Solvent free model for self-assembling fluid bilayer membranes: Stabilization of the fluid phase based on broad attractive tail potentials

We present a simple and highly adaptable method for simulating coarse-grained lipid membranes without explicit solvent. Lipids are represented by one head-bead and two tail-beads, with the interaction between tails being of key importance in stabilizing the fluid phase. Two such tail-tail potentials were tested, with the important feature in both cases being a variable range of attraction. We examined phase diagrams of this range versus temperature for both functional forms of the tail-tail attraction and found that a certain threshold attractive width was required to stabilize the fluid phase. Within the fluid phase region we find that material properties such as area per lipid, orientational order, diffusion constant, inter-leaflet flip-flop rate and bilayer stiffness all depend strongly and monotonically on the attractive width. For three particular values of the potential width we investigate the transition between gel and fluid phases via heating or cooling and find that this transition is discontinuous with considerable hysteresis. We also investigated the stretching of a bilayer to eventually form a pore and found excellent agreement with a recently published analytic theory.Comment: 14 pages 12 figure

Fast M\"obius and Zeta Transforms

M\"obius inversion of functions on partially ordered sets (posets) $\mathcal{P}$ is a classical tool in combinatorics. For finite posets it consists of two, mutually inverse, linear transformations called zeta and M\"obius transform, respectively. In this paper we provide novel fast algorithms for both that require $O(nk)$ time and space, where $n = |\mathcal{P}|$ and $k$ is the width (length of longest antichain) of $\mathcal{P}$, compared to $O(n^2)$ for a direct computation. Our approach assumes that $\mathcal{P}$ is given as directed acyclic graph (DAG) $(\mathcal{E}, \mathcal{P})$. The algorithms are then constructed using a chain decomposition for a one time cost of $O(|\mathcal{E}| + |\mathcal{E}_\text{red}| k)$, where $\mathcal{E}_\text{red}$ is the number of edges in the DAG's transitive reduction. We show benchmarks with implementations of all algorithms including parallelized versions. The results show that our algorithms enable M\"obius inversion on posets with millions of nodes in seconds if the defining DAGs are sufficiently sparse.Comment: 16 pages, 7 figures, submitted for revie

Causal Fourier Analysis on Directed Acyclic Graphs and Posets

We present a novel form of Fourier analysis, and associated signal processing concepts, for signals (or data) indexed by edge-weighted directed acyclic graphs (DAGs). This means that our Fourier basis yields an eigendecomposition of a suitable notion of shift and convolution operators that we define. DAGs are the common model to capture causal relationships between data values and in this case our proposed Fourier analysis relates data with its causes under a linearity assumption that we define. The definition of the Fourier transform requires the transitive closure of the weighted DAG for which several forms are possible depending on the interpretation of the edge weights. Examples include level of influence, distance, or pollution distribution. Our framework is different from prior GSP: it is specific to DAGs and leverages, and extends, the classical theory of Moebius inversion from combinatorics. For a prototypical application we consider DAGs modeling dynamic networks in which edges change over time. Specifically, we model the spread of an infection on such a DAG obtained from real-world contact tracing data and learn the infection signal from samples assuming sparsity in the Fourier domain.Comment: 13 pages, 11 figure

Akzeptanzprobleme beschäftigungssichernder Arbeitszeitverkürzungen : empirische Evidenz zweier Beschäftigtenbefragungen bei der Volkswagen AG und der Ruhrkohle AG (Problems with the acceptance of reductions in working hours that are intended to secure jobs)

"The article deals with reductions in working hours intended to secure jobs, with which new ground has been broken in various respects. In contrast to the previous pattern of collectively agreed cuts in working hours, they are (1) dispensed far more strongly, (2) they do not give full compensatory wage increases, (3) they are of a temporary nature and (4) they include guarantees of employment. In this way they provide an economically efficient and socially agreeable alternative to redundancies. Based on representative surveys of employees at Volkswagen AG and Ruhrkohle AG, the study examines how the employees accept the reductions in income linked with the cuts in working hours, and how happy they are with the cuts in working hours. The results show that the degree of acceptance of these reductions in working hours that are intended to secure jobs depends on how acute the threat to the jobs is, on the employees' satisfaction with the particular concrete working hours model, their private income and living situation as well as on the changes in the working situation which are triggered off or influenced by the reduction in working hours, and in particular here the intensification of performance. Although only a minority of the employees are unhappy with the cuts in working hours, the arrangement could not be transferred to other fields without difficulty. The particular company employment situation also plays a central role. The findings also refer to three aspects which seem to be significant for further reductions in the collectively agreed working hours. Firstly the advantage to be gained from an extended amount of non-working time depends to a great extent not only on the quantitative dimension of the additionally gained time units, but also on the position of the time gained and the extent to which it is available to the workers. Secondly the acceptance of reductions in working hours could turn out greater, the more successfully the close connection between shorter working hours and intensified performance is broken down. Finally good acceptance can only be expected when there is at least an average income or agreed wage level and partial compensatory wage increases, at least for those in the lower income bracket." (Author's abstract, IAB-Doku) ((en))Arbeitszeitverkürzung - Akzeptanz, Arbeitsplatzsicherung, Arbeitnehmer - Einstellungen, Arbeitsintensität, Lohnausgleich

Long-term neuromuscular sequelae of critical illness

In this observational study, we analyzed the long-term neuromuscular deficits of survivors of critical illness. Intensive care unit-acquired muscular weakness (ICU-AW) is a very common complication of critical illness. Critical illness polyneuropathy (CIP) and critical illness myopathy (CIM) are two main contributors to ICU-AW. ICU-AW is associated with an increased mortality and leads to rehabilitation problems. However, the long-term outcome of ICU-AW and factors influencing it are not well known. We analyzed the medical records of 490 survivors of critical illness, aged 18-75years and located in the area of the study center. Intensive care unit (ICU) survivors with comorbidities that might influence neuromuscular follow-up examinations, muscle strength, or results of nerve conduction studies, such as renal or hepatic insufficiency, diabetes mellitus, or vitamin deficiency were excluded. A total of 51 patients were finally included in the study. Six to 24months after discharge from the ICU, we measured the Medical Research Council (MRC) sum score, the Overall Disability Sum score (ODSS), and also performed nerve conduction studies and EMG. For all ICU survivors, the median MRC sum score was 60 (range 47-60) and the median ODSS score was 0 (range 0-8). CIP was diagnosed in 21 patients (41%). No patient was diagnosed with CIM. Patients with diagnosis of CIP showed a higher median ODSS scores 1 (range 0-8) versus 0 (range 0-5); p<0.001 and lower median MRC sum scores 56 (range 47-60) versus 60 (range 58-60); p<0.001. The three main outcome variables MRC sum score, ODSS score and diagnosis of CIP were not related to age, gender, or diagnosis of sepsis. The MRC sum score (r=−0.33; p=0.02) and the ODSS score (r=0.31; p=0.029) were correlated with the APACHE score. There was a trend for an increased APACHE score in patients with diagnosis of CIP 19 (range 6-33) versus 16.5 (range 6-28); p=0.065. Patients with the diagnosis of CIP had more days of ICU treatment 11days (range 2-74) versus 4days (range 1-61); p=0.015, and had more days of ventilator support 8days (range 1-59) versus 2days (range 1-46); p=0.006. The MRC sum score and the ODSS score were correlated with the days of ICU treatment and with the days of ventilator support. The neuromuscular long-term consequences of critical illness were not severe in our study population. As patients with concomitant diseases and old patients were excluded from this study the result of an overall favorable prognosis of ICU-acquired weakness may not be true for other patient's case-mix. Risk factors for the development of long-term critical illness neuropathy are duration of ICU treatment, duration of ventilator support, and a high APACHE score, but not diagnosis of sepsis. Although ICU-AW can be serious complication of ICU treatment, this should not influence therapeutic decisions, given its favorable long-term prognosis, at least in relatively young patients with no concomitant disease

Learning Set Functions that are Sparse in Non-Orthogonal Fourier Bases

Many applications of machine learning on discrete domains, such as learning preference functions in recommender systems or auctions, can be reduced to estimating a set function that is sparse in the Fourier domain. In this work, we present a new family of algorithms for learning Fourier-sparse set functions. They require at most $nk - k \log_2 k + k$ queries (set function evaluations), under mild conditions on the Fourier coefficients, where $n$ is the size of the ground set and $k$ the number of non-zero Fourier coefficients. In contrast to other work that focused on the orthogonal Walsh-Hadamard transform, our novel algorithms operate with recently introduced non-orthogonal Fourier transforms that offer different notions of Fourier-sparsity. These naturally arise when modeling, e.g., sets of items forming substitutes and complements. We demonstrate effectiveness on several real-world applications

Psycho-historical rivalry of complexes in mentality of the Russian autocracy

Статья посвящена оригинальной психоаналитической интерпретации становления российской государственности и самодержавия, которая ранее не проводилась в материале русского Средневековья. Автор впервые обращается к психоисторической концепции генезиса самодержавия: от формирования Московского централизованного государства до наших дней. Этот подход опирается на зарубежные психоисторические исследования, начатые Л. Де Мозом, и представляет новую и актуальную стратегию социокультурных исследований. Результаты. История страны предстает как хронология бессознательной конкуренции ведущих психических комплексов российской ментальности. Во-первых, это «новгородский комплекс неполноценности московской аристократии» - итог активного противостояния Москвы и Новгорода, вплоть до падения вечевой республики. Вторым сценарием, вытесняющим «новгородский комплекс», стал «западный комплекс превосходства». Он воспроизводил колониальное отношение империи к своей территории. Третья грань психоистории самодержавия связана с многовековым противостоянием татаро-монгольскому нашествию. Социально-политический уклад татар и других степняков очень сильно повлиял на отечественную культуру, язык и политическую традицию. Он проявился в абсолютно бессознательном комплексе «завистнического сравнения», открытом Т. Вебленом. Московская аристократия без централизованного государства вынуждена сублимировать психоисторический конфликт в форме рационализированной, православно- адаптированной идеологии. В ней была сублимирована и кочевая модель управления геополитическими пространствами, принудительно наложенная на традиционный земледельческий общинно- родовой уклад Древней и Средневековой Руси. Последующая история XV−XVI вв. лишь подтверждает факт сублимации комплексов неполноценности и завистнического сравнения по отношению к татарам.Horde on Moscow Rus predetermined the strategy of «envious» sublimation of the «steppe complex» by Moscow elite, and final abandonment of sociocultural lessons and historical perspective of the «Novgorod complex»

Spin-Peierls instability of the U(1) Dirac spin liquid

Quantum spin liquids are tantalizing phases of frustrated quantum magnets. A complicating factor in their realization and observation in materials is the ubiquitous presence of other degrees of freedom, in particular lattice distortion modes (phonons). These provide additional routes for relieving magnetic frustration, thereby possibly destabilizing spin-liquid ground states. In this work, we focus on triangular-lattice Heisenberg antiferromagnets, where recent numerical evidence suggests the presence of an extended U(1) Dirac spin liquid phase which is described by compact quantum electrodynamics in 2+1 dimensions (QED$_3$), featuring gapless spinons and monopoles as gauge excitations. Its low energy theory is believed to flow to a strongly-coupled fixed point with conformal symmetries. Using complementary perturbation theory and scaling arguments, we show that a symmetry-allowed coupling between (classical) finite-wavevector lattice distortions and monopole operators of the U(1) Dirac spin liquid generally induces a spin-Peierls instability towards a (confining) 12-site valence-bond solid state. We support our theoretical analysis with state-of-the-art density matrix renormalization group simulations. Away from the limit of static distortions, we demonstrate that the phonon energy gap establishes a parameter regime where the spin liquid is expected to be stable.Comment: 23 pages, 10 figure