Hidden Mechanisms Research Articles

The hidden mechanism under the policies: governance logic and network of the collaborative governance of air pollution control in the CCEC, China

The hidden mechanism under the policies: governance logic and network of the collaborative governance of air pollution control in the CCEC, China

Antioxidant Systematic Alteration Was Responsible for Injuries Inflicted on the Marine Blue Mussel Mytilus edulis Following Strontium Exposure.

The ionic properties of strontium (Sr), a significant artificial radionuclide in the marine environment, were estimated using a stable nuclide-substituting experimental system under controlled laboratory conditions. The bio-accumulation of Sr and its impacts, as well as any possible hidden mechanisms, were evaluated based on the physiological alterations of the sentinel blue mussel Mytilus edulis. The mussels were exposed to a series of stress-inducing concentrations, with the highest solubility being 0.2 g/L. No acute lethality was observed during the experiment, but sublethal damage was evident. Sr accumulated in a tissue-specific way, and hemolymph was the target, with the highest accumulating concentration being 64.46 µg/g wet weight (ww). At the molecular level, increases in the levels of reactive oxygen species (ROS) and malondialdehyde (MDA) and changes in ROS components (H2O2, O2-, and -OH) and antioxidant system activity indicated that the redox equilibrium state in hemocytes was disturbed. Furthermore, the rise in the hemocyte micronucleus (MN) rate (4‱ in the high-concentration group) implied DNA damage. At the cellular level, the structures of hemocytes were damaged, especially with respect to lysosomes, which play a crucial role in phagocytosis. Lysosomal membrane stability (LMS) was also affected, and both acid phosphatase (ACP) and alkaline phosphatase (AKP) activities were reduced, resulting in a significant decline in phagocytosis. The hemolymph population structure at the organ level was disturbed, with large changes in hemocyte number and mortality rate, along with changes in component ratios. These toxic effects were evaluated by employing the adverse outcome pathway (AOP) framework. The results suggested that the disruption of intracellular redox homeostasis is a possible explanation for Sr-induced toxicity in M. edulis.

Evaluation of Age and Gender-Related Patterns in Clinical Features and Hematological Findings Among Hypothyroidism Patients in the Al-Jouf Region of Saudi Arabia: A Hospital-Based Study.

The prevalence of hypothyroidism is high in Saudi Arabia and the contributing factors are iodine deficiency and lack of balanced nutrition. This study aims to correlate the gender, age, and presence of co-morbidities with the laboratory findings and clinical presentation. A cross-sectional study was done in the hospitals of the Al-Jouf region. The files of the patients diagnosed with hypothyroidism from the last two years were retrieved by non-probability consecutive sampling technique.IBMSPSS Statistics for Windows, Version 23, (Released 2015;IBMCorp., Armonk, New York, United States) was used for data entry and analysis. Descriptive statistics were presented as frequencies and proportions (for qualitative variables) and mean and standard deviation (SD) (for continuous data). Associated factors were identified through a chi-square test. A p-value less than 0.05 was considered statistically significant. Most of the patients were females within the age group of 36 to 50 years. Significant differences were observed between male and female patients with respect to the FT4 levels, hemoglobin (Hb) levels, mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC) values, and RBC counts (p-values of <0.001, <0.001, <0.001, <0.001, <0.001 and <0.001, respectively). However, no significant differences were observed between male and female patients in the TSH levels and hematocrit values. Most of the patients were euthyroid (77.24%). The pattern of thyroid function status did not show significant differences with respect to the gender of participants and the different age groups (p-values of 0.447 and 0.775, respectively). The most common co-morbidities observed were diabetes and hypertension. No significant association between the co-morbidities and the pattern of thyroid function status was observed. The most common symptoms were epigastric pain, fatigue, constipation, drowsiness, altered bowel habits, and weight gain. This hospital-based study provides valuable insights into some epidemiological characteristics, clinical features, and hematological findings in hypothyroidism patients of the Al-Jouf region. Significant differences were observed between male and female patients with respect to the FT4 levels, Hb levels, MCV, MCH, MCHC values, and RBC counts. The findings strengthen the existing knowledge base and emphasize the importance of timely detection and management of hypothyroidism in this population. Implementation of salt iodination programs and a timely evaluation of the hematological parameters is recommended. Further research is warranted to delve into the hidden mechanisms and long-term ramifications of hematological changes associated with hypothyroidism.

Tailoring Interfaces of All-Carbon Electromagnetic Interference Shielding Materials for Boosting Comprehensive Performance.

Electromagnetic interference (EMI) shielding materials with lightweight, high shielding effectiveness, excellent chemical stability, especially minimized secondary electromagnetic pollution, are urgently desired for integrated electronic systems operating in harsh working environments. Here in this study, by systematically engineering and matching the interfacial properties of carbon-based membrane materials, i.e., graphite paper, whisker carbon nanotube paper (WCNT paper), carbon nanotube film (CNT film), bucky paper (BP), and carbon cloth (CC) with three-dimensional (3D) porous carbon nanotube sponge (CNTS), we successfully constructed a series of multifunctional all-carbon EMI shielding materials, which exhibit excellent average shielding effectiveness of over 90 dB with a thickness of about 1 mm and dramatically minimized secondary electromagnetic reflection. Moreover, benefiting from the all-carbon nature and engineered interfaces, our CMC materials also exhibit excellent photothermal and Joule heating performances. These results not only provide guidance for designing advanced multifunctional all-carbon EMI shielding materials but also shed light on the hidden mechanism between interfaces and performances of composite materials.

The Hidden Mechanisms and Impact of International Economic Crime: A Bibliometric Perspective

The Hidden Mechanisms and Impact of International Economic Crime: A Bibliometric Perspective

Mendel's closet: genetics, eugenics and the exceptions of sex in Edwardian Britain

This article situates formative Mendelian and chromosomal precepts and rhetoric as an integral part of ‘reproductive’ physiology and the broader sexological terrain in Edwardian Britain. Alongside the discovery of ‘internal secretions’ (hormones), the discovery of the sex chromosomes, made around the same time as the rediscovery of Mendel's laws of heredity at the turn of the twentieth century, transformed the ways in which questions about sex determination and sex development were considered. Approaches were diverse as leading biologists including William Bateson, Leonard Doncaster, Reginald Crundall Punnett, Geoffrey Watkins Smith and their interlocutors negotiated the multiple, often conflicting, sociopolitical interpretations, uses and abuses that Mendelian approaches to sex were amenable to. Most contentiously, it was recognized that any credible model of sex biology had to account for all manner of sex phenomena, including parthenogenesis, intersexualities and transformations of sex, and that it was the variations of sex that best provided insights into the otherwise hidden mechanisms that shaped sex characteristics. Such a move, however, embroiled the new sexological genetics and the developing discipline of ‘reproductive’ physiology with vexed debates about feminism, homosexuality and eugenics. The article charts how the ensuing tensions played out across scholarly and popular platforms, including Britain's newspapers.

Application of high-velocity low-amplitude technique in cervicothoracic junction produces cardiovascular responses in subjects with C7-T1 dysfunction: Randomized crossover trial

BackgroundNeural structures of cardiac sympathetic and parasympathetic conduction emerge from the segments of the cervicothoracic spine. The application of high-velocity low-amplitude (HVLA) techniques at this segment can generate responses in heart rate (HR), blood pressure and sympathetic nervous activity of the skin. However, it is not known whether these responses occur in subjects with C7-T1 dysfunction. ObjectiveTo evaluate the effects of HVLA technique in cervicothoracic junction in HR, blood pressure and skin temperature (ST), in subjects with C7-T1 dysfunction. DesignThis is a randomized crossover trial. MethodsTwelve male subjects were randomized into two groups: HVLA and Sham. HVLA group received a single manipulation technique for C7-T1 dysfunction, while the sham group received a simulated HVLA. HR, blood pressure and ST were measured pre, immediately after and 10 min after the application of the interventions. ResultsImmediately after the application of the interventions, an increase in HR, systolic blood pressure (SBP) and ST was observed, in addition to a reduction in diastolic blood pressure (DBP). Also, 10 min after, a significant reduction in SBP and DBP was observed in the HVLA group when compared to Sham group. ConclusionThe application of a single HVLA technique in the cervicothoracic junction produced significative effects on HR, BP and ST in subjects with C7-T1 dysfunction. Implications for Practice·This study showed that a musculoskeletal technique has effect on autonomic nervous system, suggesting that there are still hidden mechanisms behind HVLA techniques.·HVLA techniques for cervicothoracic junction can generate changes in cardiovascular variables.·HVLA techniques did not cause adverse hypertensive peaks.

Mapping fine-resolution nested social-ecological system archetypes to reveal archetypical human-environmental interactions

Scaling up case-based knowledge to understand human-environmental interactions is key to addressing the sustainability challenges we face in the Anthropocene. Mapping social-ecological system (SES) archetypes has emerged as a promising tool in identifying these interactions in a spatially explicit manner and developing transferrable sustainability solutions based on context-specific challenges. However, state-of-the-art SES archetype mapping is mainly bound to administrative borders. Lack of spatial details in SES maps does not always capture the panorama of SES configurations and hidden mechanisms. Empowered by multiple open-access geospatial big data streams, this study mapped two-tier nested SES archetypes at 1 km fine resolution in the Beijing-Tianjin-Hebei (BTH) urban agglomeration with high validation accuracy. Global SES archetypes derived from top-down rule-based classification revealed broad social-ecological configurations and social-ecological gradients across SESs. Meanwhile, regional SES sub-archetypes generated by bottom-up hierarchical clustering presented detailed SES characteristics that helped to identify location-specific sustainability challenges. Additionally, by scrutinizing the relationships among SES variables, we identified empirical evidence supporting the existence of four archetypical human-environmental interactions in an urban agglomeration area, manifesting as telecoupling between human and environment, human dependence on the environment, human adaption to the environment, and human modification and conservation of the environment. Generally, fine-resolution SES archetypes demonstrate great potential in supporting the recognition of local needs and gaps in existing policies, and further promoting sustainable landscape management in the BTH region and similar regions.

Machine learning-based state maps for complex dynamical systems: applications to friction-excited brake system vibrations

In this work, a purely data-driven approach to mapping out the state of a dynamical system over a set of chosen parameters is presented and demonstrated along a case study using real-world experimental data from a friction brake system. Complex engineering systems often exhibit a rich bifurcation behavior with respect to one or several parameters, which is difficult to grasp using experimental approaches or numerical simulations. At the same time, the growing need for energy-efficient machines that can operate under varying or extreme environmental conditions also calls for a better understanding of these systems to avoid critical transitions. The proposed method combines machine learning techniques with synthetic data augmentation to create a complete state map for a dynamical system. First, a machine learning model is trained on experimental data, picking up hidden mechanisms and complex parametric relations of the underlying dynamical system. The model is then exploited to assess the state of the system for a set of synthetically generated data to obtain a state map over the complete space spanned by the chosen parameters. In addition, an extension of the concept to a probability state map is introduced. The results indicate that the proposed method can uncover hidden variables which drive dynamical transitions between different states of a system that were previously inaccessible.

Uncovering the fracture behavior of metallic cylindrical shells under internal explosive loadings via careful design of densely-arranged multi-point photon Doppler velocimetry measurements

While the expanding process of cylindrical shells under internal explosive loadings is fundamental and ubiquitous in engineering applications, the comprehensive understanding of the underlying mechanism is still a challenge due to the limitation of the spatial resolution on the current diagnostic techniques. To address this issue, an improved densely-arranged multi-point photon Doppler velocimetry (DMPDV) technique with enough spatial resolution to capture the local dynamical evolution was carefully designed. The DMPDV technique was then applied to investigate the expanding behavior of an explosively driven 304 L stainless steel cylindrical shell. As a step beyond the coarse understanding of the overall dynamical response, the expanding process can then be demonstrated comprehensively with more exact concentrations on one fragment. By the combination of DMPDV and high-speed photography, we uncovered the evolution of the expanding process which can be divided into three stages: (1) In the beginning, due to the symmetries of the specimen and the loading, the cylinder expands uniformly and all the velocity-time curves at different hoop positions are coincide with each other. (2) after the emergence of cracks at the outer surface of the cylinder, the velocity-time curves start to separate from each other and are regularly arranged according to their test positions. (3) following the penetration of the crack through the thickness of the cylinder, there is a reverse in the velocity-time curves and the fragments begin to rotate, the rotation angle can be estimated using the velocity difference. The hidden mechanism is then revealed with the help of unloading wave theory and rigid body dynamics. Here the second stage is dominated by unloading wave while the last stage is controlled by the denotation products. These experimental results provide deep insight into the detailed fracture behavior of expanding cylindrical shell and are further validated by the Mott wave models as well as numerical simulations, respectively.

Cathepsin B S-nitrosylation promotes ADAR1-mediated editing of its own mRNA transcript via an ADD1/MATR3 regulatory axis.

Genetic information is generally transferred from RNA to protein according to the classic "Central Dogma". Here, we made a striking discovery that post-translational modification of a protein specifically regulates the editing of its own mRNA. We show that S-nitrosylation of cathepsin B (CTSB) exclusively alters the adenosine-to-inosine (A-to-I) editing of its own mRNA. Mechanistically, CTSB S-nitrosylation promotes the dephosphorylation and nuclear translocation of ADD1, leading to the recruitment of MATR3 and ADAR1 to CTSB mRNA. ADAR1-mediated A-to-I RNA editing enables the binding of HuR to CTSB mRNA, resulting in increased CTSB mRNA stability and subsequently higher steady-state levels of CTSB protein. Together, we uncovered a unique feedforward mechanism of protein expression regulation mediated by the ADD1/MATR3/ADAR1 regulatory axis. Our study demonstrates a novel reverse flow of information from the post-translational modification of a protein back to the post-transcriptional regulation of its own mRNA precursor. We coined this process as "Protein-directed EDiting of its Own mRNA by ADAR1 (PEDORA)" and suggest that this constitutes an additional layer of protein expression control. "PEDORA" could represent a currently hidden mechanism in eukaryotic gene expression regulation.

STING mediates SU5416/hypoxia-induced pulmonary arterial hypertension in rats by regulating macrophage NLRP3 inflammasome activation

BackgroundThe NLRP3 inflammasome in macrophages is known to promote infection-related vascular growth, and NLRP3 inflammasome activation interacts with PAH. STING is a crucial inflammatory reaction link that can increase the overexpression of NLRP3. However, the expression and effect of STING in PAH have not been elucidated. We examined the expression and articulation of STING in PAH and researched its hidden mechanism. MethodsA SU5416 plus hypoxia (Su/Hy)-induced rat model of PAH was constructed to examine STING activation. Su/Hy induced PAH rats were given a prophylactic injection of STING the inhibitor C-176. After modeling, hemodynamic changes, right ventricular hypertrophy index, lung morphological features, inflammasome activation, and proinflammatory cytokine secretion levels were assessed. In addition, the STING agonist DMXAA or inhibitor C-176 was used to interfere with LPS-induced BMDMs, NLRP3 inflammasome activation and cytokine secretion were examined, and the effect on PASMCs was evaluated in a coculture system. ResultsSTING expression increased significantly in the lung tissue of Su/Hy-treated PAH rats compared with normoxia-treated rats. Moreover, STING inhibitors can alleviate the Su/Hy-induced increase in pulmonary artery pressure and restrain the activation of the NLRP3 inflammasome and proinflammatory cytokines. In vitro experiments confirmed that STING affected the expression of the NLRP3 inflammasome and the secretion of inflammatory cytokines in BMDMs and promoted the proliferation of PASMCs in the coculture system. ConclusionOur study shows that STING is activated in Su/Hy-induced PAH and boosts the actuation of the macrophage NLRP3 inflammasome to advance the inflammatory response and vascular proliferation in rats with Su/Hy-induced pulmonary hypertension.

Seeing Puppetry: Winter Report from New York City

Seeing Puppetry: Winter Report from New York City

КОГНІТИВНА МЕТАФОРА ЖИТТЯ/СМЕРТЬ КРІЗЬ ПРИЗМУ МОВНОЇ КАРТИНИ СВІТУ ВАСИЛЯ ШКЛЯРА

The anthropocentric approach to studying of language and speech causes linguists’ turn to literary discourse, since at the present stage of linguistic science development, it is relevant, in our opinion, there are researches of discursive phenomena, verbal conceptual models and their infl uence on the functioning of language units. This is manifested in the fact that the study of metaphorical mod-els in the cognitive and discursive structure is of particular interest. Attention to the problem of metaphor, certain aspects of its studying, is pri-marily due to the complexity of the speech phenomenon, the desire of linguists to fi nd hidden mechanisms that control the metaphorical process, the laws of its existence. In the system of linguistic structures, metaphor is considered as a dynamic linguistic phenomenon, which is characterized by such concepts as dis-course, dialogical discourse in cognitive-discursive, systemic-active and func-tional-communicative approaches, which is based on a dual orientation towards the author, the creator, who is considered as a universal language personality, and on the society represented by the addressee, the reader.Such an approach to the study of metaphor based on the formation of a com-municative-discursive paradigm indicates the need for theoretical and practical study of metaphor in a cognitive-discursive context aimed at substantiating the implementation of the language system taking into account lingual and extralin-gual factors. This is the relevance of scientifi c research, the purpose of which is to investigate the cognitive counter-metaphor LIFE / DEATH in the discursive dialogic structures of Vasyl Shkliar’s text «Zalyshents. Chornyi Voron». The study of cognitive metaphor makes it possible to make generalizations about the functioning tendencies of ideas about life and death, the embodiment of the ethnic uniqueness of world perception and the conceptual presentation of the analyzed metaphor through the prism of archetypal manifestations. The interpretation of LIFE / DEATH as a natural phenomenon is motivated by human empirical experience.In the Ukrainian picture of the world, the researched metaphors have a strong connection with archetypes, which is explained by paganism, the tradi-tions of which are deeply rooted in the Ukrainian linguistic consciousness. Prospective directions for further research should include revealing and de-termining the scope and content of the cognitive metaphor LIFE / DEATH in other works of this author.

A laser-shock-enabled hybrid additive manufacturing strategy with molten pool modulation of Fe-based alloy

A novel hybrid laser additive manufacturing (LAM) process based on laser shock modulation of molten pool (LSMMP) is proposed in this work. By using a combination of experiment and simulation, the residual stress, heat transfer, and mass transfer behaviors are comprehensively studied. Also, microstructure evolution behavior is analyzed. The relationship between the convection behavior, the evolution of microstructure and the enhancement of residual stress induced by LSMMP is established. Compared with the traditional post-treatment process, the LSMMP assisted LAM process exhibits higher efficiency in residual stress control with the same pulsed laser energy input. The hidden mechanism in microstructure evolution and residual stress enhancement is expected to be possible related to intensified molten pool convection, uniform solute distribution and improved cooling rate induced by LSMMP. The hybrid LAM process strategy based on LSMMP provides a new approach for the application of short pulse laser in hybrid manufacturing.

Aldehyde Dehydrogenase 2 (ALDH2) Elicits Protection against Pulmonary Hypertension via Inhibition of ERK1/2-Mediated Autophagy.

Pulmonary hypertension (PH) is caused by chronic hypoxia that induces the migration and proliferation of pulmonary arterial smooth muscle cells (PASMCs), eventually resulting in right heart failure. PH has been related to aberrant autophagy; however, the hidden mechanisms are still unclear. Approximately 40% East Asians, equivalent to 8% of the universal population, carry a mutation in Aldehyde dehydrogenase 2 (ALDH2), which leads to the aggregation of noxious reactive aldehydes and increases the propensity of several diseases. Therefore, we explored the potential aspect of ALDH2 in autophagy associated with PH. In vitro mechanistic studies were conducted in human PASMCs (HPASMCs) after lentiviral ALDH2 knockdown and treatment with platelet-derived growth factor-BB (PDGF-BB). PH was induced in wild-type (WT) and ALDH2-knockout (ALDH2−/−) mice using vascular endothelial growth factor receptor inhibitor SU5416 under hypoxic conditions (HySU). Right ventricular function was assessed using echocardiography and invasive hemodynamic monitoring. Histological and immunohistochemical analyses were performed to evaluate pulmonary vascular remodeling. EdU, transwell, and wound healing assays were used to evaluate HPASMC migration and proliferation, and electron microscopy and immunohistochemical and immunoblot assays were performed to assess autophagy. The findings demonstrated that ALDH2 deficiency exacerbated right ventricular pressure, hypertrophy, fibrosis, and right heart failure resulting from HySU-induced PH. ALDH2−/− mice exhibited increased pulmonary artery muscularization and 4-hydroxynonenal (4-HNE) levels in lung tissues. ALDH2 knockdown increased PDGF-BB-induced PASMC migration and proliferation and 4-HNE accumulation in vitro. Additionally, ALDH2 deficiency increased the number of autophagosomes and autophagic lysosomes together with autophagic flux and ERK1/2-Beclin-1 activity in lung tissues and PASMCs, indicating enhanced autophagy. In conclusion, the study shows that ALDH2 has a protective role against the migration and proliferation of PASMCs and PH, possibly by regulating autophagy through the ERK1/2-Beclin-1 pathway.

Hidden spatiotemporal sequence in transition to shear band in amorphous solids

Localization of plastic flow into a narrow shear band is a fundamental and ubiquitous nonequilibrium phenomenon in amorphous solids. Because of the intrinsic entangling of three types of elementary local atomic motion---shear, dilatation, and rotation---the precise physical process of shear band emergence is still an enigma. Here, to unveil this mystery, we formulate a theoretical protocol covering both affine and nonaffine components of deformation, to decode these three highly entangled local atomic-scale events. In contrast to the broad concept of the shear transformation zone, the plastic behavior can be demonstrated comprehensively as the operative manipulation of more exact shear-dominated zones, dilatation-dominated zones, and rotation-dominated zones. Their spatiotemporal evolution exhibits a transition from synchronous motion to separate distribution at the onset of the shear band. The hidden mechanism is then revealed with the help of extreme value theory and percolation analysis. Numerical evidence from extreme value theory indicates that dilatation is the dominant mode at the embryonic stage of the initial plastic units, as evidenced through the larger degree of dilatation localization compared with shear and rotation. The percolation analysis points towards the critical power-law scaling nature at the transition from stochastic activation to percolation of plastic regions. Then the comprehensive picture underlying shear banding emergence is uncovered. Firstly, dilatation triggers initial shear and rotation in soft regions, leading to the embryos of the initial flow units, which are followed by the secondary activation of rotation in neighboring hard material, thus causing an alternating distribution of rotation and shear-dilatation regions. Such rotation activation contributes to further perturbation in these regions and ultimately leads to percolation transition and shear band formation. Our findings also reinforce that the discussion of plastic behavior in disordered materials must take into account both affine and nonaffine component deformation.

Does ’class count’? The evolution of health inequalities by social class in early 21st century China (2002–2013)

ABSTRACT Does social class matter in understanding health inequalities in early 21st century China, when the country experienced unprecedented social stratification? Using nationally representative data from the latest waves of China Household Income Project surveys, we examine to what extent an individual’s health is structured by social class and how that structure evolved. We draw on a neo-Marxist measure of social class to tap into the hidden mechanism that engenders and sustains inequalities. Four classes are defined based primarily on their relationships to productive resources: owners/managers, professionals/skilled workers, less-skilled workers, and farmers. Such a measure has not been considered in the health gradient literature in the Chinese context. Our results show that, despite remedial policies that helped mitigate economic inequalities, inequalities in health have mostly widened during the early years of the current century between the ‘haves’, who own productive assets and/or managerial authority, and the ‘have-nots’. In 2002, self-rated health (SRH) was not clearly associated with class rank; in 2007, when China’s economic inequality reached a historical zenith, a gradational pattern between SRH and class emerged, and the largest health gap was found between the class of owners/managers and farmers; in 2013, when China’s income inequality reached a plateau, the health gap between owners/managers and less-skilled workers grew larger. Further, we identify job security as a mediator that links class and health among the lower social strata. In addition to improving the health of the disadvantaged, policies designed to narrow health inequalities should be orientated towards addressing social stratification.

Space and time: its understanding from philosophy to natural science

The author shows that rare problems have worried people for centuries as deeply as the secrets of space and time. Only by gradually comprehending their hidden mechanisms, one can hope to better understand where and how the existing world is going and what is the purpose of a person in it. However, even the most complex concepts sometimes begin with the most banal definitions (and one cannot avoid it). The following is well known: the concept of space expresses the coexistence and separation of things from each other, their extent, the order of their arrangement; the concept of time conveys the sequence of events, their duration. The article offers various approaches to the interpretation of space and time - from the point of view of philosophy and natural sciences. The content of such qualities of time and space as uncreability, irreversibility, uniqueness, and inevitability is revealed. The materials of the article can be used in the preparation of disciplines related to natural science.

In vivo intraoral waterflow quantification reveals hidden mechanisms of suction feeding in fish.

Virtually all fishes rely on flows of water to transport food to the back of their pharynx. While external flows that draw food into the mouth are well described, how intraoral waterflows manage to deposit food at the esophagus entrance remains unknown. In theory, the posteriorly moving water must, at some point, curve laterally and/or ventrally to exit through the gill slits. Such flows would eventually carry food away from the esophagus instead of toward it. This apparent paradox calls for a filtration mechanism to deviate food from the suction-feeding streamlines. To study this gap in our fundamental understanding of how fishes feed, we developed and applied a new technique to quantify three-dimensional (3D) patterns of intraoral waterflows in vivo. We combined stereoscopic high-speed X-ray videos to quantify skeletal motion (XROMM) with 3D X-ray particle tracking (XPT) of neutrally buoyant spheres of 1.4 mm in diameter. We show, for carp (Cyprinus carpio) and tilapia (Oreochromis niloticus), that water tracers displayed higher curvatures than food tracers, indicating an inertia-driven filtration. In addition, tilapia also exhibited a 'central jet' flow pattern, which aids in quickly carrying food to the pharyngeal jaw region. When the food was trapped at the branchial basket, it was resuspended and carried more centrally by periodical bidirectional waterflows, synchronized with head-bone motions. By providing a complete picture of the suction-feeding process and revealing fundamental differences in food transport mechanisms among species, this novel technique opens a new area of investigation to fully understand how most aquatic vertebrates feed.