Tensegrity and its role in guiding engineering sciences in the development of bio-inspired materials.

Tensegrity is the word coined by Buckminster Fuller as a contraction of tensional integrity. A tensegrity system is established when a set of discontinuous compressive components interacts with a set of continuous tensile components to define a stable volume in space. Tensegrity structures are mechanically stable not because of the strength of individual members but because of the way the entire structure distributes and balances mechanical loads. Tensile forces naturally transmit themselves over the shortest distance between two points, so the members of a tensegrity system are precisely positioned to best withstand stress. Thus, tensegrity systems offer a maximum amount of strength for a given amount of material. Man-made structures have traditionally been designed to avoid developing large tensile stresses. In contrast, nature always uses a balance of tension and compression. Tensegrity principles apply at essentially every size-scale in the human body. Macroscopically, the bones that constitute our skeleton are pulled up against the force of gravity and stabilized in a vertical form by the pull of tensile muscles, tendons and ligaments. Microscopically, a tensegrity structure has been proposed for the skeleton of cells. This report contains the results of a feasibility study and literature survey to explore the potential of applying tensegrity principles in designing materials with desired functionalities. The goal is to assess if further study of the principles of tensegrity may be exploited as an avenue for producing new materials that have intrinsic capabilities for adapting to changing loads (self-healing), as with the ongoing reconstruction of living bone under loading. This study contains a collection of literature that has been categorized into the areas of structures, mathematics, mechanics, and, biology. The topics addressed in each area are discussed. Ultimately, we conclude that because tensegrity is fundamentally a description of structure, it may prove useful for describing existing materials, but does not provide guidance in the development of new materials because it does not address the issue of how such structures form

An imaging system for standardized quantitative analysis of C. elegans behavior

BACKGROUND: The nematode Caenorhabditis elegans is widely used for the genetic analysis of neuronal cell biology, development, and behavior. Because traditional methods for evaluating behavioral phenotypes are qualitative and imprecise, there is a need for tools that allow quantitation and standardization of C. elegans behavioral assays. RESULTS: Here we describe a tracking and imaging system for the automated analysis of C. elegans morphology and behavior. Using this system, it is possible to record the behavior of individual nematodes over long time periods and quantify 144 specific phenotypic parameters. CONCLUSIONS: These tools for phenotypic analysis will provide reliable, comprehensive scoring of a wide range of behavioral abnormalities, and will make it possible to standardize assays such that behavioral data from different labs can readily be compared. In addition, this system will facilitate high-throughput collection of phenotypic data that can ultimately be used to generate a comprehensive database of C. elegans phenotypic information. AVAILABILITY: The hardware configuration and software for the system are available from [email protected]

SARS-CoV-2 viability on sports equipment is limited, and dependent on material composition

The control of the COVID-19 pandemic in the UK has necessitated restrictions on amateur and professional sports due to the perceived infection risk to competitors, via direct person to person transmission, or possibly via the surfaces of sports equipment. The sharing of sports equipment such as tennis balls was therefore banned by some sport’s governing bodies. We sought to investigate the potential of sporting equipment as transmission vectors of SARS-CoV-2. Ten different types of sporting equipment, including balls from common sports, were inoculated with 40 μl droplets containing clinically relevant concentrations of live SARS-CoV-2 virus. Materials were then swabbed at time points relevant to sports (1, 5, 15, 30, 90 min). The amount of live SARS-CoV-2 recovered at each time point was enumerated using viral plaque assays, and viral decay and half-life was estimated through fitting linear models to log transformed data from each material. At one minute, SARS-CoV-2 virus was recovered in only seven of the ten types of equipment with the low dose inoculum, one at five minutes and none at 15 min. Retrievable virus dropped significantly for all materials tested using the high dose inoculum with mean recovery of virus falling to 0.74% at 1 min, 0.39% at 15 min and 0.003% at 90 min. Viral recovery, predicted decay, and half-life varied between materials with porous surfaces limiting virus transmission. This study shows that there is an exponential reduction in SARS-CoV-2 recoverable from a range of sports equipment after a short time period, and virus is less transferrable from materials such as a tennis ball, red cricket ball and cricket glove. Given this rapid loss of viral load and the fact that transmission requires a significant inoculum to be transferred from equipment to the mucous membranes of another individual it seems unlikely that sports equipment is a major cause for transmission of SARS-CoV-2. These findings have important policy implications in the context of the pandemic and may promote other infection control measures in sports to reduce the risk of SARS-CoV-2 transmission and urge sports equipment manufacturers to identify surfaces that may or may not be likely to retain transferable virus

Stakeholder Relations and Ownership of a Community Wireless Network: The Case of iNethi

The primary objective for this study is to investigate multi-stakeholder understanding of ownership of a community wireless network (CWN) located in Ocean View, Cape Town. This is important because ownership and stakeholder relations are components that contribute to the success of a CWN. Using the convenience and snowball sampling method, we completed 11 semi-structured interviews with stakeholders from the University of Cape Town and the Ocean View community. We consider different ways ownership is conceived between stakeholders. We found that the involvement of the community at initiation of a CWN project is imperative in establishing ownership of a CWN. We characterize some of the ways in which discordant conceptions of ownership have resulted in miscommunication within this project and offer considerations for researchers to take into account as they collaborate with communities on joint initiatives

Smoking Cessation Among Women with and at Risk for HIV: Are They Quitting?

Cigarette smoking is an important risk factor for adverse health events in HIV-infected populations. While recent US population-wide surveys report annual sustained smoking cessation rates of 3.4–8.5%, prospective data are lacking on cessation rates for HIV-infected smokers. To determine the sustained tobacco cessation rate and predictors of cessation among women with or at risk for HIV infection. Prospective cohort study. A total of 747 women (537 HIV-infected and 210 HIV-uninfected) who reported smoking at enrollment (1994–1995) in the Women’s Interagency HIV Study (WIHS) and remained in follow-up after 10 years. The participants were mostly minority (61% non-Hispanic Blacks and 22% Hispanics) and low income (68% with reported annual incomes of less than or equal to $12,000). The primary outcome was defined as greater than 12 months continuous cessation at year 10. Multivariate logistic regression was used to identify independent baseline predictors of subsequent tobacco cessation. A total of 121 (16%) women reported tobacco cessation at year 10 (annual sustained cessation rate of 1.8%, 95% CI 1.6–2.1%). Annual sustained cessation rates were 1.8% among both HIV-positive and HIV-negative women (p = 0.82). In multivariate analysis, the odds of tobacco cessation were significantly higher in women with more years of education (p trend = 0.02) and of Hispanic origin (OR = 1.87, 95% CI = 1.4–2.9) compared to Black women. Cessation was significantly lower in current or former illicit drug users (OR = 0.42 95% CI = 0.24–0.74 and OR = 0.65, 95% CI = 0.49–0.86, respectively, p trend = 0.03) and women reporting a higher number of cigarettes per day at baseline (p trend < 0.001). HIV-infected and at-risk women in this cohort have lower smoking cessation rates than the general population. Given the high prevalence of smoking, the high risk of adverse health events from smoking, and low rates of cessation, it is imperative that we increase efforts and overcome barriers to help these women quit smoking

Ammonium-Acetate Is Sensed by Gustatory and Olfactory Neurons in Caenorhabditis elegans

Background: Caenorhabditis elegans chemosensation has been successfully studied using behavioral assays that treat detection of volatile and water soluble chemicals as separate senses, analogous to smell and taste. However, considerable ambiguity has been associated with the attractive properties of the compound ammonium-acetate (NH 4Ac). NH 4Ac has been used in behavioral assays both as a chemosensory neutral compound and as an attractant. Methodology/Main Findings: Here we show that over a range of concentrations NH4Ac can be detected both as a water soluble attractant and as an odorant, and that ammonia and acetic acid individually act as olfactory attractants. We use genetic analysis to show that NaCl and NH4Ac sensation are mediated by separate pathways and that ammonium sensation depends on the cyclic nucleotide gated ion channel TAX-2/TAX-4, but acetate sensation does not. Furthermore we show that sodium-acetate (NaAc) and ammonium-chloride (NH4Cl) are not detected as Na + and Cl 2 specific stimuli, respectively. Conclusions/Significance: These findings clarify the behavioral response of C. elegans to NH4Ac. The results should have an impact on the design and interpretation of chemosensory experiments studying detection and adaptation to soluble compounds in the nematode Caenorhabditis elegans

Laminin-332 alters connexin profile, dye coupling and intercellular Ca(2+ )waves in ciliated tracheal epithelial cells

BACKGROUND: Tracheal epithelial cells are anchored to a dynamic basement membrane that contains a variety of extracellular matrix proteins including collagens and laminins. During development, wound repair and disease of the airway epithelium, significant changes in extracellular matrix proteins may directly affect cell migration, differentiation and events mediated by intercellular communication. We hypothesized that alterations in cell matrix, specifically type I collagen and laminin α3β3γ2 (LM-332) proteins within the matrix, directly affect intercellular communication in ciliated rabbit tracheal epithelial cells (RTEC). METHODS: Functional coupling of RTEC was monitored by microinjection of the negatively charged fluorescent dyes, Lucifer Yellow and Alexa 350, into ciliated RTEC grown on either a LM-332/collagen or collagen matrix. Coupling of physiologically significant molecules was evaluated by the mechanism and extent of propagated intercellular Ca(2+ )waves. Expression of connexin (Cx) mRNA and proteins were assayed by reverse transcriptase – polymerase chain reaction and immunocytochemistry, respectively. RESULTS: When compared to RTEC grown on collagen alone, RTEC grown on LM-332/collagen displayed a significant increase in dye transfer. Although mechanical stimulation of RTEC grown on either LM-332/collagen or collagen alone resulted in intercellular Ca(2+ )waves, the mechanism of transfer was dependent on matrix: RTEC grown on LM-332/collagen propagated Ca(2+)waves via extracellular purinergic signaling whereas RTEC grown on collagen used gap junctions. Comparison of RTEC grown on collagen or LM-332/collagen matrices revealed a reorganization of Cx26, Cx43 and Cx46 proteins. CONCLUSION: Alterations in airway basement membrane proteins such as LM-332 can induce connexin reorganizations and result in altered cellular communication mechanisms that could contribute to airway tissue function

Gravitational waves from single neutron stars: an advanced detector era survey

With the doors beginning to swing open on the new gravitational wave astronomy, this review provides an up-to-date survey of the most important physical mechanisms that could lead to emission of potentially detectable gravitational radiation from isolated and accreting neutron stars. In particular we discuss the gravitational wave-driven instability and asteroseismology formalism of the f- and r-modes, the different ways that a neutron star could form and sustain a non-axisymmetric quadrupolar "mountain" deformation, the excitation of oscillations during magnetar flares and the possible gravitational wave signature of pulsar glitches. We focus on progress made in the recent years in each topic, make a fresh assessment of the gravitational wave detectability of each mechanism and, finally, highlight key problems and desiderata for future work.Comment: 39 pages, 12 figures, 2 tables. Chapter of the book "Physics and Astrophysics of Neutron Stars", NewCompStar COST Action 1304. Minor corrections to match published versio

Robust penetrating microelectrodes for neural interfaces realized by titanium micromachining

Neural prosthetic interfaces based upon penetrating microelectrode devices have broadened our understanding of the brain and have shown promise for restoring neurological functions lost to disease, stroke, or injury. However, the eventual viability of such devices for use in the treatment of neurological dysfunction may be ultimately constrained by the intrinsic brittleness of silicon, the material most commonly used for manufacture of penetrating microelectrodes. This brittleness creates predisposition for catastrophic fracture, which may adversely affect the reliability and safety of such devices, due to potential for fragmentation within the brain. Herein, we report the development of titanium-based penetrating microelectrodes that seek to address this potential future limitation. Titanium provides advantage relative to silicon due to its superior fracture toughness, which affords potential for creation of robust devices that are resistant to catastrophic failure. Realization of these devices is enabled by recently developed techniques which provide opportunity for fabrication of high-aspect-ratio micromechanical structures in bulk titanium substrates. Details are presented regarding the design, fabrication, mechanical testing, in vitro functional characterization, and preliminary in vivo testing of devices intended for acute recording in rat auditory cortex and thalamus, both independently and simultaneously