Singular components of spectral measures for ergodic Jacobi matrices

For ergodic 1d Jacobi operators we prove that the random singular components of any spectral measure are almost surely mutually disjoint as long as one restricts to the set of positive Lyapunov exponent. In the context of extended Harper's equation this yields the first rigorous proof of the Thouless' formula for the Lyapunov exponent in the dual regions.Comment: to appear in the Journal of Mathematical Physics, vol 52 (2011

Structure and Dynamics of amorphous Silica Surfaces

We use molecular dynamics computer simulations to study the equilibrium properties of the surface of amorphous silica. Two types of geometries are investigated: i) clusters with different diameters (13.5\AA, 19\AA, and 26.5\AA) and ii) a thin film with thickness 29\AA. We find that the shape of the clusters is independent of temperature and that it becomes more spherical with increasing size. The surface energy is in qualitative agreement with the experimental value for the surface tension. The density distribution function shows a small peak just below the surface, the origin of which is traced back to a local chemical ordering at the surface. Close to the surface the partial radial distribution functions as well as the distributions of the bond-bond angles show features which are not observed in the interior of the systems. By calculating the distribution of the length of the Si-O rings we can show that these additional features are related to the presence of two-membered rings at the surface. The surface density of these structures is around 0.6/nm^2 in good agreement with experimental estimates. From the behavior of the mean-squared displacement at low temperatures we conclude that at the surface the cage of the particles is larger than the one in the bulk. Close to the surface the diffusion constant is somewhat larger than the one in the bulk and with decreasing temperature the relative difference grows. The total vibrational density of states at the surface is similar to the one in the bulk. However, if only the one for the silicon atoms is considered, significant differences are found.Comment: 30 pages of Latex, 16 figure

Disentangling surface atomic motions from surface field effects in ultrafast low-energy electron diffraction

Ultrafast low-energy electron diffraction holds potential to provide atomic level details to the surface dynamics controlling processes from surface chemistry to exotic collective effects. Accessing the primary timescales requires subpicosecond excitation pulses to prepare the corresponding nonequilibrium state. The needed excitation for maximum contrast above background invariably leads to photoinduced electron emission with the creation of surface fields that affect diffraction and must be quantified to recover the key structural dynamics. Using 2 keV ultrashort low-energy electron bunches, we investigate this field effect on the ensuing electron distribution in projection imaging and diffraction as a function of excitation intensity. Using a structural model, we demonstrate a quantitative separation of the surface field effect on electron diffraction, enabling isolation of the structural dynamics of interest. Particle trajectory simulations provide insight into the correlation between geometrical characteristics of the charge separated region and the corresponding intensity modulation at the detector

Goal-directed fluid management based on stroke volume variation and stroke volume optimization during high-risk surgery: a pilot multicentre randomized controlled trial

Introduction: Perioperative hemodynamic optimization has been shown to be useful to improve the postoperative outcome of patients undergoing major surgery. We designed a pilot study in patients undergoing major abdominal, urologic or vascular surgery to investigate the effects of a goal-directed (GD) fluid management based on continuous stroke volume variation (SVV) and stroke volume (SV) monitoring on postoperative outcomes. Methods: Fifty-two high-risk-surgical patients (ASA 3 or 4, arterial and central venous catheter in place, postoperative admission in ICU) were randomized either to a control group (Group C, n = 26) or to a goal-directed group (Group G, n = 26). Patients with cardiac arrhythmia or ventilated with a tidal volume <7 ml/kg were excluded. In Group G, SVV and SV were continuously monitored with the FloTrac™/Vigileo™ system (Edwards Lifesciences, USA) and patients were brought to and maintained on the plateau of the Frank-Starling curve (SVV <10% and SV increase <10% in response to fluid loading). During the ICU stay, organ dysfunction was assessed using the SOFA score and resource utilization using the TISS score. Patients were followed up to 28 days after surgery for infectious, cardiac, respiratory, renal, hematologic and abdominal complications. Results: Group G and Group C were comparable for ASA score, comorbidities, type and duration of surgery (275 vs. 280 minutes), heart rate, MAP and CVP at the start of surgery. However, Group G was younger than Group C (68 vs. 73 years, P < 0.05). During surgery, Group G received more colloids than Group C (1,589 vs. 927 ml, P < 0.05) and SVV decreased in Group G (from 9.0 to 8.0%, P < 0.05) but not in Group C. The number of postoperative wound infections was lower in Group G (0 vs. 7, P < 0.01). Although not statistically significant, the proportion of patients with at least one complication (46 vs. 62%), the number of postoperative complications per patient (0.65 vs. 1.40), the maximum ICU SOFA score (5.9 vs. 7.2), and the cumulative ICU TISS score (69 vs. 83) were also lower in Group G. ICU and hospital length of stay were similar in both groups. Conclusion: Although the two groups were not perfectly matched, this pilot shows that fluid management based on SVV and SV optimization decreases wound infections. It also suggests that such a GD strategy may decrease postoperative organ dysfunction and resource utilization. However, this remains to be confirmed by a larger study

Work-related correlates of occupational sitting in a diverse sample of employees in Midwest metropolitan cities

The worksite serves as an ideal setting to reduce sedentary time. Yet little research has focused on occupational sitting, and few have considered factors beyond the personal or socio-demographic level. The current study i) examined variation in occupational sitting across different occupations, ii) explored whether worksite level factors (e.g., employer size, worksite supports and policies) may be associated with occupational sitting. Between 2012 and 2013, participants residing in four Missouri metropolitan areas were interviewed via telephone and provided information on socio-demographic characteristics, schedule flexibility, occupation, work related factors, and worksite supports and policies. Occupational sitting was self-reported (daily minutes spent sitting at work), and dichotomized. Occupation-stratified analyses were conducted to identify correlates of occupational sitting using multiple logistic regressions. A total of 1668 participants provided completed data. Those employed in business and office/administrative support spent more daily occupational sitting time (median 330 min) compared to service and blue collar employees (median 30 min). Few worksite supports and policies were sitting specific, yet factors such as having a full-time job, larger employer size, schedule flexibility, and stair prompt signage were associated with occupational sitting. For example, larger employer size was associated with higher occupational sitting in health care, education/professional, and service occupations. Work-related factors, worksite supports and policies are associated with occupational sitting. The pattern of association varies among different occupation groups. This exploratory work adds to the body of research on worksite level correlates of occupational sitting. This may provide information on priority venues for targeting highly sedentary occupation groups

Nigerian scam e-mails and the charms of capital

So-called '419' or 'advance-fee' e-mail frauds have proved remarkably successful. Global losses to these scams are believed to run to billions of dollars. Although it can be assumed that the promise of personal gain which these e-mails hold out is part of what motivates victims, there is more than greed at issue here. How is it that the seemingly incredible offers given in these unsolicited messages can find an audience willing to treat them as credible? The essay offers a speculative thesis in answer to this question. Firstly, it is argued, these scams are adept at exploiting common presuppositions in British and American culture regarding Africa and the relationships that are assumed to exist between their nations and those in the global south. Secondly, part of the appeal of these e-mails lies in the fact that they appear to reveal the processes by which wealth is created and distributed in the global economy. They thus speak to their readers’ attempts to map or conceptualise the otherwise inscrutable processes of that economy. In the conclusion the essay looks at the contradictions in the official state response to this phenomena

Patterning and process parameter effects in 3D suspension near-field electrospinning of nanoarrays

The extracellular matrix (ECM) contains nanofibrous proteins and proteoglycans. Nanofabrication methods have received growing interest in recent years as a means of recapitulating these elements within the ECM. Near-field electrospinning (NFES) is a versatile fibre deposition method, capable of layer-by-layer nano-fabrication. The maximum layer height is generally limited in layer-by-layer NFES as a consequence of electrostatic effects of the polymer at the surface, due to residual charge and polymer dielectric properties. This restricts the total volume achievable by layer-by-layer techniques. Surpassing this restriction presents a complex challenge, leading to research innovations aimed at increasing patterning precision, and achieving a translation from 2D to 3D additive nanofabrication. Here we investigated a means of achieving this translation through the use of 3D electrode substrates. This was addressed by in-house developed technology in which selective laser melt manufactured standing pillar electrodes were combined with a direct suspension near-field electrospinning (SNFES) technique, which implements an automated platform to manoeuvre the pillar electrodes around the emitter in order to suspend fibres in the free space between the electrode support structures. In this study SNFES was used in multiple operation modes, investigating the effects of varying process parameters, as well as pattern variations on the suspended nanoarrays. Image analysis of the nanoarrays allowed for the assessment of fibre directionality, isotropy, and diameter; identifying optimal settings to generate fibres for tissue engineering applications

Towards a critical theory of communication as renewal and update of Marxist humanism in the age of digital capitalism

This paper's task is to outline some foundations of a critical, Marxist-humanist theory of communication in the age of digital capitalism. It theorises the role of communication in society, communication and alienation, communication in social struggles, social struggles for democratic communication, the contradictions of digital capitalism, and struggles for digital socialist humanism. Marxist humanism is a counter-narrative, counter-theory, and counter-politics to neoliberalism, new authoritarianism, and postmodernism. A critical theory of communication can should draw on this intellectual tradition. Communication and work stand in a dialectical relationship. Communication mediates, organises and is the process of the production of sociality and therefore of the reproduction of society. Society and communication are in class and capitalist societies shaped by the antagonism between instrumental and co-operative reason. Authoritarianism and humanism are two basic, antagonistic modes of organisation of society and communication. Instrumental reason creates and universalises alienation. Digital capitalism is a dimension of contemporary society where digital technologies such as the computer, the Internet, the mobile phone, tablets, robots, and AI-driven (“smart”) technologies mediate the accumulation of capital, influence, and reputation. A Marxist-humanist theory of communication aims to inform struggles for a good, commons-based, public Internet in a good, commons-based society that has a vivid, democratic public sphere

The time of the Roma in times of crisis: Where has European neoliberal capitalism failed?

This paper argues that the economic and financial crisis that has ensnared Europe from the late 2000s has been instrumental in reshaping employment and social relations in a detrimental way for the majority of the European people. It argues that the crisis has exacerbated the socio-economic position of most Roma people, immigrants as well as of other vulnerable groups. This development is approached here as an outcome of the widening structural inequalities that underpin the crisis within an increasingly neoliberalised Europe. Through recent policy developments and public discourses from a number of European countries I show how rising inequalities nurture racialised social tensions. My account draws on classic and contemporary theoretical propositions that have been propounded about the nature of capitalism, its contemporary re-articulation as well as its ramification for the future of Europe