Scaling properties of velocity and temperature spectra above the surface friction layer in a convective atmospheric boundary layer

International audienceWe report velocity and temperature spectra measured at nine levels from 1.42 meters up to 25.7 m over a smooth playa in Western Utah. Data are from highly convective conditions when the magnitude of the Obukhov length (our proxy for the depth of the surface friction layer) was less than 2 m. Our results are somewhat similar to the results reported from the Minnesota experiment of Kaimal et al. (1976), but show significant differences in detail. Our velocity spectra show no evidence of buoyant production of kinetic energy at at the scale of the thermal structures. We interpret our velocity spectra to be the result of outer eddies interacting with the ground, not "local free convection". We observe that velocity spectra represent the spectral distribution of the kinetic energy of the turbulence, so we use energy scales based on total turbulence energy in the convective boundary layer (CBL) to collapse our spectra. For the horizontal velocity spectra this scale is (zi ?o)2/3, where zi is inversion height and ?o is the dissipation rate in the bulk CBL. This scale functionally replaces the Deardorff convective velocity scale. Vertical motions are blocked by the ground, so the outer eddies most effective in creating vertical motions come from the inertial subrange of the outer turbulence. We deduce that the appropriate scale for the peak region of the vertical velocity spectra is (z ?o)2/3 where z is height above ground. Deviations from perfect spectral collapse under these scalings at large and small wavenumbers are explained in terms of the energy transport and the eddy structures of the flow. We find that the peaks of the temperature spectra collapse when wavenumbers are scaled using (z1/2 zi1/2). That is, the lengths of the thermal structures depend on both the lengths of the transporting eddies, ~9z, and the progressive aggregation of the plumes with height into the larger-scale structures of the CBL. This aggregation depends, in top-down fashion, on zi. The whole system is therefore highly organized, with even the smallest structures conforming to the overall requirements of the whole flow

The Political Economy of the Mental Health System: A Marxist Analysis

The present paper analyses the functions of the mental health system in relation to the economic organisation of society, using concepts derived from Marx’s work on political economy and building on previous critiques. The analysis starts from the position that mental health problems are not equivalent to physical, medical conditions and are more fruitfully viewed as problems of communities or societies. Using the example of the United Kingdom, it traces how a public mental health system evolved alongside capitalism in order to manage the problems posed by people whose behaviour was too chaotic, disruptive or inefficient to participate in a labour market based on exploitation. The system provided a mixture of care and control, and under recent, Neoliberal regimes, these functions have been increasingly transferred to the private sector and provided in a capitalistic manner. Welfare payments are also part of the system and support those less seriously affected but unable to work productively enough to generate surplus value and profit. The increased intensity and precarity of work under Neoliberalism has driven up benefit claims at the same time as the Neoliberal state is trying to reduce them. These social responses are legitimised by the idea that mental disorders are medical conditions, and this idea also has a hegemonic function by construing the adverse consequences of social and economic structures as individual problems, an approach that has been particularly important during the rise of Neoliberalism. The concept of mental illness has a strategic role in modern societies, therefore, enabling certain contentious social activities by obscuring their political nature, and diverting attention from the failings of the underlying economic system. The analysis suggests the medical view is driven by political imperatives rather than science and reveals the need for a system that is more transparent and democratic. While the mental health system has some consistent functions across all modern societies, this account highlights one of the endemic contradictions of the capitalist system in the way that it marginalises large groups of people by narrowing the opportunities to make an economic contribution to society

Dissociating the effect of disruptive colouration on localisation and identification of camouflaged targets

Disruptive camouflage features contrasting areas of pigmentation across the animals’ surface that form false edges which disguise the shape of the body and impede detection. In many taxa these false edges feature local contrast enhancement or edge enhancement, light areas have lighter edges and dark areas have darker edges. This additional quality is often overlooked in existing research. Here we ask whether disruptive camouflage can have benefits above and beyond concealing location. Using a novel paradigm, we dissociate the time courses of localisation and identification of a target in a single experiment. We measured the display times required for a stimulus to be located or identified (the critical duration). Targets featured either uniform, disruptive or edge enhanced disruptive colouration. Critical durations were longer for identifying targets with edge enhanced disruptive colouration camouflage even when presented against a contrasting background, such that all target types were located equally quickly. For the first time, we establish empirically that disruptive camouflage not only conceals location, but also disguises identity. This shows that this form of camouflage can be useful even when animals are not hidden. Our findings offer insights into how edge enhanced disruptive colouration undermines visual perception by disrupting object recognition

Against the stream: Antidepressants are not antidepressants - an alternative approach to drug action and implications for the use of antidepressants

Although antidepressants are regarded as effective and specific treatments, they are barely superior to placebo in randomised trials, and differences are unlikely to be clinically relevant. The conventional disease-centred understanding of drug action regards antidepressants as targeting an underlying brain process, but an alternative 'drug-centred' view suggests they are psychoactive substances that modify normal mental states and behaviour. These alterations, such as numbing of emotions, may reduce feelings of depression, and also create amplified placebo effects in randomised trials. Patients should be informed that there is no evidence that antidepressants work by correcting a chemical imbalance, that antidepressants have mind-altering effects, and that evidence suggests they produce no noticeable benefit compared with placebo. Declaration of interest The author is co-chairperson of the Critical Psychiatry Network