Collective behaviour without collective order in wild swarms of midges

Collective behaviour is a widespread phenomenon in biology, cutting through a huge span of scales, from cell colonies up to bird flocks and fish schools. The most prominent trait of collective behaviour is the emergence of global order: individuals synchronize their states, giving the stunning impression that the group behaves as one. In many biological systems, though, it is unclear whether global order is present. A paradigmatic case is that of insect swarms, whose erratic movements seem to suggest that group formation is a mere epiphenomenon of the independent interaction of each individual with an external landmark. In these cases, whether or not the group behaves truly collectively is debated. Here, we experimentally study swarms of midges in the field and measure how much the change of direction of one midge affects that of other individuals. We discover that, despite the lack of collective order, swarms display very strong correlations, totally incompatible with models of noninteracting particles. We find that correlation increases sharply with the swarm's density, indicating that the interaction between midges is based on a metric perception mechanism. By means of numerical simulations we demonstrate that such growing correlation is typical of a system close to an ordering transition. Our findings suggest that correlation, rather than order, is the true hallmark of collective behaviour in biological systems.Comment: The original version has been split into two parts. This first part focuses on order vs. correlation. The second part, about finite-size scaling, will be included in a separate paper. 15 pages, 6 figures, 1 table, 5 video

Finite-size scaling as a way to probe near-criticality in natural swarms

Collective behaviour in biological systems is often accompanied by strong correlations. The question has therefore arisen of whether correlation is amplified by the vicinity to some critical point in the parameters space. Biological systems, though, are typically quite far from the thermodynamic limit, so that the value of the control parameter at which correlation and susceptibility peak depend on size. Hence, a system would need to readjust its control parameter according to its size in order to be maximally correlated. This readjustment, though, has never been observed experimentally. By gathering three-dimensional data on swarms of midges in the field we find that swarms tune their control parameter and size so as to maintain a scaling behaviour of the correlation function. As a consequence, correlation length and susceptibility scale with the system's size and swarms exhibit a near-maximal degree of correlation at all sizes.Comment: Selected for Viewpoint in Physics; PRL Editor's Suggestio

High overtones of Dirac perturbations of a Schwarzschild black hole

Using the Frobenius method, we find high overtones of the Dirac quasinormal spectrum for the Schwarzschild black hole. At high overtones, the spacing for imaginary part of $\omega_{n}$ is equidistant and equals to $\Im{\omega_{n+1}}-\Im{\omega_{n}} =i/8M$, ($M$ is the black hole mass), which is twice less than that for fields of integer spin. At high overtones, the real part of $\omega_{n}$ goes to zero. This supports the suggestion that the expected correspondence between quasinormal modes and Barbero-Immirzi parameter in Loop Quantum Gravity is just a numerical coincidence.Comment: 5 pages, Latex, 3 figures, Physical Review D.,at pres

Left ventricular mass increase is associated with cognitive decline and dementia in the elderly independently of blood pressure

Aims Left ventricular (LV) mass increase is considered part of composite target organ damage in hypertension and an independent risk factor for cardiovascular (CV) events. This study was designed to explore whether left ventricular mass index (LVMI) is associated with cognitive decline and dementia in elderly subjects, independently of blood pressure (BP) levels. Methods and results Four hundred subjects (mean age 79 ± 6 years) were studied. Left ventricular mass was measured echocardiographically in accordance with American Society of Echocardiography and normalized for body height to the 2.7 (LVMI). Global cognitive function was evaluated with the mini-mental state examination (MMSE) (maximum score 30). Dementia was defined as an MMSE score <21. Arterial stiffness was evaluated as carotid–femoral pulse wave velocity by Complior®. Prevalence of hypertension was 70% and diabetes mellitus was diagnosed in 25%. No significant differences in traditional CV risk factors were observed across LVMI quartiles. Mini-mental state examination showed an inverse trend across LVMI quartiles (the higher the LVMI, the lower the MMSE, P for trend <0.05); systolic and diastolic BP levels were not different across LVMI quartiles. In multivariable logistic regression models, including age, sex, BP levels, and use of antihypertensive drugs as covariates, the highest LVMI was found to be independently associated with a two-fold higher likelihood of having dementia. The association persisted significant even after adjustment for arterial stiffness. Conclusion In elderly subjects, LVMI is associated with a progressive cognitive decline. This association is independent of BP levels and/or large artery stiffness

Green roof irrigation management based on substrate water potential assures water saving without affecting plant physiological performance

Irrigation management in extensive green roofs (EGRs) is crucial in Mediterranean and semi-arid climates, as it should guarantee efficient water use while ensuring plant survival and vegetation cover. However, benefits of maintaining moderately low substrate water potential (psi(s)) have not been adequately investigated to date. An irrigation control unit based on psi(s) thresholds for irrigation (MediWater Safe [MWS]) was compared to a common irrigation timer maintaining psi(s) similar to 0 MPa (CTR) in shrub-vegetated Mediterranean EGR modules. The effect of the different irrigation regimes on substrate temperature, plant water relations (leaf conductance to water vapour, midday water potential and turgor loss point) and root vulnerability to heat stress via electrolyte leakage was tested in four shrub species. Decreasing psi(s) thresholds to -0.4 MPa reduced irrigation volumes by 68% in 3 summer months. However, the MWS unit neither influenced plant water status and vegetation cover nor induced physiological acclimation responses. Brief irrigation cycles imposed by MWS in the warmest hours reduced substrate surface temperature by 3 degrees C compared to CTR. Plant water status dynamics and root vulnerability to heat were species specific. Progressive stomatal closure and plant decline occurred only in Ceanothus thyrsiflorus and were associated to high root vulnerability to heat. Mortality occurred only in some Ceanothus plants in the CTR module, where higher psi(s) favoured the expansion of Hyperucum x moserianum. The results suggest that selecting proper psi(s) thresholds for irrigation could optimize EGR benefits, guaranteeing substantial water savings and proper plant establishment. Moreover, we claim root resistance to heat as a key parameter for plant selection in Mediterranean EGRs

Türkiye'de yetiştirilen Ankara Keçisi (Capra hircus) ırkında bir sitogenetik çalışma

Ankara Keçi ırkı Türkiye yerli hayvan genetik kaynakları acısından önemli rol oynamasına karşın bu ırkla ilgili kapsamlı bir sitogenetik çalışmaya rastlanmamıştır. Sunulan ön sitogenetik çalışma ırkın temel kromozomal yapısını araştırmak ve populasyon düzeyinde sitogenetik çalışmalara başlangıç yapmayı amaçlamaktadır. Kan kültürleri hem geleneksel metoda göre ve hem de Timidin metoduna göre düzenlenmiştir. Geleneksel ve GTG-RBA-RBG band karyotipleri elde edilerek ırkın kromozomlarının sentromer indeksleri belirlenmiştir. Band modeli karşılaştırmaları Ankara keçi ırkının keçi türü için standardize edilmiş RBA-RBG band modeli ile benzerliğini doğrulamıştır. Bu çalışma sonucunda Ankara keçisi ırkında populasyon düzeyinde sayısal ve yapısal kromozom anomalilerinin taşıyıcılarının tanımlanması, ırkın verim özeliklerinin geliştirilmesinde daha ileri düzeyde sitogenetik çalışmalara ihtiyaç duyulduğu değerlendirilmiştir.The Angora breed of goat plays an important role for the Turkiye's Native Animal genetic resources point of view; nevertheless, so far, no comprehensive cytogenetic investigation has been performed on this important economic breed. The present preliminary cytogenetic study has been conducted upon a sample of Angora goat breed reared in Turkiye in order to ascertain the basic chromosomal status of the breed and to start a cytogenetic screening at a population level. Blood cultures have been noted according to the conventional methods and synchronized with thymidine. Conventional and GTG-RBA-RBG-banded karyotypes have been produced to determine the relative length and centromeric index of the chromosomes of the breed. Banding comparison confirmed similarity of the Angora breed of goat with the established standardized RBA-RBG banding a pattern of the goat species. Further cytogenetic studies should now be addressed at a population level to identify carriers of numerical and/or structural chromosomal abnormalities in the Angora breed population for implementation of its productive and reproductive efficiency

Less safety for more efficiency: Water relations and hydraulics of the invasive tree Ailanthus altissima (Mill.) Swingle compared with native Fraxinus ornus L

Invasion of natural habitats by alien trees is a threat to forest conservation. Our understanding of fundamental ecophysiological mechanisms promoting plant invasions is still limited, and hydraulic and water relation traits have been only seldom included in studies comparing native and invasive trees. We compared several leaf and wood functional and mechanistic traits in co-occurring Ailanthus altissima (Mill.) Swingle (Aa) and Fraxinus ornus L. (Fo). Aa is one of the most invasive woody species in Europe and North America, currently outcompeting several native trees including Fo. We aimed at quantifying inter-specific differences in terms of: (i) performance in resource use and acquisition; (ii) hydraulic efficiency and safety; (iii) carbon costs associated to leaf and wood construction; and (iv) plasticity of functional and mechanistic traits in response to light availability. Traits related to leaf and wood construction and drought resistance significantly differed between the two species. Fo sustained higher structural costs than Aa, but was more resistant to drought. The lower resistance to drought stress of Aa was counterbalanced by higher water transport efficiency, but possibly required mechanisms of resilience to drought-induced hydraulic damage. Larger phenotypic plasticity of Aa in response to light availability could also promote the invasive potential of the species

Fourier ring correlation simplifies image restoration in fluorescence microscopy

Fourier ring correlation (FRC) has recently gained popularity among fluorescence microscopists as a straightforward and objective method to measure the effective image resolution. While the knowledge of the numeric resolution value is helpful in e.g., interpreting imaging results, much more practical use can be made of FRC analysis\u2014in this article we propose blind image restoration methods enabled by it. We apply FRC to perform image de-noising by frequency domain filtering. We propose novel blind linear and non-linear image deconvolution methods that use FRC to estimate the effective point-spread-function, directly from the images. We show how FRC can be used as a powerful metric to observe the progress of iterative deconvolution. We also address two important limitations in FRC that may be of more general interest: how to make FRC work with single images (within certain practical limits) and with three-dimensional images with highly anisotropic resolution

Lack of correlation between N-myc and MAX expression in neuroblastoma tumors and in cell lines: implication for N-myc-MAX complex formation

Detectable levels of MAX messenger RNA were found in a set of human neuroblastoma tumors and established cell lines. MAX mRNA levels were independent of tumor stage and N-myc genomic amplification. By contrast, N-myc mRNA transcripts were detectable only in tumors with amplification of N-myc gene and in cell lines. Analysis by reverse transcriptase polymerase chain reaction and hybridization to specific oligodeoxynucleotide probes revealed approximately equal amounts of two MAX transcripts in all cases analyzed. Immunoprecipitations with a specific antibody to MAX detected two proteins of M(r) 21,000 and 22,000 in approximately equal amounts in all neuroblastoma lines regardless of N-myc amplification and/or expression. On the other hand, protein binding to the myc DNA consensus sequence correlated with N-myc expression in neuroblastoma cells. Thus, N-myc expression might be a limiting factor in the formation of the N-myc-MAX heterodimer in neuroblastomas

How do Digital Platforms Organize Immaturity: Towards an Integrative Framework for Platform Power

The power of digital platforms is increasingly raising concern in civil society and in policy circles. A recent surge of research has separately documented various forms of platform power and power abuse. However, there are surprisingly scant attempts in providing a holistic perspective on platform power. We address this issue by developing a socio-symbolic perspective on platforms’ power dynamics, and by asking the guiding question of how platforms organize immaturity. Drawing on Bourdieu’s concepts of field, capitals, and habitus, we explain how socio-symbolic structures shape power relations and transform the field in which platforms operate. We characterize the digital habitus and identify three stages in field transformation, each explained by the predominance of specific forms of power. Our analysis derives that while a subset of these forms of power increase organized immaturity, another subset can also empower the field’s actors. Thus, we make two main contributions: (1) We develop a novel socio-symbolic view of platforms’ power dynamics and an integrative framework conceptualizing the multifaceted dimension of platform power. (2) We exploit and enrich the concept of organized immaturity