Contractile units in disordered actomyosin bundles arise from F-actin buckling

Bundles of filaments and motors are central to contractility in cells. The classic example is striated muscle, where actomyosin contractility is mediated by highly organized sarcomeres which act as fundamental contractile units. However, many contractile bundles in vivo and in vitro lack sarcomeric organization. Here we propose a model for how contractility can arise in actomyosin bundles without sarcomeric organization and validate its predictions with experiments on a reconstituted system. In the model, internal stresses in frustrated arrangements of motors with diverse velocities cause filaments to buckle, leading to overall shortening. We describe the onset of buckling in the presence of stochastic actin-myosin detachment and predict that buckling-induced contraction occurs in an intermediate range of motor densities. We then calculate the size of the "contractile units" associated with this process. Consistent with these results, our reconstituted actomyosin bundles contract at relatively high motor density, and we observe buckling at the predicted length scale.Comment: 5 pages, 4 figures, Supporting text and movies attache

Requirements for contractility in disordered cytoskeletal bundles

Actomyosin contractility is essential for biological force generation, and is well understood in highly organized structures such as striated muscle. Additionally, actomyosin bundles devoid of this organization are known to contract both in vivo and in vitro, which cannot be described by standard muscle models. To narrow down the search for possible contraction mechanisms in these systems, we investigate their microscopic symmetries. We show that contractile behavior requires non-identical motors that generate large enough forces to probe the nonlinear elastic behavior of F-actin. This suggests a role for filament buckling in the contraction of these bundles, consistent with recent experimental results on reconstituted actomyosin bundles.Comment: 10 pages, 6 figures; text shortene

Sonic Gestures Applied to a Percussive Dialogue in TanGram using Wii Remotes

TanGram, is an original music score composed by Carlos D. Perales for Percussion Quartet and Nintendo Wii Remotes used as a wireless interface for Live Electronics. This paper examines how this composition explores exiting research in interaction and communication between instruments and digital sound processing discourse to produce a unique music mixed-media score, to explore the sonic possibilities of a multi-timbrical instrument with the integration of the visual gestures of an accessible device using processes of real-time gestural mimesis.

Comparison of techniques for computing shell-model effective operators

Different techniques for calculating effective operators within the framework of the shell model using the same effective interaction and the same excitation spaces are presented. Starting with the large-basis no-core approach, we compare the time-honored perturbation-expansion approach and a model-space truncation approach. Results for the electric quadrupole and magnetic dipole operators are presented for $^6$Li. The convergence trends and dependence of the effective operators on differing excitation spaces and Pauli Q-operators is studied. In addition, the dependence of the electric-quadrupole effective charge on the harmonic-oscillator frequency and the mass number, for A=5,6, is investigated in the model-space truncation approach.Comment: 18 pages. REVTEX. 4 PostScript figure

Prevalence and predictors of video game addiction: a study based on a national representative sample of gamers

Video gaming has become a popular leisure activity in many parts of the world, and an increasing number of empirical studies examine the small minority that appears to develop problems as a result of excessive gaming. This study investigated prevalence rates and predictors of video game addiction in a sample of gamers, randomly selected from the National Population Registry of Norway (N =3389). Results showed there were 1.4 % addicted gamers, 7.3 % problem gamers, 3.9 % engaged gamers, and 87.4 % normal gamers. Gender (being male) and age group (being young) were positively associated with addicted-, problem-, and engaged gamers. Place of birth (Africa, Asia, South- and Middle America) were positively associated with addicted- and problem gamers. Video game addiction was negatively associated with conscientiousness and positively associated with neuroticism. Poor psychosomatic health was positively associated with problem- and engaged gaming. These factors provide insight into the field of video game addiction, and may help to provide guidance as to how individuals that are at risk of becoming addicted gamers can be identified

Abstract sounds and their applications in audio and perception research

International audienceRecognition of sound sources and events is an important pro- cess in sound perception and has been studied in many research domains. Conversely sounds that cannot be recognized are not often studied except by electroacoustic music composers. Besides, considerations on recogni- tion of sources might help to address the problem of stimulus selection and categorization of sounds in the context of perception research. This paper introduces what we call abstract sounds with the existing musical background and shows their relevance for different applications

Health care professionals’ experience, understanding and perception of need of advanced cancer patients with cachexia and their families: The benefits of a dedicated clinic.

BACKGROUND: Cachexia is defined as the on-going loss of skeletal muscle mass that cannot be fully reversed by conventional nutritional support. It is found in up to 80% of patients with advanced cancer and has profound psycho-social consequences for patients and their families. Previous studies demonstrate that many healthcare professionals receive little formal education in cachexia management leading them to feel that they have limited understanding of the syndrome and cannot intervene effectively. This study aims to examine the value of a dedicated cachexia clinic and its influence on staff understanding and practice. METHODS: An exploratory qualitative study was conducted. The study employed semi-structured interviews with a range of healthcare professionals responsible for designing and delivering cancer care in a large teaching hospital in Australia. This hospital had a dedicated cachexia clinic. RESULTS: In-depth interviews were conducted with 8 healthcare professionals and senior managers. Four themes were identified: formal and informal education; knowledge and understanding; truth telling in cachexia and palliative care; and, a multi-disciplinary approach. Findings show that improved knowledge and understanding across a staff body can lead to enhanced staff confidence and a willingness to address cancer cachexia and its consequences with patients and their families. CONCLUSION: Comparisons with similar previous research demonstrate the advantages of providing a structure for staff to gain knowledge about cachexia and how this can contribute to feelings of improved understanding and confidence necessary to respond to the challenge of cachexia

Occupational stress in health professionals: a study with Portuguese Nurses

Este trabalho analisa o estresse ocupacional em 286 enfermeiros de hospitais e centros de saúde portugueses. Avaliaram-se as fontes de estresse, o burnout, os problemas de saúde física, a satisfação e a realização profissional. Os resultados apontaram 30% de enfermeiros com experiências significativas de estresse e 15% com problemas de exaustão emocional. As análises de regressão múltipla apontaram maior capacidade preditiva das dimensões de estresse na exaustão emocional, na saúde física, na satisfação e na realização profissional. As análises comparativas evidenciaram maiores problemas de stresse e reacções mais negativas ao trabalho nas mulheres, nos enfermeiros mais novos e com menor experiência, nos trabalhadores com contratos a prazo, nos profissionais que realizam trabalho por turnos e nos que trabalham mais horas.This work analyses occupational stress in 286 nurses from hospitals and health care centres in Portugal. The following dimensions were evaluated: stress, burnout, physical health problems, satisfaction and professional fulfilment. Results revealed significant stress experiences in 30% of the professionals, and emotional exhaustion problems in 15%. Multiple regression analysis pointed out stress as an important predictor of emotional exhaustion, physical health, satisfaction and professional fulfilment. Comparative analysis suggested more occupational stress and professional negative experiences in the following groups: female nurses, younger and less experienced nurses, those with short-term working contracts, nurses working on a shift-basis system, and nurses working during long hours.(undefined

Therapeutic hypothermia translates from ancient history in to practice

Acute postasphyxial encephalopathy around the time of birth remains a major cause of death and disability. The possibility that hypothermia may be able to prevent or lessen asphyxial brain injury is a “dream revisited”. In this review, a historical perspective is provided from the first reported use of therapeutic hypothermia for brain injuries in antiquity, to the present day. The first uncontrolled trials of cooling for resuscitation were reported more than 50 y ago. The seminal insight that led to the modern revival of studies of neuroprotection was that after profound asphyxia, many brain cells show initial recovery from the insult during a short “latent” phase, typically lasting ~6 h, only to die hours to days later during a “secondary” deterioration phase characterized by seizures, cytotoxic edema, and progressive failure of cerebral oxidative metabolism. Studies designed around this conceptual framework showed that mild hypothermia initiated as early as possible before the onset of secondary deterioration, and continued for a sufficient duration to allow the secondary deterioration to resolve, is associated with potent, long-lasting neuroprotection. There is now compelling evidence from randomized controlled trials that mild induced hypothermia significantly improves intact survival and neurodevelopmental outcomes to midchildhood