Rigidity In Response Research Articles

Puttybot: A sensorized robot for autonomous putty plastering

AbstractPlastering is dominated manually, exhibiting low levels of automation and inconsistent finished quality. A comprehensive review of literature indicates that extant plastering robots demonstrate a subpar performance when tasked with rectifying defects in the transition area. The limitations encompass a lack of capacity to independently evaluate the quality of work or perform remedial plastering procedures. To address this issue, this research describes the system design of the Puttybot and a paradigm of plastering to solve the stated problems. The Puttybot consists of a mobile chassis, a lift platform, and a macro/micromanipulator. The force‐controlled scraper parameters have been calibrated to dynamically modify their rigidity in response to the applied putty. This strategy utilizes convolutional neural networks to identify plastering defects and executes the plastering operation with force feedback. This paradigm's effectiveness was validated during an autonomous plastering trial wherein a large‐scale wall was processed without human involvement.

Coarse Pricing Policies

AbstractThe muted volatility of inflation during the Great Recession and its aftermath has refocused attention on the constraints that firms face when adjusting prices. Using new empirical and theoretical results, I argue that each firm’s choice of how much information to acquire to set prices plays a central role in determining the patterns of pricing at the product level and the degree of aggregate price rigidity in response to shocks. In support of the information channel, I present product-level evidence that firms price goods using coarse pricing policies that are updated infrequently and consist of a small menu of prices. Firms are heterogeneous in the complexity and duration of their pricing policies, and this heterogeneity is reflected in differential responses to the Great Recession cycle, with firms exhibiting more complex policies responding more aggressively. I develop a theory of information-constrained price setting that generates coarse pricing endogenously, and quantitatively matches the discreteness, duration, and volatility of policies in the data. The information friction dampens the responsiveness of prices to shocks, and, coupled with heightened volatility, induces firms to keep prices relatively high, to protect against losses in an uncertain environment.

Programming the mechanics of cohesive fiber networks by compression.

Fibrous networks are ideal functional materials since they provide mechanical rigidity at low weight. Here, we demonstrate that fibrous networks of the blood clotting protein fibrin undergo a strong and irreversible increase in their mechanical rigidity in response to uniaxial compression. This rigidification can be precisely controlled by the level of applied compressive strain, providing a means to program the network rigidity without having to change its composition. To identify the underlying mechanism we measure single fiber-fiber interactions using optical tweezers. We further develop a minimal computational model of cohesive fiber networks that shows that stiffening arises due to the formation of new bonds in the compressed state, which develop tensile stress when the network is re-expanded. The model predicts that the network stiffness after a compression cycle obeys a power-law dependence on tensile stress, which we confirm experimentally. This finding provides new insights into how biological tissues can adapt themselves independently of any cellular processes, offering new perspectives to inspire the design of reprogrammable materials.

Development of Rigid Motion Perception in Response to Radially Expanding Optic Flow

A radially expanding flow with a linear positive speed gradient is perceived as a rigid object approaching the observer, whereas such a flow having no or a reduced speed gradient is perceived as a non‐rigid, two‐dimensionally deforming object (De Bruyn & Orban, 1990). We tested elementary school‐aged children (younger children, 6–9 years, and older children, 9–11 years) and adults (20–22 years) to examine the development of the perception of rigidity. The results suggest that the perception of rigidity in response to a radial flow pattern with a speed gradient is similar in older (but not younger) children and adults. The development of rigidity perception from a radial flow pattern may be related to the maturation of the dorsal and ventral visual pathways during the elementary school years. Copyright © 2016 John Wiley & Sons, Ltd.

One bad apple: experimental effects of psychological conflict on social resilience.

Past research suggests that small groups are self-organizing systems, and that social resilience may be measured as the meta-flexibility of group dynamics: the ability to shift back and forth from flexiblity to rigidity in response to conflict. This study extends these prior results, examining the impact of experimentally induced internal conflict and group-level conflict resolution on group dynamics-whether one bad apple can spoil the bunch. Six experimental groups with four members each participated in a series of four 25 min discussions. The first two discussions served as a baseline condition. Internal conflict was induced to one or more group members prior to discussion three, with the prediction that higher levels of conflict induction would lead to significant drops in group flexibility-creating a press on the group's resilience, whereas conflict resolution in discussion four was expected to allow for a rebound in group flexibility. Consistent with prior research, the turn-taking dynamics of each the 24 groups were distributed as inverse power laws (R (2) = 0.86-0.99) providing evidence for self-organization. Furthermore, there were significant study-wise negative correlation between levels of personality conflict and two measures of flexibility: information entropy (r = -0.47, p = 0.019) and fractal dimension (r = -0.42, p = 0.037). Altogether, these results suggest that: (i) small groups are self-organizing systems with structure and flexibility providing social resilience and (ii) individual conflict is able to spread to higher level social dynamics, creating pressure on social resilience. Practical implications for assessment of, and intervention with, psychosocial resilience are discussed.

Individual differences in the experience of cognitive workload

This study investigated the roles of four psychosocial variables – anxiety, conscientiousness, emotional intelligence, and Protestant work ethic – on subjective ratings of cognitive workload as measured by the Task Load Index (TLX) and the further connections between the four variables and TLX ratings of task performance. The four variables represented aspects of an underlying construct of elasticity versus rigidity in response to workload. Participants were 141 undergraduates who performed a vigilance task under different speeded conditions while working on a jigsaw puzzle for 90 minutes. Regression analysis showed that anxiety and emotional intelligence were the two variables most proximally related to TLX ratings. TLX ratings contributed to the prediction of performance on the puzzle, but not the vigilance task. Severity error bias was evident in some of the ratings. Although working in pairs improved performance, it also resulted in higher ratings of temporal demand and perceived performance pressure.

Specific Gtpase Dynamin Isoforms Regulate Megakaryocyte Membrane Remodeling and The Formation Of Multivesicular Bodies and Microparticles

Cdc42 interacting protein 4 (CIP4) is a membrane-associated BAR protein, which also forms a complex via its SH3 domain with the dynamins (DNMs) and Wiskott-Aldrich Syndrome (WAS) protein. Thus, CIP4 remodels the plasma membrane and cortical actin cytoskeleton. To determine its physiological function, we generated CIP4-null mice. They displayed thrombocytopenia similar to that of WAS-null mice and have abnormal megakaryocytes (MKs) with decreased proplatelet formation and underdeveloped demarcation membrane system (DMS) (Chen et al, Blood 2013). The DMS is an extensive network of membrane tubules which serves as a membrane reservoir for proplatelet formation. The membranes are enriched for polyphosphoinositides that are docking sites for BAR proteins and for pleckstrin homology domain-containing proteins such as the dynamins. Still, the formation of the DMS is poorly understood. Dynamins are cell vesicle trafficking proteins that possess a GTPase domain. They induce neck vesicle constriction and scission from the plasma membrane. When the GTPase activity is abrogated, vesicle scission does not occur; instead, the plasma membrane invagination induced by the BAR proteins results in deep plasma membrane tubulations. Of the three dynamin isoforms, DNM3 participates in MK development including DMS formation (Reems et al, Exp Hematol 2008; Wang et al, Stem Cells Dev 2011). Moreover, a recent genome-wide association study suggested that an MK-specific DNM3 isoform might play a role in human platelet size determination (Nürnberg et al, Blood 2012). However the exact mechanism for dynamin's participation in DMS formation is unclear. A double knockout for dynamin 1 and dynamin 3 in neurons causes accumulation of long invaginations from the plasma membrane (Ferguson and De Camilli, Nat Rev Mol Cell Biol 2012). We initially hypothesized that CIP4's association with DNM3 contributes to the DMS development during platelet biogenesis and wanted to test for functional redundancy with other dynamins present in MKs and platelets. To determine if CIP4 interacts with dynamin in the MK lineage, we found that following either phorbol ester (PMA) or fibronectin stimulation in the human MK cell line CHRF-288, CIP4 co-precipitated with DNM3 and colocalized by confocal microscopy. To determine dynamin's effect on membrane biophysical properties, we measured the fluorescence anisotropy, which reflects the disorder of membrane lipids due to movement and indicate membrane rigidity. Compared with controls in CHRF-288 cells, shRNA-mediated knockdown (KD) of DNM2 or DNM3 resulted in higher membrane rigidity in response to PMA. The strongest effect was seen in double KD cells with decreased fluidity by 2.6 ± 0.3%, which is similar to what was observed with CIP4 KD and is physiologically significant (Chen et al Blood 2013). KD of DNM2 resulted in aberrant morphology, greater cell diameter, and electron microscopy (EM) showed formation of new multivesicular bodies (MVBs) which are sorting compartments during α- and dense granules formation. Single DNM3 KD cells had no observable phenotype. EM imaging of DNM2 and DNM3 double KD cells revealed plasma membrane tubulation that resembles the DMS. While control CHRF-288 cells, with high DNM3 protein expression, do not have a DMS at baseline, MK cell lines Meg-01 and L8057, with respectively lower or no dynamin-3 protein expression, both have a DMS (Battinelli et al PNAS 2001; Ishida Y et al, Exp Hematol 1993). Platelet microparticles (MPs) are known to mediate a prothrombotic state in patients. Having previously found that CIP4-null mice show reduced levels of platelet MPs, we measured MPs in dynamin knockdown cell supernatant by flow cytometry and CD41/Annexin V staining. Surprisingly, we found that microparticle levels were increased 2.9-fold in DNM2 KD cells and 3.8-fold in double DNM2 and DNM3 KD cells. Our findings suggest that: 1) there is only partial functional redundancy between DNM2 and DNM3 in platelet biogenesis, 2) DNM2 controls MVB formation and MP release in MK cells, and 3) the CIP4-dynamin pathway contributes to DMS formation. It is possible that CIP4's interaction with dynamins restrains their spatial and temporal activity to allow for long invaginations to accumulate in the DMS. Dynamin depletion might also increase surface membrane availability for MP formation. Dynamins are thus potential targets to modulate thrombotic state and platelet biogenesis. Disclosures:No relevant conflicts of interest to declare.

The biological role of the glycinergic synapse in early zebrafish motility

Glycine mediates fast inhibitory neurotransmission in the spinal cord, brainstem and retina. Loss of synaptic glycinergic transmission in vertebrates leads to a severe locomotion defect characterized by an exaggerated startle response accompanied by transient muscle rigidity in response to sudden acoustic or tactile stimuli. Several molecular components of the glycinergic synapse have been characterized as an outcome of genetic and physiological analyses of synaptogenesis in mammals. Recently, the glycinergic synapse has been studied using a forward genetic approach in zebrafish. This review aims to discuss molecular components of the glycinergic synapse, such as glycine receptor subunits, gephyrin, gephyrin-binding proteins and glycine transporters, as well as recent studies relevant to the genetic analysis of the glycinergic synapse in zebrafish.

Prognostic value of changes in arterial stiffness in men with coronary artery disease

BackgroundMen with coronary artery disease (CAD) have been shown to have enhanced arterial stiffness. Arterial function may change over time according to treatment, but the prognostic value of these changes has not been investigated.ObjectivesThe aim of the present study was to assess whether an improvement in large artery rigidity in response to treatment, could predict a more favorable prognosis in a population of men with CAD.MethodsA total of 161 men with CAD (mean age 56.8 ± 10.9 years) being treated with conventional therapy underwent brachial-ankle pulse wave velocity (PWVba) measurements at baseline and after six months. Follow-up period was 3.5 years. End-points were major adverse cardiac events (MACE): acute myocardial infarction, unstable angina, coronary intervention, or cardiac death.ResultsDuring the three-year follow-up period (since initial six-month follow-up), 30 patients experienced MACE. After six-month follow-up, PWVba had not improved (ΔPWVba ≥ 0%, relative to baseline) in 85 (52.8%) of 161 men (Group 1), whereas it had improved (ΔPWVba < 0%) in the remaining 76 men (47.2%) (Group 2). During follow-up, we noticed 24 cardiovascular events in Group 1 and six events in Group 2 (P < 0.001). Cox proportional hazards analyses demonstrated that independent of conventional risk factor changes, absence of PWVba decrease was a predictor of MACE (RR 3.99; 95% CI:1.81–8.78; P = 0.004). The sensitivity of ΔPWVba was 80% and its specificity was 54%.ConclusionsThis study demonstrates that an improvement in arterial stiffness may be obtained after six months of conventional therapy and clearly identifies patients who have a more favorable prognosis.

A detailed analysis of open-field habituation and behavioral and neurochemical antidepressant-like effects in postweaning enriched rats

Our previous work has shown that male Sprague–Dawley rats reared in social isolation, standard housing and environmental enrichment differ in their spontaneous open-field activity and in some neurobehavioral depressive-like parameters. Here, we extended this evidence by using a shorter postweaning rearing period (1 month) and including additional evaluations. First, in order to obtain a better characterization of the exploratory strategies among rearing conditions we analyzed in detail the spontaneous activity at the first minute and during the 10-min session. Second, we asked whether the changes in open-field activity were related with basal anxiety levels in the elevated plus-maze. Third, behavior in the forced-swimming test was analyzed and afterward, the tissue levels of hippocampal norepinephrine and serotonin were assessed. The possible relationship between neurotransmitters and forced-swimming behavior were explored through correlation analyses. We found that rearing conditions (i) differed on locomotor habituation and on sensory-motor exploration at the first minute and during the 10-min session without modifying the plus-maze behavior; (ii) affected differentially the grooming time, its sequential components, and the relationship between grooming and locomotor parameters; (iii) modified forced-swimming behavior and the hippocampal concentration of norepinephrine, serotonin, and its turnover; and (iv) produced different correlation patterns between both neurotransmitters and forced-swimming behaviors. Overall, environmental enrichment accelerated open-field habituation and led to behavioral and neurochemical antidepressant-like effects. In contract, isolation rearing strongly impaired habituation and simple information processing, but showed marginal effects on depressive-like behavior and on hippocampal neurochemistry. The current results suggest that differential rearing is not only a useful procedure to study behavioral plasticity or rigidity in response to early experience, but also to modeling some developmental protective or risk factors underlying depressive disorders.

Heterogeneity in Price Rigidity: Evidence from a Case Study Using Microlevel Data

We combine two data sets to study price rigidity. The first consists of weekly time series of retail, wholesale, and spot prices for twelve products. These time series contain two exogenous cost shocks. We find that prices exhibit more rigidity in response to the second shock than the first. The second data set consists of all publicly available information about the shocks. Content analysis of these information reveals that the first shock is larger and more persistent, and the market has more information on it than the second. We conclude, therefore, that prices are more flexible in response to cost shocks that are larger, that are more persistent, and on which market participants have more information.

Increased rigidity and priming of polymorphonuclear leukocytes in sepsis.

It has been proposed that abnormal mechanical properties may contribute to capillary retention of polymorphonuclear leukocytes (PMN) in sepsis, leading to the development of organ dysfunction. The present study was designed to determine whether PMN rigidity is increased in severe sepsis, and whether changes in the rheologic behavior of PMN correlate with the clinical course in sepsis. Eighteen adults with severe sepsis were studied over a period of 14 d; 11 survived and seven died. PMN deformation behavior was investigated via micropore filtration, using the cell transit analyzer. On Day 0, PMN rigidity was 2.5-fold greater for sepsis patients than for five normal controls (p < 0.001). PMN rigidity progressively improved over the 14 d study period for patients who recovered, but not for those who died; clinical indicators correlated with PMN rigidity. Patient PMN also exhibited a 5-fold greater increase in rigidity in response to formyl-methionylleucylphenylalanine (fMLP) than did control PMN. Both the increased rigidity and enhanced response to fMLP could be simulated in vitro by incubation of normal PMN with tumor necrosis factor-alpha (TNF-alpha). We conclude that circulating PMN are more rigid in severe sepsis, and are "primed" for an augmented response to chemotactic stimuli. These findings support the hypothesis that cytokine-mediated increases of PMN rigidity may lead to sequestration of these cells in capillaries and to the consequent impairment of microvascular perfusion in sepsis.

Asymmetric Nominal Flexibility and Economic Fluctuations

Recent research has produced strong evidence that supports the asymmetric effects of positive and negative money supply shocks. Using quarterly data for the United States, the evidence of Cover [10] suggests that positive money supply shocks do not have an effect on output while negative money-supply shocks do. The asymmetric impact of demand shocks on real output growth is not addressed in the context of mainstream business-cycle theories which include the equilibrium explanation pioneered by Lucas [21] and neo-Keynesian models emphasizing nominal wage rigidity [14; 15] or price rigidity [2]. In the context of Lucas's paradigm, agents are scattered in informationaly isolated islands across the economy. An unexpected, positive or negative, change in aggregate demand may be misperceived by agents as being specific to their markets. In the case of a positive demand shock, producers and workers expand the output and labor supplied to take advantage of the perceived increased demand in their island. Similarly, agents are expected to contract the output produced in response to a perceived reduction in the demand for their output. This scenario does not provide an obvious theoretical channel through which the slope of the short-run supply curve can be differentiated depending on the direction of the change in aggregate demand. In the context of a contractual wage rigidity framework, the nominal wage is fixed for a duration that is determined by contractual agreements. According to this framework, a change in aggregate demand deviates the real wage from its market clearing value for a duration that is determined by the contract length. A positive demand shock will raise the price level, decrease the real wage and, in turn, cause an expansion in labor demand and the output produced in the short-run. A negative demand shock, in contrast, raises the realized real wage which has a negative impact on labor demand and the output produced in the short-run. In the absence of any stipulation in contracts that differentiates the degree of wage rigidity in response to a positive and negative demand shock, the slope of the short-run supply curve is not likely to be differentiated based on the direction of change in aggregate demand. In the context of the sticky-price explanation of business cycles, the price level across sectors of the economy is fixed for a specific duration. A change, positive or negative, in aggregate demand will be absorbed in output as long as the price level remains fixed in the short-run. In the absence of any stipulation that differentiates the upward and downward stickiness of the price

Halothane sensitivity of young pigs in vivo and in vitro

Piglets less than 8 wk of age that are known by genotype to be malignant hyperthermia-susceptible (MHS) do not usually develop characteristic hyperthermia and limb muscle rigidity in response to a brief halothane exposure (5 min of 3%). To determine whether a malignant hyperthermia (MH) episode could nevertheless be provoked by a more rigorous challenge, both genetically MHS (Pietrain) and normal (Yorkshire) 5-wk-old piglets were exposed to a combined halothane-succinylcholine challenge. Only two of eight MHS piglets developed limb rigidity; however, all MHS piglets (and no normal piglets) developed clinical signs of MH episode initiation during the 30-min challenge. Temperatures rose from 37.4 to 38.6 degrees C in MHS piglets while falling slightly in normal piglets. In MHS piglets, venous pH fell from 7.46 +/- 0.02 to 6.88 +/- 0.07, PVCO2 rose from 36 +/- 2 to 126 +/- 17 mmHg, and plasma concentration of K+ rose from 4.0 +/- 0.1 to 7.1 +/- 0.6 mM, whereas all values remained stable in normal piglets. Muscles removed from the same piglets before the halothane-succinylcholine challenge were exposed to halothane in vitro. The muscles from genetically MHS piglets responded to halothane with characteristic depression of tetanic tension and prolonged tetanus relaxation time but did not develop halothane-induced contractures. We conclude that, in the absence of either halothane-induced limb rigidity or in vitro contractures, these young animals were still susceptible to potentially fatal MH episodes on exposure to appropriate triggering agents. The MH defect is apparently partially masked in piglets and expressed fully only in older pigs.

Medical Care and the Public: Case Study of a Medical Group

Maintaining a high quality of medical care among physicians who characteristically depend upon patient choice for their success seems to be particularly difficult. One way of achieving high quality is said to be group practice. Study of patients of a medical group which gives care of high quality indicated that they are, by and large, satisfied. However, analysis of cases in which care was sought elsewhere indicated that the very attributes responsible for high professional quality were those making for a certain rigidity in response to the patient's demands. Inasmuch as the growth of group practice is likely to absorb what are now the safety-valve practices presently used by dissatisfied patients, attention must be paid to ways of restraining the development of a new pro fessional syndicalism which merely excludes and rejects patients with nowhere else to go.