be used to obtain its size, shape, and orientation. The scattering coefficient matrix describes the far field amplitude of scattered signals from a scatterer as a function of incident and scattering angles. A finite element (FE) modeling procedure is described that predicts the scattering coefficient matrix of various cracklike defects. Experimental results are presented using a commercial 64-element, 5 MHz array on 2 aluminum test samples that contain several machined slots and through thickness circular holes. To minimize the interference from the reflections of neighboring defects, a subarray approach is used to focus ultrasound on each target defect in turn and extract its scattering coefficient matrices. A circular hole and a fine slot can be clearly distinguished by their different scattering coefficient matrices over a specific range of incident angles and scattering angles. The orientation angles of slots directly below the array are deduced from the measured scattering coefficient matrix to an accuracy of a few degrees, and their lengths are determined with an error of 10%.
Increases in the abundance or density of woody plants in historically semiarid and arid grassland ecosystems have important ecological, hydrological, and socioeconomic implications. Using a ...simplified water-balance model, we propose a framework for conceptualizing how woody plant encroachment is likely to affect components of the water cycle within these ecosystems. We focus in particular on streamflow and the partitioning of evapotranspiration into evaporation and transpiration. On the basis of this framework, we suggest that streamflow and evaporation processes are affected by woody plant encroachment in different ways, depending on the degree and seasonality of aridity and the availability of subsurface water. Differences in landscape physiography, climate, and runoff mechanisms mediate the influence of woody plants on hydrological processes. Streamflow is expected to decline as a result of woody plant encroachment in landscapes dominated by subsurface flow regimes. Similarly, encroachment of woody plants can be expected to produce an increase in the fractional contribution of bare soil evaporation to evapotranspiration in semiarid ecosystems, whereas such shifts may be small or negligible in both subhumid and arid ecosystems. This framework for considering the effects of woody plant encroachment highlights important ecological and hydrological interactions that serve as a basis for predicting other ecological aspects of vegetation change-such as potential changes in carbon cycling within an ecosystem. In locations where woody plant encroachment results in increased plant transpiration and concurrently the availability of soil water is reduced, increased accumulation of carbon in soils emerges as one prediction. Thus, explicitly considering the ecohydrological linkages associated with vegetation change provides needed information on the consequences of woody plant encroachment on water yield, carbon cycling, and other processes.
This article reports a technique for near-surface ultrasonic array imaging. Information equivalent to an undelayed full matrix of inter-element responses is produced through cross-correlation of a ...later time diffuse full matrix. This reconstructed full matrix lacks the nonlinear effects of early time saturation present in a directly acquired response. Consequently the near-surface material information usually obscured by this effect is retrieved. Furthermore it is shown that a hybrid full matrix formed through a temporally weighted sum of coherent and reconstructed matrices allows for effective near-surface and bulk material imaging from a single direct-contact experimental realisation.
Phylogenetic relationships among the species of true frogs (
Rana) from North, South, and Central America were investigated based on the sequences of approximately 2
kb from the mitochondrial genome, ...sampled from most of the described species, as well as eight undescribed species. This analysis, combined with previous studies of the phylogeny of New World
Rana, served as the basis for a revised classification of the group. The American species of
Rana are not monophyletic; the western North American
Amerana is more closely related to the
R. temporaria group of Eurasia (together, these frogs form the group
Laurasiarana). The remaining species from the Americas form the monophyletic group
Novirana, which includes:
R. sylvatica;
Aquarana (the
R. catesbeiana group);
Ranula (the
R. palmipes group, including the mostly upland
Levirana species and the mostly lowland
Lithobates species);
Torrentirana (the
R. tarahumarae group, or
Zweifelia, plus
R. sierramadrensis),
Stertirana (the
R. montezumae group, or
Lacusirana, plus
R. pipiens),
Nenirana (the
R. areolata group), and
Scurrilirana (most of the southern and tropical leopard frogs). The mitochondrial sequences supported many of the previous hypotheses of relationships of New World
Rana, although there were some differences involving the placement of the species
R. pipiens,
R. sierramadrensis, and
R. sylvatica. Parametric bootstrap analyses indicated significant support for the relationships inferred from the mtDNA sequences, and rejected the previous hypotheses of relationships for these three species.
The CAnadian REgistry for Pulmonary Fibrosis (CARE-PF) is a multi-center, prospective registry designed to study the natural history of fibrotic interstitial lung disease (ILD) in adults. The aim of ...this cross-sectional sub-study was to describe the baseline characteristics, risk factors, and comorbidities of patients enrolled in CARE-PF to date.
Patients completed study questionnaires and clinical measurements at enrollment and each follow-up visit. Environmental exposures were assessed by patient self-report and comorbidities by the Charlson Comorbidity Index (CCI). Baseline characteristics, exposures, and comorbidities were described for the overall study population and for incident cases, and were compared across ILD subtypes.
The full cohort included 1285 patients with ILD (961 incident cases (74.8%)). Diagnoses included connective tissue disease-associated ILD (33.3%), idiopathic pulmonary fibrosis (IPF) (24.7%), unclassifiable ILD (22.3%), chronic hypersensitivity pneumonitis (HP) (7.5%), sarcoidosis (3.2%), non-IPF idiopathic interstitial pneumonias (3.0%, including idiopathic nonspecific interstitial pneumonia (NSIP) in 0.9%), and other ILDs (6.0%). Patient-reported exposures were most frequent amongst chronic HP, but common across all ILD subtypes. The CCI was ≤2 in 81% of patients, with a narrow distribution and range of values.
CTD-ILD, IPF, and unclassifiable ILD made up 80% of ILD diagnoses at ILD referral centers in Canada, while idiopathic NSIP was rare when adhering to recommended diagnostic criteria. CCI had a very narrow distribution across our cohort suggesting it may be a poor discriminator in assessing the impact of comorbidities on patients with ILD.
Globally, native semiarid grasslands and savannas have experienced a densification of woody plant species—leading to a multitude of environmental, economic, and cultural changes. These encroached ...areas are unique in that the diversity of tree species is small, but at the same time the individual species possess diverse phenological responses. The overall goal of this study was to evaluate the ability of very high resolution drone imagery to accurately map species of woody plants encroaching on semiarid grasslands. For a site in the Edwards Plateau ecoregion of central Texas, we used affordable, very high resolution drone imagery to which we applied maximum likelihood (ML), support vector machine (SVM), random forest (RF), and VGG-19 convolutional neural network (CNN) algorithms in combination with pixel-based (with and without post-processing) and object-based (small and large) classification methods. Based on test sample data (n = 1000) the VGG-19 CNN model achieved the highest overall accuracy (96.9%). SVM came in second with an average classification accuracy of 91.2% across all methods, followed by RF (89.7%) and ML (86.8%). Overall, our findings show that RGB drone sensors are indeed capable of providing highly accurate classifications of woody plant species in semiarid landscapes—comparable to and even greater in some regards to those achieved by aerial and drone imagery using hyperspectral sensors in more diverse landscapes.
One of the outstanding and poorly understood examples of cooperation between species is found in corals, hydras and jellyfish that form symbioses with algae. These mutualistic algae are mostly ...acquired infectiously from the seawater and, according to models of virulence evolution, should be selected to parasitize their hosts. We altered algal transmission between jellyfish hosts in the laboratory to examine the potential for virulence evolution in this widespread symbiosis. In one experimental treatment, vertical transmission of algae (parent to offspring) selected for symbiont cooperation, because symbiont fitness was tied to host reproduction. In the other treatment, horizontal transmission (infectious spread) decoupled symbiont fitness from the host, potentially allowing parasitic symbionts to spread. Fitness estimates revealed a striking shift to parasitism in the horizontal treatment. The horizontally transmitted algae proliferated faster within hosts and had higher dispersal rates from hosts compared to the vertical treatment, while reducing host reproduction and growth. However, a trade-off was detected between harm caused to hosts and symbiont fitness. Virulence trade-offs have been modelled for pathogens and may be critical in stabilising 'infectious' symbioses. Our results demonstrate the dynamic nature of this symbiosis and illustrate the potential ease with which beneficial symbionts can evolve into parasites.
PDF
