Abstract
Mantis shrimp swim via metachronal rowing, a pattern in which the pleopods (swimming limbs) stroke sequentially, starting with the last pair and followed by anterior neighbors. A similar ...swimming pattern is used at various sizes, Reynolds numbers, and advance ratios by diverse organisms including ciliates, ctenophores, copepods, krill, and lobsters. Understanding this type of locomotion is important because it is widespread and may inspire the design of underwater vehicles where efficiency, robustness, and maneuverability are desired. However, detailed measurements of the flow around free-swimming, metachronally rowing organisms are scarce, especially for organisms swimming in a high Reynolds number regime (Re ≥ 104). In this study, we present time-resolved, planar PIV measurements of a swimming peacock mantis shrimp (Odontodactylus scyllarus). Simultaneous kinematics measurements of the animal, which had body and pleopod lengths of 114 and 20 mm, respectively, reveal mean swimming speeds of 0.2–1.9 m s−1 and pleopod beat frequencies of 3.6–13 Hz, corresponding to advance ratios of 0.75–1.84 and body-based Reynolds numbers of 23,000–217,000. Further, the animal’s stroke is not purely metachronal, with a long phase lag between initiation of the first and fifth pleopod power strokes. Flow measurements in the sagittal plane show that each stroking pleopod pair creates a posteriorly moving tip vortex which evades destruction by the recovery strokes of other pleopod pairs. The vortex created by the anteriormost pleopod pair is the strongest and, owing to the animal’s high advance ratio, is intercepted by the power stroke of the posteriormost pleopod pair. The vortex strength increases as a result of this interaction, which may increase swimming speed or efficiency. A relationship for vortex interception by the posterior pleopod is proposed that relates the phase lag between the interacting pleopods to the beat frequency, distance between those pleopods, and speed of the vortex relative to the animal. We describe this interaction with a novel parameter called the interpleopod vortex phase matching Strouhal number StIVPM which is equal to the phase lag between interacting pleopods. This new nondimensional parameter may be useful in predicting the conditions where a constructive interaction may occur in other species or in physical models. Finally, we relate the advance ratio to the Reynolds number ratio, the ratio between the body-based Reynolds number and the pleopod-based Reynolds number. The importance of these parameters in promoting the interpleopod vortex interactions identified here, in dynamically scaled experiments, and in wake signatures behind schooling metachronal swimmers is discussed.
To examine whether financial stress during pregnancy mediates the association between maternal exposure to adverse childhood experiences (ACEs) and three birth outcomes (i.e., gestational age, birth ...weight, and admission to the neonatal intensive care unit NICU).
Data were obtained from a prospective cohort study of pregnant women and their infants in Florida and North Carolina. Mothers (n = 531; M
= 29.8 years; 38% Black; 22% Hispanic) self-reported their exposure to childhood adversity and financial stress during pregnancy. Data on infant gestational age at birth, birth weight, and admission to the NICU were obtained from medical records within 7 days of delivery. Mediation analysis was used to test study hypotheses, adjusting for study cohort, maternal race, ethnicity, body mass index, and tobacco use during pregnancy.
There was evidence of an indirect association between maternal exposure to childhood adversity and infant gestational age at birth (b = -0.03, 95% CI = -0.06 - -0.01) and infant birth weight (b = -8.85, 95% CI = -18.60 - -1.28) such that higher maternal ACE score was associated with earlier gestational age and lower infant birth weight through increases in financial distress during pregnancy. There was no evidence of an indirect association between maternal exposure to childhood adversity and infant NICU admission (b = 0.01, 95% CI = -0.02-0.08).
Findings demonstrate one pathway linking maternal childhood adversity to a potentially preterm birth or shorter gestational age, in addition to low birth weight at delivery, and present an opportunity for targeted intervention to support expecting mothers who face financial stress.
Benzaldehyde readily undergoes autoxidation to form benzoic acid on exposure to air at room temperature. Yet it can be formed in high yield from, for example, benzyl alcohol by oxidation using a ...variety of procedures and catalysts. Here we report the evidence to resolve this apparent paradox. It is confirmed that benzyl alcohol (and a number of other alcohols), even at low concentrations in benzaldehyde, inhibits the autoxidation. Furthermore we report on the structural features required for inhibition. Electron paramagnetic resonance spin trapping experiments demonstrate that benzyl alcohol intercepts, by hydrogen atom transfer, the benzoylperoxy radicals that play a key role in benzaldehyde autoxidation. A similar inhibition effect has also been observed for the aliphatic octanal/1-octanol system.
The lipid envelope of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is an essential component of the virus; however, its molecular composition is undetermined. Addressing this ...knowledge gap could support the design of antiviral agents as well as further our understanding of viral-host protein interactions, infectivity, pathogenicity, and innate immune system clearance. Lipidomics revealed that the virus envelope comprised mainly phospholipids (PLs), with some cholesterol and sphingolipids, and with cholesterol/phospholipid ratio similar to lysosomes. Unlike cellular membranes, procoagulant amino-PLs were present on the external side of the viral envelope at levels exceeding those on activated platelets. Accordingly, virions directly promoted blood coagulation. To investigate whether these differences could enable selective targeting of the viral envelope in vivo, we tested whether oral rinses containing lipid-disrupting chemicals could reduce infectivity. Products containing PL-disrupting surfactants (such as cetylpyridinium chloride) met European virucidal standards in vitro; however, components that altered the critical micelle concentration reduced efficacy, and products containing essential oils, povidone-iodine, or chlorhexidine were ineffective. This result was recapitulated in vivo, where a 30-s oral rinse with cetylpyridinium chloride mouthwash eliminated live virus in the oral cavity of patients with coronavirus disease 19 for at least 1 h, whereas povidone-iodine and saline mouthwashes were ineffective. We conclude that the SARS-CoV-2 lipid envelope i) is distinct from the host plasma membrane, which may enable design of selective antiviral approaches; ii) contains exposed phosphatidylethanolamine and phosphatidylserine, which may influence thrombosis, pathogenicity, and inflammation; and iii) can be selectively targeted in vivo by specific oral rinses.
The eardrums move when the eyes move Gruters, Kurtis G.; Murphy, David L. K.; Jenson, Cole D. ...
Proceedings of the National Academy of Sciences - PNAS,
02/2018, Volume:
115, Issue:
6
Journal Article
Peer reviewed
Open access
Interactions between sensory pathways such as the visual and auditory systems are known to occur in the brain, but where they first occur is uncertain. Here, we show a multimodal interaction evident ...at the eardrum. Ear canal microphone measurements in humans (n = 19 ears in 16 subjects) and monkeys (n = 5 ears in three subjects) performing a saccadic eye movement task to visual targets indicated that the eardrum moves in conjunction with the eye movement. The eardrum motion was oscillatory and began as early as 10 ms before saccade onset in humans or with saccade onset in monkeys. These eardrum movements, which we dub eye movement-related eardrum oscillations (EMREOs), occurred in the absence of a sound stimulus. The amplitude and phase of the EMREOs depended on the direction and horizontal amplitude of the saccade. They lasted throughout the saccade and well into subsequent periods of steady fixation. We discuss the possibility that the mechanisms underlying EMREOs create eye movement-related binaural cues that may aid the brain in evaluating the relationship between visual and auditory stimulus locations as the eyes move.
In contrast to the situation in plants inhabiting most of the world’s ecosystems, mycorrhizal fungi are usually absent from roots of the only two native vascular plant species of maritime Antarctica, ...Deschampsia antarctica and Colobanthus quitensis. Instead, a range of ascomycete fungi, termed dark septate endophytes (DSEs), frequently colonise the roots of these plant species. We demonstrate that colonisation of Antarctic vascular plants by DSEs facilitates not only the acquisition of organic nitrogen as early protein breakdown products, but also as non‐proteinaceous d‐amino acids and their short peptides, accumulated in slowly‐decomposing organic matter, such as moss peat. Our findings suggest that, in a warming maritime Antarctic, this symbiosis has a key role in accelerating the replacement of formerly dominant moss communities by vascular plants, and in increasing the rate at which ancient carbon stores laid down as moss peat over centuries or millennia are returned to the atmosphere as CO2.
Inflammation and macrophage foam cells are characteristic features of atherosclerotic lesions, but the mechanisms linking cholesterol accumulation to inflammation and LXR-dependent response pathways ...are poorly understood. To investigate this relationship, we utilized lipidomic and transcriptomic methods to evaluate the effect of diet and LDL receptor genotype on macrophage foam cell formation within the peritoneal cavities of mice. Foam cell formation was associated with significant changes in hundreds of lipid species and unexpected suppression, rather than activation, of inflammatory gene expression. We provide evidence that regulated accumulation of desmosterol underlies many of the homeostatic responses, including activation of LXR target genes, inhibition of SREBP target genes, selective reprogramming of fatty acid metabolism, and suppression of inflammatory-response genes, observed in macrophage foam cells. These observations suggest that macrophage activation in atherosclerotic lesions results from extrinsic, proinflammatory signals generated within the artery wall that suppress homeostatic and anti-inflammatory functions of desmosterol.
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► Desmosterol is the dominant LXR ligand formed in macrophage foam cells ► Desmosterol integrates cholesterol and fatty acid homeostasis in the macrophage ► Desmosterol inhibits activation of inflammatory responses in macrophages ► Macrophage activation in atherosclerosis is likely due to extrinsic mediators
Cholesterol accumulation in peritoneal macrophages results in unexpected suppression, rather than activation, of inflammatory gene expression, suggesting that this response is suppressed in atherosclerotic lesions by extrinsic proinflammatory signals.
Bubbles are ubiquitous in industrial and environmental processes, and bubble bursting is a widely studied and highly important physical process. Bubbles bursting at an air–water interface may produce ...high-speed gas jets and vortex rings. Here, the effect of liquid properties such as viscosity, density, and surface tension on these gas jets is examined using high-speed visualization. Bursting events are examined for 500 µm to 44 mm diameter smoke-filled bubbles in five different liquids with variations in viscosity (1–944 mPa.s), surface tension (23.3–70.7 mN/m), and density (789–1259 kg/m
3
). Gas jet speed generally increases with parent bubble size until a bubble Bond number
Bo
of approximately one and subsequently increases at a slower rate. Further, gas jet speed correlates with surface tension, with low surface tension liquids such as ethanol producing low-speed jets and high surface tension liquids such as water producing high-speed jets. Film retraction speed decreases with increasing bubble size and, in conjunction with bubble emergence, influences gas jet diameter. A new scaling law relating the pressure potential energy of the parent bubble to the kinetic energy of the emerging gas jet reveals that bubble size and surface tension control the gas jet size and speed whereas liquid viscosity and density do not significantly affect jet behavior. This scaling is compared to a previously developed scaling for the gas jet Reynolds number. The prevalence of jet drop production, which heavily depends on liquid viscosity, also is examined as a function of
Bo
and bubble Ohnesorge number
Oh
b
.
Graphical abstract
The focus of the present study was to define the human plasma lipidome and to establish novel analytical methodologies to quantify the large spectrum of plasma lipids. Partial lipid analysis is now a ...regular part of every patient's blood test and physicians readily and regularly prescribe drugs that alter the levels of major plasma lipids such as cholesterol and triglycerides. Plasma contains many thousands of distinct lipid molecular species that fall into six main categories including fatty acyls, glycerolipids, glycerophospholipids, sphingolipids, sterols, and prenols. The physiological contributions of these diverse lipids and how their levels change in response to therapy remain largely unknown. As a first step toward answering these questions, we provide herein an in-depth lipidomics analysis of a pooled human plasma obtained from healthy individuals after overnight fasting and with a gender balance and an ethnic distribution that is representative of the US population. In total, we quantitatively assessed the levels of over 500 distinct molecular species distributed among the main lipid categories. As more information is obtained regarding the roles of individual lipids in health and disease, it seems likely that future blood tests will include an ever increasing number of these lipid molecules.
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